A simple and dual responsive ultrasensitive thioether-functionalized pyrenesulfonamide for the cascade detection of mercury ion and dithiouracil, a mimetic system for molecular logic gates

Abstract

A thioether-functionalized probe with a dipodal pyrene-sulfonamide fluorophore (probe 1) was synthesized for the selective and sensitive detection of Hg2+ in aqueous solutions. In addition, a probe with a monopod pyrene-sulfonamide unit was prepared (probe 2). Among various metal ions, these two probes appeared to selectively bind to Hg2+ at a 1:1 ratio, with a stronger association of probe 1 than probe 2, as evidenced by titration experiments. The green emission displayed by probe 1 was completely quenched by the coordination of Hg2+ to sulfur (ON-OFF), presumably via energy transfer from the pyrene fluorophore to the [sulfur-Hg2+] unit. The limit of detection (LOD) was 1nM (0.22ppb), one of the lowest values obtained so far. Furthermore, the in situ-prepared [1+Hg2+] complex continued to be utilized to selectively detect dithiouracil (DTU) via an “OFF-ON” mechanism among diverse biomolecules, along with an LOD of 20nM. Thus, probe 1 alone or together with Hg2+ allowed the cascade detection of Hg2+ and DTU with high selectivity and ultra-sensitivity. The current study indicates that probe 1 not only serves as an ‘INHIBIT and AND’ logic gate, but also works as an “ON−OFF−ON” molecular switch triggered by the sequential addition of Hg2+ and DTU.