title: Controlled synthesis of monodisperse SiO(2)--TiO(2) microspheres with a yolk-shell structure as effective photocatalysts.
abstract: Monodisperse yolk-shell SiO(2) -TiO(2) microspheres were synthesized using core-shell silica microspheres as templates. In the absence of prior surface modifications, a uniform coating of the TiO(2) layer on the core-shell silica was achieved through a sol-gel route. Mesoporous silica shells between the outer TiO(2) shell and the SiO(2) core were selectively removed by using a weak base, yielding yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @TiO(2) ). Using the same templates, we synthesized Pt-encased microspheres (SiO(2) @Pt-TiO(2) ), in which Pt nanoparticles are embedded between the SiO(2) core and the TiO(2) shell. Selective etching of the silica shells in SiO(2) @Pt-TiO(2) yields Pt-encased yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @< Pt >TiO(2) ), which contain void spaces suitable for use as nanoreactors. The ys-SiO(2) @< Pt >TiO(2) catalyst shows enhanced hydrogen production from water under UV-light irradiation presumably as a result of multiple reflections within the void spaces and can be reused without losing their activity. Moreover, this core-shell template method is effective for the synthesis of other yolk-shell microspheres with different metal oxides.
authors.affiliation: Department of Chemistry, Sogang University, Seoul 121-742, Korea.
authors.forename: Jung Bo
authors.initials: JB
authors.lastname: Yoo
authors.forename: Hyo Jin
authors.initials: HJ
authors.lastname: Yoo
authors.forename: Byung Wook
authors.initials: BW
authors.lastname: Lim
authors.forename: Kang Hyuk
authors.initials: KH
authors.lastname: Lee
authors.forename: Mi Hyun
authors.initials: MH
authors.lastname: Kim
authors.forename: Donghyeon
authors.initials: D
authors.lastname: Kang
authors.forename: Nam Hwi
authors.initials: NH
authors.lastname: Hur
mesh_terms: D002384:Catalysis; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008863:Microspheres; D010316:Particle Size; D055668:Photochemical Processes; D010984:Platinum / Q000737:chemistry*; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry* / Q000528:radiation effects; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014961:X-Ray Diffraction
chemical_list: C507641:TiO2-SiO2; D010984:Platinum; D012822:Silicon Dioxide; D014025:Titanium