A Sensitive Electrochemical Sensor for Voltammetric Determination of Ganciclovir Based on Au‐ZnS Nanocomposite

An electrode modified with ZnS and gold nanoparticles (Au‐ZnS NPs) is introduced for highly sensitive voltammetric determination of ganciclovir (GCV). Surface structure and topography of the modified electrode was studied by SEM, EDX and XRD techniques. Electrochemical oxidation of GCV was investigated by cyclic (CV) and square wave voltammetry (SWV) in Briton‐Robinson buffer solution (pH 1.5). The results showed that electrochemical oxidation of GCV at the Au‐ZnS modified glassy carbon electrode (GCE) is irreversible and exhibited diffusion controlled electrode process over the pH range from 1.0 to 6.0. The oxidation potential peak and pH relationship showed that electrons and protons were transferred simultaneously over the electrochemical oxidation process. Using the proposed sensor, the linear calibration curves were obtained in the ranges of 0.04–1.50 μM and 1.5–70.0 μM with detection limit of 0.01 μM GCV by SWV technique. The modified electrode was successfully applied as a sensitive, reproducible and repeatable sensor for determination of the trace amount of GCV in human serum, urine and cymevene vials. Reasonable results were obtained from comparing the measurements of the real samples by the new sensor to high performance liquid chromatography (HPLC) as a standard method.     

High Sensitive Voltammetric Gentamicin Sensor using Poly (3-thiophenecarboxylic acid-co-3-methylthiophene) Modified Glassy Carbon Electrode

For the determination of gentamicin in biomedical applications, sensitive, fast and low cost voltammetric sensor has been developed. Prepared sensor was successfully used for determination of gentamicine in synthetic urine samples with different voltammetric measurement methods. Firstly, glassy carbon electrode was modified using cyclic voltammetry technique by electropolymerization of 3-thiophenecarboxylic acid and 3-methylthiophene. Then, optimization of the electrochemical parameters was carried out for modified electrode. With this modified electrode, gentamicin determination was performed in the linear range of 0.05–4.00 mM. The correlation coefficient, limit of detection and limit of quantitation were calculated as 0.9999, 0.039 mM and 0.129 mM, respectively.     

Electrografting of 4‐tert‐Butylcatechol on GC Electrode. Selective Electrochemical Determination of Homocysteine

A new sensor based on the grafting of 4‐tert‐butylcatechol on the surface of a glassy carbon electrode (GC) was developed for the catalytic oxidation of homocysteine ( Hcy ). The GC‐modified electrode exhibited a reversible redox response at neutral pH. Under the optimum conditions cyclic voltammetric results indicated the excellent electrocatalytic activity of modified electrode toward the oxidation of Hcy at reduced over‐potential about 350 mV. A linear dynamic range of 0.01–3.0 mM and a detection limit of 1.0 µM were obtained for Hcy . The modified electrode was used as an electrochemical sensor for selective determination of Hcy in human blood.     

Polythymine Oligonucleotide‐Modified Gold Electrode for Voltammetric Determination of Mercury(II) in Aqueous Solution

Polythymine oligonucleotide (PTO)‐modified gold electrode (PTO/Au) was developed for selective and sensitive Hg²⁺ detection in aqueous solutions. This modified electrode was prepared by self‐assembly of thiolated polythymine oligonucleotide (5′‐SH‐T₁₅‐3′) on the gold electrode via Au? S bonds, and then the surface was passivated with 1‐mercaptohexanol solution. The proposed electrode utilizes the specific binding interactions between Hg²⁺ and thymine to selectively capture Hg²⁺, thereby reducing the interference from coexistent ions. After exchanging the medium, electrochemical reduction at ?0.2 V for 60 s, voltammetric determination was performed by differential pulse voltammetry using 10 mM HEPES; pH 7.2, 1 M NaClO₄ as supporting electrolyte. This electrode showed increasing voltammetric response in the range of 0.21 nM Hg²⁺, with a relative standard deviation of 5.32% and a practical detection limit of 60 pM. Compared with the conventional stripping approach, the modified electrode exhibits good sensitivity and selectivity, and is expected to be a new type of green electrode.     

Electrochemical Fabrication of Prussian Blue Nanocube‐decorated Electroreduced Graphene Oxide for Amperometric Sensing of NADH

In this study, Prussian blue (PB) film on the electroreduced graphene oxide (ERGO)‐modified Au electrode surface (ERGO/PB) is easily prepared by means of cyclic voltammetric technique in the mixture of K₃Fe(CN)₆ and FeCl₃. Its electrochemical behaviors for NADH biosensor are studied. The structural and morphological characters of modified electrode material are analyzed with using of XPS, XRD, Raman, EDS, and SEM techniques. ERGO/PB hybrid nanocomposite for NADH biosensor is exhibited to the higher catalytic effect (linear range from 1.0 to 100 μM, detection limit of 0.23 μM at S/N=3) compared to naked Au, ERGO‐modified Au, and PB‐modified Au electrodes. In addition to, ERGO/PB electrode was used to voltammetric and amperometric detection of H₂O₂. ERGO/PB electrodes also showed the same behavior as the NADH sensor. This ERGO/PB‐modified electrode supplied a simple, new, and low‐cost route for amperometric sensing of both NADH and H₂O₂.     

Morphology dependent electrocatalytic activity of Au nanoparticles

The electrocatalytic activity of spherical shape Au particles chemically grown on a sol–gel derived 3D silicate network modified conducting surface has been studied using ascorbate as a model. The nanostructured Au particles show morphology dependent electrocatalytic activity towards ascorbate. Unusual voltammetric behavior for ascorbate has been observed. Unlike the polycrystalline Au electrode, the nanostructured electrode shows two well defined voltammetric peaks for ascorbate at 0 and 0.3 V in neutral and alkaline pHs. These voltammetric peaks are assigned for the oxidation of ascorbate to dehydroascorbate (DHA) and the further oxidation of 2,3-diketogluonic acid (DKG), the hydrolyzed product of DHA. The voltammetric peak corresponding to the oxidation of DKG is very sensitive to the supporting electrolyte anions and solution pH. Voltammetric behavior of DHA has been investigated to support the oxidation pathway of ascorbate on the nanostructured electrode. Surface morphology of the particle controls the electrocatalytic activity.     

Phenylboronic acid monolayer-modified electrodes sensitive to sugars

The surface of a gold (Au) electrode was modified with 4-mercaptophenylboronic acid (MPBA) and dithiobis(4-butyrylamino-m-phenylboronic acid) (DTBA-PBA) to prepare sugar-sensitive electrodes. MPBA and DTBA-PBA formed well-packed monomolecular layers on the Au electrode through a sulfur-Au bond. The MPBA- and DTBA-PBA-modified electrodes exhibited a nearly reversible cyclic voltammogram (CV) for the Fe(CN)(6)(3-)(/4-) ion in acidic solution, while the CVs were significantly attenuated in alkaline media as a result of addition of OH(-) ion to the boron atom to generate the negatively charged surface. In other words, the negatively charged monolayers blocked the surface of the Au electrode from the access of the Fe(CN)(6)(3-)(/4-) ion. The pK(a) values of the addition equilibrium of the OH(-) ion to the MPBA and DTBA-PBA monolayers were estimated to be 9.2 +/- 0.1 and 8.0 +/- 0.2, respectively, on the basis of the pH-dependent peak current (i(p)) in the CV of the Fe(CN)(6)(3-)(/4-) ion. On the other hand, in the presence of sugars, the addition of the OH(-) ion was accelerated by forming the phenylboronate esters of sugars on the surface of the monolayers. The pK(a) values for the MPBA and DTBA-PBA monolayers were 8.3 +/- 0.1 and 7.2 +/- 0.1, respectively, in the presence of 50 mM D-fructose. The MPBA- and DTBA-PBA-modified electrodes can be used for determining sugars on the basis of the change in i(p) of the Fe(CN)(6)(3-)(/4-) ion in the presence of sugars. The calibration curves useful for determining 1-100 mM D-glucose, D-mannose, and D-fructose were obtained.     

Voltammetric investigation of cytochrome c on gold coated with a self-assembled glutathione monolayer

The direct, reversible electrochemistry of horse-heart cytochrome c (cyt. c) was realized on a self-assembled glutathione (GSH) monolayer modified Au electrode. The voltammetric responses of cyt. c on GSH/Au electrode were found to be affected by pH during the electrode modification, metal ions and surfactants. Using potassium ferricyanide [K4Fe(CN)6] as a probe, these effects on the voltammetric responses of cyt. c were characterized by electrochemical methods. It was found that the pH during the electrode modification, metallic ions and surfactants changed GSH monolayer's charge state and the conformation on the electrode surface, and resulted in the influence on the voltammetric responses of cyt. c. The experimental results provided us information to understand the mechanism of the interfacial electron transfer of electrode-protein, as well as the electron transfer of cyt. c in life system.     

A non-enzymatic sensor for hydrogen peroxide based on polyaniline, multiwalled carbon nanotubes and gold nanoparticles modified Au electrode

We describe the construction of a polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) modified Au electrode for determination of hydrogen peroxide without using peroxidase (HRP). The AuNPs/MWCNT/PANI composite film deposited on Au electrode was characterized by Scanning Electron Microscopy (SEM) and electrochemical methods. Cyclic voltammetric (CV) studies of the electrode at different stages of construction demonstrated that the modified electrode had enhanced electrochemical oxidation of H(2)O(2), which offers a number of attractive features to develop amperometric sensors based on split of H(2)O(2). The amperometric response to H(2)O(2) showed a linear relationship in the range from 3.0 μM to 600.0 μM with a detection limit of 0.3 μM (S/N = 3) and with high sensitivity of 3.3 mA μM(-1). The sensor gave accurate and satisfactory results, when employed for determination of H(2)O(2) in milk and urine.     

Electrochemical detection of dihydromyricetin using a DNA immobilized ethylenediamine/polyglutamic modified electrode

A novel voltammetric sensor, based on DNA immobilized on the surface of an ethylenediamine/polyglutamic (En/PGA) modified glassy carbon electrode (GCE), was constructed and used for determination of dihydromyricetin (DMY). The electrochemical behaviour of DMY at this sensor was investigated in pH 3.6 NaAc-HAc buffer solutions by cyclic voltammetry (CV) and differential pulse anodic voltammetry (DPV). The oxidation of DMY is an adsorption-controlled irreversible process. The oxidation mechanism was proposed and discussed. It was found that the modified electrode exhibited a linear voltammetric response for DMY in the range of 4.0 × 10(-8) mol L(-1) to 2 × 10(-6) mol L(-1), with a detection limit of 2 × 10(-8) mol L(-1). The method was also applied successfully to detect DMY in an ampelopsis sample with satisfactory results.     

基于Fe3O4/Au/GOx的新型磁性敏感膜葡萄糖传感器研制

在核壳结构Fe3O4/Au微粒上共价固定葡萄糖氧化酶,制得磁性复合粒子Fe3O4/Au/Gox,该复合粒子保留了良好的超顺磁性。通过磁力将其固定到改进的玻碳电极上,以二茂铁为电子媒介,制得新型葡萄糖传感器。研究了该传感器的传感性能,优化了实验参数。在pH7.0的磷酸盐缓冲溶液中,葡萄糖浓度在5.0×10-5～2.0×10-2mol/L间呈良好线性关系,响应时间小于10s。该传感器有灵敏度高,选择性好,性能稳定,制作简单且易于更新的特点。     

Preparation of Polypyrrole/Nuclear Fast Red Films on Gold Electrode and Its Application on the Electrocatalytic Determination of Methyl‐dopa and Ascorbic Acid

A novel voltammetric method using the Ppyox/NFR/Au (poly pyrrole – nuclear fast red – gold) modified electrode was developed for simultaneous measurement of various combinations of ascorbic acid (AA) and methyldopa (MDA). Polypyrrole film was prepared by incorporation of nuclear fast red (NFR) as doping anion, during the electropolymerization of pyrrole onto a gold (Au) electrode in aqueous solution using cyclic voltammetric (CV) method, and then it was overoxidized at constant potential. Differential pulse voltammetry was utilized for the measurement of both analytes using modified electrode. Well‐separated voltammetric peaks were observed for ascorbic acid (AA) and methyldopa at the Ppyox/NFR/Au modified electrodes with peak separation of 0.210 V. It has been found that under optimum condition (pH 3.0), the oxidation of AA and MDA at the surface of the electrode occurs at a potential about 260 and 50 mV less positive than unmodified Au electrode respectively. The current catalytic oxidation peaks showed a linear dependent on the concentration of AA and MDA in the range of 9.0×10^?6 to 1.0×10^?3 and 1.0×10^?7 to 2.0×10^?5 mol L^?1 respectively. The detection limit of 5.8×10^?6 and 5.0×10^?8 mol L^?1 (S/N=3) were obtained for AA and MDA respectively. The modified electrode was used for determination of AA and MDA in some real samples such as human serum and tablet.     

新型电聚合交联聚苯胺电化学传感器的研制及其在抗坏血酸测定中的应用

以苯胺、对苯二胺、1,3,5-三苯胺基苯为单体,采用循环伏安法在金电极上电化学聚合制备了一种新型的交联聚苯胺(CPAN)电化学传感器。采用交流阻抗谱和电化学方法对该传感器进行了表征。结果表明:交联剂1,3,5-三苯胺基苯结构单元被成功地引入到聚苯胺链中,所得的CPAN与线性聚苯胺(LPAN)相比,导电性增强,电子传输速率加快。CPAN/Au电极对抗坏血酸具有良好的电催化氧化作用,在优化的条件下,测得抗坏血酸浓度在1.0×10-4～1.0×10-2 mol.L-1范围内与传感器峰电流呈线性关系,检出限(3S/N)为3.3×10-5 mol.L-1。该传感器的响应时间为5s,测定结果的相对标准偏差(n=6)为2.0%～2.5%,回收率在98.0%～102%之间。     

A novel H2O2 sensor based on the enzymatically induced deposition of polyaniline at a horseradish peroxide/aligned single-wall carbon nanotubes modified Au electrode

A novel H(2)O(2) sensor based on enzymatically induced deposition of electroactive polyaniline (PANI) at a horseradish peroxide (HRP)/aligned single-wall carbon nanotubes (SWCNTs) modified Au electrode is fabricated, and its electrochemical behaviors are investigated. Electrochemical impedance spectroscopy of the sensor confirmed the formation of PANI on SWCNTs through the HRP catalytic reaction. Cyclic voltammograms of PANI/HRP/SWCNTs modified Au electrodes showed a pair of well-defined redox peaks of PANI with reduction peak potentials of 0.211 and oxidation peak potentials of 0.293 V in 0.1 M HOAc-NaOAc (pH 4.3) solution. The oxidation peak current response of PANI is linearly related to H(2)O(2) concentration from 2.5 μM to 50.0 μM with a correlation coefficient of 0.9923 and a sensitivity of 200 μA mM(-1). The detection limit is determined to be 0.9 μM with a signal-to-noise ratio of 3. Thus, the synergistic performance of the enzyme, the highly efficient polymerization of PANI, and the templated deposition of SWCNTs provided an extensive platform for the design of novel electrochemical biosensors.     

石墨烯基纳米复合物修饰印刷电极伏安法测定水中镉

构建了基于石墨烯(GS) -纳米金(Au)复合纳米微粒修饰印刷电极(SPCEs)的电化学传感器(SPCEs |GS/Au),建立了微分脉冲溶出伏安(DPSV)法测定水中痕量镉的电分析方法.采用扫描电镜(SEM)对电极表面进行了表征,DPSV法研究了镉的电化学性质.在优化实验条件下,溶出峰电流与Cd2+的质量浓度在2.5...     

Effect of pH on the Enantiospecificity of Homocysteine Monolayer on Au(111) for the Redox Reaction of 3,4‐Dihydroxyphenylalanine

The effect of pH on the enantiospecificity of Au (111) electrode modified with L ‐homocysteine was evaluated for the electrochemical redox reaction of 3,4‐dihydroxyphenylalanine (DOPA). Cyclic voltammetric peaks clearly exhibited enantiospecificity at pH 0.6 and 2, whereas no enantiospecificity was observed at pH 3, 4, and 5.5. Scanning tunneling microscopy confirmed the highly ordered (2√3×3√3)R30° structure of L ‐homocysteine at pH 0.6, at which L ‐homocysteine molecules form a dimer through the hydrogen‐bond between carboxy groups (COOH), while a disordered structure was observed at pH 5.5. These results suggest that the dimer formed in the acidic solutions at pH below 3 plays an important role in providing the enantiospecificity to the Au(111) surface.     

Electrochemical Behavior and Voltammetric Determination of Curcumin at Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of curcumin by using a electrochemically reduced graphene oxide (ERGO) modified glass carbon electrode (GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The electrochemical behaviors of curcumin at ERGO/GCE were investigated by cyclic voltammetry, suggesting that the ERGO/GCE exhibits excellent electrocatalytic activity towards curcumin, compared with bare GCE and GO/GCE electrodes. The electrochemical reaction mechanisms of curcumin, demethoxycurcumin and bisdemethoxycurcumin at the ERGO/GCE were also investigated and discussed systematically. Under physiological condition, the modified electrode showed linear voltammetric response from 0.2 μM to 60.0 μM for curcumin, with the detection limit of 0.1 μm. This work demonstrates that the graphene‐modified electrode is a promising strategy for electrochemical determination of biological important phenolic compounds.     

Phase Selective Alternating Current Voltammetric Signalling Protocol: Application in Dendritic Co‐polymer Sensor for Anthracene

A sensitive anthracene (AN) sensor was developed with a gold electrode modified with a dendritic star‐copolymer film by in situ electrochemical co‐polymerization of generation 3 propylenethiophenoimine and 3‐hexylthiophene. The sensor's {Au/G3PPT‐co‐P3HT: i. e. gold‐generation 3 poly(propylenethiophenoimine)‐co‐poly(3‐hexylthiophene)} analytical response for anthracene was obtained by phase selective alternating current voltammetric (PSACV) signal transduction. An in‐phase angle of 0° yielded the most sensitive stripping signal and produced the best discrimination between the Faradaic and capacitive currents. The PSACV sensor exhibited a linear range (LR) of 3.48–56.4 nmol/L AN and a limit of detection (LOD) of 2.62 nmol/L AN. The LOD is comparable to the value of 4.4 nmol/L AN reported for glassy carbon electrode modified with graphenated polyaniline sensor. The low LOD value suggests that the AN sensor has promise for monitoring compliance to World Health Organisation (WHO) approved limit for polyaromatic hydrocarbons (PAHs) in wastewater (3.93 nmol/L). The Au/G3PPT‐co‐P3HT sensor is not as sensitive as gas chromatography coupled to tandem mass spectrometry (GC‐MS/MS) and reversed‐phase high performance liquid chromatography (RP‐HPLC) methods. However, the advantage of the PSACV signalling protocol is that real sample test results indicate that the sensor can be used for the determination of AN in oil‐polluted wastewater.     

基于血红蛋白/纳米金/二氧化锆-壳聚糖修饰的过氧化氢生物传感器

将二氧化锆(ZrO2)分散于壳聚糖(CS)中得到稳定的CS-ZrO2复合物,制备了Hb/nano-Au/CS-ZrO2/Au过氧化氢生物传感器。 用循环伏安法和计时电流法考察该修饰电极的电化学特性,发现该修饰电极对过氧化氢(H2O2)的还原有良好的电催化作用。 实验结果表明,该传感器对H2O2的线性响应范围为3.9×10-6～1.8×10-3 mol/L,线性相关系数R=0.9956,检测下限为5.6×10-7 mol/L(S/N=3),并具有选择性高、线性范围宽和响应快等优点。     

Anodic Stripping Voltammetric Detection of Arsenic(III) at Gold Nanoparticle‐Modified Glassy Carbon Electrodes Prepared by Electrodeposition in the Presence of Various Additives

The simple, fast and highly sensitive anodic stripping voltammetric detection of As(III) at a gold (Au) nanoparticle‐modified glassy carbon (GC) (nano‐Au/GC) electrode in HCl solution was extensively studied. The Au nanoparticles were electrodeposited onto GC electrode using chronocoulometric technique via a potential step from 1.1 to 0 V vs. Ag|AgCl|NaCl (sat.) in 0.5 M H₂SO₄ containing Na[AuCl₄] in the presence of KI, KBr, Na₂S and cysteine additives. Surfaces of the resulting nano‐Au/GC electrodes were characterized with cyclic voltammetry. The performances of the nano‐Au/GC electrodes, which were prepared using different concentrations of Na[AuCl₄] (0.05–0.5 mM) and KI additive (0.01–1.0 mM) at various deposition times (10–30 s), for the voltammetric detection of As(III) were examined. After the optimization, a high sensitivity of 0.32 mA cm^?2 μM^?1 and detection limit of 0.024 μM (1.8 ppb) were obtained using linear sweep voltammetry.