A Quantitative Description of the Binding Equilibria of para-Substituted Aniline Ligands and CdSe Quantum Dots
A Quantitative Description of the Binding Equilibria of para-Substituted Aniline Ligands and CdSe Quantum Dots
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DOI：
10.1021/jp109381r
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发表时间：
2010-12-30
影响因子：
3.7
通讯作者：
Weiss, Emily A.
中科院分区：
文献类型：
--
作者：
Donakowski, Martin D.;Godbe, Jacqueline M.;Weiss, Emily A.
本文描述了使用H-1 NMR光谱测量两种对位取代苯胺分子（R-An），对甲氧基苯胺（Me 0-An）和对溴苯胺（Br-An）与胶体4.1nm CdSe量子点（QD）的溶液相结合的平衡常数。位于邻位的R-An上的胺基团的芳香族质子的化学位移的变化被用来构建每个R-An/QD系统的结合等温线。这些等温线符合朗缪尔函数以产生K-a，R-An配体与QD结合的平衡常数;对于R = MeO和R = Br两者，K-a近似为150 M-1，Δ G（ads）近似为-19 kJ/mol。P-31 NMR表明，天然辛基膦酸酯配体，其中，通过电感耦合等离子体原子发射光谱法，覆盖90%的QD表面，不被取代后，结合的R-An。MeO-An配体在比Br-An低得多的浓度下淬灭QD的光致发光;因此，K-a，K-MeO-An近似于K-a，K-Br-An的观察表明，淬灭效率的这种差异仅仅是由于结合的R-An与QD的激子态的电子相互作用的性质的差异。
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.