▎ 摘　　要

Carbon, being a material of the era, has vast usefulness in the synthesis of many novel compounds. One of them is graphene quantum dots (GQDs) have drawn a great deal of attention to the scientific community owing to their low cytotoxicity, higher optical stability, and tremendous photoluminescence (PL) property, which show a new insight in the field of bio-sensing and bio-imaging. Herein, we have demonstrated a facile method to synthesise N-doped GQDs from graphene oxide (GO) using solvothermal treatment with aprotic solvent. GO was synthesised using a modified Hummers' method. The as-prepared N-GQDs showed stronger green emission with 326 nm wavelength. PL study showed that PL characteristics of as-synthesised N-GQDs are mainly due to the surface pi ->pi* and n ->pi* transitions of N containing functional groups with skeletal carbons of the graphene oxide sheet. The N-GQDs were also examined for bio-imaging of microbial cells including E. coli and Saccharomyces cescerevisiae yeast. The results (blue and green emissions under a fluorescence microscope) of this study showed biocompatibility and the photostability of N-GQDs for their application in the fields ranging from energy to biomedicine.