Linear Dipole Behavior in Single CdSe-Oligo(phenylene vinylene) Nanostructures
Linear Dipole Behavior in Single CdSe-Oligo(phenylene vinylene) Nanostructures
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DOI：
10.1021/nn800785s
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发表时间：
2009-02-01
期刊：
影响因子：
17.1
通讯作者：
Barnes, M. D.
中科院分区：
文献类型：
--
作者：
Early, K. T.;McCarthy, K. D.;Barnes, M. D.
我们报告了单个（4.3 nm）CdSe 量子点的线性偏振吸收和发射，这些量子点的表面与单分散低聚亚苯基亚乙烯基配体配位。先前显示抑制量子点闪烁，我们在此证明光激发配体与量子点核心的电子相互作用表现为吸收中的强偏振各向异性（M = 0.5），以及来自量子点核心的独特线性偶极子发射模式。此外，量子点发射矩和对应于吸收最大值的偏振方向之间存在相关性，其表现为X-Y平面中发射矩方向的波动。可以通过将激发远离配体吸收带来关闭观察到的偏振效应。我们提出了一种基于激子从光激发配体解离，然后将电子钉扎在量子点表面的机制。由此产生的斯塔克相互作用足够强，足以打破点内发射矩的二维简并性，因此可以解释线性偶极子发射特性。
We report on linearly polarized absorption and emission from individual (4.3 nm) CdSe quantum dots whose surfaces are coordinated with monodisperse oligo-phenylene vinylene ligands. Shown previously to suppress quantum dot blinking, we demonstrate here that the electronic interaction of photoexcited ligands with the quantum dot core is manifested as a strong polarization anisotropy in absorption (M = 0.5), as well as distinct linear dipole emission patterns from the quantum dot core. Further, there is a correlation between the quantum dot emission moment and polarization orientation corresponding to the absorption maxima that is manifested as fluctuations in emission moment orientation in the X-Y plane. The observed polarization effects can be switched off by tuning the excitation away from the ligand absorption band. We propose a mechanism based on exciton dissociation from the photoexcited ligand, followed by the pinning of electrons at the quantum dot surface. The resulting Stark interaction is sufficiently strong to break the 2D degeneracy of the emission moment within the dot, and may therefore account for the linear dipole emission character.