Optical and microscopic characterizations of polyethylene oxides (PEO) doped with nickel nitrate (NiNO₃) transition metal salt

Abstract

This study used a solution cast process to prepare a PEO doped with (4, 8 and 12 wt%) NiNO3 metal salt. Techniques including FTIR, optical microscope (OM), and UV–Visible-absorption spectrometry were employed to examine the structural, microscopic configuration and optical behaviors of the electrolyte. The FTIR bands indicated shifting and narrowing of PEO-O-H stretching bands by addition of 4w%NiNO3, suggesting a good interaction between the NiNO3 and the polymer. The optical microscope images showed the dark regions ascribed to amorphous phases and it is more dominant in the doped films than in the pure films. According to the optical absorption measurements optimum absorption and transmission of UV–visible light were observed at 4 wt% filler loading. Absorbance and transmittance of PEO were amplified by integrating 4 wt%NiNO3, although concentration above 4 wt% had insignificant influence on the optical behavior of PEO. The PEO:4w% NiNO3 films showed a higher value of refractive index and a greater optical conductivity in the UV wavelength which confirmed the presence of more charge carriers in the doped film. The regions attributed to band gap width and the different types of electron transitions were identified by using the Tauc's model in detail. The absorption edge shifting was distinguished for the 4 wt% doped PEO, and the optical band gap was reduced from 5.25 eV to 4.2 eV.