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1.
A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled
carbon nanotubes (MWNTs)–chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized
Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E
θ′) of −22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k
s) in the Chit–MWNTs film was evaluated as 2.58 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive Hb in the Chit–MWNTs film was estimated to be (2.48 ± 0.25) × 10−9 mol cm−2. Meanwhile, the Chit–MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis–Menten constant (K
Mapp) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 × 10−6 to 9.30 × 10−5 mol L−1 with a detection limit of 3.47 × 10−7 mol L−1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility. 相似文献
2.
Ali Eftekhari 《Mikrochimica acta》2003,141(1-2):15-21
The electrocatalytic activity of an aluminum microelectrode modified with cobalt hexacyanoferrate film is described. A simple
method was used for the preparation of the modified microelectrode. The modified microelectrode exhibits good electrocatalytic
properties for electrochemical reduction of hydrogen peroxide. The effect of solution pH and applied potential on the electrocatalytic
properties of the modified microelectrode is investigated. The results show that the best potential for the detection of hydrogen
peroxide is 0.0 vs. SCE for better response and decrease of interferences. Due to the microelectrode scale, it can be used for the determination
of small amounts of H2O2. The calibration plot is linear up to 1.7 mM (r = 0.988) with a response time of 5.1 s. The detection limit of the microelectrode as H2O2 sensor is 2 × 10−7 M. The sensivity of the H2O2 sensor is 225.6 nA mmol−1 and RSD of this sensor is less than 2.3%. In addition, effects of possible interferences and possibility of the sensor for
real samples is investigated. The present work shows the potential of the proposed method for the fabrication of modified
electrodes, as it can be used to employ for different purposes in micro scale.
Received June 20, 2001; accepted June 14, 2002 相似文献
3.
The kinetics of hydroquinone-inhibited oxidation of acrylic acid and methyl methacrylate was studied volumetrically by measuring
the oxygen uptake in the presence of an initiator (azobisisobutyronitrile) at T = 333 K and P
O
2 = 1 and 0.21 atm. The oxidation of acrylic acid inhibited by 4-methoxyphenol was studied under the same conditions for comparison.
The rate constants of the reactions of the peroxyl radicals of acrylic acid (∼CH2CH(COOH)O2·) and methyl methacrylate (∼CH2CMe(COOMe)O2·) with hydroquinone (HOC6H4OH) (1.20 × 105 and 7.16 × 104 l mol−1 s−1, respectively) and of the reaction of peroxyl radicals of acrylic acid with 4-methoxyphenol (p-CH3OC6H4OH) (3.25 × 104 l mol−1 s−1) were measured. The stoichiometric inhibition factors f were determined. The reaction between the semiquinone radical and oxygen, O2 + HOC6H4O·, plays an important role, decreasing the factor f and the efficiency of the inhibition effect of hydroquinone. The rate constants of this reaction were calculated from kinetic
data: k = 5.72 × 102 (in acrylic acid) and 4.60 × 102 l mol−1 s−1 (in methyl methacrylate). 相似文献
4.
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
5.
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
6.
Maria das Graças Nunes Matos Vivian Gouveia Diniz Cesar Augusto Moraes de Abreu Augusto Knoechelmann Valdinete Lins da Silva 《Adsorption》2009,15(1):75-80
Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this
work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr3+) and lead (Pb2+) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted
in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through
the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K
eqCr=173.42, K
eqPb=58.86) and volumetric mass transfer coefficients ((k
mCr
a)′=1.13×10−3 s−1, (k
mPb
a)′=0.89×10−3 s−1) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough
curves obtained for both metals were compared with the predicted values by the heterogeneous model (K
eqCr=171.29, K
eqPb=60.14; k
mCr
a=7.81×10−2 s−1, k
mPb
a=2.43×10−2 s−1), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery
process at low cost.
An erratum to this article can be found at 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.
This paper describes the use of an aluminum electrode plated by metallic palladium and modified by Prussian blue (PB/Pd-Al)
in the electrocatalytic reduction of hydrogen peroxide (H2O2). The effect of pH on the electroreduction of H2O2 on the modified electrode is investigated and a simple irreversible reduction pathway is suggested. The electroreduction
kinetics including transfer coefficient α, potential-dependent charge transfer rate constants k
f, and diffusion coefficient D are estimated by means of forced hydrodynamic voltammetry using a rotating disk PB/Pd-Al electrode. The mean values obtained
for kinetics are 0.38, 10−2 cm−1, and 7.6 × 10−6 cm2 s−1, respectively. The long-term stability of the modifying layers on the Al substrate was studied. 相似文献
9.
Kumar S. Ashok Wang Sea-Fue Yeh Chun-Ting Lu His-Chuan Yang Jen-Chang Chang Yu-Tsern 《Journal of Solid State Electrochemistry》2010,14(11):2129-2135
In this study, stable and homogenous thin films of multiwalled carbon nanotubes (MWCNTs) were obtained on conducting surface
using ciprofloxacin (CF, fluoroquinolone antibiotic) as an effective-dispersing agent. Further, MWCNTs/CF film modified electrodes
(glassy carbon and indium tin oxide-coated glass electrode) are used successfully to study the direct electrochemistry of
proteins. Here, cytochrome C (Cyt-C) was used as a model protein for investigation. A MWCNTs/CF film modified electrode was
used as a biocompatible material for immobilization of Cyt-C from a neutral buffer solution (pH 7.2) using cyclic voltammetry
(CV). Interestingly, Cyt-C retained its native state on the MWCNTs/CF film. The Cyt-C adsorbed MWCNTs/CF film was characterized
by scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-vis) and CV. SEM images showed the evidence for the
adsorption of Cyt-C on the MWCNTs/CF film, and UV–vis spectrum confirmed that Cyt-C was in its native state on MWCNTs/CF film.
Using CV, it was found that the electrochemical signal of Cyt-C was highly stable in the neutral buffer solution and its redox
peak potential was pH dependent. The formal potential (−0.27 V) and electron transfer rate constant (13 ± 1 s−1) were calculated for Cyt-C on MWCNTs/CF film modified electrode. A potential application of the Cyt-C/MWCNTs/CF electrode
as a biosensor to monitor H2O2 has been investigated. The steady-state current response increases linearly with H2O2 concentration from 2 × 10−6 to 7.8 × 10−5 M. The detection limit for determination of H2O2 has been found to be 1.0 × 10−6 M (S/N = 3). Thus, Cyt-C/MWCNTs/CF film modified electrode can be used as a biosensing material for sensor applications. 相似文献
10.
Samaria-doped ceria Ce0.8Sm0.2O2−δ
(SDC) and SmFe0.7Cu0.3−x
Ni
x
O3 have been synthesized by the sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy
(TEM) and scanning electron microscopy (SEM). The electrochemical synthesis of ammonia was investigated at atmospheric pressure
and low temperature, using the SFCN materials as the cathode, a Nafion membrane as the electrolyte, nickel-doped SDC (Ni-SDC)
as the anode and silver-platinum paste as the current collector. Ammonia was synthesized from 25 to 100°C when the SFCN materials
were used as cathode, with SmFe0.7Cu0.1Ni0.2O3 giving the highest rates of ammonia formation. The maximum rate of evolution of ammonia was 1.13 × 10−8 mol·cm−2·s−1 at 80°C, and the current efficiency reached as high as 90.4%.
Supported by the National Natural Science Foundation of China (Grant No. 20863007) 相似文献
11.
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
12.
Salimi Abollah Noorbakhsh Abdollah Semnani Abolfazl 《Journal of Solid State Electrochemistry》2011,15(9):2041-2052
A simple method was used to fabricate flavin adenine dinucleotide (FAD)/NiOx nanocomposite on the surface of glassy carbon
(GC) electrode. Cyclic voltammetry technique was applied for deposition nickel oxide nanostructures onto GC surface. Owing
to its high biocompatibility and large surface area of nickel oxide nanomaterials with immersing the GC/NiOx-modified electrode
into FAD solution for a short period of time, 10–140 s, a stable thin layer of the FAD molecules immobilized onto electrode
surface. The FAD/NiOx films exhibited a pair of well-defined, stable, and nearly reversible CV peaks at wide pH range (2–10).
The formal potential of adsorbed FAD onto nickel oxide nanoparticles film, E
o′ vs. Ag/AgCl reference electrode is −0.44 V in pH 7 buffer solutions was similar to dissolved FAD and changed linearly with
a slope of 58.6 mV/pH in the pH range 2–10. The surface coverage and heterogeneous electron transfer rate constant (k
s
) of FAD immobilized on NiOx film glassy carbon electrode are 4.66 × 10−11 mol cm−2 and 63 ± 0.1 s−1, indicating the high loading ability of the nickel oxide nanoparticles and great facilitation of the electron transfer between
FAD and nickel oxide nanoparticles. FAD/NiOx nanocomposite-modified GC electrode shows excellent electrocatalytic activity
toward S2O82− reduction at reduced overpotential. Furthermore, rotated modified electrode illustrates good analytical performance for amperometric
detection of S2O82−. Under optimized condition, the concentration calibration range, detection limit, and sensitivity were 3 μM–1.5 mM, 0.38 μM
and 16.6 nA/μM, respectively. 相似文献
13.
Parimal Gaikwad A. Barik K. I. Priyadarsini B. S. M. Rao 《Research on Chemical Intermediates》2010,36(9):1065-1072
Studies on the antioxidant activity of two model phenols containing either an electron withdrawing (p-nitrophenol) or electron donating (p-aminophenol) group and p-hydroxyacetophenone in different solvents are reported using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay by spectrophotometry
and stopped-flow techniques. The second-order rate constants measured with p-nitrophenol were found to be (1.2–5.5) × 10−2 dm3 mol−1 s−1 but the DPPH radical reacts much faster with p-aminophenol (k = 0.5–1.1 × 104 dm3 mol−1 s−1). The normal kinetic solvent effect in H atom transfer was seen in the case of p-nitrophenol with the solvent independent rate constant k
o = 0.1 dm3 mol−1 s−1. The IC50 values in p-nitrophenol are similar to those measured in p-hydroxyacetophenone. On the other hand, much lower IC50 values of more than four orders of magnitude with p-aminophenol were observed. This work demonstrates that the phenol with the electron donating –NH2 substituent is a better antioxidant. 相似文献
14.
An O-bonded sulphito complex, Rh(OH2)5(OSO2H)2+, is reversibly formed in the stoppedflow time scale when Rh(OH2)
6
3+
and SO2/HSO
3
−
buffer (1 <pH< 3) are allowed to react. For Rh(OH2)5OH2++ SO2 □ Rh(OH2)5(OSO2H)2+ (k1/k-1), k1 = (2.2 ±0.2) × 103 dm3 mol−1 s−1, k−1 = 0.58 ±0.16 s−1 (25°C,I = 0.5 mol dm−3). The protonated O-sulphito complex is a moderate acid (K
d
= 3 × 10−4 mol dm−3, 25°C, I= 0.5 mol dm−3). This complex undergoes (O, O) chelation by the bound bisulphite withk= 1.4 × 10−3 s−1 (31°C) to Rh(OH2)4(O2SO)+ and the chelated sulphito complex takes up another HSO
3
−
in a fast equilibrium step to yield Rh(OH2)3(O2SO)(OSO2H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH2)3(O2SO)(OSO2)- → Rh(OH2)3(O2SO)(SO3)− (k
iso
= 3 × 10−4 s−1, 31°C). A dinuclear (μ-O, O) sulphite-bridged complex, Na4[Rh2(μ-OH)2(OH)2(μ-OS(O)O)(O2SO)(SO3) (OH2)]5H2O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water
and most organic solvents and very stable to acid-catalysed decomposition 相似文献
15.
The Fe3O4-Prussian blue (PB) nanoparticles with core-shell structure have been in situ prepared directly on a nano-Fe3O4-modified glassy carbon electrode by cyclic voltammetry (CV). First, the magnetic nano-Fe3O4 particles were synthesized and characterized by X-ray diffraction. Then, the properties of the Fe3O4-PB nanoparticles were characterized by CV, electrochemical impedance spectroscopy, and superconducting quantum interference
device. The resulting core-shell Fe3O4-PB-modified electrode displays a dramatic electrocatalytic ability toward H2O2 reduction, and the catalytic current was a linear function with the concentration of H2O2 in the range of 1 × 10−7~5 × 10−4 mol/l. A detection limit of 2 × 10−8 (s/n = 3) was determined. Moreover, it showed good reproducibility, enhanced long-term stability, and potential applications in
fields of magnetite biosensors. 相似文献
16.
T. P. Rebrova V. L. Cherginets Yu. N. Dats’ko E. E. Voronkina 《Russian Journal of Inorganic Chemistry》2012,57(3):427-429
The solubility product of EuO (pP
EuO = 8.65 ± 0.5) and its dissociation constant (pK
EuO = 5.67 ± 0.5) in NaI melts at 700°C have been determined by potentiometric titration with the use of a Pt(O2)|ZrO2(Y2O3) membrane oxygen electrode. Estimated on the basis of these parameters, the total solubility of EuO in NaI melts (1.12 ×
10−3 mol/kg, logs
EuO = −2.95) is close to the value obtained by the consecutive additions method (2.8 × 10−3 mol/kg, logs
EuO = −2.55). The values obtained show that Eu2+ (EuI2) is a stable cationic activator in NaI melt, but it yet cannot be recommended as an agent for the removal of oxygen-containing
admixtures from this melt. 相似文献
17.
E. Yu. Pikalova A. A. Murashkina D. A. Medvedev 《Russian Journal of Electrochemistry》2011,47(6):681-689
CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical
devices. This work presents the results of systematic studies of structural and electric properties and oxygen nonstoichiometry
of the Ce0.8(Sm1 − x
Ca
x
)0.2O2 − δ system in a wide range of concentrations of 0 < x < 1 performed in order to establish the causes affecting the system conductivity and its behavior in a reducing medium. It
is found that a single-phase solid solution of the fluorite type is formed in the whole concentration range. Parameters of
its lattice cells decrease linearly at an increase in the concentration of Ca2+. Conductivity in air grows when calcium is added due to a decrease in the grain boundary resistance. The maximum conductivity
in air was obtained for the composition of Ce0.8(Sm0.8Ca0.2)0.2O2 − δ and is 13.71 × 10−3 S/cm at 873 K. Studies of the dependence of conductivity of the partial pressure of oxygen showed that electron conductivity
is observed at a higher oxygen partial pressure at an increase in the temperature and calcium concentration. The critical
partial pressure of oxygen ( pO2 * )\left( {p_{O_2 }^* } \right) for the compositions of Ce0.8(Sm1 − x
Ca
x
)0.2O2 − δ with x = 0; 0.2, and 0.5 is 1.83 × 10−16, 1.73 × 10−13, and 3.63 × 10−13 atm at 1173 K, respectively, and 2.76 × 10−21, 5.05 × 10−18, and 1.31 × 10−18 atm at 1023 K. 相似文献
18.
Tsung-Hsuan Tsai Tse-Wei Chen Shen-Ming Chen Ramiah Sarawathi 《Russian Journal of Electrochemistry》2012,48(3):291-301
The NiHCF-PEDOT, CuHCF-PEDOT and MnHCF-PEDOT films were prepared on glassy carbon electrode (GCE) by multiple scan cyclic
voltammetry and characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron
microscope (SEM) techniques. The advantages of these films are demonstrated for selectivity detection of ascorbic acid using
cyclic voltammetry and amperometric method. Interestingly, the NiHCF-PEDOT and CuHCF-PEDOT modified electrodes exhibited a
wide linear response range (5 × 10−6−3 × 10−4 M, R
2 = 0.9973 and 1.8 × 10−3−1.8 × 10−2 M, R
2 = 0.9924). The electrochemical sensors facilitated the oxidation of AA but not responded to other electroactive biomolecules
such as dopamine, uric acid, H2O2, glucose. The difference is MnHCF-PEDOT/GCE that no response to AA. In addition, the NiHCF-PEDOT and CuHCF-PEDOT modified
electrodes exhibited a distinct advantage of simple preparation, specificity, stability and reproducibility. 相似文献
19.
V. N. Smirnov 《Kinetics and Catalysis》2011,52(2):166-169
The results of our experimental studies and an analysis of the published data on the rate constant for the reaction Fe + O2 = FeO + O in the forward (I) and reverse (−I) direction are reported. The data obtained in this work are described by the
expressions k
1 = 6.2 × 1014exp(−11100 K/T) cm3 mol−1 s−1 and k
−1 = 6.0 × 1013exp(−588 K/T) cm3 mol−1 s−1 (T = 1500–2500 K). The generalized expressions for the temperature dependences of these rate constants derived by combining
our results with the literature data can be presented as k
1 = 9.4 × 1014(T/1000)0.022exp(−11224 K/T) cm3 mol−1 s−1 (T = 1500–2500 K) and k
−1 = 1.8 × 1014(1000/T)0.37exp(−367 K/T) cm3 mol−1 s−1 (T = 200–2500 K). 相似文献
20.
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