Optical and structural investigation of synthesized PVA/PbS nanocomposites

Polymer nanocomposite based on polyvinyl alcohol (PVA) and lead sulfide (PbS) in the average radius of (1.88-2.23) nm, have been synthesized using the chemical reduction rote and solution casting technique for different concentrations of PbS. The characterization of the polymer nanocomposite films were carried out using UV-visible spectroscopy, SEM, and XRD. The effect of various concentration of PbS NP on the optical properties of the composite has been studied to understand the optimum conditions for the synthesis process. The nanocomposite film shows high UV and visible light absorptions in the wavelength range of (200-500) nm, which correspond to the characteristics of the PbS NPs. The significant decreasing trend of the direct allowed band gap of the nanocomposite was observed upon increasing the Pb source concentration, from (6.27 eV) for pure PVA to (2.34 eV) for 0.04 M PbS concentration, which is much higher than the energy gap of bulk PbS value (0.41 eV). The calculated values of the static refractive index of Cauchy dispersion model were in the range of (1.09-1.20). X-ray diffraction analysis confirmed the cubic nanocrystalline PbS phase formation.