Nanoparticles fabricated by selective reaction of Fe100-xPtx alloy films during imidization of polyamic acid

Nanoparticles with different morphology and composition were fabricated inside a polyimide (PI) matrix based on selectively oxidizing a layer of Fe(100-x)Pt(x) alloy metal film sandwiched between two PI precursor layers. Gamma-Fe2O3, Pt, and Fe3Pt nanoparticles were formed in a monolayer between two PI layers, depending on the alloy film composition and curing conditions. These particles were well-crystallized and sized between 4 and 10 nm. X-ray photoelectron spectroscopy confirmed that Fe in the film preferentially reacted with the organic matrix whereas Pt remained metallic throughout the curing process, which enabled fabrication of particles different morphology and composition. This process can be easily extended to other alloy films, which provides an opportunity to fabricate nanoparticles relatively easily with desired composition and morphology embedded in an inert organic matrix.     

Kinetic models for solution imidization of polyamic acid containing naphthalene‐pendant group

The kinetics and mechanisms of the solution imidization of polyamic acid resulting from a diamine, bis(4‐aminophenoxy‐3,5‐dimethylphenyl)naphthylmethane, and a dianhydride, 3,3′4,4′‐diphenylsulfonetetracarboxylic dianhydride, were studied at three various temperatures (145, 165, and 180 °C). The results were confirmed by means of ¹H NMR and gel permeation chromatography (GPC). Kinetic parameters were obtained by an isothermal study, and the results were quite close to second‐order kinetics for the homogeneous solution imidization. In addition, Carother's equation, Mark–Houwink theory, and GPC were used to explain the molecular weight of the imidization processes. The apparent activation energy (E_a) was 104 KJ/mol, and the pre‐exponential factor (k₀) was 3.48 × 10¹⁴. The proposed kinetic mechanism is in good agreement with the kinetic models. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4139–4151, 2001     

Structure analysis of a soluble polysiloxane-block-polyimide and kinetic analysis of the solution imidization of the relevant polyamic acid

A series of polysiloxane-block-polyimides were synthesized by solution imidization of the polyamic acids derived from the combination of 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and diamino(polysiloxane) (PSX (M_w = 750)) in N-methyl-2-pyrrolidone (NMP). Their structures were analyzed by ¹H-, ¹³C-, and ²⁹Si-NMR spectra as well as by IR spectroscopy. The solid-state NMR spectrum was also measured to determine the spin–lattice relaxation time of the copolyimides. The observed relaxation times of both aromatic and polysiloxane segments were similar in the copolyimides having 10–30 wt % of PSX, while those in the copolyimide with 50 wt % of PSX was significantly different. This may be attributed to the morphology change due to the increase in PSX composition in the polymer backbone. The reduced viscosity of the copolyimides could be controlled by changing the monomer ratio in the feed or by adding an end-capping reagent such as phthalic anhydride into the polymerization system. The kinetic study of the solution imidization revealed that the imidization reaction obeyed second-order kinetics. The activation energy calculated for this imidization was 99.2 kJ/mol, being similar to that for the imidization of the DSDA-based aromatic polyimides. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2237–2245, 1998     

Photosensitization of TiO2 nanoparticulate thin film electrodes by CdS nanoparticles

Surface photovoltage spectra (SPS) measurements of TiO₂ show that a large surface state density is present on the TiO₂ nanoparticles and these surface states can be efficiently decreased by sensitization using CdS nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO₂ thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films. The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO₂ nanoparticulate thin film sensitized using CdS nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response. Electronic Publication     

Fabrication and characterization of TiO2 photocatalytic thin film prepared from peroxo titanic acid sol

A novel sol–gel technique using the PTA (peroxo titanic acid) sol as precursor for the fabrication of TiO₂ photocatalytic thin film is introduced in this paper. The peroxo titanic acid sol was synthesized from titanyl sulfate (TiOSO₄), ammonia and peroxide solution (H₂O₂). The transparent and porous TiO₂ thin film was prepared via a sol–gel technique using PTA sol and polyethylene glycol (PEG) as precursor and template, respectively. The TiO₂ thin film samples were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectrophotometry (UV–vis), X-ray photoelectron spectrum (XPS) and thermogravimetry and differential thermal analysis (TG-DTA) technique. The PTA sol displayed amorphous TiO₂ below 100 °C. The anatase phase formed at 200 °C to 700 °C. The crystallinity of anatase phase was improved with increasing temperature. The anatase crystals on the surface of TiO₂ film were strip-like, the size being about 100 nm in length and 40 nm in diameter. Addition of PEG to the PTA sol developed porous structures in the film and changed the size and shape of the particles. The surface of the film contained Ti, O and C elements and Na element that diffused into the film from the glass substrate. The photocatalytic performance of TiO₂ film was tested for the degradation of 10 mg/L methyl orange. The degradation of methyl orange solution reached 98.9% after irradiated for 180 min under UV light. The porous TiO₂ thin film exhibited high photocatalytic activity towards degrading methyl orange.     

Surface oxidation and thin film preparation of AlCuFe quasicrystals

This paper reviews the work carried out over the last decade by the Nancy team on surface oxidation and thin film preparation of AlCuFe icosahedral quasicrystals. After discussing the problems linked with the surfaces of these quasicrystals, this review addresses the issue of the preparation of quasicrystalline surfaces and the first steps of oxidation under very low pressure of oxygen. This paper compares the nucleation and growth of oxide on i-AlCuFe quasicrystal and on a classical crystalline phase of this alloy: ω-AlCuFe. Aluminium diffusion is studied through the aluminium segregation on the surface that occurs during exposure to oxygen. Some surface properties of quasicrystals are reviewed with regard to oxidation. The evolution of physical parameters such as surface energy, friction coefficient and optical emissivity is described. This review also deals with the preparation of i-AlCuFe thin films. Two protocols to make i-AlCuFe thin films with free surfaces are described and discussed. The mechanical resistance and the tribological behaviour of these thin films, the oxygen and carbon influence on the final crystalline structure, and the quasicrystallization kinetics are presented.     

Fabrication and optical properties of gallium phosphide nanoparticulate thin film

The gallium phosphide (GaP) nanoparticulate thin films were fabricated by colloidal suspensions deposition with GaP nanoparticles dispersed in N,N-dimethylformamide (DMF). The microstructure and optical properties of the film have been studied by scanning electron microscopy, high resolution transmission electron microscope, and optical absorption and fluorescence spectra. The morphology of the film was found to be composed of nanoparticle aggregates, and with an irregularly rough surface. From the result of fluorescence, it can be established that the film not only retains the violet and blue light emissions which ascribed to transition from conduction band to valence band of gallium phosphide particles, but has an excellent luminescence property. The correlation between the optical properties and the microstructure of the thin film is discussed.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

Hydrophobic properties of plasma polymerized thin film gas selective membranes

Hydrophobic gas separation membranes were prepared by a plasma polymerization process. Thin films of about 400–500 nm thickness deposited on porous Al₂O₃ substrates represent the composite membranes investigated. The permeation properties of the composites were examined by the pressure increase and an isobar method. Depending on the precursor composition and the plasma polymerization parameters, it is possible to prepare membranes with Knudsen-like or solution-diffusion controlled separation factors. Low plasma polymerization energy densities and a mixture of silico- and fluoro-organic precursors result in water/methane separation factors as low as α_CH4^H₂O = 0.3 and high membrane permeabilities. Infrared analysis yields that the structure of the films is mainly determined by the silico-organic component. The fluoro-organic coprecursor causes a fluorination of methyl groups of the films as manifested by an infrared absorption band at 900-880 cm⁻¹.     

Fabrication of chiral silver nanoparticles and chiral nanoparticulate film via organogel

Chiral silver nanoparticles and chiral nanoparticulate films were prepared through the in situ reduction of an organogel formed by a newly designed silver(i)-coordinated organogelator.     

Pretilt angle generation by UV exposure during imidization of polyimide

We investigated pretilt angle generation and liquid crystal (LC) alignment by ultraviolet exposure during the imidization of polyimide (PI). The generated pretilt angle of a nematic (N) LC using an in situ photo-alignment method is smaller than that using a conventional photo-alignment method on a surface of PI having side chains. The NLC pretilt angles using an in situ photo-alignment method injected at isotropic phase increased with annealing were observed.     

Molecular mass determination of polyamic acid ionic salt by size-exclusion chromatography

A methodology was developed for the determination of molecular weight aveages of polyamic acid ionic salt (PAS) by size-exclusion chromatography (SEC). Polystyrene standards were used for calibration and THF-DMF 1:1 by volume containing 0.06 M LiBr and 0.06 M H3PO4 was used as the mobile phase. The proposed methodology was found to be reproducible.     

Pretilt angle generation by UV exposure during imidization of polyimide

We investigated pretilt angle generation and liquid crystal (LC) alignment by ultraviolet exposure during the imidization of polyimide (PI). The generated pretilt angle of a nematic (N) LC using an in situ photo-alignment method is smaller than that using a conventional photo-alignment method on a surface of PI having side chains. The NLC pretilt angles using an in situ photo-alignment method injected at isotropic phase increased with annealing were observed.     

Fabrication of a covalently attached self-assembly multilayer film based on CdTe nanoparticles

A precursor film has been fabricated from TGA (thiolglycolic acid)-stabilized CdTe nanoparticles and NDR (nitro-containing diazoresin) using electrostatic interactions and the standard layer-by-layer assembly method; covalent bonds are formed under ultraviolet irradiation. XPS provided evidence for the presence of CdTe nanoparticles within the polymer ultrathin films. UV-visible spectroscopy and FTIR spectroscopy provide evidence for the formation of a covalent linkage. Moreover, the UV-visible spectroscopy and AFM measurement support the improvement of the stability of the hybrid organic/inorganic film toward polar solvents when the linkages between the nanoparticles and polymer changed from ionic bonds to covalent bonds.     

Tungstophosphoric acid nanoparticles supported on polyamic acid: A mild and recoverable heterogeneous catalyst for the selective synthesis of mono and bulky bis(1,8-dioxooctahydroxanthene)s under solvent-free conditions

A series of 1,8-dioxooctahydroxanthene derivatives and some crowded bis(1,8-dioxooctahdroxanthene) were selectively synthesized using tungstophosphoric acid nanoparticles supported on polyamic acid (TPA/PAA) as a new catalyst in solvent-free conditions. The high purity products were isolated and catalyst was easily separated in simple work-up and was recycled several times without loss of reactivity under the described reaction conditions. The reaction is characterized by short reaction time, high efficiency and environmentally friendly reaction conditions.     

壳聚糖修饰电极上的铁氰根离子对抗坏血酸的电催化氧化作用

在玻碳电极表面滴涂一层壳聚糖膜 ,壳聚糖分子中 -NH2 在酸性溶液中发生质子化 ,靠静电引力作用吸附富集荷负电的电子介体Fe(CN) 63 -,使其固定在电极表面 ,研究了此Fe(CN) 63 - 壳聚糖 GC修饰电极对抗坏血酸的催化氧化作用。抗坏血酸的浓度在 3.0× 1 0 -6～ 5 .0× 1 0 -3 mol L范围内呈很好的线性关系 ,相关系数为 0 .998,检测限达 1 .0× 1 0 -6mol L。该法已用于测定蔬菜中抗坏血酸的含量。