共查询到20条相似文献,搜索用时 15 毫秒
1.
Antonio Doménech Maria Teresa Doménech-Carbó 《Journal of Solid State Electrochemistry》2006,10(12):949-958
Chronoamperometric data for proton-assisted reduction/oxidation of a series of dyes, namely, alizarin, purpurin, luteolin, morin, and indigo are compared with the predictions of the model of Lovric and Scholz for redox conductive microcrystals assuming electron and proton hopping in mutually perpendicular directions. Upon the attachment of solid dye microparticles to paraffin-impregnated graphite electrodes in contact with aqueous electrolytes in the pH range between 4 and 7, an excellent agreement between theory and experimental data was obtained. The diffusion coefficients of electrons and protons across dye microcrystals were estimated as 5×10−7 cm2 s−1 and 1×10−10 cm2 s−1, respectively. 相似文献
2.
Sudip Kumar Mondal Subhadip Ghosh Kalyanasis Sahu Pratik Sen Kankan Bhattacharyya 《Journal of Chemical Sciences》2007,119(2):71-76
Excited-state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulphonate, HPTS) to acetate in methanol has been
studied by steady-state and time-resolved fluorescence spectroscopy. The rate constant of direct proton transfer from pyranine
to acetate (k
1) is calculated to be ∼1 × 109 M−1 s−1. This is slower by about two orders of magnitude than that in bulk water (8 × 1010 M−1 s−1) at 4 M acetate. 相似文献
3.
Mohammad Mazloum Ardakani Payam Ebrahimi Karami Hamid Reza Zare Mohammad Hamzehloo 《Mikrochimica acta》2007,159(1-2):165-173
The preparation and electrochemical characterization of glassy carbon electrodes modified with plumbagin were investigated
by employing cyclic voltammetry, chronoamperometry and rotating disc electrode techniques. The cyclic voltammograms of the
electroreduction of oxygen showed an enhanced current peak at approximately −0.289 V in air-saturated phosphate buffer pH
= 7 and scan rate 10 mV s−1. The thermodynamic and kinetic parameters of the reduction of oxygen at glassy carbon have been evaluated using cyclic voltammetry.
The experimental parameters were optimized and the mechanism of the catalytic process was discussed. The obtained values of
E°′ (V vs. Ag/AgCl), the apparent electron transfer rate constant ks (s−1), heterogeneous rate constant for the reduction of O2 at the surface of the modified electrode kh (M−1 s−1) and α (charge transfer coefficient of oxygen) were as follows: −0.146, 23.4, 9.9 × 103 and 0.57, respectively. In addition, plumbagin exhibited strong catalytic activity toward the reduction of H2O2. 相似文献
4.
Reactions of radiolytically generated CO3
•− with some ferric heme proteins, catalase, cytochrome c, and horseradish peroxidase (HRP), were studied. Carbonate radical
anion oxidized amino acid residues of these proteins, but did not react directly with heme iron. HRP and catalase lost about
30% and 20% of their activity, respectively, after the reaction with 100 μM of CO3
•−. The rate constants of the reactions of CO3
•− with the investigated proteins measured by the pulse radiolysis method at pH 8–8.4 and 10 varied from 1.0 × 108 M−1 s−1 (for cytochrome c) to 3.7 × 109 M−1 s−1 (for catalase). 相似文献
5.
Dimiter Alexandrov 《Central European Journal of Chemistry》2009,7(2):175-178
Investigation of the magnetic properties of MnGaN epitaxial layers as a function of external electrical field was performed
on the basis of field effect structure. The structure included substrate of n-type GaN, epitaxial layer of n-type MnxGa1-xN, dielectric layer and metal layer acting as field effect device gate. Each Mn atom in MnxGa1-xN contributes 4 net spins due to the electrons occupying energy levels 4F, 4D, 4P and 4G belonging to 3d orbital, and these levels are in the energy band gap and in the top of the valence band of MnxGa1-xN. The position of the Fermi level is determined to be in the energy band gap of the layer of GaN and to be above the level
4F in the layer of MnxGa1-xN. In this way application of external negative voltage on the gate causes change in the number of electrons contributing
net spins and the saturation magnetization Msat of MnxGa1-xN changes as well. It was found that Msat changes in the range 1.15 × 10−3–0.7 × 10−3 A μm−1 if the external voltage changes in the interval 0–−5V. The application of this structure for the design of spintronic devices
is discussed in this paper.
相似文献
6.
Yu-Jing Guo Jing-Hao Pan Xiao-Mei Li Fei Lu You-Qin Li 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):243-246
In this paper, a simple, rapid, sensitive and accurate electroanalytical method of Acid Blue 120 (AB120) has been established by polarography. In a supporting electrolyte of 0.01 mol l−1 Na2HPO4–KH2PO4 (pH 7.04) solution, a sensitive first derivative reduction peak (ip′) of AB120 was found by Linear Sweep Voltammetry (LSV). The peak potential is −820 mV (versus SCE). The peak current (ip′) is proportional to the concentration over the range 2.0 × 10−7–5.0 × 10−5 mol l−1 (r=0.9961–0.9991) and the limit of detection (LOD) is 1.0 × 10−7 mol l−1. The recovery of AB120 varied from 95.3 to 103.0% and the relative standard deviation (RSD) was 2.2% (n=8). The method has been expected to determination of wastewater in dye industry. In addition, the supramolecular system of AB120 with cyclodextrins has been studied. It can form 1:1 inclusion complex with six CDs. The inclusion constants were calculated and the inclusion ability of different kinds of CDs was compared. Furthermore, the inclusion mechanism was also preliminarily discussed, which provided some valuable information for further application of AB120 and CDs. 相似文献
7.
Pulse radiolysis technique has been used to characterise the transients formed by the reaction of sulphacetamide with eaq
- and subsequently study the electron transfer reactions from the transient to various electron acceptors such as thionine,
safranine-T and methyl viologen. The results indicate that the semi-reduced sulphacetamide species are highly reducing in nature as they
transfer electrons to various dyes with near diffusion controlled rates (k > 109dm3mol−1s−1) in alkaline and acidic solutions. The influence of oxygen on the decay behaviour of semi-reduced species has been investigated
and the results show that O2 reaction with SA− is very fast (k = 1.5 × l09dm3mol−1s−1) and leads to the formation of a permanent-coloured product. Reactions of H.atoms resulted in the formation of two transient
species whose spectral, kinetic and acid-base characteristics have also been investigated. 相似文献
8.
Reactions of e−aq, OH radicals and H atoms were studied with n-allylthiourea (NATU) using pulse radiolysis. Hydrated electrons reacted with
NATU (k = 2.8×109 dm3 mol−1 s−1) giving a transient species which did not have any significant absorption above 300 nm. It was found to transfer electrons
to methyl viologen. At pH 6.8, the reduction potential of NATU has been determined to be −0.527 V versus NHE. At pH 6.8, OH radicals were found to react with NATU, giving a transient species having absorption maxima at 400–410
nm and continuously increasing absorption below 290 nm. Absorption at 400–410 nm was found to increase with parent concentration,
from which the equilibrium constant for dimer radical cation formation has been estimated to be 4.9×103 dm3 mol−1. H atoms were found to react with NATU with a rate constant of 5 × 109 dm3 mol−1 s−1, giving a transient species having an absorption maximum at 310 nm, which has been assigned to H-atom addition to the double
bond in the allyl group. Acetoneketyl radicals reacted with NATU at acidic pH values and the species formed underwent reaction
with parent NATU molecule. Reaction of Cl.−2 radicals (k = 4.6 × 109 dm3 mol−1 s−1) at pH 1 was found to give a transient species with λmax at 400 nm. At the same pH, reaction of OH radicals also gave transient species, having a similar spectrum, but the yield
was lower. This showed that OH radicals react with NATU by two mechanisms, viz., one-electron oxidation, as well as addition to the allylic double bond. From the absorbance values at 410 nm, it has been
estimated that around 38% of the OH radicals abstract H atoms and the remaining 62% of the OH radicals add to the allylic
double bond. 相似文献
9.
Gabriella Poggi Mila D’Angelantonio Marialuisa Russo Salvatore S. Emmi 《Research on Chemical Intermediates》2008,34(1):1-20
The oxidation process of the cyclic acetal sorbitylfurfural (SF) has been thoroughly examined from the kinetic, spectroscopic
and theoretical point of view. Oxidation has been initiated by the radiolitically produced OH radical in the presence of variable
oxygen amounts. Two competing reaction pathways are evidenced which lead to quite different products, although they do not
affect the acetal ring integrity. The peroxidation of the hydroxylated furanic ring (k
4=(6.1±0.9)×108 M−1 s−1) maintains the ring structurevia HO2• elimination (k
6=(1.9±0.4)×105 s−1). Unlike that, the peroxidation of the pseudo-allylic radical (k
5=(1.9±0.9)×109 M−1 s−1), formedvia β-cleavage, fixes the destructured intermediate, leading to a tetroxide, which slowly decomposes through a Russell mechanism
(k
8=(2.3±0.6)×102 s−1). It is confirmed that the steady state concentration of the tetroxide is very low, which suggests a molar absorption coefficient
for it around 1.2×104 M−1 cm−1 at 265 nm. The end products of the latter pathway have been characterized as carboxylic and butenald-sorbitol derivatives. The kinetic and spectral data of every step of the process have been fitted by the above outlined mechanism.
The energetics of the mechanism has been detailed byab initio computations as well, carrying further substantiation to it. Semi-empirical calculations were also employed to describe the
spectral properties of each intermediate. 相似文献
10.
This paper describes the use of an aluminum electrode covered by metallic palladium and modified by Prussian blue prepared
by a simple and rapid electroless method for the electro-oxidation of morphine. Two different pathways for electro-oxidation
of morphine at various pH ranges were suggested. Also, some thermodynamic and kinetic parameters such as the number of electrons
involved in the rate determining step, n
α
, transfer coefficient α, and the total electrons (n) involved in morphine oxidation at the time scale of the cyclic voltammetric technique, the catalytic rate constant of the
electrochemical process k, and diffusion coefficient of morphine D were determined. The mean values obtained are 0.5, 0.5, 1, 26.8 M-1 s-1 and 3.1 × 10−5 cm2 s−1, respectively. 相似文献
11.
Biljana Šmit Biljana Petrović Sofija Sovilj Dragan Čanović Živadin D. Bugarčić 《Monatshefte für Chemie / Chemical Monthly》2008,139(10):1197-1202
The reactions of cisplatin with nizatidine and ranitidine were studied in D2O at pD 7.4 and 298 K by means of 1H NMR spectroscopy. The second order rate constants, k
2, for the reaction of cisplatin with nizatidine is (2.71 ± 0.11) × 10−4 M
−1 s−1, and for the reaction with ranitidine (6.72 ± 0.17) × 10−4 M
−1 s−1. The reactions of nizatidine and ranitidine were also studied with other Pd(II) and Pt(II) complexes. The set of the complexes
was selected because of their difference in reactivity, steric hindrance, and binding properties.
Correspondence: Prof. Dr. Živadin D. Bugarčić, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, 34000 Kragujevac,
Serbia. 相似文献
12.
Madjid Abdeli Naghi Parvini Ahmadi Rasoul Azari Khosroshahi 《Journal of Solid State Electrochemistry》2010,14(7):1317-1324
The inhibiting behavior of Nile Blue and Indigo Carmine organic dyes on mild steel corrosion was evaluated in 1 M HCl solution,
separately, by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. Results show
that the inhibition efficiency (%IE) increases with the increasing concentration of Indigo Carmine up to 9.65 × 10−05 M (%IE ~ 98) and Nile Blue up to 1.08 × 10−04 (%IE ~ 75–80). Good agreement was found between the results obtained from the different techniques used. Polarization curves
indicate that the inhibition of the both inhibitors is of a mixed anodic–cathodic nature, and Langmuir isotherm is found to
be an accurate isotherm describing the adsorption behavior. The inhibition mechanism of the inhibitors involves chemisorption
interaction between the inhibitor and the mild steel. The inhibition efficiency for both inhibitors decreased by the rising
temperature in the range of 25–55 °C, and these results verified the chemisorption behavior of both the inhibitors. 相似文献
13.
Mobolanle Adegboyega Olatunji Godwin A. Ayoko Florence O. Ohiani 《Transition Metal Chemistry》1994,19(2):253-256
Summary The stoichiometries, kinetics and mechanisms of oxidation of (NH2)2CS (1) and (Me2N)2CS (2) to the corresponding disulphides by CoIIIM (M = W12O40
∞-) in aqueous HC1O4 were investigated. The reaction with (1) follows the empirical rate law- d[oxidant] = k[reductant][oxidant] where k = 12.5 ± 0.3 m−1 s−1 at 25° C, while that with (2) follows the equation- d[oxidant] = a + b [reductant] [reductant] [oxidant] where a = 5.4 × 104 M−1s−1 and b = 3.3 × 106M−2 s−1 at 25° C. Free radicals are important in the reactions and possible reaction mechanisms are suggested and discussed. 相似文献
14.
Formations of Active Species and By-Products in Water by Pulsed High-Voltage Discharge 总被引:1,自引:0,他引:1
Formations of active species and by-products are different from bubbling different gases in a pulsed high-voltage discharge
reactor. The identification of all the products and the formation rate determination of active species are quite important
as the process is applied to wastewater disposal. Serials of measurements were conducted to do the identifications and determinations
in this paper. Amounts of · OH all increased but that of H2O2 all decreased by bubbling gas. The · OH formation rate was 3.49 × 10−7, 3.56 × 10−7, 3.21 × 10−7 and 1.94 × 10−7 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen respectively, but it was 1.61 × 10−7 mol s−1 l−1 without bubbling. Without any bubbling, the H2O2 formation rate was up to 6.53 × 10−6 mol l−1 s−1, while it was 9.97 × 10−7, 1.663 × 10−7, 1.73 × 10−6 and 3.14 × 10−6 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen, respectively. NO2− and NO3− was detected in discharged water with bubbling nitrogenous gas. Their formation made the pH decreased. 相似文献
15.
Kevin Hing-Nin Poon Yu-Ling Cheng 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(3-4):211-222
Quartz crystal microbalance (QCM) was used to study the self-assembly of per-6-thio-β-cyclodextrin (t7-βCD) on gold surfaces, and the subsequent inclusion interactions of immobilized βCD with adamantane-poly(ethylene glycol)
(5,000 MW, AD-PEG), 1-adamantanecarboxylic acid (AD-C) and 1-adamantylamine (AD-A). From a 50 μM solution of t7-βCD in 60:40 DMSO:H2O, a t7-βCD layer was formed on gold with surface density of 71.7 ± 2.7 pmol/cm2, corresponding to 80 ± 3% of close-packed monolayer coverage. Gold sensors with immobilized t7-βCD were then exposed alternately to six different concentrations of AD-PEG, 500 μM AD-C or 500 μM AD-A aqueous solutions
for association, and water for dissociation. Association of AD-PEG conformed to a Langmuir isotherm, with a best fit equilibrium
constant K = 125,000 ± 18,000 M−1. For AD-C and AD-A, association (k
a
) and dissociation (k
d
) rate constants were extracted from kinetic profiles by fitting to the Langmuir model, and equilibrium constants were calculated.
The parameters for AD-C were found to be: k
a
= 100 ± 5 M−1 s−1, k
d
= 110 (±18) × 10−4 s−1, and K = 9,400 ± 1,700 M−1. For AD-A, k
a
= 58 ± 6 M−1 s−1, k
d
= 154 (±7) × 10−4 s−1, and K = 3,800 ± 400 M−1. The results demonstrate the utility of QCM as a tool for studying small molecule surface adsorption and guest–host interactions
on surfaces. More specifically, the kinetic and thermodynamic data of AD-C, AD-A, and AD-PEG inclusion with immobilized t7-βCD form a basis for further surface association studies of AD-X conjugates to advance surface sensory and coupling applications. 相似文献
16.
Okamoto Y Monjushiro H Fukumoto T Watarai H 《Analytical and bioanalytical chemistry》2006,385(8):1430-1438
A new analytical technique, spinning microtube fluorometry (SMF), was developed and applied to the study of interfacial hydrolysis
of 5-dodecanoylaminofluorescein di-β-D-galactopyranoside (C12FDG) by β-galactosidase (β-gal) in the toluene–water system. The nonfluorescent lactone form of C12FDG in the toluene phase was converted at the interface to 5-dodecanoylaminofluorescein (C12F), which was fluorescent in the aqueous phase as a dianion at pH 7.3, though some part of C12F was extracted into the toluene phase as its nonfluorescent lactone form. The distribution ratios of C12FDG and C12F at pH 7.3 were determined as 1.4×102 and 1.97, respectively. The interfacial adsorption constants from the toluene phase to the interface at pH 7.3 were 4.8×10−4 and 1.7×10−2 dm for C12FDG and C12F, respectively. The kinetic experiments with the SMF method concluded that the rate-determining step of the enzymatic hydrolysis
at the interface and in the aqueous phase was the 1:1 reaction of C12FDG and β-gal and that the hydrolysis reaction rate constant at the interface at pH 7.3 was 1.84×103 M−1s−1, almost equal to that in the aqueous solution, 1.76×103 M−1s−1. Finally, the SMF method revealed that the contribution of the interfacial reaction to the overall hydrolysis reaction rate
of the toluene–water system was as high as 97%. 相似文献
17.
Pulse radiolysis of resveratrol was carried out in aqueous solutions at pH ranging from 6.5 to 10.5. The one-electron oxidized
species formed by the N•3 radicals at pH 6.5 and 10.5 were essentially the same with λmax at 420 nm and rate constant varying marginally (k = (5−6.5) × 109 dm3 mol−1 s−1). The nature of the transients formed by NO•2, NO• radical reaction at pH 10.5 was the same as that with N•3, due to the similarity in decay rates and the absorption maximum. Reaction of •OH radical with resveratrol at pH 7 gives an absorption maximum at 380 nm, attributed to the formation of carbon centered
radical. The repair rates for the thymidine and guanosine radicals by resveratrol were approx. 1 × 109 dm3 mol−1 s−1, while the repair rate for tryptophan was lower by nearly an order of magnitude (k = 2 × 108 dm3 mol−1 s−1). The superoxide radical anion was scavenged by resveratrol, as well as by the Cu–resveratrol complex with k = 2 × 107 and 1.5 × 109 dm3 mol−1 s−1, respectively. Its reduction potential was also measured by cyclic voltammetry. 相似文献
18.
The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH3)2*COH radicals with a bimolecular rate constant of 0.6 × 108 dm3 mol−1 s−1 in acidic aqueous-organic mixed solvent system. The transient optical absorption band (λmax = 465 nm, ɛ = 6.8 × 102 dm3 mol−1 cm−1) is assigned to ADH* formed on protonation of the radical anion. In basic solutions, (CH3)2*COH radicals react with a bimolecular rate constant of 4.6 × 108 dm3 mol−1 s−1 and the transient optical absorption band (λmax = 490 nm, ɛ = 10.4 × 103 dm3 mol−1 cm−1) is assigned to radical anion, AD*−, which has a pKa value of 8.0. The reduction potential value of the AD/AD*− couple is estimated to be between −0.99 and −1.15 V vs NHE by pulse radiolysis studies. The cyclic voltammetric studies showed
the peak potential close to −1.2 V vs Ag/AgCl. 相似文献
19.
Thato N. Mtshali Walter Purcell Hendrik G. Visser Steven S. Basson 《Transition Metal Chemistry》2008,33(4):481-491
The kinetics of the reaction between [ReN(H2O)-(CN)4]2− with different κ2
N,O-donor ligands (quin− and 2,3-dipic−, respectively) have been studied in the pH 4–12 range in aqueous solution. Two consecutive reaction steps with the formation
of the [ReN(η1-quin)(CN)4]3− and [ReN(μ2-quin) (CN)3]2− complexes, respectively, were spectrophotometrically observed and kinetically investigated. The same reaction mechanism is
proposed for these two ligands. The first fast reaction (for quin−) is attributed to the aqua substitution of [ReN(H2O)(CN)4]2− with forward and reverse rate constants of 1.96(5) × 10−1 M−1 s−1 and 5.6(3) × 10−2 s−1, while a rate of 2.64(3) M−1 s−1 was observed for the reaction between the conjugate base [ReN(OH)(CN)4]3− and quin− at 40.2 °C. Due to small absorbance changes, it was difficult to obtain any good quality data for the fast reactions for
2,3-dipic−. The second, slower reaction is attributed to cyano substitution with rate constants (k
3
K
1) of 4.17(4) × 10−3 for quin− and 4.68(7) × 10−3 M−1 s−1 for 2,3-dipic−, at 80.02 °C, respectively. The acid dissociation constant for the aqua complex was spectrophotometrically determined as
11.58(3) and 11.54(2) and kinetically as 11.51(8) and 11.41(1), at 80.4 °C, respectively. Negative values of −83.5(2) and −144.1(2) J K−1 mol−1 as well as the of 71.4(3) and 47.3(3) kJ mol−1, for the slow quin− and 2,3-dipic− reactions, respectively, point to an ordered transition state where bond formation is responsible for the major driving force
of the reaction. The and for the fast forward reaction of quin− is indicative of expected associative activation in the transition state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
Anne Vuorema Philip John A. Toby A. Jenkins Frank Marken 《Journal of Solid State Electrochemistry》2006,10(10):865-871
Colloidal indigo is reduced to an aqueous solution of leuco-indigo in a mediated two-electron process converting the water-insoluble dye into the water-soluble leuco form. The colloidal dye does not interact directly with the electrode surface, and to employ an electrochemical process for this reduction, the redox mediator 1,8-dihydroxyanthraquinone (1,8-DHAQ) is used to transfer electrons from the electrode to the dye. The mediated reduction process is investigated at a (500-kHz ultrasound-assisted) rotating disc electrode, and the quantitative analysis of voltammetric data is attempted employing the Digisim numerical simulation software package. At the most effective temperature, 353 K, the diffusion coefficient for 1,8-DHAQ is (0.84±0.08)×10−9 m2 s−1, and it is shown that an apparently kinetically controlled reaction between the reduced form of the mediator and the colloidal indigo occurs within the diffusion layer at the electrode surface. The apparent bimolecular rate constant k
app=3 mol m−3 s−1 for the rate law
\fracd[ \textleuco - \textindigo ] dt = k\textapp ×[ \textmediator ] ×[ \textindigo ]\frac{{d{\left[ {{\text{leuco}} - {\text{indigo}}} \right]}}} {{dt}} = k_{{{\text{app}}}} \times {\left[ {{\text{mediator}}} \right]} \times {\left[ {{\text{indigo}}} \right]} is determined and attributed to a mediator diffusion controlled dissolution of the colloid particles. The average particle size and the number of molecules per particles are estimated from the apparent bimolecular rate constant and confirmed by scanning electron microscopy. 相似文献