Control of density and LSPR of Au nanoparticles on graphene

In this study, we introduce the tunable density and localized surface plasmon resonance (LSPR) of plasmonic gold (Au) nanoparticles which were formed on monolayer graphene at room temperature, based on the difference of the reduction potential between graphene and the Au(3+) precursor. The size of the Au nanoparticles was ~40 nm, which is very desirable to provide an optical enhancement effect by LSPR in the full visible range. It is demonstrated that the density of the Au nanoparticles was modulated by the surface energy of the graphene on the substrate as well as the concentration of the Au(3+) precursor. Furthermore, the cycle number of the reduction process strongly affected the distribution of the nanoparticle size and their optical properties. The LSPR of the plasmonic Au nanoparticles was red-shifted from 560 to 620 nm and its full width at half maximum broadened as the Au(3+) precursor concentration was increased and the cyclic reduction process progressed. Based on the optical enhancement of the plasmonic Au nanoparticles and the extraordinary physical characteristics of graphene, the Au/graphene assembly may offer a promising optoelectronic platform for next-generation flexible optical electronics or biosensors.