Vasachar Ravindrachary

In this study, the influence of Alizarin red S (ARS) doping on the optical and fluorescence properties of polyvinyl alcohol (PVA) was systematically investigated. Pure PVA and ARS-doped PVA composite films were prepared using the solution-casting technique. Fourier transform infrared analysis confirmed the formation of chemical interactions between PVA and ARS molecules. UV–Visible absorption spectra displayed enhanced absorbance in the UV region along with a red shift in the absorption edge, indicates the reduction in the optical band gap and an increase in activation energy. The XRD results demonstrates that the modifications in the structural behaviour of PVA upon incorporation of dye concentrations and these modifications are also changes the surface morphology and good dye–polymer compatibility as reflected from SEM studies. Thermal analysis showed that the thermal stability of PVA was improved upon ARS doping. Fluorescence spectroscopy (excitation at 260 nm) revealed a progressive decrease in emission intensity with increasing ARS concentration, indicating the concentration dependent quenching dominated by non-radiative dipole-dipole energy transfer. The observed reduction in fluorescence polarization and anisotropy was attributed to an enhancement of rotational mobility of ARS molecules within the PVA matrix.

In the present study, solid polymer electrolytes (SPEs) based on poly (vinyl alcohol) (PVA) doped with lithium bromide (LiBr) were prepared by solution casting method. Fourier transform infrared spectroscopy results affirm the complexation of LiBr with PVA. X‐ray diffraction results exhibit the increase of amorphous nature of the polymer electrolytes, which is also observed in scanning electron microscopy images and atomic force microscopy topographs. Thermogravimetric analysis thermographs endorse the increase of thermal stability of the polymer due to doping. Dielectric studies exhibit non‐Debye nature of the polymer electrolytes. Conductivity spectra reveal the maximum ionic conductivity (1.15 × 10⁻⁴ S/cm) for 20 wt% LiBr/PVA electrolyte at ambient temperature. Impedance analysis reveals the decrease of ionic relaxation in the polymer electrolytes and the studied transport properties of the electrolyte show that the major contribution to the conduction in this polymer electrolyte is ions.

The study examines the effects of metal salt doping on polyethylene oxide (PEO) solid polymer electrolyte films. Sodium Bromide (NaBr) doped PEO films are prepared using a solution casting technique. The study finds that Na⁺ rom NaBr interacts with PEO's ether group (C–O–C) through complexation, as confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. X‐ray diffraction analysis reveals that NaBr reduces PEO's degree of crystallinity. The addition of NaBr improves PEO's thermal stability, as shown by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) images show smooth surface morphology of the polymer electrolyte films. The study also finds that the polymer electrolytes are non‐Debye in nature, based on dielectric studies. The highest ionic conductivity of 1.01 × 10⁻⁵ S/cm is observed for the 12.5 wt% NaBr doped PEO, with a low activation energy of 0.246 eV. Wagner's polarization technique is used to determine the charge carrier transport numbers, and the transient ionic current technique confirmed the presence of a single ionic species in the polymer electrolyte. Overall, the study suggests that 12.5 wt% NaBr doped PEO films have appropriate electrical properties for developing charge storage devices.

A nonlinear optically active single crystal of 2-bromo-5-methoxybenzohydrazide derivative has been synthesized using standard method. Using solution growth technique the compound obtained was successfully grown as single crystals. FT-IR spectrum determines the different functional groups of the newly synthesized molecule. The single crystal X-ray diffraction analysis confirms the molecular structure and characterizes the crystal as non centrosymmetric as it crystallized in an orthorhombic crystal system having P212121 space group and also calculates the lattice parameters. The optical study reveals the maximum absorption at 289 nm wavelength and wide transparency of the crystal was observed near visible region. Green light emitting property of the crystal was determined by photoluminescence study. Thermo gravimetric (TG) and Differential thermal (DT) analysis discloses the thermal strength of the material. 0.41 SHG efficiency of title molecule was estimated by powder SHG test. Molecular Hirshfeld surface analysis of the crystal structure reveals the intermolecular interaction exhibited by various inter contacts and the corresponding 2-dimensional finger print analysis further estimates the individual contribution from each atom. Density functional theory (DFT) analysis calculates the energy gap of the molecule using HOMO-LUMO values. Various global chemical reactivity descriptor (GCRD) parameters have been calculated. Using molecular electrostatic potential (MEP) map the suitable sites for electrophilic and nucleophilic reactive sites were predicted. The NLO properties such as first order molecular hyperpolarizabilities (β), polarizability (α), molecular dipole moment (μ) and anisotropy polarizability (Δα) was theoretically estimated using DFT.