"Turn on" and label-free core−shell Ag@SiO(2) nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg(2+)

A turn on and label-free fluorescent apasensor for Hg(2+) with high sensitivity and selectivity has been demonstrated in this report. Firstly, core−shell Ag@SiO(2) nanoparticles (NPs) were synthetized as a Metal-Enhanced Fluorescent (MEF) substrate, T-rich DNA aptamers were immobilized on the surface of Ag@SiO(2) NPs and thiazole orange (TO) was selected as fluorescent reporter. After Hg(2+) was added to the aptamer-Ag@SiO(2) NPs and TO mixture buffer solution, the aptamer strand can bind Hg(2+) to form T-Hg(2+)-T complex with a hairpin structure which TO can insert into. When clamped by the nucleic acid bases, the fluorescence quanta yield of TO will be increased under laser excitation and emitted a fluorescence emission. Furthermore, the fluorescence emission can be amplified largely by the MEF effect of the Ag@SiO(2) NPs. The whole experiment can be finished within 30 min and the limit of detection is 0.33 nM even with interference by high concentrations of other metal ions. Finally, the sensor was applied for detecting Hg(2+) in different real water samples with satisfying recoveries over 94%.