Functional hybrid clay mineral films

Clay minerals are layered materials that lend themselves naturally to film formation. In these films the clay mineral layers are oriented horizontally on the substrate. There are four techniques for film formation: (1) casting; (2) spin coating; (3) layer-by-layer assemblage; and (4) the Langmuir–Blodgett technique. The principles of each technique are described. When molecules are organized in the interlayer space of the clay minerals, the films carry a functionality and are called functional hybrid clay mineral films. These functionalities may be (1) sensing of adsorbed molecules; (2) nonlinear optical properties; (3) energy transfer; (4) electron transfer; and (5) magnetism. The expression of functionality depends on the functionality of a molecule, on the degree of organization of these molecules in the interlayer space and on the degree of organization of the clay mineral layers in the films. This is illustrated with examples from the literature for each of the 4 methods of film formation.