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Charge regulation effects on electrostatic patch-charge attraction induced by adsorbed dendrimers
Ionel Popa1, Georg Papastavrou, Michal Borkovec
1Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Physical Chemistry Chemical Physics : PCCP
|April 30, 2010
Summary
We measured forces between latex particles with adsorbed poly(amido amine) (PAMAM) dendrimers. Near the isoelectric point, attractive forces, stronger than van der Waals, were observed and explained by a patch-charge model.
Area of Science:
- Colloid and Surface Science
- Nanotechnology
- Biophysics
Background:
- Understanding inter-particle forces is crucial for controlling colloidal systems.
- Poly(amido amine) (PAMAM) dendrimers are widely used due to their unique properties.
- Atomic Force Microscopy (AFM) enables precise measurement of nanoscale forces.
Purpose of the Study:
- To quantify interaction forces between latex particles with adsorbed cationic PAMAM dendrimers.
- To investigate the electrostatic interactions near the isoelectric point (IEP).
- To evaluate the applicability of the patch-charge model in describing these forces.
Main Methods:
- Utilized a multi-particle colloidal probe technique with AFM.
- Measured interaction forces between individual charged latex particles.
- Adsorbed cationic PAMAM dendrimers onto latex particles.
Main Results:
- Observed attractive forces near the IEP, exceeding van der Waals interactions.
- The patch-charge model provided a semi-quantitative explanation for the observed attractions.
- Experimental results aligned with the patch-charge model's prediction of amplitude and dependence on ionic strength and dendrimer generation.
- Force curves fell between constant charge and constant potential boundary condition predictions.
Conclusions:
- The additional attractive forces are electrostatic in origin.
- Charge regulation effects likely play a significant role in the observed interactions.
- Deviations from the patch-charge model suggest the influence of disordered structures and finite interaction regions.
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