New Insights into the Complexities of Shell Growth and the Strong Influence of Particle Volume in Nonblinking "Giant" Core/Shell Nanocrystal Quantum Dots
New Insights into the Complexities of Shell Growth and the Strong Influence of Particle Volume in Nonblinking "Giant" Core/Shell Nanocrystal Quantum Dots
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DOI：
10.1021/ja212032q
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发表时间：
2012-06-13
影响因子：
15
通讯作者：
Hollingsworth, Jennifer A.
中科院分区：
文献类型：
--
作者：
Ghosh, Yagnaseni;Mangum, Benjamin D.;Hollingsworth, Jennifer A.
超厚无机CdS壳层在CdSe量子凝块（NQD）核上的生长产生了一类独特的NQD，称为“巨”NQP（g-NQD）。g-NQD的特征在于与其常规核/壳NQD对应物相比独特的光物理性质，包括抑制的荧光闪烁（闪烁）、光漂白和非辐射俄歇复合。在这里，我们报告了对影响厚壳生长复杂过程的众多合成条件的新见解。我们展示了多个反应参数（非配位溶剂和配位体的身份和浓度、前体/NQD比、前体反应时间等）的单独和集体影响确定g-NQD的形状和晶相，以及这些结构特征和光学性质之间的关系。我们发现六角纤锌矿g-NQD提供最高的系综量子产率的发射和最完整的抑制闪烁。值得注意的是，我们还揭示了g-NQD颗粒体积和闪烁抑制之间的明确相关性，使得较大的核与较小的起始核尺寸相比在相对较薄的壳处提供闪烁抑制行为，这需要应用较厚的壳来实现相同水平的闪烁抑制。我们表明，有一个共同的，阈值g-NQD体积（类似于750 nm（3）），需要观察闪烁抑制，这个粒子体积对应的NQD辐射寿命类似于65 ns，无论起始核心大小。结合对关键合成参数的新理解和优化的核/壳颗粒体积，我们证明了即使在类似于1小时的长观察时间内也能有效地完全抑制闪烁。
The growth of ultra-thick inorganic CdS shells over CdSe nanocrystal quantum clot (NQD) cores gives rise to a distinct class of NQD called the "giant" NQP (g-NQD). g-NQDs are characterized by unique photophysical properties compared to their conventional core/shell NQD counterparts, including suppressed fluorescence intermittency (blinking), photobleaching, and nonradiative Auger recombination. Here, we report new insights into the numerous synthetic conditions that influence the complex process of thick-shell growth. We show the individual and collective effects of multiple reaction parameters (noncoordinating solvent and coordinating-ligand identities and concentrations, precursor/NQD ratios, precursor reaction times, etc.) on determining g-NQD shape and crystalline phase, and the relationship between these structural features and optical properties. We find that hexagonally faceted wurzite g-NQDs afford the highest ensemble quantum yields in emission and the most complete suppression of blinking. Significantly, we also reveal a clear correlation between g-NQD particle volume and blinking suppression, such that larger cores afford blinking-suppressed behavior at relatively thinner shells compared to smaller starting core sizes, which require application of thicker shells to realize the same level of blinking suppression. We show that there is a common, threshold g-NQD volume (similar to 750 nm(3)) that is required to observe blinking suppression and that this particle volume corresponds to an NQD radiative lifetime of similar to 65 ns regardless of starting core size. Combining new understanding of key synthetic parameters with optimized core/shell particle volumes, we demonstrate effectively complete suppression of blinking even for long observation times of similar to 1 h.