Doron-Mor Ilanit, Cohen Hagai, Barkay Zahava, Shanzer Abraham, Vaskevich Alexander, Rubinstein Israel
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
Chemistry. 2005 Sep 19;11(19):5555-62. doi: 10.1002/chem.200500103.
The distance dependence of the localized surface plasmon (SP) extinction of discontinuous gold films is a crucial issue in the application of transmission surface plasmon resonance (T-SPR) spectroscopy to chemical and biological sensing. This derives from the usual sensing configuration, whereby an analyte binds to a selective receptor layer on the gold film at a certain distance from the metal surface. In the present work the distance sensitivity of T-SPR spectroscopy of 1.0-5.0 nm (nominal thickness) gold island films evaporated on silanized glass substrates is studied by using coordination-based self-assembled multilayers, offering thickness tuning in the range from approximately 1 to approximately 15 nm. The morphology, composition and optical properties of the Au/multilayer systems were studied at each step of multilayer construction. High-resolution scanning electron microscopy (HRSEM) showed no apparent change in the underlying Au islands, while atomic force microscopy (AFM) indicated flattening of the surface topography during multilayer construction. A regular growth mode of the organic layers was substantiated by X-ray photoelectron spectroscopy (XPS). Transmission UV-visible spectra showed an increase of the extinction and a red shift of the maximum of the SP band upon addition of organic layers, establishing the distance dependence of the Au SP absorbance. The distance sensitivity of T-SPR spectroscopy can be varied by using characteristic substrate parameters, that is, Au nominal thickness and annealing. In particular, effective sensitivity up to a distance of at least 15 nm is demonstrated with 5 nm annealed Au films. It is shown that intensity measurements, particularly in the plasmon intensity change (PIC) presentation, provide an alternative to the usually measured plasmon band position, offering good accuracy and the possibility of measuring at a single wavelength. The present distance sensitivity results provide the basis for further development of T-SPR transducers based on receptor-coated Au island films.
在将透射表面等离子体共振（T-SPR）光谱应用于化学和生物传感时，不连续金膜的局域表面等离子体（SP）消光的距离依赖性是一个关键问题。这源于通常的传感配置，即分析物在距金属表面一定距离处与金膜上的选择性受体层结合。在本工作中，通过使用基于配位的自组装多层膜研究了在硅烷化玻璃基板上蒸发的1.0 - 5.0 nm（标称厚度）金岛膜的T-SPR光谱的距离敏感性，该多层膜可实现约1至约15 nm范围内的厚度调节。在多层膜构建的每个步骤中研究了Au/多层膜系统的形态、组成和光学性质。高分辨率扫描电子显微镜（HRSEM）显示底层金岛没有明显变化，而原子力显微镜（AFM）表明在多层膜构建过程中表面形貌变平。X射线光电子能谱（XPS）证实了有机层的规则生长模式。透射紫外-可见光谱显示添加有机层后消光增加且SP带最大值发生红移，证实了Au SP吸光度的距离依赖性。T-SPR光谱的距离敏感性可通过使用特征性的衬底参数（即Au标称厚度和退火）来改变。特别是，对于5 nm退火的Au膜，证明了在至少15 nm的距离内具有有效的敏感性。结果表明，强度测量，特别是在等离子体强度变化（PIC）表示中，提供了一种替代通常测量的等离子体带位置的方法，具有良好的准确性并且可以在单个波长下进行测量。目前的距离敏感性结果为基于受体涂层金岛膜的T-SPR传感器的进一步发展提供了基础。
