Single-benzene-based fluorophores (SBBFs) with green luminescence: Improved sensitivity towards cysteine both in solution and solid state

We have developed a symmetric, low -molecular -weight fluorophore based on a single benzene unit with push-pull functionalities for the selective detection of cysteine. Based on the specific nucleophilic ability of thiols of cysteine, probe 1 exhibited high selectivity and sensitivity for cysteine over other amino acids and thiols. The interaction with cysteine triggers a substitution reaction, followed by rearrangement and cyclization, leading to the formation of a thiazolidine derivative with distinctive photophysical properties in the aqueous medium. The self -assembled fluorogenic probe exhibits a turn-off fluorescence upon cysteine sensing, due to the de -aggregation and loss of the push-pull nature of the corresponding adduct. Its potential applications were exemplified through its utilization in the detection of Cys within simulated urine samples. Additionally, we have designed inexpensive and portable paper strips for rapid on -site detection of cysteine, eliminating the need for complex instrumentation or trained technicians.