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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Heightened Electromagnetic Fields between Metal Nanoparticles: Surface Enhanced Raman Scattering from Metal-Cytochrome c-Metal Sandwiches
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Heightened Electromagnetic Fields between Metal Nanoparticles: Surface Enhanced Raman Scattering from Metal-Cytochrome c-Metal Sandwiches

机译：金属纳米粒子之间增强的电磁场：金属细胞色素c金属三明治的表面增强拉曼散射

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摘要

This manuscript reports the demonstration of strong interparticle electromagnetic coupling in nanoparticle:molecule:nanoparticle sandwiches. These assemblies were prepared by adsorption of cytochrome c (Cc)-coated colloidal Au nanoparticles onto aggregated colloidal Ag. Surface enhanced Raman scattering (SERS) spectra for the Cc:Au conjugates (Ag:Cc:Au) were compared to those obtained by direct adsorption of Cc (Ag:Cc) at several visible excitation wavelengths. The use of identically prepared samples with the same effective [Cc] and the same laser power allows the effects of sample geometry and interparticle coupling to be probed. As expected, at all excitation wavelengths, Ag:Cc:Au gave less intense spectra than Ag:Cc, because (i) only a small percentage of the Cc Molecules were close to the more SERS-active metal (Ag), and (ii) the heme, from which all observed vibrations arise, was oriented toward the Au, not the Ag. Nonetheless, the ratio of Ag:Cc:Au to Ag:Cc SERS intensity varied significantly with excitation wavelength, a phenomenon that can be accounted for only by a wavelength-dependent electromagnetic field. This, in turn, results from wavelength-dependent electromagnetic coupling between closely spaced colloidal Ag and colloidal Au. In addition to wavelength-dependent SERS intensity ratios, three separate lines of evidence support the existence of strong electromagnetic coupling: (i) the presence of a wavelength-shifted single particle surface plasmon band for Cc:Au conjugates upon exposure to agggregated Ag, (ii) demonstration of excitation wavelength-dependent photodriven conformational changes in Ag:Cc:Au, and (iii) dramatic increases in SERS intensities from protein-colloid conjugates prepared with Ag in place of Au.
机译：该手稿报告了在纳米粒子：分子：纳米粒子三明治结构中强粒子间电磁耦合的演示。这些组件是通过将细胞色素c（Cc）包覆的胶体金纳米颗粒吸附到聚集的胶体Ag上而制备的。将Cc：Au共轭物（Ag：Cc：Au）的表面增强拉曼散射（SERS）光谱与通过在几个可见激发波长下直接吸附Cc（Ag：Cc）获得的光谱进行了比较。使用具有相同有效[Cc]和相同激光功率的相同制备样品，可以探测样品几何形状和粒子间耦合的影响。不出所料，在所有激发波长下，Ag：Cc：Au的光谱都不如Ag：Cc，这是因为（i）只有一小部分Cc分子接近具有更高SERS活性的金属（Ag），并且（ii ）从中产生所有观察到的振动的血红素朝向Au，而不是Ag。尽管如此，Ag：Cc：Au与Ag：Cc SERS强度的比率随激发波长而显着变化，这种现象只能由与波长有关的电磁场来解释。反过来，这是由紧密间隔的胶体Ag和胶体Au之间的波长相关的电磁耦合导致的。除了取决于波长的SERS强度比外，三条单独的证据还支持强电磁耦合的存在：（i）在暴露于聚集的Ag时，Cc：Au共轭物存在波长移动的单粒子表面等离激元能带，（ ii）证明Ag：Cc：Au的激发波长依赖的光驱动构象变化，以及（iii）用Ag代替Au制备的蛋白质-胶体结合物的SERS强度急剧增加。

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