Preparation and characteristics of polyimide-TiO2 nanocomposite film

A sol-gel approach has been developed to prepare polyimide-TiO2, hybrid films fi om soluble polyimides and a modified titanium precursor. The rate of the hydrolysis reaction of titanium alkoxide can be controlled by using acetic acid as a modifier. FTIR and XPS indicated that TiO2, particles were well distributed in polyimide matrixes with particle size small per than 60 nm. Polyimide hybrid films having the TiO2, component less than or equal to 10% exhibited high thermal stability, high optical transparency and good mechanical properties and possessed higher dielectric constants than correspondingly polyimides. (C) 2000 Society of Chemical Industry.

Preparation, characterization and photophysical properties of layered zirconium bis(monohydrogenphosphate) intercalated with rare earth complexes

Two kinds of rare earth (RE) complexes were intercalated into zirconium bis(monohydrogenphosphate) (alpha -ZrP) by exchanging the RE complexes into the p-methyoxyaniline (PMA) preintercalated compound Zr(O3POH)(2). 2PMA (alpha -ZrP . 2PMA). Powder X-ray diffraction patterns reveal that Eu(DBM)(3)phen (DBM: dibenzoylmethane, phen: 1,10-phenanthroline) and Tb(AA)(3)phen (AA: acetylacetone) intercalated into alpha -ZrP . 2PMA. This was confirmed by the UV-visible spectra of both the RE complexes and the assemblies. At the same time, the assemblies have better luminescent properties, and the fluorescent lifetimes of RE3+ in the excited state in the assemblies are much longer than those in the complexes. The stabilities of the assemblies under UV radiation are much better than those of the RE complexes.

Preparation and luminescence properties of sol-gel hybrid materials incorporated with europium complexes

Microporous silica gel has been prepared by the sol-gel method utilizing the hydrolysis and polycondensation of tetraethylorthosilicate (TEOS). The gel has been doped with the luminescent ternary europium complex Eu(TTA)(3). phen: where HTTA = 1-(2-thenoyl)-3,3,3-trifluoracetone and phen = 1,10-phenanthroline. By contrast to the weak f-f electron absorption bands of Eu3+, the complex organic ligand exhibits intense near ultraviolet absorption. Energy transfer from the ligand to Eu3+ enables the production of efficient, sharp visible luminescence from this material. Utilizing the polymerization of methyl methacrylate or ethyl methacrylate, the inorganic/polymer hybrid materials containing Eu(TTA)(3). phen have also been obtained. SEM micrographs show uniformly dispersed particles in the nanometre range. The characteristic luminescence spectral features of europium ions are present in the emission spectra of the hybrid material doped with Eu(TTA)3 phen. (C) 2000 Kluwer Academic Publishers.

Study of the alkylation of isobutane with n-butene over WO3/ZrO2 strong solid acid. 1. Effect of the preparation method, WO3 loading, and calcination temperature

A series of strong solid acids composed of WO3/ZrO2 were prepared. Their crystal structure, surface state, and acidity were determined by the methods of X-ray diffraction, thermal gravimetric and differential thermal analysis, temperature-programmed reduction, laser Raman, and acidity measurement. The results revealed that ZrO2 in WO3/ZrO2 existed mainly in the tetragonal phase, the addition of WO3 plays an important role in stabilizing the tetragonal phase of ZrO2, and all of the samples possessed large surface areas. WO3 in WO3/ZrO2 is mainly monolayer dispersed, and a small amount crystallized on the ZrO2 surface and partly reacted with ZrO2 to form the bond of Zr-O-W, acting as the strong solid acid center. The catalytic properties of WO3/ZrO2 strong solid;acids for alkylation of isobutane with butene at different conditions were investigated. They had a better reaction performance than other strong solid acids; a parallel relationship could be drawn between the catalytic activity and the acid amounts as well as the acidic strength of the catalysts.

A new preparation of zinc sulfide nanoparticles by solid-state method at low temperature

A novel solid-state method of the preparation of zinc sulfide nanoparticles is reported. By solid-state reaction of zinc acetate and thioacetamide at low temperature, zinc sulfide nanoparticles of different sizes were prepared. The temperature of preparation varied from room temperature to 300 degrees C. The particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and photoluminescence spectrum. X-ray diffraction patterns revealed that the particles exhibited pure zinc-blende crystal structure and that particle size increased with increasing temperature. The TEM micrograph showed that the mean particle size was about 40 nm for the sample heated at 100 degrees C. A blue shift was observed in the photoluminescence emission spectrum. A possible mechanism of the reaction corresponding to our observation is proposed, (C) 2000 Elsevier Science Ltd. All rights reserved.

Preparation and characterization of luminescent thin films doped with rare earth (Tb3+, Eu3+) complexes derived from a sol-gel process

Sol-gel derived luminescent thin films doped with rare earth (RE) complexes were prepared using an in-situ synthesis method with a two-step hydrolysis process and the luminescence spectra were measured. Fluorescence Lifetime and thermal stability were investigated. The results show that a broad excitation band indicates the formation of RE complexes in the solid thin films. RE ions, which are restrained in a silica matrix, present longer lifetime and higher thermal stability than that in DMF/PVB films containing the corresponding pure complexes. (C) 2000 Elsevier Science B.V. All rights reserved.

Preparation and properties of conducting polymer of doped polyaniline LB film

Stable monolayer of polyaniline doped with camphor sulfonic acid at the air-water interface has been obtained and has been successfully deposited by Langmuir-Blodgett technique onto CaF2 substrate. IR and UV-Vis-NIR spectra show that the doped molecules dedoped partially from the PANI backbone during the monolayer compression or deposition. Gas-sensing measurement indicates that the doped polyaniline LB film was sensitive to ethanol vapor at room temperature.

Processible nanomaterials with high conductivity and magnetizability. Preparation and properties of maghemite/polyaniline nanocomposite films

A versatile process employing anionic surfactants has been developed for the preparation of processible nanocomposite films with electrical conductivity and magnetic susceptibility. Maghemite (g-Fe2O3) nanoclusters (similar to 10 nm in size) are coated with 4-dodecyl- benzenesulfonic acid, and polyaniline (PAn) chains are doped with 10-camphorsulfonic acid. The coated nanoclusters and doped polymers are soluble in common solvents, and casting the solutions readily gives free-standing nanocomposite films with nanocluster contents as high as similar to 50 wt %. The g-Fe2O3/PAn nanocomposites show high conductivity (82-337 S cm(-1)) and magnetizability (up to similar to 35 emu/g g-Fe2O3).

Preparation, structures, and electrochemistry of a new polyoxometalate-based organic/inorganic film on carbon surfaces

The preparation, structure, and electrochemical and electrocatalytical properties of a new polyoxometalate-based organic/inorganic film, composed of cetyl pyridinum 11-molybdovanadoarsenate (CPMVA) molecules, have been studied. Cyclic potential scanning in acetone solution led to a stable CPMVA film formed on a highly oriented pyrolytic graphite (HOPG) surface. X-ray photoelectron spectroscopy, scanning tunneling microscopy, and cyclic voltammetry were used for characterizing the structure and properties of the CPMVA film. These studies indicated that self-aggregated clusters were formed on a freshly cleaved HOPG surface, while a self-organized monolayer was formed on the precathodized HOPG electrode. The CPMVA film exhibited reversible redox kinetics both in acidic aqueous and in acetone solution, which showed that it could be used as a catalyst even in organic phase. The CPMVA film remained stable even at pH > 7.0, and the pH dependence of the film was much smaller than that of its inorganic film (H4AsMo11VO40) in aqueous solution. The CPMVA film showed strong electrocatalysis on the reduction of bromate, and the catalytic currents were proportional to the square of the concentration of bromate. The new kind of polyoxometalate with good stability may have extensive promise in catalysis.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

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,

Studies on the alkylation of isobutane with butene over WO3/ZrO2 strong solid acid (I) - Effect of preparation, load of WO3 and calcination temperature

A series of WO3/ZrO2 strong solid acid prepared under different conditions were studied. Their crystal structures, surface properties and acidities were determined by means of XRD, DTA-TG, H-2- TPR, Laser Raman and acidity measurements. The results revealed that ZrO2 in WO3/ZrO2 existed mainly in tetragonal phase, the addition of WO3 plays an important role to stabilize tetragonal phase of ZrO2 and thus the catalyst had a considerable surface area. WO3 in WO3/ZrO2 was dispersed and crystalized in WO3 crystalite on ZrO2 surface and partly reacted with ZrO2 to form the bond of Zr-O-W, which acts as the strong solid acid site. The catalytic properties of WO3/ZrO2 strong solid acid for alkylation of iso-butane with butene under the different conditions were investigated. They had a better reaction performance than other strong solid acids, a parallel relationship could be drawn between the catalytic activity and the amount of acid sites as well as the acidic strength of the catalysts.

Preparation and characterization of layered compound zirconium bis(monohydrogenphosphate)intercalated with rare earth complex

Layered compound zirconium bis(monohydrogenphosphate)(alpha-ZrP) intercalated with rare earth complex Eu(DBM)(3)phen was prepared. The pre-intercalation of p-methoxyaniline into alpha-ZrP makes the interlayer separation large enough to exchange PMA with europium complex, thus, the luminescent assembly was prepared. This was confirmed by X-ray diffraction, UV-visible spectra and elemental analysis. The fluorescence spectra and lifetime of the assembly were also presented.

Preparation, structure and luminescence of BaMAl10O17 : Eu2+ (M = Be, Mg, Ca, Zn, Cd, Mn, Co, Li) system

The BaMA(10)O(17) (M = Be, Mg, Ca, Zn, Cd, Mn, Co, Li) system has been synthesized by solid state method and characterized by XRD. The results show that when M is Mg, Zn, Mn, Co, Li, there exists the structure of beta-Al2O3 for BaMAl10O17 system, and when M indicates Cd, beta-Al2O3 structure is formed accompanying alpha-Al2O3 phase, and when M represents Be and Ca, beta-Al2O3 structure cannot be formed. This demonstrates that the condition forming beta-Al2O3 structure compounds for the system BaMAl10O17 is 0.05nm < R-M < 0.09nm (R-M represents the radius of M). The thought that if a M ion can form a stable spinel structure there exsits a corresponding magnetoplumbite and beta-alumina structure is proposed for BaMAl10O17 system according to the experimental results. When M is Li, Be, Zn, Eu2+ activator produces an emission of nearly 450 nm with half height width about 50 nm, when M is Mn, there are simultaneously the emissions of Eu2+ and Mn2+ and the excitation energy of Eu2+ can transfer to Mn2+ in the host, when M is Cd, Eu2+ displays a double-emission band, which can be explained by the Jahn-Teller's effect. It is possible for the system BaMAl10O17 with M being Li, Be, Zn to become blue-emitting component in three colour lamp through further study.

Deoxyribonucleic acid sample preparation in scanning probe microscope

The process of deoxyribonucleio acid (DNA) sample preparation in scanning tunneling microscope (STM) and atomic force microscope (AFM) is reviewed. The main discussions are devoted to the methods, advantages or drawbacks and improvement of the DNA sample's immobilization and spreading.