Electrochemical Sensing of Uric Acid Using a ZnO/Graphene Nanocomposite Modified Graphite Screen Printed Electrode

Russian Journal of Electrochemistry - An electrochemical sensor has been fabricated using ZnO/GR nanocomposite for selective determination of uric acid (UA) in a phosphate buffer solution (PBS, pH...     

电还原氧化石墨烯-金纳米棒修饰电极对酒石黄的测定

本文制备了氧化石墨烯-金纳米棒复合物(GO-GNRs).利用滴涂法制备了修饰电极(GO-GNRs/GCE),通过循环伏安法,还原了GO-GNRs复合物中的GO,制得电化学还原的石墨烯-金纳米棒修饰电极(ERGO-GNRs/GCE).研究了酒石黄在不同电极上的电流响应,结果表明,ERGO-GNRs/GCE对酒石黄的氧化有很好的电催化作用,其浓度在0.05～6.0μmol/L范围内与氧化峰电流呈良好的线性关系,检出限为15 nmol/L.利用ERGO-GNRs/GCE可完成样品中酒石黄含量的测定.     

Electrochemical Determination of Dextromethorphan on Reduced Graphene Oxide Modified Screen‐Printed Electrode after Electromembrane Extraction

In this paper, electromembrane extraction coupled with differential pulse voltammetry (DPV) on a reduced graphene oxide modified screen‐printed carbon electrode (RGO‐SPCE) for the determination of dextromethorphan (DXM) in urine and plasma has been described. DXM migrated from 4 mL of a donor phase across a thin layer of 2‐nitrophenyl octyl ether (NPOE) immobilized in the pores of a porous hollow fiber, into a 20 µL acceptor phase (HCl) present inside the lumen of the fiber. Then, 15 µL of a 0.1 M NaOH solution was added to the acceptor phase and the mixture was analyzed using DPV.     

Sensitive Voltammetric Determination of Baicalein at Thermally Reduced Graphene Oxide Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of the flavonoid baicalein by using a thermally reduced graphene oxide (TRGO) modified glassy carbon electrode (GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The surface morphology and structure of TRGO investigated by atomic force microscopy, FT‐IR spectroscopy and Raman spectroscopy reveal that the TRGO prepared maintained as single or bilayer sheets and with significant edge‐plane‐like defect sites. The TRGO/GCE modified electrode shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE and GO/GCE electrodes. The electrochemical behaviors of baicalein at the TRGO/GCE were investigated by cyclic voltammetry, suggesting that the TRGO/GCE exhibits excellent electrocatalytic activity to baicalein. Under physiological conditions, the modified electrode showed linear voltammetric response from 10 nM to 10 µM for baicalein, with a detection limit of 6.0 nM. This work demonstrates that the graphene‐modified electrode is a promising tool for electrochemical determination of flavonoid drugs.     

多巴胺在氧化锌纳米棒嵌入石墨修饰电极上的电化学行为及测定

采用水热法制备了氧化锌纳米棒,用扫描电子显微镜、红外光谱等测试方法对其进行表征,通过嵌入式修饰方法,将制备出的氧化锌纳米棒嵌入到石墨电极中制成修饰电极。 用循环伏安法和差分脉冲伏安法研究了多巴胺在修饰电极上的伏安行为和反应机理。 结果表明,该修饰电极对多巴胺显示出良好的响应,不仅使峰电流增加,并使多巴胺的氧化峰电位负移68 mV。 该电极过程的动力学参数：电子转移数n=2,电子转移系数α=0.48。 多巴胺的脉冲峰电流与其浓度在5.0×10-7~1.0×10-4 mol/L内呈良好的线性关系,检出限为1.0×10-7 mol/L(S/N=3)。 对1.0×10-5 mol/L的多巴胺平行测定8次的相对标准偏差（RSD）为3.42%。 用本法测定了盐酸多巴胺注射液中多巴胺的含量,加标回收率为94.83%~104.5%。     

Disposable Electrochemical Sensor for Food Colorants Detection by Reduced Graphene Oxide and Methionine Film Modified Screen Printed Carbon Electrode

A facile synthesis of reduced graphene oxide (rGO) and methionine film modified screen printed carbon electrode (rGO-methionine/SPCE) was proposed as a disposable sensor for determination of food colorants including amaranth, tartrazine, sunset yellow, and carminic acid. The fabrication process can be achieved in only 2 steps including drop-casting of rGO and electropolymerization of poly(L-methionine) film on SPCE. Surface morphology of modified electrode was studied by scanning electron microscopy (SEM). This work showed a successfully developed novel disposable sensor for detection of all 4 dyes as food colorants. The electrochemical behavior of all 4 food colorants were investigated on modified electrodes. The rGO-methionine/SPCE significantly enhanced catalytic activity of all 4 dyes. The pH value and accumulation time were optimized to obtain optimal condition of each colorant. Differential pulse voltammetry (DPV) was used for determination, and two linear detection ranges were observed for each dye. Linear detection ranges were found from 1 to 10 and 10 to 100 µM for amaranth, 1 to 10 and 10 to 85 µM for tartrazine, 1 to 10 and 10 to 50 µM for sunset yellow, and 1 to 20 and 20 to 60 µM for carminic acid. The limit of detection (LOD) was calculated at 57, 41, 48, and 36 nM for amaranth, tartrazine, sunset yellow, and carminic acid, respectively. In addition, the modified sensor also demonstrated high tolerance to interference substances, good repeatability, and high performance for real sample analysis.     

Electrochemical Detection of Three Monohydroxylated Polycyclic Aromatic Hydrocarbons Using Electroreduced Graphene Oxide Modified Screen‐printed Electrode

An electrochemical sensor for detection of three monohydroxylated polycyclic aromatic hydrocarbons (OH?PAHs) was fabricated by electrochemical reduction of graphene oxide (E‐rGO) on screen‐printed electrode (SPE). The E‐rGO film presents typical wrinkled structure with porous and cavity‐like nanostructure, providing large surface area, effective π‐electron system and high electrical conductivity. The developed E‐rGO/SPE sensor exhibits outstanding sensing performance for the target OH?PAHs, 2‐hydroxynaphthalene, 3‐hydroxyphenanthrene, and 1‐hydroxypyrene, within a linear range varying from 50–800 nM, 50–1150 nM, and 100–1000 nM, and with a limit of detection (LOD) of 10.1 nM, 15.3 nM, and 20.4 nM (S/N=3), respectively. The electrochemical sensor possesses excellent stability, acceptable reproducibility, and good anti‐interference ability. Additionally, the proposed sensor can be applied to the analysis of OH?PAHs in the urine samples with recoveries of 98.1–105.9 %.     

Nanostructured Screen Printed Graphite Electrode for the Development of a Novel Electrochemical Genosensor

The aim of this work is the preparation of DNA‐sensing architectures based on gold nanoparticles (AuNPs) in conjunction with an enzyme‐amplified detection to improve the analytical properties of genosensor. In order to assess the utility of study as DNA‐sensing devices, a thiolated DNA capture probe sequence was immobilized on the gold nanoparticle modified surface. After labeling of the biotinylated hybrid with a streptavidin‐alkaline phosphatase conjugate, the electrochemical detection of the enzymatic product was performed on the surface of a disposable electrode. Two different enzymatic substrates to detect the hybridization event were studied. In the first case, the enzyme catalyzed the hydrolysis of α‐naphthyl phosphate; the product is electroactive and has been detected by means of differential pulse voltammetry (DPV). In the second one, the enzyme catalyzed the precipitation of an insoluble and insulating product on the sensing interface. In this case, the electrochemical transduction of the hybridization process was performed by electrochemical impedance spectroscopy (EIS).     

A Sensitive Electrochemical Sensor for Moxifloxacin Hydrochloride Based on Nafion/Graphene Oxide/Zeolite Modified Carbon Paste Electrode

A carbon paste electrode (CPE) modified with Nafion, Graphene oxide and zeolite has been prepared and characterized, and the resulting Nafion/Graphene oxide/Zeolite modified carbon paste electrode (N/G/Z/MCPE) has been applied to the electrochemical detection of Moxifloxacin hydrochloride (MOXI). It exhibited a good electrocatalytic activity in phosphate buffer (optimum at pH 7.4), as pointed out by cyclic voltammetry (CV), and N/G/Z/MCPE can be exploited for MOXI detection by chronoamperometry, electrochemical impedance spectroscopy and differential pulse voltammetry. This latter was the most sensitive one and gave rise to a linear calibration curve in the 0.04 to 250 μM concentration range, with limits of detection and qualification estimated at 1.0 nM and 3.3 nM, respectively. Contrary to previous electrochemical sensors for MOXI (e. g., CPE modified with metal nanoparticles), this new sensor can be used for multiple successive analyses without needing to refresh its surface.     

An Electrochemical Sensing Platform Based on Graphene Oxide and Molecularly Imprinted Polymer Modified Electrode for Selective Detection of Amoxicillin

An electrochemical sensing platform based on composite material, consisting of molecularly imprinted polymer coated on graphene oxide (MIP-GO), was developed for selective and sensitive analysis of amoxicillin (AMOX). The MIP-GO composite, which was fabricated by sol-gel polymerization after removal of template molecule, was deposited as a thin film on glassy carbon electrode, and then was electrochemically characterized by cyclic voltammetry and differential pulse voltammetry. The linear response for the determination of AMOX was obtained in the concentration range from 5.0×10⁻¹⁰ to 9.1×10⁻⁷ M under the most proper conditions and the detection limit was found to be 2.94×10⁻¹⁰ M.     

Highly Sensitive Nitric Oxide Sensing Using Three‐Dimensional Graphene/Ionic Liquid Nanocomposite

A nanocomposite gel with a uniform porous structure and well‐controlled compositions prepared by mixing three‐dimensional graphene material with an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate, is used for nitric oxide detection. It shows a fast response of less than 4 seconds, an excellent sensitivity of 11.2 µA cm⁻² (µmol/L)⁻¹ and an extremely low detection limit of 16 nM with a signal‐to‐noise ratio of 3 (S/N=3), a performance superior to that of reported works based on carbon nanotubes and nanoparticles. The high sensitivity is attributed to the large electroactive surface area of the graphene gel nanocomposite towards nitric oxide oxidation. The electrochemical behavior of the gel nanocomposite is investigated and explained.     

Electrochemical Determination of Tyrosine Using Graphene and Gold Nanoparticle Composite Modified Glassy Carbon Electrode

Russian Journal of Electrochemistry - A electrochemical sensor based on graphene and gold nanoparticles modified glassy carbon electrode (GCE) was developed for the determination of tyrosine (Tyr)....     

A Selective Simultaneous Determination of Levodopa and Serotonin Using a Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotube/Chitosan Composite

A glassy carbon electrode (GCE) modified with carbon nanotube/chitosan (MWCNTs‐CHT/GCE) was used for the sensitive voltammetric determination of levodopa (Lev) and serotonin (Ser). The measurements were carried out using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). Under the optimum conditions the electrode provides a linear response versus Lev and Ser concentrations in the range of 2.0–220.0 µM and 0.5–130.0 µM, respectively, using DPV. The modified electrode was satisfactorily used for determination of Lev and Ser in human serum and urine with satisfactory results.     

First Electrochemical Report for Simultaneous Determination of Norepinephrine,Tyrosine and Nicotine Using a Nanostructure Based Sensor

A carbon paste electrode was modified with ZnO nanorods and 3‐(4′‐amino‐3′‐hydroxy‐biphenyl‐4‐yl)‐acrylic acid (3,4′AAZCPE) to cause electrocatalysis of norepinephrine oxidation. It has been found that the oxidation of norepinephrine at the surface of modified electrode occurs at a potential of about 180 mV less positive than that of an unmodified carbon paste electrode. Square wave voltammetry (SWV) exhibits linear dynamic range from 1.0×10^?7 to 8.0×10^?5 M and a detection limit of 3.9×10^?8 M for norepinephrine. In addition, this modified electrode was used for simultaneous determination of norepinephrine, tyrosine and nicotine.     

氧化石墨烯/聚吡咯插层复合材料的制备和电化学电容性能

以FeCl₃-甲基橙(MO)为模板, 通过化学原位聚合法成功制备出氧化石墨烯/聚吡咯(GO/PPy)插层复合材料. 采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、扫描电镜(SEM)和透射电镜(TEM)等测试技术对复合材料进行物性表征. 此外, 利用循环伏安、恒电流充放电和交流阻抗测试方法对复合材料在两种不同水系电解液(1 mol·L^-1 Na₂SO₄和1 mol·L^-1 H₂SO₄)中的电化学性能进行了研究. 结果显示: 氧化石墨烯和聚吡咯表现出各自优势并发挥协同作用, 使得GO/PPy插层复合材料在中性和酸性电解液中都显示出可观的比电容. 电流密度为0.5 A·g^-1时, GO/PPy 插层复合材料在Na₂SO₄和H₂SO₄电解液中的比电容分别为449.1 和619.0 F·g^-1, 明显高于纯PPy的比电容. 经过800 次循环稳定性测试后, 两种不同电解液中, 复合材料初始容量的保持率分别为92%和62%. 其中酸性电解液体系中初始容量更大, 而中性溶液中具有更稳定的循环性能.     

Reduced Graphene Oxide/Carbon Nanotube/Gold Nanoparticles Nanocomposite Functionalized Screen‐Printed Electrode for Sensitive Electrochemical Detection of Endocrine Disruptor Bisphenol A

We fabricated a highly sensitive electrochemical sensor for the determination of bisphenol A (BPA) in aqueous solution by using reduced graphene oxide (RGO), carbon nanotubes (CNT), and gold nanoparticles (AuNPs)‐modified screen‐printed electrode (SPE). GO/CNT nanocomposite was directly reduced to RGO/CNT on SPE at room temperature. AuNPs were then electrochemically deposited in situ on RGO/CNT‐modified SPE. Under optimized conditions, differential pulse voltammetry (DPV) produced linear current responses for BPA concentrations of 1.45 to 20 and 20 to 1,490 nM, with a calculated detection limit of an ultralow 800 pM. The sensor response was unaffected by the presence of interferents such as phenol, p‐nitrophenol, pyrocatechol, 2,4‐dinitrophenol, and hydroquinone.     

Graphene Oxide Modified Chemically Activated Graphite Electrodes for Detection of microRNA

In our study, graphene oxide (GO) modified graphite electrodes were used for sensitive and selective impedimetric detection of miRNA. After chemical activation of pencil graphite electrode (PGE) surface using covalent agents (CA), GO modification was performed at the surface of chemically activated PGE. Then, CA‐GO‐PGEs were applied for impedimetric miRNA detection. The microscopic and electrochemical characterization of CA‐GO‐PGEs was performed by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The optimization of experimental conditions; such as GO concentration, DNA probe concentration and miRNA target concentration was performed by using EIS technique. After the hybridization occurred between miRNA‐34a RNA target and its complementary DNA probe, the hybrid was immobilized onto the surface of CA‐GO‐PGEs. Then, the impedimetric detection of miRNA‐DNA hybridization was performed by EIS. The selectivity of our assay was also tested under the optimum experimental conditions.     

生物合成纳米金与MWCNTs/L-Cys复合修饰玻碳电极测定左旋多巴

利用荷叶萃取液生物合成纳米金,并与多壁碳纳米管/L-半胱氨酸复合成修饰电极材料,研究了左旋多巴在该修饰电极上的电化学行为.在0.2 mol/L乙酸-乙酸钠体系(pH=2.6)中,氧化峰电流与左旋多巴浓度在0.6~40μmol/L及60~120μmol/L范围内呈良好的线性关系,检出限达5.2×10-8mol/L.实验结果表明,生物合成纳米金复合多壁碳纳米管/L-半胱氨酸修饰电极具有良好的稳定性和高灵敏度,对实际样品测定的回收率在91.2%~102.5%之间.     

维生素B_6在石墨烯/纳米Cu_2O复合修饰电极上的电化学氧化

本文采用HNO3+H2SO4混酸氧化石墨烯之后,掺杂自制的粒径均一的纳米Cu2O,构建了石墨烯/纳米Cu2O复合修饰电极,并研究了维生素B6在该修饰电极上的电化学行为。结果表明,与裸玻碳电极以及单一材料修饰的电极相比,由于复合修饰电极充分发挥了石墨烯和纳米Cu2O的协同作用,从而对维生素B6的电化学氧化有显著的电催化作用。在优化实验条件下,该方法测定维生素B6的线性检测范围为5.0×10-8~1.5×10-4 mol/L,检出限为2.1×10-8 mol/L。该方法可快速、高灵敏测定药物中维生素B6。     

A Highly Sensitive and Selective Enzymatic Biosensor Based on Direct Electrochemistry of Hemoglobin at Zinc Oxide Nanoparticles Modified Activated Screen Printed Carbon Electrode

A sensitive enzymatic biosensor has been developed for the detection of hydrogen peroxide (H₂O₂), nitrite ( ) and trichloroacetic acid (TCA) by using hemoglobin (Hb) immobilized on activated screen printed carbon electrode (ASPCE) and zinc oxide (ZnO) composite. A pair of well defined redox peaks is observed with a heterogeneous electron transfer rate constant (K_s) of 5.27 s^?1 for Hb at ASPCE/ZnO. The biosensor exhibits the detection of H₂O₂, TCA and in the concentration range of 0.5–129.5 µmol L^?1, 2.5–72.5 mmol L^?1 and 0.2–674 µmol L^?1 with the detection limit of 0.083 µmol L^?1, 0.12 mmol L^?1 and 0.069 µmol L^?1, respectively.