Nitrogen-Induced Transformation of Vitamin C into Multifunctional Up-converting Carbon Nanodots in the Visible-NIR Range.

Water-soluble, biocompatible, and photoluminescent carbon nanodots have been obtained from the rationalized carbonization of vitamin C, a well-known antioxidant molecule in the presence of an amine co-reactant. Herein, we describe the positive influence of N-doping to induce a unique pH-dependent lifetime decay response that would be potentially attractive in biological backgrounds with intrinsic fluorescence fluctuations. In addition, the selectivity and sensitivity of the N-containing carbon nanoprobes towards the detection of copper ions at ppm levels is critically enhanced in comparison with the un-doped counterpart, especially in the near-infrared (NIR) range. Finally, the up-converting properties have been also successfully applied to image tumor cells in the visible range and remarkably, in the NIR region in which minimal tissue or water absorption and maximum penetration depth are expected.