Surface Functionalization and Plasmonic Interactions in PVA–TiO₂–Silver Nanoparticle Hybrid Nanocomposites

Hybrid polymer nanocomposites comprising poly(vinyl alcohol) (PVA), titanium dioxide (TiO₂), and silver nanoparticles (AgNPs) were systematically designed and synthesized to investigate the combined influence of surface functionalization and plasmonic interactions on structural, optical, dielectric, and thermal properties. TiO₂ nanoparticles (~ 25 ± 5 nm) were chemically modified using 3-aminopropyltriethoxysilane (APTES) to enhance interfacial compatibility and dispersion within the hydrophilic PVA matrix. Silver nanoparticles (~ 15 ± 3 nm) were synthesized via sodium borohydride reduction and stabilized using citrate ions to ensure colloidal stability and controlled particle size. The nanocomposites were fabricated via solution casting with varying filler concentrations, and comprehensive characterization was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM/TEM), atomic force microscopy (AFM), UV–Vis spectroscopy, dielectric spectroscopy, and thermogravimetric analysis (TGA). Structural analysis confirmed the coexistence of semicrystalline PVA, anatase TiO₂, and metallic Ag phases, while spectroscopic results verified successful surface functionalization and strong interfacial interactions. Morphological studies revealed uniform dispersion of TiO₂ and well-distributed AgNPs with minimal aggregation, contributing to increased surface roughness and interfacial heterogeneity. Optical measurements demonstrated enhanced absorption in the 400–500 nm region due to localized surface plasmon resonance (LSPR) of AgNPs, alongside intrinsic TiO₂ bandgap absorption in the UV region. Dielectric analysis showed a substantial increase in dielectric constant from 9.6 for pristine PVA to 45.2 at 1 kHz for the optimized composite (15 wt% TiO₂, 2 wt% AgNPs), with low dielectric loss (0.038), attributed to strong interfacial polarization mechanisms. Thermal analysis further indicated improved stability, with decomposition onset shifting from 275°C to 308°C. These findings highlight the synergistic role of surface functionalization and plasmonic coupling in tailoring multifunctional polymer nanocomposites, offering significant potential for applications in advanced dielectric materials, optoelectronic devices, and energy storage systems. .