Cysteine-based chiral optically active carbon dots (CDs) and their effects on cellular energy metabolism, whichis vital for essential cellular functions,have been barely reported. Ag reen and effective synthesis strategy for chiral N-S-doped CDs (fluorescence quantum yield ca. 41.26 %) based on hydrothermal treatment of l-o rd-cysteine at as low as 60 8 8C has been developed. This suggested that cysteine was instable in aqueous solutions and acts as awarning for high-temperature synthesis of nanomaterials using cysteine as stabilizer.Human bladder cancer T24 cells treated with l-CDs showed upregulated glycolysis,w hile d-CDs had no similar effects.I n contrast, no disturbance to the basal mitochondrial aerobic respiration of T24 cells was caused by either chiral CD.Carbon nanomaterials have provoked great interest in various research fields owing to their remarkable properties and potential applications in ab road range of fields. [1] Fluorescent carbon quantum dots (CDs) share the distinguishing electronic and optical characteristics of semiconductor quantum dots while significantly avoiding limitations such as intrinsic toxicity due to the use of heavy metals in their production and/or elemental scarcity. [2] Great attention has been paid to studies on the synthetic approaches of carbon dots. [3] However,c omplex procedures for the subsequent separation and purification have been obstacles to their further development. Thecomplexity also makes the production of CDs on al arge scale difficult. Furthermore,s ome issues such as their poor solubility in water, low fluorescence quantum yields,a nd difficult functionalization need to be addressed before they can truly outperform semiconductor quantum dots in areas such as bioimaging and nanomedicine. [1a,d, 4] When considering the potential biological applications of CDs,c hirality is an important factor that significantly influences material performance but has not been carefully addressed so far. [5] Natural processes include many phenomena in which the chirality of biomolecules plays an important role in the fields of biology and medicine.Adeep understanding of the fundamental concepts relevant to chirality in nanostructures is important for the further development of nanomaterials. [5,6] Some seminal work on chiral semiconductor quantum dots and noble metal nanostructures and their chirality-dependent properties has been reported. [6,7] However,chiral nanobio-interactions have barely been reported in the case of CDs,although they have exhibited great potential for biomedical applications. [8] Herein, agreen and effective synthesis strategy for chiral CDs was developed, and their effects on cellular energy metabolism were studied. Chiral l-CDs and d-CDs were obtained by hydrothermal treatment of l-o rd-cysteine at 60 8 8C, respectively.T his finding demonstrated the stability of cysteine was poor in aqueous solution. There are many amine and carboxyl groups for further functionalization on the surface of the CDs.T he photoluminescence quantum yield is as high a...
