Innovative nitrogen and boron co-doped carbon dots are hydrothermally produced using fructose, urea, and boric acid as precursors. The synthesized carbon dots possess a uniform morphology, and exhibit excellent fluorescence stability, tunable luminescence property, strong resistance
to photobleaching, low-toxicity, and excellent biocompatibility. It is also found more dopant urea is conducive to the formation of the carbon dots with more B–N bonds, and shorter wavelength of fluorescence emission. Meanwhile, the synthesized carbon dots are well utilized as a photoluminescent
probe for facile Hg2+ determination and fluorescent imaging reagent in cells.