Abstract
In the present work, we introduce a technique to achieve rapid growth of self-ordered anodic nanotubes with a well-defined tube-to-tube spacing (spaced tubes) and single-wall morphology. By optimizing the anodization conditions (electrolyte, temperature, etc.), the growth rate of spaced tubes can be ≈25 times faster than in conventional approaches while maintaining a tube-to-tube spacing of ≈100nm. We show that the origin of the tube-to-tube spacing is self-ordering of nanotubes on two different scales – the primary large tubes are embedded in a matrix of secondary, very short nanotubes with a small diameter. Preferential etching of the small tubes during anodic growth leaves behind an ordered array of spaced individual tubes with a well-defined tube-to-tube spacing.
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•Fast growth of spaced TiO2 nanotube arrays is accomplished.•Self-ordering at two different scales (two tube diameters) is demonstrated.•The tube-to-tube spacing is due to self-ordering at two different scales.•We established the key parameters determining the “spaced tube conditions”.