期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 119, 期 33, 页码 19423-19429出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.5b04306
关键词
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资金
- U.S. Department of Energy, Office of Science, Basic Energy Sciences, through the Early Career Research Award [DE-SC0003998]
- National Science Foundation [DGE-1324585]
- Center for Bio-Inspired Energy Science, an Energy Frontier Research Center - U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0000989]
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.
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