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Today's methods of energy transport and conversion and information storage are reaching their limits. Although organic molecules have the advantages of low-cost production and ease of processing, it is their tailorability that makes them viable replacements for the current technology in both areas. Additionally, numerous measurements acquired in bulk systems indicate that organic molecules may perform even better than the current state-of-the-art systems. It cannot be overstated how important the vast store of synthetic methodology will be in defining this next generation of devices. The research conducted in my laboratories creates new types of molecules that assemble into uniquely functioning devices. The cornerstone of this program is a vigorous synthetic effort that allows freedom of design so that new structural types can be created. Once the systems are synthesized, we investigate their molecular and macromolecular assembly characteristics to try to gain a deeper understanding of the interplay between molecular structure, assembly, and emergent function.
An unanswered question is how to devise general methods to assemble and interconnect organic structures into functioning molecular scale devices. To attain these crucial interconnections, several new types of self-assembly processes must be developed. For example, on a given surface, we do not know how to create useful and regular features on a scale of two to three nanometers. Even more challenging on this length scale is developing methodology to write complex surface patterns. One critical aspect is defining how the organic molecule can be efficiently interfaced with their substrates. These interconnections must be kinetically stable and at the same time provide a strong energetic match between the molecule and the surface. Once created, these types of templated surfaces will be useful for spatially addressing recognition and assembly events. For example, one could envision having several molecules arranging themselves between two patterned surfaces in close proximity to each other. In this way, the self-adjusting and plastic nature of reversibly formed assemblies could be used to compensate and maintain connectivity.
By developing reliable covalent trapping mechanisms, these systems could provide routes to self-assembled, molecular-scale wiring. This highlights how important it is for chemists to continue to develop novel molecularly based systems with several orthogonal recognition domains to attain a higher level of understanding in hierarchical assembly processes. The properties exhibited by particular small-scale devices could be significantly enhanced by not being randomized in bulk media. For example, if molecules were assembled from polar surfaces so that the nascent dipole was amplified through assembly, a polar superstructure could result. By synthetically adjusting the size of the assemblies, the nanostructures would be individually addressable with local probes. The length scale of association where the properties emerge (a consequence of polarity) could be determined experimentally. Moreover, it should also be possible to determine at what length scale these properties begin to break down from neighboring dipole interactions. Therefore, not only could these studies provide very efficient energy converting devices, they might also provide basic insight into the self-organization of polar materials. These challenges make it clear that this field of research is multidisciplinary. Students who study these problems will be required to master many tasks, including computer-aided design, organic synthesis, and analytical measurement. This broad-based education will serve to create a new set of employment opportunities for graduate and postdoctoral students in this field. To be sure, this multidisciplinary approach must not obscure the need for students to develop a strong background in organic synthesis, which will provide them with a means to adapt and grow as new research challenges emerge.
As an undergraduate student at the University of Texas at Austin, I was fortunate to have worked in the laboratories of Professor Marye Anne Fox. This experience revealed the joy of discovery that is chemical research. I try to pass on this experience because it is a vital part of under-graduate education in the chemical sciences. By incorporating a strong research component into the undergraduate curriculum, educators will empower future generations of chemists.
Colin Nuckolls |