Detachment of Particles from Surfaces: An AFM Study.

Area of Science:

• Surface Science
• Colloid and Surface Chemistry
• Physical Chemistry

Background:

• Understanding surface interactions is crucial in various fields, including colloid science and materials engineering.
• The interplay between hydrophilic and hydrophobic surfaces in aqueous and organic media remains a complex area of study.

Purpose of the Study:

• To quantify adhesion and detachment forces between hydrophilic and hydrophobic surfaces.
• To analyze these interactions using atomic force microscopy (AFM) under varying conditions.
• To compare experimental results with theoretical models like DLVO theory and surface tension component theory.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure forces between surfaces.
• Investigated interactions in aqueous media at different pH and ionic strengths, and in organic solvents.
• Analyzed particle adhesion and detachment phenomena.

Main Results:

• Hydrophilic interactions were described by DLVO theory; no long-range hydrophobic forces were observed in hydrophilic-hydrophobic systems.
• A 'jump into contact' occurred at distances beyond van der Waals predictions.
• Hydrophobic-hydrophobic interactions were dominated by long-range attraction, sensitive to substrate, pH, and electrolyte concentration.
• Estimated interfacial energies using the Derjaguin approximation showed good qualitative agreement with surface tension component theory.

Conclusions:

• The Derjaguin approximation and surface tension component theory provide a useful framework for estimating interfacial energies.
• Hydrophobic forces play a significant role in the interaction between hydrophobic surfaces.
• Experimental adhesion forces align qualitatively with hydrodynamic detachment experiments.