Nanocrystal growth and exotic doping at extremely high-pressure hydrothermal conditions

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In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Hengzhong Zhang and Jillian Banfield of the University of California at Berkeley will investigate titania nanocrystal growth, structure and morphology evolution, and structural incorporation of impurities under extremely high pressure hydrothermal conditions. The approach is to synthesize titania nanoparticles with and without the presence of dopants, to employ a special diamond anvil cell in performing an in situ synchrotron X-ray diffraction study of nanocrystal growth and structure change in supercritical water at very high temperatures and pressures, to perform ex situ microscopy and X-ray absorption studies on the nanocrystals to determine dopant distributions, and finally to use theoretical modeling methods to understand the physical and chemical properties of titania nanoparticles under such conditions. The broader impacts involve the integration of undergraduate student training and education into the research project, the incorporation of research results into the undergraduate laboratory curriculum, the broad dissemination of research results through publications, presentations and a nanogeoscience website, and the potential impacts of the research in many areas of science.Nanocrystals are small pieces of material with dimensions on the order of 1 to 100 nanometers, which is about 10,000 times smaller than the width of a human hair, and they are important for a wide range of technologies including pigments, electronics, and medical imaging. The ability to control nanocrystal growth to achieve required specifications such as phase, size, and morphology and defect structure is key to the realization of their use nanotechnologies. Nanocrystal growth under extreme temperature and pressure conditions is largely unexplored, and this project will pursue this research topic using both state-of-the-art experimental techniques and theoretical and computational modeling. Such research will enhance our knowledge about manipulating nanocrystals and potentially lead to the discovery of new nanocrystal structures and compositions.