Hybrid Langmuir-Blodgett Films Research Articles

Phase Transitions and Stabilization of the Organized Hybrid Langmuir-Blodgett Films of Alkanoic Acids/CdS and PbS Q-Particles

Phase Transitions and Stabilization of the Organized Hybrid Langmuir-Blodgett Films of Alkanoic Acids/CdS and PbS Q-Particles

Hybrid Langmuir-Blodgett Films Formed by Alternating Layers of Magnetic Polyoxometalate Clusters and Organic Donor Molecules—Towards the Preparation of Multifunctional Molecular Materials

Hybrid Langmuir-Blodgett Films Formed by Alternating Layers of Magnetic Polyoxometalate Clusters and Organic Donor Molecules—Towards the Preparation of Multifunctional Molecular Materials

Electrochemical and Photoelectrochemical Properties of New Hybrid Langmuir−Blodgett Films Containing Prussian Blue and a Tris(Bipyridine) Ruthenium Derivative

The elaboration of new Langmuir-Blodgett (LB) films containing Prussian blue and a surfactant derivative of the ruthenium tris(bipyridine) complex using a semi-amphiphilic approach is described in this paper. The redox and photoelectrochemical properties of these hybrid lamellar materials have been studied in aqueous KCl solutions. Dependencies of the cyclic voltammetry response on the number of deposited layers and the scan rate demonstrate that the hybrid LB films can be considered as a quasireversible system with a finite diffusion space. A large cathodic photocurrent is recorded when the LB films are irradiated with polychromatic light at a negative applied potential, indicating that both PB and the derivative of ruthenium tris(bipyridine) complex play an important role in the light-energy conversion process. A linear dependence of the cathodic photocurrent response on the number of deposited layers has also been exhibited and should be correlated to the presence of structural defects in the multilayers.

Hybrid Langmuir–Blodgett films of APT and cyanine with binary output modes

Hybrid Langmuir–Blodgett (LB) films were fabricated by transferring pure monolayers of an azobenzene derivative having a TCNQ (7,7,8,8-tetracyanoquinodimethane) moiety (APT) and then 1:1 mixed monolayers of cyanine/APT on solid substrates. The hybrid LB films have binary output modes. The alternate irradiation of UV and visible light yielded reversible cis- trans isomerization of APT, which was accompanied by the electrical conductivity switching associated with APT molecules and the change in the optical properties of the films due to the development of the J-band of the cyanine dye (CY). The order of the sequential deposition of the APT pure monolayers and the 1:1 mixed monolayers of CY/APT plays an important role in realizing the hybrid LB films with binary output modes.

Cooperative Photoresponse in Azobenzene Polymer/Liquid Crystal Molecular Films

The orientational properties of hybrid Langmuir-Blodgett (LB) films composed of an amphiphilic azobenzene (Az) side chain polymcr and liquid crystal (LC) molecule were investigated to gain insights into the molecular cooperativity in the interface region of the command surface system. Clear in-plane orientational induction directing perpendicular to the LB dipping direction was observed for both the Az side chains and 5CB molecules after an irradiation cycle with non-polarized UV and subsequent visible light in the normal incidence.

Modeling the Interface Region of Command Surface 2. Spectroscopic Evaluations of Azobenzene/Liquid Crystal Hybrid Langmuir−Blodgett Films under Illumination

Langmuir−Blodgett (LB) films composed of the mixture of an amphiphilic polymer containing azobenzene (Az) side chain (6Az10-PVA) and 4‘-pentyl-4-cyanobiphenyl (5CB) were prepared to mimic the two-dimensional contacting region of the LC/Az interface of the command surface which photochemically switches the LC alignment. UV−visible absorption and Fourier transform infrared spectroscopic measurements were carried out under illumination. These procedures allowed separate and simultaneous evaluations of the static state and dynamic molecular motions of both Az and LC molecules, which probably reflect the initial triggering step of the “domino-mode” response of LC. The spectroscopic data indicated the induction of reversible perpendicular/tilt orientational changes of both the Az side chain and 5CB molecule upon alternative irradiation of 365 and 436 nm light. Thus, 6Az10-PVA/5CB hybrid LB film can be regarded as a satisfactory interface model of a command surface that promotes the homeotropic/planer alignment ...

Highly Electrical Conductivity of Hybrid Langmuir-Blodgett Films of Transition Metal Dichalcogenide and Amphiphilic Compounds

Hybrid alternate layered films of transition metal dichalcogenides and amphiphilic compounds were prepared by Langmuir-Blodgett (LB) technique. The conductivity at room temperature depended on the transition metal dichalcogenide species, showing the highest value for the hybrid LB films of MoS2 system. This methodology was successfully applied to the fabrication of the hybrid LB films using various organic amphiphiles such as cyanine dyes, phthalocyanines, azobenzene, and ferrocene derivatives. The conductivity depended on the interlayer spacing: the conductivity decreased with increasing interlayer spacing of the film. The highest electrical conductivity of the hybrid LB films was over 100 Scm−.

Voltammetric and Impedance Analysis of Dimethyldioctadecylammonium/Prussian Blue Langmuir−Blodgett Films on ITO Electrodes

New hybrid Langmuir−Blodgett (LB) films containing Prussian Blue have been studied by cyclic voltammetry and electrochemical impedance spectroscopy. The dependencies of the cyclic voltammetry response on the number of deposited layers and the scan rate are described and show that the hybrid LB films can be considered as a quasi-reversible system with a finite diffusion space. On the basis of the impedance spectroscopy results, the charge transport process through the lamellar materials is modeled with an equivalent circuit considering two kinds of charge transport. The diffusion coefficients associated with the motions of the charged species are found to be very small, reflecting the fact that the insulating lipid layers considarebly hinder the diffusion of the charged species.

Phase Separation in Hybrid Langmuir−Blodgett Films of Perfluorinated and Hydrogenated Amphiphiles. Examination by Atomic Force Microscopy

Atomic force microscopic (AFM) observations were carried out for monolayer Langmuir−Blodgett (LB) films of two-component hybrids consisting of eicosanoic acid (C19H39COOH), perfluorooctadecanoic acid (C17F35COOH), perfluorotetradecanoic acid (C13F27COOH), and [2-(perfluorodecyl)-ethyl]dimorpholinophosphate (C10F21C2H4OP(O)[N(C2H4)2O]2, F10C2DMP). There were two domains with the height difference of 4 A on AFM photographs of the hybrid LB films of C17F35COOH/C19H39COOH, indicating phase separation. This phase separation was also observed for C13F27COOH/C19H39COOH and C13F27COOH/C17F35COOH hybrids. At low surface pressures, the isolated domains, which were C19H39COOH rich and C17F35COOH rich, respectively, were segregated by the continuous C13F27COOH-rich region. C13F27COOH molecules were piled up on the monolayers at high surface pressures. C13F27COOH was miscible with F10C2DMP, and the hybrid film displayed a fractal texture. The surface pressure−area isotherms of Langmuir films were discussed in relation...

Electrical conductivity of hybrid langmuir-blodgett films of transition metal dichalcogenide and amphiphilic cations

We prepared hybrkl layered alternate films of arnphiphilic eations and transition melal diehaleogenide such as MoS,, MoSe,. and WS, by Langmuir-Blodgett (LB) technique. The electrical conductivity of the hybrid LB films of MoS, and amphiphilic cations is ca. 100 Scm −1 at room temperature.

Fabrication of Hybrid Layered Films of MoS2 and an Amphiphilic Ammonium Cation Using the Langmuir−Blodgett Technique

Inorganic/organic hybrid ultrathin films of MoS2 and a cationic amphiphile, dihexadecyldimethylammonium bromide (DHA+Br-), were prepared using the Langmuir−Blodgett (LB) technique. The surface pressure−area isotherms of DHA+Br- changed by introducing exfoliated MoS2 particles into the subphase. On the other hand, the isotherms of icosanoic acid in the presence and absence of MoS2 particles in the subphase were essentially the same. The UV/vis reflection spectra of DHA+(Br-) monolayers on MoS2 suspension showed a broad absorption band assignable to MoS2, whereas that of icosanoic acid did not show any appreciable band. These results suggest the formation of hybrid monolayers consisting of DHA+ and MoS2. The hybrid monolayers were transferred successfully onto substrates using a horizontal lifting method to form LB films. That was confirmed by the infrared and UV/vis absorption spectroscopies and AFM, although the transfer ratios were not determined. The X-ray diffraction patterns of the LB films showed the layered structure in which organic and inorganic sheets are stacked alternately. The AFM image of a single-layer LB film of DHA+ and MoS2 showed flat, plate-like particles with diameters in the submicrometer region. The structure of the hybrid LB films depended strongly on the MoS2 concentration in the subphase for the preparation of the hybrid monolayers. The number of DHA+ molecules per unit area of the LB film increased with increasing MoS2 concentration in the subphase while the amount of MoS2 in the LB film remained unchanged. Further, the tilt angle of the hydrocarbons of DHA+ was large and the interlayer spacing of the LB film was small when the MoS2 concentration in the subphase was large. A model of the formation of the hybrid film was proposed.

Langmuir−Blodgett Films of Surface-Active Azodye. Investigation by Atomic Force Microscopy

Langmuir-Blodgett (LB) films of surface-active azodye, YOPE, were prepared at different surface pressures and observed by atomic force microscopy. The surface structure was compared with that of LB films of the arachidic acid/YOPE hybrid. The two-dimensional phase separation was observed in hybrid LB films. The molecular arrangement of YOPE on Langmuir films was inferred from the AFM observation of LB films and the surface pressure-area (π-A) isotherms. At lower surface pressures, the dye chromophores of YOPE molecules were lying along the air-water interface. The arithmetic additivity of π-A isotherms was substantiated for hybrids.