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Anatase TiO2 nanotubes array (ATONA) has attracted tremendous attention owing to its promising applications in solar cells, water splitting and organic pollutants photocatalytic degradation. However, the activity of ATONAs was greatly suppressed by the grain boundaries existed in the tube walls, which acted as carrier scattering and recombination centers. Herein, we report a novel strategy to prepare array of single crystalline anatase TiO2 nanotubes (SC-ATONAs) with significant enhancement of the photocatalytic activity and UV photo response performance compared to the polycrystalline counterparts. The growth of SC-ATONAs was achieved by establishing a crystallization temperature gradient along the tube wall, which ensured the crystallization started from the nucleation of a single nucleus at the bottom of amorphous TiO2 nanotubes prepared by Ti anodization. These findings pave the way to prepare single-crystalline nanotubes with superior performance for other materials.

The anatase TiO2 (001) surface has attracted extensive attention in surface science and for practical applications because of its excellent performance. However, the highly reactive (001) surface usually reconstructs to a (1 × 4)-(001) surface, which may potentially alter its properties. As a result, there are still controversial issues concerning the intrinsic performance of this surface. Recently, significant advances have been made in the surface science study of TiO2 (001), which have elucidated its intrinsic physical and chemical properties. In this review, we summarize our present understanding of the structure and properties of the reconstructed TiO2 (001) surface. First, we provide a brief background of the anatase TiO2 surfaces, including its low-index surface structures and the synthesis of anatase TiO2 nanocrystals with the (001) surface exposed. Next, we focus on the structure, formation mechanism, stability, and surface chemistry of the reconstructed TiO2 (001) surface. Finally, we finish this review by highlighting the current challenges of this subject and providing future research perspectives.

The anatase TiO2 nanocrystals with dominant (001) facets attracted tremendous attention in the past decade. However, the reported intrinsic property of the (001) surface is still a cause of controversy. A crucial reason is that the (001) surface usually undergoes a (1 × 4) reconstruction, which may result in a remarkable difference in property. Herein, we performed an in situ environmental transmission electron microscopy (ETEM) study regarding the formation and stability of the (1 × 4)-(001) surface of TiO2 nanocrystals. The systematic ETEM studies confirmed that the (1 × 4)-(001) surface could be generated at elevated temperature (above 300 °C) when the surface contaminants were removed and the formed reconstruction could survive under different conditions, which indicate the surface reconstruction should be taken into account in related property research. In addition, an oriented layer-by-layer beam damage process on the (001) surface is confirmed, and optimal imaging conditions were also investigated,...