School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA.
Small. 2009 Nov;5(21):2460-6. doi: 10.1002/smll.200900688.
It is demonstrated that bimetallic silver-gold anisotropic nanostructures can be easily assembled from various nanoparticle building blocks with well-defined geometries by means of electrostatic interactions. One-dimensional (1D) silver nanowires, two-dimensional (2D) silver nanoplates, and spherical gold nanoparticles are used as representative building blocks for bottom-up assembly. The gold nanoparticles are electrostatically bound onto the 1D silver nanowires and the 2D silver nanoplates to give bimetallic nanostructures. The unique feature of the resulting nanostructures is the particle-to-particle interaction that subjects absorbed analytes to an enhanced electromagnetic field with strong polarization dependence. The Raman activity of the bimetallic nanostructures is compared with that of the individual nanoparticle blocks by using rhodamine 6G solution as the model analyte. The Raman intensity of the best-performing silver-gold nanostructure is comparable with the dense array of silver nanowires and silver nanoplates that were prepared by means of the Langmuir-Blodgett technique. An optimized design of a single-nanostructure substrate for surface-enhanced Raman spectroscopy (SERS), based on a wet-assembly technique proposed here, can serve as a compact and low-cost alternative to fabricated nanoparticle arrays.
研究表明，通过静电相互作用，可以将具有明确定义形状的各种纳米粒子构建块容易地组装成双金属银-金各向异性纳米结构。一维（1D）银纳米线、二维（2D）银纳米板和球形金纳米粒子被用作自下而上组装的代表性构建块。金纳米粒子通过静电结合到 1D 银纳米线和 2D 银纳米板上，形成双金属纳米结构。所得纳米结构的独特之处在于颗粒间的相互作用，使吸收的分析物处于具有强极化依赖性的增强电磁场中。通过使用罗丹明 6G 溶液作为模型分析物，将双金属纳米结构的拉曼活性与单个纳米颗粒块的拉曼活性进行了比较。表现最佳的银-金纳米结构的拉曼强度可与通过 Langmuir-Blodgett 技术制备的密集银纳米线和银纳米板阵列相媲美。基于这里提出的湿组装技术，对用于表面增强拉曼光谱（SERS）的单个纳米结构衬底进行了优化设计，它可以作为制造纳米粒子阵列的紧凑且低成本的替代方案。
