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Disclosing Interfaces of ZnO Nanocrystals Using Dynamic Nuclear Polarization: Sol Gel versus Organometallic Approach

posted Sep 5, 2019, 1:43 AM by Daniel Lee   [ updated Mar 30, 2020, 7:32 AM ]
Disclosing Interfaces of ZnO Nanocrystals Using Dynamic Nuclear Polarization: Sol Gel versus Organometallic Approach. The unambiguous characterization of the coordination chemistry of nanocrystal surfaces that have been produced by a wet‐chemical synthesis presently remains a highly challenging issue. Here, zinc oxide nanocrystals (ZnO NCs) coated by monoanionic diphenyl phosphate (DPP) ligands were derived by a traditional sol‐gel process and a one‐pot self‐supporting organometallic (OSSOM) procedure, and advanced atomic‐scale characterization through dynamic nuclear polarization (DNP‐)enhanced solid‐state nuclear magnetic resonance (ssNMR) spectroscopy has notably enabled resolving their vastly different surface‐ligand interfaces. For the OSSOM‐derived NCs, DPP moieties form stable and strongly‐anchored µ2‐ and µ3‐bridging‐ligand pairs that are resistant to competitive ligand exchange processes. Contrastingly, the sol‐gel‐derived NCs contain a wide variety of coordination modes of DPP ligands and a ligand exchange process takes place between DPP ligands and glycerol molecules. This highlights the power of DNP‐enhanced ssNMR for detailed NC surface analysis and the superiority of the OSSOM approach for the preparation of high quality ZnO NCs.
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