Au-Fe3O4 decorated polydopamine hollow nanoparticles as high performance catalysts with magnetic responsive properties

We demonstrated a simple approach for fabricating Au-Fe3O4/PDA hollow nanoparticles as high-performance catalysts for water purification. The polydopamine (PDA) shell was in situ formed on the silica surface from self-polymerization, which acts as a medium support for coupling with metal ions (for Fe3O4 nanoparticle deposition) as well as a reducing agent and stabilizer for Au nanoparticle reduction and deposition. A step of simultaneous Fe3O4 nanoparticle deposition and silica core removal under alkaline conditions is first introduced in this study. This process significantly simplifies previous strategies which typically require the use of poisonous agents such as hydrogen fluoride or additional complicated post-treatment steps. Under optimized conditions, the Au-Fe3O4/PDA hollow nanoparticles show a high saturation magnetization of 18.8 emu g(-1) and an excellent catalytic performance for the rapid reduction of p-nitrophenol with the reaction kinetic constant of 0.34 min(-1). This catalyst can be easily recovered using a permanent magnet and recycled eight times with a high catalytic cycle stability. The strategy presented in this work provides a facile and versatile approach towards designing complicated Au-Fe3O4/PDA hollow nanostructures, which might have great potential for many applications within biological, energy, and environmental technologies.