Meso-Structure Control of Colloidal Nanoparticles Adsorbed on a Substrate by Applying External Electric Potential

如果纳米颗粒阵列吸附在衬底上的尺度结构可以被控制，那么各种高功能材料将被开发出来。本研究旨在开发一种控制动力学和粒子阵列结构的方法，方法是将外部电位施加到胶体纳米颗粒吸附的导电衬底上。结论如下：1。实验研究：开发了一套配有导电衬底的实验系统，其表面电位由外部电势控制，通过非原位SEM观察和原位AFM观察，观察了带正电的聚苯胶乳胶体颗粒的吸附过程。我们发现，在-28mV的极限表面电位下，胶体颗粒以相当高的密度吸附，颗粒间距离几乎均匀；在-28mV以上，即使电位为负，也几乎不发生吸附。微负电荷基底不吸附的更大原因可能是防止了表面结构水层的强吸附。这种弱吸附粒子由于在表面上的摩擦极大地减少，预计会形成有序的阵列。理论研究：对静电稳定的胶体纳米颗粒在带反电荷的基片上进行了广泛的布朗动力学模拟，以找出“单向平均力”的性质和估计方法，并发现“单向平均力”是有序/无序边界的决定因素。通过与硬盘Alder跃迁的比较，我们成功地统一了硬盘系统和胶体系统的有序/无序跃迁标准，引入了胶体粒子的有效直径，由于双层斥力的作用，胶体粒子的有效直径应该大于实际直径。有了这一成功，有序结构的先验预测和有序形成过程的动力学现在可以成为可能。综上所述，本文成功地理解了具有给定电位的表面上胶体吸附的中尺度有序形成过程，并对其进行了解析建模，为利用外加电位控制衬底上颗粒阵列的动力学和结构提供了理论基础。少

Various high-functional materials would be developed if masoscale structure of nanoparticle arrays adsorbed on a substrate can be controlled as desired. This study has been aiming at developing a methodology for controlling kinetics and structure of particle arrays by applying external electric potential to a conductive substrate onto which colloidal nanoparticles adsorb. The conclusions are as follows.1.Experimental study :Having developed an experimental system equipped with a conductive substrate with desired surface potential controlled by external electrical potential, adsorption processes of positively charged polystylene latex collodal particles were observed by ex-situ SEM observation, and by in-situ AFM observation. We found that there is a limiting surface potential of -28mV, below which colloidal particles adsorb with rather high density with almost uniform interparticle distances, and above which almost no adsorption occurs even though the potential remains negative. The re … More ason for no adsorption on the substrate with slightly negative charge may presumably be a prevention of strong adsorption by structured water layer on the surface. This kind of weakly adsorbed particles would be expected to form an ordered arrays because of extremely reduced friction on the surface.2.Theoretical study :Extensive simulations of Brownian dynamics were conducted for a electrostatically stabilized colloidal nanoparticles onto a substrate with counter charge in order to find out the nature and estimation method for "one-directional average force", which has been found to be the determinant factor for order/disorder boundary. Through comparison with the Alder transition by hard disks, we have successfully unified the criteria for order/disorder transition in both the hard-disk and colloidal systems by introducing an effective diameter for colloidal particles, which should be larger than the real diameter because of the repulsive double-layer forces. With this success a priori prediction of ordered structure and kinetics of the order-formation process can now be possible.Summarizing, a mesoscale order formation by colloidal adsorption on a surface with given potential was successfully understood and modeled analytically, which would stand for theoretical basis for the control of kinetics and structure of particle arrays on a substrate by applying external electric potential. Less