California NanoSystems Institute
CNSI
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June 03, 2003

Stan Williams
Hewlett Packard
Molecular Electronics: Defect Tolerance, Chemical Fabrication and Quantum-State Switching
Abstract:

Economic and physics considerations indicate that the rapid improvements we have come to expect in silicon integrated circuits may saturate around the year 2010. However, fundamental physical laws indicate that it should be possible to compute with a power efficiency that is at least one billion times better than present transistor electronics. The most straightforward ways currently known to achieve such efficiencies are to fabricate circuits with much smaller dimensions and fewer transistors. Thus, there is a tremendous business incentive and scientific challenge to invent new electronic devices that will have dimensions of the order of nanometers and new fabrication techniques that can inexpensively produce and connect these devices in vast quantities. In order to satisfy both requirements simultaneously, we have assembled a trans-disciplinary team of chemists, physicists, engineers and computer scientists at HP Labs to explore the use of molecules as active electronic devices in specially designed defect-tolerant architectures that are assembled by chemical processes.

May 27, 2003

Karen Wooley
Washington University, St. Louis
Methodologies for Regioselectivity in the Preparation of Complex Nanosctructured Materials
Abstract:

Synthetic methodologies for the preparation of well-defined, complex nanostructured materials have advanced rapidly over the past decade, with many target structures being modeled from biological macromolecules and nanomaterials. This presentation will emphasize the advancement of regiochemical control from the level of molecular frameworks to nanoscopic dimensions to achieve control over composition, structure, and function. Regiochemical control will be demonstrated by the thermodynamically-driven phase segregation of block copolymers in solution and in the bulk state to assemble interesting morphologies, followed by the establishment of kinetically-trapped, covalently-crosslinked nanostructured materials, with such connections being established within selective regions of the nanoscale supramolecular assemblies. Specific examples illustrating this process will include the preparation and characterization of shell crosslinked nanoparticles in aqueous solution, as individual and complex nanoscale entities, and the formation and study of amphiphilic coatings having tunable surface topographical and morphological profiles. In addition to detailing the synthetic methodologies, a significant portion of the discussion will describe the properties of these materials.

References:

Ma, Q.; Remsen, E. E.; Clark, C. G., Jr.; Kowalewski, T.; Wooley, K. L. "Chemically-induced Supramolecular Reorganization of Triblock Copolymer Assemblies: Trapping of intermediate states via a shell-crosslinking methodology", Proc. Nat'l. Acad. Sci. 2002, 99, 5058-63.

Wooley, K. L. "Shell Crosslinked Polymer Assemblies: Nanoscale constructs inspired from biological systems", J. Polym. Sci, Part A: Polymer Chemistry., 2000, 38(9), 1397-1407.

May 20, 2003

Joanna Aizenberg
Bell Laboratories, Lucent Technologies
Biologically Formed Micropatterned Single Crystals: Architecture, Mechanics, Optics and Biomimetics
Abstract:

Organisms exercise a level of molecular control over the physico-chemical properties of minerals that is unparalleled in synthetic processes. The formation of these materials is controlled at organic-inorganic interfaces by organized assemblies of biological macromolecules. This presentation is aimed at revealing some of the fundamental mechanisms of the formation of calcium carbonate in biological systems, including the regulation of the orientation, shape, mechanical and optical properties of the crystals, as well as at describing the application of these strategies to control artificial crystallization.

References:

J. Aizenberg, D. A. Muller, J. L. Grazul & D. R. Hamann (2003) Direct Fabrication of Large Micropatterned Single Crystals. Science 299, 1205-1208. J. Aizenberg, A. Tkachenko, S. Weiner, L. Addadi & G. Hendler (2001) Calcitic microlenses as part of the photoreceptor system in brittlestars. Nature 412, 819-822. J. Aizenberg, A. J. Black & G. M. Whitesides (1999) Control of nucleation by patterned self-assembled monolayers. Nature 398, 495-498. J. Aizenberg, A. J. Black & G. M. Whitesides (1998) Controlling local disorder in self-assembled monolayers by patterning the topography of their metallic supports. Nature 394, 868-871.

May 13, 2003

Frans C. DeSchryver
Catholic University of Leuven, Belgium
Time and Space Resolved Chemistry: From Ensembles to Single Molecules
Abstract:

To an increasing extent coupling of photophysical and photochemical techniques to microscopy has allowed to obtain information heterogeneous organic and bioorganic and macromolecular systems by mapping their spectral and (photo) chemical properties. Scanning confocal microscopy, eventually of laser trapped ensembles, coupled to fluorescence analysis and imaging, scanning plate confocal and scanning near field optical microscopy provide combined spectral and spatial resolution down to few tenths of nanometers.

In this contribution photophysical properties of in particular dendritic structures eventually containing either a single central chromophore or decorated with chromophores at the rim will be addressed. The assembling and manipulation of these structures using a laser trap in solution will be demonstrated.

These techniques allow not only the study of (self)-assembled ensembles of (macro) molecules but also provide the possibility to investigate single molecule excited and ground state properties and dynamics. Fundamental processes such as energy hopping, energy transfer and electron transfer in dendritic systems will be discussed.

This will be illustrated with dendrimers either with a chromophore core or decorated by a specific number of chromophores at the rim. The single molecule results are complemented with ensemble measurements using femtosecond spectroscopy and single photon counting. It will be shown that even adsorption of dyes onto dendritic structures can be investigated and shows single molecule behavior.

Addressing of single molecules by non optical techniques will be illustrated.

References:

R. Gronheid, J. Hofkens, F. Köhn, T. Weil, E. Reuther, K. Müllen, F.C. De Schryver J.Am.Chem.Soc., 124(11), 2418-2419 (2002)

T. Vosch, J. Hofkens, M. Cotlet, F. Köhn, H. Fujiwara, R. Gronheid, K. Van Der Biest, T. Weil, A. Herrmann, K. Müllen, S. Mukamel, M. Van der Auweraer, F.C. De Schryver Angew. Chem.Int.Ed., 40, N°24, 4643-4648 (2001)

M.M.S. Abdel-Mottaleb, N. Schuurmans, S. De Feyter, J. Van Esch, B.L. Feringa, F.C. De SchryverChem.Commun., 1894-1895 (2002)

S. Sarzi Sartori, S. De Feyter, J. Hofkens, M. Van der Auweraer, F.C. De Schryver, K. Brunner,J.W.Hofstraat Macromolecules, 36(2), 500-507 (2003)

May 06, 2003

Paul McEuen
Cornell University
Electronics and Mechanics with Single Molecules
Abstract:

It is now possible to make electronic and mechanical devices where an individual molecule is the active element. Examples include devices made from single-walled carbon nanotubes or single organic molecules. These molecular devices are proving to be wonderful systems for the study of the physics of materials at the nanometer scale. In this talk, I will review recent progress within our group on the electrical, electromechanical, and electrochemical properties of individual nanotubes and single molecules, as inferred from both transport and scanned probe measurements.

References:

"Coulomb blockade and the Kondo effect in single-atom transistors," Jiwoong Park, Abhay N. Pasupathy, Jonas I. Goldsmith, Connie Chang, Yuval Yaish, Jason R. Petta, Marie Rinkoski, James P. Sethna, Hector D. Abruna, Paul L. McEuen & Daniel C. Ralph, Nature, 417, 722-725 (2002).

"Scanned probe imaging of single-electron charge states in nanotube quantum dots," M.T. Woodside and P.L. McEuen, Science, 296, 1098 (2002).

April 29, 2003

Geert-Jan Boons
University of Georgia at Athens - Complex Carbohydrate Center
Modulating Biological Properties with Carbohydrate-Based Macromolecules and Nanoparticles
Abstract:

Multivalent binding events, in which multiple ligands on one entity simultaneously interact with multiple receptors on a complementary entity, are widespread in nature. This type of interaction has been demonstrated to be mechanically and functionally distinct from its monovalent alternative and relatively commonplace in carbohydrate-mediated biological events. The best-studied manifestations of multivalency include dramatic increased functional affinities, enhanced or altered selectivities, and initiation of cell signaling events.

We are employing synthetic glycopolymers and nanoparticles decorated with complex oligosaccharides to study mechanical and functional aspects of multivalent binding events. We have employed these compounds to unravel how bacterial cell wall components, such as peptidoglycan and lipopolysaccharides, induce clustering of cell surface receptor to initiate the production of endogenous proinflammatory mediators. The results of these studies have provided a scientific foundation for the development of therapeutic strategies to increase the survival rates of patients with sepsis. In another study, we have employed glycopolymers to unravel how multivalent interactions can be utilized to establish a block to polyspermy. These studies indicate that in X. laevis, the true biological function of multivalency is not to create an extremely tight-binding complex between a lectin and its natural ligand but, instead, to create a very stable protective layer that will not dissociate and is yet flexible enough to encapsulate the developing embryo. Finally, a new manifestation of multivalency will be discussed and it will been shown that bacterial sialidases, which contain a catalytic domain together with one or more carbohydrate-binding domains, are able to hydrolyze polyvalent substrates with much greater catalytic efficiency than monovalent counterparts. The striking difference in enzymatic activity displayed by these enzymes is explained by invoking a model wherein the catalytic- and lectin domains interact simultaneously with the polyvalent substrate. These findings have been exploited in the design of a novel polyvalent inhibitor of the sialidase of Vibrio cholerae that targets the lectin domain. This inhibitor is the first of its type in that it is not based on a sialic acid related scaffold and demonstrates a simple way of engineering exquisite selectivity for inhibitors of modular enzymes that possess a catalytic domain together with one or more binding domains.

References:

1. Arranz-Plaza, E., A. S. Tracy, A. Siriwardena, J. M. Pierce, and G. J. Boons. 2002. High avidity, low affinity multivalent interactions and the block to polyspermy. J. Am. Chem. Soc. 124: 13035-13046

2. Siriwardena, A., M. Jørgensen, M. A. Wolfert, N. L. Vandenplas, J. N. Moore, and G. J. Boons. 2001. Synthesis and proinflammatory effects of peptidoglycan-derived neoglycopeptide polymers. J. Am. Chem. Soc. 123: 8145-8146.

April 22, 2003

Craig Hawker
IBM Alamaden Research Center
Studies at the Interface of Organic and Polymer Chemistry: Functionalized Nanostructures for Advanced Microelectronic Applications
Abstract:

The fabrication of nanoscopic devices will increasingly rely on the precise control over materials properties and function on very small size scales, typically 5 nanometers to a few microns. The most promising approach to this is a 'bottoms-up' approach relying on chemistry, and recent developments in nanoparticles, shape persistent 3-dimensional macromolecules and 'living' free radical procedures have allowed the construction of tailor-made polymer molecules that facilitate this strategy. The design and application of these materials in advanced storage devices and microelectronics for the information technology industry will be discussed. Further examples will demonstrate that these new synthetic techniques may also have application in other areas such as bio-sensors, DNA chips, etc.

References:

James L. Hedrick, Teddie Magbitang, Eric F. Connor, Thierry Glauser, Willi Volksen, Craig J. Hawker, Victor Y. Lee, Robert D. Miller, "Application of Complex Macromolecular Architectures for Advanced Microelectronic Materials", Chem. Eur. J., 8, 3308-3319, 2002.

Shin, K.; Leach, K. A.; Goldbach, J. T.; Kim, D. H.; Jho, J. Y.; Tuominen, M.; Hawker, C. J.; Russell, T. P., "A Simple Route to Metal Nanodots and Nanoporous Metal Films" Nano Lett., 2, 933-936, 2002.

April 15, 2003

Calvin Quate
Stanford University, Electrical Engineering, Applied Physics
The Role of Scanning Probes in Nanotechnology and Nanoscience
Abstract:

If we are to reap the benefits that will surely come from the ongoing research in Nanoscience and Nanotechnology we must first 'see' nanostructures, which range in size from single molecules upwards to 100 nm. The Scanning Probes provide this and more. They can be used to 'see', to manipulate and to create nanostructures. They can be used for imaging, storage and for lithography. There are several modalities that have been tailored to image patterns of magnetic fields and the distribution of potentials.

Further, as demonstrated by Gimzewski, the microcantilevers serve as transducers for various signal domains. He has shown us how to use the deflection of levers to measure the stress induced by monomolecular films and the strength of molecular bonds with sensitivities that are unprecedented.

These are the topics that will form the basis of our presentation.

References:

Ultrathin PtSi layers patterned by scanned probe lithography; Snow,E.S.; Campbell,P.M.; Twigg,M.; Perkins,F.K.; Appl.Phys.Lett., 2001, 79, 8, 1109-1111, AIP, USA

The NanoDrive Project; Vettiger, P.; Binnig, G.; Scientific American, 2003, 288, 1, 46-53

April 08, 2003

Robert Metzger
University of Alabama
Unimolecular Rectifiers
Abstract:

Hexadecylquinolinium tricyanoquinodimethanide is confirmed to be a unimolecular rectifier, both by scanning tunneling microscopy and also as a Langmuir-Blodgett monolayer of this molecule, sandwiched between aluminum electrodes [1]. The current is due an allowed electronic transition between the highly polar zwitterionic ground state and an excited state with much less polarity [2]. Later, we observed the same rectification between gold electrodes: this required a deposition of "cold gold" atoms atop the organic monolayer [3]. The current is as high as 90,000 electrons per molecule per second [3]. The rectification ratio can be as high as 27, but decreases upon repeated scans [3]. Two new rectifiers have been found, 2,6-di[dibutylamino-phenylvinyl]-1-butylpyridinium iodide, which seems to be an interionic back-charge transfer rectifier [4], and dimethyanilinoazafullerene [5], in which Au stalagmites seem to form that can dominate the current-voltage behavior. Other molecules and mechanisms for rectification are under study. Molecular-scale electronics, or unimolecular electronics, is coming of age. Molecules, with their small size (1 to 3 nm) and fast intramolecular electronic transitions (ps to ns), may present a viable alternative to inorganic electronics when the present drive to faster and faster integrated circuits may become problematical. Gordon Moore's "law" [6] chronicled the doubling of the speed of computer circuits, as the separation ("design rule") between electronic components halved, at present roughly every 18 months. Commercial inorganic integrated circuits now use a 100 nm design rule, and 2 GHz microcomputers are now on sale.

These are exciting times. What is needed is a good way to interrogate a single molecule with three electrodes, and see power gain in an electronic device based on a single molecule. When that is done, the game will have been won.

References:

[1] R. M. Metzger, B. Chen, U. Höpfner, M. V. Lakshmikantham, D. Vuillaume, T. Kawai, X. Wu, H. Tachibana, T. V. Hughes, H. Sakurai, J. W. Baldwin, C. Hosch, M. P. Cava, L. Brehmer, and G. J. Ashwell, J. Am. Chem. Soc. 119, 10455 (1997).
[2] R. M. Metzger, Acc. Chem. Res. 32, 950 (1999).
[3] R. M. Metzger, T. Xu, and I. R. Peterson, J. Phys. Chem. B105, 7280 (2001).
[4] J. W. Baldwin, R. R. Amaresh, I. R. Peterson, W. J. Shumate, M. P. Cava, M. A. Amiri, R. Hamilton, G. J. Ashwell, and R. M. Metzger, J. Phys. Chem. B106, 12158 (2002).
[5] R. M. Metzger, J. W. Baldwin, W. J. Shumate, I. R. Peterson, P. Mani, G. J. Mankey, T. Morris, G. Szulczewski, S. Bosi, M. Prato, A. Comito and Y. Rubin, J. Phys. Chem. B107, 1021 (2003).
[6] G. E. Moore, Electronics, p. 114 (19 April 1965).
April 01, 2003

Campbell Scott
IBM Almaden Research Center
The Quest for Nanoscale Electronic Devices
Abstract:

Worldwide research on molecular electronic devices has been motivated by the increasing difficulty and cost of obeying Moore's Law and by the recognition that molecules are the smallest elements with controllable electrical properties. Analysis of the limits at which the scaling of silicon devices may fail, and the projected performance of CMOS circuitry as these limits are approached, sets the baseline for the desirable properties of molecular electronic devices. I will review the current status of molecular devices and outline the developments that must be made before they will provide the basis for a viable commercial technology.