Rhodamine-based ratiometric fluorescence sensing for the detection of mercury(II) in aqueous solution.

Novel ratiometric fluorescent silica nanoparticles with high selectivity towards Hg(2+) were synthesized for the detection of Hg(2+). Hg(2+) promoted the ring opening of spirolactam in the rhodamine moiety grafted onto the silica nanoparticles, resulting in a change in the fluorescence intensity. The fluorescence intensity was proportional to the Hg(2+) concentration, and the detection limit (S/N=3) for Hg(2+) was found to be 2.59 x 10(-9) mol L(-1) with a linear range from 0.4 to 8 x 10(-7) mol L(-1). In addition, the morphology of the silica nanoparticles, the effects of pH and co-existing substances, and the reversibility were investigated. The proposed approach was successfully applied to the determination of Hg(2+) in water samples.