The structure and properties of graphene supported on gold nanoparticles

TL;DR

This study investigates the morphology, electronic properties, and surface-enhanced Raman scattering effects of graphene supported on gold nanoparticles, revealing wavelength-dependent Raman enhancement and electronic modulation by the nanoparticles.

Contribution

It provides new insights into the plasmonic and electronic interactions in graphene-gold nanoparticle hybrids, including the tunability of SERS and local electronic states.

Findings

Raman peaks are enhanced depending on excitation wavelength and graphene-nanoparticle distance.

Surface plasmon resonance influences the Raman enhancement.

Gold nanoparticles modulate the local electronic density of states in graphene.

Abstract

Graphene covered metal nanoparticles constitute a novel type of hybrid materials, which provide a unique platform to study plasmonic effects, surface-enhanced Raman scattering (SERS), and metal-graphene interactions at the nanoscale. Such a hybrid material is fabricated by transferring graphene grown by chemical vapor deposition onto closely spaced gold nanoparticles produced on a silica wafer. The morphology and physical properties of nanoparticle-supported graphene is investigated by atomic force microscopy, optical reflectance spectroscopy, scanning tunneling microscopy and spectroscopy (STM/STS), and confocal Raman spectroscopy. This study shows that the graphene Raman peaks are enhanced by a factor which depends on the excitation wavelength, in accordance with the surface plasmon resonance of the gold nanoparticles, and also on the graphene-nanoparticle distance which is tuned by annealing at moderate temperatures. The observed SERS activity is correlated to the nanoscale corrugation of graphene. STM and STS measurements show that the local density of electronic states in graphene is modulated by the underlying gold nanoparticles.