California NanoSystems Institute
CNSI
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June 01, 2004

Tony Cheetham
UCSB
Hybrid Inorganic-Organic Nanomaterials
Inorganic and organic nanomaterials have been widely studied in recent years and there have been some spectacular discoveries in these two important fields. These developments, however, have not been paralleled by similar progress in hybrid (i.e. inorganic-organic) nanomaterials, which offer a wide range of chemical and physical properties that are only just beginning to be explored. The presentation will focus on three important classes of hybrid materials in which the inorganic and organic components are segregated at the nano-level: (i) hybrid nanocomposities, typically involving inorganic nanoparticles in organic polymers; (ii) coordination polymers, which we can define as extended arrays composed of metal atoms or clusters bridged by polyfunctional organic molecules; and (iii) hybrid frameworks in which the metal-oxygen-metal (M-O-M) linkages are one-, two- or three-dimensional; the figure shows an interesting example of this third class.

May 25, 2004

Viola Vogel
University of Washington
Switching the Functional Display of Biological Macromolecules by Mechanical Force
Abstract:

Unraveling how mechanical force can switch protein function is critical to learning how mechanical forces regulate cell functions, from force sensing to gene expression. The function of cells is tightly controlled by their interactions with the surrounding extracellular matrix. Experimental and computational techniques are used to investigate how tension applied to extracellular matrix proteins affects the exposure of their molecular recognition sites. A masterpiece engineered at the nanoscale is the adhesion protein fibronectin and modern nanotools give completely new insights into how force-induced structural perturbations affect its multiple functions. Second, we discovered that the function of the bacterial adhesin fimH is also regulated by mechanical force. A structural mechanism and the resulting functional implications will be discussed.

Selected Literature:

V. Vogel, G. Baneyx, The tissue engineering puzzle: a molecular perspective, Annual Review Biomed. Eng., 5 (2003) 441-463

G. Baneyx, L. Baugh, V. Vogel, Fibronectin extension and unfolding within cell matrix fibrils controlled by cytoskeletal tension, Proc. Natl. Acad. Sci. USA, 99 (2002) 5139-5143

D. Craig, M. Gao, K. Schulten, V. Vogel, Structural insights how sequence variations tune the mechanical stability of fibronectin type III modules, Structure, 12 (2004) 21-30.

W. E. Thomas, E. Trintchina, M. Forero, V. Vogel, E. Sokurenko, Bacterial adhesion to target cells enhanced by shear-force, Cell, 109 (2002) 913-923.

May 18, 2004

Homme Hellinga
Duke University
Protein Design: Theory, Experiments, and Applications in the Bionanosciences
Abstract:

Computational protein design has now advanced to the stage where it is possible to build new proteins with controlled functions. Such designed proteins have been incorporated as nanosensors into devices, in synthetic signal transduction pathways, and in metabolic pathways. Custom-built nanoscale components for use in nanostructured biomaterials and synthetic biological system is now within reach. This seminar will show how such components can be designed and built, and offer examples of what we can do with this new technology.

References:

D.E. Benson, D.W. Conrad, R. M. de Lorimier, S.A. Trammell, H.W. Hellinga (2001) Design of bioelectronic interfaces by exploiting hinge-bending motions in proteins. Science, 293:1641-1644

L.L. Looger, M.A. Dwyer, J.J. Smith (2003) Computational design of receptor and sensor proteins with novel functions. Nature, 423:185-190

May 11, 2004

Grant Willson
University of Texas, Austin
Step and Flash Imprint Lithography: A Low Cost Nanoscale Printing Technology
The drive to manufacture semiconductor devices with ever smaller features has driven imaging materials science and technology for about three decades. Billions of dollars have been spent in efforts to devise methods and materials that enable the printing of ever smaller features. The most advanced devices in full scale production have minimum features in the range of 70-90nm and fully functional transistors with 10nm gates have been characterized. The lithographic process that has been used to generate these structures is becoming extremely expensive and the cost of the process threatens the economics of the industry. A very different, lower cost high resolution patterning technology is emerging. Imprint lithography loosely defines this emerging set of techniques that includes several forms of embossing, stamping and molding that are showing great promise as low cost methods for producing nanostructures. These techniques take many different forms, each of which has its own special applicability. The technique we call Step and Flash Imprint Lithography is designed to allow the fabrication of high resolution, high aspect ratio images that can be aligned with precision. The process accurately replicates arbitrary shapes as small as 20nm and structures smaller than 10 nanometers in width have been faithfully reproduced. The state of high resolution imaging processes for production of devices with nanoscale features will be presented with emphasis on the Step and Flash Imprint Lithography Process.

May 04, 2004

Frank van Veggel
University of Victoria
SEMINAR CANCELLED

April 27, 2004

Bruce Dunn
UCLA


Streaming Video
  

Assembling Nanodimensional Materials into Energy Storage Systems
Abstract:

A growing body of experimental evidence indicates that nanodimensional materials exhibit improved electrochemical properties compared to their bulk counterparts. A key challenge with these materials is their assembly into electrode structures that retain the nanodimensional architecture and provide meaningful levels of power. This talk will describe our work on vanadium oxide aerogels. The high surface area and interconnected mesoporosity of these materials enhance their gravimetric energy density and lead to unique electrochemical behavior that combines both battery- and capacitor-like responses.[1] By tailoring the sol-gel chemistry, we have established methods for assembling aerogels into hierarchical structures and high-performance electrodes that incorporate carbon nanotubes.[2] Three-dimensional batteries, a new direction for battery architectures, will also be presented.

References:

[1] W. Dong, D.R. Rolison and B. Dunn, Electrochem. Solid State Letts, 3 (2000) 457.
[2] J.S. Sakamoto and B. Dunn, J. Electrochem. Soc. 149 (2002) A26.

April 20, 2004

Timothy Swager
MIT
Polyiptycenes: Nanostructures for Electronic, Photonic, and Structural Materials
Abstract:

This lecture will discuss the use of a three dimensional scaffolds based upon triptycene to organize molecules and polymers in host matrices and to generate materials with high degrees of free volume. The use of triptycenes to produce liquid crystal solutions of monomeric and polymeric chromophores with high optical anisotropy will be presented. To organize conjugated molecular wire structures stable solutions of conjugated poly(phenylene vinylene)s and poly(phenylene ethynylene)s in nematic liquid crystals have been produced as shown below. The polymers all contain triptycene unites fused into their backbone to obtain the high solubility needed to maintain solubility in complex liquid crystalline media. The polymers all displayed lower band gaps in the liquid crystal solvents relative to those obtained in standard solvents such as methylene chloride. Hence, the liquid crystal solution induces a chain extended highly conjugated structure in the polymers, which is generally associated with optimization of the polymer properties. Triptycenes having restricted rotation by multiple point attachment to the polymer backbone are shown to introduce free volume into the films, thereby lowering their dielectric constants. These characteristics are desired by the semiconductor industry for the next generation of microprocessors and memory to provide insulation of the increasingly shrinking features. The use of tryiptycenes in the formation of new high strength materials will also be demonstrated. In this case the free volume creates an interlocking structure capable of energy absorption and which also produces dramatic enhancements in the strength of materials.

References:

1. Long, T. M.; Swager, T. M. "Using "Internal Free Volume" to Increase Chromophore Alignment" J. Am. Chem. Soc. 2002, 14, 3826-3827.
2. Zhu, Z.; Swager, T. M. "Conjugated Polymer Liquid Crystal Solutions: Control of Conformation and Alignment" J. Am. Chem. Soc. 2002, 124, 9670-9671.
3. Long, T. M.; Swager, T. M. ""Internal Free Volume" Approaches Toward Low-k Dielectric Materials" J. Am. Chem. Soc. 2003, 125, 14113-14119.

April 13, 2004

Jerry Atwood
University of Missouri, Columbia
Synthesis and Applications of Molecular Capsules
The enclosure of chemical space is one of the essential attributes of a biological system. We have previously shown that macrocycles can serve as building blocks for very large assemblies. In particular, calixarenes and resorcinarenes may be used to enclose space in a manner consistent with the principles of solid geometry attributed to Plato and to Archimedes. The ability of macrocycles to effect the construction of hydrogen-bonded spherical molecular capsules is due to focussed functionality. Aided by the concepts of solid geometry and by an understanding of focussed functionality, we have now prepared a range of new, very large capsules. The use of pyrogallol[4]arenes to form hexamer 1 is particularly noteworthy. These hydrogen bonded molecular capsules are both stable and soluble in water. We have also developed a range of single-molecule molecular capsules, 2, which are sealed by hydrogen bonds. Applications of these capsules in drug delivery are being investigated.

References:

[1] L. R. MacGillivray and J. L. Atwood, Nature 1997, 389, 469.
[2] J. L. Atwood, L. J. Barbour, and A. Jerga, "Storage of Methane and Freon by Interstitial an der Waals Confinement," Science, 296, 2367 (2002).
April 06, 2004

Mihri Ozkan
UC Riverside
Nanotechnology: Applications in Biology and Engineering
Abstract:

New advances in nanoscience helped to enhance the functionality of devices or existing components that are used in diverse fields. For example, nanocrystals were adopted both for applications in biology and engineering. I will give examples both from others and from my own laboratory where we used the nanocrystals for detection of DNA and also for building devices such as LEDs or diodes.

References:

1. Ravindran S, Chaudhary S, Colburn B, Ozkan M, Ozkan CS, "Covalent coupling of quantum dots to multiwalled carbon nanotubes for electronic device applications" , Nano Letter 3 (4): 447-453, 2003.
2. S. Chaudhary, W. C. W. Chan, C. S. Ozkan, M. Ozkan, "Trilayer Hybrid Polymer-Quantum Dot Light Emitting Display", Applied Physics Letters 2004. (in press)