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首页> 外文学位 >Time resolved single molecule spectroscopy of semiconductor quantum dot/conjugated organic hybrid nanostructures.
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Time resolved single molecule spectroscopy of semiconductor quantum dot/conjugated organic hybrid nanostructures.

机译：半导体量子点/共轭有机杂化纳米结构的时间分辨单分子光谱。

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摘要

Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport between the OPV ligands and the CdSe quantum dot core. This electronic interaction greatly modify, the photoluminescence properties of both bulk and single CdSe-OPV nanostructure thin film samples. Size-correlated wide-field fluorescence imaging show that blinking suppression in single CdSe-OPV is linked to the degree of OPV coverage (inferred from AFM height scans) on the quantum dot surface. The effect of the complex electronic environment presented by photoexcited OPV ligands on the excited state property of CdSe-OPV is measured with single photon counting and photon-pair correlation spectroscopy techniques.;Time-tagged-time-resolved (TTTR) single photon counting measurements from individual CdSe-OPV nanostructures, show excited state lifetimes an order of magnitude shorter relative to conventional ZnS/CdSe quantum dots. Second-order intensity correlation measurements g(2)(tau) from individual CdSe-OPV nanostructures point to a weak multi-excitonic character with a strong wavelength dependent modulation depth. By tuning in and out of the absorption of the OPV ligands we observe changes in modulation depth from g(2) (0) ≈ 0.2 to 0.05 under 405 and 514 nm excitation respectively. Defocused images and polarization anisotropy measurements also reveal a well-defined linear dipole emission pattern in single CdSe-OPV nanostructures.;These results provide new insights into to the mechanism behind the electronic interactions in composite quantum dot/conjugated organic composite systems at the single molecule level. The observed intensity flickering , blinking suppression and associated lifetime/count rate and antibunching behaviour is well explained by a Stark interaction model. Charge transfer from photo-excitation of the OPV ligands to the surface of the CdSe quantum dot core, mixes electron/holes states and lifts the degeneracy in the band edge bright exciton state, which induces a well define linear dipole behaviour in single CdSe-OPV nanostructures. The shift in the electron energies also affects Auger assisted hole trapping rates, suppress access to dark states and reduce the excited state lifetime.
机译：对用低聚亚苯基亚乙烯基配体（CdSe-OPV）功能化的CdSe量子点的单分子研究提供了强大的电子通讯证据，可促进OPV配体与CdSe量子点核心之间的电荷和能量传输。这种电子相互作用极大地改变了整体和单个CdSe-OPV纳米结构薄膜样品的光致发光特性。大小相关的广域荧光成像显示，单个CdSe-OPV中的眨眼抑制与量子点表面上的OPV覆盖程度（从AFM高度扫描推断）有关。用单光子计数和光子对相关光谱技术测量光激发的OPV配体所呈现的复杂电子环境对CdSe-OPV的激发态性质的影响;时间标记时间分辨（TTTR）单光子计数测量单个CdSe-OPV纳米结构的结构显示出的激发态寿命相对于常规ZnS / CdSe量子点要短一个数量级。来自各个CdSe-OPV纳米结构的二阶强度相关性测量值g（2）（tau）指出，弱的多激子特性具有很强的波长依赖性调制深度。通过调入和调出OPV配体的吸收，我们观察到了g（2）（0）＆ap;从调制深度的变化。在405和514 nm激发下分别为0.2至0.05。离焦图像和极化各向异性测量还揭示了单个CdSe-OPV纳米结构中定义明确的线性偶极子发射模式;这些结果为单分子复合量子点/共轭有机复合系统中电子相互作用的机理提供了新见解。水平。 Stark相互作用模型很好地解释了观察到的强度闪烁，闪烁抑制以及相关的寿命/计数率和抗起泡行为。从OPV配体的光激发到CdSe量子点核心表面的电荷转移，混合了电子/空穴态，并提升了带边明亮激子态的简并性，从而在单个CdSe-OPV中引发了清晰定义的线性偶极子行为纳米结构。电子能量的变化还会影响俄歇辅助空穴的捕获速率，抑制进入暗态并降低激发态寿命。

著录项

  • 作者

    Odoi, Michael Yemoh.;

  • 作者单位

    University of Massachusetts Amherst.;

  • 授予单位 University of Massachusetts Amherst.;
  • 学科 Chemistry Organic.;Physics Condensed Matter.;Physics Optics.;Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 128 p.
  • 总页数 128
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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