Papers by Keyword: Zinc Oxide

Abstract: Industrialization has led to widespread aquatic contamination, with dyes being among the most prominent pollutants found in various water bodies. Major contributors to dye pollution include the textile, printing, leather, cosmetics, and chemical industries, with the textile industry alone being responsible for approximately 13% of the dyes released into aquatic environments. This study focuses on comparing the photocatalytic degradation performance of synthesized catalysts prepared in the presence of biopolymers. Pullulan was selected as a capping agent to aid the synthesis process and promote the formation of nanosized catalysts. Three types of catalysts, namely copper oxide, zinc oxide, and a composite of both, were synthesized, and their performance was evaluated through the photocatalytic degradation of methylene blue. Among the three, zinc oxide demonstrated the highest degradation efficiency (99%), followed by the composite (27%), while copper oxide exhibited negligible photocatalytic activity (14%). Further optimization of the best-performing catalyst (zinc oxide) was conducted by varying parameters such as catalyst dosage (0.05-0.15g) and solution pH (5-9). The results showed that zinc oxide achieved the highest degradation under acidic conditions (pH 5) with a dosage of 0.15 g, requiring only 70 minutes to reach nearly 100% degradation. Overall, this study provides valuable insights into the influence of catalyst type on the photocatalytic degradation of methylene blue.

Abstract: Adoption of desalination technologies to produce fresh water in developing countries remains underutilized due to the substantial energy consumption, high operational costs, and membrane fouling associated with conventional methods. Microbial desalination cells (MDCs) have emerged as a promising alternative, offering simultaneous wastewater treatment, bioelectricity generation, and salt removal. This study aimed to evaluate the bio-templating of copper and zinc oxide nanoparticles on waste-derived eggshell membranes (CZ-ESM) and subsequently incorporated into ion exchange membranes (IEMs) for MDC applications. Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS) confirmed the presence of calcinated CZ-ESM in the IEMs. The modified and control IEMs were compared based on water uptake, mechanical strength, biofouling resistance, and salt removal. Incorporation of calcinated CZ-ESM nanocomposites enhanced membrane hydrophilicity, reflected in increased water uptake while also exhibiting reduced microbial colonization, thereby improving anti-fouling performance. However, the addition of calcinated CZ-ESM nanocomposites resulted in decreased tensile strength due to nanocomposite aggregation and heterogeneous resin distribution. Modification of the IEMs showed statistically the same salt removal as that of the unmodified counterpart. These findings demonstrate the use of CZ-ESM nanocomposites as fillers for MDC membranes, highlighting their ability to enhance hydrophilicity and antifouling properties, but improvements in the mechanical properties and salt removal must be further investigated to address practical limitations in the MDC application.

Abstract: An embedded system-based spin coating machine has been developed to grow thin films. Pure zinc oxide (ZnO) and magnesium-doped zinc oxide (ZnO: Mg) thin films with different doped samples have been prepared using the spin coating technique for LPG gas sensing application. The spin coating machine is fully controlled by a PIC microcontroller (PIC16f877A), which can drive a driver circuit to drive a spinning motor, and ZnO: Mg thin films are deposited using this machine. XRD results indicated that the movie has a hexagonal wurtzite structure with a preferred orientation, and the crystallite size increases with the increasing doping concentration of Mg. The surface morphology investigation shows that grains are irregular in shape, and doping concentrations do not influence the surface morphology. From the TEM image, particle sizes observed ranged between 23 and 28 nm, with an average value of ~25.8 nm. The maximum visible average transmittance was 96% for an optimum Mg doping concentration of 10 wt% %. The investigated DC electrical conductivity of Mg-doped ZnO thin films shows enhanced electrical conductivity compared to pure ZnO, and the AC conductivity is decreased with increasing Mg doping concentrations from 5 to 10 wt%. The operation and sensing mechanism of Pure ZnO and ZnO: Mg thin films behind their impressive results has been studied in depth.

Abstract: Pure and silver-doped zinc oxide (ZnO) nanoparticles were synthesized via phyto-mediation using Stachytarpheta jamaicensis leaf extract to develop an eco-friendly method for synthesizing nanoparticles with enhanced properties. Zinc nitrate and silver nitrate were employed as precursors for ZnO and Ag-doped ZnO nanoparticles, respectively. The synthesized nanoparticles were characterized using Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy (SEM-EDS) to investigate their optical and morphological properties. Results revealed that the absorption peaks of the synthesized nanoparticles confirmed the formation of nanoparticles, with Ag doping causing a red shift in the absorption spectrum. SEM images indicated a spherical morphology, with slight agglomeration in the doped samples. Doping with silver enhanced the optical properties, which could have potential applications in catalysis, sensing, and biomedical fields. Furthermore, the nanoparticle extracts were subjected to antimicrobial test against two bacterial strains (Escherichia coli and Staphylococcus aureus) using a modified disk diffusion method and compared with the antibacterial effect with the standard antibacterial drug, Ampicillin. Ampicillin only showed antibacterial activity against S. aureus and had no antibacterial effect on E. Coli. Result of this study showed that the 5% and 10% Ag-doped ZnO NPs showed strong antibacterial activity against both gram-positive (S. aureus) and gram-negative (E. coli) bacterial strains.

Abstract: Carboxylic (COOH) functionalized zinc oxide and iron oxide (COOH-ZnO@Fe₃O₄) composites were used in this study to modify polyamide thin film composite membranes. The resultant membranes exhibit improved water permeability, greater antifouling qualities, robust stability for repeated usage, and enhanced rejection of Pb²⁺ metal ions compared to the unmodified membrane. In contrast to the unmodified PA-TFC membrane, which had an 82.36±0.01% Pb²⁺ removal efficiency, a contact angle of 82.36°±0.01, a flux recovery ratio of 33.6%, and a water permeation flux of 3.3 L·m⁻²·h⁻¹, the membrane containing 1.5% of the COOH-ZnOFe₃O₄ composite, for instance, achieved a 97.6±0.35% Pb²⁺ removal efficiency, a lower contact angle of 58°±1.86, a higher flux recovery ratio of 86.3%, and a higher water permeation flux of 10.23 L·m⁻²·h⁻¹. Additionally, by combining ZnO, Fe₃O₄ nanoparticles, and COOH groups from sodium polyacrylate as additives to the PA layer, the modified membranes demonstrated improved performance relative to the other membranes.

Abstract: This work demonstrates the successful preparation of two types of photocatalytically active nanostructured materials from an industrial waste product – Sal Ammonia Skimming – using hydrochloric acid as a leaching medium. The whole production process was developed to prepare valuable ZnO nanomaterials in both fibrous and powdered forms. This involved a sequence of hydrometallurgical processing, needle-less electrospinning, and conventional calcination of recycled environmentally polluting industrial waste. The morphologies and phase composition of the resulting ZnO powder and ZnO fibers were analyzed using SEM, EDS, and XRD analyses. The impact of the morphology of the prepared nanomaterials on the photocatalytic efficiency of the ZnO-based photocatalyst – powder versus ZnO nanofibers – was evaluated through decolorization experiments of the commonly used methylene blue dye in batch mode. Methylene blue was chosen as a model substance for toxic industrial pollutants. A 25 W UVA lamp with an emission maximum at 365 nm was used as a light source. Removal efficiencies were carefully tested and compared for different nanomaterial morphologies and preparation conditions. The most photocatalytically active ZnO-based nanomaterial was the electrospun nanofibrous one calcined at 600 °C for 1 h. This material achieved 100 % removal of a 10⁻⁵ mol/L methylene blue dye from the solution within 700 minutes at an increased catalyst-to-dye ratio of 500 mg/50 ml. Based on the obtained results, it can be stated that the prepared materials exhibit high photocatalytic activity under UV light irradiation and have a potential for photocatalytic water remediation applications.

Abstract: This research investigated the impact of Ag content supported on ZnO catalysts regarding the oxidation activity of DPM. The catalyst was synthesised through the doping of varying Ag concentrations on ZnO (e.g., 2, 4, 8, and 16 wt%) employing the incipient wetness impregnation technique. Characterisation of the synthesised catalyst was conducted utilising XRD, SEM, TEM, and H₂-TPR. The evaluation of oxidation activity and stability was performed through TGA. The characterisation findings substantiated the successful integration of Ag onto ZnO across all experimental conditions investigated. H₂-TPR profiles revealed two distinct regions of H₂ consumption: 1) at 200-400 °C, and 2) at 400-700 °C. These regions were attributed to the reduction of Ag₂O to Ag⁰ and the liberation of lattice oxygen from ZnO, respectively. An increase in Ag concentrations resulted in enhanced reduction reactions within the temperature spectrum of 400 to 700 °C, demonstrating a favourable trend towards improved reaction efficiency. The oxidation performance of DPM was markedly augmented by the Ag content, particularly at 16 wt%. Stability assessments indicated a consistent capability in facilitating DPM oxidation across five cycles. The concentration of oxygen exhibited a significant influence on the oxidation activity of DPM.

Abstract: Zinc oxide is the most widely used nanomaterial in nanotechnology due to its outstanding properties and characterizations. Enormous attention has arisen due to its unique physical properties consists of a wide energy band gap of 3.37 eV at ambient temperature and large binding energy of 60 meV, which give development to an extensive range of potential applications in many areas such as electronics, solar cells, and biological applications. The size and shape of nanoparticles are significant to ensure the process becomes faster, cheaper and more efficient compared with traditional methods. By having more active area of nanoparticles, the biological and chemical process become more effectives. The biological activity of ZnO Nanoparticles was investigated through the antibacterial activity, anti-microbial activity, as anticancer and antioxidant material. The method used to prepare the ZnO Nanoparticles also take an important part which is to reduce the by-product formation when applied in wastewater treatment. This article summarizes different preparation methods of ZnO Nanoparticles and its application uses. The ZnO nanoparticles can be used the various applications, for example for the antibacterial, anti-cancer, anti-microbial, antioxidant and for wastewater treatment applications.

Abstract: ZnO thin films were deposited on borosilicate glass substrates by confocal radio frequency (RF) magnetron sputtering and subsequently annealed in air at 300 °C and 500 °C for 60 min. The influence of thermal treatment on the structural, morphological, optical, and electrical properties was systematically investigated. X-ray diffraction (XRD) confirmed the formation of a hexagonal wurtzite phase with a pronounced (002) preferential orientation. Rietveld refinement analysis revealed that annealing led to a decrease in the lattice parameter c from 5.344 Å to 5.220 Å, an increase in crystallite size from 9.3 nm to 34.1 nm, and a reduction in microstrain from 0.0265 to 0.0027. Raman spectroscopy exhibited a sharper E₂^high mode at 438 cm^-1 and a suppressed defect-related A₁(LO) mode (583 cm^-1), evidencing enhanced crystallinity and defect passivation. Scanning electron microscopy (SEM) observations revealed grain coalescence and densification with increasing annealing temperature. The average optical transmittance improved from 70.8% to 82.2%, accompanied by a slight widening of the optical band gap from 3.22 eV to 3.27 eV. Hall measurements indicated a marked decrease in resistivity from 2.7 × 10^-2 Ω·cm to 5 × 10^-3 Ω·cm, yielding a maximum figure of merit of 1.68 × 10^-3 Ω^-1 at 500 °C. Overall, post-deposition annealing is shown to significantly enhance crystallinity, reduce structural defects, and improve the optoelectronic performance of ZnO thin films, confirming their suitability for transparent electronics and photovoltaic applications.

Abstract: Pyrolytic technology was developed to grow Zn-based nano- and microstructures. It was based on the application of a mixture of ammonium chloride, Zn and ZnO powders as source materials. Two temperature profiles were used for the synthesis. In the first and second growth processes, the maximum substrate temperatures of 250 and 410°C were reached, respectively. The granular layer of micrometer range ZnO crystals was produced in the first process. By depleting the source with NH₄Cl, the Zn polyhedra, and layered spheres were produced within 50–65 min in the second process. By increasing the NH₄Cl content in the source to 0.9 g, the Zn/ZnO core–shell spheres were synthesized. The further increase of process duration led to the out-diffusion of Zn from the core, its oxidation, and the formation of a thick, dense ZnO spherical shell. Even further annealing in residual gases caused the increase of the Zn vapor pressure inside the shell. As a result, at a certain Zn vapor pressure, the shell bursts, causing the formation of a hollow ZnO microsphere.