Controllable Two-Stage Droplet Evaporation Method and Its Nanoparticle Self-Assembly Mechanism

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• 作者：Yong Xie ; Shengming Guo ; Chuanfei Guo ; Meng He ; Dongxue Chen ; Yinglu Ji ; Ziyu Chen ; Xiaochun Wu ; Qian Liu ; Sishen Xie
• 刊名：Langmuir
• 出版年：2013
• 出版时间：May 28, 2013
• 年：2013
• 卷：29
• 期：21
• 页码：6232-6241
• 全文大小：619K
• 年卷期：v.29,no.21(May 28, 2013)
• ISSN：1520-5827

文摘

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.