An efficient rhodamine thiospirolactam-based fluorescent probe for detection of Hg ~(2+) in aqueous samples

摘要

This paper described the optimized design, synthesis and application of a novel rhodamine thiospirolactam derivative as an 'off-on' fluorescent probe for the detection of Hg ~(2+) in aqueous samples. The 'off-on' fluorescence and color signal change of the probe is based on an Hg ~(2+)-triggered domino reaction which brings on the opened-ring form of the rhodamine spirolactam to regain the conjugated system of the rhodamine skeleton. In the well designed probe, the thiospirolactam serves as both Hg ~(2+) binding unit and electron-defect carbon centre, a phenolic hydroxyl with very strong nucleophilicity after deprotonation is chosen as the attacking unit, and a benzene ring is introduced on the linker to afford steric effects, which benefits an efficient nucleophilic reaction, with a high sensitivity towards Hg ~(2+). It exhibits a stable response for Hg ~(2+) from 1.0 × 10 ~(-8) to 1.0 × 10 ~(-6) M, with a detection limit of 3.0 × 10 ~(-9) M. The response of the probe to Hg ~(2+) is highly selective and pH-insensitive, with a fast response time. All these unique features make it particularly favorable for cellular Hg ~(2+) imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg ~(2+) levels in living cells with satisfying resolution.