An NBD-based fluorescent and colorimetric chemosensor for detecting S: Practical application to zebrafish and water samples.

A novel 7-nitro-1,2,3-benzoxadiazole (NBD)-based chemosensor BOP ((5-bromopyridin-2-yl)(4-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)piperazin-1-yl)methanone) was synthesized. BOP could detect S through fluorescent quenching and colorimetric change. The detection limit was calculated to be 10.9 µM through fluorescence titration. The reaction mechanism of BOP towards S was estimated to be thiolysis of NBD amine, producing the cleavage products, NBD-S and BP ((5-bromopyridin-2-yl)(piperazin-1-yl)methanone). The thiolysis was demonstrated by H NMR titrations, ESI-mass analysis and theoretical calculations. Importantly, BOP was able to successfully monitor S in zebrafish and water samples. Additionally, test strips coated with BOP were applied to the in-the-field measurements of S.