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1.
The electrochemical behaviour of bis(diphenyldithiophosphine)disulphide (RSSR) and mercuric diphenyldithiophosphinate [(RS)2Hg] in ethanol-lithium perchlorate and ethanol-sulphuric acid media was studied by the methods of classical polarography, and electrolysis at controlled-potential and at a rotating disc platinum electrode. The data obtained show that RSSR is not reduced directly on the dropping mercury electrode but is adsorbed. It then undergoes a rapid chemical reaction causing the formation of (RS)2Hg, which is electroactive. The electrolysis at controlled potential proves that (RS)2Hg undergoes a two-electron reduction, giving diphenyldithiophosphinic acid (RSH) as a main product, whereas the oxidation of RSH leads to the production of (RS)2Hg. Regardless of the fact that the chemical and adsorption equilibria during reduction of RSSR and (RS)2Hg are complex, the coulometric generation of RSH is not difficult to achieve, and permits the use of RSSR as a coulometric reagent. 相似文献
2.
The electroreduction of insulin in pH 7.4 solution was studied at the hanging mercury drop electrode by cyclic voltammetry and at a mercury pool electrode by controlled potential coulometry. The proposed mechanism involves reduction of an adsorbed monolayer of insulin (maximum coverage of 10 μC cm?2) in a four-electron reaction at about ?0.6 V vs. SCE resulting in breakage of two of the three disulfide bonds in the molecule. Fast reoxidation leads to recovery of much of the reduced species. At longer time (ca. 100 s) a steady state is reached where the reductions and reoxidation involve reversible two-electron reactions. 相似文献
3.
The electroreduction of bovine serum albumin (BSA) in pH 7.4 solution was studied at the hanging mercury drop electrode by double potential step chronocoulometry and cyclic voltammetry, and at a mercury pool electrode by controlled potential coulometry. The proposed mechanism involves reduction of an adsorbed monolayer of BSA (maximum coverage 3.3 μC?2); at short times 3 or 4 disulfide bonds are reduced, the product remains adsorbed and may be reoxidized. On the coulometric time scale (hours) 8 or 9 of the total 17 disulfide bonds are broken and an insoluble product which cannot be oxidized is formed. 相似文献
4.
Achille De Battisti Vincenzo Faggiano Sergio Trasatti 《Journal of Electroanalytical Chemistry》1976,73(3):327-346
The adsorption of succinonitrile (SN) on a polarized Hg electrode has been studied from 0.25 M NaF aqueous solutions by means of both capacity and electrocapillary curves. Adsorption isotherms have been found to be strictly congruent with respect to both charge and potential. The charge of maximum adsorption is at ?4.6 μC cm?2 and ΔGads0, the free energy of adsorption at zero coverage, decreases more rapidly as the charge is made positive with respect to OmaxM than on the other side. The adsorption obeys a Frumkin isotherm with a=?1.87 corresponding to attraction and saturation concentration of 4.8×10?10 mol cm?2 corresponding to an area per molecule of about 34.5 Å2. Experimental results suggest that SN adsorbs flat on the surface but, unlike acetonitrile and propionitrile, the CN groups are slightly turned towards the solution. This is responsible for the absence of electronic interaction of the CN groups with the metal at positive charges, which is apparent with the other two nitriles. Implications of the particular structure of the adsorbed molecule on the other adsorption parameters are discussed in detail. 相似文献
5.
Simultaneous determination of cysteine (RSH) and cystine (RSSR), two important sulfur-containing amino acids, in capillary electrophoresis (CE) has been an analytical task. Dual-microelectrode amperometric detection seems to be a good scheme, but significant difficulty in electrode construction and poor detection limit for RSSR determination remain major short-comings. In reverse pulse amperometric (RPA) detection, the applied potentials are repeatedly pulsed back and forth between the reducing initial potential (e.g., Ei = ?1.4 V) and the oxidizing final potential (e.g., Ef = 0.0 V) at a single, gold-mercury amalgam (Au/Hg) microelectrode. At Ei, RSSR is reduced to RSH which causes catalytical oxidation of the Au/Hg amalgam microelectrode when the potential is pulsed to Ef. The resulting anodic current is then recorded. Therefore, by using RPA detection after CE separation, RSH and RSSR can be simultaneously determined. 相似文献
6.
The electrochemical properties of FAD adsorbed on graphite were studied with cyclic voltammetry. A film with a surface coverage of up to 2×10?8 mol cm?2 was formed after 4 h. The film-covered electrodes were stable for long times and they were investigated in buffers without any FAD. A single well-behaved wave was observed, k0≌1 s?1. The pH dependence of E1/2 was studied. On glassy carbon, platinum and gold much less FAD was adsorbed and it was removed with one rinse. 相似文献
7.
《Electroanalysis》2006,18(18):1808-1814
Glivec is a newly developed drug that belongs to the class of 2‐phenylaminopyrimidine. It is a potent inhibitor of ABL‐kinase, the main clinical manifestation of chronic myelogenous leukemia (CML). Based on its activity on CML, glivec is undergoing extensive evaluation for its activity against other tumor types. Detection and quantitation of glivec in biological fluids or cells is thus very important. The antileukemia drug glivec undergoes oxidation at glassy carbon electrodes and involves the formation of an oxidation product, Pglivec. The adsorption of Pglivec at the GCE surface yields a compact monolayer allowing an electrochemical study of this compound adsorbed at the GCE surface. The reversible redox reaction of the adsorbed Pglivec is pH dependent and occurs with the transfer of 2 electrons and 2 protons. The surface standard potential and the rate constant of the heterogeneous electrochemical reaction were calculated using cyclic voltammetry to be Eθ′=+180 mV and k=15.5 s?1, respectively. The total surface concentration of adsorbed Pglivec is 2.5×10?12 mol cm?2. The analytical determination of glivec was carried out by differential pulse voltammetric measurement of the anodic peak current corresponding to either the oxidation peak of glivec or the oxidation peak of Pglivec adsorbed on the GCE surface. The limits of detection of glivec and adsorbed Pglivec based on three times the noise level are 3.3×10?8 M and 2.9×10?10 M, respectively. 相似文献
8.
The ampero-mercurimetric titration of cysteine (RSH), glutathione (GSH), thioglycolic acid (TSH) and 2-mercaptoethanol (ESH) at the RMPE at pH 9 yields a sharply defined end-point corresponding to the composition (XS)2Hg. Under the same conditions with the KPtWK two lirciiks an; (ibst'rvc-d in the titration lines with RSH and GSH, corresponding to compositions (RS)2Hg and (RS)2Hg2 respectively. On the other hand, with TSHl and ESH only one clear break is found at the RPtWE corresponding to ('l'S)2Hg or (ES)2Hg Conditions liave been describcd for the accurate mercurimetric titration of the thiol compnunds at pH 2 in the pesence of 0.01 M sulfur dioxide at the RMPE, use of this can be made in the determination of disufides and in the determination of the equilibrium concentrations of the reaction betwcen a disulfide and a sulfite at varying pH. 相似文献
9.
Xi Fu Houyong Yang Ling Fu Chaozheng He Jinrong Huo Jiyuan Guo Liming Li 《中国化学快报》2021,32(3):1089-1094
Using particle swarm optimization(PSO) methodology for crystal structure prediction,we predicted a novel two-dimensional(2 D) monolayer of silicide diphosphorus compound:SiP_2,which exhibits good stability as examined via cohesive energy,mechanical criteria,molecular dynamics simulation and all positive phonon spectrum,respectively.The SiP_2 monolayer is an indirect semiconductor with the band gap as 1.8484 eV(PBE) or 2.681 eV(HSE06),which makes it more advantageous for high-frequencyresponse optoelectronic materials.Moreover,the monolayer is a relatively hard auxetic material with negative Possion's ratios,and also possesses a ultrahigh carrier mobility(1.069 × 10~5 cm~2 V~1 s~1) which is approximately four times the maximum value in phosphorene and comparable to the value of graphene and CP monolayers.Furthermore,the effects of strains on band structures and optical properties of SiP2 monolayer have been studied,as well as CO_2 molecules can be strongly chemically adsorbed on the SiP_2 monolayer.A semiconductor-to-metal transition for-9.5% strain ratio case and a huge optical absorption capacity on the order of 106 cm ~1 in visible region present.These theoretical findings endow SiP2 Monolayer to be a novel 2 D material holding great promises for applications in highperformance electronics,optoelectronics,mechanics and CO_2 capturing material. 相似文献
10.
[RuIII(EDTA)(H2O)]? (EDTA4? = ethylenediaminetetraacetate) catalyzes the oxidation of biological thiols, RSH (RSH = cysteine, glutathione, N-acetylcysteine, penicillamine) using H2O2 as precursor oxidant. The kinetics of the oxidation process were studied spectrophotometrically as a function of [RuIII(EDTA)(H2O)]?, [H2O2], [RSH], and pH (4–8). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which the RSH reacts with [RuIII(EDTA)] catalyst complex to form [RuIII((EDTA)(SR)]2? intermediate species. In the subsequent reaction step the oxidant, H2O2, reacts directly with the coordinated S of the [RuIII((EDTA)(SR)]2? intermediate leading to formation of the disulfido (RSSR) oxidation product (identified by HPLC and ESI-MS studies) of thiols (RSH). Based on the experimental results, a working mechanism involving oxo-transfer from H2O2 to the coordinated thiols is proposed for the catalytic oxidation. 相似文献
11.
Jan A. Pappas 《Chemical physics》1976,12(4):397-405
Results from an ab-initio MO LCAO SCF study of RSSR, RSH and RS? (R = H, CH3) in a minimal and a double zeta basis and cysteine [COO?CH(NH+3)CH2SH] and cysteine anion in a minimal basis are reported. The barriers and conformational preference of the disulfides are discussed and it is suggested that their origin is more confined to the disulfide region than previously believed. The proton affinities of the different RS? ions are calculated, whereas the protonation of the disulfide bond is studied by use of the molecular electrostatic potential. The good agreement of the results in the minimal and the double zeta basis is discussed. 相似文献
12.
13.
Poly(hydroxyethylmethacrylate)‐based hydrogel membranes were applied to microfabricated, microdisk electrode arrays (MDEAs) of 50 μm (5184 disks), 100 μm (1296 disks) and 250 μm (207 disks) (d/r=4; A= 0.1 cm2) and studied by cyclic voltammetry (CV) in 1.0 mM ferrocene monocarboxylic acid (FcCO2H). The membrane produced an order of magnitude decrease in current densities and a shift to quasi reversibility due to a decrease in the Dappt of FcCO2H, from 4.51×10?6 cm2 s?1 to 1.42×10?8 cm2 s?1, (2.18×10?8 cm2 s?1 from release experiments). The MDEA050 (comprising 50 μm disks) maintained its enhanced current density attributes confirming its value as an effective electrode for biosensors. Finite element modeling (FEM) simulations successfully replicated the voltammograms of the MDEAs. 相似文献
14.
Isotherms for the adsorption of β-naphthol from a buffered aqueous solution of 0.5 M K2SO4 onto graphite were detemrined over a range of potential of 1.27 V. The adsorbent was a packed bed of ?100 + 120 mesh graphite powder. Sufficient surface area was available to calculate accurately the amount adsorbed by measuring spectrophotometrically the change in adsorbate concentration in the bulk solution.At all potentials, a Langmuir adsorption isotherm, modified for the displacement of solvent molecules, was followed up to 60–65% of monolayer coverage. The ratio of projected areas of β-naphthol and water molecules was consistent with the experimentally derived number of solvent molecules displaced, six. The largest amount of adsorption observed, 2.5×10?10 mol cm?2, agreed with the calculated monolayer coverage of β-naphthol molecules lying in flat orientation on the graphite surface. Adsorption increased at more positive potentials. Over the range of potential investigated, the adsorbability constant increased sixfold. Desorption was only partially reversible. 相似文献
15.
C. Hinnen C. Nguyen Van Huong A. Rousseau J.P. Dalbera 《Journal of Electroanalytical Chemistry》1979,95(2):131-146
The admittance and differential reflectivity of an electrode of polycrystalline gold in contact with aqueous 0.02 M NaF, KClO4, 0.01 M Na2SO4 and KCl have been measured in the range of potential where the electrode is ideally polarized (?0.7 V to 0.8 V NHE). In NaF and KClO4 evidence was obtained for the compression of the adsorbed layer of water. The increase of the number of water molecules, with respect to the number in the least original state (at?4μC cm?2), is 3% at +8 μC cm?2 and at?17 μC cm?2. At the potential of zero charge the water dipoles are oriented preferentially with the oxygen towards the metal. In KCl the optical measurements confirm the existence of two types of Au?Cl? interaction and the covalent character of the bond at the most positive charges. 相似文献
16.
Greogry C. Farrington 《Journal of Electroanalytical Chemistry》1977,76(2):165-173
Interfacial Na+ ion transport between polycrystalline beta alumina and propylene carbonate has been studied using a galvanostatic transient technique which separates interfacial overpotential from bulk resistivity effects. No interfacial polarization is detected during ion entry into beta alumina and exit from beta alumina across a dry interface from 30–1000 μA cm?2. Transport across an interface contaminated with adsorbed water follows Tafel-type i/E behavior with a transition coefficient (α) of 0.24 and exchange current (i0) of 3.0×10?6 A cm?2 at 23°C. Interfacial transport appears to take place through an intermediate state in which the mobile ion is adsorbed on the interface. Large increases in interfacial polarization occur at both dry and hydrated interfaces for ionic currents exceeding the rate of adsorption or desorption. 相似文献
17.
The effect of the specific adsorption of the ClO4? ion upon the kinetics of Cu2+ reduction and Cu0(Hg) oxidation in aqueous solutions of HClO4 was investigated using chronocoulometry, d.c., normal pulse, and a.c. polarography. For this purpose three different sets of data for ClO4? adsorption were used. In the first set the absolute surface excess of water as reckoned at the outer Helmholtz plane (o.H.p.) was disregarded, in the second set it was accounted for by postulating a complete adsorbed monolayer of water molecules [32], whereas in the third set partial displacement of water molecules from this monolayer by adsorbed ClO4? ions was accounted for. Kinetic data were found to the compatible with the latter set, indicating that ClO4? adsorption affects the rate-determining step Cu2++e→Cu+ only by altering the average electric potential σd-effect). The absence of any additional electrostatic effect points out that, in the transition state for Cu2+ reduction to Cu+, the centre of charge of the reacting particle falls in the proximity of the o.H.p. 相似文献
18.
L. A. Khanova 《Russian Journal of Electrochemistry》2000,36(1):54-59
The dicarbollyliron (Cb2Fe-) redox reaction is studied at an amalgamated platinum electrode coated with a monolayer of behenic acid on top of which hemin
is adsorbed. The redox reaction of Cb2Fe- involves two stages. First, an electrochemical reaction of adsorbed hemin proceeds, which involves the electron transfer
through the dielectric monolayer; it is followed by the hemin’s chemical redox reaction with dissolved Cb2Fe-. It is shown that the adsorbed hemin transformation, no matter how small, is sufficient for the stimulation of the Cb2Fe- redox reaction. 相似文献
19.
Crystal Structure of SrHg(SCN)4 · 3 H2O SrHg(SCN)4 · 3 H2O is orthorhombic, space group Pcca, with a = 19.476(7), b = 8.150(1), c = 8.991(3) Å, V = 1427.1 Å3, Z = 4, dc = 2.67 g · cm?3, μ(AgKα) = 77.95 cm?1. The salt consists of nearly tetrahedral Hg(SCN)4 groups, Sr has a tricapped trigonal prismatic coordination: four N and five O atoms. The thiocyanate groups form end-to-end bridges and connect the Hg and Sr coordination polyhedra. 相似文献
20.
Thionine (TH) adsorbed on multiwalled carbon nanotubes (MWCNTs) increases the load and dispersion of platinum nanoparticles (PtNPs) generated by chemical reduction of H2PtCl6 with NaBH4. Under the optimum conditions, the PtNPs‐TH‐MWCNTs/Au electrode electrocatalyzed the reduction and oxidation of H2O2 with high sensitivity, and after glucose oxidase (GOx) adsorption it responded to glucose concentration with a sensitivity of 0.14 A M?1 cm?2. The cyclic voltammetric cathodic peak current for NO2? reduction on PtNPs‐TH‐MWCNTs/Au responded linearly to NO2? concentration from 0.5 to 150 µM, with a sensitivity of 5.52 A M?1 cm?2 and a detection limit of 0.2 µM. 相似文献