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The presence of Salmonella in food has been a serious threat to human health all over the world. Herein, a novel electrochemical immunosensor based on CoFe-MOFs-graphene nanocomposite was constructed to detect Salmonella in milk. The synergy of the large specific surface area and high porosity of CoFe-MOFs and the good electrical conductivity of graphene materials greatly enhanced the current signal of the nanocomposite. Gold nanoparticles were modified on CoFe-MOFs-graphene hybrids by a simple electrodeposition method. Anti-Salmonella antibody was immobilized onto the surface of the constructed electrode through the formation of a stable Au–NH2 bond. Scanning electron microscopy was employed to reveal the structure of the CoFe-MOFs-graphene nanocomposite, and the elements of the nanocomposite were observed by energy-dispersive X-ray spectroscopy. In addition, Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) were used to analyze the structure of related materials. Under optimal experimental parameters, the constructed immunosensor detected a wide linear range of Salmonella from 2.4 × 102 CFU mL−1 to 2.4 × 108 CFU mL−1 with a detection limit of 1.2 × 102 CFU mL−1 (S/N = 3). The immunosensor showed good stability, selectivity, and reproducibility. The designed immunosensor provides a new strategy for the rapid detection of foodborne pathogens. more...

The growing threat of foodborne disease has made it imperative to develop rapid and efficient detection techniques. Here, we developed dendritic superparamagnetic iron oxide nanoparticles (SPIONs) combined with low-field nuclear magnetic resonance (LF-NMR) biosensor for Salmonella detection in milk. We first used a Salmonella capture antibody and biotinylated detection antibody (BT-mAb) in the form of a sandwich in a 96-well plate to immobilize target bacteria. Then streptavidin modified polyamidoamine (SA-PAMAM) was used to connect BT-mAb and functionally modified SPIONs. PAMAM-mediated SA amplified functionalized SPIONs via streptavidin-biotin amplification system, aggregated nanoparticles to form dendritic SPIONs, and achieved dual signal amplification. Finally, the dendritic SPIONs capture complex is eluted, and the lateral relaxation time T2 of the water molecules around the SPIONs was used as the output of the target bacteria capture signal. The limit of detection of Salmonella in a buffer solution and milk was 2.6 × 104 CFU/mL, and the LF-NMR biosensor showed good specificity and anti-interference properties. Therefore, this innovative detection platform can be used as a sensitive, fast, and efficient tool for detecting foodborne pathogens. more...

Nitrogen doped TiO2 (TiO2−xNx), one of the most promising visible-light photocatalytic materials, exhibits a low photocatalytic activity owing to the rapid recombination of photogenerated electrons and holes, which is caused by the isolated energy level of N 2p formed above the valence band of TiO2. To reduce the recombination of photogenerated charges and further improve the photocatalytic performance of TiO2−xNx, in this study, Fe(III) cocatalyst was loaded on the surface of TiO2−xNx photocatalyst by a simple impregnation method. It was found that after surface modification by Fe(III) cocatalyst, the photocatalytic performance of all the TiO2−xNx photocatalysts could be greatly improved for the decomposition of MO under visible-light irradiation. Especially, the Fe(III)/TiO1.981N0.019 photocatalyst showed the highest photocatalytic activity and its rate constant k was ca. 52.5 × 10−4 min−1, which is higher than that of the corresponding TiO1.981N0.019 photocatalyst (9.9 × 10−4 min−1) by a factor of 5.3 times. Based on the present experimental results, the Fe(III) was thought to be an effective cocatalyst to significantly improve the electron transfer from the conduction band of TiO2−xNx to the adsorbed oxygen, thus facilitating the rapid separation of photogenerated charges and greatly enhancing the photocatalytic activity. In addition, the direct interfacial charge transfer from the N 2p isolated energy level to Fe(III) cocatalyst can also contribute to the enhanced photocatalytic efficiency of TiO2−xNx. Considering the abundant Fe resources and its low cost, the Fe(III)-cocatalyst modification can be regarded as an effective approach for rational design and development of high-performance visible-light photocatalysts in practical applications. more...