On the incorporation mechanism of hydrophobic quantum dots in silica spheres by a reverse microemulsion method
On the incorporation mechanism of hydrophobic quantum dots in silica spheres by a reverse microemulsion method
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DOI：
10.1021/cm703348y
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发表时间：
2008-04-08
影响因子：
8.6
通讯作者：
Meijerink, Andries
中科院分区：
文献类型：
--
作者：
Koole, Rolf;van Schooneveld, Matti M.;Meijerink, Andries
在这项工作中，我们展示了强有力的实验证据，支持通过油包水 (W/O) 反微乳液合成将疏水性半导体纳米晶体（或量子点，QD）掺入单分散二氧化硅球（直径类似于 35 nm）的机制。荧光光谱用于研究添加各种合成反应物后 QD 表面发生的快速配体交换。研究发现，水解的 TEOS 对 QD 表面具有高亲和力，并取代了疏水性胺配体，从而使 QD 能够转移到发生二氧化硅生长的胶束的亲水内部。通过使用更强的结合硫醇配体阻碍配体交换，可以控制掺入的量子点的位置，从中心到偏心，并最终控制到二氧化硅球的表面。所提出的掺入机制解释了我们如何能够高度控制单个量子点恰好掺入二氧化硅球的中间。所提出的机制很可能也适用于使用相同方法将其他疏水性纳米晶体掺入二氧化硅中。结合我们的发现，我们能够制造出量子效率达到前所未有的 35% 的 QD/二氧化硅粒子。
In this work, we show strong experimental evidence in favor of a proposed incorporation mechanism of hydrophobic semiconductor nanocrystals (or quantum dots, QDs) in monodisperse silica spheres (diameter similar to 35 nm) by a water-in-oil (W/O) reverse microemulsion synthesis. Fluorescence spectroscopy is used to investigate the rapid ligand exchange that takes place at the QD surface upon addition of the various synthesis reactants. It is found that hydrolyzed TEOS has a high affinity for the QD surface and replaces the hydrophobic amine ligands, which enables the transfer of the QDs to the hydrophilic interior of the micelles where silica growth takes place. By hindering the ligand exchange using stronger binding thiol ligands, the position of the incorporated QDs can be controlled from centered to off-center and eventually to the surface of the silica spheres. The proposed incorporation mechanism explains how we can have high control over the incorporation of single QDs exactly in the middle of silica spheres. It is likely that the proposed mechanism also applies to the incorporation of other hydrophobic nanocrystals in silica using the same method. In conjunction with our findings, we were able to make QD/silica particles with an unprecedented quantum efficiency of 35%.