Large-Scale and Predictable Organization of Nanocrystal Homo- and Heterojunctions through Polymer-Directed Processing

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The research objective of this project is the scalable fabrication of plasmonic nanojunctions, the nanometer-sized gaps created between high-curvature metal surfaces that produce intense electromagnetic ?hot spots.? In this project, metal nanocrystals will be self-organized to form precise nanojunctions by carrying out phase segregation within a nanocrystal-polymer composite. Nanocrystals will be assembled with respect to shape and orientation to create homojunction (similar) and heterojunction (dissimilar) nanocrystal pairs. Molecular simulations will be used to deduce the global phase diagram of the multicomponent nanocrystal-polymer mixtures and to predict the mechanisms and kinetics of large-scale nanocrystal assembly. Guided by simulations, nanocrystals will be chemically modified by polymer grafts with tailored chain lengths, grafting density, and charge. Detailed morphology studies of the resulting nanocomposite will provide insight into how the chemical nature of the nanocrystal surface can be used to tune the key intermolecular interactions that regulate orientation and arrangement of the plasmonic nanojunctions.The results of this project will facilitate the successful fabrication of large-area, non-close-packed plasmonic nanocrystals arrays that are currently inaccessible by top-down fabrication methods. These nanomaterials will be designed for integration into optical device platforms for applications such as subwavelength focusing, surface-enhanced Raman spectroscopy, and electromagnetic transparency. This work will also provide a fundamental understanding of the general mechanisms governing polymer-directed nanocrystal assembly. By establishing a close collaboration between experiment and theory, this work has the potential for the discovery of novel self-assembly pathways and mechanisms for achieving new and complex nanomaterials architectures. In addition, this research project will contribute to the education of pre-college, undergraduate, and graduate students in the field of nanoengineering. This includes the design of new laboratory modules and research-based coursework for undergraduates as well as outreach activities that will increase the overall diversity of the undergraduate engineering population at UCSD.