Tritopic linker-integrated fluorescent bismuth nanosheets for sensitive pesticide detection in agricultural samples

Abstract

A highly stable luminescent sensor based on bismuth-based organic nanosheets, Bi(TMA), has been developed for the rapid visual detection of the toxic pesticide dicloran (DCN) in real food matrices. Bi(TMA) is constructed from Bi(III) ions and the tridentate linker trimesic acid (TMA), yielding a two-dimensional interpenetrated architecture stabilized by extensive O-bridging coordination bonds. The framework's structural stability is attributed to carboxylic coordination and its interpenetrated architecture, which endows the nanosheets with high fluorescence stability in dimethyl sulfoxide (DMSO) across a wide pH range for up to 30 days. Under excitation at 370 nm, Bi(TMA) displays a sharp emission maximum at 452 nm, which is selectively quenched by DCN in DMSO at pH = 6.5 while remaining unchanged in the presence of a broad panel of competing pesticides. Selectivity originates from the formation of a highly stable Bi(TMA)–DCN complex mediated by imine bond formation and subsequent charge-transfer interactions, as confirmed by different types of data collected from different instruments including TRPL and zeta (ζ)-potential measurements. The sensor exhibits a detection limit of 0.03 nM, surpassing the performance of recently reported metal–organic framework (MOF)-based sensors. In spiked environmental and food samples, recoveries range from 88% to 115% with relative standard deviations ≤4%, demonstrating the practicality of Bi(TMA) for on-site pesticide monitoring. This work provides a straightforward design strategy for bismuth-based luminescent nanosheets with tunable photophysical properties and high analytical performance.