Electrocatalysis of oxygen at hemoglobin-Au colloid-1,4-benzenedimethanethiol modified electrode

A novel renewable O2 sensor based on the direct electron transfer of hemoglobin (Hb) is proposed. Hb was immobilized on a gold nanoparticles (GNP) associated with a 1,4-benzenedimethanethiol (BDT) monolayer which were modified the electrode. The direct electrochemistry of Hb was investigated by electrochemical methods and cyclic voltammetric showing a pair of redox peaks of Hb. The high efficiency of the Hb/GNP/BDT modified gold electrode towards the catalytic electro-reduction of oxygen has been observed and the potential application of Hb/GNP/BDT modified gold electrode as biosensors to monitor O2 is proposed. The electrocatalytic response showed a linear dependence on the O2 concentration ranging from 2.0 to 40.0 micromol/L.     

Voltammetric Determination of Metol on a Gold Nanoparticle Modified Carbon Molecular Wire Electrode

A carbon molecular wire electrode was fabricated using diphenylacetylene as the modifier and gold nanoparticles were electrodeposited on the surface. The morphology and electrochemical properties of this modified electrode were investigated by scanning electron microscopy and electrochemical impedance spectroscopy. Two well-defined peaks for metol appeared using this gold nanoparticle-modified carbon molecular wire electrode by cyclic voltammetry with a high current response. These results demonstrate a synergistic effect between the gold nanoparticles and the carbon molecular wire electrode resulting in a rapid electrochemical reaction. The electrochemical conditions for metol were optimized on the modified electrode and a detection limit of 0.64?µmol/L and a linear dynamic range between 2.0 to 800.0?µmol/L were obtained. This modified electrode provided good selectivity, high sensitivity, and acceptable reproducibility, demonstrating promise for the determination of metol in the water.     

Electrocatalytic oxidation of bilirubin at ferrocenecarboxamide modified MWCNT–gold nanocomposite electrodes

A glassy carbon electrode (GCE) modified with ferrocenecarboxamide, gold nanoparticles and multiwall carbon nanotubes was constructed and characterized by field emission scanning electron microscopy and cyclic voltammetry. The electrochemical behavior of bilirubin (BR) on the modified electrode was investigated and it was found that the modified electrode had an obvious electrocatalytic effect on bilirubin. Compared with a bare GCE, the modified electrode exhibited a marked enhancement in the current response for bilirubin. Amperometry was employed to investigate the electrocatalytical oxidation of bilirubin on the modified electrode. As a result, it exhibits an excellent electrocatalytic response to bilirubin with a response time of less than 5 s, a broad linear range of 1 to 100 μmol L^?1, as well as good long-term stability and reproducibility.     

Comparative studies on electrogenerated chemiluminescence of luminol on gold nanoparticle modified electrodes

Comparative studies on the electrogenerated chemiluminescence (ECL) behavior of luminol on various electrodes modified with gold nanoparticles of different size were carried out in neutral solution by conventional cyclic voltammetry (CV). The results demonstrated that the gold nanoparticle modified electrodes could generate strong luminol ECL in neutral pH conditions. The catalytic performance of gold nanoparticle modified electrodes on luminol ECL depended not only on the gold nanoparticles but also on the substrate. Gold electrode and glassy carbon electrode were the most suitable substrates for the self-assembly of gold nanoparticles. Moreover, the gold nanoparticle modified gold and glassy carbon electrode had satisfying stability and reproducibility and did not need tedious pretreatment of electrode surface before each measurement. It was also found that luminol ECL behavior depended on the size of gold nanoparticles. The most intense ECL signals were obtained on a 16-nm-diameter gold nanoparticle modified electrode. The modified electrode prepared by the self-assembly method exhibited much better catalytic effect on luminol ECL than that prepared by the electrically deposited method. The ECL behavior of luminol on a gold nanoparticle self-assembled gold electrode was also investigated by other transient-state electrochemical techniques, such as chronoamperometry, differential pulse voltammetry, normal pulse voltammetry, and square wave voltammetry. The strongest ECL intensity was obtained under square wave voltammetric condition.     

Voltammetric determination of trace amounts of gold(III) with a carbon paste electrode modified with chelating resin

A carbon paste electrode modified with chelating resin (ammino-isopropylmercaptan-type cross-linked chelating resins) for the voltammetric determination of gold(III) was characterized by cyclic voltammetry. The gold(III) ion is accumulated on the surface of the modified electrode only by the chelating effect of the modifier in the carbon paste, without application of a potential. After exchange of the medium the accumulated amount of gold(III) is determined by voltammetry in a blank electrolyte solution. The response depends on both the concentration of gold and the accumulation time. For a 5-min preconcentration time, a linear calibration graph was obtained in the range 3 × 10^?8-1 × 10^?6 M and the detection limit was about 1 × 10^?8 M. A combination of chemical and electrochemical renewal allows the use of a single modified electrode in multiple analytical determinations over several days. For ten preconcentration—determination—renewal cycles [2 × 10^?7 M Au(III)], the response could be reproduced with 4.7% relative standard deviation. Many parameters such as the composition of the paste and pH influence the response of the measurement. Many other metal ions have no or little effect on the determination of gold. The procedure was applied to the determination of gold in minerals, copper and anode mud, with good results.     

Gold Nanoparticle Modified Electrodes Show a Reduced Interference by Cu(II) in the Detection of As(III) Using Anodic Stripping Voltammetry

Interference by Cu(II) causes serious problems in the detection of As(III) using anodic stripping voltammetry at gold electrodes. The behavior of Cu(II) and As(III) were examined at both a gold macro electrode and two kinds of gold nanoparticle modified electrodes, one where gold particles are deposited on glassy carbon (GC) and the other where basal plane pyrolytic graphite (BPPG) is the substrate. The sensitivity of As(III) detection was higher on gold nanoparticle modified electrodes than those on a macro gold electrode by up to an order of magnitude. In addition, the stripping peak of As(III) was narrower and more symmetric on a gold nanoparticle‐modified GC electrode, leading to analytical data with a lower limit of detection. At a macro gold electrode, the peak currents of Cu(II) were higher than those on gold nanoparticle modified electrodes. Accordingly, through the use of gold nanoparticle modified electrodes, the effect of copper interference to the arsenic detection can be reduced.     

Direct heterogeneous electron transfer of recombinant horseradish peroxidases on gold

Clean polycrystalline gold electrodes were modified with native glycosylated horseradish peroxidases (HRP) or two different recombinant (carbohydrate free) HRPs; recombinant wild-type HRP (rec-HRP) and recombinant HRP containing a six histidine-tag at the C-terminus of the polypeptide chain (rec-HRP-His), respectively. Only the electrodes modified with the recombinant HRPs exhibited high current responses to H2O2 due to relatively rapid direct electron transfer (ET) between recombinant HRP and gold. The absence of a carbohydrate shell on rec-HRP and the additionally existing histidine-tag on rec-HRP-His improved the electrode sensitivity to H2O2 by more than 100 times if compared with the response observed at gold modified with native HRP. Rotating disk electrode experiments indicated that the heterogeneous electron transfer rates are equal to 4.7 and 7.5 s-1 for direct electron transfer between the gold electrode and rec-HRP or rec-HRP-His, respectively.     

Determination of acetaminophen by square wave voltammetry at a gold electrode modified by 4-amino-2-mercaptopyrimidine self-assembled monolayers

A 4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs/Au) modified gold electrode was prepared. The electrochemical behavior of acetaminophen on the AMP SAMs/Au was studied in Britton-Robinson (BR) buffer solution. Compared to a bare gold electrode, the modified electrode exhibits a significant enhancement in the oxidation current response for acetaminophen. The modified electrode was used for the determination of acetaminophen by square wave voltammetry. The oxidation current increased linearly with the concentration of acetaminophen in the range of 2.0 × 10⁻⁶−4.0 × 10⁻³ M. The modified electrode made it possible to eliminate the interference of dopamine (DA), brucine, epinephrine (EP), and norepinephrine (NE). The practical analytical utility was illustrated by the determination of acetaminophen in a commercially available drug. The text was submitted by the authors in English.     

Voltammetric determination of trace amounts of gold with a chemically modified carbon paste electrode

A carbon paste electrode chemically modified with anion-exchangers is used for the voltammetric determination of gold(III). Tetrachloro- or tetrabromo-aurate(III) is preconcentrated on the electrode surface, modified with Amberlite LA2, and the electrode is transferred to an electrochemical cell for voltammetric measurements by cathodic stripping. The response depends on the concentration of gold in the bulk solution, preconcentration time, and other parameters. Detection limits are 100–300 μg l^?1 depending on the conditions. Many elements forming stable halo complex anions interfere.     

Gold Electrode Modified with Self‐Assembled Monolayer of Cysteamine‐Functionalized MWCNT and Its Application in Simultaneous Determination of Dopamine and Uric Acid

The voltammetric behavior of dopamine (DA) and uric acid (UA) on a gold electrode modified with self‐assembled monolayer (SAM) of cysteamine (CA) conjugated with functionalized multiwalled carbon nanotubes (MWCNTs) was investigated. The film modifier of functionalized SAM was characterized by means of scanning electron microscopy (SEM) and also, electrochemical impedance spectroscopy (EIS) using para‐hydroquinone (PHQ) as a redox probe. For the binary mixture of DA and UA, the voltammetric signals of these two compounds can be well separated from each other, allowing simultaneous determination of DA and UA. The effect of various experimental parameters on the voltammetric responses of DA and UA was investigated. The detection limit in differential pulse voltammetric determinations was obtained as 0.02 µM and 0.1 µM for DA and UA, respectively. The prepared modified electrode indicated a stable behavior and the presence of surface COOH groups of the functionalized MWCNT avoided the passivation of the electrode surface during the electrode processes. The proposed method was successfully applied for the determination of DA and UA in urine samples with satisfactory results. The response of the gold electrode modified with MWCNT‐functionalized SAM method toward DA, UA, and ascorbic acid (AA) oxidation was compared with the response of the modified electrode prepared by the direct casting of MWCNT.     

新型纳米金修饰玻碳电极对水杨酸的电催化氧化

借助"种子媒介纳米金属生长法"制备新型的纳米金修饰玻碳电极,应用场发射扫描电镜、紫外-可见光谱分析和电化学方法等,研究该电极的表面形貌及其电化学性能.结果表明,该修饰电极对水杨酸的电化学氧化有明显的电催化作用,电极响应灵敏度是裸玻碳电极表面的1.8倍.其氧化峰电流与水杨酸浓度在5.0×10-7~8.0×10-5mol/L范围内呈良好的线性关系,可用于水中痕量水杨酸的检测.     

Thin-film electrochemical sensor for diphenylamine detection using molecularly imprinted polymers

This work reports on the development of a new voltammetric sensor for diphenylamine based on the use of a miniaturized gold electrode modified with a molecularly imprinted polymer recognition element. Molecularly imprinted particles were synthesized ex situ and further entrapped into a poly(3,4-ethylenedioxythiophene) polymer membrane, which was electropolymerized on the surface of the gold electrode. The thickness of the polymer layer was optimized in order to get an adequate diffusion of the target analyte and in turn to achieve an adequate charge transfer at the electrode surface. The resulting modified electrodes showed a selective response to diphenylamine and a high sensitivity compared with the bare gold electrode and the electrode modified with poly(3,4-ethylenedioxythiophene) and non-imprinted polymer particles. The sensor showed a linear range from 4.95 to 115 μM diphenylamine, a limit of detection of 3.9 μM and a good selectivity in the presence of other structurally related molecules. This sensor was successfully applied to the quantification of diphenylamine in spiked apple juice samples.     

L-半胱氨酸修饰金电极电化学发光法测定罗红霉素

在裸金电极上制备了L-半胱氨酸自组装膜修饰电极(L-Cys-Au/SAM/CME).考察了联吡啶钌和罗红霉素在此修饰电极上的电化学及其发光行为.结果表明,此修饰电极表现出了很好的电化学活性和电化学发光(ECL)响应.基于罗红霉素的存在可增大了联吡啶钌的发光强度,建立了测定罗红霉素片的电化学发光分析方法.在最佳实验条件下,罗红霉素浓度在1.0×10-7～1.0×10-4 mol/L范围内与其相对发光强度呈线性关系,其线性回归方程为I=2×107C+384.02, r=0.9977; 检出限(S/N=3)为1.0×10-7 mol/L.连续测定1.8×10-5 mol/L罗红霉素10次,发光强度的RSD为1.93% , 表明此修饰电极具有较好的重现性,并将本方法用于罗红霉素片剂的检测.     

细胞色素c在纳米氧化铝模板修饰电极上的直接电化学

细胞色素c(Cytochrome c,Cyt c)是生物体中最常见的氧化一还原蛋白质,研究其在电极上的直接电化学,对于理解和认识生命体内的电子转移机制具有重要意义。Cytc与裸固体电极表面的直接接触通常会使其失去生物活性,因此,Cytc的电化学研究常借助于媒介体以实现其与电极之间的电子转移。纳米金属氧化物模板的表面积大且化学和光化学性质稳定,被广泛应用于太阳能电池和金属沉积等领域,本文研究氧化铝(AAO)模板对4,4’-二硫二吡啶存在下Cytc直接电化学促进作用。     

Detection of DNA immobilized on bare gold electrodes and gold nanoparticle-modified electrodes via electrogenerated chemiluminescence using a ruthenium complex as a tag

Electrogenerated chemiluminescence (ECL) for DNA hybridization detection is demonstrated based on DNA that was self-assembled onto a bare gold electrode and onto a gold nanoparticles modified gold electrode. A ruthenium complex served as an ECL tag. Gold nanoparticles were self-assembled on a gold electrode associated with a 1,6-hexanedithiol monolayer. The surface density of single stranded DNA (ssDNA) on the gold nanoparticle modified gold electrode was 4.8?×?10¹⁴ molecules per square centimeter which was 12-fold higher than that on the bare gold electrode. Hybridization was induced by exposure of the target ssDNA gold electrode to the solution of ECL probe consisting of complementary ssDNA tagged with ruthenium complex. The detection limit of target ssDNA on a gold nanoparticle modified gold electrode (6.7?×?10^?12 mol L^?1) is much lower than that on a bare gold electrode (1.2?×?10^?10 mol L^?1). The method has been applied to the detection of the DNA sequence related to cystic fibrosis. This work demonstrates that employment of gold nanoparticles self-assembled on a gold electrode is a promising strategy for the enhancement of the sensitivity of ECL detection of DNA.     

Oligonucleotide Functionalized Microporous Gold Electrode for the Selective and Sensitive Determination of Mercury by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV)

Abstract

A novel electrode modified with oligonucleotide and microporous gold was fabricated for the determination of mercury by differential pulse adsorptive stripping voltammetry (DPAdSV). Microporous gold was synthesized by electrochemical reduction using dynamic hydrogen bubble template. The oligonucleotide was immobilized on microporous gold by self-assembly. The prepared electrode exhibited an improved electrochemical response for mercury(II) ion because of the large surface area and excellent electron transfer capacity provided by microporous gold and the specific coordination between mercury ion and thymine bases in oligonucleotides. Under the optimal experiment conditions, the oligonucleotide functionalized microporous gold electrode had a linear relationship between the stripping current and mercury ion concentration in the range from 0.5 to 30?µg/L with a detection limit of 0.021?µg/L. Moreover, the prepared electrode exhibited good selectivity, reproducibility, repeatability and stability. Furthermore, the prepared electrode was applied to detect mercury in tap water with satisfactory results.     

The effect of electrocatalytic nanoparticle injection on the electrochemical response at a rotating disc electrode

A new approach to study electrocatalytic oxidation of glucose is proposed. As opposed to numerous studies on electrodes modified with gold nanoparticles this reaction was studied in their suspension of gold nanoparticles under hydrodynamic conditions on a noncatalytic glassy carbon rotating disc electrode. It has been shown that addition of nanogram amount of positively charged Au nanoparticles results in a clear current response, whereas no clear response is seen for negatively charged ones. This effect results from the electrocatalytic oxidation of glucose on Au nanoparticles mainly adsorbed on glassy carbon electrode. The role of electrode preparation method on reproducibility of the results is emphasized.     

甲烷氧化菌素功能化金纳米层层自组装修饰电极上过氧化氢的催化还原

借助巯基试剂,在纳米金颗粒表面修饰生物活性物质Mb,制备保持有Mb生物活性的功能化金纳米巯基乙胺-Au NPs-Mb.采用UV-Vis、FTIR光谱和投射电镜表征其结构,该纳米颗粒分布均匀且粒径均一,并显著改善了金纳米颗粒团聚现象.以Mb功能化金纳米为基元,采用单层自组装及层层自组装方式将其修饰到裸金电极表面.各Mb或Mb-Cu电极的电化学测试并未借助电子传递媒介.配位Cu~(2+)后,修饰有Mb的单层及层层自组装修饰的催化还原能力均显著提升.其中Cu~(2+)配位的{巯基乙胺-Au NPs-Mb}3/Au修饰电极作为一种新型H2O2生物传感器,响应时间大约为2 s,米氏常数KappM为0.787 mmol/L,表现出了较强的还原H2O2的催化活性,且稳定性较好.     

Assembly process of CuHCF/MPA multilayers on gold nanoparticles modified electrode and characterization by electrochemical SPR

Gold nanoparticles were deposited onto 2-mercaptoethylamine (MEA)-assembled planar gold thin film to construct gold nanoparticles modified electrode by virtue of a solution-based self-assembly strategy. Subsequently, 3-mercaptopropionic acid (MPA)-bridged copper hexacyanoferrate (CuHCF) multilayers were constructed on the as-prepared gold nanoparticles modified electrode. The resulted multilayer nanostructures were investigated by electrochemical surface plasmon resonance (EC-SPR) and atomic force microscopy (AFM) with primary emphasis upon the effect of the gold nanoparticles on the MPA/CuHCF multilayers growth and their surface morphology. Compared with the multilayer system on a planar gold electrode, the different electrochemical and optical properties might result from higher curvature effect and extraordinary surface-to-volume ratio characteristic of gold nanoparticles and the nanoparticle-selective growth of CuHCF. A dendrimer-like assembly process was proposed to explain the experiment results. This new motif of multilayer on the gold nanoparticles modified electrode was different from that of on a planar gold electrode, indicating a potential application of EC-SPR technique in the study of nanocomposite materials.     

Examination of incubation time of bare gold electrode inside cysteamine solution for immobilization of multi-walled carbon nanotubes on a gold electrode modified with cysteamine

A cysteamine (CysAm) nanostructure was generated to act as an intermediate layer between gold electrode and carbon nanotubes. A bare gold electrode was placed in a solution of CysAm to create a self-assembled monolayer on its surface. The modified electrode was then incubated with a solution of multi-walled carbon nanotubes. Cyclic voltammetry and atomic force microscopy were used to characterize the modified electrode. The results indicated that the number of functionalized MWCNTs on the surface of the electrodes increased by enhancing incubation time.