2-Hydroxy benzothiazole modified rhodol: aggregation-induced emission and dual-channel fluorescence sensing of Hg2+ and Ag+ ions

Abstract

The sensitive detection and quantification of heavy and transition metal ions are particularly important. Among them, mercury(II) (Hg2+) and silver(I) (Ag+) ions, as the most ubiquitous heavy metal ion pollutants, are difficult to discriminate in the same system because of their similar reactions and coordination abilities. Herein, we designed and synthesized a “turn-on” chemosensor, RBTP, which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit to the ortho-position of the phenolic hydroxy of rhodol. RBTP showed a sensitive dual-channel fluorescence-enhanced response to Hg2+ and Ag+ at 595 and 520nm with low detection limits of 0.27 and 0.45μM, respectively. Studies of their sensing mechanism indicated that the Hg2+-induced orange fluorescence at 595nm originates from an irreversible Hg2+-promoted oxadiazole forming reaction and the Ag+-induced green fluorescence at 520nm originates from special molecular packing of the RBTP-Ag+ complex. Furthermore, the potential of probe RBTP as practical biological imaging agents was further confirmed in HepG2 cells. Simultaneously, RBTP exhibited remarkable solid-state luminescence with an aggregation-induced emission (AIE) feature. The AIE mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations.