L-Glutathione modified graphitic carbon nitride quantum dots: An ultrasensitive fluorescent sensor for detection of Pb2+ in water

Abstract

A facile, sensitive, and selective fluorescence detection method for Pb2+ ions is designed using L-Glutathione (GSH) modified graphitic carbon nitride quantum dots (GSH@g-C3N4 QDs). A carbodiimide-activated coupling reaction is used to bind GSH onto g-C3N4 QDs. When excited at 340 nm, the as-obtained passivated quantum dots exhibit strong blue emissions at 420 nm. With a relative quantum yield of 27%, the system demonstrates exceptional stability against ionic strength and photobleaching. Additionally, it is discovered that the fluorescence emission of the sensor is selectively quenched in the presence of Pb2+ ions. The limit of detection (LOD) for Pb2+ is measured to be 0.025 µM 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 studies suggest that the quenching pattern follows a static quenching mechanism. Finally, the system is used in real water samples to detect Pb2+ with a substantial recovery percentage greater than 90%.