Effect of stoichiometric ratio of organic fuel to oxidizer on performance of La0.8Sr0.2CoO3 catalysts for CH4 combustion

Perovskite-type La_0.8Sr_0.2CoO₃ mixed oxides were prepared by d,l-alanine solution combustion synthesis and used successfully in CH₄ combustion as catalysts. These samples were characterized by means of XRD, FTIR, BET, and H₂-TPR methods. The effects of stoichiometric ratio (φ) of organic fuel to oxidizer on the structure and catalytic activities of the catalysts were studied. The results indicate that all La_0.8Sr_0.2CoO₃ mixed oxides with different φ have perovskite structures. Their structures and catalytic activities vary along with the change of φ. The catalytic activity of La_0.8Sr_0.2CoO₃ mixed oxide with φ = 1.52 is the best among all the samples, whose T ₅₀ and T ₁₀₀ (the temperatures of methane conversions reaching 50 and 100%, respectively) are respectively 470 °C and 550 °C, which can be explained in terms of the smaller of average crystal size, higher specific surface area, bigger lattice distortion, lower activation energy, and higher mobility of chemically adsorbed oxygen on the surface and vacancy of the catalysts.     

Synthesis of an AIE-active fluorogen and its application in cell imaging

A fluorogen named 1-decyl-1-methyl-2,5-bis{4-[(N,N-diethylamino)methyl]phenyl}-3,4-diphenylsilole (3) was synthesized. It emitted weakly as isolated molecule but strongly as supramolecular aggregate, showing a characteristic behavior of aggregation-induced emission (AIE). The molecules of 3 formed highly emissive nanoparticles in aqueous media, which quickly and selectively marked cytoplasm of HeLa cells and posed no toxicity to the living cells. The fluorogen is thus a promising candidate material for cell imaging as a sensitive, selective and cytocompatible biosensor. Supported by the Research Grants Council of Hong Kong (Grant Nos. 603008, 601608 and 602707), the National Natural Science Foundation of China (Grant No. 20634020) and the CAO GuangBiao Foundation of Zhejiang University.     

Synthesis,characterization and performance of nanosized Bi<Subscript>0.1</Subscript>Sn<Subscript>0.9</Subscript>O<Subscript>2</Subscript>–WPU organic–inorganic hybrid coatings

A series of organic–inorganic hybrid coatings consisting of organic waterborne polyurethane (WPU) and inorganic nanosized bismuth-doped tin dioxide were successfully synthesized by the in situ polymerization approach. Bi_0.1Sn_0.9O₂ nano-powders were prepared via a new route of sol–gel combustion hybrid method using acetylene black as the fuel. The formed nano-powders were characterized by transmission electron microscopy and X-ray diffraction (XRD). Bi_0.1Sn_0.9O₂–WPU was then fabricated with isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and nano-Bi_0.1Sn_0.9O₂-poly(ε-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable contents of Bi_0.1Sn_0.9O₂. The hybrid coatings with Bi_0.1Sn_0.9O₂ loading on the glass substrate exhibited good heat insulation efficiency. The tensile strength and breaking extensibility of nanocomposite film containing 1.0% of the nano-Bi_0.1Sn_0.9O₂ were measured as 9.35 MPa and 248%, respectively. The transmittance of visible light was above 80%. The heat insulation of glass coated with nano-Bi_0.1Sn_0.9O₂–WPU hybrid was over 60 °C in contrast to the commercial blank glass.     

Ion-pairing high-performance liquid chromatography determination of amitrole in apple after solid-phase extraction and precolumn derivatization

A novel method based on solid-phase extraction was studied for the extraction of amitrole (3-amino-1,2,4-triazole), and its residue determination in apples has been developed. The samples were derivatized with 4-chloro-3,5-dinitrobenzotrifluoride (CNBF). The derivatization conditions and the influence of elution composition on the separation were investigated. In pH 9.5 H₃BO₃–Na₂B₄O₇ media, the reaction of amitrole with CNBF was complete at 60°C after 30 min. The separation of derivatized amitrole was achieved at room temperature within 13 min by gradient elution mode with cetyltrimethylammonium bromide in mobile phase as ion-pair reagent. The method correlation coefficient was 0.9996, in concentrations ranging from 1.66 to 415 mg L⁻¹. The calculated recoveries of the proposed method were from 94.17% to 105.67%, and relative standard deviations were 1.57% to 6.44% in the application to the quantitative determination of amitrole in apples. The detection limit of amitrole was 0.10 mg L⁻¹ with a signal-to-noise ratio of 3. Figure Residue determination of amitrole in apple by ion-pairing high-performance liquid chromatography     

Spectral identification of fullerene C82 isomers

Ultraviolet photoelectron spectra (UPS) of C(82) isomers have been calculated using hybrid density functional theory in combination with the Gelius model [Proceedings of the International Conference on Electron spectroscopy, edited by D. A. Shirley (North-Holland, Amsterdam, 1972), p. 311; J. Electron Spectrosc. Relat. Phenom. 5, 985 (1974)]. The calculated UPS spectra are found to be isomer dependent and in good agreement with the experimental counterparts. Near-edge x-ray absorption fine structure (NEXAFS), x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy, and the resonant inelastic x-ray scattering (RIXS) spectra of three important isomers [3(C(2)), 6(C(s)), and 9(C(2v))] have also been simulated. Strong isomer dependence has also been found for NEXAFS, XPS, and RIXS spectra.     

Simple method for determination of five terpenoids from different parts of Tripterygium wilfordii and its preparations by HPLC coupled with evaporative light scattering detection

By optimizing the extraction, separation, and analytical conditions, a reliable and accurate high-performance liquid chromatography method coupled with evaporative light scattering detection (ELSD) was developed for simultaneous determination of five terpenoids, i.e., triptolide, tripchlorolide, demethylzelastral, wilforlide B, and wilforlide A, in root, stem, leaves, root bark, twig, and root without bark of Tripterygium wilfordii Hook. f and six of its herbal preparations. This approach would thus provide a more accurate and general method for evaluating the quality of the herb and its preparations. Separation of these five terpenoids was achieved on a ZORBAX Eclipse XDB-C8 column with gradient elution using water and acetonitrile as solvents, both containing 0.05% formic acid, at a temperature of 30 degrees C and a flow rate of 0.8 mL/min. The drift tube temperature of ELSD was set at 100 degrees C, and the nitrogen flow rate at 1.5 L/min. Good linear relationships were obtained with correlation coefficients for the analytes exceeding 0.992, and the LOD and LOQ were less than 0.149 microg and 0.297 microg on column, respectively. Intra-day and inter-day precision of the analytes were less than 1.25% and 5.97%, respectively, and the average recovery rates obtained were in the range of 95.9 +/- 3.7% to 100.4 +/- 5.0% for all terpenoids with RSDs below 4.99%. Quantitative analysis of the five terpenoids in different parts of Tripterygium wilfordii and its six preparations showed that the contents of the terpenoids varied significantly. The tender root contained higher concentrations of triptolide, tripchlorolide, demethylzelastral, and wilforlide B than any other part of the herb. Correspondingly, the root bark contained the greatest concentration of wilforlide A, and the stem and twig came in second and third. This suggested that we could infer whether the medicinal materials were absolute roots without bark or not from the comparative contents of these terpenoids in the tablets in view of the fact that only the roots without bark are the valid officinal part of the plant. This method and the quantitation results obtained can provide a scientific and general as well as simple and convenient approach for the product manufacturers to set up quality control standards and for informing the public about the quality and safety of the preparations.     

Highly visible-light luminescence properties of the carboxyl-functionalized short and ultrashort MWNTs

Luminescence of the short multiwalled carbon nanotubes (MWNTs) conjugated with carboxylic acid groups has been studied. The results show that the carboxyl-functionalized short MWNTs could emit luminescence and the emission peak appears at 500 nm with a corresponding optimal excitation wavelength centering at 310 nm. When the short MWNTs are filtered through 0.15 μm polytetrafluoroethylene (PTFE) membrane, the ultrashort MWNTs are obtained from the filtrate. An interesting feature for the ultrashort MWNTs is that the emission intensity is strengthened and the peak is slightly blue shifted to 460 nm. This result indicates that the luminescence properties of MWNTs are strongly affected by the tube length. After chemical oxidization cutting, defects and carboxylic acid groups at the tube end and/or sidewall can be produced; the more shorten of MWNTs, the better dispersion and carboxylic passivation of the nanotubes, and the more intense luminescence emissions. The broad emissions are logically attributed to the trapping of excitation energy by defect sites in the carboxyl-functionalized nanotube structure.     

Synthesis of porphyrin-appended terpyridine as a chemosensor for cadmium based on fluorescent enhancement

The design and synthesis of a porphyrin-appended terpyridine, 5-(4-([2,2′:6′,2″]-terpyridin-4-yl-carboxyamidyl)phenyl)-10,15,20-triphenylporphyrin (H₂TPPTPy) and its application as potential fluoroionophore for recognition of metal ions are reported. For preparation of the fluoroionophore, a novel simple strategy with improved total yield has been applied for the synthesis of 2,2′:6′,2″-terpyridine-4′-carboxylic acid as a ligand. H₂TPPTPy shows chelation-enhanced fluorescence effect with cadmium ion via the interruption of photoinduced electron transfer (PET) process, which has been utilized as the basis of the fabrication of the Cd(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd(II)-sensitive chemosensor were investigated. It shows a linear response toward Cd(II) in the concentration range of 3.2 × 10⁻⁶ to 3.2 × 10⁻⁴ M with a limit of detection of 1.2 × 10⁻⁶ M. The chemosensor shows good selectivity for Cd(II) over a large number of cations, such as alkali, alkali earth and transitional metal ions except Cu(II) and Zn(II). The sensor has been used for determination of Cd(II) in water samples with satisfactory recoveries.     

Novel chiral solvating agents derived from natural amino acid: enantiodiscrimination for chiral α-arylalkylamines

Two benzo[de]isoquinoline 1,3-dione amino acids 1 and 2 were readily prepared, and their enantiodiscriminating ability were investigated by ¹H NMR spectroscopy. It was found that 1 exhibited an excellent chiral recognition ability toward chiral α-phenylethylamine and some of its derivatives, leading to clear baseline separation of the multiplet of the probe groups in two enantiomers. The stoichiometric ratio and association constants of some host-guest complexes were determined. The interactions between the hosts and guest 3 were further studied by intermolecular NOE experiment and ESI-MS.     

Further improvement of hydrostatic pressure sample injection for microchip electrophoresis

Hydrostatic pressure sample injection method is able to minimize the number of electrodes needed for a microchip electrophoresis process; however, it neither can be applied for electrophoretic DNA sizing, nor can be implemented on the widely used single-cross microchip. This paper presents an injector design that makes the hydrostatic pressure sample injection method suitable for DNA sizing. By introducing an assistant channel into the normal double-cross injector, a rugged DNA sample plug suitable for sizing can be successfully formed within the cross area during the sample loading. This paper also demonstrates that the hydrostatic pressure sample injection can be performed in the single-cross microchip by controlling the radial position of the detection point in the separation channel. Rhodamine 123 and its derivative as model sample were successfully separated.