Direct in situ observation of nanoparticle synthesis in a liquid crystal surfactant template.
Direct in situ observation of nanoparticle synthesis in a liquid crystal surfactant template.
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DOI：
10.1021/nn300671g
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发表时间：
2012-04-24
期刊：
影响因子：
17.1
通讯作者：
Arslan, Ilke
中科院分区：
文献类型：
--
作者：
Parent, Lucas R.;Robinson, David B.;Woehl, Taylor J.;Ristenpart, William D.;Evans, James E.;Browning, Nigel D.;Arslan, Ilke
关键词：
定制材料的受控且可重复的合成在纳米科学的许多领域中至关重要。为了控制合成，必须对纳米结构在其特征长度尺度上的演化有一个基本的了解。生长机制通常通过（扫描）透射电子显微镜 ((S)TEM) 等方法推断，其中纳米结构在生长完成后进行表征。这种事后分析技术无法提供优化合成过程所必需的信息，因为它们无法实时测量纳米结构的发展。在用于制备纳米多孔材料的复杂流变流体中尤其如此。在这里，我们展示了使用 STEM 中的流体台在纳米级高粘性溶致液晶模板中合成的直接原位观察。纳米颗粒成核并生长到约 5 nm 的颗粒，此时通过与胶束周围的其他纳米颗粒形成连接而继续生长，从而形成簇。当达到临界尺寸（>10-15 nm）时，簇在模板中变得高度移动，在生长结构中置换和捕获胶束，形成球形多孔纳米颗粒。最终产品与实验室异位合成的产品相匹配。这种直接观察流变流体（例如浓缩的水性表面活性剂）中纳米级合成的能力，为纳米材料合成的基本步骤提供了前所未有的理解。这反过来又允许合成下一代材料，这些材料可以强烈影响有机光伏、储能设备、催化和生物医学设备等重要技术。
Controlled and reproducible synthesis of tailored materials is essential in many fields of nanoscience. In order to control synthesis, there must be a fundamental understanding of nanostructure evolution on the length scale of its features. Growth mechanisms are usually inferred from methods such as (scanning) transmission electron microscopy ((S)TEM), where nanostructures are characterized after growth is complete. Such post mortem analysis techniques cannot provide the information essential to optimize the synthesis process, because they cannot measure nanostructure development as it proceeds in real time. This is especially true in the complex rheological fluids used in preparation of nanoporous materials. Here we show direct in situ observations of synthesis in a highly viscous lyotropic liquid crystal template on the nanoscale using a fluid stage in the STEM. The nanoparticles nucleate and grow to ~5 nm particles, at which point growth continues through the formation of connections with other nanoparticles around the micelles to form clusters. Upon reaching a critical size (>10–15 nm), the clusters become highly mobile in the template, displacing and trapping micelles within the growing structure to form spherical, porous nanoparticles. The final products match those synthesized in the lab ex situ. This ability to directly observe synthesis on the nanoscale in rheological fluids, such as concentrated aqueous surfactants, provides an unprecedented understanding of the fundamental steps of nanomaterial synthesis. This in turn allows for the synthesis of next generation materials that can strongly impact important technologies such as organic photovoltaics, energy storage devices, catalysis, and biomedical devices.
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