Spectral properties of the surface plasmon resonance and electron injection from gold nanoparticles to TiO2 mesoporous film: femtosecond study

Abstract

Transient absorption spectra of gold nanoparticles (AuNPs) embedded in mesoporous TiO₂ film were studied by a femtosecond laser photolysis pump–probe technique using 25 fs pulses at 740 nm (1.68 eV) and a low fluence of 24 μJ cm⁻². The shift of the bleaching peak in transient spectra by ∼100 meV is detected in the AuNP–TiO₂ system, whereas the bleaching peak shift of the same AuNPs in aqueous colloids is not more than ∼5 meV. In addition to the thermal mechanism of the nonlinear response of AuNPs connecting with the electron gas heating and the smearing effect of the Fermi distribution, the electron transfer between AuNPs and TiO₂ becomes important for the nonlinear response, in addition to the electron heating mechanism. The electron transfer can explain both the spectral shift and widening of the SPR band of AuNPs in TiO₂.