Platinum nanoparticles supported MoS2 nanosheet for simultaneous detection of dopamine and uric acid

Herein, platinum nanoparticles-decorated molybdenum disulfide(Pt NPs@MoS_2) nanocomposite has been synthesized via a microwave-assisted hydrothermal method, which was characterized by transmission electron microscopy(TEM) and powder X-ray diffraction(XRD). This MoS_2-based nanocomposite modified glass carbon electrode(Pt NPs@MoS_2/GCE) exhibited excellent electrocatalytic activity toward dopamine(DA) and uric acid(UA) due to their synergistic effect. Two well-defined oxidation peaks of DA and UA were obtained at Pt NPs@MoS_2/GCE with a large peak separation of 160 m V(DA-UA), suggesting that the modified electrode could individually or simultaneously analyze DA and AA. Under the optimal conditions, the peak currents of DA and UA were linearly dependent on their concentrations in the range of 0.5–150 and 5–1000 mmol/L with detection limit of 0.17 and 0.98 mmol/L, respectively. The proposed MoS_2-based sensor can also be employed to examine DA and UA in real samples with satisfactory results. Therefore, the Pt NPs@MoS_2 nanocomposite might offer a good possibility for electrochemical sensing and other electrocatalytic applications.     

方波伏安法测定新型修饰多壁碳纳米管糊电极对肼的电催化氧化(英文)

The application of p-aminophenol as a suitable mediator, as a sensitive and selective voltammetric sensor for the determination of hydrazine using square wave voltammetric method were described. The modified multiwall carbon nanotubes paste electrode exhibited a good electrocatalytic activity for the oxidation of hydrazine at pH = 7.0. The catalytic oxidation peak currents showed a linear dependence of the peaks current to the hydrazine concentrations in the range of 0.5–175 μmol/L with a correlation coefficient of 0.9975. The detection limit (S/N = 3) was estimated to be 0.3 μmol/L of hydrazine. The relative standard deviations for 0.7 and 5.0 μmol/L hydrazine were 1.7 and 1.1%, respectively. The modified electrode showed good sensitivity and selectivity. The diffusion coefficient (D = 9.5 × 10–4 cm2/s) and the kinetic parameters such as the electron transfer coefficient (α = 0.7) of hydrazine at the surface of the modified electrode were determined using electrochemical approaches. The electrode was successfully applied for the determination of hydrazine in real samples with satisfactory results.     

在3,4-二羟基肉桂酸介质中以多壁碳纳米管为传感器电催化检测L-半胱氨酸(英文)

A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid(3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37 × 102 mol–1 L s–1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4–115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.     

基于纳米结构的电化学传感器用于伏安法测定苄丝肼、尿酸和叶酸(英文)

A carbon paste electrode modified with carbon nanotubes and ferrocene was fabricated.An electrochemical study of the modified electrode and an investigation into its efficiency for the electrocatalytic oxidation of benserazide,uric acid and folic acid were undertaken.The electrode was also used to study the electrocatalytic oxidation of benserazide using cyclic voltammetry,chronoamperometry,and square wave voltammetry(SWV).We found that the oxidation of benserazide at the surface of the modified electrode occurs at a potential about 285 mV lower than that of unmodified carbon paste electrode.SWV gave a linear dynamic range from 8.0×10-7 to 7.0×10 4 mol/L.The detection limit was 1.0×10-7 mol/L for benserazide.This modified electrode was used for the determination of benserazide,uric acid,and folic acid in an urine sample.     

Gold nanoparticles-enhanced bisphenol A electrochemical biosensor based on tyrosinase immobilized onto self-assembled monolayers-modified gold electrode

A novel electrochemical sensor based on the immobilization of tyrosinase(tyr) onto gold nanoparticles(nano-Au) and thioctic acid amide(T-NH2) self-assembled monolayers(SAMs)-modified gold electrode has been developed for the determination of bisphenol A(BPA).It was found that the nano-Au could significantly enhance the electrochemical response of tyr/nano-Au/T-NH2/Au electrode to BPA,and the enhancement effect of nano-Au on the current response was also related to the enzyme.The results indicated that the biosensor could be used as a detector for BPA determination with a linear range from3.99 ×10-7mol/L to 2.34 ×10-4mol/L and a detection limit of 1.33×10-7mol/L.In addition,this biosensor showed good reproducibility.     

Electrochemical determination of quercetin by self-assembled platinum nanoparticles/poly(hydroxymethylated-3,4-ethylenedioxylthiophene) nanocomposite modified glassy carbon electrode

A simple and sensitive platinum nanoparticles/poly(hydroxymethylated-3,4-ethylenedioxylthiophene)nanocomposite(PtNPs/PEDOT-MeOH) modified glassy carbon electrode(GCE) was successfully developed for the electrochemical determination of quercetin.Scanning electron microscopy and energy dispersive X-ray spectroscopy results indicated that the PtNPs were inserted into the PEDOTMeOH layer.Compared with the bare GCE and poly(3,4-ethylenedioxythiophene)(PEDOT) electrodes,the PtNPs/PEDOT-MeOH/GCE modified electrode exhibited a higher electrocatalytic ability toward the oxidation of quercetin due to the synergic effects of the electrocatalytic activity and strong adsorption ability of PtNPs together with the good water solubility and high conductivity of PEDOT-MeOH.The electrochemical sensor can be applied to the quantification of quercetin with a linear range covering0.04-91 μmol L~(-1) and a low detection limit of 5.2 nmol L~(-1).Furthermore,the modified electrode also exhibited good reproducibility and long-term stability,as well as high selectivity.     

以3,4-二羟基肉桂酸为介质的多壁碳纳米管糊电极用于检测药物和尿液样品中的谷胱甘肽(英文)

A sensitive and selective electrochemical sensor for the determination of glutathione(GSH) was developed using a modified multiwall carbon nanotube paste electrode with 3,4 dihydroxy cinnamic acid as a mediator.This modified electrode showed very high electrocatalytic activity for the anodic oxidation of GSH.Under the optimized conditions,the electrocatalytic peak current showed a linear relationship with GSH concentration in the range of 0.5-400.0 μmol/L with a detection limit of 0.1 μmol/L GSH.The relative standard deviations for seven successive assays of 5.0 and 25.0 μmol/L GSH were 2.2% and 2.7%,respectively.The modified electrode was used for the determination of GSH compounds in real urine samples.     

用对氨基苯酚改性的碳纳米管糊电极同时测定羟胺和苯酚(英文)

A carbon paste electrode that was chemically modified with multiwall carbon nanotubes and p-aminophenol was used as a selective electrochemical sensor for the simultaneous detection of hydroxylamine (HX) and phenol. Cyclic voltammetry, double potential-step chronoamperometry, square wave voltammetry (SWV), and electrochemical impedance spectroscopy were used to investigate the use of p-aminophenol in the carbon nanotubes paste matrixes as a mediator for the electrocatalytic oxidation of HX and phenol in aqueous solution. The coefficient of electron transfer and catalytic reaction rate constant were determined using the electrochemical methods. Under optimized conditions, the electrocatalytic oxidation current peaks for HX and phenol increased linearly with concentration in the range of 0.5-180.0 and 10.0-650.0 μmol/L for HX and phenol, respectively. The detection limits for HX and phenol were 0.15 and 7.1 μmol/L, respectively. The anodic potential peaks of HX and phenol were separated by 0.65 V in SWV. Because of good selectivity and sensitivity, the present method provides a simple method for the selective detection of HX and phenol in practical samples such as water samples.     

Fabrication of the electrochemically reduced graphene oxide-bismuth nanoparticles composite and its analytical application for an anticancer drug gemcitabine

The present study explores an electroreduced graphene oxide-bismuth nanoparticles composite(ErGOBi) as an electrochemical sensor for the determination of an anticancer drug, gemcitabine hydrochloride(GMB). The Er-GOBi interface was prepared by drop casting of bismuth nitrate-graphene oxide suspension on a glassy carbon electrode(GCE) followed by electro-reduction in the potential range of 0.6 V to 1.7 V. SEM, FTIR, EDAX and AFM techniques were employed for the characterization of prepared materials. Cyclic voltammetric and electrochemical impedance spectroscopic methods were used to understand the charge transfer properties of stepwise modification of Er-GOBi/GCE. GMB exhibited an irreversible oxidation peak at 1.144 V on Er-GOBi/GCE in phosphate buffer of p H 3. A 100-fold enhanced oxidation peak current was observed at Er-GOBi/GCE when compared to that at bare GCE.Sensing performance of Er GO-Bi/GCE was optimized by varying peak current dependent parameters.Linear relationship between the peak current and concentration of GMB was observed in the range of 0.1–51.1 mmol/L in differential pulse voltammetric method and 2.1–61.1 mmol/L in linear sweep voltammetric method. The practical utility of the proposed sensor, Er-GOBi/GCE was demonstrated by determining GMB in pharmaceutical formulations and spiked urine samples.     

Voltammetric determination of cysteamine at multiwalled carbon nanotubes paste electrode in the presence of isoproterenol as a mediator

A sensitive electrochemical sensor for the determination of cysteamine(CA) was developed using a modified multiwall carbon nanotube paste electrode(MWCNTPE) with isoproterenol(ISPT) as a mediator.This modified electrode showed very high electrocatalytic activity for the anodic oxidation of CA.Under the optimized conditions,the electrocatalytic peak current showed a linear relationship with CA concentration in the range of 0.3–450.0 mmol/L with a detection limit of 0.09 mmol/L CA.The modified electrode was used for the determination of CA in real samples such as urine and drug samples.     

Oxidation and detection of L-cysteine using a modified Au/Nafion/glass carbon electrode

In this work,the electrochemical oxidation of L-cysteine(CySH)was investigated on a composite film modified electrode with Au nanoparticles dispersed in the fluorocarbon polymer(Nafion).The excellent electrocatalytic effect on CySH oxidation was attributed to the role of Au nanoparticles.The voltammetric studies revealed two anodic peaks for the oxidation of CySH in the pH range of 2.0–8.0.The electrode was used to detect cysteine at pH 2.0 and pH 7.0.At pH 2.0,a determination range of 3.0–50.0?mol/L was ob...     

Graphene Oxide Doped Poly（hydroxymethylated-3,4- ethylenedioxythiophene）： Enhanced Sensitivity for Electrochemical Determination of Rutin and Ascorbic Acid

A novel graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene)(PEDOT-MeOH/GO) composite film was synthesized and utilized as an efficient electrode material for simultaneous detection of rutin and ascorbic acid(AA). PEDOT-MeOH/GO films were synthesized on glassy carbon electrode(GCE) by a facile one-step electrochemical approach and were characterized by scanning electron microscopy, UV-Vis spectroscopy, FTIR spectra and electrochemical methods. Then the PEDOT-MeOH/GO/GCE was applied successfully in the simultaneous detection of rutin and AA. The results showed that the oxidation peak currents of rutin and AA obtained at the PEDOT-MeOH/GO/GCE were much higher than those at the traditional conducting polymer PEDOT/GO/GCE, PEDOT-MeOH/GCE, PEDOT/GCE and bare GCE. Under optimized conditions, the linear ranges for rutin and AA are 20 nmol/L-10 μmol/L and 8 μmol/L-1 mmol/L, respectively. The detection limit is 6 nmol/L for rutin and 2 μmol/L for AA(S/N = 3), which are lower than those of the reported electrochemical sensors.     

Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed.The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine(DA)and epinephrine(EP).Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution(PBS)and the character was used for the detection DA and EP simultaneously.The peak currents increase linearly with DA and EP concentration over the range of 8.0×10-5 to 7.0×10-4 mol/L and 5.0×10-6 to 1.0×10-4 mol/L with detection limits of 2 × 10-5 and 1×10-6 mol/L,respectively.The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid(AA).     

利用Cu0/多壁碳纳米管纳米复合物修饰玻碳电极快速非酶法检测葡萄糖和果糖(英文)

A nonenzymatic electrochemical sensor for glucose and fructose was fabricated that contained a glassy carbon electrode modified with a copper oxide (CuO)/multiwalled carbon nanotube (MWCNT) nanocomposite. The electrochemical properties of the CuO/MWCNT‐modified glassy carbon electrode were investigated. Two distinguishable anodic peaks were observed around 0.30 and 0.44 V corresponding to the oxidation of glucose and fructose, respectively, at the surface of the modified electrode. The detection limits for glucose and fructose were both 0.04 mmol/L. The sensor was used to simultaneously determine the concentrations of glucose and fructose in hydrolyzed sucrose samples, and to measure glucose in blood serum samples, demonstrating its potential as a nonenzymatic carbohydrate sensor.     

pharmaceutical and biological samples using modified multiwall carbon nanotubes paste electrode

A carbon paste electrode(CPE) chemically modified with multiwall carbon nanotubes and ferrocene(FC) was used as a selective electrochemical sensor for the simultaneous determination of trace amounts of cysteamine(CA) and folic acid(FA).This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of CA.The peak current of differential pulse voltammograms of CA and FA increased linearly with their concentration in the ranges of 0.7-200μmol/L CA and 5.0- 700μmol/L FA.The detection limits for CA and FA were 0.3μmol/L and 2.0μmoI/L,respectively.The diffusion coefficient(D) and transfer coefficient(α) of CA were also determined.These conditions are sufficient to allow determination of CA and FA both individually and simultaneously.     

Sensitive and selective molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for doxycycline hyclate determination

An electrochemical sensor for doxycycline hyclate(DC)detection with high sensitivity and good selectivity is reported.The sensor was fabricated by electro-polymerization of molecularly imprinted polymers(MIPs)in the presence of DC onto multi-walled carbon nanotubes modified glassy carbon electrode(MWCNTs/GCE).The MWCNTs can significantly increase the current response of the sensor,leading to enhanced sensitivity.The MIPs provide selective recognition sites for DC detection.The experimental parameters,such as the polymer monomer concentration,supporting electrolyte pH,the time for electro-polymerization and the incubation time of the sensor with DC were optimized.Under optimized experimental conditions,the sensor displayed a linear range of 0.05μmol/L-0.5μmol/L towards DC detection,with the detection limit of 1.3×10^-2μmol/L.The sensor was successfully applied for recovery test of DC in human serum samples.     

Immobilization and hybridization of DNA based on magnesium ion modified 2,6-pyridinedicarboxylic acid polymer and its application for label-free PAT gene fragment detection by electrochemical impedance spectroscopy

A new approach for a simple electrochemical detection of PAT gene fragment is described. Poly(2,6-pyridinedicarboxylic acid) (PDC) modified glassy carbon electrode (GCE) was prepared by potential scan electropolymerization in an aqueous solution. Mg2 ions were incorporated by immer-sion of the modified electrode in 0.5 mol/L aqueous solution of MgCl2 to complete the preparation of a generic "activated" electrode ready for binding the probe DNA. The ssDNA was linked to the conduct-ing polymer by forming a bidentate complex between the carboxyl groups on the polymer and the phosphate groups of DNA via Mg2 . DNA immobilization and hybridization were characterized with dif-ferential pulse voltammetry (DPV) by using methylene blue (MB) as indicator and electrochemical im-pedance spectroscopy (EIS). The EIS was of higher sensitivity for DNA detection as compared with voltammetric methods in our strategy. The electron transfer resistance (Ret) of the electrode surface in EIS in [Fe(CN)6]3-/4- solution increased after the immobilization of the DNA probe on the Mg/PDC/GCE electrode. The hybridization of the DNA probe with complementary DNA (cDNA) made Ret increase further. The difference between the Ret at ssDNA/Mg/PDC/GCE and that at hybridization DNA modified electrode (dsDNA/Mg/PDC/GCE) was applied to determine the specific sequence related to the target PAT gene with the dynamic range comprised between 1.0 × 10-9 and 1.0 × 10_5 mol/L. A detection limit of 3.4 × 10-10 mol/L of oligonucleotides can be estimated.     

A Novel Amperometric Nitric Oxide Sensor Based on Polythionine / Nation Modified Glassy Carbon Electrode

A novel amperometric sensor for the determination of nitric oxide was developed by coating polythionine / nafion on a glassy carbon electrode. This sensor exhibited a great enhancement to the oxidation of nitric oxide. The oxidation peak currents were linear to the concentration of nitric oxide over the wide range from 3.6×10-7 to 6.8×10-5 mol.L-1, and the detection limit was 7.2×10-8 mol.L-1. Experimental results showed that this nitric oxide sensor possessed excellent selectivity and longer stability. NO releasing from rat kidney was monitored by this sensor.     

Determination of captopril in patient human urine using ferrocenemonocarboxylic acid modified carbon nanotubes paste electrode

<正>In this work,we describe a new strategy for the electrochemical determination of captopril(CA) using ferrocenemonocarboxylic acid as a mediator and multiwall carbon nanotubes as sensors in aqueous solution at pH 7.0.The diffusion coefficient(D),and the kinetic parameters such as electron transfer coefficient(α).and heterogeneous rate constant(k_h),for CA were also determined using electrochemical approaches.Under the optimized conditions,the electrocatalytic oxidation peak current of captopril showed two linear dynamic ranges with a detection limit of 0.3×10~(-6) mol L~(-1) captopril.The linear calibration range was 0.8×10~(-6) to 65×10~(-6) mol L~(-1) using cyclic voltammetry.Finally,this modified electrode was also examined as a selective,simple and precise new electrochemical sensor for the determination of captopril in real samples such as drug and patient human urine.     

尿酸和叶酸存在下改性碳纳米管糊电极上多巴胺电催化氧化(英文)

A chemically modified carbon paste electrode (CPE), consisting of 2,2'-[ (1E)- (1,2- phenylenebis (azanylylidene)] bis (methanylylidene)]bis (benzene-1,4-diol) (PBD) and multiwalled carbon nano-tubes (CNTs), was used to study the electrocatalytic oxidation of dopamine using cyclic voltamme-try, chronoamperometry, and differential pulse voltammetry (DPV). First, the electrochemical be-havior of the modified electrode was investigated in buffer solution. Then the diffusion coefficient, electrocatalytic rate constant, and electron-transfer coefficient for dopamine oxidation at the sur-face of the PBD-modified CNT paste electrode were determined using electrochemical approaches. It was found that under optimum conditions (pH = 7.0), the oxidation of dopamine at the surface of such an electrode occurred at about 200 mV, lower than that of an unmodified CPE. DPV of dopa-mine at the modified electrode exhibited two linear dynamic ranges, with a detection limit of 1.0 μmol/L. Finally, DPV was used successfully for the simultaneous determination of dopamine, uric acid, and folic acid at the modified electrode, and detection limits of 1.0, 1.2, and 2.7 μmol/L were obtained for dopamine, uric acid, and folic acid, respectively. This method was also used for the determination of dopamine in a pharmaceutical preparation using the standard addition method.