State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China.
School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China.
J Am Chem Soc. 2020 Jun 24;142(25):11270-11278. doi: 10.1021/jacs.0c04583. Epub 2020 Jun 15.
Triplet energy transfer from colloidal nanocrystals is a novel approach to sensitizing molecular triplets that are important for many applications. Recent studies suggest that this triplet transfer can be mediated by a hole transfer process when it is energetically allowed. In contrast, electron-transfer-mediated triplet transfer has not been observed yet, which is likely due to hole-trapping in typical II-VI group nanocrystals inhibiting the hole transfer step following initial electron transfer and hence disrupting a complete triplet exciton transfer. Here we report electron-transfer-mediated triplet energy transfer from CsPbCl and CsPbBr perovskite nanocrystals to surface-anchored rhodamine molecules. The mechanism was unambiguously established by ultrafast spectroscopy; control experiments using CdS nanocrystals also confirmed the role of hole-trapping in inhibiting this mechanism. The sensitized rhodamine triplets engaged in a variety of applications such as photon upconversion and singlet oxygen generation. Compared to conventional one-step triplet transfer, the electron-transfer-mediated mechanism is less demanding in terms of interfacial electronic coupling and hence is more generally implementable. Overall, this study not only establishes a complete framework of triplet energy transfer across nanocrystal/molecule interfaces but also greatly expands the scope of molecular triplet sensitization using nanocrystals.
三重态能量转移来自胶体纳米晶体，是敏化对许多应用很重要的分子三重态的一种新方法。最近的研究表明，当能量允许时，这种三重态转移可以通过空穴转移过程来介导。相比之下，尚未观察到电子转移介导的三重态转移，这可能是由于典型的 II-VI 族纳米晶体中的空穴捕获抑制了初始电子转移后的空穴转移步骤，从而破坏了完整的三重激子转移。在这里，我们报告了 CsPbCl 和 CsPbBr 钙钛矿纳米晶体向表面锚定的罗丹明分子的电子转移介导的三重态能量转移。超快光谱学明确地建立了该机制；使用 CdS 纳米晶体的对照实验也证实了空穴捕获在抑制这种机制中的作用。敏化的罗丹明三重态参与了各种应用，如光子上转换和单线态氧生成。与传统的一步三重态转移相比，电子转移介导的机制在界面电子偶合上的要求较低，因此更具通用性。总的来说，这项研究不仅建立了纳米晶/分子界面上三重态能量转移的完整框架，而且还大大扩展了使用纳米晶敏化分子三重态的范围。
