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[en] Highlights: • ZnO based MSM UV photodetector by economical chemical spray pyrolysis technique. • Effect of substrate temperature on properties of ZnO based MSM UV photodetector. • Photoresponse mechanism by optical switching property of ZnO thin film photodetectors. - Abstract: Zinc oxide (ZnO) based metal–semiconductor–metal (MSM) ultraviolet photodetectors at different substrate temperatures were fabricated on glass substrates by economical chemical spray pyrolysis technique and its UV photoresponsivity was measured at room temperature. The samples were characterized with respect to their structural, morphological, and optical properties using various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, transmittance, reflectance etc. The synthesized ZnO thin films were c-axis oriented with hexagonal crystal structure as confirmed from XRD. All deposited films were specular and show high transmittance (∼85%) in visible region with steep fall off at 375 nm. The photoconductive MSM UV photodetector showed relatively high photocurrent (1.3 mA) and fast switching. ZnO thin films exhibited relatively high photoresponsivity (788 A/W) with cut of wavelength ∼375 nm signifying their application as UV detector
[en] The thin films of cadmium indium selenide (CdIn2Se4) have been deposited onto amorphous glass substrates using simple and low cost spray pyrolysis technique. The aqueous solutions containing precursors of Cd, In and Se have been used to obtain good quality deposits at different substrate temperatures. The preparative parameters, such as substrate temperature and concentration of precursor solution have been optimized and are found to be 280 deg. C and 0.0125 M, respectively. The films have been characterized by X-ray diffraction (XRD), optical absorption and energy dispersive analysis by X-rays (EDAX) techniques. The spray-deposited CdIn2Se4 films are polycrystalline with cubic crystal structure. The optical absorption studies reveal that the transition is direct with band gap energy Eg=1.92 eV. The EDAX studies reveal that the films obtained at substrate temperature 280 deg. C are nearly stoichiometric
[en] Highlights: • The photoactivity of sprayed WO_3 thin film. • Photoelectrocatalytic degradation of salicylic acid. • Reaction kinetics and mineralization of pollutants by COD. - Abstract: The WO_3 thin films were deposited using spray pyrolysis technique. The prepared WO_3 thin films were characterized using photoelectrochemical (PEC), X-ray diffraction, atomic force microscopy (AFM), and UV–vis absorbance spectroscopy techniques. PEC measurements of WO_3 films deposited at different deposition temperatures were carried out to study photoresponse. The maximum photocurrent (I_p_h = 261 μA/cm"2) was observed for the film deposited at the 225 °C. The monoclinic crystal structure of WO_3 has been confirmed from X-ray diffraction studies. AFM studies were used to calculate particle size and average roughness of the films. Optical absorbance was studied to estimate the bandgap energy of WO_3 thin film which was about 2.65 eV. The photoelectrocatalytic activity of WO_3 film was studied by degradation of salicylic acid with reducing concentrations as function of reaction time. The WO_3 photocatalyst degraded salicylic acid to about 67.14% with significant reduction in chemical oxygen demand (COD) value
[en] Nanoparticles of Li_0_._5_−_0_._5_xCo_xFe_2_._5_−_0_._5_xO_4 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) were synthesized by the solution combustion method. The influence of Co substitution on the structural, morphological and magnetic properties of the prepared samples was studied. The XRD studies confirm the formation of single phase cubic spinel structure of the ferrite samples. Their lattice constants vary linearly from 8.31 Å (x=0) to 8.35 Å (x=0.6) with increasing Co"2"+ content, due to the ionic volume differences of Co"2"+, Fe"3"+ and Li"1"+ ions. Also, the bond lengths and site radii of octahedral and tetrahedral sites are found to increase linearly with Co"2"+ content. The crystallite sizes of all the prepared samples estimated from the full width half maximum (FWHM) of the strongest reflection of the planes (311) almost remain constant with the increase of Co"2"+ content. The surface morphology of the prepared ferrite samples show that some of the particles have a cubic and the others have a spherical shape. The average particle sizes of the samples obtained from SEM micrographs show an initial increase up to the sample of x=0.3 and then it decreases slightly. The magnetic properties of the samples have been studied by measuring M–H plots. Moreover, the saturation magnetization, remnant magnetization, and coercivity of the prepared samples increase up to the sample of x=0.3 (140.1 emu/g, 49.4 emu/g and 714.05 Oe, respectively) and then they decrease again. The variation in the experimental magnetic moment μ_B _e_x_p with Co"2"+ content is explained on the basis of Neel's two sub-lattice model. Furthermore, the initial permeability of the prepared samples increases with increasing Co"2"+ content up to the sample of x=0.3 and then a slight decrease is observed again. - Highlights: • Co substituted Li ferrite samples were prepared by the solution combustion method. • Co"2"+ content, x was varied as x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6. • Effect of Co"2"+ content on structural and magnetic properties was studied. • The sample of x=0.3 has the maximum saturation magnetization M_s (140.1 emu/g). • μ_B _e_x_p varying depends on cation distribution and their spin alignment
[en] Cobalt ferrite thin films were deposited onto quartz substrates by spray pyrolysis technique and their gas sensing properties were investigated. X-ray diffraction study confirms that films are polycrystalline in nature and exhibit single phase spinel cubic crystal structure. DC electrical resistivity measurement indicates the semiconducting nature of the films. The surface morphology study confirms the formation of grains structure with grain size about 200–400 nm. Room temperature variation of dielectric properties with frequency suggests the normal dielectric performance of the cobalt ferrite thin film. The influence of quantities of spraying solutions on the operating temperature, sensitivity and selectivity, gas concentrations, response and recovery characteristics of gas sensor are systematically tested. The maximum gas response 95% was observed for film prepared at 50 mL quantity of solution for 80 ppm NO2. The films are extremely selective towards NO2 as compared to other target gases. Gas response attains nearly 90% of its initial value after 90 days indicates good durability of the films. - Highlights: • Synthesis of CoFe2O4 thin films by economical spray technique for gas sensing application. • Structural, morphological and electrical properties of CoFe2O4 thin films. • Systematic study of gas sensing parameters towards various oxidizing and reducing gases. • The films show higher gas response to NO2 as compared to other target gases at 150 °C. • Maximum gas sensor response of 95% to NO2 at 150 °C was observed.
[en] In the present work, nanocrystalline Li_0_._5_−_0_._5_xCo_xFe_2_._5_−_0_._5_xO_4 (for x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) ferrite systems were synthesized by solution combustion method. The Rietveld analysis of X-ray result confirms the formation of a single phase spinel cubic crystal structure of the ferrite sample. The lattice constant of the material increases from 8.33 Å to 8.36 Å with increasing cobalt content in lithium ferrite. The cation distribution study reveals that the Co–Li ferrite is in the mixed spinel structure of the composition. The DC electrical resistivity result confirms the semiconducting nature and the Curie temperature decreases with increase in Co"2"+ content. The dielectric constant, loss tangent and dielectric loss decrease with frequency and remain constant at higher frequencies are observed, showing the usual dielectric dispersion due to space charge polarization. The impedance spectroscopy analysis of samples reveals the grain interior contribution in the conduction process. The AC conductivity as a function of frequency verifies that the small polarons are responsible for conduction process
[en] The thin films of WO_3 were deposited with different solution quantities using chemical spray pyrolysis technique. The WO_3 film thickness effect on the photoelectrochemical, structural, morphological and optical properties is studied. Polycrystalline, monoclinic WO_3 films possess photoelectrochemical performance having onset potentials around +0.3 V/SCE in 0.01 M HClO_4. The maximum photocurrent density (I_p_h = 635 μA/cm"2) is observed for the film deposited with 75 ml solution quantity. The FE-SEM image shows compact structure with petals like morphology. The estimated indirect band gap of WO_3 films lies in the range of 2.60–2.65 eV. The photoelectrocatalytic degradation of benzoic acid is studied using WO_3 photoelectrode under UV light illumination and 57 ± 3% removal of benzoic acid is achieved. The mineralization of benzoic acid in aqueous solution has been studied by measuring COD values. - Highlights: • The photoactivity of sprayed tungsten trioxide (WO_3) thin film. • Structural analysis of WO_3 thin films. • Photoelectrocatalytic and photocatalytic degradation of benzoic acid. • Reaction kinetics and mineralization of pollutants by COD.
[en] The WO3 thin films were deposited with different solution concentrations using chemical spray pyrolysis technique. The prepared WO3 thin films were characterized to study the physicochemical properties. All the films have monoclinic crystal structure and film deposited with 40 mM solution concentration showed the excellent photoelectrochemical performance (photocurrent density = 629 μA/cm2 at 1.5 V/SCE). Transmittance of the films decreased with increase in solution concentration and little variation in optical band gap was observed. WO3 thin films (10 × 10 cm2) deposited with 40 mM solution concentration were studied for the photocatalytic and photoelectrocatalytic degradation of rhodamine-B under solar radiation. The photoelectrocatalytic degradation methods showed the 98% degradation efficiency of WO3 photoelectrode in 160 min. The calculated values of COD and TOC decrease from 76 to 14 (mg/L) and 54 to 10 (mg/L), respectively. - Highlights: • Photoactivity of sprayed WO3 thin film. • Photoelectrocatalytic degradation of Rhodamine-B. • Kinetic parameter and mineralization of pollutants by COD.
[en] The IR spectra of Li0.5−(x/2)CoxFe2.5−(x/2)O4 ferrite samples (0≤x≤0.6) prepared by solution combustion method have been reported. The influence of Co substitution is verified. XRD studies confirm the spinel phase formation of ferrites. Lattice constant varies linearly from 8.31 Å (x=0) to 8.35 Å (x=0.6) with composition. Evidence of two absorption bands in the IR spectra (below 800 cm−1) reveals the characteristic feature of spinel ferrite. The IR spectra featured additional three absorption bands around 550, 670 and 705 cm−1 for the samples x=0.1 and x=0.6. Absence of bands splitting specifies that Fe ions do not exist in excess form. It is found that high frequency band (ν1), due to tetrahedral (A) group, lies at around 600 cm−1 and low frequency band (ν2), due to octahedral (B) group, around 450 cm−1. The positions of bands are found to be composition dependent. The IR bands due to tetrahedral complexes shift slightly towards high frequency side with composition upto x=0.4 where as that due to octahedral complexes shift towards lower frequency side with x. Based on the data of absorption bands, force constants (kt, ko) and bond lengths (RA, RB) were estimated. Compositional dependence of force constants is explained on the basis of cation–oxygen bond distances of respective sites and cation distribution