P. Chithra lekha

Bio: P. Chithra lekha is an academic researcher from Manonmaniam Sundaranar University. The author has contributed to research in topics: Polyaniline & Thin film. The author has an hindex of 11, co-authored 20 publications receiving 227 citations. Previous affiliations of P. Chithra lekha include Indian Institute of Technology Madras & Pondicherry University.

Electrodeposition of polyaniline thin films doped with dodeca tungstophosphoric acid: Effect on annealing and vapor sensing

Abstract: Polyaniline (PAni) thin films are deposited by the electrochemical method and are also doped with Keggin type 12-tungstophosphoric acid (TPA). The doped films (PAniTPA) show a blue shift in the FTIR peaks at 1490, 1305, and 805 cm −1 . The UV–vis spectra suggest that the PAni is in the emaraldine salt form. The Tauc plot gives an optical band gap energy of 1.68 (2) eV for PAni and 1.41 (1) eV for PAniTPA and the decrease is attributable to the presence of dopant TPA. The XRD studies of as-prepared and annealed (373 K) films reveal that both PAni and PAniTPA are amorphous in nature. Arrhenius type behaviour is observed when conductivity is plotted against temperature both for PAni and PAniTPA with low activation energies, which confirm the conduction due to polarons. The agglomeration of aggregated TPA is observed in the SEM images of PAniTPA annealed at 373 K. The sensor behaviour of the thin films on exposure to acetone vapor indicates the physical adsorption of acetone on the polymer matrix with a fast recovery of the film on re-exposure to air. A better sensitivity to acetone vapor is observed with PAniTPA than PAni films.

Enhanced electrical response in Sb2S3 thin films by the inclusion of polyaniline during electrodeposition

Abstract: Thin films of polyaniline (PAni) that included Sb 2 S 3 are prepared at three different concentrations of PAni using electrodeposition method X-ray diffraction pattern indicates the polycrystalline nature of all the films and it is found that crystallite size increases with the increase in concentration of PAni The morphology of the doped films changes due to the addition of PAni The dc conductivity of samples with different concentrations of PAni has been investigated as a function of temperature and it follows three-dimensional variable range hopping PAni doped films show a shift in the FTIR peaks at 1024 and 1376 cm −1 Optical measurements show that the absorption edge red shifts on increasing the doping concentration

Influence of thickness on the optical properties of amorphous GeSe2thin films: analysis using Raman spectra, Urbach energy and Tauc parameter

Abstract: An analysis is reported of thickness-induced defects in amorphous GeSe2 thin films deposited by the vacuum evaporation technique. X-ray diffraction studies confirmed the amorphous nature of the thin films. Optical absorption measurements revealed an indirect transition with an energy gap that increases with film thickness. A blue shift in optical transmittance edges was observed in annealed GeSe2 thin films. The obtained lower values of Urbach energy (E U) indicate that as thickness increases more ordered films can be produced. Raman spectra suggest that annealing promotes corner-sharing GeSe4/2 tetrahedra and edge-sharing Ge2Se8/2 bi-tetrahedra bonding and leads to the reduction in disorder in bonding network, which is amply supported by the way of increase in band gap, increase in Tauc parameter (B 1/2) and reduction in E U from the analysis of transmittance spectra. Increasing the thickness promotes tetrahedral and bi-tetrahedral bonding through the reduction in bonding defects.

Band-gap energy estimation from diffuse reflectance measurements on sol–gel and commercial TiO2: a comparative study

Abstract: A comparison of the band gap energy estimated from UV–vis reflectance spectra of TiO2 powders prepared by sol–gel route versus commercial TiO2 powders, nanopowder, bulkpowder and P25 is reported. The experimental results obtained from the optical absorption spectra were reported for all the TiO2 samples. Graphic representations were used to calculate Eg: absorbance versus λ; F(R) versus E; (F(R) hν)n versus E, with n = ½ for an indirect allowed transition and n = 2 for a direct allowed transition. From the results, it could be seen that Eg strongly varied according to the equation used for the graphic representation. Differences in Eg up to 0.5 eV for the same semiconductor depending on the transition chosen were observed. Accurate Eg estimation in the four semiconductors studied was obtained by using the general equation α (hν) ≈ B (hν − Eg)n (where α ~ F(R)) and indirect allowed transition.

Conducting Polymers in the Fields of Energy, Environmental Remediation, and Chemical–Chiral Sensors

Abstract: Conducting polymers (CPs), thanks to their unique properties, structures made on-demand, new composite mixtures, and possibility of deposit on a surface by chemical, physical, or electrochemical methodologies, have shown in the last years a renaissance and have been widely used in important fields of chemistry and materials science. Due to the extent of the literature on CPs, this review, after a concise introduction about the interrelationship between electrochemistry and conducting polymers, is focused exclusively on the following applications: energy (energy storage devices and solar cells), use in environmental remediation (anion and cation trapping, electrocatalytic reduction/oxidation of pollutants on CP based electrodes, and adsorption of pollutants) and finally electroanalysis as chemical sensors in solution, gas phase, and chiral molecules. This review is expected to be comprehensive, authoritative, and useful to the chemical community interested in CPs and their applications.

Boosting potassium-ion batteries by few-layered composite anodes prepared via solution-triggered one-step shear exfoliation

Abstract: Earth-abundant potassium is a promising alternative to lithium in rechargeable batteries, but a pivotal limitation of potassium-ion batteries is their relatively low capacity and poor cycling stability. Here, a high-performance potassium-ion battery is achieved by employing few-layered antimony sulfide/carbon sheet composite anode fabricated via one-step high-shear exfoliation in ethanol/water solvent. Antimony sulfide with few-layered structure minimizes the volume expansion during potassiation and shortens the ion transport pathways, thus enhancing the rate capability; while carbon sheets in the composite provide electrical conductivity and maintain the electrode cycling stability by trapping the inevitable by-product, elemental sulfur. Meanwhile, the effect of the exfoliation solvent on the fabrication of two-dimensional antimony sulfide/carbon is also investigated. It is found that water facilitates the exfoliation by lower diffusion barrier along the [010] direction of antimony sulfide, while ethanol in the solvent acts as the carbon source for in situ carbonization.