Advanced Functional Materials
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Editor-in-Chief: Joern Ritterbusch, Deputy Editors: Mary De Vita, Yan Li
Online ISSN: 1616-3028
Associated Title(s): Advanced Electronic Materials, Advanced Energy Materials, Advanced Engineering Materials, Advanced Healthcare Materials, Advanced Materials, Advanced Materials Interfaces, Advanced Materials Technologies, Advanced Optical Materials, Advanced Science, Particle & Particle Systems Characterization, Small
Titania Nanotubes: Protein-Enabled Layer-by-Layer Syntheses of Aligned, Porous-Wall, High-Aspect-Ratio TiO2 Nanotube Arrays (Adv. Funct. Mater. 9/2011)
An aqueous, protein-enabled (biomimetic), layer-by-layer titania deposition process is developed, for the first time, to convert aligned-nanochannel templates into high-aspect-ratio, aligned nanotube arrays with thin (34 nm) walls composed of co-continuous networks of pores and titania nanocrystals (15 nm ave. size). Alumina templates with aligned open nanochannels are exposed in an alternating fashion to aqueous protamine-bearing and titania precursor-bearing (Ti(IV) bis-ammonium-lactato-dihydroxide, TiBALDH) solutions. The ability of protamine to bind to alumina and titania, and to induce the formation of a Ti–O-bearing coating upon exposure to the TiBALDH precursor, enables the layer-by-layer deposition of a conformal protamine/Ti–O-bearing coating on the nanochannel surfaces within the porous alumina template. Subsequent protamine pyrolysis yields coatings composed of co-continuous networks of pores and titania nanoparticles. Selective dissolution of the underlying alumina template through the porous coating then yields freestanding, aligned, porous-wall titania nanotube arrays. The interconnected pores within the nanotube walls allow enhanced loading of functional molecules (such as a Ru-based N719 dye), whereas the interconnected titania nanoparticles enable the high-aspect-ratio, aligned nanotube arrays to be used as electrodes (as demonstrated for dye-sensitized solar cells with power conversion efficiencies of 5.2 ± 0.4%).