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GCE
Kinds of GCE Selected AbstractsDental therapists' experience in the immediate management of traumatized teethDENTAL TRAUMATOLOGY, Issue 2 2006Teresa Loh Abstract,,, The optimal immediate management of traumatized teeth is known to be important for long-term success. One hundred and sixty-seven school dental therapists with General Certificate of Education ,Ordinary' (GCE ,O') level qualification were surveyed on their knowledge and experience on immediate management of dental trauma. The results showed only 41.2% felt comfortable with their present knowledge on the subject. A high proportion of the respondents (94.6%) indicated a need for more knowledge. All therapists concurred on the need to replant a permanent tooth and most (85.1%) agreed that this should be done within 30 min. More than half (54.8%) were not sure of the optimal storage medium for avulsed teeth. Their attitude towards acquiring knowledge in this aspect was good (80.5%) and all would take immediate action to settle appointments for trauma cases. [source] Poly(pyridine-3-boronic acid)/Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrodes for Simultaneous Determination of Ascorbic Acid, 3,4-Dihydroxyphenylacetic Acid and Uric AcidELECTROANALYSIS, Issue 19 2010Zhijiao Wu Abstract Poly(pyridine-3-boronic acid) (PPBA)/multiwalled carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was used for the simultaneous determination of ascorbic acid (AA), 3,4-dihydroxyphenylacetic acid (DOPAC) and uric acid (UA). The anodic peaks for AA, DOPAC and UA at the PPBA/MWCNTs/GCE were well resolved in phosphate buffer solution (pH,7.4). The electrooxidation of AA, DOPAC and UA in the mixture solution was investigated. The peak currents increase with their concentrations increasing. The detection limits (S/N=3) of AA, DOPAC and UA are 5,µM, 3,µM and 0.6,µM, respectively. [source] A New Amperometric Hydrazine Sensor Based on Prussian Blue/Single-walled Carbon Nanotube NanocompositesELECTROANALYSIS, Issue 16 2010Cong Wang Abstract A slow reaction process has been successfully used to synthesize Prussian blue/single-walled carbon nanotubes (PB/SWNTs) nanocomposites. Electrochemical and surface characterization by cyclic voltammetry (CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) confirmed the presence of PB nanocrystallites on SWNTs. PB/SWNTs modified glassy carbon electrode (GCE) exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. The fabricated hydrazine sensor showed a wide linear range of 2.0×10,6,6.0×10,3,M with a response time less than 4,s and a detection limit of 0.5,,M. PB/SWNTs modified electrochemical sensors are promising candidates for cost-effective in the hydrazine assays. [source] Green Synthesis of Silver Nanoparticles Using Ionic Liquid and Application for the Detection of Dissolved OxygenELECTROANALYSIS, Issue 6 2010Tsung-Hsuan Tsai Abstract The electrochemical synthesis of silver nanoparticles (nano-Ag) has been successfully carried out on glassy carbon electrode (GCE) and indium tin oxide electrode (ITO) using 1-butyl-3-methylimidazolium tetrafluoroborate (BMT) as green electrolytes. Further the electrodeposited nano-Ag modified ITO electrode has been examined using atomic force microscopy (AFM), and X-ray diffraction studies (XRD). The electrodeposited Ag nanoparticles on ITO were found in the size range of 5 to 35,nm. The nano-Ag film modified GCE was further coated with nafion (Nf) and BMT (1,:,1 ratio) mixture and found to be stable in BMT and in pH,7 phosphate buffer solution (PBS). The nano-Ag/BMT-Nf film modified GCE successfully applied for the oxygen reduction reaction in neutral pH (pH,7.0 PBS). The proposed film modified GCE successfully reduces the over potential and show well defined reduction peaks for the detection of dissolved oxygen using cyclic voltammetry (CV) and rotating disc voltammetry (RDE). The film also applied for the detection of dissolved oxygen using electrochemical impedance spectroscopic studies (EIS). [source] Silver Doped Poly(L -valine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Uric Acid, Ascorbic Acid and DopamineELECTROANALYSIS, Issue 5 2010Wenna Hu Abstract In this paper, a silver doped poly(L -valine) (Ag-PLV) modified glassy carbon electrode (GCE) was fabricated through electrochemical immobilization and was used to electrochemically detect uric acid (UA), dopamine (DA) and ascorbic acid (AA) by linear sweep voltammetry. In pH,4.0 PBS, at a scan rate of 100,mV/s, the modified electrode gave three separated oxidation peaks at 591,mV, 399,mV and 161,mV for UA, DA and AA, respectively. The peak potential differences were 238,mV and 192,mV. The electrochemical behaviors of them at the modified electrode were explored in detail with cyclic voltammetry. Under the optimum conditions, the linear ranges were 3.0×10,7 to 1.0×10,5,M for UA, 5.0×10,7 to 1.0×10,5,M for DA and 1.0×10,5 to 1.0×10,3,M for AA, respectively. The method was successfully applied for simultaneous determination of UA, DA and AA in human urine samples. [source] Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion BiocompositeELECTROANALYSIS, Issue 3 2010Kangfu Zhou Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source] Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs,NaDBS Modified Stannum Film ElectrodeELECTROANALYSIS, Issue 23 2009Qing Tian Abstract A multiwalled carbon nanotubes,sodium dodecyl benzene sulfonate (MWCNTs,NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs-NaDBS film electrode was prepared by applying MWCNTs,NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ,100.0,,g L,1 with detection limits of 0.9,,g L,1 for zinc(II) and 0.8,,g L,1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample. [source] Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes-gold Nanoparticles Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 22 2009Xinman Tu Abstract A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)-gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT-GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10,8 to 2×10,5 mol L,1, with a limit of detection of 7.5,nmol L,1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results. [source] Multiwalled Carbon Nanotubes Encased in Ruthenium Oxide Film as a Hybrid Material for Neurotransmitters SensorELECTROANALYSIS, Issue 16 2009Chien-Chieh Ti Abstract A hybrid film (MWCNTs-RuOx,nH2O) which contains multiwalled carbon nanotubes (MWCNTs) along with the incorporation of ruthenium oxide (RuOx,nH2O) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of MWCNTs in the hybrid film enhances surface coverage concentration (,) of RuOx,nH2O to ,2100%. The surface morphology of the hybrid film deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy. These two techniques reveal that the RuOx,nH2O incorporated on MWCNTs. Electrochemical quartz crystal microbalance study too reveals the incorporation of MWCNTs and RuOx,nH2O. The MWCNTs-RuOx,nH2O hybrid film exhibits promising enhanced electrocatalytic activity towards the biochemical compounds such as epinephrine and norepinephrine. The electrocatalytic responses of these analytes at RuOx,nH2O, MWCNTs and MWCNTs-RuOx,nH2O hybrid films have been measured using cyclic voltammetry. The obtained sensitivity values from electrocatalysis studies of analytes for MWCNTs-RuOx,nH2O hybrid film are higher than the RuOx,nH2O and MWCNTs films. Finally, the flow injection analysis has been used for the amperometric studies of analytes at MWCNTs-RuOx,nH2O hybrid film modified SPCEs. [source] The Preliminary Studies of Electrochemical Behavior of Paracetamol and Its Metabolites on Glassy Carbon Electrode by Voltammetric MethodsELECTROANALYSIS, Issue 10 2009Irena Baranowska Abstract The new, rapid and sensitive method for the determination of paracetamol (PAR) and its glucuronide (PG) and sulfate (PS) metabolites is proposed. The electrochemical properties of the compounds were examined by cyclic voltammetry (CV) on glassy carbon electrode (GCE). All measurements were carried out in Britton,Robinson buffers (BR) with different pH values over the pH range 1.81,7.24. The preliminary research indicated that PAR could be determined simultaneously with one of its metabolites. The linearity of calibration curves was obtained for concentrations between 1.65×10,5 and 1.65×10,4 M for PAR, 1.53×10,5 and 1.53×10,4 M for PG and 2.17×10,5 and 1.52×10,4 M for PS. [source] Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano-Gold Self-Assembled Glassy Carbon ElectrodeELECTROANALYSIS, Issue 10 2009Guangzhi Hu Abstract Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self-assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self-assembling gold nanoparticles on the surface of L -cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well-defined redox peaks of DA on the GNP/LC/GCE was obtained at Epa=0.197,V and Epc=0.146,V, respectively. And the peak separation between DA and AA is about 0.2,V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10,8,8.5×10,5 mol L,1 and 1.0×10,6,2.5×10,3 mol L,1, with the detection limit of 2.0×10,8 mol L,1 and 3.0×10,7 mol L,1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result. [source] Ordered Mesoporous Carbon Functionalized with Polythionine for Electrocatalytic ApplicationELECTROANALYSIS, Issue 7 2009Bin Qi Abstract A polythionine (PTH) functionalized ordered mesoporous carbon (OMC) material (PTH/OMC) was presented. The electrochemistry kinetic characteristics of this material are investigated and compared with pure OMC. The results showed that compared with OMC, PTH/OMC possesses a much higher electron transfer rate. For the application of this material, an electrocatalytic based NADH biosensor was constructed on glassy carbon electrode (GCE). Instead of 0.592,V on bare GCE and 0.206,V on OMC/GCE, the amperometric detection of NADH could be effectively performed on the present biosensor with operation potential be set at 0.0,V. In addition, the sensor showed good reproducibility and stability. [source] Direct Electrochemistry and Electrocatalysis of Hemoglobin in Lipid Film Incorporated with Room-Temperature Ionic LiquidELECTROANALYSIS, Issue 20 2008Gaiping Li Abstract A facile phospholipid/room-temperature ionic liquid (RTIL) composite material based on dimyristoylphosphatidylcholine (DMPC) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was exploited as a new matrix for immobilizing protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to characterize this composite film. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. UV-vis absorbance spectra showed that Hb still maintained its heme crevice integrity in this composite film. By virtue of the Hb/DMPC/[bmim]PF6 composite film-modified glassy carbon electrode (GCE), a pair of well-defined redox peaks of Hb was obtained through the direct electron transfer between protein and underlying GCE. Moreover, the reduction of O2 and H2O2 at the Hb/DMPC/[bmim]PF6 composite film-modified GCE was dramatically enhanced. [source] Improved Voltammetric Response of L -Tyrosine on Multiwalled Carbon Nanotubes-Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric IonELECTROANALYSIS, Issue 19 2008Liqin Liu Abstract L -Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH,5.5 its peak potential is 0.70,V (vs. SCE). When an ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF6]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu2+ ion the anodic peak of L -tyrosine increases further due to the formation of Cu2+ - L -tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu2+ - L -tyrosine complex on MWCNTs-[omim][PF6] composite coated electrode is developed for L -tyrosine. Under the optimized conditions, the anodic peak current is linear to L -tyrosine concentration in the range of 1×10,8,5×10,6 M, and the detection limit is 8×10,9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10,9 M and 4×10,6 M, respectively. [source] Glassy Carbon Electrodes Modified with Multiwall Carbon Nanotubes Dispersed in PolylysineELECTROANALYSIS, Issue 15 2008Yamile Jalit Abstract We report the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multiwall carbon nanotubes (MWCNT) in polylysine (Plys) (GCE/MWCNT-Plys). The resulting electrodes show an excellent electrocatalytic activity towards different bioanalytes like ascorbic acid, uric acid and hydrogen peroxide, with important decrease in their oxidation overvoltages. The dispersion of 1.0,mg/mL MWCNT in 1.0,mg/mL polylysine is highly stable, since after 2 weeks the sensitivity for hydrogen peroxide at GCE modified with this dispersion remained in a 90% of the original value. The MWCNT-Plys layer immobilized on glassy carbon electrodes has been also used as a platform to build supramolecular architectures by self-assembling of polyelectrolytes based on the polycationic nature of the polylysine used to disperse the nanotubes. The self-assembling of glucose oxidase has allowed us to obtain a supramolecular multistructure for glucose biosensing. The influence of glucose oxidase concentration and adsorption time as well as the effect of using polylysine or MWCNT-Plys as polycationic layers for further adsorption of GOx is also evaluated. [source] Voltammetric Reduction of a 4-Nitroimidazole Derivative on a Multiwalled Carbon Nanotubes Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 13 2008P. Jara-Ulloa Abstract We report the electrochemical behavior of a 4-nitroimidazole derivative, 1-methyl-4-nitro-2-hydroxymethylimidazole (4-NImMeOH), on glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT). As dispersing agents, dimethylformamide (DMF) and water were used. The electrochemical response of the resulting electrodes was evaluated using linear sweep, cyclic and square-wave voltammetry (LSV, CV and SWV). Several parameters such as medium pH, nature and concentration of the CNTs dispersion and accumulation time were tested. The optimal conditions determined for obtain better response were: pH,2, dispersion concentration=4,mg/mL of CNT in water, accumulation time=7,min. The MWCNT-modified GCE exhibited attractive electrochemical properties producing enhanced currents with a significant reduction in the overpotential and good signal-to-noise characteristics, in comparison with the bare GCE. The modified electrode is highly repeatable for consecutive measurements, reaching a variation coefficient of 2.9% for ten consecutive runs. [source] Selective Determination of Dopamine in the Presence of Ascorbic Acid at Porous-Carbon-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 11 2008Shuqing Song Abstract Selective dopamine (DA) determinations using porous-carbon-modified glassy carbon electrodes (GCE) in the presence of ascorbic acid (AA) were studied. The effects of structure textures and surface functional groups of the porous carbons on the electrochemical behavior of DA was analyzed based on both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. The differential pulse voltammetry of DA on the modified GCE was determined in the presence of 400-fold excess of AA, and the linear determination ranges of 0.05,0.99, 0.20,1.96, and 0.6,12.60,,M with the lowest detected concentrations of 4.5×10,3, 4.4×10,2, and 0.33,,M were obtained on the mesoporous carbon, mesoporous carbon with carboxylic and amino groups modified electrodes, respectively. [source] Electrochemical Behavior and Determination of L -Tyrosine at Single-walled Carbon Nanotubes Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 11 2008Xiaozhi Yu Abstract 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 , (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. [source] Electrocatalysis and Amperometric Detection of the Reduced Form of Nicotinamide Adenine Dinucleotide at Toluidine Blue/Zinc Oxide Coated ElectrodesELECTROANALYSIS, Issue 18 2007Ashok Kumar Abstract Thin toluidine blue (TBO) and zinc oxide (ZnO) hybrid films have been grown on glassy carbon electrode (GCE) and indium tin oxide coated (SnO2) glass electrodes by using cyclic voltammetry (CV). Scanning electron microscopy (SEM) images revealed spherical and beads-like shape of highly oriented TBO/ZnO hybrid films. Energy dispersive spectrometry (EDS) results declared that the films composed mainly of Zn and O. Moreover, TBO/ZnO hybrid films modified electrode is electrochemically active, dye molecules were not easily leached out from the ZnO matrix and the hybrid films can be considered for potential applications as sensor for amperometric determination of reduced nicotinamide adenine dinucleotide (NADH) at 0.0,V. A linear correlation between electrocatalytic current and NADH concentration was found to be in the range between 25,,M and 100,,M in phosphate buffer. In addition, we observed that dopamine, ascorbic acid and uric acid are not interference in amperometric detection of NADH in this proposed method. In addition, TBO/ZnO hybrid film modified electrode was highly stable and its response to the NADH also remained relentless. [source] Electrochemical Immunoassay for Carbohydrate Antigen-125 Based on Polythionine and Gold Hollow Microspheres Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 17 2007Xiao-Hong Fu Abstract A new electrochemical immunosensor for the detection of carbohydrate antigen-125 (CA125), a carcinoma antigen, was developed by immobilization CA125 antibody (anti-CA125) on gold hollow microspheres and porous polythionine (PTH) modified glassy carbon electrodes (GCE). The gold hollow microspheres provided a biocompatible microenvironment for proteins, and greatly amplified the coverage of anti-CA125 molecules on the electrode surface. The performance and factors influencing the immunosensor were investigated in detail. The detection is based on the current change before and after the antigen-antibody interaction. Under optimal conditions, the amperometric changes were proportional to CA125 concentration ranging from 4.5 to 36.5,U/mL with a detection limit of 1.3,U/mL (at 3,). The CA125 immunosensor exhibited good precision, high sensitivity, acceptable stability, accuracy and reproducibility. The as-prepared immunosensors were used to analyze CA125 in human serum specimens. Analytical results suggest that the developed immunoassay has a promising alternative approach for detecting CA125 in the clinical diagnosis. [source] Electrochemical Preparation of Poly(acriflavine) Film-Modified Electrode and Its Electrolcatalytic Properties Towards NADH, Nitrite and Sulfur OxoanionsELECTROANALYSIS, Issue 9 2007Shen-Ming Chen Abstract Electrochemical polymerization of acriflavine (AF) was carried out onto glassy carbon electrodes (GCE) from the aqueous buffer solution containing 1.5×10,3,M AF monomer (pH,3.5) which produced a thin electrochemically active film. This is noted as poly(AF) film modified electrodes (PAF/GCE). This modified electrode was shown a stable reversible redox couple centered at +0.22,V in pH,3.5 buffer solutions. PAF/GCE was found to be more stable in acidic solutions and its formal potential was found to be pH dependent with a slope close to ,60,mV/pH. The electrochemical deposition kinetics of poly(AF) onto gold coated quartz crystal was studied by using electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry (CV). PAF/GCE was found be good mediator for electrochemical oxidation of reduced nicotinamide adenine dinucleotide (NADH) in pH,5 buffer solutions. The electrocatalytic oxidation of SO and electrocatalytic reduction of NO, SO and S2O were carried out at PAF/GCE electrode in acidic aqueous solutions. The electrocatalytic oxidation of NADH was also investigated by using amperometric method. [source] Electrooxidation of DNA at Glassy Carbon Electrodes Modified with Multiwall Carbon Nanotubes Dispersed in ChitosanELECTROANALYSIS, Issue 7-8 2007Soledad Bollo Abstract We report on the analytical performance of glassy carbon (GCE) electrodes modified with a dispersion of multiwall carbon nanotubes (CNT) in chitosan (CHIT) for the quantification of DNA. The electroanalytical response of the resulting electrodes was evaluated using differential pulse voltammetry, while the electrochemical reactivity of the film surface was characterized using scanning electrochemical microscopy. Different treatments of the modified GCE were evaluated to improve the stability of the film and the accumulation of DNA. The guanine oxidation signal of double stranded calf-thymus DNA after 3-min accumulation was 20 times higher at GCE/CHIT-CNT cross-linked with glutaraldehyde (GTA) than at bare GCE, while the peak potential was around 45,mV less positive. The guanine oxidation signal demonstrated to be highly reproducible, with 3.4% RSD for 5 different electrodes. The treatment with sodium hydroxide demonstrated to be not effective since the resulting films were less stable and the guanine oxidation signal was ten times smaller compared to electrodes prepared with the GTA treated films. The effect of chitosan molecular weight used to prepare the dispersion and the amount of carbon nanotubes dispersed were evaluated. The response of single stranded DNA and oligo(dG)15 is also discussed. [source] Low Potential Detection of NADH at Titanium-Containing MCM-41,Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 5 2007Zhihui Dai Abstract Titanium-containing MCM-41 (Ti-MCM-41) modified glassy carbon electrode (GCE) can exhibit an excellent electrocatalytic activity towards the oxidation of ,-Nicotinamide adenine dinucleotide (NADH). A dramatic decrease in the over-voltage of NADH oxidation reaction is observed at 0.28,V (vs. SCE). The modified electrode is found to be stable and reproducible. The electrode shows a linear response for a wide range of 10,1200,,M NADH and the detection limit is 8.0,,M. Ti-MCM-41 mesoporous molecular sieves provide an efficient matrix for development of NADH biosensors and the prepared electrode not only can be used to detect the concentration of NADH in biochemical reaction, but also as the potential matrix of the construction of dehydrogenases biosensor. [source] Electrocatalysis and Voltammetric Determination of Dopamine at a Calix[4]arene Crown-4 Ether Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 4 2007Guo-Song Lai Abstract A sensitive and selective electrochemical method for the determination of dopamine (DA) was developed using a calix[4]arene crown-4 ether (CACE) film modified glassy carbon electrode (GCE). The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of DA in the pH,6.00 Britton,Robinson buffer solution, and ascorbic acid (AA) did not interfere with it. The diffusion coefficient (D=2.7×10,5,cm2 s,1), and the kinetic parameter such as the electron transfer coefficient (,=0.54) of DA at the surface of CACE were determined using electrochemical approaches. The catalytic oxidation peak currents showed a linear dependence on the DA concentration and a linear analytical curve was obtained in the range of 2.0×10,5,1.0×10,3,M of DA with a correlation coefficient of 0.9990. The detection limit (S/N=3) was estimated to be 3.4×10,6,M. This method was also examined for the determination of DA in an injection sample. In addition, effects of possible interferences were investigated. The present work shows the potential of the proposed method for the fabrication of a modified electrode, as it can be effectively used for voltammetric detection of DA. [source] Photoelectrocatalytic Oxidation of NADH with Electropolymerized Toluidine Blue OELECTROANALYSIS, Issue 2-3 2007Yusuf Dilgin Abstract A poly(Toluidine Blue O) (poly-TBO) modified electrode was successfully prepared by repeated sweeping the applied potential from ,0.6 to +0.8,V (vs. SCE) on a glassy carbon electrode (GCE) in borate buffer solution at pH,9.1,containing 0.1,M NaNO3 and 0.4,mM Toluidine Blue O (TBO). The poly-TBO modified GCE shows electrocatalytic activity toward NADH oxidation in phosphate buffer solution at pH,7.0, with an overpotential of ca. 350,mV lower than that at the bare electrode. The photoelectrocatalytic oxidation of NADH at this electrode was also successfully investigated by using cyclic voltammetry and amperometry at constant potential. When the modified electrode surface was irradiated with a 250,W halogen lamp, a photoelectrocatalytic effect was observed for NADH oxidation and the current was increased about 2.2 times. The applied potential was selected at +100,mV for amperometric and photoamperometric detection of NADH. A linear calibration graph for NADH was obtained in the range between 1.0×10,5 and 1.0×10,3 M and between 5.0×10,6 and 1.0×10,3 M for amperometric and photoamperometric studies, respectively. The effect of some interfering compounds, such as ascorbic acid and dopamine on the electrocatalytic and photoelectrocatalytic oxidation of NADH was tested. [source] Determination of Uric Acid in the Presence of Ascorbic Acid Using Poly(3,4-ethylenedioxythiophene)-Modified ElectrodesELECTROANALYSIS, Issue 24 2005Senthil Kumar, Shanmugam Abstract A poly(3,4-ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode (GCE) was used to determine uric acid in the presence of ascorbic acid at physiological pH facilitating a peak potential separation of ascorbic acid and uric acid oxidation (ca. 365,mV), which is the largest value reported so far in the literature. Also, an analytical protocol involving differential pulse voltammetry has been developed using a microchip electrode for the determination of uric acid in the concentration range of 1 to 20,,M in presence of excess of ascorbic acid. [source] DNA Hybridization at Magnetic Nanoparticles with Electrochemical Stripping DetectionELECTROANALYSIS, Issue 23 2004Ningning Zhu Abstract A simple and practical method for electrochemical DNA hybridization assay has been developed to take advantage of magnetic nanoparticles for ssDNA immobilization and zinc sulfide nanoparticle as oligonucleotide label. Magnetic nanoparticles were prepared by coprecipitation of Fe2+ and Fe3+ with NH4OH, and then amino silane was coated onto the surface of magnetite nanoparticles. The magnetic nanoparticles have the advantages of easy preparation, easy surface modification and low cost. The target ssDNA with the phosphate group at the 5, end was then covalently immobilized to the amino group of magnetite nanoparticles by forming a phosphoramidate bond in the presence of 1-ethyl-3-(3-dimeth-ylaminopropyl)carbodiimide (EDAC). The zinc sulfide (ZnS) nanoparticle-labeled oligonucleotides probe was used to identify the target ssDNA immobilized on the magnetic nanoparticles based on a specific hybridization reaction. The hybridization events were assessed by the dissolution of the zinc sulfide nanoparticles anchored on the hybrids and the indirect determination of the dissolved zinc ions by anodic stripping voltammetry (ASV) at a mercury film glassy carbon electrode (GCE). The proposed method couples the high sensitivity of anodic stripping analysis for zinc ions with effective magnetic separation for eliminating nonspecific adsorption effects and offers great promise for DNA hybridization analysis. [source] Catalytic Effect on Silver Electrodeposition of Gold Deposited on Carbon ElectrodesELECTROANALYSIS, Issue 19 2004Alfredo de, Escosura-Muñiz Abstract A new methodology, based on silver electrocatalytic deposition and designed to quantify gold deposited onto carbon paste electrode (CPE) and glassy carbon electrode (GCE), has been developed in this work. Silver (prepared in 1.0,M NH3) electrodeposition at ,0.13,V occurs only when gold is previously deposited at an adequate potential on the electrode surface for a fixed period of time. When a CPE is used as working electrode, an adequate oxidation of gold is necessary. This oxidation is carried out in both 0.1,M NaOH and 0.1,M H2SO4 at oxidation potentials. When a GCE is used as working electrode, the oxidation steps are not necessary. Moreover, a cleaning step in KCN, which removes gold from electrode surface, is included. To obtain reproducibility in the analytical signal, the surface of the electrodes must be suitably pretreated; this electrodic pretreatment depends on the kind of electrode used as working electrode. Low detection limits (5.0×10,10,M) for short gold deposition times (10,min for CPE and 5,min for GCE) were achieved with this novel methodology. Finally, sodium aurothiomalate can be quantified using silver electrocatalytic deposition and GCE as working electrode. Good linear relationship between silver anodic stripping peak and aurothiomalate concentration was found from 5.0×10,10,M to 1.0×10,8,M. [source] Multilayer Assemblies Consisting of Tri-Vanadium-Substituted Heteropolyanions and Its Electrocatalytic PropertiesELECTROANALYSIS, Issue 14 2003Shengyong Zhai Abstract We describe the controlled fabrication of ultrathin multilayer films consisting of tri-vanadium- substituted heteropolytungstate anions (denoted as P2W15V3) and a cationic polymer of quaternized poly (4-vinylpyridine) partially complexed with osmium bis(2,2,-bipyridine) (denoted as QPVP-Os) on the 4-aminobenzoic acid (4-ABA) modified glassy carbon electrode (GCE) surface based on layer-by-layer assembly. Cyclic voltammetry and UV-vis absorption spectrometry have been used to easily monitor the thickness and uniformity of thus-formed multilayer films. The V-centered redox reaction of P2W15V3 in the multilayer films can effectively catalyze the reduction of BrO and NO. The resulting P2W15V3/QPVP-Os multilayer film modified electrode behaves as a much promising electrochemical sensor because of the low overpotential for the catalytic reduction of BrO and NO, and the catalytic oxidation of ascorbic acid. [source] Adsorptive Stripping Voltammetric Detection of Single-Stranded DNA at Electrochemically Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 23 2002Huai-Sheng Wang Abstract Electrochemically modified glassy carbon electrode (GCE) was used to study the electrochemical oxidation and detection of denatured single-stranded (ss) DNA by means of adsorptive stripping voltammetry. The modification of GCE, by electrochemical oxidation at +1.75,V (vs.SCE) for 10,min and cyclic sweep between +0.3,V and ,1.3,V for 20,cycles in pH,5.0 phosphate buffer, results in 100-fold improvement in sensitivity for ssDNA detection. We speculated that the modified GCE has a high affinity to single-stranded DNA through hydrogen bond (specific static adsorption). Single-stranded DNA can accumulate at the GCE surface at open circuit and produce a well-defined oxidation peak corresponding to the guanine residues at about +0.80,V in pH,5.0 phosphate buffer, while the native DNA gives no signal under the same condition. The peak currents are proportional to the ssDNA concentration in the range of 0,18.0,,g,mL,1. The detection limit of denatured ssDNA is ca. 0.2,,g mL,1 when the accumulation time is 8,min at open circuit. The accumulation mechanism of ssDNA on the modified GCE was discussed. [source] | |||||||||||||||||||