Graphene-coated Au nanoparticle-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) is a powerful surface analytical technique; however, its lack of material and morphological generality is a longtime limitation. The invention of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) using silica shell-encapsulated Au nanoparticles (NPs) overcomes these problems. Whereas, it is difficult to obtain a silica shell (less than 1 nm thick) without pinholes for generating extremely high SERS enhancements. Graphene is one of the most promising two-dimensional materials, which has a single-atom layer thickness. Moreover, graphene can provide additional SERS chemical enhancement. Herein, we prepared graphene-coated Au (Au@G) NPs via chemical vapor deposition (CVD). The graphene shell thickness could be controlled from a few layers to multilayers, and the Au@G SERS activities were characterized using mercaptobenzoic acid (MBA) as a probe molecule. Both the pH and high-temperature stabilities of the Au@G nanoparticles were characterized. Also, Pt-on-Au@G satellite structures were developed via a self-assembly method. Whereby Au@G nanoparticles were coated with Pt nanocatalysts, and this bifunctional SERS substrate could be used to monitor in situ catalytic reaction mechanisms occurring on the Pt surface.