Surface enhanced nuclear magnetic resonance spectroscopy at solid-liquid interfaces using Overhauser dynamic nuclear polarization

Y. Rao; D. Gioffrè; M. Levien; M. Wörle; P. Pandey et al. 

While solid-liquid interfaces are ubiquitous, detecting the associated surface sites under ambient conditions remains a grand challenge. Previously, we demonstrated the hyperpolarization by Overhauser effect dynamic nuclear polarization (OE-DNP) of ligands of molecular metal complexes via chemical exchange. Here, we extend this approach to efficiently enhance the NMR signals of solid surfaces at the solid-liquid interface at ambient temperature. We use this approach to obtain DNP enhancements for the 31P signals of PPh3 ligands interacting with Rh(I) surface sites, in prototypical silica-supported materials prepared via surface organometallic chemistry. Efficient enhancement is obtained under ambient conditions simultaneously at the surface (e(surface) = 20-30) and in solution (e(solution) up to 50), enabling to detect species at both the surface and in solution, opening the possibility to monitor surface and interfacial chemistry.