INOR 62 |
| We demonstrate the self-assembly of superparamagnetic nanocrystal clusters into ordered structures which can strongly diffract visible light. By changing the relative strength of the interparticle magnetic attractive forces and electrostatic repulsive forces, one can tune the diffraction peaks over the entire visible spectrum. The key building blocks are the magnetite nanocrystal clusters which can be synthesized through a high-temperature hydrolysis reaction. Each cluster is composed of small single crystalline magnetite nanocrystals, thus avoiding the superparamagnetic-ferromagnetic transition typically found for large magnetic particles. The use of polyacrylate as the capping agent provides the nanocrystal clusters highly charged surfaces. We were able to optimize the diffraction intensity and the tuning range through studying their dependence on variables such as the size distribution and concentration of the Fe3O4 colloids or ionic strength of the solutions. The unique combination of superparamagnetic property, high magnetization per particle, and highly charged surfaces allows the successful assembly of these colloidal particles into long-range ordered structures with rapid and fully reversible field responsive optical diffractions. Such photonic materials will provide a new platform for the fabrication of novel optical microelectromechanical systems, sensors, and color display units. |
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Nanoscience - Characterization and Applications
9:00 AM-1:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 221, Oral
Division of Inorganic Chemistry |