Self-organization of TiO2 nanotubes in mono-, di- and tri-ethylene glycol electrolytes

Self-organization of TiO2 nanotubes was studied by means of titanium anodizing in electrolytes containing 1, 2 and 3 oxyethylene units in the organic chain of solvent molecule, named mono-, di-, and tri-ethylene glycols. A fundamentally different nanostructures were formed in mono- and di-electrolytes in view of their self-organization; close pack nanotubes are formed in mono-electrolyte, whereas nanotubes with large spaceing in-between are formed in di -electrolyte. The analysis of the tube bottoms and dimples formed in substrate shows formation of conical-type (alumina like) and frustum-type dimples in mono- and di -electrolytes, respectively. We discuss on the formation of frustum-type dimples with the size corresponding to the space in-between the nanotubes and link their formation to the mechanism of nanostructure growth. (C) 2016 Published by Elsevier Ltd.