Graphene Oxide Sheath on Ag Nanoparticle/Graphene Hybrid Films as an Antioxidative Coating and Enhancer of Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) has been extensively investigated since its discovery on rough Ag surface because of high sensitivity and resolution. Ag nanostructures are considered highly active for SERS but their liability to oxidization impedes their practical applications as a SERS-based sensing platform. Here, we show that graphene oxide (GO) coating on the polyallylamine hydrochloride (PAA) functionalized Ag nanoparticles (PAA-AgNP) immobilized on PAA-functionalized reduced GO (PAA-RGO) films (GO/PAA-AgNP/PAA-RGO, sandwich structure) protect AgNPs from oxidation under ambient condition for prolonged time up to 72 days with increased and reproducible SERS signals and fast adsorption kinetics of rhodamine 6G, a model Raman probe molecule. The present strategy for GO coating on top of the immobilized AgNPs will be useful for the development of an efficient SERS-based chemical and biosensor because of its simplicity, cost-effectiveness, long-term stability, and high reproducibility.