Turn-Off-and-On: Chemosensing Ensembles for Sensing Chloride in Water by Fluorescence Spectroscopy

The recognition and sensing of aqueous chloride by synthetic receptors is a challenging task. Herein we apply the chemosensing ensemble methodology to optically detect chloride in water at near physiological pH. Variants based on two closely related receptors have been explored. The sensors can be obtained in situ by mixing a rhodium complex, a bidentate N,N-chelate ligand, and a fluorescent dye in buffered aqueous solution. Upon mixing the sensor components, the rhodium complex binds to the N,N-chelate ligand to yield a metal-based receptor. This latter associates with the fluorophore to give a non-emissive ground-state complex. The chemosensing ensembles respond to chloride via a turn-on fluorescence signal and can be used for optical detection of chloride down to mid-micromolar concentrations.

合成受体识别与传感水相氯离子是一项极具挑战性的研究课题。本文采用化学传感组装体（chemosensing ensemble）策略，实现近生理pH值水相环境中氯离子的光学检测。本研究针对两种结构密切相关的受体开发了相应的传感变体。该类传感器可通过原位混合法制备：在缓冲水溶液中混合铑配合物（rhodium complex）、双齿N,N-螯合配体（bidentate N,N-chelate ligand）与荧光染料（fluorescent dye），即可原位获得目标传感器。混合传感器组分后，铑配合物会与N,N-螯合配体结合，生成金属基受体；该受体随后与荧光团（fluorophore）结合，形成无发射的基态复合物（ground-state complex）。该化学传感组装体可通过荧光启亮（turn-on）信号响应氯离子，可用于光学检测低至中微摩尔浓度级别的氯离子。