Am I Still IL? Evolution of CdS Nanocrystals from Inorganic Ligand Exchange
Year: 2025
Type: article
Abstract: Ligand exchange has become the standard route for modifying the surface chemistry of colloidal nanocrystals (NCs), providing a mechanism to tailor their optoelectronic properties, solubility, and chemical functionalization. This enables NCs to be deployed in myriad applications where the surface-solution interface is key to performance or process compatibility. Ligand-passivated surfaces are generally considered stable and chemically inert, with incoming ligands assumed to fully replace native ones. Here, we demonstrate that inorganic ligand shells on CdS NCs are dynamic, chemically evolving over time, with transformation pathways strongly dependent on ligand identity. This is evaluated for representative oxoanions (o-phosphoric acid), chalcogenides (Na 2 Se, Se 2– ), and metal-chalcogenides (thiostannate). Using multinuclear ( 1 H, 13 C, 23 Na, 31 P, 113 Cd, 119 Sn) solid-state NMR spectroscopy and electron microscopy, we show that (i) surface-bound phosphates reorganize over time into cadmium phosphate domains, degrading NC quality; (ii) sodium polyselenide ligands remain chemically stable, but associated Na + counterions exhibit dynamics that may suppress charge transport; and (iii) partial oxidation of thiostannate ligands to SnO 2 occurs, along with surface reconstruction, which improves NC passivation. Across all systems studied, residual oleylamine is detected. These findings reveal that inorganic ligand exchange does not necessarily yield chemically uniform or stable surfaces. Instead, each ligand class exhibits distinct behavior, ranging from surface degradation (phosphates), to stable yet dynamic interfaces (selenides), to hydrophilic and partially oxidized surfaces (thiostannates). This challenges the static-surface model and positions multinuclear solid-state NMR spectroscopy as a key tool for designing future functional materials.
DOI: 10.1021/jacs.5c18768
Institution: University of Manchester
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: The UK Dynamic Nuclear Polarisation Magic Angle Spinning NMR Facility, The UK Dynamic Nuclear Polarisation Magic Angle Spinning NMR Facility, The UK Dynamic Nuclear Polarisation Magic Angle Spinning NMR Facility, High-field Dynamic Nuclear Polarization Magic Angle Spinning NMR for Chemistry, Physics, Materials, Pharmaceuticals and Biomolecular Science, Passivation by Ultimate Ligand-Surface Activation Rationalized by NMR, The UK High-Field Solid-State NMR National Research Facility, G7633989764
OpenAlex ID: W4417520753