Solid-State Nanocomposite Guar Gum Electrolyte: Exploration of Electrical and Optical Characteristics

Nanocomposite electrolytes were prepared by incorporating various weight ratios (2.5, 5, 7.5, and 10% w/w) of nano (ZrO2) in the standard composite of (70 wt % guar gum (GG) + 30 wt % ZnSO4⋅7H2O) using the solution casting technique. The optical properties were examined within the 200–900 nm wavelength range through UV–Vis spectroscopy, while frequency-dependent impedance and conductivity were investigated in the 100 Hz to 1 MHz range. Key parameters including absorption edge, transmittance, extinction coefficient, optical bandgap, refractive index, optical conductivity, and optical dielectric parameters were analyzed. The absorption edge increased from 264.4 to 282.5 nm, with a maximum refractive index of 1.712 observed for 10 wt % nano. Optical band energy was calculated for all electrolyte samples, including direct and indirect bandgaps, direct and indirect forbidden bandgaps. Tauc’s model and optical dielectric loss analysis indicated a direct band gap occurred in this study, with the highest bandgap recorded as 5.44 eV for 2.5 wt % and the lowest as 5.3 eV for 10 wt % nano. Impedance decreased gradually with increased frequency and nano concentration for all samples, with the conductivity study confirming different regions in the conductivity spectra due to the polarization process according to Jonscher’s law. The lowest impedance and high conductivity were observed for the 10 wt % nano concentration, supported by optical absorbance and bandgap data.