Plasmon-enhanced stimulated Raman scattering of ethanol mediated by localized surface plasmon resonance from graphene...

Lowering the threshold and enhancing the intensity of stimulated Raman scattering (SRS) has been a major topic in nonlinear optics. In this work, we investigated the SRS characteristic of ethanol with graphene quantum dots (GQDs) through a Nd: YAG laser with wavelengths of 532 and 355 nm, respectively. Pure ethanol solution exhibits SRS characteristic peaks at 2943 cm^-1, attributed to the symmetric stretching vibration of -CH₃, the maximum energy conversion efficiency was 9.51% with 532 nm laser excitation. GQDs interact with a laser in a nanostructure environment, the edge effects of GQDs enhance light-matter interaction, contributing to localized surface plasmon resonance (LSPR) under resonant excitation, resulting in an electric field enhancement on SRS, decreasing the SRS threshold. The laser wavelength of 355 nm, which falls within the absorption band of GQDs, triggers the quantum confinement effects of GQDs, leading to the emission of fluorescence and the generation of intense LSPR. The synergistic interaction between LSPR and fluorescence enhancement effect further amplifies the SRS signal and activates the strong third-order SRS, yielding a remarkable energy conversion efficiency of 29.67% with the GQDs concentration of 0.2 mg/mL. These findings demonstrate that GQDs serve as highly efficient nonlinear optical mediators, representing an excellent candidate for advancing SRS-based photonic devices.