A novel symmetrical imidazole-containing framework as a fluorescence sensor for selectively detecting silver ions

In this study, a novel and highly efficient "turn-off" fluorescence imidazole-based sensor (BIB) with a symmetric structure was synthesized by a four-step reaction, from o-phenylenediamine, 6-bromo-2-pyridinecarboxaldehyde, and 1-bromohexane. The sensing mechanism was confirmed via fluorescence titration, HRMS, and ¹HNMR techiniques. The results showed that the binding ratio of BIB and Ag⁺ was 1 : 1 in a DMF-HEPES (pH 7.4) solution (9 : 1, v/v). The fluorescence response of BIB exhibited a good linear response within the Ag⁺ concentration ranging from 2 × 10^-7 to 8 × 10^-6 mol L^-1, and the limit of detection was calculated to be 4.591 × 10^-8 mol L^-1. BIB was successfully applied to the detection of Ag⁺ in water samples with recoveries of 97.25-109.50% and relative standard deviations (RSD) of 1.14-2.45%. In addition, BIB can successfully be applied to qualitatively and quantitatively identify Ag⁺ in water by test paper strips of BIB, which is fast and convenient. This provides a possible potential for the rapid monitoring of metal ions by sensors in environmental research.