Hybrid Langmuir-Blodgett Films Research Articles

Clay-Assisted Disaggregation and Stabilization in Hemicyanine Langmuir-Blodgett Films

Hybrid Langmuir-Blodgett films consisting of an amphiphilic hemicyanine derivative and a smectite clay have been fabricated employing a clay suspension as the subphase. This hybridization was demonstrated to be a convenient and effective means of achieving complete disaggregation of dye chromophores in a Langmuir-Blodgett film without reducing chromophore density in the two-dimensional lattice. UV-visible electronic absorption and optical second-harmonic generation measurements indicated that the molecular alignment in the films was stabilized by the hybridization.

Nonlinear optical property of Langmuir–Blodgett films consisting of metal complexes

Hybrid Langmuir–Blodgett films consisting of sodium montmorillonite (a smectite clay) and nonamphiphilic cationic metal complexes [tris(4,7-diphenyl-1,10-phenanthroline)M]perchlorate (M = Mn, Co, Ni, Cu and Zn) have been fabricated. Optical second-harmonic generation (SHG) from the films was observed by employing a repetitive pulsed Nd:YAG laser operated at the wavelength of 1064 nm. The SHG signal intensities were found to correlate with the absorbance of the films at the wavelength of the second harmonic light (532 nm).

Hybrid Langmuir and Langmuir–Blodgett films composed of amphiphilic cyclodextrins and hydrophobic azobenzene derivative

Hybrid Langmuir and Langmuir–Blodgett (LB) films consisting of amphiphilic cyclodextrins (CDs) and hydrophobic azobenzene were fabricated. Due to the larger cross-sectional area of the CD core compared with the sum of the cross-sectional areas of the attached alkyl chains, the films had free space in the hydrophobic regions. Azo(p-Hexyl) having hydrophobic terminal chains was accommodated in the free space, whereas the usage of an azobenzene derivative bearing hydrophilic groups led to the phase separation. The average tilt angle of Azo( p-Hexyl) gave minima when the free space was just filled with Azo( p-Hexyl). Photoisomerization of azobenzenes in the hybrid LB films was studied.

Clay templating Langmuir–Blodgett films of a nonamphiphilic ruthenium(II) complex

We fabricated hybrid Langmuir–Blodgett (LB) films of smectite clays and a metal complex (tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate) which has no long alkyl chain. Characteristics of films fabricated on an aqueous suspension of synthetic saponite were compared with films fabricated on an aqueous suspension of natural sodium montmorillonite by means of nonlinear and linear optical spectroscopy, pressure–area ( π– A) isotherm measurement and atomic force microscopy (AFM). AFM studies revealed that the homogeneity of a hybrid LB film fabricated on an aqueous suspension of synthetic saponite is considerably higher than that of a film fabricated on an aqueous suspension of montmorillonite.

Fabrication of an organic-inorganic hybrid LB film of a magnetic polyoxometalate

A paramagnetic organic-inorganic hybrid Langmuir-Blodgett (LB) film was produced through orientation-controlled stabilization of a Ni-containing magnetic polyoxometalate (((NBu 4) 3 [PW 9NiO 43(HOOCC 2H 4PO) 2]): Ni-POM) monolayer by attaching electrostatically hydrophobic N,N-dimethyldodecyl amine (DMDA). Although the Ni-POM itself did not show any development of surface pressure upon monolayer spreading, the surface pressure-area isotherm showed the formation of very stable monolayer on the water subphase when the polyoxometalate was spread together with DMDA. The hybrid LB films transferred on solid substrates were characterized by XPS and XRD spectra. The XPS spectra indicated the presence of Ni-POM in the LB film. The AFM image of the LB film showed that the Ni-POM particles were totally spread to monolayer. The X-ray diffraction spectra showed POMs are positioned to two-dimensionally spread multiplayer film. The peaks due to (100) and (200) planes are interpreted as the hybrid multiplayer film is composed of multilayer monolayers. The Ni-POM showed characteristic paramagnetic susceptibility, which was monitored by a SQUID magnetometer.

Fabrication and Characterization of Ruthenium Complex-Vanadium Oxide Gel Hybrid Langmuir-Blodgett Films

Hybrid Langmuir-Blodgett films of an amphiphilic ruthenium tris-bipyridine complex (DC,Ru, n = 7, 13 and 19) and vanadium oxide gel were fabricated and characterized. Langmuir monolayers of the amphiphilic molecules hybridized and stabilized with layered vanadium oxide were transferred onto a solid substrate as z-type multilayers with a transfer ratio close to unity. AFM observation revealed that the monolayer had a smooth surface with roughness of 5 nm over I μm 2 . The hybrid monolayer of the vanadium oxide and DC n Ru showed photo-induced electron transfer to methyl viologens through the conduction band of the vanadium oxide.

Morphological investigation of hybrid Langmuir-Blodgett films of arachidic acid with a hydrotalcite/dendrimer nanocomposite.

A hydrotalcite clay/dendrimer nanocomposite prepared by the ionic exchange process was adsorbed from suspension of the nanocomposite on a Langmuir monolayer of arachidic acid at the air/water interface, followed by compressing and transferring onto an arachidic acid monolayer Langmuir-Blodgett (LB) film on mica. For comparison, the hydrotalcite-adsorbed hybrid film was also prepared. The morphology of hydrotalcite and the nanocomposite studied by transmission electron microscopy indicated the layered structures with respectively 1.2 +/- 0.3 and 3.2 +/- 0.5 nm repeating distances. The hybrid Langmuir films displayed the occupied surface area of 0.24 nm2 for both hydrotalcite and the nanocomposite. The formation of hybrid Langmuir films was confirmed by Brewster angle microscopy. Atomic force microscopic images of hybrid LB films revealed the formation of plateau domains with the height difference of 6 nm for hydrotalcite and 12 nm for the nanocomposite and the presence of dendrimers adsorbed on the clay surface of the nanocomposite.

Hybrid Langmuir and Langmuir–Blodgett films of a viologen derivative and TCNQ in a mixed valence state: preparation route and characterization

Abstract Hybrid Langmuir and Langmuir–Blodgett (LB) films containing two moieties of great chemical and electrochemical interest, namely a viologen derivative and tetracyanoquinodimethane (TCNQ) in a mixed valence state, were fabricated. To do so, positively ionized monolayers of 1,1 ′ -dioctadecyl 4,4 ′ -bipyridilium were prepared onto aqueous solutions of tetracyanoquinodimethane in a mixed valence state. Surface pressure vs. area ( π – A ), surface potential vs. area (Δ V – A ), and Brewster angle microscope (BAM) images were recorded and interpreted in terms of molecular interactions as well as the incorporation of the hydrophobic anions into the monolayer. After a comprehensive study, a 10 −6 M TCNQ aqueous solution was chosen as the best one to build hybrid LB films. Thus, the floating films were transferred onto solid substrates that were characterized using several techniques including ultraviolet–visible (UV–vis), infrared (IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) proving the incorporation of the TCNQ onto the film. These films show a good optical conductivity as well as a high degree of order and layers with a constant architecture.

Efficient Photoisomerization of Hybrid Langmuir-Blodgett Films of Amphiphilie Anionic Azobenzene and Alkylammonium with Long Alkyl Chains

We fabricated stable hybrid monolayers of an anionic azobenzene and alkylammonium, while pure azobenzene did not form a stable monolayer. Efficient photoisomerization of azobenzene proceeded in the Langmuir-Blodgett films due to salt formation of the two components, allowing azobenzene to have free volume with alkylammoniums as spacers.

Fabrication and characterization of hybrid Langmuir–Blodgett films of polyquinoline/stearic acid/rare earth-substituted heteropolymolybdate

Three kinds of hybrid Langmuir–Blodgett films are obtained by the organization of poly(1-hydro-2,2,4-trimethyl)quinoline (PQ), stearic acid(SA) and rare earth-substituted heteropolymolybdates (RE(PMo 11) 2, RE=Ce III, Eu III, La III) using the Langmuir–Blodgett technique. They are characterized by π– A isotherms, absorption spectra, fluorescence spectra, IR and atomic force microscope. The absorption spectra indicate that the molecules of PQ and heteropolymolybdates are incorporated into the LB films. The atomic force microscope reveals that heteropolymolybdates aggregate at the surface of the LB film.

Fabrication, characterization and conductivity of organic–inorganic hybrid Langmuir–Blodgett films based on polyquinoline and rare earth-substituted heteropolymolybdate

The organic/inorganic hybrid Langmuir–Blodgett (LB) films were obtained by the compact organization of poly(1,2-dihydro-2,2,4-trimethyl)quinoline (PQ), octadecylamine (ODA) and rare earth-substituted heteropolymolybdates. They were characterized by surface pressure–area ( π– A) isotherms, absorption spectra, fluorescence spectra, atomic force microscope (AFM) and scanning tunneling microscopy (STM). The atomic force microscope revealed a granular surface texture of nanosized rare earth-substituted heteropolymolybdate. The scanning tunneling microscopy indicated that the hybrid LB films containing rare earth-substituted heteropolymolybdates had the better electrical conductivity than LB film of PQ/ODA.

Luminescent hybrid Langmuir–Blodgett films of polyoxometaloeuropate

Luminescent hybrid Langmuir–Blodgett (LB) films of polyoxometaloeuropate (Na 9EuW 10O 36) were successfully prepared. Low-angle X-ray diffraction data demonstrate that the LB films have a well-defined lamellar structure. The hybrid LB films can exhibit strong luminescence under UV irradiation, which can be observed by the human eye. The effect of the lipid octadecylamine on the luminescence of polyoxometaloeuropate was discussed and compared with that of the lipid dimethyldioctadecylammonium bromide. It is found that the intensity ratio for the 5D 0→ 7F 2 transition to the 5D 0→ 7F 1 transition of europium in two kinds of LB films is quite different. The X-ray photoelectron spectra data verify that there exist different interactions between two lipids and the inorganic polyanions. The different interactions between two lipids and the polyanions may result in the distortion of the site symmetry for europium to a different extent, which may account for the difference in luminescent behavior between the two kinds of LB films.

Hybrid Organic−Inorganic Langmuir−Blodgett Films Starting from Colloidal Prussian Blue Solution

Starting from Prussian Blue and an amphiphilic derivative of Ru(bpy)32+, new organic−inorganic systems have been obtained using the Langmuir−Blodgett (LB) technique. Characterization of the thin films by different techniques (infrared spectroscopy, X-ray diffraction, and transmission electronic microscopy) has demonstrated a strong dependence of LB film organization on the starting concentration of Prussian Blue in the subphase and on the time lapse between Langmuir film spreading and the formation of the LB multilayer. These trends can be ascribed to the slow adsorption of colloidal particles of Prussian Blue along the monolayer and explain the change observed in the low-temperature ferromagnetic properties of these hybrid LB films.

Structural Features of a Clay Film Hybridized with a Zwitterionic Molecule as Analyzed by Second-Harmonic Generation Behavior

AbstractHybrid Langmuir-Blodgett (LB) films of a single clay layer and a donor-(π-electron system)-acceptor (Dδ-π-Aδ−) zwitterionic molecule (ind-TCNQ), prepared from 1,3,3-trimethyl-2-methyleneindoline (donor) and 7,7,8,8-tetracyanoquinodimethane (acceptor) were prepared. The characteristics of the electrostatic interaction between the clay layer and the ind-TCNQ molecules were investigated. The amount of ind-TCNQ molecules spread onto the air-water interface was increased systematically so that mono- and multi-layers of the molecules could be formed on the clay layer. The hybrid LB films, which were deposited onto a solid substrate, were characterized by means of UV-vis absorption spectroscopy and optical second-harmonic generation measurement. The amount of ind-TCNQ molecules adsorbed on the clay layer increased with an increase in the amount of ind-TCNQ molecules spread onto the air-water interface. On the other hand, the SHG intensities of the films did not change with the change in amount of ind-TCNQ spread. The results indicate that the electrostatic interaction between the clay layer and the ind-TCNQ molecules operates only in the region where the ind-TCNQ molecules are in direct contact with the clay layer.

A novel film with a non-centrosymmetric molecular alignment of D–π–A zwitter ionic molecules fabricated at an air–water interface

The film structures prepared by means of the Langmuir–Blodgett (LB) technique were found to be quite sensitive to the conditions of the film preparation. We have prepared various kinds of hybrid LB films of a D–π–A zwitter ionic molecule and a clay by changing various parameters during the film preparation. As a result, factors such as surface pressure at film deposition, waiting time for evaporation of the solvent, and barrier speed are found to be important.

Electronic Properties of Hybrid Organic/Inorganic Langmuir−Blodgett Films Containing CdS Quantum Particles

We investigated the electronic properties of hybrid inorganic/organic thin films where the inorganic components are monodisperse CdS quantum size particles (diameters 2.5 and 5 nm). For this purpose, low-energy photoelectron spectroscopy was applied in which the energy of photoelectrons, ejected from the metal substrate or from the films themselves, is measured. The electronic properties of hybrid Langmuir-Blodgett films were studied, when the films were deposited on gold or silicon surfaces and contained particles of different sizes arranged in layers at different distances from the substrate. For comparison films containing only the organic matrix were examined, so the effect of the quantum particles (QPs) on the electronic properties of the whole film could be resolved. The present study proves the importance of the organization of hybrid structure on its electronic properties. It is clearly demonstrated that the QPs cannot be considered as insolated species and that their electronic properties are affected by the structure of the film as a whole and by the substrate. It is shown that the QP size affects both the photoelectron emission yield and the scattering efficiency of electrons from the QPs.

A Polyoxometalate Multilayer Film by Langmuir-Blodgett Technique

An organic-inorganic hybrid Langmuir-Blodgett(LB) film was produced through stabilization of a polyoxometalate (POM) monolayer by attaching electrostatically hydrophobic amine (DMDA). The surface pressure-area isotherm of POM-DMDA monolayer showed the stability against surface pressure up to 30 mN/m. The tendency of crystallization on water surface could be directly confirmed by the Brewster angle microscopy. The AFM images showed the aggregated particles of POM-DMDA. The XPS spectra indicated the presence of POM in the LB film and the molecular ratio of DMDA and POM was over 4.0. The XRD spectra showed POMs are positioned to two-dimensionally spread multilayer film.

A Polyoxometalate Multilayer Film by Langmuir-Blodgett Technique

An organic-inorganic hybrid Langmuir-Blodgett(LB) film was produced through stabilization of a polyoxometalate (POM) monolayer by attaching electrostatically hydrophobic amine (DMDA). The surface pressure-area isotherm of POM-DMDA monolayer showed the stability against surface pressure up to 30 mN/m. The tendency of crystallization on water surface could be directly confirmed by the Brewster angle microscopy. The AFM images showed the aggregated particles of POM-DMDA. The XPS spectra indicated the presence of POM in the LB film and the molecular ratio of DMDA and POM was over 4.0. The XRD spectra showed POMs are positioned to two-dimensionally spread multilayer film..

Clay and a Zwitter Ionic Molecule Hybrid Film: Analysis of the Relationship between the Film Structure and the Conditions for Film Preparation

We have studied the relationship between the film structure and the conditions for film preparation of a hybrid film of a D- ~ -A zwitter ionic molecule and a sodium montmorillonite. The films were obtained by means of the modified Langmuir-Blodgett technique. As for the D- ~ -A zwitter ionic molecule, indoline-TCNQ intramolecular charge-transfer compound (ind-TCNQ) was employed. We have prepared various kinds of hybrid films by changing a parameter during the film preparation. The films thus obtained have been characterized by means of the second-harmonic generation measurements. As a result, a surface pressure at film deposition plays an important role for maintaining the film structure. clay sodium montmorillonite zwitter ionic molecule TCNQ derivative hybrid Langmuir-Blodgett film second-harmonic generation

First observation of in-plane X-ray diffraction arising from a single layered inorganic compound film by a grazing incidence X-ray diffraction system with a conventional laboratory X-ray source

Grazing incidence angle in-plane X-ray diffraction (in-plane XRD) was applied to characterization of an organic–inorganic hybrid Langmuir–Blodgett (LB) film in a laboratory scale. The hybrid LB film consisted of octadecyl ammonium cation and sodium montmorillonite layers at Si(1 0 0) wafer. The in-plane XRD measurements of the hybrid LB film gave one diffraction peak at 20.0° (0.44 nm), which we assigned to the (1 1 0) and (0 2 0) reflections of montmorillonite. This was the first example of the in-plane diffraction from a single layered montmorillonite, presenting a clear evidence for the parallel orientation of the (0 0 1) plane with respect to a film surface.