Magnetite/Silica (Fe3O4/SiO2) nanoparticles with amino-functionalized were synthesized in a simple one-pot process. The synthetic reaction took place in a water-in-oil microemulsion system, which was composed of cyclohexane, Alkylphenols polyoxyethylene (OP-10), n – butanol and water. This method was based on a three-step process, involving: (i) synthesis of the Fe3O4 nanoparticles by adding the microemulsion containing the basic precipitant of ammonia into another microemulsion containing Fe2+ and Fe3+ with atmospheric nitrogen under ambient conditions; (ii) formation of the Fe3O4/SiO2 nanocomposites via direct decomposition of tetraethyl orthosilicate (TEOS) in the reverse micelles nanoreactors under the presence of freshly synthesized Fe3O4 nanoparticles; (iii) functionalization of the Fe3O4/SiO2 nanocomposites with amine groups by hydrolysis of 3-aminopropyl- trimethoxysilane (APTES) in situ of the above microemulsion system. The structure composition and the surface functional groups of the product were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and Fourier transform infrared analysis (FT-IR). The magnetic behavior was measured by Vibrating sample magnetometer (VSM). It was found that the synthesized product was embedded structure of Fe3O4/SiO2 nanocomposites with a diameter range from 10 to 20 nm. These magnetic silica nanocomposites with a functional surface had excellent superparamagnetic properties which implied potentially promising applications in biomedicine areas. Accordingly, the amino-functionalized Fe3O4/SiO2 nanocomposites were used as magnetic separation carriers for immobilization of catalase (CAT). Activity of the immobilized CAT was examined and contrasted with the free CAT by the catalysis of hydrogen peroxide in aqueous buffer. The results showed that the immobilized CAT obtained through covalent attachment exhibited higher resistance to pH and thermal stability than the free CAT. In addition, the immobilized CAT still retained a high activity after 10 repeated batches reaction.
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