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, we use dynamic nuclear polarization (DNP), indirect detection, or high magnetic fields to boost NMR sensitivity and improve spectral resolution. Within these materials, measurement of 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.

Speaker Bio:

Research in the Rossini group aims at developing solid-state NMR methods for the structural characterization of inorganic materials, heterogeneous catalysts and solid pharmaceuticals. Dynamic nuclear polarization (DNP) and indirect detection methods are used to enhance the sensitivity and resolution of solid-state NMR experiments with exotic and unreceptive nuclei. Aaron Rossini completed his PhD studies in September 2010 at the University of Windsor, Windsor, Ontario, Canada, under the supervision of Prof. Robert W. Schurko. In 2011 he moved to Lyon, France to work with Prof. Lyndon Emsley and Dr. Anne Lesage at the Centre de Resonance Magnetique Nucleaire à Très Haut Champs (CRMN Lyon) at the Ecole Normale Superieure de Lyon (ENS Lyon) as a Marie Curie International Incoming Fellow. In October 2014 he moved to École Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland to continue working with Prof. Emsley. In August 2015, he moved to Ames, Iowa to join the Department of Chemistry at Iowa State University as an Assistant Professor. He is also affiliated to the US Department of Energy Ames Laboratory as a faculty scientist. He was officially appointed as an Associate Professor with tenure in August 2021. In August 2023 he was promoted to Full Professor. He has authored over 190 peer-reviewed publications.