Synthesis of Highly Sensitive Fluorescent Probe Based on Tetrasubstituted Imidazole and Its Application for Selective Detection of Ag + Ion in Aqueous Media

A small molecule fluorescent probe, 4-[2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-1-yl]aniline(L) for detecting Ag+ ion was gently synthesized via one-pot multi-component reaction catalyzed by H3[PW12O40] under solvent-free microwave irradiation. When the concentration of Ag+ ion changed from 0 to 8.0×10−6 mol/L in the solution of H2O/CH3OH(19:1, volume ratio), the fluorescence emission spectrum was blue-shifted and accompanied by a gradual increase in fluorescence intensity with a low detection limit of 3.0×10−11 mol/L. Moreover, UV-Vis absorption titration experiment demonstrated a 1:1 stoichiometric ratio and an association constant of (9.95±0.44)×105 L/mol between probe L and Ag+ ion, and thus their complexation mechanism was also proposed and verified. More importantly, this fluorescent probe was remarkably specific for Ag+ ion under the interference of other metal ions and exhibited a wide pH application range of 4.0―8.0. Additionally, preliminary application of this probe was also carried out and satisfactory results were shown.