Potential Sweep Method Research Articles

Development of a Potential-Modulated Electrochemiluminescence Measurement System for Selective and Sensitive Determination of the Controlled Drug Codeine.

Codeine is a common analgesic drug that is a pro-drug of morphine. It also has a high risk of abuse as a recreational drug because of its extensive distribution as an OTC drug. Therefore, sensitive and selective screening methods for codeine are crucial in forensic analytical chemistry. To date, a commercial analytical kit has not been developed for dedicated codeine determination, and there is a need for an analytical method to quantify codeine in the field. In the present work, potential modulation was combined with electrochemiluminescence (ECL) for sensitive determination of codeine. The potential modulated technique involved applying a signal to electrodes by superimposing an AC potential on the DC potential. When tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was used as an ECL emitter, ECL activity was confirmed for codeine. A detailed investigation of the electrochemical reaction mechanism suggested a characteristic ECL reaction mechanism involving electrochemical oxidation of the opioid framework. Besides the usual ECL reaction derived from the amine framework, selective detection of codeine was possible under the measurement conditions, with clear luminescence observed in an acidic solution. The sensitivity of codeine detection by potential modulated-ECL was one order of magnitude higher than that obtained with the conventional potential sweep method. The proposed method was applied to codeine determination in actual prescription medications and OTC drug samples. Codeine was selectively determined from other compounds in medications and showed good linearity with a low detection limit (150 ng mL-1).

In Situ Precise Tuning of Bimetallic Electronic Effect for Boosting Oxygen Reduction Catalysis.

Tuning intermediate adsorption energy by shifting the d-band center offers a powerful strategy to tailor the reactivity of metal catalysts. Here we report a potential sweep method to grow Pd layer-by-layer on Au with the capability to in situ measure the surface structure through an ethanol oxidation reaction. Spectroscopic characterizations reveal charge-transfer induced valence band restructuring in the Pd overlayer, which shifts the d-band center away from the Fermi level compared to bulk Pd. Precise overlayer control gives the optimal bimetallic surface of two monolayers (ML) Pd on Au, which exhibits more than 370-fold mass activity enhancement in oxygen reduction reaction (at 0.9 V vs. reversible hydrogen electrode) and 40 mV increase in half-wave potential compared to the Pt/C. Tested in a homemade Zn-air battery, the 2-ML-Pd/Au/C exhibits a maximum power density of 296 mW/cm2 and specific activity of 804 mAh/gZn, much higher than Pt/C with the same catalyst loading amount.

Copper(I) selective chemisorption on magnetite (Fe3O4) over gold(I) ions in chloride solution with cyanide

The potential sweep method, adsorption kinetics and isotherm studies, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) after adsorption tests of copper(I) and gold(I) ions using magnetite were performed to investigate the mechanism of selective copper(I) adsorption over gold(I) ion from chloride solution with small amount of cyanide. The electrochemical analysis reveals that the reduction potential is −0.81 V for Au and + 0.38 V for copper (vs. Ag/AgCl) which lead to selective adsorption of Cu over Au from chloride solution with cyanide because the adsorption could be achieved when the reduction potential of the metal ion is higher that of Fe2O3/Fe3O4 pair in the magnetite. By the kinetics and isotherm studies, the chemisorption was found to be well fitted to the pseudo-second-order model and monolayer adsorption of Cu ions on the surface of magnetite. The XPS and TEM results indicates that the ratio of Fe(II) in the iron of the magnetite decreased from 74% to 43% due to the oxidation. Consequently, the mechanism of adsorption using magnetite was depends on the reduction potential of metal ions to selectively receive electrons generated during the oxidation of magnetite in the chloride solution with cyanide.

Effects of the composition of reduced graphene oxide/carbon nanofiber nanocomposite on charge storage behaviors

Porous carbon materials with hierarchical features are the important materials to study the electrochemical properties for supercapacitor electrode application. Depending on the synthesis procedures and the carbon precursors used, these carbon materials possess different structures, and they are always associated with different amounts of various oxygen functional groups affecting the wettability, conductivity, and electrochemical performance. In this context, various electrochemical methods are adopted to study the charge storage contribution. Among them, separation of surface-controlled (capacitive) and diffusion-controlled currents from cyclic voltammetry (CV) curve by using the potential sweep method (PSM) is a preferred method. Herein, three-dimensional “Reduced Graphene Oxide-Carbon Nanofiber” (rGO-CNF) hybrid materials are fabricated by using different rGO:CNF ratios to study the effect of the composition of rGO and CNF in the charge storage behaviors. The structural, elemental, and electrochemical characterizations of the materials are performed to quantitatively study the surface-controlled (capacitive) and diffusion-controlled charge storage contributions in the rGO-CNF hybrid. It is found that the increase of rGO content in the hybrid material significantly affects the electrochemical properties of the hybrid materials.

Electrodeposition of low-enriched uranium onto small platinum electrodes

An updated method of preparing thin, uranium-coated, 0.25-mm diameter platinum electrodes using the cyclic potential sweep method is described. Sixty-four samples were prepared using a 0.2 M UO 2 (NO 3 ) 2 solution with 19.695% enriched uranium. Improvements were made to the sample preparation, electrodeposition , and analysis methods, producing smoother samples with more uniform surface features than prior work. Alpha-particle spectrometry was used to determine the mass of uranium deposited on each sample. The average mass of uranium deposited on the metallic electrode from 100 potential sweep cycles was 0.987 × 10 −7 g with a standard deviation of 0.860 × 10 −7 g. Removing the outliers reduces the average deposited mass to 0.741 × 10 −7 g with a standard deviation of 0.410 × 10 −7 g. A smooth, uniform deposition was observed over the entire electrode after deposition and no cracking or crystalline formations were observed. This improved method of electrodeposition remains an attractive method of depositing fissile material onto small metallic substrates for the fabrication of Micro-Pocket Fission Detectors.

Electrochemical Detection of Free Chlorine Using Ni Metal Nanoparticles Combined with Multilayered Graphene Nanoshells

AbstractAn electrochemical detection of free chlorine using carbon‐metal (C−M) composite powder, with a nickel‐metal nanoparticle combined with a multilayered graphene nanoshell (Ni metal@multilayered graphene) as the main component, synthesized from CH4 via multimode microwave‐assisted catalytic decomposition, was studied. Morphological analysis of the C−M composite powder was performed by TEM–EDX and Raman spectroscopy. The C−M composite powder was packed in a porous microelectrode (PME), and its electrochemical activity with respect to free chlorine was evaluated using a potential sweep method. The C−M composite powder exhibited a sufficient activity against free chlorine. A current based on the reduction of free chlorine was observed in the potential < around+0.3 V vs. Ag/AgCl. A linear relationship was observed between the current and the concentration.

Voltammetric and chronoamperometric studies of aniline electropolymerization in different aqueous sulfuric acid solutions

The cyclic potential sweep method was applied to aniline electropolymerization on stainless steel electrode in three different concentrations of aqueous sulfuric acid solutions (0.5 M H2SO4, 1 M H2SO4 and 2 M H2SO4). The electrodeposited films of polyaniline were investigated and characterized using a simple cyclic voltammetry method to obtain information about the electrochemical properties of the deposited films. The polymerization of aniline on stainless steel via cyclic potential sweep method appears to be high in performance for protection of metal anodic in corrosive aqueous media. Also it was found that the corrosive tendency increases with increasing the concentration of the acid and decreases with increasing the cycle number. Chronoamperometry method was used to investigate the electrochemical properties of the electrodeposited film of polyaniline.

Effect of electrodeposition modes on ruthenium oxide electrodes for supercapacitors

With developments in energy storage devices, supercapacitors are gaining more attraction because of their potential to excel batteries shortly. In this work, ruthenium oxide (RuO2) has been deposited on stainless steel and studied the influence of surface modification of solid electrodes on capacitance properties. Hydrous ruthenium oxide was plated by different modes such as potential sweep method (cyclic voltammetric), constant potential method (chronoamperometry) and optimised potential pulse method using a recently reported precursor material namely ruthenium nitrosylsulfate (RuNS). The structural information and morphology of electrodeposits were characterised by X-ray diffractometer and scanning electron microscope respectively. The XRD studies indicate a poor crystalline state for RuO2 in all the modes of deposition but can contribute to a higher surface area when compared to a highly crystalline form. The SEM analysis revealed the formation of surface modification concerning the change of potential mode. Mud-cracked morphology, spherical particles and dendrimeric morphology observed on chronoamperometry, potential pulse and cyclic voltammetry respectively. Electrochemical studies were also conducted on the samples to assess their performance for supercapacitor applications. The spherical particles of hydrous RuO2 show high performance of capacitance behaviour 1180 F/g in 0.5 M H2SO4 at the scan rate of 5 mV/s. Dendrimeric morphology and mud-cracked morphology shows 573 F/g and 546 F/g respectively in same 0.5 M H2SO4 at the scan rate of 5 mV/s. The studies reveal that RuO2 electrodes can be exploited for their outstanding capacitive behaviour by properly controlling the morphology of the deposits.

銅電解精製におけるアノードの不動態化に及ぼす液組成の影響

To elucidate the effect of solution composition on the passivation of anode in Cu electrorefining, the potentiodynamic polarization curves were measured by polarizing from -0.2 V versus NHE to 1.0 V using the potential sweep method at 1.0 mV·s−1. The diffusion coefficient was measured by rotating disc electrode method under the conditions of 50, 100, 150, 200, 250 and 300 revolutions per minute of disc electrode and polarizing from 0.34 V to -0.40 V at 10.0 mV·s−1. The critical current density for passivation and the passive current density decreased linearly with total concentration of SO4 in solution regardless of solution composition and the presence of impurities such as As3+，Sb3+ and Bi3+, showing the good correlation between the current density for passivation and the total concentration of SO4. The diffusion coefficient of Cu2+ ions decreased with total concentration of SO4 in solution. The increase in passivation with the total concentration of SO4 is attributed to both decreases in solubility of CuSO4 in electrolyte and the diffusion coefficient of Cu2+ ions. On the other hand, focusing on the effect of kinds of cation on the passivation, the harmful effect on the passivation was largest with Cu2+ ions, and was larger in the order with Li+，Ni2+ and Na+ ions, and was smallest with H+ ions. The diffusion coefficient of Cu2+ ions decreased most with Ni2+ ions, and decreased secondly with Li+ and Na+, and decreased least with H+ ions. The diffusion coefficient of Cu2+ ions decreased with increasing the viscosity of solution.

Electrodeposition preparation of Ni–Fe alloy foil

In this study, the electrodeposition of a nickel (Ni)–iron (Fe) alloy foil was thoroughly investigated. Linear potential sweep and cyclic voltammetry method were used to investigate the electrochemical behaviour of the nickel–iron alloy foil. In addition, single-factor experimental studies were combined with an orthogonal test analysis to obtain optimum experimental conditions. Scanning electron microscopy and X-ray diffraction were used to investigate the surface morphology and the crystalline structure of the nickel–iron alloy foil. The obtained nickel–iron alloy foil was a face-centred cubic crystal with a bright and smooth surface, in which no pinholes or cracks appeared. The average hardness value, electrical resistivity, maximum permeability, saturation magnetic flux density (B s) and residual magnetism (B r) of the obtained nickel–iron foil were 280 HV, 38–41 μΩ cm, 0·172 mH/m, 1·093 T and 0·0088 T, respectively. Lastly, the obtained nickel–iron foil displayed good soft magnetic properties, toughness and low residual stress.

Electrochemical synthesis of novel polymer based on (4-(2,3-dihydrothieno[3,4-6][1,4][dioxin-5-yl) aniline) in aqueous solution: Characterization and application

4-(2,3-dihydrothieno[3,4-6][1,4][dioxin-5-yl) aniline, an interesting novel monomer was successfully synthesized in which α-carbon on ethylenedioxythiophene was linked to aniline at para position. The structure of the monomer was approved by infrared (IR), gas chromatography-mass spectrometry (GC-MS) and 1H nuclear magnetic resonance (1H NMR) spectroscopies. Poly (4-(2,3-dihydrothieno[3,4-6][1,4][dioxin-5-yl) aniline) and its composite with graphene were electrochemically synthesized in aqueous solution by cyclic potential sweep method. The Polymer was characterized by IR and UV–vis spectroscopies, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. Electrochemical synthesis conditions were optimized to prepare high conducting and porous polymer so it can be efficiently used as a counter electrode in fabrication of dye sensitized solar cells. Photovoltaic experiments revealed that energy conversion efficiency of the solar cell fabricated using polymer composite (7.52%) is 21% greater than that prepared by Pt counter electrode (6.19%).

Electrodeposition of uranium and thorium onto small platinum electrodes

Preparation of thin U- and Th-coated 0.3mm diameter Pt working electrodes by the cyclic potential sweep method is described. Uranyl- and thorium hydroxide layers were electrodeposited from ethanol solutions containing 0.02M natural uranyl and 0.02M natural thorium nitrate, each with 3.6M ammonium nitrate. The cell for electrodeposition was specially developed in order to accommodate the small working electrodes for this research by including a working electrode probe, 3-D translation stage, and microscope. The source material deposition was analyzed using digital microscopy and scanning electron microscopy, and confirmed using x-ray fluorescence measurements. The appropriate potential range for electrodeposition was determined to be −0.62V to −0.64V for a 0.3mm diameter Pt working electrode placed 1cm from the counter electrode. Smooth, uniform deposition was observed near the central region of the working electrode, while surface cracking and crystalline formations were found near the edge of the working electrode. The final procedure for sample substrate preparation, electrolytic solution preparation and electrodeposition are described.

Electrochemical synthesis of polymer based on 4-(2-thienyl)benzenamine in aqueous solutions: Electrochemical properties, characterization and application

4-(2-Thienyl)benzenamine (TBA) was successfully synthesized by a simple method including substitution of thiophene on p-nitroaniline followed by reduction of nitro group. Structure of the synthesized monomer was verified using IR, 1H NMR, GC–MS and elemental analysis techniques. Corresponding poly 4-(2-thienyl)benzenamine) (PTBA) was electrochemically synthesized in acidic aqueous solution by cyclic potential sweep method for the first time. Characterization of the resulting polymer was performed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), UV–vis and IR spectroscopies, and scanning electron microscopy (SEM). Effects of pH and temperature on the electroactivity of the polymer modified electrode were investigated. The corrosion behavior of PTBA in 3.5wt% NaCl solution was studied by potentiodynamic polarization test and electrochemical impedance spectroscopy. The PTBA was found to exhibit enhanced corrosion protection effect on stainless steel electrode in comparison with polyaniline (PANI) and polythiophene (PTh) homopolymers.

DNA base sensor characteristics of polymeric-nanocomposite electrode

ABSTRACTThe electrochemical synthesis of polyaniline films was carried out by potential sweep method in sulfuric acid solution at the glassy carbon electrode. The electrocatalytic behavior to DNA bases (adenine and guanine), uric acid, and dopamine of polyaniline nanocomposite sensor modified with nano-gold particles was investigated by DPV technique. By systematically examining the effects of the possible parameters affecting the electrocatalytic performance of the relevant sensor, the optimal value for the each parameter was determined. The detailed electrocatalytic studies of the optimized sensor revealed that this sensor could be used as DNA base sensor for guanine in the presence of adenine, dopamine, and uric acid. Moreover, the performance of the relevant sensor in thermally denatured fish sperm DNA was quite satisfactory.

Electrochemical synthesis of polymer based on 4-(2-furyl) benzenamine: Electrochemical properties, characterization and applications

Abstract 4-(2-Furyl) benzenamine (FBA), was successfully synthesized by a simple method including substitution of furan on p-nitroaniline followed by reduction of nitro group. Structure of the synthesized monomer was verified using IR, 1H NMR and GC–MS techniques. Corresponding poly(4-(2-furyl) benzenamine) (PFBA) was electrochemically synthesized in acidic aqueous and organic solutions by cyclic potential sweep method. Characterization of the resulting polymer was performed by cyclic voltammetry (CV), IR, UV–vis spectroscopy, and scanning electron microscopy (SEM). Effect of solvent on the electroactivity of the polymer modified electrode was investigated. The HOMO, LUMO levels and band gap energies of the doped and undoped form of the PFBA were calculated using UV–vis and CV data. The electrochromic properties and corrosion behavior of PFBA were studied. The electrochromic properties of the copolymer film, electrochemically coated on transparent conductive oxide, corroborate multi-color electrochromic behavior of the polymer whenever the applied potential was switched from reducing (yellow) to oxidizing status (green). The FBA polymer was found to exhibit enhanced corrosion protection effect on steel electrode in comparison with corresponding polyaniline (PANI) and polyfuran (PFu) homopolymers based on series of electrochemical measurements in 3.5 wt% NaCl electrolyte solutions.

Electrochemical Investigation of Gold Uptake From Chloride Solution by Magnetite

An electrochemical method (potential sweep method) was utilized to investigate the nature of the absorbed gold on magnetite and to determine the gold sorption mechanism. A magnetite electrode was prepared in the laboratory, made in contact with a gold chloride solution at different conditions, and was subjected to cyclic voltammetry. The cyclic voltammogram of the magnetite electrode pretreated in a gold chloride solution recorded an anodic current peak at around 1.0 V (vs. Ag/AgCl), which corresponds to the current generated for the anodic dissolution of metallic gold in a chloride medium. The results of the electrochemical experiments suggest that gold chloride complexes are reduced to metallic gold on the surface of magnetite. A four-stage gold uptake mechanism was proposed: (i) the transport of from the bulk solution to the magnetite surface, (ii) adsorption of ions on magnetite surface by electrostatic attraction, (iii) electrochemical reduction of to metallic Au, and (iv) the transport of soluble species to the solution phase. The electrochemical investigation also revealed that Fe3+ ions released from magnetite into the solution, suppressed the gold uptake at the acidic pH region.

Potential Sweep Method to Evaluate Rate Capability in Capacitive Deionization

Capacitive deionization (CDI) is a desalination technology attracting growing attention nowadays. To understand desalination performance in CDI, the capacitive behavior of the electrode is significantly important because desalination is accomplished through capacitive charging and the subsequent double layer formation. So far, a variety of studies have reported on desalination performance along with the electrochemical properties. However, the rate capability of desalination has been poorly defined, though it is an important indicator showing the ability of an electrode to exhibit rapid desalination. In this study, the rate capability of CDI was evaluated by introducing a potential sweep method, using electrodes with different thicknesses. The deionization capacity was obtained at various scan rates, and its retention ratio upon increasing the scan rate was used as an indicator of the rate capability. The results showed that the thinner electrode retained more deionization capacity compared to the thicker electrodes as the scan rate was increased, which indicates that the electrode thickness is one of parameters affecting the rate capability in CDI. In addition, a higher mean deionization rate was found in constant current operations for the thinner electrode. To support the desalination performance, the rate-dependent capacitive behavior was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy, which also resulted in a similar trend; the rate capability of the thinner electrode was better than that of the thicker electrodes. In particular, the ion penetrability analyzed by equivalent circuit analysis was suggested as one of the major parameters determining the rate capability. In this regard, careful consideration is required in determining the electrode thickness when developing a versatile CDI system producing various effluent concentrations with an outstanding rate capability.

A low-cost paper-based inkjet-printed platform for electrochemical analyses

An electrode platform printed on a recyclable low-cost paper substrate was characterized using cyclic voltammetry. The working and counter electrodes were directly printed gold-stripes, while the reference electrode was a printed silver stripe onto which an AgCl layer was deposited electrochemically. The novel paper-based chips showed comparable performance to conventional electrochemical cells. Different types of electrode modifications were carried out to demonstrate that the printed electrodes behave similarly with conventional electrodes. Firstly, a self-assembled monolayer (SAM) of alkanethiols was successfully formed on the Au electrode surface. As a consequence, the peak currents were suppressed and no longer showed clear increase as a function of the scan rate. Such modified electrodes have potential in various sensor applications when terminally substituted thiols are used. Secondly, a polyaniline film was electropolymerized on the working electrode by cyclic voltammetry and used for potentiometric pH sensing. The calibration curve showed close to Nerstian response. Thirdly, a poly(3,4-ethylenedioxythiophene) (PEDOT) layer was electropolymerized both by galvanostatic and cyclic potential sweep method on the working electrode using two different dopants; Cl− to study ion-to-electron transduction on paper-Au/PEDOT system and glucose oxidase in order to fabricate a glucose biosensor. The planar paper-based electrochemical cell is a user-friendly platform that functions with low sample volume and allows the sample to be applied and changed by e.g. pipetting. Low unit cost is achieved with mask- and mesh-free inkjet-printing technology.

Nanostructural characterization and catalytic analysis of hybridized platinum/phthalocyanine nanocomposites

Organic crystals, such as phthalocyanine nanocrystal, were successfully hybridized with Pt nanoparticles using a nanohybridization technique. The presence of highly dispersed Pt nanoparticles on the surface of phthalocyanine was confirmed by the combination of transmission electron microscopy and three-dimensional electron tomography. Catalytic activities of hybridized samples with different degrees of dispersions were also examined as oxygen reduction reactivity (ORR) with a linear potential sweep method. It was found that oxygen reduction activity increased with increasing Pt dispersion, and reasonably high ORR was observed on Pt-dispersed phthalocyanine nanocrystal even at 2 wt% Pt loading.

Gold cleaning methods for electrochemical detection applications

This work investigates methods for obtaining reliably clean gold film surfaces. Nine gold cleaning methods are investigated here: UV ozone photoreactor; potassium hydroxide–hydrogen peroxide; potassium hydroxide potential sweep; sulfuric acid hydrogen peroxide; sulfuric acid potential cycling; hydrochloric acid potential cycling; dimethylamine borane reducing agent solutions at 25 and 65 °C; and a dilute form of Aqua Regia. Peak-current potential-differences obtained from cyclic voltammetry and charge transfer resistance obtained from electrochemical impedance spectroscopy, as well as X-ray photo-electron spectroscopy are used to characterize surface cleanliness. A low peak-current potential-difference and charge transfer resistance indicates a cleaner surface, as does a higher percentage of elemental gold on the electrode surface. The potassium hydroxide potential sweep method is found to leave the gold surface the cleanest overall.