GC—MS分析不同方法提取的大黄挥发性成分

分别采用顶空进样法和超临界CO2萃取法提取大黄挥发性成分,采用GC-MS结合保留指数进行检测分析。顶空进样法分析鉴定出8种挥发性成分,超临界CO2萃取法鉴定出15种挥发性成分。两种提取方法分别侧重于不同类型的挥发性成分,利用GC-MS结合保留指数进行定性分析,更快速准确。     

Self-limiting growth of ZnO films on (0 0 0 1) sapphire substrates by atomic layer deposition at low temperatures using diethyl-zinc and nitrous oxide

Atomic layer deposition (ALD) of zinc oxide (ZnO) films on (0 0 0 1) sapphire substrates was conducted at low temperatures by using diethyl-zinc (DEZn) and nitrous oxide (N₂O) as precursors. It was found that a monolayer-by-monolayer growth regime occurred at 300 °C in a range of DEZn flow rates from 5.7 to 8.7 μmol/min. Furthermore, the temperature self-limiting process window for the ALD-grown ZnO films was also observed ranging from 290 to 310 °C. A deposition mechanism is proposed to explain how saturated growth of ZnO is achieved by using DEZn and N₂O. Transmission spectroscopic studies of the ZnO films prepared in the self-limiting regime show that the transmittances of ZnO films are as high as 80% in visible and near infrared spectra. Experimental results indicate that ZnO films with high optical quality can be achieved by ALD at low temperatures using DEZn and N₂O precursors.     

Experimental study on the effect of pyrolysis temperature on the NO emission and conversion during combustion

Journal of Thermal Analysis and Calorimetry - For realizing the coupling pyrolysis of coal and combustion of semi-coke, this paper explored the effect of pyrolysis temperature on the combustion...     

Ligand-Controlled Site- and Enantioselective Carbene Insertion into Carbon-Silicon Bonds of Benzosilacyclobutanes

We report herein a highly efficient palladium-catalyzed carbene insertion into strained Si−C bonds of benzosilacyclobutanes, which provides an efficient method to access α-chiral silanes. With a sterically hindered ligand, carbene insertion into the C(sp³)−Si bond of benzosilacyclobutanes occurred in excellent site- and enantioselectivity, while C(sp²)−Si bond insertion occurred selectively with less sterically hindered ligands. Reaction mechanism, in particular the roles of the chiral ligands in controlling the site-selectivity of the insertion reactions, are elucidated by using hybrid density functional theory.     

Two-Stage Incremental Three-Dimensional Spatial Mapping Approach Using a Single-Layer Lidar

Journal of Russian Laser Research - Multilayer-lidar-used solution is popular though financial consumption is extremely expensive. In addition, multilayer lidars are barely able to reconstruct an...     

Production of carbon nano- and microfibers by methane pyrolysis on zirconia

The production of carbon nano- and microfibers by pyrolysis of methane (mains gas) on three ZrO₂ samples prepared by different methods, at 400–700°C, methane flow rates of 175–1050 mL/min, and process times up to 4 h was studied. Comparatively long carbon bamboo-like microfibers having diameters of 0.24–0.31 μm were found to form on ZrO₂, their weights and linear growth rates were assessed, and the process was shown to not slow down over time. The electrical conductivities of the fibers were measured.     

Property of intrinsic drift coefficients in globally-evolving-based generalized density evolution equation for the first-passage reliability assessment

Acta Mechanica Sinica - The turbulent Poiseuille flow between two parallel plates is one of the simplest possible physical situations, and it has been studied intensively. In this paper, we propose...     

Modelling Development in Radical (Co)Polymerization of Multivinyl Monomers

Radical polymerization (RP) of multivinyl monomers (MVMs) provides a facile solution for manipulating polymer topology and has received increasing attention due to their industrial and academic significance. Continuous efforts have been made to understand their mechanism, which is the key to regulating materials structure. Modelling techniques have become a powerful tool that can provide detailed information on polymerization kinetics which is inaccessible by experiments. Many publications have reported the combination of experiments and modelling for free radical polymerization (FRP) and reversible-deactivation radical polymerizations (RDRP) of MVMs. Herein, a minireview is presented for the most important modelling techniques and their applications in FRP/RDRP of MVMs. This review hopes to illustrate that the combination of modelling and wet experiments can be a great asset to polymer researchers and inspire new thinking for the future MVMs experiment optimization and product design.     

Slowly Removing Surface Ligand by Aging Enhances the Stability of Pd Nanosheets toward Electron Beam Irradiation and Electrocatalysis

Surface ligands play an important role in shape-controlled growth and stabilization of colloidal nanocrystals. Their quick removal tends to cause structural deformation and/or aggregation to the nanocrystals. Herein, we demonstrate that the surface ligand based on poly(vinylpyrrolidone) (PVP) can be slowly removed from Pd nanosheets (NSs, 0.93±0.17 nm in thickness) by simply aging the colloidal suspension. The aged Pd NSs show well-preserved morphology, together with significantly enhanced stability toward both e-beam irradiation and electrocatalysis (e.g., ethanol oxidation). It is revealed that the slow desorption of PVP during aging forces the re-exposed Pd atoms to reorganize, facilitating the surface to transform from being nearly perfect to defect-rich. The resultant Pd NSs with abundant defects no longer rely on surface ligand to stabilize the atomic arrangement and thus show excellent structural and electrochemical stability. This work provides a facile and effective method to maintain the integrity of colloidal nanocrystals by slowly removing the surface ligand.     

A hierarchical cobalt/carbon nanotube hybrid nanocomplex-based ratiometric fluorescent nanosensor for ultrasensitive detection of hydrogen peroxide and glucose in human serum

Analytical and Bioanalytical Chemistry - Highly sensitive detection of H2O2 and glucose is critical for fundamental research and disease diagnosis. A ratiometric sensor can simultaneously afford...