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1.
Yu. V. Korneeva A. A. Novakova A. M. Ob”edkov A. A. Zaitsev G. A. Domrachev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):369-372
The structure and phase composition of a carbon nanomaterial obtained by the thermal decomposition of toluene-ferrocene mixtures are studied by Mössbauer spectroscopy, high-resolution electron microscopy, and x-ray diffraction. Variations in the structural state of the catalyst and in the quantitative yield of the nanomaterial are analyzed as functions of the synthesis time. 相似文献
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Magdalena Obłoza Dr. Łukasz Łapok Dr. Tomasz Pędziński Prof. Katarzyna M. Stadnicka Prof. Maria Nowakowska 《Chemphyschem》2019,20(19):2482-2497
A series of novel aza-BODIPY dyes substituted with p-(dimethylamino)phenyl groups were synthesized and their spectral and electrochemical properties were compared. In particular, the impact of p-(Me2N)Ph- groups on these characteristics was of consideration. For two aza-BODIPYs studied, a near-IR absorption band was observed at circa λabs=796 nm. Due to the pronounced intramolecular charge transfer (ICT) exerted by the presence of strongly electron-donating p-(Me2N)Ph- substituents, the compounds studied were weakly emissive with the singlet lifetimes (τS) in the picosecond range. Nanosecond laser photolysis experiments of the brominated aza-BODIPYs revealed T1→Tn absorption spanning from ca. 350 nm to ca. 550 nm with the triplet lifetimes (τT) ranged between 6.0 μs and 8.5 μs. The optical properties of the aza-BODIPYs studied were pH-sensitive. Upon protonation of the dimethylamino groups with trifluoroacetic acid in toluene, a stepwise disappearance of the NIR absorption band at λabs=790 nm was observed with the concomitant appearance of a blue-shifted absorption band at λabs=652 nm, which was accompanied by a prominent emission band at λfl=680 nm. The transformation from a non-emissive to an emissive compound is associated with the inhibition of the ICT. As estimated by CV/DPV measurements, all aza-BODIPYs studied exhibited two irreversible oxidation and two quasi-reversible reduction processes. All compounds studied exhibit extremely high photostability and thermal stability. 相似文献
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A. V. Kadomtseva A. M. Ob”edkov M. N. Semenov B. S. Kaverin S. A. Gusev 《Russian Journal of Applied Chemistry》2016,89(11):1797-1805
Pyrolytic tungsten coatings were deposited onto the surface of sol microspheres with tungsten hexacarbonyl used as precursor. A method was developed for reduction of germanium tetrachloride in the presence of a catalyst based on sol microspheres coated with pyrolytic tungsten. The method makes it possible to reduce the process temperature and diminish the number of stages in production of germanium. The kinetic characteristics of the catalytic reduction of germanium tetrachloride with hydrogen were determined. 相似文献
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Fernández-López JA Castellar R Obón JM Almela L 《Journal of chromatographic science》2007,45(3):120-125
The influence of pH and moderate heating (50 degrees C) on the color and individual betacyanin content of pigment extracts from cactus pear fruits (Opuntia stricta) is studied in the course of this paper. The study is carried out by using a high-performance liquid chromatograph equipped with a photodiode array detector and coupled to a mass spectrometer. The results point to a pH-dependent degradation mechanism, which is reflected in the chromatographic patterns obtained at different exposure times (0-28 h). At pH 3, 15-descarboxy-betanin is the most resistant betacyanin derivative. At pH 5, seven peaks are detected after 8 h, the most prominent being betanin, cyclo-dopa-5-O-beta-glucoside, and betalamic. In the assay conducted at pH 7, rapid color loss affects all the pigments, except for betanin. 相似文献
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W. Kucza J. Obłąkowski R. Gajerski S. Łabuś M. Danielewski A. Małecki J. Morgiel A. Michalski 《Journal of Thermal Analysis and Calorimetry》2007,88(1):65-69
The ultrasonic spray pyrolysis (USP) technique was used for synthesis
of alumina- and zirconia-based powders. The starting agents were aqueous solutions,
atomized by the ultrasonic spray generator and pyrolized in the furnace under
the open-air conditions. The powders prepared by USP were in the form of solid
and hollow aggregates (spheres) consisted of nanosize amorphous grains as
determined by the microscopy and the X-ray diffraction techniques. The alumina-based
powders were consolidated by the pulse plasma sintering resulting in single-phase
materials. Different behavior of solid and hollow particles during the isostatic
sintering is found; a higher degree of deformation of spheres is observed
in the second case. 相似文献
7.
S. Yu. Ketkov G. A. Domrachev A. M. Ob’edkov A. Yu. Vasil’kov L. P. Yur’eva C. P. Mehnert 《Russian Chemical Bulletin》2004,53(9):1932-1937
Gas-phase electronic absorption spectra of chromium bisarene complexes with oxygen- and nitrogen-containing ligands, (6-PhOMe)2Cr (1) and (6-2,6-Me2C5H3N)2Cr (2), were first measured. Rydberg bands disappearing on going to the condensed-phase spectra were revealed. The first ionization potentials of complexes 1 and 2 (5.30 and 5.40 eV, respectively) were determined from the Rydberg frequencies. The Rydberg transitions were assigned and the corresponding Rydberg term values and quantum defects were determined. The effect of heteroatoms on the Rydberg structure parameters was revealed by comparing the spectra of complexes 1 and 2 with those of unsubstituted analogs. The appearance, in the ligand side chain, of an oxygen atom capable of being involved in conjugation with the -electron system of the aromatic ring results in substantial broadening of the observed Rydberg bands. This can be associated with an increased ligand contribution to the HOMO of the sandwich compound. The influence of the oxygen atom on the ionization energy of the molecule is insignificant. In contrast to this, introduction of a nitrogen atom into the carbocycle leads to a noticeable increase in the ionization potential of the molecule, while the ligand contribution to the HOMO of the complex remains practically unchanged.Based on materials of a lecture presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1854–1859, September, 2004. 相似文献
8.
Two methods were developed for the quantitative analysis of phenolic acids in herb extracts. The methods were based on liquid
chromatography–time-of-flight mass spectrometry (LC–TOFMS) and gas chromatography–mass spectrometry (GC–MS). The methods were
compared in terms of their linearity, repeatability, selectivity, sensitivity and the speed of the analysis. The sensitivity
was good for both methods, with limits of detection of <80 ng/ml for most of the compounds. The relative standard deviations
(RSD) of the peak areas were on average 7.2% for the LC–TOFMS method and 1.4% for the GC–MS method. Both methods were found
to be suitable for the determination of the target analytes, although GC–MS was better suited to the quantitative determination
of compounds present at low concentrations. 相似文献
9.
A novel comprehensive two-dimensional liquid chromatographic (LC×LC) system was developed for the quantification of antioxidant
phenolic compounds in wine and juice. The system allows parts of the sample that are well separated in the first column to
pass directly to the detector after the first column, while the rest of the sample proceeds to the second column. The optimised
LC×LC system employed a combination of two C18 columns, the latter column with an ion-pair reagent (tetrapentylammonium bromide).
The relative standard deviations (RSD) for the retention times were better than 0.01% in the first dimension and on average
6.3% in the second. The RSD values of the peak volumes varied from 3% (protocatechuic acid) to 13% (caffeic acid, n = 3, 10 μg/ml). 相似文献
10.
A. M. Ob’edkov B. S. Kaverin S. A. Gusev A. B. Ezerskii N. M. Semenov A. A. Zaytsev V. A. Egorov G. A. Domrachev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(4):554-558
Multiwalled iron-containing carbon nanotubes were synthesized by the MOCVD method with pyrolysis of ferrocene and toluene mixtures in an argon flow at atmospheric pressure. Using the MOCVD method with vacuum pyrolysis of bis-arene-chromium compounds onto the surface of multiwalled carbon nanotubes (MWCNTs), pyrolytic chromium films were deposited and new composite materials MWCNT/pyrolytic chromium were obtained. The composite morphology depends on the conditions of pyrolytic chromium deposition. Regular bead-shaped structures were detected. The mechanism of their appearance due to the formation of bis-arene chromium compounds of the intermediate viscoplastic polymer phase and the onset of Plateau-Rayleigh instability during pyrolysis is discussed. 相似文献