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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Ultrafast Hole/Electron Transfer Dynamics in a CdSe Quantum Dot Sensitized by Pyrogallol Red: A Super-Sensitization System
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Ultrafast Hole/Electron Transfer Dynamics in a CdSe Quantum Dot Sensitized by Pyrogallol Red: A Super-Sensitization System

机译：邻苯三酚红敏化的CdSe量子点中的超快空穴/电子转移动力学：超敏化系统

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摘要

To.find a suitable hole-transporting adsorbate for CdSe quantum dots (Qps), a pyrogallol red (PGR) molecule was chosen where PGR also can sensitize CdSe QDs. Energy level diagrams suggest that the photoexcited hole can be transferred to PGR and photoexcited PGR can inject an electron into CdSe QDs. Steady-state and time-resolved emission studies suggest that the photoexcited hole is transferred to PGR; however, the process is too fast to monitor with the subnanosecond time-resolution spectroscopic technique. Femtosecond transient absorption spectroscopy has been employed to monitor the charge-transfer behavior of the above system in an early time scale. Photoexcitation of pure PGR and CdSe QDs at 400 nm laser light gives the transient absorption due to the photoexcited singlet state of PGR and charge carriers (electron/ hole) in CdSe QDs, respectively, in the visibleear-IR region of the absorption spectra. However, on photoexcitation of the CdSe/PGR composite at 400 nm, the PGR cation radical and electron in the CdSe QD were detected in the transient absorption spectra. Hole transfer time from the photoexcited CdSe QD to PGR is found to be 500 fs. The transient signal due to the PGR cation and electron in the CdSe QD also contributed to photoexcitation of PGR on the CdSe QD, where electron injection is found to be <150 fs. Charge recombination dynamics were found to be very slow with time constants of 4 ps (15%) and >200 ps (85%) confirming a grand charge-separated state in the CdSe/PGR composite system.
机译：为了找到适合CdSe量子点（Qps）的空穴传输吸附物，选择了焦三酚红（PGR）分子，其中PGR也可以使CdSe QD敏化。能级图表明，光激发空穴可以转移到PGR中，而光激发PGR可以将电子注入CdSe量子点中。稳态和时间分辨发射研究表明，光激发空穴已转移至PGR;但是，该过程太快，无法使用亚纳秒级的时间分辨率光谱技术进行监控。飞秒瞬态吸收光谱法已被用来在早期的时间尺度上监测上述系统的电荷转移行为。由于PGR和CdSe量子点中CdSe量子点中的电荷载流子（电子/空穴）分别在吸收光谱的可见/近红外区域中受光激发，因此纯PGR和CdSe量子点在400 nm激光下的光激发给出了瞬态吸收。 。但是，在400 nm处对CdSe / PGR复合材料进行光激发时，在瞬态吸收光谱中检测到CdSe QD中的PGR阳离子自由基和电子。从光激发的CdSe QD到PGR的空穴传输时间为500 fs。 CdSe QD中的PGR阳离子和电子引起的瞬态信号也有助于CdSe QD上PGR的光激发，发现电子注入<150 fs。发现电荷复合动力学非常慢，时间常数为4 ps（15％）和> 200 ps（85％），这证实了CdSe / PGR复合系统中的大电荷分离状态。

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