Ultrasensitive Silicon Nanoparticle Ratiometric Fluorescence Determination of Mercury(II)

A novel ratiometric fluorescence sensing system for the ultrasensitive detection of Hg2+ was developed. It used aminofunctionalized silicon nanoparticles and rhodamine B, which exhibit two distinct fluorescence emission peaks at 449 and 581 nm, respectively, under a single excitation wavelength (350 nm). The fluorescence of the amino-functionalized silicon nanoparticles was selectively quenched by Hg2+, while that of rhodamine B was insensitive to Hg2+. The ratio of fluorescence intensities at 449–581 nm linearly decreased with increasing concentrations of Hg2+ from 0.005–0.1 and 0.1–7 µM within 0.5 min, and a detection limit as low as 3.3 nM was achieved. Moreover, the ratiometric fluorescence sensing system exhibited good selectivity toward Hg2+ over other metal ions with relatively low background interference, even in a complex matrix such as lake water. Most importantly, the practical use of this sensing system for Hg2+ detection in real water samples was also demonstrated.