Development of New Apparatus for Measurements of Resonant Excitation of Surface Plasmons by Laser from Layers of Polymers or Proteins Adsorbed on a Metal Thin Film

1.我们研制了一种新的测量表面等离子体激元共振激发的装置，该装置用激光从一层多聚体或蛋白质以及吸附在金属薄膜上的简单分子中激发表面等离子体。该装置使我们能够用个人计算机在0.01ﾟ的精度内自动改变入射角度。反射率曲线也是自动获得的，它们可以很容易地绘制成CRT。用该装置观察了水、甲醇、乙醇、十二烷基硫酸钠(十二烷基硫酸钠)和牛血清白蛋白(BSA)吸附在银膜上的激光反射曲线。我们发现，共振角随浓度变化的曲线代表了吸附等温线。银膜对十二烷基硫酸钠的吸附等温线表明，在银膜上存在两层吸附的十二烷基硫酸钠。根据上述理论，通过对反射率曲线的分析，估算出薄膜的厚度为36.9A^ﾟ。在用水冲洗后，我们再次测量了共振角移动-浓度曲线，发现十二烷基硫酸钠单分子膜的存在紧密地吸附在银膜上。非粘土层宽度为15A^ﾟ。在牛血清白蛋白的情况下，我们从共振角-浓度曲线观察到了单层的存在，并估计了附着层的宽度为140a·ﾟ。已知牛血清白蛋白分子的形状为旋转椭球结构，其长轴长度为145a·ﾟ。因此，我们得出结论：BSA分子位于底物上，其主轴垂直于底物。给出了激光反射率和表面等离子体激元色散关系的新表达式。利用这些公式，我们对上述实验结果进行了分析。

1. We have developed a new apparatus for the measurements of resonant excitation of surface plasmons by laser from a layer of polyners or proteins as well as simple molecules adsorbed on a metal thin film. This apparatus enables us to vary automatically incident angles by means of personal computer within the precision of 0.01ﾟ. Reflectivity curves are also obtained automatically and they are drawn readily an CRT.2. Using this apparatus we have observed the reflectivity curves of laser by water,methyl alcohol,ethyl alcohol,sodium dodecylsulfat(SDS), and bovine serum albusin(BSA) adsorbed on silver thin films. We have found that the curves of the shifts of resonance angles versus concentrations of SDS and BSA represent the adsorption isotherms. The isotherm of SDS adsorbed on silver thin film shows the existence of two adlayers of SDS stacked on the substrate film. The width of adlayers was estimated to be 36.9A^^ﾟ by the analysis of reflectivity curve on the basis of theory mentioned below. After the rinse of this adlayer by water we measured again resonance angle shift vs. concentration curves and found the existence of SDS monolayer tightly adsorbed on silver film. The width of the nonclayer was 15A^^ﾟ. In the case of BSA we observed the existence of monolayer from resonance angle vs. concentration curves and the width of adlayer was estimated to be 140A^^ﾟ. It is known that the shape of BSA molecule is rotatory ellipsoidal structure and the length of its major axis is 145A^^ﾟ. So we conclude that BSA molecules stand on the substrate and their major axes are vertical to the substrate.3. We have formulated new expressions for reflectivity of laser and dispersion relation of surface plasmon polariton. Using these formulas We have analyzed our experimental results described above.