Infrared spectroscopic study on the Langmuir–Blodgett films of merocyanine dye–arachidic acid–n-octadecane ternary system

Abstract

Articles you may be interested inOligo(vinylidene fluoride) Langmuir-Blodgett films studied by spectroscopic ellipsometry and the density functional theorySize and molecular configuration of dye aggregates in mixed Langmuir-Blodgett films based on merocyanine dyeWe have studied the mobility and the orientation of the hydrocarbon chain in the Langmuir-Blodgett films of merocyanine dye ͑MS͒-arachidic acid (C 20 ) -n-octadecane (AL 18 ) with the molar mixing ratio ͓MS͔:͓C 20 ͔:͓AL 18 ͔ϭ1:2:x (xϭ0,1,2,3,4,5) by means of infrared spectroscopy. Deuterated C 20 (C 20 -d) and deuterated AL 18 (AL 18 -d) have been used to separate the infrared bands due to the hydrocarbon chain of MS. The bandwidths of CH 2 antisymmetric and CH 2 symmetric stretching modes decrease in the range from xϭ0 up to 2, indicating that the motion of the hydrocarbon chain of MS is hindered by mixing the AL 18 -d molecules as the third component. From xϭ0 to 2, the orientation of the long axis of the MS hydrocarbon chain is found to change. The change in orientation is associated with the decrease in the mobility of the MS hydrocarbon chain. It is indicated that the J aggregate is accompanied by the thermal motion of the hydrocarbon chain of MS, and that the H aggregate is accompanied by the highly packed state of the hydrocarbon chains of MS and AL 18 -d, suggesting that the aggregate formation is controlled by the state of hydrocarbon chain packing.

Conversion of the Aggregation State of Merocyanine Dye, Modification of the Subcell Packing of Arachidic Acid, and Removal of the Majority of n-Octadecane by Hydrothermal Treatment in the Liquid Phase in a Mixed Langmuir−Blodgett Film of the Ternary System

“…The solid and dotted lines denote A ∥ and A ⊥ , respectively. In Figure a, a blue-shifted peak with sharp absorption is observed at 505 nm, which is ascribed to H-aggregation. − The absorption maximum at 505 nm shows the dichroic ratio with R < 1, where R is defined as A ∥ / A ⊥ . This tendency of R originates from the MS 18 side-by-side arrangement in the H-aggregate 13-20 and the flow orientation effect .…”

“…The MS 18 concentration in the ternary system was on the order of 10 -4 M. An LB trough of the USI system (Fukuoka, Japan) was used. The preparations of the aqueous subphase containing cadmium chloride (CdCl 2 ) and sodium hydrogen carbonate (NaHCO 3 ) were the same as those reported previously. ,− After the chloroform solution was spread on an air−water interface, the monolayers were directly transferred to both sides of 13 × 38 mm 2 mica and CaF 2 substrates by the standard vertical dipping method at a surface pressure of 25 mN/m. The raising velocity of the mica substrate was 2.5 mm/min for the deposition of the monolayer, whereas the raising and dipping velocities of the CaF 2 substrate were 2.5 mm/min for up to 3 × 2 layers and then 25 mm/min afterward.…”

“…We have been engaged in research on the control of dye aggregation states by using mixed Langmuir−Blodgett (LB) films with merocyanine dye having an octadecyl group ( n = 18, MS 18 , 3-carboxymethyl-5-[2-(3-octadecylbenzothiazolin-2-ylidene)ethylidene]rhodanine; see Figure ). In a mixed LB film composed of an MS 18 −arachidic acid (C 20 ) binary system, a sharp, red-shifted J-band with an absorption maximum at 590 nm is formed, which is markedly shifted to a lower-energy side from the MS 18 monomer peak near 530 nm when it is prepared under an aqueous subphase containing a cadmium (Cd 2+ ) ion. − In addition, a blue-shifted band appears at 505 nm by adding a small amount of n -octadecane (AL 18 ) to the above MS 18 −C 20 binary system. − We assigned the 505 nm band to the H-band on the basis of the shift to the higher-energy side, sharpness, and in-plane anisotropy of the band. − …”

Spectroscopic study of J aggregates of amphiphilic merocyanine dyes formed in their pure Langmuir films

“…The minimum of E st for an antiparallel arrangement is always located at sϭ0 and an H aggregate should be formed if E st solely determines the molecular arrangement. In fact, Hirano et al [33][34][35] reported that DS forms H aggregates in L films under certain preparation conditions. Therefore, other interaction͑s͒ must compensate this electrostatic disadvantage of the J aggregates.…”

Orientation of J-aggregate molecules in Langmuir film and Langmuir–Blodgett films of merocyanine dyes mixed with arachidic acid and n-octadecane and irradiation effect of visible light

“…Hirano et al [11] compared the aggregation number and the other structural parameters of the J-and H-aggregates of the merocyanine-arachidic acid-n-octadecane ternary system estimated using the point dipole model and the extended dipole model referring to the deconvoluted spectra. Morita et al [12] indicated that the J-aggregate is accompanied by the thermal motion of the hydrocarbon chains of the merocyanine-arachidic acid-n-octadecane ternary system, and that the H-aggregate is accompanied by the highly packed state of the hydrocarbon chains of MS, suggesting that the aggregate formation is controlled by the state of hydrocarbon chain packing. Saito [13] indicated the application of MC-LB films mixed with AA to photoelectric conversion devices in expecting high efficiency photoelectric conversion, because the packing density of MC molecule increased and the defects of LB films decreased to lead an increase of the built-up proportion of J-aggregates in the MC-LB films by adding AA to the MC-LB films.…”