Orientation of J-aggregate molecules in Langmuir film and Langmuir–Blodgett films of merocyanine dyes mixed with arachidic acid and n-octadecane and irradiation effect of visible light

Langmuir (L) film and Langmuir–Blodgett (LB) films of a merocyanine dyes (MC) containing C18 alkyl chain mixed with arachidic acid (AA) and n-octadecane (OD) were fabricated. Surface-pressure–area isotherms of an L film and absorption spectra of LB films deposited on a substrate were measured. Amphiphilic molecular orientation in the L film and the built-up proportion of MC J-aggregates to monomer and H-aggregates in MC-LB films mixed with AA and OD were controlled by altering the molar ratio of AA and OD to MC. The built-up proportion of MC J-aggregates in LB films decreased and the J-aggregates decayed to monomer and H-aggregates by increasing the exposure power of a 608-nm monochromatic light.