Selective colorimetric detection of cysteine based on phenylvinylbisquinoline for its potential implementation in optoelectronic sensors

We report a sensitive colorimetric chemosensor for cysteine based on phenylvinylbisquinoline, named M1. Selectivity for l-cysteine was demonstrated, causing a colorimetric change. The interaction between M1 and l-cysteine suggests a possible click reaction that alters the optical properties, which are consistent with the predictions in the study of TD-DFT. ¹ H RMN, FTIR spectroscopies, and mass spectrometry confirmed the chemical structure obtained by the click reaction. Optical characterization revealed a bathochromic shift and a weakening of the fluorescence of M1 with increasing l-cysteine concentration. The detection limit for cysteine was 0.45 mM, the quantification limit was 1.36 mM, and the molar ratio method confirmed a stoichiometry of 1:2 between M1 and l-cysteine. This molecule can be used in electronic devices for in situ sensing of l-cysteine by a colorimetric shift.