Lee, Daniel, Małgorzata Wolska-Pietkiewicz, Saumya Badoni, Agnieszka Grala, Janusz Lewiński, and Gaël De Paëpe. “Disclosing Interfaces of ZnO Nanocrystals Using Dynamic Nuclear Polarization: Sol-Gel versus Organometallic Approach.” Angewandte Chemie International Edition 58, no. 48 (November 25, 2019): 17163–68.
https://doi.org/10.1002/anie.201906726.
The unambiguous characterization of the coordination chemistry of nanocrystal surfaces produced by wetchemical synthesis presently remains highly challenging. Here, zinc oxide nanocrystals (ZnO NCs) coated by monoanionic diphenyl phosphate (DPP) ligands were derived by a sol-gel process and a one-pot self-supporting organometallic (OSSOM) procedure. Atomic-scale characterization through dynamic nuclear polarization (DNP-)enhanced solid-state NMR (ssNMR) spectroscopy has notably enabled resolving their vastly different surface-ligand interfaces. For the OSSOM-derived NCs, DPP moieties form stable and strongly-anchored m2- and m3-bridging-ligand pairs that are resistant to competitive ligand exchange. The sol-gel-derived NCs contain a wide variety of coordination modes of DPP ligands and a ligand exchange process takes place between DPP and glycerol molecules. This highlights the power of DNP-enhanced ssNMR for detailed NC surface analysis and of the OSSOM approach for the preparation of ZnO NCs.