Ligand bonding and dynamics on colloidal nanocrystals at room temperature: The case of alkylamines on CdSe nanocrystals
by Ji, Xiaohui; Copenhaver, Danis; Sichmeller, Christopher; Peng, Xiaogang
With CdSe nanocrystals stabilized with very weak ligands (pyridine) as the starting materials, NMR techniques were applied to distinguish the bonded and free alkylamine ligands in an equilibrated adsorption/desorption system for the CdSe-amine nanocrystal-ligand pair. NMR and photoluminescence (PL) measurements were further correlated to identify the linear relationship between PL intensity and the surface ligand coverage of the amine-coated CdSe nanocrystals. For 3.5 nm CdSe nanocrystals and octylamine ligands, the chemical equilibrium constant (K) of the CdSe-amine nanocrystal-ligand adsorption/desorption process was found to be around 50-100, and the corresponding Delta(r)G degrees was calculated as 9.8-11.5 kJ/mol. With a proposed mathernatic method, the corresponding chemical kinetic constants for the desorption (k(d)) and adsorption (k(a)) processes were measured to be 0.01 s(-1) and 0.5 L mol(-1) s(-1), respectively. K, k(d), and k(a) obtained here are generally 2-4 magnitudes different from those estimated in literature. Analysis indicates that these constants are well consistent with the existing experimental observations.
- Journal of the American Chemical Society
- Start Page
- 1520-5126; 0002-7863