Interfacial electron transfer energetics studied by high spatial resolution tip-enhanced Raman spectroscopic imaging

界面电子转移(IET)在许多化学和生物过程中起着重要的作用。具体地说，染料敏化二氧化钛太阳能转换系统中的IET对新能源技术和科学至关重要。然而，从分子-表面的结构和相互作用、界面的能量流动以及界面电子的振动弛豫势垒等方面，界面电子理论的微观机制还没有得到很好的理解。这项由美国鲍林格林州立大学的Lu小组和德国图宾根Eberhard Karls大学的Meixner小组共同参与的研究工作，将重点放在染料敏化的二氧化钛纳米晶体和晶体表面模型体系的IET微观机制上。Lu在染料-二氧化钛纳米粒子上建立了强大的IET动力学和机理以及IET能级的拉曼光谱分析程序；而Meixner拥有在单晶表面进行单分子拉曼成像的尖端近场拉曼光谱技术程序。这是研究太阳能转换这一重大科学问题与世界一流先进技术的完美匹配。最先进的局部探测显微镜技术，如10 nm高空间分辨率近场光学拉曼显微镜(Meixner)、AFM/STM针尖增强型单纳米粒子拉曼光谱(Lu)与Heller理论(用于光谱分析的含时波包散射理论)(Lu)相结合，将以前所未有的空间分辨率从传统的系综平均水平理解到分子细节的桥梁。

Interfacial electron transfer (IET) plays an important role in many chemical and biological processes. Specifically, IET in dye sensitized TiO2-based solar energy conversion systems is critical to new energy technology and sciences. However, the microscopic mechanism of interfacial ET is not well understood with regard to molecule-surface structure and interaction, energy flow across the interface, and vibrational relaxation barrier of IET. This collaborative research effort involving the Lu group at Bowling Green State University (USA) and the Meixner group at Eberhard Karls University in Tubingen (Germany) will focus on microscopic mechanisms of IET for model systems of dye sensitized TiO2 nanocryostals and crystalline surfaces. Lu has established a strong program on IET dynamics and mechanism and Raman spectroscopy analysis of the IET energetics on dye-TiO2 nanoparticles; whereas Meixner has a cutting-edge near-field Raman spectroscopy technical program on singlemolecule Raman imaging on single crystal surfaces. This is a perfect match to study an important scientific problem of solar energy conversion with world-rate advanced technology. A combined approach of state-of-the art local probe microscopy techniques such as 10-nm high spatial resolution near-field optical Raman microscopy (Meixner), AFM/STM tip enhanced single-nanoparticle Raman spectroscopy (Lu) in combination with Heller theory (time dependent wave packet scattering theory for spectral analysis) (Lu) will be used to bridge the gap from conventional ensemble-averaged level understanding to molecular details with unprecedented spatial resolution.