Solvent-dependent fluorescence sensing of Cu2+, Hg2+, and CN‒ based on thiosemicarbazone-functionalized pillar[5]arene and its applications in actual water samples and molecular logic gates

Abstract

A novel solvent-dependent fluorescent probe P5T based onapillar[5]arene containing a thiosemicarbazone unit has been synthesized. This probe serves as a dual selective fluorescent probe, which can selectively detect Cu2+ and Hg2+ ions in mixed solvent systems of acetonitrile (AN) and dimethyl sulfoxide (DMSO) with water. A significant fluorescence enhancement was observed following adding Cu2+ to the AN/H2O (v/v = 7:3) solution of P5T. The Job′s plot method and the spectrometric titrations indicated a 1:1 stoichiometric ratio between Cu2+ and the P5T probe, with a detection limit as low as 2.70 × 10‒7 M. Obvious fluorescence quenching occurred when Cu2+ or Hg2+ was added to the DMSO/H2O (v/v = 7:3) solution of P5T. The stoichiometric ratio for the P5T with Cu2+ and Hg2+ are 1:1 and 1:2, respectively, with detection limits of 3.70 × 10‒7 M and 1.20 × 10‒7 M. It is noteworthy that the reversibility of the P5T probe in the presence of S2O32‒ enables the construction of an INHIBIT logic gate using Hg2+ and S2O32‒ as inputs, facilitating the rapid and efficient detection of ions in DMSO/H2O (v/v = 7:3) solutions. P5T is a solvent-dependent dual selective fluorescent probe with high sensitivity and strong anti-interference properties. Moreover, applying this method to the analysis of Cu2+ and Hg2+ in natural water samples yielded a relative standard deviation (RSD) of less than 5%. Therefore, the solvent-dependent selective recognition capabilities and molecular logic gate functionalities of the P5T probe provides a novel approach to multiple analytical detections.