Asymmetric PSt-EA/Ni-Silicate hollow microsphere with a hierarchical porous shell

Abstract

Novel asymmetric hollow microspheres with polystyrene-ethylacrylate (PSt-EA) semi-spherical cores and porous hierarchical Ni-Silicate shells have been successfully fabricated by the combination of emulsifier-free polymerization, a modified Stöber method and an in situ hydrothermal conversion reaction. During the conversion of the PSt-EA@SiO₂ core/shell microspheres to the asymmetric PSt-EA/Ni-Silicate composite, the spherical PSt-EA was melted within the hollow Ni-Silicate interior to form semi-microspheres. Upon further treating the asymmetric hollow microspheres by 500 °C calcination for 5 h, hierarchical Ni-Silicate hollow spheres were obtained. The BET area of the asymmetric hollow PSt-EA/Ni-Silicate microspheres was 58.9 m² g⁻¹ and the pore diameter was about 10–20 nm. The large porous nature of the products enable them be used as carriers for bio-molecules, and experiments indicated that the maximum adsorption ability of the asymmetric hollow microspheres could reach 8.2 μmol g⁻¹ when the concentration of Cytochrome C was 200 mmol L^¬1.