Photoexcited Plasmon-Driven Ultrafast Dynamics of the Adsorbate Probed by Femtosecond Time-Resolved Surface-Enhanced Time- Domain Raman Spectroscopy

Metal nanoparticles have high potential in light-harvesting applications by transferring absorbed photon energy to the adsorbates. However, photoexcited plasmon-driven ultrafast dynamics of the adsorbate on metal nanoparticles have not been clearly understood. We studied ultrafast plasmon-driven processes of trans-1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on gold nanoparticle assemblies (GNAs) using time-resolved surface-enhanced impulsive stimulated Raman spectroscopy (TR-SE-ISRS). After photoexciting the localized surface plasmon resonance (LSPR) band of the GNAs, we measured femtosecond time resolved surface-enhanced Raman spectra of the adsorbate, which exhibited transient bleach in the Raman signal and following biphasic recovery that proceeds on the time scale of a few tens of picoseconds. The TR-SE-ISRS data were analyzed with singular value decomposition, and the obtained species-associated Raman spectra indicated that photoexcitation of the LSPR band alters chemical interaction between BPE and the GNAs on an ultrafast time scale; initial steady-state BPE is recovered through a precursor state that has weaker interaction with the GNAs.

Automated summary

Metal nanoparticles can transfer absorbed photon energy to adsorbates, making them highly potential in light-harvesting applications. However, the ultrafast plasmon-driven dynamics of adsorbates on metal nanoparticles are not well understood. In this study, we used TR-SE-ISRS to investigate the ultrafast plasmon-driven processes of trans-1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on gold nanoparticle assemblies (GNAs). Our results revealed that photoexcitation of the localized surface plasmon resonance (LSPR) band of GNAs altered the chemical interaction between BPE and GNAs on an ultrafast timescale.