In this work, one kind of type II ZnSe/CdS/ZnS core/shell/shell nanocrystals (NCs) is synthesized, and their linear and nonlinear photophysical properties are investigated. Through measurements of the temperature-dependent photoluminescence spectra of NCs, their excitonic properties, including the coefficient of the bandgap change, coupling strength of the exciton acoustic phonons, exciton longitudinal optical (LO) phonons, and LO–phonon energy are revealed. Femtosecond transient absorption spectroscopy was employed to obtain insight into ultrafast processes occurring at the interface of ZnSe and CdS, such as those involving the injection of photo-induced electrons into the CdS shell, interfacial state bleaching, and charge separation time. At the end, their multiphoton absorption spectra were determined by using the z-scan technique, which yielded a maximum two-photon absorption cross section of 3717 GM at 820 nm and three-photon absorption cross section up to 3.9×10−77 cm6·s2·photon−2 at 1220 nm, respectively. The photophysical properties presented here may be important for exploiting their relevant applications in optoelectronic devices and deep-tissue bioimaging.

中文翻译：

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ZnSe/CdS/ZnS核/壳/壳II型纳米晶体的线性和非线性光物理特性

在这项工作中，合成了一种 II 型 ZnSe/CdS/ZnS 核/壳/壳纳米晶体 (NCs)，并研究了它们的线性和非线性光物理性质。通过测量 NC 的温度相关光致发光光谱，揭示了它们的激子特性，包括带隙变化系数、激子声子的耦合强度、激子纵向光学 (LO) 声子和 LO-声子能量。飞秒瞬态吸收光谱用于深入了解发生在 ZnSe 和 CdS 界面的超快过程，例如涉及将光生电子注入 CdS 壳层、界面状态漂白和电荷分离时间的过程。最后，通过使用 z 扫描技术确定了它们的多光子吸收光谱，其在 820 nm 处产生的最大双光子吸收截面为 3717 GM，在 1220 nm 处产生的三光子吸收截面最大为 3.9×10-77 cm6·s2·光子-2。这里介绍的光物理特性对于开发它们在光电器件和深部组织生物成像中的相关应用可能很重要。