A facilely synthesized fluorescent ionic liquid sensor for specific and broad-spectrum detection of tetracycline antibiotics in ambient waters.

Abstract

Tetracycline antibiotics (TCs) are a class of broad-spectrum antibiotics derived from actinomycetes. They persist in aquatic environments and pose long-term risks to human and animal health. In this study, a naphthalene-based ionic liquid, tetrabutylphosphonium naphthalenecarboxylate ([TBP][NA]), was synthesized for the specific detection of TCs. The addition of TCs, including chlortetracycline (CTC), doxycycline (DOX), tetracycline (TC), and methacycline (MTC), resulted in significant fluorescence quenching of [TBP][NA], attributed to a static quenching mechanism. Density functional theory (DFT) calculations indicated a reduction in the band gap of approximately 1 eV, with ground-state electrons transferring from the lowest unoccupied molecular orbital (LUMO) of [TBP][NA] to the LUMO of TCs. The experimental results demonstrate the feasibility of using [TBP][NA] for selective and broad-spectrum TC detection, likely due to a synergistic effect involving both the molecular planarity of adjacent rings and the presence of hydroxyl groups in TCs and the inner filter effect (IFE). Moreover, [TBP][NA] was shown to be capable of identifying and quantifying TCs in environmental samples, with spiked recovery rates ranging from 81.3% to 116.6%.

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