In this study, the surface zeta potential of a flat glass coated with different polyelectrolytes was measured using the Beckman Coulter DelsaNano C instrument with a flat surface sample cell.
First, the surface zeta potential of glass was determined in DI water by using probing particles, then the glass was removed and washed with distilled water. Next it was immersed for one hour in a polyelectrolyte solution. The glass was then set in the cell and the surface zeta potential was determined. Since this operation is performed repeatedly using different polyelectrolyte solutions, a laminated film of multiple layers can be formed onto the glass surface.
Two types of polyelectrolyte were used: the cationic polyelectrolyte polyethyleneimine (PEI; MP Biomedicals; Mw: 5x104 to 1x105 Dalton) and the anionic polyelectrolyte sodium polystyrene sulfonate (PSSNa; Aldrich; MwW: 7.5x104 Dalton). Iwaki micro glass slide was used as the flat glass substrate.
HPC coated polystyrene latex particles were utilized as probing particles. A flat surface cell was utilized to measure the surface zeta potential, based on the Mori-Okamoto equation. Initially, the monitor particles were dispersed in a 10 mM aqueous solution of NaCl, and the surface zeta potential of the glass was measured. The glass was then removed and rinsed well with distilled water, after which it was immersed for one hour in an aqueous solution of PEI at a concentration of 4x10-4 mol/L and rinsed well. The same monitor particles were then poured in and the surface zeta potential was measured.
The same procedure was then performed using 4x10-4 mol/L aqueous solution of PSSNa. These operations were performed repeatedly by alternately using the PEI solution and PSSNa solution and the surface zeta potentials of the glass were determined after each operation.
Figure 1 shows the surface zeta potentials of the glass. In each measurement, the sign of the zeta potential is the same as the charge of the immersed polyelectrolyte due to adsorption.
Figure 1. Surface zeta potentials obtained by alternately laminating with polyelectrolytes on a slide glass.
This study showed that multiple laminated films were formed on the surface, by means of relatively simple operations of rinsing the surface well to remove the un-adsorbed polyelectrolytes.
This information has been sourced, reviewed and adapted from materials provided by Beckman Coulter, Inc. - Particle Characterization.
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