Graphene quantum dots (GQDs) have attracted much recent attention due to their ultrafine dimensions, tunable surface functionalities and economical synthetic routes. The stable photoluminescence (PL) and low toxicity make them outstanding as an alternative to organic dyes and inorganic quantum dots (QDs) in biological applications.¹ On the other hand, due to the auto-fluorescence and light scattering background of biological specimens in the short-wavelength region, fluorescent materials of choice are expected to emit in the long-wavelength region in order to provide a deeper light penetration into the specimens, resulting in a higher imaging contrast. To date, most of the reported GQDs emit the blue to green fluorescence, which usually exhibits excitation wavelength dependence². Herein, we report the facile electrochemical exfoliation of graphite in K₂S₂O₈ solution for the synthesis of uniform small-sized red fluorescent GQDs (RF-GQDs) without any chemical modification, which has been used for cellular imaging.²

Acknowledgement: This work is supported by NSFC (21073018), the Major Research Plan of NSFC (21233003), the Fundamental Research Funds for the Central Universities.

Reference:

1. (a) S. N. Baker, G. A.Baker, Angew. Chem. Int. Ed. 2010, 49, 6726-6744; (b) J. Shen, Y. Zhu, C. Chen, X. Yang, C. Li, Chem. Commun. 2011, 47, 2580; (c) K. Habiba, V. I. Makarov, J. Avalos, M. J. F. Guinel, B. R. Weiner, G. Morell,  Carbon 2013, 64, 341.
2.  (a) Z. Fan, Y. Li, X. Li, L. Fan, S. Zhou, D. Fang, S. Yang, Carbon 2014, 70, 149; (b) M. Zhang, L. Bai, W. Shang, W. Xie, H. Ma,  D. Fang, H. Sun, L. Fan, L.; Han, M.; Liu, C.; Yang, S., J. Mater. Chem. 2012, 22, 7461.