Characterization of Cd1−x Zn x Se thin films deposited at low temperature by chemical route

Optoelectronic technologically important pseudo-binary Cd_1−x Zn _x Se thin films with a variable composition (0 < x < 1) has been developed by chemical bath deposition method. The objective to study growth kinetics, physical, microscopic, compositional, optical, electrical and structural changes. Cd_1−x Zn _x Se have been deposited on non-conducting glass substrate in tartarate bath containing Cd⁺² and Zn⁺² ions with sodium selenosulphate with an aqueous alkaline medium at 278 K. The quality and the thickness of the films are depends upon deposition temperature, deposition time and pH, etc. X-ray diffraction (XRD), atomic absorption spectroscopy, optical absorption, scanning electron microscopy and thermoelectric technique characterized the films. The XRD study indicates the polycrystalline nature in single cubic phase over whole range of composition. Analysis of absorption spectra gave direct type band gap, the magnitude of which increases non-linearly as zinc content in the film is increased and dc electrical conductivity at room temperature was found to decreases from 10⁻⁷ to 10⁻⁸ (Ω cm)⁻¹. All the films show n-type conductivity. The promising features observed are the formation of continuous solid solutions in a single cubic phase.     

Photoelectrochemical applications of In<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films by chemical deposition

Indium selenide films have been synthesized by chemical bath deposition method onto stainless steel plate. The configuration of fabricated cell is n-In₂Se₃| NaOH(1 M) + S(1 M) + Na₂S(1 M) |C_(graphite). Characterization of the photoelectrochemical cell was carried out by studying X-ray diffraction, current–voltage and capacitance–voltage characteristics in the dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that the In₂Se₃ thin films are n-type semiconductor. The junction ideality factor was found to be 3.24. The flat band potential and the barrier height were found to be 0.720 V and 0.196 eV, respectively. From the study of power output characteristics, open circuit voltage, short circuit current, fill factor and efficiency were found to be 310 mV, 20 μA, 37.64 and 0.61%, respectively. Photoresponse studies show that the lighted ideality factor is 2.78. Maximum current was observed at 575 nm.     

Preparation of zinc oxide nanorods by microwave assisted technique using ethylene glycol as a stabilizing agent

Zinc oxide nanorods have been synthesized by microwave assisted method using zinc nitrate, ethylene glycol and sodium hydroxide as a precursors. The material was characterized by XRD, SEM, EDAX and UV–Visible techniques. XRD analysis revealed all the relevant Bragg’s reflections for wurtzite (hexagonal phase) structure of zinc oxide. The average particle size was obtained 34 nm from the Williamson–Hall plot. The value of particle size determined from XRD was in good agreement with the SEM and TEM results. The direct optical band gap was found to be 3.13 eV.     

Eco-friendly synthesis of Ag-ZrO2 nanocomposites for degradation of methylene blue

In this work, we have successfully synthesized ZrO₂ nanoparticles (NPs) using Ficus benghalensis (FB) leaf extract via simple microwave-assisted method. Silver NPs were deposited on the surface of ZrO₂ through photocatalytic reduction. The synthesized ZrO₂ and Ag-ZrO₂ photocatalysts were characterized through X-ray Diffraction (XRD), UV–Vis Diffuse Reflectance Spectroscopy (DRS), Fourier Transform-Infrared Spectroscopy (FT-IR), High-Resolution Transmission Electron Microscopy (HR-TEM), Photoluminescence (PL), and Brunauer–Emmett–Teller (BET) surface area. From the aforesaid characterization of the materials, it is revealed that synthesized Ag NPs are crystalline in nature with the face-centered cubic structure (FCC), while ZrO₂ NPs have both monoclinic and tetragonal phases. TEM images indicate that both ZrO₂ and Ag-ZrO₂ nanocomposite have spherical shape with the particle size of 20 and 15 nm, respectively. The optical properties were obtained using UV–Vis DRS which showed a decrease in the band gap energy of ZrO₂ due to surface plasmon resonance (SPR) effect of Ag NPs. A lower in PL intensity of Ag-ZrO₂ compared to that of ZrO₂ NPs confirms the suppression of recombination rate of excited electron–hole pairs ultimately resulted into high photocatalytic activity. BET analysis shows that all the nanocomposites have higher surface area than pure ZrO₂. The pure ZrO₂ and Ag-ZrO₂ show the efficient photocatalytic activity towards the methylene blue (MB) and methyl orange (MO). Ag-ZrO₂ (1.0 wt.%) shows 21% increment in photocatalytic activity as compared to pure ZrO₂ within 160 min under UV–Vis light.

     

Enhanced photocatalytic activity of Ag doped TiO2 nanoparticles synthesized by a microwave assisted method

Pure anatase TiO₂ photocatalyst with different Ag contents was prepared via a controlled and energy efficient microwave assisted method. The prepared material was further characterized by several analytical techniques like X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface area measurement (BET), Fourier transform-infrared spectroscopy (FT-IR), diffused reflectance spectroscopy (DRS), and thermogravimetric–differential thermal analysis (TGA–DTA). A 10 nm average crystallite size with nano-crystals of pseudo-cube like morphology was obtained for optimal (0.25 mol%) Ag doped TiO₂. The present research work is mainly focused on the enhancement of degradation efficiency of methyl orange (MO) by doping of Ag in TiO₂ matrix using UV light (365 nm). A 99.5% photodegradation efficiency of methyl orange was achieved by utilizing 0.25 mol% Ag doped TiO₂ (1 g/dm³) at pH=3 within 70 min. Recyclability of photocatalyst was also studied, with the material being found to be stable up to five runs.     

Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

Nanocrystalline ZnMn_1−xCr_xFeO₄ (1.0 ≥ x ≥ 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm⁻¹ arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.     

Synthesis of cerium oxide nanoparticles by microwave technique using propylene glycol as a stabilizing agent

Cerium oxide nanoparticles have been synthesized by microwave method using cerium nitrate, propylene glycol and ammonia as a precursors. The material was characterized by XRD, SEM, TEM and UV–visible techniques. XRD analysis revealed all the relevant Bragg’s reflections for face centered cubic crystal structure of cerium oxide. The average particle size was obtained 9 nm from the extrapolation of the Williamson–Hall plot. The value of particle size determined from XRD was in good agreement with the SEM and TEM results. The direct optical band gap was found to be 3.12 eV.     

Synthesis and characterization of pure anatase TiO<Subscript>2</Subscript> nanoparticles

Pure anatase TiO₂ nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO₂ nanoparticles were porous structure. The XRD patterns indicated that TiO₂ after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.     

Enhancement in the photocatalytic activity of Ag loaded N-doped TiO2 nanocomposite under sunlight

A N-doped titania–silver nanocomposites have been prepared by simple microwave assisted and impregnation–reduction method for the first time. As synthesized nanocomposites with different Ag contents were characterized for their phase purity, morphology, particle size, optical properties and elemental composition. It is found that N-doped TiO₂ silver nanocomposites are pure in anatase phase with an average crystallite size of 10 nm. The catalyst was tested for dye degradation and photodegradation efficiency was found to be 99.6 and 88.7 % within 90 min under UV and sunlight respectively. A 40 % enhancement in the photodegradation efficiency was achieved by Ag loading in comparison with the N-TiO₂ under sunlight. The fluorescence quenching of Ag loaded N-TiO₂ indicates decrease in rate of electron–hole pair recombination that enhances photocatalytic performance. The effects of photocatalytic operational parameters such as method of surface modification, catalyst loading and irradiation sources on the photodegradation of methyl orange were also investigated.