The unique physicochemical properties and biocompatibility of zinc oxide nanocrystals (ZnO NCs) are strongly dependent on the nanocrystal/ligand interface, which is largely determined by synthetic procedures. Stable ZnO NCs coated with a densely packed shell of 2-(2-methoxyethoxy)acetate ligands, which act as miniPEG prototypes, with average core size and hydrodynamic diameter of 4-5 and about 12 nm, respectively, were prepared by an organometallic self-supporting approach, fully characterized, and used as a model system for biological studies. The ZnO NCs from the one-pot, self-supporting organometallic procedure exhibit unique physicochemical properties such as relatively high quantum yield (up to 28 %), ultralong photoluminescence decay (up to 2.1 μs), and EPR silence under standard conditions. The cytotoxicity of the resulting ZnO NCs toward normal (MRC-5) and cancer (A549) human lung cell lines was tested by MTT assay, which demonstrated that these brightly luminescent, quantum-sized ZnO NCs have a low negative impact on mammalian cell lines. These results substantiate that the self-supporting organometallic approach is a highly promising method to obtain high-quality, nontoxic, ligand-coated ZnO NCs with prospective biomedical applications.

The unambiguous characterization of the coordination chemistry of nanocrystal surfaces produced by wet‐chemical 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 μ2‐ and μ3‐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.

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We demonstrate for the first time a highly efficient Cu(i)-catalyzed alkyne-azide cycloaddition reaction on the surface of ZnO nanocrystals with retention of their photoluminescence properties. Our comparative studies highlight the superiority of a novel self-supporting organometallic method for the preparation of brightly luminescent and well-passivated ZnO nanocrystals over the traditional sol-gel procedure.