Study the effect of loading non-stoichiometric zinc sulfide on optical characteristics of PVA/CMC/PVP blended polymer films

In the current study, both solid-state reactions, at low temperature, and casting methods were employed to fabricate polymeric blends films based on polyvinyl alcohol/Carboxymethyl Cellulose/Polyvinylpyrrolidone (PVA/CMC/PVP) loaded with non-stoichiometric zinc sulfide (ZnS_1-x). Rietveld analysis of XRD revealed single phase ZnS for x ≤ 0.1 and biphasic ZnS/ZnO structure for x ≤ 0.5, with average crystallite size between 3.5–5 nm for ZnS and 50–65 nm for ZnO. SEM images disclosed smooth homogenous surface for the pure polymer blend, which attained some roughness upon loading with ZnS_1-x. EDS analysis revealed inclusion of O ions compensating S deficiency with elements percentages consistent with chemical composition. Various parameters such as linear refractive index, extinction coefficient, dielectric constants, optical conductivity, (surface and volume) energy loss functions and nonlinear optical parameters were calculated using diffused reflectance measurements. The direct (E_dirg) and indirect (E_indg) optical band gaps were decreased non-monotonically from (5.22 and 5.02 eV) to (4.1 and 3.18 eV), respectively. The effects of different excitation wavelengths and sulfur deficiency (x) on the emitted colors from the blended polymer were also explored. The FL intensity was greatly enhanced with the sulfur deficiency (x). The results revealed that loading the blends with ZnS_1-x increased their usability in many fields such as UV shielding, photocatalysis and new optical device applications.