Large-scale synthesis of defects-selective graphene quantum dots for cell imaging by ultrasonic-assisted liquid-phase exfoliation

Graphene quantum dots (GQDs) exhibit unique physical and chemical properties due to their quantum confinements and edge defects. In this paper, a facile, green and fast method was developed for large-scale synthesis of GQDs via an ultrasonicassisted liquid-phase exfoliation technique. GQDs with different sizes and structures were obtained through this exfoliation method with different graphitic carbon precursors, such as nano-graphite, acetylene black and even graphite powder. The luminescent properties of as-synthesized GQDs have been investigated. Different light absorption and photoluminescence (PL) properties were identified relevant to the defect characters, namely high-defects GQDs (HD-GQDs) or low-defects GQDs (LD-GQDs). The variable edges and sizes of GQDs are responsible for the variation of luminescent properties induced by changing the excitation wavelength and the pH values of the GQDs dispersions (Figure1). Attributed to the high water dispersancy, excellent biocompatibility, controllable fluorescent performances, as well as the low toxic properties, the as-synthesized HD-GQDs show high potential as fluorescence nanoprobes for bioimaging