A graphene oxide functionalized with 3-aminophenylboronic acid for the selective enrichment of nucleosides,and their separation by capillary electrophoresis

Microchimica Acta - We show that graphene oxide functionalized with 3-aminophenylboronic acid represents a useful new adsorbent for the selective enrichment of the nucleosides, adenosine,...     

An identification method to estimate surface shortwave fluxes on temperature and thickness observations of sea ice in CHINARE 2006

In this paper, a parameter identification method to determine surface shortwave fluxes using temperature and thickness measurements of sea ice in CHINARE 2006 is presented. Adopting a new standard for the calculation of the thermodynamic properties of seawater named TEOS‐10, the surface shortwave fluxes are calculated by the temperature and thickness observations that were measured at Nella Fjord around Zhongshan Station, Antarctica. New simulations for temperature profiles in a different measurement period are performed by three parameterization schemes including the present method, Zillman and Shine. All numerical results are compared with in situ measurements. Results show that better simulations of the surface shortwave radiations and temperature distributions are possible with the identification method than Zillman and Shine. Therefore this method is valid, and the obtained shortwave radiation function can be applied in sea ice modeling. Copyright © 2015 John Wiley & Sons, Ltd.     

Malononitrile-involved Michael addition polymerization: An efficient and facile route for cyano-rich polyesters with programmable thermal and mechanical properties

An efficient, atom-economic, oxygen-tolerant, and water-tolerant strategy has been established to synthesize cyano-rich polyesters. Four kinds of organic bases, 1,1,3,3-tetramethylguanidine (TMG), 4-dimethylaminopyridine, triethylamine, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were explored for accelerating Michael addition polymerization of malononitrile and 1,4-butandiol diacrylate. TMG can promote the polymerization efficiently under mild conditions to quantitatively afford polyester with high-molecular weight and moderate polydispersity. The comparison of the kinetic studies of TMG and TBD reveals that TMG shows better catalytic performance, while the catalysis of TBD brings about oligomers in spite of the higher efficiency at early age of the polymerization. Moreover, other diacrylate compounds could also be quantitatively polymerized to afford polyesters with high molecular weight. When dimethacrylate is chose as the monomer, the polymerization becomes sluggish. All the afforded polyesters display programmable thermal and mechanical properties that are closely related to their chemical structures.     

Photons can hide where they have been

Recently,the nested Mach–Zehnder interferometer[Phys.Rev.Lett.111,240402(2013)]was modified by adding Dove prisms in a paper[Quantum Stud.:Math.Found.2,255(2015)],and an interesting result is that,after the Dove prisms were inserted,a signal at the first mirror of the nested interferometer was obtained.But,according to the former original paper,the photons have never been present near that mirror.In this work,we interpret this result naturally by resorting to the three-path interference method.Moreover,we find that even though the photons have been somewhere,they can hide the trace of being there.     

Thermal decomposed behavior and kinetic study for untreated and flame retardant treated regenerated cellulose fibers using thermogravimetric analysis

Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame...     

Chemical composition and anti-complement activity of Glechomae Herba collected in different months

Glechomae Herba (GH) is derived from the dried aerial part of Glechoma longituba (Nakai) Kupr., which is harvested from spring to autumn. It has the effects of clearing heat and detoxification. The aim of this paper was to study the chemical composition and the anti-complement activity of GH collected in different months. Ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry based on predicted compounds screening and diagnostic ion filter strategy was developed for identifying the chemical composition of GH collected in different months. A total of 102 compounds—40 chlorogenic acids (CGAs), 32 phenolic acids, and 30 flavonoids—were reasonably identified in GH. Thirty-four CGAs were discovered in GH for the first time. The correlations between chemical compositions and anti-complement activities of GH collected in different months were analyzed. Phenolic acids and flavonoids were found to be negatively correlated with anti-complement activity, and CGAs were positively correlated with anti-complement activity. At the same time, six CGA standards had obvious anti-complement activity. It was demonstrated that different harvest months had a significant impact on the difference in chemical composition and anti-complement activity of GH. And CGAs might play an important role in the anti-complement activity of GH.     

Kinetics of hydrogen peroxide decomposition catalyzed by Cu-buserite over a well-sealed and thermostated kinetics assembly

Herein a well-sealed and thermostated kinetics assembly is designed and built, which can run stirred at different reaction temperatures. With the reaction assembly above and the volumetric method together, the hydrogen peroxide (H₂O₂) decomposition reaction kinetics is systematically investigated under a variety of reaction conditions over a copper-doped buserite-type layer manganese oxide (referred to as Cu-buserite) as a heterogeneous catalyst. The overall second-order rate law is fitted out by the linear regression analysis, with the reaction orders with respect to both H₂O₂ and Cu-buserite determined to each be equal to 1, and then explicitly explained by the proposed Michaelis-Menten like mechanism. The apparent activation energy E_a is estimated as 33.5 ± 2.5 kJ mol⁻¹.     

Hierarchical Mn3O4 Anchored on 3D Graphene Aerogels via C−O−Mn Linkage with Superior Electrochemical Performance for Flexible Asymmetric Supercapacitor

Flexible asymmetric supercapacitors are more appealing in flexible electronics because of high power density, wide cell voltage, and higher energy density than symmetric supercapacitors in aqueous electrolyte. In virtues of excellent conductivity, rich porous structure and interconnected honeycomb structure, three dimensional graphene aerogels show great potential as electrode in asymmetric supercapacitors. However, graphene aerogels are rarely used in flexible asymmetric supercapacitors because of easily re-stacking of graphene sheets, resulting in low electrochemical activity. Herein, flower-like hierarchical Mn₃O₄ and carbon nanohorns are incorporated into three dimensional graphene aerogels to restrain the stack of graphene sheets, and are applied as the positive and negative electrode for asymmetric supercapacitors devices, respectively. Besides, a strong chemical coupling between Mn₃O₄ and graphene via the C-O-Mn linkage is constructed and can provide a good electron-transport pathway during cycles. Consequently, the asymmetric supercapacitor device shows high rate cycle stability (87.8 % after 5000 cycles) and achieves a high energy density of 17.4 μWh cm⁻² with power density of 14.1 mW cm⁻² (156.7 mW cm⁻³) at 1.4 V.     

Iron-Catalyzed Cleavage Reaction of Keto Acids with Aliphatic Aldehydes for the Synthesis of Ketones and Ketone Esters

The radical–radical coupling reaction is an important synthetic strategy. In this study, the iron-catalyzed radical–radical cross-coupling reaction based on the decarboxylation of keto acids and decarbonylation of aliphatic aldehydes to obtain valuable aryl ketones is reported for the first time. Remarkably, when tertiary aldehydes were used as carbonyl sources, ketone esters were selectively obtained instead of ketones. The gram-scale preparation of aryl ketone through this strategy was easily achieved by using only 3 mol % of the iron catalyst. As a proof-of-concept, the bioactive molecule flurprimidol was synthesized in two steps by using this strategy.     

Hexagonal La2O3 Nanocrystals Chemically Coupled with Nitrogen-Doped Porous Carbon as Efficient Catalysts for the Oxygen Reduction Reaction

The construction of nano-scale hybrid materials with a smart interfacial structure, established by using rare earth oxides and carbon as building blocks, is essential for the development of economical and efficient catalysts for oxygen reduction reactions (ORRs). In this work, hexagonal La₂O₃ nanocrystals on a nitrogen-doped porous carbon (NPC) derived from crop radish, served as building bricks, are prepared by chemical precipitation and then calcination at elevated temperatures. The obtained La₂O₃/NPC hybrid exhibits a very high ORR activity with a half-wave potential of 0.90 V, exceeding that of commercial Pt/C (0.83 V). Both DFT theoretical and experimental results have verified that the significantly enhanced catalytic performance is ascribed to the formation of the C−O−La covalent bonds between carbon and La₂O₃. Through the covalent bonds, electrons can transfer from the carbon to La₂O₃ and occupy the unfilled e_g orbital of the La₂O₃ phase. This results in the accelerated adsorption of active oxygen and the facilitated desorption of the surface hydroxides (OH_ad⁻), thereby promoting the ORR over the catalyst.