Adsorption

The accumulation of molecules at the surface of a solid or liquid. Broadly there are two classes, weak physisorption (physical adsorption), which is predominantly due to attractive van der Waals’ intermolecular forces, and chemisorption (chemical adsorption), in which a chemical bond is formed. The magnitude of adsorption can be expressed in terms of surface coverage. A monolayer is an adsorbed surface film one molecule thick (i.e., a Langmuir film) and further adsorbed layers are called multilayers.