Spectroscopic analysis of CdCl2 doped PVA–PVP blend films

Abstract

The changes in molecular chemical structure of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), caused by doping PVA–PVP blend with cadmium chloride (CdCl2), have been studied using ultraviolet–visible (UV-Vis) spectroscopy, Fourier transform Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The formation of cadmium nano-structures and microstructures in CdCl2-doped PVA–PVP blend has been visualized using scanning electron microscopy, in the range of doping levels varying from 0.5 up to 10.2 wt% (doping level in weight percentage). The incorporation of dopant in PVA–PVP blend is confirmed using energy dispersive X-ray spectroscopy. The optical absorbance (UV-Vis) spectra of PVA–PVP blend films doped with CdCl2 from 0.5 up to 2.2 wt%, showed a prominent absorption hump with peak at the wavelength 370 nm, in addition to other intermediate energy bands caused by the interactions of CdCl2 with molecules of PVA and PVP. The photo-luminescence (emission and fluorescence) spectra show significant quenching of fluorescence in CdCl2-doped PVA–PVP blend films. Analysis of FTIR and Raman spectra suggest the possible modes of interaction of cadmium ions (Cd2+) and chlorine ions (Cl−) with reactive functional groups (C–N, hydroxyl and carbonyl groups) of polymeric molecules in the blend. A reaction scheme for interaction of CdCl2 with PVA–PVP blend is proposed, on the basis of spectroscopic studies on these films.