Oxide ZnO Research Articles

Monoazo disperse dyes based on pyrazolopyrimidinones provide added value

We treated the colored polyester texture with scatter colors that we synthesized previously or after the coloring cycle trying to give these fabric functional properties. The light fastness was studied after treating the fabric with zinc oxide ZnO nano particle size NPs., and it was tracked down that this property was extraordinarily improved. The ability of the polyester texture protect against ultraviolet radiation has been evaluated

Superior NO2 Sensing of MOF-Derived Indium-Doped ZnO Porous Hollow Cages

Introduction Highly sensitive semiconductor gas sensors hold great potential for applications in trace gas detection. Reliable detection of ppb-level NO2 is crucial for environmental monitoring, which however still remains a challenge. In this work, we adopted a one-pot encapsulation strategy for synthesizing indium-doped ZnO porous hollow cages. In(acac)3 was selected as the indium source due to its molecular diameter between the cavity size (11.6 Å) and the aperture size (3.4 Å) of ZIF-8. During the crystallization progress of ZIF-8, it was in situ trapped in the cavities and In(acac)3@ZIF-8 composites were formed (Scheme a, b). During calcination, metal ion species, composed of In(acac)3@ZIF-8, were oxidized, leading to the formation of In-doped ZnO porous hollow cages (Scheme c, d). In this case, ZIF-8 served as the host backbone for the uniform distribution of the indium source as well as the production of porous hollow structure. In doping led to significantly enhanced NO2-sensing performance, achieving a response of 3.7 to 10 ppb of NO2, a high sensitivity of 187.9 ppm-1, and a limit of detection as low as 0.2 ppb. The mechanism of enhanced NO2-sensing properties was discussed in the terms of the intrinsic excellent gas accessibility of porous hollow structure and electronic sensitization by In doping. Our findings could be extended to design other porous doped ZnO oxides for high performance gas sensors and other applications. Method In(acac)3@ZIF-8 composites were synthesized by a one-pot encapsulation method. route. Briefly, 810 mg of Zinc nitrate hexahydrate and corresponding amounts of Indium(III) acetylacetonate were dissolved into 40 mL methanol to form precursor solutions. 40 mL of methanol solutions containing 721.6 mg of 2-methylimidazole were added into above solutions under stirring. The resulting solutions were stirred for 20 min and aged for 24 h at room temperature. After precipitation, obtained ZIF-8 derivatives were washed with methanol via centrifugation. The precipitates were further dried at 60 °C for 24 h and calcined at 500 °C for 2 h to obtain pristine and In-doped ZnO powders. The obtained samples are hereafter denoted as In/ZnO-X, where X represents the nominal In/Zn atomic ratio (multiplied by 100) used during the synthesis, e.g., In/ZnO-0 for un-doped ZnO, In/ZnO-2 for In/Zn of 2.0 at.%, In/ZnO-10 for In/Zn of 10.0 at.%. Results and Conclusions Figure 1a depicts dynamic electrical resistance changes of pristine and In-doped ZnO sensors in the presence of NO2 from 0.2 to 10 ppm at 300 °C. The sensors showed typical n-type semiconductor response behavior, the increase of electrical resistance in the presence of NO2. In addition, the electrical resistance increased with the increase of NO2 concentration for all the sensors, and at each concentration the increment of electrical resistance for In/ ZnO-10 was always much higher than that for other sensors. Further investigations on the performance of In/ZnO-10 in the NO2 concentration below 0.2 ppm were conducted. Figure 1b shows the dynamic response and recovery curves for the In/ZnO-10 sensor, which were measured by alternately exposing the sensor to ambient air and air/NO2 mixture at 300°C. The In/ZnO-10 sensor was effective for the detection of NO2 at 10, 25, 50, and 100 ppb, and a high response of 3.7 to 10 ppb of NO2 gas was obtained. And the calculated limit of detection was as low as 0.2 ppb, 2 orders of magnitude lower than that (23.4 ppb) of pristine ZnO. Therefore, the In/ZnO-10 sensor could be suitable for the detection of ppb-level NO2 put forward by the WHO for monitoring environmental pollution. Figure 1c exhibits the response of pristine and In-doped ZnO sensors as a function of NO2 concentration in the range below 1 ppm at 300 °C. The response value increased linearly with the increasing NO2 concentration, and the slope (i.e., sensitivity) also became larger with increasing In content. A large sensitivity of 187.9 ppm-1 was obtained for the In/ ZnO-10 sensor, 117.4, 9.5, and 9.1 times larger than that for pristine ZnO (1.6 ppm-1), In/ZnO-2 (19.8 ppm-1) and In/ZnO-6 (20.7 ppm-1), respectively. The wide linear dependence and high sensitivity of the In/ZnO-10 sensor are favorable for calibration and determination of the NO2 concentration in practical applications. Further tests at higher concentrations above 1 ppm showed the slope decreased with the increasing NO2 concentration, indicating the sensors were near saturation (Figure 1d). Nevertheless, the In/ZnO-10 sensor still possessed the highest response value and sensitivity among the sensors in the high-concentration range.

Antimicrobial Effect of Chitosan Films on Food Spoilage Bacteria.

Synthetic materials commonly used in the packaging industry generate a considerable amount of waste each year. Chitosan is a promising feedstock for the production of functional biomaterials. From a biological point of view, chitosan is very attractive for food packaging. The purposes of this study were to evaluate the antibacterial activity of a set of chitosan-metal oxide films and different chitosan-modified graphene (oxide) films against two foodborne pathogens: Campylobacter jejuni ATCC 33560 and Listeria monocytogenes 19115. Moreover, we wanted to check whether the incorporation of antimicrobial constituents such as TiO2, ZnO, Fe2O3, Ag, and graphene oxide (GO) into the polymer matrices can improve the antibacterial properties of these nanocomposite films. Finally, this research helps elucidate the interactions of these materials with eukaryotic cells. All chitosan-metal oxide films and chitosan-modified graphene (oxide) films displayed improved antibacterial (C. jejuni ATCC 33560 and L. monocytogenes 19115) properties compared to native chitosan films. The CS-ZnO films had excellent antibacterial activity towards L. monocytogenes (90% growth inhibition). Moreover, graphene-based chitosan films caused high inhibition of both tested strains. Chitosan films with graphene (GO, GOP, GOP-HMDS, rGO, GO-HMDS, rGOP), titanium dioxide (CS-TiO2 20:1a, CS-TiO2 20:1b, CS-TiO2 2:1, CS-TiO2 1:1a, CS-TiO2 1:1b) and zinc oxide (CS-ZnO 20:1a, CS-ZnO 20:1b) may be considered as a safe, non-cytotoxic packaging materials in the future.

Structural, microstructural and photocatalytic degradation of methylene blue of zinc oxide and Fe-doped ZnO nanoparticles prepared by simple coprecipitation method

Nanoparticles of ZnO doped with Fe (0.00, 0.02, 0.05 and 0.10) were prepared by chemical co-precipitation method. The effect of iron doping on the structural, morphological and optical properties of ZnO nanoparticles was examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and UV–Visible spectroscopy. The XRD analysis revealed the single-phase of the as-made and Fe-doped ZnO nanoparticles. SEM images showed the formation of aggregates of small individual nanoparticles of various sizes. FTIR analysis indicated the existence of distinct characteristic absorption peaks at 447 cm−1 for Zn–O stretching mode with some changes in the intensities. UV–Visible measurement revealed a reduction in the energy gap with increasing Fe concentration, which is generally due to increasing mesh parameters. The photocatalytic activity of Zn1-xFexO was evaluated by analyzing the degradation of methylene blue (MB). The presence of iron from 2% to 10 at% in the ZnO nanopowder was found to decelerate the photocatalytic process.

Influence of SnO2, ZnO and TiO2 layer on the performance of CIGS and CdTe solar cells

As a type electron transmission layer, SnO2, ZnO and TiO2 layer were applied as a buffer between transparent conductive oxide and n-CdS layer in CIGS and CdTe solar cells. J-V curve of device with three different buffer layer were simulated theoretically through Poisson equation and electron-hole continuity equation. Open-circuit voltage, short-circuit current, fill factor and conversion efficiency were derived. It’s shown that for CdTe solar cells, performance of device with three kind of buffer layers SnO2, ZnO and TiO2 did not differ two much. While for the CIGS solar cells, device with TiO2 showed a small fill factor, then leading to a lower conversion efficiency. Transparent oxide SnO2 and ZnO were suggested for the buffer layer for optimization CIGS and CdTe solar structure depending on the art of manufacturing.

Heat transfer growth of sonochemically synthesized novel mixed metal oxide ZnO+Al2O3+TiO2/DW based ternary hybrid nanofluids in a square flow conduit

In the current investigation, the heat transfer development with the turbulent flow of novel metal oxide-based ternary composite nanofluids of ZnO + Al2O3+TiO2/DW at varying wt.% concentrations (0.025, 0.05, 0.075, and 0.1) in a square heat exchanger below constant heat flux conditions was discussed. The new ternary composite nanofluids were synthesized by using the sonochemical technique. The ZnO + Al2O3+TiO2/DW based ternary composite nanofluids with their respective wt. % reveals an enhancement in effective thermal conductivity and heat transfer coefficient local and average with Reynolds numbers varying from 4550 to 20,367. The extreme growth in overall effective thermal conductivity was noticed up to 1.149 W/m-K at 0.1 wt% for ternary hybrid composite nanofluids at a maximum temperature 45 °C. Similarly, at 0.075 wt%, 0.05 wt%, and 0.025 wt% the overall effective thermal conductivity was recorded 1.118 W/m-K, 1.091 W/m-K, and 1.079 W/m-K correspondingly, which is greater than that of base fluid (DW), with improved thermo-physical characteristics for novel ZnO + Al2O3+TiO2/DW ternary hybrid composite nanofluids. Also, it shows an improvement in local and average heat transfer with a maximum growth of 0.1 wt %. The maximum heat transfer was observed for ZnO + Al2O3+TiO2/DW based Ternary hybrid composite nanofluids at 0.1 wt % concentrations, up to 900–5700 W/m2K, which is 89% higher than distilled water. While, an enhancement of 900–3870 W/m2K, 900–3350 W/m2K, 900–2750 W/m2K were observed for the other three wt. % 0.075, 0.05 and 0.025, respectively. The study revealed that the metal oxide based ternary hybrid composites nanofluids are suitable for nano coolant applications due to improved thermophysical characteristics and also it is applicable for energy management in industrial applications.

The Key Role of Active Sites in the Development of Selective Metal Oxide Sensor Materials.

Development of sensor materials based on metal oxide semiconductors (MOS) for selective gas sensors is challenging for the tasks of air quality monitoring, early fire detection, gas leaks search, breath analysis, etc. An extensive range of sensor materials has been elaborated, but no consistent guidelines can be found for choosing a material composition targeting the selective detection of specific gases. Fundamental relations between material composition and sensing behavior have not been unambiguously established. In the present review, we summarize our recent works on the research of active sites and gas sensing behavior of n-type semiconductor metal oxides with different composition (simple oxides ZnO, In2O3, SnO2, WO3; mixed-metal oxides BaSnO3, Bi2WO6), and functionalized by catalytic noble metals (Ru, Pd, Au). The materials were variously characterized. The composition, metal-oxygen bonding, microstructure, active sites, sensing behavior, and interaction routes with gases (CO, NH3, SO2, VOC, NO2) were examined. The key role of active sites in determining the selectivity of sensor materials is substantiated. It was shown that the metal-oxygen bond energy of the MOS correlates with the surface acidity and the concentration of surface oxygen species and oxygen vacancies, which control the adsorption and redox conversion of analyte gas molecules. The effects of cations in mixed-metal oxides on the sensitivity and selectivity of BaSnO3 and Bi2WO6 to SO2 and VOCs, respectively, are rationalized. The determining role of catalytic noble metals in oxidation of reducing analyte gases and the impact of acid sites of MOS to gas adsorption are demonstrated.

Preparation and Characterization of Zinc Oxide (Zno)/Polymethyl Methacrylate (PMMA) Nanocomposites

A series of novel zinc oxide / Poly (methyl methacrylate) nanocomposite films with different ZnO contents were prepared through inclusion of pre-synthesized zinc oxide nanoparticles. The physical composition and morphology of the as-prepared nanocomposites were studied by XRD and TEM. The TEM analyses revealed that the zinc oxide nanoparticles have a particle size of ~3–5 nm. X-ray diffraction proved the presence of the amorphous PMMA in the nanocomposites. The intermolecular interactions within the polymer nanocomposites were explored by FTIR and XRD. FTIR spectra confirmed the dispersion of the zinc oxide nanoparticles in the Poly (methyl methacrylate) i.e. PMMA matrices. The UV-Vis absorption measurements of the ZnO/PMMA nanocomposites proved their potential optical properties.

Light Activation of Nanocrystalline Metal Oxides for Gas Sensing: Principles, Achievements, Challenges.

The review deals with issues related to the principle of operation of resistive semiconductor gas sensors and the use of light activation instead of thermal heating when detecting gases. Information on the photoelectric and optical properties of nanocrystalline oxides SnO2, ZnO, In2O3, and WO3, which are the most widely used sensitive materials for semiconductor gas sensors, is presented. The activation of the gas sensitivity of semiconductor materials by both UV and visible light is considered. When activated by UV light, the typical approaches for creating materials are (i) the use of individual metal oxides, (ii) chemical modification with nanoparticles of noble metals and their oxides, (iii) and the creation of nanocomposite materials based on metal oxides. In the case of visible light activation, the approaches used to enhance the photo- and gas sensitivity of wide-gap metal oxides are (i) doping; (ii) spectral sensitization using dyes, narrow-gap semiconductor particles, and quantum dots; and (iii) addition of plasmon nanoparticles. Next, approaches to the description of the mechanism of the sensor response of semiconductor sensors under the action of light are considered.

Optical spectra and interfacial band offsets of pulse-laser-deposited metal-oxides: SnO2, TiO2, and ZnO

Transparent conducting oxides are electrically conductive materials with high optical transmittance in the visible region of the spectrum and are useful in a wide range of applications. In this study, the optical spectra of a set of single-phase transparent conducting oxides TiO2, ZnO, and SnO2 grown by pulse laser deposition are measured by vacuum ultraviolet spectroscopic ellipsometry and the optical bandgaps are determined to be 3.30 ± 0.05 eV, 3.13 ± 0.05 eV, and 3.95 ± 0.05 eV, respectively. Differences between these values and previous measurements are discussed. SnO2 and ZnO optical responses at the bandgap reveal that they are a direct bandgap, while TiO2 appears to show an indirect type. For the interfacial electronic characteristics, the internal photoemission measurement shows that the electronic barriers of these naturally n-type-doped metal oxides adjacent to an Al2O3 layer originate from the Fermi level in their conduction bands. The band offset determination shows that the barrier heights are similar and have a small internal field dependence. The work functions are then estimated from the measured barrier heights.

Reaction pathways in the solid state and the Hubbard U correction.

We investigate how the Hubbard U correction influences vacancy defect migration barriers in transition metal oxide semiconductors. We show that, depending on the occupation of the transition metal d orbitals, the Hubbard U correction can cause severe instabilities in the migration barrier energies predicted using generalized gradient approximation density functional theory (GGA DFT). For the d0 oxide SrTiO3, applying a Hubbard correction to the Ti4+ 3d orbitals below 4-5 eV yields a migration barrier of ∼0.4 eV. However, above this threshold, the barrier increases suddenly to ∼2 eV. This sudden increase in the transition state barrier arises from the Hubbard U correction changing the Ti4+ t2g/eg orbital occupation, and hence electron density localization, along the migration pathway. Similar results are observed in the d10 oxide ZnO; however, significantly larger Hubbard U corrections must be applied to the Zn2+ 3d orbitals for the same instability to be observed. These results highlight important limitations to the application of the Hubbard U correction when modeling reactive pathways in solid state materials using GGA DFT.

Engineering of TiO2 or ZnO—Graphene Oxide Nanoheterojunctions for Hybrid Solar Cells Devices

It is currently of huge importance to find alternatives to fossil fuels to produce clean energy and to ensure the energy demands of modern society. In the present work, two types of hybrid solar cell devices were developed and characterized. The photoactive layers of the hybrid heterojunctions comprise poly (allylamine chloride) (PAH) and graphene oxide (GO) and TiO2 or ZnO films, which were deposited using the layer-by-layer technique and DC-reactive magnetron sputtering, respectively, onto fluorine-doped tin oxide (FTO)-coated glass substrates. Scanning electron microscopy evidenced a homogeneous inorganic layer, the surface morphology of which was dependent on the number of organic bilayers. The electrical characterization pointed out that FTO/(PAH/GO)50/TiO2/Al, FTO/(PAH/GO)30/ZnO/Al, and FTO/(PAH/GO)50/ZnO/Al architectures were the only ones to exhibit a diode behavior, and the last one experienced a decrease in current in a low-humidity environment. The (PAH/GO)20 impedance spectroscopy study further revealed the typical impedance of a parallel RC circuit for a dry environment, whereas in a humid environment, it approached the impedance of a series of three parallel RC circuits, indicating that water and oxygen contribute to other conduction processes. Finally, the achieved devices should be encapsulated to work successfully as solar cells.

Exogenous application of ZnO nanoparticles and ZnSO4 distinctly influence the metabolic response in Phaseolus vulgaris L.

Nanomaterials-mediated contamination (including the highly reactive metal oxides ZnO nanoparticles) is becoming one of the most concerning issues worldwide. In this study, the toxic effects of two chemical species of Zn (ZnO nanoparticles and bulk ZnSO4) were investigated in bean plants, following either foliar or soil application, at concentrations from 250 to 2000mgL-1 using biochemical assays, proteomics and metabolomics. The accumulation of Zn in plant tissues depended on the application type, zinc chemical form and concentration, in turn triggering distinctive morphological, physiological, and redox responses. Bean plants were more sensitive to the foliar than to the soil application, and high concentrations of ZnO NP and bulk ZnSO4 determined the highest plant growth inhibition and stress symptoms. However, low dosages of ZnSO4 induced a slight plant growth promotion and better physiological and antioxidative response. Low concentration of Zn leaded to increased activity of stress-related proteins and secondary metabolites with antioxidant capacity, while increasing concentration reached the exhausted phase of the plant stress response, reducing the antioxidant defense system. Such high concentrations increased lipids peroxidation, protein degradation and membranes integrity. Oxidative damage occurred at high concentrations of both chemical species of Zn. Foliar spraying impaired photosynthetic efficiency, while soil applications (especially ZnSO4) elicited antioxidant metabolites and proteins, and impaired chloroplast-related proteins involved in the electron transport chain and ATP production. Taken together, the results highlighted distinctive and nanoparticles-related toxic effects of ZnO in bean, compared to ionic forms of Zn.

Nanostructures based on ZnO and TiO2 oxides produced by PLD in open air

We report on the fabrication of highly porous metal-oxide nanostructures by pulsed laser deposition performed in air at atmospheric pressure. The depositions were performed by ablating synthesized ZnO and a mixed target of ZnO and TiO2 as initial materials. The attention was focused on the structure, morphology, optical and photocatalytic properties of the as-deposited nanostructures of the ZnO-TiO2 system. The technology applied leads to the formation of nanostructures composed of nanoparticles. The as-prepared samples possess a high transmittance in the visible and near IR region with an optical band gap in the range of 3.1 - 3.2 eV. It was demonstrated that the as-deposited ZnO and ZnO-TiO2 nanostructures degrade Rhodamine B up to 43 - 44% after 300-min UV irradiation.

Multiple doped ZnO with enhanced thermoelectric properties

ZnO has a large thermal conductivity that hinders its satisfactory thermoelectric performance. In this work, we add multiple dopants including S, C, Fe and Ni to ZnO simultaneously. A low thermal conductivity ∼3 W m−1 K−1 is obtained, with an initial composition ZnO-1%S-0.15 %C-4%Fe2O3-3%NiO (sample #7), and comparable to the lowest reported values of ZnO-based bulk samples. We attribute the reduction to the Ni induced lattice distortion and the Fe induced microstructural changes. This composition also shows the highest power factor that is ∼60% higher than ZnO due to its highest charge carrier concentration and mobility. The overall dominant carrier scattering is through acoustic phonons rather than impurities. The resultant zT is 2.4 times higher than that of undoped ZnO at 973 K. We find multiple doped ZnO exhibits better thermoelectric performance than any single doped counterpart, providing an effective way to improve the thermoelectric properties of ZnO and other oxides.

Band gap in photocatalytic ZnO–TiO2

Zinc oxide and titanium dioxide composite thin films were prepared on Corning 7059 glass substrates by co-sputtering. The reactive gas-surroundings used was ultrahigh purity oxygen. To analyze the structural, optical and photocatalytic properties of the ZnO–TiO2 samples, X-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption, Raman spectroscopy and methylene blue bleaching were carried out at room temperature. XRD pat- terns indicate the presence of TiO2 (anatase and rutile phases), ZnO, ZnTiO3, and Zn2 TiO4 crystalline structures. AFM images allow the observation of non-homogeneous surface in the ZnO–TiO2 system, suggesting the separation of different crystalline phases in the composite. Raman studies exhibit different spectra in the films depending on the area analyzed, which can be interpreted as a result of the existence of well separated crystalline regions as seen in AFM images. The photocatalytic activity (PA) of TiO –ZnO–ZnTiO3–Zn2 TiO4 composite, as expected for adequate coupling semiconductors, is larger than PA of ZnO and TiO2 oxides, used as references. A simple proposal about the probable alignment of the conduction band, the valence band, and the Fermi level is included.

Photocatalytic degradation efficiency of azo dye in aqueous phase using different photo catalysts

The new azo dye [4-(4-hydroxy-2-methylnaphthyl)diazenyl]benzoic acid was synthesized by the reaction of 2-methyl-1-naphthol with p-amino benzoic acid. The photcatalytic degradation of azo dye has been investigated by using zinc oxide and cadmium sulfide. This degradation was carried out by the irradiation of aqueous suspended solutions containing different concentrations of this dye using 0.11 g/100 mL of metal oxide (semiconductors) ZnO and CdS. A mercury lamp 125 W in a Pyrex photoreaction cell of 100 mL at room temperature was used as an irradiation source. The effect of the catalyst on the photocatalytic degradation of the prepared dye was studied via several experiments at different conditions, where they involve the effect of the catalyst mass and the effect of the dye concentrations. The irradiated solutions were studied using UV-Vis spectrophotometer. It has been the performance of photocatalytic system that using ZnO was observed to be better than cadmium sulfide system for degrade the azo compound from its aqueous solution.
 
 KEY WORDS: Photocatalytic, Degradation, Semiconductors, Zinc oxide; Cadmium sulphide, Azo dye
 
 Bull. Chem. Soc. Ethiop. 2020, 34(3), 463-469.
 DOI: https://dx.doi.org/10.4314/bcse.v34i3.3

The Influence of ZnO Oxide Layer on the Physicochemical Behavior of Ti6Al4V Titanium Alloy.

Titanium and its alloys are characterized by high biocompatibility and good corrosion resistance as a result of the ability to form a TiO2 oxide layer. However, based on literature data it can be concluded that titanium degradation products, in the form of titanium particles, metal-protein groups, oxides and ions, may cause allergic, inflammatory reactions and bone resorption. The corrosion process of Ti6Al4V in the human body environment may be intensified by a decreased pH and concentration of chloride compounds. The purpose of this article was to analyze the corrosion resistance of the Ti6Al4V alloy, obtained by the selective laser melting method in a corrosion solution of neutral pH and in a solution simulating peri-implant inflammatory conditions. Additionally, the influence of zinc oxide deposited by the atomic layer deposition method on the improvement of the physicochemical behavior of the Ti6Al4V alloy was analyzed. In order to characterize the ZnO layer, tests of chemical and phase composition as well as surface morphology investigation were performed. As part of the assessment of the physicochemical properties of the uncoated samples and those with the ZnO layer, tests of wetting angle, pitting corrosion and impedance corrosion were carried out. The number of ions released after the potentiodynamic test were measured using the inductively coupled plasma atomic emission spectrometry (ICP–AES) method. It can be concluded that samples after surface modification (with the ZnO layer) were characterized by favorable physicochemical properties and had higher corrosion resistance.

Effects of Allium cepa-mediated zinc oxide nanoparticles on male reproductive tissue and sperm abnormalities of albino mice (Mus musculus)

Green synthesis of nanoparticles (NPs) had shown the positive effects on various parameters of human health. However, this can vary depending on plant category, NPs nature, doses of green synthesized NPs and type of cell or tissue taken for experiment. The aim of this study is to evaluate the effects of Allium cepa (A. cepa)-mediated zinc oxide ZnO NPs on male reproductive tissues and aberrations in sperm structure of albino mice. The green-synthesized NPs were synthesized with A. cepa and further characterized through ultraviolet–visible spectroscopy, scanning electron microscopy (SEM), zeta potential and FTIR analysis. Various doses (75 mg, 150 mg, 225 mg and 300 mg/kg) were given orally to adult albino mice by keeping them in various groups for 28 days. Epididymis and testis were removed for assessment of spermatogenesis and histopathological analysis of testicular tissues was performed. The synthesized NPs showed absorption at 330 nm and size ranging from 50 to 90 nm through SEM. Dose-dependent significant decrease (P < 0.05) in sperm calculation, increased in sperm abnormalities and sperm motility were observed by the A. cepa mediated ZnO NPs compared to control group. Similarly, testicular tissues showed vacuolization and detachment in seminiferous tubules and degenerative sperm cells in experimental groups provided with synthesized ZnO NPs. The study concluded that ZnO NPs adversely effect on epididymal sperm parameters and testicular tissues of male albino mice.

Photocatalytic Applications of Metal Oxides for Sustainable Environmental Remediation

Along with industrialization and rapid urbanization, environmental remediation is globally a perpetual concept to deliver a sustainable environment. Various organic and inorganic wastes from industries and domestic homes are released into water systems. These wastes carry contaminants with detrimental effects on the environment. Consequently, there is an urgent need for an appropriate wastewater treatment technology for the effective decontamination of our water systems. One promising approach is employing nanoparticles of metal oxides as photocatalysts for the degradation of these water pollutants. Transition metal oxides and their composites exhibit excellent photocatalytic activities and along show favorable characteristics like non-toxicity and stability that also make them useful in a wide range of applications. This study discusses some characteristics of metal oxides and briefly outlined their various applications. It focuses on the metal oxides TiO2, ZnO, WO3, CuO, and Cu2O, which are the most common and recognized to be cost-effective, stable, efficient, and most of all, environmentally friendly for a sustainable approach for environmental remediation. Meanwhile, this study highlights the photocatalytic activities of these metal oxides, recent developments, challenges, and modifications made on these metal oxides to overcome their limitations and maximize their performance in the photodegradation of pollutants.