Using in situ Analysis to Design ex situ Solid State Syntheses for Nanoparticulate to Bulk Targets

NON-TECHNICAL SUMMARY Solid-state synthesis is a straightforward route towards new material discovery in which powders are mixed and heated to form new materials with useful properties. The exact sequence of events at the atomic level during these reactions is often not well understood; it is shrouded by a figurative synthetic “black box” that prevents the rational design of materials with precise compositions and shapes. This project, with support from the Solid State and Materials Chemistry Program in NSF’s Materials Research Section A, uses advanced microscopy combined with a heating capability to observe these atomic-scale changes as they happen in real time. The studies center on three example reactions important for future technologies: how certain iron-containing nanorods change into tiny hollow capsules with magnetic properties through a process involving an outer shell and internal particle rearrangement; how manganese oxide nanowires react with other compounds to form more complex nanowires that keep their long, thin shape, aided by temporary boundaries between tiny crystals that help the atoms diffuse; and how nanoparticles containing bismuth and iron combine to form a pure, high-quality bulk powder of a material valued for its unusual combination of electrical and magnetic behaviors. Understanding these details allows development of better ways to produce such materials in ordinary laboratory settings. Additionally, the project creates a peer mentoring program at the University of Kentucky, where more experienced undergraduate students are paired with those earlier in their studies to help them participate in research, improve their ability to communicate scientific ideas, and stay engaged in science and engineering. Overall, the research contributes new knowledge for designing materials used for medical applications, in batteries and energy storage, and lays the foundation for advanced electronic devices and discovering quantum phenomena. This project thereby advances scientific understanding, supports economic growth through technological innovation, and strengthens the national workforce in critical technical fields. TECHNICAL SUMMARY This project, with support from the Solid State and Materials Chemistry Program in NSF’s Materials Research Section A, investigates the mechanistic intricacies of solid-state reactions in oxide nanomaterials through in situ heating within the transmission electron microscope, thereby informing the rational design of laboratory-scale syntheses to yield phase-pure, morphologically precise materials. By capturing real-time transformations at the atomic and nanometer length scales, the research addresses challenges inherent in synthesizing ternary materials with controlled composition, structure, and morphology. Three prototypical systems form the focus of the work: elucidating the transformation of FeOOH nanorods into hollow iron oxide nanocapsules via a shell-induced Ostwald ripening mechanism; examining the conversion of MnO2 nanowires to LiMn2O4 or MgMn2O4 nanowires, preserving the nanowire morphology through transient grain boundary formation; and investigating the reaction of Bi2O3 and iron oxide nanoparticles to produce phase-pure bulk BiFeO3 by delineating diffusion pathways and intermediate phases. High-resolution in situ imaging, diffraction, and energy-dispersive X-ray spectroscopy systematically explore variables of temperature, particle size and shape, and composition. The project also establishes ChemConnect, a structured peer mentorship program at the University of Kentucky that pairs upper-level undergraduates with underclassmen to enhance STEM retention, foster research engagement, and cultivate skills in scientific communication. 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. NSF Award ID: 2554849 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Beth Guiton | Institution: University of Kentucky Research Foundation, LEXINGTON, KY | Award Amount: $454,793 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2554849 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2554849.html