Probing the electrical and linear/nonlinear optical properties of polyvinyl alcohol–chitosan/graphene oxide nanocomposites for next-generation optoelectronic applications

This work reports the fabrication and comprehensive characterization of polyvinyl alcohol–chitosan/graphene oxide (PVA–CS/GO) nanocomposite films with different graphene oxide (GO) nanoparticle concentrations (0–6 wt%). The nanocomposites were prepared using a simple solution casting technique and systematically investigated to understand the influence of GO incorporation on the structural, optical, dielectric, and sensing properties of the polymer matrix. FTIR analysis confirmed strong interfacial interactions between PVA–CS chains and GO nanoparticles through hydrogen bonding, while optical microscopy revealed a homogeneous dispersion of GO within the polymer network. The optical analysis demonstrated a significant enhancement in light–matter interaction after GO incorporation. The optical band gap decreased from 5.49 to 4.60 eV for allowed indirect transitions and from 5.12 to 4.19 eV for forbidden transitions with increasing GO content, indicating the formation of localized energy states within the polymer matrix. Additionally, key optical parameters such as the refractive index, dielectric constants (ε′ and ε″), and optical conductivity increased with GO loading, whereas transmittance decreased due to enhanced photon absorption. Nonlinear optical parameters including linear susceptibility χ (1), third-order susceptibility χ (3), and nonlinear refractive index ( n 2 ) exhibited noticeable improvement, suggesting enhanced optical polarizability of the nanocomposite films. Furthermore, dielectric analysis showed that the dielectric constant, dielectric loss, and AC electrical conductivity increase with nanoparticle concentration due to enhanced charge carrier mobility and interfacial polarization. The Urbach energy also increased, confirming the creation of additional defect states in the electronic structure. Pressure sensing measurements revealed improved mechanical flexibility, environmental stability, and high-pressure sensitivity compared with conventional polymer sensors. These results demonstrate that the incorporation of graphene oxide significantly tailors the optical and electrical properties of PVA–CS matrices, highlighting the novelty of this nanocomposite system as a promising material for flexible pressure sensors, optoelectronic devices, and nonlinear optical nanodevices.