In this letter, we report a one-step templating synthetic strategy to prepare aligned TiO2 nanotube and nanowire arrays on Si substrate from a solution at ambient temperature. The deposition of TiO2 and the selective-etching of the ZnO template proceeded at the same time through the careful control of process parameters. The different thickness of TiO2 sheaths, leading to the formation of nanotubes or nanorods, can be precisely controlled by the deposition time. The idea of selective etching and deposition is applicable to other oxide materials, and such a facile method is expected to find widespread applications.
Three-dimensional colloidal crystals have attracted a great deal of attention because of their potential use in photonic crystal, sensors, and other applications, but the bottlenecks in fabricating colloidal crystals include longer processing time and the lack of large-area ordered samples. A proposed capillary-enhanced method, which is a novel, efficient process for fabricating high-quality colloidal crystals in 24 h, is reported. It is necessary for increasing the processing rate by elevating the evaporation temperature but commonly resulted in the deposition of less-ordered crystals. However, high-quality colloidal crystals can be obtained in a controlled high-humidity system, resulting from the existence of secondary capillary forces present in high ambient humidity. Furthermore, the effect of secondary capillary forces will be confirmed, and it will increase with increasing humidity levels according to the semiquantitative analysis view of the surface thermodynamic behavior of small particles, including the modified Kelvin and Young-Laplace equations. Therefore, it can fine tune the relative position of the neighboring particles in the microarray and efficiently decrease the number of defects, resulting in the formation of perfect colloidal crystals with the assistance of enhanced secondary capillary forces.
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