Ultrafast Dynamics of Plasmon-Exciton Interaction of Ag Nanowire-Graphene Hybrids for Surface Catalytic Reactions

Using the ultrafast pump-probe transient absorption spectroscopy, the femtosecond-resolved plasmon-exciton interaction of graphene-Ag nanowire hybrids is experimentally investigated, in the VIS-NIR region. The plasmonic lifetime of Ag nanowire is about 150 +/- 7 femtosecond (fs). For a single layer of graphene, the fast dynamic process at 275 +/- 77 fs is due to the excitation of graphene excitons, and the slow process at 1.4 +/- 0.3 picosecond (ps) is due to the plasmonic hot electron interaction with phonons of graphene. For the graphene-Ag nanowire hybrids, the time scale of the plasmon-induced hot electron transferring to graphene is 534 +/- 108 fs, and the metal plasmon enhanced graphene plasmon is about 3.2 +/- 0.8 ps in the VIS region. The graphene-Ag nanowire hybrids can be used for plasmon-driven chemical reactions. This graphene-mediated surface-enhanced Raman scattering substrate significantly increases the probability and efficiency of surface catalytic reactions co-driven by graphene-Ag nanowire hybridization, in comparison with reactions individually driven by monolayer graphene or single Ag nanowire. This implies that the graphene-Ag nanowire hybrids can not only lead to a significant accumulation of high-density hot electrons, but also significantly increase the plasmonto- electron conversion efficiency, due to strong plasmon-exciton coupling.