Spectroscopic investigation demonstrating the enhancement of the linear/nonlinear optical properties of PVA: BSA blend films

Abstract

The aim of this study was to prepare novel blend films of poly(vinyl alcohol):bovine serum albumin at different concentrations (96:4, 92:8, 88:12, and 94:16 wt/w%) for use in optoelectronic applications. Linear optical parameters were determined from transmittance and reflectance spectra using spectroscopic data in the range 400–2500 nm. Absorption coefficient analysis gives the type of bandgap transition. The calculated values of absorption edge and optical bandgap energy were increased when the BSA content increased to 8 wt% and then decreased when BSA increased to 16 wt%. The values of Urbach energy and bandgap energy have opposite behavior to each other. Absorption and refraction indices and related parameters were calculated. The data showed significant variations that lead to improved optical parameters and confirm that photon-electron interactions in the films change. The Wemple-DiDomenico model was used to evaluate the dispersion energies and related parameters. The dispersion energy values increase from 3.412 to 12.206 eV, while the oscillator energy values decrease from 6.104 to 4.696 eV and then increase to 6.677 eV with increasing BSA content to 16 wt%. The Eo/(Eg)d ratio is found in the range 1.82–2.82 which may coincide with the prediction of a single oscillator model. Other important dielectric-optical parameters were discussed. Some nonlinear optical properties were also evaluated. Increasing the amount of BSA increased the nonlinear parameters which is beneficial for enhancing local polarization of the blend. All studied parameters are discussed and linked together. The results obtained from this study suggest that these prepared blends can be used in numerous optical applications.