Professor and B. Seymour Rabinovitch Endowed Chair in Chemistry
Adjunct Professor of Chemical Engineering
Adjunct Professor of Physics
Ph.D. University of Texas at Austin, 1979
(Nanoscience, Environmental Catalysis, Physical, and Bioanalytical Chemistry)
The Campbell group pursues basic experimental research concerning energy-related and environmental catalysis, interfaces in solar cells and microelectronics, and array-based biochemical analyses. The main unifying themes of this broad-ranging work are: 1) development of tools that measure effects at surfaces more sensitively than anywhere else in the world; 2) reactivity and physical chemistry at solid surfaces; and 3) kinetics and energetics of elementary steps in energy-related catalytic reactions on solid surfaces.
Energy-Related and Environmental Catalysis
Chemical reactions catalyzed by solid surfaces dramatically improve the world in which we live. Still, the need for basic and applied research in catalysis is stronger than ever. Improving catalysts, for example, could minimize the use of fossil fuels, thus helping solve the energy crisis while decreasing greenhouse gases. Since there is a correlation between areas with high cancer mortality rates and those with high densities of pollution, an important approach to cancer reduction is the “greening” of industrial and automotive chemical processes to minimize pollution, again by modifying existing catalysts or inventing new ones. Improved catalysts do this either directly, by minimizing polluting side products, or indirectly, by minimizing requirements for feedstocks that themselves create pollution upon production. One goal of the Campbell research group is to clarify why catalyst modifiers act to promote catalytic activity or selectivity, and how nanoscale features of the catalyst surface can tuned to make better catalysts.
Transition metal catalysts are typically in the form of particles dispersed across the surface of some oxide or carbon support. Metal chemical reactivity can be tuned by varying the metal particle size. When the particles are only a few nanometers across, they can be much more active and selective in catalysis than larger particles. Unfortunately, such metal nanoparticles often sinter (i.e., combine with nearby particles and grow larger) under reaction conditions. The Campbell group is trying to improve environmental catalysts to resist sintering. For example, substantial NOx reduction could be realized if catalysts for the complete combustion of methane with low NOx emissions could be found. While Pd nanoparticles on alumina are excellent for this reaction, their resistance to sintering needs improvement before they realize this dream. Over 90% of the pollution from cars in the U.S. comes out in the first five minutes after start-up, since the Pt and Pd catalysts in our catalytic converters do not work until they get very hot. Since supported Au nanoparticles can oxidize CO at room temperature, they might solve this so-called cold-start-up problem, but they suffer sintering problems. We study these systems with a wide array of experimental techniques. Theoretical calculations (DFT, kinetic Monte-Carlo, etc.) supply important complimentary energetic and dynamical insights.
Photovoltaic Devices: Metal / Polymer and Metal / Semiconductor Interfaces
In solar cells or photovoltaic devices, charge injection and extraction occurs at the interface between a metal or other conductor and one of the semiconducting materials (inorganic materials in most current commercial devices, but hopefully more cost effective polymer films in the future). The Campbell group studies the energetics and electronic properties of these all-important interfaces, and is the only group in the world that can measure the energetics of the surface reactions occurring during thin metal film growth or molecular beam epitaxy (MBE). They are applying their unique calorimeter that does this, together with other surface characterization techniques like electron and ion spectroscopies, to study problems at specific metal / polymer and metal / Si interfaces that are of importance not only in making solar cells, but also in making microelectronics, LEDs, electro-optic modulators, and opto-electric devices.
Thermodynamics and Kinetics of Nanomaterials for Energy Technologies
As the ability to produce nanomaterials such as nanodots and nanowires has advanced, it becomes more important to understand how the energy of the atoms in these materials is affected by their reduced dimensions. The Campbell group’s single-crystal adsorption calorimeter, this country’s first, has proven powerful in this respect, with calorimetric measurements revealing that metal energies vary with particle size much more strongly than predicted by the Gibbs-Thomson relation as taught in undergraduate physical chemistry textbooks. This has already been found to be crucial for accurate modeling of long-term sintering rates of metal nanoparticles in catalysts, but will no doubt also prove important in understanding the rapidly-developing field of nanomaterials and nanoelectronics.
Array-based Biochemical Analysis via SPR Microscopy
The Campbell group collaborates with biotechnologists to develop chips containing patterned microarrays of proteins which bind ligand and other protein, or DNAs whose sequences selectively bind proteins such as transcription factors, so that the chips serve as receptor arrays for sensitive, highly parallel detection of such proteins. Surface plasmon resonance (SPR) microscopy is being developed for probing large microarrays of biomolecules for their binding interactions with various partners and the kinetics of such binding. It is possible to simultaneously monitor binding kinetics on >1300 spots within a protein microarray with a detection limit of ~0.3 ng per cm2, or <50 femtograms per spot (<1 million protein molecules) with a time resolution of 1 s, and spot-to-spot reproducibility within a few percent. Such instruments should be capable of high-throughput kinetic studies of the binding of small (~200 Da) ligands onto large protein microarrays. The method is label free and uses orders of magnitude less of the precious biomolecules than standard SPR sensing. It also gives the absolute bound amount and binding stoichiometry.
"Surface chemistry: Key to control and advance myriad technologies” J. T. Yates Jr. and C. T. Campbell, Proc. National Academy of Sciences 108, 911-916, 2011.
"Adsorption Microcalorimetry: Recent Advances in Instrumentation and Application” M. C. Crowe and C. T. Campbell, Annual Rev. Analytical Chemistry, Vol. 4, 41-58, 2011.
"The Energy of Adsorbed Hydroxyl on Pt(111) by Microcalorimetry, W. Lew, M. C. Crowe, E. Karp, O. Lytken, J. A. Farmer, L. Árnadóttir, C. Schoenbaum and C. T. Campbell” J. Phys. Chem. C 115, 11586-11594, 2011.
"Insights into Catalysis by Gold Nanoparticles and their Support Effects through Surface Science Studies of Model Catalysts” C. T. Campbell, J. C. Sharp, Y. X. Yao, E. M. Karp and T. L. Silbaugh, Faraday Discussions 152, 227-39, 2011(invited).
"Towards Well-Defined Metal-Polymer Interfaces: Temperature-Controlled Suppression of Subsurface Diffusion and Reaction at the Ca / P3HT Interface” F. Bebensee, M. Schmid, H-P. Steinruck, C. T. Campbell, J. M. Gottfried, J. Am. Chem. Soc. (Communication), 132, 12163-5, 2010.
"Ceria Maintains Smaller Metal Catalyst Particles by Strong Metal - Support Bonding” J. A. Farmer and C. T. Campbell, Science 329, 933-936, 2010.
"Particle size dependent heats of adsorption of CO on supported Pd nanoparticles as measured with a single crystal microcalorimeter” J. H. Fischer-Wolfarth1, J. A. Farmer, J. M. Flores-Camacho1, A. Genest, I. V. Yudanov, N. Rösch, C. T. Campbell, S. Schauermann and H. J. Freund, Physical Review B (Rapid Communication) 81, 241416(R), 2010, 4 pages.
"The degree of rate control: how much the energies of intermediates and transition states control rates” C. Stegelmann, A. Andreasen, C. T. Campbell, J. Am. Chem. Soc. 131, 8077-8082, 2009 (Cover Article, highlighted in Science).
"Experimental measurements of the energetics of surface reactions” C. T. Campbell and O. Lytken, Surface Science 603, 1365-72, 2009.
"Catalytic Reaction Energetics by Single Crystal Adsorption Calorimetry: Hydrocarbons on Pt(111)” O. Lytken, W. Lew and C. T. Campbell, Chemical Society Reviews (invited in honor of Ertl’s Nobel Prize) 37, 2172-2179, 2008.
"SPR Microscopy and Its Applications to High-Throughput Analyses of Biomolecular Binding Events and Their Kinetics” C. T. Campbell and G. Kim, Biomaterials 28. 2380-2392, 2007.
Elected Fellow of the American Chemical Society, 2011.
Gerhard Ertl Lecture Award 2012
American Chemical Society Arthur W. Adamson Award for Distinguished Service in the Advancement of Surface Chemistry, 2007.
American Chemical Society Award in Colloid or Surface Chemistry (2001)
Editor-in-Chief of Surface Science (2002-present).
Fellow of the American Association for the Advancement of Science since 2010.
Ipatieff Lectureship (2010-11), Northwestern University.
Alexander von Humboldt Research Award (2003)