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1.
《Analytical letters》2012,45(11):1987-2002
Abstract A procedure for study of the effects of the temperature on the response of ion-selective electrodes in which isothermal hysteresis cum determined at several concentrations are used for obtaining the temperature variation parameters (isothermal slope and potential coefficients and isopotential points) is proposed. The procedure was tested against the classic procedure in which calibration curves are obtained at different temperatures. 'All -solid-state' Ag2S and Ag2S/Agl electrodes with sensors applied to silver- and copper-loaded epoxy supports (and commercial electrodes, for comparison) were used for this purpose. The values of the temperature parameters obtained by the two procedures (in the raw 10–60°C) are compared. This comparison show that the present procedure yields acceptable values of temperature parameters for cases like the studied where the hysteresis is not very produced. 相似文献
2.
For the purpose of employing an inexpensive alternative to conventional platinum for use by upper-division as well as graduate students, polyaniline (PANI)-deposited stainless steel (SS) and mild steel (MS) electrodes are described as indicator electrodes for potentiometry and potentiometric titrations of some redox reactions. PANI is deposited on the nonplatinum metal by electrochemical polymerization of aniline using cyclic voltammetric technique. Alternate methods to produce the PANI electrodes are also suggested. The electrodes respond to concentration changes of hydroquinone (H2O), Fe2+/Fe3+, and [Fe(CN)6]4–/[Fe(CN)6]3– in HCL electrolytes, and the potential variation with concentration follows the Nernst relationship. Under identical experimental conditions, the response time of the PANI/SS, PANI/MS, and Pt electrodes for a change in concentration of Fe3+ in a mixed electrolyte of Fe2+ and Fe3+ is found to be about 20 s. Neutralization reaction of HC1 versus NaOH, redox reaction of Fe2+ and Ce4+, and redox reaction of Fe2+ and KMnO4 in several concentrations in the range from 1 mM to 100 mM are carried out using the PANI/SS, PANI/MS, and Pt indicator electrodes. The performance of the PANI/SS and PANI/MS electrodes is as good as that of the Pt at all concentration levels of the titrations. The electrodes can be reused for several titrations by storing them in an acid electrolyte for a long period of time. Thus, the conventional inert Pt or Au can be substituted for by using a PANI-deposited nonplatinum reactive metal as a potentiometric sensor for redox titrations. 相似文献
3.
S. P. Kuksenko 《Russian Journal of Electrochemistry》2014,50(6):537-547
Comparative analysis of cycling performance of hybrid electrodes based on the MAG synthetic graphite mechanic mixtures with silicon nanopowder and “nano-Si/SiO2/hard carbon” ceramic frame-ordered composite in 1 M LiPF6 solution in a monofluoroethylene carbonate-ethyl methyl carbonate mixture (30: 70, v/v), added with 3 wt % vinylene carbonate and 2 wt % ethylene sulfite, is performed. The high capacity loading (up to 6.8 mA h cm?2 at the electrode layer thickness of 37 μm) and acceptable accumulated irreversible capacity of the composite-containing electrodes are achieved, due to the electrodes’ high density and stable silicon-containing electrode/electrolyte interface formation. 相似文献
4.
Remez I. D. Bogdanovich N. M. Terekhov V. I. Fadeev G. I. 《Russian Journal of Electrochemistry》2003,39(8):907-909
Measurements of steady-state potentials of various electrodes made of oxide compositions are performed in cells containing electrolyte ZrO2 + 10 mol % Y2O3 at a temperature of 773 K in nonequilibrium gas mixtures N2 + O2 + 20 vol % CO2 + CO, with variable CO (0.1–5 vol %) and O2 (0.5–10 vol %) contents. After adding CO into a gas phase, potentials of all electrodes shift, to one degree or another. The shift is substantially affected by the O2 content. The electrochemical systems under study are of some interest for analyzing partial pressures of CO in gas mixtures. The discovered effect must be taken into account when employing such electrodes for the determination of partial concentrations of other components of a gas mixture, for example, oxygen. 相似文献
5.
New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12 mm2, both electrodes are characterized by very good surface reproducibility (≤2%) and long‐term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1–2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16 ng L?1 to 4.8 μg L?1 for Hg(Cu)FE, and up to 6.4 μg L?1 for Hg(Ag)FE (tacc=15 s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60 s are as low as 14 ng L?1 for Hg(Cu)FE and 4 ng L?1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. 相似文献
6.
Nikola Markovi Felipe Conzuelo Julian Szczesny María Begoa GonzlezGarcía David HernndezSantos Adrian Ruff Wolfgang Schuhmann 《Electroanalysis》2019,31(2):217-221
We report a prototype air‐breathing carbon cloth‐based electrode that was fabricated starting from a commercially available screen‐printed electrode equipped with a transparent ITO working electrode (DropSens, ref. ITO10). The fabrication of the air‐breathing electrodes is straightforward, shows satisfactory reproducibility and a good electrochemical response as evaluated by means of [Fe(CN)6]3?/4? voltammetry. The gas‐diffusion electrodes were successfully modified with the O2 reducing enzyme bilirubin oxidase from Myrothecium verrucaria in a direct electron transfer regime. The enzyme modified electrodes showed a remarkable high current density for O2 reduction in passive air‐breathing mode of up to 5 mA cm?2. Moreover, the enzyme modified electrodes were applied as O2 reducing biocathodes in a glucose/air enzymatic biofuel cell in combination with a high current density glucose oxidase/redox polymer bioanode. The biofuel cell provides a high maximum power density of (0.34±0.02) mW cm?2 at 0.25 V. The straightforward design, low cost and the high reproducibility of these electrodes are considered as basis for standardized measurements under gas‐breathing conditions and for high throughput screening of gas converting (bio‐)catalysts. 相似文献
7.
Silver and gold electrodes are useful for the quantitative determination of lead and cadmium with subtractive anodic stripping voltammetry (SASV). The use of SASV is essential for achieving good separation between the two peaks, to eliminate the interference of nitrates when cadmium is present and to allow analysis at very low concentrations without the removal of oxygen. The deposition and dissolution of Pb2+ and Cd2+ proceed at underpotential (UPD) on both electrodes. The UPD properties of the deposits are the main factor determining the analytical characteristics of the ASV method and are strongly affected by the type and concentration of the electrolyte. The effects of anions (Cl−, Br−, SO42−, NO3−) and acids (HNO3, HClO4, H2SO4, HCl) are shown. The two electrodes complement each other and, in addition, enable the qualitative identification of Pb2+ and Cd2+, since the peaks appear in opposite order on the two electrodes. Analysis of mixtures of the two analytes is restricted on gold but not on silver. At gold the two peaks overlap: (i) at concentrations of cadmium higher than 250 nM at deposition times greater than 30 s, (ii) in the presence of copper at concentrations higher than 1 μM, and (iii) in the presence of Triton X-100 at concentrations above 10 mg/l. The repeatability at 10 nM analyte is better than 2.5%. The detection limits for Pb2+ and Cd2+ at 120 s deposition time and 3500 rpm rotation rate are: dlPb/Ag=0.04 nM; dlCd/Ag=0.7 nM; dlPb/Au=0.1 nM; dlCd/Au=0.3 nM. The analysis of lead and cadmium in natural waters has been performed. 相似文献
8.
Values for the mean stoichiometric activity coefficient of NaHS in the system NaHS?H2S?H2O are presented from 12 to 83°C for NaHS concentrations up to 0.2m and for H2S fugacities up to 1 atm. The measurements were made potentiometrically using a novel approach employing three commercially available specific ion electrodes (Na+ glass, H+ glass, and Ag2S) combined to form two cells without liquid junction. The results are described by the equation
t(°C) 相似文献
9.
《Electrochemistry communications》2007,9(5):1206-1211
Endotoxin can lead to irreversible shock and death, underlying the necessity for development of facile, rapid, sensitive and in situ methods to detect endotoxin. We used electrochemical impedance spectroscopy (EIS) to detect interaction of endotoxin with polymyxin B (PmB) immobilized on 4,4-dithiodibutyric acid coated gold electrodes. An equivalent circuit model with a constant phase element was used to interpret the obtained impedance spectra. The results indicated that the gold electrode after electrochemical polishing pretreatment in both 2-(N-Morpholino) ethanesulfonic acid (MES) and HClO4 solutions had a more effective surface state than that treated in H2SO4 solution. The changes in capacitance associated with a constant phase element on the PmB-modified electrodes were more sensitive, compared to those in the charge-transfer resistance, for detecting endotoxin over the 0.2–0.8 ng/mL concentrations. The activated and modified gold electrodes might be used to EIS detect endotoxin in real-time. 相似文献
10.
《Electroanalysis》2003,15(18):1437-1444
The detection of CO2 in the gas phase is possible in presence of oxygen with an amalgamated Au‐poly(tetrafluoroethylene) gas diffusion electrode and an internal electrolyte solution containing Ni(II)cyclam. For concentrations between 0.1 to 1% the electrochemical cell has a sensitivity of 3.58 mA %?1 and the detection limit is 500 ppm. In preliminary experiments at rotating disk electrodes the optimum pH‐range was found to be between 3.5 to 6 and a selectivity ratio of the catalyst for CO2/H+ of 5 : 1 could be determined. The relationship between reduction current and the square root of the angular speed is linear, indicating that the electrochemical process is limited by diffusion of CO2. Tl and Pb are presented as alternative electrode materials at which the Ni(II)cyclam catalyzed reduction of CO2 can be observed. Problems arise from fouling effects at the sensing electrode and a non‐linearity of the calibration plot at higher concentrations. 相似文献
11.
Novel polyvinyl chloride (PVC) membrane electrodes based on triheptyl dodecyl ammonium iodide have been developed. In the presence of 12.5 mM H2O2, these electrodes are capable of determining molybdate(VI) ion. The electrodes exhibit near-Nernstian responses over a wide concentration range (2.0 × 10−6 to 5.0 × 10−3 M). The proposed electrodes demonstrate satisfying selectivity for molybdate(VI) ion in the presence of a wide variety of anions other than iodide, and can be used in the pH range 5.0-7.0. Moreover, the electrodes show an average response time of 2-3 min and can be used over a period of 2 months without any significant deviation being observed. In the light of our results, the response mechanism of the electrode is discussed and HMoO2(O2)2− is suggested as the response ion. The proposed electrode has been used to measure molybdenum in ore samples, and the results were in agreement with those obtained by means of ICP analysis. 相似文献
12.
The present work reports the application of a new molybdenum disulphide (MoS2)-based electrochemical platform for highly sensitive quantitation of an iron-binding protein, bovine serum albumin (BSA). The gold screen-printed electrodes were modified with MoS2 nanoflakes, followed by bioconjugation with anti-BSA antibodies. Using the above bioelectrode, cyclic voltammetric analysis was carried out in the presence of a Fe3+/Fe2+ redox probe which exhibited a linear response of peak current with varying concentrations of BSA up to 10 ng/mL (with a detection limit of 0.006 ng/mL). This study is novel in that it shows a considerable enhancement of signal during electrochemical sensing of a protein. 相似文献
13.
Nanocrystalline Ni(OH)2 powder synthesized by a chemical precipitation method was processed using the planetary ball milling (PBM), and the physical
properties of both the ball-milled and unmilled Ni(OH)2 were characterized by scanning electron microscopy (SEM), specific surface area, particle size distribution, and X-ray diffraction.
It was found that the PBM processing could significantly break up the agglomeration, uniformize the particle size distribution,
increase the surface area, decrease the crystallite size, and reduce the crystallinity of nanocrystalline β-Ni(OH)2, which were advantageous to the improvement of the electrochemical activity of Ni(OH)2. The ball-milled nanocrystalline (BMN) Ni(OH)2 was then used to alter the microstructure of pasted nickel electrodes and improve the distribution of the active material
in the porous electrode substrate. Electrochemical performances of pasted nickel electrodes with a mixture of BMN and spherical
Ni(OH)2 as the active material were investigated, and were compared with those of pure spherical Ni(OH)2 electrodes. Charge/discharge tests showed that BMN Ni(OH)2 addition could enhance the charging efficiency, specific discharge capacity, discharge voltage, and high-rate capability
of pasted nickel electrodes. This performance improvement could be attributed to a more compact electrode microstructure,
better reaction reversibility, and lower electrochemical impedance, as indicated by SEM, cyclic voltammetry, and electrochemical
impedance spectroscopy. Thus, it was an effective method to modify the microstructure and improve the electrochemical properties
of pasted nickel electrodes by adding an appropriate amount of BMN Ni(OH)2 to spherical Ni(OH)2 as the active material. 相似文献
14.
S. V. Evdokimov 《Russian Journal of Electrochemistry》2000,36(3):236-239
The chlorine evolution kinetics are studied by taking steady-state polarization measurements on rotating disc electrodes (dimensionally
stable ones and those made of RuO2) in solutions with various chloride concentration, at various acidity and temperatures, at current densities of up to 4 A/cm2. At high temperatures and chloride concentrations, linear parts with an abnormally low slope of about 20 mV are observed
in anodic polarization curves. Their appearance is attributed to the chlorine reaction self-acceleration due to a change in
the chlorine mass transport mechanism in the anode’s porous coating. 相似文献
15.
Carmen I. Fort Mihai M. Rusu Liviu C. Cotet Adriana Vulpoi Ileana Florea Sandrine Tuseau-Nenez Monica Baia Mihaela Baibarac Lucian Baia 《Molecules (Basel, Switzerland)》2021,26(1)
Multifunctional Bi- and Fe-modified carbon xerogel composites (CXBiFe), with different Fe concentrations, were obtained by a resorcinol–formaldehyde sol–gel method, followed by drying in ambient conditions and pyrolysis treatment. The morphological and structural characterization performed by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption/desorption porosimetry, scanning electron microscopy (SEM) and scanning/transmission electron microscopy (STEM) analyses, indicates the formation of carbon-based nanocomposites with integrated Bi and Fe oxide nanoparticles. At higher Fe concentrations, Bi-Fe-O interactions lead to the formation of hybrid nanostructures and off-stoichiometric Bi2Fe4O9 mullite-like structures together with an excess of iron oxide nanoparticles. To examine the effect of the Fe content on the electrochemical performance of the CXBiFe composites, the obtained powders were initially dispersed in a chitosan solution and applied on the surface of glassy carbon electrodes. Then, the multifunctional character of the CXBiFe systems is assessed by involving the obtained modified electrodes for the detection of different analytes, such as biomarkers (hydrogen peroxide) and heavy metal ions (i.e., Pb2+). The achieved results indicate a drop in the detection limit for H2O2 as Fe content increases. Even though the current results suggest that the surface modifications of the Bi phase with Fe and O impurities lower Pb2+ detection efficiencies, Pb2+ sensing well below the admitted concentrations for drinkable water is also noticed. 相似文献
16.
通过电化学剥离法在石墨棒表面构筑了层数不等、彼此平行且垂直于基底的二维石墨纳米片(GNS)阵列, 而后采用阴极还原电沉积法在GNSs 表面均匀地包覆了一层氧化钌(RuO2·xH2O)薄膜, 形成了RuO2·xH2O/GNS 复合阵列电极. 电化学测试表明, RuO2·xH2O/GNS 复合阵列电极具有优良的超电容性能, 在0.5mol·L-1 H2SO4电解质溶液中, 扫描速率为5 mV·s-1, 电位窗口为0.9 V时, 其比电容高达4226 F·m-2, 并且具有优异的循环性能, 经过20000圈充放电循环后, 电容保持率高达94.18%. 相似文献
17.
Glassy carbon electrodes were modified electrochemically by pretreatment in sulfate, phosphate or carbonate solutions by means of cycling the potential well into the positive limit of the solvent. Electrodes treated in this manner were then used to incorporate and concentrate a variety of redox species that were either cations or aromatic containing compounds, including Ru(bpy)2+3, Ru(NH3)3+6, Cu(NH3)2+4, ferrocene, methylviologen, 1,4-benzoquinone, anthraquinone-2-sulfonate, riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Surface-equivalent concentrations ranged from 5 × 10?9 to 1 × 10?7 mol cm?2 for electrodes pretreated for 10 min in sulfuric acid. An E1/2 vs. pH study of 1,4-benzoquinone, riboflavin, FMN and FAD in modified electrodes shows that the pKa values shift toward higher pH (nearly 2 pH units). Results concerning the incorporation of redox compounds detected only by mediation with other electroactive complexes and the study of the modified electrodes in electrocatalysis are also discussed. 相似文献
18.
B. Hammouti H. Oudda A. El Maslout A. Benayada 《Analytical and bioanalytical chemistry》1999,365(4):310-313
A potentiometric method at imposed weak current between two paste electrodes, ferrocene and chloranil, permits the in situ determination of sulfuric acid concentrations (0.5–11.0 M). The different factors affecting the potential at imposed current
as current intensity, temperature and H+ ion concentration are studied. The potentials measured between ferrocene and chloranil electrodes are directly linked to
the acid concentration. The acidity Ri(H) function, which represents the determination of the H+ activity has been determined and compared to Strehlow Ro(H), Janata HGF and Hammet Ho functions. Ri(H) is numerically equal to the thermodynamic Ro(H).
Received: 19 October 1998 / Revised: 22 March 1999 / Accepted: 23 March 1999 相似文献
19.
B. Hammouti H. Oudda A. El Maslout A. Benayada 《Fresenius' Journal of Analytical Chemistry》1999,365(4):310-313
A potentiometric method at imposed weak current between two paste electrodes, ferrocene and chloranil, permits the in situ determination of sulfuric acid concentrations (0.5–11.0 M). The different factors affecting the potential at imposed current
as current intensity, temperature and H+ ion concentration are studied. The potentials measured between ferrocene and chloranil electrodes are directly linked to
the acid concentration. The acidity Ri(H) function, which represents the determination of the H+ activity has been determined and compared to Strehlow Ro(H), Janata HGF and Hammet Ho functions. Ri(H) is numerically equal to the thermodynamic Ro(H).
Received: 19 October 1998 / Revised: 22 March 1999 / Accepted: 23 March 1999 相似文献
20.
The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H2O2. The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (kapp) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT-MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H2O2 concentrations ranging from 1.0 to 30.0 μmol L−1. The values for the limit of detection (LoD) were found to be of the orders of 10−7 M using the 3δ for all the electrodes. The PA-SWCNT-MTAPc modified SPAuEs were much more sensitive compared to PA-MTAPc modified SPAuEs. 相似文献
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