Gamma irradiation-induced morphological and optical modulation in colloidal lithography-fabricated gold nanoparticle arrays

Abstract This study investigates the effects of gamma radiation (50–200 Gy) on the structural and optical properties of gold nanoparticle (AuNP) arrays fabricated via colloidal lithography. Four distinct, regularly arranged AuNP arrays were synthesized using polymethyl methacrylate (PMMA) microspheres (257–1135 nm in diameter) as lithographic masks. Two-dimensional colloidal crystals (CCs) were assembled via custom Langmuir–Blodgett-type interfacial assembly, followed by 50-nm gold thin-film deposition using magnetron sputtering. The PMMA template was removed through chemical etching and calcination, yielding well-ordered AuNP arrays. Post-irradiation, UV–visible (UV–Vis) spectroscopy and field emission scanning electron microscopy (FESEM) imaging revealed the formation of AuNP clusters, which modified plasmonic properties and the Tauc-derived optical transition parameter. Additionally, the long-term stability of irradiated arrays was assessed over one day, three weeks, and five months, providing insights into radiation-induced modifications in plasmonic nanostructures.