▎ 摘　　要

Graphene quantum dot (GQD) represents an emerging noble metal-free surface-enhanced Raman scattering (SERS)-active nanomaterials for applications such as optoelectronics, chemical sensing, and biomedical imaging and therapy. However, it lacks a scalable method to synthesize GQD with selective structures and the fundamental understanding of their SERS enhancement through charge transfer between GQD and probe molecules. Here a bottom-up liquid-phase synthesis of colloidal GQDs with selective bandgaps using atmospheric-pressure microplasmas is reported. Electron microscopic and optical spectroscopic characterizations suggest that highly crystalline GQDs with nanographene structures can be synthesized with ambient conditions using microplasmas. Moreover, the bandgaps of GQDs are tuned from 2.8 to 3.18 eV by controlling the size of organosulfate micelles. Raman spectroscopic study demonstrates that the as-synthesized GQDs exhibit a unique quantum dot bandgap-dependent SERS enhancement property with an improved charge transfer between the GQD and probe molecules. This study provides an insight into the fundamental of semiconductor-enhanced Raman scattering of GQDs and scalable production of structure-controlled GQDs using plasma-activated chemistry.