Functionalization of titanium dioxide nanotubes by various doping methods to use as selective gas sensing and energy storage applications

In recent years, the well-studied and understood properties of a bulk material are put together with the new properties acquired from its nanostructured counterpart, which in the most cases enables making improvements in applications and device performance. The concepts established using this phenomenon would find totally new input into the research and development in the field of micro- and nano-system technologies especially in the miniaturization of devices. Furthermore the enhanced chemical interactions of the material for gas sensors or energy storage applications, high specific surfaces are responsible for the observed improved efficiency of nano materials. Thus, nano-structuring is an attractive way to achieve higher performance with a material and its nanostructured counterpart.

Titanium dioxide (TiO2) has attracted considerable attention due to its high potential for application in solar cells, electronics, photo-catalysis and gas sensors mainly due to its excellent chemical stability, semi-conductive properties, non-toxicity and low cost. During last decades, TiO2-based nano-structures have been made more efficient by changing the morphological features and chemical compositions for instance photo-catalysis to gas sensors. Relying on high specific surface areas, the gas sensors made up of TiO2 nanotubes (NTs) have several advantages such as higher sensitivity, low temperature operation and better mobility of charge carriers.

In this work, self-ordered and vertically oriented the TiO2 NTs were obtained via electrochemical process by anodization of titanium or its alloy. Depending on the target application, the TiO2 NTs were modified with different doping techniques to investigate the effects of nano-structuring and doping by different characterization techniques.

Second part of this study includes investigations on the sensor behaviours of the undoped and doped TiO2 NTs to study the effects of nano-structuring and doping on TiO2 NTs on sensor properties.

Finally, the black TiO2 NTs and undoped TiO2 NTs were investigated as charge storage electrode. Beside surface morphology (bulk or nano-structure) and doping effect of crystalline structure of TiO2 NTs was figured out in this study. Cyclic voltammetry (CV) and charge-discharge measurements are the key experiments of these parts.