Synthesis of Water Dispersible and Catalytically Active Gold-Decorated Cobalt Ferrite Nanoparticles

One of the most compelling goals in the field of the nanotechnologies is the design and synthesis of hetero-structured nanoparticles containing different types of materials. This kind of structures is able to combine in a single entity the physical and chemical properties of the composing materials. Here we report a new strategy for the synthesis of cobalt ferrite (CoxFe3-xO4) decorated with ultrasmall ( d= 2-3 nm) gold nanoparticles (NPs).The synthetic procedure exploits double role of the of 2,3-meso-dimercapto succinic acid (DMSA): as phase transfer for cobalt ferrite NPs from organic to aqueous media, and as promoter of the nucleation of gold clusters only in proximity of the magnetic nanoparticle surfaces, thanks to its reducing properties. We present also a complete morphological (TEM, STEM) and chemical characterization, based on microanalysis methods (EFTEM, EELS and EDX). The new obtained nano-hertostructure combines the magnetic properties of cobalt ferrite with the catalytic properties of small noble metal clusters in a single entity (figure 1). So we investigate the catalytic activity of CoxFe3-xO4-Au NPs using a model reaction, that is the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), using NaBH4 as reducing agent. The catalyst has been magnetically recovered up to 5 times, maintaining excellent kobs over the cycles