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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Dependence of the Band Gap of CdSe Quantum Dots on the Surface Coverage and Binding Mode of an Exciton-Delocalizing Ligand, Methylthiophenolate
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Dependence of the Band Gap of CdSe Quantum Dots on the Surface Coverage and Binding Mode of an Exciton-Delocalizing Ligand, Methylthiophenolate

机译：CdSe量子点的带隙对激子离域配体甲基硫酚盐的表面覆盖率和结合方式的依赖性

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摘要

Displacement of native octylphosphonate (OPA) figands for methylthiophenolate (CH3-TP) on the surfaces of CdSe quantum dots (QDs) causes a moderate (up to SO meV) decrease in the band gap (E-g of the QD. Plots of the corresponding increase in apparent excitonic radius, Delta R, of the QDs versus the surface coverage of CH3-TP, measured by H-1 NMR, for several sizes of QDs reveal that this ligand adsorbs in two distinct binding modes, (1) a tightly bound mode (K-a = 1.0 +/- 0.3 X 10(4) M-1) capable of exciton delocalization, and (2) a more wealdy bound mode (K-a = 8.3 +/- 9.9 X 10(2) M-1) that has no discernible effect on exciton confinement For tightly bound CH3-TP, the degree of delocalization induced in the QD is approximately linearly related to the fractional surface area occupied by the ligand for all sizes of QDs. Comparison of the dependence of Delta R on surface coverage of CH3-TP over a range of physical radii of the QDs, R = 1.1-2.4 nm, to analogous plots simulated using a 3D spherical potential well model yield a value for the confinement barrier presented to the excitonic hole by tightly bound CH3-TP of similar to 1 eV.
机译：CdSe量子点（QDs）表面上的甲基硫代苯酚酸酯（CH3-TP）天然辛基膦酸酯（OPA）配体的取代导致带隙（QD的带隙）适度下降（至SO meV）。相应增加的图QD的表观激子半径Delta R对CH3-TP的表面覆盖率（通过H-1 NMR测量）对于几种尺寸的QD揭示该配体以两种不同的结合模式吸附，（1）紧密结合的模式（Ka = 1.0 +/- 0.3 X 10（4）M-1）能够进行激子离域，以及（2）更富裕的束缚模（Ka = 8.3 +/- 9.9 X 10（2）M-1）具有对激子约束没有明显的影响对于紧密键合的CH3-TP，在QD中诱导的离域化程度与所有大小的QD的配体所占的分数表面积近似线性相关。在QD的物理半径范围（R = 1.1-2.4 nm）上的CH3-TP到使用3D模拟的类似图球形势阱模型通过紧密结合的CH3-TP产生的对激子孔的限制势垒值接近1 eV。

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