Gold Nanorod@Ruthenium Oxide Core–Shell Heterostructures: Synthesis, Single‐Particle Characterizations, and Enhanced Hot Electron Generation

Abstract

AbstractA synthetic approach has been developed towards encapsulating gold nanorods (AuNRs) with conductive ruthenium oxide (RuO2) by the hydrolysis of ruthenium (III) acetylacetonate in the presence of cetyltrimethylammonium bromide (CTAB) in an autoclave. The reaction conditions are investigated systematically. The resultant AuNR@RuO2 heterostructures are encapsulated with uniform RuO2 shells and are monodispersed in aqueous solutions. Correlated dark‐field microscopic (DFM) and scanning electron microscopic (SEM) characterizations on AuNR@RuO2 nanostructures are performed at single‐particle level, providing the plasmonic properties in correspondence with the size and structure details of the core–shell nanostructures. The complex refractive indexes of RuO2 shell on single nanostructures are further determined by fitting the calculated spectra to the measured ones. Hot electron (HE) photocurrent measurement employing a photoelectrochemical cell shows the encapsulation of the AuNR with 8.2‐nm RuO2 shell results in a 2.9‐fold enhancement at 638 nm, in good agreement with the theoretical calculation. The calculation indicates enhancement ratio exceeding 50 at 800 nm. The mechanism behind is the substantial enhancement of the electric field inside the RuO2 shell as well as less loss in comparison to plasmonic metals, while the conductive nature of RuO2 allows for the transfer of HEs generated inside the shell to the environment.