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SUMMARY:Surface enhanced NMR spectroscopy
DTSTART:20170518T163000
DTEND:20170518T173000
DTSTAMP:20260407T163742Z
UID:0a6fad1126156a4a66c8591a0bfbf52631a2b1d9c770c4227fa1ba94
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Lyndon Emsley\nEPFL\, Lausanne\nSwitzerland\nA fundament
 al challenge in surface chemistry and catalysis relates to the determinati
 on of three-dimensional structures with atomic-level precision\, especiall
 y so for single site systems. In fact\, it is not even known whether molec
 ular fragments at surfaces form well defined structures or if they adopt d
 isordered 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 o
 btain three-dimensional structures to confirm such interactions.\nWe demon
 strate how surface enhanced NMR spectroscopy (SENS) can be achieved by usi
 ng dynamic nuclear polarization (DNP). In this approach\, electron polariz
 ation is transferred from an organic radical to the rare nuclei (at natura
 l isotopic abundance) at the surface\, yielding up to a 200-fold signal en
 hancement for surface species in many materials.\nWe show the full charact
 erization by DNP SENS of materials including supported active single site 
 complexes\, and Sn-b zeolites where we obtain detailed structural informat
 ion on the active-site speciation.\nWe then go on to determine the full th
 ree-dimensional structure of an organometallic complex on an amorphous sil
 ica surface using solid-state NMR measurements. The result\, in combinatio
 n 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 interact
 ion between the platinum metal center and the surface oxygen atoms.\n \n\
 n 
LOCATION:BCH 2201 https://plan.epfl.ch/?room==BCH%202201
STATUS:CONFIRMED
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