LB Monolayers Research Articles

A Slab-Optical-Waveguide Absorption Spectroscopy of Langmuir-Blodgett Films with a White Light Excitation Source

Abstract A novel slab optical waveguide (SOWG) technique with a white light excitation source was applied to the spectroscopy of LB monolayer samples. Absorption spectra of a Cu-porphyrin complex in LB films at concentrations of 0.1–0.5 monolayers were observed in the wavelength range of 380 to 650 nm. Polarized spectra giving information on the molecular orientation in the ordered thin films were also measured.

Photochemistry in LB films and its application to molecular switching devices

Abstract

Control of Distance and Size of Inorganic Nanoparticles by Organic Matrixes in Ordered LB Monolayers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTControl of Distance and Size of Inorganic Nanoparticles by Organic Matrixes in Ordered LB MonolayersXiaoGang Peng, Ran Lu, YingYing Zhao, LianHua Qu, HaiYan Chen, and TieJin LiCite this: J. Phys. Chem. 1994, 98, 28, 7052–7055Publication Date (Print):July 1, 1994Publication History Published online1 May 2002Published inissue 1 July 1994https://doi.org/10.1021/j100079a026RIGHTS & PERMISSIONSArticle Views364Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (420 KB) Supporting Info (1)»Supporting Information Supporting Information Get e-Alerts

In-plane organization of LB monolayers from FTIR spectroscopy

The in-plane organization of monolayers and multilayers of cadmium arachidate deposited, by the conventional Langmuir-Blodgett technique, onto dielectric substrates has been studied by transmittance FTIR spectroscopy. Examination of the bending CH 2 band associated with the hydrocarbon chains suggests that the first monolayer has a hexagonal subcell packing whether the interaction with the supporting substrate is hydrophilic or hydrophobic. Conversely, even-numbered multilayer stacks are arranged in bilayer structures, and their hydrocarbon chains present an orthorhombic packing with their crystallographic a axis preferentially oriented parallel to the withdrawal direction. Odd-numbered multilayer stacks are composed of a first hexagonal monolayer followed by orthorhombic bilayers.

Surface potential imaging of phase-separated LB monolayers by scanning Maxwell stress microscopy

It is well known that competing interactions such as electrostatic repulsive and van der Waals attractive forces dominate the dynamics of pattern formation in a variety of structures found in phase-separated Langmuir monolayers. However, the microscopic details of these forces are still largely left unresolved because of the technical limitation on measurements. The scanning Maxwell stress microscope, which we have been developing as a new tool for microscopic observation of electrostatic interactions in organic and biological systems, is a type of scanning probe microscope, designed to image the distribution of the Maxwell stress field over the sample surface. With this technique we have succeeded in obtaining imahes of the surface potential of a phase-separated Langmuir-Blodgett monolayer of phospholipid with submicron resolution.

Transmembrane Rectified Electron Transfer through π-Conjugated Electroactive Langmuir–Blodgett Monolayers on Gold Electrodes

Abstract Novel amphiphiles with π-conjugated electroactive groups, 1-methyl-4-[2-[4-[2-(4-pyridyl)vinyl]phenyl]vinyl]pyridinium perchlorate (1), and 1-methyl-4-[2-[4-[2-(4-quinolyl)vinyl]phenyl]vinyl]quinolinium perchlorate (2), were designed and synthesized. Both compounds formed expanded monolayers at air–water interfaces. The monolayers transferred on gold disk electrodes at 25 mN m−1 by the Langmuir–Blodgett technique (horizontal lifting method) show one electron reduction/oxidation couple: Epa = −0.86 V, Epc = −1.08 V vs. SCE for 1/Au and Epa = −0.78 V, and Epc = −0.84 V vs. SCE for 2/Au. Rectified transmembrane electron transfer through the LB monolayers of 1 and 2 on gold electrodes to [Fe(CN)6]3− in aqueous solutions has been proved by cyclic voltammetry and potential-step chronocoulometry.

The effect of the local field on the optical second-harmonic response of mixed liquid crystal-stearic acid monolayers

Optical second-harmonic generation (SHG) from mixed liquid crystal-stearic acid molecular monolayers, as a function of liquid crystal concentration, is reported. It is shown that, in concentrated monolayers, a substantial local-field effect exists which can be described, to a first approximation, by a point dipole model. The apparent molecular hyperpolarizability in pure monolayers of these liquid crystals is reduced by a factor of between six and eight, due to this local field. This is an important consideration in the design of materials for ultra-thin-film nonlinear optical devices. Hyperpolarizability measurements should be made using monolayer films where the active species is diluted by about a factor of ten by a species with negligible polarizability, such as a fatty acid, having first taken care to establish that the active species disperses uniformly. In this way the experimental hyperpolarizability may be directly compared to theoretical values from calculations of isolated molecular clusters. These LB monolayers are ideal model systems for testing theoretical approaches to the local-field problem, and progress in this area is important in understanding the optical response of surfaces and interfaces in general, and those of semiconductors in particular.

Direct observation of C 60 LB film with scanning tunneling microscopy

We report the direct imaging of monolayer LB film of C 60. The LB film was prepared onto an Au(100) surface by the vertical dipping method for scanning tunneling microscopy (STM) measurements. Ordered arrays of C 60 molecules and close-packed molecular aggregation in the film are shown on the STM images. The calculated diameters along two mutually perpendicular directions in the arrays are 0.635±0.013 and 0.572±0.024 nm, respectively. Our results demonstrate that the molecular shape of C 60 is easily compressed into an ellipsoid while forming the LB film.

Antigen recognition properties of antibody monolayers

The immunological activity of LB films of antibodies and antibody fragments deposited under various conditions and onto various substrates has been determined by an enzyme linked immunoassay. Active surface densities five times greater than those obtained by physical adsorption can be obtained by an appropriate combination of substrate with deposition method. The results are explained in terms of the increased packing density and order of LB monolayers.

SERRS of Phthalocyanine Derivatives LB Monolayer

SERRS of copper tetrakis(2,4-ditert-penthyl phenoxy) Phthalocyanine LB monolayer on Ag island film and RRS of the compound in solid state have been obtained. On comparison between the spectra, it is proposed that the macrocycle of the molecule on the Ag substrate is oriented parallel to the surface.

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, one of the most well-known redox-active sensitizer, was incorporated into the DDA copolymer. The photogalvanic effect based onthe photoinduced electron transfer using the ruthenium complex in the polymer LB monolayer was discussed.

Surface‐enhanced resonance Raman scattering of a NO2‐bisphthalocyanine adduct in Langmuir‐Blodgett monolayers

AbstractLangmuir‐Blodgett (LB) monolayers of dysprosium and holmium bisphthalocyanine complexes (DyPc2 and HoPc2) were prepared at 10°C and transferred to glass slides coated with gold island films. Surface‐enhanced resonance Raman scattering (SERRS), and visible absorption spectrometry were used to monitor the interaction between the LB monolayer and NOx (NO2‐N2O4) gas. It is shown that the absorption and inelastic scattering spectra of LB are sensitive tools to monitor the interaction between the MPc2 molecule and the NO2, allowing the spectral properties of the adduct formed by chemisroption to be determined.

Langmuir-Blodgett mono- and multilayers of poly(isocyanides)s with different sidechains

In this study poly(isocyanide)s, [RNC] n with different sidechains R are used as spreading material to form LB monolayers at the water-air interface. Poly(isocyanide)s are rigid-rod polymers with a stable, helical conformation. One of the aims of this study was to ascertain whether this rigid conformation is sufficient to enable the formation of a stable monolayer on the water surface. We find that different poly(isocyanide)s with non-polar aliphatic substituents are unable to form such stable monolayers. On the other hand, poly(( S)-1-acetoxymethylethyl-isocyanide), a polymer which has polar substituents, does form a stable monolayer. This monolayer can be transferred onto all kinds of substrates by Z-type transfer. Multilayer formation is possible with transfer ratios remaining constant up to at least 40 layers. From IR measurements it follows that the polymer helices are preferentially oriented with their main axis parallel to the transfer direction.

Stabilization of Stearic Acid LB Monolayer Film by Addition of n-Alkylthiol

Abstract Stability of stearic acid LB monolayer in an aqueous solution is remarkably improved by the addition of n-alkylthiol. n-Alkylthiol adsorbs strongly on gold surface and acts as anchor of the stearic acid monolayer so as not to diffuse away from the substrate.

Rectifying characteristics of Mg|(C16H33-Q3CNQ LB film)|Pt structures

The Mg|(LB monolayer)|Pt structures of Z-β-(1-hexadecyl-4-quinolinium)-α-cyano-4-styryldicyanomethanide (C16H33–Q3CNQ) show asymmetric current–voltage characteristics; the behaviour is attributed to the organic monolayer although whether it is due to the presence of the permanent dipole moment or molecular rectification is unclear.

Electrogenerated Chemiluminescence from Ru(bpy)<sub>2</sub>(ndbpy) LB Monolayer and Its Application to Oxalate Sensor

Electrogenerated Chemiluminescence from Ru(bpy)<sub>2</sub>(ndbpy) LB Monolayer and Its Application to Oxalate Sensor

Nonlinear Optical Studies of Mixed π-Conjugated Polymer Multilayers by Second Harmonic Generation

ABSTRACTThe structures of the mixed LB monolayers, composed of two different kinds of π-conjugated system, poly(3-hexylthiophene) (PHT) and pentacosa-10, 12-diynoic acid (DA), have been investigated mainly by a second harmonic generation (SHG) Maker fringe method. The mixed LB films partly contain a double-layered structure consisting of PHT and DA. The second harmonic radiation has been produced from slightly twisted PHT in the double layer. Both UV-polymerization of DA and successive heat-treatments enhanced the SHG intensities. The enhancement of the SHG intensities has been elucidated by the enlargement of the PHT twisting and the interaction between PHT and a newly formed π-conjugated system.

A FTIR and NEXAFS study of polypyrrole Langmuir-Blodgett films

3-n-hexadecylpyrrole and 3-n-octadecylpyrrole have been synthesized, and Langmuir Blodgett films of these compounds have been studied by means of NEXAFS and FTIR spectroscopy. By comparing the spectra of two different polarizations, it was found that the hydrocarbon chains are normal to the substrate surface for LB films with multi-layers. For the monolayer LB films, the hydrocarbon tails are tilted towards the substrate surface due to the interaction between the pyrrole ring and the platinum substrate.

The reproducibly perfect langmuir-blodgett film

It has become clear that the known techniques and précautions used in the deposition of LB films do not guarantee the absence of defects. From the existing experimental facts, it is shown that perfect LB monolayers are possible in principle, but that their electrical characteristics will be distinctly different from what has been accepted up until now. The development of the procedures necessary to achieve them reproducibly is discussed.

Orientational Effects in 3-n-Hexadecylpyrrole Langmuir-Blodgett films

Abstract 3-n-hexadecylpyrrole have been synthesized, and Langmuir-Blodgett films of this compound have been studied by means of transmission and grazing incident reflection FT-IR spectroscopy. A comparison of the spectra at the two different polarizations shows that the hydrocarbon tails are oriented normal to the substrate surface for multilayer LB films. For the single monolayer LB films, the hydrocarbon tails are tilted with respect to the substrate surface possibly due to interactions between the pyrrole head groups and the platinum substrate.