Off‐On Fluorescence Response of a Cysteine–based Perylene Diimide for Mercury Detection in Water

The development of simple, low‐cost and selective methods for quantitative detection of mercury ions in aqueous media is still a challenge. Herein, we employ a cysteine based perylene diimide (PDI‐Cys) as sensing probe for Hg 2+ ions in water. The probe selectively detects the mercury ions in 100 % aqueous solution by a fluorescence turn‐on response. The binding stoichiometry reveals a 1:2 complexation of PDI‐Cys/Hg 2+ , in which two Hg 2+ ions are bound to one PDI‐Cys molecule. The detection limit is as low as 20 ppb, close to the sensitivity requirement for drinking water, indicating the potentiality of PDI‐based probes for mercury analysis in both environmental and biological field.