Nanocrystals of different size and functionality (e.g. noble metals, semiconductors, oxides, magnetic alloys) can be induced to self-assemble into ordered binary superlattices (also known as opals or colloidal crystals) retaining the size-tunable properties of their constituents. The ability to tune interparticle separation and to build arrays based on a variety of constituents lends itself very well to the concepts of rational design of complex nanostructures. Previously, in a collaboration with C. B. Murray (UPenn) we have built a variety of novel binary BNSLs from monodisperse nanocrystals, mixing and matching these nanoscale building blocks to yield multifunctional nanocomposites (metamaterials). Superlattices with cubic, hexagonal, tetragonal and orthorhombic symmetries have been identified. Studying the formation mechanism for ordered multi-component nanoparticle superlattices not only provides opportunities to probe the unique physics of self-assembly in the nanometer scale, but also can potentially be utilized as a “bottom-up” design tool to build “metamaterials” of novel physical properties distinct from their individual components. The self-assembly of multi-component nanoparticles can involve a complex balance between different driving forces such as entropy, Coulomb interaction from particle charges, London-van der Waals forces. Therefore, for self-assembly to be really utilized as an effective modern method to design and build superlattices of novel properties, much effort is required to understand the formation mechanism. It has been suggested that a wide range of synergistic properties, especially optoelectronic, may emerge as a consequence of neighbor-neighbor interactions and it is therefore highly desirable to invent new methods to probe potential effects. An example might be size tunable energy transfer between semiconducting and metal nanoparticles within a superlattice.
A nanoparticle radius ratio dependent study of the formation of binary nanoparticle superlattices (BNSLs) of CdTe and CdSe quantum dots. While keeping all other parameters identical in the system, the effective nanoparticle radius ratio, γeff, was tuned to allow the formation of five different BNSL structures, AlB2, cub-NaZn13, ico-NaZn13, CaCu5, and MgZn2. For each structure, γeff is located close to a local maximum of its space-filling factor, based on a model for space filling principles. We demonstrate the ability to select specific BNSLs based solely on γeff, highlighting the role of entropic forces as a driver for self-assembly.
Related references
1. Chen, Z. and O’Brien, S. “Structure Direction of II-IV Semiconductor Quantum Dot Superlattices by Tuning Radius ratio”, ACS Nano, 2008, 2(6), 1219-1229.
2. Lu, C.; Chen, Z. and O’Brien, S. “Optimized Conditions for the Self-Organization of CdSe-Au Binary Nanoparticle Superlattices” Chemistry of Materials, 2008, 20(11), 3594-3600.
3. Wu, C.-K.; Hultman, K. L.; O'Brien, S.; Koberstein, J. T. “Functional Oligomers for the Control and Fixation of Spatial Organization in Nanoparticle Assemblies.” Journal of the American Chemical Society, 2008, 130(11), 3516-3520.
4. Zohar, S.; Hultman, K.; O'Brien, S.; Bailey, W. E., “Thin-film superparamagnetic resonance in a gamma-Fe(2)O(3) nanoparticle array” Journal of Applied Physics, 2008, 103.
5. Chen, Z.; Moore, J.; Radtke, G.; Sirringhaus, H and O’Brien, S “Binary Nanoparticle Superlattices in the Semiconductor-Semiconductor System: CdTe and CdSe” Journal of the American Chemical Society 2007, 129(50); 15702-15709.
6. Yin, M.; Chen, Z.; Deegan, B.; O'Brien, S. "Wustite Nanocrystals: Synthesis, Structure and Superlattice Formation" Journal of Materials Research 2007, 22(7), 1987-1995.
7. Shevchenko, E. V.; Talapin, D. V.; Murray, C. B.; O'Brien, S. "Structural Characterization of Self-Assembled Multifunctional Binary Nanoparticle Superlattices" Journal of the American Chemical Society 2006, 128, 3620-3637.
8. Shevchenko, E. V.; Talapin, D. V.; Kotov, N. A.; O'Brien, S.; Murray, C. B. "Structural diversity in binary nanoparticle superlattices" Nature 2006, 439, 55-59.
9. Zhu, Z. M.; Andelman, T.; Yin, M.; Chen, T. L.; Ehrlich, S. N.; O'Brien, S. P.; Osgood, R. M. "Synchrotron x-ray scattering of ZnO nanorods: Periodic ordering and lattice size" Journal of Materials Research 2005, 20, 1033-1041.
10. Yin, M.; Wu, C. K.; Lou, Y. B.; Burda, C.; Koberstein, J. T.; Zhu, Y. M.; O'Brien, S. "Copper oxide nanocrystals" Journal of the American Chemical Society 2005, 127, 9506-9511.
11. Shevchenko, E. V.; Talapin, D. V.; O'Brien, S.; Murray, C. B. "Polymorphism in AB(13) nanoparticle superlattices: An example of semiconductor-metal metamaterials" Journal of the American Chemical Society 2005, 127, 8741-8747.
12. Grancharov, S. G.; Zeng, H.; Sun, S. H.; Wang, S. X.; O'Brien, S.; Murray, C. B.; Kirtley, J. R.; Held, G. A. "Bio-functionalization of monodisperse magnetic nanoparticles and their use as biomolecular labels in a magnetic tunnel junction based sensor" Journal of Physical Chemistry B 2005, 109, 13030-13035.
13. Yin, M.; Willis, A.; Redl, F.; Turro, N. J.; O'Brien, S. P. "Influence of capping groups on the synthesis of gamma-Fe2O3 nanocrystals" Journal of Materials Research 2004, 19, 1208-1215.
14. Shevchenko, E.; Redl, F.; Yin, M.; Murray, C. B.; O'Brien, S. , Nanoparticle Superlattices, SPIE Proceedings, 2004; p 5554.
15. Redl, F. X.; Black, C. T.; Papaefthymiou, G. C.; Sandstrom, R. L.; Yin, M.; Zeng, H.; Murray, C. B.; O'Brien, S. P. "Magnetic, electronic, and structural characterization of nonstoichiometric iron oxides at the nanoscale" Journal of the American Chemical Society 2004, 126, 14583-14599.
16. Yin, M.; O'Brien, S. "Synthesis of monodisperse nanocrystals of manganese oxides" Journal of the American Chemical Society 2003, 125, 10180-10181.
17. Redl, F. X.; Cho, K. S.; Murray, C. B.; O'Brien, S. "Three-dimensional binary superlattices of magnetic nanocrystals and semiconductor quantum dots" Nature 2003, 423, 968-971.