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The present paper reports a simple route to fabricate high surface area anatase TiO 2 mesoflowers from electrospun TiO 2 -SiO 2 composite nanostructures. Electrospun fiberand rice-shaped TiO 2 -SiO 2 composite nanostructures upon treatment with concentrated alkali (NaOH) under hydrothermal conditions (180 C) result in chemical transformation of the TiO 2 and in situ etching of SiO 2 to give sodium titanates. The sodium titanate upon acidification followed by a low temperature sintering (180 C) results in 3D TiO 2 mesoflowers. The material is found to be superior to the commercial P-25 in photocatalysis.

A rice-shaped TiO2-ZnO composite was prepared by electrospinning a mixture comprising the precursors of TiO2 and ZnO in polyvinyl acetate polymer dissolved in N,N-dimethyl acetamide. The electrospun nanofibers upon heat treatment in air resulted in collapse of the continuous fiber morphology and the formation of the rice-shaped TiO2-ZnO composite. The TiO2-ZnO composite was then treated with dilute acetic acid under hydrothermal conditions to etch ZnO from the TiO2-ZnO composite to get coral-shaped anisotropic TiO2. The structural anisotropy of TiO2 produced by the selective etching of ZnO resulted in a high surface area of 148 m(2) g(-1) for the TiO2. The initial and final materials were characterized by scanning electron microscopy, transmission electron microscopy, Raman and XPS spectroscopies, powder X-ray diffraction and BET surface area measurements. The utility of the anisotropic TiO2 in photovoltaics and photocatalysis was explored. Dye-sensitized solar cells fabricated using the TiO2 showed a conversion efficiency of 6.54% as against 4.8% for a control experiment with the rice-shaped TiO2. The anisotropic TiO2 also showed good photocatalysis in the degradation of methyl orange dye and phenol.

We report a simple synthesis route for producing ultrafine porous TiO 2 nanofibers ($10 nm diameters) from electrospun rice-shaped TiO 2 nanostructures. The rice-shaped TiO 2 obtained by annealing the as-spun TiO 2 -PVAc composite nanofibers was treated with concentrated alkali (with KOH under hydrothermal conditions) followed by acid treatment and low temperature sintering. The alkali treatment produces the titanate (K 2 Ti 3 O 7 ) which undergoes exchange of ions (protons) during the acid treatment resulting in H 2 Ti 3 O 7 . The heat treatment of the protonated titanate (H 2 Ti 3 O 7 ) results in their conversion to ultrafine TiO 2 (titanate-derived TiO 2 ) nanofibers. The rice-shaped TiO 2 and the titanate-derived TiO 2 nanofibers were characterized by SEM, TEM, XRD, XPS, Raman and BET measurements and the latter has $2.5 times higher surface area than the former. The TiO 2 nanofibers showed superior photocatalytic applications than the commercial P-25 TiO 2 .