Medical Faculty Carl Gustav Carus, Clinical Sensoring and Monitoring, Dresden University of Technology, Fetscherstr. 74, 01307, Dresden, Germany.
Anal Bioanal Chem. 2009 Nov;395(6):1641-50. doi: 10.1007/s00216-009-3035-y. Epub 2009 Aug 21.
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) is a very sensitive technique to characterize the degree of molecular ordering in thin films on metallic surfaces. This is the first report of the coupling of a PM-IRRAS microscope to a free electron laser (FEL), a light source of highest brilliance. Some FELs emit in the infrared region and permit the mapping of molecular properties at high lateral resolution. We studied the molecular orientation of octadecanephosphonic acid (OPA) attached to a gold surface with microstructured aluminum oxide islands on the gold. The spatial resolution achieved is 12 microm which corresponds to the diffraction limit of the infrared light used in this study. This is a substantial improvement compared to previous studies using a PM-IRRA accessory together with a commercial Fourier transform infrared spectrometer, where the lateral resolution is noise-limited rather than diffraction-limited. The spectral maps reveal that OPA is preferably attached to the aluminum oxide islands via the bidentate binding mode whereas the tridentate mode is dominating in case of OPA attached to the gold areas.
偏振调制红外反射吸收光谱（PM-IRRAS）是一种非常灵敏的技术，可用于表征金属表面薄膜中分子有序度的程度。这是首次将 PM-IRRAS 显微镜与自由电子激光（FEL）耦合的报道，FEL 是一种具有最高亮度的光源。一些 FEL 发射红外区域的光，并允许以高横向分辨率绘制分子特性图。我们研究了附着在金表面上的十八烷磷酸（OPA）的分子取向，该金表面上具有微结构化的氧化铝岛。实现的空间分辨率为 12 微米，这对应于本研究中使用的红外光的衍射极限。与以前使用 PM-IRRA 附件和商业傅里叶变换红外光谱仪进行的研究相比，这是一个重大改进，在以前的研究中，横向分辨率受到噪声限制，而不是衍射限制。光谱图表明，OPA 优选通过双齿结合模式附着在氧化铝岛上，而在 OPA 附着在金区域的情况下，三齿模式占主导地位。
