Metal Oxide Nanocrystals: Building Blocks for Mesostructures and Precursors for Metal Nitrides
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1007-S13-02
Metal Oxide Nanocrystals: Building Blocks for Mesostructures and Precursors for Metal Nitrides Markus Niederberger1, Jelena Buha2, and Igor Djerdj1 1 Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, Zurich, 8093, Switzerland 2 Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Research Campus Golm, Potsdam, 14424, Germany
ABSTRACT Sol-gel routes to metal oxide nanoparticles in organic solvents under exclusion of water represent a valuable alternative to aqueous methods. In comparison to the complex aqueous chemistry, nonaqueous processes offer the possibility to better understand and to control the reaction pathways on a molecular level, enabling the synthesis of nanomaterials with high crystallinity and well-defined and uniform particle morphologies. The manifold role of the organic species in providing the oxygen for the oxide formation and in controlling the crystal growth and the assembly properties makes it possible to tailor the morphological, structural and compositional characteristics of the final inorganic products. In addition to metal oxides with nearly spherical crystallite sizes in the range of just a few nanometers, also more complex morphologies such as nanowire bundles, nanorods or lamellar organic-inorganic hybrids of varying hierarchical complexity can be achieved in one step and without the use of any surfactants. The spherical nanocrystallites are on the one hand versatile building blocks for the fabrication of fully crystalline and ordered mesoporous materials and on the other hand suitable precursors for the synthesis of metal nitride nanoparticles. This proceeding provides an overview of the various oxidic nanoparticles synthesized via the nonaqueous and surfactant-free sol-gel approach, summarizes the most frequently found formation mechanisms, and offers some insight into the crystallization pathway of nanoparticles. Furthermore, the use of metal oxide nanoparticles as nanobuilding blocks for the preparation of nano- and mesostructures as well as their transformation into metal nitride nanocrystals will be discussed. INTRODUCTION The wide variety of applications of metal oxides in catalysis, sensing, energy storage and conversion, optics and electronics moved this class of materials into the centre of interest of materials science [1,2]. In order to obtain metal oxides as nanoparticles with well-defined shape, size and crystallinity, the traditional high-temperature synthesis routes are hardly suited, and novel innovative strategies have to be developed. In spite of great efforts the synthesis of metal oxides on the nanoscale under mild reaction conditions remains a challenging task, mainly due to the fact that the conventionally applied aqueous sol-gel chemistry generally leads to amorphous products. The fast hydrolysis rate of metal oxide precursors as well as the high complexity of aqueous systems in general makes it difficult to control the structural and morphological properties of the final product. A valuable
alternative is the synthesis o
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