Bifunctional nanoscale magnetic chains with high saturation magnetization and catalytic activity

The conventional stirring method cannot be employed for chip-on-lab reactions such as microfluidic and microdroplet reactions as well as nanoscale reactions. Therefore, it is necessary to design a nanoscale magnetic stirrer with a high magnetic response towards the external magnetic field. In this work, one dimentional core@shell structured Fe-Fe₂O₃@poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) magnetic nanochains modified by nickel hydroxide (denoted as Fe-Fe₂O₃@PZS@Ni(OH)₂ NCs) as nanoscale magnetic stirrer and recyclable self-mixing nanocatalysts are successfully prepared through three steps: synthesis of Fe-Fe₂O₃ nanochains (NCs) with high saturation magnetization, coating with poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS), and nickel hydroxide's anchoring on the surface of Fe-Fe₂O₃@PZS NCs. The cross-linked polymer PZS is used to protect Fe-Fe₂O₃ NCs from chemical corrosion and as a platform for subsequent immobilization of nickel hydroxide. Characterization results show that the Fe-Fe₂O₃@PZS@Ni(OH)₂ NCs own chainlike structure and high saturation magnetization of 103 emu g^-1 at room temperature, exhibiting high magnetic response to the external rotating magnetic field. In the macro-reaction system for 4-nitrophenol (4-NP) reduction, the as-prepared Fe-Fe₂O₃@PZS@Ni(OH)₂ NCs show an apparent rate constant of about 0.60 min^-1. Furthermore, the Fe-Fe₂O₃@PZS@Ni(OH)₂ catalyst is reused ten times while no obvious loss of catalytic activity was observed. In the micro-reaction system, the Fe-Fe₂O₃@PZS@Ni(OH)₂ NCs also display good magnetic response and favorable catalytic activity for the hydrogenation of methylene blue. These results indicate that the bifunctional Fe-Fe₂O₃@PZS@Ni(OH)₂ NCs with high saturation magnetization have great potential as excellent nanocatalysts and as promising nanoscale magnetic stirrers.