Facile and large-scale synthesis of green-emitting carbon nanodots from aspartame and the applications for ferric ions sensing and cell imaging.

A facile, economical and green strategy to prepare green-fluorescent nitrogen-doped carbon nanodots (N-CDs) with a quantum yield (QY) of approximately 31.91% has been built up, while aspartame was employed as the carbon-nitrogen source for the first time. The prepared N-CDs exhibited ultrahigh brightness, favorable strong photostability and negligible cytotoxicity. The outstanding optical properties are mainly derived from the their robost composition and steric distribution of the doped nitrogen atoms, which have been characterized detailedly. The obtained N-CDs showed highly selective and sensitive response toward ferric ions (Fe3+) through a fluorescence static quenching process in a wide linear range of 0.005-60µmol/L. The detection limit was as low as 1.43nmol/L, allowing the analysis of Fe3+ in a very simple method. The excitation-dependent luminescent behavior of the obtained N-CDs guaranteed the multicolor emissive property when they were used in cell imaging. And the application for intracellular Fe3+ sensing further verified this novel N-CDs may open more opportunities in biosensor, bioimaging and biological assay.