A General and Robust Route to Highly Diverse Hollow Nanostructures with New Properties

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Non-Technical Summary Nanoscale materials with hollow interiors (i.e., hollow nanomaterials) are critical components in many areas of science and technology. The properties of hollow nanomaterials and their usefulness in applications such as biosensing and catalysis have strong dependence on their detailed structure such as shape and elemental composition and can be different than those of solid particles of the same size. Nevertheless, it has been a challenge to finely control the structure of a hollow nanomaterial in chemical synthesis. The goal of this project, which is jointly supported by the Solid State and Materials Chemistry program and the Metals and Metallic Nanostructures program, both in the Division of Materials Research, is to establish a general and effective method to synthesize hollow nanomaterials with controllable structures and new properties. In addition to synthesizing new materials, this project examines properties such as thermal stability and unusual interactions with light that will be important for eventual applications. This project provides multidisciplinary research training for graduate and undergraduate students particularly from underrepresented groups. Through a new NanoAmbassadors program, undergraduate students will be involved in outreach on nanomaterials at their former high schools. The project also provides high school students with summer research opportunities.Technical SummaryHollow nanomaterials have found widespread uses in many areas, including biomedicine, imaging, sensing, catalysis and electronics. Controlling the structure of hollow nanostructures is an effective approach to tailoring their physicochemical properties. The proposed work, which is jointly supported by the Solid State and Materials Chemistry program and the Metals and Metallic Nanostructures program, both in the Division of Materials Research, seeks to develop a general and robust method to precisely control the structure of hollow nanomaterials. This method relies on alternating processes of galvanic replacement reactions and sacrificial template regeneration. As examples, design and synthesis of hollow nanostructures made of gold, silver, platinum, palladium, copper, and materials containing multiple metals are being demonstrated. A series of hollow nanostructures with diverse structures and new properties are being generated. Detailed structures of the hollow nanomaterials and their structural responses to heating are revealed with high-performance electron microscopy. Plasmonic properties of the nanomaterials are investigated using both experimental measurements and computational simulations. This project will benefit the engagement of graduate and undergraduate students, especially those from underrepresented groups, in research. The research is also integrated into outreach activities for K-12 students. Through a new NanoAmbassadors program, undergraduate students will be involved in outreach on nanomaterials at their former high schools. The project also provides high school students with summer research opportunities.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.