A Sensitive Near-Infrared Fluorescent Probe for Detecting Heavy Metal Ag⁺ in Water Samples

Silver is a common catalyst in industrial production, and the frequent use of Ag⁺ can cause water pollution. Thus, the detection of Ag⁺ in the environment is necessary to determine the level of pollution from silver. In this work, we designed a new, highly selective near-infrared (NIR) fluorescent probe QCy to detect Ag⁺. The probe exhibits "turn-off" fluorescence quenching responses at 760 nm towards Ag⁺ over other relevant cations, with outstanding sensitivity and a low detection limit (0.03 µM), which is considerably lower than the standard of the World Health Organization (WHO) for drinking water (0.9 µM). Meanwhile, QCy showed a very good linearity at a low concentration of Ag⁺ with a 'naked eye' visible color change of solution from blue to red. The probe has been applied successfully for the detection of Ag⁺ in real water samples.