Abstract: In this study, a ratiometric fluorescence sensor based on silicon-doped carbon quantum dots (Si-CDs) and lysozyme (Lys) functionalized gold nanoclusters (Lys-AuNCs) was developed for the rapid detection of mercury (II) ion (Hg2+). In the method, Si-CDs emitted a blue light as a reference fluorescence signal, and Lys-AuNCs emitted a red light as a response fluorescence signal. Hg2+could efficiently quench the fluorescence of Lys-AuNC at 670 nm (I670) by virtue of gold affinity between Au+ and Hg2+, while the fluorescence intensity of Si-CDs at 470 nm (I470) remains unchanged. The ratio of the fluorescence intensity at 670 nm and 470 nm (I670/I470) showed a good linear relationship with the concentration of Hg2+ in the range of 0–0.016 mg/L, which was fitted as follows: I670/I470 = 1.35–64.18C (Hg2+). The recoveries of Hg2+ spiked in lake water, mineral water and running tap water were in the range of 94.3%–115.0%. The detection limit of this sensor was 0.001 mg/L (3σ) with a variation coefficient not more than 10.3%. Other metal ions exhibited no interference for this sensor.

Key words: mercury (II) ion; carbon quantum dots; gold nanoclusters; ratiometric fluorescence sensor