Selective detection of dopamine using a functionalised polyaniline composite electrode

The behaviour of a poly (aniline boronic acid) (PABA) modified glassy carbon electrode (GCE) for the detection of dopamine (DA) in the presence of excess of ascorbic acid (AA) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques is investigated. On bare GCE, both DA and AA are oxidized at ~0.16 V, whereas on PABA modified GCE they are oxidized at 0.2 and 0.054 V, respectively. Though PABA favours DA oxidation through ester formation with boronic acid motif, the AA oxidation is also promoted by polyaniline backbone through the involvement of AA in the redox of polyaniline. Since both DA and AA undergo oxidation at closely spaced potentials at a PABA electrode, Nafion®-incorporation into the PABA film was examined for selective determination of DA in the presence of AA. The selectivity was due to accumulation of DA on the electrode surface through ester formation with the boronic acid group and suppression of AA oxidative current through charge discrimination by Nafion.     

The electrochemical behavior of erythromycin A on a gold electrode

The reactivity of erythromycin (pure) was investigated on a gold electrode in neutral electrolyte by cyclic voltammetry. The resulting structural changes were observed with HPLC and FTIR spectroscopy by analyzing the bulk electrolyte after the electrochemical reactions. The results were compared with those previously obtained for azithromycin and clarithromycin under the same experimental conditions. It was found that the electrochemical behavior of erythromycin A differs from that of azithromycin dihydrate. Comparison with the electrochemical activity of basic clarithromycin suggests that the electrochemical activity of erythromycin is similar but more pronounced than that of clarithromycin.HPLC analysis confirmed these observations and showed that during the electrochemical oxidation of erythromycin A, the amount of starting macrolide decreased while the amount of starting impurities increased. Also some new products were observed. FTIR spectroscopy confirmed that erythromycin A is more reactive than clarithromycin, although similar changes in their molecular structures were observed.     

Electrochemical sensor applications of Pt supported porous gold electrode prepared using cellulose-filter

A facile and rapid method for the synthesis of porous gold (PAu) electrodes on cellulose-filters is proposed. Morphology and active surface area of the electrode greatly influence the electrochemical properties of sensor. Compared to smooth electrode and glassy carbon, PAu and Pt/PAu electrode showed high roughness due to porous structure, which is helpful in electrochemical sensing of target molecules. The electrochemical sensing performance of Pt/PAu electrode was evaluated to detect hydrogen peroxide, glucose, and perchloric acid. The amperometric results with various concentrations of target molecules showed potential applications of Pt/PAu electrode in sensitive and effective chemical sensors.     

Recovery of CO2 from flue gas using an electrochemical membrane

A novel process has been designed for the economic production of very pure carbon dioxide from flue gas. Using a molten carbonate fuel cell stack as an electrically-driven membrane concentrator, a portion of the carbon dioxide in the flue gas, along with some oxygen, is emitted as a product stream. The oxygen is recycled to enrich the flue gas entering the concentrator. Preliminary economics appear favorable, with carbon dioxide produced at $21 per ton, this product is, however, in a binary mixture with oxygen and must be separated for final use, this mixture is suitable for standard means of separation. The cost is sensitive to the cost of electricity and the installed cost of the fuel-cell stack, as can be seen in Table 1. The projected cost, however, is significantly below the typical $70 per ton sales price for carbon dioxide, so that the process could be viable at higher electricity and equipment charges.     

乙炔黑/双十六烷基磷酸复合膜传感器测定环境水样中痕量铜

报道了一种用乙炔黑(AB)/双十六烷基磷酸(DHP)复合膜修饰的电化学传感器,该传感器能高灵敏度测定水样中痕量的Cu~(2 )。在pH值为4.5的磷酸盐缓冲溶液中,于-0.08V(vs.SCE)处有一灵敏的氧化峰。该修饰电极测定Cu~(2 )的线性范围为8×10~(-9)～5×10~(-7)mol·L~(-1),富集300s检测限为3×10~(-10)mol·L~(-1)。用该修饰电极测定了环境水样中的Cu~(2 ),其结果与原子吸收测定值相符。     

Electrochemical fabrication and electrocatalytic characteristics studies of gold nanopillar array electrode (AuNPE) for development of a novel electrochemical sensor

Gold nanopillar array electrodes were prepared by electrochemical deposition of gold into the nanopores of anodic aluminum oxide membrane placed onto the gold thin film electrode surface, which was in advance modified with cysteamine self-assembled monolayer as an anchoring layer. The Au nanopillar electrode is electrochemically stable and consists of highly dense, upstanding pillars assembled on the cysteamine monolayer. The structural morphology and chemical composition of the nanoarray electrode was characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Electrochemical measurements indicate that the Au nanopillar electrode possesses high electrocatalytic activities in the reduction of hydrogen peroxide and molecular oxygen, especially in glucose oxidation due to its higher electroactive surface area. The electro-oxidation studies of several electroactive neurotransmitters demonstrate that the nanopillar electrode can be utilized as a promising material for the construction of novel electrochemical sensor.     

The electrochemical behaviour of an exfoliated graphite electrode in simulated seawater containing oil

An exfoliated graphite (EG) electrode was prepared and the electrochemical response to oil in simulated seawater was studied by means of the potential step technique and electrochemical impedance spectroscopy (EIS). The capacitance and other electrochemical characteristics of the electrode were affected by the presence of oil. The effects of temperature and salinity on the electrochemical behaviour of the EG electrode in NaCl solution containing oil were investigated by EIS. The results showed that the higher the temperature or the salinity, the higher the double layer capacitance of the electrode.     

Amperometric detection of acetaminophen by an electrochemical sensor based on cobalt oxide nanoparticles in a flow injection system

This paper reports the use of a carbon ceramic electrode as a highly-porous substrate for the electrochemical formation of cobalt oxide nanoparticles. The electrocatalyst was characterized by energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry techniques, and it was used in a homemade flow injection analysis (FIA) system for acetaminophen determination using 0.1 M KOH as the carrier solution. The rate constant (k_s) and charge transfer coefficient (α) were calculated for the electron exchange reaction of the modified film. The kinetic parameters and the mechanism of acetaminophen electrooxidation at the electrode surface were studied by cyclic voltammetry and chronoamperometry. The effects of working potential and flow rate on the performance of the FIA system were studied. Under optimized conditions, the electrode response due to the electrocatalytic oxidation of acetaminophen at 450 mV (vs. SCE) is proportional to the concentration of acetaminophen over a 5-35 μM range with an associated detection limit (S/N = 3) of 0.37 μM and a sensitivity of 0.0296 μA/μM. The relative standard deviation (RSD) was 1.6% for eight replicate measurements. The modified electrode was used to determine the acetaminophen content in tablet samples.     

Analyzing the electroactive surface of gold nanopillars by electrochemical methods for electrode miniaturization

Nanostructured surfaces have recently gained in importance for electrochemical applications because of an enhanced surface area compared to planar substrates. Due to this property, structured substrates are well suited for electrochemical (bio-)sensors, capacitive coupling with electrogenic cells, and other bioelectronic applications. However, the relationship between electrolytically exposed and redox-active surface areas of nanostructured electrodes compared to planar electrodes is still under discussion. Here, we performed a series of comparative studies to elucidate processes taking place at the electrochemically active surface of gold nanopillars. The pillars, approximately 200 nm in height and 50 nm in diameter, were fabricated using template-assisted nanostructuring. The surface area increase compared to planar electrodes was determined by scanning electron microscopy (SEM), and the redox-active surface area of the same sample was derived from cyclovoltammetric studies. We found consistency between the SEM results and the electrochemically active surfaces determined by cyclic voltammetry of immobilized ferrocenylhexanethiol, immobilized cytochrome c, and oxidation/reduction of gold for small scan rates. Similar values were derived from the capacitance measured by cyclic voltammetry, whereas impedimetric measurements revealed values twice as high. Commonly used diffusion-controlled systems, such as hexacyanoferrate, showed a smaller increase of the electroactive surface area. Finally, we conclude that the sterically restricted diffusion of redox-active species leads to an inaccurate determination of the electroactive surface area of nanosized electrodes.     

Highly sensitive electrochemical determination of nitric oxide using fused spherical gold nanoparticles modified ITO electrode

This paper describes the highly sensitive electrochemical determination of nitric oxide (NO) using the fused spherical gold nanoparticles (FAuNPs) modified ITO electrode. The FAuNPs were self-assembled on a (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film, which was preassembled on ITO electrode. The attachment of FAuNPs on MPTS sol-gel film was confirmed by UV-vis absorption spectroscopy, atomic force microscopy (AFM) and cyclic voltammetry (CV). The AFM image shows that the AuNPs retain their fused morphology after immobilized on MPTS sol-gel film. The FAuNPs modified ITO electrode shows an excellent electrocatalytic activity towards the oxidation of NO. Using FAuNPs modified electrode, the detection of 12 nM NO was achieved for the first time by amperometry method. Further, the current response was increased linearly with increasing NO concentration in the range of 1.2 × 10⁻⁸ to 7 × 10⁻⁴ M and the detection limit was found to be 3.1 × 10⁻¹⁰ M (S/N = 3). The FAuNPs modified ITO electrode displays an excellent selectivity towards the determination of 12 nM NO even in the presence of 1000-fold excess common interfering agents.     

An electrochemical and SERS study of benzyldimethylphenylammonium chloride at a polycrystalline gold electrode

The adsorption behaviour of benzyldimethylphenylammonium chloride (BDMPAC) on polycrystalline gold has been investigated by means of dc (cyclic voltammetry) and ac electrochemical techniques (differential capacitance (DC), electrochemical impedance spectroscopy) and in-situ vibrational spectroscopy (surface enhanced Raman spectroscopy (SERS)). The adsorption of this quaternary ammonium salt is found to be mediated by specifically adsorbed chloride ions in the potential domain positive to the pzc; when chloride ions are expelled from the compact layer out of electrostatic reasons, BDMPAC adsorbs interacting directly with the metal surface through one of its aromatic rings. In accordance with the DC results, SERS show a reorientation of the molecule around −200 mV versus Ag/AgCl.     

The electrochemical behavior of an enzyme biosensor electrode using an oxyfluorinated pitch-based carbon

A glucose sensor electrode was prepared by thermally treating a pitch-based carbon material. Oxyfluorination was used to modify the surface of the prepared carbon to induce the formation of hydrophilic functional groups. A glucose oxidase enzyme was effectively loaded onto the surface of the oxyfluorinated carbon and was more sensitive in glucose sensing because of the effects of the improved interfacial affinity between the electrode and the glucose oxidase. The introduced hydrophilic functional groups were examined using XPS analysis. In current–voltage measurements, a higher current was observed in the samples prepared with a higher oxygen content. In addition, a clear redox peak was observed in the surface modified samples. These results can be attributed to efficient electrical resistance measurement by easy electron transfer during glucose sensing. An efficient glucose sensor electrode was prepared using pitch-based carbon, which has beneficial electrical properties, and oxyfluorination, which improves the surface interface.     

Molecularly imprinted electrochemical sensor for the determination of ampicillin based on a gold nanoparticle and multiwalled carbon nanotube‐coated pt electrode

A novel molecularly imprinted electrochemical sensor was developed for the sensitive and selective determination of ampicillin (AMP). The sensor was prepared on a platinum electrode modified with multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), and a thin film of molecularly imprinted polymers (MIPs). MWCNTs and AuNPs were introduced to enhance the sensor's electronic transmission and sensitivity. The molecularly imprinted polymer (MIP) was synthesized using AMP as the template molecule, methacrylic acid as functional monomer, and ethylene glycol maleic rosinate acrylate (EGMRA) as cross‐linker. The performance of the proposed imprinted sensor was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results showed that the imprinted film displayed a fast and sensitive response to AMP. Under optimal conditions, response peak current had a linear relationship with the concentration of AMP in the range of 1.0 × 10^?8 mol/L to 5.0 × 10^?6 mol/L and a detection limit of 1.0 × 10^?9 mol/L (S/N = 3). This imprinted sensor was used to detect AMP in food samples with recoveries of 91.4–105%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40613.     

乙炔气柜改氢气柜总结

介绍了将干法乙炔生产装置闲置的乙炔气柜改造成氢气柜的实施过程,包括参数计算、设备配置、控制系统、系统调试及注意事项。     

In situ detection and removal of metal ion by porous gold electrode

A sensing electrode for the detection of heavy metal ions in aqueous solution selectively measured the concentrations of target materials on its functionalized surface, which has affinity to target metal ions. Target ions were adsorbed simultaneously on the functionalized electrode during the sensing process. Therefore, to understand this, experiments on the amperometric response and isotherms with an initial concentration of Hg²⁺ were tested. Detection current was dependent on the concentration of Hg²⁺, and the equilibrium concentration of Hg²⁺ adsorbed to the electrode showed a Langmuirian shape. Correlation between the detection current and removal capacity for Hg²⁺ revealed that it is possible to estimate the adsorbed concentration on the electrode during the sensing step. Although the macroporous gold electrode prepared herein showed relatively low adsorption performance compared to conventional adsorbents, when we prepare nanoporous gold electrodes with a uniform nanopore structure and large surface area, in situ detection and simultaneously removal of metal ions by nanoporous gold electrode will be possible.     

浓硫酸清净粗乙炔气工艺

介绍了用浓硫酸清净粗乙炔气工艺的原理、流程及相关要点。采用浓硫酸清净工艺,1tPVC消耗浓硫酸约17kg;采用NaClO清净工艺,1tPVC消耗NaClO约30k昏工业水约270kg。     

Wire-beam electrode: a new tool for investigating electrochemical inhomogeneity of oil coatings

The wire-beam electrode, a new type of electrode, was developed as a new tool for investigating electrochemical inhomogeneity of temporarily protective oil coatings. The feasibility of using a wire-beam electrode in studies of electrochemical inhomogeneity of temporarily protective oil coating is presented in this paper. Structure parameters of wire-beam electrodes such as the central distance of the adjacent wire pair, the diameter of the wire, the number of wires, etc., and their effect on the study of electrochemical inhomogeneity of temporarily protective oil coatings are discussed in this paper. It is suggested that the wire-beam electrode is a suitable tool for investigating electrochemical inhomogeneity of temporarily protective oil coatings.     

Characterization of a carbon composite electrode for an electrochemical immunosensor

A bioactive platform with a carbon composite electrode was developed for rapid detection of Escherichia coli O157:H7. The porous carbon composite electrode was prepared by a sol-gel method with a mixture of graphite powder and tetraethyl orthosilicate/ethanol. Escherichia coli O157:H7 antibodies were physically adsorbed onto the carbon composite electrode. Direct measurements by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of [Fe(CN)₆]^3−/4− as a redox probe showed that the immobilization of antibodies onto the carbon composite electrode surface and the binding of Escherichia coli O157:H7 cells with antibodies systematically increased the electron-transfer resistance. Those results suggest that a sol-gel derived graphite composite electrode might be utilized as a label-free electrochemical immunosensor for diagnosis, biochemical research, food industry, and so on.     

Development of a disposable sensor for electrocatalytic detection of guanine and ss-DNA using a modified sol-gel screen-printed carbon electrode

The electrocatalytic oxidation of guanine and DNA is demonstrated on a sol-gel coated carbon screen printed electrode modified with {MeReO(edt)}₂ using cyclic and differential pulse voltammetric techniques. An oxidation peak at 370 mV was found, but no corresponding reduction peaks could be detected in the negative scan, which indicates that the oxidation of guanine is completely irreversible process. The oxidation peak potentials are shifted to more negative values with increasing pH. The utility of applying the sensor for determination of guanine and ss-DNA were investigated. The linear ranges were 0.19-10.8 and 0.45-7.8 μg ml⁻¹ for guanine and DNA, respectively. Detection limits of 0.1 and 0.32 μg ml⁻¹ were obtained for guanine and ss-DNA, respectively.