Metal–Ligand Interface and Internal Structure of Ultrasmall Silver 
Nanoparticles (2 nm)

Wetzel, Oliver; Hosseini, Shabnam; Loza, Kateryna; Heggen, Marc; Prymak, Oleg; Bayer, Peter; Beuck, Christine; Schaller, Torsten; Niemeyer, Felix; Weidenthaler, Claudia; Epple, Matthias

doi:10.1021/acs.jpcb.1c02512

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Metal–Ligand Interface and Internal Structure of Ultrasmall Silver Nanoparticles (2 nm)

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Weidenthaler, Claudia
Research Group Weidenthaler, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Citation

Wetzel, O., Hosseini, S., Loza, K., Heggen, M., Prymak, O., Bayer, P., et al. (2021). Metal–Ligand Interface and Internal Structure of Ultrasmall Silver Nanoparticles (2 nm). The Journal of Physical Chemistry B, 125(21), 5645-5659. doi:10.1021/acs.jpcb.1c02512.

Cite as: https://hdl.handle.net/21.11116/0000-0008-B2FA-5

Abstract

Ultrasmall silver nanoparticles were prepared by reduction with NaBH₄ and surface-terminated with glutathione (GSH). The particles had a solid core diameter of 2 nm as shown by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). NMR-DOSY gave a hydrodynamic diameter of 2 to 2.8 nm. X-ray photoelectron spectroscopy (XPS) showed that silver is bound to the thiol group of the central cysteine in glutathione under partial oxidation to silver(+I). In turn, the thiol group is deprotonated to thiolate. X-ray powder diffraction (XRD) together with Rietveld refinement confirmed a twinned (polycrystalline) fcc structure of ultrasmall silver nanoparticles with a lattice compression of about 0.9% compared to bulk silver metal. By NMR spectroscopy, the interaction between the glutathione ligand and the silver surface was analyzed, also with ¹³C-labeled glutathione. The adsorbed glutathione is fully intact and binds to the silver surface via cysteine. In situ ¹H NMR spectroscopy up to 85 °C in dispersion showed that the glutathione ligand did not detach from the surface of the silver nanoparticle, i.e. the silver–sulfur bond is remarkably strong. The ultrasmall nanoparticles had a higher cytotoxicity than bigger particles in in vitro cell culture with HeLa cells with a cytotoxic concentration of about 1 μg mL^–1 after 24 h incubation. The overall stoichiometry of the nanoparticles was about Ag_∼250GSH_∼155.