Ratiometric Fluorescent Mercuric Sensor Based on Thiourea-Thiadiazole-Pyridine Linked Organic Nanoparticles

A novel naked-eye and ratiometric fluorescent Hg2+ probe based on thiourea-thiadiazole-pyridine linked (TTP) fluorescent organic nanoparticles (FONs) was designed and synthesized. TTP FONs show good water solubility; a 46-fold increase in fluorescence quantum yield, high selectivity for sensing, and a 98 nm red shift of the fluorescence emission upon binding Hg2+ in aqueous media are observed. Under the optimum conditions, the relative fluorescence intensity ratio, I-501/I-403, is increased linearly with the increasing logarithmic concentration of Hg2+ in the range of 2.5-40 mu M with a detection limit of 1.13 x 10(-7) M (22.6 ppb), whereas the fluorescence intensity of TTP FONs to other metal ions, including Na+, Ca2+, Ni2+, Cd2+, Cu2+, Ag+, Pb2+, Mn2+, and Mg2+, is negligible. The possible mechanism is discussed.