Synthesis using electrospinning and stabilization of single layer macroporous films and fibrous networks of poly(vinyl alcohol)

We demonstrated in this paper an electrospinning technique could be employed to prepare the single layer macroporous films and fibrous networks of poly(vinyl alcohol) (PVA). A crucial element using electrospinning on the development of these electrospun structures was to shorten the distance of from the needle tip to the collector (L), which resulted in the bond of the wet fibers deposited on the collector at the junctions. The morphologies and average pore size of electrospun structures of PVA were mainly predominated by L and the time of collecting wet fibers on the collector. In addition, experimental results showed that an increase of the PVA concentration or a decrease of the applied voltage could also diminish slightly the average pore size of electrospun productions. Furthermore, a 60 degrees C absolute ethanol soak to PVA electrospun production led them to be able to stabilize in water for 1 month against disintegration. Differential scanning calorimetry (DSC) demonstrated that the 60 degrees C ethanol soak enhanced the degree of crystallinity of PVA production. The structural characteristic of macroporous films and networks in combination with their easy processability suggests potential utility in issue engineering applications.

Nickel complexes catalyzed Heck reaction of iodobenzene and methyl acrylate

Nickel appears the most promising for the replacement of palladium among the inexpensive transition metals for that it is active for Heck reaction and about 500 times cheaper than palladium. In this article, we describe our recent results in the area of nickel-catalyzed Heck vinylations. Main focus is on the influence of ligand concentration in different organic solvents and the effects of the addition of water. The conversion is high in NMP and increases with increasing of PPh3/Ni ratio; in ethanol and toluene the conversion presents a maximum value on Ni(PPh3)(2). The effect of the addition of water is sensitive to the concentration of PPh3 and the nature of solvent, it was well explained with the formation and transfer of the active species in the different solvent systems.

Synthesis and characterization of novel polythiophenes containing poly(ethylene oxide) side chains

Thiophene copolymers and their derivatives with poly(ethylene oxide) side chains were synthesized. The starting monomers were 3-hexylthiophene and 2-(3-thienyl) ethanol with poly(ethylene oxide) grafted to the side chains. New functionalized polythiophenes were prepared by both chemical oxidation with FeCl3 and electropolymerization. The conjugating polymers were characterized. The structures of the polythiophene derivatives agreed with the design.

Studies on the stability of polyazamacrocycle-Eu (Tb) by potentiometry and its catalytic hydrolysis on phosphate diester

The stability constants and species distributions of complexes of two lanthanide ions, Eu (III) and Tb(III), with a macrocyclic ligand, 3,6, 9, 17 20, 23-hexaazo-29, 30-dihydroxy-13, 27-dimethyl-tricylco-[23,3,1,1(11,15)] triaconta-1 (28) 11,13,15 (30), 25 26-hexane (BDBPH), in 1: 1 and 2: 1 system, were determined potentiometrically in 50% ethanol solution, at 35.0 degrees C and I = 0.100 mol/L (KCl). The two metal ions could form deprotonated mono- or dinuclear complexes with BDBPH with high stability after the three protons of the ligand completely neutralized. At higher pH values, Eu(M) could not form hydroxo complexes with BDBPH, while Tb(III) could form hydroxo complexes in the types of M2L(OH) M2L(OH)(2) and M2L (OH)(2). The kinetic study on the hydrolysis reaction of his (4-nitrophenyl) phosphate (BNPP) catalyzed by Tb-BDBPH system (2:1) was carried out in aqueous solution (pH 7.0 similar to 10.0) at 35 degrees C with I = 0.1000 mol/L (KCl). The second-order rate constant k(BNPP) (2.3 x 10(-3) (mol/L)(-1)center dot s(-1)) was determined. The dinuclear monohydroxo species, L-Tb-2-OH, is kinetically active species.

Comparison of biochemical effects induced by Changle between male and female rats using NMR and ICP-MS techniques

Metabolic profiles caused by rare earth complex were investigated using NMR and ICP-MS techniques. Male and female Wistar rats were treated orally with Changle (A kind of rare earth complex applied in agriculture to raise the production of crops) at dose of 2, 5 and 20 mg (.) kg(-1) body weight/day respectively for 90 d. Urine and serum samples are collected on 90 d. The relative concentrations of important endogenous metabolites in urine and serum are determined from H-1 NMR spectra and the contents of the four rare earth elements ( La, Ce, Pr and Nd) constituting Changle in the serum samples are measured by ICP-MS technique. Changle-induced renal and liver damage in rats is found based on the increase in the amounts of the amino acids, trimethylamine N-oxide, N, N-dimethyglycine, dimethylamine, succinate, aketoglutarate and ethanol as well as rare earth concentrations. The similarities and differentiations are found in the alteration patterns of metabolites and rare earth concentrations in serum.

Preparation and characterization of nanocrystalline CeO2 by precipitation method

CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group O-H(5)-F-M3M, when calcination temperature is in the range of 250 similar to 800 degreesC. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.

Preparation and characterization of luminescent cubic MCM-48 impregnated with an Eu3+ beta-diketonate complex

We report on the preparation of luminescent silica mesoporous molecular sieves (MCM-48) activated by the europium complex Eu(DBM)(3) . 2H(2)O (where DBM = dibenzoylmethane), using a simple wet impregnation method. Different concentrations of Eu(DBM)(3) . 2H(2)O were introduced into the MCM-48 cubic structure, and the resulting samples were washed with ethanol for different times. UV-Vis absorption measurements and thermogravimetric analysis were used to estimate the amount of Eu complex that has been incorporated within the pores of the MCM-48 host. The various samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy, diffuse reflectance (DR) and fluorescence measurements. The results reveal that Eu complexes have been successfully introduced into the pores of MCM-48 without disrupting the structure. All the impregnated MCM-48 materials show the typical red luminescence of Eu3+ when excited with a UV lamp. Shifts of the absorption maxima were observed in the DR and fluorescence excitation spectra and will be discussed in relation with guest-host interactions between the organic complex and the silica matrix. The decay profiles of the europium luminescence in the different samples were also measured and discussed.

Conductive hybrids from water-borne conductive polyaniline and (3-glycidoxypropyl)trimethoxysilane

Free-standing conductive films of organic-inorganic hybrids were prepared employing the sol-gel process of (3-glycidoxypropyl)trimethoxysilane (GPTMS) and water-borne conductive polyaniline (cPANI) in water/ethanol solution. The hybrids displayed a percolation threshold for electrical conductivity at a volume fraction of 2.1% polyaniline (PANI); the maximum conductivity of the hybrids reached 0.6 S/cm. GPTMS showed good compatibility with water-borne cPANI during the sol-gel process, and freestanding conductive films were obtained at room temperature. Transmission electron microscopy images of the hybrids indicated that the cPANI was dispersed in the inorganic phase in nanoscale. Because of good confinement of cPANI chains in the inorganic network, water resistance of the hybrid films was significantly improved compared with that of pure cPANI; the electrical conductivity of the films kept stable for 6-7 days soaking in water, whereas it decreased sharply for 1 day soaking for the pure cPANI.

AFM studies of DNA structures on mica in the presence of alkaline earth metal ions

As counterions of DNA on mica, Mg2+, Ca2+, Sr2+ and Ba2+ were used for,clarifying whether DNA molecules equilibrate or are trapped on mica surface. End to end distance and contour lengths were determined from statistical analysis of AFM data. It was revealed that DNA molecules can equilibrate on mica when Mg2+, Ca2+ and Sr2+ are counterions. When Ba2+ is present, significantly crossovered DNA molecules indicate that it is most difficult for DNA to equilibrate on mica and the trapping degree is different under different preparation conditions. In the presence of ethanol, using AFM we have also observed the dependence of B A conformational transition on counterion identities. The four alkaline earth metal ions cause the B-A transition in different degrees, in which Sr2+ induces the greatest structural transition.

A transparent thin film with hexagonal mesostructure containing rhodamine 6G

A transparent thin film was prepared by depositing the sol-get mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G (R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure, was composed of nanocrystallites about 35 nm in diameter and 1-10 mum in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover, optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.

H-1 NMR analysis for metabolites in serum and urine from rats administrated chronically with La(NO3)(3)

H-1 NMR spectroscopy has been used to assess long-term toxicological effects of a rare earth. Male Wistar rats were administrated orally with La(NO3)(3) at doses of 0.1, 0.2, 2.0, 10, and 20 mg/kg body wt, resp., for 3-6 months. Urine was collected at 1, 2, and 3 months and serum samples were taken after 6 months. Numerous low-M-r metabolites in rats serum and rats urine, including creatinine, citrate, glucose, ketone bodies, trimethylamine N-oxide (TMAO), and various amino acids, were identified on 400- and 500-MHz H-1 NMR spectra. La3+-induced renal and liver damage is characterized by an increase in the amounts of the excreted ketone bodies, amino acids, lactate, ethanol, succinate, TMAO, dimethylamine, and taurine and a decrease in citrate, glucose, urea, and allantoin. Information on the molecular basis of the long-term toxicity of La(NO3)(3) was derived from the abnormal patterns of metabolite excretions. An assay of some biochemical indexes and analysis of some enzymes in plasma supported NMR results.

Study on the integrated membrane processes of dehumidification of compressed air and vapor permeation processes

Blend modified polyimide (PI) hollow fiber membranes were used in vapor permeation for gas phase dehydration of ethanol. Dry air sweeping operation was used and the dry air was supplied by a dehumidification membrane module of compressed air. An integrated membrane process was composed. The effects of some factors, such as the modification of membrane materials, the humidity and current velocity of sweeping air, the operation temperature, on the efficiency of dehydration were discussed.

Effect of rare earth element on the metabolism in rats by high resolution proton nuclear magnetic resonance spectroscopy

The high-field nuclear magnetic resonance (NMR) spectra can be used for the rapid multicomponent analysis in small amounts of biological fluids. In this paper, the effect of La (NO3)(3) on the rats' metabolism in urine was investigated by H-1 NMR analysis. The experimental groups of wistar rats were injected intraperitoneally with La(NO3)(3) at doses of 0.2, 2.0, 10 and 20mg/kg body weight. The remarkable variation of low molecular weight metabolites in urine has been identified by H-1 NMR spectra, in which dimethylamine, N, N-dimethylglycine, urea, alpha -ketoglutarate, trimethylamine N-oxide, succinate, citrate and amino acids have been suggested as NMR markers for renal damage and ethanol, lactate, taurine as the markers for liver damage. This work may assess its possible use in the early detection of biochemical changes associated with Rare Earth induced kidney and liver dysfunction.

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.