Functionalized metal nanoparticles and nanoparticle arrays.

Researchers:
Marvin Warner
Mary Schmidt
Walter Weare
 Chemical fabrication of devices that operate on the basis of Coulomb blockade promises to provide computer chips with 10,000 times more electronic devices than possible with state-of-the-art lithography. Specifically, methods involving the use of polymeric scaffolds that guide particle assembly are of particular interest to us. In order to build a single electron transistor that operates at room temperature, particles smaller than two nanometers in diameter must be used. The particle must have a well-defined ligand shell that provides spacing between particles and functional groups for tethering the particle to the biopolymer.

Utilizing powerful, new synthetic methods for preparing functionalized gold nanoparticles developed in our lab, we can control the nanoparticle's core size, solubility, interparticle spacing and reactivity by adjusting the identity and ratio of reactive bridging to inert capping ligands. We perform ligand exchange reactions wherein all the ligands in a labile starting particle are replaced by added thiol ligands. This procedure is versatile, rapid and reproducible. We can also prepare particles that are water-soluble and have only a few reactive bridging ligands. These samples should be ideally suited for interactions with scaffold polymers.

We have discovered methods for forming well-ordered nanoparticle monolayers and have explored the electrical properties of thin films of nanoparticles. These samples provide the first observation of Coulomb blockade at room temperature in a two- or three-dimensional nanoparticle array and demonstrate that our nanoparticle building blocks are well suited for the construction of Coulomb blockade devices.

The influence of polymer scaffolds on the structure, stability and electrical response of nanoparticle arrays is currently being investigated with the aim of understanding the fundamental mechanisms of charge transport in nanoparticle arrays and developing new nanoscale electronic devices.

Recent publications.

Clark, L.; Wybourne, M. N.; Yan, M.; Cai, S. X.; Brown, L. O.; Hutchison, J.; Keana, J. F. W. "Fabrication and Near-Room Temperature Transport of Patterned Gold Cluster Structures," J. Vac. Sci. Tech. B , 1997, 15, 2925-2929.

Wybourne, M. N.; Clarke, L.; Yan, M.; Cai, S. X.; Brown, L. O.; Hutchison, J.; Keana, J. F. W. "Coulomb-Blockade Dominated Transport in Patterned Gold-Cluster Structures," Jap. J. Appl. Phys. 1997, 36, 7796-7800.

Brown, L. O.; Hutchison, J. E. "Convenient Preparation of Stable, Narrow-Dispersity, Gold Nanocrystals by Ligand Exchange Reactions," J. Am. Chem. Soc. 1997, 119, 12384-12385.

Clarke, L.; Wybourne, M. N.; Brown, L. O.; Hutchison, J. E.; Yan, M.; Cai, S. X.; Keana, J. F. W. "Room Temperature Coulomb-Blockade Dominated Transport in Gold-Nanocluster Structures," Semicond. Sci. Technol. 1998, 13, A111-A114.

Brown, L. O.; Hutchison, J. E. "Controlled Growth of Gold Nanoparticles During Ligand Exchange," J. Am. Chem. Soc. 1999, 882-883.

Wybourne, M.N.; Hutchison, J.E.; Clarke, L.; Brown L.O.; Mooster, J.L. "Fabrication and Electrical Transport Characteristics of Low-Dimensional Nanoparticle Arrays Organized by Biomolecular Scaffolds," Microelcetron Eng. 1999, 47, 55-57.
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