Journal of Applied Electrochemistry (15728838)29(8)pp. 979-986
The surface roughness of porous Ni-Zn-P electrodes was studied in 1 M NaOH using in situ electrochemical techniques: ratio of the polarization current densities, electrochemical impedance spectroscopy, cyclic voltammetry, coulometric oxidation of the surface, and a new technique of a CO molecular probe. The obtained surface roughness was about 5.5×103. Good agreement was observed between the results obtained by all these techniques.
Journal of New Materials for Electrochemical Systems (14802422)8(3)pp. 213-220
The aqueous suspended RuCl3 was coated into the pores of microporous Ni-Zn-P alloy and thermally decomposed at 400°C in an open furnace to produce composite electrodes (Ni-Zn-P-RuO2). The microporous alloy was prepared via a three-step layer-by-layer galvanostatic deposition. The electrocatalytic behavior of the electrode was investigated in the hydrogen evolution reaction (HER), by steady state polarization Tafel curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) in 1M NaOH solution at 25°C. The kinetics as Tafel slopes, double layer capacitances, and charge transfer resistances towards the HER were evaluated. The electrode is characterized by (i) a large real surface area of three orders of magnitude obtained from CV and EIS measurements, and (ii) high physical and electrochemical stability of RuO2 dispersed into the surface. The poisoning effect of cyanide ion on the HER was also studied by EIS. This study allowed us to select properly data for kinetics approximation. © J. New. Mat. Electrochem. Systems.
Surface and Coatings Technology (02578972)198(1-3 SPEC. ISS.)pp. 123-128
Fabrication and electrochemical characterization of a self-assembled three layers modified gold electrode is described. The modification involves a three-step method; (i) preparation of cysteamine self-assembled monolayer, Au-CA, (ii) activation of Au-CA by glutaraldehyde to prepare Au-CA-GA, (iii) modification of Au-CA-GA by 2-Aminoethyl dihydrogen phosphate to functionalize the surface by phosphate groups, Au-CA-GA-AEDP. The resulting thin film modified electrode was tested successfully to recognize uranyl cations (UO22+) in aqueous solution. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to trace events in each step. The high affinity of the film towards the UO22+ was confirmed by EIS and CV results. The EIS data allowed recognition of UO22+ based on variation of the charge-transfer resistance (Rct) of the film as a function of the cation concentration. A dynamic range with more than three orders of magnitude was obtained. © 2004 Elsevier B.V. All rights reserved.
Bioelectrochemistry (15675394)69(2)pp. 201-208
A method is developed for quantitative determination of glucose using electrochemical impedance spectroscopy (EIS). The method is based on immobilized glucose oxidase (GOx) on the topside of gold mercaptopropionic acid self-assembled monolayers (Au-MPA-GOx SAMs) electrode and mediation of electron transfer by parabenzoquinone (PBQ). The PBQ is reduced to hydroquinone (H2Q), which in turn is oxidized at Au electrode in diffusion layer. An increase in the glucose concentration results in an increase in the diffusion current density of the H2Q oxidation, which corresponds to a decrease in the faradaic charge transfer resistance (Rct) obtained from the EIS measurements. Glucose is quantified from linear variation of the sensor response (1/Rct) as a function of glucose concentration in solution. The method is straightforward and nondestructive. The dynamic range for determination of glucose is extended to more than two orders of magnitude. A detection limit of 15.6 μM with a sensitivity of 9.66 × 10- 7 Ω- 1 mM- 1 is obtained. © 2006 Elsevier B.V. All rights reserved.
Talanta (00399140)69(3)pp. 741-746
Fabrication and application of a voltammetric sensor based on gold 2-mercaptobenzothiazole self-assembled monolayer (Au-MBT SAM) for determination of silver ion is described. Preliminary experiments were performed to characterize the monolayer. The surface pKa determined for the MBT monolayer is 7.0. This value was obtained by impedimetric titration of the monolayer in the presence of Fe(CN)6 3-/4- as a redox probe. The extent of surface coverage was evaluated as 1.52 × 10-9 mol cm-2 based on charged consumed for reductive desorption of the monolayer in the 0.50 M NaOH solution. Then the sensor was used for determination of Ag(I) by square wave voltammetry. The parameters affecting the sensor response, such as pH and supporting electrolyte, were optimized. A dynamic calibration curve with two linear parts was obtained in the concentration ranges of 5 × 10-8-8 × 10-7 and 1 × 10-6-1 × 10-5 M of Ag(I). The detection limit adopted from cathodic striping square wave voltammetry was as 1 × 10-8 M for n = 7. Furthermore, the effect of potential interfering ions on the determination of Ag(I) was studied, and an appropriate method was used for the elimination of this effect. © 2005 Elsevier B.V. All rights reserved.
Analytical Chemistry (15206882)78(14)pp. 4957-4963
Fabrication and electrochemical characterization of a novel nanosensor for determination of Cu2+ in subnanomolar concentrations is described. The sensor is based on gold cysteamine self-assembled monolayer functionalized with salicylaldehyde by means of Schiff's base formation. Cyclic voltammetry, Electrochemical impedance spectroscopy (EIS), and electrochemical quartz crystal microbalance were used to probe the fabrication and characterization of the modified electrode. The sensor was used for quantitative determination of Cu2+ by the EIS in the presence of parabenzoquinone in comparison with stripping Osteryoung square wave voltammetry (OSWV). The attractive ability of the sensor to efficiently preconcentrate trace amounts of Cu2+ allowed a simple and reproducible method for copper determination. A wide range linear calibration curve was observed, 5.0 × 10-10-5.0 × 10-6 and 5.0 × 10-10-5.0 × 10-6 M Cu2+, by using the EIS and OSWV, respectively. Moreover, the sensor presented excellent stability with lower than 10% change in the response, as tested for more than three months daily experiments, and a high repeatability with relative standard deviations of 6.1 and 4.6% obtained for a series of eight successive measurements in 5.0 × 10-7 M Cu2+ solution, by the EIS and OSWV, respectively. © 2006 American Chemical Society.
Sensors and Actuators B: Chemical (09254005)115(2)pp. 614-621
A monolayers of cysteamine (CA) was prepared on a polycrystalline gold electrode through self-assembly procedure to produce a gold cysteamine self-assembled monolayers (Au-CA SAMs) modified electrode. Characterization of the modified electrode was performed by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The EIS was used to evaluate pKa of the adsorbed CA on the gold surface, and a value of 7.6 was obtained for the Au-CA surface pKa. The charged terminal groups of monolayers served for determination of dopamine (DA) in the presence of high concentration of ascorbic acid (AA) using differential pulse voltammetry (DPV). Well-separated DA and AA voltammetric waves (∼330 mV) were observed at the Au-CA SAMs electrodes in an acidic solution. A calibration curve with two linear parts was obtained for DA, 6.00 × 10-6 to 3.84 × 10-4 M and 3.36 × 10-4 to 9.50 × 10-3 M, with correlation coefficients 0.997 and 0.992, respectively. The detection limit for DA was found to be 2.31 μM in the presence of 1.0 mM AA. The apparent charge transfer rate constants (kapp) of AA and DA were evaluated by using EIS measurements on the modified electrode as 44.0 cm s-1 × 10-8 cm s-1 and 2.45 cm s-1 × 10-8 cm s-1, respectively. © 2005 Elsevier B.V. All rights reserved.
