Tunable optical and structural characteristics with improved electrical properties of (PVA-GO-CuO) eco-friendly-polymer nanocomposites and their DFT study

Abstract

The research in this study have been motivated by the unique combination of GO (graphene oxide) and CuO nano-fillers with optimized composition in the poly vinyl alcohol (PVA) polymer. The (PVA-CuO-GO) polymer nanocomposites were created using a melt blending process with varying weight percentages of GO and CuO (ranging from 1 to 6 wt%) nanofillers. The composite was fashioned into a dumble-like structure. XRD (x-ray diffractometer), UV–Vis-NIR spectrophotometer, FESEM (field emission scanning electron microscope) and impedance analyzer were utilized to get the effect of nanofillers on the structural parameters, optical characteristics, surface morphology, and electrical properties of the composites. The influence of wt% of nano-fillers on crystalline size and micro-strain has been examined using XRD data. Tauc graphs were studied using UV–Vis-NIR spectrophotometer data for determining the direct and indirect optical bandgaps, and they show that increasing the weight percentage of nano-fillers causes the optical band gap (direct and indirect) to rise. The direct and indirect bandgap rose from 2.98 to 3.19 eV and 2.23 to 2.80, respectively, as the concentration of nano-fillers increased from 1 to 6 wt%. With increasing nanofillers amount, refractive index and Urbach energy were found to reduce; while peak extinction coefficient was found to increase. FESEM along with the EDAX analysis was also performed to investigate the smoothness of the composites' surfaces. Improvement in capacitance, dielectric constant and ac conductivity was also observed with increase in amount of nanofillers. DFT (Density functional theory) study has also been performed for Natural Bond Orbitals (NBO) analysis of charge and spin distribution, as well as HOMO, LUMO and molecular electrostatic potential (MEP). Based on the findings of the characterization results, the synthesized polymer nanocomposites can be employed in a variety of optoelectronics applications.