Mixing characterization of perylene and merocyanine Langmuir–Blodgett films

Langmuir–Blodgett (LB) films of mixtures of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), merocyanine dye (DO) and arachidic acid (C20) with different molecular ratios, were prepared on Cd2+-containing and pure-water subphases. The characterization of mixed Langmuir and LB films were performed by using, respectively, surface pressure–molecular area isothermetry and UV–Vis–IR absorption spectroscopy. The analysis indicates that interaction between the two dyes modifies their arrangements and electronic states in their mixed Langmuir films spread upon the Cd2+-containing subphase. However, the mixed LB films with the pure-water subphase are showed to be simple physical mixtures. The difference in the mixing effect observed for the Langmuir films upon the Cd-containing and pure-water subphases may be caused by the formation of metal chelation with the former subphase.