Fabrication And Photoactivity Of Short Rod-shaped Mesoporous SiO₂@TiO₂ Composites

This paper presents an improved strategy for synthesizing short rod-shaped mesoporous Si O₂@TiO₂ composites containing a TiO₂ shell by using short rod-shaped mesoporous SiO₂-polyglycidyl methacrylate?PGMA?-polyoligo?ethylene glycol?methyl ether methacrylate?PEGMA?as a template and tetrabutyl titanate?TBT?as a titanium source.SiO₂-PGMA-b-PEGMA rods were initially fabricated through grafting GMA and EGMA onto the surface of the halogen functional group of mesoporous Si O₂ using activators regenerated by electron transfer-atom transfer radical polymerization?ARGET ATRP?by using ascorbic acid as reducing agent,FeCl3×6H2O as catalyst and triphenylphosphine as ligand.TBT was hydrolyzed with the PEGMA chain through hydrogen bonding because of PEGMA hydrophilicity.The rod-shaped mesoporous SiO₂@TiO₂ structure was finally acquired through calcination by thermal removal of PGMA-PEGMA from the prepared SiO₂-PGMA-PEGMA-TiO₂.The novelties of the fabricated short rod-shaped mesoporous Si O₂@TiO₂ hybrid composites compared with previously reported ones mainly include the following aspects.First,SiO₂-PGMA-PEGMA hybrid composites were easily fabricated through ARGET ATRP.The proposed method can be used to modify Si O₂ surfaces by using a wide range of polymers to optimize the attachment of various molecules on the surface.Second,immobilization of TiO₂ nanoparticles through direct embedding in a polymer matrix causes inaccessibility of numerous particles,thereby considerably decreasing photocatalytic efficiency.Characterization results indicated that the short rod-shaped mesoporous SiO₂ was with a length of 1-1.5 ?m,a diameter of 350-450 nm and a pour of 5-10 nm,and the amphiphilic block copolymer was grafted onto the mesoporous Si O₂ surface and the thickness was about 30 nm.Moreover,the TiO₂ samples existed only in the anatase phase,and the prepared Si O₂@TiO₂ exhibited bimodal nanoporous structures.The synthesized short rod-shaped mesoporous SiO₂@TiO₂ materials demonstrated higher specific surface area and absorption rate than samples prepared from non-mesoporous or unmodified rod-shaped SiO₂.These characteristics effectively enhanced the photocatalytic activity of the composite.The photocatalytic activity of the fabricated composite was then tested on rhodamine B photodegradation.Compared with the samples prepared from non-mesoporous or unmodified rod-shaped SiO₂,the rod-shaped mesoporous Si O₂@TiO₂ materials with bimodal nanoporous structures had larger specific surface area and higher absorption rate,the percentage of RhB degradation reached approximately 97%,which thus enhanced the photocatalytic efficiency under visible light.The method for preparing short rod-shaped mesoporous SiO₂@Ti O₂ can be extended to other shells of mesoporous compositions.This work provides a new pathway for design and fabrication of novel photoactive materials for practical applications in environmental cleaning.