Structural Phase Transition of J-Aggregate Crystallites on the Binary Counter-Ion Subphase

Abstract

The recently found chromic phase transition of merocyanine J-aggregates monolayer on the aqueous subphase containing Cd ^{2 +} and Mg ^{2 +} was investigated by the grazing-incidence X-ray diffraction method. The evidence of the structural difference between the phases of J-band at 620 nm and 590 nm was obtained by the investigations on the monolayers prepared at the different molar ratios of Cd ^{2 +} and Mg ^{2 +} . The change in a Bragg's peak was observed at the ratio of the ions, where the J-band wavelength also exhibited the discrete shift. The relationship between the obtained results and the phase diagram determined by the shift of the J-band wavelength was also discussed from the viewpoint of the formation mechanism of J-aggregate crystallites.

Keywords:

• Grazing-incidence
• X-ray diffraction
• J-aggregate
• monolayer
• phase transition

Acknowledgments

The synchrotron radiation experiments were performed at the SPring-8 with the approval of the Japan Synchrotron Research Institute (JASRI) (Proposal No. 2002B0706-ND1-np), and these works were supported by the Ministry of Education, Culture, Sports, Science and Technology, the Grant-in-Aid for Encouragement of Young Scientist (13750019, 2001), Waseda University Grant for Special Research Projects (Individual Research, 2001A-111), and the Grant-in-Aid for the 21st COE Program (Physics of Systems with Self-Organization Composed of Multi-Elements).

Notes

^a Monolayer on the subphase (Langmuir film).

^b LB films were deposited at the surface pressure of 20 mN/m.

^c Data were taken from Ref. [15].