Interfacial properties of amphiphilic systems on the basis of natural polymers—chitin derivatives

A review of the amphiphilic derivatives of chitin, obtained by covalent grafting of hydrophilic and hydrophobic radicals, is given. It is shown that water-soluble alkylated derivatives of chitin and chitosan, as well as surfactant-polyelectrolyte complexes between oppositely charged surfactants, exhibit interfacial activity, forming structured (gel-like) adsorption layers (AL). Gel formation inside AL of chitin derivatives is characterized by means of interfacial dilational rheometry.     

Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst

Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant.     

Characterization and evaluation of the photocatalytic properties of wormhole-like mesoporous silica incorporating TiO2, prepared using different hydrothermal and calcination temperatures

TiO₂?CSiO₂ mesoporous materials were synthesised by deposition of TiO₂ nanoparticles prepared by the sol?Cgel method on to the internal pore surface of wormhole-like mesoporous silica. In this work we synthesised wormhole-like mesoporous silica of different surface area by changing the hydrothermal temperature (70, 100, or 130?°C). Subsequent to this, titania solution was deposited on to the inner surface of the pores and this was followed by calcination at different temperatures (400, 600, or 800?°C). The effect of different hydrothermal and calcination temperature on the photocatalytic properties was evaluated. The samples were characterized by N₂-sorption, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The effect of different hydrothermal and calcination temperatures on the photocatalytic properties was evaluated by measuring the degradation of methylene blue in aqueous solution under UV light irradiation (mercury lamp, 125?W). The results indicated that appropriate surface area and degree of crystallinity are two important factors for obtaining high photocatalytic efficiency. Samples prepared at a hydrothermal temperature of 100?°C and calcined at 800?°C had the best photocatalytic performance, because of the highest surface area and high crystallinity.     

A Nano‐Fibrillated Mesoporous Carbon as an Effective Support for Palladium Nanoparticles in the Aerobic Oxidation of Alcohols “on Pure Water”

A novel nano‐fibrillated mesoporous carbon (IFMC) was successfully prepared via carbonization of the ionic liquid 1‐methyl‐3‐phenethyl‐1H‐imidazolium hydrogen sulfate ( 1 ) in the presence of SBA‐15. The material was shown to be an efficient and unique support for the palladium nanoparticle (PdNP) catalyst Pd@IFMC ( 2 ) in aerobic oxidation of heterocyclic, benzylic, and heteroatom containing alcohols on pure water at temperatures as low as 40 °C for the first time and giving almost consistent activities and selectivities within more than six reaction runs. The catalyst has also been employed as an effective catalyst for the selective oxidation of aliphatic and allylic alcohols at 70–80 °C. The materials were characterized by X‐ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption analysis, transmission electron microscopy (TEM), and electron tomography (ET). Our compelling XPS and ET studies showed that higher activity of 2 compared to Pd@CMK‐3 and Pd/C in the aerobic oxidation of alcohols on water might be due to the presence of nitrogen functionalities inside the carbon structure and also the fibrous nature of our materials. The presence of a nitrogen heteroatom in the carboneous framework might also be responsible for the relatively uniform and nearly atomic‐scale distribution of PdNPs throughout the mesoporous structure and the inhibition of Pd agglomeration during the reaction, resulting in high durability, high stability, and recycling characteristics of 2 . This effect was clearly confirmed by comparing the TEM images of the recovered 2 and Pd@CMK‐3.     

Synthesis and Characterization of Alkyl‐Imidazolium‐Based Periodic Mesoporous Organosilicas: A Versatile Host for the Immobilization of Perruthenate (RuO4−) in the Aerobic Oxidation of Alcohols

The preparation and characterization of a set of periodic mesoporous organosilicas (PMOs) that contain different fractions of 1,3‐bis(3‐trimethoxysilylpropyl)imidazolium chloride (BTMSPI) groups uniformly distributed in the silica mesoporous framework is described. The mesoporous structure of the materials was characterized by powder X‐ray diffraction, transmission electron microscopy, and N₂ adsorption–desorption analysis. The presence of propyl imidazolium groups in the silica framework of the materials was also characterized by solid‐state NMR spectroscopy and diffuse‐reflectance Fourier‐transform infrared spectroscopy. The effect of the BTMSPI concentration in the initial solutions on the structural properties (including morphology) of the final materials was also examined. The total organic content of the PMOs was measured by elemental analysis, whereas their thermal stability was determined by thermogravimetric analysis. Among the described materials, it was found that PMO with 10 % imidazolium content is an effective host for the immobilization of perruthenate through an ion‐exchange protocol. The resulting Ru@PI‐10 was then employed as a recyclable catalyst in the highly efficient aerobic oxidation of various types of alcohols.     

Electrochemical performance of a novel ionic liquid derived mesoporous carbon

A novel nano-fibrillated mesoporous carbon (IFMC) was found to be an effective modifier in combination with ionic liquid 1-octylpyridinum hexafluorophosphate (OPFP) as a binder to give impregnated graphite electrodes with outstanding electrochemical performances.     

On a graph of ideals

We associate a graph Γ₊(R) to a ring R whose vertices are nonzero proper right ideals of R and two vertices I and J are adjacent if I+J=R. Then we try to translate properties of this graph into algebraic properties of R and vice versa. For example, we characterize rings R for which Γ₊(R) respectively is connected, complete, planar, complemented or a forest. Also we find the dominating number of Γ₊(R).     

Aqueous ionic and complementary zwitterionic soluble surfactants: molecular dynamics simulations and sum frequency generation spectroscopy of the surfaces

An aqueous ionic surfactant, 1-dodecyl-4-(dimethylamino)pyridinium (DMP) bromide, and the corresponding zwitterion 2-[4-(dimethylamino)pyridinio]dodecanoate (DPN) were explored by means of molecular dynamics (MD) simulations and, for the ionic system, by infrared-visible sum frequency generation (IR-vis SFG). The molecular structure of the interfacial layer was investigated for the ionic and zwitterionic systems as a function of surfactant concentration, both in water and in salt (KF or KBr) solutions, by MD simulations in a slab geometry. The buildup of the surface monolayer and a sublayer was monitored, and density and orientational profiles of the surfactants were evaluated. The difference between the ionic and zwitterionic systems and the effect of the added salt were analyzed at the molecular level. The results of MD simulations were compared to those of nonlinear optical spectroscopy measurements. IR-vis SFG was employed to study the DMP ionic surfactant in water and upon addition of simple salts. The influence of added salts on the different molecular moieties at the interface was quantified in detail experimentally.