Controlled spacing of self-organized anodic TiO2 nanotubes

TL;DR

This paper demonstrates how to grow self-organized TiO2 nanotube arrays with controlled and regular spacing by adjusting voltage and water content during electrochemical anodization in fluoride-containing di-ethylene glycol electrolytes.

Contribution

It introduces a method to independently control nanotube diameter and spacing, achieving true regular gaps unlike traditional close-packed structures.

Findings

Nanotube spacing is controlled by voltage and water content.

Regular and defined gaps are achieved in specific electrolyte conditions.

Diameter and spacing can be independently tuned.

Abstract

We report on how to grow and control self-organized TiO2 nanotube arrays that show defined and regular gaps between individual nanotubes. For this we use electrochemical anodization of titanium in fluoride containing di-ethylene glycol (DEG) electrolytes, with variations in voltage and water content in the electrolyte. In these specific electrolytes, such nanotubes show a true spacing, i.e. nanotubes are spaced both at top and at bottom in regular intervals, this in contrast to classic nanotubes obtained in other organic electrolytes showing a close-packed organization. We identify critical parameters, that define the region of existence i.e. under which condition tube spacing occurs as well as the intertube distance, to be the voltage and the water content. Using these findings allows to grow tubes where diameter and spacing can even be independently controlled.