Tailoring structure, nonlinear/linear optical, and dielectric properties of PVA/PVP film by spinel LiMn2O4 nanoparticles

Abstract

LiMn2O4 (LMO) nanoparticles have received significant attention owing to their role in energy storage and power supply applications. Here, the facile low-temperature synthesis of new hybrid freestanding films incorporated with different LMO nanoparticle concentrations (0, 0.037, 0.37, and 3.7 wt.%) was preceded to tunable the optical and electrical properties of the PVA-PVP blend. The formation of the nanoparticles and polymeric nanocomposite (PNC) films was confirmed using various techniques, including HRTEM, SEM, FTIR, and XRD. The relationship between the optical and dielectric properties of the films with the bandgap was tuned using the doping ratio. Two models were used to estimate the precision of the optical transition bandgap. Our results revealed that the calculated extinction coefficient, Urbach energy, optical conductivity, and refractive index of PVA-PVP were enhanced. The nonlinear optical parameters, including the third-order susceptibility (χ(3)) and refractive index (n2), also improved with a reduction in the bandgap. In addition, a hybrid film with 3.7 wt.% LMO exhibited excellent optical shielding. However, the electrical properties of the PNC films are not only affected by the applied frequency but can also be tuned by the LMO ratio. The AC conductivity and dielectric constant of the hybrid/PNC films were enhanced by the addition of LMO, and the highest values were achieved for the semi-transparent PNC with 0.37 wt.% LMO. For the oblique film with 3.7 wt.% LMO, most nanoparticles cover the significant portions of the polymer surface, which decreases the electrical properties. The dominant mechanism in all PNC films is related to barrier hopping (CBH) and follows Jonscher's power (JP) performance. The investigated hybrid films are promising for environmental optoelectronics, photosensors, optical shielding, and Li+ ion-based battery devices.