SiO2-assisted synthesis of Fe3O4@SiO2@C-Ni nanochains for effective catalysis and protein adsorption

In the current work, a facile one-step magnetically assembling method coupled with subsequent carbonization treatment was proposed to fabricate one dimensional (1D) chain-like Fe3O4@SiO2@C-Ni composites for effective catalysis and protein adsorption. Typically, Fe3O4 nanoparticles (NPs) were firstly prepared by solvent thermal method. With the assistance of an external magnetic field, 1D Fe3O4@SiO2@polydopamine-Ni2+(PDA-Ni2+) nanochains were obtained with one-step stöber method under the mechanical stirring condition. Notably, SiO2-assisted coating was essential for one-step magnetically assembling formation of 1D Fe3O4@SiO2@PDA-Ni2+ nanochains. While without the presence of silica, the spherical Fe3O4@PDA-Ni2+ composites were obtained instead. After a carbonization treatment under an inert atmosphere, the Fe3O4@SiO2@PDA-Ni2+ was converted into Fe3O4@SiO2@C-Ni composites while retaining 1D morphology. In the process of carbonization, polydopamine-chelating nickel ions were reduced to Ni NPs by PDA. Simultaneously, PDA was carbonized to be N-doped carbon shell layer, which could effectively avoid the exfoliation of Ni NPs in complex reaction system. Furthermore, the size of Ni NPs could be modulated via varying the annealing temperature. Consequently, the 1D chain-like Fe3O4@SiO2@C-Ni composites exhibit high catalysis on 4-NP and effective adsorption on histine-rich proteins. And it also can be conveniently regenerated by a magnet and showed good cyclic stability, which is important for practical applications.