Structural Phase Transition in Two-Dimensional Crystallites of Organic Dye Molecules Formed on Aqueous Subphases

Abstract

The 2D crystallites of polar organic dye molecules on an aqueous subphase exhibit a thermochromic phase transition. The visible absorption band of the crystallites depends on the temperature and the composition of the subphase. In-situ observations of the phase transition were carried out by a grazing incidence X-ray diffraction method. A shift and a split of the diffraction peaks were observed between the different phases, indicating a change in the molecular arrangement of the crystallites in their chromic transition.

Keywords:

• J-aggregate
• merocyanine dye
• monolayer at the air-water interface; Langmuir film
• synchrotron radiation
• grazing incidence X-ray diffraction