Fluorescence and magnetic nanocomposite Fe 3 O 4 @SiO 2 @Au MNPs as peroxidase mimetics for glucose detection.

In this paper, multifunction nanoparticles (MNPs), Fe3 O4 @SiO2 @Au MNPs, with properties of superparamagnetism, fluorescence and peroxidase-like catalytic activity were synthesized in the aqueous phase. The synthesized composites were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier translation infrared spectrum (FT-IR) and fluorometer. The results show that the multifunctional nanomaterials have good magnetic and fluorescence properties. Then, the mimetic properties of this material were investigated. The as-synthesized Fe3 O4 @SiO2 @Au MNPs exhibited the best catalytic activity for peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) at the reaction temperature of 70 °C and pH of 3. Compared with free Fe3 O4 MNPs and BSA-Au nanoclusters (NCs), the composites have better catalytic activity at higher temperature and lower pH, indicating that Fe3 O4 @SiO2 @Au MNPs can work in more severe environment. In practical application, we have successfully established the colorimetric method for the detection of H2 O2 and glucose with the detection range of 1 × 10-6 ∼ 4 × 10-5  M and 5 × 10-6 ∼ 3.5 × 10-4  M, and the detection limit of 6 × 10-7  M and 3.5 × 10-6  M, respectively. The method was also successfully applied in the detection of real samples. Furthermore, since the fluorescence of Fe3 O4 @SiO2 @Au MNPs was quenched by H2 O2 , a method for the visual detection of glucose was established.