Particle Size Of ZnO Research Articles

Synergistic effect of ZnO nanoparticles and hesperidin on the antibacterial properties of chitosan

In this study, hesperidin (HSP) biological agent, which has strong antioxidant properties, was successfully transferred to ZnO nanoparticles, which were first synthesized by the hydrothermal method. Then, chitosan (CS)/ZnO-HSP nanocomposites were produced by adding different ratios of the ZnO-HSPs to the biodegradable CS biopolymer by hydrothermal method. The resulting materials were characterized using various biophysical strategies, including X-ray diffraction (XRD), Fourier transform infrared spectrometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy. The mean particle size of ZnO was estimated to be 29 nm from the XRD calculations and SEM measurements. The effect of the ZnO-HSPs on the thermal properties of pure CS was investigated by thermogravimetric analysis and differential scanning calorimetry techniques, and improvements were noted in the thermal properties of CS. While the T g value of CS was 81 °C, this value increased by 13–94 °C with the addition of 6 wt% by weight of the ZnO-HSP. The antibacterial effect of materials was determined by the disc diffusion method. The ZnO-HSPs added to the CS caused the nanocomposites to have a remarkable effect against Escherichia coli and Staphylococcus aureus microorganisms. While the inhibition diameter of the CS against E. coli was 18.3, the same value increased to 22.3 for the composite containing 6 wt% the ZnO-HSP. The HSP increased the antioxidant capacity of both the ZnO-HSP particles and the CS/ZnO-HSP nanocomposites, reducing the toxic effects of ZnO nanoparticles. Thus, it was determined that the CS/ZnO-HSP nanocomposites did not have any cytotoxicity in healthy human cells. The fact that the produced nanocomposites exhibit antibacterial activity and do not harm human cells shows that they can be a safe product for health. From all these results, this triple hybrid system is hoped that it will be used in biomedical applications as a naturally-sourced, environmentally friendly, and cost-effective composite biomaterial by combining its antimicrobial and strong antioxidant properties.

Photo-response of Fe-doped ZnO electron transport interlayer on Poly(3-hexylthiophene-2,5-diyl): Phenyl-C61-butyric acid methyl ester based thin film device for photodiode application

An electron transport material - Fe doped ZnO layer with atomic ratio Zn: Fe = 90:10 was prepared for enhancing the photocurrent between an optically active poly(3-hexylthiophene-2,5-diyl): phenyl-C61-butyric acid methyl ester film and an indium tin oxide film used as an anode. The crystallite size of ZnO decreases with increasing Fe doping as estimated from major X-ray diffraction (100), (002), (101), and (110) peaks using the Scherrer formula. ZnO particle size reduction on Fe doping was also observed by field emission scanning electron microscopy. The photoluminescence study on Fe-doped ZnO shows interstitial oxygen defects band at ∼2.28 eV and the bound exciton caused by oxygen vacancy in ZnO. The X-ray photoelectron spectra show shift of the Zn2p3/2, and Zn2p1/2 peaks to lower binding energy due to Fe3+ doping in the ZnO. Time-correlated single-photon counting experiment reveals faster decay of lifetime of Fe-doped ZnO than undoped material at excitation wavelength of 650 nm due to higher electron transport rate through the interface according to Langevin recombination formula. The photoresponse property of the films was measured under solar light illumination (10 mW/cm2), and the results show that Fe-doped ZnO can be a better than undoped ZnO based multilayer device for photodiode application.

Quantum Dot Hybridization of Piezoelectric Polymer Films for Non-Transfer Integration of Flexible Biomechanical Energy Harvesters.

This work presents a low-temperature engineering strategy, from quantum dot (QD) synthesis to fabrication of a hybrid from a homogeneous dispersion to thermal annealing with elaborate use of a small organic molecule dopamine, for achieving a kind of ZnO QD-hybridized piezoelectric polymer film directly integrated into a flexible electrode and a plastic substrate. This strategy is the key for non-transfer assembly of flexible piezoelectric nanogenerators (FPENGs) with both mechanical robustness and high electrical performance via direct lamination. The rational addition of dopamine plays multiple roles of (1) significantly decreasing the size of ZnO particles to a QD level (3.77 nm), (2) formation of a stable and homogeneous dispersion of a ZnO QDs/piezoelectric polyvinylidene fluoride-co-hexafluoropropylene copolymer for uniform hybridization of a piezoelectric film, and (3) increment of the piezoelectric phase via induced crystallization at a low annealing temperature. This dopamine-assisted low-temperature annealing strategy for a hybrid piezoelectric film with a high d33 value (∼31.56 pC/N, 30.56% larger than that of a pure piezoelectric polymer film) required no additional high-voltage polarization treatment and effectively avoided the delamination, distortion, or melt phenomenon between the piezoelectric layer, flexible electrode, and plastic protective layer caused by the high temperature and thermal stress. The obtained FPENGs showed significantly enhanced output performance and mechanical robustness under repeated impact and large amounts of strain conditions. Their specific output voltage and charge density were stably maintained at 7.16 V and 2.40 nC/cm2, which were 30.7 and 50.0% higher than those of FPENGs based on a pure piezoelectric polymer film, respectively. They were further used as biomechanical energy harvesters for generating electricity to charge capacitor energy storage devices for power electronics and self-powered sensors for visual motion-detecting systems, indicating their promising applications in both wearable technology and smart homes.

Nano 5% Fe–ZnO: A highly efficient and recyclable heterogeneous solid nano catalyst for the Biginelli reaction

In this paper, we report the synthesis and catalytic application of 5% Fe–ZnO nanocatalyst for the synthesis of 3,4-dihydropyrimidin-2-one derivatives as a highly efficient heterogeneous nanocatalyst. The structural and morphological features of the synthesized nanocatalysts were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Using Debye-Scherer's formula, the average particle size for undoped ZnO was calculated to be 24.55 nm, while the average particle size for 5% Fe–ZnO was calculated to be 22.37 nm. The high resolution transmission electron microscopy (HR-TEM) revealed a hexagonal crystal lattice type. The Brunauer–Emmett–Teller (BET) surface area of ZnO and 5% Fe–ZnO was found to be 56.50 m2/g and 72.65 m2/g, respectively. Energy Dispersive X-Ray Analysis (EDX) confirmed the elemental composition of undoped ZnO and doped 5% Fe–ZnO nanocatalysts. Biginelli products were produced using a one-pot three-component reaction of urea, β-dicarbonyl compound, and various aromatic aldehydes using 5% Fe–ZnO under clean conditions. It was found that a 5% Fe–ZnO nanocatalyst is a highly efficient heterogeneous nanocatalyst for the synthesis of 3,4-dihydropirimidinones. 1H NMR and 13C NMR analysis was used to confirm the structure of the synthesized Biginelli adducts. This synthetic protocol offers several advantages, including a short reaction time and purity of the synthesized, reusability and ease of catalyst separation, and a clean and quick workup.

Investigation Photoluminescence Property of ZnO / PANI Nanocomposite Synthesized in​ [EtOHMIM+] [HSO4-] Ionic Liquid and CTAB Surfactant

In the present work, ZnO nanoparticles (NPs) were prepared using hydrothermal method with Trimethyl Ammonium Bromide (CTAB) as surfactant in 1- (hydroxyethyl)-3- methylimidazolium sulfate [EtOHMIM+] [HSO-] ionic liquid (IL). ZnO / PANI nanocomposite was prepared via in situ polymerization. The structures of the modified ZnO particles were characterized by X-ray diffraction, Raman spectroscopy and, scanning electron microscopy (SEM). The optical properties of (ZnO / PANI) nanocomposite were examined by photoluminescence (PL) analysis. XRD and, Raman analysis confirmed that pure ZnO (NPs) synthesized with (CTAB) in [EtOHMIM+] [HSO-] IL were formed. The addition of (CTAB) and [EtOHMIM+] [HSO-] IL does not change the ZnO phase but reduces the particle size of ZnO and converts shallow defects to deep defects. The SEM images of the ZnO / PANI nanocomposite showed the formation of hexagonal wurtzite ZnO (NPs) embedded in polyaniline matrix. The PL intensity of the ZnO / PANI nanocomposite is improved as compared to pure ZnO (NPs). This indicates that [EtOHMIM+] [HSO4-] IL may be acting as a dye, since it is constituted by an organic part, [EtOHMIM+]. This good performance indicates that the synthesised nanocompsite is promising material as photoanode in solar cells.

Size-dependent spectroscopic insight into the steady-state and time-resolved optical properties of ZnO photocatalysts

In this paper, we present a spectroscopic insight into the structural and optical properties of ZnO nanoparticles (NPs) applied for water depollution using the photocatalytic process. Samples of various sizes and shapes were synthesized using simple, cost-effective chemical methods. The steady-state optical properties were analyzed using absorption and fluorescence emission spectroscopy and the band-gap and emission energies revealed an inverse dependence on the ZnO particles size. The time-resolved fluorescence properties were studied using time-correlated single photon counting (TCSPC) technique. Three emissive states were identified for all ZnO samples, with lifetimes that showed an overall decrease with increasing the particles diameter. The insights into the photocatalytic process toward understanding the ZnO nanoparticles mediated photocatalysis for degradation of Rhodamine (RhB) and oxytetracycline (OTC) was elucidated. The increase of photocatalytic activity was due to charge carrier partition and mobility.

Revealing the Influence of the Shape, Size, and Aspect Ratio of ZnO Nanoparticles on Antibacterial and Mechanical Performance of Cellulose Fibers Based Paper

AbstractThe discovery and characterization of nanoparticles represent a multidisciplinary issue. Their properties and applications within many fields depend on their size, shape, aspect ratio, and so on. No single methodology can currently analyze all characteristics and reveal their influence on the specific performance. Here, antibacterial and mechanical properties are investigated of three different ZnO nanoparticles (cubes, rods, and pellets) incorporated in the cellulose matrix in order to examine the correlation between the physical and chemical characteristics and antibacterial/mechanical activities. Therefore, various particles of ZnO with different sizes, shapes, and aspect ratios are synthesized via simple precipitation method in an aqueous solution and evaluated as an antimicrobial agent against Gram‐positive and Gram‐negative model bacteria alongside the commercial ZnO powder. The bactericidal activity is evaluated as prepared cellulose/ZnO nanocomposites in the form of paper sheets. Additionally, the tests of mechanical properties of the fabricated paper sheets are carried out according to ISO 5270 standard. Microscopic and spectroscopic methods are utilized to investigate the psychic‐chemical properties of the products. This study highlights that there is a strong impact of the shape, size, and aspect ratio of ZnO particles on the antibacterial efficacy and mechanical response of the fabricated cellulose‐based paper.

Femtosecond pulse laser fabrication of zinc oxide quantum clusters/nanoparticles and their electrical, optical, and chemical characteristics

Despite various studies on the preparation of different types and sizes of ZnO, the synthesis of quantum clusters of bare metal oxide has rarely been reported. The research goals of this study were to create clusters/nanoparticles using femtosecond laser irradiation to increase the electrical, optical, and chemical functionalities of ZnO. Femtosecond pulse laser irradiation deposition technology was used here to produce ZnO from a precursor in water (pH = 5.5) and aqueous alkaline solution (pH = 10.2). These products were named ZnO(F5.5) and ZnO(F10.2), respectively. In this procedure, Zn ions react with hydroxyl radicals (OH*) produced by the decomposition of water molecules, and Zn(OH*)2 is dehydrated by femtosecond laser energy to create ZnO. The spherical particle size of ZnO(F5.5) after 1–30 min irradiation was found to be small (1–7 nm) compared to that of ZnO(F10.2) spheres (10–13 nm). Furthermore, ZnO(F5.5) shows a larger band gap (5.3–5.6 eV), a longer electron life time (40.4 ms), and a higher emission intensity (483 a.u.) compared to ZnO(F10.2). For the photodegradation of harmful pollutants, ZnO(F5.5) prepared at 1 min of laser irradiation reduces formaldehyde by 98.5% under UV light irradiation for 15 min. However, ZnO(F10.2) and other larger ZnO particles with various shapes require a longer time for formaldehyde conversion. These results confirm that an ultrasmall ZnO nanoparticle (1 nm in size) can be called a quantum cluster and has better electrical, optical, and photocatalyst characteristics. In particular, efficient photocatalytic reactions may be used to study the ecological and environmental impacts of ZnO quantum cluster.

Titanium doped Zinc Oxide nanoparticles: A study of structural and optical properties for photocatalytic applications

In this work, Structural, Optical and Photocatalytic property of Titanium doped Zinc oxide nanoparticles have been investigated in which Titanium doped Zinc Oxide nanoparticles were fabricated by microwave-assisted solvothermal method. The synthesized nanoparticles were characterized for Structural properties by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), optical properties by UV–Visible Spectroscopy, Fourier Transform Infrared Spectroscopy, Photoluminescence (PL) and photocatalytic property is tested by degrading the Malachite Green dye under visible light. The influence of titanium on ZnO has made a change in ZnO particle size, Bandgap and its degradation efficiency upon light irradiation.

Effect of ZnO particle size on piezoelectric nanogenerators and mechanical energy harvesting

Effect of ZnO particle size on piezoelectric nanogenerators and mechanical energy harvesting

Physiological responses of pumpkin to zinc oxide quantum dots and nanoparticles

The present study investigated that the potential of soil or foliar applied 15 mg/L zinc oxide quantum dots (ZnO QD, 11.7 nm) to enhance pumpkin (Cucurbita moschata Duch.) growth and biomass in comparison with the equivalent concentrations of other sizes of ZnO particles, ZnO nanoparticles (ZnO NPs, 43.3 nm) and ZnO bulk particles (ZnO BPs, 496.7 nm). In addition, ZnSO4 was used to set a Zn2+ ionic control. For foliar exposure, ZnO QD increased dry mass by 56% relative to the controls and values were 17.3% greater than that of the ZnO NPs particles. The cumulative water loss in the ZnO QD treatment was 10% greater than with ZnO NPs, suggesting that QD could better enhance pumpkin growth. For the root exposure, biomass and accumulative water loss equivalent across all Zn treatments. No adverse effects in terms of pigment (chlorophyll and anthocyanin) contents were evident across all Zn types regardless exposure routes. Foliar exposure to ZnO QD caused 40% increases in shoot Zn content as compared to the control; the highest Zn content was evident in the Zn2+ ionic treatment, although this did not lead to growth enhancement. In addition, the shoot and root content of other macro- and micro-nutrients were largely equivalent across all the treatments. The contents of other nutritional compounds, including amino acids, total protein and sugar, were also significantly increased by foliar exposure of ZnO QD. The total protein in the ZnO QD was 53% higher than the ZnO particle treatments in the root exposure group. Taken together, our findings suggest that ZnO QDs have significant potential as a novel and sustainable nano-enabled agrichemical and strategies should be developed to optimize benefit conferred to amended crops.

Improved electrical performance of solution-processed zinc oxide-based thin-film transistors with bilayer structures

A bilayer thin-film transistor (TFT) structure with ZnO and Al-doped ZnO (AZO) was fabricated using a solution process. The film thickness and sintering atmosphere of ZnO and AZO were controlled and then evaluated by measuring their electrical characteristics. By changing the sintering atmosphere, carriers attributed to oxygen vacancies in the thin film increased. Moreover, the ZnO single-layer TFT sintered in N2 exhibited good electrical characteristics. In the ZnO/AZO bilayer TFT laminated with the ZnO sintered in N2 and high-resistance AZO thin films, electrical characteristics, such as the On/Off ratio and subthreshold swing, improved compared to those of the ZnO-TFT. The On/Off ratio of the ZnO/AZO-TFT using the AZO thin film sintered in an O2 atmosphere notably improved to 3.7 × 105 compared to that of the ZnO-TFT (1.7 × 104). In addition, the subthreshold swing in the ZnO/AZO-TFT was 0.36 V/dec, while the field-effect mobility was 2.2 × 10−1 cm2/Vs, thereby exhibiting the best electrical characteristics among the fabricated samples. According to the grazing-incidence X-ray diffraction measurement, the ZnO particle size and crystallinity of the ZnO/AZO bilayer were higher than those of the ZnO single layer. Therefore, improvement of the electrical characteristics was confirmed.

Synthesis of ZnO thin film by chemical spray pyrolysis using its nano powder

The deposition of metal oxides powder faces several problems, including poor adhesion to the bases deposited on them, the presence of many cracks, poor thickness control, and other disadvantages. The current study gives a new and simple idea to deposit thin films using two ZnO powders with nano and microparticle sizes on glass substrates. This was done by transforming the powders to Zinc acetate and then using chemical spray pyrolysis to deposit ZnO thin films. Scanning electron microscope (SEM) images showed that the prepared film from the nanopowder (ZnONano) lost the independence of powder’s nanoparticles and became a homogeneous film with nano projections. But the deposited one from the micro powder (ZnOMicro) had both nanorods and nanoplates. The different shapes and sizes of ZnO particles in ZnOMicro powder were disappeared after the Spray process. The two deposited films were homogeneous, crack-free and there were controllable thicknesses during the deposition. X-ray spectroscopy (EDS) was used to measure weights and atomic percentages of elements for the deposited films. The structures of the deposited films were approximately identical as the X-ray diffraction (XRD) technique showed. The optical properties of these two films were studied and their parameters were measured and calculated.

Mechanical and antibacterial properties of ZnO/chitosan bio-composite films

Abstract In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d50 ≅ 1.5 μm) and nanometer sized (d50 ≅ 100 nm), were used to investigate the effect of ZnO particle size and concentration (0, 2, and 8% w/w of chitosan) on the mechanical and antibacterial properties of the ZnO/chitosan bio-composite films. The incorporation of the ZnO powders into the chitosan film resulted in an increase in the tensile strength (TS) and a decrease in the elongation at break (EB) values. Mechanical test results revealed that TS and EB properties were considerably affected (p < 0.05) by the concentration and particle size of the ZnO reinforcement. Disc diffusion method demonstrated good antibacterial activities of bio-composite films containing high amount of ZnO (8% w/w of chitosan) against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis. The growth-limiting effect of the films was more pronounced for S. aureus and K. pneumoniae. Due to enhanced TS and imparted antibacterial activity of the produced ZnO/chitosan bio-composite films, these materials are promising candidates for applications such as food packaging, wound dressing, and antibacterial coatings for various surfaces.

Understanding of the Key Factors Determining the Activity and Selectivity of CuZn Catalysts in Hydrogenolysis of Alkyl Esters to Alcohols

CuZn catalysts are perspective catalysts for esters hydrogenolysis, but more knowledge is needed to optimize their catalytic performance. In this work, we consider the impact of CuZn catalysts composition on their structure, activity, selectivity, and stability in esters hydrogenolysis. Four catalysts with various Cu/Zn ratio were synthesized by a co-precipitation and characterized in as-prepared, calcined, reduced, and spent state by XRF, XRD, N2 physisorption, CO2-TPD, NH3-TPD, and N2O chemisorption. XRD data revealed the effect of the composition on the size of Cu and ZnO particles. The catalytic performance was investigated using an autoclave. All catalysts exhibited high methyl hexanoate conversion about 48–60% after 3 h but their activity and selectivity were found to be dependent on Cu/Zn ratio. The conversion of methyl hexanoate and hexyl hexanoate was compared to explain the observed product selectivity. Moreover, the catalysts stability was investigated in three consecutive reaction cycles and correlated with changes in the size of constituent particles. Moreover, when different esters were tested, a slight decrease in conversion and increase in alcohol selectivity with a growth in molecule size was observed. Obtained results allow making a conclusion about the optimal composition that provides the good performance of CuZn catalysts in ester hydrogenolysis.

Pressure-induced and flaring photocatalytic diversity of ZnO particles hallmarked by finely tuned pathways

Microstructure and morphology of particles play key roles in optimizing the properties of shape-selected ZnO particles, which are essential factors for flexible and reliable applications. In particular, chemical understanding and physical measurement with scientific theory must be further integrated for the realization of finely tuned ZnO nano/microstructures with desired sizes and shapes. Herein, we deliver a detailed description of the mechanism that mimics the formation of finely-tuned, spherical ZnO nanoparticles (NPs) at the computational level. We tackled issues that significantly affect the favorable structural motifs of the spherical ZnO NPs grown hydrothermally from ethanolic solution leading to their advancing chemical and physical properties. The excellent photocatalytic activity of the spherical ZnO was addressed by an apparent-rate constant of 9.7(2)x10-2 min-1 efficiently degrading the Rhodamine B solution by ∼99% in 50 min. The apparent-rate constant for tubular ZnO particles is almost six times lower than that of spherical ZnO NPs. Comparative results revealed that the diversity of size and shape of ZnO particles distinguishes the wurtzite-to-rocksalt transformation reversibility phenomena by dictating the microstructure-dependent deformation behavior and ultimately leading to different transition-induced elastic strain responses to hydrostatic pressure up to 30 GPa.

Designing optimized ternary catalytic alloy electrode for efficiency improvement of semiconductor gas sensors using a machine learning approach

Catalytic noble metal (s) or its alloy (s) has long been used as the electrode material to enhance the sensing performance of the semiconducting oxide based gas sensors. In the present paper, design of optimized ternary metal alloy electrode, while the database is in pure or binary alloy compositions, using a machine learning methodology is reported for detection of CH4 gas as a test case. Pure noble metals or their binary alloys as the electrode on the semiconducting ZnO sensing layer were investigated by the earlier researchers to enhance the sensitivity towards CH4. Based on those research findings, an artificial neural network (ANN) models were developed considering the three main features of the gas sensor devices, viz. response magnitude, response time and recovery time as a function of ZnO particle size and the composition of the catalytic alloy. A novel methodology was introduced by using ANN models considered for optimized ternary alloy with enriched presentation through the multi-objective genetic algorithm (GA) wherever the generated pareto front was used. The prescriptive data analytics methodology seems to offer more or less convinced evidences for future experimental studies.

Combustion synthesis and characterization of visible-light-driven Tm-doped ZnO nanoparticles used for photodegradation of methylene blue

Tm-doped ZnO nanoparticles were synthesized by a tartaric acid-assisted combustion method and followed by calcination at 600 oC for 2 h. Phase and morphology of assynthesized ZnO with and without Tm dopant were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The analytical results certified that Tm3+ ions were incorporated in hexagonal wurtzite ZnO structure. The particle size of ZnO was decreased with increasing in the weight content of Tm3+ dopant because the grain boundary growth of ZnO was hindered by Tm3+ dopant. The particle sizes of ZnO, 1% Tm-doped ZnO, 3% Tm-doped ZnO and 5% Tm-doped ZnO nanoparticles are 72.09 ± 17.37 nm, 32.77 ± 11.08 nm, 23.08 ± 4.61 nm and 25.27 ± 6.03 nm, respectively. The photocatalytic activity of as-synthesized ZnO with and without Tm dopant was evaluated through the degradation of methylene blue (MB) under visible light irradiation. In this research, 3% Tm-doped ZnO nanoparticles have the highest photocatalytic activity of 97.75% under visible light irradiation within 100 min. Active spices used for degradation of MB photocatalyzed by 3% Tm-doped ZnO nanoparticles were also investigated.

Influence of yttrium doping on ZnO nanoparticles for enhanced photocatalytic degradation of methylene blue

In this work, Y-doped ZnO nanoparticles were precipitately synthesized for various yttrium molar percentage values ranging from 0 to 5%, and then utilized as photocatalysts to demonstrate methylene blue degradation. Morphology shows that the particle size of pure ZnO is 113.7733.26 nm, which is reduced to the minimum value less than one-third for the Y-doped ZnO samples. As a result, surface-to-volume ratios of Y-doped ZnO samples have successfully increased due to their decreased size. This decrease in particle size is consistent with the small crystalline size, primarily due to low crystallization in the presence of yttrium doping. However, the expansion of the crystal structure is observed. Chemical surface structures point to the major vibration of ZnO. However, some carbon-relating groups remain to appear. Optical property reveals similar trends for all Y-doped ZnO samples. The estimated band gap energy (Eg) was reduced to the minimum value for the 4 mol% condition. For use as a photocatalyst, the appropriate Y-doped ZnO for 4 mol% yttrium doping presents the maximum degradation efficiency of 61.19%. The improvement in photocatalytic degradation is caused by the synergy of decreased particle size and reduced Eg. Therefore, yttrium plays a role to decrease particle size and reduce Eg of Y-doped ZnO materials, thus leading to enhance photocatalytic performance.

Structural, optical and catalytic properties of ZnO-SiO2 colored powders with the visible light-driven activity

A set of samples of novel colorized zinc oxide-nanosilica composites was synthesized and analyzed. The color and optical properties are directly dependent on ZnO concentration in the composites. Visible light-driven (λ = 550 nm) catalytic activity on the degradation of pharmaceuticals was tested and indicated that the most active sample with 9 mmol of ZnO per 1 g of SiO2 was ca. 13 times (toward propanolol), 24 times (toward carbamazepine) and ca. 37 times (toward metoprolol) more effective than blank (catalyst-free photolysis) decontamination. Besides showing a typical charge transfer band on the UV–Vis spectra, all the samples demonstrated a visible light absorbance at ca. 500 nm. Due to the diminution of ZnO particles size, the sample with the minimal concentration of zinc oxide exhibited pronounced luminescence at the region of >500 nm. The microscopy confirmed the decrease of ZnO agglomerated crystalline phase with diminution of ZnO concentration over SiO2 matrix. XPS studies provided information about the chemical species contributing to the formation of nanocomposites, including the presence of some unexpected trace elements, and also the surface effects of incorporating ZnO nanoparticles into SiO2 matrix also. With the help of elemental analysis, certain impurities in ZnO were identified, which might be responsible for the outstanding optical and catalytic behavior of the samples. The toxicity results confirmed that applied process can be used for detoxification of wastewater.