Shape-Controlled Nanostructures of Metals

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This project will develop a scientific base for the large-scale synthesis of metallic nanostructures with well-controlled shapes and properties. The synthetic approach will be based on the polyol process, where a polyol such as ethylene glycol serves as both solvent and reducing agent and an organic polymer such as poly(vinyl pyrrolidone) (PVP) acts as the capping agent. A series of new experiments will be designed and performed to specifically address various fundamental issues that include, for example, a deeper understanding and better control of nucleation and growth in the solution phase; rapid screening and selection of a suitable capping agent for the formation of a specific shape, and elucidation of the role(s) played by the capping agents. This research will also fully examine the functions of some anions (e.g., chloride and bromide) in controlling the shape and crystallinity of seeds formed in the nucleation step. In addition, this project will investigate some intriguing applications associated with these metallic nanostructures including, for example, surface plasmonics, optical sensing, contrast-enhanced optical imaging, and heterogeneous catalysis. The project will enhance the education of both graduate and undergraduate students through multidisciplinary research and collaboration. It will also provide a platform for the PI to engage undergraduate students (in particular, those from community colleges and minority institutions) and high school students to conduct research in his laboratory.%%%This project will develop a generic approach to the large-scale synthesis of metallic nanostructures with a broad range of controllable shapes (e.g., cubes, rods, wires, quasi-spheres, and thin plates). Such control will enable us to tailor the electronic, optical, and catalytic properties of nanostructures. The research will also provide a better understanding of the nucleation and growth mechanisms associated with solution-phase synthesis of nanostructured materials, as well as new tools for the rapid screening of experimental conditions required for the evolution of a specific shape. More importantly, the research will provide a class of nanostructured materials that can serve as a new platform to radically change the way cancer is diagnosed, imaged, and treated. For example, the silver and gold nanostructures can be used in a number of different configurations for the detection of cancer-related molecules with extremely high sensitivities. Due to their tunable and extremely high extinction coefficients in the near-IR region (the transparent window of soft tissues), they also have great potential in biomedical applications such as photothermal therapy of cancer and contrast-enhanced optical imaging of tumor cells. The education of both graduate and undergraduate students will be enhanced through multidisciplinary research and collaborations. It will also provide a natural vehicle for the PI to engage undergraduate students (in particular, those from community colleges and minority institutions) and high school students to conduct research in his laboratory.