Fabrication of Inorganic Tubular Structures Using a Lipid Nanotube as a Template in Aqueous Solutions
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0922-U01-01
Fabrication of Inorganic Tubular Structures Using a Lipid Nanotube as a Template in Aqueous Solutions Qingmin Ji1, Rika Iwaura1, Masaki Kogiso1,2, and Toshimi Shimizu1,2 1 Nanoarchitectonics Research Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan 2 SORST, Japan Science and Technology Agency, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan ABSTRACT A secondary ammonium hydrochloride of a peptidic lipid, in which an L-prolyl-L-prolyl-L-proline fragment is coupled with an L-glutamate derivative carrying two long alkyl chains, self-assembles in water to form nanotube structures consisting of a single bilayer wall. This lipid nanotube has been employed as a template to perform sol−gel transcription of different metal alkoxides in the absence of solution catalysts in aqueous dispersion. TEM analysis of the aqueous gel phase, coupled with electron energy-loss spectroscopy (EELS) revealed the presence of a high population of hybrid nanotube architectures with a well-defined lipid/silica interface. Besides silica, when replacing the lipid nanotube in aqueous solutions with an iced lipid nanotube as a template, we also succeeded in the transcription to transition metal oxide nanotubes (titanium oxide, tantalum oxide, vanadium oxide). A relatively low population of positive charges on the organic templates is crucial for the formation of inorganic nanotubes. Thus, in an aqueous system, the morphology of the lipid nanotube consisting of a single bilayer wall was replicated into different inorganic nanotubes. INTRODUCTION The use of organic materials for the generation of inorganic materials with well-defined structures has received increasing attention over the last decade [1-3]. Especially, the fabrication of tubular architectures with a nanometer-sized hollow cavity is challenging from the viewpoint of their potential applications in natural science and materials science fields. Surfactant-mediated or organogel-templated fabrication provides two typical wet processes to form isolated tubular structures. However, surfactant-mediated fabrication, which can self-assemble in water, always produces silica structures with close ends and is difficult to obtain other metal oxide tubular structures. Organogel-templated fabrications carry out in organic solvents in the presence of only a small amount of water. Here we describe the aqueous sol−gel transcription from a lipid nanotube template into different inorganic nanotubes of silica, titania, tantalum oxide and vanadium oxide. We employed the synthetic cationic lipid 1, which can self-assemble to nanotube structures, in place of common surfactants. We used only water as a reaction solvent, which contained no active solution catalysts. Therefore, the present methodology clearly differs from the so-called surfactant-mediated system in aqueous media and from the organogel-templated system in organic solvents. A relatively low population of positiv
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