Jody Redepenning
Professor
Department of Chemistry
535 Hamilton Hall
Phone: (402) 472-3533
Email: jredepen@unl.edu
Jody Redepenning's Chemistry Web Page
Current Research
There are aspects of analytical, physical, and inorganic chemistry in my research interests, but the primary focus is in the field of electrochemistry. Of particular interest is the use of electrochemistry to produce novel materials.
One example is the electrochemical deposition of calcium phosphate coatings on devices such as hip implants. It is clear that coatings of hydroxyapatite (Ca5(PO4)3OH) can promote new bone formation on orthopedic appliances by providing an inorganic scaffolding upon which living tissue can gain a foothold to rapidly stabilize the device. We recently developed a low temperature electrochemical procedure for reproducibly depositing calcium phosphates materials on metal surfaces. This non-line-of-sight procedure, which relies on the use of electrochemically induced pH jumps, can be used to uniformly coat irregularly shaped objects while maintaining control over deposit crystallinity. Our present investigations in this area are focused on a second generation of electrodeposited composite materials with mechanical properties similar to living bone, a material that can be viewed as a complex composite with mechanical properties very different from crystalline hydroxyapatite. One aspect of these research efforts is to determine the experimental conditions that will allow us to control the chemical and physical characteristics of hydroxyapatite/chitosan and hydroxyapatite/collagen composites coatings. Chitosan is a biopolymer that has found significant use in medial applications. Collagen, the primary organic component of bones and teeth, is another important biopolymer. Both are soluble in slightly acidic solutions and lend themselves to being deposited on metal surfaces using our technique.
In research efforts performed in collaboration with the research groups of Professor Bernard Doudin and Professor Peter Dowben in UNL’s Department of Physics, we are helping to prepare tunnel junctions that will be used to understand and control magnetoresistance phenomena. These collaborations involve the preparation and self-assembly of organic spacers that will be inserted into the junctions. Additionally, we are investigating the influence of nanocrystalline Co clusters on spin-dependent tunneling phenomena.
Finally, in a more fundamental electrochemical project, we have constructed a device for measuring electrolyte activities in nonaqueous electrochemical solvents. Reliable thermodynamic information concerning electrolytes is quite scarce in many nonaqueous solvents. This lack of information is a significant impediment to the field of electrochemistry, whether one is developing new electrochemical sensors, interpreting the potential of an electrochemically active site imbedded in an enzyme, or simply determining formal potentials for new molecules that are not soluble in water. Our results should be beneficial to chemists in many fields by providing simple benchmarks against which they can compare their own measurements. Electroorganic synthesis, the development photoelectrochemical cells and high-energy batteries, are among the fields that will be impacted by this research.
Recent Publications
N. Stafford, E. Castro-Narro, and J. Redepenning, "Measurement of Mean Ionic Activity Coefficients for Tetra-n-butylammonium salts of PF6- and [B(C6F5)4]- in Tetrahydrofuran and Acetonitrile," invited submission to special issue of Russian Journal of Electrochemistry, in press.
A. Sokolov, C. Zhang, E. Y. Tsymbal, J. Redepenning, and B. Doudin, "Atomic motion in ferromagnetic break junctions," Nature Nanotechnology 2, 522 (2007).
A. Sokolov, C. Zhang, E. Y. Tsymbal, J. Redepenning, and B. Doudin, "Quantized magnetoresistance in atomic-size contacts," Nature Nanotechnology 2, 175 (2007).
Ch. Binek, S. Polissetty, X. He, T. Mukherjee, R. Rajesh, and J. Redepenning, "Nonextensivity in magnetic nanocluster ensembles," Phys. Rev. B 75, 054432 (2006).
Jody Redepenning, "Alkali Metals," in Encyclopedia of Electrochemistry. Vol. 7. Inorganic Electrochemistry. A. J. Bard, Ed., Wiley-VCH, New York, 2006.
D. Q. Feng, P. A. Dowben, R. Rajesh, and J. Redepenning, "The anomalous ‘stiffness’ of biphenyldimethyldithiol," Applied Physics Letters 87, 181918 (2005).
C.-S. Yang, C. Zhang, J. Redepenning, and B. Doudin, "Anisotropy magnetoresistance of quantum ballistic nickel nanocontacts," Journal of Magnetism and Magnetic Materials 286, 186 (2005).
