Takumi Nagao

Formation of organic heterostructures into p-n heterojunctions by surface pressure control

Abstract A surface-active rhodamine dye, combined with arachidic acid or with arachidic acid and merocyanine dye, is squeezed out from the monolayer at the air- water interface above a certain surface pressure and forms a two-storey structure with each component possessing an ordered molecular arrangement. Photoelectrical measurements have revealed that the two-storey structure composed of rhodamine, merocyanine and arachidic acid can be deposited on solid substrates to form an alternating p-n hetero Langmuir-Blodgett film, which is an entirely new way of constructing p-n junction heterostructures.

Surface-pressure-induced chromism in rhodamine monolayers

Abstract The optical properties of mixed monolayers incorporating a surface-active rhodamine B have been studied by using various subphases and matrices. When the proton concentration around the dye was low the visible absorption decreased completely at high surface pressures, whereas when the proton concentration was high the absorption decrease was incomplete and the contribution of high order aggregates was observed. These features are explained by a shift in the equilibrium between cation, zwitterion and lactone forms of rhodamine dye at the air-water interface.