Large-area noncurling crystallized free-standing TiO 2 nanotube (TNT) arrays have been fabricated by a twostep anodization process. These free-standing crystallized TNT arrays can be easily transferred to fluorinedoped tin oxide glass substrates without any crack. Furthermore, the investigation of these crystallized freestanding TNT arrays in dye-sensitized solar cells (DSSCs) was carried out and showed a roughly 100% enhanced conversion efficiency compared with that of the TNT array on a Ti substrate.

We present a two-step electrochemical deposition process to produce hierarchical ZnO nanostructures that involves the electrodeposition of ZnO crystals with different morphologies, followed by the electrochemical epitaxial growth of oriented nanorods on the surfaces of the primary ZnO nanostructures. A variety of hierarchical ZnO nanostructures, including 2-fold nanorod arrays on nanosheets, 6-fold nanorods on nanorods, and 6-fold nanoneedles on nanoneedles, were synthesized on a large scale. The hierarchical nanostructures obtained by this technique are pure and uniform in morphology. Furthermore, we demonstrate that the hierarchical ZnO nanostructure of nanorods on nanosheets provides a good candidate for photoanodes in dye-sensitized solar cells.

A novel type of titanium precursor, ammonium-exchanged titanate nanowires, is used to hydrothermally synthesize nanosized TiO 2 single crystals with well-defined facets. With additives of appropriate shape-capping reagents, octahedral, truncated octahedral, and spindle-like TiO 2 nanocrystals have been obtained. We proposed that the transformation mechanism from ammonium-exchanged titanate nanowires to TiO 2 may be a "dissolution-nucleation" process. Furthermore, the photocatalytic activities of anatase TiO 2 nanocrystals with different facets exposed have been investigated.