Structural and optical characterization of thiourea-poly (vinyl alcohol) composites

The present manuscript reports the effect of thiourea doping on the optical properties of poly (vinyl alcohol), PVA. Films of thiourea doped PVA samples have been prepared using casting method. Different techniques such as, XRD, FTIR, Raman spectroscopy and UV-Vis spectroscopy have been used to investigate the prepared samples. XRD results show that thiourea is highly crystalline material with an intense sharp peak at 2θ=20.69^o and the crystallinity of thiourea doped PVA samples increased with increasing the thiourea content. FTIR and Raman spectroscopy are used to investigate the change in the molecular structure PVA-thiourea composites. The optical constants of thiourea doped PVA samples have been estimated using the analysis of UV-Vis data. It is found that, values of absorption edge, direct and indirect optical gap energy are decreased with doping thiourea salt until a concentration of 5wt% and then start to increase again. Values of dispersion energy (Ed), single oscillator energy (Eo) and different parameters of dielectric constant have been estimated.