Copper-based metal–organic framework decorated by CuO hair-like nanostructures: Electrocatalyst for oxygen evolution reaction

We report a Cu-based metal–organic framework (MOF) decorated by CuO nanostructures as an efficient catalyst for the oxygen evolution reaction (OER). MIL-53(Cu) was synthesized by a hydrothermal approach using 1,4-bezenedicarboxylic acid as organic precursor and further annealed at 300°C to form CuO nanostructures on its surface. The produced electrocatalyst, CuO@MIL-53(Cu), was characterized using various techniques. Under alkaline conditions, the developed electrocatalyst exhibited an overpotential of 801 and 336 mV versus RHE at 10 and 1 mA cm⁻², respectively. The reproducibility of the catalytic performance was validated using several electrodes. It was confirmed that the CuO hair-like nanostructures grown on MIL-53(Cu) using thermal treatment exhibit high OER activity, good kinetics and durability. CuO@MIL-53(Cu) is an economic noble-metal-free OER electrocatalyst. It has potential for application as anode material for sustainable energy technologies like batteries, fuel cells and water electrolysis.     

Palladium on activated carbon catalyzed reductive amination of aldehydes and ketones by triethylsilane

Various aldehydes and ketones were efficiently transformed into the corresponding amines using amine derivatives in the presence of triethylsilane and a catalytic amount of palladium on activated carbon in ethanol. The proposed method provides a one‐pot synthesis of various amines in excellent yields after short reaction times. Copyright © 2013 John Wiley & Sons, Ltd.     

Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.     

Symmetry-breaking in periodic gravity waves with weak surface tension and gravity-capillary waves on deep waterBrisure de symétrie dans les vagues de gravité avec une faible tension de surface et les vagues de gravité-capillarité périodiques en eau profonde

The method developed by Debiane and Kharif for the calculation of symmetric gravity-capillary waves on infinite depth is extended to the general case of non-symmetric solutions. We have calculated non-symmetric steady periodic gravity-capillary waves on deep water. It is found that they appear via bifurcations from a family of symmetric waves. On the other hand we found that the symmetry-breaking bifurcation of periodic steady class 1 gravity wave on deep water is possible when it approaches the limiting profile, if it is very weakly influenced by surface tension effects. To cite this article: R. Aider, M. Debiane, C. R. Mecanique 332 (2004).     

Direct oxidative synthesis of nitrones from aldehydes and primary anilines using graphite oxide and Oxone

One-pot condensation/oxidation of aldehydes and primary anilines into nitrones using graphite oxide (GO) and Oxone as the oxidant under very mild reaction conditions is described. The proposed method provides a direct oxidative synthesis of various nitrones in good to excellent yields under metal-free conditions in short reaction times.     

Nonlocal General Boundary Value Problems of Elliptic Type in <Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">p</Emphasis></Superscript> Cases

This paper is devoted to the study of operational second-order differential equations of elliptic type with nonregular coefficient-operator boundary conditions. In the framework of UMD spaces, we give some new results by using semi-groups and interpolation theory. We define two types of solutions: semi-strict and strict solutions. We then characterizes the existence and uniqueness of such solutions.     

Amino-functionalized SBA-15 catalyzed one-step synthesis of 2-amino-5-cyano-4-hydroxy-6-aryl pyrimidines

A simple and efficient approach towards one-step synthesis of 2-amino-5-cyano-4-hydroxy-6-aryl pyrimidines has been developed. It is based on three-component condensation of aliphatic, aromatic or heterocyclic aldehydes, ethyl cyanoacetate and guanidinium carbonate in the presence of amino-functionalized SBA-15 catalyst in ethanol. In this chemical process, the tautomeric interconversion of pyrimidine derivatives has been observed. This efficient technique has the advantage to give 2-amino-pyrimidine derivatives using a heterogeneous catalyst in high yields, to be completed in short reaction times and to offer a simple product isolation procedure.     

Magnetic molecularly imprinted specific solid‐phase extraction for determination of dihydroquercetin from Larix griffithiana using HPLC

The naturally occurring quercetin flavonoid, dihydroquercetin, is widely distributed in plant tissues and has a variety of biological activities. Herein, a magnetic molecularly imprinted solid‐phase extraction was tailor made for selective determination of dihydroquercetin in Larix griffithiana using high‐performance liquid chromatography. Amino‐functionalized core‐shell magnetic nanoparticles were prepared and characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and infrared spectroscopy. The polymer had an average diameter of 250 ± 2.56 nm and exhibited good stability and adsorption for template molecule, which is enriched by hydrogen bonding interaction. Multiple factors for extraction, including loading, washing, elution solvents, and extraction time, were optimized. The limit of detection was 1.23 μg/g. The precision determined at various concentration of dihydroquercetin was less than 4% and the mean recovery was between 74.64 and 101.80%. It has therefore been shown that this protocol can be used as an alternative extraction to quantify dihydroquercetin in L. griffithiana and purify quercetin flavonoid from other complex matrices.     

Mild addition of carbon nucleophiles to pyridine and quinoline N-oxides under different activation conditions

In the course of our syntheses of functionalised pyridine and quinoline derivatives, we examined the reactivities of pyridine and quinoline N-oxides towards the nucleophilic addition of acidic carbon derivatives. Different activating reagents were used, such as PyBroP, triflic anhydride and a combination of pyrrolidine phosphoramide and triflic anhydride.     

Effect of surface roughness and chemical composition on the wetting properties of silicon-based substrates

The article reports on the wetting properties of silicon-based materials as a function of their roughness and chemical composition. The investigated surfaces consist of hydrogen-terminated and chemically modified atomically flat crystalline silicon, porous silicon and silicon nanowires. The hydrogenated surfaces are functionalized with 1-octadecene or undecylenic acid under thermal conditions. The changes occurring upon surface functionalization are characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) spectroscopy and water contact angle measurements. By increasing the surface roughness, the static water contact angle increases. The combination of high surface roughness with chemical functionalization with water repellent coating (1-octadecene) enables reaching superhydrophobicity (water contact angle greater than 150°) for silicon nanowires.