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A novel method to prepare crosslinked polyethyleneimine (CPEI) hollow nanospheres was reported. Uniform silica nanospheres were used as templates, 3-aminopropyl trimethoxysilane (APS) was immobilized on the surface of silica nanospheres as couple agent. Aziridine was initiated ring-opening polymerization with the amino groups in APS to form polyethyleneimine (PEI) shell layer. 1,4-Butanediol diacrylate was utilized to crosslink PEI polymeric shell. The silica nanospheres in core were etched by hydrofluoric acid to obtain hollow CPEI nanospheres. The hollow nanospheres were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).

Fluorinated SnO₂ hollow nanospheres (HS) were synthesized via a solvothermal treatment of stannous fluoride in the presence of hydrogen peroxide. These nanospheres with diameters from 60nm to 100nm were composed of small nanoparticles with rutile phase. A small amount of fluorine ions were observed to be adsorbed on the surface of SnO₂ physically. The introduction of polyethylene glycol 200 (PEG 200) in the reaction system could obviously improve the crystallinity and specific surface areas of the product while maintaining the hollow nanosphere structure. Furthermore, the as-prepared SnO₂ sample (HS-PEG) showed a much enhanced photocatalytic activity with 100% degradation of Rhodamine B (RhB) within only 40min under UV light irradiation.