A Phenanthroline-Based Fluorescent Probe for Highly Selective Detection of Extreme Alkalinity (pH>14) in Aqueous Solution

摘要

Although numerous fluorescent probes are designed to detect the pH value in the past decades, developing fluorescent probes for extreme alkalinity (pH?>?14) detection in aqueous solution is still a great challenge. In this work, we utilized 1H-imidazo[4,5-f][1, 10] phenanthroline (IP) group as the recognition group of hydroxyl ion and introduced two triethylene glycol monomethyl ether groups to improve its solubility. This IP derivative, BMIP, possessed good solubility (25?mg/mL) in water. It displayed high selectivity toward extreme alkalinity (pH?>?14) over other ions and pH (from extreme acidity to pH?=?14). From 3 to 6?mol/L OHˉ, the exact concentration of OHˉ could be revealed by BMIP and the whole detection process just needed a short time (≤?10?s). Meanwhile, it exhibited good anti-interference ability and repeatability during the detection process. Through optical spectra and NMR analysis, its detection mechanism was proved to be deprotonation by hydroxyl ion and then aggregation-induced enhanced emission. Our study presents a new basic group based on which researchers can develop new fluorescent probes that can detect extreme alkalinity (pH?>?14) in aqueous solution.