Abstract It has been previously shown that visible-light excitation of CdSe quantum dots (QD) functionalized with a cinnamate ligand (4-Diethylamino-2-hydroxythiocinnamate; 4DEATC) can induce uncaging of a fluorescent coumarin molecule (7-Diethylaminocoumarin; 7DEAC). In the current study, the quantum yield, QY, for this photochemical uncaging process is determined. In addition, the results of visible-light excitation of cinnamate-capped CdSe and cinnamate-capped CdSe/ZnS QDs are compared. The uncaging of coumarin is observed only for the functionalized core CdSe QDs, and not for CdSe/ZnS core-shell QDs. These results strongly support that the uncaging of coumarin from cinnamate-capped QDs occurs via an electron-transfer step from the QD to the cinnamate ligand, and the large band gap of the ZnS shell blocks electron transfer from CdSe core to the ligand. In addition, it is demonstrated that coumarin uncaging from cinnamate-capped CdSe can be induced using pulsed NIR (1064 nm) excitation of the QD via a two-photon process. The two-photon absorbance cross section and two-photon absorbance action cross section are estimated by combining the results of the one- and two-photon uncaging experiments.

中文翻译：

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单光子和双光子电子转移诱导香豆素从肉桂酸酯封端的 CdSe 量子点解笼锁

摘要 先前已经表明，用肉桂酸酯配体（4-二乙氨基-2-羟基硫肉桂酸酯；4DEATC）功能化的 CdSe 量子点（QD）的可见光激发可以诱导荧光香豆素分子（7-二乙氨基香豆素；7DEAC）的解笼锁。在当前的研究中，确定了这种光化学解笼锁过程的量子产率 QY。此外，还比较了肉桂酸酯封端的 CdSe 和肉桂酸酯封端的 CdSe/ZnS QD 的可见光激发结果。仅在功能化的 CdSe 核量子点中观察到香豆素的解笼锁，而在 CdSe/ZnS 核-壳量子点中未观察到。这些结果强烈支持香豆素从肉桂酸酯封端的量子点解笼锁是通过从量子点到肉桂酸酯配体的电子转移步骤发生的，ZnS 壳层的大带隙阻止了电子从 CdSe 核转移到配体。此外，还证明可以通过双光子过程使用 QD 的脉冲 NIR (1064 nm) 激发诱导香豆素从肉桂酸酯封端的 CdSe 解笼。双光子吸收截面和双光子吸收作用截面是通过结合单光子和双光子解笼锁实验的结果来估计的。