银纳米粒子修饰银电极法测定酪氨酸

通过NaBH₄还原AgNO₃得到胶体银纳米粒子,制作了以该纳米粒子修饰的银电极。研究了银纳米粒子修饰银电极在电催化中的应用,并对相关机理进行了探讨。该修饰电极对醋酸具有电催化活性,但酪氨酸却对该催化信号有明显的抑制作用,因此建立了用胶体银纳米粒子修饰银电极在NaAc-HAc缓冲溶液中检测酪氨酸的方法,并讨论了最佳工作条件。结果表明：在pH = 5.5时,峰电流与酪氨酸的浓度在1.0×10_-8～1.0×10_-3mol L_-1 范围内呈良好的线性关系,检出限为4.2×10_-9 mol L_-1,线性回归方程为Ip (μA) = 7.64 pC – 15.69 ( R = 99.73% )。用该方法检测氨基酸注射液中酪氨酸的含量,加标回收率在95.2%~107.8%之间。     

A Study of Nickel Electrodeposition on Paraffin‐Impregnated Graphite Electrode

The aim of the present work was to elucidate the mechanism of electrolytic deposition of Ni on paraffin‐impregnated graphite electrode (PIGE). This process is influenced by H₂ evolution, which occurs in the same potential region. On the basis of the results obtained by linear and cyclic voltammetry, elimination voltammetry with linear scan (EVLS) was used to evaluate both processes. H₂ Evolution alone was studied in sulfate supporting electrolyte, and the previously suggested mechanism for this process according to Volmer–Heyrovsky was confirmed by EVLS. It was found that both the Ni²⁺ concentration and pH affect the polarization behavior of PIGE significantly. Two separated cathodic peaks were observed at low Ni²⁺ and high H⁺ concentrations, and the separation was better at higher scan rates. EVLS confirmed the most‐probable mechanism of Ni deposition as being controlled by slow transfer of the first electron under formation of [NiOH]⁺ as an intermediate. EVLS also indicated slow reduction of H⁺ preceding the reduction of Ni²⁺. The same was confirmed by studying the anodic dissolution at different switching potentials. The results were complemented by scanning electron microscopy (SEM).     

Glucose Electro‐oxidation on Graphite Electrode Modified with Nickel/Chromium Nanoparticles

In this study, an available and inexpensive graphite substrate, was easily modified with Ni/Cr nanoparticles via electrodeposition technique in a very short time (3 min) and used as an electrocatalyst for glucose oxidation in alkaline solution. Graphite electrode modified with Ni/Cr nanoparticles demonstrated an outstanding electrocatalytic performance to glucose oxidation in comparison to examined Ni‐based electrodes or even different materials in other reports. It is noteworthy to mention that adding a little Cr led to a synergistic effect with Ni; accordingly, the presence of Cr not only resulted in a greater adsorption of glucose molecules by chromium oxide but also boosted conductivity of the nickel oxide because of the enhancement of Ni(III) amount. The electrochemical studies were performed by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The morphology and structure of catalyst layer was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and energy dispersive x‐ray spectroscopy (EDS). The linear range of the electrode by cyclic voltammetry was between 2–31 mM with a high sensitivity of 2094 μA cm^?2 mM^?1. The repeatability and reproducibility of the proposed electrode was examined in glucose solution which were 0.3 % and 4.7 %, respectively. According to the low cost, ease and fast preparation, good repeatability and high sensitivity, this electrode can be a good candidate for nonenzymatic glucose oxidation.     

银纳米修饰电极的制备及电化学行为

金属纳米粒子由于其小的体积和大的比表面积而具有独特的电子、光学和异相催化特性,是目前表面纳米工程及功能化纳米结构制备的一种理想研究对象[1]。银纳米粒子可广泛应用于催化剂材料、电池的电极材料、低温导热材料和导电材料等,成为近年来人们研究的热点[2,3]。在电化学方面,银纳米粒子具有比其他纳米粒子更为优异的导电性能和电催化性能。因此,研究银纳米粒子修饰电极有重要的应用价值和前景[4]。1实验部分1.1仪器CHI660电化学工作站(USA);TU-1901型双光束紫外可见分光光度计(北京普析通用仪器公司);KQ-100型超声清洗器(昆山市超声…     

Electrochemical Determination of Tyrosine in the Presence of Dopamine and Uric Acid at the Surface of Gold Nanoparticles Modified Carbon Paste Electrode

A gold nanoparticles modified carbon paste electrode (GN‐CPE) was used as a highly sensitive electrochemical sensor for determination of tyrosine (Tyr), dopamine (DA) and uric acid (UA) in phosphate buffer solution (PBS). The study and measurements were carried out by using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry methods. In DPV, the GN‐CPE could separate the oxidation peak potentials of DA and UA present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. The prepared electrode showed voltammetric responses with high sensitivity and selectivity for Tyr, DA and UA in optimal conditions, which makes it very suitable for simultaneous determination of these compounds. The calibration curves for Try, DA and UA were linear for the concentrations of each species. The proposed voltammetric approach was also applied to the determination of Tyr concentration in human serum as a real sample.     

纳米银粒子修饰电极法测定血红蛋白

报道了一种利用纳米材料修饰电极检测血红蛋白的新方法。制作了以纳米银粒子修饰的银电极,并研究了血红蛋白在该修饰电极上的直接电化学行为。实验结果表明,血红蛋白在该修饰电极上具有良好的电流响应。在2.0×10-7~1.0×10-5mol/L浓度范围内,血红蛋白的氧化峰电流与其浓度呈良好线性关系;检出限为7.4×10-8mol/L。研究了该修饰电极对血红蛋白的催化机理,利用该电极所建立的方法实现了对血红蛋白的分析测定。     

Electrochemical Behavior and Determination of L‐Tyrosine at Single‐walled Carbon Nanotubes Modified Glassy Carbon Electrode

Based on single‐walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE/SWCNTs), a novel method was presented for the determination of L ‐tyrosine. The GCE/SWCNTs exhibited remarkable catalytic and enhanced effects on the oxidation of L ‐tyrosine. In 0.10 mol/L citric acid‐sodium citrate buffer solution, the oxidation potential of L ‐tyrosine shifted negatively from +1.23 V at bare GCE to +0.76 V at GCE/SWCNTs. Under the optimized experimental conditions, the linear range of the modified electrode to the concentration of L ‐tyrosine was 5.0×10^?6–2.0×10^?5 mol/L (R₁=0.9952) and 2.7×10^?5–2.6×10^?4 mol/L (R₂=0.9998) with a detection limit of 9.3×10^?8 mol/L. The kinetic parameters such as α (charge transfer coefficient) and D (diffusion coefficient) were evaluated to be 0.66, 9.82×10^?5 cm² s^?1, respectively. And the electrochemical mechanism of L ‐tyrosine was also discussed.     

银纳米微球和银纳米棒自组装膜的制备及SERS研究

采用硼氢化钠还原硝酸银,用振荡器在不同转速下振荡得到单分散的银纳米微球和银纳米棒,再将银纳米微球及银纳米棒自组装于被3-氨丙基-三甲氧基硅烷(APTMS)修饰的玻璃基片上,制得了具有表面增强拉曼(SERS)活性的基底,分别以罗丹明6G(R6G)和罗丹明B(RB)为探针分子对这两种基底进行SERS活性检测,结果发现这两种基底均为较理想的SERS衬底。     

镍纳米粒子修饰碳糊电极直接电催化鸟嘌呤的研究

将镍纳米粒子与石蜡、石墨按照一定比例混合制备镍纳米粒子修饰碳糊电极,采用循环伏安法(CV)对修饰碳糊电极进行电化学表征,在0.1 mol/L B-R缓冲溶液(pH4.5)中研究了鸟嘌呤在该修饰电极上的电化学行为。结果表明,与裸碳糊电极相比,以掺杂法制备的镍纳米粒子修饰电极能够明显降低鸟嘌呤的过电位,增大其氧化电流,很好地催化氧化鸟嘌呤。在优化的实验条件下,鸟嘌呤在该修饰电极上的氧化峰电流与其浓度在1.0×10-5~5.0×10-4mol/L范围内呈良好的线性关系,检出限(3σ)为7.5×10-6mol/L。     

Synthesis and Characterization of Silver Sulfide Nanoparticles Containing Sol-Gel Derived HPC-Silica Film for Ion-Selective Electrode Application

Silver sulfide nanoparticles dispersed in sol-gel derived hydroxypropyl cellulose (HPC)-silica films have been successfully synthesized using H₂S gas diffusion method. This is the first attempt to produce silver sulfide nanoparticles using this technique. Ag₂S nanoparticles are generated through reaction of H₂S gas with AgNO₃ precursor dissolved in the HPC-silica matrix. Transmission electron microscope (TEM) and atomic force microscope (AFM) analysis reveal nanoparticles size distribution from 2.5 nm to 56 nm for H₂S gas exposed sample. The surface chemistry of Ag₂S nanoparticles and sol-gel derived HPC-silica matrix is confirmed by X-ray photoelectron spectroscopy (XPS). The negative shifts in the core-level XPS Ag (3d) binding energy of Ag₂S nanoparticles are attributed to Ag : S surface atomic ratio exhibited by these nanoparticles with varying processing conditions. Following processing and characterization, suitability of the present method to produce silver sulfide ion-selective electrode is demonstrated by depositing Ag₂S nanoparticles on a graphite rod. The high reponse function of the electrode is due to the presence of nanoparticles.     

Square‐Wave Voltammetry of Sodium Copper Chlorophyllin on Glassy‐Carbon and Paraffin‐Impregnated Graphite Electrode

Electrochemical oxidation of sodium copper chlorophyllin (CHL) has been investigated at a glassy‐carbon (GC) and paraffin‐impregnated graphite electrode (PIGE) using square‐wave voltammetry (SWV). Square‐wave voltammograms of other two chlorin‐type compounds, namely chlorin e₆ and chlorophyll a, have been studied as well. The measurements were performed in the pH range between 7 and 11. The square‐wave frequency was changed between 8 and 1000 Hz. The oxidation of studied chlorins is a complex, pH‐independent, reversible or quasireversible process, followed by the chemical transformation of the product. The product of the EC reaction of CHL is an electroactive π? π dimer, which strongly adsorbs on the electrode surface and undergoes further oxidation at more positive potential. The electrooxidation of the adsorbed dimer is a pH‐independent irreversible process with the formation of an electroinactive film. The voltammetric behaviour of chlorin e₆ on PIGE was qualitatively similar to that of CHL. The SW voltammograms of chlorin e₆ recorded on GCE and of chlorophyll a recorded on PIGE consisted of only one peak. The SW responses of studied compounds strongly depend on the stabilization of the reaction intermediate by adsorption to the electrode surface.     

Oxidation of Protopine at a Pyrolytic Graphite Electrode Using Cyclic and Square‐Wave Voltammetry

This paper describes oxidation of the isoquinoline alkaloid, protopine (PR) at a pyrolytic graphite electrode (PGE) using cyclic and square‐wave voltammetry. In the alkaline range (pH 7.5–10.5) of a Britton–Robinson (B–R) buffer, a PR oxidation can be observed as a well‐developed voltammetric peak around +0.9 V (vs. Ag|AgCl|3 M KCl). With increasing pH of the B–R buffer, the PR peak is shifted to less positive potentials. The acquired voltammetric data suggest that PR strongly adsorbs onto the surface of the pyrolytic graphite where it is subjected to irreversible electrochemical oxidation in its uncharged free (tricyclic) base form. The results are discussed in connection with the electrochemical oxidation of other isoquinoline alkaloids and the potential applications of these data.     

纳米铂微粒修饰电极上甲醛电催化氧化的电位振荡和电流振荡

通过阴极还原-阳极氧化法制备了钛基纳米铂微粒修饰电极, 扫描电镜观察发现, 分布于钛基体表面的氧化钛膜三维网状孔道中的纳米铂微粒具有高度分散状态. 采用多种电化学手段在该电极上不仅观察到甲醛在恒电流条件下产生的电位振荡, 而且在循环伏安和恒电位两种条件下均观察到强烈的电流振荡, 这进一步证明高度分散的纳米铂微粒使电极的催化活性大大提高, 促进了甲醛及其毒化中间产物的电催化氧化过程, 从而有利于电极上电化学振荡的产生. 研究结果还表明, 甲醛底物浓度、硫酸介质浓度、恒电位或恒电流大小等多种因素对振荡强度、范围或类型会产生规律性的影响.     

Cathodized Gold Nanoparticle‐Modified Graphite Pencil Electrode for Non‐Enzymatic Sensitive Voltammetric Detection of Glucose

A highly sensitive enzymeless electrochemical glucose sensor has been developed based on the simply prepared cathodized gold nanoparticle‐modified graphite pencil electrode (AuNP‐GPE). Cyclic voltammetry (CV) experiments show that AuNP‐GPE is able to oxidize glucose partially at low potential (around −0.27) whereas the bare GPE cannot oxidize glucose in the entire tested potential windows. Besides, fructose and sucrose cannot be oxidized at potential lower than +0.1 V at AuNP‐GPE. As a result, the glucose oxidation peak at around −0.27 V is suitable enough for selective detection of glucose in the presence of fructose and sucrose. Cathodization of AuNP‐GPE under optimum condition (‐1.0 V for 30 s) in the same glucose solution before voltammetric measurement enhanced glucose oxidation peak current around −0.27 V to achieve an efficient electrochemical sensor for glucose with a detection limit of 12 μM and dynamic range between 0.05 to 5.0 mM with a good linearity (R²= 0.999). Almost no interference effect was observed for sensing of glucose in the presence of ascorbic acid, alanine, phenylalanine, fructose, sucrose, and NaCl.     

介孔炭/纳米金修饰玻碳电极的制备及其应用研究

制备了介孔炭/纳米金修饰玻碳电极,并对对苯二酚(HQ)在该修饰电极上的电化学行为进行了研究。与HQ在纯介孔炭材料修饰玻碳电极上的电化学响应相比,HQ在该修饰电极上的氧化峰和还原峰电流均大大增加,表明纳米金与介孔炭复合后对HQ具有良好的催化作用。HQ在该修饰电极上经过富集后,峰电流明显增大。采用循环伏安法对HQ电化学行为进行研究,结果表明,HQ在3.0×10-8~1.0×10-6mol/L和1.0×10-6~1.0×10-4mol/L浓度范围内与峰电流呈良好的线性关系,据此建立了检测HQ的电化学分析方法。该方法的相对标准偏差为0.69%,检出限(S/N=3)为1.0×10-8mol/L,具有较高的稳定性和灵敏度。     

One‐Step Preparation of Antimicrobial Polyrhodanine Nanotubes with Silver Nanoparticles

A simple synthetic method has been developed for the fabrication of antimicrobial polyrhodanine nanotubes with silver nanoparticles. Rhodanine monomer first forms one‐dimensional complexes with silver ions due to coordinative interactions and consecutively reduces the silver ions during chemical‐oxidation polymerization. The polymerization procedure is analyzed by transmission electron microscopy and scanning electron microscopy in situ. The synthesized silver nanoparticles/polyrhodanine nanotubes are applied as an antimicrobial agent against Gram‐negative bacteria, E. coli and Gram‐positive bacteria, S. aureus. The antimicrobial tests demonstrate that the silver/polyrhodanine nanotubes have superior antimicrobial properties to silver nanoparticles and rhodanine monomer.

     

Preparation and Electrochemical Behaviour of Silver Pentacyanonitrosylferrate Film Modified Glassy Carbon Electrode and Its Electrocatalytic Oxidation to L‐cysteine

A glassy carbon (GC) electrode modified with silver pentacyanonitrosylferrate (AgPCNF) film as a redox mediator was fabricated. Cyclic voltammetry was used to study the redox property of AgPCNF modified electrode. The modified electrode showed a well‐defined redox couple due to [Ag^IFe^III/II(CN)₅NO]^1‐/2‐system. The effects of scan rates, supporting electrolytes and solution pHs were studied on the electrochemical behavior of the modified electrode. The feasibility of using the AgPCNF modified electrode to measure L ‐cysteine was investigated. It showed an excellent electrocatalytic activity towards the oxidation of L ‐cysteine and the anodic currents were proportional to the L ‐cysteine concentration in the range of 0.1 μM to 20 μM, the linear regression equation is I_pa(μA) = ‐68.58 ‐ 5.78C_{L ‐cysteine} (μM), with a correlation coefficient 0.998 for N = 23. The detection limit was down to 3.5 × 10^‐8 M (three times the ratio of signal to noise).     

Chlorpromazine Electro‐oxidation at BDD Electrode Modified with nZVI Nanoparticles Impregnated NiAl LDH

Nanocomposite of nanoscale zero‐valent iron (nZVI) and layered double hydroxide (LDH) was used as modifier for boron‐doped diamond electrode in determination of anti‐psychotic drug chlorpromazine (CPZ). nZVI nanoparticles were prepared by liquid phase reduction of ferric chloride with sodium borohydride on the surface of NiAl LDH matrix owing to the strong exchange and confinement efficiency of LDH. The structure, binding and surface properties of the nZVI@LDH nanocomposite were monitored using powder X‐ray diffractometry, FT‐IR spectroscopy, scanning and transmission microscopy and BET techniques. The electrochemical properties of the modified electrode were investigated by CV and EIS, performed in a phosphate buffer containing ferro/ferricyanide as redox probe. The modified electrode exhibited excellent electrochemical performance compared with unmodified electrode. As regard potential application of the nanocomposite surface to the CPZ detection, square‐wave voltammetric signals showed a good linear correlation over CPZ concentrations in a broad range from 0.1 to 8.0 μM with low detection limit of 0.005 μM. Nevertheless, these results suggest that the proposed nanocomposite modifier surface provides exceptional synergy and significant enhancement effect to the voltammetric response of CPZ and thus could be applied as highly efficient and stable platform of sensors in clinical analysis.     

Screen‐printed Electrode Modified with ZnFe2O4 Nanoparticles for Detection of Acetylcholine

In this paper a sensor to detect acetylcholine on the basis of ZnFe₂O₄ nanoparticles modified screen printed electrode (SPE) is reported. In the range 0.08–500.0 μM, with the detection limit of 0.024±0.001 μM, acquired anodic peak currents where shown to be linearly dependent on acetylcholine concentrations by differential pulse voltammetry (DPV). It was proven that acetylcholine oxidation at adjusted electrode surface takes place at 100 mV potential less positive compared to an unadjusted screen printed electrode. The electron transfer coefficient (α=0.51) and diffusion coefficient (D=9.3×10^?6 cm²/s) of acetylcholine oxidation were determined too. In addition, this original sensor possesses numerous benefits such as reproducibility, high stability and rapid response (20 s).     

Biomimetic Sensor for Dobutamine Employing Nano‐ TiO2/Nafion/Carbon Nanoparticles Modified Electrode

A novel voltammetric biosensor based on nano‐TiO₂/nafion/carbon nanoparticles modified glassy carbon electrode (TiO₂/N/CNP/GCE) was developed for the determination of dobutamine (DBA). Characterization of the surface morphology and property of TiO₂/N/CNP layer was carried out by the scanning electron microscopy and atomic force microscopy. The electrochemical performance of the modified electrode was investigated by means of the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy techniques. Effective experimental variables, such as the scan rate, pH of the supporting electrolyte, drop size of the casted modifier suspension and accumulation conditions of DBA on the surface of TiO₂/N/CNP/GCE were optimized. Under the optimized conditions, a significant electrochemical improvement was observed toward the electro‐oxidation of DBA on the surface of TiO₂/N/CNP/GCE compared to the bare GCE. Under the optimized conditions, a wide linear dynamic range (6 nM–1 µM) with a low detection limit of 2 nM for DBA was resulted. The prepared modified electrode shows high sensitivity, stability and good reproducibility in the determination of DBA concentrations. Satisfactory results were obtained for DBA analysis in the pharmaceutical and clinical preparations using TiO₂/N/CNP/GCE.