Interfacial effects in the relaxation dynamics of silver nanometal-glass composites probed by transient grating spectroscopy

Relaxation dynamics of silver nanoparticles (NPs) embedded in glass have been studied by picosecond time-resolved transient grating (TG) spectroscopy. Phosphate-based glasses were prepared by melting and heat-treatment processes by which two different nanometal-glass composites were produced. The first is a glass system containing silver and tin in which Ag NPs are embedded in the matrix upon heat treatment. The second is a heat-treated silver-doped glass with spectroscopic indications of Ag ⁺-Ag ⁰ pairs located at or near the surface of the NPs. The time evolution of the light-induced TG for the Ag/Sn-doped glass shows an uncommon relaxation on the nanosecond time scale. Such behavior is explained in terms of energy transfer processes between polaronic and/or excitonic states in the near-interface region of the glass matrix and the NPs. In contrast, a faster monotonic relaxation is observed for the Ag-doped nanocomposite. This result is attributed to Ag NP → Ag ⁺-Ag ⁰ plasmon resonance energy transfer.