Quantized growth of CdTe quantum dots; Observation of magic-sized CdTe quantum dots
Quantized growth of CdTe quantum dots; Observation of magic-sized CdTe quantum dots
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DOI：
10.1021/jp072516b
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发表时间：
2007-10-18
影响因子：
3.7
通讯作者：
Leppert, Valerie J.
中科院分区：
文献类型：
--
作者：
Dagtepe, Pinar;Chikan, Viktor;Leppert, Valerie J.
这项工作提出了在十六胺 (HDA)、己基膦酸 (HPA) 和三辛基氧化膦 (TOPO) 存在下，在 200 摄氏度以上条件下，CdTe 量子点 (QD) 的量子化生长的实验观察。通过原位紫外-可见吸收光谱监测 CdTe 量子点的晶体生长。高温吸收光谱表明对应于不同尺寸的量子点的多个峰的演变。生长动力学分析表明 CdTe QD 在配位溶剂混合物中的量化生长。高分辨率透射电子显微镜（HRTEM）图像和电子衍射图显示大多数量子点具有闪锌矿晶体结构。 HRTEM 图像显示较大 CdTe 量子点中存在纳米孪晶和堆垛层错。 HRTEM 图像中的域尺寸与观察到的最小幻尺寸 CdTe QD 密切相关，与实验条件下提出的聚集生长机制一致。通过在 QD 合成的初始阶段淬灭反应混合物，分离出观察到的最小直径为 1.9 +/- 0.3 nm 的闪锌矿 CdTe QD。实验观察表明，神奇大小的 CdTe 量子点的惊人稳定性是 HDA 和/或 HPA 量子点表面稳定的结果。如前所述，聚集是由 CdTe 纳米颗粒之间的偶极-偶极相互作用驱动的。结果表明，量子点的聚集在生长的早期阶段非常重要。神奇大小的量子点可以溶解在甲醇或甲苯中，这表明其表面化学的异质性。溶解在甲醇相中的量子点在400至650 nm范围内表现出相对较强的白光发射，发射量子产率约为4%。溶解在甲苯相中的量子点表现出非常弱的发射。
This work presents experimental observation of the quantized growth of CdTe quantum dots (QD) in the presence of hexadecylamine (HDA), hexylphosphonic acid (HPA), and trioctylphosphine oxide (TOPO) above 200 degrees C. The crystal growth of CdTe QDs is monitored by in situ UV-vis absorption spectroscopy. The high-temperature absorption spectra indicate the evolution of multiple peaks corresponding to various sizes of QDs. Analysis of the growth kinetics suggests quantized growth of the CdTe QDs in the coordinating solvent mixture. The high-resolution transmission electron microscopy (HRTEM) images and electron diffraction pattern show that most of the QDs have the zinc blende crystal structure. The HRTEM images indicate nanotwinning and stacking faults in larger CdTe QDs. Domain sizes in the HRTEM images correlate well with the smallest observed magic-sized CdTe QDs, in agreement with the proposed aggregation growth mechanism under the experimental conditions. The smallest observed zinc blende CdTe QDs with the diameter of 1.9 +/- 0.3 nm are isolated by quenching the reaction mixture during the initial phase of the QD synthesis. The experimental observation suggests that the surprising stability of the magic-sized CdTe QDs is the result of the surface stabilization of the QDs of the HDA and/or HPA. As previously suggested, the aggregation is driven by dipole-dipole interaction between CdTe nanoparticles. The results show that the aggregation of quantum dots could be very important at the early stage of the growth. The magic-sized QDs can be dissolved in either methanol or toluene, which suggests heterogeneity of their surface chemistry. The QDs dissolved in the methanol phase exhibit relatively strong white light emission from 400 to 650 nm with an emission quantum yield of approximately 4%. The QDs dissolved in the toluene phase exhibit very weak emission.