Nitrogen-doped carbon dots for the detection of mercury ions in living cells and visualization of latent fingerprints

Nitrogen-doped carbon dots (NCDs) were synthesised using a simple and straightforward solvothermal method. The resulting spherical NCDs showed stable fluorescence and a prominent fluorescence quantum yield (67%) with an average size of 3.52 nm. The fluorescence of the NCDs was quenched effectively by mercury ions (Hg2+), exhibiting a detection limit of 0.65 μM. Upon addition of a saturated solution of ethylenediaminetetraacetic acid to a dispersion of the NCDs/Hg2+ complex, the fluorescence of the NCDs underwent significant immediate recovery. Due to their favorable biocompatibility, NCDs were also demonstrated to be efficient for HeLa cell imaging. The detection of Hg2+ by NCDs could be realized in environmental water samples and living cells, with excellent results. Moreover, the as-synthesized fluorescent NCD nanopowders were used for visualizating latent fingerprints (LFPs) with significant third level detail.