Bottom-up approach to the synthesis of oxide materials I

SARA ALDABE BILMES

Workshop; workshop on oxide materials: novel multifunctional properties; 2014

Bottom-up approach to the synthesis of oxide materials I Sara A. Bilmes Universidad de Buenos Aires, Facultad Ciencias Exactas y Naturales, Instituto de Química Física de los Materiales, Medio Ambiente y Energía ? INQUIMAE- DQIAQF, Ciudad Universitaria Pab II, Ciudad Autónoma de Buenos Aires, C1428EHA, Argentina Oxide materials are the base for building a wide range of devices. Their specific optical or electrical properties are given from their structure and composition of the bulk and the surface, the latter being most important when dealing with materials at the nanometer scale. The synthesis of oxide materials usually starts form from molecular precursors. Among them, synthesis in solution has several advantages as it can be carried out at ambient pressure and low temperature, and the control of solution parameters allows a fine tuning of composition, size and shape of the final material in the nano and microscale. By this way simple or complex materials are designed from molecules and intermolecular interactions. The basic idea is to use molecular precursors as building blocks that are connected by covalent bonds or intermolecular interactions. This chimie douce pathway provides mild conditions for building hybrid organic-oxide materials that combine the properties of solids with those of polymers. The initial process considers the formation of nuclei through supersaturation, and then diffusion growth. The first step is controlled by the concentration of precursors and catalysts, whereas growth can be controlled by the solution species in order to give a defined shape at the nanometer scale. Thermal treatment leads to evaporation of the solvent, decomposition of organic matter, sintering and crystallization. In this lecture, the main parameters affecting nucleation and growth for the synthesis of oxides will be analyzed for oxides such as SiO2 and TiO2 and ZnO. Special attention is given to the role of molecules added for directing growth in connection to the optical and catalytic properties of these materials.