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.