Engineering Chemistry Volume 9

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Volume 9 of Engineering Chemistry

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Table of Contents

Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan

Daffa Irsyad Darmawan, Muhammad Rifani, Muthia Putri Darsini Lubis, Hizkia Alpha Dewanto, Fredy Kurniawan, Yusairie Mohd, Yunita Triana

Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Muhammad Rifani, Daffa Irsyad Darmawan, Ade Wahyu Yusariarta, Jatmoko Awali, Fredy Kurniawan, Masato Tominaga, Yusairie Mohd, Yunita Triana

Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

Irsyad Al Habib, Andi Idhil Ismail, Dewi Umanigrum, Agung Purniawan, Murni Handayani, Genki Ogata, Yasuaki Einaga, Yunita Triana

Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Akeem Adesina Bamigbade, Enock Olugbenga Dare, Biodun S. Badmus, Titilayo Bamgbose

Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Malki Fatiha, Missoum Amina, Hamza Kahina

Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Ayodunmomi Esther Olowofoyeku, Ademola Kabiru Aremu, Abel Olajide Olorunnisola, Ayobamiji Emmanuel Olowofoyeku, Ezekeil Oluwatobi Faluyi, Daniel Gbenga Adekanmi

Adsorptive Removal of Methylene Blue (MB) from Wastewater: A Comparative Modeling Study Utilizing RSM, ANN, and ANFIS Model

Ephraim Igberase, Innocentia Mkhize

Keywords Index

Authors Index

The original version of this eBook is available on https://www.scientific.net/book/engineering-chemistry-vol-9/978-3-0364-1758-5

Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 1-10

doi: 10.4028/p-ryFR6C

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

Submitted:
2024-11-19

Accepted:
2024-12-02

Online:
2025-03-10

Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040

Daffa Irsyad Darmawan , Muhammad Rifani , Muthia Putri Darsini Lubis , Hizkia Alpha Dewanto , Fredy Kurniawan e , Yusairie Mohd , Yunita Triana

Department of Material and Metallurgical Engineering, Institut Teknologi Kalimantan, Balikpapan 76127, Indonesia

Department of Chemistry, Institut Teknologi Sepuluh November, Surabaya 60111, Indonesia

Faculty of Applied Science, Universiti Teknologi MARA, Shah Alam, Selangor 40450, Malaysia

student.itk.ac.id, student.itk.ac.id, muthia_lubis@lecturer.itk.ac.id,

hizkia.ad@lecturer.itk.ac.id,

g*nita@lecturer.itk.ac.id

Keywords: AISI, Corrosion, Green, Inhibitors, Peel

Abstract

This study investigates the corrosion inhibition properties of Salak (Salacca zalacca) peel extract as a green inhibitor on AISI 1040 steel in a 1 M HCl acidic environment and focusing on secondary metabolites such as flavonoids and tannins. The qualitative phytochemical analysis showed antioxidant activity of the inhibitor extract was categorized as moderate with an IC50 value of 105.219 ppm . Functional group analysis using FTIR indicated that the flavonoids and tannins in the extract acted as antioxidants and inhibited corrosion growth. The weight loss test revealed the highest inhibition efficiency was achieved at a concentration of 200 ppm after 20 days of immersion. In the potentiodynamic polarization test, the corrosion rate was year at the same concentration and immersion time. These results suggest that Salak (Salacca zalacca) peel extract can effectively inhibit corrosion at spesific concentrations but its efficiency diminishes at higher concentrations.

Introduction

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Corrosion of metals is one of the matters with big losses in the world's industry [1], [2]. It can be seenthat the impact of corrosion on the domestic economy of various countries reaches of GDP. When damage is major, expensive maintenance and replacement is required for safe and reliable construction use, and even if the serviceability of the structure is not compromised, deterioration in appearance results in a decrease in the value of the construction.[3] Corrosion is generally known as material degradation, which is an event of damage or decrease in the quality of a material, especially metal, due to environmental reactions that provide an atmosphere for oxidation-reduction reactions [4]. A corrosion inhibitor is a chemical compound that, when added, can be attached to the material's surface and will be a protector against cove environments [5].
There are several ways to protect against corrosion, namely cathodic protection [6], and coatings [7] one of the effective alternative ways to protect against corrosion on metal surfaces is inhibitors (inorganic and organic) [8], [9]. The selection of inhibitors is not only based on their ability to inhibitor corrosion rates with high efficiency. Several methods have been used to reduce the corrosion rate ofcarbon steel corroded by acid solutions. Still, an effective use is the use of organic inhibitors [10-17], but also in terms of their level of toxicity when applied to industry against environmental pollution. For this reason, the use of inorganic inhibitors is limited, like that encouraging the development of alternative organic inhibitors or green inhibitors that are economical, easily renewable, biodegradable, and environmentally friendly from extracts of natural ingredients. Substances from natural sources exhibit antioxidants. Antioxidant compounds can be found in plantssuch as meat, roots, skin, stems, and leaves [18][22].

Salak (Salacca zalacca) is a species of palm tree (family Aracaceae) native to Indonesia. Consumerslike snake fruit with thick flesh, a sweet taste, and small seeds [19]. However, the results of the phytochemical test showed that the bark of the Salak (Salacca zalacca) fruit contained flavonoids and tannins. The ethanol extract of Salak (Salacca zalacca) fruit peels has antioxidant activity with an IC50 value of 49,45 [20] The presence of flavonoids and tannins from the bark extract of the zalacca fruit is the basis for supporting the utilization of the peel waste in this study. In addition to bark, many studies have used organic extracts on carbon steel with an HCl environmentamong sunflower seeds [21], peppers [23], jackfruit banana skin [24], and orange and mango peels [25].
In this study, the inhibitor was extracted from the bark of the Salak (Salacca zalacca) fruit cultivated at KM 21 Karang Joang. It was used as a corrosion inhibitor on AISI 1040 steel in a 1M HCl environment. The contentof AISI specimens were confirmed using OES. The 1,1- diphenyl-2picrylhydrazyl (DPPH) test wasused to determine the antioxidant activity of salak fruit bark (Salacca zalacca). The Fourier Transform Infra-Red (FTIR) technique confirmed the extract's functional groups of antioxidant compounds. Furthermore, the effects of inhibitor concentration and immersion time on inhibitor performance were reviewed through weight loss corrosion testing methods and polarization measurements. In addition, surface observations of AISI 1040 steel macrostructures were analyzed using a Scanning Electron Microscope (SEM).

Research MethodologyInhibitors Preparation

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Salak fruit skin (Salacca zalacca) obtained from KM 21 Karang Joang, North Balikpapan District, Balikpapan City, was dried by sunlight exposure for seven days. Inhibitor preparation was carried out by the maceration method by inserting 500 grams of dried zalacca skin and pulverizing it with a blender and 3000 mL of ethanol into a 5000 mL container. Immersion was carried out for 3 x 24 hours. Then the extraction results are separated between the filtrate and residue. After that, the evaporator and oven are carried out [26]

Secondary Metabolite Identification Method

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At this point testing was carried out to identify secondary metabolites, namely phytochemicals and DPPH. Phytochemical testing was done to determine the secondary metabolites contained in the skin extract of salak (Salacca zalacca), the compounds to be known were flavonoids and tannins.
After knowing the secondary metabolites of phytochemicals, then proceed with DPPH. Testing the antioxidant activity with 1,1- diphenyl-2-picrylhydrazyl (DPPH) aims to determine the antioxidant activity of salak (Salacca zalacca) bark extract.

Electrolyte Solution Preparation

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1 M HCl is produced from which the molar is 10.32 M , then HCl is diluted in 1 liter of distilled water to obtain a 1 M HCl solution [27].

Weight loss Method

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The sample used is AISI 1040 steel with a size of as shown in Fig.1. This test was done with the aim of knowing the resulting weight loss in the sample when immersed in a corrosive medium, namely 1 M HCl . This test was done with various inhibitor concentrations ( 0 ppm , , and 500 ppm ) and Immersion time ( 10 days, 20 days, and 30 days) [27]. Corrosiontesting with the weight loss method with ASTM G31-21 standard was repeated three times [28].

Fig. 1 Weight loss Method

Fig. 1. Weight loss Method

Electrochemical Experimental

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The polarization test was conducted using an autolab to gather corrosion rate data for AISI 1040 steel. This method employs a three-electrode setup which includes an reference electrode, a platinum auxiliary electrode, and AISI 1040 steel working electrode. This configuration allows precise measurement of the electrochemical behavior of the steel in the corrosive environtment and providing valuable insight into the effectiveness of the corrosion inhibitor based on concentration and soaking time as shown in Fig. 2.

Fig. 2 Schematic of three electrodes Electrochemical

Fig. 2. Schematic of three electrodes Electrochemical

Characterization

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Characterization testing was carried out to determine the functional groups content in Salak (Salacca zalacca) peel extract using Fourier Transform Infrared Spectroscopy (FTIR) to helped confirm the presence of key compounds such as flavonoids and tannins.ronScanning Electron Microscope with Energy Dispersive X-Ray ( SEM-EDX) test was carried out to observe the surface morphology of steel samples and allowing for a comparison of the extent surface damage with and without the application of inhibitors.

Results and Discussion

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Determination of Antioxidant Properties of Salak (Salacca zalacca) Peel Extract

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The results of the linear regression equation for the antioxidant activity of Salak (Salacca zalacca) peel extract was determined to be with a strong correlation coefficient of 0.91 , indicating a good fit of the data. Then, using the IC50 value is substituted for the y value as a free radical inhibitor value of so that the x value is obtained, which is the IC50 value. This provides a quantitative measure of the extract's antioxidant potential, helping to evaluate its effectiveness in reducing oxidative stress.

Table 1 Results of Measurement of Antioxidant Activity of 96% Ethanol Extract of Salak (Salacca zalacca) Peel with the DPPH method

Concentration (ppm) | Antioxidant Activity (%) | IC₅₀ (ppm) | Antioxidant Potential
0 | 0 | 105,219 | Medium
12,5 | 2,72
25 | 3,63
50 | 31,74
100 | 44,82 |  |

Qualitative Analysis of Secondary Metabolites of Salak (Salacca zalacca) Bark Extract

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Table 2 Phytochemical Test Results

Secondary Metabolites | Reactor | Results
Flavonoid | NaOH 1% + HCl 1% | +
Tanin | Lead (II) acetate (CH₃COO)₂ Pb 1% | +
Saponin | Aquadest + HCl | -
Alkaloid | HCl + dragendorf | -

Information:

: detected

: not detected

The phytochemical test results of the Salak (Salacca zalacca) bark extract revealed the presence of secondary metabolites specifically flavonoids and tannins which were detected through positive reactions in the assay. In contrast, the tests for alkaloids and saponins yielded negative results indicating their absence in the extract. These finding suggest that the corrosion inhibition properties of the extract may primarily be attributed to the flavonoid and tannins which are known for their antioxidant and metal-binding capabilities.

Analysis of Functional Groups in Salak (Salacca zalacca) Peel Extract

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Secondary metabolites in Salak (Salacca zalacca) peel extract play crucial role in the inhibition mechanism making it essential to analyze the constituent compounds involved. In this study, we conducted FTIR characterization was performed to identify these key secondary metabolite.Based on the FTIR result confirmed the presence of tannins and flavonoids which both are known to contribute the corrosion inhibition process due to their antioxidant properties and ability to form protective layers on metal surfaces.
Flavonoids contain several functional groups, including double bonds, single bonds, singlebonds, and O-H single bonds which contribute to their chemical reactivity. These functional groups play a significant role in the interaction of flavonoids with metal surfaces aiding in formation of a protetctive barrier against corrosion. Based on the molecular structure of the flavonoids detected in this assay suggest their potential effectiveness in the corrosion inhibiton process through antioxidant activity and adsorption onto metal surface.

Fig. 3 Structure of Flavonoid

Secondary metabolite compounds, namely tannins, contain functional groups such as and single bonds which contribute to their chemical properties. FTIR analysis confirmed the presence of tannins in Salak (Salacca zalacca) peel extract indicating their role in the inhibition mechanism in Fig. 4, tannin is a detectable compound.

Table 3 FTIR result of Salak (Salacca zalacca) skin

Wavenummber (cm⁻¹) | Frequency Area (cm⁻¹) | Chemical Bonds | Functional Group
3340,23 | 3200-3600 | O-H | Fenol
3010,54 | 3010-3100 | C-H | Aromatic Ring
2923,99 | 2850-2970 | C-H | Alkana
2853,93 | 2850-2970 | C-H | Alkana
2171,87 | 2100-2260 | C≡C | Alkuna
1718,54 | 1690-1760 | C = O | Aldehid, Keton
1514,54 | 1500-1600 | C = C | Aromatic Ring
1376,48 | 1300-1470 | C – H | Alkana
1223,99 | 1180-1360 | C – N | Amina, Amida
1155,99 | 1050-1300 | C – O | Alkohol, Eter, Hydroxycarboxylic acid, Ester
921,09 | 675-995 | C – H | Alkena
815,99 | 675-995 | C – H | Alkena
770,66 | 675-995 | C – H | Alkena
1718,54 | 1690-1760 | C = O | Aldehid, Keton
1514,54 | 1500-1600 | C = C | Aromatic Ring

Performance Analysis of Corrosion InhibitorsInhibition Efficiency

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In Table 4, it can be seen that the inhibition efficiency from concentrations of 0 to 500 ppm by soaking for 20 days

Table 4 Inhibiton Efficiency

Inhibitor
Concentration (ppm)
Sample Number
Initial Weight (gr)
Final Weight (gr)

0
1
10,225
8,591

2
10,582
8,649

3
10,449
8,584

100
1
10,240
8,602

2
10,257
8,553

3
10,498
8,791

200
1
10,130
8,659

2
10,223
8,640

3
10,180
8,414

300
1
10,393
8,667

2
10,195
8,512

3
10,534
8,236

400
1
10,847
8,921

2
11,055
8,324

3
10,894
8,750

Fig. 4 Inhibition Efficiency of Salak (Salacca zalacca) peel Extract in 1 M HCl Solution (a) Variation ofConcentration (b) Variation of Soaking Time

Fig. 4. Inhibition Efficiency of Salak (Salacca zalacca) peel Extract in 1 M HCl Solution (a) Variation ofConcentration (b) Variation of Soaking Time

Based on data from the most optimum concentration variation, the highest inhibition efficiency was observed at a concentration of 200 ppm , which was while the efficiency dropped drastically at 500 ppm to the significant reduction in efficiency at higher concentrations can be attributed to the saturation of adsorption sites on the steel surface. Once these sites are saturated, excess inhibitor molecules may aggregate and disrupt the uniform protective layer causing the metal surface to be exposed of the corrosive medium. On the concentration of 200 ppm , the Fig. 5 above explains that the highest inhibition efficiency was obtained with variations in soaking time at the optimum concentration of 200 ppm at 20 days of immersion time of .

Corrosion Rate

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The corrosion rate in Fig. 5 decreased from year to less than year at concentrations of 100 and 200 ppm ; then, the corrosion rate increased to more than 0.2 mm /year at concentrations of 300,400 , and 500 ppm . There is a correlation between the corrosion rate and the corrosion current ( ) so that the decrease in the corrosion rate both without and with the addition of inhibitors at each concentration indicates that the presence of an inhibitor in Salak (Salacca zalacca) bark extract helps inhibit the corrosion rate.

Fig. 5 Tafel Curve of Salak (Salacca zalacca) Peel Extract (a) Variation of Concentration(b) Variation of Soaking Time

Fig. 5. Tafel Curve of Salak (Salacca zalacca) Peel Extract (a) Variation of Concentration(b) Variation of Soaking Time

The polarization test results mirrored those of the weight loss test, showing the lowest corrosion rate at the concentration rate of 0.025 mm /year at a concentration of 200 ppm . The polarization measurements were consistent with the weight loss test results. The lowest corrosion rate combined with the highest inhibition efficiency was observed at a concentration of 200 ppm and a 20-day immersion period.

Inhibition Mechanism

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Fig. 6 Mechanism Inhibition

Fig. 6. Mechanism Inhibition

Salak (Salacca zalacca) peel extract is used to make corrosion inhibitors because Salak (Salacca zalacca) peel contains secondary metabolites that can stop corrosion growth. Flavonoids and tannins are secondary metabolites that play a role in this study.Flavonoids are plants that belong to the primary antioxidant class. They can end free radical reactionsby donating hydrogen or electrons to free radicals by turning them into a protective layer such as shown in Fig. 6. Flavonoidswith part of the hydrocarbon chain can prevent the metal surface from directly contacting the electrolyte because they are hydrophobic. Based on the results of the FTIR test, where Alkene C = C has hydrophobic properties. In addition, the functional groups of phenol and alcohol hydrogen bonds( O are hydrophilic functional groups. So that one end of the bond chain must be hydrophilic like OH so that this chain becomes a barrier for a corrosive environment for metals to come into direct contact. Then these functional groups undergo an adsorption process onto the metal surface to form aromatic groups so that the hydrophobic functional groups ( and ) will tend to reject water ions that react with the metal. Meanwhile, hydrophilic functional groups will tend to capture unwanted ions so they do not react with metals.

Fig. 7 Macrostructure Observation Results of AISI 1040 Steel (a) AISI 1040 Steel Without Treatment (b) AISI 1040 Steel with a Concentration of 0 ppm for 20 days of Soaking Time in 1 M HCl (c) AISI 1040 Steel with a Concentration of 200 ppm at 20 Days of Soaking Time in HCl 1 M
Tannins have the potential as corrosion inhibitors because of their properties which have complex compounds and polyphenolic compounds with structures that form macromolecules and contain hydroxyl groups (-OH), so they are able to absorb transition metals (Fig. 7). Tannins the complex compoundcan directly become a barrier (barrier) that will coat the metal and protect it from coming into direct contact with the solution. From the morphological results with 1000x magnification on AISI 1040 steel samples with and without inhibitors and without treatment can be seen in the following figure.

Fig. 7. Macrostructure Observation Results of AISI 1040 Steel (a) AISI 1040 Steel Without Treatment (b) AISI 1040 Steel with a Concentration of 0 ppm for 20 days of Soaking Time in 1 M HCl (c) AISI 1040 Steel with a Concentration of 200 ppm at 20 Days of Soaking Time in HCl 1 M Tannins have the potential as corrosion inhibitors because of their properties which have complex compounds and polyphenolic compounds with structures that form macromolecules and contain hydroxyl groups (-OH), so they are able to absorb transition metals (Fig. 7). Tannins the complex compoundcan directly become a barrier (barrier) that will coat the metal and protect it from coming into direct contact with the solution. From the morphological results with 1000x magnification on AISI 1040 steel samples with and without inhibitors and without treatment can be seen in the following figure.

Conclusion

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The results of the corrosion test using the weight loss method obtained the results with the highest inhibition efficiency concentrations of 200 ppm at . In the polarization test, the results with the lowest corrosion rate were obtained at a concentration of 200 ppm of year. The results in the corrosion test using the weight loss method obtained the highest inhibition efficiency with a 20 -day immersion time of . The Polarization test obtained the lowest corrosion rate at 20 days of immersion, which was year . The use of inhibitors of bark extract(Salacca zalacca) can reduce the corrosion rate of AISI 1040 steel in a 1 M HCl environment due to the influence of secondary metabolites, namely flavonoids and tannins, which act as protectors to prevent metals from interacting with electrolyte environments.

Acknowledgments

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Thank you for the facilities from Integrated Laboratory Kalimantan Institute of Technology and Research Center for Mining Technology, National Research and Innovation Agency (BRIN). Thank you for scientific suggestion and recommendation from Prof. Dr.rer.nat Fredy Kurniawan (Sepuluh November Institute of Technology) and Prof. Yusairie Mohd (Universiti Teknologi MARA, Shah Alam).

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"ASTM-G31-72-1999-".

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The original version of this eBook is available on https://www.scientific.net/book/engineering-chemistry-vol-9/978-3-0364-1758-5

Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 11-22

doi: 10.4028/p-0iyjKv

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

Submitted:
2024-11-19

Accepted:
2024-12-02

Online:
2025-03-10

Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

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Muhammad Rifani , Daffa Irsyad D. , Ade Wahyu Yusariarta , Jatmoko Awali , Fredy Kurniawan , Masato Tominaga , Yusairie Mohd , YunitaTriana

Department of Material and Metallurgical Engineering, Institut Teknologi Kalimantan, Balikpapan 76127, Indonesia

Department of Chemistry, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia

Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, 840-8502

Faculty of Applied Science, Universiti Teknologi MARA, Shah Alam, Selangor 40450, Malaysia

student.itk.ac.id, 06191017@student.itk.ac.id, adewahyu27@lecturer.itk.ac.id, jatmoko.awali@lecturer.itk.ac.id, yusairie@uitm.edu.my, nita@lecturer.itk.ac.id

Keywords: AISI, Corrosion, Green, Inhibitor, Salacca zalacca, Seed

Abstract

This study aimed to determine the effect of concentration and immersion time of Salak (Salacca zalacca) Seed extract as a green inhibitor on the corrosion inhibition efficiency and corrosion rate of AISI 1040steel in a 1 M HCl environment. The chemical composition of AISI 1040 steel was confirmed using OES testingto verify its compliance with AISI 1040 chemical standards. The antioxidant activity of the salak (Salacca zalacca) seed extract was determined through the 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) test yielding an IC50 value of 192.55 ppm , indicating weak antioxidant activity. Qualitative phytochemical analysis confirmed the presence of flavonoids and tannins in the extract, as verified by Fourier Transform Infrared (FTIR) testing. The study explored concentration variations ranging from 100 to 500 ppm and immersion time variations of 10 to 30 days were used. The highest inhibition efficiency was obtained at 500 ppm concentration, while the lowest was at 100 ppm , with values of and respectively. Additionally, the corrosion rate was reduced to year at the highest concentration of 500 ppm . These findings demonstrated the potential of salak (Salacca zalacca) seed extract as an eco-friendly, effective corrosion inhibitor for AISI 1040 steel.

Introduction

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Corrosion in a chloride-containing acidic environment is a major issue for steel structures, leading to degradation and material failures [1], [2]. This problem is particularly critical for industries utilizing steel in environments exposed to hydrochloric acid ( HCl )[3]. Traditional methods, such as cathodic protection [4], coating [5], and corrosion inhibitors [6], are widely employed to mitigate corrosion. However, many conventional inhibitors, especially inorganic compounds, are toxic, costly, and harmful to the environment [7-10]. This has spurred interest in the development of green corrosion inhibitors, which are non-toxic, readily available, and eco-friendly.
Nowadays, organic corrosion inhibitors are intensively used as steel corrosion inhibitor in different aggresive media such as acidic environment [11-15]. Chemically, natural organic inhibitors contain , and ring structures of heterocyclic compounds [16]. Green inhibitors can be sourced from plants or seeds, which usually contain tannins, organic acids or amino acids, and alkaloids, all of which are known for their ability to inhibit corrosion [17],[18]. Several studies have been conducted using plant extracts as natural product-based corrosion inhibitors. These plant extracts are usually obtained from various parts of the plant parts such as leaves [19], seeds [20], fruit shell [21], stems [22], root bark [23], fruit [24], and flowers [25].

Salak (Salacca zalacca) is a plant native to Indonesia with a high nutritional content [26]. However, not all parts of this plant are utilized properly [27]. Solid waste from salak (Salacca zalacca) seeds hasnot been processed much and only becomes organic waste. Even though salak (Salacca zalacca) seeds contain flavonoids and tannins. These compounds have been widely studied and can be used as materials to inhibit the process of corrosion [28], [29]. Salak (Salacca zalacca) seed as a corrosion inhibitor has been shown to be effective in inhibiting the release of Ni ions in stainless steel orthodentic wires [30].
In this study, salak (Salacca zalacca) seeds extracted will then be applied to the surface of AISI 1040 steel in 1 M HCl environment. The composition of AISI 1040 steel is confirmed using OES testing toprove the conformity of the composition to the AISI 1040 chemical standard. The test used 1,1- Diphenyl-2-Picrylhydrazyl (DPPH) to determine the antioxidant activity of salak (Salacca zalacca) seed extract. The content of secondary metabolites in the extract will be confirmed by using Fourier Transform Infra Red (FTIR) technique. Various concentrations were used from 100 to 500 ppm and variations in immersion time from 10 to 30 days. These variations were carried out to determine the optimum concentration and the effect of soaking time of salak (Salacca zalacca) seed extract on the corrosion rate. Then the observation of the corrosion rate per year is studied through the weight loss method and polarization measurement. Additionaly, microstructural analysis was conducted using Scanning Electron Microscope(SEM) to examine the surface morphology and assess the extent of corrosion damage.

ExperimentalMaterials

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The metal specimen used in this study was AISI 1040 steel. The size of AISI 1040 steel was used to investigate the corrosion protection efficiency of the extract in 1 M HCl is a rectangular steel piece measuring . The chemical composition testing using Optical Emission Spectroscopy (OES) was conducted to verify the compatibility of the sample composition with the AISI 1040 chemical standard.

Inhibitors

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The salak (Salacca zalacca) seeds, collected from the KM. 21 Karang Joang, North Balikpapan, Balikpapan City, were first cleaned to remove any dirt and then sun-dried for 7 days. After that, the seeds were ground into a fine powder before being soaked in 2000 mL of ethanol for three consecutive days ( hours). Then, the ethanol extract was separated from the solid residue through filtration and then evaporated at for five hours to obtain the concentrated extract. The resulting solid extract was weighed and homogenized with 1 M HCl to prepare inhibitor solutions of 100, 200, 300, and 500 ppm .

Antioxidant Activity Analysis

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The DPPH (2,2-diphenyl-1-picrylhydrazyl) test was chosen for its simplicity and accuracy in measuring free radical scavenging activity, which is a key indicator of antioxidant potential. This method is widely recognized for providing reliable quantitative data on the antioxidant activity of natural extracts, making it an ideal choice over other methods like ABTS or FRAP in this study. The results were expressed as the IC50 value, representing the concentration required to inhibit of free radicals, with an IC50 value of 192.55 ppm indicating weak antioxidant activity. Phytochemical testing was carried out to identify the secondary metabolites found in the extract of salak (Salacca zalacca) seeds. The ingredients tested are flavonoids, tannin, alkaloid, and saponin. On the other hand, 2,2-diphenyl-1-picrylhydrazyl (DPPH) is a testing method to determine the antioxidant activity in salak (Salacca zalacca) seed extract.

Characterization

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Characterization testing was carried out to determine the content of functional groups contained in salak (Salacca zalacca) seeds extract using Fourier Transform Infra-Red (FTIR). FTIR testing was conducted at the Material Characterization Laboratory, Integrated Laboratory of Kalimantan

Institute of Technology. The FTIR test was performed using an FTIR spectrophotometer (Shimadzu) with the KBr pellet method. SEM-EDX test was also conducted to see the damage on the surface of the specimen. The macrostructural changes of the AISI 1040 steel surface after the weight loss corrosion test were compared with and without the addition of an inhibitor, considering various variations of immersiontime and concentration.

Weight Loss Method

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This test was conducted to determine the weight loss in the sample when immersed in a corrosive medium , as shown in Figure 1. Various inhibitor concentrations ( ppm , and 500 ppm ) and immersion times ( 10 days, 20 days, and 30 days) were selected based on existing literature and preliminary studies, which indicate that these concentration ranges are optimal for observing the inhibition efficiency of plant-based extracts in acidic environments [31,32]. The concentration range was designed to capture both low and high inhibitor efficiencies, while the immersion times allowed for the assessment of both short-term and long-term performance of the extract [33]. Corrosion testing with the weight loss method was repeated three times to ensure the accuracy and reproducibility of the results.

Fig. 1. Illustration of Weight Loss Method

Fig. 1. Illustration of Weight Loss Method

Electrochemical Experimental

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To determine the corrosion rate per year on the specimen used with open circuit potential (OCP) test. OCP testing was carried out using a potentiostat/galvanostat (Figure 2) and tafel curve analysis using the software Origin 2020. In the potentiodynamic polarization method, there are three electrodes, namely the reference electrode, platinum auxiliary electrode, and AISI 1040 steel working electrode. Corrosion rate calculation from Icorr in the polarization curve is calculated by:

Fig. 2. Electrochemical cell circuit

Fig. 2. Electrochemical cell circuit

Result and Discussion

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Analysis of Organic Inhibitor Compounds of Salak (Salacca zalacca) Seed Extract Determination of Antioxidant Properties of Salak (Salacca zalacca) Seed Extract

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The results of the linear regression equation from the plot of the percentage of antioxidant activity of salak (Salacca zalacca) seed extract is with . After the value of 50is substituted for the y value, x will be obtained as the IC50 value. The IC50 value obtained was af 192.55 ppm (Table 1). From the IC50 value, the salak (Salacca zalacca) extract exhibited weak antioxidant activity (IC50 ) because the IC50 value is in the range of 150 ppm 200 ppm . The weak antioxidant activity indicates that the extract's ability to neutralize free radicals is limited, suggesting that its corrosion inhibition performance primarily
relies on the adsorption of compounds like flavonoids and tannins onto the metal surface, rather than oxidative protection. Despite weak antioxidant capacity, these compounds can still form a protective barrier, reducing metal exposure to corrosive agents. This mechanism has been similarly observed in other plant-based inhibitors, where surface adsorption plays a more significant role than antioxidant effects in corrosion inhibition [20, 34].

Table 1. Results of Measurement of Antioxidant Activity of Salak (Salacca zalacca) Seed Extract using the DPPH Method

Compound | Reactor | Results
Flavonoid | NaOH 1% + HCl 1% | +
Tannin | (CH₃COO)₂ Pb 1% | +
Alkaloid | HCl + Dragendorff | -
Saponin | Aquades + HCl | -

These results differ from previous research conducted by [29] which showed that the ethanol extract of salak (Salacca zalacca) seeds has an antioxidant activity of 229.27 ppm . Then in the research conducted by [41], it was shown that the ethanol extract of salak (Salacca zalacca) seeds has an antioxidant activity of 293.8 ppm . The difference in the value of the antioxidant activity obtained can be influenced by various reasons including the type of solvent, differences in drying methods andvarieties so that it has a real effect on the content of the extract and antioxidant activity [37], [38].

Qualitative Analysis of Secondary Metabolites of Salak (Salacca zalacca) Seed Extract

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Condensed extract of Salak (Salacca zalacca) seeds was tested for the content of secondary metabolites using a color reaction. The results indicated that the salak (Salacca zalacca) seed extract contains flavonoids and tannins. As seen on Table 2, for alkaloids and saponins, the results were negative, meaning that these compounds were not detected. The absence of alkaloids and saponins may reduce the overall inhibition efficiency, as alkaloids are known for their ability to donate electrons, enhancing adsorption onto metal surfaces, while saponins can form protective films. However, the presence of flavonoids and tannins, both rich in functional groups like hydroxyl and carbonyl, remains sufficient to provide effective corrosion inhibition through strong adsorption and the formation of a barrier layer on the steel surface [34, 35].

Table 2. Results of Phytochemical Tests on Salak (Salacca zalacca) Seed Extract

Compound | Reactor | Results
Flavonoid | NaOH 1% + HCl 1% | +
Tannin | (CH₃COO)₂ Pb 1% | +
Alkaloid | HCl + Dragendorff | -
Saponin | Aquades + HCl | -

(+) = Detected
Not Detected

Functional Group Analysis of Salak (Salacca zalacca) Seed Extract

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The IR spectrum of the isolated compound shows information that there is an absorption peak of the hydroxyl group at wave number . The hydroxyl group is stretched -OH bonded (can be hydrogen bonded), and the bonded OH is visible by forming a widening band and a strong intensity. This hydroxyl group is strengthened by -C-O- stretching at wave . The absorption band at wave number shows the presence of aliphatic stretching and is reinforced by the appearance of absorption at wave number indicating the presence of stretching. The absorption band at wave number showed the presence of alkene groups and was strengthened by the appearance of alkene groups at wave numbers and 923.15 . In the frequency area Two amine/amide groups were found each at wave number and . Then in the frequency area of
aromatic ring group was obtained at wave numbers and with great intensity. The presence of electronegative atoms such as N and O as well as double bonds in alkene groups gives the extract potential as a corrosion inhibitor [39]. These findings are consistent with studies of other plant-based corrosion inhibitors, where tannins and flavonoids, with their hydroxyl and carbonyl groups, play a crucial role in adsorption onto metal surfaces [9, 20]. The presence of electronegative atoms ( N and O ) and double bonds in alkene groups strengthens the potential of the extract as an effective corrosion inhibitor, similar to findings in other plant-derived inhibitors [10, 35]. Based on the results of the FTIR test, it is indicated that the compounds contained are tannins and flavonoids as seen on Table 3.

Organic Molecular Structure Annotation
Compound

Table 3. Organic Compounds in Salak (Salacca zalacca) Seed Extract

Flavonoid

Flavonoids possess various functional groups, including double bond , double bond , single bond , single bond , and single bond . Based on the results of FTIR analysis, it indicates the presence of flavonoid compounds

Tannin

Tannins have phenolic (-OH) groups and exhibit colloidal properties. Other functional groups present include aliphatic and aromatic double bond . Based on the results of FTIR analysis, it is indicated that the compoundpresent is tannin.

Performance Analysis of Corrosion InhibitorsDetermination of Inhibition Efficiency

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Fig. 3. Effect of (a) Concentration and (b) Immersion Time on Inhibition Efficiency

Fig. 3. Effect of (a) Concentration and (b) Immersion Time on Inhibition Efficiency

Based on Figure 3a, it is shown that the lowest inhibition efficiency in specimens soaked for 20 days with various concentrations was at a concentration of 100 ppm with an efficiency value of . While the highest inhibition efficiency was obtained at a concentration of 500 ppm with an inhibition efficiency value of . Moreover, based on Figure 3b of variations in immersion time, it is shown that the lowest inhibition efficiency was found in specimens soaked with a concentration of 500 ppm in various immersion times at 30 days with an efficiency value of . Meanwhile, the highest inhibition efficiency was obtained for ten days of immersion with an inhibition efficiency
value of . These results indicate that the inhibition efficiency of Salak (Salacca zalacca) seed extract decreases over time, suggesting potential limitations in its long-term performance. Variability in efficiency may be influenced by factors such as concentration, immersion time, and the gradual degradation of the protective layer formed by the extract.

Determination of Corrosion Rate

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Measurement was conducted using the potentiodynamic polarization method. This method involves a series of 3 electrodes, with AISI 1040 steel as the working electrode, as the reference electrode, and platinum as the auxiliary electrode. Measurements were performed with a scan rate of and a potential of -100 mV to 100 mV . The testing was performed based on variations in concentration and immersion time. Inhibitors can be classified as anodic inhibitors or cathodic inhibitors if the shift in corrosion potential (Ecorr) is greater than 85 mV from blank to the anodic or cathodic direction [6]. In the Tafel curve shown in Figure 4a, it can be seen that there is a shift in thecorrosion potential of 114 mV towards the anodic so it can be said that the extract is classified as ananodic inhibitor. Anodic inhibitors have a mechanism to reduce the corrosion rate by forming or facilitating the formation of a film layer which will inhibit the reaction of dissolving the anode metal. The test data also show indications of adsorption on the steel surface and control of the anodic dissolution process.

Fig. 4. Tafel Curve with Variation (a) Concentration and (b) Immersion Time ofSalak (Salacca zalacca) Seed Inhibitor

Fig. 4. Tafel Curve with Variation (a) Concentration and (b) Immersion Time ofSalak (Salacca zalacca) Seed Inhibitor

The steel added with the inhibitor of salak (Salacca zalacca) seed extract decreased the corrosion rate to year at an inhibitor concentration of 500 ppm . The corrosion rate on the specimen decreased with the addition of inhibitor extract concentration. In addition, it can be seen that the value of the corrosion current (Icorr) is directly proportional to the corrosion rate. The higher the corrosion current, the higher the value of the corrosion rate in the material. And then, the steel with the addition of 500 ppm inhibitor which is immersed in various variations of immersion time experiences an increase in the corrosion rate. The longer the steel is immersed in corrosive media, the higher the measured corrosion rate will be. The lowest corrosion rate value was obtained at ten days of immersion time while the highest corrosion rate value was obtained at 30 days of immersion (Figure4b).

Inhibition Mechanism

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The organic inhibitor from salak (Salacca zalacca) seeds has the ability to inhibit the corrosion rate due to the presence of secondary metabolite compounds such as flavonoids and tannins. These compounds have their own mechanisms in protecting metals from corrosion. Flavonoids, according to [40], have free electron pairs and double bonds in their molecular structure, which serve as a medium for the inhibitor to react with iron metal. Flavonoids are also known as antioxidant
compounds because they can capture free radicals by releasing hydrogen atoms from their hydroxyl groups. On the other hand, tannins will form complex compounds with iron ions, forming ferric tannate on the metal surface.

Fig. 5. Mechanism of Formation of Tannin Complexes with [36]

Fig. 5. Mechanism of Formation of Tannin Complexes with [36]

Tannin compounds can form complex compounds with iron (II) and iron (III). The iron (II) - tannin complex compound is colorless and has properties that are easily soluble and oxidized. In the presence of oxygen, this complex compound transforms into iron (III) - tannin complex known as tannate. The Fe-tannate complex compound acts as a barrier and coats the metal, preventing direct contact between the solution and the iron metal [42].
The two compounds will form a thin barrier layer on the metal surface as illustrated in Figure 6. In many studies (including acidic media), the adsorption of inhibitor molecules tends to be initiated using a physical adsorption mechanism and then propagated using a chemical adsorption mechanism which is called the physiochemical mechanism of adsorption [43].

Fig. 6. Illustration of Inhibition Mechanism

Fig. 6. Illustration of Inhibition Mechanism

The indications of the formed layer on the metal surface can be observed based on the results of the Scanning Electron Microscopy (SEM) test shown below.

Fig. 7. The Morphology Observation Results of AISI 1040 Steel Surface: (a) Untreated Specimen, (b) Specimen with 0 ppm Inhibitor and 20 Days of Immersion, (c) Specimen with 500 ppmInhibitor and 20 Days of Immersion, (d) Specimen with 500 ppm Inhibitor and 10 Days of Immersion

Fig. 7. The Morphology Observation Results of AISI 1040 Steel Surface: (a) Untreated Specimen, (b) Specimen with 0 ppm Inhibitor and 20 Days of Immersion, (c) Specimen with 500 ppmInhibitor and 20 Days of Immersion, (d) Specimen with 500 ppm Inhibitor and 10 Days of Immersion

Fig. 7 illustrates the comparison of surface morphology between specimens with and without the addition of an inhibitor. The observation results indicate that the specimen immersed without the addition of an inhibitor (Figure 7b) exhibits a rougher and more damaged surface due to metal erosion caused by oxidation reactions during immersion. It can be observed that the specimen is indicated to undergo uniform corrosion and pitting corrosion on its surface. By adding an inhibitor (Fig. 7c-d), the metal dissolution process can be minimized through the formation of a passive layer that acts as a barrier in preventing the metal from acting as an anode in a corrosive environment.

Conclusion

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The optimal inhibitor concentration was 500 ppm , achieving an efficiency of and a corrosion rate of year . The highest inhibition efficiency was observed after 10 days of immersion, but the efficiency declined over time, indicating potential limitations in long-term performance. These findings suggest that salak (Salacca zalacca) seed extract is a viable, ecofriendly corrosion inhibitor for short-term applications, but its long-term stability requires further improvement. Future research should explore the synergistic effects of combining salak (Salacca zalacca) seed extract with other natural inhibitors to enhance durability and performance over extended periods. Additionally, studies on the extract's behavior in other corrosive environments and on different metal types would provide a more comprehensive understanding of its potential industrial applications.

Acknowledgements

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Thank you for the facilities from Integrated Laboratory Institut Teknologi Kalimantan and Research Center for Mining Technology, National Research and Innovation Agency (BRIN). Thank you for scientific suggestion and recommendation from Prof. Dr.rer.nat Fredy Kurniawan (Sepuluh Nopember Institute of Technology) and Prof. Yusairie Mohd (Universiti Teknologi MARA, Shah Alam).

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Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 23-32

doi: 10.4028/p-WWOjR2

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

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2025-03-10

Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

The original version of this paper is available on https://www.scientific.net/EC.9.23.pdf

Irsyad Al Habib , Andi Idhil Ismail , Dewi Umanigrum , Agung Purniawan , Murni Handayani , Genki Ogata , Yasuaki Einaga , Yunita Triana

Department of Materials and Metallurgical Engineering, Institut Teknologi Kalimantan, Balikpapan 76127, Indonesia

Department of Mechanical Engineering, Institut Teknologi Kalimantan, Balikpapan 76127, Indonesia

Department of Chemistry, Universitas Lambung Mangkurat, Banjarmasin, 70123

Department of Materials and Metallurgical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia

Research Centre for Advanced Materials, National Research and Innovation Agency (BRIN), Tangerang Selatan, 15314, Banten

Department of Chemistry and Chemistry, Keio University, Yokohama 2238533, Japan

06191028@student.itk.ac.id, a.idhil@lecturer.itk.ac.id., dumaningrum@ulm.ac.id, nita@lecturer.itk.ac.id*

Keywords: Boron-Doped Diamond, Cyclic Voltammetry, Quinine, Reduction.

Abstract

This study investigates the electrochemical reduction of quinine (QN) detection using boron-doped diamond electrodes (BDD). Different pulse voltammetry (DPV) of QN in a 0.1 M PB solution exhibits reduction peaks at . Additionally, the effects of pH and scan rate were explored to investigate the reduction mechanism within a potential range of -1.4 V to -0.4 V (vs. ). Furthermore, a linear calibration curve was observed in the concentration range of to with a detection limit of .

Introduction

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Quinine ( QN ) is an alkaloid plant with effective medicinal use as an adjunctive therapy for immunodeficiency syndrome and neurodermatitis and has antipyretic, anti-inflammatory, analgesic, muscle relaxant and antimalarial properties. In excess, QN can cause gastrointestinal problems, cinchonism, visual disturbances, damage central nervous system, and cardiac dysrhythmias [1-3]. To prevent overdose, the level of QN in the body must be maintained. The therapeutic plasma concentration range of QN is , and blood concentrations greater than . Between 1965 and 2006, FDA documented 665 cases of serious adverse reactions associated with the use of QN, including 93 fatalities. [6].
Due to its side effects and potential toxicity, several analytical methods have been reported to determine QN detection use in biological, pharmaceutical, and food samples. Methods include highperformance liquid chromatography [6,7], mass [8], chemiluminescence [9,10], gas chromatography mass spectrometry [11,12], and capillary electrophoresis [13]. However, these methods are costly, time-intensive, and utilize hazardous reagents. Moreover, some recent reports have indicated electrochemical methods for determining QN; which have proved to be more beneficial in terms of simplicity, rapid response, high sensitivity, low detection limits, the absence of expensive and complex devices, and the ease of integration with other systems, for example. The choice of working electrode materials for electrochemical sensors is crucial as it affects the cost, sensitivity, selectivity, and stability of these devices [14-16].

Based on the advantages of electrochemical analytical techniques described above, previous research has been conducted using pretreated graphite pencils [8], bentonite modified electrodes [17], and modified glassy carbon electrodes [2] [18]. It is proven that QN detection determination achieves good accuracy and precision compared with other detection methods[14], [19-21]. However, the use of modified working electrodes will increase cost and time in the modification process. Recently, the QN detection was carried out using Boron Doped Diamond (BDD) electrodes with Britton-Robinson buffer (BRB) as the supporting electrolyte and this electrode offers simple preparation and good sensitivity. Thus, BDD is one of the working electrodes widely used today for detection in electrochemical methods.
BDD is an effective working electrode used in electrochemical sensors and is suitable for use in dilute and solid electrolytes [22]. BDD offers several advantages in electrochemical sensing applications, such as a broad potential window, low background current, excellent chemical and mechanical stability, and strong resistance to impurities [23,24]. The use of BDD in electrochemical sensors includes as a method of detecting pollutants in water [25],[26], as a gas detection method [22,27], as a drug detection method [21] and for medical purposes. Therefore, based on the advantages of the present study, research will be carried out by replacing the working electrode using a BDD with boron content.
In this study, QN detection was performed using BDD and phosphate buffer solution (PB) as support electrolytes. The pH of the electrolyte and the scan rate of the CV technique were systematically varied to explore the electrochemical behavior of QN. Then, the performance of the BDD is investigated by calculating the detection limit (LOD) on the basis of changes in the concentration of the analyte.

Experimental

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Preparation of BDD Electrodes

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The BDD is deposited on a thin BDD polycrystalline layer on a wafer substrate through the microwave plasma-assisted chemical vapor deposition (MP-CVD) method for the MP-CVD method. Boron base material is trimethyl borate and carbon base material is acetone. Boron-carbon ratio was with deposition carried out for 7 h at 5 kW [24,28].

Preparation of Reagents

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Reagents solution was derived from 10 mM QN dissolved in DMSO stock solution. First, the PB was prepared by mixing and in distilled water with 0.1 M concentration. Afterward, the stocks solution was diluted in PB 0.1 M at pH 7.4 .

Electrochemical Measurement

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The electrochemical cell was configured using a three-electrode system consisting of electrode as the reference, BDD electrode as the counter, and another BDD electrode as the working electrode, with 0.025 mM QN in 0.1 M PB serving as the electrolyte. Initially, the electrochemical circuit is connected to the PGSTAT204, and the potential window is set at potential -1.4 V to -0.4 V (vs. ). The BDD working electrode previously was washed in aqua regia solution containing a 3:1 combination of HCl and HNO 3 for 30 min . BDD soaking procedure cleans the surface of the BDD of metallic species contamination while improving its electrochemical performance [29], [30]. BDD electrode was thoroughly rinsed with distilled water for 15 min and subsequently dried using nitrogen gas. Then, BDD was chronoamperometry in solution with a potential of for 5 min to produce oxygen-terminated boron-doped diamond and for 10 min to form hydrogen-terminated boron-doped diamond (HBDD) [31]. Data were then collected through Autolab/PGSTAT101 using cyclic voltammetry and differential pulse voltammetry.

Results and Discussion

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Effect of Surface Termination on Electrochemical Properties

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Surface termination type plays a crucial role in influencing the electrical and electrochemical properties of the BDD surface. Furthermore, the surface termination of BDD can affect significantly its electrochemical properties. [32,33]. The results show that the reduction peak current value at both terminations is different, where the reduction peak current at H-BDD (blue) is higher than in O-BDD (red) (see Fig. 3). This is influenced by the surface conductivity of H-BDD and increased sensitivity, while O-BDD shows lower electrochemical activity [28,34,35]. Based on these results, the surface termination of is used in this study for the detection of QN.

Fig. 1. Electrochemical Measurement Setup Scheme

Fig. 1. Electrochemical Measurement Setup Scheme

Fig. 2. Voltammogram of QN in 0.1 M PB

Fig. 2. Voltammogram of QN in 0.1 M PB

Electrochemical Reduction of QN

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CVs were recorded at , in the potential range -0.4 V to -1.5 V (vs. ). Based on the observation of QN electrochemical reduction by CV technique from -0.4 V to -1.5 V (vs ) there is a peak current in the voltammogram in the range of . This indicates a reduction reaction that occurs during the measurement by the CV method without any oxidation reaction seen throughout the potential range (Fig. 4A). It was also observed using the DPV method from the range of -1.00 V to , where it can be confirmed that there is a peak reduction current in the potential of vs. . The reaction on the electrode surface can be analyzed from the relationship between current and potential on the electrode, where the DPV potential has shifted compared to CV (see Fig. 4B). This shift is due to the difference in concentration of QN, scan rate, and pH electrolyte [36].

Fig. 3 Voltammogram QN (A) CV QN at pH 7 in 0.1 M PB
(B) DPV QN at pH 7 in 0.1 M PB

Fig. 3. Voltammogram QN (A) CV QN at pH 7 in 0.1 M PB (B) DPV QN at pH 7 in 0.1 M PB

To study the reduction mechanism, CVs were conducted at various scan rates. The scan rate range of 40 to was employed within the potential window of 0.4 V to using a QN concentration of 25 M (Fig. 4). The higher the scan rate, the higher the peak current appearing. This is due to the fact that as the scan rate increases, the thickness of the diffusion layer decreases and the concentration of electroactive substances on the electrode surface changes faster, which can result in an increase in current and a shift in peak potential. Thus, the maximum potential may shift to a more positive or negative value, depending on the electrochemical reaction and experimental conditions [37], [38]. This also indicates that the QN reaction occurs irreversibly on the surface of the BDD [18]. This phenomenon can also be described by the Randles-Sevcik equation [39]. The number of electrons involved can be calculated using the Randles-Sevcik equation for irreversible processes (1). The diffusion coefficient (D) is the slope value of the calibration curve of Fig. 5. D value of reduction reaction derived by slope. The diffusion coefficient obtained from the results of the calculation findings was . At the same time, the predicted value for the number of electrons involved ( n ) was about 2 electrons for the reduction.

Where Ip is the maximum current (A), n is the number of electrons, is the charge transfer coefficient, is the number of electrons involved in the charge transfer step, (D) is the diffusion coefficient or the slope value at reduction reaction, A is the electrode surface area of the electrode , v is the scan rate ( ), and C is the concentration in solution ( ).

Fig. 4. Cyclic Voltammogram of QN with Variation of Scanning Rate at pH 7 in 0.1 M PB

Fig. 4. Cyclic Voltammogram of QN with Variation of Scanning Rate at pH 7 in 0.1 M PB

Fig. 5 Linear Curve of Current as a Function of Square Root of Scan Rate

Fig. 5. Linear Curve of Current as a Function of Square Root of Scan Rate

Based on the voltammogram using the scan rate dependence, the plot of the relationship between the maximum current and the square root of the scan rate (Fig. 6) obtained results that are more linear than the maximum current with the scan rate with a slope of . It indicates that the reaction process on BDD is influenced by diffusion controlled [17], [19], [40]. Moreover, the number of electrons involved (n) in the reduction process is approximately 2 electrons [3]. The scheme of the reduction reaction is shown in Fig. 8.
Then, different pulse voltammetry (DPV) methods were used to determine the effect of the pH of the solution on the reaction mechanism and peak currents during the test. This study was carried out using pH dependence of three conditions including pH 5 (acid), 7 (neutral) and 9 (alkaline). Based on DPV voltammogram, it was obtained that the reduction peak shifted along the pH changing (see Fig. 7). The potential reduction peak is at pH 9 and the potential reduction peak is 0.81 V (vs. ) at pH 5 . This result can be explained by the Nernst equation, where the lower the pH (the higher the concentration of ions), the more positive the potential value [41].

Fig. 6. Different Pulse Voltamogram of Potential Shift on pH Variation

Fig. 6. Different Pulse Voltamogram of Potential Shift on pH Variation

Fig. 7 Schematic of QN reduction reaction [40]

Fig. 7. Schematic of QN reduction reaction [40]

Limit of Detection (LOD) Determination

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Determination of the detection limit using a variation of the QN concentration value in PB solution using DPV technique in the potential range of -1.00 V to -0.70 V (vs. ). Based on Fig. 9A, the higher concentration shows the higher current density. The curves have good linearity ( ) in the concentration range of as shown in Fig. 9B. By calculating using the equation of LOD (2) below:

The LOD calculation results obtained a detection limit value of . Therefore, the BDD detection method is used to detect QN, whose maximum concentration in the human blood is .

Fig. 8. (A) Different Pulse Voltammogram on Concentration Variation (B) Linear regression curve plot of peak current against concentration variation

Fig. 8. (A) Different Pulse Voltammogram on Concentration Variation (B) Linear regression curve plot of peak current against concentration variation

Furthermore, the stability of the BDD was investigated by measuring the peak current 10 times. As shown in Fig. 10, constant currents were obtained on BDD with a 0.000269 deviation standard and an average of . The graph indicates that consistent measurement values are acquired.

Fig. 9. Peak current of QN QN on BDD electrodes versus number of measurements

Fig. 9. Peak current of QN QN on BDD electrodes versus number of measurements

Conclusion

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This work reports the electrochemical behavior of QN detection using BDD. The BDD has been studied for detection of low QN concentrations. The advantages of the BDD electrode are as follows: (1) the detection target of the reduction reaction on the BDD is observed, (2) the reaction mechanism shows that the number of electrons involved in the reduction process ( n ) is approximately two electrons, and (3) the detection limit is low, and can't be achieved with other electrodes. These results suggest that BDD is potentially can be used as QN sensor.

Acknowledgements

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The research funding program is from the World Class Professor (WCP) 2022, Internal Research Funding ITK (PPP IKN) and supported by Prof. Dr. Yasuaki Einaga, Keio University Japan.

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Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 33-51

doi: 10.4028/p-Sv736e

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

Submitted:
2024-09-27

Revised:
2024-12-03

Accepted:
2024-12-11

Online:
2025-03-10

Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

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Akeem Adesina Bamigbade , Enock Olugbenga Dare , Biodun S. Badmus and Janet Titilayo Bamgbose

¹Chemistry Department, Federal University of Agriculture Abeokuta

Physics Department, Federal University of Agriculture Abeokuta

dbamgbosejt@funaab.edu.ng

Keywords: Silver nanoparticle; Sodium tripolyphosphate; Glucose; Characterization; Electrochemical, Sensor

Abstract

The development of non-enzymatic glucose biosensor has been the concern of many researchers mainly because enzymes based sensor despite having excellent sensitivity and selectivity, has the limitations such as poor stability, complicated enzyme immobilization, critical operating conditions such as optimum temperature and reproducibility. This study developed a cheap biocompatible non-enzymatic glucose biosensor based on silver nanoparticle (AgNPs) stabilized with sodium tripolyphosphate (NaTPP) cross-linked chitosan. Direct electron transfer and electro-catalytic activity of the AgNPs modified glassy carbon electrode (AgNPGCE) was investigated using potentiometric and amperometric techniques. AgNPs was prepared and characterized by Fourier transform Infra-red spectroscopy (FTIR), X-ray diffractometry (XRD) and Scanning electron microscopy (SEM). The crystalline size of the AgNPs was revealed with XRD. However, the SEM micrograph of AgNPs revealed the spherical shape with a non-uniform granular shape attributed to bio-mediated ionic gelation process. The FTIR spectra of AgNPs shown peaks at suggesting the presence of phosphonate linkages between ammonium, of chitosan and moieties of NaTPP during cross linking process. Electro-catalytic oxidation of glucose at the AgNPGCE surface and the mechanism involved in glucose oxidation was revealed via cyclic voltammetry. The AgNPGCE showed a better electrochemical response towards glucose. This glucose sensor showed high sensitivity at +0.54 V . A low detection limit of (the confident level ), and wide linear range of 2 to with a correlation coefficient of 0.9987 were obtained. The calculated parameters revealed that AgNPGCE had shown better overall electrochemical performance and response than enzymatic biosensor.

Introduction

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Diabetes mellitus is a protracted disease that occurs when the pancreas fails to produce enough insulin to regulate blood sugar or when the body is incapable to use the insulin produced efficiently. Failure to treat diabetes effectively, will largely result into a number of other health complications, such as eye problems (blindness), neuropathy, foot complications, kidney disease, heart diseases, hypertension, stroke, hyperglycemic nonketonic syndrome, gastroparesis, heart disease, and mental health disorders; death and disability in the entire globe, it may also affect pregnancy [1,2]. Glucose ( ) is an essential energy-providing substance in life, but excessive glucose concentration in the body can result into many severe and even life-threatening diseases, such as diabetes [3]. Particularly, accurate glucose measurement for diabetics is an effective tool in the detection and treatment of diabetes mellitus [4].
For diabetic patients, a normal blood glucose level in human serum before a meal is around and after 2 hours of mealtime [5]. Regular testing of physiological blood glucose levels is necessary to avoid diabetic emergencies and is crucial for
the confirmation of effective treatment [6]. For effective therapy and to prevent any hyperglycemia or hypoglycemia, regular monitoring of physiological blood glucose levels is crucial.
Therefore, researchers have been looking for fast, accurate and steady methods to determine glucose levels in vivo and in vitro [7]. Glucose sensors with high sensitivity, high stability and high accuracy produced by optical [8], electrochemical [9] and other techniques are of great importance in blood glucose monitoring of diabetic patients. The detection of blood glucose is of great significance in the food process application, clinical medicine, and biology [10, 11]. Therefore, the production of high sensitive, low-cost, reliable glucose sensors having an outstanding selectivity has been the subject of interest for decades, not only in medical science but also in the food industries [12]. Glucose oxidase (GOx)-based glucose biosensors have prevalently dominated the glucose sensor research and development over the last four decades and the market place as well. This is due to the increasing demand of sensitive and reliable blood glucose monitoring in biological and clinical aspects [13-15]. Enzymes based sensor displays excellent sensitivity and selectivity.
The main restrictions to these sensors are poor stability and reproducibility, which can impede the sensor properties. Apart from deactivation of the enzyme some other disadvantages of enzymebased glucose determination includes complicated enzyme immobilization, critical operating conditions such as optimum temperature and pH , chemical instability, and high cost [4, 16].
Electrochemical sensing techniques are versatile and powerful tools in providing real time and onsite measurement in a variety of areas, including clinical diagnostic, environmental, agricultural, and food monitoring [17-19]. The electrochemical sensing offers advantages in providing high sensitivity, selectivity, accuracy, and cost effectiveness.
Therefore, non-enzymatic glucose sensors developed mainly based on creation of electrode surface by direct oxidation of glucose without the help of enzyme, which had sustainable advantages in terms of simplicity, manufacturability, portability, selectivity, stability, sensitivity and their low cost [20-22]. Non-enzymatic glucose biosensors can escape that problem because of direct catalytic oxidation of glucose on the surface of electrode [20,21].
In order to increase specific surface areas and improve mass transport ability, these electrodes could use nanomaterials as substrates like carbon nanotubes (CNTs) [22], nanowires [23, 24], meso porous structure [25], etc., and modified with mental nanoparticles such as Pt [26], Ni [27], Ag [28], and Cu [29]. In the present research, we want to investigate the synthesis of silver nanoparticles by an environmental friendly procedure involving the in situ reduction of silver ( Ag ) and to investigate the electrocatalytic activity of silver nanoparticle stabilized by chitosan on oxidation of glucose in order to explore the possibility of developing biosensor that will respond to glucose measurement in any system.

Experimental Procedure

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Apparatus

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Electrochemical measurements were carried out with a potentiostat/ galvanostat with a single compartment Voltammetric cell coupled to a computer, equipped three electrodes: glassy carbon electrode as working electrode with dimension of 5.0 mm diameter and 8.0 mm length, an electrical contact provided by a copper wire, an (with 3 M KCl ) reference electrode of 4.0 mm diameter, a copper wire contact, and a platinum wire acting as the counter electrode (diameter of 0.5 mm ). An ultrasonic bath, magnetic stirrer and a Thermostarted bath were also used.

Reagents

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Chitosan produced from lobster shell wastes with degree of deacetylation was purchased from Aldrich and used as supplied. Hydrochloric acid, glacial acetic acid and Sodium hydroxide, were supplied by Aldrich. Sodium borohydride , sodium tripolyphosphate (NaTPP), Silver nitrate glucose, acetone and Ethanol were obtained from Sigma Chemical and Co and used as received.

All solutions were prepared with double distilled water, and all chemicals were used without further purification. All the experiments were carried out at ambient temperature of .

Preparation and characterization of silver-chitosan Nanoparticle (AgNPs)

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A silver-chitosan nanoparticle (AgNPs) was prepared according to a modified literature procedure [30-32].
60 mg chitosan was dissolved in 20 mL of acetic acid to obtain chitosan solution. of NaTPP solution was added to chitosan solution in the ratio of to chitosan, with mild stirring until an opalescent suspension was obtained. 10 mL of of silver nitrate solution was added to the chitosan-NaTPP hydrogel and stirred continuously for 30 minutes to obtain homogeneous solution.
Final stage of the synthesis was the addition of 10 mL of 0.01 M sodium borohydride (reducing agent). Chitosan- NaTPP gelatine is a colourless solution, but once the reducing agent was introduce to the polymer suspensions, there was immediate colour change to dark brown, indicating the formation of silver nanoparticle [30, 32]. The chitosan-silver nanoparticle was separated from the liquid by centrifugation for one hour at . The supernatant was discarded and the particles were washed thoroughly with acetone, ethanol, distilled water and then vacuum filtered. The obtained particles were oven-dried at .
The silver nanoparticle prepared was characterized using Fourier-transformed Infra-red spectroscopy (FTIR), X-ray diffractometer (XRD), Ultraviolet-visible spectrophotometer, and Scanning electron microscope (SEM).

Note: The positive charges on the amino groups of chitosan resulting from its dissolution in acetic acid interact with the negative charges on the tripolyphosphate anions, causing ionic-gelation and formation of hydrogel.

Figure 1. Note: The positive charges on the amino groups of chitosan resulting from its dissolution in acetic acid interact with the negative charges on the tripolyphosphate anions, causing ionic-gelation and formation of hydrogel.

Fig. 1. Schematic representation of reaction path for the preparation of the Chitosan-silver nanoparticle

Electrode preparation

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The surface of the Glass Carbon Electrode (GCE) was polished with the alumina suspension using a polishing cloth to a mirror finish. The electrode surface was then cleaned in an ultrasonic bath for 15 minutes and washed with ethanol and deionized water to remove adsorbed particles [33, 34]. This procedure was repeated after each voltammetric experiment. Other materials, including glassware, containers, pipette tips and the electrochemical vessels, were washed and sterilized with heat prior to use.

Preparation of silver nanoparticle (AgNPs) modified glassy carbon electrode (GCE)

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The electrode surface was uniformly coated with of silver nanoparticle solution in acetic acid and air-dried, after which it was immersed in of 0.1 M NaOH (to stabilize the silver nanoparticle) and again air-dried.

The electrochemical characteristics of silver nanoparticle-supported glassy carbon electrode

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The electrochemical performance of the silver nanoparticle modified glass carbon electrode (AgNPGCE) and bare glass carbon electrode (GCE) as control was investigated in 2 mM glucose and 5 ml of 0.1 M sodium hydroxide as supporting electrolyte at scan through cyclic voltammetry (CVs) procedure. The electro-catalytic activity of AgNPs-modified glassy carbon electrode was investigated through cyclic voltammetry using 10 mM glucose in 5 ml of 0.1 M sodium hydroxide solution, at different scan rate of and , with a potential window of 0.0 V and 1.0 V at .

Electro-catalytic characterization and charge transfer kinetics of AgNPs-glassy carbon electrode

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Cyclic voltammetry assay of AgNPs-glassy carbon electrode was performed in air-saturated 5 ml of 0.1 M sodium hydroxide (supporting electrolyte) at room temperature at scan rate of within a potential window of 0.0 V and 1.0 V at , with addition of different concentrations of glucose corresponding to (a) 2, (b) 4, (c) 6, (d) 8 , (e) 10 mM [34-36].

Results and Discussion

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Silver nanoparticles (AgNP) prepared from chitosan was characterized using scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform Infra-red spectroscopy (FTIR). The SEM micrograph of silver nanoparticle derivatives were recorded and the micrograph are shown in figure 2, while the XRD and FT-IR spectra of silver nanoparticle derivatives are shown in figure 3 and 4 respectively.

Fig. 2. Scanning Electron Micrograph (SEM) of AgNPs

Fig. 2. Scanning Electron Micrograph (SEM) of AgNPs

The morphological features of silver nanoparticles derivatives were studied by NOVA Nano Scanning Electron Microscope (JSM-6480 LV). The SEM slides were prepared by making a smear of the solutions on slides. A thin layer of platinum was coated to make the samples conductive. Then the samples were characterized in the SEM at an accelerating voltage of 5 KV , emission current of and working distance of . The particle morphology was determined via SEM analysis. Silver nanoparticles image enlargement was carried out on a scale of with HV 5.0 Kv as presented in figure 2 above. The surface morphology of the silver nanoparticle morphology presented in figure 2 shows a relatively spherical shape, high density structure with a non-uniform granular shape credited to bio-mediated ionic gelation process. The surface of the synthesized silver nanoparticles has a spherical shape and slightly elongated with a big propensity to aggregate and form larger particle clusters.

XRD Analysis

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The phase variety and grain size of synthesized silver nanoparticles was determined by X-ray diffraction Spectroscopy (Philips PAN analytical). The synthesized nanoparticle was studies with radiation at voltage of 30 kV and current of 20 mA with scan rate of .
Figure 3 presents XRD spectra of silver nanoparticle derived hybrid. The XRD spectrum of silver nanoparticle in figure 3 shows that silver nanoparticles have been formed. The structures of synthesized silver nanoparticles confirm the cubic face-centered structure of silver nanoparticle. This was supported by the observed sharp four diffraction peaks with peaks intense appeared at , and as shown in figure 3 which are indexed to , and 311 Bragg's reflection [37], respectively. This confirms the crystalline structure of silver nanoparticles. The data obtained was matched with JCPDS card no. (65-2871) and the sharpness of the peak clearly reveals the crystalline nature of the particles. The crystallite size of the obtained silver nanoparticles were calculated to be 16 nm applying Debye-Scherrer Equation ( ) with a relative deviation of , where D is the average crystallite size of the nanoparticles, k is the geometric factor called Scherrer constant with a value of is the wavelength of X-ray radiation source is the Bragg's angle and is the angular full-width at half maximum ( ) of the XRD peak at the diffraction angle [38]. XRD patterns (JCPDS, File No. 04-0783) and the structure of synthesized silver nanoparticles were found to be face-centered cubic (FCC) crystal as reported by [39].

Fig. 3. XRD spectrum of Silver Nanoparticle (AgNPs)

Fig. 3. XRD spectrum of Silver Nanoparticle (AgNPs)

FTIR Analysis

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The FTIR spectra of silver nanoparticle derivative are shown in figure 4. Silver nanoparticle spectrum gave peaks at signifying the presence of phosphonate linkages between ammonium, of chitosan and moieties of NaTPP during cross linking process. The spectrum showed two peaks, one at and another at , indicating symmetric and asymmetric stretching of phosphonate linkage, respectively [40]. It was also observed that the asymmetric peak is known to occur due to restricted rotation [41]. The two terminals groups of NaTPP molecule appears to be connected with two groups of two chitosan monomers.
Meanwhile the spectrum of silver nanoparticle display a broadening of the band starting at approximately and extending to and almost obscuring the stretching region around . There is also and a loss of the small features on the band. This broadening is suggestive of increased intermolecular hydrogen bonding between NH and OH. A maximum at approximately is exhibited by the silver nanoparticle. This band broadening is similar to that found in the literature for chitosan-NaTPP nanoparticles and for chitosan succinlyated nanoparticles [42] and is ascribed to the formation of hydrogen bonded networks. The AgNPs show a low intensity but very broad band centred around . This observation suggests that silver chitosan complexes prepared contain mostly nanoparticles.

Fig. 4. FTIR spectrum of Silver Nanoparticle (AgNPs)

Fig. 4. FTIR spectrum of Silver Nanoparticle (AgNPs)

UV-Visible Analysis

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The brown colored silver nanoparticle solution that formed due to excitation of surface Plasmon vibrations of the silver nanoparticles was subjected to UV-Visible spectra recording using Shimadzu UV-1601 double beam spectrometer with quartz cuvettes of 1 cm path length. The UVVisible spectrum of AgNPs is presented in figure 5. Surface Plasmon Resonance (SPR) peak of AgNPs which is an equivalent of maximum absorbance peak occurred at around 420 nm . Previous report confirmed that AgNPs with size range mostly show the SPR peaks at 420 nm as reported by Modrzejewska et al 2010 [43].

The absorbance and broadening of the peak at around 420 nm shows that the particles were monodispersed and indicating the surface plasmon resonance (SPR) absorption band as a result of combined vibration of electrons in resonance with UV-visible light [44-46]. The overall observations suggest that the bio reduction of (silver ions) to was confirmed by UVVisible spectroscopy.

Fig. 5. UV-visible spectrum of Silver Nanoparticle (AgNPs)

Fig. 5. UV-visible spectrum of Silver Nanoparticle (AgNPs)

Comparison Of Bare Glassy Carbon Electrode (DCE) And Silver Nanoparticle Modified Glassy Carbon Electrode (AgNPGCE)

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Fig. 6.Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) and bare glass carbon electrode (GCE) in the presence of 2 mM glucose and scan rate.

Fig. 6. Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) and bare glass carbon electrode (GCE) in the presence of 2 mM glucose and scan rate.

Figure 6 shows the cyclic voltammograms (CVs) of the bare GCE and AgNPGCE with glucose recorded in 0.1 M sodium hydroxide at a scan rate of . The bare GCE did not give any noticeable redox peaks in the potential range recorded. However, high catalytic activity with an observable redox peaks against glucose oxidation in the alkaline solution was found for AgNPGCE compared to the bare GCE due to the increase in the active surface area of the electrochemically modified electrode as offered by the AgNPs attached to the GCE which suggest that the prepared
electrode can be useful for glucose sensing phenomena [47, 48]. The AgNPs modified electrode exhibited an improved electrochemical reactivity, only one anodic peak at was observed, which represent the oxidation of to , while a cathodic peak at 0.32 V was also noticed and may be connected with the reversible conversion of back to . The electrochemical redox phenomena of which occur at the working electrode surface in a basic solution can be represented as

An oxidation reaction was suggested by the working electrode potential covered in silver nanoparticles and the electrode kinetic reaction at the surface of the AgNPGCE is represented thus.

Fig. 7. Description of the mechanism of redox process at the electrode/analyte interface

Fig. 7. Description of the mechanism of redox process at the electrode/analyte interface

This suggested that gluconolactone is produced by the glucose oxidation at the surface of AgNPGCE. The mechanism of oxidation of glucose at the AgNPGCE surface is as follow:

Furthermore, the existence of chitosan stabilized silver nanoparticles may increase the electrode surface area with the analyte, thereby increasing the voltage. This is because using AgNPs on the electrode facilitate increased direct electron transfer between the glucose and the electrode surface. This is because the use of silver nanoparticles on electrode could increase the direct electron transfer between the glucose and the electrode surface, adding that the presence of silver nanoparticles stabilized with chitosan could increase the surface of the electrode with the analyte thereby increasing the voltage.

Effect of Different Scan Rate on the Electrochemical Responses of Silver Nanoparticle Modified Electrode (AgNPGCE)

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Figure 8 shows the cyclic voltammograms of AgNPGCE with different scan rates in 0.1 M sodium hydroxide solution containing 1 mM of glucose. The peak current ( ) is increased with increasing scan rates 10, 25, 50100 and . As can be seen in the figure 9, the plot of versus scan rates and it shows that was increased linearly with increasing scan rate. The redox peak currents and peak potential separations increased with scan rates. The reduction and oxidation peak currents were directly proportional with scan rates from 10 to , the result suggesting that the electrochemical kinetic is a characteristic surface-confined process i.e. the process is regulated by surface adsorption of glucose molecule at AgNPGCE [49, 50].

It can also be seen from the voltammograms that at , the observed redox peaks had formal peak potential ( ) of 0.43 V and peak-to-peak separation ( ) of 54.8 mV ; the result was similar to previous literatures [51], which indicates reversible electrochemical reactions and rapid electron transfer process.
The anodic and cathodic peak current had a linear relationship with the square root of scan rates as shown in figure 10. The heterogeneous electron transfer rate constant ( ) and transfer coefficient ( ) were estimated using Laviron's equation [52]. The heterogeneous electron transfer rate constant ( ) was estimated to be while the electron transfer or symmetry coefficient ( ) was found to be 0.54 which is close to the theoretical value of 0.5 for reversible system. This indicates that electron transfer was effectively and efficiently promoted on the AgNPs electrode.
The surface coverage ( ) was found to be . This value is much higher than that reported in other literatures [53,54], suggesting AgNPs had high adsorption capacity for GCE.

Fig. 8. Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) in the presence of 2 mM glucose at different scan rate

Fig. 8. Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) in the presence of 2 mM glucose at different scan rate

Fig. 9. Anodic and cathodic peak currents versus scan rate

Fig. 9. Anodic and cathodic peak currents versus scan rate

Fig.10. Anodic and cathodic peak currents versus square root of scan rate

Fig.10. Anodic and cathodic peak currents versus square root of scan rate

Effect of Concentration Changes on the Electrochemical Responses of Silver Nanoparticle Modified Glassy Carbon Electrode (AgNPGCE)

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Furthermore, the electron transfer capacity between electrolyte and electrode surface with the glucose concentrations ranging from 2 mM to 10 mM was investigated using cyclic voltammetry in 0.1 M sodium hydroxide solution at and the result is shown in figure 11. Anodic peak at +0.54 V increases as concentration of glucose increases i.e.; peak current varied linearly in proportional to the concentration of glucose in the range of , presented in figure 12. It can be seen from figure 6 that at every scan rate the anodic peak was observed at 0.54 V , therefore, 0.54 V is chosen as the ideal detection potential. The electro-catalytic oxidation of glucose is mainly particle size dependent, which can provide the active sites for redox reaction and biological electrical signal transmission at AgNPGCE. Hence, the synergistic influence can result in enhanced performance for detection of glucose [55].

Fig. 11. Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) in air-saturated at scan rate of with the additional of mM (c), 8 mM (d) and 10 mM (e)

Fig. 11. Cyclic voltammograms of silver nanoparticle modified glass carbon electrode (AgNPGCE) in air-saturated at scan rate of with the additional of mM (c), 8 mM (d) and 10 mM (e)

Fig. 12. Plot of relation between oxidation peak currents and concentrations of glucose Amperiometric Detection of Glucoses

Fig. 12. Plot of relation between oxidation peak currents and concentrations of glucose Amperiometric Detection of Glucoses

To further investigate the relationship between oxidation current and glucose concentration, the chronoamperometry technique was used and the results obtained are presented in figure 13a and 13b respectively.

Fig. 13a. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to

Fig. 13. a. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to

Fig. 13b. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to

Fig. 13. b. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to

Figure 13a and Figure 13b display a typical current time response of AgNPGCE modified electrode was assessed by the successive addition of glucose concentrations over the range of M and respectively into 0.1 M sodium hydroxide at an optimal detection potential of +0.54 V under constant stirring at room temperature. The response time was less than 5 s , signifying a facile electron transfer occurred through the AgNPGCE, which displayed well-defined concentration dependence.
The relationship between the steady-state oxidation current with increasing glucose concentration is shown in figure 14a and 14b respectively.

Fig. 14a. Calibration plot of stead-state current versus concentration of glucose

Fig. 14. a. Calibration plot of stead-state current versus concentration of glucose

Fig. 14b. Calibration plot of steady-state current versus concentration of glucose

Fig. 14. b. Calibration plot of steady-state current versus concentration of glucose

As it shown in figures 14a and 14b above, the current was linear over the glucose concentration range of 2 to with a correlation coefficient of 0.9987 . With higher concentrations of glucose, the currents also increased linearly over a wide concentration ranges from 86 to . The sensitivity determination is done by dividing the slope from the linearity curve with the surface area of the working electrode used which gave the sensitivity value of for the modified electrode and the results are presented in table 1.

Table 1. Electrochemical Parameters of AgNPGCE Electrode for glucose sensing in aqueous solution at room temperature

AgNPGCE | Values
Heterogeneous electron transfer rate constant ( ke ) | 6.736 x 10⁻⁷ cms⁻¹
Charge transfer coefficient ( α ) | 0.54
Sensitivity | 25.02 μA/mM/cm²
Detection limit | 1.22 μM
Regression coefficient | 0.9987
The surface coverage ( φ ) | 3.46 x 10⁻⁹ molcm⁻²

While the detection limit is obtained from the equation, Detection limit or limit of detection (LOD) where is a constant chosen to be 2 or value 2 corresponds to a confident level of while value 3 corresponds to a confident level of . sb is the standard deviation of the blank and m is the calibration sensitivity which is the slope of the linear plot between concentration and current. The detection limit obtained was found to be taken value to be equal 3. This result of the developed AgNPs modified electrode compared favorably well with previously reported enzymatic glucose biosensor [54, 56], suggesting electro-catalytic activity of the silver nanoparticle on glucose, which shows that the working electrode coated with silver nanoparticles has a good ability to measure glucose levels. The non-enzymatic glucose sensors have shown pronounced long-term stability than the enzyme-based glucose sensors.
The eco-friendly stability of the chitosan based silver nanoparticle sensor was examined by keeping in air for three weeks under varying environmental conditions and its sensitivity was examined in accordance with the established procedure and the results are presented in figure 15a and 15b respectively.

Fig. 15a. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to (after being kept in air for two weeks)

Fig. 15. a. Amperometric current versus time curve of silver nanoparticle modified glass carbon electrode (AgNPGCE) for successive glucose addition in the ranges of to (after being kept in air for two weeks)

Fig. 15b. Calibration plot of steady-state current versus concentration of glucose

Fig. 15. b. Calibration plot of steady-state current versus concentration of glucose

The fabricated silver nanoparticle sensor shows comparable sensitivity of which equivalent to of the initial value this demonstrate a very good sensitivity and durability of the sensor for the glucose detection. The good adhesion towards electrode and structural stability of silver nanoparticles could be ascribed to long-term stability. relative standard deviation (RSD) with highly reproducible current for eight successive amperometric measurements was gotten for 2 mM glucose on the AgNPGCE electrode. This demonstrates that AgNPGCE electrode can be repeatedly used and the electrode was not infected by the product of oxidation. The highly reproducible mode of fabrication was established with the attainment of of RSD using eight electrodes responses measured towards 2 mM glucose.

Conclusion

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Silver nanoparticle was prepared and characterized by Fourier transform Infra-red spectroscopy (FTIR), X-ray diffractometry (XRD) and Scanning electron microscopy (SEM). The electrocatalytic activity of the synthesized AgNPs was investigated through potentiometric and amperometric techniques. The crystalline size of the AgNPs was revealed with XRD. The cubic face-centered structure of the synthesized silver nanoparticle was confirmed. This was supported by the observed sharp four diffraction peaks with peaks intense appeared at , , and . However, the SEM micrograph of the synthesized AgNPs revealed the spherical shape of AgNPs with a non-uniform granular shape attributed to bio-mediated ionic gelation process. The surface of the synthesized AgNPs has a spherical shape and slightly elongated with a big tendency to aggregate and form larger particle clusters. Whereas, FTIR spectra of AgNPs gave peaks at suggesting the presence of phosphonate linkages between ammonium, of chitosan and - moieties of NaTPP during cross linking process. The electro-catalytic oxidation of glucose at the electrode was examined and the mechanism involved in glucose oxidation was revealed. The silver nanoparticle modified glassy carbon electrode (AgNPGCE) electrode showed a better electrochemical response towards glucose. This glucose sensor shows high sensitivity at +0.54 V . A low detection limit of taken the confident level to be 3, and wide linear range of 2 to with a correlation coefficient of 0.9987 were obtained. The
calculated parameters revealed that AgNPGCE has shown better overall electrochemical performance with a response which compare and compete favorably well with enzymatic biosensor. The fabricated AgNPGCE sensor shows comparable sensitivity ( ) of the initial value, demonstrating the very good sensitivity and durability for the glucose sensing. The long-term stability and reproducibility of the AgNPGCE could be ascribed to the good adhesion of AgNPs towards the electrode and its structural stability.

References

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Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 53-60

doi: 10.4028/p-MxwzR2

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

Submitted:
2024-11-14

Revised:
2025-01-26

Accepted:
2025-01-27

Online:
2025-03-10

Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

The original version of this paper is available on https://www.scientific.net/EC.9.53.pdf

Malki Fatiha , Missoum Amina and Hamza Kahina

¹Laboratoire de recherche sur les produits bioactifs et valorisation de la biomasse, Ecole Normale Supérieure, BP 92, Kouba, Algiers, Algeria

Keywords: amphoteric surfactant, pyrimidinium betaine, synthesis, surface activity, critical micelle concentration (CMC).

Abstract

A novel series of fatty betaines containing a pyrimidine ring with different alky chain lengths were synthesized by condensation of fatty -diphenylalkylamidines with a specific highly reactive malonic ester derivative under mild conditions. The chemical structures of products were characterized by common spectroscopic analyses (FTIR, mass spectra, NMR, and NMR spectrometry). Equilibrium surface tension and conductivity as a function of concentration of dodecyl pyrimidinum betaine ( betaine with a 12 -carbon alkyl chain) in ethanolic solutions were measured and the critical micelle concentration (CMC) was determined at . The results showed that the critical micelle concentration (CMC) of dodecyl pyrimidinum betaine is and the corresponding surface tension is respectively. These results revealed that the synthesized fatty pyrimidinium betaines are efficient amphoteric surfactants making them promising candidates for applications in a very large number of areas.

Introduction

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Amphoteric surfactants possess long hydrophobic chain with positively and negatively charged hydrophilic head groups [1]. Due to the various properties demonstrated in the amphoteric surfactants (remarkable interfacial activity, lower CMC, solubility, less harm to the skin, less toxic and more biodegradable-depending on the polar headgroups), they have a lot of different uses in cosmetics, enhanced oil recovery, electrochemistry, nanoscience, polymer chemistry, etc ... [2-3].
In recent decades, amphoteric surfactants have attracted considerable interest in academic and industrial research, due to their unique properties such as: solubility, micellization and surface tension [4].

Betaine amphoteric surfactants contain both a positively charged group and a negatively charged group within the same molecule. Betaine- type amphoteric surfactants have been shown to exhibit antimicrobial activity against various microorganisms [5]. They have a variety of applications in biological research, medicine, pharmacy and other scientific fields [6-8]. Betaine derivatives are widely used in personal care products, detergents, as antistatic agents and are applied in enhanced oil recovery [9]. An important factor determining the properties of betaine surfactants is their chemical structure. The zwitterionic form of betaine exhibits a much lower CMC and a much higher surface activity [10], favoring the formation of micelles and a greater surfactant activity at the air-water interface [11].

Betaines containing a pyrimidine ring are a special class of mesoionic compounds [12]. Mesoionic pyrimidinium betaines have been of a great interest for their particular structure [13] and their chemical stability [14]. They also possess various bioactivities [15, 16] which have raised much interest as biologically active compounds [17].

In recent years, many studies have been conducted on the effect of modifying hydrophobic groups, hydrocarbon chain length and types of hydrophilic head group [18]. Several works have focused on the synthesis of imidazolinium-based fatty surfactants and have studied their surface activity [19, 20, 21]. No studies on the surface tension of alkyl pyrimidinium betaines were reported.

In the present work, a series of novel betaines containing a pyrimidine ring with different alkyl chain lengths were synthesized, and characterized by FTIR, NMR, NMR and mass
spectrometry. In addition, the surface tension of the prepared compounds was investigated using both tensiometric and conductometric techniques [22]. The critical micelle concentration (CMC) and the corresponding surface tension ( ) were measured at .

Materials and Methods

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Materials. All of the chemicals and reagents used were of analytical grade and used directly without purification. Chemicals were purchased from Sigma-Aldrich, Merck, Fluka and Prolabo and were of analytical grade purity. Triethylamine was purified by distillation and the solvents were dried using conventional techniques. Thin layer chromatographic analysis, using Aluminum plates precoated with silica gel was used to monitor the reaction's progress and the chromatograms were visualized using UV at 254 . Melting points were measured in a capillary tube, using a Büchi 540 type digital apparatus. UV-Visible absorption spectra were carried out using a Shimadzu 160 double-beam spectrophotometer. FTIR spectra were recorded as KBr pellets on a Jasco system NMR and NMR spectra were acquired on a Bruker AC 200 instrument at 300 and 75 MHz respectively. Electron impact mass spectra (EIMS) were performed on a Nermag R10-10 type apparatus.

Synthesis. The synthesis of pyrimidinium betaine surfactants involves three steps. The first step consists of the synthesis of fatty '-diphenyalkylamidines 3a-e, from the corresponding alkylanilides 2a-e, themselves prepared from the homologous carboxylic acids 1a-e [23] (Scheme 1). The second step includes the synthesis of bispentachlorophenyl ester of phenyl malonic acid by the action of pentachlorophenol on phenyl malonic acid 4 [24] (Scheme 2). The third step involves the synthesis of fatty pyrimidinium betaines 6a-e from the condensation of fatty amidine derivatives 3a with malonic ester derivative 5, according to a previously reported procedure [23,25,26] (Scheme 3). The synthesis pathways of the reagents 3a-e and are as follows :

Scheme 1. Synthesis route of fatty N, N'- diphenylalkylamidines 3a-e

Figure 1. Scheme 1. Synthesis route of fatty N, N'- diphenylalkylamidines 3a-e

Scheme 2. Preparation of bispentachlorophenyl ester of phenyl malonic acid 5

Figure 2. Scheme 2. Preparation of bispentachlorophenyl ester of phenyl malonic acid 5

General procedure for the synthesis of fatty chain pyrimidinium betaines 6a-e. Fatty chain pyrimidinium betaines 6a-e were synthesized according to the Dvortsak procedure [25] by reacting 1 mmol of fatty N,N'-alkylamidines 3a-e with 1 mmol of the bis pentachlorophenyl ester of phenyl malonic acid 5 in diethyl ether [26] under stirring at room temperature (Scheme 3), To the milky suspension obtained, 2 mmol of triethylamine was added. Less than a minute after this last addition a white solid precipitated. The entire system was then stirred for 30 min . The products were isolated by filtration. Their purification after several successive extractions afforded powdery white solids [26]. The purity of the synthesized fatty betaines was confirmed by TLC technique.

Scheme 3. Synthetic pathway of fatty pyrimidinium betaines 6a-e

Figure 3. Scheme 3. Synthetic pathway of fatty pyrimidinium betaines 6a-e

Measurements. In this work our study focused on a pyrimidinium betaine with a 12 -carbon alkyl chain 6b (dodecyl pyrimidinium betaine BT12) as an example.

Surface tension measurements. A series of ethanolic solutions of dodecyl pyrimidinium betaine surfactant BT12 were prepared at different concentrations from to . The surface tension was measured at using a Krüss GmbH , K 6 tensiometer by the ring tear-off method. All measurements were repeated three times and the average value was taken [9, 27, 28].

Conductivity measurements. The conductivity of ethanolic solutions of dodecyl pyrimidinium betaine surfactant BT12 was measured by a HI 8633 conductivity meter. The conductivity measurements were carried out at different concentrations at [22,29].

Results and Discussion

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Characterization of synthesized compounds. Betaines with fatty alkyl chain 6a-e containing a pyrimidine moiety were realized according to a previously reported procedure [23, 26]. As presented in Table 1, the different alkyl betaines were isolated in low to moderate yields, .

Table 1. Yields of synthesized fatty alkyl pyrimidinium betaines 6a-e

Betaine | R | Aspect | Yield (%)
6a | C₉H₁₉ | white solid | 39
6b | C₁₁H₂₃ | white solid | 45
6c | C₁₃H₂₇ | white solid | 31
6d | C₁₅H₃₁ | white solid | 30
6e | C₁₇H₃₅ | white solid | 35

The fatty pyrimidinium betaines 6a-e were also characterized by the spectral analyses and their different spectra were found to be identical. As an example, UV-Visible, FTIR, MS, H NMR and C NMR spectral results of dodecyl pyrimidinium betaine are compiled in Table 2.

Table 2. UV-Visible, IR, and NMR spectral results of dodecyl pyrimidinium betaine

Dodecyl pyrimidinium Betaine 6b (BT12). | Chemical formula | Mol. Mass. (g/mol) | m.p. (°C) | UV-Visible (dioxane) λmax (nm) | IR (KBr) ṽ (cm⁻¹) | ¹H NMR (CDCl₃) δ (ppm) | ¹³H NMR (CDCl₃) δ (ppm) | EI Mass
(6-oxo-2-dodecyl,1,3,5-tripheny-1,6-dihydropyrimidin-3-ium-4-olate) | C₃₃H₃₈N₂O₂ | 494 | 124–128 | 352 | 3055 (C-H, Ar.), 1647 (C=O), 1597 (C=C, Ar.) | 7.91–7.14 (15H, Ar.), 2.41–0.78 (23H, aliph.) | 161.42 (C-14,16), 159.00 (C-12), 136.27-125.76 (C, Ar.), 32.77–14.11 (C, aliph.) | 495[M+1]⁺

Surface Activity

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Surface tension measurements. Measuring surface tension allows us to know the surface free energy per unit area at the air-liquid interface. This data is necssary to establish the CMC and study the micellization and adsorption properties [22]. The surface tension of dodecyl pyrimidinium betaine surfactant BT12 as a function of concentration at was determined and plotted in Figure 1.

Fig. 1. Variation of surface tension as a function of the concentration of the pyrimidinium betaine surfactant BT12 in ethanolic solution at

Fig. 1. Variation of surface tension as a function of the concentration of the pyrimidinium betaine surfactant BT12 in ethanolic solution at

Fig. 2. Determination of CMC value by tensiometric technique

Fig. 2. Determination of CMC value by tensiometric technique

As illustrated in the figures above, the surface tension values decrease rapidly with increasing surfactant concentration due to the adsorption of molecules at the air-liquid interface. Then a distinct break point appears, known as critical micelle concentration (CMC) [29]. At the CMC values the surfactant begins to form micelles to decrease the electrostatic energies of the system [20]. The CMC and surface tension at CMC ( ) values were estimated from the breakpoints of these plots. After the breaking point, the surface tension remains almost constant with increasing BT12 concentrations [18]. This is due to the saturation of the air-liquid interface with BT12 molecules [28] . Figure 1 and 2 show that and CMC values of BT12 are and respectively. The results obtained reveal that the synthesized pyrimidinium betaine surfactant has a great ability to reduce the surface tension of the system [28]. It appears that the length of the alkyl chain of the fatty pyrimidinium betaine studied has a significant effect on the reduction of surface tension [19,29].
In general, the CMC value of surfactants is a sign of surface properties. The corresponding surface tension value indicates the ability of surfactants to reduce surface tensions and, therefore, the CMC indicates the effectiveness [9]. This means that BT12 with a long alkyl chain has excellent micellization capacity at low concentrations.

Conductivity measurements. The variations of conductivity against concentration of BT12 at are shown in Figure 3.

Fig. 3. Dependence of conductivity on the concentration of the pyrimidinium betaine surfactant BT12 in ethanolic solution at .

Fig. 3. Dependence of conductivity on the concentration of the pyrimidinium betaine surfactant BT12 in ethanolic solution at .

Fig. 4. Determination of CMC value by conductometric technique

Fig. 4. Determination of CMC value by conductometric technique

As showed in Figures 3 and 4, the experimental results correspond in two straight lines with a significant change in direction at the breakpoint [22,30]. The conductivity of the solution increases rapidly in the pre-micellar region. This is due to the increase in the concentration of current carriers which increases with increasing surfactant concentration. Regarding the conductivity measurements, CMC value was obtained at the point of intersection of the linear parts of the conductivity versus concentration plots [28]. As depicted in Figure 4 the value of CMC obtained is .

By comparing the results obtained using both tensiometric and conductometric techniques we concluded that the CMC values are very close.

Summary

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In the present work, a series of new fatty betaines containing a pyrimidine ring were prepared and their chemical structures were characterized using FTIR, NMR, NMR and mass spectra. The surface activity of dodecyl pyrimidinium betaine surfactant in ethanolique solutions at was investigated by surface tension and conductivity measurements. The synthesized surfactant has proved satisfactory surface properties. This work has demonstrated that it is possible to obtain amphoteric surfactant with appropriate surface properties based on fatty acids, available and inexpensive products. The synthesized compounds could therefore have wide potential applications. They can be used in several industrial application such as laundry detergent, corrosion/rust inhibitor and lubricating emulsion.

Acknowledgements

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Authors are grateful for the financial support from the Algerian Ministry of Higher Education and Scientific Research (Projet de Recherche Formation-Universitaire. PRFU B00L01EN160220180003). Authors deeply thank the researchers of Laboratory of organic synthesis, university of science and technology, Houari-Boumédiène (USTHB), Algiers, Algeria, for kindly providing a tensiometer. We are also grateful to Doctor Michel Baltas for the NMR and mass spectra performed in the Laboratory of Synthesis and Physiochemistry of Molecules of Biological Interest, UMR 5068, University Paul Sabatier Toulouse, France.

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The original version of this eBook is available on https://www.scientific.net/book/engineering-chemistry-vol-9/978-3-0364-1758-5

Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 61-83

doi: 10.4028/p-7adOG1

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

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2025-03-10

Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

The original version of this paper is available on https://www.scientific.net/EC.9.61.pdf

Ayodunmomi Esther Olowofoyeku , Ademola Kabiru Aremu , Abel Olajide Olorunnisola , Ayobamiji Emmanuel Olowofoyeku , Ezekiel Oluwatobi Faluyi , Daniel Gbenga Adekanmi

Pan African University Life and Earth Sciences Institute (Including Health and Agriculture), PAULESI, University of Ibadan, Ibadan, Nigeria.

Department of Agriculture and Environmental Engineering, University of Ibadan, Ibadan, Nigeria.

Department of Wood Products Engineering, University of Ibadan, Ibadan, Nigeria.

Faculty of Chemical Science, Olusegun Agagu University of Science and Technology, Ondo, Nigeria.

Facultad de Ciencias Químicas, Universidad Autónoma de Coahuila, Saltillo, Coahuila, 25280, México.

ªayoolowo1122@gmail.com, bademolaomooroye@gmail.com, cabelolorunnisola@yahoo.com, banjiolowo1@gmail.com, e_faluyi@uadec.edu.mx, danieladekanmi@uadec.edu.mx Corresponding author: ayoolowo1122@gmail.com

Keywords: Photoluminescent polymers, Composites, Controlled environment agriculture, Luminescent materials, Light conversion polymers.

Abstract

Light is essential for plant growth and plays a crucial role in photosynthesis. However, sunlight often falls short of ensuring photosynthesis efficiency due to its wavelength composition, changing weather conditions, and the unique characteristics of plants, which create challenges for agricultural productivity. To address this, many innovative farming practices have been developed, including controlled environment agriculture, which creates microclimates that optimize conditions for plants. To improve light efficiency in these microclimates, researchers have turned to luminescent and light-conversion materials. These materials are incorporated into polymers to convert underutilized wavelengths, such as ultraviolet-visible (UV) and blue light, into photosynthetically active radiation (PAR). Luminescent materials like fluorescent pigments, quantum dots, and rare-earth-doped compounds, when incorporated into polymers, produce films that enhance light absorption and improve spectral energy distribution. They have shown great potential to increase crop yield, biomass, and the quality of fruits and vegetables. Despite their potential, challenges remain on the path to widespread adoption. Environmental impact, scalability, and economic feasibility are significant concerns. This review explores the integration and functionality of photoluminescent polymer nanocomposites as light-converting materials. It also examines current limitations while offering future perspectives on how these materials can be used for sustainable light solutions to improve agricultural productivity.

Introduction

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Agriculture thrives on light and light is a fundamental element driving photosynthesis-the process that transforms sunlight into the energy plants need to grow. While light is essential for plant health, its availability is often inconsistent [1-4]. Some regions face challenges of insufficient sunlight, while others contend with excessive exposure, leading to plant stress and reduced yields. Climate change further aggravates these challenges, exacerbating external stressors and stagnating crop productivity. With the global population increasing and per capita arable land decreasing, these challenges demand urgent solutions [5-8].
Controlled Environment Agriculture (CEA) provides a promising path forward and involves using precisely regulated conditions to enhance crop efficiency and resilience. In CEA, regulated light
exposure ensures optimal growing conditions. However, using artificial lighting systems can significantly increase the operational costs of farms [3, 5, 7, 9-11]. A promising alternative is photoluminescent polymer composites. These materials absorb natural or artificial light and re-emit it as wavelengths optimized for photosynthesis, enhancing plant growth, reducing energy waste, and potentially increasing crop yields. This article reviews the potential of photoluminescent polymers in agriculture, focusing on their role in addressing light-related challenges and enhancing photosynthetic efficiency. It highlights their contributions to sustainable farming practices through innovative light management techniques. It also explores the synthesis of these polymers, reported increases in productivity due to their integration into farming systems, and future perspectives for improved outcomes.

Factors that affect photosynthesis

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Photosynthesis is a biochemical process in which plants and certain microorganisms convert gaseous carbon (iv) oxide and water into glucose in the presence of light. The glucose formed is stored or used for their growth and development. This process also replenishes oxygen in the atmosphere. This process occurs in chloroplasts through light absorption by chlorophyll which triggers electron transport and a series of enzymatic reactions that produce essential organic compounds and release oxygen. It is dependent on internal factors, such as chlorophyll content, stomatal function, leaf structure, and nutrient availability. Nutrients like nitrogen and magnesium support chlorophyll production and enzymatic activity and are therefore vital contributors. Also, younger, healthier plants photosynthesize more efficiently than older or stressed ones [12-15]. External factors play an equally crucial role: Photosynthetic rate is influenced by light quality, particularly red and blue wavelengths. Atmospheric carbon (iv) oxide levels and temperature also impact enzyme activity. Stressors like pollution and extreme weather damage plant tissues, reducing photosynthetic efficiency and highlighting the need for balance [12, 15, 16].

Light and its crucial role in photosynthesis

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The Sun provides warmth to sustain life and sunlight for visibility and photosynthesis [1]. Using sunlight, plants convert carbon (iv) oxide from the air and water absorbed from the soil into glucose and oxygen through the summarized chemical reaction below (Equation 1):

Equation 1
Sunlight comprises infrared, visible light, and ultraviolet radiation, each uniquely contributing to plant growth [19, 20]. Chlorophyll absorbs light most effectively in the blue ( and red ( ) regions of the spectrum. Beyond these wavelengths, photosynthetic efficiency declines particularly for above 680 nm . However, the Emerson enhancement effect demonstrates that combining long- and short-wavelength photons boosts photosynthetic activity. So, far-red photons aid photosynthesis in shaded environments, while green photons penetrate deeper into plant tissues, enhancing carbon fixation [9, 21-24].
In terms of the availability of optimal light wavelength, useable light for plant activities is limited by various factors. For example, seasonal changes affect light availability and can also affect crop growth cycles. In spring and summer longer daylight hours provide more sunlight for photosynthesis which leads to vigorous growth and higher yields while shorter days in autumn and winter result in reduced light availability and slower growth rates, especially in crops that are sensitive to light. While some amount of shade can favor some types of plants, excessive shading can be deleterious. Campos et al. and Costa et al. demonstrated the effects of shading on plant growth by comparing greenhouses with and without reflective aluminized shading materials. The results demonstrated that appropriate shading can enhance yield quality by decreasing unmarketable fruit [25, 26]. However, structures in urban environments can create artificial covers and shadows beyond the control of farmers, thereby limiting sunlight reception for crops. The erratic nature of weather due to climate change worsens these issues through cloud cover and frequent storms which may cause inconsistent sunlight exposure during critical growth periods. Insufficient light conditions harm the physical structure, health, and weak immunity of plants against pests and diseases [6,27]. Conversely, excessive light can cause
photoinhibition where plants are overwhelmed and cannot process it effectively. This condition causes photo stress and reduces photosynthetic performance and reactive oxygen species (ROS) accumulation in plant cells which then damages chlorophyll molecules and disrupts photosynthetic pathways. Excess UV exposure damages plant DNA, negatively affecting growth [3, 28-31].
Claypool et al. confirmed that broad-spectrum light is most effective for plant growth, in line with the Emerson effect. Their study on bell pepper seedlings revealed that green light significantly improved physical characteristics such as plant height and leaf area compared to monochromatic red or blue light [32]. Also, in an attempt to supplement natural sunlight with artificial light enhancement, Adibian et al. used various combinations of red and blue light-emitting diodes (LEDs) and observed an enhancement in fruit yield and quality parameters of sweet pepper (Capsicum annuum L.) grown in greenhouses under low natural sunlight conditions [33]. Similarly, Hyeon-Do et al. observed that artificial Red-Green-Blue (RGB) LED lighting resulted in the highest chlorophyll content and overall seedling vigor in the germination of lettuce cultivars compared to each light alone [27].
These observations are helpful for modern farmers who can adopt farming practices independent of sunlight in the form of Controlled Environment Agriculture (CEA), although energy consumption challenges the feasibility of this method. While the decreasing cost of LEDs and improvements in efficiency and smart systems designed for adjusting light spectra can help reduce operational costs, innovative light management systems such as spectra-shaping films and sunlight redirection methods are also emerging [7, 12, 34]. Sunlight remains the most cost-effective light source and there are ongoing efforts to optimize its use while minimizing damage from harmful wavelengths. One of these methods involves the use of polymers and their nanocomposites.

Polymers

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Polymers are macromolecules formed from repeating units called monomers. Natural examples include proteins in animals and cellulose in plants, while synthetic polymers such as plastics and rubbers are chemically engineered. Nowadays their application cuts across many spaces since they are cheap substitutes for metals and ceramic materials [35-37]. The modern understanding of polymers began in the 19th century with discoveries like the vulcanization of rubber by Charles Goodyear and the synthesis of the first synthetic plastic, Bakelite, by Leo Baekeland during the same period. Since then, many more synthetic polymers such as polyethylene, polystyrene, and nylon have been made and used in household and technological products [38].
Polymers can be classified based on their origin, structure, and properties. Natural polymers have complex structures that play critical roles in biological processes. In contrast, synthetic polymers may be engineered for specific applications. Structurally, polymers could be linear polymers (e.g., polyvinyl chloride), branched polymers (e.g., low-density polyethylene), and cross-linked polymers (e.g., Bakelite). Polymers are synthesized through methods categorized as either addition or condensation polymerization. In addition polymerization, monomers have a double or triple bond and are therefore joined through a bond-opening reaction that does not result in the loss of small molecules, while condensation polymerization involves reactions that release by-products like water or methanol. Examples of polymers formed through addition polymerization include polyethylene and polypropylene while polymers like nylon and polyester are formed through condensation reaction [39-41].

Applications of polymers in agriculture

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Polymers play an essential role in modern agriculture by enhancing productivity and efficiency. Their versatile properties make them invaluable for various applications, particularly in farming systems such as greenhouses, mulching, and irrigation. These materials provide benefits such as improved soil temperature control, moisture retention, and protection of crops from external stressors like pests and extreme weather. Their global adoption in farming practices is inked with their cost-effectiveness and ease of adoption [42-45].
Polymers such as polyethylene, polyvinyl chloride (PVC), and polypropylene are commonly used due to their favorable physical and chemical properties. Polyethylene, particularly low-density polyethylene (LDPE) is a widely used polymer in agriculture. It is used in the production of
greenhouse covers and mulch films. It is strong enough to provide a barrier against pests and weeds while being optimally transparent for adequate sunlight penetration. It is flexible and can conform to soil surfaces. Its impermeability helps retain moisture and regulate soil temperature which is very beneficial in arid regions where water conservation is paramount. Innovative applications of polyethylene have led to the production of films with varying thicknesses and colors to modify light absorption and reflectance properties for specific crops. For example, clear polyethylene film maximizes light transmission and is ideal for regions with abundant sunlight. White diffused polyethylene film produces a gentler lightening effect and warmth by scattering sunlight which prevents scorching of delicate plants. Black-and-white films produce controlled light exposure also referred to as photoperiod control. The effects of light-diffusing and clear film on the growth of Batavia lettuce (Lactuca sativa L.) in two greenhouses over five growth periods were studied by [46]. Results indicated that lettuce grown under the light-diffusing film was smaller (up to ) and had fewer leaves with reduced leaf area. However, they had higher total macroelement contents (up to 10 %) and increased leaf nitrate levels than their counterpart cultivated under the clear film. This supports the need for specificity in the application of light diffusion films [46]. Also, the effects of polyolefin (PO) film and ethylene-vinyl acetate (EVA) film on lettuce growth were compared. It was observed that greenhouses covered with PO had higher temperatures and humidity. In addition, PO film provided more average illumination intensity of and light transmittance, compared to and for EVA film. The PO film also enhanced chlorophyll content and crop productivity which indicates potential for effective use in vegetable cultivation [47]. Polypropylene is also used as covers, spreads, and plant pots because it has high tensile strength and is resistant to chemical degradation, making it suitable for harsh chemical environments. Polypropylene fabrics are often used to suppress weed growth in the form of landscape fabrics which allow water and nutrients to permeate the soil [48, 49].

Limitations of traditional polymers light optimization

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Conventional polymers are limited in light applications in agricultural settings. For example, noncolored traditional agricultural films primarily provide a barrier against environmental factors rather than optimizing light quality. Even the colored ones do not adequately filter harmful ultraviolet (UV) radiation or adjust the light spectrum to favor specific wavelengths that enhance plant growth. Also, most polymers become brittle after prolonged exposure to UV radiation due to photo-oxidative degradation of their polymer chains. This causes a loss of mechanical properties, reduced functionality, and reduced lifespan. As they degrade, they may become less effective at regulating temperature or moisture levels around crops which translates to increased costs for farmers due to replacements [50-52].

Photoluminescent materials

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Photoluminescent materials (PMs) have emerged as pivotal components in various fields, including optoelectronics, lighting, display technologies, personalized medicine, and agriculture due to their high energy efficiency and stability [53,54]. Photoluminescence refers to the emission of light by a material after it absorbs photons, which excites electrons to higher energy levels. These electrons release energy as they return to their ground state, making the materials with such ability invaluable for light conversion and enhancement applications. However, photoluminescence can be an upconversion or downconversion process where light is either absorbed or emitted at different energy levels. Upconversion occurs when lower-energy photons are absorbed and re-emitted as higherenergy photons, like in a material that converts infrared light into visible light, as seen in upconverting phosphors [55-57]. In contrast, downconversion involves the absorption of high-energy photons, which are then re-emitted as lower-energy photons, such as when ultraviolet light is absorbed and emitted as visible light in phosphorescent materials [58-60]. In practical terms, down-converting luminous material, , was developed by Zhu et al. to emit red light in the dark after excitation by combining a light conversion agent with , [61]. Also, nanoparticles synthesized by [57] were used as up-converting
luminophores, capable of converting infrared radiation into visible light, with emissions observed at , and 525 nm for possible photosynthesis applications [57].
Broadly, PMs can be classified into fluorescent dyes, conjugated polymers, organic rare-earth complexes, and inorganic rare-earth complexes. Each category offers specific advantages in luminescent polymer application. Fluorescent dyes, such as 2-([1,1'-biphenyl]-4-yl)-3,3diphenylacrylonitrile [62], 2,4,6-tris (4-methoxy-3-methyl-N-phenylaniline) 1,3,5-triazine [1], and 3and 4-position naphthalimide [63] have been embedded in polymers. Organic rare earth complexes have metal ion luminescent centers surrounded by organic ligands. Qiao et al. developed luminescent kaolinite clay by incorporating N-methylimidazole (NMI) molecules and salts into it. The luminescent material was thereafter incorporated into polyvinylidene fluoride [64]. Inorganic rareearth complexes on the other hand are purely inorganic. Examples are Eu-doped which was embedded into low-density polyethylene [65] and Eu-doped calcium carbonate was incorporated into polyethylene [66]. Similarly, another sunlight-converting film made from supported the growth of Chlorella as a broadband near-infrared converter [67].
An ideal photoconversion system for photosynthetic applications should possess several features: efficient solar spectrum transmittance in photosynthetically active ranges, sufficiently high quantum yield of re-emission, suitable surface modifications for targeted photoreactions, high chemical, and photostability, and minimized reabsorption losses [68]. Such PMs absorb sunlight, typically in the UV or green spectrum ( ), and re-emit it as red light ( ). By this, they play an active part in enhancing photosynthetically active radiation. This re-emission aligns with the absorption spectrum of chlorophyll-a, a critical pigment in photosystem II, thus improving photosynthetic efficiency even in low-light or diffuse-light environments.

Polymer nanocomposites (PNCs) and photoluminescent polymer nanocomposites (PPNCs)

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Generally, polymer nanocomposites (PNCs) consist of a polymer matrix with nanoparticles dispersed within it [69]. Usually, nanofillers, which can have various morphological characteristics, modify the polymer matrix's mechanical strength, thermal stability, barrier performance, electrical conductivity, and optical properties. The large surface area and high aspect ratio of the nanofillers facilitate strong interactions with the polymer material. Nanomaterials like silica, calcium carbonate, graphene, or metal oxides have been used to improve the functionality of polymers [69-71]. Many non-luminescent polymer composites have been made using non-luminescent materials. Such films have also been used in agricultural settings. For example, a study investigated the effects of different colored lightquality selective plastic films (transparent, red, yellow, green, blue, and purple) on the growth, photosynthetic abilities, and fruit quality of strawberries. The results indicated that the red film significantly enhanced leaf area, petiole length, and biomass, improved photosynthetic performance by increasing pigment content and quantum yield while reducing energy dissipation as heat, and also boosted fruit weight along with the content of total sugar, anthocyanin, and soluble protein, suggesting that red light is optimal for strawberry production [72].
However, Photoluminescent Polymer nanocomposites (PPNCs) are unique in the fact that the nanofillers used have photoluminescent properties. In agricultural settings, PPNCs are used as light conversion films in greenhouse and field planting areas to improve sunlight utilization as shown in Fig. 1. Depending on the purpose and the type of photoluminescent materials embedded in the polymer matrix, PPNCs can exhibit various optical properties. When carbon-based nanomaterials, which have photoluminescent properties, are incorporated into films, they produce effective downconversion PPNCs for converting ultraviolet (UV) light into radiation that plants can use for photosynthesis [73-75]. For example, vinyl alcohol-encapsulated carbon dots (CDs) have demonstrated the ability to convert UV light into blue light, which significantly improves photosynthetic efficiency in lettuce [76]. Similarly, amine-functionalized CDs can bind effectively to chloroplast surfaces, enhancing photosynthesis by facilitating a faster solar energy conversion [77]. In a study by Li et al., researchers created an innovative dual-wavelength luminescent CD that not only absorbs UV light efficiently but also emits blue and red light, perfectly matching the wavelengths that chloroplasts can absorb [78]. He et al. developed a light conversion film by embedding blue-
light-emitting carbon dots (CDs) with red-light-emitting europium ions ( ) in a polyvinyl alcohol (PVA) matrix through the direct recombination method. The research demonstrated that the photoluminescence properties of the composite could be tuned by adjusting the ratio of CDs to doped , allowing for customized light components to meet the specific needs of different plant species [79]. Barman et al. reported the synthesis of a transparent plastic material that effectively blocks ultraviolet (UV) light while emitting blue light at 440 nm , using polyvinyl alcohol (PVA) as the matrix to disperse nitrogen-doped carbon dots (N-CDs) created through a hydrothermal process. The resulting N-CD/PVA composite achieves a quantum yield of when excited in the UV-A range ( ), demonstrating enhanced UV absorption proportional to film thickness without compromising luminescence, making it a promising eco-friendly solution for applications such as UV shielding, anti-counterfeiting, and greenhouse sheathing to promote plant growth [80]. Also, the rareearth material and its (3-Aminopropyl) triethoxysilane (KH550)-modified version enhanced the crystallinity of polylactide (PLA) films and improved red-light conversion. These films emitted fluorescence at UV wavelengths of 254 nm and 365 nm , significantly promoting plant growth [81]. Wu et al. observed the average diameter of light conversion filler in the -based film to be 500 nm , and for the film's mechanical properties, it was observed that the tensile strength of the film increased from 9.86 to 12.16 MPa and the strain at breakage rose from to when compared with the blank film. The film also effectively converted UV to plant-friendly red light [65].
Films containing luminescent quantum dots (QD) were also used to modify the solar spectrum to improve plant productivity and in bioregenerative life-support systems for potential human settlements beyond Earth. The results showed that these QD films effectively down-converted ultraviolet and blue light to red emissions at 600 and 660 nm , leading to significant increases in biomass accumulation in red romaine lettuce, with edible dry mass increasing by and , respectively, and total leaf area increasing by up to , indicating enhanced photosynthetic efficiency and potential for greater productivity in both terrestrial greenhouses and space environments [82].

Fig. 1. Light conversion attributes of photoluminescent polymer nanocomposites.

Fig. 1. Light conversion attributes of photoluminescent polymer nanocomposites.

Fabrication of PPNCs

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The method used to fabricate PPNCs can influence their performance due to the degree of dispersion and interaction of nanofillers within the polymer matrix. Common methods like in situ polymerization, solution mixing, and melt blending are applicable depending on the desired properties of the final composite, and each method offers specific advantages tailored to those properties as shown in Fig. 2. Table 1 compares the various methods discussed below.

Fig. 2. Methods of photoluminescent polymer synthesis

Fig. 2. Methods of photoluminescent polymer synthesis

In situ polymerization involves the polymerization of monomers in the presence of dispersed photoluminescent nanoparticles and offers the advantage of strong interfacial bonding and uniform integration. The light-emitting nanoparticle materials are mixed with polymer monomers before polymerization to create solid-state polymer nanocomposites. Zhang et al. reported a semi-aromatic polyamides polymer composite made with upconversion nanoparticles in a one-pot double in-situ synthetic method combining hydrothermal and melt polycondensation techniques [83]. De et al. also synthesized hyperbranched epoxy resin/carbon dots polymer nanocomposite with in situ incorporation of carbon dots during the formation of hyperbranched epoxy resin [84]. Both authors reported transparent uniformly dispersed and photoluminescent materials. Shi et al. synthesized nanocrystals in methyl methacrylate via a one-pot method. They achieved a high quantum yield of and narrow emission linewidth of 20 nm . The UV-cured PNC-PMMA films were stable and showed improved optical performance [85]. Jang et al. took a different approach by dispersing QDs in a siloxane resin to create a thermally stable QD/siloxane hybrid, which proved to be highly stable even under extreme conditions [86].
Solution mixing is effective when there is a solvent that can interact effectively with both the fillers and polymer matrix. The solution is evaporated after the composition is formed. It is effective for both thermosetting and thermoplastic polymers provided the right solvent is used. This method allows the use of techniques like molding, spin-coating, dip-coating, electrospinning, and drop-casting, to refine the final structure of the composites. For example, carbon polymer composites in the form of supraballs, films, and fibers have been fabricated using solution-based methods [87-90]. Polymers commonly used for these processes include polyvinyl alcohol (PVA), chitosan, polycaprolactone (PCL), and polyvinyl pyrrolidone (PVP) [91-93]. Mutlugun et al. used this approach to embed QDs into PMMA films using hexane as a solvent which produced materials with quantum yields exceeding and vibrant color output [94]. Similarly, Chen et al. fabricated QD/acrylate films by incorporating green and red QDs into a UV-curable acrylic resin. The approximately thick films were made by coating the mixture onto PET substrates and curing under a mercury lamp [95]. Melt blending, or melt mixing, involves dispersing the nanoparticles into a molten polymer using extruders and kneaders. It is better suited for thermoplastic polymers like polyethylene or polypropylene and offers scalability. It is also cheap to implement and solvent-free [65, 96, 97]. Strontium aluminate phosphors ( and ) were combined with lowdensity polyethylene, high-density polyethylene, polypropylene matrices by melt mixing and extrusion and the luminescence and durability were observed using the Hamburg wheel test. It was observed that the polymer matrix affected the luminescence of the composite although their emission wavelength was retained [97].

Table 1. Comparison between different methods of photoluminescent polymer synthesis.

Method | Polymerization | Solvent Usage | High Shear Forces | Thermal Processing | Key Advantage | Limitations | References
In Situ Polymerization | Yes | Optional | No | No | Strong nanoparticle-polymer bonding. | Complex processing conditions required. | [83, 84]
Solution Mixing | No | Yes | No | No | Excellent dispersion of nanoparticles. | Potential solvent residue issues. | [89, 94]
Melt Blending | No | No | Yes | Yes | Solvent-free and scalable process. | Limited to thermoplastic materials. | [96, 97]

Factors influencing the performance and stability of PPNCs

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The design of PPNCs involves several critical factors: the choice of luminescent materials, the polymer matrix, the fabrication method, and the dispersion of nanomaterials within the matrix. The polymer matrix must not exhibit quenching effects on the luminescent materials and should efficiently scatter light to ensure uniform distribution of re-emitted light. The dispersion of nanoparticles within the polymer matrix is crucial. Fillers with strong Van der Waals forces tend to aggregate, reducing the effective surface area available for polymer-nanocomposite interaction. Aggregation also creates weak points in the composite thereby weakening the mechanical, thermal, and electrical properties of the product. It has been observed that surface modification or functionalization of nanoparticles enhances their compatibility when integrated into polymer matrices.
Surface modification may introduce functional groups or protective shells around nanoparticles which improve their bonding with polymers and enhance dispersion, stability, and thermal resistance as shown in Fig. 3. Surface modification of nanoparticles may also increase their surface area or increase active sites which aid blending into both synthetic and natural polymer matrices. Treating nanoparticles with silanes, surfactants, or grafted polymers enhances compatibility with the polymer matrix and improves dispersion [98-102]. In the case of photoluminescent materials surface modification improves stability and minimizes photoluminescence quenching which results from aggregation [103-105]. Surface modification of quantum dots was carried out using mercaptopropionic polyethyleneimine (MPPEI) to create acid and base-resistant photoluminescent particles whose quantum yield of above [106]. Wang et al. achieved surface modification of ZnS-based QDs using 3-Mercaptopropyltrimethoxysilane ligands for effective dispersion into bacterial cellulose and reported a quantum yield of about [107]. Surface modification of photoluminescent salicylic acid and o-phenanthroline doped , and was carried out thereafter light conversion films were produced by incorporating them into ethylene-1-hexene copolymer film through blow molding. The film effectively converted ultraviolet light ( to red light which indicates suitability for plant photosynthesis and performance for agricultural applications [108]. In addition, highly resistant and vapor-proof films based on fluoropolymers, combined with nanoparticles or quantum dots, have demonstrated the ability to convert UV and violet light into blue and red wavelengths, enhancing photosynthesis and plant growth without additional energy consumption. These coatings maintain stability under fluctuating weather conditions, which is vital for agricultural resilience [57, 109].

Fig. 3. Effect of surface modification on photoluminescent nanoparticles in polymer matrices.

Fig. 3. Effect of surface modification on photoluminescent nanoparticles in polymer matrices.

Assessing the effectiveness of surface modification and the dispersion of fillers in polymer composites is a necessary aspect of the characterization process. This evaluation often requires a combination of analytical techniques, including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy-Dispersive X-ray Spectroscopy (EDX). SEM generates highresolution images of the polymer surface which shows the distribution of filler particles and any agglomeration or uneven dispersion present. TEM offers a nanoscale perspective for confirming homogeneity and detection of any phase separation through visualization of the fillers' integration within the polymer matrix at the molecular level. When coupled with SEM, EDX maps the elemental composition, offering precise insights into the spatial distribution of fillers and ensuring their uniform integration across the polymer. Together, these techniques deliver a comprehensive analysis of filler dispersion, verifying their effective incorporation into the polymer matrix and contributing to the overall performance and reliability of the PPNC [110-115].

Impact of photoluminescent films on crop farming

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Using the physical attributes of plants and quality parameters of crops the benefits of PPNCs have been established as highlighted in Table 2. This enhances growth conditions by mimicking natural sunlight, with red light boosting fruiting and flowering and blue light supporting leafy growth, addressing natural light inefficiencies that limit crop yields. Enhanced light availability also bolsters plant immunity, resulting in stronger, more resilient crops [116-118]. Research in China has focused on developing these films since the late 1980s, leading to innovations such as the incorporation of rare earth elements and various light conversion agents into polyethylene and polyvinyl chloride films, which have demonstrated increases in crop yields and improved quality. Notable developments include the introduction of light conversion films that enhance the growth of crops like rice, tomatoes, and cucumbers by optimizing light conditions in greenhouses. Ongoing research aims to further improve the efficiency and functionality of these films, with projections indicating significant growth in the agricultural film industry by 2026 [119].
Studies demonstrate the transformative effects of integrating photoluminescent materials into greenhouse films. Modified light spectra, such as green-to-red (GtR) conversions, have significantly boosted crop yields, plant biomass, and fruit quality. For instance, sweet pepper plants exposed to GtR films exhibited enhanced photosynthesis, with higher chlorophyll fluorescence, improved photosynthetic light-response curves, and greater dry mass accumulation. These findings highlighted the role of optimized light conditions in elevating photosynthetic efficiency. Not only that, it was observed that the GtR-modified spectrum enhanced dry mass, improved photosynthetic lightresponse curves, and significantly increased chlorophyll fluorescence parameters, indicating better electron transfer and overall photosynthetic efficiency [120].
Specific applications of these films have demonstrated remarkable results. For example, -based films improved the growth and nutritional profile of Chinese flowering cabbages, increasing plant dimensions by up to and enhancing polyphenol, protein, and sugar content [65]. Similarly, Gao et al. reported that rare-earth light conversion films (RPO) enhanced the growth and
yield of sweet peppers by improving the temperature and light conditions. They also recorded better fruit quality and high nutritive value in terms of ascorbic acid (Vitamin C), soluble protein, and soluble sugar. These films increased photosynthetic activity and plant hormone levels (gibberellic acid 3, indole-3-acetic acid (IAA), and zeatin riboside), resulting in a yield improvement compared to polyolefin films [121].
Another study by Yanykin et al. demonstrated the effects of glasses coated with up-converting luminescent nanoparticles on tomato cultivation. Using nanoparticles, tomatoes exhibited a increase in total leaf area, a increase in stem length, improved chlorophyll content, and reduced recovery time for photosystem II quantum yield from three weeks to three days. These results affirm that increased red light in the growth spectrum enhances photosynthetic activity and overall plant development [57].
Beyond optimizing light conditions, these films also provide thermal regulation by converting UV light, which can accelerate surface water loss, into photosynthetically active radiation (PAR), thereby reducing heat stress and maintaining ideal growing conditions. This feature is particularly valuable in extreme climates such as those in the Middle East and Sub-Saharan Africa [42, 122-124]. Additionally, incorporating photoluminescent materials into greenhouse systems facilitates energysaving solutions, such as solar-powered lighting and irrigation. These innovations reduce reliance on artificial lighting and lower energy costs, making them essential for sustainable agriculture and future food security. PPNCs polymers can improve soil quality by fostering beneficial microbial activity and enhancing nutrient availability through their capacity to retain moisture and decrease reliance on chemical fertilizers creating a balanced soil environment that supports healthy plant growth [1,125].

Table 2. Impact of Luminescent and Light-Conversion Materials on Crop Growth, Yield, and Quality

Crop | Luminescent Material | Polymer/Film | PAR/Light Effects | Growth Effects | Quality Effects | Additional Benefits | Reference
Strawberry (Fragaria x ananassa 'Elsanta') | Fluorescent pigments (Blue, Red1, Red2, Red3) | Photoselective greenhouse films | Blue pigments increased total PAR transmission (1 – 3 %), while Red pigments lowered it. Red3 increased red: far-red ratio by 10 %. | Blue films increased fruit production by 11 %; Red3 films delayed production and reduced yield by 10 %. | Blue films produced brighter, more saturated fruits but with higher acidity (lower pH). Red films produced sweeter fruits due to lower acidity. | Blue films showed potential for enhancing fruit yield and quality, while red films negatively impacted yield. | [126]
Red romaine lettuce (Lactuca sativa) | CuInS2/ZnS quantum dots | Luminescent QD films | Converted UV/blue to red (600 and 660 nm) | Increased dry mass (13 %, 9 %) and fresh mass (11 %); larger leaf area (8 %, 13 %). | Photosynthetic efficiency 13 % | Boosts plant productivity in greenhouses on Earth and space environments. Provided | [82]
Cabbage (Brassica oleracea var. capitata) and lettuce (Lactuca sativa) | Yttrium oxysulfide doped with europium photoluminophore | Photoluminescent spunbond fabric | Converted UV to red light (610 – 640 nm); improved RL/FRL ratio. | Increased biomass by 30 – 50 %; improved water-use efficiency; reduced transpiration and stomatal conductance. | Enhanced photosynthesis, phytochrome activation, and stress resistance. | Boosts growth via spectral optimization and soil microflora interaction; increases productivity in shaded areas. | [127]
Chinese flowering cabbage (Brassica rapa) | Light-conversion agents (500 nm average diameter) | Low-density polyethylene | Enhanced red-orange light (600 - 700 nm), reduced blue (under 560 nm) and UV light | Increased plant height (24.43 %), leaf length (15.30 %), leaf width (15.60 %), leaf breadth (19.07 %) | increased soluble protein (9.09 %), polyphenol content (21.27 %), soluble sugar content (19.15 %) | improved biomass yield, chlorophyll and carotenoid content, and enhanced photosynthesis leading to better | [65]

Possibilities and challenges in sustainable use of photoluminescent nanocomposites

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The high electricity demand for running greenhouses remains a significant drawback and challenges their sustainable operation [130, 131]. Integrating polymers and photoluminescent polymer nanocomposites (PPNCs) into agriculture presents exciting possibilities for advancing sustainable farming practices because it is dependent on the use of renewable energy which decreases the cost of energy and the footprint of controlled environment farming [3]. However, this integration is not without its challenges.
The practical implementation of these photoluminescent systems is hindered by several issues. Organic fluorophores are prone to rapid burnout, while rare-earth metal-based alternatives like europium, despite their improved stability, exhibit low quantum yield [68, 126, 132]. Furthermore, integrating nanoparticles with plasmon or exciton emissions, such as cadmium-selenium and zincsulfur, into polymer matrices remains challenging due to their sensitivity to reactive oxygen species generated during operation. This implies that there is a need for continued innovation in photoconversion technologies to balance performance with sustainability in agricultural practices [68, 133, 134].
As the exploration of nanomaterial-based solutions increases concerns about biosafety and environmental impacts, especially for heavy-metal-based nanoparticles like cerium oxide and silver are rising and demand careful consideration. Issues such as nanoparticle aggregation, which reduces their effectiveness and raises toxicity risks, highlight the need for materials that are both stable and environmentally friendly. Advances in surface modifications, such as conjugation with chitosan, have shown promise; for instance, Cu -chitosan has enhanced plant growth while combating fungal pathogens. Similarly, alternatives like nanoparticles, derived from essential micronutrients, offer safer options with their ability to scavenge reactive oxygen species (ROS) and boost plant stress resistance. Prioritizing non-toxic, nutrient-based nanomaterials with high dispersibility is essential for developing sustainable nano-enabled agricultural practices [135-137].
Integrating polymers and photoluminescent polymer nanocomposites (PPNCs) in agriculture offers a promising pathway toward sustainable farming practices. A key consideration in this integration is ensuring biodegradability, allowing these materials to break down over time and reducing the risk of microplastic accumulation in soils. This approach not only helps mitigate plastic pollution but also enhances long-term soil health [9]. Plastic contamination in agricultural soils is an escalating environmental concern due to its detrimental effects on the soil ecosystem and potential risks to water resources. Several studies have quantified and analyzed the distribution and sources of macro-plastics
(MaPs) and microplastics (MiPs) in agricultural soils under diverse farming systems. Greenhouse plastic contamination studies reveal significant MaPs and MiPs presence in surface and subsurface soils, as well as groundwater. Dominant contaminants include polyethylene and polyvinyl chloride, with microplastic concentrations averaging pieces/kg in greenhouse soils and 2.3 pieces/l in groundwater. Similarly, research in North China's Quzhou County highlights variations in MaPs/MiPs across six farming systems, with cotton fields showing the highest contamination levels. The prevalence of MiPs in the soil layer underscores the impact of tillage practices and plastic film usage, with polyethylene fragments ( ) being predominant. A strong correlation exists between plastic management practices and the size and abundance of soil plastics. A comprehensive review of 120 studies from 2018 to 2022 revealed Asia as the dominant region for research on agricultural soil plastic contamination (60%) [43]. The studies emphasized mulching, sludge placement, and greenhouse abandonment as key contamination sources, and recommend density-based flotation methods like NaCl for light plastics and ZnCl for heavy plastics as efficient extraction techniques. These findings underline the necessity for sustainable plastic waste management in agriculture and further exploration of plastic fragmentation mechanisms and their effects on soil health [43-45, 138].
The cost implications of adopting these innovations present a challenge for farmers [1,125]. Balancing profitability, performance, and environmental impact can be difficult, especially when considering the substantial initial investment required for implementing these light conversion technologies. Nevertheless, these costs can lead to significant long-term benefits. Improved light conditions can result in higher yields, enhancing profitability and providing a strong return on investment. Furthermore, the use of these polymers can increase crop resilience to pests and diseases, reducing the need for chemical pesticides and fertilizers. This not only lowers operational costs but also aligns with the growing consumer demand for sustainably produced food. A thorough economic analysis should take these factors into account, weighing initial expenses against potential savings from reduced input requirements and increased marketable yields.

Future directions for advanced photoluminescent polymers in agriculture

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The use of photoluminescent polymer nanocomposites (PPNCs) in agriculture presents a promising frontier for sustainable farming practices. However, plastic contamination needs to be addressed creatively. Efforts to reduce plastic contamination are increasingly focusing on sustainable, renewable polymer nanocomposites. Biodegradable polymers like polylactic acid, polyhydroxyalkanoates, and polycaprolactone, when reinforced with nanoscale fillers such as cellulose nanocrystals, carbon nanostructures, and nanohydroxyapatite, offer promising solutions by maintaining strength, stability, and functionality while breaking down into environmentally safe byproducts [139-143]. Studies like those by Gouda et al. [144], Zhang et al. [145], and Singh et al. [146] highlight the potential of these composites, showing their capability in various applications, from smart windows and photoluminescent films to anti-counterfeiting technologies. Though not directly related to agricultural films, these innovations underscore the versatility of renewable polymers and their potential for reducing plastic contamination without sacrificing performance. However, current agricultural light conversion films, often based on rare earth elements like europium ions ( ), face significant challenges, including poor biodegradability and performance degradation under outdoor exposure [1, 147]. Future efforts should focus on developing eco-friendly alternatives that address these environmental concerns and optimize light conversion properties for agricultural applications, building on the insights gained from sustainable polymer nanocomposites.
PPNCs also hold the potential for precision farming through crop-specific designs. Looking to the future, the development of advanced photoluminescent polymers tailored to specific crop needs could revolutionize agricultural practices. By engineering materials to optimize specific spectral output, these polymers can significantly enhance photosynthetic efficiency, particularly for crops grown in shaded or suboptimal lighting conditions. This targeted approach will address yield challenges and mitigate the effects of environmental stressors. Additionally, these materials could contribute to soil conditioning by improving moisture retention and nutrient availability, creating a more favorable
environment for plant root systems. Such advancements in soil amendment could further amplify the impact of PPNCs on agricultural productivity.
Nano-photoluminescent particles can be designed to dynamically adapt to fluctuating light conditions, ensuring optimal illumination throughout a crop's growth cycle. Pairing these materials with smart sensors capable of monitoring soil moisture, nutrient levels, and plant health could further refine resource allocation, reducing environmental impact and enhancing sustainability. Also, the adoption of these advanced materials requires a thorough evaluation of their environmental footprint. Comprehensive life cycle analyses will be crucial to assessing their sustainability from production through degradation. A critical research priority is improving their biodegradability by exploring biopolymer alternatives derived from renewable resources. Such efforts would ensure minimal disruption to soil ecosystems while enriching soil health through environmentally friendly degradation processes.
Pests and diseases remain persistent threats to global agriculture, and PPNCs could play a pivotal role in early detection and mitigation. Their fluorescence signaling capabilities can be adapted to monitor subtle changes in plant physiology, such as nutrient deficiencies or early-stage fungal infections, enabling timely interventions before visible symptoms arise. Furthermore, designing PPNCs that emit specific wavelengths to deter pests while optimizing light for photosynthesis could offer an ecofriendly alternative to chemical pesticides, fostering healthier ecosystems and reducing reliance on synthetic inputs.
The multifunctionality of PPNCs could extend beyond traditional applications, enabling their integration into IoT-enabled smart farming systems. Fluorescent probes embedded in PPNCs could facilitate real-time monitoring and site-specific management of crops through drones or autonomous systems. This technology would allow farmers to make precise adjustments, ensuring optimal conditions for each crop and driving efficiency in resource use. Innovative applications of photoluminescent polymers could also address challenges beyond photosynthetic optimization. For example, incorporating these materials into post-harvest packaging solutions could regulate light exposure, preserving freshness and reducing spoilage during storage and transport.
While the possibilities for PPNCs in agriculture are vast, their successful implementation hinges on addressing cost-related barriers. Ensuring that these technologies are affordable and accessible to farmers is critical for widespread adoption. Balancing the initial investment with long-term benefits, such as reduced reliance on chemical inputs, higher yields, and improved crop resilience, will be essential to drive their integration into mainstream agricultural practices.
In summary, photoluminescent polymers and their nanocomposite counterparts represent a transformative opportunity for modern agriculture that can provide multifunctional applications as shown in Fig. 4.

Fig. 4. Expanded applications of photoluminescent polymer nanocomposites

Fig. 4. Expanded applications of photoluminescent polymer nanocomposites

Conclusion

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Light plays an important role in photosynthesis, yet its natural variability presents challenges for controlled-environment farming. Photoluminescent polymer nanocomposites (PPNCs) offer an innovative path toward more sustainable and efficient agricultural practices. By converting lessutilized wavelengths, such as ultraviolet and blue light, into plant-friendly spectra, PPNCs enhance the availability of photosynthetically active radiation (PAR). This not only increases photosynthetic efficiency but also supports healthier crops with higher yields, reducing the need for chemical fertilizers and pesticides. The effectiveness of PPNCs relies on both the quality of the photoluminescent materials and the robustness of the polymer matrix. Fabricated using methods like in situ polymerization, solution mixing, and melt blending, these materials have shown notable improvements in plant growth metrics, including biomass production, fruit yield, and crop quality. By enabling resource-efficient and customizable farming solutions, PPNCs are paving the way for precision agriculture. While the potential of PPNCs is immense, further investigation is necessary to create biodegradable polymer matrices and to assess the long-term effects of luminescent materials on soil and plant health. By harmonizing sustainability with productivity, PPNCs represent a promising advancement in agriculture, fostering a resilient future for both farmers and the environment.

Acknowledgments

The original version of this paper is available on https://www.scientific.net/EC.9.61.pdf

Ayodunmomi Esther Olowofoyeku gratefully acknowledges the African Union and the Pan African University Life and Earth Sciences Institute for providing a Ph.D. scholarship, which supported this review as part of her doctoral research.

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The original version of this eBook is available on https://www.scientific.net/book/engineering-chemistry-vol-9/978-3-0364-1758-5

Engineering Chemistry, ISSN: 2813-6535, Vol. 9, pp 85-92

doi: 10.4028/p-Z9rTBB

© 2025 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

Submitted:
2024-12-28

Revised:
2025-02-19

Accepted:
2025-02-25

Online:
2025-03-10

Adsorptive Removal of Methylene Blue (MB) from Wastewater: A Comparative Modeling Study Utilizing RSM, ANN, and ANFIS Model

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

Ephraim Igberase and Innocentia Mkhize

Durban University of Technology, Department of Chemical Engineering, Steve Biko Campus, Durban, South Africa

a ephraimi@dut.ac.za, innocentiaM2@dut.ac.za

Keywords: Response surface; Adsorption; Removal efficiency; Neural network; Chitosan

Abstract

The exceptional properties of chitosan and its effective technique of adsorbing contaminants even to near-zero concentrations are the primary reasons for special attention. The adsorption studies analyzed various elements, such as pH , concentration, reaction time, and adsorbent dose. The study used these factors as input data, with the output data concentrating on MB removal efficiency. For prediction and optimization, MB adsorption used response surface methodology/central composite design (RSM-CCD), artificial neural network (ANN), and adaptive neuron-fuzzy inference system (ANFIS) models. In developing the ANN and ANFIS models, of the data was allocated for training, 15% for validation, and 15% for testing. Based on the RSM-CCD findings, the optimum value for the considered parameters was obtained at pH 7 , contact time of 55 min , 6.0 grams of adsorbent, and adsorbate concentration. However, an ideally trained neural network is described using training, testing, and validation phases, and the values at these phases were found to be , and 1 , respectively. The statistical results based on comparative modeling indicated that the ANFIS approach outperformed the RSM and ANN model approaches.

Introduction

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The release of dyes into water bodies can have adverse effects on natural creatures and ecosystems. Also, the rapid growth of industrial practices such as leather, food, and paper industries are the primary sources of dyes [1-5]. These dyes, such as cationic dye, are non-biodegradable substances that have a negative impact on humans, such as cancer, Acrimony, skin irritation, allergies, heart attack, and mutations [6]. Because of these hazardous effects, there is an increasing need for resourceful contaminant elimination techniques. Ion exchange, chemical precipitation, adsorption, electrolysis, Filtration, and sedimentation are some methods that have been applied to maximize the number of pollutants in wastewater. Adsorption is among the most effective techniques because it is inexpensive and environmentally friendly process for removing dyes [7]. Various materials such as chitosan, zeolites, and many more are used as active adsorbents. Chitosan is considered an ideal adsorbent for dye removal since it is environmentally friendly. However, chitosan is said to be soluble in acid solution, limiting its use in adsorption studies; therefore, cross-linking using cross-linkers such as glutaraldehyde is required to make the substance insoluble at low pH . Several studies, including [8,9], have suggested that cross-linking lowers chitosan's adsorption ability. This observation may be because some amine groups are used up during cross-linking reactions. As a result, grafting some functionality onto the cross-linked material becomes vital. Grafting chitosan allows for the formation of functional derivatives by covalently attaching a molecule to the backbone of chitosan. This technique is frequently used to improve the binding qualities of chitosan.
This research investigated how RSM, ANN, and ANFIS models explain the relationship and essential dynamics of the process variables. A new contribution to adsorption studies is a comparative assessment of these techniques for forecasting MB adsorption using a chitosan derivative in synthetic wastewater. This study offers a clear road map for choosing suitable models depending on the adsorption system complexity, availability of data, and the intended agreement between interpretability and accuracy by highlighting the result of the discrepancy. This knowledge closes the gap between creating theoretical models and real-world implementation in environmental and
industrial adsorption research. ANFIS balances accuracy and interpretability. RSM is best for simplicity, while ANN is accurate for pure prediction. The decision is based on the problem's complexity and the requirement for interpretability. This study also provides the groundwork for using hybrid intelligence systems in further adsorption research by proving that ANFIS is a better option than conventional RSM and ANN. This could result from improved predicted accuracy in practical applications, lower experimental costs, and more effective system designs. Although [10] and [11] showed that ANN is more accurate than RSM in predicting adsorption efficiency, they also pointed out that overfitting was a problem when training limited datasets. On the other hand, this study applied a regularized ANN model with a larger dataset, which led to a considerable decrease in overfitting and improved prediction performance. This work also found that ANFIS is the most reliable model by surpassing both RSM and ANN in capturing nonlinear dynamics, a result that has never been documented in adsorption studies of this magnitude. These developments demonstrate how hybrid machine-learning models can improve the design of adsorption systems. The study's results could facilitate the development and refinement of adequate water treatment systems and the choice of the optimal modeling method for adsorption processes and also contribute significantly to the emerging field of predictive modeling in adsorption studies by explaining the comparative advantages of RSM, ANN, and ANFIS.

Material and Methods

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Analytical-grade chemicals from Sigma-Aldrich, South Africa, were used in this study. These chemicals include Sodium hydroxide, ethanol, hydrochloric acid, acetic acid, glutaraldehyde, MB, and aniline, with a purity level of meter was used to maintain the pH level of the solution and was obtained from China. To produce the stock solution for MB, 1 g of MB was dissolved in 1L of distilled water to achieve the stock solution. The stock solution was again diluted to different initial concentrations of Methyl-Blue. Chitosan (MW=2.0 ) was obtained from Tokyo, Japan. Chitosan solution was prepared by diffusing 30g of chitosan powder in 1L of 5.0% (V/V) acetic acid. The prepared solution was pipetted into 1 M sodium hydroxide solution to create chitosan gel beads. The beads were transferred into a beaker containing 2.5% glutaraldehyde solution and agitated for 2 hours for a cross-linking reaction. The cross-linked beads were grafted with aniline using a microwave oven. The functional groups that are available for binding were shown using FTIR. The infrared spectra of the beads were done with Shimadzu FTIR model 8300 Kyoto, Japan. The spectra were estimated between . In the adsorption study, a BIS incubator shaker from China was used to stir the beakers at an observed rotating speed of 250 RPM.

Results and Discussion

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

FTIR Analysis

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

Infrared spectroscopy was utilized to demonstrate comparable differences between chitosan ( XB ), cross-linked chitosan ( XXB ), and grafted cross-linked chitosan ( GXXB ) in Figure 1. The broadband shows amine and hydroxyl groups at wavelengths , and , and GXXB, respectively. The shift in the band might be due to exchangeable protons during the modification process [12]. XB and XXB demonstrated the presence of oxygenated functional groups from alcohols and aliphatic ethers at wavelengths of . It suggests that specific properties of the XB material were maintained even after modification. However, the wavelength changed to 1020 when the cross-linked beads were grated, which also provided evidence of a successful modification process.

Fig. 1. FTIR of pattern , and GXXB respectively.

Fig. 1. FTIR of pattern , and GXXB respectively.

Response Surface Methodology Analysis

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Table 1 presents the experimental design/matrix and the related response for binding MB onto GXXB using RSM/CCD. This table illustrates how various parameters impact the outcome. Using analysis of variance (ANOVA), the effect of solution pH , MB concentration, GXXB dose, and contact time on MB removal efficiency was determined. Eq. 1 displays the quadratic polynomial equation. A correlation coefficient of 0.999 was obtained for both experimental and predicted values.

Table 1. Design matrix showing the input variables and response.

STD
Factor 1
A: pH
Factor 2
B: Adsorbent
dose (g)
Factor 3
C: Initial
concentration
(mg/L)
Factor 4
D: Reaction time
(Min)
Response: Removal
efficiency of MB
(%)

1
10.00
2.00
200.00
100.00
49.63

2
10.00
2.00
50.00
100.00
72.07

3
10.00
10.00
200.00
10.00
59.63

4
4.00
10.00
50.00
100.00
85.07

5
10.00
10.00
50.00
10.00
73.07

6
4.00
2.00
200.00
10.00
35.63

7
4.00
10.00
200.00
100.00
78.63

8
4.00
2.00
125.00
10.00
59.07

9
4.00
6.00
125.00
55.00
91.61

10
10.00
6.00
125.00
55.00
80.61

11
7.00
6.00
125.00
10.00
88.61

12
7.00
6.00
50.00
100.00
90.79

13
7.00
6.00
50.00
55.00
96.41

14
7.00
6.00
125.00
55.00
80.48

15
7.00
2.00
125.00
55.00
75.61

16
7.00
10.00
125.00
55.00
74.61

17
7.00
6.00
125.00
55.00
93.47

18
7.00
6.00
125.00
55.00
92.47

19
7.00
6.00
125.00
55.00
92.47

20
7.00
6.00
125.00
55.00
92.47

21
7.00
6.00
125.00
55.00
92.47

Three Dimensional (3D) RSM plots

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

The results obtained from the 3D RSM-CCD analysis are shown in Figure . The graph demonstrates the correlation between two factors and their effect on the removal efficiency of MB when other parameters are kept constant. Figure shows that the optimum removal efficiency of MB on GXXB occurred at pH 7, illustrating the importance of pH on the binding of pollutants. The results of [5] indicate that pH is crucial to adsorption processes because it can significantly impact the ionization of chemically reactive sites on the adsorbent's surface. Figure 2 (a and d) illustrates that the adsorbent dosage is an essential factor influencing the binding of pollutants. However, raising the mass of GXXB employed in adsorption studies can decrease the charge of the outer layer of cells, resulting in the blockage of binding sites needed for MB adsorption. Previous studies have documented this behavior [9,10]. The influence of reaction time on pollutant binding is depicted in Figure and d . The reaction time was varied from 10 to 100 min , and it was shown that a contact time of 55 minutes was sufficient for maximal MB removal. This is due to the availability of wellaligned binding sites for the adsorption of MB. Figure and d shows how the initial concentration affects the removal efficiency of MB . However, at lower initial concentrations of MB , the process of adsorption is not affected by the starting concentration. This is due to the small quantity of GXXB compared to the large proportion of pollutant cations. A higher initial concentration of MB increases the amount of MB available, resulting in improved percentage removal for a fixed mass of GXXB.

Fig. 2. The 3D plot showing the response against two variables for MB adsorption.

Fig. 2. The 3D plot showing the response against two variables for MB adsorption.

ANN result

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

This study used the ANN approach with the ANN Toolbox V4.0 in MATLAB 2019. The LevenbergMarquardt (LM) coding process conditions changed as the network parameters were adjusted. Figure 3 shows the ANN architecture, while Figure 4 shows how the network correlated with the training, testing, and validation data. The correlation coefficients were respectively found to be , and 0.91416 for training, testing, validation, and overall data. The predicted results from the model
correlate with the experimental data. The ANN model has great prediction ability, as shown by the overall correlation coefficient, and is suited for accurately predicting data.

Fig. 3. The ANN architecture and LM algorithm in predicting removal efficiency of MB by GXXB.

Fig. 3. The ANN architecture and LM algorithm in predicting removal efficiency of MB by GXXB.

Fig. 4. The network response regression analysis results between the ANN output and the corresponding target.

Fig. 4. The network response regression analysis results between the ANN output and the corresponding target.

ANFIS modelling

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

A fuzzy inference system approach was used to create the four-layered neural network [13]. To generate the fuzzy network, each parameter in the input layer was given three membership functions (MFs), as seen in Figure 5. The high correlation value of 0.999 obtained from the ANFIS model suggests that the fuzzy inference system network can accurately forecast the removal efficiency of MB from the solution using GXXB. The primary benefit of ANFIS is that it lowers errors by adding self-learning capabilities to fuzzy controllers [13]. The fuzzy network demonstrated an error size of 0.005 after seven training epochs, indicating that it is suitable for modeling the removal of MB. Furthermore, the low MSE value showed that there was no over-fitting during the training process and that the ANFIS model could accurately determine the binding of MB by GXXB. One of the strengths of ANFIS in adsorption studies is its skill in dealing with numerical variable input. As a result, it serves as a valuable tool for modeling systems facing data uncertainties or challenges in measuring some input variables. Figure 5 describes a hierarchical structure of fuzzy inference systems.

Fig. 5. ANFIS architecture describing a four-layer input neural network using a fuzzy inference system approach.

Fig. 5. ANFIS architecture describing a four-layer input neural network using a fuzzy inference system approach.

Statistical prediction of the models

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

Table 2 displays the parameters and data utilized in the training procedure based on the ANFIS and ANN models. The analysis of predicted and actual removal rates illustrates that these models can effectively predict data from the experiment. To correlate the three models, statistical analysis was utilized to investigate the significance and distribution of errors in the expected removal efficiency. The outcomes of the statistical analysis are displayed in Table 3. However, the table compares the error functions obtained by the ANN, ANFIS, and RSM models. ANFIS outperformed ANN and RSM by achieving a lower error function. Consequently, the values for the three models exhibit a high degree of similarity, describing a good correlation between the anticipated and actual data. Consequently, the quality and unpredictability of wastewater data present several obstacles to the practical application of RSM, ANN, and ANFIS in wastewater treatment, which may compromise the accuracy and dependability of the models. Complex nonlinear interactions are complicated for RSM to capture. While ANN works well for these systems, it needs large, high-quality datasets and can overfit or generalize poorly to other plants. Even though ANFIS is more resilient to noise and uncertainty, configuring it for large-scale systems can be time-consuming and computationally demanding. The model's applicability is further limited by variations in pollutant kinds, treatment technologies, and operating conditions, which further restrict scalability and adaptability. Furthermore, real-time adaptation and control require computational resources that might not be easily accessible, and plant operators may find it challenging to understand and implement ANN and ANFIS without specialized knowledge. Integrating these models into realistic wastewater treatment processes is made more difficult by operational and financial limitations, such as tight budgets and a lack of technical expertise.
However, regarding computational demand and data requirements, RSM is computationally efficient, but it requires well-designed experimental datasets and has difficulty dealing with nonlinear systems. ANN can model complicated relationships but requires vast, high-quality datasets and is computationally expensive, particularly for large-scale processes. Furthermore, significant resources are needed for retraining and fine-tuning. ANFIS compromises interpretability and accuracy, but as inputs and fuzzy rules increase, it becomes resource-intensive and depends on structured datasets for efficient rule building. These restrictions highlight the importance of guaranteeing sufficient processing power and data quality for real-world applications.

Table 2. Back-propagation data employed in the ANFIS and ANN models

ANFIS model |  | ANN model |
Characteristic | Value | Characteristic | Results
Fuzzy rules | 34 | Epochs number | 30
Checking data | 4 | Learning rule | Levenberg
Testing data | 4 | Output nodes | 1
Training data | 18 | Input nodes | 4
Number of parameters | 26 | Number of neurons | 10
Linear parameters | 208 | Error | 0
Non-linear parameters | 314 | Mu | 10e-5
Number of nodes | 320 |  |

Table 3. ANN, ANFIS, and RSM statistical metrics for non-linear error function fit.

Statistical function | ANN | ANFIS | RSM
MPSD | 0.0061 | 0.0082 | 0.0693
χ² | 0.0019 | 0.0026 | 0.0432
RMSE | 0.0032 | 0.0043 | 0.0966
MSE | 0.0030 | 0.0021 | 0.0665
SSE | 0.0022 | 0.0044 | 0.0322
ARE | 0.0058 | 0.0065 | 0.0984

Conclusion

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

This study presents an efficient prediction model for MB adsorption utilizing GXXB as an adsorbent. The L-M algorithm (4-10-1) with the ANN approach produced a low MSE. ANFIS, ANN, and RSM were shown to be equivalent and dependable in MB uptake prediction. Five statistical functions showed that the ANFIS model is the most reliable and produces the best outcome, followed by the ANN and RSM models. A three-layer back-propagation neural network was developed to describe MB binding in a synthetic mixture. The outcomes of these models demonstrated that they could adequately predict and reproduce the behavior of the process. The adsorption of MB was represented by equations that were developed using experimental data sets. This study can be scaled up by focusing on the bulk production of cost-effective, long-lasting, and reusable GXXB. Also, pilot-scale testing and process optimization with RSM, ANN, and ANFIS can improve dye removal efficiency in real-world conditions. Continuous flow systems should be adopted, and dynamic control should be automated with predictive models. Finally, ensure economic viability, environmental sustainability, and regulatory compliance for wastewater discharge.

Acknowledgments

The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

The author wishes to thank the Durban University of Technology's Department of Chemical Engineering for providing continuous working facilities.

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The original version of this paper is available on https://www.scientific.net/EC.9.85.pdf

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Keywords Index

A

Aisi Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Amphoteric Surfactant Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

B

Boron-doped Diamond Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

C

Composites Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Controlled Environment Agriculture Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Corrosion Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Critical Micelle Concentration (cmc) Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Cyclic Voltammetry Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

G

Green Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

I

Inhibitor Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Inhibitors Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan

L

Light Conversion Polymers Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Luminescent Materials Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

P

Peel Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan

Photoluminescent Polymers Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Pyrimidinium Betaine Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Q

Quinine Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

R

Reduction Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

Response Surface; Adsorption; Removal Efficiency; Neural Network; Chitosan Adsorptive Removal of Methylene Blue (MB) from Wastewater: A Comparative Modeling Study Utilizing RSM, ANN, and ANFIS Model

S

Salacca Zalacca Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Seed Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Sensor Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Silver Nanoparticle; Sodium Tripolyphosphate; Glucose; Characterization; Electrochemical Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Surface Activity Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Synthesis Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Authors Index

A

Adekanmi, D. Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Amina, M. Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Aremu, A. Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Awali, J. Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

B

Badmus, B. Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Bamgbose, T. Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Bamigbade, A. Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

D

Dare, E. Direct Electron Transfer and Electro-Catalytic Activity of Non-Enzymatic Glucose Biosensor Based on Silver Nanoparticle (AgNPS) Stabilized with Sodium Tripolyphosphate (NaTPP) Cross-Linked Chitosan

Darmawan, D. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Dewanto, H. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan

E

Einaga, Y. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

F

Faluyi, E. Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Fatiha, M. Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

H

Habib, I. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

Handayani, M. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

I

Igberase, E. Adsorptive Removal of Methylene Blue (MB) from Wastewater: A Comparative Modeling Study Utilizing RSM, ANN, and ANFIS Model

Ismail, A. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

K

Kahina, H. Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium betaines

Kurniawan, F. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

L

Lubis, M. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan

M

Mkhize, I. Adsorptive Removal of Methylene Blue (MB) from Wastewater: A Comparative Modeling Study Utilizing RSM, ANN, and ANFIS Model

Mohd, Y. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

O

Ogata, G. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

Olorunnisola, A. Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

Olowofoyeku, A. Photoluminescent Polymer Nanocomposites: Innovative Materials for Enhanced Light Management and Crop Yield Optimization

P

Purniawan, A. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

R

Rifani, M. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

T

Tominaga, M. Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel

Triana, Y. Promising Organic Inhibitor of Salak (Salacca zalacca) Peel Extract on AISI 1040Daffa Irsyad Darmawan; Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel; Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

U

Umanigrum, D. Detection of Quinine in Phospate Buffered 0,1 M by Using Boron-Doped Diamond Electrodes

Y

Yusariarta, A. Performance of Salak (Salacca zalacca) Seed Extract to GreenCorrosion Inhibitor on AISI 1040 Steel