Nanomaterials: Electronic, Photonic, and Bionic Applications

 David Bahr
Susmita Bose
K.W. Hipps
Marie-Pierre Laborie
Alexander D. Li

Dr. Kerry Hipps received a Ph.D. in chemical physics from Washington State University in 1977. He was awarded a National Science Foundation-Energy Related Postdoctoral Fellowship, which he used to study at the University of Michigan. He joined the faculty at WSU as an assistant professor in 1979 and rose through the ranks to full professor in 1984. He is a founding member of the Material Science Program. He is an Alfred P. Sloan Fellow and is recognized by the University as a distinguished researcher. He is the author of more than 118 scientific publications. National Science Foundation, Public Research Foundation, Research Corp., and the Environmental Protection Agency have supported his research. He is best known for his work on electron tunneling and for striking STM images of metalorganic molecules. He received awards for his teaching and is currently organizing an American Chemical Society funded summer school — “Physical Chemistry on the Nanometer Scale” (www.wsu.edu/~nano/).

Chemistry and Materials Science
K. W. Hipps
Electron Transfer at the Sub-molecular Level

Scanning tunneling microscopy (STM) and orbital mediated tunneling spectroscopy (OMTS) are used to probe the structure and electronic states of single molecules. Atomic force microscopy (AFM) is used to study nanomechanical properties.
OMTS measures both occupied and unoccupied states of molecules thereby obtaining ‘finger prints’ that allow the identification of physically similar molecules.

OMTS can be measured with atomic precision. Thus, one can determine which parts of molecules contribute to a particular electronic state. This also allows us to evaluate how changes in environment experienced on the molecular scale affect the electronic states of a particular molecule.

The STM image taken at an appropriate applied bias voltage (as determined by OMTS) shows the physical origin of electrons in oxidation processes and their destination in reduction. The figure shows an example of this.

When the tunneling electron energy is adjusted such that the tunneling process does not involve direct use of molecules orbitals, the STM image (center) is very similar to a conventional molecular model. If the tunneling electrons are near resonant with the highest occupied molecular orbital (oxidation) or the lowest energy unoccupied orbital (reduction) very different pictures result [left and right images, respectively]. When the molecule is oxidized, charge flows from the carbon framework of the porphyrin ring. When it is reduced, charge is injected into the central nickel(II) ion and the coordinating nitrogens.

AFM is used to measure the mechanical properties of biological particles and Langmuir-Blodgett films.

Bottom-Up Construction
Our goal is the development of methods for the rational ‘bottom up’ construction of nanostructures and the systematic design of self organized layers. We focus on the production of two-dimensional surface structures using weak non-covalent interactions. Our work follows closely the three-dimensional ideas of crystal engineering and applies these concepts to molecular systems constrained to two dimensions by physisorption on a metal or liquid surface.

Contact Information
Kerry W. Hipps, Ph.D.
Professor
Chemical and Materials Science

Washington State University
PO Box 644630
Pullman, WA 99164-4630

Telephone: 509-335-3033
E-mail: hipps@wsu.edu