Supports matter: unraveling the role of charge transfer in the plasmonic catalytic activity of silver nanoparticles

Abstract

The immobilization of plasmonic nanoparticles onto supports with suitable electronic properties represents an intuitive strategy for the modulation of nanoscale charge-transfer processes and thus the optimization of plasmonic catalytic performances. Here, we report the investigation of the effect of two kinds of bi-dimensional (2D) supports, i.e., partially reduced graphene oxide (prGO) and ultrathin titanate nanosheets (Ti_xO₂), on the plasmonic catalytic performances of Ag nanoparticles (NPs). As prGO and Ti_xO₂ act as electron donor and acceptor materials, respectively, when combined with plasmonic nanoparticles under 633 nm excitation, their similar 2D morphologies enabled us to systematically probe and compare how charge transfer to and from Ag NPs affected their plasmonic catalytic activities. By employing the SPR-mediated oxidation of p-aminothiophenol (PATP) to p,p′-dimercaptoazobenzene (DMAB) as a model reaction, we found that the performances of the hybrids were superior relative to unsupported Ag NPs and that the PATP oxidation mechanism and conversion were dependent on the nature of the support. We also prepared the tri-component hybrid comprised of Ag NPs, prGO and Ti_xO₂ nanosheets (Ag/Ti_xO₂/prGO), which displayed a similar performance to Ag/prGO. In this material, a mechanism based on the cooperative effect of the supports was proposed, in which charge transfer from prGO to Ag NPs is intensified by the presence of Ti_xO₂ nanosheets. We believe that our results expand the understanding on the electronic behavior of complex plasmonic systems, which can allow the rational design of nanoparticle systems with improved performances towards plasmonically triggered or enhanced transformations.