Mesoporous silica-loaded gold nanocluster with enhanced fluorescence and ratiometric fluorescent detection of thiram in foods

A core-shell QDs@mSiO(2)@y-AuNCs nanoprobe was prepared, and a new ratiometric fluorescent sensor for thiram detection was developed. The mechanism of thiram sensing was investigated using FTIR, surface-enhanced Raman, XPS spectra, etc. The sensing of thiram was mainly ascribed to the formation of Au-S bonds between thiram and Au atoms on y-AuNCs surface, resulting in the dissociation of 11-MUA ligand from the y-AuNCs surface and the charge transfer between thiram and y-AuNCs. In the ratiometric fluorescence detection of thiram based on QDs@mSiO(2)@y-AuNCs, a linear range of 0.5-60 ng/mL was obtained with a LOD of 0.19 ng/mL. Compared with the fluorescence detection based on y-AuNCs, the ratiometric fluorescence detection of thiram demonstrated 3-fold enhanced sensitivity. The improvement was ascribed to two aspects: the fluorescence emission of y-AuNCs was enhanced after they were loaded onto the QDs@mSiO(2) nanoparticles; the ratiometric detection mode provided more precise sensing. The detection of thiram can be completed immediately after mixing the nanoprobe with thiram. Good recoveries of thiram in apple and pear samples were achieved. All the above results demonstrated the high potential of this method in practical applications.

Automated summary

By preparing a core-shell QDs@mSiO(2)@y-AuNCs nanoprobe, a new ratiometric fluorescent sensor for thiram detection was successfully developed. The mechanism of thiram sensing was attributed to the formation of Au-S bonds between thiram and Au atoms on y-AuNCs surface, leading to the dissociation of 11-MUA ligand from the y-AuNCs surface and the charge transfer between thiram and y-AuNCs. The ratiometric fluorescence detection of thiram based on QDs@mSiO(2)@y-AuNCs showed a 3-fold enhanced sensitivity compared to fluorescence detection based on y-AuNCs, with a linear range of 0.5-60 ng/mL and a LOD of 0.19 ng/mL.