Azad Kumar

Photoconduction in amorphous thin films of Se90Sb10-xAgx glassy alloys

ABSTRACT The present paper reports the steady state photoconductivity and photosensitivity response of thermally evaporated amorphous thin films of Se90Sb10-xAgx(x = 2, 4, 6, 8, 10). Temperature dependence of dark conductivity is studied and activation energy is calculated for different samples. Temperature dependence of photoconductivity is also studied at different intensities. From temperature dependence of photoconductivity activation energy is computed at different intensities which are found to vary from 0.26 to 0.47 eV. Intensity dependence of photoconductivity has also been studied at different temperatures. These curves are plotted on logarithmic scale and found to be straight lines which show that photoconductivity follows a power law with intensity. Composition dependence of dark conductivity, activation energy of DC conduction and photosensitivity show that these parameters are highly. composition dependent and show a discontinuity at a particular composition when Ag concentration becomes 6 at. %. This is explained in terms of transition from floppy state to mechanically stabilized state at this composition.

Preparation and photocatalytic activity of TiO2/PPy/GO for the degradation of Rose Bengal and Victoria Blue dye in visible light in aqueous solution

This research work describes a proficient method for synthesis of TiO2/PPy and TiO2/PPy/GO nanocomposites. These nanocomposites were prepared by one-step in-situ deposition oxidative polymerization of pyrrole hydrochloride using ammonium persulphate as an oxidant in the presence of TiO2 nanoparticles (NPs) cooled in an ice bath. The obtained nanocomposites were characterized by X-ray diffraction, transmission electron microscope, scanning electron microscope, UV-Visible, Brunauer– Emmett–Teller, and photoluminescence spectra techniques. The obtained results showed that TiO2 NPs have been encapsulated by PPy with a strong effect on the morphology of TiO2/PPy and TiO2/ PPy/GO nanocomposites. The photocatalytic degradation of Rose Bengal and Victoria Blue dyes were done at different condition viz. concentration of dye, time of illumination, pH, and dose of photocatalyst. The maximum photodegradation of dyes was found at 7 pH, 20 ppm concentration of Victoria Blue and 25 ppm of Rose Bengal dye solution, 800 mg/L for Victoria Blue dye (VB) and 1,600 mg/L for Rose Bengal dye (RB) amount of photocatalyst, and 120 min irradiation of visible light. Kinetics of photodegradation was investigated for VB and RB dye and found first-order kinetics.

Photocatalytic Degradation of Citric Acid in Wastewater in Presence of Visible Light by La:Ni:TiO 2 Nanocomposite

In this study, nanocomposites of La:Ni:TiO 2 nanocomposite was prepared by the co-precipitation method. The material was found in the nano dimension by the SEM and TEM analysis. The rutile and anatase both phases were present in XRD analysis of the synthesized materials. The particle size was found 24 and 82 nm in the case of La:Ni:TiO 2 nanocomposite and pure Titania respectively. The surface area of Titania and La:Ni:TiO 2 nanocomposite were found 6.4 and 43.2 m 2 /g. The band gap energy of Titania and La:Ni:TiO 2 nanocomposite were found 3.2 eV and 3.0 eV respectively. The photodegradation of Citric Acid was investigated at different parameters such as temperature, concentration, pH of the reaction mixture, the dose of photocatalyst and time of illumination of visible light. The photodegradation of Citric Acid occurs 60-90% in presence of La:Ni:TiO 2 nanocomposite, while in presence of titania 10-18%. It is found that photodegradation of Citric Acid follows the first order kinetics.

Quantitative investigation of light induced defects in glassy Se90Ag10 thin films

An attempt is made to investigate light induced defects (LID) in amorphous chalcogenide Se90Ag10 thin films prepared by vacuum evaporation technique. For the determination of light induced defects quantitatively, space charge limited current (SCLC) measurements have been made in a vacuum ~ 10−3 Torr before and after exposing amorphous films to white light for different exposure times (0 to 6 hours). Results indicate that light induced defects are created due to prolonged exposure of light which is explained by a microscopic model for light induced defects creation proposed by Shimakawa and co-workers.