A sensitive, selective, and rapid fluorescent probe for thiophenol detection with a broad linear range and simple...

Thiophenols are aromatic organosulfur compounds widely used in industry, but their presence in the environment poses significant health and ecological risks. Fluorescent probes offer a rapid, cost-effective, and highly sensitive alternative to conventional analytical techniques for real-time monitoring of these pollutants. In this work, we present a fluorescein-based fluorescent probe (1) for the selective and sensitive detection of thiophenols. Probe 1 reacts with thiophenols at neutral pH via nucleophilic aromatic substitution (S_NAr), generating a fluorescent signal at 515 nm. This second-order reaction enables quantitative measurement of thiophenol concentration in both aqueous and semi-aqueous matrices. This method exhibits excellent selectivity, effectively distinguishing thiophenols from other thiols due to their enhanced nucleophilicity at neutral pH. It also exhibits high sensitivity, achieving a detection limit of 50 nM, with a broad linear range spanning 0-32 μM. It is also remarkably fast, with a measurable signal within 2 min and optimal detection at 10 min. Additionally, probe 1 is synthesized in a single step, making it practical for broad application. As a proof of concept, we successfully quantified thiophenols in spiked river water samples with 98-103 % recovery. The combination of high sensitivity, rapid response, and simple synthesis highlights the potential of probe 1 for real-world applications, including environmental monitoring.