丁胺包裹的CdSe量子点敏化的TiO2纳米晶薄膜电子转移机制

利用超快光谱技术系统研究了在丁胺包裹的CdSe量子点敏化的TiO₂纳米晶薄膜起始时刻界面间电子转移动力学。与之前的报道不同,该实验结果表明:CdSe量子点经过表面修饰后,两相电子注入机制--热电子和冷电子注入得以被证实,即:电子能分别从CdSe量子点导带中高的振动能级和导带底转移到TiO₂的导带。该机制详细描绘了电子在纳米界面间转移的图景。进一步研究发现:热电子注入的电子耦合强度(3.6±0.1 meV)比弛豫后的基态电子注入高两个数量级,基于Marcus理论,伴随着0.083 eV的重组能,冷电子注入的耦合强度值为~50 μeV。

Electron transfer mechanism of butylamine-capped CdSe quantum dot sensitized nanocrystalline TiO2 films

In this paper, we have investigated the initial interfacial electron transfer dynamics in butylamine-capped CdSe quantum dot(QD)-sensitized nanocrystalline TiO₂ films by ultrafast spectroscopy. Different with previous reports, the experiment results indicate that after surface modification of CdSe QDs, a two-phase electron injection mechanism(hot and cold electron injection) is validated, namely, electrons transfer from high vibration energy levels in conduction band and conduction band bottom of CdSe quantum dots into conduction band of TiO₂, respectively. This mechanism depicts a picture on the detailed charge transfer processes at the nano interfaces. We further find that the electron coupling strength (3.6±0.1 meV) of hot electron injection is two orders of magnitude larger than that of relaxed ground-state electron injection, which gives a value of ~50 μeV accompanied with reorganization energy 0.083 eV on the basis of Marcus theory.