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Quantitative and Qualitative Examination of Particle-particle Interactions Using Colloidal Probe Nanoscopy
Published on: July 18, 2014
Electric field induced charging of colloidal particles in a nonpolar liquid
Caspar Schreuer1, Stijn Vandewiele1, Filip Strubbe1
1Electronics and Information Systems, Ghent University, Technologiepark-Zwijnaarde 15, 9052 Gent, Belgium.
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.
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