Studies on microstructural dependence of nonlinear optical properties in PSAN/CdS polymer nanocomposites

The Cadmium Sulphide (CdS) nanoparticles were synthesized by microwave hydrothermal method. Poly(styrene-co-acrylonitrile) (PSAN)/CdS polymer nanocomposites with different wt% of CdS nanoparticles (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared by the solution casting technique. The PSAN/CdS polymer nanocomposites were characterized by UV–Visible spectroscopy (UV–Vis), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Z-scan and Positron Annihilation Lifetime spectroscopy (PALS). The UV–Vis and XRD study suggest decreased optical energy band gap ( E g ) and crystallinity ( χ c ) of PSAN/CdS polymer nanocomposites up to 0.6 wt% of CdS nanoparticles loading. The positron lifetime parameters viz., free volume ( V f ), o-Ps intensity ( I 3 ) and fractional free volume ( F v ) are increased up to 0.6 wt% of CdS nanoparticles loading. The nonlinear absorption coefficient ( β ), nonlinear refractive index ( n 2 ) and nonlinear susceptibility ( χ ( 3 ) ) vary with the free volume size in PSAN/CdS polymer nanocomposites. The formation of bigger free volumes provides large space for the alignment of polarizable groups in PSAN/CdS polymer nanocomposites.