Jin Tao, Zhang Zhendian, He Sheng, Kaledin Alexey L, Xu Zihao, Liu Yawei, Zhang Peng, Beratan David N, Lian Tianquan
Department of Chemistry, Emory University, 1515 Dickey Dr, Atlanta, Georgia 30322, United States.
Department of Chemistry, Duke University, Durham, North Carolina 27708, United States.
J Am Chem Soc. 2025 May 14;147(19):16282-16292. doi: 10.1021/jacs.5c01838. Epub 2025 Apr 30.
Quantum dot (QD)-sensitized triplet energy transfer (TET) has found promising applications in photon upconversion and photocatalysis. However, the underlying mechanism of TET in the QD-acceptor complex remains unclear despite the well-developed TET theory for the molecular donor-acceptor systems. Herein, the coupling strength of TET from CdSe/CdS core-shell QDs to 9-anthracene carboxylic acid (ACA) was studied by measuring the TET rate as a function of shell thickness with time-resolved photoluminescence. The change of TET-coupling strength with increasing shell thickness was further compared to those of electron and hole transfers from QDs so that we could test whether QD-sensitized TET is mediated by the charge transfer virtual state and can be considered as simultaneous electron and hole transfers as in molecular donor-acceptor systems. The measured coupling strength of TET from the CdSe/CdS QD decreases exponentially with the CdS shell thickness : ||() = ||(0)e, with an exponential decay factor β of 0.19 Å, which is smaller than the sum of the measured decay factors for electron transfer to methyl viologen (0.18 Å) and hole transfer to phenothiazine (0.29 Å) from the same QD. This inconsistency is explained by the broadening of QD shell thicknesses in the distance dependence study, which significantly modifies the TET-coupling strength and driving force, resulting in a shallower distance dependence of the TET rate constants. This study sheds light on the fundamental mechanisms of QD-sensitized TET reactions.
量子点（QD）敏化的三重态能量转移（TET）在光子上转换和光催化领域展现出了广阔的应用前景。然而，尽管分子供体 - 受体系统的TET理论已较为成熟，但QD - 受体复合物中TET的潜在机制仍不明确。在此，通过利用时间分辨光致发光测量TET速率随壳层厚度的变化，研究了从CdSe/CdS核壳量子点到9 - 蒽甲酸（ACA）的TET耦合强度。进一步将TET耦合强度随壳层厚度增加的变化与量子点的电子和空穴转移变化进行比较，以便我们能够检验QD敏化的TET是否由电荷转移虚态介导，以及是否能像分子供体 - 受体系统那样被视为同时发生的电子和空穴转移。测量得到的从CdSe/CdS量子点的TET耦合强度随CdS壳层厚度呈指数下降：||() = ||(0)e，指数衰减因子β为0.19 Å，该值小于从同一量子点向甲基紫精的电子转移（0.18 Å）和向吩噻嗪的空穴转移（0.29 Å）所测得的衰减因子之和。这种不一致性可通过距离依赖性研究中量子点壳层厚度的展宽来解释，这显著改变了TET耦合强度和驱动力，导致TET速率常数的距离依赖性变浅。本研究揭示了QD敏化TET反应的基本机制。
