Construction of Hybrid Fluorescent Sensor for Cu2+ Detection Using Fluorescein-functionalized CdS Quantum Dots Via FRET

A new hybrid fluorescent nanosensor (Flu@Mea-CdS) for the Cu2+ detection in aqueous solution was constructed through fluorescence resonance energy transfer (FRET). The Flu@Mea-CdS was fabricated by amide linkage between CdS quantum dots capped with cysteamine (Mea-CdS) and fluorescein. With the formation of FRET process from Mea-CdS quantum dots to fluorescein, the fluorescence intensity of fluorescein at 520 nm was significantly enhanced. In addition, the sensor based on FRET has high selectivity for Cu2+ ions detection. With the presence of Cu2+ ions, Cu2+ ions were transferred to Cu2S by the reaction with Flu@Mea-CdS, which caused the inhibition of FRET process and quenched the fluorescence signal of 520 nm. Compared with Mea-CdS quantum dots, the Flu@Mea-CdS sensor has a lower detection limit for Cu2+. The linear range is 4–14 μM, and the detection limit is 0.17 μM. The sensor has been successfully applied to the detection of Cu2+ ions in practical samples, which shows its potential application value in environmental monitoring.