Elucidating the binding modes of ligands on nanoparticles is crucial to understand their stabilizing role. Here we show how sensitivity enhancements provided by dynamic nuclear polarization (DNP) allow access to the organic-inorganic interface in a range of technologically relevant nanoparticles and nanocrystals using magic-angle-spinning (MAS) solid-state NMR. In particular we will show how chemical shifts can be used to directly obtain complete three-dimensional structures for organic capping groups in combination with machine learning methods. Notably in the case of gold nanoparticles, we determine the three-dimensional structure, packing and coordination modes of citrate, acetate, succinate and glutarate from carbon-13 and sodium-23 chemical shifts in combination XPS and TEM measurements. In the case of CdSe nanocrystals and CdSe/CdS core/crown nanoplatelets this approach enables the differentiation between surface and core atoms in all major forms of size- and shape-engineered nanoplatelets and their epitaxial nanoheterostructures. NMR signals are assigned to specific crystal facets of oleate-terminated ZB structured CdSe NCs, and interpreted in terms of the surface structures.

Atomic-level structures of the organic-inorganic interface by NMR crystallography

2019 Spring National Meeting

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