Dynamics of Mesoscale Order Formation by Colloidal Nanoparticles Adsorbing onto a Solid Surface

纳米粒子有序阵列通常具有独特的性质，作为高功能材料受到广泛关注。为了开发这样的材料和器件，必须知道颗粒-颗粒和颗粒-基底相互作用的影响，例如，建立的结构。因此，迫切需要一种模拟方法来预测有序形成过程的动力学。本研究旨在发展一种介于分子动力学和离散元方法之间的胶体吸附系统的介观模拟方法。主要结论如下：1.理论研究：基于朗之万方程，我们成功开发了布朗动力学模拟代码。对静电稳定的胶体纳米颗粒在带有反电荷的基底上进行了广泛的模拟。通过对仿真结果的分析，得出以下三点结论。第一章 ...更多信息 有序形成的决定因素不是吸附粒子之间的平均相互作用势能，这是过去提出的，迄今为止被认为是有效的。相反，我们发现这个因素是我们所说的“单向平均力”。2)基于上述发现的决定因素，有序结构可以由吸附颗粒之间的受控间距构成。3)证明了订单形成过程本质上是一个随机过程，并成功地建立了订单形成概率随时间变化的模型.实验研究：为了使颗粒吸附在基底上，基底必须具有相反的电荷，然后将蓝宝石板用于二氧化硅颗粒，而将云母板用于带正电荷的聚苯乙烯颗粒。吸附过程通过非原位SEM观察，并通过原位AFM观察。结果表明，胶体吸附的速率过程和表面粒子的迁移率对有序化过程的影响是非常重要的。综上所述，本文成功地建立了胶体吸附系统的介观模拟方法，该方法可以提供大量的吸附和有序化过程的详细信息。此外，在理论和实验方面，成功地模拟了胶体吸附体系中的许多重要过程和现象。少

Ordered arrays of nanoparticles often exhibit unique characteristics, which are attracting much attention recently to be utilized as high-functional materials. For the development of such materials and devices, one has to know effects of particle-particle and particle-substrate interactions, e.g., onto the established structure. Thus a simulation method for predicting the dynamics of the order-formation process must be pressing need. This study has been aiming at developing a mesoscale simulation method for colloidal adsorption system, which would stand between the molecular dynamics and the discrete element method. The conclusions are as follows.1. Theoretical study: Based on the Langevin equation, we successfully developed a Brownian dynamics simulation code. Extensive simulations were conducted for a electrostatically stabilized colloidal nanoparticles onto a substrate with counter charge. The findings through the analysis of the simulation results are the following three items. 1) … More The determinant factor for order formation was NOT the average interaction potential energies between adsorbed particles, which was proposed in the past and has been believed to be valid so far. Instead, the factor was found to be what we call "one-directional average force". 2) Based on the above found determinant factor, the ordered structure can be made up with a controlled spacing between adsorbed particles. 3) The order formation process was proven to be essentially a stochastic process, and a model to estimate the probability of order formation against time was successfully developed.2. Experimental study: The substrate must possess a counter charge to have particles adsorbed on it. Then a sapphire plate was used for silica particles, while mica plate was used with polystylene particle with positive charge. Adsorption processes were observed by ex-situ SEM observation, and by in-situ AFM observation. As a result, we clarified the rate process of adsorption, and the importance of the mobility of particles on the surface that severely affects the onset of the order formation.Summarizing, a mesoscale simulation method for colloidal adsorption system was successfully developed, which can give a large amount of detailed information on the adsorption and order formation process. Further, both in theoretical and experimental aspects, many important process and phenomena in colloidal adsorption system were modeled successfully. Less