M.A. Mahadik

Visible light catalysis of rhodamine B using nanostructured Fe2O3, TiO2 and TiO2/Fe2O3 thin films

The Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) composite films are deposited using spray pyrolysis method onto glass and FTO coated substrates. The structural, morphological, optical and photocatalytic properties of Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films are studied. XRD analysis confirms that films are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO(2) respectively. The photocatalytic activity was tested for the degradation of Rhrodamine B (Rh B) in aqueous medium. The rate constant (-k) was evaluated as a function of the initial concentration of species. Substantial reduction in concentrations of organic species was observed from COD and TOC analysis. Photocatalytic degradation effect is relatively higher in case of the TiO(2)/Fe(2)O(3) than TiO(2) and Fe(2)O(3) thin film photoelectrodes in the degradation of Rh B and 98% removal efficiency of Rh B is obtained after 20min. The photocatalytic experimental results indicate that TiO(2)/α-Fe(2)O(3) photoelectrode is promising material for removing of water pollutants.

Photoelectrocatalytic decolorization and degradation of textile effluent using ZnO thin films

Zinc oxide (ZnO) thin films have been successfully deposited onto fluorine doped tin oxide coated glass at substrate temperature of 400 °C and used as electrode in photoelectrocatalytic reactor. The untreated textile effluent was circulated through photoelectrocatalytic reactor under UVA illumination for the decolorization and degradation. Textile effluent was decolorized by 93% within 3h at room temperature with significant reduction in COD (69%). High performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR) analysis of samples before and after decolorization confirmed the degradation of dyes molecules from textile effluent into simpler oxidizable products. Phytotoxicity study revealed reduction in toxic nature of textile effluent after treatment.

Photoelectrocatalytic degradation of methyl blue using sprayed WO3 thin films

WO3 thin films have been deposited using simple chemical spray pyrolysis technique and successfully applied as photoanode for photoelectrocatalytic degradation of methylene blue. The films were deposited on bare glass and fluorine doped tin oxide coated glass substrates to study photoelectrochemical (PEC) properties, crystal structure, surface morphology, chemical composition and optical studies. The PEC results indicate that, the films deposited at 300xa0°C show the improved the photocurrent response relative to other deposited thin films. The monoclinic crystal structure of WO3 has been confirmed from X-ray diffraction studies. The Raman spectra of optimized films show two strong peaks at 271.34 and 327.27xa0cm−1 can be assigned to the bending δ (OWO) vibrations in the monoclinic WO3 structure. Field emission scanning electron microscopy showed that the film surface constituted of aggregates of very small seed like nanoparticles. UV–vis spectrophotometry shows that the WO3 film deposited at the 300xa0°C shows a band gap of ~2.66xa0eV and has emerged as one of the visible light photocatalysts, which can absorb light below 520xa0nm wavelength. The photocatalytic degradation of methyl blue has been investigated in aqueous solution. The removal of the color and decrease of UV–Visible absorbance was simultaneously able to show the oxidation of methylene blue dye.

Photoelectrocatalytic degradation of benzoic acid using Au doped TiO2 thin films

Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

Fabrication of ZnFe2O4 films and its application in photoelectrocatalytic degradation of salicylic acid.

ZnFe2O4 thin films are successfully deposited onto bare and fluorine doped tin oxide (FTO) coated quartz substrate using the spray pyrolysis method. The structure and morphology of ZnFe2O4 photoelectrodes were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The X-ray diffraction pattern confirms the polycrystalline nature of films with a spinel cubic crystal structure. The AFM micrographs shows the granular nature of the films. The dielectric constant and dielectric loss shows dispersion behavior as a function of frequency measured in the range from 20Hz to 1MHz. Photoelectrocatalysis degradation of salicylic acid using ZnFe2O4 photoelectrode under sunlight illumination has been investigated. The result shows that the degradation percentage of salicylic acid on ZnFe2O4 photoelectrodes is reached 49% under neutral conditions after 320min illumination. The decrease in values of COD from 19.4mg/L to 6.4mg/L indicates there is mineralization of salicylic acid with time.

Oxidative degradation of industrial wastewater using spray deposited TiO2/Au:Fe2O3 bilayered thin films

The Fe2O3, Au:Fe2O3, TiO2/Fe2O3 and TiO2/Au:Fe2O3 thin films are successfully prepared by the spray pyrolysis technique at an optimised substrate temperature of 400 °C and 470 °C, respectively onto amorphous and F:SnO2 coated glass substrates. The effect of TiO2 layer onto photoelectrochemical (PEC), structural, optical and morphological properties of Fe2O3, Au:Fe2O3, TiO2/Fe2O3 and TiO2/Au:Fe2O3 thin films is studied. The PEC characterization shows that, maximum values of short circuit current (Isc) and open circuit voltage (Voc) are (Isc = 185 μA and Voc = 450 mV) are at 38 nm thickness of TiO2. Deposited films are polycrystalline with a rhombohedral and anatase crystal structure having (104) preferred orientation. SEM and AFM images show deposited thin films are compact and uniform with seed like grains. The photocatalytic activities of the large surface area (64 cm(2)) TiO2/Au:Fe2O3 thin film photocatalysts were evaluated by photoelectrocatalytic degradation of industrial wastewater under sunlight light irradiation. The results show that the TiO2/Au:Fe2O3 thin film photocatalyst exhibited about 87% and 94% degradation of pollutant in sugarcane and textile industrial wastewater, respectively. The significant reduction in COD and BOD values from 95 mg/L to 13 mg/L and 75 mg/L to 11 mg/L, respectively was also observed.

Enhanced photocatalytic activity of sprayed Au doped ferric oxide thin films for salicylic acid degradation in aqueous medium

Various doping percentage of Au were successfully introduced into the Fe2O3 photocatalysts via a spray pyrolysis method different. The effect of Au doping on photoelectrochemical, structural, optical and morphological properties of these deposited thin films is studied. The PEC characterization shows that, the photocurrent increases gradually with increasing Au content initially up to 2at.% indicating the maximum values of short circuit current (Isc) and open circuit voltage (Voc) are (Isc=90μA and Voc=220.5mV) and then decreases after exceeding the optimal Au doping content. Therefore, the photocurrent of Au doped Fe2O3 photocatalysts can be adjusted by the Au content. Deposited films are polycrystalline with a rhombohedral crystal structure having (104) preferred orientation. SEM and AFM images show deposited thin films are compact and uniform. The photocatalytic activities of the Fe2O3 and Au:Fe2O3 photocatalyst were evaluated by photoelectrocatalytic degradation of salicylic acid under sunlight irradiation. The results show that the Au:Fe2O3 thin film photocatalyst exhibited about 45% more degradation of pollutants than the pure Fe2O3. Thus, in Au doped Fe2O3 photocatalysts, the interaction between Au and Fe2O3 reduces the recombination of photogenerated charge carriers and improve the photocatalytic activity.

Structural and electrical properties of barium titanate (BaTiO3) thin films obtained by spray pyrolysis method

Abstract Barium titanate (BaTiO3) thin films have been prepared using the spray pyrolysis method. The films were deposited onto a glass substrate at varying substrate temperature ranging from 250 to 350 °C with the interval of 50 °C. The structural, morphological, electrical and dielectric properties of the deposited films have been studied. The X-ray diffraction pattern confirmed the polycrystalline nature of the films with a cubic crystal structure. X-ray photoelectron spectroscopy (XPS) showed a good agreement of the thin films stoichiometry with BaTiO3. A presence of Ba, Ti and O in the BaTiO3 thin films was observed by energy dispersive X-ray analysis. The scanning electron microscopy (SEM) showed the heterogeneous distribution of cubical grains all over the substrate. The grain size decreased with an increase in substrate temperature. The dielectric constant and dielectric loss showed the dispersion behaviour as a function of frequency, measured in the frequency range of 20 Hz to 1 MHz. The AC conductivity (σac) measurement showed the linear nature of obtained films, which confirms conduction mechanism due to small polarons. Impedance spectroscopy has been used to study the electrical behaviour of BaTiO3 ferroelectric thin films. The ferroelectric hysteresis loop has been recorded at room temperature.

Fabrication of Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered thin films obtained by spray pyrolysis method for magnetoelectric (ME) effect measurement

The Ni0.4Zn0.6Fe2O4 ferrite, BaTiO3 ferroelectric and Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered magnetoelectric thin films have been synthesized onto the quartz substrates at optimized substrate temperatures (400, 250xa0°C) using the simple spray pyrolysis technique. These films were characterized for their structural, morphological, dielectric and magnetic properties. The XRD studies reveal that the films are polycrystalline in nature with spinel cubic structure. The morphological study shows the formation of agglomerated cubes like grains. The dielectric constant and dielectric loss is measured as a function of frequency in the frequency range 20xa0Hz–1xa0MHz. Impedance spectroscopy is used to study the electrical behavior of these thin films. The saturation magnetization of Ni0.4Zn0.6Fe2O4 ferrite and Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered thin films are 141 and 111xa0emuxa0cm−3, respectively. The value of magnetoelectric voltage obtained for Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered thin films is about 221xa0mV.