Development of Multi-dimensional Simultaneous Isotope Exchange, SIX(n) - a Novel Probe of Structure and Dynamics of Soluble Metal Oxide Nanostructures and Solid Surfaces

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Igor Kaltashov and his group at the University of Massachusetts-Amherst are developing novel approaches for studying water-soluble metal oxide nanostructures (frequently referred to as polyoxometalates, or POMs). POMs are viewed as the missing link between the single-molecule and the nanoparticular (or indeed the bulk material) scales. Metal oxide nanoparticles have many important uses in the biomedical field, catalysis and energy storage. One factor that remains a major impediment vis-à-vis wider utilization of these entities in modern technology is the lack of robust and versatile analytical tools that can be used to characterize their structure and behavior at the atomic level. This gap proved difficult to address due to the dramatic increase in size and complexity upon transitioning from the single-molecule scale to the nano-objects. Professor Kaltashov and his team target metal oxide molecular entities that are sufficiently large to resemble nanoparticles and share many of their traits, and at the same time are sufficiently small to be chemically defined. The structure and stability of these objects are probed with a new technique that uses stable isotope exchange and state-of-the-art spectroscopic tools. The project also provides opportunities for undergraduate students to (i) be involved in research focusing on the role of metal oxide-based materials in fighting the H. pylori infection, and (ii) increase the awareness of this frequently asymptomatic disease within the communities that are particularly hard-hit by it and its consequences. The new experimental tool will utilize stable isotope exchange in solution followed by mass spectrometric (MS) detection to probe the structure and dynamic behavior of both chemically defined metal oxide particles (such as POMs) and the macroscopic objects (such as metal oxide surfaces). At the initial stage, oxygen exchange (18O/16O) in solution will be used to detect and characterize transient dynamic events affecting decavanadate, a paradigmatic member of the POM family. This will be followed by developing SIX(n) - Simultaneous Isotope eXchange in solution (e.g., 18O/16O, 17O/16O and 15N/14N) with high-resolution MS detection - to study transient dynamic events affecting the structure of POM-based nanocages and elucidate their role in the cargo capture/release processes. Further modification of this experimental strategy shall expand the scope of inquiry to include dynamic processes at the surface of metal oxide materials. Successful development of these novel experimental tools will undoubtedly catalyze progress in many branches of material science where the metal oxides behavior is one of the major contributors to the materials quality. 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.