Two-Step Nucleation and Growth of InP Quantum Dots via Magic-Sized Cluster Intermediates
Two-Step Nucleation and Growth of InP Quantum Dots via Magic-Sized Cluster Intermediates
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DOI：
10.1021/acs.chemmater.5b00286
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发表时间：
2015-02-24
影响因子：
8.6
通讯作者：
Cossairt, Brandi M.
中科院分区：
文献类型：
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作者：
Gary, Dylan C.;Terban, Maxwell W.;Cossairt, Brandi M.
我们报告了神奇大小的簇（MSC）作为从分子前体合成磷化铟量子点（InP QD）的关键中间体的作用。观察到从 MSC 直接到 InP QD 的异质生长，没有中间尺寸的颗粒。这些观察结果表明，之前通过调节前体反应性来控制成核和生长的努力已被这些动力学持久性 MSC 在 QD 形成之前的形成所破坏。 InP MSC 的热稳定性受到外源碱的存在以及阴离子配体组的选择的影响。研究发现，向羧酸盐封端的 MSC 中添加伯胺（以前 InP QD 合成中的常见添加剂）可以绕过 MSC 的形成，从而允许 InP QD 通过连续的可分离尺寸均匀生长。用羧酸盐配体组取代磷酸盐配体组，将一种特定的 InP MSC 的热稳定性提高到 400 摄氏度。通过 UVvis 吸收光谱、粉末 XRD 分析以及溶液 P-31{H-1} 和 H-1 NMR 光谱研究了具有羧酸盐和膦酸盐配体组的 MSC 的结构和光学性质。最后，羧酸盐封端的 MSC 被确定为合成高质量 InP QD 的有效单源前体 (SSP)。采用 InP MSC 作为 QD 的 SSP 可以有效地将 MSC 的形成与随后的第二次成核事件和 InP QD 的生长分开。这种 SSP 反应的浓度依赖性以及 TEM 观察到的颗粒形状均匀性表明，从 MSC 直接到 QD 的逐步生长是通过第二次成核事件而不是聚集生长机制进行的。
We report on the role of magic-sized clusters (MSCs) as key intermediates in the synthesis of indium phosphide quantum dots (InP QDs) from molecular precursors. Heterogeneous growth from the MSCs directly to InP QDs was observed without intermediate sized particles. These observations suggest that previous efforts to control nucleation and growth by tuning precursor reactivity have been undermined by formation of these kinetically persistent MSCs prior to QD formation. The thermal stability of InP MSCs is influenced by the presence of exogenous bases as well as choice of the anionic ligand set. Addition of a primary amine, a common additive in previous InP QD syntheses, to carboxylate-terminated MSCs was found to bypass the formation of MSCs, allowing for homogeneous growth of InP QDs through a continuum of isolable sizes. Substitution of the carboxylate ligand set for a phosphonate ligand set increased the thermal stability of one particular InP MSC to 400 degrees C. The structure and optical properties of the MSCs with both carboxylate and phosphonate ligand sets were studied by UVvis absorption spectroscopy, powder XRD analysis, and solution P-31{H-1} and H-1 NMR spectroscopy. Finally, the carboxylate-terminated MSCs were identified as effective single-source precursors (SSPs) for the synthesis of high-quality InP QDs. Employing InP MSCs as SSPs for QDs effectively decouples the formation of MSCs from the subsequent second nucleation event and growth of InP QDs. The concentration dependence of this SSP reaction, as well as the shape uniformity of particles observed by TEM suggests that the stepwise growth from MSCs directly to QDs proceeds via a second nucleation event rather than an aggregative growth mechanism.