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Highlights: [•] Amorphous precursor was used to prepare titanate nanostructure by hydrothermal process. [•] Morphology evolution from nanoparticles to nanosheets and then nanowires was observed. [•] It provides direct evidence to support the dissolution/recrystallization mechanism. [Copyright &y& Elsevier]

Abstract: A simple approach based on an organically modified sol–gel process has been developed to fabricate PbTiO3 (PT) nanocrystals on Si (100) substrate, where the amorphous powder modified by acetylacetone (acac) was used as precursor. After dropping the amorphous powder precursor prepared by freeze-drying process, PT nanocrystals on Si (100) substrate were obtained after heat treatment at 720°C for 30min in air. PT nanocrystals have been detected by XRD to be tetragonal perovskite structure. With the increase of acac/Pb molar ratio, the relative (100)/(001) diffraction peak intensity gradually increases, which probably suggested an oriented growth of PT nanocrystal along [100] on Si (100) substrates. In addition, Atomic force microscopy (AFM) results indicated that the height and the average lateral size of PT nanocrystal increased and then decreased as the acac/Pb molar ratio increased. Piezoelectric force microscopy (PFM) results demonstrated that all the samples show obvious piezoelectric activity. These results implied that the acetylacetone molecular mediated the growth of PT nanocrystals on Si (100) substrates possibly by the acac/Pb molar ratio. This simple method has been suggested to be attractive for tailoring an oriented growth of the nanostructures of perovskite oxide systems on Si substrates. [Copyright &y& Elsevier]

Abstract: We report the controlled hydrothermal growth of rutile TiO2 nanorods on Si wafers by using an anatase TiO2 nanodot film as an assisted growth layer. The anatase nanodot film was prepared on the wafer by phase-separation-induced self-assembly and subsequent heat-treatment at 500°C. The nanodots on the wafer were then subjected to hydrothermal treatment to induce the growth of rutile TiO2 nanorod films. The size and dispersion density of the resulting TiO2 nanorods could be varied by adjusting the Ti ion concentration in the growth solution. The TiO2 nanorods were of the rutile phase and grew in the [001] direction. The growth mechanism reveals that the growth of the rutile nanorods was wholly dependent on the existence of rutile TiO2 seeds, which could be formed by the dissolution–reprecipitation of the anatase nanodots during hydrothermal treatment or under the high-temperature conditions of the subsequent heat-treatment of the as-prepared nanodots. In controlling the rutile nanorod growth, the anatase nanodots show more efficiency than a dense anatase film. Preliminary evaluations of the rutile nanorod films have demonstrated that the wettability changed from highly hydrophobic to superhydrophilic and that the photocatalytic activity was enhanced with increasing nanorod dispersion density. [Copyright &y& Elsevier]

Abstract: Single-crystal SrTiO3 dendritic nanostructures were synthesized for the first time via a simple hydrothermal method without any surfactant. Structure characterizations suggest that the SrTiO3 dendrites show preferential orientation along [110]. Additionally, it is found that KOH concentration plays an important role in the formation of SrTiO3 dendrites, and the morphology of SrTiO3 crystallites can vary from cubic-like, star-like to dendritic shape. A rational mechanism is proposed to illustrate the growth of SrTiO3 dendrites. [Copyright &y& Elsevier]