Chemical modification of iron oxide surface with organosilicon and organophosphorous compounds

The feasibility of modifying iron oxides (α-Fe₂O₃, γ-Fe₂O₃, and an oxide covering the surface of carbonyl iron) with various organosilicon and organophosphorous compounds has been studied. It has been shown that the surfaces of these oxides can be successfully modified with ethoxysilanes and diethyl ester of butylphosphonic acid. Resultant grafted layers have being found to be rather hydrolytically and thermally stable. The effect of the modification on the corrosion and erosion stability of carbonyl iron has been investigated. It has been demonstrated that the modifying layers can efficiently protect carbonyl iron particles from corrosion.     

Microcalorimetric Study of Water Adsorption on Initial and Polyfluoroalkylated Silicas

Water adsorption on initial and modified Silochrom samples was studied by the adsorption calorimetry. Integral heats of immersional wetting by water were measured simultaneously. It was shown that hydroxyl groups both free and sterically screened by a modifier remain on the modified Silochrom surface. Concentrations of these groups and OH groups chemically interacted with the modifier were estimated. The heat of reaction of water molecules with a free surface OH groups of modified sorbents was determined (≈60 kJ/mol). It was found that the modifying layers of the sorbents are getting loose under the effect of adsorbed water, and water molecules gain access to the sterically screened OH groups; the heat of water interaction with these groups is 54–55 kJ/mol. The energy is consumed for getting the modifying layers loose and the rupture of point contacts between Aerosil particles of the secondary structure of both initial and modified Silochrom that significantly affects the heat of immersion, the differential heat of adsorption, the form of the heat release curve, and the dependence of the differential heat on the adsorption value.     

Natural-sciences education in secondary school in the USSR and Russia: History, trends, and challenges of modernization

Changes in teaching natural sciences (physics, chemistry, and biology) and mathematics in secondary school in the USSR at different times and in post-Soviet era were analyzed. The trends of these changes were discussed and analyzed. The results of passing the Unified State Examination in these classroom disciplines in recent years, as well as the results shown by Russian secondary school learners in the Program for International Student Assessment in 2000, 2003, 2006, and 2009 were discussed. A conclusion was made that teaching natural sciences is deteriorating year after year. The causes of this phenomenon were analyzed, and measures to improve the training of secondary school learners on these subjects were proposed.     

The effect of hydrocarbon chain length and end-capping on the liquid chromatographic properties of stationary phases containing bonded nitrile groups

Summary Stationary phases containing bonded nitrile groups have been synthesized. The effect of the n-alkyl chain length connecting the nitrile groups to the surface and of the end-capping on the chromatographic properties was studied. The synthesized material was compared with commercial nitrile phases in the separation of isomeric cresols and xylenols.     

The percolation transition in filling a nanoporous body by a nonwetting liquid

The paper presents the results of an experimental study of the percolation transition in filling by nonwetting liquids of nanoporous bodies of various natures with different specific surface areas and mean pore and granule sizes. The liquid that we used was an aqueous solution of ethylene glycol. The hysteresis and non-outflow phenomena observed in this transition at various (known) surface energies of liquids were studied by varying the concentration of ethylene glycol. This helped us explain the mechanism of the percolation transition in filling nanoporous bodies with nonwetting liquids. It was shown that, to quantitatively describe the observed dependences in terms of percolation theory taking into account energy barriers to filling, we must use a non-scaling distribution function of clusters of accessible and filled pores that admits the formation of pore clusters of arbitrary dimensions.     

Preparation and study of colloid-chemical and optical properties of the nanocrystals of zinc sulfide modified with amino acids

The effect of some amino acids: cysteine, methionine, glycine, lysine, and aspartic acid, on the formation of nanoparticles of zinc sulfide in aqueous solutions at pH 5.5–10.0 was investigated. A method of obtaining stable sols of ZnS particles of 2–4 nm size with narrow distribution of the particle size was developed. The investigated nanoparticles are shown to be sphalerite, the cubic modification of zinc sulfide. The ZnS sols modified with methionine and glycine show intense luminescence at 415–425 nm.     

Synthesis and investigation of chemically modified silicas with the island structure of the grafted layer

Island structures on the chemically modified surface of silica are synthesized by the method of matrix prints. Dichlorosilicon phthalocyanine and copper naphthalocyanine were used as molecular templates. Two types of heterogeneous surfaces are prepared by this method: the islands of nonmodified silica on the trimethylsilylated silica (the first type) and the islands of aminopropyl silica on the esteric groups grafted on silica (the second type). The structure of the surfaces prepared is studied by ESR spectroscopy with the use of paramagnetic probes.     

Photochemical chlorination of nanodiamond and interaction of its modified surface with C-nucleophiles

A procedure for the photochemical chlorination of nanodiamond by molecular chlorine in the liquid phase was proposed. This process was studied quantitatively for the first time. Hydrolytic stability of the chlorinated nanodiamond surface in air and in a 0.05 M solution of NaOH was determined. A possibility of disintegration of the initial aggregates (<60 μm) to finer aggregates (<200 nm) was shown. The reactions of a series of C-nucleophiles (organolithium reagents, CN⁻ ion) with the chlorinated surface were carried out. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2130–2137, December, 2006.     

Chemically Modified Oxide Surfaces Capable of Molecular Recognition

Main directions in the use of molecular imprinting for the formation of oxide materials with surfaces capable of molecular recognition are reviewed. Various methods for the production of highly selective catalysts and adsorbents, as well as highly organized nanostructures, on the surface of various substrates are described. The results obtained are estimated, and main prospects of further investigations are outlined.     

Grafted surface compounds in chemical sensors and biosensors

The use of grafted surface compounds for covalent immobilization of molecules and nanoparticles on the surface of sensors of various types is discussed. The classification of immobilization methods is based on the chemical nature of the surface of the material used in the sensitive element of a sensor: noble metals; inogranic oxides and salts; carbon and polymeric materials.