Polypropylene as a carbon source for the synthesis of multi-walled carbon nanotubes via catalytic combustion

Multi-walled carbon nanotubes (MWCNTs) were efficiently synthesized by catalytic combustion of polypropylene (PP) using nickel compounds (such as Ni2O3, NiO, Ni(OH)(2) and NiCO3 (.) 2Ni(OH)(2)) as catalysts in the presence of organic-modified montmorillonite (OMMT) at 630-830 degrees C. Morphologies of the sample undergoing different combustion times were observed to investigate actual process producing MWCNTs by this method. The obtained MWCNTs were characterized by X-ray diffraction (XRD), transmission electron microscope and Raman spectroscopy. The yield of MWCNTs was affected by the composition of PP mixtures with OMMT and nickel compounds and the combustion temperature. The proton acidic sites from the degraded OMMT layers due to the Hoffman reaction of the modifiers at high temperature played an important role in the catalytic degradation of PP to supply carbon sources that are easy to be catalyzed by nickel catalyst for the growth of MWCNTs. The XRD measurements demonstrated that the nickel compounds were in situ reduced into the Ni(0) state with the aid of hydrogen gas and/or hydrocarbons in the degradation products of PP, and the Ni(O) was really the active site for the growth of MWCNTs. The combination of nickel compounds with OMMT was a key factor to efficiently synthesize MWCNTs via catalytic combustion of PP.

Vaterite-type YBO3 : Eu3+ crystals: hydrothermal synthesis, morphology and photoluminescence properties

Vaterite-type YBO3:Eu3+ crystals with interesting flower and hedgehog fungus-like structures composed of nanosheets were obtained by controlled crystallization of Y2O3 and Eu2O3 in H3BO3 solutions under acidic hydrothermal (HT) conditions. Nanosheets of uniform thicknesses were formed by preferential crystal growth along the (100) crystallographic plane and specific three-dimensional structures were further developed through a homocentric growth mechanism. Optical emission measurements showed that the HT-grown nanosheet crystals exhibited a higher ratio of the emitted red-to-orange light ratio than crystals grown from solid-state reactions. The photoluminescence intensity and emission lifetimes were also studied as a function of the Eu3+ dopant concentration and the HT synthesis temperature. The effect of some additives: a chelating ligand, a surfactant and a polymer, on the YBO3:Eu3+ crystals morphology was also investigated.

Stable ordered mesoporous silica materials templated by high-temperature stable surfactant micelle in alkaline media

Ordered hexagonal mesoporous silica material (JLU-30) has been successfully synthesized in alkaline media at high temperature (> 160 degreesC, using cationic (1,3-dimethyl-2-imidazolidin-2-ylidene)hexadecylmethyl-ammonium bromide (DIHAB) as a template, and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, differential thermal analysis (DTA), and thermogravimetric analysis (TG), as well as Al-27 and Si-29 nuclear magnetic resonance (NMR) spectroscopy. Mesoporous JLU-30 shows much higher hydrothermal stability than MCM-41. Si-29 NMR spectra indicate that the pore walls of JLU-30 samples synthesized at high temperature (160 degreesC) are fully condensed, giving a Q(4)/Q(3) ratio as high as 6.2. In contrast, MCM-41 synthesized at relatively low temperature (100 degreesC) shows the Q(4)/Q(3) + Q(2) ratio at 1.1. Such unique structural feature might be responsible for the observed highly hydrothermal stability of the mesoporous silica materials (JLU-30).

Purification and structure identification of hyaluronic acid

Polysaccharide produced by mutated strain of Streptococcus zooepidemicus was purified by the procedures including Savage method, quaternary ammonium compound precipitation, DEAE-cellulose(DE52) chromatography and Sephadex G-75 gel filtration. The structure of the purified polysaccharide has been characterized by means of chemical composition analysis, C-13 NMR spectrum, infrared spectrum and circular dichroism (CD). All the results showed that the purified polysaccharide was hyaluronic acid (HA). The single helix conformation of the purified HA was determined by Congo red experiment. The molecular weight of the HA was about 1.16x10(6)D, which was measured by viscosity method.

Synergistic extraction of zinc(II) and cadmium(II) with mixtures of primary amine N1923 and neutral organophosphorous derivatives

Synergistic extraction of zinc(IT) and cadmium(11) from hydrochloric acid solution with primary amine N1923 and neutral organophosphorus derivatives Cyanex 923 and Cyanex 925 is the focus of this paper. Extraction mechanisms are discussed as well as how the acidity of the aqueous phase, the composition of the organic phase, and the experimental temperature affect the rates of extraction of metal ions. Differences between synergistic efficiency of Zn(II) and Cd(II) with mixtures of primary amines N1923 and either Cyanex 923 or Cyanex 925 are observed. The equilibrium constants, the composition, and the formation constants of the extracted complexes as well as the values of the thermodynamic functions are calculated. According to the synergy coefficient formula, the synergy effect on the extraction of Zn(II) is in the following order:N1923 + Cyanex 925 > N1923 + Cyanex 923 This order is reversed in the case of cadmium(II). For the same synergistic system, the extraction rate follows the order: Zn(II) > Cd(II). Furthermore, the stereochemical structures of the various extractants and their effect on metal ion extraction rate are also investigated.

Synthesis of chitosan-stabilized gold nanoparticles in the absence/presence of tripolyphosphate

Gold nanoparticles were prepared by reducing gold salt with a polysaccharide, chitosan, in the absence/ presence of tripolyphosphate (TPP). Here, chitosan acted as a reducing/stabilizing agent. The obtained gold nanoparticles were characterized with UV-vis spectroscopy and transmission electron microscopy. The results indicated that the shape and size distribution of gold nanoparticles changed with the molecular weight and concentration of chitosan. More interestingly, the gelation of chitosan upon contacting with polyanion (TPP) can also affect the shape and size distribution of gold nanoparticles. By adding TPP to chitosan solution before the reduction of gold salt, gold nanoparticles have a bimodal size distribution, and at the same time, polygonal gold particles were obtained in addition to spherical gold nanoparticles.

Micellization and reversible pH-sensitive phase transfer of the hyperbranched multiarm PEI-PBLG copolymer

A novel, hyperbranched, amphiphilic multiarm biodegradable polyethylenimine-poly(gamma-benZyl-L-gluta- mate) (PEI-PBLG) copolymer was prepared by the ring-opening polymerization of gamma-benzyl-L-glutamate-N-car-boxyanhydride (BLG-NCA) with hyperbranched PEI as a macroinitiator. The copolymer could self-assemble into core-shell micelles in aqueous solution with highly hydrophobic micelle cores. As the PBLG content was increased, the size of the micelles increased and the critical micelle concentration (CMC) decreased. The surface of the micelles had a positive potential. The cationic micelles were capable of complexing with plasmid DNA (pDNA), which could be released subsequently by treatment with polyanions. The PEI-PBLG copolymer formed unimolecular micelles in chloroform solution. ne pH-sensitive phase-transfer behavior exhibited two critical pH points for triggering the encapsulation and release of guest molecules. Both the encapsulation and release processes were rapid and reversible. Under strong acidic or alkaline conditions, the release process became partially or completely irreversible.

Sequential deprotonation of meso-(p-hydroxyphenyl)porphyrins in DMF: From hyperporphyrins to sodium porphyrin complexes

Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (H-1 NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character.

Medicated wound dressings based on poly(vinyl alcohol)/poly(N-vinyl pyrrolidone)/chitosan hydrogels

Poly(vinyl alcohol) /poly(N-vinyl pyrrolidone) (PVP)/chitosan hydrogels were prepared by a low-temperature treatment and subsequent Co-60 -gamma-ray irradiation and then were medicated with ciprofloxacin lactate (an antibiotic) and chitosan oligomer (molecular weight = 3000 g/mol). The gel content, swelling ratio, tensile strength, and crystallinity of the hydrogels were determined. The effects of the chitosan molecular weight, the low-temperature treatment procedure, and the radiation dosage on the hydrogel properties were examined. The molecular weight of chitosan was lowered by the irradiation, but its basic polysaccharide structure was not destroyed. Repeating the low-temperature treatment and gamma-ray irradiation caused effective physical crosslinking and chemical crosslinking, respectively, and contributed to the mechanical strength of the final hydrogels. The incorporation of PVP and chitosan resulted in a significant improvement in the equilibrium swelling ratio. and elongation ratio of the prepared hydrogels. The ciprofloxacin lactate and chitosan oligomer were soaked into the hydrogels. Their in vitro release behaviors were examined, and they were found to follow diffusion-controlled kinetics.

Kinetics of Y(III) stripping for the system Y/HCl/Cyanex 272-P507/heptane with constant interfacial area cell with laminar flow

Kinetics and mechanism of stripping of yttrium(III) previously extracted by mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272, HA), and 2-ethylhexyl phosphonic acid mono-2-ethylhexl ester (P507, HB) dissolved in heptane have been investigated by constant interfacial-area cell by laminar flow. The corresponding equilibrium stripping equation and equilibrium constant were obtained. The studies of effects of the stirring rate and temperature on the stripping rate show that the stripping regime is dependent on the stripping conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of mixtures of Cyanex 272 and P507 at heptane-water interfaces makes the interface the most probable locale for the chemical reactions. The stripping rate constant is obtained, and the value is compared with that of the system with Cyanex 272 and P507 alone. It is concluded that the stripping ability with the mixtures is easier than that of P507 due to lower the activation energy of the mixtures. The stripping rate equation has also been obtained, and the rate-determining steps are the two-step interfacial chemical reactions as predicted from interfacial reaction models.

Extraction and stripping of ytterbium (III) from H2SO4 medium by Cyanex 923

The extraction and stripping of ytterbium (III) from sulfuric acid medium using Cyanex 923 in heptane solution was investigated. The effects of extractant concentration, pH and sulfate ion as well as stripping agents, acidity and temperature on the extraction and stripping were studied. The equilibrium constants and thermodynamic parameters, such as Delta H (10.76 kJ(.)mol(-1)), Delta G (-79.26 kJ(.)mol(-1)) and Delta S (292.41 J(.)K(-1.)mol(-1)), were calculated. The extraction mechanism and the complex species extracted were determined by slope analysis and FrIR spectra. Furthermore, it was found that the extraction of Yb (III) from sulfuric acid medium by Cyanex 923 increased with pH, concentration of SO42-, HSO4-, and extractant concentration, and approximately a quantitative extraction of Yb (III) was achieved at an equilibrium pH near 3.0, and the extracted complex was YbSO4(HSO4)(.)2Cyanex923((o)).

Electrochemical Metalloimmunoassay Based on Enlargement of Gold Nanoparticle Label Treated with Ag Enhancement System

A novel sensitive electrochemical immunoassay with colloidal gold as the antibody labeling tag and subsequent signal amplification by silver enhancement is described. Colloidal gold was treated by a light-sensitive silver enhancement system which made silver deposit on the surface of colloidal gold(form Au/Ag core-shell structure), followed by the release of the metallic silver atoms anchored on the antibody by oxidative dissolution of them in an acidic solution and the indirect determination of the dissolved Ag+ ions by anodic stripping voltammetry(ASV) at a carbon fiber microelectrode. The electrochemical signal is directly proportional to the amount of analyte(goat IgG) in the standard or a sample. The method was evaluated by means of a noncompetitive heterogeneous immunoassay of immunoglobulin G(IgG) with a concentration as low as 0.2 ng/ mL. The high performance of the method is related to the sensitive ASV determination of silver(I) at a carbon fiber microelectrode and to the release of a large number of Ag+ ions from each silver shell anchored on the analyte(goat IgG).

Direct tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection of polyamines separated by capillary electrophoresis

Capillary electrophoresis (CE) with tris(2,2'-bipyridyl) ruthenium (II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) detection technique was developed for the analysis of four polyamines (putrescine (Put), cadaverine (Cad), spermidine (Spd), and spermine (Spm)) analysis. The four polyamines contain different amine groups, which have different ECL activity. There are several parameters which influence the resolution and ECL peak intensities, including the buffer pH and concentrations, separation voltage, sample injection, electrode materials, and Ru(bpy)(3)(2+) concentrations. Polyamines are separated by capillary zone electrophoresis in an uncoated fused-silica capillary (50 cm x 25 mum (ID) filled with acidic phosphate buffer (200 mmol/L phosphate, pH 2.0) - 1 mol/L phosphoric acid (9:1 v/v) and a separation voltage of 5 kV (25 muA), with end-column Ru(bpy)(3)(2+) ECL detection. A 5 mmol/L Ru(bpy)(3)(2+) solution plus 200 mmol/L phosphate buffer (pH 11.0) is added into the reagent reservoir. The calibration curve is linear over a concentration range of two or three orders of magnitude for the polyamines. The analysis time is less than 25 min. Detection limits for Put and Cad are 1.9 x 10(-7) mol/L and 7.6 x 10(-9) mol/L for Spd and Spm, respectively.

Chemical characteristic of bioactive polysaccharides isolated from Ornithogalum caudatum Ait.

A water-soluble crude extract prepared from Ornithogalum caudatum Ait. (OCA) showing a high immunomodulating activitiy was isolated and characterized by virtue of get filtration and column chromatography. The presence of the monosaccharides has been established by the chemical analysis. The quantitative analysis of the alditol acetate derivatives of them showed the ratios of the monosaccharides analyzed by means of GC respectively. The concentrations of protein(280 nm) and carbohydrate (496 nm) were detected respectively. The information of the molecular weight from the pure polysaccharide was obtained by several standard Dextrans from the Sephadex chromatography.

Arabinogalactan as a carrier for contrast agent in magnetic resonance imaging

Arabinogalactan-Gd-DTPA was synthesized by the reaction of diethylenetriaminepenta-acetic acid (DTPA) bisanhydride with polysaccharide in dry DMSO and characterized by FTIR, elemental analysis and ICP-AES. Its stability was investigated by competition with Ca2+, EDTA, DTPA. The t(1)-relaxivity is 8.06 mmol(-1) . L . s(-1) in D2O, 8.48 mmol(-1) . L . s(-1) in 0.725 mmol . L-1 BSA, respectively. t(1)-weighted MR imaging of rat kidney and liver showed a remarkable enhancement post injection of Arabinogalactan-Gd-DTPA. The results indicate that the arabinogalactan-Gd-DTPA is a potential contrast agent for MRI.