Cascade Fluorescent Determination of Mercury (II) and Captopril Using Tungsten-Nitrogen Doped Carbon Dots

Tungsten and nitrogen co-doped carbon dots (W, N-CDs) with a high quantum yield of 51.08% were synthesized by a facile hydrothermal process. Doping of tungsten effectively enhanced luminescent properties of the carbon dots, and the quantum yield was increased by 10.3%. The surface composition and morphology of the synthesized W, N-CDs were characterized. W, N-CDs were employed as nanoprobes to develop a sensor for the selective and sensitive determination of Hg2+ and captopril. Under the optimal conditions, the linear response range for Hg2+ and captopril were 0.125 to 9.0 μM and 0.5 to 10 μM with detection limits of 40 nM and 300 nM, respectively. The developed sensor was successfully applied for the determination of Hg2+ in water and captopril in urine with recoveries from 95.50 to 105.50% and 96.33 to 105.13%, which demonstrates suitable accuracy and reliability. The fluorescence mechanisms of W, N-CDs toward Hg2+ and captopril were also evaluated.