Hypothesis

Colloidal particles in a pure nonpolar solvent are expected to be in a state of dynamic equilibrium where a particle’s charge fluctuates around a stable mean value. However, we find that PHSA-coated PMMA microparticles in dodecane gain positive charge over time. We hypothesize that this phenomenon is prompted by the high electric field (∼1 V/µm) that is applied in these measurements. Hence, we expect the reaction rate at which charge builds up on the particle to change when modifying the measurement parameters.

Experiments

Single elementary charging and discharging events can be resolved by measuring the charge of PHSA-coated PMMA particles with optical trapping electrophoresis. With this technique, the influence of the electric field amplitude and frequency, particle size, electrode material and acquired charge can be investigated.

Findings

The rate of the charging phenomenon is proportional to the amplitude of the applied electric field and the charging stops when the voltage is switched off. We propose a reaction mechanism where the particle sheds negatively charged ions. This mechanism can account for all the experimental observations of the electric field induced charging phenomenon.

中文翻译：

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电场诱导非极性液体中的胶体粒子带电

假设

预计纯非极性溶剂中的胶体颗粒处于动态平衡状态，其中颗粒的电荷围绕稳定的平均值波动。但是，我们发现十二烷中的PHSA涂层PMMA微粒会随着时间的流逝而获得正电荷。我们假设这种现象是由在这些测量中施加的高电场（〜1 V / µm）引起的。因此，我们期望在修改测量参数时，电荷在颗粒上累积的反应速率会发生变化。

实验

单个基本的充电和放电事件可以通过使用光阱电泳测量PHSA涂层的PMMA颗粒的电荷来解决。利用这种技术，可以研究电场幅度和频率，粒径，电极材料和获得的电荷的影响。

发现

充电现象的速率与施加的电场的幅度成比例，并且当电压关闭时，充电停止。我们提出了一种反应机制，其中颗粒会散发出带负电的离子。该机制可以解释电场感应充电现象的所有实验观察结果。