A novel experimental method for obtaining multi-layered TiO2 nanotubes through electrochemical anodizing

In this study, a new parameter having influence on the TiO2 nanotubes formation process is reported. Except of previously mentioned and well-known anodizing parameters such as voltage, time of anodizing, type of electrolyte, temperature, etc., samples' configuration in the electrochemical cell represents an important factor in the anodizing procedure. The electrochemical anodization is a group of interconnected processes and factors, each one of them having its specific weight on the final result. It was observed that the very short distance in between two titanium plates connected to the anodic terminal of the electrochemical cell is the decisive factor for creating superimposed TiO2 nanotube layers. More precisely, it was found that the configuration of two parallel Ti plates being in close contact to each other, mounted to the anodic terminal and in parallel with the graphite cathode, favors the formation through electrolysis of multi-layered TiO2 nanotubes. The microscopic observation of multi-layered TiO2 nanotubes was performed through the removal of the upper layer of nanotubes using sonication. This peculiar result was interpreted using existed theories such as First Fick's law and Nerst diffusion layer in combination with recently published research findings related to the effect of inter-electrode distance.