A sensitive hydrazine electrochemical sensor based on electrodeposition of gold nanoparticles on choline film modified glassy carbon electrode

A highly sensitive hydrazine sensor was developed based on the electrodeposition of gold nanoparticles onto the choline film modified glassy carbon electrode (GNPs/Ch/GCE). The electrochemical experiments showed that the GNPs/Ch film exhibited a distinctly higher activity for the electro-oxidation of hydrazine than GNPs with 3.4-fold enhancement of peak current. The kinetic parameters such as the electron transfer coefficient (α) and the rate of electron exchange (k) for the oxidation of hydrazine were determined. The diffusion coefficient (D) of hydrazine in solution was also calculated by chronoamperometry. The sensor exhibited two wide linear ranges of 5.0 × 10⁻⁷-5.0 × 10⁻⁴ and 5.0 × 10⁻⁴-9.3 × 10⁻³ M with the detection limit of 1.0 × 10⁻⁷ M (s/n = 3). The proposed electrode presented excellent operational and storage stability for the determination of hydrazine. Moreover, the sensor showed outstanding sensitivity, selectivity and reproducibility properties. All the results indicated a good potential application of this sensor in the detection of hydrazine.     

Modified glassy carbon electrode with multiwall carbon nanotubes as a voltammetric sensor for determination of noscapine in biological and pharmaceutical samples

A simple and highly sensitive method is described for direct voltammetric determination of noscapine in blood and pharmaceutical sample. Glassy carbon electrode with effective method is modified with multiwall carbon nanotubes (MWNTs) to cause activation of multiwall carbon nanotubes structures for electrocatalyzes of noscapine oxidation. The cyclic voltammetric (CV) results indicated that MWNTs remarkably enhances electrocatalytic activity toward the oxidation of noscapine, which is leading to considerable improvement of anodic peak current for noscapine, and allows the development of a highly sensitive voltammetric sensor for detection of noscapine in pharmaceutical and clinical samples. Under the optimum condition, the calibration curve was linear in the concentration range 4.0 × 10⁻⁷–1.0 × 10⁻⁴ mol L⁻¹ with the detection limit of 8.0 × 10⁻⁸ mol L⁻¹ and relative standard deviation (R.S.D.%) lower than 1.0% (n = 5). Finally, some kinetic parameters were determined and multistep mechanism for oxidation of noscapine for first time was proposed.     

Sensitive electrochemical determination of acetaminophen in pharmaceutical formulations at multiwalled carbon nanotube-alumina-coated silica nanocomposite modified electrode

A highly sensitive electrochemical sensor for the determination of acetaminophen at the multiwalled carbon nanotube-alumina-coated silica (MWCNT-ACS) nanocomposite modified glassy carbon electrode is reported. The morphology of the MWCNT-ACS nanocomposite was characterized by field emission scanning electron microscopy. The electrocatalytic properties of the MWCNT-ACS nanocomposite modified glassy carbon electrode were characterized by cyclic voltammetry and square-wave voltammetry in the presence of acetaminophen. The MWCNT-ACS nanocomposite modified glassy carbon electrode exhibited the abilities to raise the current response and to decrease the electrooxidation potential. In cyclic voltammetric responses, the oxidation peak current of acetaminophen obtained at the MWCNT-ACS modified glassy carbon electrode was 100 times greater than that of bare glassy carbon electrode. The MWCNT-ACS nanocomposite modified glassy carbon electrode for the determination of acetaminophen displayed a sensitivity of 376.5 A M⁻¹ cm⁻² and a detection limit of 0.05 μM using square-wave voltammetry. The analytical applicability of the developed method was achieved by analyzing the content of acetaminophen in five commercial drugs without pretreatment.     

基于纳米银/石墨烯/酪氨酸酶/聚酰胺-胺的双酚A传感器

采用石墨烯纳米材料,并结合酪氨酸酶、聚酰胺-胺(PAMAM)和纳米银修饰玻碳电极研制了新型BPA生物传感器。运用循环伏安法和电化学交流阻抗考察了修饰电极的电化学行为。由于石墨烯独特的物理化学性质,结合聚酰胺-胺和纳米银的协同作用,该修饰电极对于BPA有较好的电流响应。在最佳条件下,该传感器对双酚A的线性检测范围为1.0×10-7～3.3×10-5mol/L,检测限为3.0×10-8 mol/L(信噪比为3),相关系数为0.998。     

Pt石墨烯-碳纳米管修饰玻碳电极对甲醛的电催化氧化

该文首先制备了石墨烯-碳纳米管复合材料,然后通过水热法将Pt纳米粒子修饰于该复合材料表面,制成了Pt／石墨烯（Graphene,Gr）-碳纳米管（Carbonnanotubes,CNTs）／玻碳电极（Glassycarbonelectrode,GCE）传感器。在磷酸盐缓冲溶液（pH=2．3）中利用循环伏安法研究了甲醛在Pt／Gr—CNTs／GCE上的电化学行为。实验结果表明,Pt／Gr-CNTs对甲醛具有良好的电催化氧化作用。     

肉桂酸修饰电极对尿酸的研究测定

用恒电位沉积方法制备了肉桂酸修饰电极,研究了尿酸(UA)在该修饰电极上的电化学行为.研究表明,在优化的实验条件下,尿酸在修饰电极上有良好的电催化响应,其氧化峰电流与浓度在2.0×10-6～4.0×10-4 mol/L范围内成很好的线性关系,检出限为1.0×10-6 mol/L.该修饰电极制备简单、稳定性好、检测方便.     

苯磺酸氨氯地平在石墨烯修饰玻碳电极上的电分析方法

研究了苯磺酸氨氯地平(ADB)在石墨烯(GR)修饰玻碳电极(GR/GCE)上的电化学行为及电化学动力学性质,据此建立了ADB电分析方法。采用电化学阻抗(EIS)法,循环伏安(CV)法,计时电流(CA)法,计时电量法(CC)等测定电极动力学参数。结果表明,ADB在GCE上的直接电化学较迟缓,GR对ADB的电化学氧化具有明显的电催化作用,其氧化峰电流增大了近4倍。用微分脉冲伏安法(DPV)在优化条件下测得氧化峰电流与ADB在6×10-7~1×10-4mol/L浓度范围内呈良好线性关系,检出限(S/N=3)为8.0×10-8 mol/L。该方法可用于市售ADB药品含量的电化学定量测定。     

辣根过氧化酶在纳米银修饰玻碳电极上的直接电化学研究1

通过自组装依次将纳米银粒子和辣根过氧化酶(HRP)固定到巯基乙胺(Cys)修饰的玻碳电极上,制备了HRP/Ag/Cys膜修饰电极.用交流阻抗技术表征了电极的自组装过程.用循环伏安法和计时电流法考察了HRP与电极之间的直接电化学行为及酶对过氧化氢电催化特性.电极响应对过氧化氢有良好的电催化还原性质,性能稳定,响应时间小于5 s.有望应用于制备第三代生物传感器     

一种基于纳米金／石墨烯／普鲁士蓝（PB）修饰玻碳电极非标记免疫传感器

采用电聚合的方法将普鲁士蓝（PBl聚合在玻碳电极表面,再将石墨烯修饰在PB上面,然后再采用电沉积的方法将HAuCL直接还原成纳米金粒子,沉积在石墨烯表面,最后将羊抗人IgG抗体直接固定于该修饰的玻碳电极表面,制备了用于人IgG抗原检测的非标记电化学免疫传感器。利用循环伏安法和交流阻抗研究了修饰电极表面的电化学特性,用差分脉冲伏安法对人IgG抗原进行了测定。实验表明,此免疫传感器在含不同浓度人IgG的PBS溶液（pH6．98）中测定,响应电流与人IgG浓度在5．55～455．5ng／mL范围内有良好的线性关系,其相关系数r=0．9926,检测限为0．015ng／mL（S／N=3）。该免疫传感器具有制备简单、响应时间快（5min）、稳定性好等特点。     

Electrochemical determination of imidacloprid using nanosilver Nafion/nanoTiO2 Nafion composite modified glassy carbon electrode

A novel biocompatible environment friendly nanosilver Nafion^®/nanoTiO₂ Nafion^® modified glassy carbon electrode was prepared by a simple procedure and characterized. This modified electrode was used as a sensing electrode for the detection of imidacloprid. Cyclic voltammetry, differential pulse voltammetry and amperometry were used in this work. The reduction potential of imidacloprid on this electrode is lower compared to other electrodes reported in the literature. The LOD and LOQ values obtained for the sensing of imidacloprid on this modified electrode are comparable to the values reported in the literature.     

1,10-Phenanthroline modified glassy carbon electrode for voltammetric determination of cadmium(II) ions

This study reports the electrochemical modification of glassy carbon (GC) electrode surface with the electro-polymerized form of 1,10-phenanthroline monohydrate (PMH), the characterization of this polyphenanthroline modified electrode (PPMH/GC) and the electroanalytical application suitable for the determination of Cd(II) ions. The PPMH/GC electrode was characterized by cyclic voltammetry, chronoamperometry and atomic force microscopy and formation of polyphenanthroline layer grafted to surface of GC electrode was evidenced. Selectivity of PPMH/GC electrode towards heavy metal ions was investigated by square wave voltammetry. The PPMH/GC electrode was found to be suitable for selective determination of Cd(II) in the solutions containing the mixture of heavy metal ions and showed high stability and reproducibility. The analytical methodology was successfully applied for monitoring the toxic metal ions in real samples.     

Anodic stripping voltammetric determination of copper(II) using a functionalized carbon nanotubes paste electrode modified with crosslinked chitosan

The development and application of a functionalized carbon nanotubes paste electrode (CNPE) modified with crosslinked chitosan for determination of Cu(II) in industrial wastewater, natural water and human urine samples by linear scan anodic stripping voltammetry (LSASV) are described. Different electrodes were constructed using chitosan and chitosan crosslinked with glutaraldehyde (CTS-GA) and epichlorohydrin (CTS-ECH). The best voltammetric response for Cu(II) was obtained with a paste composition of 65% (m/m) of functionalized carbon nanotubes, 15% (m/m) of CTS-ECH, and 20% (m/m) of mineral oil using a solution of 0.05 mol L⁻¹ KNO₃ with pH adjusted to 2.25 with HNO₃, an accumulation potential of −0.3 V vs. Ag/AgCl (3.0 mol L⁻¹ KCl) for 300 s and a scan rate of 100 mV s⁻¹. Under these optimal experimental conditions, the voltammetric response was linearly dependent on the Cu(II) concentration in the range from 7.90 × 10⁻⁸ to 1.60 × 10⁻⁵ mol L⁻¹ with a detection limit of 1.00 × 10⁻⁸ mol L⁻¹. The samples analyses were evaluated using the proposed sensor and a good recovery of Cu(II) was obtained with results in the range from 98.0% to 104%. The analysis of industrial wastewater, natural water and human urine samples obtained using the proposed CNPE modified with CTS-ECH electrode and those obtained using a comparative method are in agreement at the 95% confidence level.     

碳纳米管组装电化学免疫传感器测定IgG抗体的研究

应用吸附法将IgG抗原固定于多壁碳纳米管修饰的玻碳电极表面,制备用于IgG抗体检测的电化学免疫传感器。以辣根过氧化物酶为标记物,对苯二酚为底物,利用辣根过氧化物酶标记IgG抗体与待测IgG抗体竞争电极表面固定的IgG抗原,建立了免疫竞争法检测IgG抗体的高灵敏度电化学分析方法。碳纳米管的大比表面积和电化学催化作用,提高了分子识别物质的固定量和电化学检测的灵敏度。工作电位为 0.030 V(vs.SCE)时,响应电流与IgG抗体浓度在0.30~10μg/mL范围内呈良好的线性关系,检出限为0.11μg/mL。     

基于石墨烯修饰玻碳电极伏安法测定6-苄氨基嘌呤

该文利用石墨烯修饰电极,构建了一种测定6-苄氨基嘌呤的新型的电化学方法。循环伏安实验表明,石墨烯修饰电极能显著降低6-苄氨基嘌呤的测定电位,提高其响应电流。6-苄氨基嘌呤在石墨烯修饰电极表面的电化学过程为扩散控制。在优化的实验条件下,6-苄氨基嘌呤与峰电流在浓度为1.0×10-8~1.0×10-6mol/L范围内呈现良好的线性关系,检测限为5.0×10-9 mol/L。考察了一些无机离子和有机化合物对6-苄氨基嘌呤测定的干扰,结果表明该传感器有较好的抗干扰能力。加标回收实验表明该修饰电极的回收率在91.0%~104.5%之间,表明该传感器能用于实际样品的检测。     

Voltammetric behavior of multi-walled carbon nanotubes modified electrode-hexacyanoferrate(II) electrocatalyst system as a sensor for determination of captopril

The study of electrochemical behavior and determination of captopril, as an angiontensin-converting enzyme inhibitor, is reported on multi-walled carbon nanotube (MCNT) modified glassy carbon electrode (GCE) and hexacyanoferrate(II) (HCF) electrocatalyst. The cyclic voltammetric results indicate that MCNTs and HCF system can remarkably enhance electrocatalytic activity toward the oxidation of captopril in acidic solutions. It is leading to a considerable improvement of the anodic peak current for captopril, and allows the development of a highly sensitive voltammetric sensor for detection of captopril in pharmaceutical and clinical samples. The investigation of captopril oxidation on the iron oxide nanoparticles modified carbon paste electrode does not show any electrocatalytic effect on the oxidation of captopril, suggesting that iron oxide impurities in the MCNTs are not the active sites in captopril sensing. Under optimized conditions on MCNTs-HCF system, the proposed method with respect to other reported electrochemical methods shows wider dynamic range (0.5–600 μM) with suitable selectivity, practical detection limit of 0.2 μM and good precision (R.S.D. <3%).     

银掺杂聚L-甲硫氨酸修饰电极测定6-巯基嘌呤

利用循环伏安法制备了银掺杂聚L-甲硫氨酸修饰玻碳电极(Ag-PLM/GCE),研究了6-巯基嘌呤在该修饰电极上的电化学行为,建立了循环伏安法测定6-巯基嘌呤的新方法.在pH6.5磷酸盐缓冲溶液中,扫描速率为140mV/s,6-巯基嘌呤在银掺杂聚L-甲硫氨酸修饰玻碳电极上出现一个氧化峰,峰电位为0.410V.用循环伏安法测定时,其峰电流与6-巯基嘌呤的浓度在3.00× 10-5～5.00×10-3mol/L范围内呈现良好的线性关系,检出限为5.0×10-6 mol/L.用于乐疾宁片剂中6-巯基嘌呤含量的测定,结果满意.     

一次性酶免疫传感电极快速检测福氏志贺氏菌的研究

为研究快速检测福氏志贺氏菌的电化学免疫传感电极,将羧基化多壁碳纳米管(MWCNT)与壳聚糖(chitosan)制备成复合物,应用此复合物将辣根过氧化物酶标记的福氏志贺氏菌抗体(HRP-anti-S.flexnefi)上步直接固定在四通道丝网印刷碳电极表面,制成快速检测福氏志贺氏菌的酶免疫传感电极.采用原子力显微镜表征不同修饰电极的表面形态,循环伏安法考察不同电极的电化学特性和监测酶促反应,利用还原峰峰电流的减小来测定福氏志贺氏菌.在优化的测定条件下,免疫电极对福氏志贺氏菌的检测范围为104～1010cfu/mL,检出限为2.3×104du/mL(S/N=3).而且该酶免疫传感电极具有较好的特异性、重现性、稳定性和准确性,该方法还具有快速、简便、易于操作和价格低廉等优点,具有用于福氏志贺氏菌快速筛检的潜力.     

Cyclic voltammetry on electrode surfaces covered with porous layers: An analysis of electron transfer kinetics at single-walled carbon nanotube modified electrodes

Cyclic voltammetry is recorded of the oxidation of ferrocyanide on a glassy carbon electrode modified with multiple layers of single-walled carbon nanotubes. The current response is interpreted in terms of semi-infinite planar diffusion towards the macro-electrode surface and in terms of oxidation of the electroactive species trapped in pockets in between the nanotubes. A thin layer model is used to illustrate the effects of diffusion within a porous layer. It is found that a semi-infinite planar diffusion model alone is not appropriate for interpreting the kinetics of the electron transfer at this electrode surface. In particular, caution should be exercised in respect of comparing voltammetric peak-to-peak potential separations between naked electrodes and nanotube-modified electrodes for the inference of electrocatalysis via electron transfer via the nanotubes.     

Application of carbon ionic liquid electrode for the electrooxidative determination of catechol

A carbon ionic liquid electrode (CILE) was constructed using graphite powder mixed with N-butylpyridinium hexafluorophosphate (BPPF₆) in place of paraffin as the binder, which showed strong electrocatalytic activity to the direct oxidation of catechol. In pH 3.0 phosphate buffer solution (PBS) a pair of redox peaks appeared on the CILE with the anodic and the cathodic peak potential located at 387 and 330 mV (vs. SCE), respectively. The electrochemical behaviors of catechol on the CILE were carefully investigated, and the electrochemical parameters were calculated with the results of the electrode reaction standard rate constant k_s as 1.27 s⁻¹, the charge-transfer coefficient α as 0.58 and the electron transferred number n as 2. Under the selected conditions, the anodic peak current increased linearly with the catechol concentration over the range from 1.0 × 10⁻⁶ to 8.0 × 10⁻⁴ mol L⁻¹ by cyclic voltammetry at the scan rate of 100 mV s⁻¹. The detection limit was calculated as 6.0 × 10⁻⁷ mol L⁻¹ (3σ). The CILE showed good ability to separate the electrochemical responses of catechol and ascorbic acid (AA) with the anodic peak potential separation as 252 mV (vs. SCE). The proposed method was further applied to the synthetic samples determination with satisfactory results.     

Adsorptive voltammetry of Hg(II) ions at a glassy carbon electrode coated with electropolymerized methyl-red film

The glassy carbon electrode coated with electropolymerized methyl-red film, 1.2 × 10⁻⁶ m in thickness, (PMRE) showed high sensitivity towards Hg(II) ions. PMREs were adopted to accumulate and detect Hg(II) ions in a pH 2.56 Britton–Robinson buffer solution. Cyclic voltammogram of the accumulated Hg species on PMREs exhibited an anodic wave at 0.64 V and a cathodic wave at 0.13 V, due to the oxidation of accumulated Hg species on PMREs and the reduction of Hg(II) ions in the solution, respectively. For this heterogeneous adsorption of Hg(II) ions onto PMREs, the maximum surface concentration, adsorption equilibrium, and Gibbs energy change were evaluated to be 5.12 × 10⁻⁶ mol m⁻², 3.7 × 10⁵ l mol⁻¹, and −30.1 kJ mol⁻¹, respectively. The anodic peak current at 0.64 V was linear with the concentration of Hg(II) ions in the range of 1.1 × 10⁻¹⁰ to 1.1 × 10⁻⁷ M with a detection limit of 4.4 × 10⁻¹¹ M. The proposed method was utilized successfully for the detection of Hg(II) ions in the lake water.