Langmuir films of dichroic dyes with fluorescent properties (original) (raw)
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Thin Solid Films, 1997
Diagrams of molecular areas depending on the composition of dye-fatty acid for six various dyesand fatty acids have been investigated by the monolayer method. The diagram positions differed relative to the additivity line (the line connecting the molecular areas of tile individual substances). Weobtained three types ofdiagrams for theinvestigated dyes.Thefirst is located below theadditivity line, thesecond above. andthethird is of mixed type possessing theintersection point with theadditivity line. Thecorrelation between thediagram characters anddye spectral properties in Langmuir-Blodgett films have also been investigated.
Zeitschrift für Naturforschung A, 2003
Two-component films of 4-octyl-4’-cyanobifenyl (8CB) and non-amphiphilic azo dye (1) at different molar fractions were studied at the air-water interface on the basis of the surface potentialmean molecular area dependence recorded simultaneously with the surface pressure-mean molecular area isotherm. Conventional Langmuir technique was used to form 1/8CB (guest-host) films during reduction and expansion of an area occupied by the molecules. From the surface potential value the effective dipole moment in the first monolayer formed on the water was calculated. Moreover, the number of dipole moments directed to the air with respect to those directed towards the water was estimated. A model of the microscopic polar ordering of the molecules in 1/8CB films at the air-water interface is proposed.
Thin Solid Films, 2003
Properties of the monolayer of octadecyl amine (ODA) molecules on aqueous solution of bromocresol purple (Bcp) dye have been studied over a wide range of pH by measuring the surface pressure-area isotherms. A strong interaction of ODA molecule was observed with the dye molecule in the pH range of 4-9. Under the present study, the dye molecules were adsorbed on the ODA monolayer at the water surface and subsequently a Langmuir-Blodgett (LB) film of ODA-dye complex was transferred from the air-water interface onto a solid substrate. Alternatively, dye molecules were incorporated into LB film by immersing the predeposited LB film of pure ODA into the dye solution, i.e. by adsorption of dye molecule at the solid-liquid interface. The adsorption behavior of ODA-Bcp dye complexes obtained through these two different routes was characterised with the help of UV-Visible spectroscopy. The nature of the ODA-dye complex deposited from air-water interface using the LB technique was found to be quite different from that of the complex formed by the adsorption of the dye into the pure ODA LB film. The adsorption spectra of the ODA-dye complex obtained from the air-water interface did not change with pH, while those of the ODA-dye complex formed from the solid-liquid interface showed pH dependence. ᮊ
Structure-fluorescence properties of some naphthoylene-benzimidazole-based Langmuir-Blodgett films
Thin Solid Films, 1996
Naphthoylene benzimidazoles (NBIs) and related polymers possess promising spectral properties for photonic applications. In the present study we focus on the possibilities of a controlled variation of molecular aggregation of NBI chromophores of various chemical compositions and symmetries in Langmuir-Blodgett (LB) films. Very different ~r-A isotherms are found for the NBI-stearic acid (SA) complexes with different NB! isomers (cis-, trans-or a I/2-NBI chromophore units). The interface behavior is explained by consideration of differences in molecular conformations at the water surface under lateral pressure. This addresses also a different type of chromophore aggregation within the LB films. Spectroscopic, atomic force microscopy (AFM), and X-ray scattering methods are used thoroughly to study mono-and multilayers of NBI:SA complexes. We propose a fiat-on arrangement for trans-NB! molecules and an edge-on orientation for cis-and 1/2NBI chromophores at the water surface and then in the LB films. A strong tendency for aggregation in the solution leads to a formation of different types of dimers and n-mers (depending on the isomer used) in the LB films. The type of aggregation of NB! chromophores in molecular films affects their spectroscopic properties. J-aggregation formation is revealed from the fluorescence spectra.
Immobilization of a fluorescent dye in Langmuir-Blodgett films
Bioelectrochemistry, 2004
We immobilized a hemicyanine dye, Di-8-ANEPPS, in ordered thin films of an organic matrix, dihexadecyl phosphate (DHP), and we transferred the mixed monolayers onto solid support by the Langmuir-Blodgett technique. We used gold and quartz slides and indium tin oxide (ITO) evaporated on glass slides as substrates. The multilayers formation was confirmed by ellipsometric and contact angle measurements. The optical response of the nanostructures was investigated collecting UV -Vis absorption and fluorescence emission intensity profiles. D
MRS Proceedings, 1997
We report on the organization of different disperse red dye derivatized methacrylate homo- and copolymers as Langmuir monolayers at the air-water interface. The monolayers were investigated using surface pressure and surface potential isotherms. Methacrylic homopolymers containing disperse red-1 (HPDR1) and disperse red-13 (HPDR13) and methacrylic copolymers with different mole percentages of the dye and hydroxyethyl spacer groups were synthesized and characterized. A comparison of the monolayer characteristics of HPDR1 and HPDR13 revealed the influence of the chlorine substitution in the aromatic ring of the dye. Studies with copolymers indicated a clear transition in the monolayer behavior with the change of mole percentage of the dye incorporated in the polymer. While copolymers with low dye content (up to about 5 mole%) presented an expanded monolayer, the copolymers containing higher dye content (12% and above) formed a condensed monolayer similar to that of the homopolymer. Th...
Molecular aggregation in Langmuir–Blodgett films of azo dye/liquid crystal mixtures
Dyes and Pigments, 2008
Studies of azo dye/liquid crystal mixtures in monolayers formed at an airewater interface (Langmuir films) and on a solid surface (Lang-muireBlodgett films) were performed. Six azo dyes with various molecular structures and two liquid crystal materials: 4-octyl-4 0 -cyanobiphenyl (8CB) and trans-4-octyl(4 0 -cyanophenyl)-cyclohexane (8PCH) were used. The dyes were added to the liquid crystal matrices at various concentrations and the surface pressureemean molecular area isotherms for the resultant Langmuir films were recorded. On the basis of the isotherm runs, conclusions concerning the molecular organization and the miscibility of the components in the ultrathin films were drawn. Absorption spectra for the LangmuireBlodgett films, using both natural and linearly polarized light were recorded. Information regarding intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal, with the polar terminal group was obtained. The ability of dye molecules to form self-aggregates at the airesolid substrate interface was observed. The influence of the molecular structure and the concentration of a dye on aggregates' geometry is discussed. It was found that at low dye concentrations in the liquid crystal J-type aggregates are formed. High dye contents are conducive to the creation of H-type aggregation, which improve the molecular packing in the LangmuireBlodgett film.
Langmuir, 1992
The monolayer behavior at the air-water interface of a chiral nonlinear optical dye was evaluated. The dye alone, an ester of palmitic acid and 4-nitro-4'-[(3R)-hydroxypyrrolidinol-1,l'-azobis[benzenel, did not form a stable monolayer at 23 *C at the airwater interface. However, mixtures of the dye with amylose acetate formed stable monolayers when the amount of the dye did not exceed 50 mol 9%. The surface structure of monolayers of the dye alone and of the mixtures was studied by transmission electron microscopy. This showed that molecular mixing did not occur. The mixtures are composed of domains of amylose acetate and two-dimensional crystallites of the dye molecules. The domains of the dye behave like H aggregates. It is argued that boundary lines between the crystallites of the dye and amylose acetate might play an important role of the stabilization process. As far as this study goes, the stabilization of the dye in mixed systems is only found for amylose esters as matrices.
Surface potential measurements of Langmuir films of azo dye/liquid crystal mixtures
Dyes and Pigments, 2009
Two-component films of a non-amphiphilic azo dye and a liquid crystal with strongly polar-CN group were studied at an air-water interface on the basis of the surface potential-mean molecular area dependence recorded simultaneously with the surface pressure-mean molecular area isotherm. Additionally, the morphology of the films was monitored with the aid of Brewster angle microscope. A conventional Langmuir technique was used to form dye/liquid crystal films during reduction and expansion of an area occupied by the molecules. From the surface potential value, the effective dipole moment in the first monolayer formed on the water was calculated. Moreover, the number of molecules with dipole moments directed from the water to the air with respect to those directed towards water was estimated. The influence of the two components' miscibilities upon the surface potential after addition of the dye to the liquid crystal was determined.