共查询到20条相似文献,搜索用时 31 毫秒
1.
E. P. Grishina A. M. Pimenova L. M. Ramenskaya 《Russian Journal of Electrochemistry》2009,45(12):1358-1362
The methods of potentiometry, electrochemical impedance spectroscopy, cyclic voltammetry, and gravimetry were used to study
the electrochemical behavior of a silver electrode in low-temperature ionic liquids of BMImBr and BMImBr—AgBr, and also the
process of cathodic reduction of Ag(I) compounds out of a BMImBr—AgBr melt. It is shown that an AgBr film is formed on the
silver surface and its properties are determined by the ionic liquid composition. It is found that the process of silver electrodeposition
from a BMImBr—AgBr binary alloy occurs irreversibly, at a high current efficiency (up to 100%) and a good quality of the deposit
at low current densities. At 70°C, the transfer coefficients of the cathodic process (α = 0.56 and 0.16) and diffusion coefficients
(D
Ag(I) = 0.48 × 10−7 cm2/s and 3.3 × 10−7 cm2/s) of silver-containing ions are determined in ionic liquids with the AgBr concentration of 0.81 and 1.53 mol/kg BMImBr,
accordingly. 相似文献
2.
A. S. Shalabi M. A. Kamel H. Y. Ammar 《International journal of quantum chemistry》2005,103(4):432-448
The FA1:Cs+ and FA2:Li+ color centers at the low coordination (100) and (110) surfaces of AgCl and AgBr play important roles in laser light generation and color image formation. Double‐well potentials at these surfaces are investigated by using ab initio calculations. Quantum clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces, and ions that are the nearest neighbors to the FA ? defect site are allowed to relax to equilibrium. The calculated Stokes shifts suggest that laser light generation is sensitive to the simultaneous effects of the vibrational coupling mode, the impurity cation, the coordination number of the surface ion, the lattice anion, and the choice of the basis set centered on the anion vacancy. An attempt has been made to explain these effects in terms of Madelung potential, electron affinity, and optical–optical conversion efficiency. All relaxed excited states of the defect‐containing surfaces are deep below the lower edges of the conduction bands of the ground‐state defect‐free surfaces, suggesting that the FA(I):Cs+ and FA(II):Li+ centers are suitable laser defects. The dependence of orientational destruction, recording sensitivity, and exciton (energy) transfer on the empty cation; the coordination number of the surface ion; and the lattice anion is clarified. The Glasner–Tompkins empirical rule was generalized to include the impurity cation and the coordination number of the surface ion. As far as color image formation is concerned, the supersensitizer was found to increase the sensitizing capabilities of two primary dyes in the excited states by increasing the relative yield of quantum efficiency. The (110) surfaces of AgBr and AgCl were more sensitive than the corresponding (100) surfaces, and AgBr thin film was found to be more sensitive than that of AgCl. On the basis of quasi‐Fermi levels, the difference in the sensitizing capabilities between the examined dyes in the excited states is determined. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
3.
K. H. Ott F. W. Rllgen P. Dhling J. J. Zwinselman R. H. Fokkens N. M. M. Nibbering 《Journal of mass spectrometry : JMS》1981,16(8):336-338
The anionization of molecules supplied from the gas phase onto a negatively charged [Cl]? or [NO3]? ion donating surface has been investigated. The charged surface was prepared by exposing an aqueous solution of LiCl (or LiNO3) and polyethylene oxide to a high external field as is done in negative ion field desorption mass spectrometry. The ionization of some monosaccharides and adenosine by [Cl]? and [NO3]? attachment and of some acids by proton abstraction is reported. 相似文献
4.
Novel F‐doped Ag/AgBr photocatalysts containing various amounts of F? were synthesized by an ion exchange method. The photocatalysts were characterized using X‐ray diffraction (XRD), scanning and transmission electron microscopies, X‐ray photoelectron, ultraviolet–visible absorption and photoluminescence spectroscopies and electron spin resonance (ESR). Powder XRD revealed that F? was inserted into the crystal lattices of AgBr and partially replaced Br?, resulting in the contraction of the AgBr lattices. Methyl orange photodegradation experiments showed that the photocatalytic activity of F‐doped Ag/AgBr was significantly dependent on the amount of F?. Ag/AgBr doped with 0.02 M F? achieved the highest activity of 91% after 8 min. ESR showed the main active species in methyl orange degradation was ?OH. The main enhancement mechanism is that F? inhibits the recombination of electron–hole pairs. 相似文献
5.
James L. Stephenson Scott A. McLuckey 《Journal of the American Society for Mass Spectrometry》1998,9(9):957-965
Multiply charged poly(ethylene glycol) ions of the form (M+nNa) n+ derived from electrospray ionization have been subjected to reactions with negative ions in the quadrupole ion trap. Mixtures of multiply charged positive ions ranging in average mass from about 2000 to about 14,000 Da were observed to react with perfluorocarbon anions by either proton transfer or fluoride transfer. Iodide anions reacted with the same positive ions by attachment. In no case was fragmentation of the polymer ion observed. In all cases, the multiply charged positive ion charge states could be readily reduced to +1, thereby eliminating the charge state overlap observed in the normal electrospray mass spectrum. With all three reaction mechanisms, however, the +1 product ions were comprised of mixtures of products with varying numbers of sodium ions, and in the case of iodide attachment and fluoride transfer, varying numbers of halogen anions. These reactions shift the mass distributions to higher masses and broaden the distributions. The extents to which these effects occur are functions of the magnitudes of the initial charges and the width of the initial charge state distributions. Care must be taken in deriving information about the polymer molecular weight distribution from the singly charged product ions arising from these ion/ion reactions. The cluster ions containing iodide were shown to be intermediates in sodium ion transfer. Dissociation of the adduct ions can therefore lead to a +1 product ion population that is comprised predominantly of M+Na+ ions. However, a strategy based on the dissociation of the iodide cluster ions is limited by difficulties in dissociating high mass-to-charge ions in the quadrupole ion trap. 相似文献
6.
Ming-Yue Ding De-Shui Meng Yan-Hong Tang Cheng-Bin Liu Sheng-Lian Luo 《Chemical Papers》2015,69(11):1411-1420
One-dimensional (1D) Ag/AgBr/TiO2 nanofibres (NFs) have been successfully fabricated by the one-pot electrospinning method. In comparison with bare TiO2 NFs and Ag/AgBr/PVP (polyvinylpyrrolidone) NFs, the 1D Ag/AgBr/TiO2 NFs photocatalyst exhibits much higher photocatalytic activity in the degradation of a commonly used dye, methylene blue (MB), under visible light. The photocatalytic removal efficiency of MB over Ag/AgBr/TiO2 NFs achieves almost 100 % in 20 min. The photocatalytic reaction follows the first-order kinetics and the rate constant (k) for the degradation of MB by Ag/AgBr/TiO2 NFs is 5.2 times and 6.6 times that of Ag/AgBr/PVP NFs and TiO2 NFs, respectively. The enhanced photocatalytic activity is ascribed to the stronger visible light absorption, more effective separation of photogenerated electron-hole pairs, and faster charge transfer in the long nanofibrous structure. The Ag/AgBr/TiO2 NFs maintain a highly stable photocatalytic activity due to its good structural stability and the self-stability system of Ag/AgBr. The mechanisms for photocatalysis associated with Ag/AgBr/TiO2 NFs are proposed. The degradation of MB in the presence of scavengers reveals that h+ and ?O 2 ? significantly contribute to the degradation of MB. 相似文献
7.
William J. Herron Douglas E. Goeringer Scott A. McLuckey 《Journal of the American Society for Mass Spectrometry》1995,6(6):529-532
Isolated triply and doubly charged anions of the single-stranded deoxynucleotide 5′-d(AAAA)-3′ were allowed to undergo ion-ion proton transfer reactions with protonated pyridine cations within a quadrupole ion trap mass spectrometer. Sufficiently high ion number densities and spatial overlap of the oppositely charged ion clouds could be achieved to yield readily measurable rates. Three general observations were made: (1) the ion-ion reaction rate constants were estimated to be 10? (7 ? 8) cm3 ion?1 s?1; (2) the ion-ion reaction rates were found to be dependent on the reactant ion number density, which could be controlled by both the reactant ion number and the pseudopotential well depth, and (3) very little fragmentation, if any, was observed, as might normally be expected with highly exothermic proton transfer reactions. 相似文献
8.
Klaus G. Heumann und Wilhelm Schindlmeier 《Fresenius' Journal of Analytical Chemistry》1981,306(4):245-251
Zusammenfassung Die Entwicklung einer massenspektrometrischen Isotopenverdünnungsanalyse zur Bromidbestimmung wird beschrieben. Dabei werden in einer Zweiband-Ionenquelle negative Thermionen erzeugt. Die Abhängigkeit der Br–-Ionenstromintensität und des gemessenen79Br/81Br-Verhältnisses von Ionisierungsbandtemperatur und -material sowie von der chemischen Probenform wird untersucht. Mit Re-Bändern und AgBr als Probensubstanz werden relative Standardabweichungen der Bromisotopenverhältnismessung von 0,08% erreicht. In verschiedenen Chemikalien werden Bromidspurengehalte im Bereich von 1,3 ppb bis 136 ppm mit relativen Standardabweichungen zwischen 1 und 15% bestimmt. Dabei erfolgt die Bromidabtrennung entweder über eine Anionenaustauschersäule oder durch Ausfällung als AgBr.
Mass spectrometric isotope dilution analysis for bromide trace determination and its application for the analysis of pure chemicals
Summary The development of a mass spectrometric isotope dilution analysis for bromide trace determination is described. Negative thermal ions are produced in a double-filament ion source. The Br– ion beam intensity and the measured79Br/81Br isotope ratio in dependence on the ionization filament temperature and filament material as well as on the chemical state of the sample are investigated. Using rhenium filaments and AgBr as a sample, relative standard deviations of 0.08% are obtained for the bromine isotope ratio determination. In different chemicals the trace content of bromide has been determined to be within the range of 1.3 ppb to 136 ppm with relative standard deviations of 1–15%. For the bromide separation a chromatographic column with an anion-exchange resin or a precipitation of Br– as AgBr is used.
Herrn Prof. Dr. K. H. Lieser zum 60. Geburtstag gewidmet 相似文献
9.
A novel NH2+ ion implantation‐modified indium tin oxide (NH2/ITO) electrode was prepared. Acid‐pretreated, negatively charged MWNTs were firstly modified on the surface of NH2+ ion implantation electrode, then, positively charged Mb was adsorbed onto MWNTs films by electrostatic interaction. The assembly of MWNTs and Mb was characterized with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The immobilized Mb showed a couple of quasireversible cyclic voltammetry peaks in pH 7.0 phosphate buffer solution (PBS). The apparent surface concentration of Mb at the electrode surface was 1.06×10?9 mol cm?2. The Mb/MWNTs/NH2/ITO electrode also gave an improved electrocatalytic activity towards the reduction of hydrogen peroxide. The catalysis currents increased linearly to the H2O2 concentration in a wide range from 9×10?7 to 9.2×10?5 M with a correlation coefficient of 0.999. The detection limit was 9.0×10?7 M. The experiment results demonstrated that the modified electrode provided a biocompatible microenvironment for protein and supplied a necessary pathway for its direct electron transfer. 相似文献
10.
《Journal of Saudi Chemical Society》2014,18(4):299-307
The catalytic activities of carbon-based AgBr nanocomposites (AgBr/CNT, AgBr/GP, AgBr/EG, and AgBr/AC) for CO2 reduction to hydrocarbons under visible light were investigated in this study. The carbon-based AgBr nanocomposites were prepared on carbon-based supporting materials (CNT, GP, EG, and AC) by the deposition–precipitation method in the presence of cetyltrimethylammonium bromide (CTAB). The photocatalytic activities of AgBr nanocomposites on different supporting materials (CNT, GP, EG, and AC) were investigated by CO2 reduction yield in the presence of water under visible light (λ > 420 nm). The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that AgBr nanoparticles were well dispersed on the surface of supporting materials. AgBr/CNT and AgBr/GP had a relatively higher reduction yield under visible light due to the transfer of photoexcited electrons from the conduction band of well-dispersed AgBr to carbon supporting materials. In addition, the carbon-based AgBr nanocomposites were stable in the repeated uses under visible light. The total product yields of carbon-based AgBr nanocomposites after the 5 repeated uses almost remained about 83% of the first run. Therefore, carbon-based AgBr nanocomposite is an effective and stable visible-light-driven photocatalyst for CO2 photoreduction. 相似文献
11.
Dr. Albert Sommerauer Dr. Donald L. Sussman Dr. Werner Stumm 《Colloid and polymer science》1968,225(2):147-154
Summary Flocculation of negatively charged colloids by anionic polyelectrolytes, resulting from the adsorption of polymers on the colloid surface and from bridging of polymer chains between solid particles, is only possible if an appropriate concentration of electrolyte is present in the solution. Complex formation in the immediate vicinity of the sol surface between the counter cation and the functional groups of the polyelectrolyte plays a major role in the attachment of anionic polyelectrolytes to negative hydrophobic sols.Stability constants for Cu(II) polyacrylate and for the Ca complexes of a polyacrylic acid, hydrolyzed polyacrylamide and polystyrene sulfonate have been determined, and the effect of solution variables upon flocculation of AgBr/Br– sols by anionic polyelectrolytes have been investigated. Ca+2 ions affect the adsorption of polystyrenesulfonate on a negatively polarized mercury surface, as reflected in measurements of the differential capacitance; the presence of complex bound functional groups apparently changes the structure and orientation ability of the adsorbed polymer.With 5 figures in 10 details and 2 tables 相似文献
12.
Novel Bi/BiOBr/AgBr composite microspheres were prepared by a rational in situ ion exchange reaction between Bi/BiOBr microspheres and AgNO3. The characteristic of the as-obtained ternary microspheres was tested by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL). Under visible light irradiation, Bi/BiOBr/AgBr microspheres exhibited an excellent photocatalytic efficiency for rhodamine B (RhB) degradation, which was about 1.4 and 4.9 times as high as that of Bi/BiOBr and BiOBr/AgBr, demonstrating that the highest separation efficiency of charge carriers in the heterostructured Bi/BiOBr/AgBr. The photocatalytic activity of Bi/BiOBr/AgBr microspheres just exhibited a slight decrease after three consecutive cycles. The photocatalytic mechanism investigation confirmed that the superoxide radicals (O2•−) were the dominant reactive oxygen species for RhB degradation in Bi/BiOBr/AgBr suspension. 相似文献
13.
A New p‐Metal‐n Structure AgBr‐Ag‐BiOBr with Superior Visible‐Light‐Responsive Catalytic Performance
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Dr. Yuming Dong Cuiyun Feng Jingjing Zhang Prof. Dr. Pingping Jiang Dr. Guangli Wang Xiuming Wu Hongyan Miao 《化学:亚洲杂志》2015,10(3):687-693
A novel visible‐light‐driven AgBr‐Ag‐BiOBr photocatalyst was synthesized by a facile hydrothermal method. Taking advantage of both p‐n heterojunctions and localized surface plasmon resonance, the p‐metal‐n structure exhibited a superior performance concerning degradation of methyl orange under visible‐light irradiation (λ>420 nm). A possible photodegradation mechanism in the presence of AgBr‐Ag‐BiOBr composites was proposed, and the radical species involved in the degradation reaction were investigated. HO2?/?O2? played the same important role as ?OH in the AgBr‐Ag‐BiOBr photocatalytic system, and both the electron and hole were fully used for degradation of organic pollutants. A dual role of metallic Ag in the photocatalysis was proposed, one being surface plasmon resonance and the other being an electron‐hole bridge. Due to the distinctive p‐metal‐n structure, the visible‐light absorption, the separation of photogenerated carriers and the photocatalysis efficiency were greatly enhanced. 相似文献
14.
L. L. édel'shtein I. I. Sheikhet B. Ya. Simkin 《Theoretical and Experimental Chemistry》1991,26(5):561-565
A method for investigating solutions in the region near an electrode has been developed in the framework of the Monte Carlo method. The energies of the reorganization of water upon the transfer of an electron to a hydroxonium ion from the unpolarized surface of an absolutely solid charged electrode in the range of surface charge densities from +0.056 to –0.640 C/m2 and upon the reverse process have been calculated. The hydration energies of an H3O+ cation and an H3O– radical in the region near an electrode have been calculated. The effective interactions of an ion and a nonpolar molecule with an electrode in a solution have been analyzed.Translated from Teoreticheskaya i Éksperimental/naya Khimiya, Vol. 26, No. 5, pp. 596–600, September–October, 1990. 相似文献
15.
Muhammad A. Shehzad Yaoming Wang Aqsa Yasmin Xiaolin Ge Yubin He Xian Liang Yuan Zhu Min Hu Xinle Xiao Liang Ge Chenxiao Jiang Zhengjin Yang Michael D. Guiver Liang Wu Tongwen Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12776-12784
Artificial counterparts of conical‐shaped transmembrane protein channels are of interest in biomedical sciences for biomolecule detection and selective ion permeation based on ionic size and/or charge differences. However, industrial‐scale applications such as seawater desalination, separation of mono‐ from divalent cations, and treatment of highly‐saline industrial waste effluents are still big challenges for such biomimetic channels. A simple monomer seeding experimental approach is used to grow ionically conductive biomimetic charged nanocone pores at the surface of an acid‐functionalized membrane. These readily scalable nanocone membranes enable ultra‐fast cation permeation (Na+=8.4× vs. Mg2+=1.4×) and high ion charge selectivity (Na+/Mg2+=6×) compared to the commercial state‐of‐the‐art permselective membrane (CSO, Selemion, Japan) owing to negligible surface resistance and positively charged conical pore walls. 相似文献
16.
Mark Salomon 《Journal of solution chemistry》1990,19(12):1225-1236
Conductivity data are used to determine thermodynamic complex formation constants for cases in which both the initial electrolyte and the complexed electrolyte form ion pairs. Using the method described in the text, the complex formation constants of Li+, Na+ and K+ with the crown ether 18-crown-6 and of Li+ with the ligand triphenylphosphine oxide in propylene carbonate have been evaluated from conductance data. The complexation of AgBr in propylene carbonate solutions of n-etrabutylammonium bromide has also been studied by the measurement of molar conductivities. The results of these studies indicate that ion pairing should not be neglected, even in high permittivity solvents such as propylene carbonate, and that the ion pair association constants correlate well with structural studies on cation-crown ether molecular conformations. 相似文献
17.
We present a theoretical comparison of the surface forces between two graphite-like surfaces at salt concentrations below 10 mM with surfaces charged by various mechanisms. Surface forces include a surface charging or chemisorption contribution to the total free energy. Surfaces are charged by charge regulation (H+ binding), site competition (H+ and cation binding) and redox charging with electrodes coupled to a countercell. Constant surface charge is also considered. Surface parameters are calibrated to give the same potential when isolated. Nonelectrostatic physisorption energies of the potential determining ions provide a specific and significant contribution to the charging energy. Consequently ion specificity is found in the surface forces at concentrations of 1–10 mM, which is not observed under constant charge conditions. The force between redox electrodes continues to show Hofmeister effects at 0.01 mM. We refer to this low concentration Hofmeister effect as “Hofmeister charging”, and suggest that the more common high concentration ion specific effects may be known as “Hofmeister screening”. Hofmeister series are considered over LiCl, NaCl, KCl and NaNO3, NaClO4, NaSCN with the cations (or H+) being the potential determining ions. A K+ anomaly is attributed to the small size of the weakly hydrated chaotropic K+ ion, with Li+ and Na+ explicitly modelled as strongly hydrated cosmotropes. 相似文献
18.
J. Flad H. Stoll H. Preuss 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1987,6(3):287-292
The adsorption of Ag+ and Ag on a (100) AgBr surface is investigated. Interstitial subsurface sites and incomplete surfaces (with ledges and kinks) are also considered. Equilibrium geometries, adsorption energies and ionization potentials have been calculated. Migration of neutral Ag on the surface and crystal growth of AgBr are discussed, and a comparison with other theoretical results is given. 相似文献
19.
Brad J. Hall Jennifer S. Brodbelt 《Journal of the American Society for Mass Spectrometry》1999,10(5):402-413
The formation and collisionally activated dissociation (CAD) behavior of a series of complexes containing cyclic or linear diketone ligands and alkali, alkaline earth, or transition metal ions are investigated. Electrospray ionization (ESI) is utilized for introduction of the metal ion complexes into a quadrupole ion trap mass spectrometer. The proximity of the carbonyl groups is crucial for formation and detection of ion complexes by ESI. For example, no metal ion complexes are observed for 1,4-cyclohexanedione, but they are readily detected for the isomers, 1,2-and 1,3-cyclohexanedione. Although the diketones form stable doubly charged complexes, the formation of singly charged alkaline earth complexes of the type (nL + M2+ ? H+)+ where L = 1,3-cyclohexanedione or 2,4-pentanedione is the first evidence of charge reduction. CAD investigations provide further evidence of charge reduction processes occurring in the gas-phase complexes. The CAD studies indicate that an intramolecular proton transfer between two diketone ligands attached to a doubly charged metal ion, followed by elimination of the resulting protonated ligand, produces the charge reduced complex. For transition metal complexation, the preference for formation of doubly charged versus singly charged complexes correlates with the keto-enol distribution of the diketones in solution. 相似文献
20.
Abstract— This paper reports the present conclusions of an extended investigation on photo-sensitization of silver bromide. A general molecular packing structure for dye aggregates on the AgBr (111) surface is proposed. This structure, along with the observed spectral absorption displacements of small aggregates, is used to elucidate the phenomena of antisensitization and supersensitization. Supersensitization is seen as a partitioning of large dye aggregates into small aggregates by a deliberately added second component or by gaps between the aggregates. This partitioning isolates antisensitizing dye in a small fraction of the aggregates and minimizes its effect. The smallest aggregates are least likely to contain an antisensitizer, and show the highest quantum efficiency for photoconductivity and photographic action. Photoconductivity measurements establish that supersensitization occurs before the electron appears in the AgBr phase.
The question of direct electron injection vs. energy transfer as mechanisms for AgBr photosensitization is examined in terms of radiationless transfer to surface Ag2 S on AgBr. The absorption of surface Ag2 S is shown to be adequate for acceptance of Förster transfer from the dye, and surface Ag2 S is known to be photographically active. However, this mechanism is inefficient, and inadequate to account for observed high efficiency infrared sensitization. Direct electron injection is seen as the more probable mechanism for efficient dye sensitization of AgBr. 相似文献
The question of direct electron injection vs. energy transfer as mechanisms for AgBr photosensitization is examined in terms of radiationless transfer to surface Ag