Nishimura Satoshi, Matsumura Hideo, Kosuge Katsunori, Yamaguchi Tomohiko
Nanotechnology Research Institute, National Institute of Advanced Industrial Science & Technology, Ibaraki, Japan.
Langmuir. 2008 Nov 4;24(21):12695-703. doi: 10.1021/la800645c. Epub 2008 Oct 8.
We have tackled in situ electric conductance measurements under microscopic observations for alignments of silica particles that are induced by ionic polarization of the electrical double layer (EDL) around the particles. Using the in situ conductance measurements, we have presented evidence that electro-osmotic flow at a vessel bottom/water interface would be coupled with the ionic polarization in the EDL of spherical silica particles settling at the bottom (Langmuir 2007, 23, 8797). In this study, we followed this phenomenon further. We altered the zeta potential of a platform of a glass plate on which a pearl chain of silica particles was formed under an ac electric field to control the mobility of electro-osmotic flow at the macroscopic interface of the platform/water. As the magnitude of the zeta potential of the platform increased, the surface distance between neighboring particles in the pearl chains decreased and the in situ conductance totally increased due to the enhancement of the dipole moments induced by the ionic polarizations of the particles. These results could be explained by considering that the electro-osmotic contribution to the surface conduction around the particles would be coupled with that occurring at the platform/water interface.
我们在显微镜观察下进行了原位电导测量，以研究由颗粒周围双电层（EDL）的离子极化引起的二氧化硅颗粒排列情况。通过原位电导测量，我们提供了证据表明，在容器底部/水界面处的电渗流将与沉降在底部的球形二氧化硅颗粒的EDL中的离子极化相耦合（《朗缪尔》，2007年，第23卷，第8797页）。在本研究中，我们进一步探究了这一现象。我们改变了玻璃板平台的zeta电位，在交流电场下，二氧化硅颗粒的珍珠链在该平台上形成，以控制平台/水宏观界面处电渗流的迁移率。随着平台zeta电位的幅值增加，珍珠链中相邻颗粒之间的表面距离减小，并且由于颗粒离子极化诱导的偶极矩增强，原位电导总体增加。考虑到颗粒周围表面传导的电渗贡献将与平台/水界面处发生的电渗贡献相耦合，这些结果可以得到解释。
