A simple sol-gel method was used to prepare magnetic Fe3O4/SiO2/TiO2 composites with core-shell structure. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) have been applied to investigate the structure and morphology of the resultant composites. The obtained composites showed excellent magnetism and higher photodegradation ability than pure TiO2. The photocatalytic mechanism was also discussed. The magnetic composites should be extended to various potential applications, such as photodegradation, catalysis, separation, and purification processes. 1. Introduction Currently, there has been great interest in the preparation of core-shell micro- and nanoparticles for their widespread potential applications in catalysis, chromatography separation, drug delivery, chemical reactors, and protection of environmentally sensitive materials [1–4]. Heterogeneous photocatalysis using semiconducting oxide catalysts is an effective way to purify wastewater or gas. TiO2-based semiconductors have attracted considerable attention due to their high efficiency, good stability, availability, and nontoxicity [5–9]. In recent years, in order to enhance the photocatalytic activity, great efforts have been made to prepare ideal structure of TiO2-based semiconductors [10–12]. Magnetic separation provides a very convenient approach for removing and recycling magnetic composites by applying an added magnetic field. The incorporation of Fe3O4 magnetic particles into TiO2 matrix may block the aggregation of nanoparticles during renewal and can increase the durability of the catalysts [13, 14]. Moreover, such catalysts have a high surface area and well-defined pore size, which enhance their photocatalytic activity . However, magnetic nanoparticles would inescapably encounter an hindrance when applied in practice due to the fact that a photocatalytic reaction is conducted in a suspension. It is not allowed to use magneton to agitate the mixed solutions. Therefore, in the experiment, Ar gas is purged so as to make the magnetic particles suspend in the methylene blue (MB) solution. Many efforts have been made in the development of the design and preparation of magnetic core-shell microspheres. Ye et al. and Yu et al. reported the magnetic material/SiO2/TiO2 composites with core-shell-shell structure [16, 17]. Their methods involve superparamagnetic Fe3O4 and γ-Fe2O3 with an inner layer of SiO2 and outer layer of TiO2 [18, 19]. Their resultant samples exhibit
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