Formation of sunken hexagonal TiO2 nanotube-clusters in sol electrolyte

Abstract Sunken hexagonal TiO2 nanotube-clusters were prepared by anodizations in sol electrolyte. Nanotube-clusters are separated by compact dams. Dams between nanotubes increase adhesion between TiO2 nanotube layer and substrate. Formation mechanism of TNS is presented. Oxygen bubbles were first formed at the bottom of the nanotubes. Subsequently, the oxygen bubbles escaped from the nanotubes and emerged as large bubbles on the surface of the nanotubes under micelles. Sunken TiO2 nanotube-clusters were formed under the pressure of large oxygen bubbles. Oxides on the top were extruded to the voids between the oxygen bubbles, thereby forming dams between the large oxygen bubbles.