Colorimetric and ratiometric fluorescent dual-mode sensitive detection of Hg2+ based on UiO-66-NH2@Au composite

A colorimetric and ratiometric fluorescent dual-mode assay is constructed for sensitive and specific Hg 2+ sensing based on UiO-66-NH 2 and Au composite (UiO-66-NH 2 @Au). The addition of Hg 2+ stimulates the peroxidase-like activity of UiO-66-NH 2 @Au by the formation of Au-Hg amalgam, promoting the oxidizing of chromogenic substrate OPD to DAP with the aid of H 2 O 2 , which lead to the change of colorimetric and fluorescent signals. The absorbance of the sensing system at 450 nm is linear positive correlation with Hg 2+ concentration of 30–1400 nM and the color of the solution under visible light shaded from light yellow to dark yellow. With the increase of Hg 2+ concentration, the fluorescence signal at 570 nm (DAP) increased whereas that at 455 nm (intrinsic fluorescence of UiO-66-NH 2 ) decreased due to inner filter effect (IFE), the fluorescence intensity ratio (F 455 /F 570 ) decreasing linearly with Log [Hg 2+ ] over the range 60–1700 nM; the fluorescence emission of sensing system under UV excitation changed from blue to yellow, which can easily be discerned visually. This assay was successfully applied to the determination of Hg 2+ in tap water and river water. The results indicate that the colorimetric and ratiometric fluorescent dual-mode assay based on UiO-66-NH 2 @Au realized visual determination of Hg 2+ rapidly and reliably, revealed application prospect in Hg 2+ monitoring.