Red emissive N, Cl-doped carbon dots for detection of tea polyphenols and lysosomal imaging at the cellular level

Tea polyphenols (TP), which is accounting for 15-30% of the dry weight of green tea and are widely used in the food industry as antioxidants, preservatives, color preservatives, and flavoring agents. To determine the concentration of TP, a fluorescent method based on nitrogen and chlorine co-doped carbon dots (R-CDs) was investigated. The R-CDs we prepared showed red emission with an absolute quantum yield (QY) of approximately 16.67 ± 0.85%. The limit of detection (LOD) was calculated to be approximately 68 ± 0.94 ng/mL, with an R 2 of 0.999 over the TP range of 1-20 μg/mL. Compared to the ferrous tartrate standard curve method, the concentration of TP in green tea, which was purchased from the market, detected using our method showed an error within 5%, indicating good potential applications in the food industry. Cell imaging experiments suggested that the R-CDs exhibit excellent lysosomal targeting as the Pearson’s correlation coefficient (PCC) in colocalization analysis was found to be 0.91. Further experiments showed that owing to their excitation-independent emission and high QY, the R-CDs could be applied to not only for detecting TP content but also for targeting lysosomes as substitute for commercial dyes. • The prepared R-CDs possess red emission with high quantum yield. • The R-CDs could detect TP with high selectivity and sensitivity. • The R-CDs showed wonderful lysosomal targeting compared to commercial dyes.