ZnO Crystalline Structure Research Articles

Preparation of ZnO Thick Films Activated with UV-LED for Efficient H2S Gas Sensing

In this work, ZnO thick films were synthesized via two simple and easy methods, mechanochemical synthesis and screen-printing deposition. The ZnO powders were obtained through milling at low temperature with milling times of 20, 40, and 60 min. The ZnO thick films were fabricated by depositing 10 cycles of ZnO inks onto glass substrates. The characterization of ZnO thick films revealed a thickness ranging from 4.9 to 5.4 µm with a surface roughness between 85 and 88 nm. The structural analysis confirmed a hexagonal wurtzite crystalline structure of ZnO, both in powders and in thick films, with a preferred orientation on the (002) and (101) planes. Nanostructures with sizes ranging from 36 to 46 nm were observed, exhibiting irregular agglomerated shapes, with an energy band found between 2.77 and 3.02 eV. A static experimental set up was fabricated for gas sensing tests with continuous UV-LED illumination. The ZnO thick films, well adhered to the glass substrate, demonstrated high sensitivity and selectivity to H2S gas under continuous UV-LED illumination at low operating temperatures ranging from 35 to 80 °C. The sensitivity was directly proportional, ranging from 3.93% to 22.40%, when detecting H2S gas concentrations from 25 to 600 ppm.

Photodegradation of cationic and anionic dyes by ZnO and S/ZnO biosynthesized nano‐photocatalysts

Photocatalysis is considered a promising and efficient oxidation technique for wastewater treatment. Developing more environmentally biocompatible, simple, effective, and inexpensive photocatalysts enables photocatalysis technology to be at the forefront of wastewater treatments. As an alternative to harmful chemicals, this work focused on the biosynthesis of a variety of ZnO and doped ZnO based on the extract of the brown alga Cystoseira crinite. X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform‐infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–vis) spectroscopy were used to characterize the structure, phase, morphology, and UV–vis properties of the biosynthesized samples. XRD showed the crystalline structure of ZnO and S‐doped ZnO. SEM analysis revealed agglomerated spherical particles of the prepared samples. EDX analysis confirmed the formation of S‐doped ZnO. FTIR spectra exhibited that phenolic compounds and protein molecules are present in the Cystoseira crinite extract. The photocatalytic efficiency of biosynthesized materials was examined by monitoring the degradation of crystal violet (CV) and methyl orange (MO) dyes, which serve as cationic and anionic dye models, respectively. The various factors that influence the efficacy of the photodegradation process were investigated. In total, 5% S‐doped ZnO decomposed 97.40% and 89.18% of CV and MO dyes, respectively. The dye degradation was most efficient in samples calcined at 500 °C. The photodegradation of CV dye was enhanced at high pH, while the highest photocatalytic activity of MO dye was observed at low pH values. The kinetic study confirmed that the photodegradation follows the first‐order reaction.

Experimental and density functional theory studies on some metal oxides and the derived nanoclusters: a comparative effects on human ferritin

A comprehensive investigation into the green synthesis of metal oxide nanoparticles (NPs) has garnered significant attention due to its commendable reliability, sustainability, and environmentally friendly attributes. Green synthesis methods play a crucial role in mitigating the adverse effects associated with conventional approaches employed for nanostructure preparation. This research endeavors to examine the impact of ginger plant extract-assisted green synthesis of metal oxides NPs on the serum ferritin levels of anemic diabetic patients in vitro, focusing specifically on α-Fe2O3 and ZnO NPs. Sixty diabetic volunteers with anemia (35–50 years) and thirty healthy volunteers were enrolled as controls. The assessment was conducted using the VIDAS Ferritin (FER) assay. Photoluminescence (PL) spectroscopy measurements were performed to elucidate the intrinsic and extrinsic transitions of these NPs, affirming the successful formation of α-structured iron oxide. Density functional theory (DFT) calculations were carried out at the B3LYP/6-311++G(d,2p) level of theory to investigate the geometry optimization and molecular electrostatic potential maps of the NPs. Furthermore, TD-DFT calculations were employed to explore their frontier molecular orbitals and various quantum chemical parameters. The binding affinity and interaction types of ZnO and α-Fe2O3 NPs to the active site of the human H-Chain Ferritin (PDB ID: 2FHA) target were determined with the help of molecular docking. Results unveiled the crystalline structure of ZnO and the α-structure of α-Fe2O3. Analysis of the frontier molecular orbitals and dipole moment values demonstrated that ZnO (total dipole moment (D) = 5.80 µ) exhibited superior chemical reactivity, biological activity, and stronger molecular interactions with diverse force fields compared to α-Fe2O3 (D = 2.65 µ). Molecular docking of the metal oxides NPs with human H-chain ferritin provided evidence of robust hydrogen bond interactions and metal-acceptor bonds between the metal oxides and the target protein. This finding could have a great impact on using metal oxides NPs-ferritin as a therapeutic protein, however, further studies on their toxicity are required.Graphical abstract

Defect analysis and microstructural characterization of zinc-substituted cadmium oxide nanocrystallites by positron annihilation and supplementary methods

Pure and zinc-doped cadmium oxide nanocrystallites of sizes in the range 25 nm to 16 nm are synthesized by adopting a chemical precipitation method and by varying the doping concentration from 0.0 to 0.25. The decrease in nanocrystallite sizes with increasing substitution is expected from the smaller ionic radii of Zn2+. But more revealing is the interfacial defects formation at higher concentration of doping, which is attributed to the dissimilar crystalline structure of ZnO and CdO. X-ray diffraction patterns show well defined peaks and additional characterisation is done through transmission electron microscopy. The optical band gap measurements indicate the dominance of substitution-induced disorder over the confinement of excitons, leading to a decrease in the band gap energies. The results of positron annihilation studies confirm the cancellation of the existing vacancy type defects in the initial stage, followed by the substitution. Photoluminescence spectra reveal the distinct peaks of optical plasmonic excitations and the defect population in the bandgap and the intensity variations agreed with that of the defect related positron annihilation lifetime intensity. The segregation of ZnO phase leading to the formation of interfacial boundaries is found as a strong deterrent against the success of continued substitution.

Influence of Copper Doping on Structural and Opto-Electronic Properties of Zinc Oxide Nanoparticles

In this work, we elucidate the opto-electronic properties of pure zinc oxide and copper- doped zinc oxide nanoparticles prepared via the sol-gel method. Here, the main objective is to study the impact of copper doping on the crystalline structure of ZnO and to explore the composition dependent variations in opto-electronic properties. Synthesized ZnO nanoparticles were characterized by SEM, FTIR, UV–vis-nir, and Raman Spectroscopy. The structural and opto-electronic properties are further correlated using UV-vis-nir and high-resolution X- ray diffractometer data analysis. The size of synthesized nanoparticles are found in the range of 9.2 nm to 95.5 nm. Bandgaps are found both in the visible range (2.72 eV – 2.96 eV) as well as in the infrared regions (1.54 eV-1.58 eV). The transmittance of copper doped ZnO nanoparticles increases with increase in the doping concentrations.

ZnO and C/ZnO Catalysts Synthesized via Plant Mediated Extracts for Photodegradation of Crystal Violet and Methyl Orange Dyes

In this study, aqueous Cystoseira crinite extract was used to successfully biosynthesize ZnO and C-doped ZnO samples. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX), FTIR, and UV–vis techniques were used to characterize the biosynthesized samples. XRD technique confirmed the crystalline structure of ZnO and C-doped ZnO. EDX confirmed the formation of C-doped ZnO. SEM analysis revealed the spherical shape of the samples with agglomeration. FTIR spectra showed that phenolic compounds and protein molecules are present in the Cystoseira crinite extract. The photocatalytic activity of the prepared photocatalysts was investigated using crystal violet (CV) as a model of the cationic dyes and methyl orange (MO) as a model of the anionic dyes. 5%C-doped ZnO calcined at 500 °C showed an optimum photocatalytic efficiency of 92.7% and 87.8% for CV and MO dyes, respectively. The improved photocatalytic activity could be attributed to the narrower optical band gap of C doped ZnO than pure ZnO. The photocatalytic activity of CV and MO dyes follows the first-order kinetics with high correlation coefficient values.Graphical

Preparation and characterization of nanocomposites based on chitosan with ZnO-Curcumin

The present paper studied the possibility to obtain nanocomposites of chitosan incorporated with ZnO NP, whose surface has been modified with bioactive compounds. To obtain ZnO nanoparticles, the biogenic method was used and the anchoring of curcumin (CRC) on the surface of the particles was followed. Chitosan-based ZnO-CRC were synthesized using ex-situ method that involves the separate preparation of ZnO particles and their dispersion in the chitosan matrix by mechanical and ultrasonic mixing. The structural and morphological studies of the synthesized samples were carried out using X-ray diffraction, SEM microscopy, FTIR and EDX spectroscopy, and the wetting capacity. The XRD analysis revealed wurtzite crystalline structure of ZnO, anchoring of curcumin to the oxide surface, with an average crystallite size about 18.7 nm. The morphological study shows that the particles have spherical formations, with dimensions in the nanometric range and a relatively uniform distribution of ZnO particles in the matrix. Elemental composition of samples was identified using EDX analysis. Contact angle was measured to evaluate the hydrophilic and/or hydrophobic character of the surfaces. The results demonstrate that the synthesized materials have morpho-structural and wetting characteristics that allow the extension of applicability in biotechnological fields as coating systems.

Comparative study of zinc oxide nanoparticles synthesized through biogenic and chemical route with reference to antibacterial, antibiofilm and anticancer activities

The present focused on comparative study on synthesis of ZnO nanoparticles (ZnO NPs) using chemical method via alkaline precipitation method (ZnO(A) NPs) using NaOH and biogenic method using termite mound extract (ZnO(B) NPs). GC-MS analysis revealed that D-limonene present in termite mound extract might be responsible for the synthesis of ZnO(B) NPs. XRD patterns confirmed hexagonal crystalline structure of ZnO(A) and (B) NPs. Results of antibacterial activity illustrated that ZnO(B) NPs showed its potential against Pseudomonas aeruginosa, ESBL-1, ESBL-2 and EBSL-3. Antibiofilm studies revealed that ZnO(B) NPs exhibited optimum decline in MRSA biofilm formation than ZnO(A) NPs. In addition, ZnO(B) NPs showed potent cytotoxic effect against lung cancer cell lines A549 with IC50 of 35.16 ± 0.10 μg/mL in comparison with ZnO(A) NPs (IC50- 55.09 ± 0.30 μg/mL). Overall, the results revealed that biogenic synthesis of ZnO NPs ensures its biosafety level and enhanced biological activity when compared to chemical synthesis method.

Elucidation of the role of ZnO in sulfur cure in novel EPDM-CTS blends

A new concept is introduced in this study, suggesting the role played by the ZnO crystal in sulfur crosslinking polymers, particularly, rubber blends of EPDM-CTS. The study is conducted in a polymer blend of ethylene propylene diene terpolymer (EPDM) and cyclic tetrasulfide (CTS). CTS is a reactive low molecular weight polymer, which can act as a sulfur donor. It is proposed that the sulfur crosslinking occurs at the surface of the ZnO crystals. A reaction site is created on the surface of the ZnO crystal by the reaction with stearic acid, which creates a “template” or active site on the surface as a catalytic site for the CTS reaction to take place. Various experiments are performed to substantiate the newly proposed role the crystalline ZnO structure plays in influencing the initiation of the sulfur crosslinking. The investigation is conducted in rubber compounds in the absence of fillers and other additives and additionally in chemical model studies. The analyses conducted in rubber compounds are performed on fully or partially cured rubber to study the evolution of the chemical process involved in the CTS reaction and the curing of the rubber blends. Step-cured compound allows analyses of the transformation of the ZnO crystal size during the sulfur crosslinking process, and the ability to gauge the step transformation that the ZnO crystal is undergoing during the crosslinking process. Additional chemical model studies are used in the study of the influence of the ZnO crystal on sulfur crosslinking, to confirm the reaction path and by-products of reaction. Lastly, quantum mechanical (QM) and molecular mechanics (MM) calculations are applied in support of the suggested mechanism of reaction.

The Influence of Al Doping on the Optical Characteristics of ZnO Nanopowders Obtained by the Low-Cost Sol-Gel Method

In this work, the influence of Al (0, 2, 4, and 6 wt.%) on the optical properties of ZnO has been briefly investigated and described. The undoped and doped samples were characterized using a UV-visible spectrophotometer and Photoluminescence (PL). The X-ray diffraction (XRD) data in our preceding study is also indexed, and materials are said to have a wurtzite-structured hexagonal phase and exhibit no impurity phases. The average crystallite sizes of the pure ZnO were found to increase, i.e., from 14.19 nm to 34.17 nm with an increase in temperature, and in the case of Al-doped ZnO, at a constant temperature, from 35.05 nm to 18.89 nm, respectively. The average crystallite size of AZO (Al-doped ZnO) decreases with increasing Al content. With the increasing temperature, increases in crystallinity and size of the pure ZnO have been observed. In the case of Al doping, with an increase in the concentration of doping the crystallite size is seen to be decreased, without any change in the temperature. Al doping improves the formation of the well-ordered crystalline structure of ZnO up to a certain limit of doping. The absorbance spectra were used to determine the optical band gap of the samples. The optical photoluminescence (PL) spectra of both ZnO and AZO nanopowder are obviously influenced by the increasing temperature and Al doping content, respectively. Different optical properties of ZnO and AZO were observed for different contents of Al in ZnO. The band gap of AZO nanopowder with different concentrations has been seen to be lower than that of undoped ZnO (3.10 eV), suggesting broad application potential. Also, the optical properties of ZnO were tailored by Al doping in the near visible region, suggesting various potential uses.

Development of antibacterial and superabsorbent wound composite sponges containing carboxymethyl cellulose/gelatin/Cu-doped ZnO nanoparticles

This study aimed to develop a novel antibacterial and superabsorbent dressing by introducing the Cu-doped ZnO nanoparticles into the carboxymethyl cellulose/gelatin glutaraldehyde-crosslinked composite sponge that is fabricated by lyophilization method. Undoped and Cu-doped ZnO (Zn1−xCuxO, x = 0.03 and 0.05) nanoparticles were synthesized through the stabilizing agent-used precipitation process and characterized by XRD, FESEM, FTIR, and ICP-OES techniques. The XRD evaluation determined that the concentration of copper in ZnO is limited to below 5%. Additionally, The ICP-OES analysis confirmed the effect of the doping process on the ZnO crystalline structure by releasing more zinc and copper ions from Cu-doped ZnO, which resulted to improve antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains. The effect of ZnO nanoparticles on the physical and mechanical performance of the optimized composite sponge indicated that the incorporation of 3 wt% ZnO nanoparticles produces a well-interconnected porous structure (~156 µm) with high water absorption (~3089%) and proper elongation (~49%) in a wet medium. The incorporation of Cu-doped ZnO nanoparticles enhanced antibacterial potential of the composite sponge. Meanwhile, all sponge groups are safe for viability, proliferation and adhesion of human dermal fibroblast cells. Overall, the obtained data has proved the potential of carboxymethyl cellulose/gelatin/Cu-doped ZnO dressing as a promising candidate for managing infected wounds.

Photocatalytic Degradation of Methylene Blue Dye with Green Zinc Oxide Doped with Nitrogen

The non-biodegradability of organic pollutants and their adverse effects on plant and living organisms makes their removal from the environment vital for the preservation of the ecosystem. In this study, Photocatalysis (one of the advanced oxidation processes) was employed for the removal of methylene blue dye (MBD). Phyto-enhanced synthesized Zinc oxide (G.S ZnO) were precipitated from an aqueous solution of zinc nitrate hexahydrate and Papaya leaf extracts. The precipitates were dried at 100 oC for 24 hours, and doped hydrothermally with nitrogen from Urea at different doping ratios (10%, 5% and 2%). Preliminary degradation of MBD with the different compositions of Photocatalyst revealed that 5% G.S N-ZnO had superior photocatalytic capabilities than pure ZnO, 10% G.S N-ZnO, 2% G.S N-ZnO. The effects of solution pH, 5% G.S N-ZnO dosage and initial solution concentration on MBD degradation were studied. An optimum percentage degradation of 83% and 97.5% were observed for pure ZnO and G.S. N-ZnO photocatalyst at a solution pH of 9.0, MB solution concentration of 10 mg/L and photocatalyst of dosage of 100 mg. Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR) were used to study morphology, structural properties, surface area and pore volume, and functional groups of Pure ZnO and 5% G.S N-ZnO. FTIR spectra of the 5% G.S N-ZnO was in the range of 4000-500cm-1, and the ZnO group of G.S N-ZnO was at a low wavenumber. The BET result revealed the surface area of 5% G.S N-ZnO to be 113.3cm2/g which was five times that of pure ZnO. The BET result showed an increase in pore volume and diameter (2.118nm and 0.055cm3/g) of 5% G.S N-ZnO against that of pure ZnO (1.452 nm and 0.010 cm3/g). The shift of the XRD pattern between pure ZnO and 5% G.S N-ZnO affirms the presence of dopants in the crystalline structure of ZnO. The average crystallite sizes of pure ZnO and 5% G.S N-ZnO were 34.7nm and 24.8nm, respectively. The findings from this research revealed that the simultaneous use of green synthesis and doping could further improve the degradation of methylene blue dye compounds in industrial effluents and ultimately increase the efficiency of wastewater treatment processes/systems.

Synthesize of Cerium-doped ZnO nanoparticles as antioxidant agent

Zinc oxide nanoparticles are potential metal oxide for antioxidant agent. This paper investigates antioxidant activity of cerium-doped zinc oxide (Ce-doped ZnO) nanoparticles. Ce-doped ZnO nanoparticles was prepared by precipitation method with calcination temperature of 200˚C. The product of precipitate was characterized by X-ray diffraction measurement, and UV-Vis spectrophotometer. The antioxidant activity of Ce-doped ZnO nanoparticles was investigated using 1,1-diphenyl-2-pcrylhydrazyl (DPPH) method. The X-ray diffraction pattern showed the growth of Ce-doped ZnO crystalline structure of hexagonal wurtzite with crystallite size of 42 nm. UV-Vis absorbance spectrum analysis revealed the band gap energy of Ce-doped ZnO nanoparticles was smaller than band gap energy of bulk ZnO. Ce-doped ZnO nanoparticles could scavenge DPPH free radicals and exhibited moderate antioxidant activity.

Chemical synthesis versus green synthesis to obtain ZnO powders: Evaluation of the antibacterial capacity of the nanoparticles obtained by the chemical method

In this work, zinc oxide nanoparticles (ZnO-NPs) were synthesized using both a chemical route (polymeric complex method) and a green route (controlled precipitation, using suspensions of garlic, Allium sativum, and chili, Capsicum annuum, as solvents). The obtained solids were characterized using infrared and Raman spectroscopies, X-ray diffraction (XRD) and scanning electron microscopy (SEM). While the solid synthesized by the chemical pathway presented a wurtzite-like crystalline structure of ZnO, those obtained by green synthesis were essentially amorphous. In the IR spectra of the materials synthesized by the two methods, the presence of the characteristic bands of ZnO was evidenced, as well as the active groups of garlic and chili pepper in the IR spectrum of the sample obtained by green synthesis. Something similar happened with the Raman spectra of the synthesized samples. To account for the alterations found in both structure and composition of the obtained solids, a series of reactions were proposed between the zinc precursor with both the active garlic and chili molecules present in the solvent during green synthesis. Considering the potential use of synthesized ZnO as antibacterial material, the action of ZnO-NPs (< 100 nm with a spheroidal morphology) obtained by the chemical route was evaluated on a strain of Escherichia coli in the absence of UV radiation. The results indicated that the synthesized ZnO-NPs, in high and medium concentrations (between 500 and 32 µg/mL), inhibited growth of the bacteria, from ~ 70% to ~ 50% respectively, with a minimum inhibitory concentration, MIC50, of 30.40 µg/mL

Photocatalytic degradation of atrazine under visible light using Gd-doped ZnO prepared by supercritical antisolvent precipitation route

Supercritical antisolvent precipitation route was employed for the first time to prepare Gd-doped ZnO photocatalysts to be tested in the photocatalytic degradation of atrazine under visible light. Physical-chemical characterization data show that the addition of Gd does not change the crystalline structure of ZnO and that Gd3+ ions are successfully introduced into the semiconductor lattice, leading to a decrease of band gap energy value and inducing the formation of oxygen vacancies inside the ZnO framework. The photocatalytic performances of the as-prepared samples are determined by analyzing the degradation of atrazine under visible light irradiation. The doped photocatalyst with a Gd loading of 0.7 mol% exhibits the highest photocatalytic activity under visible light irradiation compared to the other prepared photocatalysts. The possible reaction mechanism of the optimized photocatalyst is also discussed.

Immunosensor Based on Zinc Oxide Nanocrystals Decorated with Copper for the Electrochemical Detection of Human Salivary Alpha-Amylase.

(1) Background: Nanocrystals (NCs)-based electrochemical sensors have been proposed for biomarkers detection, although immunosensors using ZnO NCs decorated with copper are still scarce. (2) Methods: Electrochemical immunodetection of human salivary alpha-amylase (HSA) used ZnO, CuO, and ZnO:xCu (x = 0.1, 0.4, 1.0, 4.0, and 12.0) NCs. (3) Results: Substitutional incorporation of Cu2+ in the crystalline structure of ZnO and formation of nanocomposite were demonstrated by characterization. Graphite electrodes were used and the electrochemical signal increased by 40% when using ZnO:1Cu and 4Cu (0.25 mg·mL−1), in an immunosensor (0.372 mg·mL−1 of anti-alpha-amylase and 1% of casein). Different interactions of HSA with the alpha-amylase antibody were registered when adding the NCs together, either before or after the addition of saliva (4 μL). The immunosensor changed specificity due to the interaction of copper. The ZnO:1Cu and ZnO:4Cu samples showed 50% interference in detection when used before the addition of saliva. The immunosensor showed 100% specificity and a sensitivity of 0.00196 U·mL−1. (4) Conclusions: Results showed that the order of NCs addition in the sensors should be tested and evaluated to avoid misinterpretation in detection and to enable advances in the validation of the immunosensor.

Flexible zinc oxide photoelectrode for photo electrochemical energy conversion

Photoelectrochemical properties have been investigated for flexible photoelectrodes containing 310 nm thick ZnO film on spin-coated ITO/PET. The high crystalline structure of ZnO was studied using x-ray diffraction pattern. A value of 3.4 eV has been estimated for optical band gap from its absorption spectra. The flexible ZnO photoelectrode was demonstrated to generate photoelectrochemical current. The photocurrents are enhanced by 4% whereas flat-band potential is shifted by 8 V due to the illumination. Values of 1.022 and 0.714 AW−1 were found to be for photo switching and photoresponsivity, respectively. ZnO/ITO/PET can be used as a substrate for making flexible hybrid PEC devices to generate solar power and solar fuels.

Structural characterization of starch capped ZnO nanoparticles

Zinc oxide nanoparticles have been synthesized by a simple green synthesis route using soluble starch as a capping agent in an aqueous medium. The results of structural investigation of ZnO nanoparticles using various techniques such as X-ray diffraction, scanning electron microscope and Fourier transforms spectroscopy have been presented. XRD confirms the formation of c-axis orientated hexagonal wurtzite crystalline structure of ZnO with average particle size in the range of 21 nm to 25 nm. The morphology of the ZnO samples were determined by SEM images, indicating nano rod like structure with hexagonal phase for starch capped ZnO nanoparticles. Further, the presence of starch and different functional group in synthesized ZnO nanoparticles have been studied by Fourier transform spectroscopy approve the different bonding between starch with Zn.

Characterization of Zinc Oxide-Urea Formaldehyde Nano Resin and Its Impact on the Physical Performance of Medium-Density Fiberboard.

The main purpose of this research work is to characterize zinc oxide-urea formaldehyde nano resin and identify the physical performance of medium-density fiberboard (MDF). Considering the dry weight of natural fibers, the ZnO nanoparticles were added to urea formaldehyde (UF) glue at four levels—0.0%, 1.0%, 2.0% and 3.0%—and their effects were investigated in terms of the physical properties of MDF. The surface morphology and crystalline structure of ZnO, UF and UF-ZnO nanofillers were characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analysis and significant improvements were achieved as a result of the addition of nanoparticles. Thermal properties were analyzed by means of differential scanning calorimetry (DSC) and thermogravemetric analysis (TGA) and it was observed that increasing the concentration of ZnO nanoparticles ultimately enhanced the curing of UF-ZnO nanofillers. Finally, density, thickness swelling and water absorption properties were investigated and it was observed that thickness swelling and water absorption properties were improved by 38% and 12%, respectively, when compared to control MDF.

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.