Recent Advances Of PVA/ Chitosan/ITO Nanocomposites in Structural, Optical, Dielectric, And Nonlinear Optical Properties

Polyvinyl alcohol/chitosan (PVA/CS)–based nanocomposite films incorporating indium tin oxide (ITO) nanoparticles were successfully synthesized via a solution-casting technique to investigate their structural, linear, and nonlinear optical properties. ITO nanoparticles were introduced at concentrations of 2–5 wt% to tailor the optoelectronic performance of the polymer matrix. X-ray diffraction analysis revealed a progressive enhancement in crystallinity with increasing ITO content, evidenced by an increase in crystallite size from 25.7 to 32.8 nm and a concomitant reduction in dislocation density and microstrain, indicating improved structural ordering. FTIR and Raman spectroscopy confirmed strong interfacial interactions between ITO nanoparticles and the PVA/CS matrix, including characteristic Sn–O vibrations and shifted ITO phonon modes, validating successful nanoparticle incorporation. SEM and EDX analyses demonstrated uniform nanoparticle dispersion at low loadings, with the onset of agglomeration observed at 5 wt% ITO. UV–Vis–NIR spectroscopy showed a systematic reduction in optical transmittance and a red shift in the absorption edge with increasing ITO content. The optical band gap decreased from 4.49 to 4.13 eV, attributed to the formation of localized states and enhanced electronic interactions within the nanocomposite. Optical constants, dielectric parameters, and dispersion energies derived from the Wemple–DiDomenico and Sellmeier models exhibited pronounced enhancement with ITO loading, reflecting increased polarizability and charge carrier density. Photoluminescence measurements revealed concentration-dependent quenching behavior and defect-related emissions, indicating modified recombination dynamics. Furthermore, significant improvements in third-order nonlinear optical susceptibility (χ⁽³⁾) and nonlinear refractive index (n₂) were observed, driven by reduced band gap energy and increased electronic polarization. These results demonstrate that low-level ITO incorporation effectively tailors the structural and optoelectronic properties of PVA/CS nanocomposites, highlighting their strong potential for advanced applications in flexible optoelectronics, photonic devices, nonlinear optics, and sensing technologies.