Multifunctional Magnetic Composite Microspheres with in Situ Growth Au Nanoparticles: A Highly Efficient Catalyst System

Multifunctional magnetic composite microspheres which possess the precise control of the size, morphology, surface chemistry, and assembly process of each component have been successfully prepared. These functional nano composite microspheres possess a core of silica-protected magnetite particles and in situ growth active gold nanoparticles (ca. 4 nm) on the outer shell by layer-by-layer electrostatic self-assembly. The well-designed microspheres have high magnetization (23.9 emu/g), uniform sphere size (ca. 500 nm), and stably confined and active small Au nanoparticles. As a result, the very little composite microspheres show high performance in catalytic reduction of 4-nitrophenol (with conversion of 95% in 12 min), special convenient magnetic separability, long life, and good reusability. The unique nanostructure makes the microsphere a novel stable and highly efficient catalyst system for various catalytic industry processes.