Copper nanoparticle and point defect formation in Cu+–Na+ ion-exchanged glass using protons of 2 MeV energy

Abstract

There are several applications for irradiating materials with protons that could provide alternative methodologies to synthesize and induce the formation of new compounds of different size scales. In this study, we explored the effects of proton irradiation oncommercial glass silicate that was previously subjected to a Cu⁺–Na⁺ ion exchange (IE) treatment at 600 °C for a duration of 60 min. The ion-exchanged glass samples were irradiated with protons (p⁺) of 2 MeV energy at doses in the range of thousands of grays (3.3 × 10³, 7.9 × 10³ Gy) and hundreds of thousands of grays (3.6 × 10⁵ Gy). Significant changes in the optical and structural properties were observed post the radiation treatment. The UV-Visible absorption spectra of the irradiated samples revealed the appearance of overlapping absorption bands, which could be deconvoluted into three Gaussian-shaped bands peaking at 566, 620 and 680 nm. These three bands could be attributed to the surface plasmon resonance (SPR) of copper nanoparticles, non-bridging oxygen hole centers (NBOHCs) and self-trapped hole (STH) defects, respectively. Prominent photoluminescence (PL) was observed in the Cu-exchanged and irradiated samples, mainly induced by the presence of both Cu⁺ and Cu₂O. Increasing the irradiation dose led to an increase in the PL intensity due to the conversion of Cu²⁺ ions into Cu⁺. This result was confirmed by electron paramagnetic resonance (EPR) spectroscopy that shows a decrease in the Cu²⁺ signal when increasing the dose of proton exposure. Transmission electron microscopy (TEM) and high-resolution TEM (TEM and HRTEM) observations confirmed the presence of copper nanoparticles (CuNPs) in the doped and p⁺ irradiated Cu-exchanged glass silicate samples. These CuNPs were found to be crystalline with an average size of 12.39 nm.