Tailoring the structural, optical and paramagnetic properties of GO-PVA-AgNW nanocomposites by gamma irradiation.

Graphene oxide (GO)-polyvinyl alcohol (PVA)-silver nanowire (AgNW) ternary nanocomposites are of increasing interest as radiation-resistant materials, yet their structural and physicochemical response under high absorbed gamma doses remains largely unexplored. In this study, GO-PVA-AgNW nanocomposite films were exposed to high-dose γ-irradiation (250, 500, and 1500 kGy) from a 60Co source, and the resulting morphological, structural, optical, thermal, and paramagnetic modifications were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, thermogravimetric analysis (TGA), and electron paramagnetic resonance (EPR) spectroscopy. XRD and Raman analyses revealed a pronounced reduction in crystallite size (from 1.75 to 0.92 nm) accompanied by an increase in microstrain (from 0.115 to 0.217) and defect density with increasing dose. UV-vis spectroscopy showed a progressive red shift of the absorption edge and a decrease in the optical band gap from 5.07 (pristine) to 3.82 at 1500 kGy. TGA demonstrated enhanced thermal stability of the primary polymer backbone and an increase in residual carbonaceous content from 10.15% to 14.09%, indicating that crosslinking becomes the dominant process over chain scission at high absorbed doses. EPR measurements confirmed a dose-dependent increase in the concentration of carbon-centered π-radicals, together with a narrowing of the peak-to-peak linewidth and an evolution of the asymmetry factor toward unity, reflecting enhanced spin-exchange interactions and a more homogeneous radical distribution.