Red fluorescent carbon dots for tetracycline antibiotics and pH discrimination from aggregation-induced emission mechanism

Red fluorescent carbon dots (R-CDs) have been developed for the “turn-on” determination of pH and tetracycline antibiotics (TCs), including tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). The CDs were fabricated via one-pot hydrothermal treatment using neutral red and thiourea as precursors. As-obtained CDs possess excellent photobleaching resistance, good photostability and biocompatibility, and low cytotoxicity. Importantly, the CDs displayed a remarkable emission enhancement upon the introduction of TCs based on aggregation induced emission enhancement (AIEE) mechanism. For TC, OTC, and CTC, the linear correlation detection ranges are 3 − 35 μM, 2 − 50 μM, and 5 − 50 μM, respectively, and the limit of detections are 12, 23, and 25 nM, respectively. The proposed method has been successfully applied to the determination of TCs in milk products. Furthermore, the CDs exhibited a distinct H+-sensitive feature, and have been used to construct fluorescent pH sensor in linear range of 6.0–8.0 with a pKa of 7.08. Notably, the nanosensor has been also extended to monitor TCs and pH in cellular systems, demonstrating the proposed methodology presents promising biosensing application prospect.