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排序方式: 共有825条查询结果,搜索用时 15 毫秒
791.
Vladimir A. Kurmaz Alexander S. Kotkin Galina V. Simbirtseva 《Journal of Solid State Electrochemistry》2011,15(10):2119-2126
Electrode reactions of intermediates formed during capture of OH radicals by dimethylsulfoxide molecules were studied by laser
photoemission in aqueous buffer solutions and pH range from acidic to basic. The results were compared with those obtained
previously for electrochemical behaviour of methyl radicals generated via photoemission from CH3Cl. The essential similarity was found for parameters of irreversible one-electron transfer from/to these intermediates, i.e.
the potentials E
1/2 on time-resolved voltammograms and rate constants at E = E
1/2. Hence, both active particles were concluded to be equivalent and corresponded to methyl radical. The primary product of
OH radicals capture by DMSO molecules, i.e. adduct (CH3)2SO·(OH), was spontaneously decomposed to form ·CH3 with time as low as <2 × 10−5 s. A simultaneous increase of the reduction wave height was observed at pH transition from low basic to low acidic and at
illumination times T
m of an electrode with UV light if T
m ≥ 90–300 ms. The increase exceeded considerably the one-electron reduction level. These features were presumably caused by
the rather slow formation of organomercury intermediates as interaction products of the components of the system with a mercury
electrode. 相似文献
792.
Dr. Jarosław J. Panek Dr. Aneta Jezierska‐Mazzarello Prof. Aleksander Koll Prof. Galina Dovbeshko Dr. Olena Fesenko 《Chemphyschem》2011,12(13):2485-2495
Adsorption of guest molecules on host surfaces can lead to dramatic changes in the spectral properties of the guest. One such effect is surface‐enhanced infrared absorption (SEIRA), observed when the guest is adsorbed on, for example, thin films, metal surfaces, or nanotubes. p‐Nitrobenzoic acid (p‐NBA) exhibits a SEIRA effect when adsorbed on Ag and Au. Herein, the IR spectra of p‐NBA adsorbed on a homemade rough Au surface, recorded in reflection mode with an angle of incidence of 16.5°, are reported. This SEIRA experiment reveals more bands than found by previous SEIRA studies. The intensities of both symmetric and asymmetric COO? and NO2 stretching, in‐plane CH, and C?C ring stretching modes are enhanced. Theoretical models constructed on the basis of density functional theory reveal the binding mode of p‐NBA to gold “particles”. The p‐NBA anion binds to gold much more strongly than the neutral form, and interaction via the carboxylic oxygen atoms is preferred over the nitro group–gold contact. A significant charge transfer during chemisorption is found, which is considered to be crucial in leading to a high SEIRA enhancement factor. 相似文献
793.
Burova TG Ermolenkov VV Ten GN Shcherbakov RS Baranov VI Lednev IK 《The journal of physical chemistry. A》2011,115(38):10600-10609
An experimental and theoretical study of the tautomeric composition of adenine (Ade) in water using Raman spectroscopy is reported. Experimental resonance Raman spectra of adenine at excitation wavelengths of 200, 218, and 266 nm were compared with quantum-mechanical calculations of N(9)H- and N(7)H-adenine tautomers and their cations. Both theoretical and experimental studies of nonresonance Raman spectra (457 nm excitation) of adenine were also performed for comparison. A satisfactory agreement of the calculated results with the experimental data was obtained. The Raman spectra are interpreted, and the basic regularities of the Raman intensity distribution are explained. On the basis of the analysis performed, the tautomeric composition of adenine in water is revealed. It is shown that the Ade-N(9),N(1)H(+) cation is the predominant form and that some neutral forms of Ade-N(9)H and Ade-N(7)H tautomers exist in water at pH 3. 相似文献
794.
Elza A. Zakharova Galina N. Noskova Neil V. Rees Richard G. Compton 《International journal of environmental analytical chemistry》2013,93(11):1105-1115
The determination of total arsenic through As(V) anodic stripping voltammetry (ASV) is, in some cases, preferable over As(III) ASV. The As(V) ASV procedure has no chemical reduction step from As(V) into As(III), which results in decreased analysis time and no contamination from reducting reagents. A simple and reliable procedure of As(V) determination is proposed. Anodic stripping determination of trace As(V) at gold microelectrode ensembles in diluted HCl solution in the presence of dissolved oxygen is shown. The electrode is based on a carbon black (30%)–polyethylene composite. The sensor was prepared by gold electrodeposition on the surface of the composite electrode. The given sensor is cheap, reliable and stable, especially when electrochemical activation is employed. The experimental parameters for the electrochemical determination were optimized, namely 0.005?M HCl as the background electrolyte, the deposition potential ?2.2?V (versus Ag/AgCl in 1?M KCl) and 180?mV?s?1 linear scan rate. Calibration curves were obtained and were linear in [As(V)] over the 1.5–45?µg?L?1 range, with a LOD of 0.5?µg?L?1. The effect of common interfering species is studied. The electrochemical behaviour of As(III) form is studied in the same experimental conditions. It was found that As(III) is deposited at lower potentials (starting at ?0.6?V) and the sensitivity of As(III) detection is higher, but dependant on the presence of dissolved oxygen. The speciation of inorganic forms of arsenic is discussed. 相似文献
795.
Galina Rodionova Bård Hoff Marianne Lenes Øyvind Eriksen Øyvind Gregersen 《Cellulose (London, England)》2013,20(3):1167-1174
The barrier properties of microfibrillated cellulose (MFC) films were improved by heterogeneous gas-phase esterification using various combinations of trifluoroacetic acid anhydride, acetic acid and acetic anhydride. The temperature, reagent ratio and reaction time were varied in the experimental design. The effects of two different purification procedures on the barrier properties of esterified MFC films were investigated. Washing with water did not affect the barrier properties compared to those of the films that were not washed, while the use of diethyl ether led to improved barrier properties as measured by the contact angle (CA) of water. The chemical composition of the modified films was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Alterations in hydrophobicity and oxygen permeability were evaluated using dynamic CA and oxygen transmission rate measurements, respectively. 相似文献
796.
Elena V. Suprun Maria S. Zharkova Galina E. Morozevich Alexander V. Veselovsky Victoria V. Shumyantseva Alexander I. Archakov 《Electroanalysis》2013,25(9):2109-2116
Direct redox activity of different proteins was investigated on the surface of carbon screen printed electrodes (SPE). The signal attributed to the electrochemical oxidation of amino acid residues (cysteine (Cys), tryptophan (Trp) and tyrosine (Tyr)) was registered at Emax from 0.6 to 0.7 V (vs. Ag/AgCl). Based on the difference in the redox behavior of L ‐tyrosine and 3‐nitro‐L ‐tyrosine, the selective electrochemical detection of native and nitrated albumins was demonstrated. It was shown that the electrochemical signal correlated with the surface density of electroactive amino acid residues on the protein molecule. A simple electrochemical method for the total protein analysis was proposed. 相似文献
797.
Rafael A. Cherkasov Vladimir I. Galkin Galina A. Chmutova Nina A. Polezhaeva Irina V. Kalinina Arcady N. Pudovik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1717-1719
The phosphorylation reactions of the oxygen- and nitrogen-containing halocyclenes--3,4-dichloro-5-hydroxyfuranone, 3,4-dichloro-5-substi- tuted pyrrolinon-2-ones and N-phenyl-4,5 dichloropyridazin-2-one by 3 -phosphorus compounds--trialkylphoshphites, triphenylphosphine, and some P-functionalized derivatives of the trivalent phosphorus are studied. The reactions' mechanisms are discussed; the possible and preferable reactions' routes and the relative thermodynamic stabilities of the products and intermediates are estimated via the quantum-chemical methods. 相似文献
798.
799.
The reaction of 1-chloro-, 2-chloro-, 1,5-dichloro-, 1,8-dichloro-, 1-hydroxy-4-chloro-, 1-hydroxy-2,4-dichloro- and 1,4-dihydroxy-5-chloro-9,10-anthraquinones with 2-ethoxyethanol activated by fluoride anion in the presence of alumina affords reasonable to high yields of the corresponding mono- and dialkoxy derivatives. 相似文献
800.
The binding ability of Zn-tetraarylporphyrins with two, four and eight 4-carbazolylphenyl-1,2,3-triazole end groups towards 1,4-diazabicyclo[2.2.2]octane, pyridine and 1,2,3-triazole in toluene was studied by spectrophotometric and 1H NMR titration. It was determined that due to a good geometric match of the ligand size to the size of the intramolecular cavities of the porphyrinic receptor, and by the existence of additional π–π and/or hydrogen bonding interactions between the ligand and the triazole fragments of the porphyrin, the Zn-tetraarylporphyrin with eight 4-carbazolylphenyl-1,2,3-triazole end groups could be used as an effective receptor for 1,2,3-triazole and other small heterocycles such as pyridine. Taking into account the fact that binding is accompanied by a clear and easily identifiable response in the UV–vis spectra of the reaction mixture, this metalloporphyrin could be considered as a molecular optical sensing device for small heterocyclic substrates. 相似文献