级联带结构CdS / CdSe和CdS / CdTe核-壳中的电荷离域，用Re（I）-聚吡啶配合物敏化,The Journal of Physical Chemistry C

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级联带结构CdS / CdSe和CdS / CdTe核-壳中的电荷离域，用Re（I）-聚吡啶配合物敏化
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-05-03 00:00:00 , DOI: 10.1021/acs.jpcc.6b01654
Partha Maity ₁ , Tushar Debnath ₁ , Tanmay Banerjee ₂ , Amitava Das _{2,

3} , Hirendra N. Ghosh ₁

Affiliation

对CdS量子点（QD）和CdS / CdSe I型和CdS / CdTe II型C-S / CdTe II型核-壳纳米晶体（NCs）进行Re（I）-聚吡啶基配合物敏化的电荷载流子动力学进行了重点研究。对载流子离域和Re-复合物作为空穴受体和敏化剂分子的作用。我们的研究证实了光激发空穴从CdS和CdS / CdSe转移到Re-络合物，而在CdS / CdTe-Re-络合物系统中没有观察到空穴转移。通过对相对能级的评估可以合理地解释这一点，该结果表明，与CdTe的价带（VB）相比，由于Re-复合物的低位最高占据分子轨道（HOMO），这种空穴迁移在能量上不利。壳; 然而，在所有三个QD和核-壳系统的存在下，观察到Re-复合物的高激发态的发光猝灭，这归因于电子从Re-复合物的热态（能量高于LUMO态）注入到C-核。 QD的导带（CB）。瞬态吸收（λ飞秒时域中记录的Re-复合致敏CdS和CdS / CdSe复合物的_泵浦= 400 nm，λ_探针= 450–750 nm）光谱显示在580–750 nm范围内有宽的瞬态吸收带，峰值在595附近纳米，这归因于Re-络合物的阳离子自由基的形成，通过捕获来自NC的光激发空穴或将电子注入NC的CB来实现。如预期的那样，在400 nm激发后，对于CdS / CdTe-Re-复合复合材料系统未观察到此类光谱。从光激发的Re-复合物到CdS QD和CdS / CdSe核-壳的电子注入被发现<100 fs，而空穴从光激发的CdS QD和CdS / CdSe核-壳到复合物的空穴转移在一定时间内发生分别为900 fs和2.5 ps。

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Charge Delocalization in the Cascade Band Structure CdS/CdSe and CdS/CdTe Core–Shell Sensitized with Re(I)–Polypyridyl Complex

Charge-carrier dynamics of CdS quantum dot (QD) and CdS/CdSe type-I and CdS/CdTe type-II core–shell nanocrystals (NCs) sensitized with a Re(I)–polypyridyl complex have been carried with special emphasis on studies on carrier delocalization and the role of Re-complex as a hole acceptor and sensitizer molecule. Our investigation confirmed photoexcited hole transfer from CdS and CdS/CdSe to the Re-complex, while no hole transfer was observed in the CdS/CdTe–Re-complex system. This was rationalized by the evaluation of the relative energy levels, which revealed that such hole migration was not energetically favorable due to low-lying highest occupied molecular orbital (HOMO) of the Re-complex as compared with the valence band (VB) of CdTe shell; however, luminescence quenching from upper excited states of Re-complex was observed in the presence of all three QD and core–shell systems, which has been attributed to electron injection from hot state (energetically higher than the LUMO state) of the Re-complex to the conduction band (CB) of the QDs. Transient absorption (λ_pump = 400 nm, λ_probe = 450–750 nm) spectra recorded for Re-complex-sensitized CdS and CdS/CdSe composite in the femtosecond time domain revealed a broad transient absorption band in the 580–750 nm region with a peak around 595 nm, and this was attributed to the cation radical formation for Re-complex, either by capturing photoexcited hole from the NCs or by injecting electron to the CB of the NCs. As anticipated, no such spectrum was observed for the CdS/CdTe–Re-complex composite system after 400 nm excitation. Electron injection from photoexcited Re-complex to CdS QD and CdS/CdSe core–shell was found to be <100 fs, while the hole transfer from photoexcited CdS QD and CdS/CdSe core–shell to Re-complex took place within the time scale of 900 fs and 2.5 ps, respectively.

更新日期：2016-05-03

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