Core-shell structured γ-Fe2O3@SiO2@AgBr:Ag composite with high magnetic separation efficiency and excellent visible light activity for acid orange 7 degradation

Core-shell structured gamma-Fe2O3@SiO2@AgBr:Ag composite microspheres with narrow size distribution were synthesized by a versatile multistep route, including solvothermal method to fabricate magnetic core, modified Stober method to coat SiO2 interlayer, electrostatic assembly to deposit AgBr shell, and light reduction to form Ag nanoparticles. Spherical core with a diameter of 250 nm consists of primary magnetic nanoparticles, making the composite photocatalyst show high saturation magnetization under the premise of keeping a certain superparamagnetic property. SiO2 interlayer with a thickness of 15 nm is uniformly coated on the surface of magnetic core, favorable to enhancing the chemical stability of magnetic core as well as preventing the deterioration of photocatalytic activity. gamma-Fe2O3@SiO2@AgBr:Ag composite exhibits excellent visible light photocatalytic activity for the degradation of acid orange (AO7) dye, due to the fact that both Ag nanoparticles and AgBr can response to visible light. Beneficial from the narrow size distribution as well as high saturation magnetization and superparamagnetic property, the core-shell structured photocatalyst shows high efficiency in magnetic separation and recovery. The optimal loading amount of AgBr for obtaining both uniform morphology and high activity is similar to 42 wt.%. (C) 2013 Elsevier B.V. All rights reserved.