NiO Nanoparticles-Embedded Polysulfone: Toward High-Performance Dielectric and Optical Properties for Prospective Applications

This study investigates the fabrication and systematic characterization of polysulfone (PS)/nickel oxide (NiO) nanocomposite films prepared via solution casting with varying filler fractions (1–9 wt.%). Structural analysis confirmed successful NiO integration without secondary phases. XRD showed that increasing NiO content suppressed the polymer’s broad amorphous scattering feature, reducing apparent crystallinity from 27.7% to 11.7%. FTIR spectra indicated localized molecular rearrangements at the interfaces without forming new chemical bonds. FESEM and EDX verified uniform nanoparticle dispersion alongside localized clustering at high loading fractions. Optical analysis revealed decreased diffuse reflectance and a significant narrowing of direct (3.60–3.03 eV) and indirect (2.56–1.76 eV) band gaps. This systematic bandgap contraction was directly governed by filler-induced localized defect states, as corroborated by the progressive widening of the Urbach energy tails (185–438 meV). Furthermore, NiO incorporation significantly enhanced the real dielectric constant (ε′) through interfacial polarization, while maintaining low dielectric loss (tanδ) and an exceptional quality factor across the tested frequencies. These combined traits render these PS/NiO nanocomposites highly promising for energy storage, embedded capacitors, low-loss dielectric substrates, and high-frequency optoelectronic applications.