Tunable Visible Light and Energy Transfer Mechanism in Tm³⁺ and Silver Nanoclusters within Co-Doped GeO₂-PbO Glasses

This study introduces a novel method for producing Ag nanoclusters (NCs) within GeO₂-PbO glasses doped with Tm³⁺ ions. Sample preparation involved the melt-quenching method, employing adequate heat treatment to facilitate Ag NC formation. Absorption spectroscopy confirmed trivalent rare-earth ion incorporation. Ag NC identification and the amorphous structure were observed using transmission electron microscopy. A tunable visible emission from blue to the yellow region was observed. The energy transfer mechanism from Ag NCs to Tm³⁺ ions was demonstrated by enhanced 800 nm emission under 380 and 400 nm excitations, mainly for samples with a higher concentration of Ag NCs; moreover, the long lifetime decrease of Ag NCs at 600 nm (excited at 380 and 400 nm) and the lifetime increase of Tm³⁺ ions at 800 nm (excitation of 405 nm) corroborated the energy transfer between those species. Therefore, we attribute this energy transfer mechanism to the decay processes from S₁→T₁ and T₁→S₀ levels of Ag NCs to the ³H₄ level of Tm³⁺ ions serving as the primary path of energy transfer in this system. GeO₂-PbO glasses demonstrated potential as materials to host Ag NCs with applications for photonics as solar cell coatings, wideband light sources, and continuous-wave tunable lasers in the visible spectrum, among others.