Multineedle TiO2 Nanostructures, Self-Assembled Surface Coatings, and Their Novel Properties

Flower-like multincedle TiO2 nanostructures were successfully fabricated by mild aqueous chemistry. Tapered needle crystals grew along the c-axis from the center of the particles to cover their surfaces with a-faces. Furthermore, microstructured silicon substrates were uniformly coated with the nanostructures by one-step immersion. Transmission electron microscopy, electron diffraction, field emission scanning electron microscopy, and X-ray diffraction revealed a unique multineedle morphology, surface features, anisotropic crystal growth, crystal phase, lattice constant, and orientation of TiO2. Raman, Fourier transform IR spectroscopy, UV-vis, N-2 adsorption, and X-ray photoelectron spectroscopy showed optical properties, band gap, chemical bonds, atomic ratio, quantum size effects, defects, fluorine doping, and high surface area. The analyses clarified the unique morphology, crystal growth mechanism, and physicochemical profiles of the newly developed TiO2 systems.