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| Searle Chemical Laboratory 017 |
| Searle Chemical Laboratory 022 |
| 773-834-1877 |
| 773-702-0805 |
| rongchao@uchicago.edu |
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| Ph.D. Chemistry, Northwestern University, Evanston IL, USA |
| M.S. Catalysis, Dalian Institute of Chemical Physics/Chinese Academy of Sciences, |
| Dalian, China |
| B.S. Chemical Physics, University of Science and Technology of China, Hefei, China |
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| Nanocrystals and nanomaterials are having a major impact on research in a broad breadth, including chemistry, physics, materials, and biological and environmental sciences. When a material’s dimensions reach the nanometer scale (typically, 2-100 nm, 1nm =10^(-9) m), most of its physical, chemical, and thermodynamic properties are drastically changed and are no longer analogous to their bulk counterparts. For example, nanosized Au particles in colloids show a distinct ruby-red color, in contrast to the golden color of bulk Au. Colloid chemistry began in the 19th century. In 1857, Michael Faraday prepared the first aqueous Au colloids. His work had stimulated a great deal of research in the synthesis of metal colloid and studies of optical properties. Colloidal science reached its first climax in the 1920s. It is worthy to mention two Nobel laureates, R. A. Zsigmondy (1925) and T. Svedberg (1926). Over the past two decades, colloidal science has experienced a renaissance and been one of the core areas for nanoscience and technology.
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| One of our research thrusts is to develop nanocrystal-based novel functional materials, e.g. plasmonic materials for controlling 2-D and 3-D light propagation. To realize this goal, the central task is to develop new techniques for controlling nanoparticle nucleation/growth kinetics and ultimately the particle size and shape. Metal nanocrystals, such as Au and Ag (2-100 nm), show distinct plasmon resonance absorption and Rayleigh-scattering in the visible regime. Studies of their nonlinear optical property on a single-particle level are currently being pursued with a combination of a femtosecond laser and a far-field optical microscope.
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| Very small metal particles (or “clusters”, typically < 2nm), which are in contrast to those relatively large nanoparticles with a crystalline core- whose optical properties can well be interpreted by classical electrodynamics, show discrete energy-level structures due to the strong quantum confining effect. These clusters are typically composed of several to tens of atoms-being too small to exhibit core crystallinity, thus, their structure and electronic properties are of particular interests to us. In order to understand the fundamentals and exploit the rich properties of metal clusters, it is of great importance to develop new strategies for synthesizing clusters with well-defined structures and specific functionality as well as enhanced stability. Recently, we developed a thermal method for converting colloidal Au nanoparticles into atomic Au clusters (trimers) with high yields. These Au clusters are highly luminescent and show extraordinary stability. Spectroscopic studies of their electronic properties and photoluminescence are currently being pursued.
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