Controllable Two-Stage Droplet Evaporation Method and Its Nanoparticle Self-Assembly Mechanism
Controllable Two-Stage Droplet Evaporation Method and Its Nanoparticle Self-Assembly Mechanism
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可控两级液滴蒸发方法及其纳米粒子自组装机制
DOI：
10.1021/la400736b
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发表时间：
2013-05-28
期刊：
影响因子：
3.9
通讯作者：
Xie, Sishen
中科院分区：
文献类型：
--
作者：
Xie, Yong;Guo, Shengming;Xie, Sishen
自下而上的自组装能够构建多种结构，并且被认为是一种用于先进纳米制造的有前途的方法。液滴蒸发作为最简单的方法，已被用于各种自组装中。然而，组装面积不够大，且有序性仍然没有得到很好的控制。在此，我们展示了一种通过调节蒸发液滴的湿度和温度的简便且可控的两阶段液滴蒸发方法。以高度单分散的金纳米棒（GNRs）为例，可重复地实现了大面积的自组装单层阵列。为了理解自组装机制，我们采用简化模型来分析纳米棒之间的相互作用。结果表明，存在二次能量最小的亚稳态，特别是在组装过程的后期，从而导致了有序阵列的形成。组装阵列之间的较大静电势垒阻止了多层结构的形成，进而导致了优先形成单层结构。此外，我们预测了纳米棒不同类型组装的可能性，并最终给出了一个示意性的相图。这里的结果可能为用于增强光谱学、传感器或纳米器件的高质量自组装纳米粒子超晶格提供一种方法。
Bottom-up self-assembly is able to constitute a variety of structures and has been thought to be a promising way for advanced nanofabrication. Droplet evaporation, as the simplest method, has been used in various self-assemblies. However, the assembled area is not large enough and the order is still not well controlled. Here we show a facile and controllable two-stage droplet evaporation method by adjusting the humidity and temperature of the evaporating droplet. Taking the highly monodispersed gold nanorods (GNRs) as an example, large-area, self-assembly monolayer arrays are reproducibly achieved. To understand the self-assembly mechanism, we adopted simplified models to analyze the interactions between the nanorods. The results show that a metastable state of secondary-energy-minimum exists, especially in the latter stage of the assembly process, leading to the ordered arrays. A large electrostatic barrier between the assembled arrays prevents the formation of the multilayer structures and thereby leads to the preferential monolayers. Moreover, we predict possibilities of different types of assemblies of the nanorods, and a schematic phase diagram is finally given. The results here may offer a way toward high quality self assembled nanoparticles superlattices for use in enhanced spectroscopy, sensors, or nanodevices.