A performance study of enhanced visible-light-driven photocatalysis and magnetical protein separation of multifunctional yolk–shell nanostructures

Abstract

Synthesis of functional yolk–shell nanostructures (YSNs) containing SiO₂ nanoparticle yolk and a mesoporous shell of NiTiO₃ is reported. SiO₂@TiO₂ core–shell spheres were first prepared via a sol–gel approach, and then a Ni(OH)₂ nanowhisker was deposited on the surface of a TiO₂ layer and SiO₂ nanoparticle-core etching took place simultaneously in a H₂O–ethanol–ammonia solution reaction, and then a SiO₂@void@TiO₂@Ni(OH)₂ structure was obtained. Finally, the TiO₂@Ni(OH)₂ shell was transformed into the NiTiO₃ shell via calcination treatment, and the SiO₂@NiTiO₃ YSNs were achieved. The chemical composition and photoresponsive properties of the SiO₂@NiTiO₃ yolk–shell material can be easily tailored by adjusting the molar ratio of the Ni/Ti precursors. Their visible-light-induced photocatalytic activities were evaluated by the degradation of methylene blue. The SiO₂@NiTiO₃ YSNs exhibited enhanced and stable photocatalytic performance due to the unique yolk–shell structure, large surface area, fast diffusion of reactants, and multiple reflections of visible light within the sphere interior voids. Furthermore, the present synthesis method can be extended to the preparation of other functional YSNs, such as magnetic YSNs consisting of SiO₂-coated Fe₃O₄ yolk and a Ni(OH)₂-coated TiO₂ shell, for the application of magnetic separation of proteins.