Plasmon Mediated Electron Transfer and Temperature Dependent Electron-Phonon Scattering in Gold Nanoparticles...

Excitation of localized surface plasmon resonance in metal nanoparticles (NPs) embedded in a glassy matrix generates hot electrons, which can be extracted for different optoelectronic applications. The insights of plasmon relaxation dynamics with varying surrounding dielectric environments and temperature dependence electron-phonon scattering process in gold (Au) NPs are still not very clear. Here, we have employed ultrafast transient absorption (TA) spectroscopy to explore the hot plasmon mediated electron transfer (PMET) and electron-phonon dynamics of photo-excited Au NPs in glassy film matrix with variable SiO₂ /TiO₂ compositions at cryogenic (5 K) to room temperature (300 K). Herein, we have chosen two pump excitation wavelengths (400 and 700 nm). The 400 nm excitation (d→sp) generates hot electron and the 700 nm excitation (sp→sp) provide information of direct plasmon relaxation. Drastic reduction of the transient signal of Au NPs in the high TiO₂ content film as compared to pure SiO₂ confirm hot electron transfer (HET) from Au plasmon to TiO₂ . Electron-phonon scattering time constant (τ_e-ph ) of Au NPs in the glassy film is found to be faster in presence of TiO₂ due to facile electron transfer/injection. Temperature dependent TA studies suggest that electron-phonon scattering time decreases with temperature. These findings would assist to develop more advanced photo-voltaic, opto-electronic and quantum optic-based devices using the plasmonic metal NPs.