Search

The use of renewable energy, especially water resources, through hydrogen evolution reduction (HER) is an important topic in research. In this survey, carbon cloth electrode (CCE) was applied as the working electrode, and NiBTC, Ni, Ni-Pt, and Ni-PtBTC were in situ electrosynthesized on the surface CCE as modifiers electrodes. After microstructural characterization of each modified electrode by field emission scanning electron microscopy (FE-SEM), their elemental analysis was accomplished by energy-dispersive X-ray analysis. The electrocatalytic performance of each presented modified CCEs toward HER was compared by linear scanning voltammetry and Tofel plot slope. Among these modified carbon cloth electrodes, Ni-PtBTC-modified CCE was shown the highest electroactive properties with an onset potential of 170 mV and Tafel slope of 40 mV dec−1. The results showed a minimum charge transfer resistance (Rct) of 112.3 Ω cm2 for Ni-PtBTC-modified CCE, and this modified electrode showed good stability under HER conditions despite low amount of platinum. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide (GO) was prepared by Hummers' method. Then a composite of Cu-Al-layered double hydroxide (Cu-Al-LDH) and GO was prepared by placing and combining Cu-Al-LDH by co-precipitation method. This composite was used as a modifier of carbon paste electrode (CPE), and their structural characteristics were studied by using X-ray diffraction, Fourier transform infrared, field emission scanning microscopy, energy-dispersive X-ray and Brunauer–Emmett–Teller techniques. The catalytic performance of this modified CPE for methanol oxidation reaction (MOR) in alkaline media was also evaluated by using various electrochemical methods such as cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Comparing the activity of Cu-Al-LDH/GO, Cu-Al-LDH and GO catalysts in CPE for electrocatalysis of MOR in 0.5 M methanol with a scan rate of 50 mV s−1 showed the current densities 2.1 mA/cm2, 0.6 mA/cm2 and 0.33 mA/cm2, respectively. This result indicates that GO provides many active sites and transmission ways to catalyze MOR by creating a high surface area and preventing Cu-Al-LDH accumulation. Also, some effective parameters, such as the percentage of Cu-Al-LDH/GO in the preparation of Cu-Al-LDH/GO/CPE electrode, methanol concentration, the scan rate of potential and switching potential, were investigated in the electrocatalysis of MOR. [ABSTRACT FROM AUTHOR]

An electrochemical aptasensor has been developed to detect Acinetobacter baumannii (A. baumannii). The proposed system was developed by modifying carbon screen–printed electrodes (CSPEs) with a synthesized MWCNT@Fe3O4@SiO2-Cl nanocomposite and then binding A. baumannii–specific aptamer using covalent immobilization on the modified electrode surface and the interaction of methylene blue (MB) with Apt as an electrochemical redox indicator. As a result of the incubation of the A. baumannii bacteria as a target on the proposed aptasensor, a cathodic peak current density (Jpc) of MB decreased due to the formation of the Apt-A. baumannii complex and MB being released from the immobilized Apt on the surface of the modified electrode. In addition to increasing the electron transfer kinetics, the nanocomposite provides a relatively stable matrix to improve the loading Apt sequence. The suggested aptasensor was demonstrated to be capable of detecting A. baumannii with a linear range of 10.0–1.0 × 107 colony-forming unit (CFU) mL−1 and a detection limit of 1 CFU mL−1 (S/N = 3) using differential pulse voltammetry (DPV) studies at a working potential of ~0.29 V and a scan rate of 100 mV s−1. The outcomes revealed that the aptasensor exhibited high A. baumannii detection sensitivity, stability, reproducibility, and specificity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel H 3 PW 12 O 40 @CS-MWCNTs-βCD nanocomposite sensor for electrochemical sensing. • Simultaneous detection of 2-AP and 4-CP with high sensitivity. • Easy-to-prepare, stable, and cost-effective electrochemical sensor. • Good results to investigate the practical application in environmental monitoring. Herein, we designed a new electrochemical sensor based on a carbon paste electrode modified with polyoxometalates@carbon spheres-multiwalled carbon nanotubes and β-cyclodextrin composite (H 3 PW 12 O 40 @CS-MWCNTs-βCD/CPE) for the simultaneous determination of phenolic compounds. The CSs were synthesized from glucose using a hydrothermal carbonization (HTC) process. The prepared CS were then modified with H 3 PW 12 O 40. Following characterization studies of the synthesized compounds using various electron microscopy and spectroscopic methods, an electrochemical sensor was developed based on a CPE modified with the H 3 PW 12 O 40 @CS-MWCNTs-βCD composite. This electrochemical sensor was employed for the detection and determination of phenolic compounds, such as 2-aminophenol (2-AP) and 4-chlorophenol (4-CP), in aqueous media. The obtained results demonstrated the facilitated electron and mass transfer of 2-AP and 4-CP, attributed to the high conductivity and porous structure of the H 3 PW 12 O 40 @CS-MWCNTs-βCD modifier. Consequently, the differential pulse voltammetry displayed a wide two-step linear dynamic range (LDR), (0.005–0.100 µM and 5–100 µM), with limits of detection (LODs) ranging from 0.0014 to 0.0015 µM under optimal condition. The prepared electrochemical sensor boasts numerous advantages, including excellent electrocatalytic performance, low LOD, wide LDR, and high reproducibility for the simultaneous detection of 2-AP and 4-CP in aqueous media. Furthermore, the constructed electrochemical sensor exhibited good recovery results (97 %–112 %, RSD ≤ 6 %) for 2-AP and 4-CP in real samples. [ABSTRACT FROM AUTHOR]

In this study, a new electrochemical sensor based on magnetite graphene oxide/modified carbon paste electrode (Fe3O4–GO/CPE) was applied for determination of a cardiovascular drug, propranolol (PRO) in solution containing sodium dodecyl sulfate (SDS) as a surfactant. Results show that combination of modified electrode with surfactant addition, considerably increased electroanalytical signal for PRO determination and resulted to sensitive detection of PRO with linear range of 10–1500 μM, limit of detection of 4.5 μM and sensitivity of 166 µA mM–1. Applicability of this analytical method for detection of PRO in pharmaceutical formulations was studied and acceptable results obtained. [ABSTRACT FROM AUTHOR]

The article titled "Retraction Note to: Nickel modified ionic liquid/carbon paste electrode for highly efficient electrocatalytic oxidation of methanol in alkaline medium" has been retracted by the Editor-in-Chief due to similarities between figures and overlapping materials with a previously published article by the same author group. The authors do not agree with the retraction. The publisher, Springer Nature, remains neutral in regards to jurisdictional claims and institutional affiliations. The original article can be accessed online at the provided link. [Extracted from the article]

We used electroactive label crystal violet (CVi) as a G-quadruplex (G4) DNA intercalator for sensitive electrochemical sensing of Tl+. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques were applied for electrochemical determination of Tl+ at the surface of carbon paste electrode as working electrode. Under optimized conditions, the difference in the DPV reduction peak currents of CVi before and after its intercalation into the formed G4 (ΔI) used an analytical signal for determination of Tl+ was linearly related to the concentration of Tl+ over the ranges of 0.4–50.0 nM and 0.1–10 μM. Limit of detection was calculated 0.341 nM (S/N = 3). The biosensor showed good selectivity and satisfactory results in real sample analysis of Tl+. [ABSTRACT FROM AUTHOR]

A novel type of carbon paste electrode modified by multi‐walled carbon nanotubes and antimony trioxide (Sb2O3/CNTCPE) was applied for square wave anodic stripping voltammetry (SWASV) of Cd2+ and Pb2+. Important parameters (deposition potential, deposition time, HCl concentration) were optimized and linear concentration dependence was obtained in the range of 10–100 ppb with LOD 1.7 ppb for Cd2+ and 1.2 ppb for Pb2+. The practical applicability was tested on the determination of Cd2+ and Pb2+ in tap water. The potentiometric stripping analysis at Sb2O3/CNTCPE was tested for the determination of Cd2+ and Pb2+ to compare this method with SWASV. [ABSTRACT FROM AUTHOR]

A novel type of carbon paste electrode modified by multi‐walled carbon nanotubes and antimony trioxide (Sb2O3/CNTCPE) was applied for square wave anodic stripping voltammetry (SWASV) of Cd2+ and Pb2+. Important parameters (deposition potential, deposition time, HCl concentration) were optimized and linear concentration dependence was obtained in the range of 10–100 ppb with LOD 1.7 ppb for Cd2+ and 1.2 ppb for Pb2+. The practical applicability was tested on the determination of Cd2+ and Pb2+ in tap water. The potentiometric stripping analysis at Sb2O3/CNTCPE was tested for the determination of Cd2+ and Pb2+ to compare this method with SWASV. [ABSTRACT FROM AUTHOR]

Anode electrode is an important component and a main factor limiting the performance of microbial fuel cells (MFCs). Among various anode materials which have been used so far to improve the performance of MFCs are carbon nanotubes (CNTs) whose usage are limited due mainly to their cellular toxicity features. In this work, a practical solution to this problem was introduced through coupling CNTs with the synthesized gold nanoparticles (GNPs). Four different anodes such as: bare carbon paste electrode (CPE), CNT-modified carbon paste electrode (CNT/CPE), GNP-modified CPE (GNP/CPE), and GNP-modified CNT/CPE (GNP/CNT/CPE) were fabricated and then their electrochemical behaviors were investigated by electrochemical techniques. Also, the electrocatalytic behavior of these electrodes was studied in the anodic chamber of a two-chambered MFC system. By applying the GNP/CNT/CPE, the MFC system produced a maximum power density of 80 mW/m2 and a maximum current density of 460 mA/m2, which was, respectively, about 30- and 15-fold higher than that of the unmodified CPE. Therefore, the GNP/CNT/CPE seemed to have a great potential as a biocompatible nano-bioanode to be used in MFCs for further electricity generation improvement. Finally, the electron transfer rate constants of both bare CPE and GNP/CNT/CPE were calculated. [ABSTRACT FROM AUTHOR]

In this paper, a new and facile method for the electrochemical determination of l -tyrosine was designed. First, 3-mercaptopropyl trimethoxysilane-functionalized silica nanoparticles were added to a paper disc. Then, the banana peel tissue and the mediator potassium hexacyanoferrate were dropped onto the paper, respectively. The modified paper disc was placed on the top of the graphite screen printed electrode and electrochemical characterization of this biosensor was studied by cyclic voltammetry and electrochemical impedance spectroscopy methods. The effective parameters like pH, banana peel tissue percentage, and the amount of mediator loading were optimized. l -tyrosine measurements were done by differential pulse voltammetry with a little sample (3 μL) for analysis. The biosensor showed a linear response for l -tyrosine in the wide concentration range of 0.05–600 μM and a low detection limit about 0.02 μM because of the co-catalytic effect of enzyme and nanoparticles. The stability of the biosensor and its selectivity were evaluated. This biosensor was applied for the voltammetric determination of l -tyrosine in the blood plasma sample. The results of the practical application study were comparable with the standard method (HPLC). In conclusion, a simple, inexpensive, rapid, sensitive and selective technique was successfully applied to the l -tyrosine analysis of the little samples. [ABSTRACT FROM AUTHOR]

Electrochemical DNA biosensors offer simple and rapid tools for detection of DNA sequences or damaged genes associated with human disease. The performance of electrochemical DNA sensors is critically dependent on the quality of the DNA immobilisation. Many DNA biosensors have been focused on studying DNA hybridisation preformed under relatively mild assay conditions, while the development of stable DNA biosensors to study DNA damage under a much harsher condition typically in the presence of reactive oxygen species is more challenging. In this article, we developed an electrochemical DNA biosensor based on a stable diazonium-modified screen-printed carbon electrode (SPCE) for the detection of damage in DNA sequences related to the BRCA1 gene by using electrochemical impedance spectroscopy (EIS). The successful preparation of the DNA sensor was confirmed by FTIR-ATR, contact angle and electrochemical measurements. The DNA sensor exhibited good reproducibility and high stability and could also have potential for investigation of the glutathione antioxidant effect. [ABSTRACT FROM AUTHOR]

A simple low-cost method is proposed to fabricate a functionalized multi-wall carbon nanotube (MWCNT) with 1,1,3,3-tetramethyldisilazane (TMDS) molecule. The techniques of scanning electron microscope (SEM) with electron diffraction and energy dispersive X-ray (EDAX) analysis were applied to characterize the functionalized TMDS-MWCNT. The results showed that a MWCNT with high functionalization of TMDS can be obtained using this simple method. A new nanostructure sensor was constructed based on a glassy carbon electrode modified with TMDS-MWCNT (TMDS-MWCNT/GCE). It was found that the TMDS-MWCNT/GCE exhibits good catalytic activity toward oxidation of pramipexole (PPX) drug, leading to a concentration range of 0.8 to 600 μM with a detection limit of 0.2 μM at 3 σ using the differential pulse voltammetry technique, a sensitivity of 0.084 μA μM − 1 , and a correlation coefficient of 0.991. Furthermore, the TMDS-MWCNT/GCE was used for PPX detection in tablets and human blood serum samples. The method showed no interference from tablet excipients; hence, it can be useful and fit for the quantification of PPX in bulk and tablet dosage forms. The proposed method was validated successfully as applied to the quantification of the drug in tablet dosage forms. The accuracy of detection results using the proposed method was evaluated as excellent comparing with those obtained by the reference method. [ABSTRACT FROM AUTHOR]

Determination of strontium ions (Sr2+) is crucial with regard to human health and environmental protection. In this work, an electrochemical aptasensor was designed using carboxylated graphene oxide (CGO)-modified carbon paste electrode (CGO/CPE) for ultrasensitive determination of Sr2+ ions. The electrochemical determination was accomplished with employing the constructed G-quadruplex (G4) aptamer at the surface of aptasensor in presence of carmoisine (CA) as an electrochemical label. Moreover, NH 2 -functionalized aptamer was immobilized onto CGO/CPE via carboxylic group. Hence, differential pulse voltammetry was applied for detection of any possible signal changes of CA on the aptasensor surface. The reduction peak currents of CA in the absence and presence of Sr2+ in solution were different and this difference was linearly dependent to the concentration of Sr2+ in solution. The analytical results revealed that our novel aptasensor showed two appropriate linear ranges (0.1–8.0 pM and 3.0–20.0 nM) versus to Sr2+ ion concentrations with the limit of detection of 0.06 pM (S/N = 3). Excellent stability, selectivity and reproducibility were achieved with this new electrochemical aptasensor. Additionally, the aptasensor showed good achievements in analysis of Sr2+ in aqueous and urine real samples, which making this proposed method a promising candidate for electrochemical detection of Sr2+ in real samples. [Display omitted] • A novel aptasensor was constructed for electrochemical determination of Sr2+ ions. • The carboxylated graphene oxide (CGO) was used for modification of CPE. • Ultrasensitive determination of Sr2+ ions was done in the presence of carmoisine. • The aptasensor has good stability, selectivity, reproducibility and wide LDR. [ABSTRACT FROM AUTHOR]

A novel oxidizer-less and high performance microbial fuel cell (MFC) was developed using DNA modified carbon paste electrode (DNA/CPE) as a biocathode in the cathodic chamber. Applying bare CPE as the cathode, the output power of MFC differed when adding various oxidizers such as: permanganate (289.76 mW/m 2 at 621.87 mA/m 2 ), ferricyanide (111.94 mW/m 2 at 377.5 mA/m 2 ), and oxygen (41.77 mW/m 2 at 210.11 mA/m 2 ). While for DNA/CPE as biocathode, the maximum power and current density of MFC (510.13 mW/m 2 at 1200.01 mA/m 2 ) were the same in presence of various oxidizers. Furthermore, the type of oxidizer had also no effect on the performance of MFC. Finally, the effect of DNA sequence, composed of pure bases including only adenine, cytosine, thymine, and guanine sequences, on the output power of MFC was examined. The obtained results confirmed that the performance of biocathode remained independent from both the type of base and the quality of DNA. [ABSTRACT FROM AUTHOR]

Cytosine-rich DNA sequences can form a highly ordered structure known as i-motif in slightly acidic solutions. The stability of the folded i-motif structure is a good strategy to inhibit the telomerase reaction in cancer cells. The electrochemical biosensor was prepared by modifying carbon paste electrode with SiO 2 nanoparticles to investigate drugs which can stabilize this structure. Tamoxifen (Tam), an antiestrogen hormonal agent for treatment of breast cancer, was chosen as the model ligand and its interaction with i-motif structure was examined. The interaction between i-motif DNA and Tam was studied in PBS buffer and [Fe(CN) 6 ] 3− through the cyclic voltammetry and square wave voltammetry methods. The oxidation peak of Tam, due to the i-motif DNA/Tam interaction, was observed after i-motif immobilized on the surface of the electrode. The i-motif formation was investigated by circular dichroism spectroscopy and the results showed that this structure can certainly be made with pH around 4.5, but its stability reduced by going to the more alkaline pH. The selectivity which was studied in the presence of complementary strand demonstrated that i-motif structure could be stabilized in acidic pH even in the presence of its complementary strand. [ABSTRACT FROM AUTHOR]

In this work, for the first time, the electrocatalytic oxidation of formaldehyde in 0.5 M sulfuric acid solution at spherical bimetallic palladium-copper nanoparticles (Pd-Cu NPs) deposited on the poly ( o -Anisidine) film modified electrochemically pretreated carbon paste electrode (POA/pCPE) has been investigated. Highly porous POA film prepared by electropolymerization onto the pCPE was used as a potent support for deposition of the Pd-Cu NPs. The Pd-Cu NPs were prepared through spontaneous and irreversible reaction via galvanic replacement between Pd II ions and the Cu 0 particles. The prepared Pd-Cu NPs were characterized by scanning electron microscopy, energy dispersive spectroscopy and electrochemical methods. The obtained results showed that the utilization of Cu nanoparticles and pretreatment technique enhances the electrocatalytic activity of the modified electrode towards formaldehyde oxidation. The influence of several parameters on formaldehyde oxidation as well as stability of the Pd-Cu/POA/pCPE has been investigated. [ABSTRACT FROM AUTHOR]

A carbon paste electrode modified with ZnO nanoparticle (ZnO/NPs) and room-temperature ionic liquid, 1-methyl-3-butylimidazolium chloride was fabricated. The direct electro-oxidation behavior of acetaminophen (AC) was carefully studied by cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS) and the kinetic parameters such as the electron transfer coefficient, α, and the diffusion coefficient, D of AC at the IL/ZnO/NPs/CPE surface was estimated. The results exhibited remarkable increase in the electron transfer rate and significant decrease in the overpotential for AC oxidation reaction in contrast to that on the bare carbon paste electrode (CPE), also, the sensor effectively resolved the overlapping anodic peaks of AC and dihydronicotinamide adenine dinucleotide (NADH). Under the optimal conditions, the oxidation peak current was linear to the AC concentration over the range of 0.1 to 550 μmol L − 1 with a detection limit of 0.07 μmol L − 1 . The proposed sensor has been successfully applied in urine, serum and pharmaceutical samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Prussian blue nanoparticles (PBNPs) were prepared by a self-assembly process on a electrode (GCE) modified with poly( o-phenylenediamine) (PoPD) film. The stepwise fabrication process of PBNP-modified PoPD/GCE was characterized using scanning and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of the modified electrode. The PBNPs/PoPD/GCE showed electrocatalytic activity towards the oxidation of pyridoxine (PN) and was used as an amperometric sensor. The modified electrode exhibited a linear response for PN oxidation over the concentration range 3-38.5 μM with a detection limit of ca 6.10 × 10−7 M ( S/ N = 3) and sensitivity of 2.79936 × 103 mA M−1 cm−2 using an amperometric method. The mechanism and kinetics of the catalytic of PN were investigated using cyclic voltammetry and chronoamperometry. The values of α, kcat and D were estimated as 0.36, 1.089 × 102 M−1 s−1 and 8.9 × 10−5 cm2 s−1, respectively. This sensor also exhibited good anti-interference and selectivity. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An efficient procedure for the physical entrapment of proteins within a biocompatible matrix and their immobilization on electrode surfaces is of utmost importance in the fabrication of biosensors. In this work, the magnetic entrapment of hemoglobin (Hb) at the surface of a screen-printed carbon electrode (SPCE), through mixed hemi/ad-micelles (MHAM) array of positively charged surfactant supported iron oxide magnetic nanoparticles (Mag-NPs), is reported. The Hb/MHAM@Mag-NPs biocomposite is captured at SPCE by a super magnet (Hb/MHAM@Mag-NPs/SPCE). To gain insight in the configuration of the mixed hemi/ad-micelles of CTAB at Mag-NPs, zeta-potential measurements were performed. The entrapment of Hb at MHAM@Mag-NPs was confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR). Direct electron transfer of the Hb intercalated into the composite film showed a pair of well-defined quasi-reversible redox peak at formal potential of −0.255 V vs. Ag/AgCl corresponding to heme Fe(III)/Fe(II) redox couple. It shows that the MHAM@Mag-NPs composite could increase the adsorption ability for Hb, thus provides a facile direct electron transfer between the Hb and the substrate. The proposed biosensor showed excellent electrocatalytic activity to the H 2 O 2 reduction in the wide concentration range from 5.0 to 300.0 µM obtained by amperometric measurement. The Michaelis–Menten constant ( K m ) value of Hb at the modified electrode is 55.4 µM, showing its high affinity. Magnetic entrapment offers a promising design for fast, convenient and effective immobilization of protein within a few minutes for determination of the target molecule in low sample volume at disposable cost-effective SPCE. [ABSTRACT FROM AUTHOR]

In this work, a new and facile method for preparation of platinum nanoparticles (Pt-NPs) at the surface of glassy carbon electrode (GCE) is reported. Firstly, nickel nanoparticles (Ni-NPs) as sacrificial templates are uniformly electrodeposited onto the GCE by using potentiostatic method at a fixed potential (− 1.0 V vs. Ag│AgCl│KCl (3 M)) in 0.5 M H 2 SO 4 solution. Then, Pt-NPs are prepared through a spontaneous and irreversible process via galvanic replacement reaction (GRR) between PtCl 6 2 − and Ni-NPs. The obtained results indicate that the Ni-NPs are completely replaced with Pt-NPs in acid solution. The obtained results from cyclic voltammetry and chronoamperometry reveal that the Pt-NPs demonstrate an enhanced electrocatalytic activity for methanol and formaldehyde oxidation. The effect of several parameters such as electrodepositing potential, NiSO 4 concentration, electrodeposition and GRR time for methanol oxidation as well as stability of the modified electrode has been investigated. [ABSTRACT FROM AUTHOR]

A new label-free electrochemical DNA biosensor is presented based on carbon paste electrode (CPE) modified with gold (Au) and platinum (Pt) nanoparticles to prepare the bimetallic nanocomposite electrode. The proposed sensor was made by immobilization of 15-mer single stranded oligonucleotide probe related to p53 gene for detection of DNA plasmid samples. The hybridization detection relied on the alternation in the guanine oxidation signal following hybridization of the probe with complementary genomic DNA. The technique of differential pulse voltammetry (DPV) was used for monitoring guanine oxidation. To optimize the performance of the modified CPE, different electrodes were prepared in various percentages of Au and Pt nanoparticles. The modified electrode containing 15% Au/Pt bimetallic nanoparticles (15% Au/Pt-MCPE) was selected as the best working electrode. The selectivity of the sensor was investigated using plasmid samples containing non-complementary oligonucleotides. The detection limit of the biosensor was studied and calculated to be 53.10 pg μ L. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Glassy carbon electrode modified by Pt–Co nanostructures decorated on graphene nanosheets (Pt–Co/G/GCE), is fabricated. Co nanostructures are electro-deposited on graphene modified GC electrode and then Pt nanostructures are loaded on the surface of modified electrode by galvanic replacement reaction between Co nanostructures and H2PtCl6. The physical and electrochemical properties of Pt–Co/G/GCE are investigated by scanning electron microscopy, energy dispersive X-ray, cyclic voltammetry and chronoamperometry. The morphology of as-prepared graphene nanosheets is investigated by transmission electron microscopy. The prepared Pt–Co/G is used as the anode electrocatalyst for methanol electrooxidation. The fabricated electrocatalyst exhibits an enhanced electrocatlytic performance for methanol electrooxidation. [Copyright &y& Elsevier]

Abstract: For the first time, simultaneous voltammetric determination of Noradrenaline (NA), Acetaminophen (AC), Xanthine (XN) and Caffeine (CF) has been investigated at a flavonoid nanostructured sensor. The construction of modified electrode was performed through the electrodeposition of luteolin on a functionalized multi-wall carbon nanotube immobilized on the surface of a glassy carbon electrode (Lt/fMWCNT/MGCE). During modification process, luteolin is oxidized to the corresponding o-quinone derivative and attached to the surface of fMWCNT/GCE through Michael type addition reaction. Electrochemical properties of the modified electrode were investigated by electrochemical impedance spectroscopy (EIS). The Lt/fMWCNT/MGCE offered substantially lower overpotential for electro-oxidation of NA, AC, XN and CF in phosphate buffer solution (pH 7.0) compared with Lt/GCE, fMWCNT/GCE and bare GCE. Differential pulse voltammogram peak currents of NA, AC, XN and CF increased linearly with their concentration at the ranges of 0.7–100.0μM, 0.9–80.0μM, 1.0–70.0μM and 10.0–110.0μM, respectively, and the detection limits for NA, AC, XN and CF were sequentially 0.53μM, 0.78μM, 0.65μM and 3.54μM. Furthermore, this electrochemical sensor was successfully implemented for the determination of NA in pharmaceutical samples using standard addition method and the obtained results were found to be satisfactory. [Copyright &y& Elsevier]

Abstract: In this work, carbon nanotube paste electrode (CNTPE) was used as a substrate for deposition of bimetallic Cu/Pt particles. At first, a Cu film was prepared by electrochemical reduction of Cu ions onto the CNTPE in 0.1 M H2SO4 solution. Cu/Pt catalysts were prepared by partial galvanic replacement of Cu with Pt by simply immersion of the Cu-coated CNTPE in 2.0 mM H2PtCl6 solution. The nature and surface morphology of the bare CNTPE and fabricated Cu/Pt species were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The Cu/Pt-modified CNTPE exhibits remarkable electrocatalytic activity towards methanol oxidation. It has been shown that carbon nanotubes improve the electrocatalytic activity of the catalysts towards oxidation. Then, the influence of various parameters such as Cu source concentration, electrodeposition time, replacement time, and methanol concentration on its oxidation as well as long-term stability of the modified electrode have been investigated by electrochemical methods. [Copyright &y& Elsevier]

Highlights: [•] The first report on the electrocatalytic oxidation of methadone. [•] Selective determination of methadone in the presence of acetaminophen. [•] Reaction pathway for electrooxidation of methadone was presented. [•] Some kinetic parameters for methadone were investigated by CV and chronoamprometry. [•] Methadone was determined in urine, saliva and pharmaceutical samples. [Copyright &y& Elsevier]

In this study, we prepared a modified carbon paste electrode consisting of Nickel entrapped in synthesized ZSM-5 zeolite (Ni/ZMCPE). Then Ni(II) ions were incorporated to electrode by immersion of modified electrode in 1 M Ni(II) ion solution. Cyclic voltammetry and chronoamperometry experiments were used for electrochemical study of this modified electrode; a good redox behavior of Ni(OH)2/NiOOH couple at the surface of electrode can be observed, the excellent capability of this modified electrode for catalytic oxidation of formaldehyde was demonstrated during the anodic potential sweep in alkaline solution. The amount of transfer coefficient (α), surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for formaldehyde were evaluated. Thus, it can be a candidate as an anode for fuel cell application. [ABSTRACT FROM AUTHOR]

In present work, the ionic liquid, 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide was incorporated in the carbon paste electrode as the binder (IL-CPE). O-anisidine (OA) monomer is electropolymerized in the presence of an aqueous acidic solution onto IL-CPE (POA/IL-CPE). The as-prepared substrate is used as a porous matrix for dispersion of Ni(II) ions by immersing the modified electrode in a nickel(II) nitrite solution. The modified electrodes are characterized by scanning electron microscopy (SEM) and electrochemical methods. The POA/IL-CPE was applied successfully to highly efficient (current density of 18.2 mA cm−2) electrocatalytic oxidation of formaldehyde in alkaline medium. Finally, the rate constant for chemical reaction between formaldehyde and redox sites of the electrode was calculated. [ABSTRACT FROM AUTHOR]

Abstract: In this study, nitrite electroreduction and phenylhydrazine electrooxidation were investigated on poly(o-anisidine) formed by cyclic voltammetry at the surface of ionic liquid carbon paste electrode. The films were characterized by cyclic voltammetry and scanning electron microscopy (SEM) and were contrasted with poly(o-anisidine) prepared under identical conditions in the absence of ionic liquid in carbon paste electrode. This carbon paste modified electrode exhibits a good electrocatalytic capability (via an EC’ mechanism) for both electrooxidation and electroreduction of some important molecules. The obtained results showed that the catalytic oxidation peak currents of phenylhydrazine and catalytic reduction peak currents of nitrite at the surface of this simple (unfunctionalized) polymeric electrode were linearly dependent on their concentrations. Electrode was successfully applied for determination of nitrite and phenylhydrazine in real samples. [Copyright &y& Elsevier]

We report a simple and effective strategy for fabrication of the nanocomposite containing chitosan (CS) and multiwall carbon nanotube (MWNT) coated on a glassy carbon electrode (GCE). The characterization of the modified electrode (CS-MWNT/GC) was carried out using scanning electron microscopy (SEM) and UV-vis absorption spectroscopy. The electrochemical behavior of CS-MWNT/GC electrode was investigated and compared with the electrochemical behavior of chitosan modified GC (CS/GC), multiwalled carbon nanotube modified GC (MWNT/GC) and unmodified GC using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). The chitosan films are electrochemically inactive; similar background charging currents are observed at bare GC. The chitosan films are permeable to anionic Fe(CN)63−/4− (FC) redox couple. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)63−/4− redox probe at FC/CS-MWNT/GC electrode is comparable to values reported for cast chitosan films. This modified electrode also showed electrocatalytic effect for the simultaneous determination of D-penicillamine ( D-PA) and tryptophan (Trp). The detection limit of 0.9 μM and 4.0 μM for D-PA and Trp, respectively, makes this nanocomposite very suitable for determination of them with good sensitivity. [ABSTRACT FROM AUTHOR]

Poly(o-aminophenol) (POAP) was formed by successive cyclic voltammetry in monomer solution in the presence of sodium dodecyl sulfate (SDS) on the surface of a carbon paste electrode (CPE). Ni(II) ions were incorporated into the electrode by immersion of the polymeric modified electrode having amine groups in 0.1 M Ni(II) ion solution. Electrochemical study of this modified electrode shows a good redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic oxidations of glucose and other carbohydrates at the surface of the Ni/SDS-POAP/CPE were studied in a 0.1 M NaOH solution. Compared to POAP/CPE, the SDS-POAP/CPE significantly enhanced the catalytic efficiency of Ni ions for carbohydrates oxidation. Finally, using chronoamperometric method, the catalytic rate constants ( k) for carbohydrates were calculated. [ABSTRACT FROM AUTHOR]

Abstract: The electrocatalytic oxidation of amoxicillin was investigated on a nickel-based (Ni(II)–curcumin) chemically modified electrode. This modified electrode was prepared by electropolymerization of complex (curcumin = 1,7-bis[4-hydroxyl-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) in alkaline solution. For the first time, the catalytic oxidation of amoxicillin was demonstrated by cyclic voltammetry, chronoamperometry, chronocoulometry and amperometry methods at the surface of this modified carbon paste electrode. The obtained results showed that NiOOH acts as an electrocatalyst for oxidation of amoxicillin. This electrocatalytic oxidation exhibited a good linear response for amoxicillin concentration over the range of 8×10−6–1×10−4 M with a detection limit of 5×10−6 M. Therefore, this electrocatalytic method was used as a simple, selective and rapid method able to determine amoxicillin in pharmaceutical preparations and biological media. [Copyright &y& Elsevier]

Abstract: For the first time, simultaneous determination of levodopa (LD), uric acid (UA) and tyramine (Tyr) has been investigated at a glassy carbon electrode modified with functionalized multi-walled carbon nanotubes and quercetin. The simple modification of electrode was performed through the electrodeposition of quercetin on a functionalized multi-wall carbon nanotube immobilized on the surface of a glassy carbon electrode (Q/fMWCNT/MGCE). Electrochemical properties of the modified electrode were investigated by electrochemical impedance spectroscopy (EIS). Also, the electrocatalytic properties of Q/fMWCNT/MGCE toward the electrocatalytic oxidation of LD, UA and Tyr were studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The Q/fMWCNT/MGCE offered substantially lower overpotential for electro-oxidation of LD, UA and Tyr in phosphate buffer solution (pH 7.0) compared with Q/GCE, fMWCNT/GCE and bare GCE. Differential pulse voltammogram peak currents of LD, UA and Tyr increased linearly with their concentration at the ranges of 0.90–85.0μM, 1.0–125.0μM and 0.70–75.0μM, respectively and the detection limits for LD, UA and Tyr were sequentially 0.381μM, 0.575μM and 0.647μM. Furthermore, this sensor was employed for the simultaneous determination of LD, UA and Tyr in biological and pharmaceutical samples and the obtained results were found to be satisfactory. [Copyright &y& Elsevier]

The utilization of catechol as an electrochemical indicator for the presence of D-penicillamine ( D-PA) at a carbon paste electrode (CPE) has been investigated in aqueous media using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and double step potential chronoamperometry methods. The results show that D-PA participates in Michael type addition reaction with electrogenerated quinone from electrooxidation of catechol at CPE to form the corresponding thioquinone derivative. The reoxidation of the adduct leads to the increase in the oxidative current which is proportional to the concentration of D-PA. Therefore, in the optimum condition (pH 7.00) by CV, the oxidation of D-PA occur at a potential about 343 mV less positive than that in the absence of catechol at the surface of CPE. The practical utility of the method showed much reproducible responses, short response time, low detection limit and high sensitivity for determination of D-PA. The proposed method is useful for the routine analysis of D-PA in pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Abstract: In present work, o-toluidine (OT) monomer is electropolymerized in the presence of an aqueous acidic solution containing Triton X-100 (TX-100) non-ionic surfactant onto multi-walled carbon nanotube paste electrode (CNTPE). The as-prepared substrate is used as a porous matrix for dispersion of Ni (II) ions by immersing the modified electrode in a nickel (II) sulfate solution. The modified electrodes are characterized by field emission scanning electron microscopy (FE-SEM) and electrochemical methods. The electrochemical characterization of the nickel/poly (o-toluidine)/Triton X-100 film modified carbon nanotube paste electrode (Ni/POT (TX-100)/MCNTPE) exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that POT/TX-100 film at surface of the CNTPE improves efficiency of the catalyst toward formaldehyde electrooxidation. Moreover, the effects of various parameters such as TX-100 concentration, formaldehyde concentration, OT concentration, film thickness and accumulation time on the electrooxidation of formaldehyde as well as long-term stability of the Ni/POT (TX-100)/MCNTPE have also been investigated. [Copyright &y& Elsevier]

Abstract: The silver nanoparticles were prepared on the glassy carbon (GC) electrode, modified with p-iso propyl calix[6]arene, by preconcentration of silver ions in open circuit potential and followed by electrochemical reduction of silver ions. The stepwise fabrication process of Ag nanoparticles was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The prepared Ag nanoparticles were deposited with an average size of 70nm and a homogeneous distribution on the surface of electrode. The observed results indicated that the presence of calixarene layer on the electrode surface can control the particle size and prevent the agglomeratione and electrochemical deposition is a promising technique for preparation of nanoparticles due to its easy-to-use procedure and low cost of implementation. Cyclic voltammetry experiments showed that Ag nanoparticles had a good catalytic ability for the reduction of hydrogen peroxide (H2O2). The effects of p-isopropyl calix[6]arene concentration, applied potential for reduction of Ag+, number of calixarene layers and pH value on the electrocatalytic ability of Ag nanoparticles were investigated. The present modified electrode exhibited a linear range from 5.0×10−5 to 6.5×10−3 M and a detection limit 2.7×10−5 M of H2O2 (S/N=3) using amperometric method. [Copyright &y& Elsevier]

Abstract: In this work, carbon paste electrode is coated with poly (m-toluidine) film by potentiodynamic electropolymerization of m-toluidine monomer in the presence of cetyltrimethyl ammonium bromide (CTAB-PMT/MCPE). Then electrolysis at fixed potential (−1.0 V versus reference electrode for 15 min) is employed for electrodepositing of Ni from 1.5 M NiSO4 acidic solution at the surface of polymer-modified electrode for preparation of Ni/CTAB-PMT/MCPE. The general electrochemical behaviors of these modified electrodes are characterized by cyclic voltammetry in alkaline media. In alkaline medium (i.e. NaOH 0.1 M) a good redox behavior of Ni(III)/Ni(II) couple at the surface of these electrodes can be observed. The nickel particles electrodeposited at the surface of Ni/CTAB-PMT/MCPE exhibits a significant electrocatalytic activity towards oxidation of formaldehyde. Moreover, the effects of various parameters such as concentration of CTAB, concentration of formaldehyde, film thickness and monomer concentration on the electrooxidation of formaldehyde as well as long-term stability of the Ni/CTAB-PMT/MCPE have also been investigated. [Copyright &y& Elsevier]

Abstract: Poly (p-aminoacetanilide) (PPAA) was prepared by oxidation of PAA in acidic aqueous solution in the presence of sodium dodecyl sulfate (SDS) at the surface of carbon paste electrode (CPE). Then Ni (II) ions were incorporated to the polymer by immersion of the modified electrode in a 0.1 M Ni (II) ions solution. The electrochemical behavior of this modified electrode (Ni/SDS–PPAA/CPE) was investigated by using cyclic voltammetry and chronoamperometry techniques. The experimental results exhibited the stable redox behavior of the Ni (III)/Ni (II) couple immobilized at the polymeric electrode. This polymeric modified electrode has a very good activity toward the ethylene glycol (EG) electrooxidation in a 0.1 M NaOH solution. By comparison of the different responses to EG oxidation using electrodes Ni/SDS–PPAA/CPE, Ni/PPAA/CPE and Ni/CPE, we observed that Ni/SDS–PPAA/CPE is a more effective catalyst for the electrooxidation of ethylene glycol. The anodic peak current of EG increases with increasing ethylene glycol concentration up to 0.08 M. A diffusion-controlled process at low EG concentrations and a kinetic-controlled process at high EG concentrations are predominant. Finally, the catalytic rate constant (k) for the ethylene glycol oxidation reaction was calculated 1.1 × 104 cm3 mol−1 s−1 by using a chronoamperometric technique. [Copyright &y& Elsevier]

Nickel ions were incorporated in NaY zeolite according to cation exchange mechanism. Then NiY zeolite was used as modifier for preparation of modified carbon paste electrode. The electrochemical behavior of NiY-modified carbon paste electrode (NiY/CPE) was studied in alkaline solution using cyclic voltammetry method. Ability of different electrodes containing NiY/CPE, Ni-NiY/CPE, Ni-NaY/CPE, and Ni/CPE for electrocatalytic oxidation of methanol was compared (three last electrodes prepared by open circuit accumulation of Ni(II) ions on the surface of NiY/CPE, NaY/CPE, and bare CPE, respectively). Results show that Ni-NiY/CPE is best catalyst for the electrochemical oxidation of methanol in alkaline solution and both process of earlier Ni ion incorporation through cation exchange in NaY zeolite and open circuit accumulation of Ni ion on the surface of electrode are essential to have good catalyst. Effect of graphite-zeolite ratio on electrocatalytic current was studied and 3:1 ratio of graphite-zeolite was selected as optimum ratio for preparing electrode. Ni-NiY/CPE has very good stability toward the methanol oxidation in concentration range of 0.005 to 0.5 M. Finally, using chronoamperometric method, the catalytic rate constant ( k) for methanol was found to be 1.56 × 10 cm mol s. [ABSTRACT FROM AUTHOR]

Abstract: In the present work we demonstrate the carbon paste as a new electrode substrate for the electropolymerization of 2-aminodiphenylamine and fabrication of polymer film modified electrode. Then transition metal of copper is incorporated into the polymer by electrodepositing of Cu(II) from CuCl2 acidic solution using potentiostatic technique. The electrocatalytic oxidation of methanol was studies by cyclic voltammetry and chronoamperometry methods at the surface of obtained Cu/P(2ADPA)/MCPE. It has been found that in the course of an anodic potential sweep, the electro-oxidation of methanol follows the formation of Cu(III) and is catalyzed by this species through a mediated electron transfer mechanism. The obtained current density for this catalytic oxidation is very high which could be come from high surface area of caused by the P(2ADPA) modification. The effects of various parameters such as the copper loading, scan rate and methanol concentration on the electrocatalytic oxidation of methanol were also investigated at the surface of Cu/P(2ADPA)/MCPE. Finally, using a chronoamperometric method, the catalytic rate constant (k) for methanol was found to be 0.2×105 cm3 mol−1 s−1 that the high k can be ascribed for the fast electron transfer process due to electrode modification. [Copyright &y& Elsevier]

The electrooxidation of D-penicillamine ( D-PA) has been studied in the presence of potassium iodide in various buffered aqueous solutions (4.00 ≤ pH ≤ 9.00) at the surface of glassy carbon electrode using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. It has been found that under optimum pH (pH 5.00) in cyclic voltammetry, the electrooxidation of D-PA in the presence of potassium iodide as a homogeneous mediator occurred at a potential about 220 mV less positive than that in absence of potassium iodide at the surface of glassy carbon electrode. The homogeneous electrocatalytic oxidation current wave of D-penicillamine was linearly dependent on the D-PA concentration and a linear calibration curve was obtained in the ranges 3.0 × 10−1.5 × 10 M and 9.0 × 10−1.2 × 10 M of D-PA with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (2σ) were determined as 3.0 × 10 and 3.5 × 10 M with CV and DPV, respectively. This method was also used for voltammetric determination of D-PA in pharmaceutical preparation by standard addition method. [ABSTRACT FROM AUTHOR]

In this study, direct electron transfer (ET) has been achieved between an immobilised non-symbiotic plant haemoglobin class II from Beta vulgaris (nsBvHb2) and three different screen-printed carbon electrodes based on graphite (SPCE), multi-walled carbon nanotubes (MWCNT-SPCE), and single-walled carbon nanotubes (SWCNT-SPCE) without the aid of any electron mediator. The nsBvHb2 modified electrodes were studied with cyclic voltammetry (CV) and also when placed in a wall-jet flow through cell for their electrocatalytic properties for reduction of HO. The immobilised nsBvHb2 displayed a couple of stable and well-defined redox peaks with a formal potential ( E°′) of −33.5 mV (vs. Ag|AgCl|3 M KCl) at pH 7.4. The ET rate constant of nsBvHb2, k, was also determined at the surface of the three types of electrodes in phosphate buffer solution pH 7.4, and was found to be 0.50 s on SPCE, 2.78 s on MWCNT-SPCE and 4.06 s on SWCNT-SPCE, respectively. The average surface coverage of electrochemically active nsBvHb2 immobilised on the SPCEs, MWCNT-SPCEs and SWCNT-SPCEs obtained was 2.85 × 10 mol cm, 4.13 × 10 mol cm and 5.20 × 10 mol cm. During the experiments the immobilised nsBvHb2 was stable and kept its electrochemical and catalytic activities. The nsBvHb2 modified electrodes also displayed an excellent response to the reduction of hydrogen peroxide (HO) with a linear detection range from 1 μM to 1000 μM on the surface of SPCEs, from 0.5 μM to 1000 μM on MWCNT-SPCEs, and from 0.1 μM to 1000 μM on SWCNT-SPCEs. The lower limit of detection was 0.8 μM, 0.4 μM and 0.1 μM at 3σ at the SPCEs, the MWCNT-SPCEs, and the SWCNT-SPCEs, respectively, and the apparent Michaelis-Menten constant, $$ {\hbox{K}}_{\rm{M}}^{\rm{app}} $$, for the HO sensors was estimated to be 0.32 mM , 0.29 mM and 0.27 mM, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this work for first time, the electrocatalytic oxidations of some cephalosporins were carried out by poly(o-anisidine)/SDS/Ni modified carbon paste electrode using cyclic voltammetry, chronoamperometry and chronocoulometry methods. At first, poly(o-anisidine) was formed by cyclic voltammetry in monomer solution containing sodium dodesyl sulfate (SDS), on carbon paste electrode surface. Then, Ni(II) ions were incorporated to electrode by immersion of the polymeric modified electrode having amine group in 0.1molL−1 Ni(II) ion solution. A good redox behavior was observed for the Ni(OH)2/NiOOH couple on the surface of this electrode. Cephalosporins were successfully oxidized on the surface of this nickel ions dispersed poly(o-anisidine) modified carbon paste electrode. The electrocatalytic oxidation peak currents of cephalosporins were linearly dependent on their concentration. Electrode was successfully applied to determine cephalosporins in pharmaceutical preparations. [Copyright &y& Elsevier]

Abstract: A new electrochemical DNA biosensor is presented based on carbon past electrode (CPE) for immobilization and detection of short DNA sequences with brilliant cresyl blue (BCB) as electroactive label. The interaction of BCB with DNA is electrochemically detected and BCB displays different signals in the interaction to ssDNA and dsDNA and variation in the BCB signal represents the extent of hybridization at the electrode surface. The effect of solution pH on electrochemical behavior of BCB was investigated. Additionally, the effect of solution pH on BCB accumulation on the CPE was studied. Furthermore, experiments showed that the solution pH could influence the differential pulse voltammetry (DPV) signal of BCB accumulated on the electrode and the highest BCB signal was obtained in pH 7.00. The effect of electrochemical pretreatment of CPE on the ability of electrode in probe adsorption, BCB accumulation and conditions of probe immobilization including potential and time was investigated and optimum conditions were suggested. The peak currents of BCB were linearly related to the concentration of the target oligonucleotide sequence in the range of 1.0×10−8 to 5.0×10−6 M. The detection limit of this approach was 9.00nM. The selectivity of the biosensor was studied using noncomplementary oligonucleotide. [Copyright &y& Elsevier]

Nickel-salophen-modified glassy carbon electrodes prepared by transferring one drop of Ni-salophen complex solution on the electrode surface. This modified electrode has been used for the electrocatalytic oxidation of methanol in alkaline solutions with various methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrooxidation was observed as large anodic peaks, and early stages of the cathodic direction of potential sweep around 20 mV vs. Ag| AgCl|KClsat. A mechanism based on the electrochemical generation of Ni (Ш) active sites and their subsequent consumptions by methanol have been discussed. EIS studies were employed to unveil the charge transfer rate as well as the electrical characteristics of the catalytic surface. For the electrochemical oxidation of methanol at 5.0 M concentration, charge transfer resistance of nearly 0.936 kΩ was obtained, while the resistance of the electro-catalyst layer was about 111.6 Ω. [ABSTRACT FROM AUTHOR]

Abstract: The film of poly(8-hydroxyquinoline) was formed by cyclic voltammetery method on the surface of glassy carbon electrode and poly(8-hydroxyquinoline) modified glassy carbon electrode, p(8-HQ)MGCE, was prepared. Cu2+ ion was adsorbed on the polymer matrix due to complexation with 8-hydroxyquinoline units Copper nanoparticles were deposited onto p(8-HQ)MGCE by applying potential and prepared copper nanoparticles galvanic replaced with platinum to fabricate poly(8-hydroxyquinoline)–Pt/Cu composite on the surface of GCE. Stripping voltammetery of Cu in aqueous 0.1M KSCN+Britton–Robinson buffer, pH=2.0, solution was used to quantify the copper present on the electrode surface. The amount of platinum was estimated from the electrooxidation peak of Pt in aqueous 0.1M H2SO4 solution. The nature of Cu/Pt–p(8-HQ) on the surface of GCE was characterized by scanning electron microscopy. Cu/Pt–p(8-HQ) modified GCE can be used as a convenient conducting substrate for electrocatalytic hydrogen evolution reaction (HER). The effects of different parameters such as number of cycles, replacement time, scan rate of potential, and etc were investigated to obtaining optimum condition for HER. [Copyright &y& Elsevier]

Abstract: Functionalized poly N,N-dimethylaniline film was prepared by adsorption of ferrocyanide onto the polymer forming at the surface of carbon paste electrode (CPE) in aqueous solution. The electrocatalytic ability of poly N,N-dimethylaniline/ferrocyanide film modified carbon paste electrode (PDMA/FMCPE) was demonstrated by oxidation of l-cysteine. Cyclic voltammetry and chronoamperometry techniques were used to investigate this ability. In the optimum pH (6.00), the electrocatalytic ability about 480mV and the catalytic reaction rate constant, (k h), can be seen 3.08×103 M−1 s−1. The catalytic oxidation peak current determined by cyclic voltammetry method was linearly dependent on the l-cysteine concentration and the linearity range obtained was 8.00×10−5 –2.25×10−3 M. Detection limit of this method was determined as 6.17×10−5 M (2σ). At a fixed potential under hydrodynamic conditions (stirred solution), the calibration plot was linear over the l-cysteine concentration range 7.40×10−6 M–1.38×10−4 M. The detection limit of the method was 6.38×10−6 M (2σ). [Copyright &y& Elsevier]

Abstract: In this work, m-toluidine is electropolymerized at the surface of carbon paste electrode using consecutive cyclic voltammetry in 20mM monomer aqueous solution in the presence of 6mM cetyltrimethyl ammonium bromide (CTAB) as surfactant. Then transition metal of nickel is incorporated into the polymer by electrodepositing of Ni (II) from 1.5M NiSO4 acidic solution using chronoamperometry technique (−1.0V versus Ag|AgCl|KCl (3M) for 15min). In alkaline medium (i.e. NaOH 0.1M) a good redox behavior of Ni (III)/Ni (II) couple at the surface of Ni/poly (m-toluidine) modified carbon paste electrode (Ni/PMT/MCPE) in the absence and presence of CTAB (Ni/CTAB-PMT/MCPE) can be observed. Electrocatalytic oxidation of methanol has been studied on Ni/PMT/MCPE and Ni/CTAB-PMT/MCPE. The results show that CTAB significantly enhances the catalytic efficiency of nickel particles on the oxidation of methanol in aqueous alkaline media. Moreover, the effects of various parameters such as concentration of CTAB, concentration of methanol, electrodepositing time, film thickness and monomer concentration on the electrooxidation of methanol as well as long-term stability of the Ni/CTAB-PMT/MCPE have also been investigated. This polymeric modified electrode can oxidize the methanol with high current density (over 40mAcm−2). [Copyright &y& Elsevier]

Abstract: A modified carbon paste electrode was prepared by incorporating TiO2 nanoparticles and ferrocene carboxylic acid (FCCa) in carbon paste matrix. Electrochemical impedance spectroscopy (EIS) indicates that the TiO2 nanoparticles efficiently decreased the charge transfer resistance value of electrode and increased the porous microcrystalline structure of it to improve the electron transfer kinetic between FCCa and electrode. FCCa acted as a mediator between the analyte and electrode surface. The electrocatalytic oxidation of glutathione (GSH) and tryptophan (Trp) is individually and simultaneously investigated at the surface of FCCa–TiO2 modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrode is able to completely resolve the voltammetric response of GSH and Trp from potentially interfering species, e.g. ascorbic acid (AA) and tyrosine (Tyr), respectively. The linear range of the analytical plot remains constant in binary mixture solutions of GSH and Trp. High sensitivity and selectivity together with very low detection limit of the electrode response make it very suitable for simultaneous and individual determination of trace amounts of GSH and Trp in pharmaceutical and clinical preparations. [Copyright &y& Elsevier]

Abstract: This research in finding a cheap and efficient catalyst for electrooxidation of formaldehyde give us an attempt to make and examine the behavior of poly(N-methylaniline)/nickel modified carbon paste electrode (Ni/P(NMA)/MCPE) in absence and presence of formaldehyde. This involves in situ electropolymerization of N-methylaniline at carbon paste electrode, which is following to the incorporation of Ni(II) to polymeric layer by immersion of modified electrode in 1.0M nickel sulphate solution. The electrocatalytic oxidation of formaldehyde was studied by cyclic voltammetry and chronoamperometry methods. The effects of scan rate and formaldehyde concentration on the electrocatalytic oxidation of formaldehyde were also investigated at the surface of Ni/P(NMA)/MCPE. The diffusion coefficient (D =14.1×10−5 cm2 s−1), and some kinetic parameters such as the transfer coefficient (α =0.45) and also second-order rate constant (k =8.96×10−4 cm3 mol−1 s−1) of formaldehyde were calculated. [Copyright &y& Elsevier]