In this research supported by the Analytical and Surface Chemistry Program, Professor Ferguson and his group will examine and explore new methods for the selective placement of monolayer films on gold surfaces. Self-assembly of monolayers on gold and other substrates has provided a convenient and facile method for surface modification that is useful in a variety of fields, ranging from biology to electrical engineering. The facility of the method, however, belies an important limitation -difficulty in controlling the location of monolayer formation when more than one possible substrates present. Instead of relying on spontaneous reactions to form monolayers, these researchers will use electrochemistry to direct the self-assembly, thereby significantly increasing the level of spatial and chemical control in this widely used process.
The impact of this research should be broad and significant because it seeks to extend the substantial current usefulness of self-assembled monolayers (SAMs) in science and technology. For example, the results of these studies should be valuable in the on-going development and refinement of an emerging technology, chemically diverse sensor arrays (i.e., "ENoses" and "ETongues"). Such array sensors have attracted increasing attention, especially in light of our nation's recent focus on homeland security. A key challenge in this area, however, has been the preparation of different coatings on neighboring microelectrodes. By using electrical potential to control the reactivity between a potential adsorbate and an electrode surface, these studies aim to harness richness of chemical structure compatible with self-assembly and provide an unprecedented level of chemical diversity in such electrode arrays. The project will integrate research and education by development of a cross-discipline Chemistry/Electrical Engineering undergraduate laboratory. Electrical Engineering students will fabricate a device, Chemistry students will prepare and analyze monolayers on gold metallization in the device, and both groups will participate in measuring and analyzing the performance of the device.
This project addressed one of the most fundamental goals of chemical research —to find new ways to manipulate matter at the molecular scale so that it may have useful effects beyond that scale. Our studies focused on the modification of individual electrode surfaces on a microelectronic chip by incorporating an electrical 'on-off switch' to direct chemistry only to the desired surface. The result is a stepwise method for producing arrays of electrodes, each bearing its own chemical structure, as summarized schematically in the accompanying figure. This project also allowed us to develop new insights into chemical processes, as well as new methods for analyzing complex surfaces, relevant to the systems we studied. The scientific discoveries resulting from this project are potentially useful in the development and refinement of emerging sensor technology (e.g., 'electronic noses') and molecular diagnostics that require the precise placement of particular chemical species at particular locations on a surface. In addition to fundamental research, this project has also contributed to the education of numerous graduate and undergraduate students, half of whom are women. These students were involved in all aspects of the project, from the design and conduct of experiments to the interpretation of the results. Our studies have resulted in several publications in peer-reviewed journals, presentations at professional conferences, and invited talks at other colleges and universities. We also successfully incorporated our research into the undergraduate curriculum at Lehigh University by designing a 2-week laboratory experiment based on our research that was integrated into one of the upper level courses in the Chemistry Department (Chem 335, Advanced Chemistry Laboratory II) during the spring 2011 semester.
