Christopher Exstrom, Professor
Department of Chemistry, UNK
University of Nebraska–Kearney
417 Bruner Hall, 905 W. 25th St.
Kearney, Nebraska 66849-1150
Professors Christopher Exstrom and Scott Darveau lead the UNK Solar Energy and Nanoscience Research Group (SENRG) which is active in the development and study of nanocrystalline semiconductor and noble metal materials. At UNK, our lab equipment and capabilities include a physical vapor deposition apparatus used for solid-state reactions and annealing, single-gun magnetron sputtering for substrate preparation, micro-Raman spectroscopy, ICP-OES for elemental analysis, infrared and UV-vis spectroscopy for bandgap measurements, and low-voltage electron microscopy for SEM and TEM imaging.
Much of our effort focuses on solvent-based preparations of nanocrystalline chalcopyrite and earth-abundant sulfide materials with potential applications in high-efficiency photovoltaic solar cells. The use of solvent in these preparations is an attractive, low-cost alternative to the existing high-vacuum techniques commonly employed in the solar cell industry. Efforts to maximize product compositional and structural control while minimizing reaction system cost and complexity have resulted in previously unreported nanocrystalline materials and preparation techniques.
In affiliation with the UNL-based Center for Nanohybrid Functional Materials, our group is investigating the formation, growth, and immobilization of branched Au nanoparticles for applications in nanoscale biosensors. There are several advantages to employing branched nanoparticles as biosensor device components in place of nanorods that are currently used: 1) branched nanoparticles have larger surface area-to-volume ratios than nanorods of equal mass (enabling the binding of more biosensor molecules), 2) excessively high concentrations of surfactants or other NP shape-directing agents are not necessarily required, and 3) one-pot syntheses are feasible.
- “M-M Bond-Stretching Energy Landscapes for M2(dimen)42+ (M = Rh, Ir; dimen = 1.8-dissocyanomenthane) Complexes,” Hunter, B.M.; Villahermosa, R.M.; Exstrom, C.L.; Hill, M.G.; Mann, K.R.; Gray, H.B., Inorganic Chemistry, 2012, 51, 6898-6905.
- “Thermoelectric Properties of p-type CuInSe2 Chalcopyrites Enhanced by Introduction of Manganese,” Yao, J.; Takas, N.J.; Schliefert, M.L.*; Paprocki, D.S.*; Blanchard, P.E.R.; Mar, A.; Exstrom, C.L.; Darveau, S.A.; Poudeu, P.F.P.; Aitken, J.A., Physical Review B, 2011, 84, 075203.
- “Properties of CuIn1-xGaxSe2 Films Prepared by the Rapid Thermal Annealing of Spray-deposited CuIn1-xGaxS2 and Se,” Slaymaker, L.E.*; Hoffman, N.M.*; Ingersoll, M.A.*; Jensen, M.R.*; Olejníček, J.; Exstrom, C.L.; Darveau, S.A.; Soukup, R.J.; Ianno, N.J.; Sarkar, A.; Kment, Š., Materials Research Society Symposium Proceedings, 2011, 1324, DOI: 10.1557/opl.2011.1152.
- “Formation of CuIn1-xAlxSe2 Thin Films Studied by Raman Scattering,” Olejníček, J.; Kamler, C.A.; Darveau, S.A.; Exstrom, C.L.; Slaymaker, L.E.*; Vandeventer, A.R.*; Ianno, N.J.; Soukup, R.J. Thin Solid Films, 2011, 519, 5329-5334.
- “CuIn1-xAlxS2 Thin Films Prepared by Sulfurization of Metallic Precursors,” Olejníček, J.; Slaymaker, L.E.*; Darveau, S.A.; Exstrom, C.L.; Kment, Š.; Prabukanthan, P.; Ianno, N.J.; Soukup, R.J. Journal of Alloys and Compounds, 2011, 509, 10020-10024.
- “Air Stable, Photosensitive, Phase Pure Iron Pyrite Nanocrystal Thin Films for Photovoltaic Application,” Bu, Y.; Yuan, Y.; Exstrom, C.L.; Darveau, S.A.; Huang, J., Nano Letters, 2011, 11, 4953-4957.
- “A Non-vacuum Process for Preparing Nanocrystalline CuIn1-xGaxSe2 Materials Involving an Open-air Solvothermal Reaction” Olejníček, J.; Kamler, C.A.; Mirasano, A.*; Martinez-Skinner, A.*; Ingersoll, M.*; Exstrom, C.L.; Darveau, S.A.; Huguenin-Love, J.; Diaz, M.; Ianno, N.J.; Soukup, R.J. Solar Energy Materials and Solar Cells, 2010, 94, 8-11.
- J. Olejní?ek, C.A. Kamler, A. Mirasano, A.L. Martinez-Skinner, M.A. Ingersoll, C.L. Exstrom, S.A. Darveau, J.L. Huguenin-Love, M. Diaz, N.J. Ianno, R.J. Soukup, "A Non-vacuum Process for Preparing Nanocrystalline CuIn1-xGaxSe2 Materials Involving an Open-air Solvothermal Reaction", Solar Energy Materials and Solar Cells, in press (2009), available online, doi:10.1016/j.solmat.2009.03.024.
- C.L. Exstrom, J. Olejní?ek, S.A. Darveau, A. Mirasano, D.S. Paprocki, M.L. Schliefert, M.A. Ingersoll, L.E. Slaymaker, R.J. Soukup, N.J. Ianno, C.A. Kamler, "Solvothermal Preparation, Processing, and Characterization of Nanocrystalline CuIn1-xAlxSe2 Materials", Materials Research Symposium Proceedings,accepted for publication (2009).
- C.A. Kamler, R.J. Soukup, N.J. Ianno, J.L. Huguenin-Love, J. Olejní?ek, S.A. Darveau, C.L. Exstrom, "Thin Films Formed by Selenization of CuInxB1-x Precursors in Se Vapor", Solar Energy Materials and Solar Cells, 93, 45-50 (2009).
- N.J. Ianno, R.J. Soukup, T. Santero, C.A. Kamler, J.L. Huguenin-Love, S.A. Darveau, J. Olejní?ek, C.L. Exstrom, "Copper-Indium-Boron-Diselenide Absorber Materials", Materials Research Symposium Proceedings,1012, Y03-21 (2007).
Graduates and Current Affiliations
(Note: The UNK Department of Chemistry has undergraduate programs only.)
- Laura Slaymaker, graduate school, University of Wisconsin
- Matt Jensen, graduate school, University of Minnesota
- Nathan Hoffman, graduate school, Washington State University
- Andrea Martinez-Skinner, graduate school, UNMC
- Nobutoshi Ota, graduate school, University of Illinois
- Ruth Udey, graduate school, Michigan State University
- A.L. Martinez-Skinner, graduate school, UNMC
- N. Ota, graduate school, University of Illinois
- R.N. Udey, graduate school, Michigan State University