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Lloyd E. and Florence M. West Endowed Professor of Chemistry
Adjunct Professor of Chemical Engineering
Co-Director, PNNL/UW Joint Institute for Nanotechnology
Ph.D. University of Texas at Austin, 1979
(Nanoscience, Environmental Catalysis, Physical and Bioanalytical Chemistry)
(206) 616-6085
Email: campbell@chem.washington.edu
Campbell group website
Research Interests
The Campbell research group pursues basic experimental research concerning environmental and energy-related 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, and (2) reactivity and physical chemistry at solid surfaces.
Environmental and Energy-Related 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 decreasing greenhouse gasses. Since there is a correlation between areas with high cancer death 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.
Transition metal catalysts are typically in the form of particles dispersed across the surface of some oxide 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 US comes out in the first 5 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. They 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 (Si in current commercial devices, but hopefully cheaper-to-make polymer films in the future). The Campbell group studies the energetics and electronic properties of these all-important interfaces. It 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 electronic 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.
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.
Thermodynamics and Kinetics of Nanomaterials
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. Their calorimetric measurements reveal that metal energies vary with particle size much more strongly than predicted by the Gibbs-Thomson relation, 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.
"Small Pd clusters, up to the tetramer at least, are highly mobile on the MgO(100) surface", L. Xu, G. Henkelman, C. T. Campbell and H. Jonsson, Phys. Rev. Letts. 95, 146103, 2005 (4 pages). reprint
"Growth and Sintering of Pd Clusters on a-Al2O3(0001)", S. L. Tait, L. T. Ngo, Q. Yu, S. C. Fain, Jr., and C. T. Campbell, J. Chem. Phys. 122, art. 064712, 2005. reprint
"Calorimetric Measurement of the Heat of Adsorption of Benzene on Pt(111)", H. Ihm, H. M. Ajo, J. M. Gottfried, P. Bera and C. T. Campbell, J. Phys. Chem. B, 108, 14627-33, 2004. (Issue in honor of G. Ertl). reprint
"Parallel, Quantitative Measurement of Protein Binding to a 120-Element Double-Stranded DNA Array in Real Time Using SPR Microscopy", J. Shumaker-Parry, R. A. Aebersold and C. T. Campbell, Anal. Chem. 76; 2071-2082, 2004. reprint
"The Effect of Size-Dependent Nanoparticle Energetics on Catalyst Sintering", C. T. Campbell, S. C. Parker and D. E. Starr, Science 298, 811-4, 2002. reprint
"Metal Adsorption and Adhesion Energies on MgO(100)", C. T. Campbell and D. E. Starr, J. Am. Chem. Soc. 124, 9212-18, 2002. reprint
American Chemical Society Arthur W. Adamson Award, 2007. [article]
Paul Hopkins Faculty Award of the Chemistry Department, 2006-7.
Alexander von Humboldt Research Award, 2003
ACS Award in Colloid or Surface Chemistry, 2001
John Yarwood Memorial Award of the British Vacuum Council, 1989
Dreyfus Teacher/Scholar Award, 1988
Alfred P. Sloan Research Fellowship, 1986