Chemistry Department, Wilfrid Laurier University, 75 University Avenue W, Waterloo, Ontario, Canada N2L 3C5.
Nanoscale. 2012 Nov 21;4(22):6981-9. doi: 10.1039/c2nr32031b.
We describe the synthetic preparation of well-defined symmetric multifaceted prismatic silver nanoparticles with chemically controlled faceting advantageous for strong and tunable surface-enhanced Raman scattering, SERS. These silver nanoparticles, that have been termed nanoflowers, AgNFls for their characteristic morphologies, have been prepared by a one-pot aqueous reaction under ambient conditions. AgNFl faceting is synthetically controlled by selective nanoparticle growth driven by chloride ions. Selective chloride binding to the surface of growing AgNFls results in nanoparticle enlargement predominantly at the points of their highest energy. These growth points are located at the tips of prismatic polygons in precursor prismatic morphologies that have been produced from thiolate-protected silver clusters whose coalescence is triggered with a strong base. For the practical aspects of AgNFl synthesis, concentrations of thiol and a strong base were found to be the key variables reliably controlling the extent of AgNFl faceting, as well as the kinetics of AgNFl formation and their stability. The selective growth of AgNFls progresses slower compared to that of non-faceted prisms: fewer nuclei can form leading to larger AgNFls with the diameter ranging from 130 to 2250 nm and asperity sizes on the order of 20 to 100 nm. Self-assembly of AgNFls yields columnar stacking. AgNFls were demonstrated to function as a promising substrate for surface-enhanced Raman scattering. SERS measurements were performed for a series of AgNFls with variable faceting, where the enhancement factors of 4.6 × 10(8) and 425 have been achieved for dry solid films and aqueous dispersions of non-aggregated AgNFls with single-particle enhancement, respectively. These SERS results are promising, especially in combination with that AgNFl nanoscale asperities can be conveniently tailored synthetically. Overall, AgNFls offer valuable opportunities for a system with synthetically variable nanoscale asperities.
我们描述了具有化学控制的面的规则对称多面棱柱状银纳米粒子的合成制备，这有利于强和可调谐的表面增强拉曼散射，SERS。这些银纳米粒子，因其特征形态而被称为纳米花，AgNFls，是通过在环境条件下的一锅水相反应制备的。AgNFl 的面是通过氯离子驱动的选择性纳米粒子生长来合成控制的。选择性地将氯离子结合到生长中的 AgNFl 的表面导致纳米粒子主要在其能量最高点处增大。这些生长点位于前体棱柱状形态的棱柱形多边形的尖端，这些形态是由巯基保护的银簇自组装而成的，其自组装是由强碱引发的。对于 AgNFl 合成的实际方面，发现硫醇和强碱的浓度是可靠地控制 AgNFl 面的程度、AgNFl 形成的动力学及其稳定性的关键变量。与非面棱柱相比，AgNFl 的选择性生长进展较慢：形成的核较少，导致 AgNFl 较大，直径范围为 130 至 2250nm，粗糙度尺寸约为 20 至 100nm。AgNFl 的自组装产生柱状堆积。AgNFl 被证明是一种很有前途的表面增强拉曼散射基底。进行了一系列具有可变面的 AgNFl 的 SERS 测量，在干燥固体薄膜和非聚集 AgNFl 的水溶液中，分别实现了 4.6×10^8 和 425 的增强因子，具有单粒子增强。这些 SERS 结果很有前途，特别是与 AgNFl 纳米级粗糙度可以方便地进行合成修饰相结合时。总的来说，AgNFl 为具有合成可变纳米级粗糙度的系统提供了有价值的机会。
