Session 7-2

Abstract

We have successfully synthesized a variety of molecularly thin 2D metal oxides by exfoliating a precursor layered compound [1,2]. Hydration-driven swelling induced by reaction with aqueous solutions of amine/organoammonium hydroxides could homogeneously prop the interlayer gallery up to a hundred times, which eventually brought about the total disintegration of the layered system into unilamellar 2D crystals The oxide nanosheets can be obtained in diverse composition and structure, leading to a range of useful functionalities. For example, Ti or Nb oxide nanosheets of Ti_{1- δ}O₂4δ- and Ca₂Nb₃O₁₀- work as wide-gap semiconductors, showing photocatalytic property, while Mn- or W-based oxide nanosheets such as MnO₂0.4- and Cs₂W₁₁O₃₆2- show electrochemical redox activity and chromic property.
Because the oxide nanosheets are colloidal polyanions dispersed in aqueous media, we can apply solution-based processes to organize them as a building block into various nanostructured materials such as nanocomposites, nanofilms and hydrogels [1-3]. Particularly, electrostatic self-assembly, Langmuir-Blodgett deposition and spin-coating methods are effective to enable artificial layer-by-layer deposition to tailor precisely organized lamellar nanostructures [4,5]. In this talk, typical examples for function design through this approach will be presented.