Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa.
Department of Chemistry, Rhodes University, Grahamstown, South Africa.
Luminescence. 2016 May;31(3):694-703. doi: 10.1002/bio.3013. Epub 2015 Sep 2.
In this work, we synthesized water-soluble L-cysteine-capped alloyed CdSeTe core quantum dots (QDs) and investigated the structural and optical properties of deposition of each of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed that the overcoating of a CdS shell around the alloyed CdSeTe core [quantum yield (QY) = 8.4%] resulted in effective confinement of the radiative exciton with an improved QY value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS surface decreased the QY value to 24.7%, but an increase in the QY value of up to 49.5% was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe surface. QDs with shell layers showed improved stability relative to the core. Data obtained from time-resolved fluorescence measurements provided useful insight into variations in the photophysical properties of the QDs upon the formation of each shell layer. Our study suggests that the formation of CdSeTe/CdS core/shell QDs meets the requirements of quality QDs in terms of high photoluminescence QY and stability, hence further deposition of additional shells are not necessary in improving the optical properties of the core/shell QDs.
在这项工作中，我们合成了水溶性 L-半胱氨酸封端的合金 CdSeTe 核量子点（QDs），并研究了沉积每一层 CdS、CdS/ZnSe 和 CdS/ZnSe/ZnS 壳层的结构和光学性质。光物理结果表明，在合金 CdSeTe 核周围沉积一层 CdS 壳（量子产率（QY）=8.4%）有效地限制了辐射激子，QY 值提高到 93.5%。随后在 CdSeTe/CdS 表面沉积一层 ZnSe 壳，将 QY 值降低至 24.7%，但当在 CdSeTe/CdS/ZnSe 表面沉积一层 ZnS 壳时，QY 值增加到 49.5%。具有壳层的 QDs 相对于核表现出更好的稳定性。通过时间分辨荧光测量获得的数据提供了有关在形成每个壳层时 QDs 光物理性质变化的有用见解。我们的研究表明，CdSeTe/CdS 核/壳 QDs 的形成在高光荧光 QY 和稳定性方面满足高质量 QDs 的要求，因此进一步沉积额外的壳层对于改善核/壳 QDs 的光学性质并不是必需的。
