Super-long aligned TiO₂/carbon nanotube arrays

5 mm long aligned titanium oxide/carbon nanotube (TiO₂/CNT) coaxial nanowire arrays have been prepared by electrochemically coating the constituent CNTs with a uniform layer of highly crystalline anatase TiO ₂ nanoparticles. While the presence of the TiO₂ coating was confirmed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and x-ray diffraction, the resultant TiO₂/CNT coaxial arrays were demonstrated to exhibit minimized recombination of photoinduced electron-hole pairs and fast electron transfer from the long TiO₂/CNT arrays to external circuits. This, in conjunction with the aligned macrostructure, facilitates the fabrication of TiO₂/CNT arrays for various device applications, ranging from photodetectors to photocatalytic systems. Thus, the millimeter long TiO₂/CNT arrays represent a significant advance in the development of new macroscopic photoelectronic nanomaterials attractive for a variety of device applications beyond those demonstrated in this study.