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

Novel ratiometric fluorescent silica nanoparticles with high selectivity towards Hg2+ were synthesized for the detection of Hg2+. Hg2+ 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 Hg2+ concentration, and the detection limit (S/N = 3) for Hg2+ was found to be 2.59 × 10−9 mol L−1 with a linear range from 0.4 to 8 × 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 Hg2+ in water samples.