Distinguishing Electron and Hole Dynamics in Functionalized CdSe/CdS Core/Shell Quantum Dots Using Complementary Ultrafast Spectroscopies and Kinetic Modeling
Distinguishing Electron and Hole Dynamics in Functionalized CdSe/CdS Core/Shell Quantum Dots Using Complementary Ultrafast Spectroscopies and Kinetic Modeling
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使用互补超快光谱和动力学建模区分功能化 CdSe/CdS 核/壳量子点中的电子和空穴动力学
DOI：
10.1021/acs.jpcc.0c07037
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Baxter, Jason B.
中科院分区：
文献类型：
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作者：
Taheri, Mohammad M.;Elbert, Katherine C.;Yang, Shengsong;Diroll, Benjamin T.;Park, Jungmi;Murray, Christopher B.;Baxter, Jason B.
利用瞬态吸收（TA）光谱等技术可以在超快时间尺度上探测用分子受体功能化的半导体量子点（QD）中激发能和光生电荷的演化。然而，历史上的解释，1 S（e）-1S3/2（h）的转变在镉硫族化物量子点是完全归因于电子可能是误导，多指数模型用于拟合TA动力学不直接对应于特定的电子物理过程。在这里，我们提出了可见光波长和中红外TA和时间分辨的光致发光测量通知一个全面的动力学模型的光激发的CdSe/CdS核/壳量子点功能化与钝化油酸（OA），空穴接受二茂铁，或电子接受萘双酰亚胺（NBI）。我们发现，大约30%的1 S信号和72%的IR信号可以来自于钝化的核/壳量子点中的空穴。我们还证明了在OA封端的核/壳量子点中的电子捕获的证据，在用NBI官能化的量子点中具有额外的电子转移和空穴捕获。电子（空穴）俘获和释放的时间分别为450 ± 100 ps（430 ± 70 ps）和340 ± 100 ps（1.1 ± 0.4 ns），电子转移到NBI的时间常数为1.8 ns。由互补的超快技术和动力学建模提供的物理过程的全面图像可以加速纳米结构和分子系统的基础科学和应用开发。
The evolution of excitation energy and photogenerated charges in semiconductor quantum dots (QDs) functionalized with molecular acceptors can be probed on ultrafast time scales using techniques such as transient absorption (TA) spectroscopy. However, historical interpretations that the 1S(e)-1S3/2(h) transition in Cd-chalcogenide QDs is fully attributable to electrons may be misleading, and multiexponential models used to fit TA kinetics do not correspond directly to specific photophysical processes. Here, we present visible-wavelength and mid-IR TA and time-resolved photoluminescence measurements to inform a comprehensive kinetic model of the photoexcited CdSe/CdS core/shell QDs functionalized with passivating oleic acid (OA), hole-accepting ferrocene, or electron-accepting naphthalene bisimide (NBI). We show that ∼30% of the 1S signal and 72% of the IR signal can originate from holes in well-passivated core/shell QDs. We also demonstrate evidence of electron trapping in OA-capped core/shell QDs, with additional electron transfer and hole trapping in the QDs functionalized with NBI. Electron (hole) trapping and detrapping occur in 450 ± 100 ps (430 ± 70 ps) and 340 ± 100 ps (1.1 ± 0.4 ns) respectively, while the time constant for electron transfer to NBI is ∼1.8 ns. The comprehensive picture of photophysical processes provided by the complementary ultrafast techniques and kinetic modeling can accelerate both the fundamental science and application development of nanostructured and molecular systems.