Yu. G. Kolyagin

Double stabilization of nanocrystalline silicon: a bonus from solvent

Double stabilization of the silicon nanocrystals was observed for the first time by 29Si and 13C MAS NMR spectroscopy. The role of solvent, 1,2-dimethoxyethane (glyme), in formation and stabilization of silicon nanocrystals as well as mechanism of modification of the surface of silicon nanocrystals by nitrogen-heterocyclic carbene (NHC) was studied in this research. It was shown that silicon nanocrystals were stabilized by the products of cleavage of the C–O bonds in ethers and similar compounds. The fact of stabilization of silicon nanoparticles with NHC ligands in glyme was experimentally detected. It was demonstrated that MAS NMR spectroscopy is rather informative for study of the surface of silicon nanoparticles but it needs very pure samples.Graphical Abstract

Iron(III) chloride supported on MCM-41 molecular sieve as a catalyst for the liquid-phase oxidation of phenol

FeCl3 was supported on MCM-41 mesoporous molecular sieve via adsorption or coordination bonding and by embedding as an anionic constituent of covalently immobilized imidazolium ionic liquid (IL). The synthesized materials were characterized by N2-BET, SEM, TEM, FT-IR, 1H, 13C, and 29Si NMR, and DSC-TG. All of the catalysts were shown to be active for the liquid-phase oxidation of phenol by hydrogen peroxide. Supported FeCl3 species present as tetrachloroferrate counterions of immobilized IL are the most resistant to iron leaching.

Polymers Based on 3-amino-7-dimethylamino-2-methylphenazine hydrochloride: Synthesis, structure, and properties

Heterocyclic polymers based on 3-amino-7-dimethylamino-2-methylphenazine hydrochloride are synthesized for the first time via chemical oxidative polymerization in aqueous solutions of acetonitrile and DMF. The effects of the concentrations of reagents, their ratios, temperature, and the time of reaction on the yields and chemical structures of the polymers are studied. The structures of the polymers are investigated via FTIR spectroscopy, electron spectroscopy, X-ray photoelectron spectroscopy, and solid-state CP/MAS 13C NMR spectroscopy. It is found that polymer chains grow via the addition of C–N groups between 3-amino groups and the para position of phenyl rings relative to nitrogen. During the oxidative polymerization of 3-amino-7-dimethylamino-2-methylphenazine hydrochloride, abstraction of Cl–and one methyl group from the 7-dimethylamino group yields poly(3-amino-7-methylamino-2-methylphenazine). The resulting polymers are amorphous, electroactive, and thermally stable.

Effect of an Amino Acid on the Formation of Calcium Phosphate Particles on Chitosan Macromolecules

This paper presents a study aimed at producing new mineral–polymer composites for damaged bone tissue restoration after extended surgery and injuries. We have obtained materials based on chitosan and calcium phosphates and determined their likely structure by 13C NMR spectroscopy.

Composition of structural fragments and the mineralization rate of organic matter in zonal soils

Comparative analysis of the climatic characteristics and the recalcitrance against decomposition of organic matter in the zonal soil series of European Russia, from peat surface-gley tundra soil to brown semidesert soil, has assessed the relationships between the period of biological activity, the content of chemically stable functional groups, and the mineralization of humus. The stability of organic matter has been determined from the ratio of functional groups using the solid-state 13C NMR spectroscopy of soil samples and the direct measurements of organic matter mineralization from CO2 emission. A statistically significant correlation has been found between the period of biological activity and the humification indices: the CHA/CFA ratio, the aromaticity, and the alkyl/O-alkyl ratio in organic matter. The closest correlation has been observed between the period of biological activity and the alkyl/O-alkyl ratio; therefore, this parameter can be an important indicator of the soil humus status. A poor correlation between the mineralization rate and the content of chemically stable functional groups in soil organic matter has been revealed for the studied soil series. At the same time, the lowest rate of carbon mineralization has been observed in southern chernozem characterized by the maximum content of aromatic groups (21% Corg) and surface-gley peat tundra soil, where an extremely high content of unsubstituted CH2 and CH3 alkyl groups (41% Corg) has been noted.

Transformation of the organic matter in an agrogray soil and an agrochernozem in the course of the humification of corn biomass

The transformation of the organic matter in the course of corn residues humification in an agrogray soil and an agrochernozem was studied in long-term experiments using the method of solid-phase 13C-nuclear magnetic resonance spectroscopy. The humification of the plant residues was found to be accompanied by a decrease in the content of the O-alkyl fragments comprising polysaccharides and polypeptides, an increase in the unsubstituted alkyds content, and by the relative accumulation of aromatic fragments and carboxyl groups. The most strongly transformed pool of the organic matter, as compared to the initial plant residues, was the humic acids with their maximal content of aromatic and carboxyl functional groups and the minimal content of O-alkyls. The chemically stable aromatic fragments were concentrated not only in the pool of humic acids; their content was 64–89% of the pool of the aromatic fragments identified in the soil organic matter. Therefore, to assess the stable pool, the distribution of the functional groups is necessary to be analyzed not only in the humic acids but also in the whole soil organic matter.

Catalytic activity of in situ synthesized MoWNi sulfides in hydrogenation of aromatic hydrocarbons

MoWNi–sulfide catalysts were obtained in situ by thermal decomposition of metal–polymer precursors based on the copolymers of polymaleic anhydride in a hydrocarbon raw material. The activity of the synthesized catalysts in hydrogenation of bicyclic aromatic hydrocarbons was studied, and the composition and structure of active phase nanoparticles were determined.

Studies of silicon nanocluster ligand coating by solid-state NMR

Silicon nanoclusters were studied by 29Si and 13C MAS NMR (magic angle spinning) spectroscopy. We for the first time confirmed the cleavage of ordinary ether C—O bonds of the solvent in the process of the synthesis of nanoclusters and the “binding” of the decomposition products to the surface of silicon nanoparticles as ligands. The applicability of MAS NMR spectroscopy in the studies of silicon nanocluster ligand coating and in the determination of the processes leading to the formation of the nanoparticle ligand shell was demonstrated.

Reactivity of a phosphonate layer grafted onto a surface of dispersed hydroxyapatite

The reactivity of a grafted layer contained on the surface of hydroxyapatite modified with diethyl butylphosphonate is studied. Modified hydroxyapatite is shown to interact with nucleophilic agents. The composition of reaction products depends on the nature of the latter.

Solid-State NMR Spectroscopic Study of the Structure of Grafted Layers of Phosphonic Acid Ester-Modified Hydroxyapatite

Interaction of hydroxyapatite (HAP) surface with phosphonic acid esters is studied under different conditions. The urgency of the study is due to the fact that HAP is one of the main components of bone tissue and is widely applied in the production of materials designed for filling bone defects. Modification of the surface properties of HAP may result in the development of materials with increased biocompatibility. It is revealed that, in the absence of solvents or in the medium of an aprotic solvent, phosphonic acid esters interact with HAP surface to yield pyrophosphate groups. The interaction with the surface does not take place in the presence of protic solvents.