title: R6G on graphene: high Raman detection sensitivity, yet decreased Raman cross-section.
abstract: Several recent studies have demonstrated the use of single and few-layer graphene as a substrate for the enhancement of Raman scattering by adsorbed molecules in a method termed graphene-enhanced Raman spectroscopy (GERS). Here we determine the resonance Raman scattering cross-section for the dye molecule rhodamine 6G (R6G) adsorbed on bilayer graphene. For the 1650 cm(-1) R6G mode, we obtain a cross-section of 5.1 × 10(-24) cm(2)·molecule(-1), a greater than 3-fold reduction from the previously reported solution value. We show that the absorption spectrum of adsorbed R6G can be measured using micro-optical contrast spectroscopy, and we find that detuning of the molecular resonance explains the decreased Raman scattering cross-section. We find no evidence for a graphene Raman enhancement process. We also study the graphene thickness dependence of the adsorbed R6G Raman signal and show that a model incorporating electromagnetic interference effects can qualitatively explain the decrease in signal with increasing graphene thickness.
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Thrall
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Crowther
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Yu
authors.forename: Louis E
authors.initials: LE
authors.lastname: Brus
mesh_terms: D006108:Graphite / Q000032:analysis* / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods; D049329:Nanostructures / Q000032:analysis* / Q000737:chemistry / Q000648:ultrastructure*; D010316:Particle Size; D012235:Rhodamines / Q000032:analysis*; D012680:Sensitivity and Specificity; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D012235:Rhodamines; C026188:rhodamine 6G; D006108:Graphite