Wiederkehr Rodrigo S, Mendes Sergio B
Department of Physics and Astronomy, University of Louisville, Louisville 40292, Kentucky, USA.
Analyst. 2014 Mar 21;139(6):1396-402. doi: 10.1039/c3an02201c.
We report here the fabrication, characterization, and application of a single-mode integrated optical waveguide (IOW) spectrometer capable of acquiring optical absorbance spectra of surface-immobilized molecules in the visible and ultraviolet spectral region down to 315 nm. The UV-extension of the single-mode IOW technique to shorter wavelengths was made possible by our development of a low-loss single-mode dielectric waveguide in the UV region based on an alumina film grown by atomic layer deposition (ALD) over a high quality fused silica substrate, and by our design/fabrication of a broadband waveguide coupler formed by an integrated diffraction grating combined with a highly anamorphic optical beam of large numerical aperture. As an application of the developed technology, we report here the surface adsorption process of bacteriochlorophyll a on different interfaces using its Soret absorption band centred at 370 nm. The effects of different chemical compositions at the solid-liquid interface on the adsorption and spectral properties of bacteriochlorophyll a were determined from the polarized UV-Vis IOW spectra acquired with the developed instrumentation. The spectral extension of the single-mode IOW technique into the ultraviolet region is an important advance as it enables extremely sensitive studies in key characteristics of surface molecular processes (e.g., protein unfolding and solvation of aromatic amino-acid groups under surface binding) whose spectral features are mainly located at wavelengths below the visible spectrum.
我们在此报告一种单模集成光波导（IOW）光谱仪的制造、表征及应用，该光谱仪能够在可见光和紫外光谱区域（低至315 nm）获取表面固定分子的光吸收光谱。单模IOW技术向更短波长的紫外扩展之所以成为可能，是因为我们基于在高质量熔融石英衬底上通过原子层沉积（ALD）生长的氧化铝膜，开发了一种紫外区域的低损耗单模介质波导，以及我们设计/制造了一种由集成衍射光栅与大数值孔径的高度变形光束组合而成的宽带波导耦合器。作为所开发技术的一个应用，我们在此报告利用其位于370 nm的Soret吸收带，细菌叶绿素a在不同界面上的表面吸附过程。通过使用所开发的仪器获取的偏振紫外 - 可见IOW光谱，确定了固 - 液界面处不同化学成分对细菌叶绿素a吸附和光谱特性的影响。单模IOW技术向紫外区域的光谱扩展是一项重要进展，因为它能够对表面分子过程的关键特性（例如，表面结合下蛋白质的展开和芳香族氨基酸基团的溶剂化）进行极其灵敏的研究，这些过程的光谱特征主要位于可见光谱以下的波长处。
