Carbon-supported Ni and MoO2 nanoparticles with Fe3O4 cores as a protein adsorbent

Abstract

Decoration of transition metal Ni nanoparticles (NPs) on magnetic supports is of special interest for histine-rich protein adsorption. Through a combination of a hydrothermal reaction, a mussel-inspired coating and a carbonization strategy, we have investigated two synthetic paths to access hierarchical nickel-based magnetic nanostructures: (1) Fe₃O₄ spheres are covered with hierarchical NiMoO₄ nanosheets and subsequently coated with a polydopamine (PDA) layer, and Fe₃O₄@MoO₂∩C–Ni composites are synthesized after pyrolysis in a nitrogen atmosphere, and (2) Fe₃O₄ spheres are coated with PDA and subsequently covered with hierarchical NiMoO₄ nanosheets, and then Fe₃O₄@C∩MoO₂–Ni composites are obtained after pyrolysis in a nitrogen atmosphere. We find that only route 1, which can be defined as a space-confined carbonization strategy, results in the formation of a high coverage of nickel NPs with tiny diameter decorated on Fe₃O₄ spheres. Route 2, defined as a non-space-confined carbonization strategy, leads to the formation of low density and large size Ni NPs. Detailed examination of the nickel-based magnetic composites obtained by route 1 displayed superior adsorption capacity for BHb than that of route 2. The results demonstrated that the space-confined strategy is greatly beneficial for the synthesis of Ni-based magnetic composites with high coverage, which would pave a novel way for synthesizing high density Ni-based magnetic composites.