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Sol–gel dip coating method has been employed for the deposition of nanostructured single nickel oxide (NiO) and zinc oxide (ZnO) films and multilayered NiO/ZnO/NiO and ZnO/NiO/ZnO films. The structural, morphology and optical properties of prepared films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis spectroscopy, respectively. XRD analysis showed that ZnO-based films crystallized in write phase and presented an epitaxial orientation depending on the substrate. SEM images also showed uniform size distribution around 30–70 nm for all samples. Antibacterial effectiveness of NiO and ZnO- based films were tested against general Escherichia coli (E. coli ATCC 25922) and Streptococcus aureus (S. aureus, ATCC 29213) as Gram negative and Gram positive model, respectively, using the so-called drop-test method under UV light illumination and dark conditions. ZnO/NiO/ZnO film was found to be the most toxic among tested samples, followed by ZnO, NiO/ZnO/NiO and NiO films. Samples exposure to UV light resulted in higher activity compared to dark conditions against both E. coli and S. aureus, but considerably more effective in the former case. The obtained results were discussed according to the lattice matching between the heteroepitaxial films and structural modification as key roles on the preferential growth orientation and antibacterial activity.

ZnO and Indium doped ZnO nanostructures with different morphologies have been synthesized by mild solvothermal method in the presence of cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS) and Tritron X-100 as cationic, anionic and nonionic surfactants, respectively. The hydrothermal growth mechanism was influenced by Indium impurity and surfactant. Hexagonal, flower, polyhedral and nearly spherical morphologies of ZnO were obtained. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) methods. The role of surfactant charge on the ZnO growth orientation was investigated and related mechanism discussed. The highest degradation rate constant was observed for In doped flower-like ZnO synthesized using CTAB. The effects of In doping and surfactant charge on the structure, morphology, optical properties and photocatalytic activity (PCA) of ZnO nanostructures were investigated and discussed in detail. Obtained results can be utilized in the synthesis of ZnO NSs with desired growth orientation and consequently enhanced properties.

SiO 2 doped samples with different cobalt loading and pure SiO 2 and Co 3 O 4 nanopowders were synthesized by the solvothermal method and their antibacterial activities were studied. The morphology and crystallinity of the powders were analyzed by scanning electron microscopy and X-ray diffractometry patterns, respectively. The increase of particle size with doping concentration was obtained for cobalt-doped samples. The optical properties were studied using UV–vis spectroscopy. Optical studies showed a blue shift in the absorbance spectrum with increasing the doping concentration. The antibacterial activities of undoped SiO 2 , Co-doped SiO 2 and pure Co 3 O 4 nanoparticles against a Gram-negative bacterium Escherichia coli ( E. coli , ATCC 25922) and a Gram-positive bacterium Staphylococcus aureus ( S. aureus , ATCC 29213) were investigated under UV illumination and in the dark condition. Bactericidal effects were determined by the minimum inhibitory concentration (MIC) method. There was no activity for pure SiO 2 and Co 3 O 4 , however, cobalt doping significantly improved antibacterial activity against both bacteria. Bacterial growth inhibition was observed under dark condition with lower efficiency than under UV illumination. The antibacterial efficiencies were affected by the physiological status of the bacterial cells, different morphologies, particle sizes and optical properties of samples.

SnO 2 hierarchical architectures were synthesized by a surfactant-free hydrothermal synthesis route. The influence of hydrothermal temperature and treatment time on the final morphology of the nanomaterials was studied. The as-synthesized nanoparticles were characterized by X-ray powder diffraction (XRD), UV–vis spectroscopy, scanning electron microscopy (SEM) and adsorption isotherm measurement. Degradation of aniline, 4-nitroaniline and 2,4-dinitroaniline as model organic pollutants was studied in the presence and absence of ultraviolet radiation. The effects of experimental parameters including irradiation time, solution pH and organics structure on the degradability were studied. The photodegradation of the pollutants followed first-order kinetics. The influence of SnO 2 morphology on its photocatalytic activity was comparatively investigated. The SnO 2 flower-shaped catalysts showed higher activity compared with others suggesting that the morphology of the catalysts exerts a noticeable influence on their performances.

The enhanced sonophotocatalytic degradation of Chrome Intra Orange G (C.I. 18745), an azo dye, in aqueous solution under UV light has been carried out using solvothermally sensitized ZnO nanoparticles as catalyst. The effects of sonolysis, sonocatalysis, photocatalysis and sonophotocatalysis have been examined to study the influences on the degradation rates by varying the initial dye concentration, dye solution pH, catalyst morphology and loading to ascertain the synergistic effect on the degradation techniques. ZnO sonophotocatalysis was always faster than the respective individual processes. Ultrasound may modify the rate of photocatalytic degradation by promoting the deaggregation of the catalyst and ultrasound-induced increase of its active surface area, by increasing the amount of reactive radical species through cavitation leading to water splitting and formation of H 2 O 2 by both photocatalysis and sonolysis. To further verify the direct relation of the effective surface area offered by ZnO to its reaction rate, sonophotocatalysis experiments were conducted using nanorods of different dimensions and aspect ratios. Higher aspect ratio values correspond to an enhancement of the sonophotocatalytic activity.

The textile industry is characterized by high consumption of water, fuel, and chemicals. The wastewater treatment and recycling possibilities in the textile industry are environmentally of the highest importance. The most common chemical pollutants present in textile industry wastewater are the azo-dyes. The solution based sol–gel method was used to synthesize ZnO thin films using different solvents to evaluate the morphology-dependent photocatalytic activity toward the degradation of two azo dyes including sodium [3-[(4,5-dihydro- 3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-2-hydroxy-5-nitrobenzenesulp-honato (3-)] hydroxychromate (1-) and sodium (5-((4′-((2,6-dihydroxy-3-((2-hydroxy-5-sulfophenyl)azo)phenyl)azo)-4-biphenylylazo) salicylato (4-)) cuprate (2-) in water. 2-Propanol, methanol, ethanol, and 1,4-butanediol were used as solvents. The photocatalytic degradation rates depend on the dye structure and concentration, solvent-dependent ZnO film morphologies, pH of the medium and excitation light source. The observed rate constants of ZnO film prepared using 2-propanol and of ZnO film prepared using methanol were enhanced approximately by a factor of 3 under UV light and under visible light, respectively. The obtained results were discussed according to the structure and morphology of ZnO films as key parameters in photocatalytic activity.

In the present study, the effects of the heterojunctions on the optical and structural characteristics and the resulting photocatalytic properties of multilayered ZnO-based thin films were investigated. The junctions were composed of semiconducting ZnO nano-porous films coated on the In2O3 and SnO2 counterpart layers. The multilayered ZnO films based on the triple-layered Ag-doped indium oxide (AIO)/tin oxide (TO)/zinc oxide (ZnO), indium oxide (IO)/Ag-doped tin oxide (ATO)/zinc oxide (ZnO), indium oxide (IO)/tin oxide (TO)/zinc oxide (ZnO) and tin oxide (TO)/ indium oxide (IO)/zinc oxide (ZnO) have been fabricated by subsequent sol‐gel dip coating. Their structural and optical properties combined with photocatalytic characteristics were examined toward degradation of Solantine Brown BRL (C.I. Direct Brown), an azo dye using in Iran textile industries as organic model under UV light irradiation. Effects of operational parameters such as initial concentration of azo dye, irradiation time, solution pH, absence and presence of Ag doping and consequent of sublayers on the photodegradation efficiencies of ZnO nultilayered thin films were also investigated and optimum conditions were established. It was found that the photocatalytic degradation of azo dye on the composite films followed pseudo-first order kinetics. Photocatalytic activity of AIO/TO/ZnO interface composite film was higher compared with other films and the following order was observed for films activities: AIO/TO/ZnO > IO/TO/ZnO > ATO/IO/ZnO > TO/IO/ZnO. Differences in the film efficiencies can be attributed to differences in crystallinity, interfacial lattice mismatch, and surface morphology. Besides, the presence of Ag doping between layers that may act as trap for electrons generated in the ZnO over layer thus preventing electron‐hole recombination. # 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Nanostructure single ZnO, SnO2, In2O3 and composite ZnO/SnO2, ZnO/In2O3 and ZnO/SnO2/In2O3 films were prepared using sol–gel method. The obtained composite films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis spectroscopy. The photocatalytic activities of composite films were investigated using phenol (P), 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) and 4-aminophenol (4-AP) as a model organic compounds under UV light irradiation. Hybrid semiconductor thin films showed a higher photocatalytic activity than single component ZnO, SnO2 and In2O3 films. The substituted phenols degrade faster than phenol. The ease of degradation of phenols is different for each catalyst and the order of catalytic efficiency is also different for each phenol. The use of multiple components offered a higher control of their properties by varying the composition of the materials and related parameters such as morphology and interface. It was also found that the photocatalytic degradation of phenolic compounds on the composite films and single films followed pseudo-first order kinetics.

Indium oxide (In 2 O 3 ), zinc oxide (ZnO), stannic oxide (SnO 2 ), and titanium dioxide (TiO 2 ) thin films were prepared on glass substrates using electron beam evaporation. The samples characterized by UV–vis spectroscopy, diffraction ray-X and scanning electron microscopy techniques. The photocatalytic degradation of methylene blue in an aqueous solution, as a model compound, was investigated using different metal oxides in an attempt to compare the decomposition reaction rate. The progress of degradation was monitored using UV–vis spectrophotometry. The effects of various experimental parameters such as initial concentration of methylene blue (5–10 mg/l), pH of the solution (2–8), annealing temperature (250–550 °C), and catalyst nature and its microstructure were systematically studied in order to achieve maximum degradation efficiency. The results obtained were fitted with the Langmuir–Hinshelwood model to study the degradation kinetics and discussed in detail. Nearly complete degradation was obtained at optimal operational parameters including the higher annealing temperature of thin film and the increase in MB solution pH. The degradation with In 2 O 3 was more efficient than with SnO 2 , ZnO and TiO 2 films.

Photocatalytically active indium tin oxide thin film electrodes were prepared by electron beam evaporation technique onto a glass substrate having thickness 120 nm. Degradation of reactive dye yellow direct 42 has been performed using photoeletrocatalysis. A biased potential is applied across indium tin oxide photoelectrode illuminated by UV light. The best experimental conditions were found to be dye concentration 1.0 × 10− 5 mol L− 1, pH 5.25 and 0.5 mol L− 1 NaCl as supporting electrolyte when the photoelectrode was biased at + 0.5 V versus saturated calomel electrode. The effects of other electrolytes, dye concentration, pH solution, electrode annealing temperature and applied potentials have been also investigated and are discussed. Several common inorganic salts Na2SO4, Na2CO3, NaNO3 and NaCl were chosen to act as supporting electrolytes, which was added into the dye solution. It is shown that the charge-transfer resistance of photoanode can be calculated by the analysis of its electrochemical impedance spectroscopy, and the photoelectrocatalytic degradation rate of yellow direct 42 was inversely proportional to the value of charge-transfer resistance of photoelectrodes at different pH. The value of charge-transfer resistance is smaller, the higher its photoelectro-activity is.