Thermal Behavior of H-Aggregate in a Mixed Langmuir−Blodgett Film of Merocyanine Dye, Arachidic Acid, and n-octadecane Ternary System Investigated by UV−visible and IR Absorption Spectroscopy

Abstract

We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.

Influence of heat treatment in air, and subsequent hydrothermal treatment in the liquid phase or water treatment in the liquid phase on a mixed Langmuir–Blodgett film of merocyanine dye-arachidic acid-n-octadecane ternary system

“…2b, referring to the information not only on electronic excitation state but also on electronic ground state. The intramolecular charge transfer means the delocalization of p electrons in the butadiene group from the rhodanine group to the benzothiazolydine group [6][7][8][9][12][13][14]17,19], and in the C@S bond in the rhodanine group [6][7][8][9]14] (Fig. 1).…”

“…In Fig. 4a, the peaks at 2954, 2924 and 2852 cm À1 are assignable to the CH 3 asymmetric, and the CH 2 antisymmetric and symmetric stretching modes [12,15,19,23,24] of the MS 18 hydrocarbon chain [6][7][8][9], respectively. The latter two positions shift upward compared to those before treatment (see Supporting information 1 and Fig.…”

“…Therefore, we have been engaged in studies on the control of dye aggregation states using Langmuir-Blodgett (LB) films containing merocyanine dye with an octadecyl group (n = 18, MS 18 , 3-carboxymethyl-5-[2-(3-octadecyl-benzothiazolin-2-ylidene)-ethylidene]rhodanine), see Fig. 1) [5][6][7][8][9]. The J-and H-aggregates can be easily controlled in as-deposited LB films of MS 18 [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], and the former and latter formation mechanisms have been so far elucidated by and our group [6], respectively.…”

“…1) [5][6][7][8][9]. The J-and H-aggregates can be easily controlled in as-deposited LB films of MS 18 [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], and the former and latter formation mechanisms have been so far elucidated by and our group [6], respectively. Recently, we have attempted conversions from the red-shifted J-to blue-shifted aggregates [7], and from the blue-shifted H-to redshifted aggregates [8] using the perturbation because of the investigation into the possibility of controlling dye aggregation states, and the confirmation of dye alignments of J- [13][14][15] and H-aggregates [6] clarified in the MS 18 LB films.…”

The molecular aggregation of pyronin Y in natural bentonite clay suspension

“…Aggregation process is usually observed for many dye compounds depending on their molecular structure and concentration in water. The aggregate forms of dye compounds induce changes in the absorption characteristics due to strong dipole-dipole interactions between dye molecules [45]. For instance, the concentration of 3.70 Â 10 À 6 M PyY indicates monomeric behavior in deionized water and its absorption maximum occurs at 547 nm [36].…”