More or less hollow, but always nano: Titania templates

The fact that the structure of materials can be manipulated on a scale as small as the nanoscale remains fascinating in itself. However, in the face of the enormous potential of applications, researchers have long since directed their efforts to more down-to-earth aspects – prominently to the question how nanoscale structures can be fabricated cost-efficiently. Much less effort is required when the materials take care of the tedious task of structuring and ordering their tiny details themselves, so approaches offering self-organizational processes are attractive. Templates are another concept that can be of great assistance in any large-scale production process.

Electrochemical anodization of Ti to fabricate titania templates combines these two concepts, and researchers from the Academy of Sciences of Moldova now report their progress on the remaining challenge, namely controlling the resulting structures in an easy-to-use, systematic and predictable way, in newly published work.

They demonstrate that anodization of Ti sheets in ethylene glycol and HF containing electrolyte leads to the formation of ordered arrays of double-walled TiO2 nanotubes. Moreover, they can keep the outer nanotube diameter and the density of the hollow nanotubes constant while varying the inner diameter in the range from 10 to 250 nm. After the outer diameter generically connects to the self-organized nucleation layer, the change of the inner diameter is accomplished simply through a change of the electrolyte temperature, and the relation turns out to be linear.

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