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1.
Iridium oxide film modified microelectrode was fabricated by anodic oxidation method onto the tip of an etched iridium wire in diluted sulfuric acid solution by cyclic voltammetry. The iridium oxide film microelectrode exhibited very promising pH sensing performance, with an ideal Nernstian in the tested pH range of 0 to 14. This method for preparing microelectrode allowed accurately control of the deposited amount and the rate of the iridium oxide film growth. The electrodes demonstrated advantages of long lifetime, good selectivity and fast response with a relative time less than 0.2 s for pH changes in a large scale. The microelectrode was not interfered by a wide variety of inorganic ions and organic compounds. Furthermore, the electrodes were successfully applied to the measurement of pH in microscale of apples. 相似文献
2.
In this work, a new approach named “capillary melt method” was developed to fabricate micro antimony wires, and the wire surface was then oxidized in a nitrate melt at high temperature to obtain an antimony/antimony oxide pH electrode. Characterization results show that the oxide layer on the wire surface is porous, and consists of Sb 2O 3 crystal phase. The pH electrode, made using this method, showed good sensing performance in buffer solutions in the tested pH range of 2–12. Its EMF signal was found to have a linear relationship with pH value of the solution, with a sensitivity of 54.1 mV/pH and a fitting correlation coefficient of R2=1.00. The advantages of the electrode are long‐term stability, fast response, reproducibility and low cost. 相似文献
3.
Abstract Iridium oxide film modified microelectrode with a tip diameter of 25 µm was constructed using anodically grown iridium oxide film. The iridium oxide film, which was formed at the tip of the iridium wire by cyclic voltammetry in dilute sulfuric acid, showed excellent catalytic activity towards the oxidation of epinephrine. The stability and electrochemical properties of iridium oxide film modified microelectrode along with catalytic oxidation of epinephrine was studied. An oxidation peak was observed at 0.28 V. The electron‐transfer number ( n) was 2. The iridium oxide film modified microelectrode was used as a detector in flow injection system for determination of epinephrine. Under the optimized conditions, the calibration curve was linear in the concentration range of 1.0×10 ?8 to 1.0×10 ?5 mol/l for epinephrine, with a detection limit of 1.0×10 ?9 mol/l. The iridium oxide film modified microelectrode was used for direct determination of the epinephrine in human serum samples. The flow injection analysis was precise detection method of epinephrine and time saving device. 相似文献
4.
Iridium oxide films (IROFs) are known to have an enhanced or the so‐called super‐Nernstian (<59 mV/pH) pH‐sensitivity. The intention in the present study was to find out the reasons of such behavior and also to elucidate the nature of iridium anodic oxidation processes. The methods employed were combined cyclic voltammetry and chronopotentiometry. Iridium layers of 0.1 to 0.2 μm thickness, deposited thermally on titanium or gold‐plated titanium substrates, were used for investigations. IROFs on the surface of working electrodes were formed anodically by applying a constant potential in deaerated and oxygen‐containing solutions of 0.5 M H 2SO 4, 0.1 M KOH and 0.5 M H 3PO 4+KOH. Linear pH‐dependences of the stationary open‐circuit potential with the slopes close to 59 mV/pH were found for iridium electrode oxidized at 0.4 V–0.8 V (RHE) in deaerated and at 0.8 V–1.2 V (RHE) in O 2‐containing solutions. They were attributed to reversible Ir/Ir(OH) 3 and Ir/ IrO 2? nH 2O metal‐oxide electrodes, respectively. It has been suggested that the main current peaks seen in the voltammograms of iridium electrode in acid and alkaline solutions are of different nature. The difference between iridium electrode surface states in acid and alkaline solutions has been presumed to be the main reason of super‐Nernstian pH‐sensitivity of the IROFs. On the basis of the results obtained standard potential of Ir/Ir(OH) 3 electrode and the solubility product of Ir(OH) 3 have been evaluated: =0.78±0.02 V and Ksp=3.3×10 ?64. 相似文献
5.
Iridium oxide (IrOx) films formed electrochemically on the surface boron doped diamond electrode by potential cycling in the range −0.2 to 1.2 V from a saturated solution of alkaline iridium(III) solution. A strongly adherent deposit of iridium oxide is formed after 5–10 potential scans. The properties, stability and electrochemical behavior of iridium oxide layers were investigated by atomic force microscopy and cyclic voltammetry. The boron doped diamond (BDD) electrode modified with electrodeposition of a thin film, exhibited an excellent catalytic activity for oxidation of Hg(I) over a wide pH range. The modified electrode shows excellent analytical performance for Hg(I) amperometric detection. The detection limit, sensitivity, response time and dynamic concentration ranges are 3.2 nM, 77 nA μM −1, 100 ms and 5 nM–5 μM. These analytical parameters compare favorably with those obtained with modern analytical techniques and recently published electrochemical methods. 相似文献
6.
Platinum oxide electrode, as an important part of hydrogen concentration monitoring sensor built in containment, needs to withstand extreme conditions such as high temperature, high humidity, and high irradiation and can still work normally even in the case of serious accidents, which puts forward higher requirements for its performance. In present study, platinum oxide film electrode was successfully prepared with three-dimensional nano-dendritic, uniform, and crack-free on platinum substrate by reactive magnetron sputtering, and the influence of different substrate temperature and sputtering atmosphere on the composition, morphology, and electrocatalytic property of the film was investigated. The results show that platinum oxide film is composed of PtO and PtO 2. As the temperature increases from room temperature (RT) to 200°C, the oxygen vacancies in the amorphous film are gradually repaired and convert to the crystalline state, which shows increasing PtO 2 ratio, increasing electrochemical active area (ECSA), and improved stability. When the temperature is rising to 400°C, the film shows decreasing oxygen vacancies, increasing average grain size. Because PtO 2 decomposes into PtO and Pt, and thus ECSA decreases, the stability and oxygen reduction activity of the films decreases gradually. At the same temperature, the crystalline film obtained in Ar/50%O 2 has higher concentration of oxygen vacancies and smaller average grain size than that obtained in O 2, resulting in larger ECSA and relatively good stability. By contrast, the platinum oxide film electrode prepared in Ar/50%O 2 and 200°C has better stability and excellent electrocatalytic activity for oxygen reduction. 相似文献
7.
A solid‐state pH sensor was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. The sensor slope was found to increase as the temperature of the solution was increased. The performance of the sensor was investigated in the pH range from 2.2 to 11.19. The E‐pH curve is linear with slope of 0.054 V at 298.15 K. This value is closed to the theoretical value 2.303RT/F (0.059 V at 298.15). The standard potential of this electrode, E°, is computed as 177.58 mV with respect to the SCE as reference electrode. Results obtained by the suggested sensor compares very well with conventional pH electrodes where the square of the correlation coefficient was 0.998. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten NaNO 3. K 2Cr 2O 7 was potentiometrically titrated with Na 2O 2 and K 2CO 3 as titrants in molten NaNO 3 at 350°C, using the above mentioned indicator electrodes. An acidity/basicity scale of the oxyanions was established in molten NaNO 3 at 350°C. 相似文献
8.
The new iridium oxide film electrode, applied for the determination of lead(II), cadmium(II) and copper(II) traces using differential pulse anodic stripping voltammetry (DP ASV) is presented. The electrode display an interesting stripping voltammetric performance which compares with electrodes commonly used in voltammetry. The deposited film is known as anodically electrodeposited iridium oxide film (AEIROF). The AEIROF electrode is characterized by long‐term stability (more than 40 days) and very good reproducibility of the analytical signals in this time (≤12% for 0.5 μM of lead). The regeneration of iridium film is very simple in a time shorter than 60 seconds. The effects of various factors such as: thickness of AEIROF film, preconcentration potential and time, supporting electrolyte composition, potential interferences are optimized. The detection limit for AEIROF film electrode based on glassy carbon for an accumulation time of 30 s is as low as 7 nM for lead(II). The repeatability of the method at a concentration level of the lead(II) as low as 0.5 μM, expressed as RSD is 2.5% ( n=10). The proposed method was successfully applied and validated by studying certified reference material CTA‐OTL‐1. Such an attractive use of ‘mercury–free’ ‐ environmentally friendly electrodes offers great promise to measure trace metals. 相似文献
9.
In this work, the polymeric precursor method was used to prepare low-cost solid-state sensors for pH determination based on iridium oxide as the main pH sensitive material. The iridium content was reduced with addition of TiO 2, forming the binary system IrO x–TiO 2, whose electroanalytical properties were evaluated in comparison with a commercial glass pH electrode. The minimum iridium content which gave suitable results was 30 mol%, and the electrode presented Nernstian and fast response in the pH range from 1 to 13, with no hysteresis effect observed. Besides, the electrode showed high selectivity in the presence of alkali ions as Li +, Na + or K +. The amount of iridium in the prepared electrodes was very small (<0.1 mg), supporting the efficiency of this method on the simple preparation of functional low-cost pH electrodes. 相似文献
10.
The use of a zinc substrate as an electrode and the modification of its surface by means of a thin film of platinum-doped nickel hexacyanoferrate (Pt-NiHCF) were developed. The modification conditions of the zinc surface including the electroless deposition of metallic nickel on the electrode surface from NiCl 2 solution, chemical derivatization of the deposited nickel to the NiHCF film in 0.5 M K 3[Fe(CN) 6] solution, and electrochemical penetration of metallic platinum into the modified film are described. The modified zinc electrodes prepared under optimum conditions show a well-defined redox couple due to the [Ni IIFe III/II(CN) 6] 1–/2–
system. The effects of pH, the alkali metal cation, and the anion of the supporting electrolyte on the electrochemical characteristics of the modified electrode were studied in detail. The diffusion coefficients of hydrated alkali metal cations in the film ( D), the transfer coefficient ( ), and the transfer rate constant for the electron ( ks) were calculated in the presence of some alkali metal cations. The electrocatalytic activity of the modified electrode for methanol oxidation was demonstrated. The stability of the modified electrode under various experimental conditions was investigated. 相似文献
11.
Mesoporous TiO 2 (m-TiO 2) nanoparticles were used to prepare the porous film electrodes for dye-sensitized solar cells, and a second metal oxide (MgO, ZnO, Al 2O 3, or NiO) modifi-cation was carried out by dipping the m-TiO 2 electrode into their respective nitrate solution followed by annealing at 500 oC. Experimental results indicated that the above second metal oxide modifications on m-TiO 2 electrode are shown in all cases to act as barrier layer for the interfacial charge transfer processes, but film electron transport and interfacial charge recombination characteristics under applied bias voltage were dependent significantly on the existing states and kinds of these second metal oxides. Those changes based on sec-ond metal oxide modifications showed good correlation with the current-voltage analyses of dye-sensitized solar cell, and all modifications were found to increase the open-circuit photo-voltage in various degrees, while the MgO, ZnO, and NiO modifications result in 23%, 13%, and 6% improvement in cell conversion efficiency, respectively. The above observations indi-cate that controlling the charge transport and recombination is very important to improve the photovoltaic performance of TiO 2-based solar cell. 相似文献
12.
A solid‐state Glass/TiO 2 electrode was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten nitrate. NH 4VO 3, KH 2PO 4, K 2HPO 4, and their mixture were titrated with Na 2O 2 at 350°C using the glass/TiO 2 electrode in molten NaNO 3. 相似文献
13.
Direct anodic oxidation of perfluoroalkylvinyl ethers R FOCF=CF 2 (PVE) and terminal fluoroolefins R FCF=CF 2 (TFO) in fluorosulfonic acid is studied using cyclic voltammetry; electrolysis at a monitored potential; and analyses of synthesized products by 19F NMR, gas-liquid chromatography, and chromato-mass spectrometry, with simultaneous preparative isolation of the products. Proposals on some regularities of the direct oxidation of PVE and TFO are made. The corrosion behavior of platinum, iridium, and their alloys is studied. The formation of oxide films on various electrode materials and a fluorosulfate film on glassy carbon is found to correlate with catalytic activity in reactions of direct oxidation of perfluoroolefins. 相似文献
14.
A solid‐state glass/TiO 2 electrode was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten NaNO 3 · Na 2HAsO 4, NaPO 3, Na 4P 2O 7, and their binary mixtures were potentiometrically titrated with Na 2O 2 as titrants in molten NaNO 3 at 350°C, using the above mentioned indicator electrode. 相似文献
15.
Herein, a simplified fabrication method for the producing of a pH-sensitive iridium electrode is developed. The in situ electrochemical fabrication of an iridium oxide film is optimized and shown to be achievable under neutral conditions rather than the acidic conditions hitherto employed. The formation of a pH sensitive Ir(III/IV) hydrous film is confirmed via XPS. The amperometric pH-sensing properties of this electrochemically generated material were investigated using square wave voltammetry. In the pH range 2–13, the iridium oxide redox signal has a pH dependency of 86.1 ± 1.1 mV per pH unit for midpoint potentials with uncertainties being ± 0.01–0.05 pH. Finally, the newly developed pH sensor was used to measure the pH of a natural water sample with excellent results as compared to a conventional glass pH probe. 相似文献
16.
The application of nanocatalysis based on metal oxides for biomass conversion is of considerable interest in fundamental research and practical applications. New acidic transition‐metal oxide molecular wires were synthesized for the conversion of cellulosic biomass. The ultrafine molecular wires were constructed by repeating (NH 4) 2[XW 6O 21] (X=Te or Se) along the length, exhibiting diameters of only 1.2 nm. The nanowires dispersed in water and were observed using high‐angle annular dark‐field scanning transmission electron microscopy. Acid sites were created by calcination without collapse of the molecular wire structure. The acidic molecular wire exhibited high activity and stability and promoted the hydrolysis of the glycosidic bond. Various biomasses including cellulose were able to be converted to hexoses as main products. 相似文献
17.
Horseradish peroxidase (HRP) was immobilized into a new type of sol–gel-derived nano-sized tin oxide/gelatin composite film (SnO 2 composite film) using a sol–gel film/enzyme/sol–gel film “sandwich” configuration. Direct electrochemistry and electrocatalysis of HRP incorporated into the composite films were investigated. HRP/SnO 2 composite film exhibited a pair of stable and quasi-reversible cyclic voltammetric peaks for the HRP Fe(III)/HRP Fe(II) redox couple with a formal potential of about −0.25 V (vs. SCE) in a pH 6.0 phosphate buffer solution. The electron transfer between the enzyme and the underlying electrode was greatly enhanced in the microenvironment with nano-SnO 2 particles and nanoporous structures. Morphologies and microstructures of the composite films and HRP/composite films were characterized with TEM, AFM. Electrochemical impedance spectroscopy (EIS) was also used to feature the HRP incorporated into composite films. FTIR and UV–Vis spectroscopy demonstrated that HRP in the composite film could retain its native secondary structure. With the advantages of organic–inorganic hybrid materials, the HRP/SnO 2 composite film modified electrode displayed good stability and electrocatalytic activity to the reduction of H 2O 2, The apparent Michaelis-Menten constant was estimated to be 0.345 mM, indicating a high affinity of HRP entrapped into the composite film toward H 2O 2. 相似文献
18.
Stable metal clusters that can resist both highly concentrated acid and alkali are unknown. Herein, we present a discrete neutral cluster, Hf 13(μ 4‐O) 8(OCH 3) 36 ( 1 ), which features extraordinary chemical stability by preserving its crystalline state in concentrated aqueous solutions of both acid (10 m HNO 3) and alkali (20 m boiling NaOH). Importantly, 1 can serve as a luminescent probe for detecting both concentrated alkali (20 m NaOH) and strong acid (1 m HNO 3) with high selectivity and repeatability. DFT studies of the electronic structure and bonding revealed that 1 has an extremely large HOMO–LUMO gap due to strong d π–p π bonding that accounts for the ultrahigh stability. 相似文献
19.
Electropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta 2O 5) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (i d), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, i d = 10–20 mA cm ?2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta 2O 5 layers. The PPy film showed a high electrical conductivity (110 s cm ?1), adhered well and covered the Ta 2O 5 layer. The resulting PPy/Ta 2O 5/Ta system is therefore proved to have excellent properties as a capacitor. 相似文献
20.
Modification of an aluminum electrode by means of a thin film of cobalt hexacyanoferrate (CoHCF) using electroless and electrochemical
procedures is described. The modification conditions of the aluminum surface, including the electroless deposition of metallic
cobalt on the electrode surface from CoCl 2+NaF solution and the chemical derivatization of the deposited cobalt to give a CoHCF film in 0.25 M KCl+0.25 M K 3[Fe(CN) 6] solution, have been determined. The modified Al electrodes prepared under optimum conditions show one or two well-defined
redox couples in phosphate buffer solutions of pH 7.2, depending on the preparation procedure, due to the [Co IIFe III/II(CN) 6] –/2– system. The effect of pH, alkali metal cations, and anions of the supporting electrolyte on the electrochemical characteristics
of the modified electrode were studied. Diffusion coefficients of hydrated Na + in the film, the transfer coefficient, and the transfer rate constant for electrons were determined. The stability of the
modified electrodes under various experimental conditions was studied and their high stability in the sodium phosphate buffer
solutions was confirmed. Enhanced stability was observed when the modified electrode was scanned in fresh solutions of RuCl 3 between 0 and 1 V for at least 20 cycles, due to the formation of mixed hexacyanoferrates of cobalt and ruthenium.
Electronic Publication 相似文献
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