Enhancement of the structure and linear/nonlinear optical properties of PVA/chitosan/Ag nanocomposites for optoelectronic and antibacterial applications.

Polyvinyl alcohol/chitosan/silver (PVA/Cs/Ag) nanocomposites are prepared using casting method for eco-friendly applications. The microstructure and optical properties are investigated using X-ray diffraction, Fourier transform infrared and UV/Vis spectroscopy. XRD analysis revealed that the structural parameters such as lattice strain, crystallites per unit area, dislocation density and stacking fault are affected upon incorporating AgNPs. UV/Vis measurements exhibited that the indirect and direct optical bandgap are reduced from 4.34/5.22 eV for PVA/Cs blend to 3.38/4.78 eV for PVA/Cs/1wt%Ag nanocomposite. Analysis of Wemple-DiDomenico model exhibited clear enrichment of the linear/nonlinear parameters and it is found that the third order nonlinear optical parameter (χ⁽³⁾) and nonlinear refractive index, n₂ are enhanced and increased from (0.025 × 10^-12/0.612 × 10^-12 esu) for PVA/Cs blend to (4.874 × 10^-12/2.413 × 10^-12 esu) for PVA/Cs/1wt%Ag nanocomposite. The significant decrease in the energy gap as well as the remarkable change in the nonlinear optical parameters make these materials a strong candidate for many applications in the optoelectronic field. Antibacterial activity measurements strongly suggest that these nanocomposites could be used in the fabrication of antibacterial devices with biomedical applications.