A highly sensitive fluorescent sensor with aggregation-induced emission characteristics for the detection of iodide and mercury ions in aqueous solution

In this work, we report a highly sensitive fluorescent sensor (TPE-QN) with aggregation-induced emission (AIE) characteristics for the detection of iodide (I-) and mercury (Hg2+) ions. TPE-QN is based on tetraphenylethene (TPE)-functionalized quinolinium salts with hexafluorophosphate (PF6-) as the counterion, and exhibits intense red emission in aqueous media when nanoaggregates are formed. In the presence of I-, the emission of TPE-QN can be effectively quenched due to synergistic electrostatic interactions and drastic collisions between aggregates of TPE-QN and I-, enabling TPE-QN to work as a fluorescent turn-off'' sensor for I- with a detection limit of 22.6 nM. Moreover, the complex of TPE-QN and I- (TPE-QN-I) can secondarily recognize Hg2+ by showing a fluorescence turn-on'' signal because of the high affinity between Hg2+ and I-, and the detection limit for Hg2+ is as low as 71.8 nM. Furthermore, the high selectivity and sensitivity of TPE-QN makes it quite qualified for detecting the low concentration of I- and Hg2+ in real samples such as running water and urine.