Facile preparation of polymer dots for tetracycline and Al3+ detection and exploration of anti-counterfeiting applications via the fluorescence "ON-OFF-ON" strategy.

Polymer dots (PT-PDs) were obtained through a "synthesis-modification integration" method by using polyethyleneimine (PEI) and tartaric acid (TA) as raw materials. The designed PT-PDs displayed a nanoscale structure with an average size of 1.6 nm, and bright blue fluorescence (FL) emission with a fluorescence quantum yield (QY) of 14.3%. Moreover, the PT-PDs were used as a sensing platform for the sensitive and quantitative detection of tetracyclines (TCs) and Al3+ via fluorescence quenching and recovery. The LODs for tetracycline hydrochloride (TCH), doxycycline (DOX), and Al3+ were 94.8 nM, 76.7 nM, and 177.8 nM, respectively. In addition, PT-PDs incorporated with polyacrylamide were used for the recognition of TCs and Al3+ in a portable manner on the basis of the fluorescence "ON-OFF-ON" strategy, which revealed great application in the field of anti-counterfeiting and encryption.