Tunable Optoelectronic Polymers: Effect of Magnesium Nitrate on PVP/Chitosan Blend Films

In this study, solid polymer electrolyte (SPE) films were fabricated using a 50:50 blend of polyvinylpyrrolidone (PVP) and chitosan (Cs), doped with varying weight percentages of magnesium nitrate (Mg(NO3)2) via solution-casting technique. Structural characterization through XRD analysis verified the modified crystalline nature of the composite films, while FTIR spectroscopy confirmed successful complexation between the host binary blend and the magnesium salt. Additionally, TGA results indicated that the integration of Mg(NO3)2 significantly improved the thermal stability of the host matrix. Optical properties were evaluated using UV-Visible absorption spectra, treated with models specific to non-crystalline materials. Critical parameters including optical band gap (Eg), refractive index (n), optical conductivity, and dielectric constants demonstrated a strong dependence on dopant concentration. Specifically, the optical band gap decreased from 3.8 eV for the pristine PVP:Cs blend to 2.5 eV for the sample containing 25 wt% Mg(NO3)2. Conversely, both the refractive index and optical dielectric constants exhibited a proportional increase with higher salt loading, highlighting the tunable nature of these electrolytes for optoelectronic applications.