Influence of Nanoscale Surface Topography and Self- Assembled Monolayers on Derjaguin–Landau–Verwey– Overbeek Theory Interactions in Aqueous Media

Surface forces play a crucial role in many technological and scientific systems, including colloids, cells, dispersions, micro/nanofluidics, and coatings. In liquids, interactions between surfaces are mainly governed by electrostatic double-layer forces and van der Waals–Casimir forces, collectively known as DLVO forces. These interactions, together with chemically specific effects, control processes such as adhesion, self-assembly, dispersion, and agglomeration. Understanding and quantifying these forces is essential for directing the assembly and stability of nanoscale systems.
Although many studies focus on homogeneous surfaces (hydrophilic or hydrophobic), most real technological surfaces are heterogeneous and contain regions with different wetting properties. Interactions between such surfaces remain only partially understood. This thesis aims to improve the understanding and control of DLVO forces in liquid environments by investigating the roles of nanoscale surface roughness and chemical modification using self-assembled monolayers (SAMs).
Using Atomic Force Microscopy (AFM) in a sphere–plate geometry, interaction forces between gold-coated surfaces were systematically measured in air, pure liquids, and electrolyte solutions. The results demonstrate that nanoscale roughness significantly affects adhesion and DLVO forces, sometimes strengthening and sometimes weakening capillary, electrostatic, and Casimir interactions depending on the surrounding medium. Surface chemistry was further modified using SAMs, revealing that chemical functionalization, combined with surface morphology, can tune the electric double-layer properties and surface potentials.
Overall, the findings highlight the complex interplay between surface roughness and chemistry in determining nanoscale interactions and provide insights for controlling surface forces in applications such as colloidal stabilization, biosensors, nanomechanical devices, and energy systems.