Bipolar anodization enables the fabrication of controlled arrays of TiO2 nanotube gradients

Abstract

We report here a new concept, the use of bipolar electrochemistry, which allows the rapid and wireless growth of self-assembled TiO₂ NT layers that consist of highly defined and controllable gradients in NT length and diameter. The gradient height and slope can be easily tailored with the time of electrolysis and the applied electric field, respectively. As this technique allows obtaining in one run a wide range of self-ordered TiO₂ NT dimensions, it provides the basis for rapid screening of TiO₂ NT properties. In two examples, we show how these gradient arrays can be used to screen for an optimized photocurrent response from TiO₂ NT based devices such as dye-sensitized solar cells.