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.
Preparation of bioresorbable polymer/calcium sulfate composites. Redepenning, Jody. (Board of Regents of the University of Nebraska, USA). PCT Int. Appl. (2008), 26pp. CODEN: PIXXD2 WO 2008095083 A1 20080807 Application: WO 2008-US52624 20080131. Priority: US 2007-887414 20070131. CAN 149:224782
TI Measurement of mean ionic activity coefficients for tetra-n-butyl ammonium salts of PF6- and [B(C6F5)(4)](-) in tetrahydrofuran and acetonitrile, Stafford, N., Castro-Narro, E., Redepenning, J., Russian Journal of Electrochemistry, (2008), 44 (1), 60-66.
Reconstruction of Anorganic Mammalian Bone by Surface-Initiated Polymerization of L-Lactide. Wiegand, Troy, Karr, Jeremy, Steinkruger, Jay D., Hiebner, Kris, Simetich, Bobby, Beatty, Mark, Redepenning, Jody. Department of Chemistry, University of Nebraska, Lincoln, Ne, USA. Chemistry Materials (2008) ACS ASAP. Publisher: American Chemical Society.
Electrolytic deposition of coatings for prosthetic metals and alloys, Redepenning, Jody (USA). U.S. Pat. Number 11/254,710. (2008)
Measurement of mean ionic activity coefficients for tetra-n-butyl ammonium salts of PF-6 and [B(C6F5)4]- in tetrahydrofuran and acetonitrile. Stafford, N.; Castro-Narro, E.; Redepenning, J.. Electronics R&D Group, American Air Liquide, Newark, DE, USA. Russian Journal of Electrochemistry (2008), 44(1), 60-66. Publisher: Pleiades Publishing, Ltd.
Bioresorbable polymer reconstituted ceramic matrixes. Redepenning, Jody. (University of Nebraska Office of Technology Development, USA). PCT Int. Appl. (2007), 38pp.
Bioresorbable polymer reconstituted bone and methods of formation thereof. Redepenning, Jody. (University of Nebraska, USA). PCT Int. Appl. (2007), 39pp.
Atomic motion in ferromagnetic break junctions - Response A. Sokolov, C. Zhang, E. Y. Tsymbal, J. Redepenning, B. Doudin, Nature Nanotechnology 2, 522 (2007).
Quantized magnetoresistance in atomic-size contacts A. Sokolov, C. Zhang, E. Y. Tsymbal, J. Redepenning, B. Doudin, Nature Nanotechnology 2, 175 (2007).
Nonextensivity in magnetic nanoparticle ensembles Binek, Ch.; Polisetty, S.; He, Xi; Mukherjee, T.; Rajesh, R.; Redepenning, J.. Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA. Physical Review B: Condensed Matter and Materials Physics (2006), 74(5), 054432/1-054432/7.
Alkali metals Redepenning, Jody. University of Nebraska, Lincoln, NE, USA. Editor(s): Bard, Allen J.; Stratmann, Martin. Encyclopedia of Electrochemistry (2006), 7a 333, 335-349.
Bioresorbable composites, their formation, and use in bone replacement Redepenning, Jody G.. (University of Nebraska, USA). PCT Int. Appl. (2006), 35 pp.
Anisotropy magnetoresistance of quantum ballistic nickel nanocontacts C. S. Yang, C. Zhang, J. Redepenning, B. Doudin, Journal of Magnetism and Magnetic Materials 2005, 286, 186-190.
Determination of Activity Coefficients for Non-Aqueous Electrolytes N. A. Stafford, J. Redepenning, Abstracts, 40th Midwest Regional Meeting of the American Chemical Society, Joplin, MO, United States, October 26-29 2005, LIN05-190.
Polymerization of L-Lactide with Solid Hydroxyapatite J. J. Karr, J. Redepenning, Abstracts, 40th Midwest Regional Meeting of the American Chemical Society, Joplin, MO, United States, October 26-29 2005, LIN05-186.
The anomalous \"stiffness\" of biphenydimethyldithiol D. Q. Feng, P. A. Dowben, R. Rajesh, J. Redepenning, Applied Physics Letters 2005, 87, 181918/181911-181918/181913.
In situ magnetoresistance of nickel nanocontacts C. S. Yang, C. Zhang, J. Redepenning, B. Doudin, Applied Physics Letters 2004, 84, 2865-2867.
Orientation and bonding of biphenyldimethyldithiol A. N. Caruso, R. Rajesh, G. Gallup, J. Redepenning, P. A. Dowben, Journal of Physics: Condensed Matter 2004, 16, 845-860.
Orientation and Bonding of 4,4'-Biphenyldiisocyanide A. N. Caruso, R. Rajesh, G. Gallup, J. Redepenning, P. A. Dowben, Journal of Physical Chemistry B 2004, 108, 6910-6914.
Reversible Electrochemical Generation of a Rhodium(II) Porphyrin: Thwarting Disproportionation with Weakly Coordinating Anions H. Sun, F. Xue, A. P. Nelson, J. Redepenning, S. G. DiMagno, Inorganic Chemistry 2003, 42, 4507-4509.
Resonant tunneling in magnetoresistive Ni/NiO/Co nanowire junctions A. Sokolov, I. F. Sabirianov, E. Y. Tsymbal, B. Doudin, X. Z. Li, J. Redepenning, Journal of Applied Physics 2003, 93, 7029-7031.
Electrochemical preparation of chitosan/hydroxyapatite composite coatings on titanium substrates J. Redepenning, G. Venkataraman, J. Chen, N. Stafford, Journal of Biomedical Materials Research, Part A 2003, 66A, 411-416.
Metal/self-assembled monolayer/metal junctions for magnetoelectronic applications Y. A. Ovchenkov, C. Zhang, J. Redepenning, B. Doudin, Materials Research Society Symposium Proceedings 2003, 746, 169-173.
The electronic structure of metal/alkane thiol self-assembled monolayers/metal junctions for magnetoelectronics applications Y. A. Ovchenkov, H. Geisler, J. M. Burst, S. N. Thornburg, C. A. Ventrice, C. Zhang, J. Redepenning, Y. Losovyj, L. Rosa, P. A. Dowben, B. Doudin, Chemical Physics Letters 2003, 381, 7-13.
Substrate dependent bonding of chemisorbed 1,1'-biphenyl-4,4'-dimethanethiol A. N. Caruso, R. Rajesekaran, J. Redepenning, Y. B. Losovyi, P. A. Dowben, Materials Research Society Symposium Proceedings 2003, 775, 135-140.
In-situ characterization of ultra-small magnetic junctions made by electrochemical techniques A. Sokolov, J. R. Jennings, C. S. Yang, J. Redepenning, B. Doudin, Materials Research Society Symposium Proceedings 2001, 674, T5.9.1-T5.9.7.
Influence of supporting electrolyte activity on formal potentials measured for dissolved internal standards in acetonitrile J. Redepenning, E. Castro-Narro, G. Venkataraman, E. Mechalke, Journal of Electroanalytical Chemistry 2001, 498, 192-200.
Electrochemistry and in situ spectroelectrochemistry of a perfluorinated rhodium porphyrin in coordinating and noncoordinating media S. G. DiMagno, H. Sun, J. G. Redepenning, F. Xue, Abstracts of Papers, 221st ACS National Meeting, San Diego, CA, United States, April 1-5, 2001, INOR-109.