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(PMo11)(2), RE = Ce-III, Eu-III, La-III) using the Langmuir-Blodgett technique. They are characterized by pi-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.

Study on highly ordered luminescent Langmuir-Blodgett films of heteropolytung state complexes containing lanthanide

Luminescent thin films of heteropolytungstate complexes containing lanthanide (europium or samarium) were successfully fabricated by the Langmuir-Blodgett (LB) technique. The pressure-area isotherm of the monolayer of dimethyldioctadecylammonium. bromide (DODA) is modified rather markedly when the subphase contains the complex of Na9EuW10O36 or Na9SmW10O36. The above results indicate that the monolayer of DODA has a strong interaction with the polyanions of EuW10O369-. (or SmW10O369-). X-ray photoelectron spectra and fluorescent spectra verify that europium and tungsten atoms are 36 36 incorporated into the LB films. Ultraviolet (UV), fluorescent spectra and low-angle X-ray diffraction experiments demonstrate that these LB films have a well-defined lamellar structure. The LB film containing EuW10O369- can give off strong fluorescence 16 on UV irradiation. The characteristic emission behaviors of europium ions in LB films and in the powder of Na9EuW10O369- are discussed. It is found that the intensity ratio of the D-5(0)-F-7(2) transition to the D-5(0)-->F-7(1) transition in LB film is quite different from that in the powder of Na9EuW10O36. The difference of the ratio indicates that the site symmetry of europiurn is distorted in LB film, which is probably due to the strong electrostatic interactions between DODA and polyanions.

Gas sensitivity of composite Langmuir-Blodgett films of Fe2O3 nanoparticle-copper phthalocyanine

The Langmuir-Blodgett (LB) composite films, ferric oxide nanoparticle composite with tris-(2,3-di-t-amylphenoxy)-(8-quinolinolinolyl) copper phthalocyanine (CuPcA(2)), were obtained by capped type and alternated type and characterized by X-ray photoelectron spectroscopy (XPS) and visible spectra. The gas sensitivity of the composite films and the pure ferric oxide and pure CuPcA(2) LB films to ammonia and ethanol were measured at room temperature. The composite films could be used as the C2H5OH sensors in the range of 2-8 or 100-200 ppm. The XPS data suggested that the adduct complex NH3-CuPcA(2) was formed after the capped film was exposed to the detected gas of ammonia. (C) 2000 Elsevier Science B.V. All rights reserved.

Luminescent properties of Langmuir-Blodgett films of europium bisphthalocyanine

Eu(III)-octa-4-(tetrahydrofurfuroxy) phthalocyanine (EuPc2') was synthesied and characterized by elementary analysis, IR, MS, UV-vis spectra. EuPc2' has good film-forming ability from determination of isotherm of pi-A. The complex LB film was formed by depositing of EuPc2' on a quartz slide with the LB techniques of the Z-type, The luminescent properties of pure and doped LS films were determined. The results showed that pure films have good luminescent properties, the thicker the LB films, the stronger the fluorescent intensity. The films doped with o-phenanthroline (abbreviated as phen) made the relative intensity of fluorescent emission behavior enhance in comparison to that of pure LB film, But the amount of phen may be not too much. Our results showed that EuPc2':phen = 1: 10 (molar ratio) has the best fluorescent behavior. The electronic spectroscopic characterization of the LB films is also given.

LB multilayers and superlattice films of erbium fatty acid salts

Multilayers of Y-type bilayers of pure and mixed erbium palmitate(EP), nonadecanate(Er) and behenate(EB) on CaF2 substrates were prepared by conventional Langmuir-Blodgett (LB) method. II is demonstrated that two systems composed of alternating bilayer of different fatty acid salts are unidimensional superlattices. These LB films were characterized by means of x-ray photoelectronic Spectrometry (XPS), FTIR and x-ray diffraction (XRD) measurements.

Langmuir-Blodgett films of octadecanethiol on gold sols subphase

An octadecanethiol monolayer was formed on an aqueous gold sols subphase, it's LB films were characterized by means of pi-A isotherms, TEM (transmission electron microscopy), XRD (X-ray diffraction) and UV-Vis spectroscopy. (C) 1998 Elsevier Science Limited. All rights reserved.

THE CHARACTERIZATION OF 2 COPPER PHTHALOCYANINE LANGMUIR-BLODGETT-FILMS AND THEIR GAS-SENSITIVE PROPERTIES

The monolayer and deposition behaviour of a symmetrically substituted copper tetra-4-(2, 4-di-t-amylphenoxy) phthalocyanine (tapCuPc) and an asymmetrically substituted copper [tri-4-(2, 4-di-t-amylphenoxy)-mono-4-(-2-methoxyethoxy)]phthalocyanine (AsyCuPc) were investigated. The results on monolayer behaviour and spectroscopic characterization of the LB films show that both CuPc molecules in a monolayer at the air-water interface and the LB films are stacked and inclined. The gas-sensitive properties show that the responding speed of AsyCuPc LB film is faster than that of tapCuPc LB film.

Nanopatterning and functionalization of phospholipid-based Langmuir-Blodgett and Langmuir-Schaefer films

Durant les dernières décennies, la technique Langmuir-Blodgett (LB) s’est beaucoup développée dans l’approche « bottom-up » pour la création de couches ultra minces nanostructurées. Des patrons constitués de stries parallèles d’environ 100 à 200 nm de largeur ont été générés avec la technique de déposition LB de monocouches mixtes de 1,2-dilauroyl-sn-glycéro-3-phosphatidylcholine (DLPC) et de 1,2-dipalmitoyl-sn-glycéro-3-phosphatidylcholine (DPPC) sur des substrats de silicium et de mica. Afin d’amplifier la fonctionnalité de ces patrons, la 1-palmitoyl-2-(16-(S-methyldithio)hexadécanoyl)-sn-glycéro-3-phosphatidylcholine (DSDPPC) et la 1-lauroyl-2-(12-(S-methyldithio)dodédecanoyl)-sn-glycéro-3-phosphatidylcholine (DSDLPC) ont été employées pour la préparation de monocouches chimiquement hétérogènes. Ces analogues de phospholipide possèdent un groupement fonctionnel méthyldisulfide qui est attaché à la fin de l’une des chaînes alkyles. Une étude exhaustive sur la structure de la phase des monocouches Langmuir, Langmuir-Schaefer (LS) et LB de la DSDPPC et de la DSDLPC et leurs différents mélanges avec la DPPC ou la DLPC est présentée dans cette thèse. Tout d’abord, un contrôle limité de la périodicité et de la taille des motifs des stries parallèles de DPPC/DLPC a été obtenu en variant la composition lipidique, la pression de surface et la vitesse de déposition. Dans un mélange binaire de fraction molaire plus grande de lipide condensé que de lipide étendu, une vitesse de déposition plus lente et une plus basse pression de surface ont généré des stries plus continues et larges. L’addition d’un tensioactif, le cholestérol, au mélange binaire équimolaire de la DPPC/DLPC a permis la formation de stries parallèles à de plus hautes pressions de surface. La caractérisation des propriétés physiques des analogues de phospholipides a été nécessaire. La température de transition de phase de la DSDPPC de 44.5 ± 1.5 °C comparativement à 41.5 ± 0.3 °C pour la DPPC. L’isotherme de la DSDPPC est semblable à celui de la DPPC. La monocouche subit une transition de phase liquide-étendue-à-condensée (LE-C) à une pression de surface légèrement supérieure à celle de la DPPC (6 mN m-1 vs. 4 mN m-1) Tout comme la DLPC, la DSDLPC demeure dans la phase LE jusqu’à la rupture de la monocouche. Ces analogues de phospholipide existent dans un état plus étendu tout au long de la compression de la monocouche et montrent des pressions de surface de rupture plus basses que les phospholipides non-modifiés. La morphologie des domaines de monocouches Langmuir de la DPPC et de la DSDPPC à l’interface eau/air a été comparée par la microscopie à angle de Brewster (BAM). La DPPC forme une monocouche homogène à une pression de surface (π) > 10 mN/m, alors que des domaines en forme de fleurs sont formés dans la monocouche de DSDPPC jusqu’à une π ~ 30 mN m-1. La caractérisation de monocouches sur substrat solide a permis de démontrer que le patron de stries parallèles préalablement obtenu avec la DPPC/DLPC était reproduit en utilisant des mélanges de la DSDPPC/DLPC ou de la DPPC/DSDLPC donnant ainsi lieu à des patrons chimiquement hétérogènes. En général, pour obtenir le même état de phase que la DPPC, la monocouche de DSDPPC doit être comprimée à de plus hautes pressions de surface. Le groupement disulfide de ces analogues de phospholipide a été exploité, afin de (i) former des monocouches auto-assemblées sur l’or et de (ii) démontrer la métallisation sélective des terminaisons fonctionnalisées des stries. La spectrométrie de photoélectrons induits par rayons X (XPS) a confirmé que la monocouche modifiée réagit avec la vapeur d’or pour former des thiolates d’or. L’adsorption de l’Au, de l’Ag et du Cu thermiquement évaporé démontre une adsorption préférentielle de la vapeur de métal sur la phase fonctionnalisée de disulfide seulement à des recouvrements sub-monocouche.

Study of Langmuir-Blodgett Films of Self-Assembled Diblock Copolymers

L'auto-assemblage des copolymères à bloc (CPBs) attire beaucoup d'intérêt grâce à leur capacité de générer spontanément des matériaux ordonnés avec des propriétés uniques. Les techniques Langmuir-Blodgett (LB) et Langmuir-Schaefer (LS) sont couramment utilisées pour produire des monocouches ou des films ultraminces à l'interface air/eau suivi de transfert aux substrats solides. Les films LB/LS de CPBs amphiphiles s'auto-assemblent dans des morphologies variables dépendamment de la composition du CPB ainsi que d'autres facteurs. Dans notre travail, nous avons étudié les films LB/LS de polystyrène-b-poly(4-vinyl pyridine) (PS-P4VP) et leurs complexes supramoléculaires avec le naphtol (NOH), l'acide naphtoïque (NCOOH) et le 3-n-pentadécylphenol (PDP). La première partie de ce mémoire est consacré à l'investigation du PS-P4VP complexé avec le NOH et le NCOOH, en comparaison avec le PS-P4VP seul. Il a été démontré qu'un plateau dans l'isotherme de Langmuir, indicatif d'une transition de premier ordre, est absent à des concentrations élevées des solutions d'étalement des complexes. Cela a été corrélé avec l'absence de morphologie en nodules avec un ordre 2D hexagonal à basse pression de surface. L'ordre au-delà de la pression de cette transition, lorsque présente, change à un ordre 2D carré pour tout les systèmes. La deuxième partie du la mémoire considère à nouveau le système PS-P4VP/ PDP, pour lequel on a démontré antérieurement que la transition dans l'isotherme correspond a une transition 2D d'un ordre hexagonal à un ordre carré. Cela est confirmé par microscopie à force atomique, et, ensuite, on a procédé à une étude par ATR-IR des films LB pour mieux comprendre les changements au niveau moléculaire qui accompagnent cette transition. Il a été constaté que, contrairement à une étude antérieure dans la littérature sur un autre système, il n'y a aucun changement dans l'orientation des chaînes alkyles. Au lieu de cela, on a découvert que, aux pressions au-delà de celle de la transition, le groupe pyridine, qui est orienté à basse pression, devient isotrope et qu'il y a une augmentation des liaisons hydrogènes phénol-pyridine. Ces observations sont rationalisées par un collapse partiel à la pression de transition de la monocouche P4VP, qui à basse pression est ordonné au niveau moléculaire. Cette étude a mené à une meilleure compréhension des mécanismes moléculaires qui se produisent à l'interface air/eau, ce qui fournit une meilleure base pour la poursuite des applications possibles des films LB/LS dans les domaines de nanotechnologie.

Using phospholipid Langmuir and Langmuir-Blodgett films as matrix for urease immobilization

The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many biotechnological applications. In this paper, we used the Langmuir-Blodgett (LB) technique to obtain controlled architectures of urease immobilized in solid supports, whose physicochemical properties were investigated in detail. Urease molecules were adsorbed at the air-water interface and incorporated into Langmuir monolayers of the phospholipid dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation of urease made DPPG monolayers more flexible and caused the reduction of the equilibrium and dynamic elasticity of the film. Urease and DPPG-urease mixed monolayers could be transferred onto solid substrates, forming LB films. A close packing arrangement of urease was obtained, especially in the mixed LB films, which was inferred with nanogravimetry and electrochemistry measurements. From the blocking effect of the LB films deposited onto indium tin oxide (ITO) substrates, the electrochemical properties of the LB films pointed to a charge transport controlled by the lipid architecture. (c) 2007 Elsevier Inc. All rights reserved.

Fabrication, structural characterization, and applications of Langmuir and Langmuir-Blodgett films of a poly(azo)urethane

The synthesis of a poly(azo)urethane by fixing CO2 in bis-epoxide followed by a polymerization reaction with an azodiamine is presented. Since isocyanate is not used in the process, it is termed clean method and the polymers obtained are named NIPUs (non-isocyanate polyurethanes). Langmuir films were formed at the air-water interface and were characterized by surface pressure vs mean molecular area per met unit (Pi-A) isotherms. The Langmuir monolayers were further studied by running stability tests and cycles of compression/expansion (possible hysteresis) and by varying the compression speed of the monolayer formation, the subphase temperature, and the solvents used to prepare the spreading polymer solutions. The Langmuir-Blodgett (LB) technique was used to fabricate ultrathin films of a particular polymer (PAzoU). It is possible to grow homogeneous LB films of up to 15 layers as monitored using UV-vis absorption spectroscopy. Higher number of layers can be deposited when PAzoU is mixed with stearic acid, producing mixed LB films. Fourier transform infrared (FTIR) absorption spectroscopy and Raman scattering showed that the materials do not interact chemically in the mixed LB films. The atomic force microscopy (AFM) and micro-Raman technique (optical microscopy coupled to Raman spectrograph) revealed that mixed LB films present a phase separation distinguishable at micrometer or nanometer scale. Finally, mixed and neat LB films were successfully characterized using impedance spectroscopy at different temperatures, a property that may lead to future application as temperature sensors. Principal component analysis (PCA) was used to correlate the data.

Taking Advantage of Electrostatic Interactions To Grow Langmuir-Blodgett Films Containing Multilayers of the Phospholipid Dipalmitoylphosphatidylglycerol

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Incorporation of a liquid crystal to enhance the luminescence properties of Langmuir-Blodgett films of OC1OC6-PPV

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Langmuir and langmuir-blodgett films of polyfluorenes and their use in polymer light-emitting diodes

The Langmuir and Langmuir-Blodgett (LB) film properties of two polyfluorene derivatives, namely poly(2,7-9,9'-dihexylfluorene-dyil) (PDHF) and poly(9,9 dihexylfluorene-dyil-vynilene-alt-1,4-phenylene-vyninele) (PDHF-PV), are reported. Surface pressure (Pi-A) and surface potential (Delta V-A) isotherms indicated that PDHF-PV forms true monolayers at the air/water interface, but PDHF does not. LB films could be transferred onto various types of substrate for both PDHF and PDHF-PV. Only the LB films from PDHF-PV could withstand deposition of a layer of evaporated metal to form a light-emitting diode (PLED), which had typical rectifying characteristics and emitted blue light. It is inferred that the ability of the polymer to form true monomolecular layers at the air/water interface seems to be associated with the viability of the LB films in PLEDs.

Langmuir-Blodgett films incorporating an ionic europium complex

Langmuir-Blodgett (LB) technique is a powerful tool to fabricate ultrathin films with highly ordered structures and controllable molecular array for efficient energy and electron transfer, allowing the construction of devices at molecular level. One method to obtain LB films consists in the mixture of classical film-forming molecules, for example Stearic Acid (SA) and functional metal complex. In this work NH(4)[Eu(bmdm)(4)], where the organic ligand bmdm is (butyl methoxy-dibenzoyl-methane) or (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione) was used to build up Langmuir and LB films. Langmuir isotherms were obtained from (i) NH(4)[Eu(bmdm)(4)] complex and (ii) NH(4)[Eu(bmdm)(4)]/SA (1:1). Results indicated that (i) form multilayer structure; however the surface pressure was insufficient to obtain LB films, and (ii) can easily reproduce and build LB films. The dependence of number of layers in the UV absorption spectra suggest that the complex did not hydrolyze or show decomposition, UV spectral differences observed between the solution and the LB film indicate that the complex has a highly ordered arrangement in the film and the complex has an interaction with SA. Excitation spectra confirm a ligand-europium energy transfer mechanism. The transition lines of Eu(3+) ion were observed in emission spectra of all films, the photoluminescence spectra indicate a fluorescence enhanced effect with the number of LB layers. (C) 2009 Elsevier B.V. All rights reserved.