Fig. 1. Synthetic route and characterization of the l-cysteine-rich chiral carbon quantum dots (LC-CQDs). (a) Synthetic route of the LC-CQDs by heating citric acid and l-cysteine. The fluorescence quantum yield (QY) of the LC-CQDs is 68%. (b1) HRTEM image of the LC-CQDs. (b2 and b3) Lattice spacing of a typical single LC-CQD. (c) FTIR spectrum. (d) Circular dichroism spectra of both LC-CQDs and DC-CQDs. The DC-CQDs were prepared by heating citric acid and d-cysteine. (e) Fluorescence spectra (solid lines) and UV/Vis absorption spectrum (dotted line) of the LC-CQDs. Inset: Photographs of the LC-CQDs under illumination by white light (left) and UV (365 nm) light (right). (f) Photostability of fluorescein isothiocyanate (FITC), fluorescein, CdTe QDs, and the LC-CQD aqueous solution under continuous irradiation using a 280 W xenon lamp.