Multifunctional Fe2O3–Au Nanoparticles with Different Shapes: Enhanced Catalysis, Photothermal Effects, and Magnetic Recyclability

We investigate Au-decorated Fe 2 O 3 nanoparticle catalysts, Fe 2 O 3 –Au, where the supporting Fe 2 O 3 nanoparticles are of different shapes: spheres, rings, and tubes. The decoration procedure for the Fe 2 O 3 –Au nanoparticles is identical for each shape, and is analogous to the synthesis of pure Au nanoparticles (AuNPs). These similarities allows for direct comparison between the different shapes and the pure AuNPs. The morphological, optical, and magnetic characterizations reveal that the Fe 2 O 3 –Au nanoparticles are hybrid structures exhibiting both plasmonic and magnetic properties. The different shape Fe 2 O 3 –Au nanoparticles and the AuNPs are evaluated for their ability to catalytically reduce 4-nitrophenol. Remarkably, it is found that Fe 2 O 3 –Au nanoparticles are more efficient catalysts than AuNPs because they can achieve the same, or better, catalytic reaction rates using significantly smaller quantities of Au, which is the catalytically active material. Taking into account the Au-loadings, the Fe 2 O 3 rings and tubes are superior to the Fe 2 O 3 spheres as catalytic supports due to their γ-Fe 2 O 3 crystal phase. It is also shown that the Fe 2 O 3 –Au nanoparticles have the additional benefit for catalysis in that they can be recovered and reused via magnetic collection. Furthermore, the Fe 2 O 3 –Au nanoparticles and AuNPs are found to efficiently transduce heat from light through plasmonic absorbance, and this phenomenon is exploited to demonstrate the photothermal catalytic reduction of 4-nitrophenol.