Mesoporous iron oxide-layered titanate nanohybrids have been synthesized through a reassembling reaction between exfoliated titanate nanosheets and iron hydroxide nanoclusters, in which an electrostatic attraction between both nanosized species could be achieved at low pH of 1.5. The formation of the layer-by-layer ordered heterostructure with the repeating unit of 1.33 nm was clearly evidenced by powder X-ray diffraction and transmission electron microscopic analysis. According to Fe K-edge X-ray absorption spectroscopy, the hybridized iron oxide crystallizes with loosely packed network of three edge-shared FeO6 octahedra units. N2 adsorption−desorption isotherm and diffuse reflectance UV−vis measurements clearly demonstrated that the present iron oxide-layered titanate nanohybrids showed greatly expanded surface areas with mesopores (∼190−230 m2g−1) and narrow bandgap energies (∼2.3 eV), which are of crucial importance in creating a visible light-active photocatalyst. The test of photocatalytic activity revealed that the present nanohybrids could induce the photodegradation of organic pollutant molecules under visible light illumination (λ > 420 nm). Of special interest is that the chemical stability of iron oxide became remarkably improved upon the hybridization, which could be understood as a result of the encapsulation with titanate layers. In this regard, we could conclude that the present hybridization route is very effective in synthesizing novel visible light-active photocatalysts as well as in stabilizing chemically labile species like iron oxides.

No abstract

The nanoscale hybridization of titanium oxide with copper oxide was carried out to control the phase transformation behavior of titanium oxide and develop a new photocatalyst active in visble light. Analysis by X-ray diffraction, electron microscopy, and nitrogen adsorption-desorption isotherm to gauge pore size distribution showed that intercalative hybridization between copper oxide and titanium oxide produced a mesoporous layer-by-layer interstratified heterostructure with a repeating distance of $24.2A and an average pore size of $52 A. X-ray absorption spectroscopy at Cu K-and Ti K-edges clearly demonstrated that divalent copper oxides were interstratified with lepidocrocite-type titanium oxide. As a result of the modification of band structure, the resulting nanohybrids showed high activity for photoinduced degradation of organic dye molecules under visible light illumination. Heat-treatment of the nanohybrids at 500 C produced anatase TiO 2 at the expense of intermediate rutile TiO 2 formed in the lower temperature region (300-400 C). This suggests a phase transition from rutile TiO 2 to anatase TiO 2 . This phenomenon is related to the variation in the surface energy of titania caused by the redox process of hybridized copper oxide and by the phase transition of co-existing Ti-deficient titanium oxide.