Orientation of Merocyanine Dye in Mixed Langmuir-Blodgett Films Investigated by Visible Absorption Spectroscopy

ABSTRACT

We have investigated the out-of-plane and the in-plane orientations of the transition dipole moments of merocyanine dye (MS) with various aggregation states including J- and H-aggregates in the mixed LB films by means of visible absorption spectroscopy. The results of the MS orientation estimated using the simple geometrical model suggest that the MS transition dipole moments lie in the film plane in all the aggregation states, and that the relationships between the dichroic behaviors observed and the in-plane order parameters obtained from the model are well recognized in the individual red-shifted and the blue-shifted aggregates.

Keywords:

• H-aggregate
• J-aggregate
• Langmuir-Blodgett (LB) films
• merocyanine dye
• simple geometrical model
• visible absorption spectroscopy

Notes

^a The molar mixing ratio is [MS]:[C₂₀]:[AL₁₈] = 1:2:x.

^b ⟨sin² Θ⟩-, ⟨sin² Θ sin² Φ⟩-, and p-values have been estimated assuming the absorption position at 580 nm.