Size-Dependent Optical Properties of Colloidal PbS Quantum Dots
Size-Dependent Optical Properties of Colloidal PbS Quantum Dots
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DOI：
10.1021/nn900863a
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发表时间：
2009-10-01
期刊：
影响因子：
17.1
通讯作者：
Hens, Zeger
中科院分区：
文献类型：
--
作者：
Moreels, Iwan;Lambert, Karel;Hens, Zeger
我们定量研究胶体PbS纳米晶体或量子点（Qdots）的尺寸依赖的光学性质相结合的Qdot吸收光谱与详细的元素分析的Qdot悬浮液。在高能量下，摩尔消光系数ε随着非体积d（3）而增加，并且与使用Maxwell-Garnett有效介质理论和Qdot介电函数的体积值的理论计算一致。这表明量子限制在该光谱范围内对E没有影响，并且它提供了计算Qdot浓度的准确方法。在带隙周围，λ仅随d（1.3）增加，并且值与PbSe量子点的λ相当。数据与带隙跃迁的振子强度f（if）有关，结果与理论紧束缚计算吻合得很好，预测f（if）对d的线性依赖性。对于PbS和PbSe量子点两者，激子寿命τ由f（If）计算。我们发现1和3亩之间的值，与实验文献数据从时间分辨发光光谱。我们的结果提供了一个全面的一般框架来计算和理解悬浮胶体量子点的光学性质。最重要的是，它突出了在这些系统中的本地字段的因素的意义。
We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots) by combining-the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases With the Not volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on E in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the epsilon of PbSe Qdots. The data are related to the oscillator strength f(if) of the band gap transition and results agree well with theoretical tight-binding calculations, predicting a linear dependence of f(if) on d. For both PbS and PbSe Qdots, the exciton lifetime tau is calculated from f(if). We find values ranging between 1 and 3 mu s, in agreement with experimental literature data from time-resolved luminescence spectroscopy. Our results provide a thorough general framework to calculate and understand the optical properties of suspended colloidal quantum dots. Most importantly, it highlights the significance of the local field factor in these systems.