Recently, we have found that the hydrothermal treatment (HTT), which is a heat treatment under relative humidity of 100%, is

effective for controlling the dye aggregation states when it is applied to the well-known MS-C20 binary LB film [16–26]. The as-deposited J-band originally located around 590 nm is reorganized by HTT to form a new phase associated with a further narrowing and a red shift of the peak [16–26]. We have already investigated kinetics of hydrothermally induced reorganization of J-aggregate in the mixed MS-C20 LB system and have pointed out that the UV-visible absorption spectra can be deconvoluted to three components: Band I (centered at 500 to 515 nm), Band II (centered at 545 to 555 nm), and Band III (centered at 590 to 598 nm) [17, 19, 22, 26]. Band I, Quizartinib concentration BAY 73-4506 clinical trial Band II, and Band III are assigned as the blue-shifted dimer, monomer, and red-shifted J-aggregate, respectively. Furthermore, the HTT process consists of following two stages. The first stage is characterized by the decrease in the Band III component

associated with the increase in the Band I component, which is hypothesized as a dissociation process of the original J-aggregate (Band III centered at 590 nm) to the blue-shifted dimer (centered at 500 to 515 nm). The second stage is characterized as the reorganization of Band III (centered at 597 to 599 nm) from Band I (500 to 515 nm). Since the component of Band II (centered 4��8C at 545 to 555 nm) is almost unchanged throughout the whole HTT process, we have described that the growth and decay processes in the second stage are assumed to be a first-order reaction between Band I and Band III components [22, 26]. We have also reported that the HTT process induces a unique superstructure in the MS-C20 binary LB systems [18, 20–25]. Giant round-shaped domains with diameters reaching 100 μm are observed by optical microscopy. In those papers, we have touched

upon the sizes of the round-shaped domains depending on heating temperature (T H) and heating time (t H) and found that the average size of the domains tends to increase superlinearly depending on T H and t H. However, due to insufficient color sensitivity and resolution of the optical microscope used for the observation, the surface structure had not been characterized in detail [18, 20–25]. Since J-aggregate is known to emit intense fluorescence, fluorescence (FL) microscopy is considered to be a powerful tool to characterize the system. In this paper, we report on surface morphology of the MS-C20 binary LB films before and after HTT process combining bright field (BF) microscopy and FL microscopy and discuss the possible mechanisms of the J-aggregate reorganization. Methods Fabrication of the mixed LB films of Merocyanine and arachidic acid The film-forming materials, merocyanine dye (MS in Figure 1) and arachidic acid (C20 in Figure 1), were purchased from Hayashibara Biochemical Lab. Inc. (Okayama, Japan) and Fluka AG (St.