This Research award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports work by Professor Raymond Schaak at the Pennsylvania State University to apply concepts from molecular chemistry to the synthesis of complex one-dimensional inorganic nanostructures. By developing a library of chemical reactions that transform one type of metal nanostructure into a more complex one, it will be possible to apply a total synthesis approach to the formation of inorganic nanowires using the concepts of orthogonal reactivity, protection/deprotection, and site-specific modification. This research will generate fundamental new knowledge about inorganic reactions that occur on nanoscale solids and will lay the groundwork for the synthesis of complex nanowires with target features that include composition gradients, homogeneous dopants, core-shell structures, and highly-crystalline regions within complex nanowire systems. The chemistry is being designed to be simple and straightforward, making it broadly applicable to a diverse group of scientists and engineers for widespread utilization. Undergraduate researchers will play a prominent and active role in the development of these chemical reactions. The chemistry and target systems will serve as a springboard for open-forum discussions about scientific ethics that will include undergraduate students, graduate students, postdocs, and faculty. In the future, these results will help researchers design next-generation nanomaterials for advancing applications as diverse as nano/microelectronics, thermoelectric refrigeration, superconducting interconnects, catalysis, and mechanical actuation.
Nanoscale architectures that contain multiple distinct materials components in precise locations relative to one another are important platforms for applications in areas that include solar energy conversion, catalysis, optics, and biomedicine. To advance these application areas, scientists seek to create new nanostructured materials with increasingly sophisticated features with high levels of precision. In this regard, new capabilities are needed for turning dreams into reality, for moving from a design or model system to one that can actually be made and studied experimentally. Chemists routinely construct sophisticated multi-functional molecular architectures using a synthetic framework referred to as "total synthesis." Here, small molecular fragments that are cheap and readily obtained in large quantities are used as a starting point. Chemists then transform these simple molecular building blocks into the larger and more complex molecule that they want to target by applying to them a series of chemical reactions. These chemical reactions allow them to build their target molecule step by step in a rational and predictable way. The goal of this project was to introduce a conceptually analogous "total synthesis" framework for the synthesis of complex multi-component inorganic nanostructures, where such capabilities are not established. We succeeded in this by demonstrating that targeted multi-component inorganic nanowires and nanoparticles could be constructed in a step-by-step manner. Specifically, we showed that chemical reactions that can transform one type of material into another can be applied selectively to specific locations in a multi-component nanostructure. We also showed that complex nanoparticles with three and four distinct materials components in precise locations could be constructed by applying a sequence of known chemical reactions in a stepwise manner. This is indeed conceptually analogous to the construction of a complex molecule by applying a sequence of chemical reactions to a small molecular building block. This work continues as we develop additional capabilities for constructing complex inorganic nanostructures and learn more about how they can be precisely controlled, so that design targets for the applications listed above can be made and studied experimentally. Several graduate and undergraduate students participated in this project and played instrumental roles in initiating and implementing it. Because of the unique combination of technical training, collaborative research, academic education, and professional development that they received by working on this project, all participants have been highly successful. Those who have graduated with a Ph.D. degree have gone on to high-impact positions in industry and academia. Several undergraduate researchers participated in this project as well, and they have all transitioned to top graduate, medical, and dental programs. As part of this project, unique learning modules were introduced into freshman and upper-level undergraduate courses, as well as into group meetings. These learning modules focused on broader issues at the interface between science and society, and included scientific ethics, communication, public policy, law, and an exploration of the direct societal impacts of scientific discoveries. Students supported on this project were actively involved in K-12 outreach activities and in providing undergraduate students at small colleges with access to advanced research instrumentation.
