Forces between different latex particles in aqueous electrolyte solutions measured with the colloidal probe technique

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Materials Science

Background:

• Understanding colloidal particle interactions is crucial in various scientific fields.
• The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is a cornerstone for describing interparticle forces.
• Direct force measurements provide critical data for validating theoretical models.

Purpose of the Study:

• To present direct force measurements between colloidal particles in monovalent salts.
• To assess the applicability of DLVO theory at nanoscale distances.
• To investigate the behavior of surface potential for particles with varying charges.

Main Methods:

• Utilized the colloidal probe technique, a method based on Atomic Force Microscopy.
• Performed direct force measurements between similar and dissimilar colloidal particles.
• Analyzed interaction forces in solutions containing monovalent salts.

Main Results:

• DLVO theory generally provides satisfactory quantification of interaction forces down to a few nanometers.
• Observed a sign reversal in surface potential for near-neutral particles, dependent on the counter-particle's charge.
• This phenomenon challenges the conventional view of surface potential as solely dependent on particle and bulk properties.

Conclusions:

• DLVO theory remains a robust model for colloidal interactions in many scenarios.
• The study highlights the complex interplay of surface charge and environment, particularly for weakly charged particles.
• Re-evaluation of surface potential assumptions may be necessary in specific colloidal systems.