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

Abstract

Multifunctional magne-tic 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 nanocomposite 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.

Catalytic performance in 4-nitrophenol reduction by Ag nanoparticles stabilized on biodegradable amphiphilic copolymers

“…Because there is only one product, 4-aminophenol, and the extent of reaction can be followed by measuring the change in UV/Vis absorbance at 400 and 300 nm (29,30). For comparison, in the absence of Ag NPs, first, 0.005 mol/L 4-NP solution was prepared and monitored for the change of absorption.…”

Basic concepts and recent advances in nitrophenol reduction by gold- and other transition metal nanoparticles

“…4 nm) by layer-by-layer electrostatic Reprinted with permission from Ref. [94]. Copyright 2011, American Chemical Society.…”

“…The composite microspheres obtained showed high performance in catalytic reduction of 4-NP with rate constant k of 5.7 × 10 −3 s −1 . The catalysts are easily recycled with an external magnetic field for more than 10 times without visible decrease in the catalytic activities [94].…”

Preparation of nanoporous alumina hollow spheres with a highly ordered hole arrangement

“…29,30 Fig. 9 shows Au/ alumina composite hollow spheres formed through the chemical deposition of Au nanoparticles on the surface of the alumina hollow spheres.…”