Spatial and temporal variation of surface-enhanced Raman scattering at Ag nanowires in aqueous solution
Spatial and temporal variation of surface-enhanced Raman scattering at Ag nanowires in aqueous solution
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DOI：
10.1039/c2cp43424e
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发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Hu, Dehong
中科院分区：
文献类型：
--
作者：
Clayton, Daniel A.;McPherson, Tyler E.;Hu, Dehong
为了更好地理解银纳米线结构与SERS增强能力之间的关系，给出了水溶液中银纳米线(NWS)的局域场增强拉曼散射(SERS)的时空变化。交叉的Ag NW和Ag NW束的SERS增强因子远高于单一的Ag NW，这是因为当导线靠近时，表面等离子体耦合形成的间隙密度更高。使用未纯化的含银纳米粒子的银纳米粒子或通过电偶置换反应和化学沉积的方法在银纳米粒子表面修饰金纳米粒子，可以增强银纳米粒子的间隙的作用。与纯化的单个银核相比，这导致了更好的SERS增强能力。拉曼成像显示了水溶液中SERS信号的时间响应与没有拉曼活性分子的银纳米粒子的光致发光背景不同。这种不同的时间响应可能用于将SERS信号从荧光背景中分离出来。首次用离散偶极子近似(DDA)方法计算了两个交叉和平行的银原子核的局域场强。通过选择一束未提纯的Ag NW束的扫描电子显微镜图像与其拉曼图像的比较，说明了间隙原子的SERS空间分布的不均一性及其与入射光偏振的关系。
The spatial and temporal variation of local field enhanced Raman scattering (SERS) at Ag nanowires (NWs) in aqueous solution is presented for an improved understanding of the NW structure-SERS enhancement capability relationship. Crossed Ag NWs and Ag NW bundles are found to have SERS enhancement factors much higher than single Ag NWs because of the higher density of interstitials formed by strong surface plasmon coupling when the wires are close to each other. The role of the interstitials of Ag NWs is enhanced by using unpurified Ag NWs containing Ag nanoparticles or decorating the Ag NWs surface with gold nanoparticles using galvanic replacement reaction and electroless deposition methods. This leads to an improved SERS enhancement capability as compared to purified single Ag NWs. Raman imaging reveals a different temporal response of the SERS signal in aqueous solution in comparison to the photoluminescence background of Ag NWs in the absence of Raman-active molecules. Such a different temporal response can be potentially used to separate the SERS signal from the fluorescence background. The Discrete Dipole Approximation (DDA) method is used for the first time to calculate the local field intensity of two crossed and parallel Ag NWs. Heterogeneities in the SERS spatial distribution of the interstitials and their incident-light polarization dependence are illustrated by comparing the SEM image of a selected unpurified Ag NW bundle with its Raman image.