Interaction between photocatalyst surface nanostructures and ultraviolet light by apertureless scanning nearfield optical microscopy

通过扫描隧道显微镜（STM）观察到，紫外线（UV）照射在二氧化钛表面上产生了明显的结构变化，这是UV光对表面电子激发的结果。利用STM在原子尺度上观察了金红石型TiO_2（110）表面的局域光响应。在325 nm紫外光照射下，（110）面上几乎所有的区域都有响应，响应强度与最小带隙（3.2eV）电子跃迁一致，其中台阶和（1×2）脊区的响应强度较高。当用442 nm的蓝光照射同一表面时，大部分表面区域处于休眠状态，但台阶区域和（1×2）脊结构的某些区域对蓝光有响应。这些网站是与表面上的氧缺乏，这可能会给一个线索的可能性，表面工程的二氧化钛光催化剂被雇用在可见light.We还进行了全面的开尔文探针力显微镜（KPFM）的“经典”的有机太阳能电池系统组成的MDMO-PPV：PCBM共混物的研究。的KPFM方法产生详细的信息，在纳米尺度上的地形和局部功函数。实验在黑暗中或在442 nm或675 nm的激光照射下进行，以提取局部分辨表面光电压（SPV）。我们确定了氯苯和甲苯浇铸共混物膜的表面上的能量的明显差异。结合高分辨率扫描电子显微镜（SEM）实验，我们能够解释KPFM的结果，并得出一些结论，在太阳能电池配置的阴极的电子传输。结果表明，甲苯流延膜表面对电子向阴极传播的阻挡行为，通常在有机太阳能电池的膜顶部蒸发。

Ultraviolet (UV) irradiation on titanium dioxide surface gives apparent structural changes as observed by scanning tunneling microscopy (STM), which are the consequence of electronic excitation of the surface by UV light. Here local photoresponse of a rutile TiO_2(110) surface is visualized at atomic scale by STM. Almost all the areas on the (110) surface responded to the illumination of 325-nm ultra-violet (UV) light, in accordance with the minimum band-gap (3.2eV) electron transition, with steps and (1×2) ridge areas exhibiting higher response intensities. When the same surface is illuminated with blue light at 442nm, which is well below the minimum band-gap transition energy, most of the surface areas were dormant, but certain areas at step regions and (1×2) ridge structures responded to the blue light. These sites are associated with oxygen deficiency on the surface, which may give a clue to the possibility of surface engineering of titania photocatalyst to be employed under visible light.We also conducted a comprehensive Kelvin probe force microscopy (KPFM) study on the "classical" organic solar cell system consisting of MDMO-PPV:PCBM blends. The KPFM method yields detailed information of topography and local work function at nanometer scale. Experiments were performed either in dark or under laser illumination at 442nm or 675nm to extract the locally resolved surface photovoltage (SPV). We identified distinct differences in the energetics on the surface of chlorobenzene and toluene cast blend films. Together with high resolution scanning electron microscopy (SEM) experiments we were able to interpret the KPFM results and to draw some conclusions for the electron transport towards the cathode in the solar cell configuration. The results suggest a blocking behavior of the toluene cast film surfaces against electron propagation towards the cathode, usually evaporated on top of the films in organic solar cells.