Interfacial Electron Transfer Dynamics in a Single CdTe Quantum Dot-Pyromellitimide Conjugate
Interfacial Electron Transfer Dynamics in a Single CdTe Quantum Dot-Pyromellitimide Conjugate
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DOI：
10.1021/jp807591d
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发表时间：
2008-12-11
影响因子：
3.7
通讯作者：
Majima, Tetsuro
中科院分区：
文献类型：
--
作者：
Cui, Shi-Cong;Tachikawa, Takashi;Majima, Tetsuro
由于半导体量子点在发光二极管和太阳能电池等器件中的重要作用，量子点之间的电荷转移引起了人们极大的兴趣。我们现在报告的CdTe量子点和均苯四甲酸酰亚胺衍生物与羧酸（PI-CA）使用合奏和单粒子光谱之间的电子转移（ET）过程的机理研究。首先，为了确认光化学反应是否通过QD的激发而发生，使用稳态和时间分辨发射光谱检查了PI-CA以及对照底物对QD发射的淬灭。结果表明，PI-CA分子与量子点表面紧密结合，对675 nm附近的光致发光有明显的猝灭作用。纳秒瞬态吸收测量也表明，PI中心点-形成在激光闪光光解的共轭CdTe量子点和PI-CA在氯仿溶液中。利用单粒子PL光谱来阐明通过硫醇连接基修饰在玻璃表面上的单个CdTe/PI-CA共轭物内的界面ET过程。根据扩散控制电子转移（DCET）理论，讨论了修饰后的PI-CA分子对单个量子点发光的影响，即所谓的闪烁现象.最后，在实验和分析结果的基础上，得出结论，观察到的闪烁特性为个人的CdTe/PI-CA共轭物是由于能量扩散远离和回到共振条件满足的受体状态的能量导致在界面ET氧化还原周转率的间歇性变化。
Charge transfer to and from semiconductor quantum dots (QDs) is of intense interest because of its important roles in QD-based devices, such as light emitting diodes and solar cells. We now report a mechanistic study of the electron transfer (ET) processes between CdTe QDs and a pyromellitimide derivative with a carboxylic acid (PI-CA) using ensemble and single-particle spectroscopies. First, to confirm whether the photochemical reactions occur by excitation of the QDs, the quenching of the QD emission by PI-CA as well as control substrates was examined using steady-state and time-resolved emission spectroscopies. It was found that the PI-CA molecules are strongly bound to the surface of the QDs and significantly quench the photoluminescence (PL) band near 675 nm. Nanosecond transient absorption measurements also revealed that PI center dot- was formed during the laser flash photolysis of the conjugates between CdTe QD and PI-CA in chloroform solution. The single-particle PL spectroscopy was utilized to clarify the interfacial ET processes within individual CdTe/PI-CA conjugates-modified on the glass surface via thiol linkers. The influences of the modified PI-CA molecules on the luminescence intermittency, the so-called blinking phenomenon, of single QDs were discussed in terms of a diffusion-controlled electron transfer (DCET) theory for the probability distributions of the "on" or "off" events. Finally, on the basis of the experimental and analytical results, it was concluded that the blinking characteristics observed for individual CdTe/PI-CA conjugates are due to the energy diffusions away from and back to a resonance condition fulfilled by the energy of the acceptor states resulting in the intermittent changes in the interfacial ET redox turnover rates.