Department of Chemistry

Neal R. Armstrong

Professor of Chemistry
Professor of Optical Sciences
nra@u.arizona.edu
Chemical Sciences Building 218
Phone: (520) 621-8242
Fax: (520) 621-8242

Honors

Alexander von Humboldt Senior Research Prize - T.U. Dresden & MPIP-Mainz, 2002
NSF-Chemistry Special Award for Creativity, 2000
Career Teaching Award, College of Science, University of Arizona, 1996

Education and Appointments

B.S. 1970, Chemistry, University of New Mexico
Ph.D. 1974, Analytical Chemistry, University of New Mexico

Research Interests

Analytical
Materials Synthesis and Characterization
Surface Science
Bioanalytical
Instrumentation
Polymers

Research Summary

Molecular Assemblies/Organic Electroluminescent and Photovoltaic Materials/Interfacial Science/Electrochemistry

RECENT RESEARCH HIGHLIGHTS:
	Recent studies of organic solar cells have focused on heterojunctions based on near-IR absorbing phthalocyanines (Pc) and C60, and the impact of phase changes of the Pc on photovoltaic performance. Increases in short-circuit photocurrent (J SC) are accompanied by changes in open-circuit photopotential (V OC), which correlated with changes in frontier orbital energy offsets, determined by UV-photoelectron spectroscopy (UPS).
Surface/interface characterization techniques, such as UPS/XPS and conducting tip AFM (C-AFM) are essential components of our research studies of organic/organic’ heterojunctions, and the heterojunctions between transparent conducting oxides (TCO) and organic films.
	We have recently demonstrated the formation of highly ordered phthalocyanine thin films, using solution deposition of Pcs with H-bonding side chains. C-AFM studies have allowed the elucidation of the conductivity per Pc layer – leading to formation of new PV devices based on these ordered materials.
We have recently shown that new photovoltaic poly(thiophene) materials can be grown, and nano-textured, via electrodeposition. Device performance is directly correlated with the degree of electrochemical doping of the polymer film.
	Semiconductor nanoparticles (e.g. CdSe) can be ligand-capped with electroactive functional groups, allowing for their electrochemical incorporation into polymer hosts. The resultant thin film materials can be used as photoelectrochemical catalysts for H 2-production, or as sensitizers in new hybrid material solar cells.
Organic light emitting diodes can be combined with organic photovoltaic detectors to create new chemical sensor platforms, emphasizing the convenience and simplicity of an all on-chip platform, where light source and detector are combined to do ATR spectrometry, refractometry and spectroscopy.
Current Research Funding:
“ Ultrathin Film Molecular Electronic Materials: Self-Organizing Discotic Mesophases and Organic Heterojunctions,” National Science Foundation.
“Critical Interfaces in Organic Solar Cell and High Energy Density Capacitor Nano-Materials,” Office of Naval Research.
“Electrochemically Wired” Semiconductor Nanoparticles: Toward Vectoral Electron Transport in Hybrid Materials –with Jeff Pyun, Scott Saavedra, Department of Energy, Basic Energy Sciences – Solar Hydrogen Initiative.
“Ion channel/membrane arrays on electroactive waveguides for biomolecular assays,” with Scott Saavedra, Craig Aspinwall, Sergio Mendes, Henry K. Hall, National Institutes of Health.
Member of the “Science and Technology Center for Materials and Devices for Information Technology Research,” Division of Materials Research -- National Science Foundation.
“Photosensitized Electron Transfer in Semiconductor Nanoparticle-Polymer Hybrid Materials,” with S. Scott Saavedra, Jeff Pyun, Arizona Research in Solar Energy (AzRISE).

Selected Publications

“Discotic Mesophase Materials: Their Use in Organic Field-Effect Transistors and Organic Photovoltaics,” Neal R. Armstrong, Wei Xia, Britt Minch, Adam Simmonds, Chet Carter, Carrie L. Donley, Rebecca A.P. Zangmeister, Anthony Drager, Samir K. Cherian, Lynn LaRussa, Bernard Kippelen, Seunghyup Yoo, Benoit Domercq, David L. Mathine, David F. O’Brien, in “Electron Transfer in Nanomaterials,” G. Rumbles, T. Lian, K. Murakoshi, eds. ECS Publications – PV 2004-22, 376-384 (2006).
“pH-Sensing Properties of Poly(Aniline) Ultrathin Films Self-Assembled on Indium-Tin Oxide,” Chenhao Ge, Neal R. Armstrong, S. Scott Saavedra, Analytical Chemistry, 79, 1401-1410, (2007).
“Small Molecule Chemisorption on Indium-Tin Oxide Surfaces: Enhancing Probe Molecule Electron Transfer Rates and the Performance of Organic Light Emitting Diodes,” Chet Carter, Michael Brumbach, Carrie Donley, Richard D. Hreha, Seth R. Marder, Benoit Domercq, SeungHyup Yoo, Bernard Kippelen, Neal R. Armstrong, J. Phys. Chem. B., 2006 110, 25191-25202.
“Modification of Indium-Tin Oxide Electrodes with Thiophene Copolymer Thin Films: Optimizing Electron Transfer to Solution Probe Molecules,” F. Saneeha Marrikar, Michael Brumbach, Dennis H. Evans, Ariel Lebrón-Paler, Jeanne E. Pemberton, Ronald J. Wysocki, Neal R. Armstrong, Langmuir, 23, 1530-1542 (2007).
“Potential-Modulated, Attenuated Total Reflectance Spectroscopy of Poly(3,4 Ethylenedioxythiophene) (PEDOT) and Poly(3,4-Ethylenedioxythiophene Methanol) (PEDTM) Copolymer Films on Indium-Tin Oxide,” Walter J. Doherty III, Ronald J. Wysocki Jr., Neal R. Armstrong, and S. Scott Saavedra, J. Phys. Chem. B. 110, 4900-4907 (2006).
“Electrochemical Copolymerization and Spectroelectrochemical Characterization of 3,4-Ethylenedioxythiophene (EDOT) and 3,4-Ethylenedioxythiophene Methanol (EDTM) Copolymers on Indium-Tin Oxide,” Walter Doherty, Ronald Wysocki, Neal R. Armstrong, S. Scott Saavedra, Macromolecules, 39, 4418-4424 (2006).
“Conducting Polymer Growth in Porous Sol-Gel Thin Films: Formation of Nanoelectrode Arrays and Mediated Electron Transfer to Sequestered Macromolecules,” Walter J. Doherty III, Neal R. Armstrong, S. Scott Saavedra, Chemistry of Materials, 17, 3652-3660 (2005).
"Modification of Transparent Conducting Oxide (TCO) Electrodes Through Silanization and Chemisorption of Small Molecules," Michael Brumbach, Neal R. Armstrong, Encyclopedia of Electrochemistry. Volume 10 - Modified Electrodes, M. Fujihira, I. Rubenstein, J. Rusling, (Volume 10 eds.), A.J. Bard, M. Stratmann, eds. Wiley-VCH, 15-29 (2007).
“Octakis(2-benzyloxyethylsulfanyl) Copper (II) Phthalocyanine: A New Liquid Crystalline Discotic Material with Benzyl-Terminated, Thioether-linked-Side Chains,” Britt A. Minch, Wei Xia, Carrie L. Donley, Ryan M. Hernandez, Chet Carter, Michael D. Carducci, Alice Dawson, David F. O’Brien, Neal R. Armstrong, Chemistry of Materials, 17, 1618-1627 (2005).
“LB Films of Rod-Like Phthalocyanine Aggregates: Specular X-Ray Reflectivity Studies of the Effect of Interface Modification on Coherence and Microstructure,” Wei Xia, Britt Minch, Mike Carducci, N.R. Armstrong, Langmuir, 20, 7998-8005 (2004).
“Anisotropies in the Electrical Properties of Rod-Like Aggregates of Liquid Crystalline Phthalocyanines: D.C. Conductivities and Field-Effect Mobilities,” C.L. Donley, R.A.P. Zangmeister, W. Xia, B. Minch, A.S. Drager, S.K. Cherian, L. LaRussa, B. Kippelen, B. Domercq, D.L. Mathine, D.F. O’Brien, N.R. Armstrong, Journal of Materials Research, 19, 2087- 2099 (2004).
“Interface Dipoles Arising from Self-Assembled Monolayers on Gold: UV-Photoemission Studies of Alkanethiols and Partially Fluorinated Alkanethiols,” D. Alloway, M. Hofmann, D.L. Smith, N.E. Gruhn, A.L. Graham, R. Colorado, Jr., V.H. Wysocki, T. R. Lee, P.A. Lee, N.R. Armstrong, J. Phys. Chem. B. 107, 11690-11699 (2003).

“Anisotropies in the Electrical Properties of Rod-Like Aggregates of Liquid Crystalline Phthalocyanines: D.C. Conductivities and Field-Effect Mobilities,” C.L. Donley, R.A.P. Zangmeister, W. Xia, B. Minch, A.S. Drager, S.K. Cherian, L. LaRussa, B. Kippelen, B. Domercq, D.L. Mathine, D.F. O’Brien, N.R. Armstrong, Journal of Materials Research, 19, 2087- 2099 (2004).
“Interface Dipoles Arising from Self-Assembled Monolayers on Gold: UV-Photoemission Studies of Alkanethiols and Partially Fluorinated Alkanethiols,” D. Alloway, M. Hofmann, D.L. Smith, N.E. Gruhn, A.L. Graham, R. Colorado, Jr., V.H. Wysocki, T. R. Lee, P.A. Lee, N.R. Armstrong, J. Phys. Chem. B. 107, 11690-11699 (2003).