A sensitive PET “turn on” fluorescent probe for specific detection of 4-methoxy-thiophenol

Thiophenols as a series of industrial products are widely used and high toxicity to the organisms and the environment. The fluorescent probe technique offers important insights into thiophenols convenient sensing. Herein, we report a 1,8-naphthalimide/ triphenylamine-based fluorescent probe (TPA-NI-NO2) for the specific detection of 4-methoxy-thiophenol (MTP). The probe can "turn on" specific detect MTP with the limit of detection (LOD) of 80 nM among various relevant analytes and homologues (p-Cl-C6H4SH, p-NO2-C6H4SH, C6H5SH and o-CH3-C6H5SH). The sensing mechanism was explored by the HPLC experiment and the PET process was determined by density functional theory (DFT) calculations. In addition, the specificity of the probe was also studied by the Gibbs free energy (ΔG) analysis of the reaction between the probe and different thiophenols. The reaction between probe and MTP gives the minimum of the DΔG value (∼ -9.7280 kcal/mol) and that of other thiophenols-mediated is -2.5283 to -5.8911 kcal/mol, which proves the thermodynamic chemical equilibrium can optimize the design of reaction-based fluorescent probes with excellent specificity. At last, TPA-NI-NO2 was successfully applied to Hela cells imaging.