Silica nanoparticles doped with a benzo[e]indolium-tethered iridium(III) complex for reversible detection of HSO3- and Hg2+/Cu2+ in water

A reusable colorimetric and phosphorescent probe for continuous detection of bisulfite and Hg2+/Cu2+ in water has been rationally designed by silica nanoparticles doped with a new iridium(III) complex. In the presence of HSO3-, it demonstrated intensively enhanced phosphorescence as well as instantaneous solution color change from dark-green to light-yellow. However, it is interesting that the enhanced phosphorescence caused by bisulfite can be subsequently quenched by Hg2+ or Cu2+, and then be re-enhanced by the further addition of bisulfite. Moreover, a good linearity was observed between phosphorescent intensities of the probe and concentrations of HSO3-, Hg2+ and Cu2+ with satisfactory detection limits of 0.80, 0.77 and 0.85 mu M, respectively. It should be noted that this off-on-off phosphorescent process can be circled for several times by adding bisulfite and Hg2+ or Cu2+ alternately. As a result, the newly designed probe can be repeatedly used for detection of HSO3-, Hg2+ and Cu2+ at low detection limits, which would be more efficient and less expensive than a one-to-one analysis method.