Deciphering Ligands' Interaction with Cu and Cu sub(2)O Nanocrystal Surfaces by NMR Solution Tools

• Published in: Chemistry : a European journal 2015-01, Vol.21 (3), p.1169-1178
• Main Authors: Glaria, Arnaud, Cure, Jeremy, Piettre, Kilian, Coppel, Yannick, Turrin, Cedric-Olivier, Chaudret, Bruno, Fau, Pierre
• Format: Article
• Language: English
• Subjects: Copper; Ligands; Nanocrystals; Nanoparticles; Nanostructure; Nuclear magnetic resonance; Oxidation; Oxidation rate
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201403835

The hydrogenolysis of [Cu sub(2){(iPrN) sub(2)(CCH sub(3))} sub(2)] in the presence of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) in toluene leads to 6-9nm copper nanocrystals. Solution NMR spectroscopy has been used to describe the nanoparticle surface chemistry during the dynamic phenomenon of air oxidation. The ligands are organized as multilayered shells around the nanoparticles. The shell of ligands is controlled by both their intermolecular interactions and their bonding strength on the nanocrystals. Under ambient atmosphere, the oxidation rate of colloidal copper nanocrystals closely relies on the chemical nature of the employed ligands (base or acid). Primary amine molecules behave as soft ligands for Cu atoms, but are even more strongly coordinated on surface Cu super(I) sites, thus allowing a very efficient corrosion protection of the copper core. On the contrary, the TDPA ligands lead to a rapid oxidation rate of Cu nanoparticles and eventually to the re-dissolution of Cu super(II) species at the expense of the nanocrystals. Scratch the surface: An in-depth NMR study of long alkyl chain ligands' interactions with copper nanoparticles is presented (see figure). The effects of the functional head group on the oxidation process of the nanoparticles are investigated.