A simple carbon dots based method to discriminate doxycycline, chlortetracycline from tetracyclines

• A simple method to discriminate doxycycline, chlortetracycline from tetracyclines. • The CDs greatly enhance the fluorescence emission of the doxycycline-Ca 2+ complex. • The CDs considerably enhance the fluorescence emission of chlortetracycline. It is rather difficult to differentiate tetracyclines (TCs) by only using carbon dots (CDs) based fluorescence methods due to their similar structures and optical properties. In this work, a simple method based on CDs to discriminate doxycycline (DOX), chlortetracycline (CTC) from TCs by combining the unique optical properties of the CDs and the complex of DOX with Ca 2+ . The CDs were synthesized by a hydrothermal treatment of phthalic acid and ethylene diamine. DOX and Ca 2+ can form a stable complex with weak fluorescence emission at 511 nm, which can be significantly enhanced by the CDs through fluorescence resonance energy transfer (FRET), accompanied by a decrease in the fluorescence peak of the CDs at 390 nm due to inner filter effect (IFE). Moreover, CTC emits very weak fluorescence at 428 nm, which can be greatly enhanced by the CDs due to FRET. Correspondingly, DOX and CTC can be discriminated from the mixture solution of DOX, CTC and tetracycline (TC). In addition, TC could quench the fluorescence of the CDs due to IFE. Therefore, the CDs also can be used as a probe to detect TC in the samples only containing itself without interferences from other TCs.