Preparation And Application Of Silica-based Janus Composite Nanosheets And Porous Spheres

Janus materials have unique performance due to their special morphology and diverse composition.Among them,Janus nanosheets have gained extensive interests because they can obviously lower the interfical tension and enhance the stability of the emulsion.Amphiphilic Janus porous SiO2 spheres have promising application in mass transfer and catalysis.In view of the excellent performance of Janus nanosheets and porous spheres,functional Janus composite nanosheets and porous spheres based on SiO2 have been prepared in this dissertation,and the properties and applications of Janus composite nanosheets have been systematically investigated..The research works are as follows:(1)Preparation and properties of the catalytic Janus composite nanosheets.At first,Janus SiO2 hollow sphers were prepared through a self-assembled sol-gel process at the temporal Janus emulsion interface,which including an oil phased containing paraffin,tetraethyl orthosilicate,(3-aminopropyl)trimethoxysilane and an aqueous phase containing styrene-maleic anhydride copolymer.Janus SiO2 nanosheets with one side tetherd with—NH2 groups were derived from the mechanically crushing the Janus hollow spheres.Then,Au nanoparticles were selectively grown onto the amine-tethered side of the Janus SiO2 nanosheets owing to the complexation between gold precursor and the-NH2 groups.In addition,SiO2@TiO2 composite nanosheets were prepared by the interaction of Titanium butoxide and SiO2 nanosheets.Finally,the catalytic performance of SiO2@Au and SiO2@TiO2 composite nanosheets were fully investigated using the reduction reaction of p-nitrophenol andphotocatalytic reaction of malachite green dyes as model reactions,respectively.(2)Preparation of SiO2/polymer Janus composite porous spheres.At first,core-shell Fe3O4@mSiO2 particles with Fe3O4 core and SiO2 shell were prepared as a template.The mesoporous SiO2 shell layer was modified with 4-chloromethyl phenyl trichlorosilane,forming a reactive surface.Then,styrene(St)and vinylpyridine(P4 VP)were polymerization on the reactive surface and generated Fe3O4@mSiO2@PS and Fe3O4@mSiO2@P4VP spheres,respectively.Finally,mSiO2@PS and mSiO2@P4VP porous spheres were derived after etching Fe3O4 core with HCl.This approach is general for the preparation of inorganic/polymer Janus composite porous spheres,a large number of inorganic/polymer Janus composite porous spheres with different thickness can be derived by verifing siliane precursors and monomers,and functional Janus composite porous spheres can be further obtained by selectively modification with special species.