Preparation of merocyanine-dye Langmuir-Blodgett films and some of their physicochemical properties

J-Aggregates in Langmuir−Blodgett Films of a Merocyanine Dye without Metallic Cations: Using FT-IR to Observe Changes in the Electronic Structure of the Molecules upon Aggregation

“…Together with a broad band at 500−550 nm (abbreviated as band D), a distinct red-shifted band near 605 nm is observed for the mixed films, indicating the formation of J-aggregates in the mixed systems. On the other hand, the band D is dominant in the pure film and only a small J-band can be detected, similar to the spectra for either pure DS films or DS films mixed with FA and prepared at an air−“pure water” interface. ,,, Therefore, the atmosphere used for the LB deposition is crucial for obtaining J-aggregates of DS without metallic or ammonium cations in the DS−FA binary mixed systems.…”

“…The analysis on the IR spectra described in section 3.3 supports this assumption. In addition, A + ( λ ) − A - ( λ ) for the pure film can also be considered as a J-band, although the J-aggregate is a minor component in this film 2 Difference spectra described by eq 7 for the DS−FA mixed (molar ratios of 1:4, 1:2, 1:1) films prepared under nitrogen, difference spectrum described by eq 8 for the DS−FA mixed (1:1) films prepared under nitrogen and air with k = 0.74, and difference spectra described by eq 9 for the DS−FA mixed films prepared under nitrogen with k ‘ = 0.77.…”

“…In refs and , by comparing the absorption spectra of DS in acetone and aqueous acetone solutions to that of cast films of pure DS and DS−FA mixtures, the authors assigned the absorption peaks near 504 and 540 nm to the dimeric and monomeric bands, respectively. However, the shoulder near 500 nm seen in the acetone solution spectrum may not correspond to the dimer, as for CHCl 3 solutions described in ref .…”

“…J-aggregates in Langmuir−Blodgett (LB) films of merocyanine dyes, especially 3-carboxy-methyl-5-[2-(3-octadecylbenzothiasolin-2-ylidene)-ethylidene]rhodanine (abbreviated as DS and shown in the inset of Figure ), have attracted much attention because of their interesting properties, such as photoconduction, , in-plane anisotropy, , thermo- and chemichromism, , and nonlinear optics. , The formation mechanism of the J-aggregates has also been studied in LB films of DS − and other merocyanine dyes. ,, As for the pure DS system, which bears one alkyl chain and one carboxylic group, Iriyama et al reported that the J-band is much more distinct on a Cd-containing buffer solution than on pure water, although they could detect a small J-band on pure water. Therefore, buffer solutions containing metal or ammonium cations are commonly used as the subphase for the LB deposition of DS. − An exception to this is the well-developed J-band that has been reported for LB films of a 1:1:1 ternary mixture of DS, fatty acids (FA), and hexadecane, prepared on pure water . However, to our knowledge this ternary system has not been well characterized.…”

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

“…Amphiphilic merocyanine dye (MD) molecules ( Fig. 1(a)) form the J-aggregates on the aqueous subphase containing counter-ions such as Cd 2+ [8]. We have investigated the domain structure of MD monolayers [9,10] and found that MD J-aggregates are 2 dimensional (2D) crystallites of MD molecules and are second harmonic generation active [11][12][13].…”