Charge-Transfer Mechanism in Graphene-Enhanced Raman Scattering

In the chemical enhancement Mechanism for Raman scattering the two types of charge transfer models,. the excited state and the ground state charge transfer mechanisms, present the different dependence of the enhanced Raman signals on the excitation. wavelength. To investigate the type of charge transfer mechanism in graphene-enhanced Raman scattering (GERS); the Raman excitation profiles of the copper phthalocyanine.(CuPc) molecule were obtained in the range of 545-660 nm. The profiles in the GERS system were fitted Well with the function of the ordinary resonant Raman scattering expression, Where the incident and scattered resonance peaks Were well-distinguished with the energy difference equaling the energy of the Molecular vibrations. This result meets the prediction of ground-state charge transfer, in which model the dependence of the enhanced Raman signals on the excitation :Wavelength is the same as that of the ordinary;Raman scattering, and rules out the prediction of the excited-state charge transfer because of the possible charge-transfer resonance peak observed: Therefore, the GERS was proved to be a ground-state charge-transfer:Mechanism:Meanwhile,because the Raman excitation profiles of molecule can be obtained in the GEM system easily, Which is usually difficult to obtain due. to the absorption of the molecules, GERS opens up a new way to suppress this effect: This work contributes the deeper understanding, : of the graphene-enhanced Raman scattering.