Papers by Keyword: Zinc Oxide

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.

Abstract: Zinc oxide (ZnO) is a common photocatalyst for dye degradation, but its efficiency is limited by surface properties, photocorrosion, and pH sensitivity. This study functionalized ZnO with 2-aminophenol (ZnO-AP) to enhance dye adsorption and stability under varying pH. FTIR, XRD, and UV-Vis confirmed successful synthesis, with ZnO-AP showing a reduced band gap for improved visible light absorption. Photodegradation tests using Brilliant Blue G (BBG) revealed that ZnO-AP has the highest efficiency (36.17%) at pH 4, driven by strong electrostatic interactions. Performance decreased at pH 7 and 11 due to reduced dye adsorption, especially at basic pH with electrostatic repulsion. Functionalization also protected ZnO against photocorrosion, improving stability in acidic conditions. These results highlight 2-AP functionalization as a promising strategy to enhance the photocatalytic performance of ZnO across pH ranges.

Abstract: Zinc oxide (ZnO) thin films have attracted considerable attention due to their versatile applications in optoelectronic devices, transparent electrodes and surface acoustic wave devices. In particular, their photocatalytic properties make them interesting for wastewater treatment. In this study, we investigate the influence of substrate and film thickness on the structure and photocatalytic activity of ZnO thin films prepared by atomic layer deposition (ALD). The photocatalytic activity of ZnO films on Si, glass, Al, and porous Al substrates was investigated under UV irradiation, focusing on the decomposition of methylene blue (MB) as a model for an organic pollutant. To understand the mechanism of photodegradation, detailed information on the morphology of the nanostructured ZnO surface and the surface chemistry was obtained by scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). We have shown that the photocatalytic activity depends on ZnO film thickness and that it reaches saturation at a film thickness of about 20 nm, independent of the substrate. Furthermore, we compared the photocatalytic activity of ZnO films on flat substrates and porous aluminum (prepared by electrochemical anodization) at an optimal film thickness of 20 nm. Our results show that the ZnO thin film on porous aluminum has a significantly higher photocatalytic activity. After 300 minutes of UV lamp exposure, the ZnO thin film deposited on flat aluminum demonstrated the least photocatalytic activity, leading to a reduction of approximately 35% in the concentration of the MB solution. In contrast, the ZnO film coated on a porous anodic aluminum substrate exhibited the highest photocatalytic efficiency, with a reduction in the MB solution concentration by approximately 85%.

Abstract: Am-241 is an alpha emitting isotope which can be used to fuel a nuclear battery via alphavoltaic effect by using a semiconductor to convert alpha radiation to electricity. The main issue of alphavoltaic battery is the radiation damage due to high energy alpha particle, resulted in a rapid decline in performance. Zinc oxide (ZnO) is known as a semiconductor with high radiation tolerance. In this study, the effect of annealing temperature to ZnO crystal was studied along with its alteration due to Am-241 irradiation overtime. The annealing temperatures were set at 450°C and 650°C. The irradiation process was carried out using Am-241 isotope for 12 days with an activity of 44.85 mCi and approximately 0.0866 MGy of absorbed dose. The crystal structure of fabricated and irradiated ZnO were investigated through X-ray Diffraction (XRD). The XRD diffraction pattern indicates that the crystal structure of ZnO is hexagonal wurtzite and still maintained after irradiation process. Raising the annealing temperature from 450°C to 650°C leads to a reduction in peak intensity. This change correlates with an increase in grain size post-irradiation. After exposure to alpha particle radiation, changes occurred in the diffraction peaks of ZnO. At 450°C annealing temperature, the intensity decreased by 94.822%, while at 650°C annealing temperature, the intensity decrease was 85.489%. This shows that increasing the annealing temperature can reduce the decrease in intensity after irradiation with alpha particles. The (002) plane shifted by 0.057˚ at 450°C annealing temperature and by 0.042˚ at 650°C after irradiation. In addition, the crystal lattice parameters increased after irradiation, which led to a change in the FWHM value and an increase in the crystal grain size.