New applications of Pd‐catalyzed coupling reactions (Suzuki–Miyaura, Sonogashira, and Stille–Migita coupling) for post‐conjugation of nucleic acids have been developed recently. Breakthroughs in this area might now pave the way for the development of sophisticated DNA probes, which might be of great interest in chemical biology, nanotechnology, and bioanalysis, as well as in diagnostic domains. 相似文献
Cu2ZnSnS4 (CZTS)/ZnS heterojunctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates. The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties. CZTS/ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures. The obtained results exhibit a good rectifying behavior of the realized heterojunction. Analysis of these results yields saturation current, series resistance and ideality factor determination. From the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution. 相似文献
In this study, we followed the deformation microstructure and texture evolution during the cold wire drawing of a perlitic steel wire intended for civil engineering applications. The deformation level effect on the microstructure evolution and on the texture evolution is characterized. Wire drawing induces the lengthening of the perlitic grains along the drawing axis and leads to a strong hardness increase. X-ray texture measurements were performed. The reference state (initial wire) revealed an isotropic texture. The quantitative analysis show the development of the α fibre (<110>//ND (ND // wire) with the deformation. Moreover, the {001}?<?110?>?orientation (rotated Cube) is also present. The experimental techniques used in this study are the: Optical Microscopy (OM), the Electron Back Scattered Diffraction (EBSD), the X-ray diffraction, the Neutron diffraction and the Vickers microhardness. 相似文献
Digital micromirror devices (DMD) are increasingly used in laser-based manufacturing for a maskless beam shaping in order to realize simultaneous 2D/3D material processing. Thereby, the DMD has to be irradiated under a sharp angle to achieve acceptable projection quality with negligible distortion phenomena. In this article, we present a novel setup for DMD-based laser material processing. It enables the irradiation under large angles (up to 60\(^{\circ }\)), the reduction of optical elements as well as machine size. Occurring optical distortions during the amplitude-based laser beam shaping are characterized. To eliminate these phenomena, we implement an optical modelling of the DMD patterns, taking into account the propagation through the tilted interfaces. The resulting imaging of different desired shapes is verified experimentally for its geometrical properties such as length, radius and aspect ratio. Thereby, an angle-dependent correction and high shape accuracy of the image projection is shown. This novel arrangement may have applications in direct laser writing and photochemical machining. 相似文献
An efficient and unprecedented palladium‐catalyzed S‐glycosylation reaction of a range of alkenyl and alkynyl halides by using thiosugars as nucleophile partners has been established. With palladium diacetate in combination with Xantphos as the catalytic system, a variety of β‐alkenylthioglycosides as well as β‐alkynylthioglycosides can be prepared in good to excellent yields. The efficiency of this general protocol was well‐demonstrated by the formal synthesis of a leaf‐closure β‐glucosidase inhibitor.
This paper reports the study of physicochemical, surface, and catalytic properties of two series of VMgO catalysts prepared by two different methods: wet impregnation and sol–gel. The characterizations of the elaborated materials were performed using N2-sorption (Brunauer, Emmett and Teller (BET)), X-ray diffraction, Raman, transmission electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analyses. The catalytic properties of the elaborated materials were investigated in the isopropanol decomposition reaction to determine their acid–base character and in the selective oxidation of n-butane to evaluate their dehydrogenation properties. The preparation method and vanadium content strongly affected the properties of our materials. The sol–gel method leads to smaller crystallite size, higher specific surface area, and uniform particle distribution compared to the impregnation one. Both impregnation and SG solids promote the formation of acetone, which is related to the presence of strong basic sites (O2? species) on the catalytic exposed surface. The more pronounced basic character was obtained through the SG samples. The sol–gel samples exhibited the highest catalytic activity and C4-olefin selectivity in the partial oxidation of n-butane. Whatever the preparation procedure, the nature of surface oxygen species plays an important role in the orientation of catalytic performances. 相似文献