Microsegmented Flow-Through Synthesis of Silver Nanoprisms with Exact Tunable Optical Properties
Microsegmented Flow-Through Synthesis of Silver Nanoprisms with Exact Tunable Optical Properties
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DOI：
10.1021/jp210842g
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发表时间：
2012-04-26
影响因子：
3.7
通讯作者：
Koehler, J. Michael
中科院分区：
文献类型：
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作者：
Knauer, Andrea;Csaki, Andrea;Koehler, J. Michael
在这项工作中，一个多步骤的微连续的流通合成过程中产生的均匀，高品质的银纳米棱镜。颗粒合成是基于硝酸银在聚阴离子聚合物聚（苯乙烯磺酸钠）存在下的湿化学还原。为了获得一个高产量的均匀的棱柱形银纳米粒子与三角形的基础上，两个主要的实验步骤是必要的。第一步是种子颗粒的合成。为了匹配小的、均匀的晶种颗粒的质量标准，在微连续流通系统中进行合成。恒定的停留时间和反应物的有效混合，实现了微段流技术的应用。良好的反应物混合的优点也适用于第二个实验步骤。在连续流通合成过程中，在微流体段内再次通过还原晶种颗粒的未封端表面上的硝酸银来生长银纳米棱镜。所得的胶体溶液，银种子和银纳米棱镜，进行了分析，使用差示离心沉降，紫外-可见分光光度法，和扫描电子显微镜。各个工艺步骤的产品颗粒的粒度分布非常窄。对于Ag种子颗粒，发现平均颗粒直径为3.8 nm，分布半宽度为2.3 nm。Ag纳米棱柱的边长可以在35和180 nm之间变化，同时尺寸分布保持窄，并且所需形状的颗粒产率高。由于纳米棱镜的光学性质从几何方面的强敏感性，银纳米棱镜承诺传感器应用的高潜力。这些应用对纳米颗粒的限制，如均匀性和窄的尺寸分布，可以通过微反应技术来满足。特别地，通过应用微段流，由于增强的段内部混合和停留时间分布的抑制，可以实现产品质量的改善。
In this work, a multistep microcontinuous flow-through synthesis procedure for the generation of homogeneous, high-quality silver nanoprisms is presented. The particle synthesis is based on the wet chemical reduction of silver nitrate in the presence of the polyanionic polymer poly(sodium styrenesulphonate). To obtain a high yield of homogeneous prism-shaped Ag nanoparticles with a triangular base, two main experimental steps are necessary. The first step is the synthesis of seed particles. To match the quality criteria for small, homogeneous seed particles, the synthesis was carried out in a microcontinuous flow-through system. Constant residence times and an effective mixing of the reactants were realized by the application of the microsegmented flow technique. The advantage of good reactant mixing was also adapted in the second experimental step. The growth of silver nanoprisms by reduction of silver nitrate on the noncapped surfaces of the seed particles was again carried out within microfluid segments during a continuous flow-through synthesis. The obtained colloidal solutions of both, Ag seeds and Ag nanoprisms, were analyzed using differential centrifugal sedimentation, UV-vis spectrophotometry, and scanning electron microscopy. The size distributions of the product particles of the individual process steps were extremely narrow. For the Ag seed particles, an average particle diameter of 3.8 nm with a distribution half-width of 2.3 nm was found. The edge length of the Ag nanoprisms could be varied between 35 and 180 nm, while the size distribution remained narrow and the yield of particles of the desired shape high. Because of the strong sensitivity of the optical properties of the nanoprisms from the geometrical aspects, Ag nanoprisms promise a high potential for sensor applications. Constraints on nanoparticles presented by these applications, such as uniformity and narrow size distributions, can be met by microreaction technology. In particular, by applying a microsegmented flow, an improvement of the product quality can be achieved because of the enhanced segment-internal mixing and the suppression of a residence time distribution.