Nanocomposite Carbon‐PDMS Material for Chip‐Based Electrochemical Detection

This paper presents an alternative approach to create low‐cost and patternable carbon electrodes suitable for microfluidic devices. The fabrication and the electrochemical performances of electrodes made of Polydimethylsiloxane doped with commercially available carbon black (C‐PDMS) are described. Conductivity and electrochemical measurements performed on various carbon to PDMS ratios showed that electrodes with suitable electrochemical properties were obtained with a ratio of 25 %.     

Some Electrochemical Characteristics of Boron‐ and Phosphorus‐Doped Glassy Carbon Electrodes

Three glassy carbon (GC) samples: undoped and doped with boron or phosphorus, prepared at 1000 °C, were compared in respect to hydrodynamic current‐potential curves in acidic medium, cyclic voltammograms for Fe^3+/2+ and Fe(CN)₆^3?/4? and argentometric titrations of halides. Some experiments were also carried out using standard Tokai and Sigri GC and Ag electrode. It appeared that GC doped with boron and phosphorus exhibited significant increase in hydrogen evolution overpotential. As for the electrode kinetics (ΔE_p criterion), no significant difference was observed between doped and undoped electrodes. In the potentiometric titrations the phosphorus‐doped electrode was advantageous over the other GC and Ag electrodes as it enabled more precise end‐point detection.     

Electrochemical Behaviour of Carbamazepine in Acetonitrile and Dimethylformamide Using Glassy Carbon Electrodes and Microelectrodes

The electrochemical reduction of carbamazepine in acetonitrile (ACN) and dimethylformamide (DMF) using a glassy carbon electrode and microelectrodes has been studied. The reduction process is consistent with an electrochemical‐chemical mechanism (EC) involving a two electron transfer followed by a first order reaction, as shown by the cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Half‐wave potential, number of electron transferred, diffusion coefficient and rate constant of the associated chemical reaction are reported. Limits of detection (LOD) for DPV are 0.92 and 0.76 µg mL^?1 (3.89×10^?6 mol L^?1 and 3.21×10^?6 mol L^?1) in ACN and DMF, respectively. Precision (%RSD) and recovery (%) values when pharmaceutical compounds (200mg carbamazepine tablets) and spiked plasma samples were tested ranged from 1.09 to 9.04 % and % recoveries ranged from 96 to 104.1 %.     

Sensitive Voltammetric Response of p‐Nitroaniline on Single‐Wall Carbon Nanotube‐Ionic Liquid Gel Modified Glassy Carbon Electrodes

An ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexafluorophosphate, BMIMPF₆)‐single‐walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF₆‐SWNT/GCE) is fabricated. At it the voltammetric behavior and determination of p‐nitroaniline (PNA) is explored. PNA can exhibit a sensitive cathodic peak at ?0.70 V (vs. SCE) in pH 7.0 phosphate buffer solution on the electrode, resulting from the irreversible reduction of PNA. Under the optimized conditions, the peak current is linear to PNA concentration over the range of 1.0×10^?8–7.0×10^?6 M, and the detection limit is 8.0×10^?9 M. The electrode can be regenerated by successive potential scan in a blank solution for about 5 times and exhibits good reproducibility. Meanwhile, the feasibility to determine other nitroaromatic compounds (NACs) with the modified electrode is also tested. It is found that the NACs studied (i.e., p‐nitroaniline, p‐nitrophenol, o‐nitrophenol, m‐nitrophenol, p‐nitrobenzoic acid, and nitrobenzene) can all cause sensitive cathodic peaks under the conditions, but their peak potentials and peak currents are different to some extent. Their peak currents and concentrations show linear relationships in concentration ranges with about 3 orders of magnitude. The detection limits are 8.0×10^?9 M for p‐nitroaniline, 2.0×10^?9 M for p‐nitrophenol, 5.0×10^?9 M for o‐nitrophenol, 5.0×10^?9 M for m‐nitrophenol, 2.0×10^?8 M for p‐nitrobenzoic acid and 8.0×10^?9 M for nitrobenzene respectively. The BMIMPF₆‐SWNT/GCE is applied to the determination of NACs in lake water.     

Carbon Black‐Modified Electrodes as Sensitive Tools for the Electrochemical Detection of Nitrite and Nitrate

Both screen‐printed electrodes modified with a dispersion of carbon black (CB) and solid paste electrodes prepared using a nanostructured CB were developed and characterized. Indeed, increasing the peak currents and/or their shifting to negative potentials were observed, exhibiting efficient electrocatalytic activity towards nitrite oxidation with high sensitivity and low detection limit. Solid carbon paste electrodes (SCPEs) and solid carbon black paste electrodes (SCBPEs) were challenged in amperometric mode with nitrite since detection limit reached is 65 and 5 nM respectively. Nitrate was first reduced to nitrite in reductor column, then detected on SCBPEs. Nitrate and nitrite were determined in real samples.     

纳米碳管电极的制备与电化学检测性能研究

纳米碳管由于其独特的物理和化学性能及广阔的应用前景而备受关注,其相关研究涉及到众多领域[1￣3]。在电化学分析领域,与其它碳电极材料相比,纳米碳管电极具有较大的电极表面积和较高的电子传递速率,其使用能增大响应电流、降低检出限,是目前电化学分析电极中一个十分引人注目     

Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.     

中空介孔碳球修饰的丝网印刷碳电极用于尼古丁的电化学检测

将一步法合成的中空介孔碳球(HMCS)修饰在丝网印刷碳电极(SPCE)上,得到了用于尼古丁电化学检测的新型电极(HMCS/SPCE)。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、粉末X射线衍射(XRD)、X射线光电子能谱(XPS)以及拉曼光谱等方法对HMCS及修饰电极HMCS/SPCE进行表征。由于HMCS具有较大的电化学活性面积和良好的导电性,修饰电极HMCS/SPCE对尼古丁表现出良好的电催化活性。在优化实验条件下,电极HMCS/SPCE对尼古丁的检测线性范围为0~500μmol/L,灵敏度为0.850 m A/(cm~2·mmol·L~(-1)),检出限为0.058μmol/L。制备的传感器具有重复性好、稳定性高等特点,可用于实际烟草样品中尼古丁的检测。     

Electrocatalytic Oxidation and Voltammetric Determination of Nitrite on Hydrophobic Ionic Liquid‐Carbon Nanotube Gel‐Chitosan Composite Modified Electrodes

A novel room temperature ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, OMIMPF₆)‐multiwall carbon nanotube (MWNT) gel‐chitosan (Chi) composite modified glassy carbon electrode (GCE) was fabricated and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The OMIMPF₆‐MWNT gel‐Chi composite showed good conductivity, stability, and extraction effect due to the synergic action of OMIMPF₆, MWNT, and Chi. Furthermore, it was found that the OMIMPF₆‐MWNT gel‐Chi composite had strong electrocatalytic effect on the oxidation of nitrite and at the OMIMPF₆‐MWNT gel‐Chi/GCE nitrite could produce a very sensitive anodic peak. Under optimized conditions, the peak current was linear to nitrite concentration from 2.0×10^?8 to 6.0×10^?5 M. The detection limit was 1.0×10^?8 M. The electrode also exhibited acceptable stability, repeatability and selectivity. It was used successfully for the determination of nitrite in soil, sewage and sausage samples.     

Fast Electrochemical Characterization of Historical Glasses Using Carbon Screen‐Printed Electrodes and Ultrasonic Assisted Sampling

A new method for lead oxide (PbO) analysis in glasses, using a carbon screen printed electrode (SPE) is proposed. A suspension of the powdered glass sample in nitric acid is prepared using an ultrasonic probe, 100 µL of slurry are deposited on the SPE and the voltammetric measurement is carried out. Structural information of PbO in the glass matrix is obtained by CV. Lead quantification is performed by DPV. In the best conditions a LOD of 2.30 wt% of PbO was obtained. The method has been applied with good results in the analysis of historical glasses samples.     

Zinc Oxide Nanoparticle‐modified Glassy Carbon Electrode as a Highly Sensitive Electrochemical Sensor for the Detection of Caffeine

Zinc oxide nanoparticles (ZnO NPs ) were prepared by a simple, convenient, and cost‐effective wet chemical method using the biopolymer starch. The prepared ZnO NPs were characterized by X‐ray diffraction (XRD ), scanning electron microscopy (SEM ), energy‐dispersive X‐ray (EDX ), Fourier transform infrared (FT‐IR ), and UV ‐visible spectroscopic techniques. The average crystallite size calculated from XRD data using the Debye–Scherer equation was found to be 15 nm. The electrochemical behavior of caffeine (CAF ) was studied using a glassy carbon electrode (GCE ) modified with zinc oxide nanoparticles by cyclic voltammetry (CV ) and differential pulse voltammetry (DPV ). Compared to unmodified GCE , ZnO NPs‐ modified GCE (ZnO NPs MGCE ) exhibited excellent electrocatalytic activity towards CAF oxidation, which was evident from the increase in the peak current and decrease in the peak potential. Electrochemical impedance study suggested that the charge‐transfer capacity of GCE was significantly enhanced by ZnO NPs . The linear response of the peak current on the concentrations of CAF was in the range 2–100 μM . The detection limit was found to be 0.038 μM. The proposed sensor was successfully employed for the determination of CAF in commercial beverage samples.     

Carbon Nanotube@N‐Doped Mesoporous Carbon Composite Material for Supercapacitor Electrodes

Here, carbon nanotube@N‐doped mesoporous carbon (CNT@N‐PC) composites were synthesized by using resorcinol‐formaldehyde resin as carbon source, ionic liquids (ILs) as template, and nitrogen sources and tetraethyl orthosilicate (TEOS) as assistant agent. The use of ILs‐modified CNT with nitrogen and TEOS facilitated the generation of a richer mesoporous structure. The obtained CNT@N‐PC was composed of a CNT core and mesoporous carbon particles around it. CNT@N‐PC showed a 3D network structure like “dewy cobwebs” and had a high surface area of 857 m² g^?1, uniform pore size distribution (3.0 nm), and suitable N content (4.9 at.%). When used as supercapacitor electrode, the CNT@N‐PC exhibited a high specific capacitance (244 F g^?1 at 1 A g^?1), good rate capability and favorable capacitance retention (92.5 % capacitive retention after 5000 cycles), demonstrating the potential for application in high‐performance supercapacitors.     

用碳糊修饰电极测定氨基酸的伏安法研究：Ⅱ.组氨酸在氧化铝修饰碳糊 …

用１０％氧化铝的修饰碳糊电极研究了测定组氨酸的伏安法。在０．０５ｍｏｌ／Ｌ丁二酸－硼砂（ｐＨ＝３．５）底液中在－０．６Ｖ出现一还原峰,结合２．５次微分技术测定组氨酸,在３．２０～１３０μｍｏｌ／Ｌ浓度范围内有良好的线性关系,相对标准偏差为３．４％,检出限为０．４μｍｏｌ／Ｌ。检测灵敏度比文献报道有较大的提高。文中还讨论了电极过程。     

Additional Studies on the Electrochemical Behaviour of Three Macrolides on Pt and Carbon Based Electrodes

The voltammetric behaviour of the macrolide based antibiotic: Erythromycin (ERT), Clarithromycin (CLA) and Azithromycin (AZT) was presented in this work. Carbon electrodes and platinum (Pt) electrode were applied as working electrodes. Cyclic voltamograms of each molecule in each electrode were recorded and similar electrochemical behaviour of macrolides was observed for all carbon based electrodes, which gave more defined current intensity peaks than platinum. Other organic compounds were tested trying to clarify electro-active groups of macrolides. Experiments on mechanism of electrochemical reaction were performed, and studies on the influence of pH on peak current and peak potential were also carried out.     

Electrochemical Oxidation and Detection of Morphine at Ordered Mesoporous Carbon Modified Glassy Carbon Electrodes

In this work, three ordered mesoporous carbons (OMCs) with different structural parameters were synthesized by a simple variation of the hydrothermal temperature of the silica templates (SBA‐15). X‐ray diffraction and nitrogen adsorption‐desorption results show these OMCs exhibit an ordered 2D hexagonal mesostructure with tunable pore diameter. OMC‐modified glassy carbon electrodes exhibit efficient electrocatalytic reactivity toward oxidation of morphine (MO). The amperometric detection of MO in pH 7.0 phosphate buffered saline at +0.39 V versus Ag/AgCl is the lowest potential reported to‐date. A linear range from 0.2 to 197.6 μM and a detection limit of 0.03 μM MO were obtained.     

Electrochemical Determination of Anti-Hyperlipidemic Drug Ezetimibe Based on its Oxidation on Solid Electrodes

Ezetimibe is the first of a new class of drugs that selectively inhibits cholesterol absorption in the small intestine and reduces plasma LDL cholesterol. In this study, electrochemical oxidation of ezetimibe was investigated on carbon based electrodes and a single and irreversible peak at both electrodes was observed. A linear response was detected between 2 × 10^?6 and 8 × 10^?5 M with glassy carbon electrode and between 2 × 10^?6 and 2 × 10^?4 M with a boron-doped diamond electrode in 0.1 M H₂SO₄ supporting electrolyte. The proposed methods were successfully applied for the determination of ezetimibe from pharmaceutical dosage forms and human serum samples.     

New Electrochemical Sensor of Prolonged Application for Metformin Determination Based on Hydrated Ruthenium Dioxide‐Carbon Black‐Nafion Modified Glassy Carbon Electrode

Metformin (MET) is an antidiabetic drug most commonly used in treatment of diabetes mellitus type 2 (T2D). Adsorptive stripping voltammetric method using carbon black – hydrated ruthenium dioxide – Nafion modified glassy carbon electrode (CB‐RuO₂‐Nafion GC electrode) have been developed for metformin determination in pharmaceutical formulations. By using ruthenium dioxide, electrode's lifespan was extended to at least 3 weeks (change of metrological parameters estimated as 3–4 %) what is an excellent result concerning other solutions previously described in the literature. Moreover the fabrication of the sensor is simple and fast. Deposition step was carried out at the potential 0 mV for 15 s. The best results were obtained in 0.05 M acetate buffer (pH 4.6). Important aspect was fixed MET : Cu(II) ratio equal to 1 : 8, otherwise linear dependence between register current and MET concentration could not be obtained. In addition, a significant improvement in the parameters of the calibration curve was obtained. Limit of detection was equal to 0.7 μM. Developed method was successfully applied in analysis of 2 pharmaceuticals products and in wastewater and river water. Accuracy of the method was estimated using recoveries, which were in the range 101–110 %. In order to adapt developed system into hydrodynamic conditions, amperometry in hydrodynamic transport conditions and flow injection analysis (FIA) measurements have been conducted. Conducted FIA measurements prove that developed method has potential for application in automized flow systems without frequent calibration.     

聚苯胺/活性碳复合型超电容器的电化学特性

电化学电容器作为一种新型储能器件具有广泛的应用.采用(NH₄)₂S₂O₈化学氧化聚合苯胺法制备了聚苯胺电极材料，采用化学物理二次催化活化法制备了高比表面积活性碳材料.并用循环伏安、恒流充放电以及交流阻抗等方法对上述电极材料的电化学特性进行了研究.实验结果表明,所制备的聚苯胺电极材料具有高于420 F•g^－1的法拉第赝电容和良好的电化学特性，所制备的活性碳电极材料则具有160 F•g^－1的双电层电容量.分别采用聚苯胺作为正极，活性碳作为负极，38％硫酸作为电解液制备了复合型电化学电容器.复合型电容器工作电压达到1.4 V, 电容器单体比电容达到57 F•g^－1，最大比能量和最大真实比功率分别达到15.5 W•h•kg^－1和2.4 W•g^－1, 峰值比功率达到20.4 W•g^－1,电容器循环工作寿命超过500次. 与活性碳双电层电容器相比，复合型电容器还具有较低的自放电率.     

Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes

The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g^?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g^?1 for the CNOs/Ppy bilayer (electrochemical deposition).     

A Paper‐based Mitochondrial Electrochemical Biosensor for Pesticide Detection

In this article, we detail a paper‐based three‐electrode electrochemical biosensor using a mitochondria modified Toray carbon paper working electrode. Cyclic voltammetry performed on the paper‐based biosensor and similar electrodes in a common laboratory setup (not in an integrated paper‐based device) compare favorably. In addition, instant detection of malathion with a detection limit of 20 nM by cyclic voltammetry is demonstrated, showing the device can potentially be used as a portable platform for pesticides detection.