g-C3N4 Dots Functionalized with L-Glutathione for Fluorescent Sensing of Pb2+ in Aqueous Media

Abstract

A facile, sensitive, and selective fluorescent detection method for Pb2+ ions was designed using g-C3N4 dots functionalized with L-Glutathione (GSH). A carbodiimide-activated coupling reaction was used to bind GSH onto g-C3N4 QDs. When excited at 340 nm, the asobtained passivated quantum dots exhibited strong blue emissions at 420 nm. With a relative quantum yield of 27%, the system demonstrated exceptional stability against ionic strength and photobleaching. Additionally, it was discovered that the fluorescence emission of the sensor was selectively quenched on the adition of Pb2+ ions. The limit of detection (LOD) for Pb2+ was measured to be 0.025 µM (S/N=3) in a linear range of 0.01 µM-0.1 µM. The average lifetime calculations from the lifetime decay experiment along with UV–vis. absorption and TEM studies suggested that the quenching pattern followed was static quenching. Finally, the sensor system was used in real water samples to detect Pb2+ with recovery percentage greater than 90%.