时间分辨红外发射光谱研究C2H3+NO反应体系

C2H3是一个不饱和自由基及烃类化合物燃烧过程中的重要中间体,它的基元反应是影响燃烧过程速率和最终产物的重要反应.已有人在实验和理论方面研究了C2H3和O2,H2等体系[1－12]的基元反应,但迄今为止,我们还没有看到对于C2H3＋NO体系的研究报导.本文报导了用时间分辨傅立叶变换红外发射光谱（TR-FTIR）研究C2H3＋NO基元反应的结果.1实验　　C2H3自由基是在248nm（KrF激光,Lambda,Physik,LPX305i,单脉冲能量约为110mJ）光解C2H3Br产生的.时间分辨傅立叶变换红外发射光谱（FTIR）方法在我们以前的文章中已有介绍[13].实验…     

Transport and co-transport of carboxylate ions and alcohols in cation exchange membranes

Understanding multi-component transport behavior through hydrated dense membranes is of interest for numerous applications. For the particular case of photoelectrochemical CO₂ reduction cells (PEC-CRC), it is important to understand the multi-component transport behavior of CO₂ electrochemical reduction products including mobile carboxylates (formate and acetate) and alcohols (methanol and ethanol) in the ion exchange membranes as one role of the membrane in these devices is to minimize the permeation of these CO₂ reduction products to the anolyte as they often oxidize back to CO₂. Cation exchange membranes (CEM) are promising candidates for such devices as they act to minimize the permeation of mobile anions, such as carboxylates. However, the design of new CEMs is necessary as the permeation of carboxylates often increases in co-permeation with alcohols. Here, we investigate the transport behavior of carboxylates and alcohols in two types of CEMs (1) a crosslinked CEM was prepared by free-radical copolymerization of a sulfonated monomer (AMPS) with a crosslinker (PEGDA), and (2) Nafion® 117. We observe an increase in both PEGDA-AMPS and Nafion® 117 diffusivities to carboxylates in co-diffusion with alcohols. We attribute this behavior to charge screening by co-diffusing alcohol that reduces the electrostatic repulsion between bound sulfonates and mobile carboxylates.     

Microwave assisted fabrication of polymethyl methacrylate-graphene composite nanoparticles applied for the preparation of SBS modified asphalt with enhanced high temperature performance

In order to improve the high temperature rutting resistance ability and stability of styrene-butadiene-styrene (SBS) modified asphalt, microwave heating emulsion polymerization strategy was used to prepare polymethyl methacrylate (PMMA) and graphene nanoparticles (GNPs) composite (PMMA-GNPs) which was used to prepare PMMA-GNPs/SBS modified asphalt. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis characterizations showed that PMMA-GNPs particles were successfully prepared having a weight ratio of GNPs: PMMA of 1:9. Microwave heating reduced the reaction time from 5 h to 30 min compared to conventional oil bath heating. Dynamic shear rheological test and multi-stress creep recovery test confirmed that 0.06% PMMA-GNPs/SBS modified asphalt (0.06% PMMA-GNPs of the mass of base asphalt) exhibited an increase of 14.2% in elastic modulus (G′), while rutting resistance was enhanced and sensitivity to stress changes was reduced as compared to those of 5% SBS modified asphalt. Fluorescence microscopy analysis and phase separation test revealed that an appropriate amount of PMMA-GNPs can be uniformly dispersed in SBS modified asphalt and enhance the mutual interaction of SBS with base asphalt. Based on the results of mechanical tests and characterizations, a suitable modification mechanism of PMMA-GNPs particles in the original SBS modified asphalt was described in detail. This study proposes a simple, cost effective and fast strategy for the preparation of PMMA-GNPs incorporated SBS modified asphalt and hence can be envisioned of great promise in construction and highway industries.     

Characterization of Hydrogels Made of a Novel Spider Silk Protein eMaSp1s and Evaluation for 3D Printing

Recombinantly produced spider silk proteins have high potential for bioengineering and various biomedical applications because of their biocompatibility, biodegradability, and low immunogenicity. Here, the recently described small spider silk protein eMaSp1s is assembled into hydrogels, which can be 3D printed into scaffolds. Further, blending with a recombinantly produced MaSp2 derivative eADF4(C16) alters the mechanical properties of the resulting hydrogels. Different spider silk hydrogels also show a distinct recovery after a high shear stress deformation, exhibiting the tunability of their features for selected applications.     

Stability diagram of rice starch as determined with FTIR

Abstract

In this study, we followed in situ changes in the infrared spectrum at different conditions of pressure and temperature. Cooperative changes were observed when temperature or pressure was increased. Plotting the midpoints of cooperative transitions in a pressure-temperature plane results in an outline similar to the stability curve of proteins. We can assume that it is the first time that the pressure-temperature dependent gelation diagram is determined in situ for starch.     

High‐spatial‐resolution mapping of superhydrophobic cicada wing surface chemistry using infrared microspectroscopy and infrared imaging at two synchrotron beamlines

The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS‐IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin‐Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self‐cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher‐spatial‐resolution distribution images in a shorter time than was achievable at the AS‐IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS‐IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications.     

EVA-layered double hydroxide (nano)composites: Mechanism of fire retardancy

Composites of ethylene-vinyl acetate copolymer with two different layered double hydroxides have been obtained by melt blending and these have been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, thermogravimetric analysis connected to mass spectroscopy and cone calorimetry. There is some small difference in dispersion between the zinc-containing and the magnesium-containing layered double hydroxides in EVA, but both these are microcomposites with good dispersion at the micrometer level and relatively poor dispersion at the nanometer level. There is a good reduction in the peak heat release rate at 10% LDH loading. In addition to chain stripping, which involves the simultaneous loss of both acetate and a hydrogen atom, forming acetic acid, and the formation of poly(ethylene-co-acetylene), side chain fragmentation of the acetate group also occurs and may be the dominant pathway of thermal degradation in the first step. The presence of the LDH causes acetone, rather than acetic acid, to be evolved in the initial step of the degradation.     

Combining multiset resolution and segmentation for hyperspectral image analysis of biological tissues

Hyperspectral images can provide useful biochemical information about tissue samples. Often, Fourier transform infrared (FTIR) images have been used to distinguish different tissue elements and changes caused by pathological causes. The spectral variation between tissue types and pathological states is very small and multivariate analysis methods are required to describe adequately these subtle changes.     

Analysis of artist’s palette on a 16th century wood panel painting by portable and laboratory Raman instruments

Non-destructive analysis of the artist’s palette of ancient wooden panel paintings is a difficult task and studies are rare. Here we compare different methods of analysis of a wooden panel painting, dated to the early sixteenth century, mainly by Raman and infrared spectroscopies. Raman spectra were recorded on collected/sampled micrometric fragments using portable Raman instruments with laser excitation lines at 532 and 785 nm and transportable Raman instruments at 532, 633 and 785 nm; a fixed 1064 nm Raman spectrometer was also used. Infrared analyses were performed in Attenuated Total Reflection (ATR-FTIR) mode. Using the portable instrument, the Raman spectra evidenced white lead, calcite and vermilion only. Raman spectra recorded by transportable and fixed instruments enabled the identification of most of the artist’s palette: (i) white lead, calcite, gypsum and cerussite for white colour; (ii) vermilion, red lead, litharge, haematite for red; (iii) azurite, indigo and lapis lazuli for blue. IR spectra gave information on the organic binding media. XRF analysis on a brown pigment suggested an heterogeneous mixture of a red pigment (such as haematite and/or minium) and a green one as malachite. GC-MS analysis allowed identifying terpenic resin in the composition of the outer protective layer.     

Processing and characterization of oriented electrospun poly(vinylidene fluoride) mats

Mats of highly oriented poly(vinylidene fluoride) nanofibers were electrospun by means of a conventional electrospinning equipment; the orientation, however, was obtained using a disk collector rotating at a speed of 4000 rpm and a device that reduced the influence of air displacement during nanofiber orientation. Thermal transitions of the mats were determined by differential scanning calorimetry, the predominant crystalline phase by Fourier transform infrared spectroscopy and wide‐angle X‐ray scattering and the nanofiber orientation and morphology by scanning electron microscopy. Relative permittivity, loss index, stable remnant polarization, and coercive field of the mats were also determined and compared with those obtained for a mat electrospun at 2000 rpm and an oriented commercial film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000–000, 2012