PHYS 98 |
| Because of their unique physical properties, nanoparticles are often described as “artificial atoms.” The ability to assemble these artificial atoms into desired and higher ordered architectures (e.g., nanoparticle superlattices) may open a new way to fabricate functional materials of interest for applications such as biomedical diagnosis, catalysis, plasmonics, and high-density data storage. To date, methods have been developed for the preparation of nanoparticle thin films and colloidal crystals with a variety of superlattice structures, from which new collective properties have been discovered. However, a major challenge still remains: the inability to prepare nanoparticle superlattices with well-controlled size and shape (i.e., supercrystalline collections of artificial atoms in the form of “superparticles,” SPs). Here we present a general approach for making well-defined supercrystalline colloidal SPs from artificial atoms that are nonpolar-solvent-dispersible nanoparticles such as Fe3O4, Au, and quantum dots (CdSe). We find that the major driving force for the formation of SPs is the solvophobic interaction between nanoparticle building blocks and the growth solution. After a crystallization stage, the SPs exhibit superlattice fringes under a low-resolution transmission electron microscope (TEM), providing an interesting analog to the lattice fringes of colloidal nanocrystals under a high-resolution TEM. Moreover, the properties of these novel SPs are tailorable by doping with organic dyes. Furthermore, these SPs can be assembled into close-packed solid structures, demonstrating their role as a new type of building block in nanoscience. These results suggest that the ability to synthesize supercrystalline SPs should lead to a versatile route to new nanoparticle-based materials with desired properties. |
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Nanostructured Materials
8:20 AM-12:00 PM, Monday, April 7, 2008 Morial Convention Center -- Rm. 338/339, Oral
Division of Physical Chemistry |