Hydrothermal Growth And Characterization Of TiO₂ Nanorod Films With An Assisted Layer

As one of the most important wide bandgap semiconductor materials, titanium dioxide (TiO2) in nanoscale has a wide range of applications in photoelectric conversion, environment, energy fields because the nanostructured TiO2 shows much incomparable superior performance than bulk materials in chemical activities and other physical properties. TiO2 nano-materials based on substrates play an important role in applications for electronic devices. One-dimensional nanomaterials as constructing basic units can be used to produce different kinds of devices, and also have higher surface area. Hence, the research on controlled preparations of various types of one-dimensional functional nanomaterials with specific performance is one of the most important works. This work reported that hydrothermal growth of TiO2 nanorod structures on Si substrate, and their wettability, photocatalytic properties were investigated.A layer of nanodots on Si substrate was prepared through phase-separation-induced self-assembly and post-heat treatment at different temperatures before hydrothermal process. The nanodot film displayed a stronger assisting role for nanorod growth, and the role will be intensified when TiO2 nanodot film hadrutile phase.The morphology, size and density of TiO2 nanorods could be tuned by changing the parameters of the hydrothermal treatment. The results of SEM illustrate that the TiO2 nanorods were needle-like when titanium trichloride as Ti precursor, and columnar when titanium butoxide as Ti precursor. At the same growth time for different Ti precursors, the density, diameter and length of the nanorod films varied within range -3.7-83μm-2,-35-244nm and -180-826nm, respectively. A similar variation trend for different hydrothermal growth time appeared.The results of XRD and TEM illustrate that the TiO2 nanorod films were rutile, the growth direction of the nanorods was [101] or [001] when titanium trichloride or titanium butoxide was used as Ti precursor.For the possible hydrothermal growth mechanism, it suggested that the nanodots of the assisted layer in high acid solution were partially dissolved first, then fine rutile particles deposited as the seeds for the growth of rutile TiO2 nanorods. Through the orientation adhesion, the TiO2 nanorods grew. With increasing of TiO2 nanorod density, the TiO2 nanorod films showed a transition from hydrophobicity to superhydrophilicity, and the photocatalytic degradation ability was strengthened consequently.