Aligned TiO2 nanorod arrays synthesized by oxidizing titanium with acetone

We report on well-aligned TiO2 nanorod arrays formed on a titanium substrate using acetone as the oxygen source in the oxidation of Ti at 850 degreesC. For comparison, TiO2 films were also prepared by oxidizing Ti substrates with pure oxygen and with a mixture of argon with a low concentration of oxygen. X-Ray diffraction, transmitting electron microscopy and Raman studies show that all the TiO2 films fabricated in this study have the same rutile phase. However, the microstructures of these TiO2 films, characterized using scanning electron microscopy, are dramatically different. The use of pure oxygen yielded crystalline grain films, whereas the use of argon with a low concentration of oxygen produced random nanofibers growing from the ledges of the TiO2 grains; in contrast, highly dense and well-aligned TiO2 nanorod arrays were formed with acetone as the oxygen source. Measurements of the water contact angle on these samples show that the wetting properties of the TiO2 films are dictated by their structure, varying from a hydrophilic surface ( polycrystalline grains) to hydrophobic ( random nanofibers), and towards a highly hydrophobic surface (well-aligned nanorod arrays). The origin of the different wetting properties and the possible growth mechanisms for these oxide films are discussed.