▎ 摘　　要

In this study, nitrogen-doped graphene quantum dots (N-GQDs) exhibiting high water solubility were produced based on the hydrothermal approach. Ethylenediamine (EDA) was used as the nitrogen dopant and microcrys-talline cellulose (MCC), extracted from pineapple leaf fiber (PALF) biomass, used as the carbon source. The as-prepared N-GQDs exhibited an average size of 3.7 nm, 8-10 layers and the excitation wavelength-dependent fluorescence. It was noteworthy that controlling the pH value of the EDA solution in the hydrothermal process could change the fluorescence color of the N-GQDs, exhibiting unique green, cyan and blue light. Besides, because of the effective fluorescence quenching effect of N-GQDs by mercury (II) ions (Hg2 +), the as-prepared N-GQDs were successfully employed as the efficient nanosized fluorescence sensors to selectively detect Hg2+ in aqueous solutions with the detection limit of 0.25 nM and a linear range of 0 similar to 30 M. The selectivity experiments indi-cated that as-prepared N-GQDs were specific for Hg2+ even with interference by high concentrations of other metal ions. Notably, the N-GQDs could be well adopted to determine Hg2+ in river water samples.