Sulfate radical-dominated colorimetric sensing platform for ultrafast and portable monitoring of tetracycline in environment

Tetracycline (TC) is one of the most frequently detected antibiotics in environmental. Monitoring the concentration of TC is essential for understanding environmental fate of antibiotics. In this work, bimetallic N-doped carbon catalysts of M/Co@NC (M= Ni, Mn, Cu, Zn, Fe) were rationally synthesized via molten salt-assisted pyrolysis. The distinctive synergistic interplay between Cu and Co endowed Cu/Co@NC superior activation capacity for peroxymonosulphate (PMS). Inspired by the advantages of sulfate radical (SO4•−), an original colorimetric sensing platform was developed by using PMS as oxidant and rhodamine B(RhB) as chromogenic agents. Notably, this platform achieved an ultrafast visual reaction within 60 s and exhibited broad pH applicability under pH 2-9. Then, leveraging a competitive inhibition mechanism, dual-mode colorimetric and fluorescent sensing platforms were established for TC detection under neutral conditions. The fluorescent platform exhibited a reliable liner range from 0.001 to 15 μg/mL with limit of detection of 2 ng/mL. Excellent selectivity was found for TC even among different antibiotics. Theoretical calculations elucidated that the superior selectivity arises from a higher electrophilic attack (f -) of TC. Based on these finding, a smartphone-assisted test strip was developed and successfully deployed for the rapid monitoring of TC in practical water samples. This work not only synthesized an efficient PMS activator, but also proposed a novel visual sensing mode with ultrafast detection times, wide pH applicability and portable operation.