Photoluminescent multilayer films based on polyoxometalates

Ultrathin multilayer films consisting of the polyoxotungstoeuropate cluster K-12[EuP5W30O110] (EuP5W30) and poly( allylamine hydrochloride) (PAH) have been prepared by the layer-by-layer self-assembly method. The (EuP5W30 /PAH) multilayer films have been characterized by small-angle X-ray reflectivity measurements, X-ray photoelectron spectra, and atomic force microscopy (AFM). From the AFM images, the thickness of the {PEI/PSS/PAH(EuW30/PAH)} multilayer film was estimated to be 6.5 nm, corresponding to an average thickness of ca. 1.1 nm for a EuW30/PAH layer pair. The photoluminescent behavior of the film at room temperature was investigated to show the characteristic Eu3+ emission pattern of D-5(0)-->F-7(J). The fluorescence behavior of the multilayer film is essentially identical to that of H-n[EuP5W30O110]((12-n)-) in a concentrated aqueous solution, except for the relative intensities and peak bandwidths. The occurence of photoluminescent activity confirms the potential for creating luminescent multilayers with polyoxometalates (see ref. 23).

An organic-inorganic hybrid ultrathin film: preparation and characterization of copper phthalocyanine derivative-ferric oxide nanoparticles

A nanoparticulate ferric oxide-copper tris(2,4-di-tert-amylphenoxy)-8-quinolinolylphthalocyanine hybrid ultrathin film was constructed from alternate layers by the Langmuir-Blodgett technique. The composition, morphology and structure of the film were studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, atomic force microscopy, small-angle X-ray diffraction, visible spectroscopy and polarized UV-Vis spectroscopy. All the above analyses suggest that the thin film is a kind of one-dimensional superlattice, composed of organic and inorganic components. The XPS data reveal that the nanoparticulate ferric oxide exists as an alpha-Fe2O3 phase in the films. Gas-sensing measurements show that the hybrid LB film has very fast response-recovery characteristics towards 2 ppm C2H5OH vapor.

Covalently attached multilayer assemblies containing photoreactive diazo-resins and conducting polyaniline

We reported on the multilayer architecture containing diazo-resins (DAR) as polycations and polyaniline poly(aniline-co-N-propanesulfonic acid aniline) (PAPSAH) as polyanions held together by electrostatic interaction. Upon UV irradiation, the adjacent interfaces of the multilayer reacted to form a covalently crosslinking structure which greatly improved the stability of the films as confirmed by solvent etching experiments. These changes were confirmed by UV-Vis and FTIR spectroscopy. The thickness of the covalently attached films were characterized with small angle X-ray diffraction (SAXD) and a value of 30.0 Angstrom per bilayer was obtained. This type of film was further characterized by cyclic voltammetry which showed that the electroactive property of PAPSAH was still kept in the films after photoreaction. (C) 2000 Elsevier Science B.V. All rights reserved.

Preparation, structure, and properties of three-dimensional ordered alpha-Fe2O3 nanoparticulate film

alpha-Fe2O3 nanoparticulate films could be formed on the surface of alpha-Fe2O3 hydrosol after aging of the hydrosol or by compressing of the nanoparticles on the sol surface, in. which a three-dimensional ordered structure was constructed by the Langmuir-Blodgett; technique and colloid chemical methods. The structure of the LB film was characterized by AFM, TEM, XPS, and UV-vis spectra and small-angle X-ray diffraction. Gas-sensing measurement shows that the LB film has good sensitivity to alcohols at room temperature,

Formation and characterization of heteropolyacid/polycation multilayer films on gold electrode

Ultrathin multilayer films of a polybasic lanthanide heteropoly tungstate-molybdate complex and a cationic polymer of quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) have been fabricated on a gold electrode precoated with a cysteamine self-assembled monolayer. The multilayer films have been characterized by optical spectroscopy, small-angle X-ray diffraction, and electrochemical methods (cyclic voltammetry and electrochemical impedance). Especially, the electrochemical impedance spectroscopy is developed to monitor the layer deposition processes. It provides important information such as double-layer capacitance and charge-transfer resistance. All obtained results reveal regular film growth with each layer adsorption. (C) 2001 The Electrochemical Society.

Langmuir-Blodgett film formation from surfactant-capped zinc sulfide nanoparticles spread on water surface

The surfactant-capped ZnS nanoparticulate multilayer film has been fabricated by Langmuir-Blodgett(LB) technique. ZnS LB firm was investigated by the small-angle x-ray diffraction(XRD), atomic force microscopy(AFM) and transmission electron microscopy(TEM). The results indicate that ZnS nanoparticulate LB film is one-dimensional superlattice.

Preparation and characterization of doped polyaniline films

Stable monolayer of the polyaniline doped with camphor sulfonic acid at the air-water interface has been obtained, of which multilayers have been successfully deposited by Langmuir-Blodgett technique onto CaF2 substrate. The limiting mean molecular area and collapse pressure are found to be 0.294 nm(2) and 41 mN/m, respectively. The multilayers were characterized by IR and W-Vis-NIR spectroscopies. X-ray small-angle diffraction data show that the multilayer was periodic layer structure with the layer spacing of 1.60 nm. The comparisons are also made with characterization of the casting film. (C) 1999 Elsevier Science S.A. All rights reserved.

Stability of Mo/Si multilayer structure used in Bragg-Fresnel optics

The thermal and chemical stabilities of Mo/Si multilayer structure used in Bragg-Fresnel optics were studied to get optimal technological parameters of pattern generation. Mo/Si multilayers were annealed at temperature ranging from 360 to 770 K, treated with acetone and 5 parts per thousand NaOH solution, and characterized by small-angle x-ray diffraction technique as well as x-ray photoelectron spectroscopy, and Olympus microscopy.

Study on Ordered Assembly of SnO2 Nonoparticles-Arachidic Acid Composite LB Films

The hydrosol of SnO2 nanoparticles (NP) have been prepared by colloid chemistry method. The composite LB monolayer and multilayer of SnO2 NP-AA have been obtained by LB technique at the gas-liquid interface of the hydrosol subphase. The structures of the monolayer and multilayer were characterized by IR, UV-Vis, small angle X-ray diffraction spectroscopy and TEM technique, The results indicate that the coverage of SnO2 NP at the composite monolayer's surface is high and the sites of SnO2 NP are similar. The multilayer has good periodic structure.

Small-dynamic-angle measurement using tangent relationship and phase-modulating technique

A method using two prisms for measurement of small dynamic angles is proposed in which the measurement is based on a simple tangent equation and a phase-modulating interferometer with a laser diode to measure dynamic optical path differences with higher accuracy. Owing to the simple tangent equation, the symmetry requirement on the two prisms in the optical configuration is eliminated, and easy measurement of the separations between two parallel beams with a position-sensitive detector is achieved. Small-dynamic-angle measurements are experimentally demonstrated with high accuracy. (C) 2007 Society of Photo-Optical Instrumentation Engineers.

Small-dynamic-angle measurement using tangent relationship and phase-modulating technique

A method using two prisms for measurement of small dynamic angles is proposed in which the measurement is based on a simple tangent equation and a phase-modulating interferometer with a laser diode to measure dynamic optical path differences with higher accuracy. Owing to the simple tangent equation, the symmetry requirement on the two prisms in the optical configuration is eliminated, and easy measurement of the separations between two parallel beams with a position-sensitive detector is achieved. Small-dynamic-angle measurements are experimentally demonstrated with high accuracy. (C) 2007 Society of Photo-Optical Instrumentation Engineers.

Subtraction of scattering parameters for small-signal modulation characteristics of laser diode

An extended subtraction method of scattering parameters for characterizing laser diode is proposed in this paper. The intrinsic response is extracted from the measured transmission coefficients of laser diode, and the parasitics of packaging net-work laser chip are determined from the measured reflection coefficient of laser diode simultaneously. It is shown that the theories agree well with the experimental results.

Studies of instrumental spreading in gel permeation chromatography by coupling with a two-angle laser light scattering detector

The instrumental spreading of a high temperature gel permeation chromatograph (GPC) was evaluated by coupling with a two-angle laser light scattering (TALLS) detector, using narrow polystyrene, polyethylene, and syndiotactic polypropylene samples. The determined spreading factor increased with increasing molecular weight of polymers, and no maximum for spreading 174 tor was observed in the studied retention volume, while the spreading factors for single low molecular weight alkanes are independent of their molecular weight. Neglecting of the spreading effect for GPC would not introduce much error in molecular weight calculation when high quality high performance columns were used, especially when equipped with a laser light scattering detector. The scaling relationship between radius of gyration and molecular weight of polymer, determined by GPC with a TALLS detector, was independent of the instrumental spreading.