CAREER: Spectroscopic Imaging of Nanoscale Structure and Chemistry at Soft-Hard Interfaces

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NON-TECHNICAL SUMMARY This NSF CAREER award project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, combines research, education, and outreach in electron microscopy and its application to characterizing soft-hard interfaces. Understanding the structure and chemistry at soft-hard interfaces is a key challenge across materials science, chemistry, and medicine. Surface atoms represent a large fraction of each nanocrystal, making their surface chemistry a defining property. This project aims to develop methods to visualize the arrangement of molecules on the surfaces of nanoparticles by using the latest generation of scanning transmission electron microscopes in combination with new methods to prepare nanoparticles for high resolution imaging. Together, these techniques will enable studies that measure how the density and uniformity of molecular distributions are related to properties of the metal nanoparticle surface, including its local composition, crystal orientation, and geometry. The insights gained will speed the design and development of next-generation technologies including minimally-invasive cancer therapies, high-efficiency photovoltaics, and medical imaging agents.In addition to the research described above, this project includes an education and outreach plan that aims to broaden the reach of cutting-edge electron microscopy to the next generation of scientists and engineers. Electron microscopes are becoming a widespread, cross-disciplinary tool for characterizing the composition of materials on the scale of atoms. This project includes outreach, teaching, and training in electron microscopy spanning K-12, undergraduate, and graduate students. These efforts include: engaging the public through exhibits on electron microscopy and nanoscience, enhancing the national research infrastructure via high-throughput, active learning methods for user training, and redesigning an electron microscopy course for graduate and undergraduate students. These efforts also support a diverse, nationally-recognized user facility and have direct impact in training over 100 new users in the theory and practice of electron microscopy each year. TECHNICAL SUMMARY This NSF CAREER award project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, aims to produce a fundamental understanding of the surface chemistry at soft-hard interfaces of colloidal nanoparticles using electron microscopy and spectroscopy. Experiments will generate new insights by increasing the scale of quantitative information generated through electron microscopy, and then mining the resulting datasets to study trends and statistical distributions in surface chemistry that occur within and between individual nanoparticles. A particular focus will be understanding the origins of inhomogeneous and anisotropic distributions of molecules on nanoparticle surfaces. This work will make it possible to directly test and refine theoretical models of molecular packing and provide insight into how molecular coatings can be tailored on the nanoscale. This project includes outreach, teaching, and training in electron microscopy spanning K-12, undergraduate, and graduate students. These efforts include: engaging the public through exhibits on electron microscopy and nanoscience, enhancing the national research infrastructure via high-throughput, active learning methods for user training, and redesigning an electron microscopy course for graduate and undergraduate students. The project's education and outreach plan will utilize newly available open-source software for image simulation, data processing, and remote operation in order to broaden the reach of cutting-edge analytical electron microscopy across disciplines.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.