Investigating the Relationship between Adhesion Forces and Surface Functionalization Using Atomic Force Microscopy

Abstract

Surface chemistry impacts technology, advancing the development of new heterogeneous catalysts, semiconductor devices, and materials synthesis. Carbon surfaces are ubiquitous in various fields, and the surface reactivity can be altered by surface functionalization on the molecular scale, introducing functional groups, thus shifting their macroscale properties. In this physical chemistry lab experiment, students use atomic force microscopy to investigate the surface of graphite (organic) and gold (inorganic) samples (solid phase) to compare topographical features, surface roughness, and adhesion forces of the samples. Students relate the force–displacement measurements with the Lennard-Jones potential to obtain measurable adhesion forces. Emphasis is placed on quantification of the adhesion forces between a hydrophobic highly oriented pyrolytic graphite (HOPG) surface, a hydrophilic (hydroxy) functionalized HOPG surface, and a metallic gold-coated glass slide. The surface of each sample is explored, allowing students to compare the difference between the hydrophobic and hydrophilic surfaces from surface functionalization.