3rd TAGRA

Silk fibroin has attracted considerable interest as a sustainable biopolymer for flexible electronics, biointegrated sensors, dielectric layers, and frequency-selective devices because of its biocompatibility, mechanical flexibility, film-forming ability, and solution processability. However, pristine fibroin is generally characterized by high electrical resistance and broad non-Debye relaxation behavior, which restrict its use in applications requiring controlled charge transport and frequency-dependent electrical performance. Incorporating metal-oxide nanoparticles into fibroin represents an effective strategy for modifying its dielectric properties through the formation of additional charge-transport pathways and electrically active interfaces. Among these nanofillers, TiO₂ is particularly attractive because of its chemical stability, high dielectric response, and sensitivity to defect engineering. Neutron irradiation can modify the defect structure and electronic properties of TiO₂ by generating or stabilizing Ti³⁺/oxygen-vacancy centers and producing transmutation-related dopants. Therefore, this study investigates the impedance relaxation and charge-transport behavior of silk fibroin composites containing pristine and neutron-modified TiO₂ nanoparticles. At higher TiO₂ loading, however, stronger Maxwell–Wagner–Sillars polarization and increased interfacial heterogeneity may broaden or partially slow the relaxation response. Neutron modification changes this balance by increasing the electrical activity of the TiO₂ nanofillers. Irradiation-induced Ti³⁺/oxygen-vacancy centers can serve as donor-like states and support defect-assisted or small-polaron hopping between neighboring titanium sites. Neutron-transmutation-generated vanadium dopants may provide an additional contribution to carrier density and local electronic conductivity. Consequently, charge exchange across the fibroin–TiO₂ interface becomes more efficient, the interfacial resistance decreases, and the characteristic impedance relaxation shifts toward higher frequencies. The response of the nanocomposites is therefore determined by the combined effects of thermally activated motion in the fibroin matrix, filler concentration, Maxwell–Wagner–Sillars polarization, and the defect structure of the TiO₂ nanoparticles. This interpretation provides a consistent physical framework for understanding how neutron-modified nanofillers can be used to regulate the macroscopic electrical behavior of flexible biopolymer composites.