A Quantitative Description of the Binding Equilibria of para-Substituted Aniline Ligands and CdSe Quantum Dots

作者：Donakowski Martin D; Godbe Jacqueline M; Sknepnek Rastko; Knowles Kathryn E; de la Cruz Monica Olvera; Weiss Emily A^*

来源：Journal of Physical Chemistry C, 2010, 114(51): 22526-22534.

DOI：10.1021/jp109381r

This paper describes the use of H-1 NMR spectroscopy to measure the equilibrium constants for the solution-phase binding of two para-substituted aniline molecules (R-An), p-methoxyaniline (Me0-An) and p-bromoaniline (Br-An), to colloidal 4.1 nm CdSe quantum dots (QDs). Changes in the chemical shifts of the aromatic protons located ortho to the amine group on R-An were used to construct a binding isotherm for each R-An/QD system. These isotherms fit to a Langmuir function to yield K-a, the equilibrium constant for binding of the R-An ligands to the QDs; K-a approximate to 150 M-1 and Delta G(ads) approximate to -19 kJ/mol for both R = MeO and R = Br. P-31 NMR indicates that the native octylphosphonate ligands, which, by inductively coupled plasma atomic emission spectroscopy, cover 90% of the QD surface, are not displaced upon binding of R-An. The MeO-An ligand quenches the photoluminescence of the QDs at much lower concentrations than does Br-An; the observation, therefore, that K-a,K-MeO-An approximate to K-a,K-Br-An shows that this difference in quenching efficiencies is due solely to differences in the nature of the electronic interactions of the bound R-An with the excitonic state of the QD.

• 出版日期2010-12-30
• 单位西北大学