共查询到20条相似文献,搜索用时 546 毫秒
1.
Sheela Berchmans R. G. Nirmal G. Prabaharan A. K. Mishra V. Yegnaraman 《Journal of Solid State Electrochemistry》2006,10(7):439-446
Self-assembled monolayers (SAMs) of thiols with carboxylic acid terminal groups were formed on gold substrates. The electron transfer characteristics of redox species on the above SAM-modified electrodes were studied in acid and neutral media with the help of voltammetry under two different conditions: (1) solution phase electron transfer and (2) bridge mediated electron transfer. Two redox systems, viz., [Fe(CN)6]4-/3− and Ru[(NH3)6]2+/3+ were chosen for the solution phase study. Investigations of bridge mediated electron transfer were carried out by functionalising the SAM with redox moieties and then studying their redox behaviour. For this study, ferrocene carboxylic acid and 1,4-diamino anthraquinone were used and they were linked to carboxylic acid terminated thiols by covalent linkage. The voltammetric results with mercaptoundecanoic acid SAM demonstrate the difference in behaviour between solution phase and bridge mediated electron transfer processes. 相似文献
2.
L. M. Doubova 《Russian Journal of Electrochemistry》2010,46(4):450-460
The kinetics of Ru[(NH3)6]3+ reduction in 1 M NaNO3 solution at Ag(210) and Ag(111) singlecrystal electrodes modified by n-decanthiol monolayer is studied by electrochemical impedance spectroscopy and cyclic voltammetry. By using these two methods,
standard rate constants of the redox reaction involving Ru[(NH3)6]3+/2+ redox couple in the absence and in the presence of the n-decanthiol film were estimated. The equivalent circuit describing the experimental data in the presence of the self-assembled
organic monolayer and in the absence of redox reaction is an electrical circuit comprising a large resistance (∼106 Ω) connected in parallel with a capacitance (∼10−8 F). Analysis of kinetic data and extrapolation of Tafel lines resulted in the determination of the rate constant at unmodified
Ag-electrode, which is characteristic of very fast heterogeneous electron transfer. The calculated rate constants for n-decanthiol-modified silver singlecrystal faces (210) and (111) in 1 M NaNO3 solution (pH 6.3) equal 4.63 × 10−5 and 3.05 × 10−5 cm/s, respectively. The results are compared with the data at hand reported by different authors for gold electrodes in indifferent
electrolyte solution in the absence and in the presence of self-assembled monolayer. 相似文献
3.
This paper describes the ionic self-assembly method to fabricate supramolecular one-dimensional microrods in solution. Such
microrods were formed in a one-step process through the mixing aqueous Ru(NH3)6Cl3 and K3Fe(CN)3 solutions at room temperature. Chemical composition of the resulting structures, which are composed of from Fe(CN)64− and Ru(NH3)63+, was determined by energy-dispersed spectroscopy. The data show that the formation of microrods depends on the molar ratio
and concentration of the reactants. 相似文献
4.
Sulfonated ormosil hydrogels (~80% water) were prepared using tetramethyl orthosilicate as a silica precursor and 2(4-chlorosulfonylphenyl)ethyltrichlorosilane to provide sulfonate functionality for ion-exchange and ion conductivity. Ruthenium(III) hexamine was used as a redox probe in electrochemical studies performed on porous carbon fibre paper electrodes impregnated with the gel. The gel-modified electrodes extracted Ru(NH3)63+ from solutions in 0.1 M CF3CO2Na(aq) with a partition coefficient of ~36, and with ~100% of the sulfonate sites being accessible for ion exchange. The Ru(NH3)63+/2+ couple exhibited reversible and facile electrochemistry in the gel, with a Ru(NH3)62+ diffusion coefficient of 4.9×10–8 cm2 s–1 determined by chronoamperometry. This is an order of magnitude higher than the mobility of this complex in Nafion. The hydrogel-modified electrodes were stable for days, and could be repeatedly loaded with Ru(NH3)63+.Special Issue to celebrate the 70th birthday of Professor Zbigniew Galus 相似文献
5.
Lidong Li Hongtao Zhao Zhengbo Chen Xiaojiao Mu Lin Guo 《Analytical and bioanalytical chemistry》2010,398(1):563-570
This paper presents a simple electrochemical approach for the detection of thrombin, using aptamer-modified electrodes. The
use of gold nanoparticles results in significant signal enhancement for subsequent detection. 1,6-Hexanedithiol was used as
the medium to link Au nanoparticles to a bare gold electrode. Anti-thrombin aptamers were immobilized on the gold nanoparticles’
surfaces by self-assembly. The packing density of aptamers was determined by cyclic voltammetric (CV) studies of redox cations
(e.g., [Ru(NH3)6]3+) which were electrostatically bound to the DNA phosphate backbones. The results indicate that the total amount of aptamer
probes immobilized on the gold nanoparticle surface is sixfold higher than that on the bare electrode, leading to increased
sensitivity of the aptasensor and a detection limit of 1 pmol L−1. Based on the Langmuir model, the sensor signal displayed an almost perfect linear relationship over the range of 1 pmol
L−1 to 30 nmol L−1. Moreover, the proposed aptasensor is highly selective and stable. In summary, this biosensor is simple, highly sensitive,
and selective, which is beneficial to the ever-growing interest in fabricating portable bio-analytical devices with simple
electrical readout procedures. 相似文献
6.
Marcin Opallo 《Journal of Solid State Electrochemistry》1998,2(5):347-354
The electrochemical redox reactions: Fe(CN)6
4−−e−↔ Fe(CN)6
3−, Ru(NH3)6
3++e−↔ Ru (NH3)6
2+ and Fc(CH2OH)2−e−↔ Fc(CH2OH)2
+ (Fc–ferrocene) were investigated in tetrabutylammonium halide hydrates at temperatures below and above the electrolyte melting
point. They were studied by cyclic voltammetry, potential step chronoamperometry and impedance spectroscopy. Freezing of
the electrolyte affects both the shape and position of the cyclic voltammogram on the potential scale. Also the shapes of
the current-time relationship and the impedance spectra change at temperatures below the melting point. It has been proposed
that this behaviour is caused by slow transport of the reactant and the heterogeneous nature of the electrolyte. The activation
energies of reactant transport are about four times larger in frozen electrolytes than those in liquid. It has been concluded
that reactant transport is restricted to the intergrain space of the electrolyte.
Received: 16 December 1997 / Accepted: 10 February 1998 相似文献
7.
Cobalt, despite an essential biological element, imposes threat to humans when exposed to high concentration or even to low concentration for long term which demands the development of highly sensitive and selective analytical methods for its trace analysis. In the present work, self‐assembly of p‐aminothiophenol (p‐ATP) on gold surface (Au?ATP SAM) was carried out and for the first time, applied as a platform for impedimetric and potentiometric sensing of Co2+. Au?ATP SAM was characterized using electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), in the presence of two redox probes: [Fe(CN)6]3?/4? and [Ru(NH3)6]2+/3+ to evaluate associated passivating behaviour. Au?ATP SAM completely blocked [Fe(CN)6]3?/4? as compared to [Ru(NH3)6]2+/3+ which may be attributed to inner‐sphere and outer‐sphere ET mechanisms, respectively. Au?ATP SAM was found to exhibit excellent sensitivity towards Co2+ in a wider concentration range from 1.0×10?12 M to 1.0×10?5 M (r2=0.963) at pH 5.5 with a detection limit of 6.0×10?13 M and superior selectivity. Further, carbon paste electrode (CPE) was prepared by incorporating p‐ATP bound gold nanoparticles and explored for potentiometric sensing of Co2+ which exhibited Nernstian slope of 29.2±0.2 mV/dec in linear concentration range of 1.0×10?6 M–1.0×10?1 M (r2=0.971) with a detection limit of 8.0×10?7 M. The proposed sensors were successfully applied for estimation of Co2+ content in water samples. 相似文献
8.
Aqueous solutions of indium(III) undergo 1e− reductions by Sm(II) (E0-1.55 V) and by Yb(II) (−1.05 V), but not by U(III) (−0.52 V). The facile and irreversible reduction, by In+
aq, of Ru(NH3)6
3+ (E0+0.067 V) at reagent concentrations near 10−3 M implies a potential more negative than −0.23 V for In(II,I) and, in conjunction with the known value of −0.44 V for In(III,I),
a complementary potential less negative than −0.65 V for In(III,II). These observations, taken together, support le− indium potentials EII,I
o−0.2 V and EIII,II
0−0.6 V. 相似文献
9.
《Electroanalysis》2003,15(22):1756-1761
Mercaptoundecanoic acid (MUA) and glutathione (GSH) self‐assembled monolayers were prepared on gold‐ wire microelectrode. Cyclic voltammetry was used to investigate the influence of temperature on electrochemical behaviors of Fe(CN)63?/4? and Ru(NH3)63+/2+ at these SAMs modified electrodes in aqueous solution. It is found that temperature shows great influence on electron transfer (ET) and mass transport (MT) for the two SAMs modified electrodes and the influence of temperature depends on the charge properties of the redox couples and terminal groups of SAMs and the structure of the monolayer on gold surface. The temperature can greatly increase MT rate of Fe(CN)63?/4? at both MUA and GSH modified electrodes. However, the increased MT rate doesn't have any effect on the CV's for Fe(CN)63?/4? /MUA system. For Ru(NH3)63+/2+ , temperature can greatly improve the electrochemical reaction in both MUA and GSH modified electrodes, which is ascribed to temperature‐induced diffusion and convection and the electrostatic interaction between Ru(NH3)63+/2+ and negatively charged carboxyl groups on the electrode surface. 相似文献
10.
de la Escosura-Muñiz A González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,384(3):742-750
A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon
electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was
bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological
reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I)
bound to the anti-HSA was electrodeposited in 0.1 mol L−1 HCl at −1.00 V for 5 min then oxidised in 0.1 mol L−1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were
then performed in aqueous 1.0 mol L−1 NH3–2.0×10−4 mol L−1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10−10 to 1.0×10−8 mol L−1 and 1.0×10−10 to 1.0×10−9 mol L−1 HSA, respectively, with estimated detection limits of 1.5×10−10 mol L−1 (10 ng mL−1) and 1.0×10−10 mol L−1 (7 ng mL−1), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay
formats. 相似文献
11.
L. M. Doubova S. Rondinini A. Vertova L. Bulgariu 《Russian Journal of Electrochemistry》2013,49(1):26-37
The electrochemical behavior of the gold/electrolyte interface in aqueous 1 M NaNO3 solutions in the presence of an organic monolayer of n-decanethiol (CH3(CH2)9S) is studied by electrochemical impedance spectroscopy in the frequency range of 10–105 Hz and also by cyclic voltammetry. It is experimentally shown that in the potential interval from 0 to ?0.5 V (vs. SCE), the dense monolayer film decreases the measured current density approximately 40-fold. The measured capacitance falls down to 1–2 μF/cm2. Based on the analysis of impedance characteristics acquired with the use of empirical equivalent circuits comprising ideal and nonideal analogues of electric circuits, the tentative estimates of the thickness of organic monolayers formed on Au electrodes with various roughness factors are obtained. Using the complex nonlinear regression (CNLS) method and a model of microarray electrode, the porous structure of adsorbed monolayers is revealed and the transition frequency of interfaces under study is determined. The degree of inhibition of the electron transfer across the Au/n-decanethiol/solution interface is determined by comparing the rate constants for the Ru[(NH3)6]3+/2+ redox process on clean and modified electrodes. The acquired results are compared with available literature data. 相似文献
12.
A. I. Gubanov N. V. Kuratieva E. Yu. Filatov S. V. Korenev 《Journal of Structural Chemistry》2012,53(3):503-508
The structures of two salts [Co(NH3)6][Rh(NO2)6] (I) and [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x (μ-OH)2−x Rh(NO2)3]·(2−x)(H2O), x = 0.17 (II) are solved. Single crystals of the salts are obtained by the counter diffusion method through the gel of aqueous solutions of [Co(NH3)6]Cl3 and Na3[Rh(NO2)6]. The structure of [Co(NH3)6][Rh(NO2)6] is consistent with the diffraction data for a polycrystalline sample of poorly soluble fine salt formed in the exchange reaction between aqueous solutions of [Co(NH3)6]Cl3 and Na3[Rh(NO2)6]. The structure of [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x (μ-OH)2−x Rh(NO2)3]·(2−x)(H2O), x = 0.17 exhibits the stabilizing effect of a large cation in the formation of novel, unknown previously coordination ions: [(NO2)3Rh(μ-NO2)(μ-OH)2Rh(NO2)3]3− and [(NO2)3Rh(μ-NO2)2(μ-OH)Rh(NO2)3]3−. 相似文献
13.
A quartz crystal microbalance (QCM) sensor for selenite ions in aqueous solution was constructed based on crystal formation
of cadmium selenite, immobilized with a self-assembly monolayer (SAM) of phosphorylated 11-mercapto-1-undecanol (MUD) on a
QCM gold electrode surface. The mass change caused by the selective adsorption of selenite ions on the cadmium selenite crystals
at the solid/solution interface was detected by the QCM. The response (−ΔF) of the modified QCM oscillator increased with
increasing selenite ion concentrations in sample solutions, ranging from 9.7×10−5 to 9.0×10−4 M at pH 7.4. The synthetic process of anchoring cadmium selenite crystals on the phosphorylated MUD organic film was also
followed by using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The atomic concentrations measured
by XPS confirmed the crystal growth of cadmium selenite on the phosphorylated MUD SAM at the QCM gold electrode surface. From
the AFM images, changes in surface topographic features were followed: the MUD SAM and phosphorylated MUD on the QCM gold
electrode had similar surface roughness; however the difference for the cadmium selenite film on the phosphorylated MUD SAM
was clearly seen. The observed QCM frequency change of the modified QCM oscillator per unit time was found to be proportional
to the square of the supersaturation of cadmium selenite, indicating the crystal growth of cadmium selenite at the solid/solution
interface. The modified QCM oscillator exhibited selectively strong QCM response to SeO3
2− ion. In contrast, the responses to tested interfering anions were almost negligible. The order of anion selectivities of
the present modified QCM sensor was SeO3
2−≫CO3
2−>SeO2−
4, SO4
2−, Br−, I−, NO3
−. These selectivities were basically attributable to the differences in solubility products and solubilities for the salts
of each anion with cadmium (II) ion.
Received May 12, 1998. Revision December 29, 1998. 相似文献
14.
The reductions of [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+, by TiIII in aqueous acidic solution have been studied spectrophotometrically. Kinetic studies were carried out using conventional
techniques at an ionic strength of 1.0 mol dm−3 (LiCl/HCl) at 25.0 ± 0.1 °C and acid concentrations between 0.015 and 0.100 mol dm−3. The second-order rate constant is inverse—acid dependent and is described by the limiting rate law:- k2 ≈ k0 + k[H+]−1,where k=k′Ka and Ka is the hydrolytic equilibrium constant for [Ti(H2O)6]3+. Values of k0 obtained for [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+ are (1.31 ± 0.05) × 10−2 dm3 mol−1 s−1, (4.53 ± 0.08) × 10−2 dm3 mol−1 s−1 and (1.7 ± 0.08) × 10−2 dm3 mol−1 s−1 respectively, while the corresponding k′ values from reductions by TiOH2+ are 10.27 ± 0.45 dm3 mol−1 s−1, 14.99 ± 0.70 dm3 mol−1 s−1 and 17.93 ± 0.78 dm3 mol−1 s−1 respectively. Values of K
a
obtained for the three complexes lie in the range (1–2) × 10−3 mol dm−3 which suggest an outer-sphere mechanism. 相似文献
15.
《Supramolecular Science》1997,4(3-4):329-333
Alkylthiol molecules, C22H45-SO2-C6H4-O-C4H8-SH, HS-(CH2)21-OH and HS-(CH2)10-COOH, were used to stabilise gold clusters, formed in a two-phase system. The gold nanoparticles were investigated by using transmission electron microscopy, Fourier transform infra-red spectroscopy, ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy. The results show that surfactant-coated nanoparticles are indeed formed and the incorporation of a dipole or a terminal functionality into the surfactant does not hinder the self-assembling process. 相似文献
16.
Izaura Cirino Nogueira Diógenes Francisco Carlos Nart Mônica B. P. Mello Barreto Marcia Laudelina Arruda Temperini Ícaro de Sousa Moreira 《Journal of Solid State Electrochemistry》2007,11(11):1585-1590
Surface-Enhanced Raman Scattering (SERS) spectra of [Ru(CN)5(pyS)]4− (RupyS) complex self-assembled monolayer (SAM) were obtained on gold and silver surfaces at 632.8 and 413.1 nm excitation
radiations, respectively. The bands assigned to the heme iron of the cytochrome c (cyt c) metalloprotein group were observed
by using the RupyS SAM on silver at 413.1 nm. The Surface-Enhanced Resonance Raman Scattering (SERRS) spectra of the RupyS
SAM on silver in the cyt c solution obtained at −0.2 and +0.2 V present bands at 1,365 and 1,374 cm−1 characteristic of the heme group, indicating the reduced and oxidized states of this protein, respectively. The bands observed
at 1,464, 1,504, and 1,638 cm−1 are used to confirm the redox state of cyt c. The presence of the oxidized and reduced bands in function of different applied
potential is an evidence that the protein is interacting with the modifier.
This paper is dedicated to Prof. Francisco Nart, in memoriam. 相似文献
17.
Self-assembled monolayer of 8-mercaptoquinoline (MQ) on the surface of gold from MQ dilute ethanolic solutions is investigated by electrochemical methods. Some aqueous redox probes, such as ferrocene carboxylic acid and Fe(CN)6
4–/3– can sufficiently diffuse into the monolayer because significant diffusion-limited current peaks are observed when the redox reactions take place, showing that the monolayer is very loosely packed or dominated by defects. However, the study on the electron transfer of other aqueous probes, such as Cu2+ and Ru(NH3)6
3+/2+, confirm that the monolayer can block the electron transfer on the gold electrode surface rather effectively for its low ratio of pinhole defects. These studies show that the MQ monolayer on the electrode can provide an excellent barrier for penetration of some probes but cannot resist the penetration of other probes effectively. The unusual properties of the self-assembled monolayers are attributed to the entity of the very large heterocyclic moiety. 相似文献
18.
Krisztina Kurin-Cs?rgei Viktor Horváth Miklós Orbán 《Reaction Kinetics and Catalysis Letters》2007,90(2):405-411
The BrO
3
−
— BrAc — Ru(bpy)
3
2+
subsystem is shown to represent the core oscillator that serves as source of the long lasting temporal and spatial periodic
behaviors observed in the BrO
3
−
— H2PO
2
−
— acetone — Mn2+ — Ru(bpy)
3
2+
— acid “double substrate-double catalyst” oscillatory batch system. The BrAc — the substrate of the core oscillator — is
formed and accumulated in the reactions taking place in the six-component system. BrAc was produced in a separate experiment
with bromide, acetone, acid and excess bromate and the mixture was used for bringing about patterns in the thin solution layer
after adding the Ru(bpy)
3
2+
catalyst. The two-dimensional reaction-diffusion patterns that appear in the subsystem and its parent system are very similar
in wave speed, wavelength, color and in the duration of the pattern evolution, therefore a common chemical origin is supposed
to exist in their formation. The role that the BrAc may play in the mechanism of the BrO
3
−
— reductant — acetone — catalyst type oscillators (∼ 30 variants) is also pointed out. 相似文献
19.
Haijuan Wang Wansheng You Bifang Meng Xianfeng Sun Hongwei Cheng Wenjuan Shan 《Journal of Cluster Science》2010,21(4):857-865
A new complex based on monosubstituted Keggin anions, formulated as [Hpy]2{[Co(4,4′-Hbpy)2(H2O)2][SiCoW11O39]} 1, was hydrothermally synthesized and structurally characterized by elemental analysis, single-crystal X-ray diffraction, IR,
XRD and TG. Complex 1 exhibits a 2D layered structure constructed by bridging {SiCoW11O39}n6n− chains via [Co(4,4′-Hbpy)2(H2O)2]4+ fragments. The electrocatalysis of 1-CPEs (carbon paste electrodes) was performed in 0.5 M sodium acetate buffer (pH 4.5) containing 1 mM [Ru(bpy)3]2+ solution. It is found that 1-CPEs are active to the electrocatalytic redox of [Ru(bpy)3]3+/[Ru(bpy)3]2+ and the electrocatalytic oxidation of H2O into O2. 相似文献
20.
Marko Kullapere Margus Marandi Leonard Matisen Fakhradin Mirkhalaf Adriana E. Carvalho Gilberto Maia V?ino Sammelselg Kaido Tammeveski 《Journal of Solid State Electrochemistry》2012,16(2):569-578
The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The
electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium
salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz
crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl
groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the
Fe(CN)63−/4− redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode
results. 相似文献