Lysosome targeting, Cr(vi) and l-AA sensing, and cell imaging based on N-doped blue-fluorescence carbon dots

N-doped blue-fluorescence carbon dots (N-CDs) were fabricated via a one-pot hydrothermal method using folic acid and p-phenylenediamine. The obtained N-CDs exhibited strong fluorescence (FL) with a considerable quantum yield (QY) of 21.8% and exceptional optical stability under different conditions. Upon introducing Cr(vi), blue FL of N-CDs was distinctly quenched. On subsequent addition of l-AA, the FL of N-CDs could be partially recovered. The fluorescence changes of N-CDs have been utilized to detect Cr(vi) and l-AA in aqueous solutions with linear ranges of 0.10-150 μM and 0.75-2.25 mM, respectively, as well as limit of detection values of 9.4 nM and 25 μM, respectively. Furthermore, as-obtained N-CDs can be extended to monitor the fluctuation of intracellular Cr(vi) and l-AA. More intriguingly, N-CDs can target lysosomes with a satisfactory Pearson correction coefficient of 0.87, which indicates a promising application prospect in the biomedical field.