Magnetically Recyclable Gold-Magnetite Nanocatalysts for Reduction of Nitrophenols

The Au-Fe3O4 heterostructures by thermal decomposition of iron-oleate complex in the presence of Au nanoparticles (NPs) have been successfully fabricated using different sizes of Au NPs as the seeds for magnetically recyclable catalysis of p-nitrophenol reduction. The heterostructures exhibit bifunctional properties with high magnetization and excellent catalytic activity towards p-nitrophenol reduction. The epitaxial linkages in dumbbell- and flower-like heterostructures arc different, leading to the change in magnetic and catalytic properties of the nanocatalysts. The pseudo-first-order rate constants for p-nitrophenol reduction are 0.61 +/- 0.08 and 0.32 +/- 0.04 min(-1) for dumbbell- and flower-like Au-Fe3O4 heterostructures, respectively. In addition, the heterostructured nanocatalysts show good separation ability and reusability which can be repeatedly applied for nearly complete reduction of p-nitrophenols for at least 6 successive cycles. The kinetics of nitrophenol reduction was obtained by monitoring the absorbance at 400 nm by UV-Vis spectroscopy. The kinetic data could be well-described by the Langmuir-Hinshelwood model. These unique properties make Au-Fe3O4 heterostructures an ideal platform to study various heterogeneous catalytic processes which can be potentially applied in a wide variety of fields in purification, catalysis, sensing devices, and green chemistry.