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Rapid detection of aflatoxin B1 (AFB1) is a very important task in food safety monitoring. However, it is still challenging to achieve highly sensitive detection without antibody or aptamer biomolecules. In this work, a rapid detection of aflatoxin B1 was achieved using a ratiometric fluorescence probe without antibody or aptamer for the first time. In the ratiometric fluorescence system, the fluorescence emission of AFB1 at 433 nm was significantly enhanced due to the β-cyclodextrin-AFB1 host-guest interaction and the complexation of AFB1 and Pt

A core–shell QDs@mSiO2@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@mSiO2@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@mSiO2 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.

A core-shell QDs@mSiO

In this work, glutathione capped CdTe QDs (GSH-QDs) were prepared through a one-pot process and found to be quenched by Cr3+, Ag+ and Cu2+ ions. Cr3+ and chromium (III) picolinate could be quantitatively measured after masking Cu2+ and Ag+ ions by sulfide. Under optimal conditions, linear quenching was observed for Cr3+ in the ranges of 0–2.0 μM and the limit of detection was 3.0 nM. The recoveries for Cr3+ in vitamin supplements obtained were from 92.5% to 106%. The determination results of chromium (III) picolinate in vitamin supplement samples were compared to that obtained using flame atomic absorption spectrometry (FAAS) method, and the result showed good reliability. Keywords: CdTe QDs, Fluorescence, Chromium ions, Vitamin supplements

A sensitive colorimetric method for detection of copper ions (Cu2+) was developed based on surface modification of Ag/Pt nanoclusters (Ag/Pt NCs) and regulation of the peroxidase-like activity. It was found that 3-mercaptopropionic acid (MPA) could inhibit the catalytic ability of Ag/Pt NCs, however it would lose the inhibition toward catalytic ability of Ag/Pt NCs after oxidization by oxygen through the catalysis of Cu2+. On the basis of this, a colorimetric method was developed for the detection of Cu2+ by measuring the colorimetric signal variation of the TMB-H2O2 reaction. This method exhibited high sensitivity and selectivity toward Cu2+ over a panel of other metal ions, in the linear range of 10–100 nM with a detection limit of 5.0 nM. The method was simple and low cost, and suitable for Cu2+ detection in real water samples.