Enhanced Raman Scattering on Functionalized Graphene Substrates

TL;DR

This study investigates how different functional groups on graphene substrates affect the enhancement of Raman signals from Rhodamine 6G molecules, considering the Fermi energy and phonon interactions to explain the observed variations.

Contribution

It introduces a novel approach linking graphene doping levels and phonon energies to Raman enhancement, validated by experimental data across different excitation energies.

Findings

Raman enhancement varies with functional groups on graphene.

The Fermi energy and phonon energy jointly influence enhancement.

Theoretical predictions match experimental results across excitation energies.

Abstract

The graphene-enhanced Raman scattering of Rhodamine 6G molecules on pristine, fluorinated and 4-nitrophenyl functionalized graphene substrates was studied. The uniformity of the Raman signal enhancement was studied by making large Raman maps. The relative enhancement of the Raman signal is demonstrated to be dependent on the functional groups, which was rationalized by the different doping levels of pristine, fluorinated and 4-nitrophenyl functionalized graphene substrates. The impact of the Fermi energy of graphene and the phonon energy of the molecules was considered together for the first time in order to explain the enhancement. Such approach enables to understand the enhancement without assuming anything about the uniformity of the molecules on the graphene surface. The agreement between the theory and our measured data was further demonstrated by varying excitation energy.