Surface enhanced NMR spectroscopy
Event details
| Date | 18.05.2017 |
| Hour | 16:30 › 17:30 |
| Speaker |
Prof. Lyndon Emsley EPFL, Lausanne Switzerland |
| Location | |
| Category | Conferences - Seminars |
A fundamental challenge in surface chemistry and catalysis relates to the determination of three-dimensional structures with atomic-level precision, especially so for single site systems. In fact, it is not even known whether molecular fragments at surfaces form well defined structures or if they adopt disordered conformations. For example, specific metal-surface interactions have been proposed to be essential in stabilizing active site structures in many heterogeneous catalysts, but so far it has not been possible to obtain three-dimensional structures to confirm such interactions.
We demonstrate how surface enhanced NMR spectroscopy (SENS) can be achieved by using dynamic nuclear polarization (DNP). In this approach, electron polarization is transferred from an organic radical to the rare nuclei (at natural isotopic abundance) at the surface, yielding up to a 200-fold signal enhancement for surface species in many materials.
We show the full characterization by DNP SENS of materials including supported active single site complexes, and Sn-b zeolites where we obtain detailed structural information on the active-site speciation.
We then go on to determine the full three-dimensional structure of an organometallic complex on an amorphous silica surface using solid-state NMR measurements. The result, in combination with EXAFS, is a detailed structure for the surface complex determined with a precision of 0.7 Å. We observe a single well-defined conformation that is folded towards the surface in such a way as to include an interaction between the platinum metal center and the surface oxygen atoms.
We show the full characterization by DNP SENS of materials including supported active single site complexes, and Sn-b zeolites where we obtain detailed structural information on the active-site speciation.
We then go on to determine the full three-dimensional structure of an organometallic complex on an amorphous silica surface using solid-state NMR measurements. The result, in combination with EXAFS, is a detailed structure for the surface complex determined with a precision of 0.7 Å. We observe a single well-defined conformation that is folded towards the surface in such a way as to include an interaction between the platinum metal center and the surface oxygen atoms.
Practical information
- General public
- Free
Organizer
Contact
- Annick Gaudin Delmonaco