Organized monolayers and monolayer assemblies as potential components of molecular devices

The assembly of molecules to functional units and their interconnection in molecular dimensions to achieve processes like sensing, signal storage and processing, or catalysis of particular reactions is a challenge to modern science. Various phenomena are reviewed that may be considered relevant to the design and construction of molecular devices. The propagation of mechanical excitations of the monolayer-covered air–water interface as a model for signal transmission has been investigated using energy-transfer processes or fast formation of dye aggregates for optical detection. The lateral conductivity in specially designed monolayers can be modulated photochemically, thus providing a possibility of switching. Fast transfer of energy by incoherent exciton hopping can be used to harvest light by concentrating the energy absorbed in large area on a reactive center. Molecular fluorescent probes are sensors for electrical potentials, structure of the local environment, and average ion concentration. At the air–water interface, molecules may self-organize to larger units with new properties. Examples are the formation of extended two-dimensional aggregates of dyes and the reorganization of mixed monolayers to form a replica of adsorbed molecules.