Aaron J. Rossini, Iowa State University

Advancing the Science of Nanomaterials with Solid-State NMR Spectroscopy

Abstract: “Inorganic nanomaterials are often disordered, making atomic-level characterization a persistent and unresolved challenge. In this talk I will describe how high-resolution solid-state NMR spectroscopy can be used for the precise structural characterization of nanomaterials including CdSe nanocrystals, 2D silicon and germanium, metal-organic chalcogenolates (MOCs) and MXenes. Many of these materials feature exotic and unreceptive NMR isotopes that yield low sensitivity and/or broad NMR signals. To overcome these challenges and boost sensitivity and resolution, we use dynamic nuclear polarization (DNP), indirect detection, or high magnetic fields. Within these materials, observing chemical shifts or quadrupolar coupling constants allows the local structure around a given nucleus to be determined. 2D NMR experiments are used to confirm the spatial proximity of different structure units within the materials. Additionally, we show that dipolar dephasing NMR experiments like REDOR or SEDOR represent a general strategy to validate structural models of these nanomaterials. We demonstrate simple procedures to calculate dipolar dephasing curves expected for extended nanometer-scale structural models, enabling precise structural models for these materials to be determined or validated.”