We demonstrate through systematic studies on wavelength dependent Raman signal and spatial mapping of Raman signal from dipolar chromophores, that enhanced Raman signal from a dipolar molecule latched on to graphene is likely due to a chemical enhancement mechanism. Mechanically exfoliated graphene was utilized as a substrate to probe the Raman signal of pyrene tethered Disperse Red 1 (DR1P). The enhancement factor of Raman signal of DR1P was found to be in the range of 29 ~ 69 at 532 nm excitation. As surface coverage of DR1P increases, Raman intensity increases and saturates at a certain concentration. Quantitative analysis shows a higher Raman scattering cross-section compared to the solution value. The saturation of the Raman intensity at higher DR1P concentrations, shifts in the G and 2D bands as well as increased Raman cross-section suggests a chemical mechanism due to charge transfer between the molecule and graphene through doping.

Raman enhancement by doping graphene with dipolar molecules

246th National Meeting (2013)

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