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Multilingual abstracts in the five official working languages of the United Nations. (PDF 236 kb)

This paper describes the first synthesis of cadmium sulfide (CdS)-poly(lactic acid) (PLA) nanocomposites and their transparent fluorescent films by covalently grafting PLA onto the surfaces of CdS nanocrystals (NCs). Synthesis of the nanocomposites involved two steps. Lactic acid (LA)-capped CdS NCs were first prepared by reacting cadmium chloride (CdCl2) with sodium sulfide (Na2S) using LA as the organic ligand in H2O/N,N-dimethylformamide (DMF) solution. CdS–PLA nanocomposites were then formed by in situ ring-opening polymerization of lactide on the surface of modified CdS NCs. We also demonstrated herein the fabrication of the transparent fluorescent films of CdS–PLA nanocomposites by blending as-prepared nanocomposites with high-molecular-weight PLA. The as-prepared CdS NCs and their nanocomposites were studied by transmission electron microscopic imaging, thermogravimetric analyses, and spectroscopic measurements (ultraviolet–visible absorption and photoluminescence). The results revealed that the CdS–polymer nanocomposites exhibited good optical properties in terms of their photoluminescence and transparency.

A facile catalytic chain transfer polymerization (CCTP) technique has been developed to synthesize covalently linked CdS nanocrystal-polymer hybrids with good optical properties. The in situ polymerization of methyl methacrylate (MMA) on the surface of modified CdS nanocrystals (NCs) with diameter of 5 nm via CCTP process yielded CdS-polymethylmethacrylate (PMMA) hybrid nanocomposites; while the incorporation of hydroxyl-coated CdS NCs into poly(methacryloxypropyltrimethoxysilane) (PMPS)-co-PMMA matrices prepared by CCTP afforded CdS-PMPS-co-PMMA hybrid nanocomposites, which were further cross-linked by free radical polymerization to form CdS NC-polymer network. The spectroscopic studies indicate that as-prepared CdS NC-polymer hybrids show good photoluminescence (PL) and the NC-polymer network exhibits highly enhanced PL property with respect to that before cross-linking. Also described are the probable mechanism for the catalytic chain transfer polymerization on the surface of modified nanocrystal and the measurement of chain transfer constants.

The solution of ion mobility's nonlinear function coefficients α2 and α4 is the basis for achieving substance identification of High Field Asymmetric waveform Ion Mobility Spectrometry (FAIMS). Currently, nonlinear function coefficients α2 and α4 lack priors, meanwhile, existed solving results about α2 and α4 are deficient in error evaluation standard. In this article, acetone, isopropanol and 1, 2-dichlorobenzene were detected under different dispersion voltage by homemade FAIMS. In general, the spectrum peak of same sample at different dispersion voltage value is unique. Different dispersion voltage and corresponding compensation voltage value determines the value of α2 and α4. According to sample spectra at different dispersion voltage value, groups of spectral characteristics were obtained. Affirmatory number of data which were selected from multiple sets of compensation voltage value and dispersion voltage value, so that they were utilized to solved out lots of α2 and α4. Lots of factor have an effect on the accuracy of the solving results of α2 and α4, for instance, value of compensation voltage and dispersion voltage, style of fetching points of dispersion voltage, and so on. Comparing to other factors, style and amount of dispersion voltage is likely to control. By data analyzing huge amounts of α2 and α4 data, this paper explored their characteristic of distribution and correlation about them, research influence of number and method to fetch dispersion voltage detected points for error of solving results. After fitting frequency of α2 and α4, it was found that they conform to normal distribution, goodness of fitting exceed 0. 96, thus standard deviation of their distribution are able to evaluate error of solving results. In addition, a strong correlation exists between them, relevance of sample is -0. 977, -0. 968, -0. 992 respectively. With increasing of computing selected points, the corresponding error of solving results decrease. By comparing the standard deviation of method to fetch dispersion voltage detected points, found that detecting frequency in case of detecting maximum and the 70% of maximum of dispersion voltage value is lower at approximately same standard deviation, solving effect was optimized in unique fetching points style. Based on the premise of ensuring the accuracy of solving results of α2 and α4, it is obvious that reducing the frequency of detections for FAIMS effectively. It created favorable conditions for rapid field detection and precise spectral analysis.

For establishing the fermentation system of synthetic schizandrin A and schizandrin B, culture conditions of the Schisandra chinensis callus and the suspension cell were studied in this paper. The friable calluses of Schisandra chinensis (Turcz.) Baill. were induced from hypocotyls in Murashige-Skoog (MS) solidified medium supplemented with hormone 6-benzylaminopurine (6-BA) and 2,4-Dichlorophenoxyacetic butyl acetate (2,4-D) in different concentrations, and suspension cells initiated from friable callus were cultured in MS liquid medium with various concentrations and combinations of 6-BA, 2,4-D and kinetin (KT). The optimal culture condition for callus inducement was found to be MS solidified medium with 6-BA 1.0 mg/l and 2,4-D 0.3 mg/l and the optimal condition for suspension cells was MS liquid medium with 6-BA 1.0 mg/l, 2,4-D 0.2 mg/l and KT 0.5 mg/l. UPLC/Q-TOF-MS method was used for accurate identification of schisandrin A and schisandrin B in the seeds, callus and suspension cells of S. chinensis. And HPLC analytical method was used successfully for identification and quantification of these metabolites in cultures of S. chinensis. As a result, schisandrin A was obtained 0.251 mg/g, 0.118 mg/g and 0.115 mg/g from seeds, callus and suspension cells and schisandrin B was 0.142 mg/g, 0.086 mg/g and 0.05 mg/g from seeds, callus and suspension cells, respectively. Our datas indicate that callus and suspension cells had capability as seeds of S. chinensis for schisandrin A and schisandrin B synthesizing and can be used as potential sources of these biologically active lignans.

FAIMS is a fast and high sensitive technique for detecting trace volatile organic compounds. Spectra of acetone, benzene and toluene were obtained on a homemade high-field asymmetric waveform ion mobility spectrometer and they can be easily separated in the spectra. Three xylene isomeric compounds were also successfully separated in FAIMS. Effect of carrier gas flow rate on the ion intensity was analyzed, and the optimal flow rate of carrier gas was 220 L x h(-1) which can be used for the optimization of FAIMS instrument. The detection limit for acetone is 100 ng x L(-1) that is an order of magnitude lower than the foreign traditional IMS.

We developed a convenient method by coupling frontal elution paper chromatography with desorption corona beam ionization mass spectrometry (FEPC/DCBI-MS) for rapid analysis of powder samples. In this method, the powder was deposited directly onto a coarse strip near the base of a triangular paper sheet, and then a strong elution solvent was pipetted onto the base of the paper sheet in the open air for developing. The sample zone migrated at the solvent front under strong elution conditions. Target analytes were finally condensed at the V-shaped tip which was then placed under the visible plasma beam of DCBI for ionization. Steps of solvent extraction and developing were performed on a paper sheet simultaneously. The overall procedure requires less than two minutes. Signal intensities of target analytes were improved significantly due to analyte condensation at the tip and matrix effect reduction. Fundamentals and applications of FEPC/DCBI-MS were demonstrated by analysis of chlorphenamine in herbal medicines, clenbuterol in pig feed powder and nicotine in house-hold dust. The limits of detection ranged from 0.35 μg g−1 to 1.5 μg g−1 (0.52–2.2 ng, absolute) in full-scan positive-ion mode. The linear range was 5.0 μg g−1 to 5.0 × 102 μg g−1 with satisfactory linear coefficient (R2 = 0.885–0.956). Good reproducibility was achieved with relative standard deviations (RSDs) less than 20% and the recoveries ranged from 70 to 90%. The results demonstrate that the improved FEPC-DCBI-MS method is satisfactory for semi-quantitative evaluation of analytes in powder samples.