Ni nanoparticles decorated onto graphene oxide with SiO ₂ as interlayer for high performance on histidine-rich protein separation

Sandwich-like structure of graphene oxide (GO) @SiO ₂ @C-Ni nanosheets were prepared by combining an extended stöber method with subsequent carbonization treatment, in which polydopamine was used as reducing agent and carbon source. Firstly, the GO nanosheets were covered with SiO ₂ interlayer and finally coated with a outer shell of nickel ion doped polydopamine (PDA-Ni ²⁺ ) with an extended stöber method. Followed by a carbonization to produce the GO@SiO ₂ @C-Ni sheets with metallic nickel nanoparticles embedded in PDA-derived thin graphic carbon layer. Notably, silica interlayer played a vital role in the formation of such GO@SiO ₂ @C-Ni sheets. Without the protection of SiO ₂ , the hydrophobic graphene@C-Ni composites were obtained instead. While with silica layer as the spacer, the obtained hydrophilic GO@SiO ₂ @C-Ni composites were not only well dispersed in the solution, but also can be adjusted in terms of the size and density of Ni nanoparticles (NPs) on surface by changing the calcination temperature or the molar ratio between dopamine and nickel salt. Furthermore, nickel nanoparticles decorated on GO@SiO ₂ sheets were employed to enrich His-rich proteins (BHb and BSA) via specific metal affinity force between polyhistidine groups and nickel nanoparticles.