Observations of merocyanine J-aggregate domains in mixed molecular monolayers using SHC/fluorescence and atomic force microscopes

Using a newly developed microscope, which enables us to obtain the optical second-harmonic and fluorescence (FL) images and the FL and absorption spec tra of the same site of specimen, the monolayer of merocyanine dye (MD) mix ed with arachidic acid (AA) was observed at the air-water interface. It was revealed that the cigar-shaped J-aggregate domains have a non-centrosymmet ric structure with the polar axis inclined by similar to 30 degrees from th e long axis of the domain. Complemental AFM observations of the Langmuir-Bl odgett monolayer clarified that the monolayer consists of three topographic ally different phases: the MD J-aggregate domain, monomer MD, and AA. (C) 1 999 Elsevier Science B.V. All rights reserved.