Hitchhiker's Guide to Voltammetry: Acute and Chronic Electrodes for in Vivo Fast-Scan Cyclic Voltammetry.

PubMed

Rodeberg, Nathan T; Sandberg, Stefan G; Johnson, Justin A; Phillips, Paul E M; Wightman, R Mark

2017-02-15

Fast-scan cyclic voltammetry (FSCV) has been used for over 20 years to study rapid neurotransmission in awake and behaving animals. These experiments were first carried out with carbon-fiber microelectrodes (CFMs) encased in borosilicate glass, which can be inserted into the brain through micromanipulators and guide cannulas. More recently, chronically implantable CFMs constructed with small diameter fused-silica have been introduced. These electrodes can be affixed in the brain with minimal tissue response, which permits longitudinal measurements of neurotransmission in single recording locations during behavior. Both electrode designs have been used to make novel discoveries in the fields of neurobiology, behavioral neuroscience, and psychopharmacology. The purpose of this Review is to address important considerations for the use of FSCV to study neurotransmitters in awake and behaving animals, with a focus on measurements of striatal dopamine. Common issues concerning experimental design, data collection, and calibration are addressed. When necessary, differences between the two methodologies (acute vs chronic recordings) are discussed. The topics raised in this Review are particularly important as the field moves beyond dopamine toward new neurochemicals and brain regions.

Instrumentation and Methodology for Generation of an Electrochemical Data Base for Pattern Recognition.

DTIC Science & Technology

1982-05-01

and mercury drop hang time all produced changes in cyclic differential capacity curves and -..-- DD 0A" 1473 EDITION OF 1 NOV 6S IS OBSOLETE S/N 0102...scan rate, and mercury drop hang time all produced changes in cyclic differential capacity curves and cyclic staircase voltammograms which were unique...Faradaic measurements with staircase voltammetry have been enumerated elewhere (24, 25). -4- EXPERIMENTAL Experimental Design The seven variables which

Electrochemical Deposition of Si-Ca/P on Nanotube Formed Beta Ti Alloy by Cyclic Voltammetry Method.

PubMed

Jeong, Yong-Hoon; Choe, Han-Cheol

2015-08-01

The purpose of this study was to investigate electrochemical deposition of Si-Ca/P on nanotube formed Ti-35Nb-10Zr alloy by cyclic voltammetry method. Electrochemical deposition of Si substituted Ca/P was performed by pulsing the applied potential on nanotube formed surface. The surface characteristics were observed by field-emission scanning electron microscopy, X-ray diffractometer, and potentiodynamic polarization test. The phase structure and surface morphologies of Si-Ca/P deposition were affected by deposition cycles. From the anodic polarization test, nanotube formed surface at 20 V showed the high corrosion resistance with lower value of Icorr, I300, and Ipass.

Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications.

PubMed

Bertoluzzi, Luca; Badia-Bou, Laura; Fabregat-Santiago, Francisco; Gimenez, Sixto; Bisquert, Juan

2013-04-18

A simple model is proposed that allows interpretation of the cyclic voltammetry diagrams obtained experimentally for photoactive semiconductors with surface states or catalysts used for fuel production from sunlight. When the system is limited by charge transfer from the traps/catalyst layer and by detrapping, it is shown that only one capacitive peak is observable and is not recoverable in the return voltage scan. If the system is limited only by charge transfer and not by detrapping, two symmetric capacitive peaks can be observed in the cathodic and anodic directions. The model appears as a useful tool for the swift analysis of the electronic processes that limit fuel production.

Effects of Electrodeposition Mode and Deposition Cycle on the Electrochemical Performance of MnO2-NiO Composite Electrodes for High-Energy-Density Supercapacitors.

PubMed

Rusi; Majid, S R

2016-01-01

Nanostructured network-like MnO2-NiO composite electrodes were electrodeposited onto stainless steel substrates via different electrodeposition modes, such as chronopotentiometry, chronoamperometry, and cyclic voltammetry, and then subjected to heat treatment at 300°C for metal oxide conversion. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to study the crystalline natures and morphologies of the deposited films. The electrochemical properties were investigated using cyclic voltammetry and charge/discharge tests. The results revealed that the electrochemical performance of the as-obtained composite electrodes depended on the electrodeposition mode. The electrochemical properties of MnO2-NiO composite electrodes prepared using cyclic voltammetry exhibited the highest capacitance values and were most influenced by the deposition cycle number. The optimum specific capacitance was 3509 Fg-1 with energy and power densities of 1322 Wh kg-1 and 110.5 kW kg-1, respectively, at a current density of 20 Ag-1 in a mixed KOH/K3Fe(CN)6 electrolyte.

Effects of Electrodeposition Mode and Deposition Cycle on the Electrochemical Performance of MnO2-NiO Composite Electrodes for High-Energy-Density Supercapacitors

PubMed Central

Rusi; Majid, S. R.

2016-01-01

Nanostructured network-like MnO2-NiO composite electrodes were electrodeposited onto stainless steel substrates via different electrodeposition modes, such as chronopotentiometry, chronoamperometry, and cyclic voltammetry, and then subjected to heat treatment at 300°C for metal oxide conversion. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to study the crystalline natures and morphologies of the deposited films. The electrochemical properties were investigated using cyclic voltammetry and charge/discharge tests. The results revealed that the electrochemical performance of the as-obtained composite electrodes depended on the electrodeposition mode. The electrochemical properties of MnO2-NiO composite electrodes prepared using cyclic voltammetry exhibited the highest capacitance values and were most influenced by the deposition cycle number. The optimum specific capacitance was 3509 Fg−1 with energy and power densities of 1322 Wh kg−1 and 110.5 kW kg−1, respectively, at a current density of 20 Ag−1 in a mixed KOH/K3Fe(CN)6 electrolyte. PMID:27182595

Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid.

PubMed

Yang, Guangming; Li, Ling; Jiang, Jinhe; Yang, Yunhui

2012-08-01

Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3 min and 2 min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02×10(-7)-5.23×10(-4) mol L(-1) and 1.43×10(-7)-4.64×10(-4) mol L(-1), the detection limits were 1.12×10(-8) mol L(-1) and 2.24×10(-8) mol L(-1), respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results. Copyright © 2012 Elsevier B.V. All rights reserved.

Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Bing-Ang; Li, Bin; Lin, Jie

This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

DOE PAGES

Mei, Bing-Ang; Li, Bin; Lin, Jie; ...

2017-10-27

This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

Conductive polymer/reduced graphene oxide/Au nano particles as efficient composite materials in electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Shabani Shayeh, J.; Ehsani, A.; Ganjali, M. R.; Norouzi, P.; Jaleh, B.

2015-10-01

Polyaniline/reduced graphene oxide/Au nano particles (PANI/rGO/AuNPs) as a hybrid supercapacitor were deposited on a glassy carbon electrode (GCE) by cyclic voltammetry (CV) method as ternary composites and their electrochemical performance was evaluated in acidic medium. Scanning electron micrographs clearly revealed the formation of nanocomposites on the surface of the working electrode. Scanning electron micrographs (SEM) clearly revealed the formation of nanocomposites on the surface of working electrode. Different electrochemical methods including galvanostatic charge-discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out in order to investigate the applicability of the system as a supercapacitor. Based on the cyclic voltammogram results obtained, PANI/rGO/AuNPs gave higher specific capacitance, power and energy values than PANI at a current density of 1 mA cm-2. Specific capacitance (SC) of PANI and PANI/rGO/AuNPs electrodes calculated using CV method are 190 and 303 F g-1, respectively. The present study introduces new nanocomposite materials for electrochemical redox capacitors with advantages including long life cycle and stability due to synergistic effects of each component.

Examining the Complex Regulation and Drug-Induced Plasticity of Dopamine Release and Uptake Using Voltammetry in Brain Slices

PubMed Central

2013-01-01

Fast scan cyclic voltammetry in brain slices (slice voltammetry) has been used over the last several decades to increase substantially our understanding of the complex local regulation of dopamine release and uptake in the striatum. This technique is routinely used for the study of changes that occur in the dopamine system associated with various disease states and pharmacological treatments, and to study mechanisms of local circuitry regulation of dopamine terminal function. In the context of this Review, we compare the relative advantages of voltammetry using striatal slice preparations versus in vivo preparations, and highlight recent advances in our understanding of dopamine release and uptake in the striatum specifically from studies that use slice voltammetry in drug-naïve animals and animals with a history of psychostimulant self-administration. PMID:23581570

Finite-element simulations of the influence of pore wall adsorption on cyclic voltammetry of ion transfer across a liquid-liquid interface formed at a micropore.

PubMed

Ellis, Jonathan S; Strutwolf, Jörg; Arrigan, Damien W M

2012-02-21

Adsorption onto the walls of micropores was explored by computational simulations involving cyclic voltammetry of ion transfer across an interface between aqueous and organic phases located at the micropore. Micro-interfaces between two immiscible electrolyte solutions (micro-ITIES) have been of particular research interest in recent years and show promise for biosensor and biomedical applications. The simulation model combines diffusion to and within the micropore, Butler-Volmer kinetics for ion transfer at the liquid-liquid interface, and Langmuir-style adsorption on the pore wall. Effects due to pore radius, adsorption and desorption rates, surface adsorption site density, and scan rates were examined. It was found that the magnitude of the reverse peak current decreased due to adsorption of the transferring ion on the pore wall; this decrease was more marked as the scan rate was increased. There was also a shift in the half-wave potential to lower values following adsorption, consistent with a wall adsorption process which provides a further driving force to transfer ions across the ITIES. Of particular interest was the disappearance of the reverse peak from the cyclic voltammogram at higher scan rates, compared to the increase in the reverse peak size in the absence of wall adsorption. This occurred for scan rates of 50 mV s(-1) and above and may be useful in biosensor applications using micropore-based ITIES.

Affordable Cyclic Voltammetry

ERIC Educational Resources Information Center

Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

2009-01-01

Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

Micropatterned ferrocenyl monolayers covalently bound to hydrogen-terminated silicon surfaces: effects of pattern size on the cyclic voltammetry and capacitance characteristics.

PubMed

Fabre, Bruno; Pujari, Sidharam P; Scheres, Luc; Zuilhof, Han

2014-06-24

The effect of the size of patterns of micropatterned ferrocene (Fc)-functionalized, oxide-free n-type Si(111) surfaces was systematically investigated by electrochemical methods. Microcontact printing with amine-functionalized Fc derivatives was performed on a homogeneous acid fluoride-terminated alkenyl monolayer covalently bound to n-type H-terminated Si surfaces to give Fc patterns of different sizes (5 × 5, 10 × 10, and 20 × 20 μm(2)), followed by backfilling with n-butylamine. These Fc-micropatterned surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The charge-transfer process between the Fc-micropatterned and underlying Si interface was subsequently studied by cyclic voltammetry and capacitance. By electrochemical studies, it is evident that the smallest electroactive ferrocenyl patterns (i.e., 5 × 5 μm(2) squares) show ideal surface electrochemistry, which is characterized by narrow, perfectly symmetric, and intense cyclic voltammetry and capacitance peaks. In this respect, strategies are briefly discussed to further improve the development of photoswitchable charge storage microcells using the produced redox-active monolayers.

A kinetic study of ferrocenium cation decomposition utilizing an integrated electrochemical methodology composed of cyclic voltammetry and amperometry.

PubMed

Singh, Archana; Chowdhury, Debarati Roy; Paul, Amit

2014-11-21

A novel, easy, quick, and inexpensive integrated electrochemical methodology composed of cyclic voltammetry and amperometry has been developed for the determination of the kinetic stability of higher oxidation states for inorganic complexes. In this study, ferrocene and its derivatives have been used as model systems and the corresponding ferrocenium cations were generated in situ during the electrochemical experiments to determine their kinetic stabilities. The study found that the ferrocenium cations decompose following the first-order kinetics at 27 ± 3 °C in the presence of ambient oxygen and water. The half-lives of the ferrocenium, carboxylate ferrocenium, and decamethyl ferrocenium cations were found to be 1.27 × 10(3), 1.52 × 10(3), and ≫11.0 × 10(3) s, respectively, in acetonitrile solvent having a 0.5 M tetrabutylammonium hexafluorophosphate electrolyte. These results are in agreement with the previous reports, i.e. the ferrocenium cation is unstable whereas the decamethyl ferrocenium cation has superior stability. The new methodology has been established by performing various experiments using different concentrations of ferrocene, variable scan rates in cyclic voltammetry, different time periods for amperometry, and in situ spectroelectrochemical experiments.

Doping effect of polyaniline/MWCNT composites on capacitance and cyclic stability of supercapacitors.

PubMed

Karthikeyan, G; Sahoo, S; Nayak, G C; Das, C K

2012-03-01

Polyaniline doped by Zn2+ ions was synthesized as nanocomposites with multiwalled carbon nanotubes (MWCNT) by in-situ oxidative polymerization and investigated as electrode material for supercapacitors. The uniform coating of polyaniline on MWCNT was characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effect of Zn2+ ions on nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances were investigated by cyclic voltammetry (CV), constant current charging/discharging cyclic test (CC) and electrochemical impedance spectroscopy (EIS) using a three-electrode system. The doped polyaniline composites show higher specific capacitance and better cyclic stability.

Failure of Standard Training Sets in the Analysis of Fast-Scan Cyclic Voltammetry Data.

PubMed

Johnson, Justin A; Rodeberg, Nathan T; Wightman, R Mark

2016-03-16

The use of principal component regression, a multivariate calibration method, in the analysis of in vivo fast-scan cyclic voltammetry data allows for separation of overlapping signal contributions, permitting evaluation of the temporal dynamics of multiple neurotransmitters simultaneously. To accomplish this, the technique relies on information about current-concentration relationships across the scan-potential window gained from analysis of training sets. The ability of the constructed models to resolve analytes depends critically on the quality of these data. Recently, the use of standard training sets obtained under conditions other than those of the experimental data collection (e.g., with different electrodes, animals, or equipment) has been reported. This study evaluates the analyte resolution capabilities of models constructed using this approach from both a theoretical and experimental viewpoint. A detailed discussion of the theory of principal component regression is provided to inform this discussion. The findings demonstrate that the use of standard training sets leads to misassignment of the current-concentration relationships across the scan-potential window. This directly results in poor analyte resolution and, consequently, inaccurate quantitation, which may lead to erroneous conclusions being drawn from experimental data. Thus, it is strongly advocated that training sets be obtained under the experimental conditions to allow for accurate data analysis.

C-FSCV: Compressive Fast-Scan Cyclic Voltammetry for Brain Dopamine Recording.

PubMed

Zamani, Hossein; Bahrami, Hamid Reza; Chalwadi, Preeti; Garris, Paul A; Mohseni, Pedram

2018-01-01

This paper presents a novel compressive sensing framework for recording brain dopamine levels with fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode. Termed compressive FSCV (C-FSCV), this approach compressively samples the measured total current in each FSCV scan and performs basic FSCV processing steps, e.g., background current averaging and subtraction, directly with compressed measurements. The resulting background-subtracted faradaic currents, which are shown to have a block-sparse representation in the discrete cosine transform domain, are next reconstructed from their compressively sampled counterparts with the block sparse Bayesian learning algorithm. Using a previously recorded dopamine dataset, consisting of electrically evoked signals recorded in the dorsal striatum of an anesthetized rat, the C-FSCV framework is shown to be efficacious in compressing and reconstructing brain dopamine dynamics and associated voltammograms with high fidelity (correlation coefficient, ), while achieving compression ratio, CR, values as high as ~ 5. Moreover, using another set of dopamine data recorded 5 minutes after administration of amphetamine (AMPH) to an ambulatory rat, C-FSCV once again compresses (CR = 5) and reconstructs the temporal pattern of dopamine release with high fidelity ( ), leading to a true-positive rate of 96.4% in detecting AMPH-induced dopamine transients.

Studies on niobium triselenide cathode material for lithium rechargeable cells

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Ni, C. L.; Distefano, S.; Somoano, R. B.; Bankston, C. P.

1988-01-01

NbSe3 exhibits superior characteristics such as high capacity, high volumetric and gravimetric energy densities, and high discharge rate capability, as compared to other intercalating cathodes. This paper reports the preparation, characterization, and performance of NbSe3. Several electrochemical techniques, such as cyclic voltammetry, constant-current/constant-potential discharges, dc potentiodynamic scans, ac impedance, and ac voltammetry, have been used to give insight to the mechanisms of intercalation of three lithiums with NbSe3 and also into the rate determining process in the reduction of NbSe3.

A Practical Beginner's Guide to Cyclic Voltammetry

ERIC Educational Resources Information Center

Elgrishi, Noémie; Rountree, Kelley J.; McCarthy, Brian D.; Rountree, Eric S.; Eisenhart, Thomas T.; Dempsey, Jillian L.

2018-01-01

Despite the growing popularity of cyclic voltammetry, many students do not receive formalized training in this technique as part of their coursework. Confronted with self-instruction, students can be left wondering where to start. Here, a short introduction to cyclic voltammetry is provided to help the reader with data acquisition and…

Highly stable multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) core-shell composites with three-dimensional porous nano-network for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Zhou, Haihan; Han, Gaoyi; Chang, Yunzhen; Fu, Dongying; Xiao, Yaoming

2015-01-01

A facile and feasible electrochemical polymerization method has been used to construct the multi-wall carbon nanotubes@poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (MWCNTs@PEDOT/PSS) core-shell composites with three-dimensional (3D) porous nano-network microstructure. The composites are characterized with Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. This special core-shell nanostructure can significantly reduce the ions diffusion distance and the 3D porous nano-network microstructure effectively enlarges the electrode/electrolyte interface. The electrochemical tests including cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy tests are performed, the results manifest the MWCNTs@PEDOT/PSS core-shell composites have superior capacitive behaviors and excellent cyclic stability, and a high areal capacitance of 98.1 mF cm-2 is achieved at 5 mV s-1 cyclic voltammetry scan. Furthermore, the MWCNTs@PEDOT/PSS composites exhibit obviously superior capacitive performance than that of PEDOT/PSS and PEDOT/Cl electrodes, indicating the effective composite of MWCNTs and PEDOT noticeably boosts the capacitive performance of PEDOT-based electrodes for electrochemical energy storage. Such a highly stable core-shell 3D network structural composite is very promising to be used as electrode materials for the high-performance electrochemical capacitors.

Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor.

PubMed

Heydari, Hamid; Gholivand, Mohammad B; Abdolmaleki, Abbas

2016-09-01

In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. Copyright © 2016. Published by Elsevier B.V.

Excimer laser assisted very fast exfoliation and reduction of graphite oxide at room temperature under air ambient for Supercapacitors electrode

NASA Astrophysics Data System (ADS)

Malek Hosseini, S. M. B.; Baizaee, S. M.; Naderi, Hamid Reza; Dare Kordi, Ali

2018-01-01

Excimer laser was used for reduction and exfoliation of graphite oxide (GO) at room temperature under air ambient. The prepared excimer laser reduced graphite oxide (XLRGO) is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption (BET method), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption techniques for surface, structural functional groups and band gap analysis. Electrochemical properties are investigated using cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS) and continues cyclic voltammetry (CCV) in 0.5 M Na2SO4 as electrolyte. Electrochemical investigations revealed that XLRGO electrode has enhanced supercapacitive performance including specific capacitance of 299 F/g at a scan rate of 2 mV/s. Furthermore, CCV measurement showed that XLRGO electrode kept 97.8% of its initial capacitance/capacity after 4000 cycles. The obtained results from electrochemical investigations confirm that the reduction of GO by using an excimer laser produces high-quality graphene for supercapacitor applications without the need for additional operations.

Synthesis and Electrochemical Analysis of Algae Cellulose-Polypyrrole-Graphene Nanocomposite for Supercapacitor Electrode.

PubMed

Aphale, Ashish; Chattopadhyay, Aheli; Mahakalakar, Kapil; Patra, Prabir

2015-08-01

A novel nanocomposite has been developed using extracted cellulose from marine algae coated with conductive polypyrrole and graphene nanoplateletes. The nanocomposite fabricated via in situ polymerization was used as an electrode for a supercapacitor device. The nanocomposite material has been electrochemically characterized using cyclic voltammetry to test its potential to super-capacitive behavior. The specific capacitance of polypyrrole-graphene-cellulose nanocomposite as calculated from cyclic voltammetry curve is 91.5 Fg-1 at the scan rate 50 mV s-1. Transmission electron microscope images show the polymerized polypyrrole -graphene coated cellulosic nanofibers. Scanning electron microscope images reveal an interesting "necklace" like beaded morphology on the cellulose fibers. It is observed that the necklace like structure start to disintegrate with the increase in graphene concentration. The open circuit voltage of the device with polypyrrole-graphene-cellulose electrode was found to be around 225 mV and that of the polypyrrole-cellulose device is only 53 mV without graphene. The results suggest marked improvement in the performance of the nanocomposite supercapacitor device upon graphene inclusion.

Thermal, structural and electrochemical properties of new aliphatic-aromatic imine with piperazine moieties blended with titanium dioxide

NASA Astrophysics Data System (ADS)

Różycka, Anna; Fryń, Patryk; Iwan, Agnieszka; Bogdanowicz, Krzysztof Artur; Filapek, Michal; Górska, Natalia; Dąbczyński, Paweł; Rysz, Jakub; Pociecha, Damian; Hreniak, Agnieszka; Marzec, Monika

2018-02-01

A new piperazine imine, (7E)-N-((4-((E)-(4-hexadecylphenylimino)methyl)piperazin-1-yl)methylene)-4-dodecylbenzenamine, has been synthesized by the condensation of 1,4-piperazinedicarboxaldehyde with 4-hexadecylaniline. The imine was characterized by cyclic voltammetry, Fourier transform middle-infrared absorption spectroscopy and X-ray diffraction. Thermal properties of imine was analyzed by differential scanning calorimetry method during first and second heating scan at 10 and 20 °C/min. Texture of imine was investigated by polarized optical microscopy and atomic force microscopy. Furthermore, imine was blended with titanium dioxide in anatase form and fully characterized by the same methods. Piperazine imine and its mixture with titanium dioxide exhibited only a transition from crystal to isotropic state. Imine exhibits two-step reduction wave attributed to one-electron transfer in each step as was found by cyclic voltammetry. Both titanium dioxide and poly(3-hexylthiophene) change the electrochemical properties of piperazine imine, however, in different ways. Studied imine blended with titanium dioxide exhibited higher value of energy band gap than pure piperazine imine and lower Eg than pure poly(3-hexylthiophene).

Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release.

PubMed

Nguyen, Michael D; Venton, B Jill

2015-01-01

Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future.

Enzyme-modified carbon-fiber microelectrode for the quantification of dynamic fluctuations of nonelectroactive analytes using fast-scan cyclic voltammetry.

PubMed

Lugo-Morales, Leyda Z; Loziuk, Philip L; Corder, Amanda K; Toups, J Vincent; Roberts, James G; McCaffrey, Katherine A; Sombers, Leslie A

2013-09-17

Neurotransmission occurs on a millisecond time scale, but conventional methods for monitoring nonelectroactive neurochemicals are limited by slow sampling rates. Despite a significant global market, a sensor capable of measuring the dynamics of rapidly fluctuating, nonelectroactive molecules at a single recording site with high sensitivity, electrochemical selectivity, and a subsecond response time is still lacking. To address this need, we have enabled the real-time detection of dynamic glucose fluctuations in live brain tissue using background-subtracted, fast-scan cyclic voltammetry. The novel microbiosensor consists of a simple carbon fiber surface modified with an electrodeposited chitosan hydrogel encapsulating glucose oxidase. The selectivity afforded by voltammetry enables quantitative and qualitative measurements of enzymatically generated H2O2 without the need for additional strategies to eliminate interfering agents. The microbiosensors possess a sensitivity and limit of detection for glucose of 19.4 ± 0.2 nA mM(-1) and 13.1 ± 0.7 μM, respectively. They are stable, even under deviations from physiological normoxic conditions, and show minimal interference from endogenous electroactive substances. Using this approach, we have quantitatively and selectively monitored pharmacologically evoked glucose fluctuations with unprecedented chemical and spatial resolution. Furthermore, this novel biosensing strategy is widely applicable to the immobilization of any H2O2 producing enzyme, enabling rapid monitoring of many nonelectroactive enzyme substrates.

The thermodynamic and transport properties of GdCl3 in molten eutectic LiCl-KCl derived from the analysis of cyclic voltammetry signals

NASA Astrophysics Data System (ADS)

Samin, Adib; Wu, Evan; Zhang, Jinsuo

2017-02-01

Pyroprocessing technology is a promising tool for recycling nuclear fuel and producing high purity gadolinium for industrial applications. An efficient implementation of pyroprocessing entails a careful characterization of the electrochemical and transport properties of lanthanides in high temperature molten salts. In this work, the cyclic voltammetry signals of Gd in molten LiCl-KCl salt were recorded for a combination of three temperatures (723 K, 773 K, and 823 K) and three concentration levels (3 wt. %, 6 wt. %, and 9 wt. %) including concentration levels higher than previously reported and relevant for a realistic application of pyroprocessing for molten salt recycle, and the concentration effects were investigated. Four scan rates (200 mV/s to 500 mV/s) were used for each condition, and the signals were examined using conventional Cyclic Voltammetry (CV) analysis equations and by utilizing a two-plate Brunauer, Emmett, and Teller (BET) model accounting for mass diffusion, kinetics, adsorption, and the evolution of electrode morphology via a nonlinear least squares procedure for fitting the model to the experimental signals. It was determined that the redox process is quasi-reversible for the scan rates being used. Furthermore, the applicability of the conventional equations for CV analysis was shown to be problematic for the conditions used, and this is thought to be due to the fact that these equations were derived under the assumption of reversible conditions. The model-derived values for diffusivity are consistent with the literature and are shown to decrease with increasing concentration. This may be due to increased interactions at higher concentration levels. It was also shown that the formal redox potential increased with a concentration and was slightly more positive on the covered electrode.

Electrochemical Determination of Pentachlorophenol in Water on a Multi-Wall Carbon Nanotubes-Epoxy Composite Electrode

PubMed Central

Remes, Adriana; Pop, Aniela; Manea, Florica; Baciu, Anamaria; Picken, Stephen J.; Schoonman, Joop

2012-01-01

The aim of this study was the preparation, characterization, and application of a multi-wall carbon nanotubes-epoxy composite electrode (MWCNT-EP) with 25%, wt. MWCNTs loading for the voltammetric/amperometric determination of pentachlorophenol (PCP) in aqueous solutions. The structural and morphological aspects of the MWCNT-EP composite electrode were examined by scanning electron microscopy. The electrical properties were characterized by direct-current conductivity measurements in relation with the percolation threshold. The electrochemical behavior of PCP at the MWCNT-EP composite electrode was investigated using cyclic voltammetry in 0.1 M Na2SO4 supporting electrolyte in order to establish the parameters for amperometric/voltammetric determination of PCP. The linear dependence of current vs. PCP concentrations was reached in a wide concentration range from 0.2 to 12 μM PCP using cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry, chronoamperometry, and multiple-pulsed amperometry techniques. The best electroanalytical performances of this composite electrode were achieved using a pre-concentration/square-wave voltammetric technique and also multiple-pulsed amperometry techniques envisaging the practical applications. The ease of preparation, high sensitivity, and stability of this composite electrode should open novel avenues and applications for fabricating robust sensors for detection of many important species. PMID:22969335

Investigation on Electrochemical Properties of Polythiophene Nanocomposite with Graphite Derivatives as Supercapacitor Material on Breath Figure-Decorated PMMA Electrode

NASA Astrophysics Data System (ADS)

Azimi, Mona; Abbaspour, Mohsen; Fazli, Ali; Setoodeh, Hamideh; Pourabbas, Behzad

2018-03-01

Breath figures have been formed by the direct breath figure method on polymethyl methacrylate electrode sand hexagonal oriented holes with 0.5- to 10- μm2 surface area have been created. Deposition of materials on the electrodes has been performed by the spray-coating method. polythiophene (PTh) nanoparticles, polythiophene-graphene oxide (PTh-GO) and polythiophene-reduced graphene oxide (PTh-G) nanocomposites were synthesized by emulsion polymerization, while characterization of synthetic materials have been carried out by Fourier transform infrared, Χ-ray diffraction, transmission electron microscopy, UV-Vis spectroscopy and field emission scanning electron microscopy techniques. Also, the electrochemical properties of the designed electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques. Specific capacitance of porous electrodes coated by PTh nanoparticles, PTh-GO and PTh-G nanocomposites were calculated from cyclic voltammetry curves at 5 mV/s scan rate, andthe values are 3.5 F/g, 16.39 F/g, and 28.68 F/g, respectively. Also, the energy density of each electrode at 5 mV/s scan rate has been calculated and the results show that incorporation of GO and G nanolayers with PTh nanoparticles enhances the electrochemical properties of electrodes.

Evaluating the Passivation of Corrosion of API-X100 Steel with Cyclic Voltammetry

NASA Astrophysics Data System (ADS)

Eliyan, Faysal Fayez; Alfantazi, Akram

2017-10-01

In this research, cyclic voltammetry, in oxygen-free low bicarbonate-carbonate solutions, was used to study the corrosion reactions of a high-strength steel, API-X100. With cycles of different scan ranges, the effects of cycling, transpassivation, and cathodic reduction on the electrochemistry of the passive films were analyzed. It was found that carbonate in higher concentrations reduces the anodic activity and the cathodic reactions of the surface. Bicarbonate in small concentrations in solutions that contained low carbonate concentrations catalyzed dissolution and disrupted the formation of the passive films, in reference to the measured anodic currents. From the experiments, there was electrochemical evidence that with more cycles, the passive films were growing thicker, the transpassivation deteriorated the passive films, and during the cathodic reduction, the dissolution was occurring at lower potentials to facilitate later the passivation at higher potentials.

Electrochemical performance of PVA stabilized nickel ferrite nanoparticles via microwave route

NASA Astrophysics Data System (ADS)

William, J. Johnson; Babu, I. Manohara; Muralidharan, G.

2017-05-01

Nanosized nickel ferrite nanoparticles were effectively synthesized through microwave route.PVA is used as a stabilizer. The cubic inverse spinel crystal structure was identified from the X-ray diffraction pattern. FTIR spectrum identified the octahedral site vibrations of the Ni2+ ions and tetrahedral sites vibrations of Fe3+ ions, which additionally confirms the existence of nickel ferrite nanoparticles. Nano-granular morphology was observed from scanning electron microscope. The tuning of morphology was clearly seen in SEM images. Electrochemical performance of nickel ferrite nanoparticles was studied using cyclic voltammetry and chronopotentiometry. Highest specific capacitance of 459 F g-1 was achieved through cyclic voltammetry at 2 mV s-1 for NF10. Also, non-linearity was observed in chronopotentiometry which confirms the pseudocapacitance nature of nickel ferrite nanoparticles. The estimated specific capacitance was 341 F g-1 at 2.5 A g-1.

Synthesis and immobilization of Ag(0) nanoparticles on diazonium modified electrodes: SECM and cyclic voltammetry studies of the modified interfaces.

PubMed

Noël, Jean-Marc; Zigah, Dodzi; Simonet, Jacques; Hapiot, Philippe

2010-05-18

A versatile method was used to prepare modified surfaces on which metallic silver nanoparticles are immobilized on an organic layer. The preparation method takes advantage, on one hand, of the activated reactivity of some alkyl halides with Ag-Pd alloys to produce metallic silver nanoparticles and, on the other hand, of the facile production of an anchoring polyphenyl acetate layer by the electrografting of substituted diazonium salts on carbon surfaces. Transport properties inside such modified layers were investigated by cyclic voltammetry, scanning electrochemical microscopy (SECM) in feedback mode, and conducting AFM imaging for characterizing the presence and nature of the conducting pathways. The modification of the blocking properties of the surface (or its conductivity) was found to vary to a large extent on the solvents used for surface examination (H(2)O, CH(2)Cl(2), and DMF).

Cyclic voltammetry using silver as cathode material: a simple method for determining electro and chemical features and solubility values of CO2 in ionic liquids.

PubMed

Reche, Irene; Gallardo, Iluminada; Guirado, Gonzalo

2015-01-28

A report is presented on the use of cyclic voltammetry using silver as a working electrode. The combined electrocatalytic properties of silver and ionic liquids allow cyclic voltammetry to be turned into an ideal tool for the rapid and accurate access to diffusion coefficient values and solubility values of carbon dioxide in ionic liquids under standard conditions.

Cyclic Voltammetric Wave-Shapes for Microdisk Electrodes: Coupled Effects of Solution Resistance, Double-Layer Capacitance, and Finite Electrochemical Kinetics

DTIC Science & Technology

1991-05-01

vaveshapea. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of pa 20...waveshapes. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of P...2 1 󈧚 Aoki et al have in- 23 vestigated linear sweep voltammetry at microdisks in the reversible case, and Zoski and co-workers have developed

Examination of Rapid Dopamine Dynamics with Fast Scan Cyclic Voltammetry During Intra-oral Tastant Administration in Awake Rats.

PubMed

Wickham, Robert J; Park, Jinwoo; Nunes, Eric J; Addy, Nii A

2015-08-12

Rapid, phasic dopamine (DA) release in the mammalian brain plays a critical role in reward processing, reinforcement learning, and motivational control. Fast scan cyclic voltammetry (FSCV) is an electrochemical technique with high spatial and temporal (sub-second) resolution that has been utilized to examine phasic DA release in several types of preparations. In vitro experiments in single-cells and brain slices and in vivo experiments in anesthetized rodents have been used to identify mechanisms that mediate dopamine release and uptake under normal conditions and in disease models. Over the last 20 years, in vivo FSCV experiments in awake, freely moving rodents have also provided insight of dopaminergic mechanisms in reward processing and reward learning. One major advantage of the awake, freely moving preparation is the ability to examine rapid DA fluctuations that are time-locked to specific behavioral events or to reward or cue presentation. However, one limitation of combined behavior and voltammetry experiments is the difficulty of dissociating DA effects that are specific to primary rewarding or aversive stimuli from co-occurring DA fluctuations that mediate reward-directed or other motor behaviors. Here, we describe a combined method using in vivo FSCV and intra-oral infusion in an awake rat to directly investigate DA responses to oral tastants. In these experiments, oral tastants are infused directly to the palate of the rat--bypassing reward-directed behavior and voluntary drinking behavior--allowing for direct examination of DA responses to tastant stimuli.

Impulse radio ultra wideband wireless transmission of dopamine concentration levels recorded by fast-scan cyclic voltammetry.

PubMed

Ebrazeh, Ali; Bozorgzadeh, Bardia; Mohseni, Pedram

2015-01-01

This paper demonstrates the feasibility of utilizing impulse radio ultra wideband (IR-UWB) signaling technique for reliable, wireless transmission of dopamine concentration levels recorded by fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) to address the problem of elevated data rates in high-channel-count neurochemical monitoring. Utilizing an FSCV-sensing chip fabricated in AMS 0.35μm 2P/4M CMOS, a 3-5-GHz, IR-UWB transceiver (TRX) chip fabricated in TSMC 90nm 1P/9M RF CMOS, and two off-chip, miniature, UWB antennae, wireless transfer of pseudo-random binary sequence (PRBS) data at 50Mbps over a distance of <;1m is first shown with bit-error rates (BER) <; 10(-3). Further, IR-UWB wireless transmission of dopamine concentration levels prerecorded with FSCV at a CFM during flow injection analysis (FIA) is also demonstrated with transmitter (TX) power dissipation of only ~4.4μW from 1.2V, representing two orders of magnitude reduction in TX power consumption compared to that of a conventional frequency-shift-keyed (FSK) link operating at ~433MHz.

Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release

PubMed Central

Nguyen, Michael D.; Venton, B. Jill

2014-01-01

Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future. PMID:26900429

Development of electrochemical sensor for the determination of palladium ions (Pd2+) using flexible screen printed un-modified carbon electrode.

PubMed

Velmurugan, Murugan; Thirumalraj, Balamurugan; Chen, Shen-Ming; Al-Hemaid, Fahad M A; Ajmal Ali, M; Elshikh, Mohamed S

2017-01-01

To date, the development of different modified electrodes have received much attention in electrochemistry. The modified electrodes have some drawbacks such as high cost, difficult to handle and not eco friendly. Hence, we report an electrochemical sensor for the determination of palladium ions (Pd 2+ ) using an un-modified screen printed carbon electrode has been developed for the first time, which are characterized and studied via scanning electron microscope and cyclic voltammetry. Prior to determination of Pd 2+ ions, the operational conditions of un-modified SPCE was optimized using cyclic voltammetry and showed excellent electro-analytical behavior towards the determination of Pd 2+ ions. Electrochemical determination of Pd 2+ ions reveal that the un-modified electrode showed lower detection limit of 1.32μM with a linear ranging from 3 to 133.35μM towards the Pd 2+ ions concentration via differential pulse voltammetry. The developed sensor also applied to the successfully determination of trace level Pd 2+ ions in spiked water samples. In addition, the advantage of this type of electrode is simple, disposable and cost effective in electrochemical sensors. Copyright © 2016 Elsevier Inc. All rights reserved.

Synthesis and bioelectrochemical behavior of aromatic amines.

PubMed

Shabbir, Muhammad; Akhter, Zareen; Ahmad, Iqbal; Ahmed, Safeer; Bolte, Michael; McKee, Vickie

2017-12-01

Four aromatic amines 1-amino-4-phenoxybenzene (A 1 ), 4-(4-aminophenyloxy) biphenyl (A 2 ), 1-(4-aminophenoxy) naphthalene (A 3 ) and 2-(4-aminophenoxy) naphthalene (A 4 ) were synthesized and characterized by elemental, spectroscopic (FTIR, NMR), mass spectrometric and single crystal X-ray diffraction methods. The compounds crystallized in monoclinic crystal system with space group P2 1 . Intermolecular hydrogen bonds were observed between the amine group and amine/ether acceptors of neighboring molecules. Electrochemical investigations were done using cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV). CV studies showed that oxidation of aromatic amines takes place at about 0.9 V (vs. Ag/AgCl) and the electron transfer (ET) process has irreversible nature. After first scan reactive intermediate were generated electrochemically and some other cathodic and anodic peaks also appeared in the succeeding scans. DPV study revealed that ET process is accompanied by one electron. DNA binding study of aromatic amines was performed by CV and UV-visible spectroscopy. These investigations revealed groove binding mode of interaction of aromatic amines with DNA. Copyright © 2017 Elsevier Inc. All rights reserved.

Simultaneous measurement and quantitation of 4-hydroxyphenylacetic acid and dopamine with fast-scan cyclic voltammetry.

PubMed

Shin, Mimi; Kaplan, Sam V; Raider, Kayla D; Johnson, Michael A

2015-05-07

Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of -0.4 V to +1.3 V to -0.4 V at 600 V s(-1), repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores.

Simultaneous Measurement and Quantitation of 4-Hydroxyphenylacetic acid and Dopamine with Fast-Scan Cyclic Voltammetry

PubMed Central

Shin, Mimi; Kaplan, Sam V.; Raider, Kayla D.; Johnson, Michael A.

2015-01-01

Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenylacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of −0.4 V to +1.3 V to −0.4 V at 600 V/s, repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores. PMID:25785694

One-Step Hydrothermal-Electrochemical Route to Carbon-Stabilized Anatase Powders

NASA Astrophysics Data System (ADS)

Tao, Ying; Yi, Danqing; Zhu, Baojun

2013-04-01

Black carbon-stabilized anatase particles were prepared by a simple one-step hydrothermal-electrochemical method using glucose and titanium citrate as the carbon and titanium source, respectively. Morphological, chemical, structural, and electrochemical characterizations of these powders were carried out by Raman spectroscopy, Fourier-transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and cyclic voltammetry. It was revealed that 200-nm carbon/anatase TiO2 was homogeneously dispersed, and the powders exhibited excellent cyclic performance at high current rates of 0.05 V/s. The powders are interesting potential materials that could be used as anodes for lithium-ion batteries.

Synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent and the catalytic oxidation of α-naphthylamine

NASA Astrophysics Data System (ADS)

Song, Y. Z.; Song, Y.; Cheng, Z. P.; Zhou, J. F.; Wei, C.

2013-01-01

Electrochemical synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent was proposed. The gold nanoparticles were characterized by scanning electron microscopy, cyclic voltammetry, IR spectra, UV spectra, and powder X-ray diffraction spectra. The electro-chemical catalysis of penicillin for α-naphthylamine was demonstrated.

Characterization of Local pH Changes in Brain Using Fast-Scan Cyclic Voltammetry with Carbon Microelectrodes

PubMed Central

Takmakov, Pavel; Zachek, Matthew K.; Keithley, Richard B.; Bucher, Elizabeth; McCarty, Gregory S.; Wightman, R. Mark

2010-01-01

Transient local pH changes in the brain are important markers of neural activity that can be used to follow metabolic processes that underlie the biological basis of behavior, learning and memory. There are few methods that can measure pH fluctuations with sufficient time resolution in freely moving animals. Previously, fast-scan cyclic voltammetry at carbon-fiber microelectrodes was used for the measurement of such pH transients. However, the origin of the potential dependent current in the cyclic voltammograms for pH changes recorded in vivo was unclear. The current work explored the nature of these peaks and established the origin for some of them. A peak relating to the capacitive nature of the pH CV was identified. Adsorption of electrochemically inert species, such as aromatic amines and calcium could suppress this peak, and is the origin for inconsistencies regarding in vivo and in vitro data. Also, we identified an extra peak in the in vivo pH CV relating to the presence of 3,4-dihydroxyacetic acid (DOPAC) in the brain extracellular fluid. To evaluate the in vivo performance of the carbon-fiber sensor, carbon dioxide inhalation by an anesthetized rat was used to induce brain acidosis induced by hypercapnia. Hypercapnia is demonstrated to be a useful tool to induce robust in vivo pH changes, allowing confirmation of the pH signal observed with FSCV. PMID:21047096

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chlistunoff, Jerzy; Pivovar, Bryan

In this paper, the oxygen reduction reaction (ORR) at the interface between platinum and Nafion 1100 equivalent weight was studied as a function of temperature (20–80 °C), humidity (10–100%), scan rate, the manner in which Nafion film was deposited, and the state of the Pt surface using ultramicroelectrodes employing cyclic voltammetry and chronoamperometry. ORR on smooth electrodes was strongly inhibited under specific conditions dependent on temperature, humidity, and scan rate. From the data presented, we postulate that dynamic changes in the molecular structure of the ionomer at the platinum interface result in differences in ORR voltammetry for films prepared andmore » equilibrated under different conditions. The lack of similar changes for rough, platinized electrodes has been attributed to differences in initial ionomer structure and a higher energy barrier for ionomer restructuring. Finally, these model system studies yield insight into the ionomer-catalyst interface of particular interest for polymer electrolyte fuel cells.« less

Sonochemical synthesis of terbium tungstate for developing high power supercapacitors with enhanced energy densities.

PubMed

Sobhani-Nasab, Ali; Rahimi-Nasrabadi, Mehdi; Naderi, Hamid Reza; Pourmohamadian, Vafa; Ahmadi, Farhad; Ganjali, Mohammad Reza; Ehrlich, Hermann

2018-07-01

Sonochemically prepared nanoparticles of terbium tungstate (TWNPs) were evaluated through scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, and the optimal products were further characterized in terms of their electrochemical properties using conventional and continuous cyclic voltammetry (CV, and CCV), galvanostatic charge/discharge technique, and electrochemical impedance spectroscopy (EIS). The CV studies indicated the TWNPs to have specific capacitance (SC) values of 336 and 205 F g -1 at 1 and 200 mV s -1 , and galvanostatic charge-discharge tests revealed the SC of the TWNP-based electrodes to be 300 F g -1 at 1 Ag -1 . Also continuous cyclic voltammetry evaluations proved the sample as having a capacitance retention value of 95.3% after applying 4000 potential cycles. In the light of the results TWNPs were concluded as favorable electrode materials for use in hybrid vehicle systems. Copyright © 2018 Elsevier B.V. All rights reserved.

The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Zheng, Liping; Wang, Ying; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie; Guo, Jia

Calcium carbide (CaC 2)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N 2 sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g -1 measured by cyclic voltammetry at 1 mV s -1. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.

Cyclic voltammetry of fast conducting electrocatalytic films.

PubMed

Costentin, Cyrille; Savéant, Jean-Michel

2015-07-15

In the framework of contemporary energy challenges, cyclic voltammetry is a particularly useful tool for deciphering the kinetics of catalytic films. The case of fast conducting films is analyzed, whether conduction is of the ohmic type or proceeds through rapid electron hopping. The rate-limiting factors are then the diffusion of the substrate in solution and through the film as well as the catalytic reaction itself. The dimensionless combination of the characteristics of these factors allows reducing the number of actual parameters to a maximum of two. The kinetics of the system may then be fully analyzed with the help of a kinetic zone diagram. Observing the variations of the current-potential responses with operational parameters such as film thickness, the potential scan rate and substrate concentration allows a precise assessment of the interplay between these factors and of the values of the rate controlling factors. A series of thought experiments is described in order to render the kinetic analysis more palpable.

Effect of slightly acid pH with or without chloride in radioactive water on the corrosion of maraging steel

NASA Astrophysics Data System (ADS)

Bellanger, G.; Rameau, J. J.

1996-02-01

This study was carried out to ascertain the behavior of maraging steel used in the tanks of French plants for reprocessing radioactive water which may contain chloride ions at pH 3. The rest or corrosion potentials can be either in the transpassive or active regions due to the presence of radiolytic species. The corrosion current and potential depend on the pH and intermediates formed on the surface in the active region; therefore, maraging steel behavior was studied by cyclic voltammetry without and with electrode rotation and different acid pH which provide an indication of mechanisms, modification of local pH and transient formation. In the passive -transpassive region, breakdown and porosity in the oxide appear with or without chloride, according to electrochemical impedance spectroscopy. In presence of chloride, the corrosion kinetics were obtained by cyclic voltammetry and electrochemical impedance spectroscopy. The anodic and cathodic areas of maraging steel corroded by pitting were shown using the Scanning Reference Electrode Technique.

Cyclic Voltammetry Experiment.

ERIC Educational Resources Information Center

Van Benschoten, James J.; And Others

1983-01-01

Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

Non-platinum metal-organic framework based electro-catalyst for promoting oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Das, Dipanwita; Raut, Vrushali; Kireeti, Kota V. M. K.; Jha, Neetu

2018-04-01

We developed two non-precious Metal Organic Framework (MOF) based electrocatalysts, MOF-5 and MOF-i using solvothermal and refluxing methods. The MOFs prepared has been characterized by powder X-ray diffractometer (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) for structural and morphological insights. SEM images reveal cubic shape for solvothermally synthesized MOF-5, whereas refluxing method leads to platelet morphology of MOF-i. The synthesized MOFs has been investigated for Oxygen Reduction Reaction (ORR) studies using Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV), with MOF modified Glassy Carbon (GC) as working electrode. The electrochemical data suggests higher activity of MOF-5 towards ORR compared to MOF-i.

Diagnostic criteria for the characterization of quasireversible electron transfer reactions by cyclic square wave voltammetry.

PubMed

Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A

2014-08-19

Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

Characterization of local electrochemical doping of high performance conjugated polymer for photovoltaics using scanning droplet cell microscopy☆

PubMed Central

Gasiorowski, Jacek; Mardare, Andrei Ionut; Sariciftci, Niyazi Serdar; Hassel, Achim Walter

2013-01-01

The electrochemical oxidation of a next generation low bandgap high performance photovoltaic material namely poly[4,8-bis-substituted-benzo[1,2-b:4,5-b0]dithiophene-2,6-diyl-alt-4-substituted-thieno[3,4-b] thiophene-2,6-diyl] (PBDTTT-c) thin film was investigated using a scanning droplet cell microscope. Cyclic voltammetry was used for the basic characterization of the oxidation/doping of PBDTTT-c. Application of the different final potentials during the electrochemical study provides a close look to the oxidation kinetics. The electrical properties of both doped and undoped PBDTTT-c were analyzed in situ by electrochemical impedance spectroscopy giving the possibility to correlate the changes in the doping level with the subsequent changes in the resistance and capacitance. As a result one oxidation peak was found during the cyclic voltammetry and in potentiostatic measurements. From Mott–Schottky analysis a donor concentration of 2.3 × 1020 cm−3 and a flat band potential of 1.00 V vs. SHE were found. The oxidation process resulted in an increase of the conductivity by two orders of magnitude reaching a maximum for the oxidized form of 1.4 S cm−1. PMID:25843970

A Cyclic Voltammetry Experiment for the Instrumental Analysis Laboratory.

ERIC Educational Resources Information Center

Baldwin, Richard P.; And Others

1984-01-01

Background information and procedures are provided for experiments that illustrate the nature of cyclic voltammetry and its application in the characterization of organic electrode processes. The experiments also demonstrate the concepts of electrochemical reversibility and diffusion-controlled mass transfer. (JN)

WINCS-BASED WIRELESS ELECTROCHEMICAL MONITORING OF SEROTONIN (5-HT) USING FAST-SCAN CYCLIC VOLTAMMETRY: PROOF OF PRINCIPLE

PubMed Central

Griessenauer, Christoph J.; Chang, Su-Youne; Tye, Susannah J.; Kimble, Christopher J.; Bennet, Kevin E.; Garris, Paul A.; Lee, Kendall H.

2010-01-01

Object We previously reported the development of a Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for measuring dopamine and suggested that this technology may be useful for evaluating deep brain stimulation (DBS)-related neuromodulatory effects on neurotransmitter systems. WINCS supports fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) for real-time, spatially resolved neurotransmitter measurements. The FSCV parameters used to establish WINCS dopamine measurements are not suitable for serotonin, a neurotransmitter implicated in depression, because they lead to CFM fouling and a loss of sensitivity. Here, we incorporate into WINCS a previously described N-shaped waveform applied at a high scan rate to establish wireless serotonin monitoring. Methods FSCV optimized for the detection of serotonin consisted of an N-shaped waveform scanned linearly from a resting potential of, in V, +0.2 to +1.0, then to −0.1 and back to +0.2 at a rate of 1000 V/s. Proof of principle tests included flow injection analysis and electrically evoked serotonin release in the dorsal raphe nucleus of rat brain slices. Results Flow cell injection analysis demonstrated that the N waveform applied at a scan rate of 1000 V/s significantly reduced serotonin fouling of the CFM, relative to that observed with FSCV parameters for dopamine. In brain slices, WINCS reliably detected sub-second serotonin release in the dorsal raphe nucleus evoked by local high-frequency stimulation. Conclusion WINCS supported high-fidelity wireless serotonin monitoring by FSCV at a CFM. In the future such measurements of serotonin in large animal models and in humans may help to establish the mechanism of DBS for psychiatric disease. PMID:20415521

Cyclic Voltammetry.

ERIC Educational Resources Information Center

Evans, Dennis H.; And Others

1983-01-01

Cyclic voltammetry is a simple experiment that has become popular in chemical research because it can provide useful information about redox reactions in a form which is easily obtained and interpreted. Discusses principles of the method and illustrates its use in the study of four electrode reactions. (Author/JN)

Study of Copper and Purine-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry

PubMed Central

Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek

2008-01-01

Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes. PMID:27879715

Analytical solutions of the planar cyclic voltammetry process for two soluble species with equal diffusivities and fast electron transfer using the method of eigenfunction expansions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samin, Adib; Lahti, Erik; Zhang, Jinsuo, E-mail: zhang.3558@osu.edu

Cyclic voltammetry is a powerful tool that is used for characterizing electrochemical processes. Models of cyclic voltammetry take into account the mass transport of species and the kinetics at the electrode surface. Analytical solutions of these models are not well-known due to the complexity of the boundary conditions. In this study we present closed form analytical solutions of the planar voltammetry model for two soluble species with fast electron transfer and equal diffusivities using the eigenfunction expansion method. Our solution methodology does not incorporate Laplace transforms and yields good agreement with the numerical solution. This solution method can be extendedmore » to cases that are more general and may be useful for benchmarking purposes.« less

Cyclic Voltammetry Simulations with DigiSim Software: An Upper-Level Undergraduate Experiment

ERIC Educational Resources Information Center

Messersmith, Stephania J.

2014-01-01

An upper-division undergraduate chemistry experiment is described which utilizes DigiSim software to simulate cyclic voltammetry (CV). Four mechanisms were studied: a reversible electron transfer with no subsequent or proceeding chemical reactions, a reversible electron transfer followed by a reversible chemical reaction, a reversible chemical…

Cyclic voltammetry of apple fruits: Memristors in vivo.

PubMed

Volkov, Alexander G; Nyasani, Eunice K; Tuckett, Clayton; Blockmon, Avery L; Reedus, Jada; Volkova, Maya I

2016-12-01

A memristor is a resistor with memory that exhibits a pinched hysteretic relationship in cyclic voltammetry. Recently, we have found memristors in the electrical circuitry of plants and seeds. There are no publications in literature about the possible existence of memristors and electrical differentiators in fruits. Here we found that the electrostimulation of Golden Delicious or Arkansas Black apple fruits by bipolar periodic waves induces hysteresis loops with pinched points in cyclic voltammograms at low frequencies between 0.1MHz and 1MHz. At high frequencies of 1kHz, the pinched hysteresis loop transforms to a non-pinched hysteresis loop instead of a single line I=V/R for ideal memristors because the amplitude of electrical current depends on capacitance of a fruit's tissue and electrodes, frequency and direction of scanning. Electrostimulation of electrical circuits in apple fruits by periodic voltage waves also induces electrotonic potential propagation due to cell-to-cell electrical coupling with electrical differentiators. A differentiator is an electrical circuit in which the output of the circuit is approximately directly proportional to the rate of change of the input. The information gained from electrostimulation can be used to elucidate and to observe electrochemical and electrophysiological properties of electrical circuits in fruits. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical studies of biocatalytic anode of sulfonated graphene/ferritin/glucose oxidase layer-by-layer biocomposite films for mediated electron transfer.

PubMed

Inamuddin; Haque, Sufia Ul; Naushad, Mu

2016-06-01

In this study, a bioanode was developed by using layer-by-layer (LBL) assembly of sulfonated graphene (SG)/ferritin (Frt)/glucose oxidase (GOx). The SG/Frt biocomposite was used as an electron transfer elevator and mediator, respectively. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose oxidation biocatalyst. The electrocatalytic oxidation of glucose using GOx modified electrode increases with an increase in the concentration of glucose in the range of 10-50mM. The electrochemical measurements of the electrode was carried out by using cyclic voltammetry (CV) at different scan rates (20-100mVs(-1)) in 30mM of glucose solution prepared in 0.3M potassium ferrocyanide (K4Fe(CN)6) and linear sweep voltammetry (LSV). A saturation current density of 50±2mAcm(-2) at a scan rate of 100mVs(-1) for the oxidation of 30Mm glucose is achieved. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of ionomer morphology on oxygen reduction on Pt

DOE PAGES

Chlistunoff, Jerzy; Pivovar, Bryan

2015-05-21

In this paper, the oxygen reduction reaction (ORR) at the interface between platinum and Nafion 1100 equivalent weight was studied as a function of temperature (20–80 °C), humidity (10–100%), scan rate, the manner in which Nafion film was deposited, and the state of the Pt surface using ultramicroelectrodes employing cyclic voltammetry and chronoamperometry. ORR on smooth electrodes was strongly inhibited under specific conditions dependent on temperature, humidity, and scan rate. From the data presented, we postulate that dynamic changes in the molecular structure of the ionomer at the platinum interface result in differences in ORR voltammetry for films prepared andmore » equilibrated under different conditions. The lack of similar changes for rough, platinized electrodes has been attributed to differences in initial ionomer structure and a higher energy barrier for ionomer restructuring. Finally, these model system studies yield insight into the ionomer-catalyst interface of particular interest for polymer electrolyte fuel cells.« less

Electrochemical studies and analysis of 1-10 wt% UCl3 concentrations in molten LiCl-KCl eutectic

NASA Astrophysics Data System (ADS)

Hoover, Robert O.; Shaltry, Michael R.; Martin, Sean; Sridharan, Kumar; Phongikaroon, Supathorn

2014-09-01

Three electrochemical methods - cyclic voltammetry (CV), chronopotentiometry (CP), and anodic stripping voltammetry (ASV) - were applied to solutions of up to 10 wt% UCl3 in the molten LiCl-KCl eutectic salt at 500 °C to determine electrochemical properties and behaviors and to help provide a scientific basis for the development of an in situ electrochemical probe for determining the concentration of uranium in a used nuclear fuel electrorefiner. Diffusion coefficients of UCl4 and UCl3 were calculated to be (6.72 ± 0.360) × 10-6 cm2/s and (1.04 ± 0.17) × 10-5 cm2/s, respectively. Apparent standard reduction potentials were determined to be (-0.381 ± 0.013) V and (-1.502 ± 0.076) V vs. 5 mol% Ag/AgCl or (-1.448 ± 0.013) V and (-2.568 ± 0.076) V vs. Cl2/Cl- for the U(IV)/U(III) and U(III)/U redox couples, respectively. In comparing this data with supercooled thermodynamic data to determine activity coefficients, the thermodynamic database used was important with resulting activity coefficients ranging from 2.34 × 10-3 to 1.08 × 10-2 for UCl4 and 4.94 × 10-5 to 4.50 × 10-4 for UCl3. Of anodic stripping voltammetry and cyclic voltammetry anodic or cathodic peaks, the CV cathodic peak height divided by square root of scan rate was shown to be the most reliable method of determining UCl3 concentration in the molten salt.

Cyclic Square Wave Voltammetry of Surface-Confined Quasireversible Electron Transfer Reactions.

PubMed

Mann, Megan A; Bottomley, Lawrence A

2015-09-01

The theory for cyclic square wave voltammetry of surface-confined quasireversible electrode reactions is presented and experimentally verified. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. These criteria were experimentally confirmed using two well-established surface-confined analytes. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

Detection of gamma-irradiation effect on DNA and protein using magnetic sensor and cyclic voltammetry.

PubMed

Park, Duck-Gun; Song, Hoon; Kishore, M B; Vértesy, G; Lee, Duk-Hyun

2013-11-01

In this study, a magnetic sensor utilizing Planar Hall Resistance (PHR) and cyclic Voltammetry (CV) for detecting the radiation effect was fabricated. Specifically, we applied in parallel a PHR sensor and CV device to monitor the irradiation effect on DNA and protein respectively. Through parallel measurements, we demonstrated that the PHR sensor and CV are sensitive enough to measure irradiation effect. The PHR voltage decreased by magnetic nanobead labeled DNA was slightly recovered after gamma ray irradiation. The behavior of cdk inhibitor protein p21 having a sandwich structure of Au/protein G/Ab/Ag/Ab was checked by monitoring the cyclic Voltammetry signal in analyzing the gamma ray irradiation effect.

Effects of transition-metal ions on the morphology and electrochemical properties of δ-MnO2 for supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Jia-Wei; Chen, Ya; Chen, Bai-Zhen

2014-11-01

δ-MnO2 materials doped with transition-metal cations (Zn, Co, and Ag) were successfully synthesized using a hydrothermal technique. The structures and morphologies of the obtained oxides were analyzed using X-ray diffraction, scanning electron microscopy and Brunauer-Emmett-Teller measurements. Additionally, the electrochemical properties were evaluated through cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic cycling measurements. The results indicate that the pure and doped samples crystallize in the δ form with a layered structure and that the Mn/Zn, Mn/Co and Mn/Ag molar ratios are all approximately 1:0.09. Both the Zn-doped and pure MnO2 materials exhibit a petal-like morphology; however, the former has a higher specific surface area of up to 98.97m2 g-1. Furthermore, the Zn-doped MnO2 exhibits a near-rectangular cyclic voltammetry (CV) curve with broad quasi-reversible redox peaks and a specific capacitance of 182.9 F g-1 at a CV scan rate of 2 mV s-1. The Co-doped material exhibits a distinct spiny-fiber morphology, and the electrochemical performance of this material is significantly worse than that of pure MnO2. The average attenuation rate of the Ag-doped material is only 0.028% after 1000 cycles, which is lower than that of pure MnO2.

Decoration of nitrogen-doped reduced graphene oxide with cobalt tungstate nanoparticles for use in high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Naderi, Hamid Reza; Sobhani-Nasab, Ali; Rahimi-Nasrabadi, Mehdi; Ganjali, Mohammad Reza

2017-11-01

A composite of cobalt tungstate nanoparticles coated on nitrogen-doped reduced graphene oxide (CoWO4/NRGO) was prepared through an in situ sonochemical approach. The composite was next evaluated as an electrode material for use supercapacitors electrodes. The characterization of the various CoWO4/NRGO nanocomposite samples was carried out through field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Brunauer-Emmett-Teller (BET) method and Raman spectroscopy. Complementary studies were also performed through cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS), and continues cyclic voltammetry (CCV). The electrochemical evaluations were carried out in a 2 M H2SO4 solution as the electrolyte. The electrochemical evaluations on the nano-composite samples indicated that CoWO4/NRGO-based electrodes reveal enhanced supercapacitive characteristics (i.e. a high specific capacitance (SC) of 597 F g-1 at a scan rate of 5 mV s-1, an energy density (ED) value of 67.9 W h kg-1, and high rate capability). CCV studies indicated that CoWO4/NRGO-based electrodes keep 97.1% of their original capacitance after 4000 cycles. The results led to the conclusion that CoWO4/NRGO effectively merge the merits of CoWO4 and CoWO4/RGO in one new nanocomposite material.

Fast-scan cyclic voltammetry demonstrates that L-DOPA produces dose-dependent regionally selective, bimodal effects on striatal dopamine kinetics in vivo.

PubMed

Harun, R; Hare, K M; Brough, M E; Munoz, M J; Grassi, C M; Torres, G E; Grace, A A; Wagner, A K

2015-11-27

Parkinson's disease (PD) is a debilitating condition that is caused by a relatively specific degeneration of dopaminergic (DAergic) neurons of the substantia nigra pars compacta. Levodopa (L-DOPA) was introduced as a viable treatment option for PD over 40 years ago and still remains the most common and effective therapy for PD. Though the effects of L-DOPA to augment striatal DA production are well known, little is actually known about how L-DOPA alters the kinetics of DA neurotransmission that contribute to its beneficial and adverse effects. In this study, we examined the effects of L-DOPA administration (50mg/kg carbidopa + 0, 100, and 250mg/kg L-DOPA) on regional electrically stimulated DA response kinetics using fast-scan cyclic voltammetry (FSCV) in anesthetized rats. We demonstrate that L-DOPA enhances DA release in both the dorsal striatum (D-STR) and nucleus accumbens (NAc), but surprisingly causes a delayed inhibition of release in the D-STR. In both regions, L-DOPA progressively attenuated reuptake kinetics, predominantly through a decrease in Vmax. These findings have important implications on understanding the pharmacodynamics of L-DOPA, which can be informative for understand its therapeutic effects and also common side effects like L-DOPA induced dyskinesias (LID). This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Quantitation of Hydrogen Peroxide Fluctuations and Their Modulation of Dopamine Dynamics in the Rat Dorsal Striatum Using Fast-Scan Cyclic Voltammetry

PubMed Central

2013-01-01

The dopaminergic neurons of the nigrostriatal dopamine (DA) projection from the substantia nigra to the dorsal striatum become dysfunctional and slowly degenerate in Parkinson’s disease, a neurodegenerative disorder that afflicts more than one million Americans. There is no specific known cause for idiopathic Parkinson’s disease; however, multiple lines of evidence implicate oxidative stress as an underlying factor in both the initiation and progression of the disease. This involves the enhanced generation of reactive oxygen species, including hydrogen peroxide (H2O2), whose role in complex biological processes is not well understood. Using fast-scan cyclic voltammetry at bare carbon-fiber microelectrodes, we have simultaneously monitored and quantified H2O2 and DA fluctuations in intact striatal tissue under basal conditions and in response to the initiation of oxidative stress. Furthermore, we have assessed the effect of acute increases in local H2O2 concentration on both electrically evoked DA release and basal DA levels. Increases in endogenous H2O2 in the dorsal striatum attenuated electrically evoked DA release, and also decreased basal DA levels in this brain region. These novel results will help to disambiguate the chemical mechanisms underlying the progression of neurodegenerative disease states, such as Parkinson’s disease, that involve oxidative stress. PMID:23556461

Fast-scan cyclic voltammetry reveals that L-Dopa produces regionally selective, bimodal influences on striatal dopamine kinetics in vivo

PubMed Central

Harun, R; Munoz, M; Grassi, C; Hare, K; Brough, E; Torres, GE; Grace, AA; Wagner, AK

2016-01-01

Parkinson’s disease (PD) is a debilitating condition that is caused by a relatively specific degeneration of dopaminergic (DAergic) neurons of the substantia nigra pars compacta. Levodopa (L-Dopa) was introduced as a viable treatment option for PD over 40 years ago and still remains the most common and effective therapy for PD. Though the effects of L-Dopa to augment striatal DA production are well known, little is actually known about how L-Dopa alters the kinetics of DA neurotransmission that contribute to its beneficial and adverse effects. In this study, we examined the effects of L-Dopa administration (100mg/kg carbidopa/250mg/kg L-Dopa) on regional electrically stimulated DA response kinetics using fast-scan cyclic voltammetry (FSCV) in anesthetized rats. We demonstrate that L-Dopa enhances DA release in both the dorsal striatum (D-STR) and nucleus accumbens (NAc), but surprisingly causes a delayed inhibition of release in the D-STR, a finding that may be related to high-dose L-Dopa effects. In both regions, L-Dopa progressively attenuated reuptake kinetics through a decrease in Vmax and an increase in Km. This finding is consistent with recent clinical studies suggesting that L-Dopa chronically down-regulates the DA transporter (DAT), which may relate to the common development of L-Dopa induced dyskinesias (LID) in PD subjects. PMID:26611352

Quantitative Comparison of Enzyme Immobilization Strategies for Glucose Biosensing in Real-Time Using Fast-Scan Cyclic Voltammetry Coupled with Carbon-Fiber Microelectrodes.

PubMed

Smith, Samantha K; Lugo-Morales, Leyda Z; Tang, C; Gosrani, Saahj P; Lee, Christie A; Roberts, James G; Morton, Stephen W; McCarty, Gregory S; Khan, Saad A; Sombers, Leslie A

2018-05-22

Electrochemical monitoring of non-electroactive species requires a biosensor that is stable and selective, with sensitivity to physiological concentrations of targeted analytes. We have combined glucose oxidase-modified carbon-fiber microelectrodes with fast-scan cyclic voltammetry for real-time measurements of glucose fluctuations in brain tissue. Work presented herein quantitatively compares three approaches to enzyme immobilization on the microelectrode surface-physical adsorption, hydrogel entrapment, and entrapment in electrospun nanofibers. The data suggest that each of these methods can be used to create functional microbiosensors. Immobilization of glucose oxidase by physical adsorption generates a biosensor with poor sensitivity to glucose and unstable performance. Entrapment of glucose oxidase in poly(vinyl alcohol) nanofibers generates microbiosensors that are effective for glucose measurements over a large linear range, and that may be particularly useful when targeting glucose concentrations in excess of 3 mm, such as in blood. Hydrogel entrapment is the most effective in terms of sensitivity and stability. These microbiosensors can be used for simultaneous monitoring of glucose and dopamine in real time. The findings outlined herein should be applicable to other oxidase enzymes, and thus they are broadly important for the development of new tools for real-time measurements of fluctuating molecules that are not inherently electroactive. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Introduced Hybrid Graphene/Polyaniline Composites for Improvement of Supercapacitor

NASA Astrophysics Data System (ADS)

Tayel, Mazhar B.; Soliman, Moataz M.; Ebrahim, Shaker; Harb, Mohamed E.

2016-01-01

Supercapacitors represent an attractive alternative for portable electronics and automotive applications due to their high capacitance, specific power and extended life. In fact, the growing demand of portable systems and hybrid electric vehicles, memory protection in complementary metal-oxide-semiconductor (CMOS), logic circuit, videocassette recorders (VCRs), compact disc (CD) players, personal computers (PCs), uninterruptible power supply (UPS) in security alarm systems, remote sensing, smoke detectors, etc. require high power in short-term pulses. Therefore, in the last 20 years, supercapacitors have been required for the development of large and small devices driven by electrical power. In this paper, graphene oxide (GO) was synthesized by improved Hummers method. Two polyaniline (PANI)/graphene oxide nanocomposites electrode materials were prepared from aniline, GO and ammoniumpersulfate (APS) by in situ chemical polymerization with the mass ratios (mGO:mAniline) 10:90 and 30: 70 in ice bath. The crystal structure and the surface topography of all materials were characterized by means of x-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical properties of the composites were evaluated by cyclic voltammetry (CV), charge-discharge measurements and electrical impedance spectroscopy (EIS), respectively. The results show that the composites have similar and enhanced cyclic voltammetry performance compared with pure PANI based electrode material. The graphene/PANI composite synthesized with the mass ratio (mANI:mGO) 90:10 possessed good capacitive behavior with a specific capacitance as high as 1509.35 F/g at scan rate of 1 mV/s in scanning potential window from -0.8 V to 0.8 V.

Optimizing the Temporal Resolution of Fast-Scan Cyclic Voltammetry

PubMed Central

2012-01-01

Electrochemical detection with carbon-fiber microelectrodes has become an established method to monitor directly the release of dopamine from neurons and its uptake by the dopamine transporter. With constant potential amperometry (CPA), the measured current provides a real time view of the rapid concentration changes, but the method lacks chemical identification of the monitored species and markedly increases the difficulty of signal calibration. Monitoring with fast-scan cyclic voltammetry (FSCV) allows species identification and concentration measurements but often exhibits a delayed response time due to the time-dependent adsorption/desorption of electroactive species at the electrode. We sought to improve the temporal resolution of FSCV to make it more comparable to CPA by increasing the waveform repetition rate from 10 to 60 Hz with uncoated carbon-fiber electrodes. The faster acquisition led to diminished time delays of the recordings that tracked more closely with CPA measurements. The measurements reveal that FSCV at 10 Hz underestimates the normal rate of dopamine uptake by about 18%. However, FSCV collection at 10 and 60 Hz provide identical results when a dopamine transporter (DAT) blocker such as cocaine is bath applied. To verify further the utility of this method, we used transgenic mice that overexpress DAT. After accounting for the slight adsorption delay time, FSCV at 60 Hz adequately monitored the increased uptake rate that arose from overexpression of DAT and, again, was similar to CPA results. Furthermore, the utility of collecting data at 60 Hz was verified in an anesthetized rat by using a higher scan rate (2400 V/s) to increase sensitivity and the overall signal. PMID:22708011

Thin-layer voltammetry of soluble species on screen-printed electrodes: proof of concept.

PubMed

Botasini, S; Martí, A C; Méndez, E

2016-10-17

Thin-layer diffusion conditions were accomplished on screen-printed electrodes by placing a controlled-weight onto the cast solution and allowing for its natural spreading. The restricted diffusive conditions were assessed by cyclic voltammetry at low voltage scan rates and electrochemical impedance spectroscopy. The relationship between the weight exerted over the drop and the thin-layer thickness achieved was determined, in such a way that the simple experimental set-up designed for this work could be developed into a commercial device with variable control of the thin-layer conditions. The experimental results obtained resemble those reported for the voltammetric features of electroactive soluble species employing electrodes modified with carbon nanotubes or graphene layers, suggesting that the attainment of the benefits reported for these nanomaterials could be done simply by forcing the solution to spread over the screen-printed electrodic system to form a thin layer solution. The advantages of thin-layer voltammetry in the kinetic characterization of quasi-reversible and irreversible processes are highlighted.

Rank estimation and the multivariate analysis of in vivo fast-scan cyclic voltammetric data

PubMed Central

Keithley, Richard B.; Carelli, Regina M.; Wightman, R. Mark

2010-01-01

Principal component regression has been used in the past to separate current contributions from different neuromodulators measured with in vivo fast-scan cyclic voltammetry. Traditionally, a percent cumulative variance approach has been used to determine the rank of the training set voltammetric matrix during model development, however this approach suffers from several disadvantages including the use of arbitrary percentages and the requirement of extreme precision of training sets. Here we propose that Malinowski’s F-test, a method based on a statistical analysis of the variance contained within the training set, can be used to improve factor selection for the analysis of in vivo fast-scan cyclic voltammetric data. These two methods of rank estimation were compared at all steps in the calibration protocol including the number of principal components retained, overall noise levels, model validation as determined using a residual analysis procedure, and predicted concentration information. By analyzing 119 training sets from two different laboratories amassed over several years, we were able to gain insight into the heterogeneity of in vivo fast-scan cyclic voltammetric data and study how differences in factor selection propagate throughout the entire principal component regression analysis procedure. Visualizing cyclic voltammetric representations of the data contained in the retained and discarded principal components showed that using Malinowski’s F-test for rank estimation of in vivo training sets allowed for noise to be more accurately removed. Malinowski’s F-test also improved the robustness of our criterion for judging multivariate model validity, even though signal-to-noise ratios of the data varied. In addition, pH change was the majority noise carrier of in vivo training sets while dopamine prediction was more sensitive to noise. PMID:20527815

Synthesis of trimethoprim metal complexes: Spectral, electrochemical, thermal, DNA-binding and surface morphology studies.

PubMed

Demirezen, Nihat; Tarınç, Derya; Polat, Duygu; Ceşme, Mustafa; Gölcü, Ayşegül; Tümer, Mehmet

2012-08-01

Complexes of trimethoprim (TMP), with Cu(II), Zn(II), Pt(II), Ru(III) and Fe(III) have been synthesized. Then, these complexes have been characterized by spectroscopic techniques involving UV-vis, IR, mass and (1)H NMR. CHN elemental analysis, electrochemical and thermal behavior of complexes have also been investigated. The electrochemical properties of all complexes have been investigated by cyclic voltammetry (CV) using glassy carbon electrode. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV spectroscopy and cyclic voltammetry. UV studies of the interaction of the complexes with DNA have shown that these compounds can bind to CT DNA. The binding constants of the complexes with CT DNA have also been calculated. The cyclic voltammograms of the complexes in the presence of CT DNA have shown that the complexes can bind to CT DNA by both the intercalative and the electrostatic binding mode. The antimicrobial activity of these complexes has been evaluated against three Gram-positive and four Gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with the reference drug TMP. Almost all types of complexes show excellent activity against all type of bacteria and fungi. The morphology of the CT DNA, TMP, metal ions and metal complexes has been investigated by scanning electron microscopy (SEM). To get the SEM images, the interaction of compounds with CT DNA has been studied by means of differential pulse voltammetry (DPV) at CT DNA modified pencil graphite electrode (PGE). The decrease in intensity of the guanine oxidation signals has been used as an indicator for the interaction mechanism. Copyright © 2012 Elsevier B.V. All rights reserved.

Role of Au(NPs) in the enhanced response of Au(NPs)-decorated MWCNT electrochemical biosensor

PubMed Central

Mehmood, Shahid; Ciancio, Regina; Carlino, Elvio; Bhatti, Arshad S

2018-01-01

Background The combination of Au-metallic-NPs and CNTs are a new class of hybrid nanomaterials for the development of electrochemical biosensor. Concentration of Au(nanoparticles [NPs]) in the electrochemical biosensor is crucial for the efficient charge transfer between the Au-NPs-MWCNTs modified electrode and electrolytic solution. Methods In this work, the charge transfer kinetics in the glassy carbon electrode (GCE) modified with Au(NPs)–multiwalled carbon nanotube (MWCNT) nanohybrid with varied concentrations of Au(NPs) in the range 40–100 nM was studied using electrochemical impedance spectroscopy (EIS). Field emission scanning electron microscopy and transmission electron microscopy confirmed the attachment of Au(NPs) on the surface of MWCNTs. Results The cyclic voltammetry and EIS results showed that the charge transfer mechanism was diffusion controlled and the rate of charge transfer was dependent on the concentration of Au(NPs) in the nanohybrid. The formation of spherical diffusion zone, which was dependent on the concentration of Au(NPs) in nanohybrids, was attributed to result in 3 times the increase in the charge transfer rate ks, 5 times increase in mass transfer, and 5% (9%) increase in Ipa (Ipc) observed in cyclic voltammetry in 80 nM Au(NP) nanohybrid-modified GCE from MWCNT-modified GCE. The work was extended to probe the effect of charge transfer rates at various concentrations of Au(NPs) in the nanohybrid-modified electrodes in the presence of Escherichia coli. The cyclic voltammetry results clearly showed the best results for 80 nM Au(NPs) in nanohybrid electrode. Conclusion The present study suggested that the formation of spherical diffusion zone in nanohybrid-modified electrodes is critical for the enhanced electrochemical biosensing applications. PMID:29713161

Evaluation of homogeneous electrocatalysts by cyclic voltammetry.

PubMed

Rountree, Eric S; McCarthy, Brian D; Eisenhart, Thomas T; Dempsey, Jillian L

2014-10-06

The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (η), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed.

Electrodeposited nanostructured MnO{sub 2} for non-enzymatic hydrogen peroxide sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, B., E-mail: barnamala.saha@gmail.com; Jana, S. K.; Banerjee, S.

2015-06-24

Electrodeposited MnO{sub 2} nanostructure was synthesized on indium tin oxide coated glass electrode by cyclic voltammetry. The as obtained samples were subsequently characterized by atomic force microscopy and their electro-catalytic response towards hydrogen peroxide in alkaline medium of 0.1M NaOH was studied using cyclic voltammetry and amperometry.

Diagnostic Criteria for the Characterization of Electrode Reactions with Chemically Coupled Reactions Preceding the Electron Transfer by Cyclic Square Wave Voltammetry.

PubMed

Helfrick, John C; Mann, Megan A; Bottomley, Lawrence A

2016-08-18

Theory for cyclic square wave voltammetry of electrode reactions with chemical reactions preceding the electron transfer is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

NASA Astrophysics Data System (ADS)

Cabrita, Joana F.; Viana, Ana S.; Eberle, Christoph; Montforts, Franz-Peter; Mourato, Ana; Abrantes, Luisa M.

2009-08-01

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py 2-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.

Electrochemical synthesis of gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode and their application

NASA Astrophysics Data System (ADS)

Song, Y. Z.; Li, X.; Song, Y.; Cheng, Z. P.; Zhong, H.; Xu, J. M.; Lu, J. S.; Wei, C. G.; Zhu, A. F.; Wu, F. Y.; Xu, J.

2013-01-01

Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed.

Characterization of graphene oxide produced by Hummers method and its supercapacitor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akgül, Ö., E-mail: omeraakgul@gmail.com; Tanrıverdi, A., E-mail: aa.kudret@hotmail.com; Alver, Ü., E-mail: ualver@ktu.edu.tr

2016-03-25

In this study, Graphene Oxide (GO) is produced using Hummers method. The produced GO were investigated by x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), UV-Vis spectrum, Raman spectroscopy and scanning electron microscopy (SEM). GO films on Ni foam were prepared by doctor-blading technique. The electrochemical performances of the as-synthesized GO electrode was evaluated using cyclic voltammetry (CV) in 6 M KOH aqueous solution. Capacitances of GO electrode was measured as 0.76 F/g.

Pulse Voltammetry in Single Cells Using Platinum Microelectrodes

DTIC Science & Technology

1991-11-22

E. and the range for Ed in multiple pulse voltammetry can be chosen from examination of voltammograms obtained by cyclic voltammetry or lin-ir sweep ... voltametry [3,13]. As pointed out by Sinru et al. [14) the potential and time of each pulse has a direct effect on the nature of the voltammetry

Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms▿ †

PubMed Central

Marsili, Enrico; Rollefson, Janet B.; Baron, Daniel B.; Hozalski, Raymond M.; Bond, Daniel R.

2008-01-01

While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 μm) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes. At low scan rates, cyclic voltammetry revealed catalytic electron transfer between cells and the electrode, similar to what has been observed for pure enzymes attached to electrodes under continuous turnover conditions. Differential pulse voltammetry and electrochemical impedance spectroscopy also revealed features that were consistent with electron transfer being mediated by an adsorbed catalyst. Multiple redox-active species were detected, revealing complexity at the outer surfaces of this bacterium. These techniques provide the basis for cataloging quantifiable, defined electron transfer phenotypes as a function of potential, electrode material, growth phase, and culture conditions and provide a framework for comparisons with other species or communities. PMID:18849456

The redox status of experimental hemorrhagic shock as measured by cyclic voltammetry.

PubMed

Mittal, Anubhav; Göke, Friederike; Flint, Richard; Loveday, Benjamin P T; Thompson, Nichola; Delahunt, Brett; Kilmartin, Paul A; Cooper, Garth J S; MacDonald, Julia; Hickey, Anthony; Windsor, John A; Phillips, Anthony R J

2010-05-01

Hemorrhagic shock (HS) leads to reactive oxygen species production. However, clinicians do not have access to bedside measurements of the redox status during HS. Cyclic voltammetry (CyV) is a simple electrochemical method of measuring redox status. The aims of this study were to 1) report the first application of cyclic voltammetry to measure the acute changes in serum redox status after HS, 2) to contrast it with another severe systemic disease with a different redox pathology (acute pancreatitis [AP]), and 3) to describe the response of CyV over time in a resolving model of AP. In the acute study, 24 male Wistar rats were randomized into three groups: groups 1 (control), 2 (AP), and 3 (HS). In the time-course study, 28 rats were randomized to a sham-control as well as 6 and 24 h post-AP cohorts, respectively.Cyclic voltammetry was performed using a three-electrode system. In the acute study, the first and second voltammetric peaks increased significantly in HS. In contrast, within the AP group, only the first voltammetric peak showed a significant increase. The first voltammetric peak correlated with plasma protein carbonyls (PCs) and with thiobarbituric acid-reactive substances, whereas the second voltammetric peak correlated positively with plasma protein carbonyls. In the second study, the first voltammetric peak correlated with physiological improvements. Here, we showed that serum CyV could respond to the serum redox change in HS and AP. Cyclic voltammetry warrants evaluation as a potential real-time beside measure of a patient's redox status during shock.

Development and Use of a Cyclic Voltammetry Simulator to Introduce Undergraduate Students to Electrochemical Simulations

ERIC Educational Resources Information Center

Brown, Jay H.

2015-01-01

Cyclic voltammetry (CV) is a popular technique for the study of electrochemical mechanisms because the method can provide useful information on the redox couple. The technique involves the application of a potential ramp on an unstirred solution while the current is monitored, and then the ramp is reversed for a return sweep. CV is sometimes…

Cyclic voltammetry modeling of proton transport effects on redox charge storage in conductive materials: application to a TiO2 mesoporous film.

PubMed

Kim, Y S; Balland, V; Limoges, B; Costentin, C

2017-07-21

Cyclic voltammetry is a particularly useful tool for characterizing charge accumulation in conductive materials. A simple model is presented to evaluate proton transport effects on charge storage in conductive materials associated with a redox process coupled with proton insertion in the bulk material from an aqueous buffered solution, a situation frequently encountered in metal oxide materials. The interplay between proton transport inside and outside the materials is described using a formulation of the problem through introduction of dimensionless variables that allows defining the minimum number of parameters governing the cyclic voltammetry response with consideration of a simple description of the system geometry. This approach is illustrated by analysis of proton insertion in a mesoporous TiO 2 film.

One-Step Electrochemical Fabrication of Reduced Graphene Oxide/Gold Nanoparticles Nanocomposite-Modified Electrode for Simultaneous Detection of Dopamine, Ascorbic Acid, and Uric Acid

PubMed Central

Lee, Chang-Seuk; Yu, Su Hwan; Kim, Tae Hyun

2017-01-01

Here, we introduce the preparation of the hybrid nanocomposite-modified electrode consisting of reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) using the one-step electrochemical method, allowing for the simultaneous and individual detection of dopamine (DA), ascorbic acid (AA), and uric acid (UA). RGO/AuNPs nanocomposite was formed on a glassy carbon electrode by the co-reduction of GO and Au3+ using the potentiodynamic method. The RGO/AuNPs nanocomposite-modified electrode was produced by subjecting a mixed solution of GO and Au3+ to cyclic sweeping from −1.5 V to 0.8 V (vs. Ag/AgCl) at a scan rate 10 mV/s for 3 cycles. The modified electrode was characterized by scanning electron microscopy, Raman spectroscopy, contact angle measurement, electrochemical impedance spectroscopy, and cyclic voltammetry. Voltammetry results confirm that the RGO/AuNPs nanocomposite-modified electrode has high catalytic activity and good resolution for the detection of DA, AA, and UA. The RGO/AuNPs nanocomposite-modified electrode exhibits stable amperometric responses for DA, AA, and UA, respectively, and its detection limits were estimated to be 0.14, 9.5, and 25 μM. The modified electrode shows high selectivity towards the determination of DA, AA, or UA in the presence of potentially active bioelements. In addition, the resulting sensor exhibits many advantages such as fast amperometric response, excellent operational stability, and appropriate practicality. PMID:29301209

Dopamine Dynamics during Continuous Intracranial Self-Stimulation: Effect of Waveform on Fast-Scan Cyclic Voltammetry Data

PubMed Central

2016-01-01

The neurotransmitter dopamine is heavily implicated in intracranial self-stimulation (ICSS). Many drugs of abuse that affect ICSS behavior target the dopaminergic system, and optogenetic activation of dopamine neurons is sufficient to support self-stimulation. However, the patterns of phasic dopamine release during ICSS remain unclear. Early ICSS studies using fast-scan cyclic voltammetry (FSCV) rarely observed phasic dopamine release, which led to the surprising conclusion that it is dissociated from ICSS. However, several advances in the sensitivity (i.e., the use of waveforms with extended anodic limits) and analysis (i.e., principal component regression) of FSCV measurements have made it possible to detect smaller, yet physiologically relevant, dopamine release events. Therefore, this study revisits phasic dopamine release during ICSS using these tools. It was found that the anodic limit of the voltammetric waveform has a substantial effect on the patterns of dopamine release observed during continuous ICSS. While data collected with low anodic limits (i.e., +1.0 V) support the disappearance of phasic dopamine release observed in previous investigation, the use of high anodic limits (+1.3 V, +1.4 V) allows for continual detection of dopamine release throughout ICSS. However, the +1.4 V waveform lacks the ability to resolve narrowly spaced events, with the best balance of temporal resolution and sensitivity provided by the +1.3 V waveform. Ultimately, it is revealed that the amplitude of phasic dopamine release decays but does not fully disappear during continuous ICSS. PMID:27548680

Detection of Norepinephrine in Whole Blood via Fast Scan Cyclic Voltammetry.

PubMed

Nicolai, Evan N; Trevathan, James K; Ross, Erika K; Lujan, J Luis; Blaha, Charles D; Bennet, Kevin E; Lee, Kendall H; Ludwig, Kip A

2017-05-01

Bioelectronic Medicines is an emerging field that capitalizes on minimally-invasive technology to stimulate the autonomic nervous system in order to evoke therapeutic biomolecular changes at the end-organ. The goal of Bioelectronic Medicines is to realize both 'precision and personalized' medicine. 'Precise' stimulation of neural circuitry creates biomolecular changes targeted exactly where needed to maximize therapeutic effects while minimizing off-target changes associated with side-effects. The therapy is then 'personalized' by utilizing implanted sensors to measure the biomolecular concentrations at, or near, the end-organ of interest and continually adjusting therapy to account for patient-specific biological changes throughout the day. To realize the promise of Bioelectronic Medicines, there is a need for minimally invasive, real-time measurement of biomarkers associated with the effects of autonomic nerve stimulation to be used for continuous titration of therapy. In this study we examine the feasibility of using fast scan cyclic voltammetry (FSCV) to measure norepinephrine levels, a neurochemical relevant to end-organ function, directly from blood. FSCV is a well-understood method for measuring electroactive neurochemicals in the central nervous system with high temporal and high spatial resolution that has yet to be adapted to the study of the autonomic nervous system. The results demonstrate that while detecting the electroactive neurochemical norepinephrine in blood is more challenging than obtaining the same FSCV measurements in a buffer solution due to biofouling of the electrode, it is feasible to utilize a minimally invasive FSCV electrode to obtain neurochemical measurements in blood.

Background Signal as an in Situ Predictor of Dopamine Oxidation Potential: Improving Interpretation of Fast-Scan Cyclic Voltammetry Data.

PubMed

Meunier, Carl J; Roberts, James G; McCarty, Gregory S; Sombers, Leslie A

2017-02-15

Background-subtracted fast-scan cyclic voltammetry (FSCV) has emerged as a powerful analytical technique for monitoring subsecond molecular fluctuations in live brain tissue. Despite increasing utilization of FSCV, efforts to improve the accuracy of quantification have been limited due to the complexity of the technique and the dynamic recording environment. It is clear that variable electrode performance renders calibration necessary for accurate quantification; however, the nature of in vivo measurements can make conventional postcalibration difficult, or even impossible. Analyte-specific voltammograms and scaling factors that are critical for quantification can shift or fluctuate in vivo. This is largely due to impedance changes, and the effects of impedance on these measurements have not been characterized. We have previously reported that the background current can be used to predict electrode-specific scaling factors in situ. In this work, we employ model circuits to investigate the impact of impedance on FSCV measurements. Additionally, we take another step toward in situ electrode calibration by using the oxidation potential of quinones on the electrode surface to accurately predict the oxidation potential for dopamine at any point in an electrochemical experiment, as both are dependent on impedance. The model, validated both in adrenal slice and live brain tissue, enables information encoded in the shape of the background voltammogram to determine electrochemical parameters that are critical for accurate quantification. This improves data interpretation and provides a significant next step toward more automated methods for in vivo data analysis.

Dopamine Dynamics during Continuous Intracranial Self-Stimulation: Effect of Waveform on Fast-Scan Cyclic Voltammetry Data.

PubMed

Rodeberg, Nathan T; Johnson, Justin A; Bucher, Elizabeth S; Wightman, R Mark

2016-11-16

The neurotransmitter dopamine is heavily implicated in intracranial self-stimulation (ICSS). Many drugs of abuse that affect ICSS behavior target the dopaminergic system, and optogenetic activation of dopamine neurons is sufficient to support self-stimulation. However, the patterns of phasic dopamine release during ICSS remain unclear. Early ICSS studies using fast-scan cyclic voltammetry (FSCV) rarely observed phasic dopamine release, which led to the surprising conclusion that it is dissociated from ICSS. However, several advances in the sensitivity (i.e., the use of waveforms with extended anodic limits) and analysis (i.e., principal component regression) of FSCV measurements have made it possible to detect smaller, yet physiologically relevant, dopamine release events. Therefore, this study revisits phasic dopamine release during ICSS using these tools. It was found that the anodic limit of the voltammetric waveform has a substantial effect on the patterns of dopamine release observed during continuous ICSS. While data collected with low anodic limits (i.e., +1.0 V) support the disappearance of phasic dopamine release observed in previous investigation, the use of high anodic limits (+1.3 V, +1.4 V) allows for continual detection of dopamine release throughout ICSS. However, the +1.4 V waveform lacks the ability to resolve narrowly spaced events, with the best balance of temporal resolution and sensitivity provided by the +1.3 V waveform. Ultimately, it is revealed that the amplitude of phasic dopamine release decays but does not fully disappear during continuous ICSS.

Cyclic Voltammetry Probe Approach Curves with Alkali Amalgams at Mercury Sphere-Cap Scanning Electrochemical Microscopy Probes.

PubMed

Barton, Zachary J; Rodríguez-López, Joaquín

2017-03-07

We report a method of precisely positioning a Hg-based ultramicroelectrode (UME) for scanning electrochemical microscopy (SECM) investigations of any substrate. Hg-based probes are capable of performing amalgamation reactions with metal cations, which avoid unwanted side reactions and positive feedback mechanisms that can prove problematic for traditional probe positioning methods. However, prolonged collection of ions eventually leads to saturation of the amalgam accompanied by irreversible loss of Hg. In order to obtain negative feedback positioning control without risking damage to the SECM probe, we implement cyclic voltammetry probe approach surfaces (CV-PASs), consisting of CVs performed between incremental motor movements. The amalgamation current, peak stripping current, and integrated stripping charge extracted from a shared CV-PAS give three distinct probe approach curves (CV-PACs), which can be used to determine the tip-substrate gap to within 1% of the probe radius. Using finite element simulations, we establish a new protocol for fitting any CV-PAC and demonstrate its validity with experimental results for sodium and potassium ions in propylene carbonate by obtaining over 3 orders of magnitude greater accuracy and more than 20-fold greater precision than existing methods. Considering the timescales of diffusion and amalgam saturation, we also present limiting conditions for obtaining and fitting CV-PAC data. The ion-specific signals isolated in CV-PACs allow precise and accurate positioning of Hg-based SECM probes over any sample and enable the deployment of CV-PAS SECM as an analytical tool for traditionally challenging conditions.

Removal of Differential Capacitive Interferences in Fast-Scan Cyclic Voltammetry.

PubMed

Johnson, Justin A; Hobbs, Caddy N; Wightman, R Mark

2017-06-06

Due to its high spatiotemporal resolution, fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes enables the localized in vivo monitoring of subsecond fluctuations in electroactive neurotransmitter concentrations. In practice, resolution of the analytical signal relies on digital background subtraction for removal of the large current due to charging of the electrical double layer as well as surface faradaic reactions. However, fluctuations in this background current often occur with changes in the electrode state or ionic environment, leading to nonspecific contributions to the FSCV data that confound data analysis. Here, we both explore the origin of such shifts seen with local changes in cations and develop a model to account for their shape. Further, we describe a convolution-based method for removal of the differential capacitive contributions to the FSCV current. The method relies on the use of a small-amplitude pulse made prior to the FSCV sweep that probes the impedance of the system. To predict the nonfaradaic current response to the voltammetric sweep, the step current response is differentiated to provide an estimate of the system's impulse response function and is used to convolute the applied waveform. The generated prediction is then subtracted from the observed current to the voltammetric sweep, removing artifacts associated with electrode impedance changes. The technique is demonstrated to remove select contributions from capacitive characteristics changes of the electrode both in vitro (i.e., in flow-injection analysis) and in vivo (i.e., during a spreading depression event in an anesthetized rat).

The Influence of Acidity on Microbial Fuel Cells Containing Shewanella Oneidensis (PREPRINT)

DTIC Science & Technology

2008-09-01

d a fi b i s a h t s p t o m d C H p F 8 ig. 4. Cyclic voltammetry of filter sterilized media after 4 days of growth of S. neidensis MR-1 or S...of autologous mediators in the rowthmedium changeswith pH.We analyzed filter sterilized cul- ure supernatants by cyclic voltammetry (Fig. 4), and HPLC...Marsili et al., 2008). Cyclic voltammetrywas used to detect redox-active compounds n growthmedia supernatants fromMR-1 andDSP10 cultures. Fig. 4 hows

Gold leaf counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Shimada, Kazuhiro; Toyoda, Takeshi

2018-03-01

In this study, a gold leaf 100 nm thin film is used as the counter electrode in dye-sensitized solar cells. The traditional method of hammering gold foil to obtain a thin gold leaf, which requires only small amounts of gold, was employed. The gold leaf was then attached to the substrate using an adhesive to produce the gold electrode. The proposed approach for fabricating counter electrodes is demonstrated to be facile and cost-effective, as opposed to existing techniques. Compared with electrodes prepared with gold foil and sputtered gold, the gold leaf counter electrode demonstrates higher catalytic activity with a cobalt-complex electrolyte and higher cell efficiency. The origin of the improved performance was investigated by surface morphology examination (scanning electron microscopy), various electrochemical analyses (cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy), and crystalline analysis (X-ray diffractometry).

Natural polyhydroxyalkanoate-gold nanocomposite based biosensor for detection of antimalarial drug artemisinin.

PubMed

Phukon, Pinkee; Radhapyari, Keisham; Konwar, Bolin Kumar; Khan, Raju

2014-04-01

The worrisome trend of antimalarial resistance has already highlighted the importance of artemisinin as a potent antimalarial agent. The current investigation aimed at fabricating a biosensor based on natural polymer polyhydroxyalkanoate-gold nanoparticle composite mounting on an indium-tin oxide glass plate for the analysis of artemisinin. The biosensor was fabricated using an adsorbing horse-radish peroxidase enzyme on the electrode surface for which cyclic voltammetry was used to monitor the electro-catalytic reduction of artemisinin under diffusion controlled conditions. Electrochemical interfacial properties and immobilization of enzyme onto a polyhydroxyalkanoate-gold nanoparticle film were evaluated, and confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. The differential pulse voltammetric peak current for artemisinin was increased linearly (concentration range of 0.01-0.08μg mL(-1)) with sensitivity of 0.26μAμg mL(-1). The greater sensitivity of the fabricated biosensor to artemisinin (optimum limits of detection were 0.0035μg mL(-1) and 0.0036μg mL(-1) in bulk and spiked human serum, respectively) could be of much aid in medical diagnosis. Copyright © 2014 Elsevier B.V. All rights reserved.

Microwave synthesis and electrochemical characterization of Mn/Ni mixed oxide for supercapacitor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasankumar, T.; Jose, Sujin P., E-mail: sujamystica@yahoo.com; Ilangovan, R.

Nanostructured Mn/Ni mixed metal oxide was synthesized at ambient temperature by facile microwave irradiation technique. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction analysis confirmed the formation of Mn/Ni mixed oxide in rhombohedral phase and the grain size calculated was found to be 87 nm. The irregular spherical morphology of the prepared sample was exhibited by the SEM images. The characteristic peaks of FTIR at about 630 cm{sup −1} and 749 cm{sup −1} were attributed to the Mn-O and Ni-O stretching vibrations respectively. The presence of both Mn and Ni inmore » the prepared sample was validated by the EDS spectra which in turn confirmed the formation of mixed oxide. Cyclic voltammetry and galvanostatic chargedischarge measurements were employed to investigate the electrochemical performance of the mixed oxide. The cyclic voltammetry curves demonstrated good capacitive performance of the sample in the potential window −0.2V to 0.9V. The charge discharge study revealed the suitability of the prepared mixed oxide for the fabrication of supercapacitor electrode.« less

Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

NASA Astrophysics Data System (ADS)

Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

2017-09-01

The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

Electrochemical Sensors Based on Screen-Printed Electrodes: The Use of Phthalocyanine Derivatives for Application in VFA Detection

PubMed Central

Ndiaye, Amadou L.; Delile, Sébastien; Brunet, Jérôme; Varenne, Christelle; Pauly, Alain

2016-01-01

Here, we report on the use of electrochemical methods for the detection of volatiles fatty acids (VFAs), namely acetic acid. We used tetra-tert-butyl phthalocyanine (PcH2-tBu) as the sensing material and investigated its electroanalytical properties by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). To realize the electrochemical sensing system, the PcH2-tBu has been dropcast-deposited on carbon (C) orgold (Au)screen-printed electrodes (SPEs) and characterized by cyclic voltammetry and scanning electron microscopy (SEM). The SEM analysis reveals that the PcH2-tBu forms mainly aggregates on the SPEs. The modified electrodes are used for the detection of acetic acid and present a linear current increase when the acetic acid concentration increases. The Cmodified electrode presents a limit of detection (LOD) of 25.77 mM in the range of 100 mM–400 mM, while the Aumodified electrode presents an LOD averaging 40.89 mM in the range of 50 mM–300 mM. When the experiment is realized in a buffered condition, theCmodified electrode presents a lower LOD, which averagesthe 7.76 mM. A pronounced signal decay attributed to an electrode alteration is observed in the case of the gold electrode. This electrode alteration severely affects the coating stability. This alteration is less perceptible in the case of the carbon electrode. PMID:27598214

Electrochemical quantification of some water soluble vitamins in commercial multi-vitamin using poly-amino acid caped by graphene quantum dots nanocomposite as dual signal amplification elements.

PubMed

Shadjou, Nasrin; Hasanzadeh, Mohammad; Omari, Ali

2017-12-15

Rapid analyses of some water soluble vitamins (Vitamin B2, B9, and C) in commercial multi vitamins could be routinely performed in analytical laboratories. This study reports on the electropolymerization of a low toxic and biocompatible polymer "poly aspartic acid-graphene quantum dots" as a novel strategy for surface modification of glassy carbon electrode and preparation a new interface for measurement of selected vitamins in commercial multi vitamins. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of graphene quantum dots nanostructures on a poly aspartic acid using cyclic voltammetry techniques in the regime of -1.5 to 2 V. The field emission scanning electron microscopy indicated immobilization of graphene quantum dots onto poly aspartic acid film. The modified electrode possessed as an effective electroactivity for detection of water soluble vitamins by using cyclic voltammetry, chronoamperometry and differential pulse voltammetry. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of poly aspartic acid as semiconducting polymer, graphene quantum dots as high density of edge plane sites and chemical modification. Under the optimized analysis conditions, the prepared sensor for detection of VB2, VB9, and VC showed a low limit of quantification 0.22, 0.1, 0.1 μM, respectively. Copyright © 2017. Published by Elsevier Inc.

In-situ microwave irradiation synthesis of ZnO-graphene nanocomposite for high-performance supercapacitor applications

NASA Astrophysics Data System (ADS)

Gunaseelan, R.; Venkatachalam, V.; Raj, A. Antony

2018-04-01

In this paper, the ZnO/G nanocomposite was synthesized by facile in-situ microwave irradiation method. The as-prepared ZnO/G composite has been characterized with X-ray powder diffraction. The electrochemical properties of the obtained composite electrode for supercapacitor have been studied by cyclic voltammetry and electrochemical impedance spectra analyses. The ZnO/G nanocomposites showed a good capacitive behavior with a higher specific capacitance of 140.4 F/g at a scan rate of 5 mV/s scan rate in 1M KOH electrolyte. Based on the electrochemical results revealed that the composite electrode is a suitable candidate for supercapacitor applications.

Corrosion resistance evaluation of Pd-free Ag-Au-Pt-Cu dental alloys.

PubMed

Fujita, Takeshi; Shiraishi, Takanobu; Takuma, Yasuko; Hisatsune, Kunihiro

2011-01-01

The corrosion resistance of nine experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.9% NaCl solution was investigated using cyclic voltammetry (CV), optical microscopy, and scanning electron microscopy (SEM). CV measurements revealed that the breakdown potential (E(bd)) and zero current potential (E(zc)) increased with increasing Au/(Au+Ag) atomic ratio. Thus, the Au/(Au+Ag) atomic ratio, but not the Cu content, influenced the corrosion resistance of Ag-Au-Pt-Cu alloys. After the forward scan of CV, both optical and scanning electron microscope images showed that in all the experimental alloys, the matrix phase was corroded but not the second phase. From corrosion resistance viewpoint, the Ag-Au-Pt-Cu alloys seemed to be suitable for clinical application.

Nanotubular polyaniline electrode for supercapacitor application

NASA Astrophysics Data System (ADS)

Athira, A. R.; Vimuna, V. M.; Vidya, K.; Xavier, T. S.

2018-05-01

Polyaniline(PANI) nanotubes have been successfully synthesised at room temperature by the chemical oxidative polymerization of aniline with Ammoniumpersulphate(APS) in aqueous acetic acid. Chemically synthesised PANI nanotubes were characterized using Field emission scanning electron microscopy(FESEM), Brunauer - Emmett-Teller (BET) analysis, X ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR). The super capacitive performance of the synthesised PANI nanotubes was tested using cyclic voltammetry (CV) technique in H2SO4 electrolyte with in potential range of -0.2 to 0.8V. The effect of scan rates on specific capacitance of PANI electrode was studied. The highest specific capacitance of 232.2Fg-1 was obtained for the scan rate of 5mVs-1. This study suggests that the synthesized PANI nanotubes are excellent candidate for developing electrode materials for supercapacitors.

The theory of cyclic voltammetry of electrochemically heterogeneous surfaces: comparison of different models for surface geometry and applications to highly ordered pyrolytic graphite.

PubMed

Ward, Kristopher R; Lawrence, Nathan S; Hartshorne, R Seth; Compton, Richard G

2012-05-28

The cyclic voltammetry at electrodes composed of multiple electroactive materials, where zones of one highly active material are distributed over a substrate of a second, less active material, is investigated by simulation. The two materials are assumed to differ in terms of their electrochemical rate constants towards any given redox couple. For a one-electron oxidation or reduction, the effect on voltammetry of the size and relative surface coverages of the zones as well as the rate constant of the slower zone are considered for systems where it is much slower than the rate constant of the faster zones. The occurrence of split peak cyclic voltammetry where two peaks are observed in the forward sweep, is studied in terms of the diffusional effects present in the system. A number of surface geometries are compared: specifically the more active zones are modelled as long, thin bands, as steps in the surface, as discs, and as rings (similar to a partially blocked electrode). Similar voltammetry for the band, step and ring models is seen but the disc geometry shows significant differences. Finally, the simulation technique is applied to the modelling of highly-ordered pyrolytic graphite (HOPG) surface and experimental conditions under which it may be possible to observe split peak voltammetry are predicted.

Integrated wireless fast-scan cyclic voltammetry recording and electrical stimulation for reward-predictive learning in awake, freely moving rats

NASA Astrophysics Data System (ADS)

Li, Yu-Ting; Wickens, Jeffery R.; Huang, Yi-Ling; Pan, Wynn H. T.; Chen, Fu-Yu Beverly; Chen, Jia-Jin Jason

2013-08-01

Objective. Fast-scan cyclic voltammetry (FSCV) is commonly used to monitor phasic dopamine release, which is usually performed using tethered recording and for limited types of animal behavior. It is necessary to design a wireless dopamine sensing system for animal behavior experiments. Approach. This study integrates a wireless FSCV system for monitoring the dopamine signal in the ventral striatum with an electrical stimulator that induces biphasic current to excite dopaminergic neurons in awake freely moving rats. The measured dopamine signals are unidirectionally transmitted from the wireless FSCV module to the host unit. To reduce electrical artifacts, an optocoupler and a separate power are applied to isolate the FSCV system and electrical stimulator, which can be activated by an infrared controller. Main results. In the validation test, the wireless backpack system has similar performance in comparison with a conventional wired system and it does not significantly affect the locomotor activity of the rat. In the cocaine administration test, the maximum electrically elicited dopamine signals increased to around 230% of the initial value 20 min after the injection of 10 mg kg-1 cocaine. In a classical conditioning test, the dopamine signal in response to a cue increased to around 60 nM over 50 successive trials while the electrically evoked dopamine concentration decreased from about 90 to 50 nM in the maintenance phase. In contrast, the cue-evoked dopamine concentration progressively decreased and the electrically evoked dopamine was eliminated during the extinction phase. In the histological evaluation, there was little damage to brain tissue after five months chronic implantation of the stimulating electrode. Significance. We have developed an integrated wireless voltammetry system for measuring dopamine concentration and providing electrical stimulation. The developed wireless FSCV system is proven to be a useful experimental tool for the continuous monitoring of dopamine levels during animal learning behavior studies of freely moving rats.

Integrated wireless fast-scan cyclic voltammetry recording and electrical stimulation for reward-predictive learning in awake, freely moving rats.

PubMed

Li, Yu-Ting; Wickens, Jeffery R; Huang, Yi-Ling; Pan, Wynn H T; Chen, Fu-Yu Beverly; Chen, Jia-Jin Jason

2013-08-01

Fast-scan cyclic voltammetry (FSCV) is commonly used to monitor phasic dopamine release, which is usually performed using tethered recording and for limited types of animal behavior. It is necessary to design a wireless dopamine sensing system for animal behavior experiments. This study integrates a wireless FSCV system for monitoring the dopamine signal in the ventral striatum with an electrical stimulator that induces biphasic current to excite dopaminergic neurons in awake freely moving rats. The measured dopamine signals are unidirectionally transmitted from the wireless FSCV module to the host unit. To reduce electrical artifacts, an optocoupler and a separate power are applied to isolate the FSCV system and electrical stimulator, which can be activated by an infrared controller. In the validation test, the wireless backpack system has similar performance in comparison with a conventional wired system and it does not significantly affect the locomotor activity of the rat. In the cocaine administration test, the maximum electrically elicited dopamine signals increased to around 230% of the initial value 20 min after the injection of 10 mg kg(-1) cocaine. In a classical conditioning test, the dopamine signal in response to a cue increased to around 60 nM over 50 successive trials while the electrically evoked dopamine concentration decreased from about 90 to 50 nM in the maintenance phase. In contrast, the cue-evoked dopamine concentration progressively decreased and the electrically evoked dopamine was eliminated during the extinction phase. In the histological evaluation, there was little damage to brain tissue after five months chronic implantation of the stimulating electrode. We have developed an integrated wireless voltammetry system for measuring dopamine concentration and providing electrical stimulation. The developed wireless FSCV system is proven to be a useful experimental tool for the continuous monitoring of dopamine levels during animal learning behavior studies of freely moving rats.

Development of a cyclic voltammetry method for the detection of Clostridium novyi in black disease.

PubMed

Liu, L L; Jiang, D N; Xiang, G M; Liu, C; Yu, J C; Pu, X Y

2014-03-17

Black disease is an acute disease of sheep and cattle. The pathogen is the obligate anaerobe, Clostridium novyi. Due to difficulties of anaerobic culturing in the country or disaster sites, a simple, rapid, and sensitive method is required. In this study, an electrochemical method, the cyclic voltammetry method, basing on loop-mediated isothermal amplification (LAMP), electrochemical ion bonding (positive dye, methylene blue), was introduced. DNA extracted from C. novyi specimens was amplified through the LAMP reaction. Then the products combined were with methylene blue, which lead to a reduction in the oxidation peak current (ipA) and the reduction peak current (ipC) of the cyclic voltammetry. The changes of ipA/ipC were real-time measured by special designed electrode, so the DNA was quantitatively detected. The results displayed that this electrochemical detection of C. novyi could be completed in 1-2 h with the lowest bacterial concentration of 10(2) colony forming units/mL, and high accuracy (96.5%), sensitivity (96%), and specificity (97%) compared to polymerase chain reation. The cyclic voltammetry method was a simple and fast method, with high sensitivity and high specificity, and has great potential to be a usable molecular tool for fast diagnosis of Black disease.

Effect of inhibitors on Zn-dendrite formation for zinc-polyaniline secondary battery

NASA Astrophysics Data System (ADS)

Kan, Jinqing; Xue, Huaiguo; Mu, Shaolin

The effects of Pb 2+, sodium lauryl sulfate and Triton X-100 on inhibition of Zn-dendrite growth in Zn-polyaniline batteries were studied by scanning electron micrograph and cyclic voltammetry. The results show that Triton X-100 in the region of 0.02-500 ppm in the electrolyte containing 2.5 M ZnCl 2 and 2.0 M NH 4Cl with pH 4.40 can effectively inhibit zinc-dendrite growth during charge-discharge cycles of the battery and yield longer cycles.

Low temperature electrodeposition of silicon layers

NASA Astrophysics Data System (ADS)

Pauporté, Thierry; Qi, Shuo; Viana, Bruno

2018-02-01

The electrodeposition of silicon at room temperature in 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and N-Propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids containing SiCl4 salt is shown. The electrodeposition window has been determined by cyclic voltammetry. Layers have been deposited in a three electrode cell placed in an inert atmosphere and at constant applied potential. The characterizations by x-ray diffraction and Raman spectroscopy showed the formation of a layer made of amorphous silicon. The scanning electron microscopy examination revealed that the layers were featureless and well-covering.

Polythiophene nanocomposites as high performance electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Vijeth, H.; Niranjana, M.; Yesappa, L.; Ashokkumar, S. P.; Devendrappa, H.

2018-04-01

A polythiophene-aluminium oxide nanocomposite is prepared by in situ chemical polymerisation in presence of anionic surfactant camphor sulfonic acid (CSA). The characterisation of nano composite was done by X-ray Diffraction (XRD), surface morphology was studied using Atomic Force Microscopy (AFM). The electrochemical performance is evaluated using cyclic voltammetry in 1M H2SO4. As an electroactive material, it exhibits high specific capacitance of 654.5 and 757 F/g for PTH and PTHA nanocomposites at scan rate of 30mV s-1 respectively.

Sub-second changes in accumbal dopamine during sexual behavior in male rats.

PubMed

Robinson, D L; Phillips, P E; Budygin, E A; Trafton, B J; Garris, P A; Wightman, R M

2001-08-08

Transient (200--900 ms), high concentrations (200--500 nM) of dopamine, measured using fast-scan cyclic voltammetry, occurred in the nucleus accumbens core of male rats at the presentation of a receptive female. Additional dopamine signals were observed during subsequent approach behavior. Background-subtracted cyclic voltammograms of the naturally-evoked signals matched those of electrically-evoked dopamine measured at the same recording sites. Administration of nomifensine amplified natural and evoked dopamine release, and increased the frequency of detectable signals. While gradual changes in dopamine concentration during sexual behavior have been well established, these findings dramatically improve the time resolution. The observed dopamine transients, probably resulting from neuronal burst firing, represent the first direct correlation of dopamine with sexual behavior on a sub-second time scale.

Preparation of glucose sensors using gold nanoparticles modified diamond electrode

NASA Astrophysics Data System (ADS)

Fachrurrazie; Ivandini, T. A.; Wibowo, W.

2017-04-01

A glucose sensor was successfully developed by immobilizing glucose oxidase (GOx) at boron-doped diamond (BDD) electrodes. Prior to GOx immobilization, the BDD was modified with gold nanoparticles (AuNPs). To immobilize AuNPs, the gold surface was modified to nitrogen termination. The characterization of the electrode surface was performed using an X-ray photoelectron spectroscopy and a scanning electron microscope, while the electrochemical properties of the enzyme electrode were characterized using cyclic voltammetry. Cyclic voltammograms of the prepared electrode for D-glucose in phosphate buffer solution pH 7 showed a new reduction peak at +0.16 V. The currents of the peak were linear in the concentration range of 0.1 M to 0.9 M, indicated that the GOx-AuNP-BDD can be applied for electrochemical glucose detection.

Determination of band structure parameters and the quasi-particle gap of CdSe quantum dots by cyclic voltammetry.

PubMed

Inamdar, Shaukatali N; Ingole, Pravin P; Haram, Santosh K

2008-12-01

Band structure parameters such as the conduction band edge, the valence band edge and the quasi-particle gap of diffusing CdSe quantum dots (Q-dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q-dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi-empirical pseudopotential method (SEPM)-especially in the strong size-confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q-dots, the difference between the quasi-particle gap and the optical band gap gives the electron-hole Coulombic interaction energy (J(e1,h1)). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.

The photoelectrocatalytic activity, long term stability and corrosion performance of NiMo deposited titanium oxide nano-tubes for hydrogen production in alkaline medium

NASA Astrophysics Data System (ADS)

Mert, Mehmet Erman; Mert, Başak Doğru; Kardaş, Gülfeza; Yazıcı, Birgül

2017-11-01

In this study, titanium oxide nano-tubes are doped with Ni and Mo particles with various chemical compositions, in order to put forth the efficiency of single and binary coatings on hydrogen evolution reaction (HER) in 1 M KOH. The characterization was achieved by cyclic voltammetry, scanning electron microscopy and energy dispersive X-ray analysis. The water wettability characteristics of electrode surfaces were investigated using contact angle. The long-term catalyst stability and corrosion performance were determined by current-potential curves and electrochemical impedance spectroscopy. Furthermore, photoelectrochemical behavior was determined via linear sweep voltammetry. Results showed that, nano-structured Ni and Mo deposited titanium oxide nano-tubes decrease the hydrogen over potential and increase HER efficiency, it is stable over 168 h electrolysis and it exhibits higher corrosion performance.

The (2 × 2) tunnels structured manganese dioxide nanorods with α phase for lithium air batteries

NASA Astrophysics Data System (ADS)

Ghouri, Zafar Khan; Zahoor, Awan; Barakat, Nasser A. M.; Alsoufi, Mohammad S.; Bawazeer, Tahani M.; Mohamed, Ahmed F.; Kim, Hak Yong

2016-02-01

The (2 × 2) tunnels structured manganese dioxide nanorods with α phase (α-MnO2) are synthesized via simplistic hydrothermal method at low temperature. The obtained tunnels structured α-MnO2 nanorods are characterized by, Transmission electron microscopy, Scanning electron microscopy, and X-ray diffraction techniques. The oxygen reduction reaction (ORR) activity was studied by cyclic voltammetry and rotating ring-disc electrode voltammetry techniques in alkaline media. Moreover; the highly electrocatalytic tunnels structured α-MnO2 nanorods were then also applied as cathode in rechargeable Li-O2 cells. The Li-O2 cells exhibited initial discharge capacity as high as ∼4000 mAh/g with the tunnels structured α-MnO2 nanorods which was double the original capacity of the cells without any catalyst. Also we obtained 100% round trip efficiency upon cycling with limited capacity for more than 50 cycles.

Performance of carbon nanofiber supported Pd-Ni catalysts for electro-oxidation of ethanol in alkaline medium

NASA Astrophysics Data System (ADS)

Maiyalagan, T.; Scott, Keith

Carbon nanofibers (CNF) supported Pd-Ni nanoparticles have been prepared by chemical reduction with NaBH 4 as a reducing agent. The Pd-Ni/CNF catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical voltammetry analysis. TEM showed that the Pd-Ni particles were quite uniformly distributed on the surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of the Pd-Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential was 200 mV lower and the peak current density four times higher for ethanol oxidation for Pd-Ni/CNF compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 °C had a great effect on increasing the ethanol oxidation activity.

A Highly Sensitive Oligonucleotide Hybridization Assay for Klebsiella pneumoniae Carbapenemase with the Probes on a Gold Nanoparticles Modified Glassy Carbon Electrode.

PubMed

Pan, Hong-zhi; Yu, Hong- Wei; Wang, Na; Zhang, Ze; Wan, Guang-Cai; Liu, Hao; Guan, Xue; Chang, Dong

2015-01-01

To develop a new electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase, a highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-nano). The Au-nano/GCE was characterized by scanning electromicroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The hybridization detection was measured by differential pulse voltammetry using methylene blue as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-11) to 1 × 10(-8) M, with an LOD of 1 × 10(-12) M. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The Au-nano/GCE showed significant improvement in electrochemical characteristics, and this biosensor was successfully applied for determination of K. pneumoniae.

On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study.

PubMed

Lovelock, Kevin R J; Ejigu, Andinet; Loh, Sook Fun; Men, Shuang; Licence, Peter; Walsh, Darren A

2011-06-07

The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 μm Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied.

Modeling Fast-scan Cyclic Voltammetry Data from Electrically Stimulated Dopamine Neurotransmission Data Using QNsim1.0.

PubMed

Harun, Rashed; Grassi, Christine M; Munoz, Miranda J; Wagner, Amy K

2017-06-05

Central dopaminergic (DAergic) pathways have an important role in a wide range of functions, such as attention, motivation, and movement. Dopamine (DA) is implicated in diseases and disorders including attention deficit hyperactivity disorder, Parkinson's disease, and traumatic brain injury. Thus, DA neurotransmission and the methods to study it are of intense scientific interest. In vivo fast-scan cyclic voltammetry (FSCV) is a method that allows for selectively monitoring DA concentration changes with fine temporal and spatial resolution. This technique is commonly used in conjunction with electrical stimulations of ascending DAergic pathways to control the impulse flow of dopamine neurotransmission. Although the stimulated DA neurotransmission paradigm can produce robust DA responses with clear morphologies, making them amenable for kinetic analysis, there is still much debate on how to interpret the responses in terms of their DA release and clearance components. To address this concern, a quantitative neurobiological (QN) framework of stimulated DA neurotransmission was recently developed to realistically model the dynamics of DA release and reuptake over the course of a stimulated DA response. The foundations of this model are based on experimental data from stimulated DA neurotransmission and on principles of neurotransmission adopted from various lines of research. The QN model implements 12 parameters related to stimulated DA release and reuptake dynamics to model DA responses. This work describes how to simulate DA responses using QNsim1.0 and also details principles that have been implemented to systematically discern alterations in the stimulated dopamine release and reuptake dynamics.

Fast-Scan Cyclic Voltammetry (FSCV) Detection of Endogenous Octopamine in Drosophila melanogaster Ventral Nerve Cord.

PubMed

Pyakurel, Poojan; Privman Champaloux, Eve; Venton, B Jill

2016-08-17

Octopamine is an endogenous biogenic amine neurotransmitter, neurohormone, and neuromodulator in invertebrates and has functional analogy with norepinephrine in vertebrates. Fast-scan cyclic voltammetry (FSCV) can detect rapid changes in neurotransmitters, but FSCV has not been optimized for octopamine detection in situ. The goal of this study was to characterize octopamine release in the ventral nerve cord of Drosophila larvae for the first time. A FSCV waveform was optimized so that the potential for octopamine oxidation would not be near the switching potential where interferences can occur. Endogenous octopamine release was stimulated by genetically inserting either the ATP sensitive channel, P2X2, or the red-light sensitive channelrhodopsin, CsChrimson, into cells expressing tyrosine decarboxylase (TDC), an octopamine synthesis enzyme. To ensure that release is due to octopamine and not the precursor tyramine, the octopamine synthesis inhibitor disulfiram was applied, and the signal decreased by 80%. Stimulated release was vesicular, and a 2 s continuous light stimulation of CsChrimson evoked 0.22 ± 0.03 μM of octopamine release in the larval ventral nerve cord. Repeated stimulations were stable with 2 or 5 min interstimulation times. With pulsed stimulations, the release was dependent on the frequency of applied light pulse. An octopamine transporter has not been identified, and blockers of the dopamine transporter and serotonin transporter had no significant effect on the clearance time of octopamine, suggesting that they do not take up octopamine. This study shows that octopamine can be monitored in Drosophila, facilitating future studies of how octopamine release functions in the insect brain.

Enhanced dopamine release by dopamine transport inhibitors described by a restricted diffusion model and fast scan cyclic voltammetry

PubMed Central

Hoffman, Alexander F.; Spivak, Charles E.; Lupica, Carl R.

2016-01-01

Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple, 5 parameter, two compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using non-linear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altered Ca2+/Mg2+ ratio or tetrodotoxin (TTX), reduced the release parameter with no effect on the uptake parameter. The DAT inhibitors methylenedioxypyrovalerone (MDPV), cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa-opioid receptor (KOR) agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data. PMID:27018734

Enhanced Dopamine Release by Dopamine Transport Inhibitors Described by a Restricted Diffusion Model and Fast-Scan Cyclic Voltammetry.

PubMed

Hoffman, Alexander F; Spivak, Charles E; Lupica, Carl R

2016-06-15

Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple five-parameter, two-compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using nonlinear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altering the Ca(2+)/Mg(2+) ratio or adding tetrodotoxin reduced the release parameter with no effect on the uptake parameter. DAT inhibitors methylenedioxypyrovalerone, cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa opioid receptor agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data.

Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

PubMed Central

Tan, Yih Horng; Davis, Jason A.; Fujikawa, Kohki; Ganesh, N. Vijaya; Demchenko, Alexei V.

2012-01-01

Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N2 gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C18-SH (coverage of 2.94 × 1014 molecules cm−2 based from the decomposition of the C18-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the ‘C’ parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology. PMID:22822294

Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry

PubMed Central

Walsh, Paul L.; Petrovic, Jelena

2011-01-01

Electrical stimulation is an indispensible tool in studying electrically excitable tissues in neurobiology and neuroendocrinology. In this work, the consequences of high-intensity electrical stimulation on the release of catecholamines from adrenal gland slices were examined with fast-scan cyclic voltammetry at carbon fiber microelectrodes. A biphasic signal, consisting of a fast and slow phase, was observed when electrical stimulations typically used in tissue slices (10 Hz, 350 μA biphasic, 2.0 ms/phase pulse width) were applied to bipolar tungsten-stimulating electrodes. This signal was found to be stimulation dependent, and the slow phase of the signal was abolished when smaller (≤250 μA) and shorter (1 ms/phase) stimulations were used. The slow phase of the biphasic signal was found to be tetrodotoxin and hexamethonium independent, while the fast phase was greatly reduced using these pharmacological agents. Two different types of calcium responses were observed, where the fast phase was abolished by perfusion with a low-calcium buffer while both the fast and slow phases could be modulated when Ca2+ was completely excluded from the solution using EGTA. Perfusion with nifedipine resulted in the reduction of the slow catecholamine release to 29% of the original signal, while the fast phase was only decreased to 74% of predrug values. From these results, it was determined that high-intensity stimulations of the adrenal medulla result in depolarizing not only the splanchnic nerves, but also the chromaffin cells themselves resulting in a biphasic catecholamine release. PMID:21048165

Detection of Norepinephrine in Whole Blood via Fast Scan Cyclic Voltammetry

PubMed Central

Nicolai, Evan N.; Trevathan, James K.; Ross, Erika K.; Lujan, J. Luis; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.; Ludwig, Kip A.

2017-01-01

Bioelectronic Medicines is an emerging field that capitalizes on minimally-invasive technology to stimulate the autonomic nervous system in order to evoke therapeutic biomolecular changes at the end-organ. The goal of Bioelectronic Medicines is to realize both ‘precision and personalized’ medicine. ‘Precise’ stimulation of neural circuitry creates biomolecular changes targeted exactly where needed to maximize therapeutic effects while minimizing off-target changes associated with side-effects. The therapy is then ‘personalized’ by utilizing implanted sensors to measure the biomolecular concentrations at, or near, the end-organ of interest and continually adjusting therapy to account for patient-specific biological changes throughout the day. To realize the promise of Bioelectronic Medicines, there is a need for minimally invasive, real-time measurement of biomarkers associated with the effects of autonomic nerve stimulation to be used for continuous titration of therapy. In this study we examine the feasibility of using fast scan cyclic voltammetry (FSCV) to measure norepinephrine levels, a neurochemical relevant to end-organ function, directly from blood. FSCV is a well-understood method for measuring electroactive neurochemicals in the central nervous system with high temporal and high spatial resolution that has yet to be adapted to the study of the autonomic nervous system. The results demonstrate that while detecting the electroactive neurochemical norepinephrine in blood is more challenging than obtaining the same FSCV measurements in a buffer solution due to biofouling of the electrode, it is feasible to utilize a minimally invasive FSCV electrode to obtain neurochemical measurements in blood. PMID:29177248

Expanding neurochemical investigations with multi-modal recording: simultaneous fast-scan cyclic voltammetry, iontophoresis, and patch clamp measurements.

PubMed

Kirkpatrick, D C; McKinney, C J; Manis, P B; Wightman, R M

2016-08-02

Multi-modal recording describes the simultaneous collection of information across distinct domains. Compared to isolated measurements, such studies can more easily determine relationships between varieties of phenomena. This is useful for neurochemical investigations which examine cellular activity in response to changes in the local chemical environment. In this study, we demonstrate a method to perform simultaneous patch clamp measurements with fast-scan cyclic voltammetry (FSCV) using optically isolated instrumentation. A model circuit simulating concurrent measurements was used to predict the electrical interference between instruments. No significant impact was anticipated between methods, and predictions were largely confirmed experimentally. One exception was due to capacitive coupling of the FSCV potential waveform into the patch clamp amplifier. However, capacitive transients measured in whole-cell current clamp recordings were well below the level of biological signals, which allowed the activity of cells to be easily determined. Next, the activity of medium spiny neurons (MSNs) was examined in the presence of an FSCV electrode to determine how the exogenous potential impacted nearby cells. The activities of both resting and active MSNs were unaffected by the FSCV waveform. Additionally, application of an iontophoretic current, used to locally deliver drugs and other neurochemicals, did not affect neighboring cells. Finally, MSN activity was monitored during iontophoretic delivery of glutamate, an excitatory neurotransmitter. Membrane depolarization and cell firing were observed concurrently with chemical changes around the cell resulting from delivery. In all, we show how combined electrophysiological and electrochemical measurements can relate information between domains and increase the power of neurochemical investigations.

A baseline drift detrending technique for fast scan cyclic voltammetry.

PubMed

DeWaele, Mark; Oh, Yoonbae; Park, Cheonho; Kang, Yu Min; Shin, Hojin; Blaha, Charles D; Bennet, Kevin E; Kim, In Young; Lee, Kendall H; Jang, Dong Pyo

2017-11-06

Fast scan cyclic voltammetry (FSCV) has been commonly used to measure extracellular neurotransmitter concentrations in the brain. Due to the unstable nature of the background currents inherent in FSCV measurements, analysis of FSCV data is limited to very short amounts of time using traditional background subtraction. In this paper, we propose the use of a zero-phase high pass filter (HPF) as the means to remove the background drift. Instead of the traditional method of low pass filtering across voltammograms to increase the signal to noise ratio, a HPF with a low cutoff frequency was applied to the temporal dataset at each voltage point to remove the background drift. As a result, the HPF utilizing cutoff frequencies between 0.001 Hz and 0.01 Hz could be effectively used to a set of FSCV data for removing the drifting patterns while preserving the temporal kinetics of the phasic dopamine response recorded in vivo. In addition, compared to a drift removal method using principal component analysis, this was found to be significantly more effective in reducing the drift (unpaired t-test p < 0.0001, t = 10.88) when applied to data collected from Tris buffer over 24 hours although a drift removal method using principal component analysis also showed the effective background drift reduction. The HPF was also applied to 5 hours of FSCV in vivo data. Electrically evoked dopamine peaks, observed in the nucleus accumbens, were clearly visible even without background subtraction. This technique provides a new, simple, and yet robust, approach to analyse FSCV data with an unstable background.

Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing

NASA Technical Reports Server (NTRS)

Chung, Deborah D. L.; Shui, Xiaoping; Frysz, Christine A.

1993-01-01

Hairy carbon is a new material developed by growing submicron carbon filaments on conventional carbon substrates. Typical substrate materials include carbon black, graphite powder, carbon fibers, and glassy carbon. A catalyst is used to initiate hair growth with carbonaceous gases serving as the carbon source. To study the electrochemical behavior of hairy carbons, cyclic voltammetry (CV) and discharge testing were conducted. In both cases, hairy carbon results surpassed those of the substrate material alone.

Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study.

PubMed

Sarkar, Tanmay; Kumar, Parveen; Bharadwaj, Mridula Dixit; Waghmare, Umesh

2016-04-14

A double layer δ-NH4V4O10, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids. While it possesses better stability, and higher ionic and electronic conductivity than the most widely explored V2O5, the mechanisms of its cyclability are yet to be understood. Here, we present a theoretical cyclic voltammetry as a tool based on first-principles calculations, and uncover structural transformations that occur during Li(+)/Na(+) insertion (x) into (Lix/Nax)NH4V4O10. Structural distortions associated with single-phase and multi-phase structural changes during the insertion of Li(+)/Na(+), identified through the analysis of voltage profile and theoretical cyclic voltammetry are in agreement with the reported experimental electrochemical measurements on δ-NH4V4O10. We obtain an insight into its electronic structure with a lower band gap that is responsible for the high rate capability of (Lix/Nax) δ-NH4V4O10. The scheme of theoretical cyclic voltammetry presented here will be useful for addressing issues of cyclability and energy rate in other electrode materials.

Catalytic mechanism in cyclic voltammetry at disc electrodes: an analytical solution.

PubMed

Molina, Angela; González, Joaquín; Laborda, Eduardo; Wang, Yijun; Compton, Richard G

2011-08-28

The theory of cyclic voltammetry at disc electrodes and microelectrodes is developed for a system where the electroactive reactant is regenerated in solution using a catalyst. This catalytic process is of wide importance, not least in chemical sensing, and it can be characterized by the resulting peak current which is always larger than that of a simple electrochemical reaction; in contrast the reverse peak is always relatively diminished in size. From the theoretical point of view, the problem involves a complex physical situation with two-dimensional mass transport and non-uniform surface gradients. Because of this complexity, hitherto the treatment of this problem has been tackled mainly by means of numerical methods and so no analytical expression was available for the transient response of the catalytic mechanism in cyclic voltammetry when disc electrodes, the most popular practical geometry, are used. In this work, this gap is filled by presenting an analytical solution for the application of any sequence of potential pulses and, in particular, for cyclic voltammetry. The induction principle is applied to demonstrate mathematically that the superposition principle applies whatever the geometry of the electrode, which enabled us to obtain an analytical equation valid whatever the electrode size and the kinetics of the catalytic reaction. The theoretical results obtained are applied to the experimental study of the electrocatalytic Fenton reaction, determining the rate constant of the reduction of hydrogen peroxide by iron(II).

A combined electrocoagulation-electrooxidation treatment for industrial wastewater.

PubMed

Linares-Hernández, Ivonne; Barrera-Díaz, Carlos; Bilyeu, Bryan; Juárez-GarcíaRojas, Pablo; Campos-Medina, Eduardo

2010-03-15

This study addresses the elimination of persistent organic compounds in industrial wastewater using a synergistic combination of electrocoagulation and electrooxidation. Electrocoagulation is a relatively quick process (30 min), which is very effective in removing colloidal and suspended particles, as seen in changes in coliforms, turbidity, and color and in the general absorbance by UV-vis spectroscopy. However, it is relatively ineffective in eliminating stable persistent organic compounds--in this work, only half of the COD was eliminated from wastewater and an oxidation peak in the cyclic voltammetry scan remained. Electrooxidation is very effective in breaking down organic compounds through oxidation as reflected in the elimination of COD, BOD(5), and oxidative peak in cyclic voltammetry, but requires so much time (21 h) that it has very limited practicality, especially when colloidal and suspended particles are present. Electrooxidative mineralization of electrocoagulated wastewater, in which most of the colloids and charged species have been removed, takes less than 2h. In the coupled technique, electrocoagulation quickly coagulates and removes the colloidal and suspended particles, as well as many charged species, then electrooxidation oxidizes the remaining organics. The coupled process eliminates COD, BOD(5), color, turbidity, and coliforms in a practical amount of time (2h). (c) 2009 Elsevier B.V. All rights reserved.

A novel electrochemical sensor based on metal-organic framework for electro-catalytic oxidation of L-cysteine.

PubMed

Hosseini, Hadi; Ahmar, Hamid; Dehghani, Ali; Bagheri, Akbar; Tadjarodi, Azadeh; Fakhari, Ali Reza

2013-04-15

A novel electrochemical sensor based on Au-SH-SiO₂ nanoparticles supported on metal-organic framework (Au-SH-SiO₂@Cu-MOF) has been developed for electrocatalytic oxidation and determination of L-cysteine. The Au-SH-SiO₂@Cu-MOF was characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and cyclic voltammetry. The electrochemical behavior of L-cysteine at the Au-SH-SiO₂@Cu-MOF was investigated by cyclic voltammetry. The Au-SH-SiO₂@Cu-MOF showed a very efficient electrocatalytic activity for the oxidation of L-cysteine in 0.1 M phosphate buffer solution (pH 5.0). The oxidation overpotentials of L-cysteine decreased significantly and their oxidation peak currents increased dramatically at Au-SH-SiO₂@Cu-MOF. The potential utility of the sensor was demonstrated by applying it to the analytical determination of L-cysteine concentration. The results showed that the electrocatalytic current increased linearly with the L-cysteine concentration in the range of 0.02-300 μM and the detection limit was 0.008 μM. Finally, the sensor was applied to determine L-cysteine in water and biological samples. Copyright © 2012 Elsevier B.V. All rights reserved.

A novel route for electrosynthesis of CuCr(2)O(4) nanocomposite with p-type conductive polymer as a high performance material for electrochemical supercapacitors.

PubMed

Shayeh, Javad Shabani; Sadeghinia, Mohammad; Siadat, Seyed Omid Ranaei; Ehsani, Ali; Rezaei, Mehran; Omidi, Meisam

2017-06-15

In this work, supercapacitive performance of polypyrrole copper chromate nano particles (Ppy/CuCr 2 O 4 NPs) was studied. CuCr 2 O 4 NPs with the average size of 20nm were synthesized simply by hydrothermal method and the composite electrodes were then electropolymerized on the surface of glassy carbon electrode. Common surface analysis techniques such as scanning electron microscopy (SEM), transmission electron microscopy(TEM) and Fourier transform infrared (FTIR) were used to study the morphology and structure of the composite. Furthermore, for electrochemical evaluation of composite electrodes, techniques including cyclic voltammetry (CV), galvanostatic charge discharge (CD) and impedance spectroscopy (EIS) were used. Using cyclic voltammetry, the specific capacitance values of Ppy and Ppy/CuCr 2 O 4 NPs were calculated to be 109 and 508 F g -1 , respectively. Results show that using CuCr 2 O 4 NPs in the structure of polymeric films led to increased specific capacitance of composite electrodes more than four times that of poly pyrrole. Increasing the conductivity and stability of composite electrodes through continuous cycles are the other advantages of using CuCr 2 O 4 NPs as active materials in a polymeric structure. Copyright © 2017 Elsevier Inc. All rights reserved.

Enhancement of Electrode Stability Using Platinum-Cobalt Nanocrystals on a Novel Composite SiCTiC Support.

PubMed

Millán, María; Zamora, Héctor; Rodrigo, Manuel A; Lobato, Justo

2017-02-22

PtCo alloy catalysts for high temperature PEMFCs (protonic exchange membrane fuel cells) were synthesized on a novel noncarbonaceous support (SiCTiC) using the impregnation method with NaBH 4 as the reducing agent at different synthesis temperatures to evaluate the effect of this variable on their physicochemical and electrochemical properties. The catalysts were characterized by inductively coupled plasma optical emission spectrometry, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscope-energy dispersive X-ray,and temperature-programmed reduction. In addition, the electrochemical characterization (i.e., cyclic voltammetry, oxygen reduction reaction, and chronoamperometry) was carried out with a rotating disk electrode. For the cyclic voltammetry investigation, 400 cycles were performed in hot phosphoric acid and a half-cell to evaluate the stability of the synthesized catalysts. The catalyst synthesized on SiCTiC exhibited excellent durability compared to the catalyst synthesized on a Vulcan support. In addition, all synthesized catalysts exhibited better catalytic activity than that of the PtCo/C catalysts. The best results were observed for the catalyst synthesized at 80 °C due to its shorter Pt-Pt nearest-neighbor and higher alloy degree. Finally, a preliminary stability test was conducted in an HT-PEMFC, and promising results in terms of stability and performance were observed.

Fully printed flexible and disposable wireless cyclic voltammetry tag.

PubMed

Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

2015-01-29

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to -500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health.

Fully printed flexible and disposable wireless cyclic voltammetry tag

PubMed Central

Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

2015-01-01

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to −500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health. PMID:25630250

Fully printed flexible and disposable wireless cyclic voltammetry tag

NASA Astrophysics Data System (ADS)

Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

2015-01-01

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to -500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health.

Detection of the Pseudomonas Quinolone Signal (PQS) by cyclic voltammetry and amperometry using a boron doped diamond electrode.

PubMed

Zhou, Lin; Glennon, Jeremy D; Luong, John H T; Reen, F Jerry; O'Gara, Fergal; McSweeney, Christina; McGlacken, Gerard P

2011-10-07

2-Heptyl-3-hydroxy-4-quinolone, known as the Pseudomonas Quinolone Signal, is a key regulator of bacterial cooperative behaviour known as quorum sensing. A simple electrochemical strategy was employed for its sensitive detection using a bare boron-doped diamond electrode by cyclic voltammetry and amperometry. PQS (and potentially other quinolones) was then detected in cultures of P. aeruginosa pqsL(-) mutant strains. This journal is © The Royal Society of Chemistry 2011

Electrochemical and nonenzymatic glucose biosensor based on MDPA/MWNT/PGE nanocomposite.

PubMed

Surucu, Ozge; Abaci, Serdar

2017-09-01

The nonenzymatic detection of glucose has been widely investigated in a variety of fields ranging from biomedical applications to ecological approaches. Among these fields, electrochemical methods have great advantages such as high electrocatalytic ability, high sensitivity, good selectivity and low-cost for the electrooxidation of glucose. Future trends on glucose sensing are nanostructured electrodes depending upon the development of nanotechnology. In this study, an electrochemical and nonenzymatic glucose sensor based on (E)-4-((5-methylthiazole-2-yl)diazenyl)-N-phenylaniline (MDPA)/multi-walled carbon nanotube (MWNT)/pencil graphite electrode (PGE) was performed. Electrochemical measurements were obtained using cyclic voltammetry and square wave voltammetry techniques, and characterization of surfaces was carried out using scanning electron microscope and electrochemical impedance spectroscopy techniques. The modification of PGE was made using MDPA and MWNT, and 10 cycles coating was used to prepare the proposed electrode. The effects of scan rate and pH on the peak potential and the peak current were determined. The limit of detection and linear range were calculated using various concentrations of glucose. The interference study was made using coexisting substances including metal ions such as Al 3+ , Cu 2+ , Fe 3+ and ascorbic acid. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication and Demonstration of Mercury Disc-Well Probes for Stripping-Based Cyclic Voltammetry Scanning Electrochemical Microscopy.

PubMed

Barton, Zachary J; Rodríguez-López, Joaquín

2017-03-07

Scanning electrochemical microscopy (SECM) is a rising technique for the study of energy storage materials. Hg-based probes allow the extension of SECM investigations to ionic processes, but the risk of irreversible Hg amalgam saturation limits their operation to rapid timescales and dilute analyte solutions. Here, we report a novel fabrication protocol for Hg disc-well ultramicroelectrodes (UMEs), which retain access to stripping information but are less susceptible to amalgam saturation than traditional Hg sphere-caps or thin-films. The amalgamation and stripping behaviors of Hg disc-well UMEs are compared to those of traditional Hg sphere-cap UMEs and corroborated with data from finite element simulations. The improved protection against amalgam saturation allows Hg disc-wells to operate safely in highly concentrated environments at long timescales. The utility of the probes for bulk measurements extends also to SECM studies, where the disc geometry facilitates small tip-substrate gaps and improves both spatial and temporal resolution. Because they can carry out slow, high-resolution anodic stripping voltammetry approaches and imaging in concentrated solutions, Hg disc-well electrodes fill a new analytical niche for studies of ionic reactivity and are a valuable addition to the electrochemical toolbox.

Role of Additives in Minimizing Zinc Electrode Shape Change: The Effect of Lead on the Kinetics of Zn(II) Reduction in Concentrated Alkaline Media.

DTIC Science & Technology

1985-07-01

adherent, and showed excellent physical stability. U -12- 4. RESULTS AND DISCUSSION 4.1 CYCLIC VOLTAMETRY AT A SILVER DISK ELECTRODE Silver screens are...45% KOH containing 5.5% ZnO is shown in Figure 17A. Several sweeps are recorded at scan rates of 10, 20, 50, 100, 200, and 500 mV/s with the highest...voltammetry curves is difficult since the anodic peak depends on the amount of metal deposition in the previous cathodic sweep (16).) The peak currents versus

Two-dimensional nickel hydroxide nanosheets as high performance pseudo-capacitor electrodes

NASA Astrophysics Data System (ADS)

Bhat, Karthik S.; Nagaraja, H. S.

2018-04-01

Electrochemical supercapacitor is a vital technology for the progress of consistent energy harvesting devices. Herein, we report the fabrication of supercapacitor electrodes based on nickel hydroxide nanosheets synthesized via one-pot hydrothermal method. Structure and shape of synthesized materials were analyzed with XRD and SEM measurements. Pseudo-capacitive performances of the fabricated electrodes were evaluated through cyclic voltammetry and galvanostatic charge-discharge measurements with three-electrode configurations. Results indicated the specific capacitance of l80 F g-1 at 5 mV s-1 scan rate and complimented with capacitance retention of 76% for l500 cycles.

Investigation of using wavelet analysis for classifying pattern of cyclic voltammetry signals

NASA Astrophysics Data System (ADS)

Jityen, Arthit; Juagwon, Teerasak; Jaisuthi, Rawat; Osotchan, Tanakorn

2017-09-01

Wavelet analysis is an excellent technique for data processing analysis based on linear vector algebra since it has an ability to perform local analysis and is able to analyze an unspecific localized area of a large signal. In this work, the wavelet analysis of cyclic waveform was investigated in order to find the distinguishable feature from the cyclic data. The analyzed wavelet coefficients were proposed to be used as selected cyclic feature parameters. The cyclic voltammogram (CV) of different electrodes consisting of carbon nanotube (CNT) and several types of metal phthalocyanine (MPc) including CoPc, FePc, ZnPc and MnPc powders was used as several sets of cyclic data for various types of coffee. The mixture powder was embedded in a hollow Teflon rod and used as working electrodes. Electrochemical response of the fabricated electrodes in Robusta, blend coffee I, blend coffee II, chocolate malt and cocoa at the same concentrations was measured with scanning rate of 0.05V/s from -1.5 to 1.5V respectively to Ag/AgCl electrode for five scanning loops. The CV of blended CNT electrode with some MPc electrodes indicated the ionic interaction which can be the effect of catalytic oxidation of saccharides and/or polyphenol on the sensor surface. The major information of CV response can be extracted by using several mother wavelet families viz. daubechies (dB1 to dB3), coiflets (coiflet1), biorthogonal (Bior1.1) and symlets (sym2) and then the discrimination of these wavelet coefficients of each data group can be separated by principal component analysis (PCA). The PCA results indicated the clearly separate groups with total contribution more than 62.37% representing from PC1 and PC2.

Determination of the wine preservative sulphur dioxide with cyclic voltammetry using inkjet printed electrodes.

PubMed

Schneider, Marion; Türke, Alexander; Fischer, Wolf-Joachim; Kilmartin, Paul A

2014-09-15

During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrochemical sensor for ranitidine determination based on carbon paste electrode modified with oxovanadium (IV) salen complex.

PubMed

Raymundo-Pereira, Paulo A; Teixeira, Marcos F S; Fatibello-Filho, Orlando; Dockal, Edward R; Bonifácio, Viviane Gomes; Marcolino, Luiz H

2013-10-01

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicyllideneiminato)oxovanadium (IV) complex ([VO(salen)]) as well as its application for ranitidine determination are described. The electrochemical behavior of the modified electrode for the electroreduction of ranitidine was investigated using cyclic voltammetry, and analytical curves were obtained for ranitidine using linear sweep voltammetry (LSV) under optimized conditions. The best voltammetric response was obtained for an electrode composition of 20% (m/m) [VO(salen)] in the paste, 0.10 mol L(-1) of KCl solution (pH 5.5 adjusted with HCl) as supporting electrolyte and scan rate of 25 mV s(-1). A sensitive linear voltammetric response for ranitidine was obtained in the concentration range from 9.9×10(-5) to 1.0×10(-3) mol L(-1), with a detection limit of 6.6×10(-5) mol L(-1) using linear sweep voltammetry. These results demonstrated the viability of this modified electrode as a sensor for determination, quality control and routine analysis of ranitidine in pharmaceutical formulations. Copyright © 2013. Published by Elsevier B.V.

The use of cyclic voltammetry to study the oxidation of l-5-methyltetrahydrofolate and its preservation by ascorbic acid.

PubMed

Rozoy, Elodie; Simard, Stephan; Liu, Yazheng; Kitts, David; Lessard, Jean; Bazinet, Laurent

2012-06-01

A cyclic voltammetry study of 1mM l-5-methyltetrahydrofolate (l-5-MTHF) was performed in pH 5.5 Britton-Robinson buffer at room temperature to study the stability of l-5-MTHF alone and in combination with ascorbic acid (AA). The degradation of l-5-MTHF and AA over a period of 12h both followed first order reaction kinetics. Using this technique, oxidation peaks of l-5-MTHF were identified at +0.17 and +1.18V, and another oxidation peak appeared after 4h under air at +0.89V. Cyclic voltammetry and HPLC quantification enable us to confirm that l-5-MTHF can be highly preserved by the addition of an equimolar concentration of AA. This treatment was equivalent to a purge of nitrogen used to remove oxygen and thus minimise oxidation of l-5-MTHF when present in aqueous solutions. HPLC confirmed the fact that a full regeneration of oxidised l-5-MTHF occurred with the addition of sodium ascorbate, thus denoting that the redox character of l-5-MTHF can be controlled by the presence of reducing agents. Cyclic voltammetry proved to be a sensitive and accurate method for characterising l-5-MTHF oxidation and potential preservation with ascorbic acid. To our knowledge, this is the first study that has demonstrated the number of oxidation sites on l-5-MTHF. Copyright © 2011 Elsevier Ltd. All rights reserved.

Poly arginine-graphene quantum dots as a biocompatible and non-toxic nanocomposite: Layer-by-layer electrochemical preparation, characterization and non-invasive malondialdehyde sensory application in exhaled breath condensate.

PubMed

Hasanzadeh, Mohammad; Mokhtari, Fozieh; Shadjou, Nasrin; Eftekhari, Aziz; Mokhtarzadeh, Ahad; Jouyban-Gharamaleki, Vahid; Mahboob, Soltanali

2017-06-01

This study reports on the electropolymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots (PARG-GQDs) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for biomedical application. The fabrication of PARG-GQDs on GCE was performed using Layer-by-layer regime. Scanning electron microscopy (SEM) was confirmed dispersion of GQDs on the surface of PARG which lead to increase of surface coverage of PARG. The redox behavior of prepared sensor was then characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA), square wave voltammetry (SWV), linear sweep voltammetry (LSV). The electroactivity of PARG-GQDs coating towards detection and determination of malondialdehyde (MDA) as one of the most common biomarkers of oxidative stress, was then studied. Then, application of prepared sensor for the detection of MDA in exhaled breath condensate (EBC) is described. Electrochemical based sensor shows the lower limit of quantification (LLOQ) were 0.329nanomolar. This work is the first report on the integration of GQDs to poly amino acids. Further development can lead to monitoring of MDA or other exhaled breath biomarkers by GQDs functionalized poly amino acids in EBC using electrochemical methods. Copyright © 2017. Published by Elsevier B.V.

Ni-CeO2 spherical nanostructures for magnetic and electrochemical supercapacitor applications.

PubMed

Murugan, Ramachandran; Ravi, Ganesan; Vijayaprasath, Gandhi; Rajendran, Somasundharam; Thaiyan, Mahalingam; Nallappan, Maheswari; Gopalan, Muralidharan; Hayakawa, Yasuhiro

2017-02-08

The synthesis of nanoparticles has great control over the structural and functional characteristics of materials. In this study, CeO 2 and Ni-CeO 2 spherical nanoparticles were prepared using a microwave-assisted method. The prepared nanoparticles were characterized via thermogravimetry, X-ray diffraction (XRD), Raman, FTIR, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and cyclic voltammetry (CV). The pure CeO 2 sample exhibited a flake-like morphology, whereas Ni-doped CeO 2 showed spherical morphology with uniform shapes. Spherical morphologies for the Ni-doped samples were further confirmed via TEM micrographs. Thermogravimetric analyses revealed that decomposition varies with Ni-doping in CeO 2 . XRD revealed that the peak shifts towards lower angles for the Ni-doped samples. Furthermore, a diamagnetic to ferromagnetic transition was observed in Ni-doped CeO 2 . The ferromagnetic property was attributed to the introduction of oxygen vacancies in the CeO 2 lattice upon doping with Ni, which were confirmed by Raman and XPS. The pseudo-capacitive properties of pure and Ni-doped CeO 2 samples were evaluated via cyclic voltammetry and galvanostatic charge-discharge studies, wherein 1 M KOH was used as the electrolyte. The specific capacitances were 235, 351, 382, 577 and 417 F g -1 corresponding to the pure 1%, 3%, 5% and 7% of Ni doped samples at the current density of 2 A g -1 , respectively. The 5% Ni-doped sample showed an excellent cyclic stability and maintained 94% of its maximum specific capacitance after 1000 cycles.

Lignin-based Biochar/graphene Oxide Composites as Supercapacitor Electrode Materials

NASA Astrophysics Data System (ADS)

Cai, Z.; Jiang, C.; Xiao, X. F.; Zhang, Y. S.; Liang, L.

2018-05-01

The lignin-based biochar/graphene composites were effectively obtained via an easy and rapid co-precipitation method. The chemical structure, microstructure, electrochemical properties of lignin/graphene oxide composites before and after carbonization were investigated by Fourier transformation infrared spectrum (FTIR), Scanning electron microscope (SEM), x-ray diffraction (XRD) and cyclic voltammetry (CV). FTIR results confirmed that the oxygen-containing groups of lignin, GO and their composites were partly removed after 800 °C carbonization and GO had a positive impact on the formation of graphitic structure for lignin. XRD results showed that lignin could completely block the restacking of GO sheets. The electrochemical test presented that lignin/graphene oxide composites exhibited a typical CV curve and the specific capacitance reached ∼103F/g at a scan rate of 20mv/s.

The Nickel(111)/Alkaline Electrolyte Interface

NASA Technical Reports Server (NTRS)

Wang, Kuilong; Chottiner, G. S.; Scherson, D. A.; Reid, Margaret A.

1991-01-01

The electrochemical properties of Ni (111) prepared and characterized in ultra high vacuum, UHV, by surface analytical techniques have been examined in alkaline media by cyclic voltammetry using an UHV-electrochemical cell transfer system designed and built in this laboratory. Prior to the transfer, the Ni(111) surfaces were exposed to saturation coverages of CO in UHV in an attempt to protect the surface from possible contamination with other gases during the transfer. Temperature Programmed Desorption, TPD, of CO-dosed Ni (111) surfaces displaying sharp c(4x2), LEED patterns, subsequently exposed to water-saturated Ar at atmospheric pressure in an auxiliary UHV compatible chamber and finally transferred back to the main UHV chamber, yielded CO2 and water as the only detectable products. This indicates that the CO-dosed surfaces react with water and/or bicarbonate and hydroxide as the most likely products. Based on the integration of the TPD peaks, the combined amounts of H2O and CO2 were found to be on the order of a single monolayer. The reacted c(4x2)CO/Ni(111) layer seems to protect the surface from undergoing spontaneous oxidation in strongly alkaline solutions. This was evidenced by the fact that the open circuit potential observed immediately after contact with deaerated 0.1 M KOH was about 0.38 V vs. DHE, drifting slightly towards more negative values prior to initiating the voltametric scans. The average ratio of the integrated charge obtained in the first positive linear scan in the range of 0.35 to 1.5 V vs. DHE (initiated at the open circuit potential) and the first (and subsequent) linear negative scans in the same solution yielded for various independent runs a value of 3.5 +/- 0.3. Coulometric analysis of the cyclic voltammetry curves indicate that the electrochemically formed oxyhydroxide layer involves a charge equivalent to 3.2 +/- 0.4 layers of Ni metal.

EFFECTS OF POLYCYCLIC AROMATIC HYDROCARBON OF SAM-COATED ELECTRODES USING FERRYICYANIDE AS THE REDOX INDICATOR

EPA Science Inventory

Electrochemical responses on self-assembled monolayer (SAM)-coated polycrystalline gold electrodes were investigated using cyclic voltammetry and square wave voltammetry with a three electrode system. Experimental results show potential in the application of pyrene-imprinted SAM...

Partially Reduced Graphene Oxide Modified Tetrahedral Amorphous Carbon Thin-Film Electrodes as a Platform for Nanomolar Detection of Dopamine

DOE PAGES

Wester, Niklas; Sainio, Sami; Palomäki, Tommi; ...

2017-03-16

Here, we present for the first time tetrahedral amorphous carbon (ta-C)—a partially reduced graphene oxide (PRGO) hybrid electrode nanomaterial platform for electrochemical sensing of dopamine (DA). Graphene oxide was synthesized with the modified Hummer’s method. Before modification of ta-C by drop casting, partial reduction of the GO was carried out to improve electrochemical properties and adhesion to the ta-C thin film. A facile nitric acid treatment that slightly reoxidized the surface and modified the surface chemistry was subsequently performed to further improve the electrochemical properties of the electrodes. The largest relative increase was seen in carboxyl groups. The HNO 3more » treatment increased the sensitivity toward DA and AA and resulted in a cathodic shift in the oxidation of AA. The fabricated hybrid electrodes were characterized with scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and electrochemical impedance spectroscopy (EIS). Moreover, compared to the plain ta-C electrode the hybrid electrode was shown to exhibit superior sensitivity and selectivity toward DA in the presence of ascorbic acid (AA), enabling simultaneous sensing of AA and DA close to the physiological concentrations by cyclic voltammetry (CV) and by differential pulse voltammetry (DPV). Two linear ranges of 0–1 μM and 1–100 μM and a detection limit (S/N = 3.3) of 2.6 nM for DA were determined by means of cyclic voltammetry. Thus, the current work provides a fully CMOS-compatible carbon based hybrid nanomaterial that shows potential for in vivo measurements of DA.« less

Partially Reduced Graphene Oxide Modified Tetrahedral Amorphous Carbon Thin-Film Electrodes as a Platform for Nanomolar Detection of Dopamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wester, Niklas; Sainio, Sami; Palomäki, Tommi

Here, we present for the first time tetrahedral amorphous carbon (ta-C)—a partially reduced graphene oxide (PRGO) hybrid electrode nanomaterial platform for electrochemical sensing of dopamine (DA). Graphene oxide was synthesized with the modified Hummer’s method. Before modification of ta-C by drop casting, partial reduction of the GO was carried out to improve electrochemical properties and adhesion to the ta-C thin film. A facile nitric acid treatment that slightly reoxidized the surface and modified the surface chemistry was subsequently performed to further improve the electrochemical properties of the electrodes. The largest relative increase was seen in carboxyl groups. The HNO 3more » treatment increased the sensitivity toward DA and AA and resulted in a cathodic shift in the oxidation of AA. The fabricated hybrid electrodes were characterized with scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and electrochemical impedance spectroscopy (EIS). Moreover, compared to the plain ta-C electrode the hybrid electrode was shown to exhibit superior sensitivity and selectivity toward DA in the presence of ascorbic acid (AA), enabling simultaneous sensing of AA and DA close to the physiological concentrations by cyclic voltammetry (CV) and by differential pulse voltammetry (DPV). Two linear ranges of 0–1 μM and 1–100 μM and a detection limit (S/N = 3.3) of 2.6 nM for DA were determined by means of cyclic voltammetry. Thus, the current work provides a fully CMOS-compatible carbon based hybrid nanomaterial that shows potential for in vivo measurements of DA.« less

Development of a Molecularly Imprinted Polymer-Based Sensor for the Electrochemical Determination of Triacetone Triperoxide (TATP)

PubMed Central

Mamo, Samuel Kassahun; Gonzalez-Rodriguez, Jose

2014-01-01

The explosive triacetone triperoxide (TATP), which can be prepared from commercially readily available reagents following an easy synthetic procedure, is one of the most common components of improvised explosive devices (IEDs). Molecularly-imprinted polymer (MIP) electrochemical sensors have proved useful for the determination of different compounds in different matrices with the required sensitivity and selectivity. In this work, a highly sensitive and selective molecularly imprinted polymer with electrochemical capabilities for the determination of TATP has been developed. The molecular imprinting has been performed via electropolymerisation onto a glassy carbon electrode surface by cyclic voltammetry from a solution of pyrrole functional monomer, TATP template and LiClO4. Differential Pulse Voltammetry of TATP, with LiClO4 as supporting electrolyte, was performed in a potential range of −2.0 V to +1.0 V (vs. Ag/AgCl). Three-factor two-level factorial design was used to optimise the monomer concentration at 0.1 mol·L−1, template concentration at 100 mmol·L−1 and the number of cyclic voltammetry scan cycles to 10. The molecularly imprinted polymer-modified glassy carbon electrode demonstrated good performance at low concentrations for a linear range of 82–44,300 μg·L−1 and a correlation coefficient of r2 = 0.996. The limits of detection (LoD) and quantification (LoQ) achieved were 26.9 μg·L−1 and 81.6 μg·L−1, respectively. The sensor demonstrated very good repeatability with precision values (n = 6, expressed as %RSD) of 1.098% and 0.55% for 1108 and 2216 μg·L−1, respectively. It also proved selective for TATP in the presence of other explosive substances such as PETN, RDX, HMX, and TNT. PMID:25490589

Graphene nanoplate-MnO2 composites for supercapacitors: a controllable oxidation approach

NASA Astrophysics Data System (ADS)

Huang, Huajie; Wang, Xin

2011-08-01

Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material.Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material. Electronic supplementary information (ESI) available: Fig. S1, AFM image (5 μm × 5 μm) of graphene nanoplate-MnO2 composite obtained at 3 h; Fig. S2, nitrogen adsorption/desorption isotherm of graphene nanoplate-MnO2 composite obtained at 3 h. See DOI: 10.1039/c1nr10229j

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids

PubMed Central

Covey, Dan P.; Bunner, Kendra D.; Schuweiler, Douglas R.; Cheer, Joseph F.; Garris, Paul A.

2018-01-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement. PMID:27038339

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids.

PubMed

Covey, Dan P; Bunner, Kendra D; Schuweiler, Douglas R; Cheer, Joseph F; Garris, Paul A

2016-06-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Monitoring In Vivo Changes in Tonic Extracellular Dopamine Level by Charge-Balancing Multiple Waveform Fast-Scan Cyclic Voltammetry.

PubMed

Oh, Yoonbae; Park, Cheonho; Kim, Do Hyoung; Shin, Hojin; Kang, Yu Min; DeWaele, Mark; Lee, Jeyeon; Min, Hoon-Ki; Blaha, Charles D; Bennet, Kevin E; Kim, In Young; Lee, Kendall H; Jang, Dong Pyo

2016-11-15

Dopamine (DA) modulates central neuronal activity through both phasic (second to second) and tonic (minutes to hours) terminal release. Conventional fast-scan cyclic voltammetry (FSCV), in combination with carbon fiber microelectrodes, has been used to measure phasic DA release in vivo by adopting a background subtraction procedure to remove background capacitive currents. However, measuring tonic changes in DA concentrations using conventional FSCV has been difficult because background capacitive currents are inherently unstable over long recording periods. To measure tonic changes in DA concentrations over several hours, we applied a novel charge-balancing multiple waveform FSCV (CBM-FSCV), combined with a dual background subtraction technique, to minimize temporal variations in background capacitive currents. Using this method, in vitro, charge variations from a reference time point were nearly zero for 48 h, whereas with conventional background subtraction, charge variations progressively increased. CBM-FSCV also demonstrated a high selectivity against 3,4-dihydroxyphenylacetic acid and ascorbic acid, two major chemical interferents in the brain, yielding a sensitivity of 85.40 ± 14.30 nA/μM and limit of detection of 5.8 ± 0.9 nM for DA while maintaining selectivity. Recorded in vivo by CBM-FSCV, pharmacological inhibition of DA reuptake (nomifensine) resulted in a 235 ± 60 nM increase in tonic extracellular DA concentrations, while inhibition of DA synthesis (α-methyl-dl-tyrosine) resulted in a 72.5 ± 4.8 nM decrease in DA concentrations over a 2 h period. This study showed that CBM-FSCV may serve as a unique voltammetric technique to monitor relatively slow changes in tonic extracellular DA concentrations in vivo over a prolonged time period.

In Vivo Comparison of Norepinephrine and Dopamine Release in Rat Brain by Simultaneous Measurements with Fast-Scan Cyclic Voltammetry

PubMed Central

Park, Jinwoo; Takmakov, Pavel; Wightman, R. Mark

2011-01-01

Brain norepinephrine and dopamine regulate a variety of critical behaviors such as stress, learning, memory, and drug addiction. Here, we demonstrate differences in the regulation of in vivo neurotransmission for dopamine in the anterior nucleus accumbens (NAc) and norepinephrine in the ventral bed nucleus of the stria terminalis (vBNST) of the anesthetized rat. Release of the two catecholamines was measured simultaneously using fast-scan cyclic voltammetry (FSCV) at two different carbon-fiber microelectrodes, each implanted in the brain region of interest. Simultaneous dopamine and norepinephrine release was evoked by electrical stimulation of a region where the ventral noradrenergic bundle (VNB), the pathway of noradrenergic neurons, courses through the ventral tegmental area/substantia nigra (VTA/SN), the origin of dopaminergic cell bodies. The release and uptake of norepinephrine in the vBNST were both significantly slower than for dopamine in the NAc. Pharmacological manipulations in the same animal demonstrated that the two catecholamines are differently regulated. The combination of a dopamine autoreceptor antagonist and amphetamine significantly increased basal extracellular dopamine whereas a norepinephrine autoreceptor antagonist and amphetamine did not change basal norepinephrine concentration. α-Methyl-p-tyrosine, a tyrosine hydroxylase inhibitor, decreased electrically evoked dopamine release faster than norepinephrine. The dual-microelectrode FSCV technique along with anatomical and pharmacological evidence confirms that dopamine in the NAc and norepinephrine in the vBNST can be monitored selectively and simultaneously in the same animal. The high temporal and spatial resolution of the technique enabled us to examine differences in the dynamics of extracellular norepinephrine and dopamine concurrently in two different limbic structures. PMID:21933188

Neurobiological model of stimulated dopamine neurotransmission to interpret fast-scan cyclic voltammetry data.

PubMed

Harun, Rashed; Grassi, Christine M; Munoz, Miranda J; Torres, Gonzalo E; Wagner, Amy K

2015-03-02

Fast-scan cyclic voltammetry (FSCV) is an electrochemical method that can assess real-time in vivo dopamine (DA) concentration changes to study the kinetics of DA neurotransmission. Electrical stimulation of dopaminergic (DAergic) pathways can elicit FSCV DA responses that largely reflect a balance of DA release and reuptake. Interpretation of these evoked DA responses requires a framework to discern the contribution of DA release and reuptake. The current, widely implemented interpretive framework for doing so is the Michaelis-Menten (M-M) model, which is grounded on two assumptions- (1) DA release rate is constant during stimulation, and (2) DA reuptake occurs through dopamine transporters (DAT) in a manner consistent with M-M enzyme kinetics. Though the M-M model can simulate evoked DA responses that rise convexly, response types that predominate in the ventral striatum, the M-M model cannot simulate dorsal striatal responses that rise concavely. Based on current neurotransmission principles and experimental FSCV data, we developed a novel, quantitative, neurobiological framework to interpret DA responses that assumes DA release decreases exponentially during stimulation and continues post-stimulation at a diminishing rate. Our model also incorporates dynamic M-M kinetics to describe DA reuptake as a process of decreasing reuptake efficiency. We demonstrate that this quantitative, neurobiological model is an extension of the traditional M-M model that can simulate heterogeneous regional DA responses following manipulation of stimulation duration, frequency, and DA pharmacology. The proposed model can advance our interpretive framework for future in vivo FSCV studies examining regional DA kinetics and their alteration by disease and DA pharmacology. Copyright © 2015 Elsevier B.V. All rights reserved.

A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samin, Adib J.

In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level and may be useful for analyzing qualitative features observed in experimentally recorded signals.

The Influence of Uncompensated Solution Resistance on the Determination and Standard Electrochemical Rate Constants Using Cyclic Voltammetry, and Some Comparisons with AC Voltammetry.

DTIC Science & Technology

1987-09-25

rate constants, k2r using cyclic voltametry . The res tss are expressed in terms of systematic deviations oP sapparent measured" rate constants, k~b(app...concentration was taken to be lum unless otherwise noted. The voltammetric sweep rate was set at 20 V sŕ unless specified otherwise. The general procedure...peaks for the negative- and positive-going potential sweeps have opposite signs, the measured cathodic-anodic peak separation, AEp, will clearly be

Redox protein noncovalent functionalization of double-wall carbon nanotubes: electrochemical binder-less glucose biosensor.

PubMed

Pumera, Martin; Smíd, Bretislav

2007-10-01

Double wall carbon nanotubes are noncovalently functionalized with redox protein and such assembly is used for construction of electrochemical binder-less glucose biosensor. Redox protein glucose oxidase performs as biorecognition element and double wall carbon nanotubes act both as immobilization platform for redox enzyme and as signal transducer. The double carbon nanotubes are characterized by cyclic voltammetry and specific surface area measurements; the redox protein noncovalently functionalized double wall carbon nanotubes are characterized in detail by X-ray photoelectron spectroscopy, cyclic voltammetry, amperometry, and transmission electron microscopy.

A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects

NASA Astrophysics Data System (ADS)

Samin, Adib J.

2016-05-01

In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level and may be useful for analyzing qualitative features observed in experimentally recorded signals.

Feather like highly active Co3O4 electrode for supercapacitor application: a potentiodynamic approach

NASA Astrophysics Data System (ADS)

Niveditha, C. V.; Aswini, R.; Jabeen Fatima, M. J.; Ramanarayan, Rajita; Pullanjiyot, Nijisha; Swaminathan, Sindhu

2018-06-01

This investigation focuses on the in situ preparation of cobalt oxide through a less explored potentiodynamic approach under ambient conditions. A spinel structured feather like p-type cobalt oxide is obtained having dual bandgaps. Gracing Incidence x-ray Diffraction, Raman spectroscopy, UV-Visble spectroscopy, Scanning Electron Microscope and Hall measurement are used to study the structural, optical, morphological and electrical characteristics of the film. The prepared film showed an excellent cyclic stability upto 1600 number of cycles and good charge retention as obtained from cyclic voltammetry and galvanostatic charge-discharge measurements. A high specific capacitance of 396.67 F g‑1, specific energy 71.40 Wh kg‑1 and specific power 10.02 kW kg‑1 is obtained, implying supercapacitive nature of the material. Overall a sustainable energy storage material, prepared by template free potentiodynamic method for new generation devices has been explored in this work.

Biosynthesis of Bacterial Cellulose/Carboxylic Multi-Walled Carbon Nanotubes for Enzymatic Biofuel Cell Application

PubMed Central

Lv, Pengfei; Feng, Quan; Wang, Qingqing; Li, Guohui; Li, Dawei; Wei, Qufu

2016-01-01

Novel nanocomposites comprised of bacterial cellulose (BC) with carboxylic multi-walled carbon nanotubes (c-MWCNTs) incorporated into the BC matrix were prepared through a simple method of biosynthesis. The biocathode and bioanode for the enzyme biological fuel cell (EBFC) were prepared using BC/c-MWCNTs composite injected by laccase (Lac) and glucose oxidase (GOD) with the aid of glutaraldehyde (GA) crosslinking. Biosynthesis of BC/c-MWCNTs composite was characterized by digital photos, scanning electron microscope (SEM), and Fourier Transform Infrared (FTIR). The experimental results indicated the successful incorporation of c-MWCNTs into the BC. The electrochemical and biofuel performance were evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The power density and current density of EBFCs were recorded at 32.98 µW/cm3 and 0.29 mA/cm3, respectively. Additionally, the EBFCs also showed acceptable stability. Preliminary tests on double cells indicated that renewable BC have great potential in the application field of EBFCs. PMID:28773310

Electrocatalytic oxidation and voltammetric determination of ciprofloxacin employing poly(alizarin red)/graphene composite film in the presence of ascorbic acid, uric acid and dopamine.

PubMed

Zhang, Xin; Wei, Youli; Ding, Yaping

2014-07-04

A glassy carbon electrode modified with poly(alizarin red)/electrodeposited graphene (PAR/EGR) composite film was prepared and applied to detect ciprofloxacin (CPFX) in the presence of ascorbic, uric acid and dopamine. The morphology and interface property of PAR/EGR films were examined by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrocatalytic oxidation of CPFX on AR/EGR was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The linearity ranged from 4 × 10(-8) to 1.2 × 10(-4) M with a detection limit (S/N=3) of 0.01 μM. The modified electrode could be applied to the individual determination of CPFX as well as the simultaneous determination of CPFX, ascorbic acid, uric acid and dopamine. This method proved to be a simple, selective and rapid way to determine CPFX in pharmaceutical preparation and biological media. Copyright © 2014. Published by Elsevier B.V.

Bromomethane Contamination in the Cathode of Proton Exchange Membrane Fuel Cells.

PubMed

Zhai, Yunfeng; Baturina, Olga; Ramaker, David E; Farquhar, Erik; St-Pierre, Jean; Swider-Lyons, Karen E

2016-09-20

The effects of bromomethane (BrCH 3 ), an airborne contaminant, on the performance of a single PEMFC are compared with that of another halocarbon, chlorobenzene. Under a constant current of 1 A cm -2 and at 45 °C, 20 ppm bromomethane causes approximately 30% cell voltage loss in approximately 30 h, as opposed to much more rapid performance degradation observed with chlorobenzene. Electrochemical impedance spectroscopy, cyclic voltammetry, linear scanning voltammetry, and polarization measurements are applied to characterize the temporary electrochemical reaction effect and permanent performance effects. X-ray absorption spectroscopy is used to confirm that Br is adsorbed on the Pt electrocatalyst surface. We conclude that airborne bromomethane poisons a PEMFC in a different way from chlorobenzene because it is largely hydrolyzed to bromide, Br - , which is then excluded from the Pt catalyst by the negatively charged Nafion ionomer. The little Br - and bromomethane that adsorbs on the Pt surface can be partially removed by cycling but causes some irreversible surface area loss.

Bromomethane Contamination in the Cathode of Proton Exchange Membrane Fuel Cells

PubMed Central

Baturina, Olga; Ramaker, David E.; Farquhar, Erik; St-Pierre, Jean; Swider-Lyons, Karen E.

2016-01-01

The effects of bromomethane (BrCH3), an airborne contaminant, on the performance of a single PEMFC are compared with that of another halocarbon, chlorobenzene. Under a constant current of 1 A cm−2 and at 45 °C, 20 ppm bromomethane causes approximately 30% cell voltage loss in approximately 30 h, as opposed to much more rapid performance degradation observed with chlorobenzene. Electrochemical impedance spectroscopy, cyclic voltammetry, linear scanning voltammetry, and polarization measurements are applied to characterize the temporary electrochemical reaction effect and permanent performance effects. X-ray absorption spectroscopy is used to confirm that Br is adsorbed on the Pt electrocatalyst surface. We conclude that airborne bromomethane poisons a PEMFC in a different way from chlorobenzene because it is largely hydrolyzed to bromide, Br−, which is then excluded from the Pt catalyst by the negatively charged Nafion ionomer. The little Br− and bromomethane that adsorbs on the Pt surface can be partially removed by cycling but causes some irreversible surface area loss. PMID:27695133

Electrochemistry of raloxifene on glassy carbon electrode and its determination in pharmaceutical formulations and human plasma.

PubMed

Bagheri, Akbar; Hosseini, Hadi

2012-12-01

The electrochemical behavior of raloxifene (RLX) on the surface of a glassy carbon electrode (GCE) has been studied by cyclic voltammetry (CV). The CV studies were performed in various supporting electrolytes, wide range of potential scan rates, and pHs. The results showed an adsorption-controlled and quasi-reversible process for the electrochemical reaction of RLX, and a probable redox mechanism was suggested. Under the optimum conditions, differential pulse voltammetry (DPV) was applied for quantitative determination of the RLX in pharmaceutical formulations. The DPV measurements showed that the anodic peak current of the RLX was linear to its concentration in the range of 0.2-50.0μM with a detection limit of 0.0750μM, relative standard deviation (RSD %) below 3.0%, and a good sensitivity. The proposed method was successfully applied for determination of the RLX in pharmaceutical and human plasma samples with a good selectivity and suitable recovery. Copyright © 2012 Elsevier B.V. All rights reserved.

Polyaniline/carbon nanotubes platform for sexually transmitted disease detection.

PubMed

Singh, Renu; Dhand, Chetna; Sumana, Gajjala; Verma, Rachna; Sood, Seema; Gupta, Rajinder Kumar; Malhotra, Bansi Dhar

2010-01-01

Polyaniline/carbon nanotubes composite (PANI-CNT) electrochemically deposited onto indium-tin-oxide (ITO) coated glass plate has been utilized for Neisseria gonorrhoeae detection by immobilizing 5'-amino-labeled Neisseria gonorrhoeae probe (aDNA) using glutaraldehyde as a cross-linker. PANI-CNT/ITO and aDNA-Glu-PANI-CNT/ITO electrodes have been characterized using scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). This bioelectrode can be used to detect N. gonorrhoeae using methylene blue (MB) as redox indicator with response time of 60 s and stability of about 75 days when stored under refrigerated conditions. DPV studies reveal that this bioelectrode can detect complementary DNA concentration from 1 x 10(-6) M to 1 x 10(-17) M with detection limit of 1.2 x 10(-17) M. Further, this bioelectrode (aDNA-Glu-PANI-CNT/ITO) exhibits specificity toward N. gonorrhoeae species and shows negative response with non-Neisseria gonorrhoeae Neisseria species (NgNS) and other gram negative bacteria (GNB).

Facile synthesis of fluoro, methoxy, and methyl substituted ferrocene-based urea complexes as potential therapeutic agents.

PubMed

Asghar, Faiza; Badshah, Amin; Lal, Bhajan; Zubair, Shumaila; Fatima, Saira; Butler, Ian S

2017-06-01

In the present work, the synthesis, characterization (FT-IR, multinuclear ( 1 H and 13 C) NMR, AAS, Raman, and elemental analysis), DNA binding (cyclic voltammetry, UV-Vis spectroscopy and viscometry), and in vitro biological assessment of nine new ferrocene-based ureas are reported. The desulphurization of ferrocenyl thioureas to the corresponding oxo analogues using aqueous sodium hydroxide and mercuric chloride led to the ferrocenyl ureas (F1-F9) in high yields. The DNA binding studies performed by cyclic voltammetry and UV-Vis spectroscopy produced results that are in close agreement with one another for the binding constants (K) and an electrostatic mode of interaction was observed. The nature and the extent of interaction with DNA was further investigated by viscometry. The DFT/B3LYP method was used to determine the charge distribution and HOMO/LUMO energies of the optimized structure. The DFT calculated HOMO and LUMO energies correlate well with the experimentally determined redox potential values. The synthesized ferrocenyl derivatives exhibited good scavenging activity against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). These complexes were also scanned for their in vitro cytotoxicity against human carcinoma cell line THP-1 (leukemia cells). The results showed a moderate level of cytotoxicity against the subjected cancer cell line as compared with the standard chemotherapeutic drug (cisplatin). Copyright © 2017 Elsevier Inc. All rights reserved.

Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

PubMed Central

2016-01-01

17α-Ethinyl estradiol (EE2), which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs) in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV) with a hanging mercury drop electrode (HMDE) in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at −1.16 ± 0.02 V versus Ag/AgCl. The experimental parameters were as follows: −0.7 V accumulation potential, 150 s accumulation time, and 60 mV s−1 scan rate. The limit of detection was 0.49 μg L−1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%. PMID:27738548

Electrochemical and spectroscopic studies of the interaction of proflavine with DNA.

PubMed

Aslanoglu, Mehmet

2006-03-01

The interaction of proflavine with herring sperm DNA has been investigated by cyclic voltammetry and UV-Vis spectroscopy as well as viscosity measurements. Shifts in the peak potentials in cyclic voltammetry, spectral changes in UV absorption titration, an increase in viscosity of DNA and the results of the effect of ionic strength on the binding constant strongly support the intercalation of proflavine into the DNA double helix. The binding constant for the interaction between proflavine and DNA was K = 2.32 (+/- 0.41) x 10(4) M(-1) and the binding site size was 2.07 (+/- 0.1) base pairs, estimated in voltammetric measurements. The value of the binding site size was determined to be closer to that expected for a planar intercalating agent. The standard Gibbs free-energy change is ca. -24.90 kJ/mol at 25 degrees C, indicating the spontaneity of the binding interaction. The binding constant determined by UV absorption measurements was K = 2.20 (+/- 0.48) x 10(4) M(-1), which is very close to the value determined by cyclic voltammetry assuming that the binding equilibrium is static.

Hydrogen-bonding effect on spin-center transfer of tetrathiafulvalene-linked 6-oxophenalenoxyl evaluated using temperature-dependent cyclic voltammetry and theoretical calculations.

PubMed

Nishida, Shinsuke; Fukui, Kozo; Morita, Yasushi

2014-02-01

The stable tetrathiafulvalene (TTF)-linked 6-oxophenalenoxyl neutral radical exhibits a spin-center transfer with a continuous color change in solution caused by an intramolecular electron transfer, which is dependent on solvent and temperature. Cyclic voltammetry measurements showed that addition of 2,2,2-trifluoroethanol (TFE) to a benzonitrile solution of the neutral radical induces a redox potential shift that is favorable for the spin-center transfer. Temperature-dependent cyclic voltammetry of the neutral radical using a novel low-temperature electrochemical cell demonstrated that the redox potentials change with decreasing temperature in a 199:1 CH2Cl2/TFE mixed solvent. Furthermore, theoretical calculation revealed that the energy levels of the frontier molecular orbitals involved in the spin-center transfer are lowered by the hydrogen-bonding interaction of TFE with the neutral radical. These results indicate that the hydrogen-bonding effect is a key factor for the occurrence of the spin-center transfer of TTF-linked 6-oxophenalenoxyl. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combined characterization of bovine polyhemoglobin microcapsules by UV-Vis absorption spectroscopy and cyclic voltammetry.

PubMed

Knirsch, Marcos Camargo; Dell'Anno, Filippo; Salerno, Marco; Larosa, Claudio; Polakiewicz, Bronislaw; Eggenhöffner, Roberto; Converti, Attilio

2017-03-01

Polyhemoglobin produced from pure bovine hemoglobin by reaction with PEG bis(N-succynimidil succinate) as a cross-linking agent was encapsulated in gelatin and dehydrated by freeze-drying. Free carboxyhemoglobin and polyhemoglobin microcapsules were characterized by UV-Vis spectroscopy in the absorption range 450-650 nm and cyclic voltammetry in the voltage range from -0.8 to 0.6 mV to evaluate the ability to break the bond with carbon monoxide and to study the carrier's affinity for oxygen, respectively. SEM used to observe the shape of cross-linked gelatin-polyhemoglobin microparticles showed a regular distribution of globular shapes, with mean size of ~750 nm, which was ascribed to gelatin. Atomic absorption spectroscopy was also performed to detect iron presence in microparticles. Cyclic voltammetry using an Ag-AgCl electrode highlighted characteristic peaks at around -0.6 mV that were attributed to reversible oxygen bonding with iron in oxy-polyhemoglobin structure. These results suggest this technique as a powerful, direct and alternative method to evaluate the extent of hemoglobin oxygenation.

Influence of the different carbon nanotubes on the development of electrochemical sensors for bisphenol A.

PubMed

Goulart, Lorena Athie; de Moraes, Fernando Cruz; Mascaro, Lucia Helena

2016-01-01

Different methods of functionalisation and the influence of the multi-walled carbon nanotube sizes were investigated on the bisphenol A electrochemical determination. Samples with diameters of 20 to 170 nmwere functionalized in HNO3 5.0 mol L(-1) and a concentrated sulphonitric solution. The morphological characterisations before and after acid treatment were carried out by scanning electron microscopy and cyclic voltammetry. The size and acid treatment affected the oxidation of bisphenol A. The multi-walled carbon nanotubes with a 20-40 nm diameter improved the method sensitivity and achieved a detection limit for determination of bisphenol A at 84.0 nmol L(-1).

Sol gel method for synthesis of semiconducting ferrite and the study of FTIR, DTA, SEM and CV

NASA Astrophysics Data System (ADS)

Alva, Sagir; Hua, Tang Ing; Kalmar Nizar, Umar; Wahyudi, Haris; Sundari, Rita

2018-03-01

In this study, a sol gel method using citric acid as anionic surfactant is used for synthesis of magnesium ferrite. Calcinations of magnesium ferrite at temperature (300°C, 600°C and 800°C) have been conducted after sol gel process. Characterization study of the prepared magnesium ferrite related to calcinations using Fourier transform infrared spectrometry (FTIR), Differential thermogravic analysis (DTA), and Scanning electron microscope (SEM) has been discussed. The study of Cyclic voltammetry (CV) of the prepared magnesium ferrite has been examined to assay the semiconducting behavior of magnesium ferrite in relation to its electrochemical behavior.

Enhanced optical and electrochemical properties of polyaniline/cobalt oxide nano composite

NASA Astrophysics Data System (ADS)

Niranjana, M.; Yesappa, L.; Ashokkumar, S. P.; Vijeth, H.; Basappa, M.; Devendrappa, H.

2018-05-01

Polyaniline and its composites at different wt. % of Cobalt oxide nano (PDC1, PDC2 and PDC5) were prepared by in-situ chemical reaction method The optical property was carried out using UV-Vis. Absorption Spectroscopy. The electrochemical property like cyclic voltammetry and galvonostatic charging-discharging was carried out for PANI and PDC nanocomposite electrode materials. A specific capacitance of 212.08 F/g and 336.41 F/g with scan rates 100 and 200 mV/s at 0.4 A/g current density respectively. These results are suggesting PDC composite is a prominent candidate for supercapacitor properties applications.

Redox properties of samarium, europium and ytterbium in molten eutectic mixture of sodium, potassium and cesium chlorides

NASA Astrophysics Data System (ADS)

Golovanova, O. A.; Tropin, O. A.; Volkovich, V. A.

2017-09-01

The redox behavior of samarium, europium and ytterbium ions was investigated in the ternary 6NaCl-9KCl- 5CsCl eutectic based melts between 823 and 1073 K employing cyclic voltammetry on a tungsten working electrode. Ln(II)/Ln(III) (Ln=Sm, Eu, Yb) reduction-oxidation is reversible and controlled by diffusion of the electroactive species at the potential scan rates up to 0.1 V/s. Formal standard redox potentials E*Ln(II)/Ln(III) were determined, and the thermodynamic and transport properties of the corresponding Ln(III) and Ln(II) ions were estimated.

Electrodeposition of polymer electrolyte in nanostructured electrodes for enhanced electrochemical performance of thin-film Li-ion microbatteries

NASA Astrophysics Data System (ADS)

Salian, Girish D.; Lebouin, Chrystelle; Demoulin, A.; Lepihin, M. S.; Maria, S.; Galeyeva, A. K.; Kurbatov, A. P.; Djenizian, Thierry

2017-02-01

We report that electrodeposition of polymer electrolyte in nanostructured electrodes has a strong influence on the electrochemical properties of thin-film Li-ion microbatteries. Electropolymerization of PMMA-PEG (polymethyl methacrylate-polyethylene glycol) was carried out on both the anode (self-supported titania nanotubes) and the cathode (porous LiNi0.5Mn1.5O4) by cyclic voltammetry and the resulting electrode-electrolyte interface was examined by scanning electron microscopy. The electrochemical characterizations performed by galvanostatic experiments reveal that the capacity values obtained at different C-rates are doubled when the electrodes are completely filled by the polymer electrolyte.

Development and Use of an Open-Source, User-Friendly Package to Simulate Voltammetry Experiments

ERIC Educational Resources Information Center

Wang, Shuo; Wang, Jing; Gao, Yanjing

2017-01-01

An open-source electrochemistry simulation package has been developed that simulates the electrode processes of four reaction mechanisms and two typical electroanalysis techniques: cyclic voltammetry and chronoamperometry. Unlike other open-source simulation software, this package balances the features with ease of learning and implementation and…

Fabrication and characterization of electrochemically prepared bioanode (polyaniline/ferritin/glucose oxidase) for biofuel cell application

NASA Astrophysics Data System (ADS)

ul Haque, Sufia; Inamuddin; Nasar, Abu; Asiri, Abdullah M.

2018-01-01

Porous matrix of polyaniline (PANI) has been electrodeposited along with the entrapment of biocompatible redox mediator ferritin (Frt) and glucose oxidase (GOx) on the surface of glassy carbon (GC) electrode. The characterizations have been carried out by X-ray Diffraction (XRD) and Transmission electron microscopy (TEM). The enhanced electrochemical signal transfer rate from enzyme to the electrode surface was due to the intimate contact of the enzyme with the electrochemically polymerized conducting PANI matrix. The PANI/Frt/GOx modified GC bioanode was used to investigate the electrocatalytic activity as a function of the concentration of glucose in the range of 10-60 mM. It was confirmed by the electrochemical impedance spectroscopy (EIS), the thick deposition of PANI layer becomes more compact due to which the charge transfer resistance of PANI matrix becomes higher. All the electrochemical measurements of the electrode were carried out by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). CV curves were recorded at different scan rates (20-100 mV/s) at 50 mM of glucose in 0.3 M potassium ferrocyanide. A normalized saturation current density of 22.3 ± 2 mA/cm2 was observed for the oxidation of 50 mM glucose at a scan rate of 100 mV/s.

Preparation of porous palladium nanowire arrays and their catalytic performance for hydrogen peroxide electroreduction in acid medium

NASA Astrophysics Data System (ADS)

Wang, Xin; Ye, Ke; Gao, Yinyi; Zhang, Hongyu; Cheng, Kui; Xiao, Xue; Wang, Guiling; Cao, Dianxue

2016-01-01

Nanoporous palladium supported on the carbon coated titanium carbide (C@TiC) nanowire arrays (Pd NP/C@TiC) are successfully prepared by a facile chemical vapor deposition of three-dimensional (3D) C@TiC substrate, followed by electrochemical codeposition of Pd-Ni and removal of Ni via dealloying. The structure and morphology of the obtained Pd NP/C@TiC electrodes are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) are used to examine the catalytic performances of the electrodes for H2O2 electroreduction in H2SO4 solution. The Pd NP/C@TiC electrode exhibits a largely effective specific surface area owing to its open nanoporous structure allowing the full utilization of Pd surface active sites. At the potential of 0.2 V in 2.0 mol L-1 H2O2 and 2 mol L-1 H2SO4 solutions, the reduction current density reaches 3.47 A mg-1, which is significantly higher than the catalytic activity of H2O2 electroreduction achieved previously with precious metals as catalysts.

A functional graphene oxide-ionic liquid composites-gold nanoparticle sensing platform for ultrasensitive electrochemical detection of Hg2+.

PubMed

Zhou, Na; Li, Jinhua; Chen, Hao; Liao, Chunyang; Chen, Lingxin

2013-02-21

A simple and sensitive electrochemical assay strategy of stripping voltammetry for mercury ions (Hg(2+)) detection is described based on the synergistic effect between ionic liquid functionalized graphene oxide (GO-IL) and gold nanoparticles (AuNPs). The AuNPs-GO-IL modified onto glassy carbon electrode (GCE) resulted in highly enhanced electron conductive nanostructured membrane and large electroactive surface area, which was excellently examined by scanning electron microscopy and cyclic voltammetry. After accumulating Hg(2+), anodic stripping voltammetry (ASV) was performed, and differential pulse voltammetry (DPV) was employed for signal recording of Hg(2+). Several main experimental parameters were optimized, i.e., deposition potential and time of AuNPs were -0.2 V and 180 s, respectively, and accumulation potential and time of Hg(2+) were -0.3 V and 660 s, respectively. Under the optimal conditions, this AuNPs-GO-IL-GCE sensor attained a good linearity in a wide range of 0.1-100 nM (R = 0.9808) between the concentration of the Hg(2+) standard and peak current. The limit of detection was estimated to be 0.03 nM at a signal-to-noise ratio of 3σ. A variety of common coexistent ions in water samples were investigated, showing no obvious interferences on the Hg(2+) detection. The practical application of the proposed sensor has been carried out and demonstrated as feasible for determination of trace levels of Hg(2+) in drinking and environmental water samples.

Preparation and characterization of RuO2/polypyrrole electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Li, Xiang; Wu, Yujiao; Zheng, Feng; Ling, Min; Lu, Fanghai

2014-11-01

Polypyrrole (PPy) embedded RuO2 electrodes were prepared by the composite method. Precursor solution of RuO2 was coated on tantalum sheet and annealed at 260 °C for 2.5 h to develop a thin film. PPy particles were deposited on RuO2 films and dried at 80 °C for 12 h to form composite electrode. Microstructure and morphology of RuO2/PPy electrode were characterized using Fourier transform infrared spectrometer, X-ray diffraction and scanning electron microscopy, respectively. Our results confirmed that counter ions are incorporated into RuO2 matrix. Structure of the composite with amorphous phase was verified by X-ray diffraction. Analysis by scanning electron microscopy reveals that during grain growth of RuO2/PPy, PPy particle size sharply increases as deposition time is over 20 min. Electrochemical properties of RuO2/PPy electrode were calculated using cyclic voltammetry. As deposition times of PPy are 10, 20, 25 and 30 min, specific capacitances of composite electrodes reach 657, 553, 471 and 396 F g-1, respectively. Cyclic behaviors of RuO2/PPy composite electrodes are stable.

Oxidation management of white wines using cyclic voltammetry and multivariate process monitoring.

PubMed

Martins, Rui C; Oliveira, Raquel; Bento, Fatima; Geraldo, Dulce; Lopes, Vitor V; Guedes de Pinho, Paula; Oliveira, Carla M; Silva Ferreira, Antonio C

2008-12-24

The development of a fingerprinting strategy capable to evaluate the "oxidation status" of white wines based on cyclic voltammetry is proposed here. It is known that the levels of specific antioxidants and redox mechanisms may be evaluated by cyclic voltammetry. This electrochemical technique was applied on two sets of samples. One group was composed of normal aged white wines and a second group obtained from a white wine forced aging protocol with different oxygen, SO(2), pH, and temperature regimens. A study of antioxidant additions, namely ascorbic acid, was also made in order to establish a statistical link between voltammogram fingerprints and chemical antioxidant substances. It was observed that the oxidation curve presented typical features, which enables sample discrimination according to age, oxygen consumption, and antioxidant additions. In fact, it was possible to place the results into four significant orthogonal directions, compressing 99.8% of nonrandom features. Attempts were made to make voltammogram fingerprinting a tool for monitoring oxidation management. For this purpose, a supervised multivariate control chart was developed using a control sample as reference. When white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity. Finally, quantification of substances implicated in the oxidation process as reagents (antioxidants) and products (off-flavors) was tried using a supervised algorithmic the partial least square regression analysis. Good correlations (r > 0.93) were observed for ascorbic acid, Folin-Ciocalteu index, total SO(2), methional, and phenylacetaldehyde. These results show that cyclic voltammetry fingerprinting can be used to monitor and diagnose the effects of wine oxidation.

IMPACT OF POLYCYCLIC AROMATIC HYDROCARBONS OF THE ELECTROCHEMICAL RESPONSES OF A FERRICYNIDE PROBE AT TEMPLATE-MODIFIED SELF ASSEMBLED MONOLAYERS ON GOLD ELECTRODES

EPA Science Inventory

The impact of pyrene on the electrochemical response of the ferricyanide probe using Self Assembled Monolayer (SAM)-modified gold electrodes was investigated using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV). These results suggest the feasibility of using SAMs, par...

Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry.

PubMed

Ammar, Hafedh Belhadj; Brahim, Mabrouk Ben; Abdelhédi, Ridha; Samet, Youssef

2016-02-01

The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2μmolL(-1), with a detection limit of 0.065μmolL(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

Comparative study of the antioxidant capacity and polyphenol content of Douro wines by chemical and electrochemical methods.

PubMed

Rebelo, M J; Rego, R; Ferreira, M; Oliveira, M C

2013-11-01

A comparative study of the antioxidant capacity and polyphenols content of Douro wines by chemical (ABTS and Folin-Ciocalteau) and electrochemical methods (cyclic voltammetry and differential pulse voltammetry) was performed. A non-linear correlation between cyclic voltammetric results and ABTS or Folin-Ciocalteau data was obtained if all types of wines (white, muscatel, ruby, tawny and red wines) are grouped together in the same correlation plot. In contrast, a very good linear correlation was observed between the electrochemical antioxidant capacity determined by differential pulse voltammetry and the radical scavenging activity of ABTS. It was also found that the antioxidant capacity of wines evaluated by the electrochemical methods (expressed as gallic acid equivalents) depend on background electrolyte of the gallic acid standards, type of electrochemical signal (current or charge) and electrochemical technique. Copyright © 2013 Elsevier Ltd. All rights reserved.

Synthesis and characterization of a new porphyrin-polyoxometalate hybrid material and investigation of its catalytic activity.

PubMed

Araghi, Mehdi; Mirkhani, Valiollah; Moghadam, Majid; Tangestaninejad, Shahram; Mohammdpoor-Baltork, Iraj

2012-03-14

In the present work, the preparation of a new organic-inorganic hybrid material in which tetrakis(p-aminophenylporphyrin) is covalently linked to a Lindqvist structure of polyoxometalate, is reported. This new porphyrin-polyoxometalate hybrid material was characterized by (1)H NMR, FT-IR and UV-Vis spectroscopic methods and cyclic voltammetry. These spectro- and electrochemical studies provided spectral data of the synthesis of this compound. Cyclic voltammetry showed the influence of the porphyrin on the redox process of the polyoxometalate. The catalytic activity of this hybrid material was investigated in the alkene epoxidation with NaIO(4).

Variation sweep rate cyclic voltammetry on the capacitance electrode activated carbon/PVDF with polymer electrolyte

NASA Astrophysics Data System (ADS)

Rohmawati, L.; Setyarsih, W.; Nurjannah, T.

2018-03-01

Sweep rate of the process voltammetry cyclic characterization is very influential towards the electrode capacitance value, especially on activated carbon electrodes/PVDF. A simple method of this research by use a mixing for electrode activated carbon/10 wt. % PVDF and the separator is made of a polymer electrolyte (PVA/H3PO4) by a sol gel method. The prototype supercapacitor is made in the form of a sandwich with a separator placed between two electrodes. Electrodes and separators are arranged in layers at a pressure of 1500 psi, then heated at 50°C for 10 minutes. Next done cyclic voltammetry in a potential range of -1 V to 1 V with a sweep rate of 5 mV/s, 10 mV/s, 20 mV/s, 25 mV/s and 50 mV/s. This results of curves voltammogram is reversible, the most wide curve on the sweep rate of 5 mV/s and most narrow curve on a sweep rate of 50 mV/s. Supercapacitor capacitance values obtained by 86 F/g, 43 F/g, 21 F/g, 16 F/g, and 8 F/g.

SILAR deposited Bi2S3 thin film towards electrochemical supercapacitor

NASA Astrophysics Data System (ADS)

Raut, Shrikant S.; Dhobale, Jyotsna A.; Sankapal, Babasaheb R.

2017-03-01

Bi2S3 thin film electrode has been synthesized by simple and low cost successive ionic layer adsorption and reaction (SILAR) method on stainless steel (SS) substrate at room temperature. The formation of interconnected nanoparticles with nanoporous surface morphology has been achieved and which is favourable to the supercapacitor applications. Electrochemical supercapacitive performance of Bi2S3 thin film electrode has been performed through cyclic voltammetry, charge-discharge and stability studies in aqueous Na2SO4 electrolyte. The Bi2S3 thin film electrode exhibits the specific capacitance of 289 Fg-1 at 5 mVs-1 scan rate in 1 M Na2SO4 electrolyte.

Vertically aligned cobalt hydroxide nano-flake coated electro-etched carbon fiber cloth electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Cheng, Qian; Tang, Jie; Zhang, Han; Qin, Lu-Chang

2014-11-01

We describe preparation and characterization of nanostructured electrodes using Co(OH)2 nano-flakes and carbon fiber cloth for supercapacitors. Nanostructured Co(OH)2 flakes are produced by electrodeposition and they are coated onto the electro-etched carbon fiber cloth. A highest specific capacitance of 3404.8 F g-1 and an area-normalized specific capacitance of 3.3 F cm-2 have been obtained from such electrodes. Morphology and structure of the nanostructured electrodes have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties have been studied by cyclic voltammetry (CV), constant-current charge and discharge, electrochemical impedance spectroscopy (EIS), and long-time cycling.

Supercapacitive transport of pharmacologic agents using nanoporous gold electrodes.

PubMed

Gittard, Shaun D; Pierson, Bonnie E; Ha, Cindy M; Wu, Chung-An Max; Narayan, Roger J; Robinson, David B

2010-02-01

In this study, nanoporous gold supercapacitors were produced by electrochemical dealloying of gold-silver alloy. Scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed completion of the dealloying process and generation of a porous gold material with approximately 10 nm diameter pores. Cyclic voltammetry and chronoamperometry of the nanoporous gold electrodes indicated that these materials exhibited supercapacitor behavior. The storage capacity of the electrodes measured by chronoamperometry was approximately 3 mC at 200 mV. Electrochemical storage and voltage-controlled delivery of two model pharmacologic agents, benzylammonium and salicylic acid, was demonstrated. These results suggest that capacitance-based storage and delivery of pharmacologic agents may serve as an alternative to conventional drug delivery methods.

Characterisation of embroidered 3D electrodes by use of anthraquinone-1,5-disulfonic acid as probe system

NASA Astrophysics Data System (ADS)

Aguiló-Aguayo, Noemí; Bechtold, Thomas

2014-05-01

New electrode designs are required for electrochemical applications such as batteries or fuel cells. Embroidered 3D Cu porous electrodes with a geometric surface of 100 cm2 are presented and characterised by means of the anthraquinone-1,5-disfulfonic acid (AQDS2-) redox system in alkaline solution. The electrochemical behaviour of the 3D electrode is established by the comparison of cyclic voltammetry responses using a micro cell and a 100 cm2 plane Cu-plate electrode. Dependencies of the peak currents and peak-to-peak potential separation on scan rate and AQDS2- concentration are studied. The AQDS2- characterisation is also performed by means of spectroelectrochemical experiments.

Preparation of Shape-Controlled Graphene/Co3O4 Composites for Supercapacitors

NASA Astrophysics Data System (ADS)

Chen, Jun; Chen, Ningna; Feng, Xiaomiao; Hou, Wenhua

2016-09-01

Graphene/Co3O4 nanocomposites with different morphologies were fabricated by hydrothermal method. The morphology of nanocomposites was characterized by scanning electron microscopy. These composites could be used as the electrode materials for supercapacitors. The eletrochemical behavior of the composite was tested by cyclic voltammetry and galvanostatic charge-discharge measurements in 1.0 mol/L KOH solution. The results showed that the graphene/Co3O4 nanopetal composite exhibited excellent electrochemical performance. The specific capacitance value could reach up to 714 F/g at a scan rate of 2 mV/s. Besides, the capacitance of the graphene/Co3O4 nanopetal composite was 841 F/g at a current density of 0.1 A/g. After galvanostatic charge-discharge 1000 laps at the current density of 0.4 A/g, the specific capacitance could keep 96.7% of original capacitive value, demonstrating its good cycling stability.

High rate performance supercapacitor based on Nb2O5 nanoparticles

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Ahmed, Ahsan; Rafat, M.

2018-05-01

In the present communication, we report the successful preparation of Nb2O5 nanoparticles from precursor NbCl5 using hydrothermal method, followed by thermal annealing. The surface morphology of the as-prepared material was studied using scanning electron microscopy (SEM) while crystal structure and vibrational response was characterized using X-ray diffraction (XRD) and Raman spectroscopy. The observed results indicate the successful synthesis of Nb2O5 nanoparticles. The electrochemical properties of the material was investigated in two-electrode assembly in 1 M LiClO4 solution using the techniques of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Both EIS and CV studies show high rate performance of the assembled supercapacitor cells. Fabricated cell offers low response time (˜17.1 ms), and the shape of CV pattern remains almost rectangular, even for high scan rates (˜20 V s-1).

Voltammetry Method Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoyt, N.; Pereira, C.; Willit, J.

2016-07-29

The purpose of the ANL MPACT Voltammetry project is to evaluate the suitability of previously developed cyclic voltammetry techniques to provide electroanalytical measurements of actinide concentrations in realistic used fuel processing scenarios. The molten salts in these scenarios are very challenging as they include high concentrations of multiple electrochemically active species, thereby creating a variety of complications. Some of the problems that arise therein include issues related to uncompensated resistance, cylindrical diffusion, and alloying of the electrodeposited metals. Improvements to the existing voltammetry technique to account for these issues have been implemented, resulting in good measurements of actinide concentrations acrossmore » a wide range of adverse conditions.« less

Electrochemical studies of quinine in surfactant media using hanging mercury drop electrode: a cyclic voltammetric study.

PubMed

Dar, Riyaz Ahmad; Brahman, Pradeep Kumar; Tiwari, Sweety; Pitre, Krishna Sadashiv

2012-10-01

The electrochemical behavior of quinine was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV) using surfactant. The reduction peak current of quinine increases remarkably in presence of 1% CTAB. Its electrochemical behavior is quasi-reversible in the Britton-Robinson buffers of pH 10.38 by exhibiting the well-defined single cathodic and anodic waves and the ratio of I(p)(a)/I(p)(c) approaching one at the scan rate of 500 mVs(-1). On the basis of CV, SWV and Coulometry, electrochemical reduction mechanism of quinine has been proposed which has shown that protonation occurs on the nitrogen of the quinoline moiety. Linearity was obtained when the peak currents (I(p)) were plotted against concentrations of quinine in the range of 30.0-230.0 ng mL(-1) with a detection limit of 0.132 ng mL(-1) in SWV and 90.0-630.0 ng mL(-1) with a detection limit of 0.238 ng mL(-1) in DPV. Fast and sensitive SWV has been applied for the quantitative analysis of quinine in bark of Cinchona sp. and in soft drinks and a good recovery was obtained. The accuracy and precision of the method are determined and validated statistically. No interferences from other food additives were observed. The relative standard deviation for intraday and interday assay was 0.89 and 0.73% (n=3) respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Facile fabrication of novel silver-polypyrrole-multiwall carbon nanotubes nanocomposite for replacement of platinum in dye-sensitized solar cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafique, Shaista; Sharif, Rehana; Ghani, Sheeba

This paper demonstrates the facile synthesis of high performance silver-polypyrrole-multiwall carbon nanotubes (Ag-PPy-FMWCNTS) nanocomposites via electrodeposition method on stainless steel substrate and its application as a low cost counter electrode (CE) for the precious platinum (Pt) free DSSC. The nanocomposites were characterized by variety of techniques such as Fourier transforms infrared (FTIR), X-ray diffraction, Scanning electron microscope (SEM), cyclic voltammetry (CV) and Four probe technique respectively. The cyclic voltammetry and Tafel polymerization measurements of Ag-PPy-FMWCNTS nanocomposites CE reveal the favorable electrocatalytic activity and low charge transfer resistance R{sub ct}(2.50 Ω cm{sup 2}) for I{sub 3}{sup −}/I{sup −} redox solution. Themore » four probe studies showed the large electrical conductivity (226S cm{sup −1}) of Ag-PPy-FMWCNTS nanocomposite. The DSSC assembled with Ag-PPy-FMWCNTS nanocomposites CE display the considerable short circuit current density (13.95 mA cm{sup −2}) and acceptable solar to electrical conversion efficiency of 7.6%, which is higher to the efficiency of DSSC with thermally decomposed Pt reference electrode 7.1%. The excellent conversion efficiency, rapid charge transfer in combination with low cost and simple fabrication method of Ag-PPy-FMWCNTS nanocomposites can be exploited as an efficient and potential candidate to replace the Pt CE for large scale production of DSSC.« less

Removal of urea from dilute streams using RVC/nano-NiO x -modified electrode.

PubMed

Tammam, Reham H; Touny, Ahmed H; Saleh, Mahmoud M

2018-05-08

Reticulated vitreous carbon (RVC), a high surface area electrode (40 cm 2 /cm 3 ), has been modified with nickel oxide nanoparticles (nano-NiO x ) and used for electrochemical oxidation of urea from alkaline solution. For the cyclic voltammetry measurements, the used dimensions are 0.8 cm × 0.8 cm × 0.3 cm. The purpose was to offer high specific surface area using a porous open network structure to accelerate the electrochemical conversion. NiO x nanoparticles have been synthesized via an electrochemical route at some experimental conditions. The morphological, structural, and electrochemical properties of the RVC/nano-NiO x are characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and potentiostatic measurements. The fabricated electrode, RVC/nano-NiO x , demonstrates high electrocatalytic activity towards urea oxidation in an alkaline electrolyte. The onset potential of the RVC/nano-NiO x compared to that of the planar GC/NiO x is shifted to more negative value with higher specific activity. The different loadings of the NiO x have a substantial influence on the conversion of urea which has been evaluated from concentration-time curves. The urea concentration decreases with time to a limit dependent on the loading extent. Maximum conversion is obtained at 0.86 mg of NiO x per cm 3 of the RVC matrix.

A Facile Synthesis of a Palladium-Doped Polyaniline-Modified Carbon Nanotube Composites for Supercapacitors

NASA Astrophysics Data System (ADS)

Giri, Soumen; Ghosh, Debasis; Malas, Asish; Das, Chapal Kumar

2013-08-01

Supercapacitors have evolved as the premier choice of the era for storing huge amounts of charge in the field of energy storage devices, but it is still necessary to enhance their performance to meet the increasing requirements of future systems. This could be achieved either through advancing the interfaces of the material at the nanoscale or by using novel material compositions. We report a high-performance material composition prepared by combining a transition metal (palladium)-doped conductive polymer with multiwalled carbon nanotubes (MWCNTs). MWCNTs/palladium-doped polyaniline (MWCNTs/Pd/PANI) composites and multiwalled carbon nanotube/polyaniline (MWCNTs/PANI) composites (for comparison) were prepared via in situ oxidative polymerization of aniline monomer. The reported composites were characterized by Fourier-transform infrared (FTIR), x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) studies. FESEM and TEM studies indicated the narrow size distribution of the π-conjugated polymer-protected palladium nanoparticles on the surface of the carbon nanotubes. All the electrochemical characterizations were executed using a three-electrode system in 1 M H2SO4 electrolyte. Cyclic voltammetry (CV) analysis was performed to observe the capacitive performance and redox behavior of the composites. The ion transfer behavior and cyclic stability of the composites were investigated by electrochemical impedance spectroscopy (EIS) analysis and cyclic charge-discharge (CCD) testing, respectively. The MWCNTs/Pd/PANI composite was found to exhibit an especially high specific capacitance value of 920 F/g at scan rate of 2 mV/s.

Synthesis and electrochemical performance of polyaniline-MnO2 nanowire composites for supercapacitors

NASA Astrophysics Data System (ADS)

Chen, Ling; Song, Zhaoxia; Liu, Guichang; Qiu, Jieshan; Yu, Chang; Qin, Jiwei; Ma, Lin; Tian, Fengqin; Liu, Wei

2013-02-01

Polyaniline-MnO2 nanowire (PANI-MNW) composites were prepared by in situ chemical oxidative polymerization of aniline monomer in a suspension of MnO2 nanowires. The structure and morphology of the PANI-MNW composites were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their electrochemical properties were investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 mol/L KOH electrolyte. The PANI-MNW composites show significantly better specific capacity and redox performance in comparison to the untreated MnO2 nanowires. The enhanced properties can be mainly attributed to the composite structure wherein high porosity is created between MnO2 nanowires and PANI during the process of fabricating the PANI-MNW nanocomposites. A specific capacitance as high as 256 F/g is obtained at a current density of 1 A/g for PANI-MNW-5, and the composite also shows a good cyclic performance and coulomb efficiency.

Electrochemical Properties of RuO2 Electrodes as a Function of Thin Film Thickness

NASA Astrophysics Data System (ADS)

Li, Xiang; Xiong, Jian; Luo, Yuan; Luo, Yongmei

2018-01-01

A thin film RuO2 electrode was prepared by spin coating thermal decomposition methods. Precursor containing RuCl3·nH2O and isopropyl alcohol was coated on tantalum substrate and annealed at 250-260°C for 3 h to form a thin film RuO2 electrode of about 2.5 μm, 5.6 μm, 11.4 μm, and 14.5 μm in thickness. X-ray diffraction revealed that peak intensities of those electrodes were similar and close to each other. Scanning electron microscopy showed that thin film of 5.6 μm in thickness was dense and free of cracks. Electrochemical performances of electrodes were examined by cyclic voltammetry, galvanostatic charge/discharge as well as equivalent series resistance. The highest specific capacitance value of 725 F g-1 was registered for the electrode of 5.6 μm in thickness with good constant current charge/discharge and equivalent series resistance of 0.36 Ω as well as cyclic stability.

Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps

PubMed Central

Sharma, Abeera; Bhattarai, Jay K.; Alla, Allan J.; Demchenko, Alexei V.; Stine, Keith J.

2015-01-01

An electrochemical method for annealing the pore sizes of nanoporous gold is reported. The pore sizes of nanoporous gold can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of nanoporous gold due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the nanoporous gold surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in nanoporous gold are also reported. The effect of the annealing process on the application of nanoporous gold as a substrate for glucose electro-oxidation is briefly examined. PMID:25649027

Graphene based nanocomposite hybrid electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Aphale, Ashish N.

There is an unmet need to develop high performance energy storage systems (ESS), capable of storing energy from both renewable and non-renewable sources to meet the current energy crisis and depletion of non-renewable sources. Amongst many available ESS, supercapacitors (ECs) are the most promising because they exhibit a high charge/discharge rate and power density, along with a long cycle life. The possibility of exploring the use of atomically thin carbon allotropes like graphene, carbon nanotubes (CNTs) and electrically conducting polymers (ECPs) such as polypyrrole (PPy) has been studied as a high performance conducting electrodes in supercapacitor application. A novel templated sustainable nanocomposite electrode has been fabricated using cellulose extracted from Cladophora c. aegagropila algae as component of the assembled supercapacitor device which later has been transitioned to a unique template-less freestanding nanocomposite supercapacitor electrode. The specific capacitance of polypyrrole-graphene-cellulose nanocomposite as calculated from cyclic voltammetry curve is 91.5 F g -1 at the scan rate 50 m Vs-1 in the presence of 1M NaCl electrolyte. The open circuit voltage of the device with polypyrrole -graphene-cellulose electrode was found to be around 225 m V and that of the polypyrrole -cellulose device is only 53 m V without the presence of graphene in the nanocomposite electrode. Understanding the fundamentals by fabricating template nanocomposite electrode, it led to fabricate a unique nanocomposite template-less freestanding film which comprises of polypyrrole-graphene-CNT hybrid. Various experiments have been performed using different electrolytes such ascorbic acid, sodium sulfate and sulfuric acid in different scan rates. The specific capacitance of polypyrrole-graphene-CNT nanocomposite with 0.1 wt% of graphene-CNT, as calculated from cyclic voltammetry curve is 450 F g-1 at the scan rate 5 m V s-1. For the first time a nanofibrous membrane has been developed as a separator which acts as an electrolyte reservoir and ionic diffusion membrane. The performance of the fabricated supercapacitor device has been analyzed using a multimeter and compared with a conventional alkaline (1.5 V) battery. Lighting up of 2.2 V light emitting diode has been demonstrated using the fabricated supercapacitor.

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance.

PubMed

Sagasti, Ariane; Bouropoulos, Nikolaos; Kouzoudis, Dimitris; Panagiotopoulos, Apostolos; Topoglidis, Emmanuel; Gutiérrez, Jon

2017-07-25

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb's electrochemical behavior towards hydrogen peroxide. Hb oxidation by H₂O₂ was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer's elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H₂O₂ drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H₂O₂. The measured catalysis currents increase linearly with the H₂O₂ concentration in a wide range of 25-350 μM with a correlation coefficient 0.99. The detection limit is 25-50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H₂O₂, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H₂O₂ concentration with a slope of 152 ng/μM, which is probably due to H₂O₂ adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment when only PBS solution was present for a long time.

Electrodeposited nitrogen-doped graphene/carbon nanotubes nanocomposite as enhancer for simultaneous and sensitive voltammetric determination of caffeine and vanillin.

PubMed

Jiang, Lin; Ding, Yaping; Jiang, Feng; Li, Li; Mo, Fan

2014-06-23

A nitrogen-doped graphene/carbon nanotubes (NGR-NCNTs) nanocomposite was employed into the study of the electrochemical sensor via electrodeposition for the first time. The morphology and structure of NGR-NCNTs nanocomposite were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Meanwhile, the electrochemical performance of the glassy carbon electrode (GCE) modified with electrodeposited NGR-NCNTs (ENGR-NCNTs/GCE) towards caffeine (CAF) and vanillin (VAN) determination was demonstrated by cyclic voltammetry (CV) and square wave voltammetry (SWV). Under optimal condition, ENGR-NCNTs/GCE exhibited a wide linearity of 0.06-50 μM for CAF and 0.01-10 μM for VAN with detection limits of 0.02 μM and 3.3×10(-3) μM, respectively. Furthermore, the application of the proposed sensor in food products was proven to be practical and reliable. The desirable results show that the ENGR-NCNTs nanocomposite has promising potential in electrocatalytic biosensor application. Copyright © 2014 Elsevier B.V. All rights reserved.

Square-wave adsorptive stripping voltammetric determination of nanomolar levels of bezafibrate using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film.

PubMed

Ardila, Jorge Armando; Oliveira, Geiser Gabriel; Medeiros, Roberta Antigo; Fatibello-Filho, Orlando

2014-04-07

A highly sensitive method for bezafibrate determination using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film based on square-wave adsorptive stripping voltammetry (SWAdSV) is proposed. The electrochemical behaviour of bezafibrate has been studied by cyclic voltammetry, showing an irreversible anodic peak at a potential of 1.09 V in 0.1 mol L(-1) phosphate buffer solution (pH 2.0). A study of the scan rate showed that the oxidation of bezafibrate is an adsorptive-controlled process, involving the transfer of two electrons and two protons per molecule. The analytical curve was linear over a bezafibrate concentration range from 50 to 910 nmol L(-1), with a detection limit of 16 nmol L(-1). This analytical method was successfully applied for benzafibrate determination in pharmaceutical formulations, with results showing good agreement with those obtained using a comparative spectrophotometric method, and has the potential for field application.

A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode.

PubMed

Kong, Fen-Ying; Xu, Mao-Tian; Xu, Jing-Juan; Chen, Hong-Yuan

2011-10-15

In this paper, gold nanoparticle-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased the peak current of THi in the GNP-THi-GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10-500 pg/mL with a detection limit of 4 pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels. Copyright © 2011 Elsevier B.V. All rights reserved.

A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents--Proof-of-principle application in microfluidic separations and voltammetry.

PubMed

Koutilellis, G D; Economou, A; Efstathiou, C E

2016-03-01

This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents—Proof-of-principle application in microfluidic separations and voltammetry

NASA Astrophysics Data System (ADS)

Koutilellis, G. D.; Economou, A.; Efstathiou, C. E.

2016-03-01

This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

Electrochemical DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles and graphene for sensitive determination of Klebsiella pneumoniae carbapenemase.

PubMed

Pan, Hong-zhi; Yu, Hong-wei; Wang, Na; Zhang, Ze; Wan, Guang-cai; Liu, Hao; Guan, Xue; Chang, Dong

2015-11-20

We describe the fabrication of a sensitive electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase (KPC). The highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-NPs) and graphene (Gr). Then Au-NPs/Gr/GCE was characterized by scanning electro microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization detection was measured by diffierential pulse voltammetry (DPV) using methylene blue (MB) as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-12) to 1 × 10(-7)mol/L, with a detection limit of 2 × 10(-13)mol/L. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The results demonstrated that the Au-NPs/Gr nanocomposite was a promising substrate for the development of high-performance electrocatalysts for determination of KPC. Copyright © 2015 Elsevier B.V. All rights reserved.

Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell

PubMed Central

Dong, Feng; Zhang, Peng; Li, Kexun; Liu, Xianhua; Zhang, Pingping

2016-01-01

In this work, Cu2O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the carbon cloth, which improved the electrochemical activity of cathode. The cathode with a deposition time of 100 s showed the best performance, with a power density twice that of bare carbon cloth. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) results revealed that moderate deposition of nano copper oxide on carbon cloth could dramatically reduce the charge transfer resistance, which contributed to the enhanced electrochemical performance. The mediation mechanism of copper oxide nanocatalyst was illustrated by the fact that the recycled conversion between cupric oxide and cuprous oxide accelerated the electron transfer efficiency on the cathode. PMID:28335366

Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell.

PubMed

Dong, Feng; Zhang, Peng; Li, Kexun; Liu, Xianhua; Zhang, Pingping

2016-12-09

In this work, Cu₂O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the carbon cloth, which improved the electrochemical activity of cathode. The cathode with a deposition time of 100 s showed the best performance, with a power density twice that of bare carbon cloth. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) results revealed that moderate deposition of nano copper oxide on carbon cloth could dramatically reduce the charge transfer resistance, which contributed to the enhanced electrochemical performance. The mediation mechanism of copper oxide nanocatalyst was illustrated by the fact that the recycled conversion between cupric oxide and cuprous oxide accelerated the electron transfer efficiency on the cathode.

The Enhanced Photo-Electrochemical Detection of Uric Acid on Au Nanoparticles Modified Glassy Carbon Electrode

NASA Astrophysics Data System (ADS)

Shi, Yuting; Wang, Jin; Li, Shumin; Yan, Bo; Xu, Hui; Zhang, Ke; Du, Yukou

2017-07-01

In this work, a sensitive and novel method for determining uric acid (UA) has been developed, in which the glassy carbon electrode (GCE) was modified with electrodeposition Au nanoparticles and used to monitor the concentration of UA with the assistant of visible light illumination. The morphology of the Au nanoparticles deposited on GCE surface were characterized by scanning electron microscope (SEM) and the nanoparticles were found to be well-dispersed spheres with the average diameter approaching 26.1 nm. A series of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements have revealed that the introduction of visible light can greatly enhance both the strength and stability of response current due to the surface plasmon resonance (SPR). Specifically, the DPV showed a linear relationship between peak current and UA concentration in the range of 2.8 to 57.5 μM with the equation of I pa (μA) = 0.0121 c UA (μM) + 0.3122 ( R 2 = 0.9987). Herein, the visible light illuminated Au/GCE possesses a potential to be a sensitive electrochemical sensor in the future.

One-step engineered self-assembly Co3O4 nanoparticles to nanocubes for supercapacitors

NASA Astrophysics Data System (ADS)

Nagajyothi, P. C.; Pandurangan, M.; Sreekanth, T. V. M.; Shim, Jaesool

2018-02-01

Tricobalt tetraoxide or cobalt oxide (Co3O4) nanocubes (NCs) were synthesized from the self-assemblies of Co3O4 nanoparticles (NPs) via a simple one-step hydrothermal method. X-ray diffraction analysis confirmed the cubic crystal structure of Co3O4 NCs. The surface properties were investigated by x-ray photoelectron spectroscopy, which suggests the co-existence of Co in +2 and +3 states. The self-assemblies of aggregation of NPs to NCs were inspected using scanning electron microscopy, which is supported by transmission electron microscopy. The electrochemical properties of Co3O4 NCs were carried out by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) curves and impedance analysis. The areal capacitance of 3.04 mF cm-2 was obtained at current density of 10 μA cm-2. The Co3O4 NCs electrode exhibits good long-cyclic stability with 92.1% capacitance retention over 3000 cycles. The CV, GCD and impedance curves of Co3O4 NCs were recorded after cyclic test, which are similar to the curves recorded before the test. Therefore, the Co3O4 NCs serves good candidate as positive electrode materials for asymmetric supercapacitors.

Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

NASA Astrophysics Data System (ADS)

Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

2017-02-01

A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V ( vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

Enzymatic biosensor based on entrapment of d-amino acid oxidase on gold nanofilm/MWCNTs nanocomposite modified glassy carbon electrode by sol-gel network: Analytical applications for d-alanine in human serum.

PubMed

Shoja, Yalda; Rafati, Amir Abbas; Ghodsi, Javad

2017-05-01

Sensing and determination of d-alanine is studied by using an enzymatic biosensor which was constructed on the basis of d-amino acid oxidase (DAAO) immobilization by sol-gel film onto glassy carbon electrode surface modified with nanocomposite of gold nanofilm (Au-NF) and multiwalled carbon nanotubes (MWCNTs). The Au-NF/MWCNT nanocomposite was prepared by applying the potentiostatic technique for electrodeposition of Au-NF on the MWCNT immobilized on glassy carbon electrode surface. The modified electrode is investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), linear sweep voltammetry (LSV) and cyclic voltammetry(CV) techniques. The linear sweep voltammetry was used for determination of d-alanine and the results showed an excellent linear relationship between biosensor response and d-alanine concentration ranging from 0.25μM to 4.5μM with correction coefficient of 0.999 (n=20). Detection limit for the fabricated sensor was calculated about 20nM (for S/N=3) and sensitivity was about 56.1μAμM -1 cm -2 . The developed biosensor exhibited rapid and accurate response to d-alanine, a good stability (4 weeks) and an average recovery of 98.9% in human serum samples. Copyright © 2017 Elsevier Inc. All rights reserved.

Simultaneous voltammetry detection of dopamine and uric acid in human serum and urine with a poly(procaterol hydrochloride) modified glassy carbon electrode.

PubMed

Kong, Dexian; Zhuang, Qizhao; Han, Yejian; Xu, Lanping; Wang, Zeming; Jiang, Lili; Su, Jinwei; Lu, Chun-Hua; Chi, Yuwu

2018-08-01

In the present study, procaterol hydrochloride (ProH) was successfully electropolymerized onto a glass carbon electrode (GCE) with simply cyclic voltammetry scans to construct a poly(procaterol hydrochloride) (p-ProH) membrane modified electrode. Compared with the bare GCE, much higher oxidation peak current responses and better peak potentials separation could be obtained for the simultaneous oxidation of dopamine (DA) and uric acid (UA), owning to the excellent electrocatalytic ability of the p-ProH membrane. And it's based on that a square wave voltammetry (SWV) method was developed to selective and simultaneous measurement of DA and UA. Under the optimum conditions, the linear dependence of oxidation peak current on analyte concentrations were found to be 1.0-100 μmol/L and 2-100 μmol/L, giving detection limits of 0.3 μmol/L and 0.5 μmol/L for DA and UA, separately. The as prepared modified electrode shows simplicity in construction with the merits of good reproducibility, high stability, passable selectivity and nice sensitivity. Finally, the proposed p-ProH membrane modified electrode was successfully devoted to the detection of DA and UA in biological fluids such as human serum and urine with acceptable results. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of different nickel precursors on capacitive behavior of electrodeposited NiO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kore, R. M.; Ghadge, T. S.; Ambare, R. C.

2016-04-13

In the present study, the effect of nickel precursors containing different anions like nitrate, chloride and sulphate on the morphology and pseudocapacitance behavior of NiO is investigated. The NiO samples were prepared by using a potentiondynamic electrodeposition technique in the three electrode cell. Cyclic voltammetry technique was exploited for potentiodynamic deposition of the films. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The XRD reveals the cubic crystal structure for all samples. The SEM micrograph shows nanoflakelike, up grown nanoflakes and honeycomb like nanostructured morphologies for nitrate, chloride and sulphate precursors respectively. The capacitivemore » behavior of these samples was recorded using cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The specific capacitance values of NiO samples obtained using CV for nitrate, chloride and sulphate precursors were 136, 214 and 893 Fg{sup −1} respectively, at the scan rate of 5 mVs{sup −1}. The charge discharge study shows high specific energy for the sample obtained from sulphate (23.98 Whkg{sup −1}) as compared to chloride (9.67 Whkg{sup −1}) and nitrate (4.9 Whkg{sup −1}), whereas samples of cholride (13.9 kWkg{sup −1} and nitrate (10.5 kWkg{sup −1}) shows comparatively more specific power than samples obtained from sulphate (7.6 kWkg{sup −1}). The equivalent series resistance of NiO samples observed from EIS study are 1.34, 1.29 and 1.27 Ω respectively for nitrate, chloride and sulphate precursors. These results emphasizes that the samples obtained from sulphate precursors provides very low impedance through honeycomb like nanostructured morphology which supports good capacitive behavior of NiO.« less

Supersensitive Kappa Opioid Receptors Promotes Ethanol Withdrawal-Related Behaviors and Reduce Dopamine Signaling in the Nucleus Accumbens.

PubMed

Rose, Jamie H; Karkhanis, Anushree N; Chen, Rong; Gioia, Dominic; Lopez, Marcelo F; Becker, Howard C; McCool, Brian A; Jones, Sara R

2016-05-01

Chronic ethanol exposure reduces dopamine transmission in the nucleus accumbens, which may contribute to the negative affective symptoms associated with ethanol withdrawal. Kappa opioid receptors have been implicated in withdrawal-induced excessive drinking and anxiety-like behaviors and are known to inhibit dopamine release in the nucleus accumbens. The effects of chronic ethanol exposure on kappa opioid receptor-mediated changes in dopamine transmission at the level of the dopamine terminal and withdrawal-related behaviors were examined. Five weeks of chronic intermittent ethanol exposure in male C57BL/6 mice were used to examine the role of kappa opioid receptors in chronic ethanol-induced increases in ethanol intake and marble burying, a measure of anxiety/compulsive-like behavior. Drinking and marble burying were evaluated before and after chronic intermittent ethanol exposure, with and without kappa opioid receptor blockade by nor-binaltorphimine (10mg/kg i.p.). Functional alterations in kappa opioid receptors were assessed using fast scan cyclic voltammetry in brain slices containing the nucleus accumbens. Chronic intermittent ethanol-exposed mice showed increased ethanol drinking and marble burying compared with controls, which was attenuated with kappa opioid receptor blockade. Chronic intermittent ethanol-induced increases in behavior were replicated with kappa opioid receptor activation in naïve mice. Fast scan cyclic voltammetry revealed that chronic intermittent ethanol reduced accumbal dopamine release and increased uptake rates, promoting a hypodopaminergic state of this region. Kappa opioid receptor activation with U50,488H concentration-dependently decreased dopamine release in both groups; however, this effect was greater in chronic intermittent ethanol-treated mice, indicating kappa opioid receptor supersensitivity in this group. These data suggest that the chronic intermittent ethanol-induced increase in ethanol intake and anxiety/compulsive-like behaviors may be driven by greater kappa opioid receptor sensitivity and a hypodopaminergic state of the nucleus accumbens. © The Author 2015. Published by Oxford University Press on behalf of CINP.

Microfluidic platform for neurotransmitter sensing based on cyclic voltammetry and dielectrophoresis for in vitro experiments.

PubMed

Mathault, Jessy; Zamprogno, Pauline; Greener, Jesse; Miled, Amine

2015-08-01

This paper presents a new microfluidic platform that can simultaneously measure and locally modulate neurotransmitter concentration in a neuron network. This work focuses on the development of a first prototype including a potentiostat and electrode functionalization to detect several neurotransmitter's simultaneously. We tested dopamine as proof of concept to validate functionality. The system is based on 320 bidirectional electrode array for dielectrophoretic manipulation and cyclic voltammetry. Each electrode is connected to a mechanical multiplexer in order to reduce noise interference and fully isolate the electrode. The multiplexing rate is 476 kHz and each electrode can drive a signal with an amplitude of 60 V pp for dielectrophoretic manipulation.

Electrochemical investigation of [Co4(μ3-O)4(μ-OAc)4(py)4] and peroxides by cyclic voltammetry.

PubMed

Clatworthy, Edwin B; Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

2016-12-13

Two oxidative redox processes of the neutral cobalt(iii) cubane, [Co 4 (μ 3 -O) 4 (μ-OAc) 4 (py) 4 ], were investigated by cyclic voltammetry at a glassy carbon electrode in acetonitrile. In addition to the first quasi-reversible one-electron oxidation at E 1/2 = 0.283 V vs. Fc 0/+ , a second quasi-reversible one-electron oxidation was observed at E 1/2 = 1.44 V vs. Fc 0/+ . Oxidation at this potential does not facilitate water oxidation. In the presence of tert-butylhydroperoxide the peak current of this second oxidation increases, suggesting oxidation of the peroxide by the doubly oxidised cubane.

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method

PubMed Central

Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N.

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination. PMID:29301258

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

PubMed

Aldalbahi, Ali; Rahaman, Mostafizur; Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

STM, SECPM, AFM and Electrochemistry on Single Crystalline Surfaces

PubMed Central

Wolfschmidt, Holger; Baier, Claudia; Gsell, Stefan; Fischer, Martin; Schreck, Matthias; Stimming, Ulrich

2010-01-01

Scanning probe microscopy (SPM) techniques have had a great impact on research fields of surface science and nanotechnology during the last decades. They are used to investigate surfaces with scanning ranges between several 100 μm down to atomic resolution. Depending on experimental conditions, and the interaction forces between probe and sample, different SPM techniques allow mapping of different surface properties. In this work, scanning tunneling microscopy (STM) in air and under electrochemical conditions (EC-STM), atomic force microscopy (AFM) in air and scanning electrochemical potential microscopy (SECPM) under electrochemical conditions, were used to study different single crystalline surfaces in electrochemistry. Especially SECPM offers potentially new insights into the solid-liquid interface by providing the possibility to image the potential distribution of the surface, with a resolution that is comparable to STM. In electrocatalysis, nanostructured catalysts supported on different electrode materials often show behavior different from their bulk electrodes. This was experimentally and theoretically shown for several combinations and recently on Pt on Au(111) towards fuel cell relevant reactions. For these investigations single crystals often provide accurate and well defined reference and support systems. We will show heteroepitaxially grown Ru, Ir and Rh single crystalline surface films and bulk Au single crystals with different orientations under electrochemical conditions. Image studies from all three different SPM methods will be presented and compared to electrochemical data obtained by cyclic voltammetry in acidic media. The quality of the single crystalline supports will be verified by the SPM images and the cyclic voltammograms. Furthermore, an outlook will be presented on how such supports can be used in electrocatalytic studies. PMID:28883327

Guanine oxidation signal enhancement in DNA via a polyacrylonitrile nanofiber-coated and cyclic voltammetry-treated pencil graphite electrode

NASA Astrophysics Data System (ADS)

Aladag Tanik, Nilay; Demirkan, Elif; Aykut, Yakup

2018-07-01

This study investigated the electrochemical detection of specific nucleic acid hybridization sequences using a nanofiber-coated pencil graphite biosensor. The biosensor was developed to detect Val66Met single point mutations in the brain-derived neurotrophic factor gene, which is frequently observed in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and bipolar disorder. The oxidation signal of the most electroactive and stable DNA base, i.e., guanine, was used at approximately +1.0 V. Pencil graphite electrode (PGE) surfaces were coated with polyacrylonitrile nanofibers by electrospinning. Cyclic voltammetry was applied to the nanofiber-coated PGE to pretreat its surfaces. The application of cyclic voltammetry to the nanofiber-coated PGE surfaces before attaching the probe yielded a four fold increase in the oxidation signal for guanine compared with that using the untreated and uncoated PGE surface. The signal reductions were 70% for hybridization, 10% for non-complementary binding, and 14% for a single mismatch compared with the probe. The differences in full match, non-complementary, and mismatch binding indicated that the biosensor selectively detected the target, and that it was possible to determine hybridization in about 65 min. The detection limit was 0.19 μg/ml at a target concentration of 10 ppm.

Hawaii Energy and Environmental Technologies (HEET) Initiative

DTIC Science & Technology

2010-08-01

segmented cell system for investigation of PEMFC performance distribution using both cyclic voltammetry (CV) and linear sweep voltammetry (LSV). In...mitigation strategies. Under prior work it was shown that SO2 contamination in the cathode of a PEMFC resulted in a two-stage degradation of cell...emission rate in a PEMFC is an important parameter for monitoring the Nafion degradation. Generally, the Nafion electrolyte degradation is

Graphene nanoplate-MnO2 composites for supercapacitors: a controllable oxidation approach.

PubMed

Huang, Huajie; Wang, Xin

2011-08-01

Graphene nanoplate-MnO(2) composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO(2) nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material. This journal is © The Royal Society of Chemistry 2011

Electrochemical Study of Cobalt in Urea and Choline Chloride

NASA Astrophysics Data System (ADS)

Li, Min; Shi, Zhongning; Wang, Zhaowen; Reddy, Ramana G.

The nucleation mechanism of Co(II) in urea-choline chloride-CoCl2 melt at 373 K was studied using chronoamperometry. Chronoamperometry experiments confirm that the electrodeposition of cobalt on tungsten electrode is governed by three-dimensional (3D) progressive nucleation and diffusion-controlled growth mechanisms. The average diffusion coefficient of Co(II) in the melt at 373 K is 1.1 × 10-6 cm2 s-1, which is in good agreement with the estimated value obtained from cyclic voltammetry data. Characterization of the Co electrodeposit using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) techniques indicate that the electrodeposit obtained at -0.75 V and 373 K contain dense and compact surface formed from pure cobalt metal.

Electrodeposition of CuZn Alloys from the Non-Cyanide Alkaline Baths

NASA Astrophysics Data System (ADS)

Li, Minggang; Wei, Guoying; Hu, Shuangshuang; Xu, Shuhan; Yang, Yejiong; Miao, Qinfang

2015-10-01

Effect of copper sulfate on CuZn alloys electroplating from non-cyanide baths are investigated by different electrochemical methods. Cyclic voltammetry and current transient measurements are used to characterize the CuZn alloys electroplating system in order to analyze the nucleation and growth mechanism. The reduction of Cu and CuZn alloy on sheet iron substrates shows an instantaneous nucleation process. However, the reduction of Zn on sheet iron substrates shows a progressive nucleation process. The structure and surface morphology of CuZn alloys are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The morphology of CuZn alloys obtained with 50 g L-1 copper sulfate presents a smooth and compact deposit and the size of crystal particle is uniform.

Multilayered films of cobalt oxyhydroxide nanowires/manganese oxide nanosheets for electrochemical capacitor

NASA Astrophysics Data System (ADS)

Zheng, Huajun; Tang, Fengqiu; Lim, Melvin; Mukherji, Aniruddh; Yan, Xiaoxia; Wang, Lianzhou; (Max) Lu, Gao Qing

Multilayered films of cobalt oxyhydroxide nanowires (CoOOHNW) and exfoliated manganese oxide nanosheet (MONS) are fabricated by potentiostatic deposition and electrostatic self-assembly on indium-tin oxide coated glass substrates. The morphology and chemical composition of these films are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS) and the potential application as electrochemical supercapacitors are investigated using cyclic voltammetry and charge-discharge measurements. These ITO/CoOOHNW/MONS multilayered film electrodes exhibit excellent electrochemical capacitance properties, including high specific capacitance (507 F g -1) and long cycling durability (less 2% capacity loss after 5000 charge/discharge cycles). These characteristics indicate that these newly developed films may find important application for electrochemical capacitors.

Nickel as a catalyst for the electro-oxidation of methanol in alkaline medium

NASA Astrophysics Data System (ADS)

Abdel Rahim, M. A.; Abdel Hameed, R. M.; Khalil, M. W.

The use of Ni as a catalyst for the electro-oxidation of methanol in alkaline medium was studied by cyclic voltammetry. It was found that only Ni dispersed on graphite shows a catalytic activity towards methanol oxidation but massive Ni does not. Ni was dispersed on graphite by the electro-deposition from acidic NiSO 4 solution using potentiostatic and galvanostatic techniques. The catalytic activity of the C/Ni electrodes towards methanol oxidation was found to vary with the amount of electro-deposited Ni. The dependence of the oxidation current on methanol concentration and scan rate was discussed. It was concluded from the electro-chemical measurements and SEM analysis that methanol oxidation starts as Ni-oxide is formed on the electrode surface.

Facile synthesis of nickel-based metal organic framework [Ni3(HCOO)6] by microwave method and application for supercapacitor

NASA Astrophysics Data System (ADS)

Luo, Jujie; Yang, Xing; Wang, Shumin; Bi, Yuhong; Nautiyal, Amit; Zhang, Xinyu

The metal organic framework (MOF) [Ni3(HCOO)6] was synthesized via the simple and fast microwave method, and the effect of irradiation power on crystallinity of synthesized Ni-based MOF was studied. The samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The synthesized Ni-based MOF was electrochemically characterized by using galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. The synthesized MOF showed the highest specific capacitance of 1196.2F/g at 1A/g with excellent cyclability (86.04% capacitance retention after 2,000 cycles), thereby demonstrating its potential application in supercapacitors.

Electrochromic NiO thin films prepared by spin coating

NASA Astrophysics Data System (ADS)

Özütok, F.; Demiri, S.; Özbek, E.

2017-02-01

Recently, smart windows are very important because they are often being used in smart buildings and car glasses (windows). At this point, producing effective electrochromic materials is so necessary. In this study, we produced NiO thin films by using spin coating technique on In-doped SnO2 (ITO) substrate. Nickel proportions of these nickel oxide (NiO) films are 3, 5 and 7 %. Nickel acetate tetrahydrate is the initial solution and solvents are ethylene gl ycol and n-hexzane. Structural properties and surface images are investigated by using x-ray diffactometer (XRD) and scanning electron microscope (SEM) device, respectively. In addition, electrochemical behavior is investigated by cyclic voltammetry. A correlation between surface morphology and electrochromic performance was observed as well.

Low-Temperature-Annealed Reduced Graphene Oxide-Polyaniline Nanocomposites for Supercapacitor Applications

NASA Astrophysics Data System (ADS)

Liao, Chen-Yu; Chien, Hung-Hua; Hao, Yu-Chuan; Chen, Chieh-Wen; Yu, Ing-Song; Chen, Jian-Zhang

2018-04-01

Screen-printed reduced graphene oxide (rGO)-polyaniline (PANI) nanocomposites with/without post-annealing were used as the electrode of a supercapacitor with a polyvinyl alcohol/H2SO4 quasi-solid-state gel electrolyte. Annealing can remove part of the ineffective organic binders and thus enhance the supercapacitive performance. However, too high an annealing temperature may damage PANI, thus reducing the pseudocapacitance. Annealing at 100°C for 10 min results in the best achieved areal capacitance of 102.73 mF/cm2, as evaluated by cyclic voltammetry (CV) under a potential scan rate of 2 mV/s. The capacitance retention rate is 88% after 1000 CV cycles under bending with a bending radius of 0.55 cm.

Voltammetry as a Tool for Characterization of CdTe Quantum Dots

PubMed Central

Sobrova, Pavlina; Ryvolova, Marketa; Hubalek, Jaromir; Adam, Vojtech; Kizek, Rene

2013-01-01

Electrochemical detection of quantum dots (QDs) has already been used in numerous applications. However, QDs have not been well characterized using voltammetry, with respect to their characterization and quantification. Therefore, the main aim was to characterize CdTe QDs using cyclic and differential pulse voltammetry. The obtained peaks were identified and the detection limit (3 S/N) was estimated down to 100 fg/mL. Based on the convincing results, a new method for how to study stability and quantify the dots was suggested. Thus, the approach was further utilized for the testing of QDs stability. PMID:23807507

The dynamics of charge transfer with and without a barrier: A very simplified model of cyclic voltammetry.

PubMed

Ouyang, Wenjun; Subotnik, Joseph E

2017-05-07

Using the Anderson-Holstein model, we investigate charge transfer dynamics between a molecule and a metal surface for two extreme cases. (i) With a large barrier, we show that the dynamics follow a single exponential decay as expected; (ii) without any barrier, we show that the dynamics are more complicated. On the one hand, if the metal-molecule coupling is small, single exponential dynamics persist. On the other hand, when the coupling between the metal and the molecule is large, the dynamics follow a biexponential decay. We analyze the dynamics using the Smoluchowski equation, develop a simple model, and explore the consequences of biexponential dynamics for a hypothetical cyclic voltammetry experiment.

Evaluation studies on carbon supported catalysts for oxygen reduction in alkaline medium

NASA Technical Reports Server (NTRS)

Srinivasan, Vakula S.; Singer, Joseph

1986-01-01

This paper describes tests designed to predict the performance of fuel cell electrodes, as applied to an alkaline oxygen-fuel cell having specially fabricated porous-carbon electrodes with various amounts of dispersed platinum or gold as active catalysts. The tests are based on information obtained from the techniques of cyclic voltammetry and polarization. The parameters obtained from cyclic voltammetry were of limited use in predicting fuel cell performance of the cathode. On the other hand, half-cell polarization measurements offered close simulation of the oxygen electrode, although a predictor of the electrode life is still lacking. The very low polarization of the Au-10 percent Pt catalytic electrode suggests that single-phase catalysts should be considered.

Scanning electrochemical microscopy of menadione-glutathione conjugate export from yeast cells

PubMed Central

Mauzeroll, Janine; Bard, Allen J.

2004-01-01

The uptake of menadione (2-methyl-1,4-naphthoquinone), which is toxic to yeast cells, and its expulsion as a glutathione complex were studied by scanning electrochemical microscopy. The progression of the in vitro reaction between menadione and glutathione was monitored electrochemically by cyclic voltammetry and correlated with the spectroscopic (UV–visible) behavior. By observing the scanning electrochemical microscope tip current of yeast cells suspended in a menadione-containing solution, the export of the conjugate from the cells with time could be measured. Similar experiments were performed on immobilized yeast cell aggregates stressed by a menadione solution. From the export of the menadione-glutathione conjugate detected at a 1-μm-diameter electrode situated 10 μm from the cells, a flux of about 30,000 thiodione molecules per second per cell was extracted. Numerical simulations based on an explicit finite difference method further revealed that the observation of a constant efflux of thiodione from the cells suggested the rate was limited by the uptake of menadione and that the efflux through the glutathione-conjugate pump was at least an order of magnitude faster. PMID:15148374

Supercapacitors based on ordered mesoporous carbon derived from furfuryl alcohol: effect of the carbonized temperature.

PubMed

Li, Na; Xu, Jianxiong; Chen, Han; Wang, Xianyou

2014-07-01

Supercapacitors are successfully prepared from ordered mesoporous carbon (OMC) synthesized by employing the mesoporous silica, SBA-15 as template and furfuryl alcohol as carbon source. It is found that the carbonized temperature greatly influences the physical properties of the synthesized mesoporous carbon materials. The optimal carbonized temperature is measured to be 600 degrees C under which OMC with the specific surface area of 1219 m2/g and pore volume of 1.31 cm3/g and average pore diameter of - 3 nm are synthesized. The OMC materials synthesized under different carbonized temperature are used as electrode material of supercapacitors and the electrochemical properties of the OMC materials are compared by using cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge-discharge and self-discharge tests. The results show that the electrochemical properties of the OMC materials are directly related to the specific surface area and pore volume of the mesoporous carbon and the electrode prepared from the OMC synthesized under the carbonized temperature of 600 degrees C (OMC-600) exhibits the most excellent electrochemical performance with the specific capacitance of 207.08 F/g obtained from cyclic voltammetry at the scan rate of 1 mV/s, small resistance and low self-discharge rate. Moreover, the supercapacitor based on the OMC-600 material exhibits good capacitance properties and stable cycle behavior with the specific capacitance of 105 F/g at the current density of 700 mA/g, and keeps a specific capacitance of 98 F/g after 20000 consecutive charge/discharge cycles.

A Study on the Copper Effect on gold leaching in copper-ethanediamine-thiosulphate solutions

NASA Astrophysics Data System (ADS)

Liu, Qiong; Xiang, Pengzhi; Huang, Yao

2018-01-01

A simple, fast and sensitive square-wave voltammetry (SWV), cyclic voltammetry(CV) and tafel method for the determination of various factors of gold in thiosulphate solution in this paper. We present our study on the effect of copper(II) on the leaching of gold in thiosulphate solutions. The current study aims to establish the interaction of copper in the leaching process by electrochemical method.

Electrochemical mechanism of tin membrane electrodeposition under ultrasonic waves.

PubMed

Nan, Tianxiang; Yang, Jianguang; Chen, Bing

2018-04-01

Tin was electrodeposited from chloride solutions using a membrane cell under ultrasonic waves. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHR), and chronopotentiometry were applied to investigate the electrochemical mechanism of tin electrodeposition under ultrasonic field. Chronoamperometry curves showed that the initial process of tin electrodeposition followed the diffusion controlled three-dimensional nucleation and grain growth mechanism. The analysis of the cyclic voltammetry and linear sweep voltammetry diagrams showed that the application of ultrasound can change the tin membrane electro-deposition reaction from diffusion to electrochemical control, and the optimum parameters for tin electrodeposition were H + concentration 3.5 mol·L -1 , temperature 35 °C and ultrasonic power 100 W. The coupling ultrasonic field played a role in refining the grain in this process. The growth of tin crystals showed no orientation preferential, and the tin deposition showed a tendency to form a regular network structure after ultrasonic coupling. While in the absence of ultrasonic coupling, the growth of tin crystals has a high preferential orientation, and the tin deposition showed a tendency to form tin whiskers. Ultrasonic coupling was more favorable for obtaining a more compact and smoother cathode tin layer. Copyright © 2017 Elsevier B.V. All rights reserved.

SnO2/CNT nanocomposite supercapacitors fabricated using scanning atmospheric-pressure plasma jets

NASA Astrophysics Data System (ADS)

Xu, Chang-Han; Chiu, Yi-Fan; Yeh, Po-Wei; Chen, Jian-Zhang

2016-08-01

SnO2/CNT electrodes for supercapacitors are fabricated by first screen-printing pastes containing SnO2 nanoparticles and CNTs on carbon cloth, following which nitrogen atmospheric pressure plasma jet (APPJ) sintering is performed at various APPJ scan rates. The APPJ scan rates change the time intervals for which the reactive plasma species and the heat of the nitrogen APPJs influence the designated sintering spot on the carbon cloth, resulting in APPJ-sintered SnO2/CNT nanocomposites with different properties. The water contact angle decreases with the APPJ scan rate. The improved wettability can facilitate the penetration of the electrolyte into the nanopores of the SnO2/CNT nanocomposites, thereby improving the charge storage and specific capacitance of the supercapacitors. Among the three tested APPJ scan rates, 1.5, 3, and 6 mm s-1, the SnO2/CNT supercapacitor sintered by APPJ under the lowest APPJ scan rate of 1.5 mm s-1 shows the best specific capacitance of ˜90 F g-1 as evaluated by cyclic voltammetry under a potential scan rate of 2 mV s-1. A high APPJ scan rate may result in low degree of materials activation and sintering, leading to poorer performance of SnO2/CNT supercapacitors. The results suggest the feasibility of an APPJ roll-to-roll process for the fabrication of SnO2/CNT nanocomposite supercapacitors.

Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes.

PubMed

Walsh, Darren A; Lovelock, Kevin R J; Licence, Peter

2010-11-01

The high viscosity and unusual properties of room temperature ionic liquids (RTILs) present a number of challenges when performing steady-state voltammetry and scanning electrochemical microscopy in RTILs. These include difficulties in recording steady-state currents at ultramicroelectrode surfaces due to low diffusion coefficients of redox species and problems associated with unequal diffusion coefficients of oxidised and reduced species in RTILs. In this tutorial review, we highlight the recent progress in the use of RTILs as electrolytes for ultramicroelectrode voltammetry and SECM. We describe the basic principles of ultramicroelectrode voltammetry and SECM and, using examples from the recent literature, we discuss the conditions that must be met to perform steady-state voltammetry and SECM measurements in RTILs. Finally, we briefly discuss the electrochemical insights that can be obtained from such measurements.

Study of quinones reactions with wine nucleophiles by cyclic voltammetry.

PubMed

Oliveira, Carla M; Barros, António S; Ferreira, António C S; Silva, Artur M S

2016-11-15

Quinones are electrophilic species which can react with various nucleophiles, like wine antioxidants, such as sulfur dioxide or ascorbic acid, thiols, amino acids, and numerous polyphenols. These reactions are very important in wine aging because they mediate oxygen reactions during both production and bottle aging phases. In this work, the major challenge was to determine the interaction between ortho-quinones and wine nucleophiles (amino acids, thiols, and the antioxidants SO2 and ascorbic acid), by cyclic voltammetry. Wine-model solutions with gallic acid, caffeic acid, or (+)-catechin and nucleophilic compounds were used. To understand the effect of nucleophilic addition in wine, a white wine with the same added nucleophiles was also analysed. Cyclic voltammograms were taken with glassy carbon electrode or screen-printed carbon electrodes, respectively, for wine-model and white wines solutions, in the absence and in the presence of nucleophiles. A nucleophilic order profile related to the cathodic current intensity decrease was observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Flexible and High Performance Supercapacitors Based on NiCo2O4for Wide Temperature Range Applications

NASA Astrophysics Data System (ADS)

Gupta, Ram K.; Candler, John; Palchoudhury, Soubantika; Ramasamy, Karthik; Gupta, Bipin Kumar

2015-10-01

Binder free nanostructured NiCo2O4 were grown using a facile hydrothermal technique. X-ray diffraction patterns confirmed the phase purity of NiCo2O4. The surface morphology and microstructure of the NiCo2O4 analyzed by scanning electron microscopy (SEM) showed flower-like morphology composed of needle-like structures. The potential application of binder free NiCo2O4 as an electrode for supercapacitor devices was investigated using electrochemical methods. The cyclic voltammograms of NiCo2O4 electrode using alkaline aqueous electrolytes showed the presence of redox peaks suggesting pseudocapacitance behavior. Quasi-solid state supercapacitor device fabricated by sandwiching two NiCo2O4 electrodes and separating them by ion transporting layer. The performance of the device was tested using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The device showed excellent flexibility and cyclic stability. The temperature dependent charge storage capacity was measured for their variable temperature applications. Specific capacitance of the device was enhanced by ~150% on raising the temperature from 20 to 60 °C. Hence, the results suggest that NiCo2O4 grown under these conditions could be a suitable material for high performance supercapacitor devices that can be operated at variable temperatures.

Flexible and High Performance Supercapacitors Based on NiCo2O4for Wide Temperature Range Applications.

PubMed

Gupta, Ram K; Candler, John; Palchoudhury, Soubantika; Ramasamy, Karthik; Gupta, Bipin Kumar

2015-10-20

Binder free nanostructured NiCo2O4 were grown using a facile hydrothermal technique. X-ray diffraction patterns confirmed the phase purity of NiCo2O4. The surface morphology and microstructure of the NiCo2O4 analyzed by scanning electron microscopy (SEM) showed flower-like morphology composed of needle-like structures. The potential application of binder free NiCo2O4 as an electrode for supercapacitor devices was investigated using electrochemical methods. The cyclic voltammograms of NiCo2O4 electrode using alkaline aqueous electrolytes showed the presence of redox peaks suggesting pseudocapacitance behavior. Quasi-solid state supercapacitor device fabricated by sandwiching two NiCo2O4 electrodes and separating them by ion transporting layer. The performance of the device was tested using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The device showed excellent flexibility and cyclic stability. The temperature dependent charge storage capacity was measured for their variable temperature applications. Specific capacitance of the device was enhanced by ~150% on raising the temperature from 20 to 60 °C. Hence, the results suggest that NiCo2O4 grown under these conditions could be a suitable material for high performance supercapacitor devices that can be operated at variable temperatures.

Flexible and High Performance Supercapacitors Based on NiCo2O4for Wide Temperature Range Applications

PubMed Central

Gupta, Ram K.; Candler, John; Palchoudhury, Soubantika; Ramasamy, Karthik; Gupta, Bipin Kumar

2015-01-01

Binder free nanostructured NiCo2O4 were grown using a facile hydrothermal technique. X-ray diffraction patterns confirmed the phase purity of NiCo2O4. The surface morphology and microstructure of the NiCo2O4 analyzed by scanning electron microscopy (SEM) showed flower-like morphology composed of needle-like structures. The potential application of binder free NiCo2O4 as an electrode for supercapacitor devices was investigated using electrochemical methods. The cyclic voltammograms of NiCo2O4 electrode using alkaline aqueous electrolytes showed the presence of redox peaks suggesting pseudocapacitance behavior. Quasi-solid state supercapacitor device fabricated by sandwiching two NiCo2O4 electrodes and separating them by ion transporting layer. The performance of the device was tested using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The device showed excellent flexibility and cyclic stability. The temperature dependent charge storage capacity was measured for their variable temperature applications. Specific capacitance of the device was enhanced by ~150% on raising the temperature from 20 to 60 °C. Hence, the results suggest that NiCo2O4 grown under these conditions could be a suitable material for high performance supercapacitor devices that can be operated at variable temperatures. PMID:26482921

Study binding of Al-curcumin complex to ds-DNA, monitoring by multispectroscopic and voltammetric techniques

NASA Astrophysics Data System (ADS)

Ahmadi, F.; Alizadeh, A. A.; Shahabadi, N.; Rahimi-Nasrabadi, M.

2011-09-01

In this work a complex of Al 3+ with curcumin ([Al(curcumin) (EtOH) 2](NO 3) 2) was synthesized and characterized by UV-vis, FT-IR, elemental analysis and spectrophotometric titration techniques. The mole ratio plot revealed a 1:1 complex between Al 3+ and curcumin in solution. For binding studies of this complex to calf thymus-DNA various methods such as: UV-vis, fluorescence, circular dichroism (CD), FT-IR spectroscopy and cyclic voltammetry were used. The intrinsic binding constant of ACC with DNA at 25 °C was calculated by UV-vis and cyclic voltammetry as 2.1 × 10 4 and 2.6 × 10 4, respectively. The thermodynamic studies showed that the reaction is enthalpy and entropy favored. The CD results showed that only the Δ-ACC interacts with DNA and the Δ-ACC form has not any tendency to interact with DNA, also the pure curcumin has not any stereoselective interaction with CT-DNA. Fluorimetric studies showed that fluorescence enhancement was initiated by a static process in the ground state. The cyclic voltammetry showed that ACC interact with DNA with a binding site size of 2. From the FT-IR we concluded that the Δ-ACC interacts with DNA via partial electrostatic and minor groove binding. In comparison with previous works it was concluded that curcumin significantly reduced the affinity of Al 3+ to the DNA.

Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin

NASA Astrophysics Data System (ADS)

Dhifaoui, Selma; Mchiri, Chadlia; Quatremare, Pierre; Marvaud, Valérie; Bujacz, Anna; Nasri, Habib

2018-02-01

In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV-visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C-H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.

Exhaustive thin-layer cyclic voltammetry for absolute multianalyte halide detection.

PubMed

Cuartero, Maria; Crespo, Gastón A; Ghahraman Afshar, Majid; Bakker, Eric

2014-11-18

Water analysis is one of the greatest challenges in the field of environmental analysis. In particular, seawater analysis is often difficult because a large amount of NaCl may mask the determination of other ions, i.e., nutrients, halides, and carbonate species. We demonstrate here the use of thin-layer samples controlled by cyclic voltammetry to analyze water samples for chloride, bromide, and iodide. The fabrication of a microfluidic electrochemical cell based on a Ag/AgX wire (working electrode) inserted into a tubular Nafion membrane is described, which confines the sample solution layer to less than 15 μm. By increasing the applied potential, halide ions present in the thin-layer sample (X(-)) are electrodeposited on the working electrode as AgX, while their respective counterions are transported across the perm-selective membrane to an outer solution. Thin-layer cyclic voltammetry allows us to obtain separated peaks in mixed samples of these three halides, finding a linear relationship between the halide concentration and the corresponding peak area from about 10(-5) to 0.1 M for bromide and iodide and from 10(-4) to 0.6 M for chloride. This technique was successfully applied for the halide analysis in tap, mineral, and river water as well as seawater. The proposed methodology is absolute and potentially calibration-free, as evidenced by an observed 2.5% RSD cell to cell reproducibility and independence from the operating temperature.

An Investigation of Methyl Viologen Functionalized Reduced Graphene Oxide: Chitosan as a Support for Pt Nanoparticles Towards Ethanol Electrooxidation

NASA Astrophysics Data System (ADS)

Ekrami-Kakhki, Mehri-Saddat; Farzaneh, Nahid; Abbasi, Sedigheh; Beitollahi, Hadi; Ekrami-Kakhki, Seyed Ali

2018-05-01

In this research, graphene oxide was prepared by a modified Hummers' method, and then functionalized with 1, 1'-dimethyl-4, 4'-bipyridinium dichloride (MV), and chitosan (CH) to get a MV-RGO-CH support. Pt nanoparticles were prepared on this support to get Pt/MV-RGO-CH catalyst. The morphology and microstructure of Pt/MV-RGO-CH catalyst were characterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity of the prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scan rate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV-RGO-CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV-RGO-CH catalyst for ethanol oxidation was compared with those of Pt/CH and Pt/MV-RGO catalysts. The higher electrocatalytic performance of Pt/MV-RGO-CH than Pt/CH and Pt/MV-RGO catalysts towards ethanol electrooxidation indicated that Pt/MV-RGO-CH could be a promising catalyst for application in direct ethanol fuel cells.

Application of graphene-ionic liquid-chitosan composite-modified carbon molecular wire electrode for the sensitive determination of adenosine-5'-monophosphate.

PubMed

Shi, Fan; Gong, Shixing; Xu, Li; Zhu, Huanhuan; Sun, Zhenfan; Sun, Wei

2013-12-01

In this paper, a graphene (GR) ionic liquid (IL) 1-octyl-3-methylimidazolium hexafluorophosphate and chitosan composite-modified carbon molecular wire electrode (CMWE) was fabricated by a drop-casting method and further applied to the sensitive electrochemical detection of adenosine-5'-monophosphate (AMP). CMWE was prepared with diphenylacetylene (DPA) as the modifier and the binder. The properties of modified electrode were examined by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical behaviors of AMP was carefully investigated with enhanced responses appeared, which was due to the presence of GR-IL composite on the electrode surface with excellent electrocatalytic ability. A well-defined oxidation peak of AMP appeared at 1.314 V and the electrochemical parameters were calculated by electrochemical methods. Under the selected conditions, the oxidation peak current of AMP was proportional to its concentration in the range from 0.01 μM to 80.0 μM with the detection limit as 3.42 nM (3σ) by differential pulse voltammetry. The proposed method exhibited good selectivity and was applied to the detection of vidarabine monophosphate injection samples with satisfactory results. © 2013.

Introduction of a carbon paste electrode based on nickel carbide for investigation of interaction between warfarin and vitamin K1.

PubMed

Torkashvand, Maryam; Gholivand, Mohammad Bagher; Taherpour, Avat Arman; Boochani, Arash; Akhtar, Arsalan

2017-05-30

In this paper a novel electrochemical sensor based on nickel carbide (Ni 3 C) nanoparticles as a new modifier was constructed. Ni 3 C nanoparticle was synthesized and characterized by scanning electron microscopy, X-ray diffraction and first-principles study. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies confirmed the electrode modification. Afterwards, the new electrode for the first time was used for interaction study between vitamin K1 and warfarin as an anticoagulant drug by differential pulse voltammetry. The adduct formation between the drug and vitamin K1 was improved by decreasing in anodic peak current of warfarin in the presence of different amounts of vitamin K1. The binding constant between warfarin and vitamin K1 was obtained by voltammetric and UV-vis and fluorescence spectroscopic methods. The molecular modeling method was also performed to explore the structural features and binding mechanism of warfarin to vitamin K1. The different aspects of modeling of vitamin K1 and warfarin and their adduct structures confirmed the adduct formation by hydrogen bonding. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly sensitive determination of sunset yellow FCF (E110) in food products based on Chitosan/Nanoparticles/MWCNTs with modified gold electrode

NASA Astrophysics Data System (ADS)

Rovina, K.; Siddiquee, S.; Shaarani, S. M.

2016-06-01

Sunset Yellow belongs to the family of azo dyes, commonly used in food industry. High consumption of Sunset Yellow can cause health problem to human. Due to arising of the health issues, there are several analytical methods available for determination of Sunset Yellow. However, these methods are required skilled manpower, complicated procedures, time consuming and high cost. Herein, an electrochemical sensor was developed based on the combination of chitosan (CHIT), calcium oxide nanoparticles (CaONPs) and multiwall carbon nanotubes (MWCNTs) sensing film for detection of Sunset Yellow in food products. Electrochemical behavior of the modified gold electrode in the presence of Sunset Yellow was studied by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The morphological characteristics of CHIT/CaONPs/MWCNTs were observed under scanning electron microscope and transmission electron microscope. Under optimal conditions, the DPV was detected with different concentrations of Sunset Yellow in the range of 0.9 to 10 ppm, with detection limit of 0.8 ppm. The developed method has successfully applied for monitoring the presence of Sunset Yellow with different food products including candy, royal jelly, ice cream and soft drink with satisfactory results.

Electrochemical preparation of nickel and copper oxides-decorated graphene composite for simultaneous determination of dopamine, acetaminophen and tryptophan.

PubMed

Liu, Bingdi; Ouyang, Xiaoqian; Ding, Yaping; Luo, Liqing; Xu, Duo; Ning, Yanqun

2016-01-01

In the present work, transition metal oxides decorated graphene (GR) have been fabricated for simultaneous determination of dopamine (DA), acetaminophen (AC) and tryptophan (Trp) using square wave voltammetry. Electro-deposition is a facile preparation strategy for the synthesis of nickel oxide (NiO) and copper oxide (CuO) nanoparticles. GR can be modified by using citric acid to produce more functional groups, which is conducive to the deposition of dispersed metal particles. The morphologies and interface properties of the obtained NiO-CuO/GR nanocomposite were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Moreover, the electrochemical performances of the composite film were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode exhibited that the linear response ranges for detecting DA, AC and Trp were 0.5-20 μM, 4-400 μM and 0.3-40 μM, respectively, and the detection limits were 0.17 μM, 1.33 μM and 0.1 μM (S/N=3). Under optimal conditions, the sensor displayed high sensitivity, excellent stability and satisfactory results in real samples analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Application of nickel zinc ferrite/graphene nanocomposite as a modifier for fabrication of a sensitive electrochemical sensor for determination of omeprazole in real samples.

PubMed

Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

2017-06-01

In the present study, a simple and highly sensitive sensor for the determination of omeprazole based on nickel-zinc ferrite/graphene modified glassy carbon electrode is reported. The morphology and electro analytical performance of the fabricated sensor were characterized with X-ray diffraction spectrometry, Fourier transform infrared spectrometry, scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetry and operation of the sensor. Results were compared with those achieved at the graphene modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions, linear response was over the range of 0.03-100.0µmolL -1 . The lower detection limit was found to be 0.015µmolL -1 . The effect of different interferences on the anodic current response of OMZ was investigated. By measuring the concentrations of omeprazole in plasma and pharmaceutical samples, the practical application of the modified electrode was evaluated. This revealed that the nickel-zinc ferrite/graphene modified glassy carbon electrode shows excellent analytical performance for the determination of omeprazole with a very low detection limit, high sensitivity, and very good accuracy. Copyright © 2017 Elsevier Inc. All rights reserved.

Preparation of NiCoP Hollow Quasi-Polyhedra and Their Electrocatalytic Properties for Hydrogen Evolution in Alkaline Solution.

PubMed

Li, Yapeng; Liu, Jindou; Chen, Chen; Zhang, Xiaohua; Chen, Jinhua

2017-02-22

Double metal phosphide (NiCoP) with hollow quasi-polyhedron structure was prepared by acidic etching and precipitation of ZIF-67 polyhedra and further phosphorization treatment with NaH 2 PO 2 . The morphology and microstructure of NiCoP quasi-polyhedron and its precursors were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and a micropore and chemisorption analyzer. Electrocatalytic properties were examined by typical electrochemical methods, such as linear sweep voltammetry, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy in 1.0 M KOH aqueous solution. Results reveal that, compared with CoP hollow polyhedra, NiCoP hollow quasi-polyhedra exhibit better electrochemical properties for hydrogen evolution with a low onset overpotential of 74 mV and a small Tafel slope of 42 mV dec -1 . When the current density is 10 mA cm -2 , the corresponding overpotential is merely 124 mV, and 93% of its electrocatalytic activity can be maintained for 12 h. This indicates that NiCoP with hollow quasi-polyhedron structure, bimetallic merit, and low cost may be a good candidate as electrocatalyst in the practical application of hydrogen evolution.

A new electrochemical sensor for the simultaneous determination of acetaminophen and codeine based on porous silicon/palladium nanostructure.

PubMed

Ensafi, Ali A; Ahmadi, Najmeh; Rezaei, Behzad; Abarghoui, Mehdi Mokhtari

2015-03-01

A porous silicon/palladium nanostructure was prepared and used as a new electrode material for the simultaneous determination of acetaminophen (ACT) and codeine (COD). Palladium nanoparticles were assembled on porous silicon (PSi) microparticles by a simple redox reaction between the Pd precursor and PSi in an aqueous solution of hydrofluoric acid. This novel nanostructure was characterized by different spectroscopic and electrochemical techniques including scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, fourier transform infrared spectroscopy and cyclic voltammetry. The high electrochemical activity, fast electron transfer rate, high surface area and good antifouling properties of this nanostructure enhanced the oxidation peak currents and reduced the peak potentials of ACT and COD at the surface of the proposed sensor. Simultaneous determination of ACT and COD was explored using differential pulse voltammetry. A linear range of 1.0-700.0 µmol L(-1) was achieved for ACT and COD with detection limits of 0.4 and 0.3 µmol L(-1), respectively. Finally, the proposed method was used for the determination of ACT and COD in blood serum, urine and pharmaceutical compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

Sex determination based on amelogenin DNA by modified electrode with gold nanoparticle.

PubMed

Mazloum-Ardakani, Mohammad; Rajabzadeh, Nooshin; Benvidi, Ali; Heidari, Mohammad Mehdi

2013-12-15

We have developed a simple and renewable electrochemical biosensor based on carbon paste electrode (CPE) for the detection of DNA synthesis and hybridization. CPE was modified with gold nanoparticles (AuNPs), which are helpful for immobilization of thiolated bioreceptors. AuNPs were characterized by scanning electron microscopy (SEM). Self-assembled monolayers (SAMs) of thiolated single-stranded DNA (SH-ssDNA) of the amelogenin gene was formed on CPE. The immobilization of the probe and its hybridization with the target DNA was optimized using different experimental conditions. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical response of ssDNA hybridization and DNA synthesis was measured using differential pulse voltammetry (DPV) with methylene blue (MB) as an electroactive indicator. The new biosensor can distinguish between complementary and non-complementary strands of amelogenin ssDNA. Genomic DNA was extracted from blood and was detected based on changes in the MB reduction signal. These results demonstrated that the new biosensor could be used for sex determination. The proposed biosensor in this study could be used for detection and discrimination of polymerase chain reaction (PCR) products of amelogenin DNA. Copyright © 2013 Elsevier Inc. All rights reserved.

Highly selective determination of amitriptyline using Nafion-AuNPs@branched polyethyleneimine-derived carbon hollow spheres in pharmaceutical drugs and biological fluids.

PubMed

Zad, Zeinab Rezayati; Davarani, Saied Saeed Hosseiny; Taheri, Ali Reza; Bide, Yasamin

2016-12-15

In this paper, AuNPs@Polyethyleneimine-derived carbon hollow spheres were synthesized by a versatile and facile method in three steps and successfully developed and validated as Amitriptyline sensor using cyclic voltammetry (CV), chronoamperometry (CA) and differential pulse voltammetry (DPV) methods. The characterization of the electrode surface has been carried out by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), x-ray photo-electron spectrum (XPS), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC). The obtained negatively charged modified electrode was highly selective to Amitriptyline and it was shown a wide linear range from 0.1 to 700μmolL(-1), with a lower detection limit of 0.034μmolL(-1) (n=5, S/N=3), revealing the high-sensitivity properties. The modified electrode is used to achieve the real-time quantitative detection of AMT for biological applications, and satisfactory results are obtained. Due to the advantages of the sensor, its selectivity, sensitivity and stability, it will have a bright future in the field of medical diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical determination of L-phenylalanine at polyaniline modified carbon electrode based on β-cyclodextrin incorporated carbon nanotube composite material and imprinted sol-gel film.

PubMed

Hu, Yu-fang; Zhang, Zhao-hui; Zhang, Hua-bin; Luo, Li-juan; Yao, Shou-zhuo

2011-04-15

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of L-phenylalanine has been proposed by utilizing β-cyclodextrin (β-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol-gel film. The electrochemical behavior of the sensor towards L-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for L-phenylalanine was based on the inclusion interaction of β-CD and molecular recognition capacity of the imprinted film for L-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0 × 10(-7) to 1.0 × 10(-4) mol L(-1) with a detection limit of 1.0 × 10(-9) mol L(-1). With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect L-phenylalanine in blood plasma samples successfully. Copyright © 2011 Elsevier B.V. All rights reserved.

Nanomolar electrochemical detection of caffeic acid in fortified wine samples based on gold/palladium nanoparticles decorated graphene flakes.

PubMed

Thangavelu, Kokulnathan; Raja, Nehru; Chen, Shen-Ming; Liao, Wei-Cheng

2017-09-01

Amalgamation of noble metal nanomaterials on graphene flakes potentially paves one way to improve their physicochemical properties. This paper deals with the simultaneous electrochemical deposition of gold and palladium nanoparticles on graphene flakes (Au/PdNPs-GRF) for the sensitive determination of caffeic acid (CA). The physiochemical properties of the prepared Au/PdNPs-GRF was characterized by using numerous analytical techniques such as scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy and electrochemical impedance spectroscopy. The enhanced electrochemical determination of CA at Au/PdNPs deposition on GRF were studied by using cyclic voltammetry and differential pulse voltammetry. In results, Au/PdNPs-GRF electrode exhibited an excellent electrocatalytic activity towards CA with wide linear range and low limit of detection of 0.03-938.97µM and 6nM, respectively. Eventually, the Au/PdNPs-GRF was found as a selective and stable active material for the sensing of CA. In addition, the proposed sensor showed the adequate results in real sample analysis. Copyright © 2017 Elsevier Inc. All rights reserved.

Electrochemically reduced graphene oxide/Poly-Glycine composite modified electrode for sensitive determination of l-dopa.

PubMed

Palakollu, Venkata Narayana; Thapliyal, Neeta; Chiwunze, Tirivashe E; Karpoormath, Rajshekhar; Karunanidhi, Sivanandhan; Cherukupalli, Srinivasulu

2017-08-01

A facile preparation strategy based on electrochemical technique for the fabrication of glycine (Poly-Gly) and electrochemically reduced graphene oxide (ERGO) composite modified electrode was developed. The morphology of the developed composite (ERGO/Poly-Gly) was investigated using field emission scanning electron microscope (FE-SEM). The composite modified glassy carbon electrode (GCE) was characterized using fourier transform-infrared (FT-IR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical characterization results revealed that ERGO/Poly-Gly modified GCE has excellent electrocatalytic activity. Further, it was employed for sensing of l-dopa in pH5.5. Differential pulse voltammetry (DPV) was used for the quantification of l-dopa as well as for the simultaneous resolution of l-dopa and uric acid (UA). The LOD (S/N=3) was found to be 0.15μM at the proposed composite modified electrode. Determination of l-dopa could also be achieved in the presence of potentially interfering substances. The sensor showed high sensitivity and selectivity with appreciable reliability and precision. The proposed sensor was also successfully applied for real sample analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrochemical Quantification of Extracellular Local H2O2 Kinetics Originating from Single Cells.

PubMed

Bozem, Monika; Knapp, Phillip; Mirčeski, Valentin; Slowik, Ewa J; Bogeski, Ivan; Kappl, Reinhard; Heinemann, Christian; Hoth, Markus

2017-05-15

H 2 O 2 is produced by all eukaryotic cells under physiological and pathological conditions. Due to its enormous relevance for cell signaling at low concentrations and antipathogenic function at high concentrations, precise quantification of extracellular local H 2 O 2 concentrations ([H 2 O 2 ]) originating from single cells is required. Using a scanning electrochemical microscope and bare platinum disk ultramicroelectrodes, we established sensitive long-term measurements of extracellular [H 2 O 2 ] kinetics originating from single primary human monocytes (MCs) ex vivo. For the electrochemical techniques square wave voltammetry, cyclic and linear scan voltammetry, and chronoamperometry, detection limits for [H 2 O 2 ] were determined to be 5, 50, and 500 nM, respectively. Following phorbol ester stimulation, local [H 2 O 2 ] 5-8 μm above a single MC increased by 3.4 nM/s within the first 10 min before reaching a plateau. After extracellular addition of H 2 O 2 to an unstimulated MC, the local [H 2 O 2 ] decreased on average by 4.2 nM/s due to degradation processes of the cell. Using the scanning mode of the setup, we found that H 2 O 2 is evenly distributed around the producing cell and can still be detected up to 30 μm away from the cell. The electrochemical single-cell measurements were validated in MC populations using electron spin resonance spectroscopy and the Amplex ® UltraRed assay. Innovation and Conclusion: We demonstrate a highly sensitive, spatially, and temporally resolved electrochemical approach to monitor dynamics of production and degradation processes for H 2 O 2 separately. Local extracellular [H 2 O 2 ] kinetics originating from single cells is quantified in real time. Antioxid. Redox Signal. 00, 000-000.

Fabrication of biomolecules self-assembled on Au nanodot array for bioelectronic device.

PubMed

Lee, Taek; Kumar, Ajay Yagati; Yoo, Si-Youl; Jung, Mi; Min, Junhong; Choi, Jeong-Woo

2013-09-01

In the present study, an nano-platform composed of Au nanodot arrays on which biomolecules could be self-assembled was developed and investigated for a stable bioelectronic device platform. Au nanodot pattern was fabricated using a nanoporous alumina template. Two different biomolecules, a cytochrome c and a single strand DNA (ssDNA), were immobilized on the Au nanodot arrays. Cytochorme c and single stranded DNA could be immobilized on the Au nanodot using the chemical linker 11-MUA and thiol-modification by covalent bonding, respectively. The atomic structure of the fabricated nano-platform device was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrical conductivity of biomolecules immobilized on the Au nanodot arrays was confirmed by scanning tunneling spectroscopy (STS). To investigate the activity of biomolecule-immobilized Au-nano dot array, the cyclic voltammetry was carried out. This proposed nano-platform device, which is composed of biomolecules, can be used for the construction of a novel bioelectronic device.

Effect of Fe doping on the electrochemical capacitor behavior of MnO2 nanocrystals

NASA Astrophysics Data System (ADS)

Poonguzhali, R.; Shanmugam, N.; Gobi, R.; Senthilkumar, A.; Viruthagiri, G.; Kannadasan, N.

2015-10-01

In this work, the influence of Fe doping on the capacitance behavior of MnO2 nanoparticles synthesized by chemical precipitation was investigated. During the doping process the concentration of Fe was increased from 0.025 M to 0.125 M in steps of 0.025 M. The products obtained were characterized by X-ray diffraction, Fourier infrared spectroscopy, scanning electron microscopy and N2 adsorption-desorption isotherms. To demonstrate the suitability of Fe-doped MnO2 for capacitor applications, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance were recorded. Among the different levels of doping, the specific capacitance of 912 F/g was delivered by 0.075 M of Fe-doped MnO2 at a scan rate of 10 mV/s, which is almost more than fourfold that of the bare MnO2 electrode (210 F/g). Moreover, for the same concentration the charge, discharge studies revealed the highest specific capacitance of 1084 F/g at a current density of 10 A/g.

Hydrothermal synthesis of β-Ni(OH)2 and its supercapacitor properties

NASA Astrophysics Data System (ADS)

Waghmare, Suraj S.; Patil, Prashant B.; Baruva, Shiva K.; Rajput, Madhuri S.; Deokate, Ramesh J.; Mujawar, Sarfraj H.

2018-04-01

In present manuscript, we synthesized the Nickel hydroxide as an electrode material or supercapacitor application, using hydrothermal method with nickel nitrate as nickel source and hexamethylenetetramine as a directing agent. The reaction was carried out at 160°C temperature for 18 hrs. The structural, morphological and electrochemical characterizations were studied by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) respectively. Phase purity and crystalline nature of as prepared nickel hydroxide β-Ni(OH)2 was reveled from X-ray study. Using Debye Scherer's formula crystallite size of ˜15 nm was estimated for Nickel hydroxide. SEM reveals β-platelets like morphology of Ni(OH)2 average of platelets length of the order of 1 µm. Electrochemical studies (CV and GCD) were carried out in 2M KOH electrolyte solution. The maximum capacitance of 225 Fg-1 was observed for scan rate 5 mV within the potential window of 0.1 to 0.4 V.

In-situ synthesis of Co3O4/graphite nanocomposite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Gopalakrishnan, M.; Srikesh, G.; Mohan, A.; Arivazhagan, V.

2017-05-01

In this work, a low cost and pollution free in-situ synthesis of phase pure Co3O4 nanoparticles and Co3O4/graphite nanocomposite have been successfully developed via co-precipitation method followed by the thermal treatment process. The prepared samples were characterized by powder X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Fourier Transform Infrared Spectroscopy and electrochemical measurements. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy were carried out in 6 M KOH aqueous electrolytic solution. The results show the excellent maximum specific capacitive behavior of 239.5 F g-1 for pure and 395.04 F g-1 for Co3O4/graphite nanocomposite at a current density of 0.5 A g-1. This composite exhibits a good cyclic stability, with a small loss of 2.68% of maximum capacitance over a consecutive 1000 cycles. The investigation indicates that the prepared electrode material could be a potential and promising candidate for electrochemical supercapacitors.

Microfabricated FSCV-Compatible Microelectrode Array for Real-time Monitoring of Heterogeneous Dopamine Release

PubMed Central

Zachek, Matthew K.; Park, Jinwoo; Takmakov, Pavel; Wightman, R. Mark; McCarty, Gregory S.

2010-01-01

Fast scan cyclic voltammetry (FSCV) has been used previously to detect neurotransmitter release and reuptake in vivo. An advantage that FSCV has over other electrochemical techniques is its ability to distinguish neurotransmitters of interest (i.e. monoamines) from their metabolites using their respective characteristic cyclic voltammogram. While much has been learned with this technique, it has generally only been used in a single working electrode arrangement. Additionally, traditional electrode fabrication techniques tend to be difficult and somewhat irreproducible. Described in this report is a fabrication method for a FSCV compatible microelectrode array (FSCV-MEA) that is capable of functioning in vivo. The microfabrication techniques employed here allow for better reproducibility than traditional fabrication methods of carbon fiber microelectrodes, and enable batch fabrication of electrode arrays. The reproducibility and electrochemical qualities of the probes were assessed along with cross talk in vitro. Heterogeneous release of electrically stimulated dopamine was observed in real-time in the striatum of an anesthetized rat using the FSCV-MEA. The heterogeneous effects of pharmacology on the striatum was also observed and shown to be consistent across multiple animals. PMID:20464031

Reutilization of the expired tetracycline for lithium ion battery anode.

PubMed

Hou, Hongying; Dai, Zhipeng; Liu, Xianxi; Yao, Yuan; Liao, Qishu; Yu, Chengyi; Li, Dongdong

2018-07-15

Waste antibiotics into the natural environment are the large challenges to the environmental protection and the human health, and the unreasonable disposal of the expired antibiotics is a major pollution source. Herein, to achieve the innocent treatment and the resource recovery, the expired tetracycline was tried to be reutilized as the electrode active material in lithium ion battery (LIB) for the first time. The micro-structure and element component of the expired tetracycline were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the corresponding electrochemical performances were also investigated by galvanostatic charge/discharge and cyclic voltammetry (CV). To be satisfactory, the expired-tetracycline-based electrode delivered the initial specific discharge capacity of 371.6mAh/g and the reversible specific capacity of 304.1mAh/g after 200cycles. The decent results will not only offer an effective strategy to recycle the expired tetracycline, but also shed a new light on the cyclic economy and the sustainable development. Copyright © 2018 Elsevier B.V. All rights reserved.

Electrochemical behavior of lead alloys in sulfuric and phosphoric acid solutions

NASA Astrophysics Data System (ADS)

Paleska, I.; Pruszkowska-Drachal, R.; Kotowski, J.; Dziudzi, A.; Milewski, J. D.; Kopczyk, M.; Czerwiński, A.

The electrochemical behavior of lead, lead-antimony, and lead-calcium-aluminium-tin alloys has been studied in solutions containing various concentrations of sulfuric and phosphoric acids. The dependence of these electrode processes on some experimental conditions (mainly sweep rate and potential range) has been studied. The measurements were performed using a cyclic voltammetry technique. The study and the analysis of the morphology of alloys have been performed using a scanning electron microscope (SEM). Cyclic voltammograms of the lead-antimony alloy electrodes, similarly to pure lead electrode, also show the "anodic excursion" peak under some experimental conditions. Well defined current waves, corresponding to the oxidation and reduction processes of Sb, are observed, if the alloy surface is freshly abraded. The oxidation of antimony starts at potentials at which the formation of PbO takes place. The peak current of Sb oxidation reaction decreases during successive cycles, suggesting that Sb dissolves from the alloy surface during the first CV sweeps. Another explanation for this effect might be the formation of a PbSO 4 selective membrane.

Improvement of amperometric transducer selectivity using nanosized phenylenediamine films

NASA Astrophysics Data System (ADS)

Soldatkina, O. V.; Kucherenko, I. S.; Pyeshkova, V. M.; Alekseev, S. A.; Soldatkin, O. O.; Dzyadevych, S. V.

2017-11-01

In this work, we studied the conditions of deposition of a semipermeable polyphenylenediamine (PPD)-based membrane on amperometric disk platinum electrodes. Restricting an access of interfering substances to the electrode surface, the membrane prevents their impact on the sensor operation. Two methods of membrane deposition by electropolymerization were compared—at varying potential (cyclic voltammetry) and at constant potential. The cyclic voltammetry was shown to be easier in performing and providing better properties of the membrane. The dependence of PPD membrane effectiveness on the number of cyclic voltammograms and phenylenediamine concentration was analyzed. It was shown that the impact of interfering substances (ascorbic acid, dopamine, cysteine, uric acid) on sensor operation could be completely avoided using three cyclic voltammograms in 30 mM phenylenediamine. On the other hand, when working with diluted samples, i.e., at lower concentrations of electroactive substances, it is reasonable to decrease the phenylenediamine concentration to 5 mM, which would result in a higher sensitivity of transducers to hydrogen peroxide due to a thinner PPD layer. The PPD membrane was tested during continuous operation and at 8-day storage and turned out to be efficient in sensor and biosensors.

New porphyrin-polyoxometalate hybrid materials: synthesis, characterization and investigation of catalytic activity in acetylation reactions.

PubMed

Araghi, Mehdi; Mirkhani, Valiollah; Moghadam, Majid; Tangestaninejad, Shahram; Mohammdpoor-Baltork, Iraj

2012-10-14

New hybrid complexes based on covalent interaction between 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatozinc(II) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatotin(IV) chloride, and a Lindqvist-type polyoxometalate, Mo(6)O(19)(2-), were prepared. These new porphyrin-polyoxometalate hybrid materials were characterized by (1)H NMR, FT IR and UV-Vis spectroscopic methods and cyclic voltammetry. These spectro- and electrochemical studies provided several spectral data for synthesis of these compounds. Cyclic voltammetry showed the influence of the polyoxometalate on the redox process of the porphyrin ring. The catalytic activity of tin(IV)porphyrin-hexamolybdate hybrid material was investigated in the acetylation of alcohols and phenols with acetic anhydride. The reusability of this catalyst was also investigated.

Electrooxidation of morin hydrate at a Pt electrode studied by cyclic voltammetry.

PubMed

Masek, Anna; Chrzescijanska, Ewa; Zaborski, Marian

2014-04-01

The process and the kinetics of the electrochemical oxidation of morin in an anhydrous electrolyte have been investigated using cyclic and differential pulse voltammetry. The oxidation mechanism proceeds in sequential steps related to the hydroxyl groups in the three aromatic rings. The oxidation of the 2',4'dihydroxy moiety at the B ring of morin occurs first, at very low positive potentials, and is a one-electron, one-proton irreversible reaction. The rate constant, electron transfer coefficient and diffusion coefficients involved in the electrochemical oxidation of morin were determined. The influence of the deprotonation of the ring B hydroxyl moiety is related to the electron/proton donating capacity of morin and to its radical scavenging antioxidant activity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Electrochemical sensing of ammonium ion at the water/1,6-dichlorohexane interface.

PubMed

Ribeiro, José A; Silva, F; Pereira, Carlos M

2012-01-15

In this work, ion transfer and facilitated ion transfer of ammonium ion by a lipophilic cyclodextrin is investigated at the water/1,6-dichlorohexane micro-interface, using electrochemical approaches (cyclic voltammetry, differential pulse voltammetry and square wave voltammetry). The association constant has been obtained for the complex between ammonium ion and the cyclodextrin. Experimental conditions for the analytical determination of ammonium ion were established and a detection limit of 0.12 μM was obtained. The amperometric sensor gave a current response proportional to the ammonium ion concentration in the range from 4.2 to 66 μM. Copyright © 2011 Elsevier B.V. All rights reserved.

One-step solvothermal synthesis of carnation flower-like SnS2 as superior electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Mishra, Rajneesh Kumar; Baek, Geun Woo; Kim, Kyuwon; Kwon, Hyuck-In; Jin, Sung Hun

2017-12-01

We report the synthesis of carnation flower-like SnS2 (CF-SnS2) via a one-step solvothermal method for potential application as supercapacitor electrodes in energy storage devices. The structural and morphological properties of CF-SnS2 were characterized by X-ray diffraction, Raman analysis, and field-emission scanning and transmission electron microscopies. X-ray photoelectron spectroscopy and scanning tunneling electron microscopy with color mapping verified the distribution of Sn and S, and depicted the successful formation of SnS2. Electrochemical studies were performed to explore the supercapacitive nature of CF-SnS2. Supercapacitors with CF-SnS2 electrodes delivered excellent cyclic voltammetry performances, superior gravimetric specific capacitances, and high power densities. The evaluated specific capacitance and power density reached ∼524.5 F/g and 12.3 W/kg, respectively, at a current density of 0.08 A/g, and ∼215.9 F/g and 61.4 W/kg, respectively, at a current density of 0.38 A/g. These values are at least two times higher than those previously reported. The long-term cyclic stability was also tested to demonstrate the endurance of the CF-SnS2-based supercapacitor, with a 66% rate retention and galvanostatic charge/discharge reversibility. These electrochemical findings indicate that CF-SnS2 is a promising candidate for electrode materials in supercapacitor applications.

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance

PubMed Central

Sagasti, Ariane; Bouropoulos, Nikolaos; Kouzoudis, Dimitris; Panagiotopoulos, Apostolos; Topoglidis, Emmanuel; Gutiérrez, Jon

2017-01-01

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H2O2 was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer’s elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H2O2 drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H2O2. The measured catalysis currents increase linearly with the H2O2 concentration in a wide range of 25–350 μM with a correlation coefficient 0.99. The detection limit is 25–50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H2O2, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H2O2 concentration with a slope of 152 ng/μM, which is probably due to H2O2 adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment when only PBS solution was present for a long time. PMID:28773209

Role of annealing duration on the microstructure and electrochemical performance of β-V2O5 thin films

NASA Astrophysics Data System (ADS)

Jeyalakshmi, K.; Muralidharan, G.

2014-03-01

Vanadium pentoxide thin films have been prepared by sol-gel spin coating method. The eight-layered films coated on fluorine-doped tin oxide substrate and glass substrate were subjected to different durations of annealing under a constant annealing temperature of 300 °C from 30 to 120 min. The X-ray diffraction spectrum reveals crystallinity along (2 0 0) direction. The SEM images of these films show the variation in the surface morphology with increase in annealing duration. The supercapacitor behaviour has been studied using cyclic voltammetry technique and electrochemical impedance spectroscopy. The film annealed for 60 min exhibits a maximum specific capacitance of 346 F/g at a scan rate of 5 mV/s with a charge transfer resistance of 172 Ω.

Polythiophene-carbon nanotubes composites as energy storage materials for supercapacitor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thakur, A. K., E-mail: anukulphyism@gmail.com; Choudhary, R. B.; Sartale, S. D.

Polythiophene incorporated carbon materials have sought huge attention due to various improved electrochemical properties including enhanced electrical conductivity. Our work includes the synthesis of polythiophene (PTP)-multi-wallcarbon nanotubes (MWCNTs) via in-situ polymerization method. The homogeneous distribution of MWCNT in PTP was confirmed by Field Emission Scanning Electron Microscope (FESEM). Examination of the specimen using X-Ray diffraction (XRD), Fourier Transform-Infrared (FTIR) and Raman spectroscopy confirmed the composite formation. Other electrochemical characterizations like electrochemical impendence spectroscopy (EIS) and cyclic voltammetry (CV)of the PTP-MWCNT composite affirmed that incorporation of MWCNT improves the electrochemical properties of neat PTP including a significant increase in the capacitance.more » Hence making PTP-MWCNT isa better material for supercapacitor application than neat PTP.« less

Ag-doped CdO nanocatalysts: Preparation, characterization and catechol oxidase activity

NASA Astrophysics Data System (ADS)

El-Kemary, Maged; El-Mehasseb, Ibrahim; El-Shamy, Hany

2018-06-01

Silver doped cadmium oxide (Ag/CdO) nanoparticles with an average size of 41 nm have been successfully synthesized via thermal decomposition and liquid impregnation technique. The structural characterization has been performed by using several spectroscopic techniques, e.g., X-ray diffraction (XRD), scanning electron microscopy (SEM) and fourier-transform infrared (FT-IR). The catechol oxidase has been studied by UV-visible absorption spectroscopy and fourier-transform infrared as well as the mechanism has been assured by cyclic voltammetry and fluorescence spectroscopy. The results indicate that the oxidation does not occur in the presence of unsupported cadmium oxide particles by silver and in the same time, the catechol oxidase activity of silver doped CdO nanoparticles were improved by about three orders of magnitude than silver ions.

Neurochemical measurements in the zebrafish brain

PubMed Central

Jones, Lauren J.; McCutcheon, James E.; Young, Andrew M. J.; Norton, William H. J.

2015-01-01

The zebrafish is an ideal model organism for behavioral genetics and neuroscience. The high conservation of genes and neurotransmitter pathways between zebrafish and other vertebrates permits the translation of research between species. Zebrafish behavior can be studied at both larval and adult stages and recent research has begun to establish zebrafish models for human disease. Fast scan cyclic voltammetry (FSCV) is an electrochemical technique that permits the detection of neurotransmitter release and reuptake. In this study we have used in vitro FSCV to measure the release of analytes in the adult zebrafish telencephalon. We compare different stimulation methods and present a characterization of neurochemical changes in the wild-type zebrafish brain. This study represents the first FSCV recordings in zebrafish, thus paving the way for neurochemical analysis of the fish brain. PMID:26441575

Protective Behavior of Poly(m-aminophenol) and Polypyrrole Coatings on Mild Steel

NASA Astrophysics Data System (ADS)

Yahaya, Sabrina M.; Harun, M. K.; Rosmamuhamadani, R.; Bonnia, N. N.; Ratim, S.

2018-01-01

Electrodeposition of polypyrrole (PPy) and poly (m-aminophenol) (PMAP) films on mild steel (MS) substrate was achieved in 0.3M oxalic acid solution and 0.3M NaOH, water:ethanol (70:30) solvent respectively using cyclic voltammetry technique. The morphology of the films constructed was determined by scanning electron microscope (SEM) while energy dispersive X-Ray analyzer (EDX) was used to establish the presence of organic PMAP and PPy film coating and its compositions. The corrosion performance of MS coated with both polymer films were investigated after 0.5 hours immersed in 0.5M NaCl aqueous solution by using polarization curves. It was found that PPy coating provides anodic protection while PMAP coating provides cathodic protection towards corrosion protection of mild steel substrate.

Characterization of an electrochemical mercury sensor using alternating current, cyclic, square wave and differential pulse voltammetry.

PubMed

Guerreiro, Gabriela V; Zaitouna, Anita J; Lai, Rebecca Y

2014-01-31

Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and Electrochemistry of Cyclopentadienylcarbonyliron Tetramer: An Advanced Experiment.

ERIC Educational Resources Information Center

White, A. J.; Cunningham, Alice J.

1980-01-01

Describes an advanced level experiment in which a transition metal cluster compound, cyclopentadienylcarbonyliron tetramer, is synthesized and characterized spectroscopically. Its redox properties are then explored through cyclic voltammetry. (CS)

Smartphone-based cyclic voltammetry system with graphene modified screen printed electrodes for glucose detection.

PubMed

Ji, Daizong; Liu, Lei; Li, Shuang; Chen, Chen; Lu, Yanli; Wu, Jiajia; Liu, Qingjun

2017-12-15

Smartphone-based electrochemical devices have such advantages as the low price, miniaturization, and obtaining the real-time data. As a popular electrochemical method, cyclic voltammetry (CV) has shown its great practicability for quantitative detection and electrodes modification. In this study, a smartphone-based CV system with a simple method of electrode modification was constructed to perform electrochemical detections. The system was composed of these main portions: modified electrodes, portable electrochemical detector and smartphone. Among them, the detector was comprised of an energy transformation module applying the stimuli signals, and a low-cost potentiostat module for CV measurements with a Bluetooth module for transmitting data and commands. With an Application (App), the smartphone was used as the controller and displayer of the system. Through controlling of different scan rates, the smartphone-based system could perform CV detections for redox couples with test errors less than 3.8% compared to that of commercial electrochemical workstation. Also, the reduced graphene oxide (rGO) and sensitive substance could be modified by the system on the screen printed electrodes for detections. As a demonstration, 3-amino phenylboronic acid (APBA) was used as the sensitive substance to fabricate a glucose sensor. Finally, the experimental data of the system were shown the linear, sensitive, and specific responses to glucose at different doses, even in blood serum as low as about 0.026mM with 3δ/slope calculation. Thus, the system could show great potentials of detection and modification of electrodes in various fields, such as public health, water monitoring, and food quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified Poisson-Nernst-Planck Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hainan; Thiele, Alexander; Pilon, Laurent

2013-11-15

This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |z i| of either ion species. By contrast, the ionmore » diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τ CV and the “RC time scale” τ RC corresponding to the characteristic time of ions’ electrodiffusion. For τ RC ← τ CV, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τ RC → τ CV, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.« less

Differential thermal voltammetry for tracking of degradation in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Billy; Yufit, Vladimir; Merla, Yu; Martinez-Botas, Ricardo F.; Brandon, Nigel P.; Offer, Gregory J.

2015-01-01

Monitoring of lithium-ion batteries is of critical importance in electric vehicle applications in order to manage the operational condition of the cells. Measurements on a vehicle often involve current, voltage and temperature which enable in-situ diagnostic techniques. This paper presents a novel diagnostic technique, termed differential thermal voltammetry, which is capable of monitoring the state of the battery using voltage and temperature measurements in galvanostatic operating modes. This tracks battery degradation through phase transitions, and the resulting entropic heat, occurring in the electrodes. Experiments to monitor battery degradation using the new technique are compared with a pseudo-2D cell model. Results show that the differential thermal voltammetry technique provides information comparable to that of slow rate cyclic voltammetry at shorter timescale and with load conditions easier to replicate in a vehicle.

An Electrochemical Experiment Using an Optically Transparent Thin Layer Electrode

ERIC Educational Resources Information Center

DeAngelis, Thomas P.; Heineman, William R.

1976-01-01

Describes a unified experiment in which an optically transparent thin layer electrode is used to illustrate the techniques of thin layer electrochemistry, cyclic voltammetry, controlled potential coulometry, and spectroelectrochemistry. (MLH)

Determination of glucose in human urine by cyclic voltammetry method using gold electrode

NASA Astrophysics Data System (ADS)

Riyanto; Supwatul Hakim, Muh.

2018-01-01

This study has been the determination of glucose in human urine by cyclic voltammetry method using gold electrode. The gold electrode was prepared using gold wire with purity 99.99%, size 1.0 mm by length and wide respectively, connected with silver wire using silver conductive paint. The effect of electrolyte, pH and glucose concentration has been determined to produce the optimum method. The research showed the KNO3 is a good electrolyte for determination of glucose in human urine using gold electrode. The effect of glucose concentration have the coefficient correlation is R2 = 0.994. The results of the recovery using addition method showed at range95-105%. As a conclusion isa gold electrode is a good electrode for electrochemical sensors to the determination of glucose in human urine.

Synthesis, characterization, structure and properties of heterobimetallic complexes [CuNi(μ-OAc) (μ-OH) (μ-OH2) (bpy)2] (BF4)2 and [CuNi(bz)3(bpy)2] ClO4 from 2,2‧ bipyridine

NASA Astrophysics Data System (ADS)

Kurbah, Sunshine D.; Kumar, A.; Syiemlieh, I.; Dey, A. K.; Lal, R. A.

2018-02-01

Heterobimetallic complexes of the composition [CuNi(bpy)2 (μ-OAc) (μ-OH) (μ-OH2)](BF4)2 (1) and [CuNi(bz)3 (bpy)2]ClO4 (2) were synthesized in moderate yield through solid state reaction and have been characterized by elemental analyses, molar conductance, mass spectra, magnetic moment, EPR, UV-Vis, IR spectroscopies and cyclic voltammetry. The ground state in complex (1) is doublet while that in complex (2), the ground state is a mixture of doublet and quartet, respectively. The structure of the complexes has been established by X-ray crystallography. The electron transfer reactions of the complexes have been investigated by cyclic voltammetry.

Electrochemical hydrogenation of thiophene on SPE electrodes

NASA Astrophysics Data System (ADS)

Huang, Haiyan; Yuan, Penghui; Yu, Ying; Chung, Keng H.

2017-01-01

Electrochemical reduction desulfurization is a promising technology for petroleum refining which is environmental friendly, low cost and able to achieve a high degree of automation. Electrochemical hydrogenation of thiophene was performed in a three-electrode system which SPE electrode was the working electrode. The electrochemical desulfurization was studied by cyclic voltammetry and bulk electrolysis with coulometry (BEC) techniques. The results of cyclic voltammetry showed that the electrochemical hydrogenation reduction reaction occurred at -0.4V. The BEC results showed that the currents generated from thiophene hydrogenation reactions increased with temperature. According to Arrhenius equation, activation energy of thiophene electrolysis was calculated and lower activation energy value indicated it was diffusion controlled reaction. From the products of electrolytic reactions, the mechanisms of electrochemical hydrogenation of thiophene were proposed, consisting of two pathways: openingring followed by hydrogenation, and hydrogenation followed by ring opening.

Role of structural H 2O in TiO 2 nanotubes in enhancing Pt/C direct ethanol fuel cell anode electro-catalysts

NASA Astrophysics Data System (ADS)

Song, Huanqiao; Qiu, Xinping; Guo, Daojun; Li, Fushen

TiO 2 nanotubes (TNTs) with different structural water were obtained by heat treatment under different temperatures. The role of the structural water in TNTs co-catalyzing ethanol oxidation with Pt/C catalyst was studied systematically. Electrochemical studies using cyclic voltammetry and CO stripping voltammetry indicated that more structural water in TNTs was favorable for improving the tolerance of Pt/C to poisoning species; while chronoamperometry curves and repeated cyclic voltammograms showed that slightly less structural water in TNTs actually led to higher catalytic activity and better stability of Pt/C catalysts for ethanol oxidation. This strange result has been analyzed and was ascribed to the appropriate balance of bi-functional mechanism and ethanol transfer in the catalyst layer with less structural water.

Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Rui-Tao, E-mail: Ruitao.Wen@angstrom.uu.se; Granqvist, Claes G.; Niklasson, Gunnar A.

2014-10-20

Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li{sup +} ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO{sub 4} in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 10{sup 4} cycles when the applied voltage was limited to 4.1 V vs Li/Li{sup +}. Our results allow lifetime assessments for one of themore » essential components in an electrochromic device such as a “smart window” for energy-efficient buildings.« less

Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry

PubMed Central

Pisoschi, Aurelia Magdalena; Danet, Andrei Florin; Kalinowski, Slawomir

2008-01-01

A method was developed for assessing ascorbic acid concentration in commercial fruit juice by cyclic voltammetry. The anodic oxidation peak for ascorbic acid occurs at about 490 mV on a Pt disc working electrode (versus SCE). The influence of the potential sweep speed on the peak height was studied. The obtained calibration graph shows a linear dependence between peak height and ascorbic acid concentration in the domain (0.1–10 mmol·L−1). The equation of the calibration graph was y = 6.391x + 0.1903 (where y represents the value of intensity measured for the anodic peak height, expressed as μA and x the analyte concentration, as mmol·L−1, r2 = 0.9995, r.s.d. = 1.14%, n = 10, Cascorbic acid = 2 mmol·L−1). The developed method was applied to ascorbic acid assessment in fruit juice. The ascorbic acid content determined ranged from 0.83 to 1.67 mmol·L−1 for orange juice, from 0.58 to 1.93 mmol·L−1 for lemon juice, and from 0.46 to 1.84 mmol·L−1 for grapefruit juice. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.35% and 104%. Ascorbic acid determination results obtained by cyclic voltammetry were compared with those obtained by the volumetric method with dichlorophenol indophenol. The results obtained by the two methods were in good agreement. PMID:19343183

Preparation of Binary and Ternary Oxides by Molten Salt Method and its Electrochemical Properties

NASA Astrophysics Data System (ADS)

Reddy, M. V.; Theng, L. Pei; Soh, Hulbert; Beichen, Z.; Jiahuan, F.; Yu, C.; Ling, A. Yen; Andreea, L. Y.; Ng, C. H. Justin; Liang, T. J. L. Galen; Ian, M. F.; An, H. V. T.; Ramanathan, K.; Kevin, C. W. J.; Daryl, T. Y. W.; Hao, T. Yi; Loh, K. P.; Chowdari, B. V. R.

2013-07-01

We report simple binary oxides namely SnO2, TiO2, CuO, MnO2, Fe2O3, Co3O4 and ternary oxides like MnCo2O4 by molten salt method at a temperature range of 280°C to 950°C in air and discuss the effect of morphology, crystal structure and electrochemical properties of binary and ternary oxides. Materials were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods. XRD patterns showed all MSM prepared materials exhibited characteristic lattice parameter values. BET surface area varies depending on the nature of the material, molten salt and preparation temperature and the obtained values are in the range, 1 to 160 m2/g. Electrochemical properties were studied using cyclic voltammetry (CV) and electrochemical performance studies were carried in the voltage range, 0.005-1.0V for SnO2, 1.0-2.8V for TiO2 and Fe2O3, MCo2O4 (M = Co, Mn), MnO2 and CuO were cycled in the range, 0.005-3.0V. At a current rates of 30-100 mA/g and a scan rate of 0.058 mV/sec was used for galvanostatic cycling and cyclic voltammetry. SnO2 showed that an alloying-de-alloying reaction occurs at ˜0.2 and ˜0.5 V vs. Li. TiO2 main intercalation and de-interaction reactions at ˜1.7 and ˜1.8 V vs. Li. Co3O4, MnCo2O4, and MnO2 main discharge potentials at ˜1.2, 0.9V and 0.4V, resp. and charge potentials peak ˜2.0V and 1.5V vs. Li. CuO prepared at 750°C exhibited main anodic peak at ˜2.45V and cathodic peaks at ˜0.85V and ˜1.25V. We discussed the possible reaction mechanisms and Li-storage performance values in detail.

Microbial biosensor for detection of methyl parathion using screen printed carbon electrode and cyclic voltammetry.

PubMed

Kumar, Jitendra; D'Souza, S F

2011-07-15

Whole cells of recombinant Escherichia coli were immobilized on the screen printed carbon electrode (SPCE) using glutaraldehyde. Recombinant E. coli was having high periplasmic expression of organophosphorus hydrolase enzyme, which hydrolyzes the methyl parathion into two products, p-nitrophenol and dimethyl thiophosphoric acid. Cells immobilized SPCE was studied under SEM. Cells immobilized SPCE was associated with cyclic voltammetry and cyclic voltammograms were recorded before and after hydrolysis of methyl parathion. Detection was calibrated based on the relationship between the changes in the current observed at +0.1 V potential, because of redox behavior of the hydrolyzed product p-nitrophenol. As concentration of methyl parathion was increased the oxidation current also increased. Only 20 μl volume of the sample was required for analysis. Detection range of biosensor was calibrated between 2 and 80 μM of methyl parathion from the linear range of calibration plot. A single immobilized SPCE was reused for 32 reactions with retention of 80% of its initial enzyme activity. Copyright © 2011 Elsevier B.V. All rights reserved.

Anodic Oxidation of Etodolac and its Linear Sweep, Square Wave and Differential Pulse Voltammetric Determination in Pharmaceuticals

PubMed Central

Yilmaz, B.; Kaban, S.; Akcay, B. K.

2015-01-01

In this study, simple, fast and reliable cyclic voltammetry, linear sweep voltammetry, square wave voltammetry and differential pulse voltammetry methods were developed and validated for determination of etodolac in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of etodolac at platinum electrode in acetonitrile solution containing 0.1 M lithium perchlorate. The well-defined oxidation peak was observed at 1.03 V. The calibration curves were linear for etodolac at the concentration range of 2.5-50 μg/ml for linear sweep, square wave and differential pulse voltammetry methods, respectively. Intra- and inter-day precision values for etodolac were less than 4.69, and accuracy (relative error) was better than 2.00%. The mean recovery of etodolac was 100.6% for pharmaceutical preparations. No interference was found from three tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Etol, Tadolak and Etodin tablets as pharmaceutical preparation. PMID:26664057

Microelectrode voltammetry of multi-electron transfers complicated by coupled chemical equilibria: a general theory for the extended square scheme.

PubMed

Laborda, Eduardo; Gómez-Gil, José María; Molina, Angela

2017-06-28

A very general and simple theoretical solution is presented for the current-potential-time response of reversible multi-electron transfer processes complicated by homogeneous chemical equilibria (the so-called extended square scheme). The expressions presented here are applicable regardless of the number of electrons transferred and coupled chemical processes, and they are particularized for a wide variety of microelectrode geometries. The voltammetric response of very different systems presenting multi-electron transfers is considered for the most widely-used techniques (namely, cyclic voltammetry, square wave voltammetry, differential pulse voltammetry and steady state voltammetry), studying the influence of the microelectrode geometry and the number and thermodynamics of the (electro)chemical steps. Most appropriate techniques and procedures for the determination of the 'interaction' between successive transfers are discussed. Special attention is paid to those situations where homogeneous chemical processes, such as protonation, complexation or ion association, affect the electrochemical behaviour of the system by different stabilization of the oxidation states.

Simultaneous noncontact topography and electrochemical imaging by SECM/SICM featuring ion current feedback regulation.

PubMed

Takahashi, Yasufumi; Shevchuk, Andrew I; Novak, Pavel; Murakami, Yumi; Shiku, Hitoshi; Korchev, Yuri E; Matsue, Tomokazu

2010-07-28

We described a hybrid system of scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) with ion current feedback nanopositioning control for simultaneous imaging of noncontact topography and spatial distribution of electrochemical species. A nanopipette/nanoring electrode probe provided submicrometer resolution of the electrochemical measurement on surfaces with complex topology. The SECM/SICM probe had an aperture radius of 220 nm. The inner and outer radii of the SECM Au nanoring electrode were 330 and 550 nm, respectively. Characterization of the probe was performed with scanning electron microscopy (SEM), cyclic voltammetry (CV), and approach curve measurements. SECM/SICM was applied to simultaneous imaging of topography and electrochemical responses of enzymes (horse radish peroxidase (HRP) and glucose oxidase (GOD)) and single live cells (A6 cells, superior cervical ganglion (SCG) cells, and cardiac myocytes). The measurements revealed the distribution of activity of the enzyme spots on uneven surfaces with submicrometer resolution. SECM/SICM acquired high resolution topographic images of cells together with the map of electrochemical signals. This combined technique was also applied to the evaluation of the permeation property of electroactive species through cellular membranes.

Carbon-polyaniline nanocomposites as supercapacitor materials

NASA Astrophysics Data System (ADS)

Sathish Kumar, M.; Yamini Yasoda, K.; Batabyal, Sudip Kumar; Kothurkar, Nikhil K.

2018-04-01

Polyaniline-based nanocomposites containing carbon nanotubes (CNT), reduced graphene oxide (rGO) and mixture of CNTs and rGO were synthesized. UV-visible spectroscopy and FT-IR spectroscopy confirmed the presence of polyaniline (PANi) and carbon nanomaterials. Scanning electron microscopy revealed that the neat PANi had a granular morphology, which can lead to increased electrical resistance to high interfacial resistance between domains of PANi. Cyclic voltammetry of PANi, PANi/CNT, PANi/rGO and PANi/CNT/rGO showed that in general, specific capacitance reduces with increasing scan rate within the range (10–100 mV s‑1). Also the specific capacitance values at any given scan rate within the above range, for PANi, PANi/CNT, PANi/rGO and PANi/CNT/rGO were found to be in increasing order. The specific capacitance of the PANi/CNT/rGO nanocomposite as measured by galvanostatic charge-discharge measurements, was found to be 312.5 F g‑1. The introduction of the carbon nanomaterials (CNTs, rGO) in PANi in general leads to improved specific capacitance, while the addition of CNTs and rGO together leads to synergistic improvement in the specific capacitance, owing to a combination of factors.

Nanoporous carbon derived from agro-waste pineapple leaves for supercapacitor electrode

NASA Astrophysics Data System (ADS)

Sodtipinta, Jedsada; Amornsakchai, Taweechai; Pakawatpanurut, Pasit

2017-09-01

By using KOH as the chemical activating agent in the synthesis, the activated carbon derived from pineapple leaf fiber (PALF) was prepared. The structure, morphology, and the surface functional groups of the as-prepared activated carbon were investigated using x-ray diffraction, field emission scanning electron microscope equipped with energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The electrochemical behavior and performance of the as-synthesized activated carbon electrode were measured using the cyclic voltammetry and the electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte solution in three-electrode setup. The activated carbon electrode exhibited the specific capacitance of 131.3 F g-1 at a scan rate of 5 mV s-1 with excellent cycling stability. The capacitance retention after 1000 cycles was about 97% of the initial capacitance at a scan rate of 30 mV s-1. Given these good electrochemical properties along with the high abundance of PALF, this activated carbon electrode has the potential to be one of the materials for future large-scale production of the electrochemical capacitors. Invited talk at 5th Thailand International Nanotechnology Conference (Nano Thailand-2016), 27-29 November 2016, Nakhon Ratchasima, Thailand.

Poly(malachite green) at nafion doped multi-walled carbon nanotube composite film for simple aliphatic alcohols sensor.

PubMed

Umasankar, Yogeswaran; Periasamy, Arun Prakash; Chen, Shen-Ming

2010-01-15

Conductive composite film which contains nafion (NF) doped multi-walled carbon nanotubes (MWCNTs) along with the incorporation of poly(malachite green) (PMG) has been synthesized on glassy carbon electrode (GCE), gold and indium tin oxide (ITO) electrodes by potentiostatic methods. The presence of MWCNTs in the composite film (MWCNTs-NF-PMG) enhances surface coverage concentration (Gamma) of PMG to approximately 396%, and increases the electron transfer rate constant (k(s)) to approximately 305%. Similarly, electrochemical quartz crystal microbalance study reveals the enhancement in the deposition of PMG at MWCNTs-NF film. The surface morphology of the composite film deposited on ITO electrode has been studied using scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). These two techniques reveal that the PMG incorporated on MWCNTs-NF film. The MWCNTs-NF-PMG composite film also exhibits promising enhanced electrocatalytic activity towards the simple aliphatic alcohols such as methanol, ethanol and propanol. The electroanalytical responses of analytes at NF-PMG and MWCNTs-NF-PMG films were measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). From electroanalytical studies, well defined voltammetric peaks have been obtained at MWCNTs-NF-PMG composite film for methanol, ethanol and propanol at Epa=609, 614 and 602mV respectively. The sensitivity of MWCNTs-NF-PMG composite film towards methanol, ethanol and propanol in CV technique are 0.59, 0.36 and 0.92microAmM(-1)cm(-2) respectively, which are higher than NF-PMG film. Further, the sensitivity values obtained using DPV are higher than the values obtained using CV technique.

Application of fast-scan cyclic voltammetry for the in vivo characterization of optically evoked dopamine in the olfactory tubercle of the rat brain.

PubMed

Wakabayashi, Ken T; Bruno, Michael J; Bass, Caroline E; Park, Jinwoo

2016-06-21

The olfactory tubercle (OT), as a component of the ventral striatum, serves as an important multisensory integration center for reward-related processes in the brain. Recent studies show that dense dopaminergic innervation from the ventral tegmental area (VTA) into the OT may play an outsized role in disorders such as psychostimulant addiction and disorders of motivation, increasing recent scientific interest in this brain region. However, due to its anatomical inaccessibility, relative small size, and proximity to other dopamine-rich structures, neurochemical assessments using conventional methods cannot be readily employed. Here, we investigated dopamine (DA) regulation in the OT of urethane-anesthetized rats using in vivo fast-scan voltammetry (FSCV) coupled with carbon-fiber microelectrodes, following optogenetic stimulation of the VTA. The results were compared with DA regulation in the nucleus accumbens (NAc), a structure located adjacent to the OT and which also receives dense DA innervation from the VTA. FSCV coupled with optically evoked release allowed us to investigate the spatial distribution of DA in the OT and characterize OT DA dynamics (release and clearance) with subsecond temporal and micrometer spatial resolution for the first time. In this study, we demonstrated that DA transporters play an important role in regulating DA in the OT. However, the control of extracellular DA by uptake in the OT was less than in the NAc. The difference in DA transmission in the terminal fields of the OT and NAc may be involved in region-specific responses to drugs of abuse and contrasting roles in mediating reward-related behavior.

Early detection of Candida albicans biofilms at porous electrodes.

PubMed

Congdon, Robert B; Feldberg, Alexander S; Ben-Yakar, Natalie; McGee, Dennis; Ober, Christopher; Sammakia, Bahgat; Sadik, Omowunmi A

2013-02-15

We describe the development of an electrochemical sensor for early detection of biofilm using Candida albicans. The electrochemical sensor used the ability of biofilms to accept electrons from redox mediators relative to the number of metabolically active cells present. Cyclic voltammetry and differential pulse voltammetry techniques were used to monitor the redox reaction of K(3)Fe(CN)(6) at porous reticulated vitreous carbon (RVC) (238.7 cm(2)) working electrodes versus Ag/AgCl reference. A shift in the peak potential occurred after 12 h of film growth, which is attributed to the presence of C. albicans. Moreover, the intensity of the ferricyanide reduction peak first increased as C. albicans deposited onto the porous electrodes at various growth times. The peak current subsequently decreased at extended periods of growth of 48 h. The reduction in peak current was attributed to the biofilm reaching its maximum growth thickness, which correlated with the maximum number of metabolically active cells. The observed diffusion coefficients for the bare RVC and biofilm-coated electrodes were 2.2 × 10(-3) and 7.0 × 10(-6) cm(2)/s, respectively. The increase in diffusivity from the bare electrode to the biofilm-coated electrode indicated some enhancement of electron transfer mediated by the biofilm to the porous electrode. Verification of the growth of biofilm was achieved using scanning electron microcopy and laser scanning confocal imaging microscopy. Validation with conventional plating techniques confirmed that the correlation (R(2) = 0.9392) could be achieved between the electrochemical sensors data and colony-forming units. Copyright © 2012 Elsevier Inc. All rights reserved.

Demon voltammetry and analysis software: Analysis of cocaine-induced alterations in dopamine signaling using multiple kinetic measures

PubMed Central

Yorgason, Jordan T.; España, Rodrigo A.; Jones, Sara R.

2011-01-01

The fast sampling rates of fast scan cyclic voltammetry make it a favorable method for measuring changes in brain monoamine release and uptake kinetics in slice, anesthetized, and freely moving preparations. The most common analysis technique for evaluating changes in dopamine signaling uses well-established Michaelis-Menten kinetic methods that can accurately model dopamine release and uptake parameters across multiple experimental conditions. Nevertheless, over the years, many researchers have turned to other measures to estimate changes in dopamine release and uptake, yet to our knowledge no systematic comparison amongst these measures has been conducted. To address this lack of uniformity in kinetic analyses, we have created the Demon Voltammetry and Analysis software suite, which is freely available to academic and non-profit institutions. Here we present an explanation of the Demon Acquisition and Analysis features, and demonstrate its utility for acquiring voltammetric data under in vitro, in vivo anesthetized, and freely moving conditions. Additionally, the software was used to compare the sensitivity of multiple kinetic measures of release and uptake to cocaine-induced changes in electrically evoked dopamine efflux in nucleus accumbens core slices. Specifically, we examined and compared tau, full width at half height, half-life, T20, T80, slope, peak height, calibrated peak dopamine concentration, and area under the curve to the well-characterized Michaelis-Menten parameters, dopamine per pulse, maximal uptake rate, and apparent affinity. Based on observed results we recommend tau for measuring dopamine uptake and calibrated peak dopamine concentration for measuring dopamine release. PMID:21392532

Effect of lithium and sodium salt on the performance of Nb2O5/rGO nanocomposite based supercapacitor

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Rafat, M.

2018-03-01

The present work reports the synthesis of Nb2O5/rGO composite using hydrothermal method and thermal annealing process. The prepared composite was found to have suitable characteristics necessary to be used as electrode material in supercapacitors. These characteristics were ascertained employing the techniques of scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy and N2 adsorption-desorption isotherm. Further, the electrochemical performance of the prepared composite was compared in two different organic electrolytes, of lithium and sodium salt using the techniques of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge-discharge measurements. The organic electrolyte solutions were prepared by dispersing 1 M LiClO4/NaClO4 in a mixture of ethylene carbonate/propylene carbonate (1:1 by volume). The observed results indicate that the composite of Nb2O5/rGO offers higher value of specific capacitance in sodium salt electrolyte and higher cyclic stability in lithium salt electrolyte. This is probably due to ion properties of electrolyte. Specific capacitance is observed according to efficient ion/charge diffusion/exchange and relaxation time (Li+ < Na+), while the cyclic stability is observed according to cation size (Na+ > Li+). Thus, the present study reveals the significant effect of electrolyte ions on electrochemical performance of Nb2O5/rGO composite.

Hydrothermal synthesis of NiCo2O4 nanowires/nitrogen-doped graphene for high-performance supercapacitor

NASA Astrophysics Data System (ADS)

Yu, Mei; Chen, Jianpeng; Ma, Yuxiao; Zhang, Jingdan; Liu, Jianhua; Li, Songmei; An, Junwei

2014-09-01

NiCo2O4 nanowires/nitrogen-doped graphene (NCO/NG) composite materials were synthesized by hydrothermal treatment in a water-glycerol mixed solvent and subsequent thermal transformation. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The electrochemical performance of the composites was evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrum techniques. NiCo2O4 nanowires are densely coated by nitrogen-doped graphene and the composite displays good electrochemical performance. The maximum specific capacitance of NCO/NG is 1273.13 F g-1 at 0.5 A g-1 in 6 M KOH aqueous solution, and it exhibits good capacity retention without noticeable degradation after 3000 cycles at 4 A g-1.

Voltammetric Determination of Ferulic Acid Using Polypyrrole-Multiwalled Carbon Nanotubes Modified Electrode with Sample Application

PubMed Central

Abdel-Hamid, Refat; Newair, Emad F.

2015-01-01

A polypyrrole-multiwalled carbon nanotubes modified glassy carbon electrode-based sensor was devised for determination of ferulic acid (FA). The fabricated sensor was prepared electrochemically using cyclic voltammetry (CV) and characterized using CV and scanning electron microscope (SEM). The electrode shows an excellent electrochemical catalytic activity towards FA oxidation. Under optimal conditions, the anodic peak current correlates linearly to the FA concentration throughout the range of 3.32 × 10−6 to 2.59 × 10−5 M with a detection limit of 1.17 × 10−6 M (S/N = 3). The prepared sensor is highly selective towards ferulic acid without the interference of ascorbic acid. The sensor applicability was tested for total content determination of FA in a commercial popcorn sample and showed a robust functionality. PMID:28347090

A combined electrocoagulation-sorption process applied to mixed industrial wastewater.

PubMed

Linares-Hernández, Ivonne; Barrera-Díaz, Carlos; Roa-Morales, Gabriela; Bilyeu, Bryan; Ureña-Núñez, Fernando

2007-06-01

The removal of organic pollutants from a highly complex industrial wastewater by a aluminium electrocoagulation process coupled with biosorption was evaluated. Under optimal conditions of pH 8 and 45.45 Am(-2) current density, the electrochemical method yields a very effective reduction of all organic pollutants, this reduction was enhanced when the biosorption treatment was applied as a polishing step. Treatment reduced chemical oxygen demand (COD) by 84%, biochemical oxygen demand (BOD(5)) by 78%, color by 97%, turbidity by 98% and fecal coliforms by 99%. The chemical species formed in aqueous solution were determined. The initial and final pollutant levels in the wastewater were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the biosorbent was characterized with scanning electron microscopy (SEM) and energy dispersion spectra (EDS).

Facile synthesis of graphene-wrapped honeycomb MnO2 nanospheres and their application in supercapacitors.

PubMed

Zhu, Jiayi; He, Junhui

2012-03-01

Graphene-wrapped MnO(2) nanocomposites were first fabricated by coassembly between honeycomb MnO(2) nanospheres and graphene sheets via electrostatic interaction. The materials were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and thermogravimetric analysis. The novel MnO(2)/graphene hybrid materials were used for investigation of electrochemical capacitive behaviors. The hybrid materials displayed enhanced capacitive performance (210 F/g at 0.5 A/g). Additionally, over 82.4% of the initial capacitance was retained after repeating the cyclic voltammetry test for 1000 cycles. The improved electrochemical performance might be attributed to the combination of the pesudocapacitance of MnO(2) nanospheres with the honeycomb-like "opened" structure and good electrical conductivity of graphene sheets. © 2012 American Chemical Society

Highly sensitive and selective electrochemical dopamine sensing properties of multilayer graphene nanobelts

NASA Astrophysics Data System (ADS)

Karthick Kannan, Padmanathan; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

2016-02-01

In the present study, we report the electrochemical sensing property of multi-layer graphene nanobelts (GNBs) towards dopamine (DA). GNBs are synthesized from natural graphite and characterized by using techniques like field-emission scanning electron microscopy, atomic force microscopy and Raman spectroscopy. An electrochemical sensor based on GNBs is developed for the detection of DA. From the cyclic voltammetry and amperometry studies, it is found that GNBs possess excellent electrocatalytic activity towards DA molecules. The developed DA sensor showed a sensitivity value of 0.95 μA μM-1 cm-2 with a linear range of 2 μM to 0.2 mM. The interference data exhibited that GNB is highly selective to DA even in the presence of common interfering species like ascorbic acid, uric acid, glucose and lactic acid.

Highly sensitive and selective electrochemical dopamine sensing properties of multilayer graphene nanobelts.

PubMed

Kannan, Padmanathan Karthick; Moshkalev, Stanislav A; Rout, Chandra Sekhar

2016-02-19

In the present study, we report the electrochemical sensing property of multi-layer graphene nanobelts (GNBs) towards dopamine (DA). GNBs are synthesized from natural graphite and characterized by using techniques like field-emission scanning electron microscopy, atomic force microscopy and Raman spectroscopy. An electrochemical sensor based on GNBs is developed for the detection of DA. From the cyclic voltammetry and amperometry studies, it is found that GNBs possess excellent electrocatalytic activity towards DA molecules. The developed DA sensor showed a sensitivity value of 0.95 μA μM(-1) cm(-2) with a linear range of 2 μM to 0.2 mM. The interference data exhibited that GNB is highly selective to DA even in the presence of common interfering species like ascorbic acid, uric acid, glucose and lactic acid.

Covalent Modification of Highly Ordered Pyrolytic Graphite with a Stable Organic Free Radical by Using Diazonium Chemistry.

PubMed

Seber, Gonca; Rudnev, Alexander V; Droghetti, Andrea; Rungger, Ivan; Veciana, Jaume; Mas-Torrent, Marta; Rovira, Concepció; Crivillers, Núria

2017-01-26

A novel, persistent, electrochemically active perchlorinated triphenylmethyl (PTM) radical with a diazonium functionality has been covalently attached to highly ordered pyrolytic graphite (HOPG) by electrografting in a single-step process. Electrochemical scanning tunneling microscopy (EC-STM) and Raman spectroscopy measurements revealed that PTM molecules had a higher tendency to covalently react at the HOPG step edges. The cross-section profiles from EC-STM images showed that there was current enhancement at the functionalized areas, which could be explained by redox-mediated electron tunneling through surface-confined redox-active molecules. Cyclic voltammetry clearly demonstrated that the intrinsic properties of the organic radical were preserved upon grafting and DFT calculations also revealed that the magnetic character of the PTM radical was preserved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical Detection of Nicotine Using Cerium Nanoparticles Modified Carbon Paste Sensor and Anionic Surfactant

NASA Astrophysics Data System (ADS)

Fekry, A. M.; Azab, S. M.; Shehata, M.; Ameer, M. A.

A promising electrochemical sensor for the determination of nicotine (NIC) was developed by electrodeposition of Ce-Nanoparticles on a carbon paste electrode (CPE). The interaction of nicotine was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Scanning electron microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) techniques, in both aqueous and micellar media. The NIC Measurements were carried out in Britton-Robinson (B-R) buffer solution of pH range (2.0-8.0) containing (1.0 mM) sodium dodecylsulfate (SDS). The linear response range of the sensor was between 8 × 10-6 and 10-4 M with a detection limit of 9.43 × 10-8 M. Satisfactory results were achieved for the detection of NIC in real samples as urine and different brands of commercial cigarettes.

Spray pyrolytic deposition of α-MoO3 film and its use in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Tamboli, Parvin S.; Jagtap, Chaitali V.; Kadam, Vishal S.; Ingle, Ravi V.; Vhatkar, Rajiv S.; Mahajan, Smita S.; Pathan, Habib M.

2018-04-01

Thermal decomposition of ammonium para molybdate tetrahydrate precursor has been studied to determine degradation temperatures in air atmosphere. Current work explores the synthesis of α-MoO3 films by an economical spray pyrolysis technique using ammonium para molybdate tetrahydrate precursor in the presence of compressed air. A variety of characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared, and Raman spectroscopy were carried out, and the studies have confirmed that orthorhombic phase formation of MoO3 takes place with spongy mesh-type structure. The study of electro-catalytic activity of α-MoO3 in titania-based dye-sensitized solar cell is also carried out by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel curves to evaluate its performance as a counter electrode.

Simple and fast method for fabrication of endoscopic implantable sensor arrays.

PubMed

Tahirbegi, I Bogachan; Alvira, Margarita; Mir, Mònica; Samitier, Josep

2014-06-26

Here we have developed a simple method for the fabrication of disposable implantable all-solid-state ion-selective electrodes (ISE) in an array format without using complex fabrication equipment or clean room facilities. The electrodes were designed in a needle shape instead of planar electrodes for a full contact with the tissue. The needle-shape platform comprises 12 metallic pins which were functionalized with conductive inks and ISE membranes. The modified microelectrodes were characterized with cyclic voltammetry, scanning electron microscope (SEM), and optical interferometry. The surface area and roughness factor of each microelectrode were determined and reproducible values were obtained for all the microelectrodes on the array. In this work, the microelectrodes were modified with membranes for the detection of pH and nitrate ions to prove the reliability of the fabricated sensor array platform adapted to an endoscope.

Direct electrochemistry and electrocatalytic behavior of hemoglobin entrapped in Ag@C nanocables/gold nanoparticles nanocomposites film.

PubMed

Hu, Xiao-Wei; Mao, Chang-Jie; Song, Ji-Ming; Niu, He-Lin; Zhang, Sheng-Yi; Cui, Rong-Jing

2012-10-01

Direct electrochemistry of hemoglobin (Hb) was successfully fabricated by immobilizing Hb on the nanocomposites containing of Ag@C nanocables and Au nanoparticles (AuNPs) modified glassy carbon electrode (GCE). The immobilized Hb retained its biological activity and shown high catalytic activities to the reduction of H2O2 by circular dicroism (CD) spectrum, fourier transform infrared (FT-IR) spectrum and cyclic voltammetry (CV). Experimental conditions such as scan rate and pH Value were studied and optimized. The results indicated that the resulting biosensor are linear to the concentrations of H2O2 in the ranges of 6.67 x 10(-7)-2.40 x 10(5) M, and the detection limit is 2.02 x 10(-7) M. The electrochemical biosensor has also high stability and good reproducibility.

Formation of hybrid nanocomposites polymethylolacrylamide/silver

NASA Astrophysics Data System (ADS)

Kolzunova, L. G.; Shchitovskaya, E. V.; Rodzik, I. G.

2018-05-01

In this study, polymethylolacrylamide/silver composites have been formed by incorporating silver nanoparticles into the pre-electrosynthesized polymer film. The composites were formed in a two-step process involving the sorption of silver nitrate by a polymer matrix followed by chemical reduction of Ag-ions. The presence of crystalline silver phase in the polymer was confirmed by X-ray phase analysis (XRD), plasmon resonance and scanning electron microscopy (SEM). The small-angle X-ray scattering (SAXS) method has obtained the distribution functions of silver particles over radii. It is established that the content of silver in composites without chitosan is 10-15 times higher than with its additive. The dependences of cyclic voltammetry in pure phosphate buffer (pH 6.86) and in the presence of hydrogen peroxide were obtained. It has been shown that polymer/silver composites exhibit selectivity to hydrogen peroxide.

Chitosan coated carbon fiber microelectrode for selective in vivo detection of neurotransmitters in live zebrafish embryos

PubMed Central

Özel, Rıfat Emrah; Wallace, Kenneth N.; Andreescu, Silvana

2011-01-01

We report the development of a chitosan modified carbon fiber microelectrode for in vivo detection of serotonin. We find that chitosan has the ability to reject physiological levels of ascorbic acid interferences and facilitate selective and sensitive detection of in vivo levels of serotonin, a common catecholamine neurotransmitter. Presence of chitosan on the microelectrode surface was investigated using scanning electron microscopy (SEM) and cyclic voltammetry (CV). The electrode was characterized using differential pulse voltammetry (DPV). A detection limit of 1.6 nM serotonin with a sensitivity of 5.12 nA/µM, a linear range from 2 to 100 nM and a reproducibility of 6.5 % for n=6 electrodes were obtained. Chitosan modified microelectrodes selectively measure serotonin in presence of physiological levels of ascorbic acid. In vivo measurements were performed to measure concentration of serotonin in the live embryonic zebrafish intestine. The sensor quantifies in vivo intestinal levels of serotonin while successfully rejecting ascorbic acid interferences. We demonstrate that chitosan can be used as an effective coating to reject ascorbic acid interferences at carbon fiber microelectrodes, as an alternative to Nafion, and that chitosan modified microelectrodes are reliable tools for in vivo monitoring of changes in neurotransmitter levels. PMID:21601035

Sensitive, selective, disposable electrochemical dopamine sensor based on PEDOT-modified laser scribed graphene.

PubMed

Xu, Guangyuan; Jarjes, Zahraa A; Desprez, Valentin; Kilmartin, Paul A; Travas-Sejdic, Jadranka

2018-06-01

The fabrication of a novel, and highly selective electrochemical sensor based on a poly(3,4-ethylenedioxythiophene) (PEDOT) modified laser scribed graphene (LSG), and detection of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA) is described. LSG electrodes were produced with a 3-dimensional macro-porous network and large electrochemically-active surface area via direct laser writing on polyimide sheets. PEDOT was electrodeposited on the LSG electrode, and the physical properties of the obtained films were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray diffraction microanalysis (EDAX). The modified electrodes were applied for the determination of DA in the presence of AA and UA using cyclic voltammetry (CV), and differential pulse voltammetry (DPV) techniques. The linear range for dopamine detection was found to be 1-150 µM with a sensitivity of 0.220 ± 0.011 µA μM -1 and a detection limit of 0.33 µM; superior values to those obtained without PEDOT. For the first time, PEDOT-modified LSG have been fabricated and assessed for high-performance dopamine sensing using cost-effective, disposable electrodes, with potential for development in further sensing applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Nano-TiO₂ modified carbon paste sensor for electrochemical nicotine detection using anionic surfactant.

PubMed

Shehata, M; Azab, S M; Fekry, A M; Ameer, M A

2016-05-15

A newly competitive electrochemical sensor for nicotine (NIC) detection was successfully achieved. Nano-TiO2 with a carbon paste electrode (CPE) were used for the sensor construction, where Nano-TiO2 was considered as one of the richest and highly variable class of materials. The sensor showed electrocatalytic activity in both aqueous and micellar media toward the oxidation of NIC at Britton-Robinson (B-R) buffer solution (4×10(-2)M) of pH range (2.0-8.0) containing (1.0mM) sodium dodecylsulfate (SDS) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) techniques were also used. The linear range of detection for NIC using the new Nano-TiO2 Modified Carbon Paste sensor (NTMCP) was detected using diffrential pulse voltammetry (DPV) technique and it was found between 2×10(-6)M and 5.4×10(-4)M with a detection limit of 1.34×10(-8)M. The obtained results clarified the simplicity, high sensitivity and selectivity of the new NTMCPE for nicotine determination in real cigarettes and urine samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Nanostructured NiO-based reagentless biosensor for total cholesterol and low density lipoprotein detection.

PubMed

Kaur, Gurpreet; Tomar, Monika; Gupta, Vinay

2017-03-01

Nanostructured nickel oxide (NiO) thin film has been explored as a matrix to develop a reagentless biosensor for free and total cholesterol as well as low density lipoprotein (LDL) detection. The redox property of the matrix has been exploited to enhance the electron transfer between the enzyme and the electrode as well as to eliminate the toxic mediator in solution. X-ray diffraction, scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy were carried out to characterize the NiO thin film. Biosensing response studies were accomplished using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The developed biosensors exhibited a high sensitivity of 27 and 63 μA/mM/cm 2 over a linear range of 0.12-10.23 and 1-12 mM, respectively, for free and total cholesterol. Reagentless estimation of LDL was also achieved over the wide range 0.018-0.5 μM with a sensitivity of 0.12 mA/μM/cm 2 . The results are extremely promising for the realization of an integrated biosensor for complete detection of cholesterol in the serum samples. Graphical Abstract Reagentless sensing mechanism of (a) free cholesterol and (b) total cholesterol using nanostructured NiO matrix.

Electrochemical reduction of nalidixic acid at glassy carbon electrode modified with multi-walled carbon nanotubes.

PubMed

Patiño, Yolanda; Pilehvar, Sanaz; Díaz, Eva; Ordóñez, Salvador; De Wael, Karolien

2017-02-05

The aqueous phase electrochemical degradation of nalidixic acid (NAL) is studied in this work, using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) as instrumental techniques. The promotional effect of multi-walled carbon nanotubes (MWCNT) on the performance of glassy carbon electrodes is demonstrated, being observed that these materials catalyze the NAL reduction. The effect of surface functional groups on MWCNT -MWCNT-COOH and MWCNT-NH 2 -was also studied. The modification of glassy carbon electrode (GCE) with MWCNT leads to an improved performance for NAL reduction following the order of MWCNT>MWCNT-NH 2 >MWCNT-COOH. The best behavior at MWCNT-GCE is mainly due to both the increased electrode active area and the enhanced MWCNT adsorption properties. The NAL degradation was carried out under optimal conditions (pH=5.0, deposition time=20s and volume of MWCNT=10μL) using MWCNT-GCE obtaining an irreversible reduction of NAL to less toxic products. Paramaters as the number of DPV cycles and the volume/area (V/A) ratio were optimized for maximize pollutant degradation. It was observed that after 15 DPV scans and V/A=8, a complete reduction was obtained, obtaining two sub-products identified by liquid chromatography-mass spectrometry (LC-MS). Copyright © 2016 Elsevier B.V. All rights reserved.

Amphetamine Augments Action Potential-Dependent Dopaminergic Signaling in the Striatum in Vivo

PubMed Central

Ramsson, Eric S.; Covey, Daniel P.; Daberkow, David P.; Litherland, Melissa T.; Juliano, Steven A.; Garris, Paul A.

2011-01-01

Amphetamine (AMPH) is thought to disrupt normal patterns of action potential-dependent dopaminergic signaling by depleting dopamine (DA) vesicular stores and promoting non-exocytotic DA efflux. Voltammetry in brain slices concurrently demonstrates these key drug effects, along with competitive inhibition of neuronal DA uptake. Here we perform comparable kinetic and voltammetric analyses in vivo to determine whether AMPH acts qualitatively and quantitatively similar in the intact brain. Fast-scan cyclic voltammetry measured extracellular DA in dorsal and ventral striata of urethane-anesthetized rats. Electrically evoked recordings were analyzed to determine Km and Vmax for DA uptake and vesicular DA release, while background voltammetric current indexed basal DA concentration. AMPH (0.5, 3, and 10 mg/kg i.p.) robustly increased evoked DA responses in both striatal subregions. The predominant contributor to these elevated levels was competitive uptake inhibition, as exocytotic release was unchanged in the ventral striatum and only modestly decreased in the dorsal striatum. Increases in basal DA levels were not detected. These results are consistent with AMPH augmenting action potential-dependent dopaminergic signaling in vivo across a wide, behaviorally relevant dose range. Future work should be directed at possible causes for the distinct in vitro and in vivo pharmacology of AMPH. PMID:21443523

Construction of an electrochemical sensor based on the electrodeposition of Au-Pt nanoparticles mixtures on multi-walled carbon nanotubes film for voltammetric determination of cefotaxime.

PubMed

Shahrokhian, Saeed; Rastgar, Shokoufeh

2012-06-07

Mixtures of gold-platinum nanoparticles (Au-PtNPs) are fabricated consecutively on a multi-walled carbon nanotubes (MWNT) coated glassy carbon electrode (GCE) by the electrodeposition method. The surface morphology and nature of the hybrid film (Au-PtNPs/MWCNT) deposited on glassy carbon electrodes is characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode is used as a new and sensitive electrochemical sensor for the voltammetric determination of cefotaxime (CFX). The electrochemical behavior of CFX is investigated on the surface of the modified electrode using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable improvement in the oxidation peak current of CFX compared to glassy carbon electrodes individually coated with MWCNT or Au-PtNPs. Under the optimized conditions, the modified electrode showed a wide linear dynamic range of 0.004-10.0 μM with a detection limit of 1.0 nM for the voltammetric determination of CFX. The modified electrode was successfully applied for the accurate determination of trace amounts of CFX in pharmaceutical and clinical preparations.

Symmetrical N-acylsubstituted dihydrazones containing bithiophene core - Photophysical, electrochemical and thermal characterization

NASA Astrophysics Data System (ADS)

Jarczyk-Jedryka, Anna; Filapek, Michal; Malecki, Grzegorz; Kula, Slawomir; Janeczek, Henryk; Boharewicz, Bartosz; Iwan, Agnieszka; Schab-Balcerzak, Ewa

2016-04-01

Four symmetrical N-acylsubstituted dihydrazones containing bithiophene core were synthesized from condensation of 2,2‧-bithiophene-5,5‧-dicarboxyaldehyde with benzoic, isonicotinoyl, 2-thiophenic and 2-furoic hydrazide. The obtained compounds were characterized through the data from 1H nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), elemental analysis, UV-vis absorption spectroscopy, photoluminescence (PL), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. Additionally, the electronic properties including orbital energies and resulting energy gaps were calculated by density functional theory (DFT). Their thermal behavior was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). They were thermal sable up to 320 °C. The prepared N-acylsubstituted dihydrazones emitted light with λem in the range of 499-530 nm in solution, whereas, in solid state as blend with PMMA blue emission was observed. They undergo quasi-reversible and irreversible electrochemical reduction and oxidation processes, respectively. Additionally, the selected compounds were tested preliminary as component of active layer in organic photovoltaic cells. The highest value of power conversion efficiency, equal to 1.68% under simulated 100 mW/cm2 AM 1.5G irradiation was found for device with the architecture ITO/PEDOT:PSS/P3HT:PCBM:FBTH (1:2:2)/Al.

Electrochemical Determination of Chlorpyrifos on a Nano-TiO₂Cellulose Acetate Composite Modified Glassy Carbon Electrode.

PubMed

Kumaravel, Ammasai; Chandrasekaran, Maruthai

2015-07-15

A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature.

Electrochemical Studies of Sulfur Oxychlorides.

DTIC Science & Technology

1988-03-28

It had been proposed to study sulfuroxyhalides (1) as solutes in a non-aqueous solvent, (2) undiluted, employing lithium tetrachloroaluminate and (3...electrodes in N,N-dimethylforeamide (DNF) with tetra-butylammonium hexafluorophosphate (TBAPF6 ) as supporting electrolyte. Cyclic voltammetry showed

Kinetic determinations of accurate relative oxidation potentials of amines with reactive radical cations.

PubMed

Gould, Ian R; Wosinska, Zofia M; Farid, Samir

2006-01-01

Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.

Simultaneous detection of iodine and iodide on boron doped diamond electrodes.

PubMed

Fierro, Stéphane; Comninellis, Christos; Einaga, Yasuaki

2013-01-15

Individual and simultaneous electrochemical detection of iodide and iodine has been performed via cyclic voltammetry on boron doped diamond (BDD) electrodes in a 1M NaClO(4) (pH 8) solution, representative of typical environmental water conditions. It is feasible to compute accurate calibration curve for both compounds using cyclic voltammetry measurements by determining the peak current intensities as a function of the concentration. A lower detection limit of about 20 μM was obtained for iodide and 10 μM for iodine. Based on the comparison between the peak current intensities reported during the oxidation of KI, it is probable that iodide (I(-)) is first oxidized in a single step to yield iodine (I(2)). The latter is further oxidized to obtain IO(3)(-). This technique, however, did not allow for a reasonably accurate detection of iodate (IO(3)(-)) on a BDD electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

Electron Affinity of Phenyl-C61-Butyric Acid Methyl Ester (PCBM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, Bryon W.; Whitaker, James B.; Wang, Xue B.

2013-07-25

The gas-phase electron affinity (EA) of phenyl-C61-butyric acid methyl ester (PCBM), one of the best-performing electron acceptors in organic photovoltaic devices, is measured by lowtemperature photoelectron spectroscopy for the first time. The obtained value of 2.63(1) eV is only ca. 0.05 eV lower than that of C60 (2.68(1) eV), compared to a 0.09 V difference in their E1/2 values measured in this work by cyclic voltammetry. Literature E(LUMO) values for PCBM that are typically estimated from cyclic voltammetry, and commonly used as a quantitative measure of acceptor properties, are dispersed over a wide range between -4.3 and -3.62 eV; themore » reasons for such a huge discrepancy are analyzed here, and the protocol for reliable and consistent estimations of relative fullerene-based acceptor strength in solution is proposed.« less

Nanoalloy electrocatalysis: simulating cyclic voltammetry from configurational thermodynamics with adsorbates.

PubMed

Wang, Lin-Lin; Tan, Teck L; Johnson, Duane D

2015-11-14

We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd-Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites that is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. The method provides a more complete means to design nanoalloys for electrocatalysis.

Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots.

PubMed

Osipovich, Nikolai P; Poznyak, Sergei K; Lesnyak, Vladimir; Gaponik, Nikolai

2016-04-21

The application of electrochemical methods for the characterization of colloidal quantum dots (QDs) attracts considerable attention as these methods may allow for monitoring of some crucial parameters, such as energetic levels of conduction and valence bands as well as surface traps and ligands under real conditions of colloidal solution. In the present work we extend the applications of cyclic voltammetry (CV) to in situ monitoring of degradation processes of water-soluble CdTe QDs. This degradation occurs under lowering of pH to the values around 5, i.e. under conditions relevant to bioimaging applications of these QDs, and is accompanied by pronounced changes of their photoluminescence. Observed correlations between characteristic features of CV diagrams and the fluorescence spectra allowed us to propose mechanisms responsible for evolution of the photoluminescence properties as well as degradation pathway of CdTe QDs at low pH.

Nanoalloy electrocatalysis: Simulating cyclic voltammetry from configurational thermodynamics with adsorbates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lin -Lin; Tan, Teck L.; Johnson, Duane D.

2015-02-27

We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd–Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites thatmore » is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. As a result, the method provides a more complete means to design nanoalloys for electrocatalysis.« less

Kinetics and Antioxidant Capacity of Proanthocyanidins Encapsulated in Zein Electrospun Fibers by Cyclic Voltammetry.

PubMed

Wang, Hualin; Hao, Lilan; Niu, Baicheng; Jiang, Suwei; Cheng, Junfeng; Jiang, Shaotong

2016-04-20

The proanthocyanidins encapsulated in zein (zein-PA) fibers was via electrospinning technique. The kinetics and antioxidant capacity of PA from zein fibers was investigated by cyclic voltammetry. Circular dichroism was used to investigate the secondary structure change of zein and its influence on the shape of fibers. The addition of PA caused a significant increase in viscosity and made fibers wider. These hydrogen bonds between zein and PA molecules would favor the α-helix change and decrease the β-folds of zein in electrospinning solutions, leading to a round-shaped tendency of fibers and enhancing the thermal properties slightly. Zein-PA fibers showed high encapsulation efficiency close to 100%, and the encapsulated PA retained its antioxidant capacity in fibers. Zein-PA fibers showed a good controlled release toward PA, and the predominant release of PA from fibers was Fickian diffusion, which could be well described by first-order model and Hixson-Crowell model.

Synthesis of Benzofuran-2-One Derivatives and Evaluation of Their Antioxidant Capacity by Comparing DPPH Assay and Cyclic Voltammetry.

PubMed

Miceli, Martina; Roma, Elia; Rosa, Paolo; Feroci, Marta; Loreto, M Antonietta; Tofani, Daniela; Gasperi, Tecla

2018-03-21

The present work aimed to synthesise promising antioxidant compounds as a valuable alternative to the currently expensive and easily degradable molecules that are employed as stabilizers in industrial preparation. Taking into account our experience concerning domino Friedel-Crafts/lactonization reactions, we successfully improved and extended the previously reported methodology toward the synthesis of 3,3-disubstituted-3 H -benzofuran-2-one derivatives 9 - 20 starting from polyphenols 1 - 6 as substrates and either diethylketomalonate ( 7 ) or 3,3,3-trifluoromethyl pyruvate ( 8 ) as electrophilic counterpart. The antioxidant capacity of the most stable compounds ( 9 - 11 and 15 - 20 ) was evaluated by both DPPH assay and Cyclic Voltammetry analyses performed in alcoholic media (methanol) as well as in aprotic solvent (acetonitrile). By comparing the recorded experimental data, a remarkable activity can be attributed to few of the tested lactones.

Mechanism-Based Condition Screening for Sustainable Catalysis in Single-Electron Steps by Cyclic Voltammetry.

PubMed

Liedtke, Theresa; Spannring, Peter; Riccardi, Ludovico; Gansäuer, Andreas

2018-04-23

A cyclic-voltammetry-based screening method for Cp 2 TiX-catalyzed reactions is introduced. Our mechanism-based approach enables the study of the influence of various additives on the electrochemically generated active catalyst Cp 2 TiX, which is in equilibrium with catalytically inactive [Cp 2 TiX 2 ] - . Thioureas and ureas are most efficient in the generation of Cp 2 TiX in THF. Knowing the precise position of the equilibrium between Cp 2 TiX and [Cp 2 TiX 2 ] - allowed us to identify reaction conditions for the bulk electrolysis of Cp 2 TiX 2 complexes and for Cp 2 TiX-catayzed radical arylations without having to carry out the reactions. Our time- and resource-efficient approach is of general interest for the design of catalytic reactions that proceed in single-electron steps. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kinetic and thermodynamic hysteresis imposed by intercalation of proflavine in ferrocene-modified double-stranded DNA.

PubMed

Gebala, Magdalena; La Mantia, Fabio; Schuhmann, Wolfgang

2013-07-22

Surface-confined immobilized redox species often do not show the expected zero peak separation in slow-scan cyclic voltammograms. This phenomenon is frequently associated to experimental drawbacks and hence neglected. However, a nonzero peak separation, which is common to many electrochemical systems with high structural flexibility, can be rationally assigned to a thermodynamic hysteresis. To study this phenomenon, a surface-confined redox species was used. Specifically, a DNA strand which is tagged with ferrocene (Fc) moieties at its 5' end and its complementary capture probe is thiolated at the 3' end was self-assembled in a monolayer at a Au electrode with the Fc moieties being located at the bottom plane of the double-stranded DNA (dsDNA). The DNA-bound Fc undergoes rapid electron transfer with the electrode surface as evaluated by fast scan cyclic voltammetry. The electron transfer is sensitive to the ion transport along the DNA strands, a phenomenon which is modulated upon specific intercalation of proflavine into surface-bound dsDNA. The electron transfer rate of the Fc(0/+) redox process is influenced by the cationic permselectivity of the DNA monolayer. In addition to the kinetic hindrance, a thermodynamic effect correlated with changes in the activity coefficients of the Fc(0/+) moieties near the gold-dsDNA interface is observed and discussed as source of the observed hysteresis causing the non-zero peak separation in the voltammograms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effects of electrolyte on the supercapacitive performance of activated calcium carbide-derived carbon

NASA Astrophysics Data System (ADS)

Wu, Hao; Wang, Xianyou; Jiang, Lanlan; Wu, Chun; Zhao, Qinglan; Liu, Xue; Hu, Ben'an; Yi, Lanhua

2013-03-01

Porous calcium carbide-derived carbon (CCDC) has been prepared by one-step route from CaC2 in a freshly prepared chlorine environment at lower temperature, and following activated by ZnCl2 to get activated CCDC. The performances of the supercapacitors based on activated CCDC as electrode active material in aqueous KOH, K2SO4, KCl and KNO3 electrolytes are studied by cyclic voltammetry, constant current charged/discharged, cyclic life and electrochemical impedance spectroscopy. It has been found that the supercapacitor using 6 M KOH as electrolyte shows an energy density of 8.3 Wh kg-1 and a power density of 1992 W kg-1 based on the total weight of the electrode active materials with a voltage range 0 V-1 V. Meanwhile, the specific capacitance of the supercapacitor in 6 M KOH electrolyte is 68 F g-1 at the scan rate of 1 mV s-1 in the voltage range of 0 V-1 V, the charge-transfer resistance is extremely low and the relaxation time is the least of all. The supercapacitor also exhibits a good cycling performance and keeps 95% of initial capacity over 5000 cycles.

RuO2/Activated Carbon Composite Electrode Prepared by Modified Colloidal Procedure and Thermal Decomposition Method

NASA Astrophysics Data System (ADS)

Li, Xiang; Zheng, Feng; Gan, Weiping; Luo, Xun

2016-01-01

RuO2/activated carbon (AC) composite electrode was prepared by a modified colloidal procedure and a thermal decomposition method. The precursor for RuO2/AC was coated on tantalum sheet and annealed at 150°C to 190°C for 3 h to develop thin-film electrode. The microstructure and morphology of the RuO2/AC film were characterized by thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The TGA results showed the maximum loss of RuO2/AC composite film at 410°C, with residual RuO2 of 23.17 wt.%. The amorphous phase structure of the composite was verified by XRD analysis. SEM analysis revealed that fine RuO2 particles were dispersed in an activated carbon matrix after annealing. The electrochemical properties of RuO2/AC electrode were examined by cycling voltammetry, galvanostatic charge-discharge, and cyclic behavior measurements. The specific capacitance of RuO2/AC electrode reached 245 F g-1. The cyclic behavior of RuO2/AC electrode was stable. Optimal annealing was achieved at 170°C for 3 h.

Nickel/silicon core/shell nanosheet arrays as electrode materials for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, X.H., E-mail: drhuangxh@hotmail.com; Zhang, P.; Wu, J.B.

Highlights: • Ni nanosheet arrays is the core and Si layer is the shell. • Ni nanosheet arrays act as a three-dimensional current collector to support Si. • Ni nanosheet arrays can improve the conductivity and stability of the electrode. • Ni/Si nanosheet arrays exhibit excellent cyclic and rate performance. - Abstract: Ni/Si core/shell nanosheet arrays are proposed to enhance the electrochemical lithium-storage properties of silicon. The arrays are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The arrays are micro-sized in height, which are constructed by interconnected Ni nanosheet as themore » core and Si coating layer as the shell. The electrochemical properties as anode materials of lithium ion batteries are investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. The arrays can achieve high reversible capacity, good cycle stability and high rate capability. It is believed that the enhanced electrochemical performance is attributed to the electrode structure, because the interconnected Ni nanosheet can act as a three-dimensional current collector, and it has the ability of improving the electrode conductivity, enlarging the electrochemical reaction interface, and suppressing the electrode pulverization.« less

Novel flame synthesis of nanostructured α-Fe2O3 electrode as high-performance anode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Yang; Roller, Justin; Maric, Radenka

2018-02-01

Nanostructured electrodes have significant potential for enhancing the kinetics of lithium storage in secondary batteries. A simple and economical manufacturing approach of these electrodes is crucial to the development and application of the next generation lithium ion (Li-ion) batteries. In this study, nanostructured α-Fe2O3 electrode is fabricated by a novel one-step flame combustion synthesis method, namely Reactive Spray Deposition Technology (RSDT). This process possesses the merits of simplicity and low cost. The structure and morphology of the electrode are investigated with X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of the nanostructured α-Fe2O3 electrodes as the anodes for Li-ion batteries is evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in coin-type half-cells. The as-prepared electrodes demonstrate superior cyclic performance at high current rate, which delivers a high reversible capacity of 1239.2 mAh g-1 at 1 C after 500 cycles. In addition, a discharge capacity of 513.3 mAh g-1 can be achieved at 10 C.

Chemically prepared La2Se3 nanocubes thin film for supercapacitor application.

PubMed

Patil, S J; Lokhande, V C; Chodankar, N R; Lokhande, C D

2016-05-01

Lanthanum selenide (La2Se3) nanocubes thin film is prepared via successive ionic layer adsorption and reaction (SILAR) method and utilized for energy storage application. The prepared La2Se3 thin film is characterized by X-ray diffraction, field emission scanning electron microscopy and contact angle measurement techniques for structural, surface morphological and wettability studies, respectively. Energy dispersive X-ray microanalysis (EDAX) is performed in order to obtain the elemental composition of the thin film. The La2Se3 film electrode shows a maximum specific capacitance of 363 F g(-1) in a 0.8 M LiClO4/PC electrolyte at a scan rate of 5 mV s(-1) within 1.3 V/SCE potential range. The specific capacitive retention of 83 % of La2Se3 film electrode is obtained over 1000 cyclic voltammetry cycles. The predominant performance, such as high energy (80 Wh kg(-1)) and power density (2.5 kW kg(-1)), indicates that La2Se3 film electrode facilitates fast ion diffusion during redox processes. Copyright © 2016 Elsevier Inc. All rights reserved.

Synthesis of Carbon Nano Materials Originated from Waste Cooking Oil Using a Nebulized Spray Pyrolysis

NASA Astrophysics Data System (ADS)

Arie, A. A.; Hadisaputra, L.; Susanti, R. F.; Devianto, H.; Halim, M.; Enggar, R.; Lee, J. K.

2017-07-01

Synthesis of nanocarbon on snake fruit-peel’s activated carbon from waste cooking oil palm was conducted by a nebulized spray pyrolysis process (NSP) by varying the processing temperature from 650 to 750 °C. Ferrocene was used as a catalyst with constant concentration of 0.015 g/ml of carbon source. The structure of nanocarbon was studied by using scanning electron microscope (SEM),x-ray diffraction (XRD), surface area analyzer and Raman spectroscopy. SEM results showed that the structures of carbon products was in the the form of carbon nanopsheres (CNS). XRD and Raman analysis confirmed the CNS structure. The carbon producs were then tested as electrode’s materials for lithium ion capacitors (LIC) by cyclic voltammetry (CV) instruments. From the CV results the specific capacitance was estimated as 79.57 F / g at a scan rate of 0.1 mV / s and voltage range from 2.5 - 4 V. This study shows that the nano carbons synthesized from the waste cooking oil can be used as prospective electrode materials for LIC.

Self-Assembled Structures of Benzoic Acid on Au(111) Surface

NASA Astrophysics Data System (ADS)

Vu, Thu-Hien; Wandlowski, Thomas

2017-06-01

Electrochemical scanning tunneling microscopy combined with cyclic voltammetry were employed to explore the self-assembly of benzoic acid (BA) on a Au(111) substrate surface in a 0.1-M HClO4 solution. At the negatively charged surface, BA molecules form two highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High-resolution scanning tunneling microscopy images reveal the packing arrangement and internal molecular structures. The striped pattern and zigzag structure of the BA adlayers are composed of parallel rows of dimers, in which two BA molecules are bound through a pair of O-H···O hydrogen bonds. Increasing the electrode potential further to positive charge densities of Au(111) leads to the desorption of the physisorbed hydrogen-bonded networks and the formation of a chemisorbed adlayer. BA molecules change their orientation from planar to upright fashion, which is accompanied by the deprotonation of the carboxyl group. Furthermore, potential-induced formation and dissolution of BA adlayers were also investigated. Structural transitions between the various types of ordered adlayers occur according to a nucleation and growth mechanism.

Spectroelectrochemistry and Electrochemistry of Europium Ions in Alkali Chloride Melts

NASA Astrophysics Data System (ADS)

Uehara, Akihiro; Shirai, Osamu; Nagai, Takayuki; Fujii, Toshiyuki; Yamana, Hajimu

2007-04-01

In order to investigate the redox equilibrium of europium ions in molten NaCl-2CsCl, UV-Vis absorption spectrophotometry measurements were performed for Eu2+ and Eu3+ in molten NaCl- 2CsCl at 923 K under simultaneous electrolytic control of their ratio. Molar absorptivities of EuCl3 and EuCl2 in NaCl-2CsCl at 923 K were determined to be (420±21) M -1cm-1 at 31200 cm-1 and (1130±56) M-1cm-1 at 30300 cm-1, respectively. The formal redox potential of the Eu2+/Eu3+ couple in NaCl-2CsCl melt at 923 K was determined to be (-0.941 ±0.004) V vs. Cl2/Cl- by electromotive force measurements on varying concentration ratios of Eu2+ and Eu3+, which were performed using a technique based on the combination of electrolysis and spectrophotometry. Cyclic voltammetry was also carried out in order to examine the characteristics of the voltammograms for the Eu2+/Eu3+ couple in NaCl-2CsCl melt. The formal redox potential of the Eu2+/Eu3+ couple determined by a spectroelectrochemical method agreed with that determined by cyclic voltammetry [(-0.946±0.008) V vs. Cl2/Cl-]. The effects of temperature on the redox potential of the Eu2+/Eu3+ couple in NaCl-2CsCl, NaCl-KCl, LiCl-KCl, and CsCl melts were studied by cyclic voltammetry in the range from 923 to 1123 K.

Computer Series, 70.

ERIC Educational Resources Information Center

Moore, John W.

1986-01-01

Describes: (1) spreadheet programs (including VisiCalc) for experiments; (2) event-driven data acquisition (using ADALAB with an Acculab Infrared Spectometer); (3) microcomputer-controlled cyclic voltammetry; (4) inexpensive computerized experiments; (5) the "KC? Discoverer" program; and (6) MOLDOT (space-filling perspective diagrams of…

Graphene decorated microelectrodes for simultaneous detection of ascorbic, dopamine, and folic acids by means of chemical vapor deposition

NASA Astrophysics Data System (ADS)

Namdar, N.; Hassanpour Amiri, M.; Dehghan Nayeri, F.; Gholizadeh, A.; Mohajerzadeh, S.

2015-09-01

In this paper, high quality and large area graphene layers were synthesized using thermal chemical vapour deposition on copper foil substrates. We use graphene incorporated electrodes to measure simultaneously ascorbic acid, dopamine and folic acid. Cyclic voltammetry and differential pulse voltammetry methods were used to evaluate electrochemical behaviour of the grown graphene layers. The graphene-modified electrode shows large electrochemical potential difference compared to bare gold electrodes with higher current responses. Also our fabricated electrodes configuration can be used easily for microfluidic analysis.

Spectroscopic and electrochemical behavior of the novel tetra-2-methyl-pyrazinoporphyrazines

NASA Astrophysics Data System (ADS)

Pişkin, Mehmet; Öztürk, Naciye; Durmuş, Mahmut

2017-12-01

This study presents the synthesis and characterization of novel metal-free (H2Pc) and metallo porphyrazines (magnesium(II) (MgPz), copper(II) (CuPz), iron(II) (FePz), manganese(II) (MnPz) and nickel(II) (NiPz)) substituted with four 2-methylpyrazine groups on the peripheral positions. The spectroscopic properties of newly synthesized porphyrazines were investigated. The electrochemical behaviors of these porphyrazines were also determined in DMSO solution by cyclic voltammetry (CV) and square wave voltammetry (SWV) methods on edge plane pyrolytic graphite electrode (EPPG) electrode.

Determination of Bosentan in Pharmaceutical Preparations by Linear Sweep, Square Wave and Differential Pulse Voltammetry Methods

PubMed Central

Atila, Alptug; Yilmaz, Bilal

2015-01-01

In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation. PMID:25901151

Determination of bosentan in pharmaceutical preparations by linear sweep, square wave and differential pulse voltammetry methods.

PubMed

Atila, Alptug; Yilmaz, Bilal

2015-01-01

In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation.

Testing Metal Chlorides For Use In Sodium-Cell Cathodes

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

1992-01-01

Cyclic voltammetric curves of transition-metal wires in molten NaAlCl4 electrolyte used to eliminate suitability of transition metals as cathodes in sodium cells. Cyclic voltammetry used in conjunction with measurement of galvanostatic polarization curves determines whether given metal chloride suitable as cathode material in such cell. Cells useful in such high-energy-density and high-power-density applications as leveling loads on electric-power plants, supplying power to electric ground vehicles, and aerospace applications.

Lanthanide Diphthalocyanines. Electrochemistry and Display Applications.

DTIC Science & Technology

1982-01-01

transients, cyclic voltametry (Nicholson and Galiardi, 1977, 1978; Noskalev and Shapkin, 1978). and a novel solid-state moving-boundary technique...was confirmed for the reverse process by linear potential- sweep voltammetry. Although the hydrazine hydrate my not have been simply an inert solvent

Reductive electrografting of benzene (p-bisdiazonium hexafluorophosphate): a simple and effective protocol for creating diazonium-functionalized thin films.

PubMed

Marshall, Nicholas; Locklin, Jason

2011-11-01

In this Article, we describe a protocol for surface functionalization of benzenediazonium hexafluorophosphate monolayers by in situ electrochemical reduction of bis(benzenediazonium) hexafluorophosphate. Due to the considerable difference in potential between the first and second reduction of this species, it is possible to form a high density of surface-bound diazonium groups by use of a mild potential which selectively reduces only one diazonium group per ring. The resulting diazonium-containing monolayer reacts readily with solutions of electron-rich aromatic compounds. The reaction with ferrocene produces a dense (2.7 × 10(-10) mol/cm(2)) ferrocene-containing monolayer through a Gomberg-Bachmann type arylation. The resulting ferrocene group exhibits relatively rapid electron transfer to the electrode due to the conjugated linker layer as measured by alternating current voltammetry (ACV) and cyclic voltammetry. Aromatic systems with π-donor substitutents (N,N-dimethylaniline, N,N,N',N'-tetramethyldiaminobenzophenone, and hydroquinone) react through an azo-coupling to form monolayers linked to the surface through an azobenzene moiety. The redox properties of these electron-rich species tethered to the surface were observed and quantified using cyclic voltammetry. This simple and versatile functionalization procedure has a wide variety of potential applications in surface science and materials research.

Instrumental, theoretical, and experimental aspects of determining thermodynamic and kinetic parameters from steady-state and non-steady-state cyclic voltammetry at microelectrodes in high-resistance solvents: Application to the fac/mer-[Cr(CO){sub 3}({eta}{sup 3}-Ph{sub 2}PCH{sub 2}CH{sub 2}P(Ph)CH{sub 2}CH{sub 2}PPh{sub 2})]{sup +/0} square reaction sheme in dichloromethane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bond, A.M.; Feldberg, S.W.; Greenhill, H.B.

1992-05-01

Instrumental, experimental and theoretical approaches required to quantify the thermodynamic and kinetic aspects of the square reaction scheme relating the fac{sup +/0} and mer{sup +/0} redox couples in the high-resistance solvent dichloromethane, at microelectrodes, under both steady-state and fast scan rate (transient) conditions, are presented. fac{sup +}, mer{sup +}, fac{sup 0}, and mer{sup 0} represent the facial and meridional isomers of Cr-(CO){sub 3}({eta}{sup 3}-Ph{sub 2}PCH{sub 2}CH{sub 2}P(Ph)CH{sub 2}CH{sub 2}PPh{sub 2}) in the oxidized 17 electron (fac{sup +}, mer{sup +}) and reduced 18 electron (fac{sup 0}, mer{sup 0}) configurations, respectively. A computationally efficient simulation method based on the DuFort-Frankel algorithm ismore » readily applied to microelectrodes and enables simulations to be undertaken for both steady-state and transient voltammetry at electrodes of microdisk geometry. The minimal ohmic drop present under steady-state conditions enables a limited set of parameters to be calculated for the square scheme. However, data relevant to species generated as a product of electron transfer have to be determined from the transient voltammetry at fast scans rates. For the latter experiments, a newly designed electrochemical cell was developed along with relevant electronic circuitry to minimize the background current and uncompensated resistance. The cell contains two matched working microelectrodes (one in the test solution and one in the separated electrolyte solution) and a common quasi-reference electrode which passes through both compartments of the cell. It is concluded that a judicious choice of steady-state and transient techniques, such as those described in this work, are necessary to characterize complex reaction schemes in high-resistance solvents. 46 refs., 7 figs., 3 tabs.« less

Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, F. B.; Jing, B.; Cui, Y.

2015-04-15

The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond filmmore » are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.« less

An electrochemiluminescence sensor based on a Ru(bpy)3(2+)-silica-chitosan/nanogold composite film.

PubMed

Cai, Zhi-min; Wu, Yan-fang; Huang, Yun-he; Li, Qiu-ping; Chen, Xiao-mei; Chen, Xi

2012-05-30

Chitosan, a cationic polysaccharide containing amino and hydroxyl groups, was used to fabricate an electrochemiluminescence (ECL) sensor. In the sensor construction, a glassy carbon electrode (GCE) was first coated by a chitosan film which embedded gold nanoparticles, and then the film was modified by introducing carboxyl groups on the surface, which were used to immobilize tris(2,2'-bipyridyl)ruthenium(II) doped amino-functional silica nanoparticles (NH(2)-RuSiNPs) through amido links. The successful modification was confirmed by scanning electronic microscopy and cyclic voltammetry. A binding model between the chitosan/nanogold composite film and NH(2)-RuSiNPs was also proposed, in which the amido link was the dominant bonding, accompanied with hydrogen bond interaction. ECL studies revealed that the sensor had very good response to different concentrations of 2-(dibutylamino) ethanol. This sensor was also applied in methamphetamine determination. Copyright © 2012 Elsevier B.V. All rights reserved.

Hydrothermal synthesis of PEDOT/rGO composite for supercapacitor applications

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Rafat, M.

2018-01-01

In this study, PEDOT/rGO composite has been successfully synthesized using hydrothermal method. Precursor solution of EDOT monomer was mixed with a predetermined solution of graphene oxide (GO). The resultant mixture was then hydrothermally treated. Surface morphology, crystal structure vibrational response and thermal stability have been studied using standard characterization techniques: field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy and thermo-gravimetric analysis. The observed results confirm that the required composite of PEDOT/rGO has indeed been synthesized. Electrochemical properties of the synthesized product were studied in 6 M KOH aqueous solution, using characterization techniques such as: cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements. The results show a high value of specific capacitance (102.8 F g-1) at 10 mV s-1, indicating that the composite can be profitably used for energy storage devices.

Electro-catalytic degradation of sulfisoxazole by using graphene anode.

PubMed

Wang, Yanyan; Liu, Shuan; Li, Ruiping; Huang, Yingping; Chen, Chuncheng

2016-05-01

Graphite and graphene electrodes were prepared by using pure graphite as precursor. The electrode materials were characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) measurements. The electro-catalytic activity for degradation of sulfisoxazole (SIZ) was investigated by using prepared graphene or graphite anode. The results showed that the degradation of SIZ was much more rapid on the graphene than that on the graphite electrode. Moreover, the graphene electrode exhibited good stability and recyclability. The analysis on the intermediate products and the measurement of active species during the SIZ degradation demonstrated that indirect oxidation is the dominant mechanism, involving the electro-catalytic generation of OH and O2(-) as the main active oxygen species. This study implies that graphene is a promising potential electrode material for long-term application to electro-catalytic degradation of organic pollutants. Copyright © 2015. Published by Elsevier B.V.

Electrochemical Analysis of Neurotransmitters

NASA Astrophysics Data System (ADS)

Bucher, Elizabeth S.; Wightman, R. Mark

2015-07-01

Chemical signaling through the release of neurotransmitters into the extracellular space is the primary means of communication between neurons. More than four decades ago, Ralph Adams and his colleagues realized the utility of electrochemical methods for the study of easily oxidizable neurotransmitters, such as dopamine, norepinephrine, and serotonin and their metabolites. Today, electrochemical techniques are frequently coupled to microelectrodes to enable spatially resolved recordings of rapid neurotransmitter dynamics in a variety of biological preparations spanning from single cells to the intact brain of behaving animals. In this review, we provide a basic overview of the principles underlying constant-potential amperometry and fast-scan cyclic voltammetry, the most commonly employed electrochemical techniques, and the general application of these methods to the study of neurotransmission. We thereafter discuss several recent developments in sensor design and experimental methodology that are challenging the current limitations defining the application of electrochemical methods to neurotransmitter measurements.

An integrated electrocoagulation-phytoremediation process for the treatment of mixed industrial wastewater.

PubMed

Cano, Rodríguez Claudia Teodora; Amaya-Chávez, Araceli; Roa-Morales, Gabriela; Barrera-Díaz, Carlos Eduardo; Ureña-Núñez, Fernando

2010-01-01

The elimination of organic contaminants in highly complex wastewater was tested using a combination of the techniques: electrocoagulation with aluminum electrodes and phytoremediation with Myriophyllum aquaticum. Under optimal operating conditions at a pH of 8 and a current density of 45.45 A m(-2), the electrochemical method produces partial elimination of contaminants, which was improved using phytoremediation as a polishing technique. The combined treatment reduced chemical oxygen demand (COD) by 91%, color by 97% and turbidity by 98%. Initial and final values of contaminants in wastewaters were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and the elemental composition of the biomass were characterized with using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The presence of Al in the roots of plants in the system indicates that the aluminum present in the test solution could be absorbed.

Supercapacitors from Activated Carbon Derived from Granatum.

PubMed

Wang, Qiannan; Yang, Lin; Wang, Zhao; Chen, Kexun; Zhang, Lipeng

2015-12-01

Granatum carbon (GC) as electrode materials for supercapacitors is prepared via the chemical activation with different activating agent such as ZnC2 and KOH with an intention to improve the surface area and their electrochemical performance. The structure and electrochemical properties of GC materials are characterized with N2 adsorption/desorption measurements, scanning electron microscope (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). The obtained results show that the specific surface area of the granatum-based activated carbons increased obviously from 573 m2 x g(-1) to 1341 m2 x g(-1) by ZnC2 activation and to 930 m2 x g(-1) by KOH treatment. Furthermore, GCZ also delivers specific capacitance of 195.1 Fx g(-1) at the current density of 0.1 A x g(-1) in 30 wt.% KOH aqueous electrolyte and low capacitance loss of 28.5% when the current density increased by 10 times.

Graphene-Wrapped Ni(OH)2 Hollow Spheres as Novel Electrode Material for Supercapacitors.

PubMed

Sun, Jinfeng; Wang, Jinqing; Li, Zhangpeng; Ou, Junfei; Niu, Lengyuan; Wang, Honggang; Yang, Shengrong

2015-09-01

Graphene-wrapped Ni(OH)2 hollow spheres were prepared via electrostatic interaction between poly(diallyldimethylammonium chloride) (PDDA) modified Ni(OH)2 and graphene oxide (GO) in an aqueous dispersion, followed by the reduction of GO. Morphological and structural analysis by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis confirmed the successful coating of graphene on Ni(OH)2 hollow spheres with a content of 3.8 wt%. And then its application as electrode material for supercapacitor has been investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. Results show that the sample displays a high capacitance of 1368 F g(-1) at a current density of 1 A g(-1), much better than that of pure Ni(OH)2, illustrating that such composite is a promising candidate as electrode material for supercapacitors.

Reduced Graphene Oxide/Carbon Nanotube Composites as Electrochemical Energy Storage Electrode Applications.

PubMed

Yang, Wenyao; Chen, Yan; Wang, Jingfeng; Peng, Tianjun; Xu, Jianhua; Yang, Bangchao; Tang, Ke

2018-06-15

We demonstrate an electrochemical reduction method to reduce graphene oxide (GO) to electrochemically reduced graphene oxide (ERGO) with the assistance of carbon nanotubes (CNTs). The faster and more efficient reduction of GO can be achieved after proper addition of CNTs into GO during the reduction process. This nanotube/nanosheet composite was deposited on electrode as active material for electrochemical energy storage applications. It has been found that the specific capacitance of the composite film was strongly affected by the mass ratio of GO/CNTs and the scanning ratio of cyclic voltammetry. The obtained ERGO/CNT composite electrode exhibited a 279.4 F/g-specific capacitance and showed good cycle rate performance with the evidence that the specific capacitance maintained above 90% after 6000 cycles. The synergistic effect between ERGO and CNTs as well as crossing over of CNTs into ERGO is attributed to the high electrochemical performance of composite electrode.

High performance supercapacitor using porous carbon nanomaterial from corn cob

NASA Astrophysics Data System (ADS)

Sharma, Nallin; Mishra, Neeraj; Sharon, Madhuri; Sharon, Maheshwar

2013-06-01

Carbon synthesized from corn-cob has been used as an electrode in Electrochemical Double Layer Capacitor (EDLC). Dried Corn Cobs, soaked in 1N KOH, 1N HCl or 5% ZnCl2 at 10 0°C for 24 hr, were pyrolyzed in presence of Ar using Co as catalyst at 700-900 °C having dwell time of 60-180 min. The morphology of thus obtained carbon was studied under SEM that showed it to be porous carbon. All the carbon samples synthesized using different parameters were used as electrode for EDLC. Cyclic Voltammetry was used to measure the capacitance. Carbon synthesized from corn cobs pre-treated with 5% ZnCl2 using Co as catalyst pyrolyzed at 700°C for a dwell time of 120 min gave higher Specific capacitance of 270 F/g at scan rate of 5 mV/s. Moreover, this carbon, as observed under SEM, exhibited larger pore size.

Electrochemical capacitance of nanostructured ruthenium-doped tin oxide Sn1- x Ru x O2 by the microemulsion method

NASA Astrophysics Data System (ADS)

Saraswathy, Ramanathan

2017-12-01

Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstructure of synthesized nanoparticles were analyzed by SEM and TEM. The vibration mode of nanoparticles was investigated using FTIR and Raman studies. The electrochemical behavior of the Ru-doped SnO2 electrode was evaluated in a 0.1 mol/L Na2SO4 solution using cyclic voltammetry. The 5% Ru-doped SnO2 electrode exhibited a high specific capacitance of 535.6 F/g at a scan rate 20 mV/s, possessing good conductivity as well as the electrocycling stability. The Ru-doped SnO2 composite shows excellent electrochemical properties, suggesting that this composite is a promising material for supercapacitors.

Simultaneous determination of dopamine and uric acid using layer-by-layer graphene and chitosan assembled multilayer films.

PubMed

Weng, Xuexiang; Cao, Qingxue; Liang, Lixin; Chen, Jianrong; You, Chunping; Ruan, Yongmin; Lin, Hongjun; Wu, Lanju

2013-12-15

Multilayer films containing graphene (Gr) and chitosan (CS) were prepared on glassy carbon electrodes with layer-by-layer (LBL) assembly technique. After being characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), the electrochemical sensor based on the resulted films was developed to simultaneously determine dopamine (DA) and uric acid (UA). The LBL assembled electrode showed excellent electrocatalytic activity towards the oxidation of DA and UA. In addition, the self-assembly electrode possessed an excellent sensing performance for detection of DA and UA with a linear range from 0.1 μM to 140 µM and from 1.0 µM to 125 µM with the detection limit as low as 0.05 µM and 0.1 µM based on S/N=3, respectively. © 2013 Elsevier B.V. All rights reserved.

Tremella-like graphene-Au composites used for amperometric determination of dopamine.

PubMed

Li, Cong; Zhao, Jingyu; Yan, Xiaoyi; Gu, Yue; Liu, Weilu; Tang, Liu; Zheng, Bo; Li, Yaru; Chen, Ruixue; Zhang, Zhiquan

2015-03-21

Electrochemical detection of dopamine (DA) plays an important role in medical diagnosis. In this paper, tremella-like graphene-Au (t-GN-Au) composites were synthesized by a one-step hydrothermal method for selective detection of DA. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterize as-prepared t-GN-Au composites. The t-GN-Au composites were directly used for the determination of DA via cyclic voltammetry (CV) and the chronoamperometry (CA) technique. CA measurement gave a wide linear range from 0.8 to 2000 μM, and the detection limit of 57 nM (S/N = 3) for DA. The mechanism and the heterogeneous electron transfer kinetics of the DA oxidation were discussed in the light of rotating disk electrode (RDE) experiments. Moreover, the modified electrode was applied to the determination of DA in human urine and serum samples.

Facile preparation and electrochemical characterization of kassite-based materials for supercapacitor applications

NASA Astrophysics Data System (ADS)

Meng, Weijie; Zhao, Gaoling; Song, Bin; Xie, Junliang; Lu, Wangwei; Han, Gaorong

2017-12-01

In this study, kassite was synthesized by employing a simple, green hydrothermal method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy were carried out to study its crystal phases, morphologies and electrochemical performance. With the extension of reaction time, the crystallinity of the samples became higher and the specific capacitance increased correspondingly. The result shows that kassite has a promising application in electrode material for capacitors. To improve the electrical conductivity of kassite and the accessibility of the surface area, graphene nanosheet (GNS) was introduced to form composites with kassite. The capacitive performance improved with increasing weight percentage of GNS and reached an optimum with the specific capacitance of 129.8 F/g at weight percentage of 10%, then decreased with further increasing GNS, showing a synergistic effect of kassite and the GNS.

Development and surface characterization of a glucose biosensor based on a nanocolumnar ZnO film

NASA Astrophysics Data System (ADS)

Rodrigues, A.; Castegnaro, M. V.; Arguello, J.; Alves, M. C. M.; Morais, J.

2017-04-01

Highly oriented nanostructured ZnO films were grown on the surface of stainless steel plates (ZnO/SS) by chemical bath deposition (CBD). The films consisted of vertically aligned ZnO nanocolumns, ∼1 μm long and ∼80 nm wide, as observed by SEM (scanning electron microscopy) and FIB (focused ion beam). XRD (X-ray diffraction) confirmed the c-axis preferred orientation of the ZnO columns, which were functionalized with the glucose oxidase (GOx) enzyme into a biosensor of glucose. The electrochemical response studied by CV (cyclic voltammetry) proved that the biosensor was capable of detecting glucose from 1.5 up to 16 mM concentration range. XPS (X-ray photoelectron spectroscopy) analysis, excited with synchrotron radiation, probed the atom specific chemical environment at the electrode's surface and shed some light on the nature of the ZnO-GOx interaction.

Graphene-gold nanoparticle composite: application as a good scaffold for construction of glucose oxidase biosensor.

PubMed

Sabury, Sina; Kazemi, Sayed Habib; Sharif, Farhad

2015-04-01

In the present work we report a facile method for fabrication of glucose oxidase immobilized on the partially reduced graphene-gold nanocomposite (PRGO-AuNPs/GOx) as a novel biosensor for determination of glucose concentration. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of PRGO and PRGO-AuNPs. Also, fast Fourier transformation infrared spectroscopy (FTIR) and UV-Vis spectroscopy were used to confirm formation of graphene and graphene-gold composite. Then, the electrochemical behavior of PRGO-AuNPs/GOx modified electrode was studied by cyclic voltammetry (CV). Our electrochemical studies, especially chronoamperometry (CA), showed that the PRGO-AuNPs/GOx modified electrode has excellent electrocatalytic activity towards the glucose. The limit of detection and sensitivity towards glucose were estimated as 0.06μM and 15.04mAmM(-1), respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing.

PubMed

Shamsipur, Mojtaba; Tabrizi, Mahmoud Amouzadeh

2014-12-01

In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28 mV in 0.1 M phosphate buffer solution (pH7.0) with a scan rate of 50 mV/s. The average surface coverage is 2.62×10(-10) mol cm(-2). The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8 mM (R(2)=0.9878), good reproducibility and detection limit of 40.8 μM. The results from the biosensor were similar (±5%) to those obtained from the clinical analyzer. Copyright © 2014 Elsevier B.V. All rights reserved.

Influence of defect luminescence and structural modification on the electrical properties of Magnesium Doped Zinc Oxide Nanorods

NASA Astrophysics Data System (ADS)

Santoshkumar, B.; Biswas, Amrita; Kalyanaraman, S.; Thangavel, R.; Udayabhanu, G.; Annadurai, G.; Velumani, S.

2017-06-01

Magnesium doped zinc oxide nanorod arrays on zinc oxide seed layers were grown by hydrothermal method. X-ray diffraction (XRD) patterns revealed the growth orientation along the preferential (002) direction. The hexagonal morphology was revealed from the field emission scanning electron microscope (FESEM) images. The elemental composition of the samples was confirmed by energy dispersive x-ray analysis spectra (EDS) and mapping dots. Carrier concentration, resistivity and mobility of the samples were obtained by Hall measurements. I-V characteristic curve confirmed the increase in resistivity upon doping. Photoluminescence (PL) spectra exposed the characteristic of UV emission along with defect mediated visible emission in the samples. Electrochemical impedance spectroscopy and cyclic voltammetry were undertaken to study the charge transport property. Owing to the change in the structural parameters and defect concentration the electrical properties of the doped samples were altered.

Synthesis and Characterization of Cellulose-Based Hydrogels to Be Used as Gel Electrolytes

PubMed Central

Navarra, Maria Assunta; Dal Bosco, Chiara; Serra Moreno, Judith; Vitucci, Francesco Maria; Paolone, Annalisa; Panero, Stefania

2015-01-01

Cellulose-based hydrogels, obtained by tuned, low-cost synthetic routes, are proposed as convenient gel electrolyte membranes. Hydrogels have been prepared from different types of cellulose by optimized solubilization and crosslinking steps. The obtained gel membranes have been characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic-extensional properties, respectively. Hydrogels liquid uptake capability and ionic conductivity, derived from absorption of aqueous electrolytic solutions, have been evaluated, to assess the successful applicability of the proposed membranes as gel electrolytes for electrochemical devices. To this purpose, the redox behavior of electroactive species entrapped into the hydrogels has been investigated by cyclic voltammetry tests, revealing very high reversibility and ion diffusivity. PMID:26633528

Fabrication and Performance Study on Individual Zno Nanowires Based Bioelectrode

NASA Astrophysics Data System (ADS)

Zhao, Yanguang; Yan, Xiaoqin; Kang, Zhuo; Lin, Pei

2012-08-01

One-dimensional zinc oxide nanowires (ZnO NWs) have unique advantages for use in biosensors as follows: oxide stable surface, excellent biosafety, high specific surface area, high isoelectric point (IEP = 9.5). In this work, we have prepared a kind of electrochemical bioelectrode based on individual ZnO NWs. Here, ZnO NWs with high quality were successfully synthesized by CVD method, which were characterized by scanning electron microscopy, X-ray diffraction and photoluminescence. Then the Raman spectra and electrical characterization demonstrated the adsorption of uricase on ZnO wires. At last, a series of electrochemical measurements were carried out by using an electrochemical workstation with a conventional three-electrode system to obtain the cyclic voltammetry characteristics of the bioelectrodes. The excellent performance of the fabricated bioelectrode implies the potential application for single ZnO nanowire to construct electrochemical biosensor for the detection of uric acid.

A hydrothermally synthesized LiFePO4/C composite with superior low-temperature performance and cycle life

NASA Astrophysics Data System (ADS)

Wu, Guan; Liu, Na; Gao, Xuguang; Tian, Xiaohui; Zhu, Yanbin; Zhou, Yingke; Zhu, Qingyou

2018-03-01

The LiFePO4/C composites have been successfully synthesized by a hydrothermal process, with the combined carbon sources of fructose and calcium lignosulfonate. The morphology and microstructure of LiFePO4/C were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The electrochemical properties were evaluated by the constant-current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The uniform carbon coating layer derived from calcium lignosulfonate can effectively improve the electronic conductivity, lithium-ion diffusivity and surface stability of the LiFePO4/C composites and prevent the side reactions between the LiFePO4 particles and electrolytes. The LiFePO4/C composites display excellent rate capability, superior cycle life and outstanding low temperature performance, which are promising for lithium-ion battery applications in electrical vehicles and electrical energy storage systems.

Freeze-drying synthesis of three-dimensional porous LiFePO4 modified with well-dispersed nitrogen-doped carbon nanotubes for high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Tu, Xiaofeng; Zhou, Yingke; Song, Yijie

2017-04-01

The three-dimensional porous LiFePO4 modified with uniformly dispersed nitrogen-doped carbon nanotubes has been successfully prepared by a freeze-drying method. The morphology and structure of the porous composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performances are evaluated using the constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The nitrogen-doped carbon nanotubes are uniformly dispersed inside the porous LiFePO4 to construct a superior three-dimensional conductive network, which remarkably increases the electronic conductivity and accelerates the diffusion of lithium ion. The porous composite displays high specific capacity, good rate capability and excellent cycling stability, rendering it a promising positive electrode material for high-performance lithium-ion batteries.

Mesoporous carbon synthesized from different pore sizes of SBA-15 for high density electrode supercapacitor application

NASA Astrophysics Data System (ADS)

Jamil, Farinaa Md; Sulaiman, Mohd Ali; Ibrahim, Suhaina Mohd; Masrom, Abdul Kadir; Yahya, Muhd Zu Azhan

2017-12-01

A series of mesoporous carbon sample was synthesized using silica template, SBA-15 with two different pore sizes. Impregnation method was applied using glucose as a precursor for converting it into carbon. An appropriate carbonization and silica removal process were carried out to produce a series of mesoporous carbon with different pore sizes and surface areas. Mesoporous carbon sample was then assembled as electrode and its performance was tested using cyclic voltammetry and impedance spectroscopy to study the effect of ion transportation into several pore sizes on electric double layer capacitor (EDLC) system. 6M KOH was used as electrolyte at various scan rates of 10, 20, 30 and 50 mVs-1. The results showed that the pore size of carbon increased as the pore size of template increased and the specific capacitance improved as the increasing of the pore size of carbon.

Hydrothermal synthesis of poly(3,4-ethylenedioxythiophene) for high-rate performance supercapacitor

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Parvaz, M.; Johari, Rahul; Bilal, M.; Ahmad, Sultan; Zaid, M.; Hussain, S.; Islamuddin, Khan, Zishan H.; Rafat, M.

2018-05-01

This work reports the successful preparation of Poly (3,4-ethylenedioxythiophene) (PEDOT) from monomer ethylenedioxythiophene (EDOT), employing hydrothermal method. The structure of the prepared sample was characterized by Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) and the results indicates the successful polymerization of EDOT to the formation of polymer PEDOT. The capacitive performance of the prepared sample were investigated in two-electrode assembly using aqueous solution of 6 M KOH. The assembled capacitor cell shows high rate capability which is evident from both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies. The observed CV patterns are almost rectangular even for high scan rates (˜30 V s-1), confirming the high rate performance, while high knee frequency (˜1 kHz), and low response time (˜5.8 ms) observed by impedance analysis confirms the high rate capability of supercapacitor.

Microwave assisted synthesis of graphene oxide - MnO2 nanocomposites for electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Vimuna, V. M.; Athira, A. R.; Xavier, T. S.

2018-05-01

Grapheneoxide-MnO2 nanocomposite was successfully synthesized through the self-limiting deposition of nano scale MnO2 on the surface of graphene oxide under microwave- irradiation in a water- isopropyl alcohol system. The structural and morphological properties of as synthesized samples have been studied. These nanostructured graphene oxide-MnO2 (GMC) hybrid materials are used for investigation of electrochemical behaviours. It was found that the electrochemical performance of as prepared nanocomposite could be enhanced by chemical interaction between GO and MnO2. Cyclic voltammetry is employed to assess the properties of these nanocomposites for use in supercapacitors. The specific capacitance of the synthesized sample corresponding to scan rate of 20mV/s is calculated to be 280 Fg-1. Furthermore, we emphasize the fabrication challenges and future perspectives of such materials for energy storage.

Transpassive Dissolution of Copper and Rapid Formation of Brilliant Colored Copper Oxide Films

NASA Astrophysics Data System (ADS)

Fredj, Narjes; Burleigh, T. David; New Mexico Tech Team

2014-03-01

This investigation describes an electrochemical technique for growing adhesive copper oxide films on copper with attractive colors ranging from gold-brown to pearl with intermediate colors from red violet to gold green. The technique consists of anodically dissolving copper at transpassive potentials in hot sodium hydroxide, and then depositing brilliant color films of Cu2O onto the surface of copper after the anodic potential has been turned off. The color of the copper oxide film depends on the temperature, the anodic potential, the time t1 of polarization, and the time t2, which is the time of immersion after potential has been turned off. The brilliant colored films were characterized using glancing angle x-ray diffraction, and the film was found to be primarily Cu2O. Cyclic voltammetry, chronopotentiometry, scanning electron microscopy, and x-ray photoelectron spectroscopy were also used to characterize these films.

One-step synthesis of polyaniline fibers with double-soft templates and evaluation of their doping process

NASA Astrophysics Data System (ADS)

Chen, Yong; Zhao, Hui; Han, Bing

2014-12-01

In this paper, we have developed a simple, facile, and efficient approach to synthesize polyaniline fibers (PANI fibers) from aniline in the presence of (NH4)2S2O8 with sodium dodecyl benzene sulfonate (SDBS) and L-camphorsulfonic acid (L-CSA) as double templates. The chemical constituents of the composites are characterized by Fourier transformation infrared spectroscopy (FTIR). The results demonstrate that the PANI fibers were synthesized successfully. The morphology of the composites was characterized by scanning electron microscopy (SEM). The SEM and UV-Vis images show an interesting growth and doping process. Moreover, cyclic voltammetry (CV) was used to characterize the electrochemical properties of PANI microfibers. They also give a pair of redox peaks and have better operation stability, which indicates that the composites show distinct electrochemical performance. So the PANI microfibers would have potential applications in the fields of analytical chemistry, bioanalysis, etc.

Polyoxometalate-Graphene Nanocomposite Modified Electrode for Electrocatalytic Detection of Ascorbic Acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Weiying; Du, Dan; Gunaratne, Don

Phosphomolybdate functionalized graphene nanocomposite (PMo 12-GS) has been successfully formed on a glassy carbon electrode (GCE) for the detection of ascorbic acid (AA). The obtained PMo 12-GS modified GCE, was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy and compared with GCE, GS modified GCE, and PMo 12 modified GCE. It shows an increased current and a decrease in over-potential of ~210 mV. The amperometric signals are linearly proportional to the AA concentration in a wide concentration range from 1×10 -6 M to 8×10 -3 M, with a detection limit ofmore » 0.5×10 -6 M. Finally, the PMo 12-GS modified electrode was employed for the determination of the AA level in vitamin C tablets, with recoveries between 96.3 and 100.8 %.« less

Sonoelectrochemical one-pot synthesis of Pt - Carbon black nanocomposite PEMFC electrocatalyst.

PubMed

Karousos, Dionysios S; Desdenakis, Kostantinos I; Sakkas, Petros M; Sourkouni, Georgia; Pollet, Bruno G; Argirusis, Christos

2017-03-01

Simultaneous electrocatalytic Pt-nanoparticle synthesis and decoration of Vulcan XC-72 carbon black substrate was achieved in a novel one-step-process, combining galvanostatic pulsed electrodeposition and pulsed ultrasonication with high power, low-frequency (20kHz) ultrasound. Aqueous chloroplatinic acid precursor baths, as well as carbon black suspensions in the former, were examined and decoration was proven by a combination of characterization methods, namely: dynamic light scattering, transmission electron microscopy, scanning electron microscopy with EDX-analysis and cyclic voltammetry. In particular, PVP was shown to have a beneficial stabilizing effect against free nanoparticle aggregation, ensuring narrow size distributions of the nanoparticles synthesized, but is also postulated to prevent the establishment of a strong metal-substrate interaction. Current pulse amplitude was identified as the most critical nanoparticle size-determining parameters, while only small size particles, under 10nm, appeared to be attached to carbon black. Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

PubMed

Pullamsetty, Ashok; Sundara, Ramaprabhu

2016-10-01

Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. Copyright © 2016 Elsevier Inc. All rights reserved.

Preparation and Characterization of Silanes Films to Protect Electrogalvanized Steel

NASA Astrophysics Data System (ADS)

Seré, Pablo R.; Egli, Walter; Di Sarli, Alejandro R.; Deyá, Cecilia

2018-03-01

Silanes are an interesting alternative to chromate-based surface treatments for temporary protection of electrogalvanized steel. In this work, the protective behavior of 3-mercaptopropyltrimethoxysilane (MTMO), 3-aminopropyltriethoxysilane (AMEO), or 3-glycidoxypropyltrimethoxysilane (GLYMO) films applied on electrogalvanized automotive quality steel sheets has been studied. The silane coating morphology, composition, and porosity were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray fluorescence, immersion in copper sulfate, and cyclic voltammetry. The corrosion protection was evaluated by polarization curves, electrochemical noise measurements, electrochemical impedance spectrometry, and accelerated humidity chamber tests. The results showed that the silanes protect temporarily electrogalvanized steel from corrosion. MTMO forms a relatively thick and cracked film. AMEO and GLYMO films were so thin that they could not be observed by SEM but silicon was detected by EDS. MTMO provided good temporary protection, being an alternative to replace Cr(VI) as protector of electrogalvanized steel.

On the cobalt and cobalt oxide electrodeposition from a glyceline deep eutectic solvent.

PubMed

Sakita, Alan M P; Della Noce, Rodrigo; Fugivara, Cecílio S; Benedetti, Assis V

2016-09-14

The electrodeposition of cobalt and cobalt oxides from a glyceline deep eutectic solvent is reported. Cyclic voltammetry, chronoamperometry, scanning electron microscopy, and Raman spectroscopy are employed to study the Co deposition processes. Surface analysis reveals that metallic cobalt is deposited at potentials less negative than the current peak potential whereas cobalt oxides are detected and electrochemically observed when the deposition is done at more negative potentials. i-t transients are analyzed by applying the Scharifker and Hills (SH) theoretical model. It is concluded that cobalt deposition occurs via a progressive nucleation and growth mechanism for concentrations higher than 0.05 mol L -1 cobalt ions. For concentrations ≤0.025 mol L -1 cobalt ions and low overpotentials, the mechanism changes to instantaneous nucleation. The i m -t m relationships of the SH model are used to determine the values of the kinetic parameters and the cobalt ion diffusion coefficient.

Effect of Ultrasonic on Copper Electroplating from the Non-Cyanide Alkaline Baths

NASA Astrophysics Data System (ADS)

Li, Minggang; Hu, Shuangshuang; Yang, Yejiong; Xu, Shuhan; Zhao, Xixi; Wei, Guoying

2014-06-01

Effects of the different ultrasonic powers on copper electrodeposition from non-cyanide alkaline baths by using pyrophosphate as complexing agent were investigated by different electrochemical methods. Cyclic voltammetry and current transient measurements were used to characterize the nucleation and growth mechanism. It is very obvious that the reduction potential moves to more positive one as the ultrasonic power increases. The quartz crystal microbalance (QCM) and chronoamperometric method were used to study the relationship between the mass change and the deposition time. It was found that the current efficiency of electrolyte under 0, 60, 80 and 100 W is 91.95%, 92.14%, 89.25% and 96.11%, respectively measured by QCM measurements. The surface morphology of the electrodeposited Cu films is analyzed by scanning electron microscopy (SEM). The morphology of copper films electrodeposited under the power of 60 W and 80 W presents a compact surface and the grains are fine and uniform.

Hollow raspberry-like PdAg alloy nanospheres: High electrocatalytic activity for ethanol oxidation in alkaline media

NASA Astrophysics Data System (ADS)

Peng, Cheng; Hu, Yongli; Liu, Mingrui; Zheng, Yixiong

2015-03-01

Palladium-silver (PdAg) alloy nanospheres with unique structure were prepared using a one-pot procedure based on the galvanic replacement reaction. Their electrocatalytic activity for ethanol oxidation in alkaline media was evaluated. The morphology and crystal structure of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical characterization techniques, including cyclic voltammetry (CV) and chronoamperometry (CA) measurements were used to analyze the electrochemical performance of the PdAg alloy nanospheres. The SEM and TEM images showed that the PdAg alloy nanospheres exhibit a hierarchical nanostructure with hollow interiors and porous walls. Compared to the commercial Pd/C catalyst, the as-prepared PdAg alloy nanospheres exhibit superior electrocatalytic activity and stability towards ethanol electro-oxidation in alkaline media, showing its potential as a new non-Pt electro-catalyst for direct alcohol fuel cells (DAFCs).

Preparation and electrocatalytic properties of Pt-SiO2 nanocatalysts for ethanol electrooxidation.

PubMed

Liu, B; Chen, J H; Zhong, X X; Cui, K Z; Zhou, H H; Kuang, Y F

2007-03-01

Due to their high stability in general acidic solutions, SiO(2) nanoparticles were selected as the second catalyst for ethanol oxidation in sulfuric acid aqueous solution. Pt-SiO(2) nanocatalysts were prepared in this paper. The micrography and elemental composition of Pt-SiO(2) nanoparticles were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The electrocatalytic properties of Pt-SiO(2) nanocatalysts for ethanol oxidation were investigated by cyclic voltammetry. Under the same Pt loading mass and experimental conditions for ethanol oxidation, Pt-SiO(2) nanocatalysts show higher activity than PtRu/C (E-Tek), Pt/C (E-Tek), and Pt catalysts. Additionally, Pt-SiO(2) nanocatalysts possess good anti-poisoning ability. The results indicate that Pt-SiO(2) nanocatalysts may have good potential applications in direct ethanol fuel cells.

A comparative study of layered transition metal oxide cathodes for application in sodium-ion battery.

PubMed

Hasa, Ivana; Buchholz, Daniel; Passerini, Stefano; Hassoun, Jusef

2015-03-11

Herein, we report a study on P-type layered sodium transition metal-based oxides with a general formula of NaxMO2 (M = Ni, Fe, Mn). We synthesize the materials via coprecipitation followed by annealing in air and rinsing with water, and we examine the electrodes as cathodes for sodium-ion batteries using a propylene carbonate-based electrolyte. We fully investigate the effect of the Ni-to-Fe ratio, annealing temperature, and sodium content on the electrochemical performances of the electrodes. The impact of these parameters on the structural and electrochemical properties of the materials is revealed by X-ray diffraction, scanning electron microscopy, and cyclic voltammetry, respectively. The suitability of this class of P-type materials for sodium battery application is finally demonstrated by cycling tests revealing an excellent electrochemical performance in terms of delivered capacity (i.e., about 200 mAh g(-1)) and charge-discharge efficiency (approaching 100%).

Simple and Fast Method for Fabrication of Endoscopic Implantable Sensor Arrays

PubMed Central

Tahirbegi, I. Bogachan; Alvira, Margarita; Mir, Mònica; Samitier, Josep

2014-01-01

Here we have developed a simple method for the fabrication of disposable implantable all-solid-state ion-selective electrodes (ISE) in an array format without using complex fabrication equipment or clean room facilities. The electrodes were designed in a needle shape instead of planar electrodes for a full contact with the tissue. The needle-shape platform comprises 12 metallic pins which were functionalized with conductive inks and ISE membranes. The modified microelectrodes were characterized with cyclic voltammetry, scanning electron microscope (SEM), and optical interferometry. The surface area and roughness factor of each microelectrode were determined and reproducible values were obtained for all the microelectrodes on the array. In this work, the microelectrodes were modified with membranes for the detection of pH and nitrate ions to prove the reliability of the fabricated sensor array platform adapted to an endoscope. PMID:24971473

3D-Printed Graphene/Polylactic Acid Electrodes Promise High Sensitivity in Electroanalysis.

PubMed

Manzanares Palenzuela, C Lorena; Novotný, Filip; Krupička, Petr; Sofer, Zdeněk; Pumera, Martin

2018-05-01

Additive manufacturing provides a unique tool for prototyping structures toward electrochemical sensing, due to its ability to produce highly versatile, tailored-shaped devices in a low-cost and fast way with minimized waste. Here we present 3D-printed graphene electrodes for electrochemical sensing. Ring- and disc-shaped electrodes were 3D-printed with a Fused Deposition Modeling printer and characterized using cyclic voltammetry and scanning electron microscopy. Different redox probes K 3 Fe(CN) 6 :K 4 Fe(CN) 6 , FeCl 3 , ascorbic acid, Ru(NH 3 ) 6 Cl 3 , and ferrocene monocarboxylic acid) were used to assess the electrochemical performance of these devices. Finally, the electrochemical detection of picric acid and ascorbic acid was carried out as proof-of-concept analytes for sensing applications. Such customizable platforms represent promising alternatives to conventional electrodes for a wide range of sensing applications.

Correlation of surface site formation to nanoisland growth in the electrochemical roughening of Pt(111)

NASA Astrophysics Data System (ADS)

Jacobse, Leon; Huang, Yi-Fan; Koper, Marc T. M.; Rost, Marcel J.

2018-03-01

Platinum plays a central role in a variety of electrochemical devices and its practical use depends on the prevention of electrode degradation. However, understanding the underlying atomic processes under conditions of repeated oxidation and reduction inducing irreversible surface structure changes has proved challenging. Here, we examine the correlation between the evolution of the electrochemical signal of Pt(111) and its surface roughening by simultaneously performing cyclic voltammetry and in situ electrochemical scanning tunnelling microscopy (EC-STM). We identify a `nucleation and early growth' regime of nanoisland formation, and a `late growth' regime after island coalescence, which continues up to at least 170 cycles. The correlation analysis shows that each step site that is created in the `late growth' regime contributes equally strongly to both the electrochemical and the roughness evolution. In contrast, in the `nucleation and early growth' regime, created step sites contribute to the roughness, but not to the electrochemical signal.

Investigation of Charge Transfer Kinetics at Carbon/Hydroquinone Interfaces for Redox-Active-Electrolyte Supercapacitors.

PubMed

Park, Jinwoo; Kumar, Vipin; Wang, Xu; Lee, Pooi See; Kim, Woong

2017-10-04

The redox-active electrolyte supercapacitor (RAES) is a relatively new type of energy storage device. Simple addition of selected redox species in the electrolyte can greatly enhance the energy density of supercapacitors relative to traditional electric double layer capacitors (EDLCs) owing to redox reactions. Studies on the kinetics at the interface of the electrode and redox mediator are important when developing RAESs. In this work, we employ highly accurate scanning electrochemical microscopy (SECM) to extract the kinetic constants at carbon/hydroquinone interfaces. The charge transfer rate constants are 1.2 × 10 -2 and 1.3 × 10 -2 cm s -1 for the carbon nanotube/hydroquinone and reduced graphene oxide/hydroquinone interfaces, respectively. These values are higher than those obtained by the conventional cyclic voltammetry method, approximately by an order of magnitude. The evaluation of heterogeneous rate constants with SECM would be the cornerstone for understanding and developing high performance RAESs.

Effect of hydroxyl group position at imine structure on corrosion inhibition of mild steel in 0.5 m NaCl

NASA Astrophysics Data System (ADS)

Mohd, Yusairie; Dzolin, Syaidah Athirah; Bahron, Hadariah; Halim, Nurul Huda Abdul

2017-12-01

Corrosion is inherent for mild steel and it can be retarded through many approaches including electrodeposition of inert inhibitors in the form of organic molecules. Salicylideneaniline (L1) and 4-hydroxybenzalaniline (L2) were electrodeposited on mild steel using cyclic voltammetry (CV) using 0.1 M inhibitor concentration in 0.3 M NaOH. The scanning potential range for coating via CV was set from 0 - 2 V and back to 0 V for five cycles. A yellow film was observed covering the surface of the mild steel. The corrosion behavior of coated and uncoated mild steel was studied using Linear Polarization Resistance (LPR) in 0.5 M NaCl. Both coated mild steel specimens showed better corrosion resistance than the uncoated, with L1 providing a better inhibition protection with the inhibition efficiency of 80.51 %.

Flow injection amperometric detection of insulin at cobalt hydroxide nanoparticles modified carbon ceramic electrode.

PubMed

Habibi, Esmaeil; Omidinia, Eskandar; Heidari, Hassan; Fazli, Maryam

2016-02-15

Cobalt hydroxide nanoparticles were prepared onto a carbon ceramic electrode (CHN|CCE) using the cyclic voltammetry (CV) technique. The modified electrode was characterized by X-ray diffraction and scanning electron microscopy. The results showed that CHN with a single-layer structure was uniformly electrodeposited on the surface of CCE. The electrocatalytic activity of the modified electrode toward the oxidation of insulin was studied by CV. CHN|CCE was also used in a homemade flow injection analysis system for insulin determination. The limit of detection (signal/noise [S/N] = 3) and sensitivity were found to be 0.11 nM and 11.8 nA/nM, respectively. Moreover, the sensor was used for detection of insulin in human serum samples. This sensor showed attractive properties such as high stability, reproducibility, and high selectivity. Copyright © 2015 Elsevier Inc. All rights reserved.

Electrochemical Analysis of Neurotransmitters

PubMed Central

Bucher, Elizabeth S.; Wightman, R. Mark

2016-01-01

Chemical signaling through the release of neurotransmitters into the extracellular space is the primary means of communication between neurons. More than four decades ago, Ralph Adams and his colleagues realized the utility of electrochemical methods for the study of easily oxidizable neurotransmitters, such as dopamine, norepinephrine, and serotonin and their metabolites. Today, electrochemical techniques are frequently coupled to microelectrodes to enable spatially resolved recordings of rapid neurotransmitter dynamics in a variety of biological preparations spanning from single cells to the intact brain of behaving animals. In this review, we provide a basic overview of the principles underlying constant-potential amperometry and fast-scan cyclic voltammetry, the most commonly employed electrochemical techniques, and the general application of these methods to the study of neurotransmission. We thereafter discuss several recent developments in sensor design and experimental methodology that are challenging the current limitations defining the application of electrochemical methods to neurotransmitter measurements. PMID:25939038

Experimental and computational study of electronic, electrochemical and thermal properties of quinoline phosphate

NASA Astrophysics Data System (ADS)

Ben Issa, Takoua; Ben Ali Hassine, Chedia; Ghalla, Houcine; Barhoumi, Houcine; Benhamada, Latifa

2018-06-01

In this work, the electronic behavior, charge transfer, non linear optical (NLO) properties, and thermal stability of the quinoline phosphate (QP) have been investigated. The experimental UV-Vis spectrum has been recorded in the range of 200-800 nm. Additionally, the absorption spectrum was reproduced by time-dependent density functional theory (TD-DFT) method with B3LYP functional and with empirical dispersion corrections D3BJ in combination with the 6-311+G(d,p) basis set. The electronic properties such as HOMO-LUMO energy gap and chemical reactivity have been calculated. The electrochemical characterization of the title compound is investigated using cyclic voltammetry and impedance spectroscopy methods. Finally, the thermal stability of the QP is discussed in term of differential scanning calorimetry (DSC) measurement, which showed that QP compound is thermally stable up to 150 °C.

A simple ultrasensitive electrochemical sensor for simultaneous determination of gallic acid and uric acid in human urine and fruit juices based on zirconia-choline chloride-gold nanoparticles-modified carbon paste electrode.

PubMed

Shahamirifard, Seyed Alireza; Ghaedi, Mehrorang; Razmi, Zahra; Hajati, Shaaker

2018-08-30

The determination of gallic acid (GA) and uric acid (UA) is essential due to their biological properties. Numerous methods have been reported for the analysis of GA and UA in various real samples. However, the development of a simple, rapid and practical sensor still remains a great challenge. Here, a carbon paste electrode (CPE) was modified by nanocomposite containing zirconia nanoparticles (ZrO 2 NPs), Choline chloride (ChCl) and gold nanoparticles (AuNPs) to construct ZrO 2 -ChCl-AuNPs/CPE as electrochemical sensor for the simultaneous electro-oxidation of GA and UA. Characterization was performed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The modified electrode was investigated by different methods including electrochemical impedance spectroscopy and cyclic voltammetry. Kinetic parameters such as charge transfer coefficient, standard heterogeneous electron transfer rate constant and other parameters were calculated via voltammetry techniques. Differential pulse voltammetry was used for simultaneous determination of GA and UA applying the ZrO 2 -ChCl-AuNPs/CPE electrode. At the optimum conditions, this sensor showed a linear response in the ranges 0.22- 55 and 0.12-55 µM for GA and UA, respectively. In addition, low detection limits of 25 and 15 nM were obtained for GA and UA, respectively. Furthermore, ZrO 2 -ChCl-AuNPs/CPE was successfully applied for the independent determination of GA in green tea and fruit juice as well as the simultaneous determination of GA and UA in human urine samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Nanomolar determination of 4-nitrophenol based on a poly(methylene blue)-modified glassy carbon electrode.

PubMed

Giribabu, Krishnamoorthy; Suresh, Ranganathan; Manigandan, Ramadoss; Munusamy, Settu; Kumar, Sivakumar Praveen; Muthamizh, Selvamani; Narayanan, Vengidusamy

2013-10-07

A poly(methylene blue)-modified glassy carbon electrode (PMB/GCE) was fabricated by electropolymerisation of methylene blue on a GCE and further utilized to investigate the electrochemical determination of 4-nitrophenol (4-NP) by cyclic voltammetry (CV), differential pulse voltammetry and chronocoulometry. The morphology of the PMB on GCE was examined using a scanning electron microscope (SEM). An oxidation peak of 4-NP at the PMB modified electrode was observed at 0.28 V, and in the case of bare GCE, no oxidation peak was observed, which indicates that PMB/GCE exhibits a remarkable effect on the electrochemical determination of 4-NP. Due to this remarkable effect of PMB/GCE, a sensitive and simple electrochemical method was proposed for the determination of 4-NP. The effect of the scan rate and pH was investigated to determine the optimum conditions at which the PMB/GCE exhibits a higher sensitivity with a lower detection limit. Moreover, kinetic parameters such as the electron transfer number, proton transfer number and standard heterogeneous rate constant were calculated. Under optimum conditions, the oxidation current of 4-NP is proportional to its concentration in the range of 15-250 nM with a correlation coefficient of 0.9963. The detection limit was found to be 90 nM (S/N = 3). The proposed method based on PMB/GCE is simple, easy and cost effective. To further confirm its possible application, the proposed method was successfully used for the determination of 4-NP in real water samples with recoveries ranging from 97% to 101.6%. The interference due to sodium, potassium, calcium, magnesium, copper, zinc, iron, sulphate, carbonate, chloride, nitrate and phosphate was found to be almost negligible.

Adenine-functionalized Spongy Graphene for Green and High-Performance Supercapacitors

PubMed Central

El-Gendy, Dalia M.; Ghany, Nabil A. Abdel; El Sherbini, E. E. Foad; Allam, Nageh K.

2017-01-01

A simple method is demonstrated to prepare spongy adenine-functionalized graphene (SFG) as interconnected, porous 3-dimensional (3D) network crinkly sheets. Such 3D network structure provides better contact at the electrode/electrolyte interface and facilitates the charge transfer kinetics. The fabricated SFG was characterized by X-ray diffraction (XRD), FTIR, scanning electron microscopy (FESEM), Raman spectroscopy, thermogravimetric analysis (TGA), UV−vis absorption spectroscopy, and transmission electron microscopy (TEM). The synthesized materials have been evaluated as supercapacitor materials in 0.5 M H2SO4 using cyclic voltammetry (CV) at different potential scan rates, and galvanostatic charge/discharge tests at different current densities. The SFG electrodes showed a maximum specific capacitance of 333 F/g at scan rate of 1 mV/s and exhibited excellent cycling retention of 102% after 1000 cycles at 200 mV/s. The energy density was 64.42 Wh/kg with a power density of 599.8 W/kg at 1.0 A/g. Those figures of merit are much higher than those reported for graphene-based materials tested under similar conditions. The observed high performance can be related to the synergistic effects of the spongy structure and the adenine functionalization. PMID:28216668

Surface-Enhanced Raman Scattering for Redox-Active Adsorbates: Pentaammineosmium(III)/(II) and Pentaammineruthenium(II) Containing Nitrogen Heterocycle Ligands.

DTIC Science & Technology

1984-04-01

Ill) and Os(Il) as determined using SERS are in good agreement with those obtained from rapid cyclic voltametry . The bulk-phase Raman spectra exhibit...under conventional conditions -i ( sweep rates ca. 100-500 mV sec ; reactant concentration ca. 1 ml_ for which the contribution from any initially...couple can also be obtained using cyclic voltammetry. -1 This entails using sufficiently rapid sweep rates (Z 20 V sec ) and small bulk reactant

Fabrication of Carbon Nanotube Networks on Three-Dimensional Building Blocks and Their Applications

DTIC Science & Technology

2012-10-27

increases the detection efficiency via sorting of analyte. There are some reports for sorting or separating blood cell, colloidal and bacteria by...the substrates for cyclic voltammetry (CV), pulsed bias of ECD was applied at -1.2 V during 90, 120 and 150 sec for 1, 3 and 5 μm pillar substrates...Deposition with Al2O3: The atomic layer deposition (ALD, Cyclic 4000, Genitech) was introduced to deposit the Al2O3 on the surfaces of network

Fabrication strategies, sensing modes and analytical applications of ratiometric electrochemical biosensors.

PubMed

Jin, Hui; Gui, Rijun; Yu, Jianbo; Lv, Wei; Wang, Zonghua

2017-05-15

Previously developed electrochemical biosensors with single-electric signal output are probably affected by intrinsic and extrinsic factors. In contrast, the ratiometric electrochemical biosensors (RECBSs) with dual-electric signal outputs have an intrinsic built-in correction to the effects from system or background electric signals, and therefore exhibit a significant potential to improve the accuracy and sensitivity in electrochemical sensing applications. In this review, we systematically summarize the fabrication strategies, sensing modes and analytical applications of RECBSs. First, the different fabrication strategies of RECBSs were introduced, referring to the analytes-induced single- and dual-dependent electrochemical signal strategies for RECBSs. Second, the different sensing modes of RECBSs were illustrated, such as differential pulse voltammetry, square wave voltammetry, cyclic voltammetry, alternating current voltammetry, electrochemiluminescence, and so forth. Third, the analytical applications of RECBSs were discussed based on the types of target analytes. Finally, the forthcoming development and future prospects in the research field of RECBSs were also highlighted. Copyright © 2017 Elsevier B.V. All rights reserved.

Reagentless Detection of Low-Molecular-Weight Triamterene Using Self-Doped TiO2 Nanotubes.

PubMed

Hudari, Felipe F; Bessegato, Guilherme G; Bedatty Fernandes, Flávio C; Zanoni, Maria V B; Bueno, Paulo R

2018-06-19

TiO 2 nanotube electrodes were self-doped by electrochemical cathodic polarization, potentially converting Ti 4+ into Ti 3+ , and thereby increasing both the normalized conductance and capacitance of the electrodes. One-hundred (from 19.2 ± 0.1 μF cm -2 to 1.9 ± 0.1 mF cm -2 for SD-TNT) and two-fold (from ∼6.2 to ∼14.4 mS cm -2 ) concomitant increases in capacitance and conductance, respectively, were achieved in self-doped TiO 2 nanotubes; this was compared with the results for their undoped counterparts. The increases in the capacitance and conductance indicate that the Ti 3+ states enhance the density of the electronic states; this is attributed to an existing relationship between the conductance and capacitance for nanoscale structures built on macroscopic electrodes. The ratio between the conductance and capacitance was used to detect and quantify, in a reagentless manner, the triamterene (TRT) diuretic by designing an appropriate doping level of TiO 2 nanotubes. The sensitivity was improved when using immittance spectroscopy (Patil et al. Anal. Chem. 2015, 87, 944-950; Bedatty Fernandes et al. Anal. Chem. 2015, 87, 12137-12144) (2.4 × 10 6 % decade -1 ) compared to cyclic voltammetry (5.8 × 10 5 % decade -1 ). Furthermore, a higher linear range from 0.5 to 100 μmol L -1 (5.0 to 100 μmol L -1 for cyclic voltammetry measurements) and a lower limit-of-detection of approximately 0.2 μmol L -1 were achieved by using immittance function methodology (better than the 4.1 μmol L -1 obtained by using cyclic voltammetry).

Synthesis of 2-Azulenyltetrathiafulvalenes by Palladium-Catalyzed Direct Arylation of 2-Chloroazulenes with Tetrathiafulvalene and Their Optical and Electrochemical Properties.

PubMed

Shoji, Taku; Araki, Takanori; Sugiyama, Shuhei; Ohta, Akira; Sekiguchi, Ryuta; Ito, Shunji; Okujima, Tetsuo; Toyota, Kozo

2017-02-03

Tetrathiafulvalene (TTF) derivatives with 2-azulenyl substituents 5-11 were prepared by the palladium-catalyzed direct arylation reaction of 2-chloroazulenes with TTF in good yield. Photophysical properties of these compounds were investigated by UV-vis spectroscopy and theoretical calculations. Redox behavior of the novel azulene-substituted TTFs was examined by using cyclic voltammetry and differential pulse voltammetry, which revealed their multistep electrochemical oxidation and/or reduction properties. Moreover, these TTF derivatives showed significant spectral change in the visible region under the redox conditions.

Electrochemical evaluation of sweet sorghum fermentable sugar bioenergy feedstock

USDA-ARS?s Scientific Manuscript database

Redox active constituents of sorghum, e.g., anthocyanin, flavonoids, and aconitic acid, putatively contribute to its pest resistance. Electrochemical reactivity of sweet sorghum stem juice was evaluated using cyclic voltammetry (CV) for five male (Atlas, Chinese, Dale, Isidomba, N98) and three fema...

Variable Effect during Polymerization

ERIC Educational Resources Information Center

Lunsford, S. K.

2005-01-01

An experiment performing the polymerization of 3-methylthiophene(P-3MT) onto the conditions for the selective electrode to determine the catechol by using cyclic voltammetry was performed. The P-3MT formed under optimized conditions improved electrochemical reversibility, selectivity and reproducibility for the detection of the catechol.

Improved Electrochemical Detection of Zinc Ions Using Electrode Modified with Electrochemically Reduced Graphene Oxide

PubMed Central

Kudr, Jiri; Richtera, Lukas; Nejdl, Lukas; Xhaxhiu, Kledi; Vitek, Petr; Rutkay-Nedecky, Branislav; Hynek, David; Kopel, Pavel; Adam, Vojtech; Kizek, Rene

2016-01-01

Increasing urbanization and industrialization lead to the release of metals into the biosphere, which has become a serious issue for public health. In this paper, the direct electrochemical reduction of zinc ions is studied using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The graphene oxide (GO) was fabricated using modified Hummers method and was electrochemically reduced on the surface of GCE by performing cyclic voltammograms from 0 to −1.5 V. The modification was optimized and properties of electrodes were determined using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The determination of Zn(II) was performed using differential pulse voltammetry technique, platinum wire as a counter electrode, and Ag/AgCl/3 M KCl reference electrode. Compared to the bare GCE the modified GCE/ERGO shows three times better electrocatalytic activity towards zinc ions, with an increase of reduction current along with a negative shift of reduction potential. Using GCE/ERGO detection limit 5 ng·mL−1 was obtained. PMID:28787832

Electrochemical synthesis of poly(pyrrole-co-o-anisidine)/chitosan composite films

NASA Astrophysics Data System (ADS)

Yalçınkaya, Süleyman; Çakmak, Didem

2017-05-01

In this study, poly(pyrrole-co-o-anisidine)/chitosan composite films were electrochemically synthesized in various monomers feed ratio (pyrrole: o-anisidine; 9:1, 7:3, 1:1, 3:7 and 1:9) of pyrrole and o-anisidine on the platinum electrode. Electrochemical synthesis of the composite films was carried out via cyclic voltammetry technique. They were characterized by FT-IR, cyclic voltammetry, SEM micrographs, digital images, TGA and DSC techniques. The SEM results indicated that the particle size of the composite decreased with increasing o-anisidine ratio and the films became more likely to be smooth morphology. The TGA results proved that the film of the composite with 1:1 ratio showed highest final degradation temperature and lowest weight loss (83%) compared to copolymer and 9:1 1:9 composite films. The 1:1 composite film had higher thermal stability than copolymer and the other composite films (9:1 1:9). Meanwhile, electrochemical studies exhibited that the 1/9 composite film had good electrochemical stability as well.

Access to enhanced differences in Marcus-Hush and Butler-Volmer electron transfer theories by systematic analysis of higher order AC harmonics.

PubMed

Stevenson, Gareth P; Baker, Ruth E; Kennedy, Gareth F; Bond, Alan M; Gavaghan, David J; Gillow, Kathryn

2013-02-14

The potential-dependences of the rate constants associated with heterogeneous electron transfer predicted by the empirically based Butler-Volmer and fundamentally based Marcus-Hush formalisms are well documented for dc cyclic voltammetry. However, differences are often subtle, so, presumably on the basis of simplicity, the Butler-Volmer method is generally employed in theoretical-experimental comparisons. In this study, the ability of Large Amplitude Fourier Transform AC Cyclic Voltammetry to distinguish the difference in behaviour predicted by the two formalisms has been investigated. The focus of this investigation is on the difference in the profiles of the first to sixth harmonics, which are readily accessible when a large amplitude of the applied ac potential is employed. In particular, it is demonstrated that systematic analysis of the higher order harmonic responses in suitable kinetic regimes provides predicted deviations of Marcus-Hush from Butler-Volmer behaviour to be established from a single experiment under conditions where the background charging current is minimal.

Synthesis, crystal structure, photophysical properties and theoretical studies of a novel bis(phenylisoxazolyl) benzene derivative

NASA Astrophysics Data System (ADS)

de Brito, A. C. F.; Correa, R. S.; Pinto, A. A.; Matos, M. J. S.; Tenorio, J. C.; Taylor, J. G.; Cazati, T.

2018-07-01

Isoxazoles have well established biological activities but, have been underexplored as synthetic intermediates for applications in materials science. The aims of this work are to synthesis a novel isoxazole and analyze its structural and photophysical properties for application in electronic organic materials. The novel bis (phenylisoxazolyl) benzene compound was synthesized in four steps and characterized by NMR, high resolution mass spectrometry, differential thermal analysis, infrared spectroscopy, cyclic voltammetry, ultraviolet-visible spectroscopy, fluorescence spectroscopy, DFT and TDDFT calculations. The molecule presented optical absorption in the ultraviolet region (from 290 nm to 330 nm), with maximum absorption length centered at 306 nm. The molar extinction coefficients (ε), fluorescence emission spectra and quantum efficiencies in chloroform and dimethylformamide solution were determined. Cyclic voltammetry analysis was carried out for estimating the HOMO energy level and these properties make it desirable material for photovoltaic device applications. Finally, the excited-state properties of present compound were calculated by time-dependent density functional theory (TDDFT).

Cyclic voltammetry to evaluate the antioxidant potential in winemaking by-products.

PubMed

José Jara-Palacios, M; Luisa Escudero-Gilete, M; Miguel Hernández-Hierro, J; Heredia, Francisco J; Hernanz, Dolores

2017-04-01

Grape pomace is composed of seeds, skins and stems that are an important source of phenolic substances, which have antioxidant properties and potential benefits to human health. Cyclic voltammetry (CV) has been used to measure the total antioxidant potential of different winemaking by-products. The electrochemical behavior of pomace, seeds, skins and stems was measured by CV and lipid peroxidation inhibition by thiobarbituric acid reactive substances (TBARS) method. Differences for the electrochemical parameter were found between the by-products, pomace and seeds, which presented the greatest voltammetric peak area. Furthermore, the by-products induced inhibition of lipid peroxidation in rat liver homogenates. Pomace and seeds showed higher capacity to inhibit lipid peroxidation than stems and skins, which could be because these by-products are richer in flavanols. Simple regression analyses showed that voltammetric parameters are highly correlated to the values obtained for lipid peroxidation inhibition. CV is a promising technique to estimate the total antioxidant potential of phenolic extract from winemaking by-products. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of PEMFC System Contaminants on the Performance of Pt Catalyst via Cyclic Voltammetry: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, H.; Macomber, C.; Dinh, H. N.

2012-07-01

Using electrochemical cyclic voltammetry as a quick ex-situ screening tool, the impact of the extracted solution and the individual leachable constituents from prospective BOP component materials on the performance and recoverability of the platinum catalyst were evaluated. Taking an extract from Zytel{trademark} HTN51G35HSLR (PPA) as an example, the major leachable organic components are caprolactam and 1,6 hexanediol. While these organic compounds by themselves do poison the Pt catalyst to some extent, such influence is mostly recoverable by means of potential holding and potential cycling. The extracted solution, however, shows a more drastic poisoning effect and it was not recoverable. Thereforemore » the non-recoverable poisoning effect observed for the extracted solution is not from the two organic species studied. This demonstrates the complexity of such a contaminant study. Inorganic compounds that are known poisons like sulfur even in very low concentrations, may have a more dominant effect on the Pt catalyst and the recoverability.« less

The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry.

PubMed

Wang, Xinghao; Liu, Jiaoqin; Qu, Ruijuan; Wang, Zunyao; Huang, Qingguo

2017-08-10

Nanostructured manganese oxides, e.g. MnO 2 , have shown laccase-like catalytic activities, and are thus promising for pollutant oxidation in wastewater treatment. We have systematically compared the laccase-like reactivity of manganese oxide nanomaterials of different crystallinity, including α-, β-, γ-, δ-, and ɛ-MnO 2 , and Mn 3 O 4 , with 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 17β-estradiol (E2) as the probing substrates. The reaction rate behaviors were examined with regard to substrate oxidation and oxygen reduction to evaluate the laccase-like catalysis of the materials, among which γ-MnO 2 exhibits the best performance. Cyclic voltammetry (CV) was employed to assess the six MnO x nanomaterials, and the results correlate well with their laccase-like catalytic activities. The findings help understand the mechanisms of and the factors controlling the laccase-like reactivity of different manganese oxides nanomaterials, and provide a basis for future design and application of MnO x -based catalysts.

Synthesis of hydrothermally reduced graphene/MnO2 composites and their electrochemical properties as supercapacitors

NASA Astrophysics Data System (ADS)

Li, Zhangpeng; Wang, Jinqing; Liu, Sheng; Liu, Xiaohong; Yang, Shengrong

2011-10-01

Hydrothermally reduced graphene/MnO2 (HRG/MnO2) composites were synthesized by dipping HRG into the mixed aqueous solution of 0.1 M KMnO4 and 0.1 M K2SO4 for different periods of time at room temperature. The morphology and microstructure of the as-prepared composites were characterized by field-emission scanning electron microscopy, X-ray diffraction, Raman microscope, and X-ray photoelectron spectroscopy. The characterizations indicate that MnO2 successfully deposited on HRG surfaces and the morphology of the HRG/MnO2 shows a three-dimensional porous structure with MnO2 homogenously distributing on the HRG surfaces. Capacitive properties of the synthesized composite electrodes were studied using cyclic voltammetry and electrochemical impedance spectroscopy in a three-electrode experimental setup using 1 M Na2SO4 aqueous solution as electrolyte. The main results of electrochemical tests are drawn as follows: the specific capacitance value of HRG/MnO2-200 (HRG dipped into the mixed solution of 0.1 M KMnO4 and 0.1 M K2SO4 for 200 min) electrode reached 211.5 F g-1 at a potential scan rate of 2 mV s-1; moreover, this electrode shows a good cyclic stability and capacity retention. It is anticipated that the synthesized HRG/MnO2 composites will find promising applications in supercapacitors and other devices in virtue of their outstanding characters of good cycle stability, low cost and environmentally benign nature.

Functional Fast Scan Cyclic Voltammetry Assay to Characterize Dopamine D2 and D3 Autoreceptors in the Mouse Striatum

PubMed Central

2010-01-01

Dopamine D2 and D3 autoreceptors are located on presynaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate putamen and nucleus accumbens core and shell. The dopamine D2 agonists (−)-quinpirole hydrochloride and 5,6,7,8-tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate putamen and nucleus accumbens (core and shell) on the basis of their EC50 values and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (±)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in the caudate putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.1 μM lowered the uptake rate in caudate putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the preagonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonists as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum. PMID:20567609

One-step electrodeposition of graphene loaded nickel oxides nanoparticles for acetaminophen detection.

PubMed

Liu, Gui-Ting; Chen, Hui-Fen; Lin, Guo-Ming; Ye, Ping-ping; Wang, Xiao-Ping; Jiao, Ying-Zhi; Guo, Xiao-Yu; Wen, Ying; Yang, Hai-Feng

2014-06-15

An electrochemical sensor of acetaminophen (AP) based on electrochemically reduced graphene (ERG) loaded nickel oxides (Ni2O3-NiO) nanoparticles coated onto glassy carbon electrode (ERG/Ni2O3-NiO/GCE) was prepared by a one-step electrodeposition process. The as-prepared electrode was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrocatalytic properties of ERG/Ni2O3-NiO modified glassy carbon electrode toward the oxidation of acetaminophen were analyzed via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrodes of Ni2O3-NiO/GCE, ERG/GCE, and Ni2O3-NiO deposited ERG/GCE were fabricated for the comparison and the catalytic mechanism understanding. The studies showed that the one-step prepared ERG/Ni2O3-NiO/GCE displayed the highest electro-catalytic activity, attributing to the synergetic effect derived from the unique composite structure and physical properties of nickel oxides nanoparticles and graphene. The low detection limit of 0.02 μM (S/N=3) with the wide linear detection range from 0.04 μM to 100 μM (R=0.998) was obtained. The resulting sensor was successfully used to detect acetaminophen in commercial pharmaceutical tablets and urine samples. Copyright © 2014 Elsevier B.V. All rights reserved.

A glassy carbon electrode modified with cerium phosphate nanotubes for the simultaneous determination of hydroquinone, catechol and resorcinol.

PubMed

Li, Zhen; Yue, Yuhua; Hao, Yanjun; Feng, Shun; Zhou, Xianli

2018-03-12

A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM -1  cm -2 . The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC. Graphical abstract ᅟ.

A high-sensitivity electrochemical immunosensor based on mobile crystalline material-41-polyvinyl alcohol nanocomposite and colloidal gold nanoparticles.

PubMed

Omidfar, Kobra; Zarei, Hajar; Gholizadeh, Fatemeh; Larijani, Bagher

2012-02-15

A novel competitive immunosensor was developed as a model system using anti-human serum albumin (HSA)-conjugated gold nanoparticles (AuNPs) as an electrochemical label and mobile crystalline material-41 (MCM-41)-polyvinyl alcohol (PVA) mesoporous nanocomposite as an immobilization platform. However, no attempt has yet been made to use the MCM-41 as the supporting electrolyte for the electrosynthesis of nonconducting polymer nanocomposite. This hybrid membrane was evaluated extensively by using field emission scanning electron microscopy (FESEM), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) to determine its physicochemical and electrochemical properties in immunosensor application. FESEM revealed an appropriate and stable attachment between HSA and MCM-41 and also a dense layer deposition of MCM-41-HSA-PVA film onto the electrode surfaces. DPV was developed for quantitative determination of antigen in biological samples. A decrease in DPV responses was observed with increasing concentrations of HSA in standard and real samples. In optimal conditions, this immunosensor based on MCM-41-PVA nanocomposite film could detect HSA in a high linear range (0.5-200 μg ml⁻¹) with a low detection limit of 1 ng ml⁻¹. The proposed method showed acceptable reproducibility, stability, and reliability and could also be applied to detect the other antigens. Copyright © 2011 Elsevier Inc. All rights reserved.

Electrochemical Investigation of DA and UA on Carboxylated Graphene Oxide/lanthanum Electrodes with Sundry Content of Ctab

NASA Astrophysics Data System (ADS)

Jiang, J.; Zhu, L.; Qian, W.; Chen, H.; Feng, C.; Han, S.; Lin, H.; Ye, F. Y.

Glassy carbon electrodes (GCE) were modified by carboxylated graphene oxide/lanthanum with various concentrations of hexadecyl trimethyl ammonium bromide (CTAB), and the treated electrodes, called CTAB/GO-COOLa/GCE, were prepared for the detection of uric acid (UA) and dopamine (DA) by using the differential pulse voltammetry (DPV) and the cyclic voltammetry (CV). The results show that the modified electrode’s electrocatalytic activity could be affected by several factors in the examination, they are the pH value of the system, the main content of CTAB, various concentrations and rates of scan. With a combination of carboxylated graphene oxide/lanthanum and CTAB, the resulted CTAB/GO-COOLa/GCE sensors showed preeminent selectivity and obvious catalytic property toward the electro-oxidation of UA and DA. In optimized conditions, the response of the CTAB/GO-COOLa/GCE electrode for DA was linear in the region of 0.03-500.0μM with detection limits of 0.036μM (S/N=3). Two linear response ranges for the determination UA were obtained from ranges of 1 to 200μM and 200 to 1300μM with a detection limit of 0.42μM (S/N=3). Moreover, the refined electrode was used in the inspection of DA and UA in real samples of serum and urine successfully, displaying its potential application of real samples involved in electroanalysis.

Electrocatalytic oxidation of dopamine based on non-covalent functionalization of manganese tetraphenylporphyrin/reduced graphene oxide nanocomposite.

PubMed

Sakthinathan, Subramanian; Lee, Hsin Fang; Chen, Shen-Ming; Tamizhdurai, P

2016-04-15

In the present work, a reduced graphene oxide (RGO) supported manganese tetraphenylporphyrin (Mn-TPP) nanocomposite was electrochemically synthesized and used for the highly selective and sensitive detection of dopamine (DA). The nuclear magnetic resonance, scanning electron microscopy and elemental analysis were confirmed the successful formation of RGO/Mn-TPP nanocomposite. The prepared RGO/Mn-TPP nanocomposite modified electrode exhibited an enhanced electrochemical response to DA with less oxidation potential and enhanced response current. The electrochemical studies revealed that the oxidation of the DA at the composite electrode is a surface controlled process. The cyclic voltammetry, differential pulse voltammetry and amperometry methods were enable to detect DA. The working linear range of the electrode was observed from 0.3 to 188.8 μM, limit of detection was 8 nM and the sensitivity was 2.606 μA μM(-1) cm(-2). Here, the positively charged DA and negatively charged porphyrin modified RGO can accelerate the electrocatalysis of DA via electrostatic attraction, while the negatively charged ascorbic acid (AA) repulsed by the negatively charged electrode surface which supported for good selectivity. The good recovery results obtained for the determination of DA present in DA injection samples and human pathological sample further revealed the good practicality of RGO/Mn-TPP nanocomposite film modified electrode. Copyright © 2016 Elsevier Inc. All rights reserved.

Detection of Quinoline in G. boninense-Infected Plants Using Functionalized Multi-Walled Carbon Nanotubes: A Field Study.

PubMed

Akanbi, Fowotade Sulayman; Yusof, Nor Azah; Abdullah, Jaafar; Sulaiman, Yusran; Hushiarian, Roozbeh

2017-07-01

Carbon nanotubes (CNTs) reinforced with gold nanoparticles (AuNPs) and chitosan nanoparticles (CTSNPs) were anchored on a screen-printed electrode to fabricate a multi-walled structure for the detection of quinoline. The surface morphology of the nanocomposites and the modified electrode was examined by an ultra-high resolution field emission scanning electron microscope (FESEM), and Fourier-transform infrared (FT-IR) spectroscopy was used to confirm the presence of specific functional groups on the multi-walled carbon nanotubes MWCNTs. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to monitor the layer-by-layer assembly of ultra-thin films of nanocomposites on the surface of the electrode and other electrochemical characterizations. Under optimized conditions, the novel sensor displayed outstanding electrochemical reactivity towards the electro-oxidation of quinoline. The linear range was fixed between 0.0004 and 1.0 μM, with a limit of detection (LOD) of 3.75 nM. The fabricated electrode exhibited high stability with excellent sensitivity and selectivity, specifically attributable to the salient characteristics of AuNPs, CTSNPs, and MWCNTs and the synergistic inter-relationship between them. The newly developed electrode was tested in the field. The Ipa increased with an increase in the amount of quinoline solution added, and the peak potential deviated minimally, depicting the real capability of the newly fabricated electrode.

Crumpled rGO-supported Pt-Ir bifunctional catalyst prepared by spray pyrolysis for unitized regenerative fuel cells

NASA Astrophysics Data System (ADS)

Kim, In Gyeom; Nah, In Wook; Oh, In-Hwan; Park, Sehkyu

2017-10-01

Three-dimensional (3D) crumpled reduced graphene oxide supported Pt-Ir alloys that served as bifunctional oxygen catalysts for use in untized regenerative fuel cells were synthesized by a facile spray pyrolysis method. Pt-Ir catalysts supported on rGO (Pt-Ir/rGOs) were physically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to observe change in composition by heat treatment, alloying, and morphological transition of the catalysts. Their catalytic activities and stabilities for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) conditions were electrochemically investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), potential cycling and hold tests on the rotating disk electrode (RDE). Pt-Ir/rGO with no post heat-treatment (Pt-Ir/rGO_NP) showed a lower activity for ORR and OER although metal nanoparticles decorated on the support are relatively small. However, Pt-Ir/rGO showed remarkably enhanced activity following heat treatment, depending on temperature. Pt-Ir/rGO heat-treated at 600 °C after spray pyrolysis (Pt-Ir/rGO_P600) exhibited a higher activity and stability than a commercially available Pt/C catalyst kept under the ORR condition, and it also revealed a comparable OER activity and durability versus the commercial unsupported Ir catalyst.

K4[Fe(CN)6] immobilized anion sensitive protonated amine functionalized polysilsesquioxane films for ultra-low electrochemical detection of dsDNA.

PubMed

Silambarasan, Krishnamoorthy; Narendra Kumar, Alam Venugopal; Joseph, James

2016-03-14

Charge transport in polymeric films bound by redox reagents is a topic of current interest. The dynamics of electroinactive ions across the interface is studied by immobilizing ferrocyanide anion in a polysilsesquioxanes (PSQs) modified electrode. Redox reagents can stay in the polymeric film by either physical forces or electrostatic binding. The present work describes the immobilization of ferro/ferricyanide redox couples in PSQ films possessing protonated amine functional groups by electrostatic interactions. Charge transport in [Fe(CN)6](4-)-PSQs film was found to be anion dependent, and its formal potential value varied with the relative hydrophilic or hydrophobic nature of the anion used in the supporting electrolyte, unlike the observed dependence on solution cation for electrodes modified with metal hexacyanoferrates (Prussian Blue analogues). The [Fe(CN)6](4-) bound PSQs films were extensively characterized by varying different supporting electrolytes anions using cyclic voltammetry. The redox peak currents were linearly proportional to the square root of the scan rate, implying that the transport of charge carriers is accompanied with redox ion diffusion and electron hopping in a confined space. dsDNA molecules were found to interact with this polymer matrix through anionic phosphate groups. Both voltammetry and A.C. impedance spectroscopy studies revealed that these interactions could be exploited for the determination of ultra-low level (0.5 attomolar) of dsDNA present in aqueous solution.

Development and application of 3-chloro-1,2-propandiol electrochemical sensor based on a polyaminothiophenol modified molecularly imprinted film.

PubMed

Sun, Xiulan; Zhang, Lijuan; Zhang, Hongxia; Qian, He; Zhang, Yinzhi; Tang, Lili; Li, Zaijun

2014-05-21

In this work, a novel electrochemical sensor for 3-chloro-1,2-propandiol (3-MCPD) detection based on a gold nanoparticle-modified glassy carbon electrode (AuNP/GCE) coated with a molecular imprinted polymer (MIP) film was constructed. p-Aminothiophenol (p-ATP) and 3-MCPD were self-assembled on a AuNP/GCE surface, and then a MIP film was formed by electropolymerization. The 3-MCPD template combined with p-ATP during self-assembly and electropolymerization, and the cavities matching 3-MCPD remained after the removal of the template. The MIP sensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and scanning electron microscopy (SEM). Many factors that affected the performance of the MIP membrane were discussed and optimized. Under optimal conditions, the DPV current was linear with the log of the 3-MCPD concentration in the range from 1.0 × 10(-17) to 1.0 × 10(-13) mol L(-1) (R(2) = 0.9939), and the detection limit was 3.8 × 10(-18) mol L(-1) (S/N = 3). The average recovery rate of 3-MCPD from spiked soy sauce samples ranged from 95.0% to 106.4% (RSD < 3.49%). Practically, the sensor showed high sensitivity, good selectivity, excellent reproducibility, and stability during the quantitative determination of 3-MCPD.

Lable-free quadruple signal amplification strategy for sensitive electrochemical p53 gene biosensing.

PubMed

Wang, Zonghua; Xia, Jianfei; Song, Daimin; Zhang, Feifei; Yang, Min; Gui, Rijun; Xia, Lin; Bi, Sai; Xia, Yanzhi

2016-03-15

A versatile label-free quadruple signal amplification biosensing platform for p53 gene (target DNA) detection was proposed. The chitosan-graphene (CS-GR) modified electrode with excellent electron transfer ability could provide a large specific surface for high levels of AuNPs-DNA attachment. The large amount of AuNPs could immobilize more capture probes and enhance the electrochemical signal with the excellent electrocatalytic activity. Furthermore, with the assist of N.BstNB I (the nicking endonuclease), target DNA could be reused and more G-quadruplex-hemin DNAzyme could be formed, allowing significant signal amplification in the presence of H2O2. Such strategy can enhance the oxidation-reduction reaction of adsorbed methylene blue (MB) and efficiently improve the sensitivity of the proposed biosensor. The morphologies of materials and the stepwise biosensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) signals of MB provided quantitative measures of the concentrations of target DNA, with a linear calibration range of 1.0 × 10(-15)-1.0 × 10(-9)M and a detection limit of 3.0 × 10(-16)M. Moreover, the resulting biosensor also exhibited good specificity, acceptable reproducibility and stability, indicating that the present strategy was promising for broad potential application in clinic assay. Copyright © 2015 Elsevier B.V. All rights reserved.

A Nano-Au/C-MWCNT based label free amperometric immunosensor for the detection of capsicum chlorosis virus in bell pepper.

PubMed

Sharma, Anshul; Kaushal, Ankur; Kulshrestha, Saurabh

2017-07-01

Accurate and on time diagnosis of plant viruses is an essential prerequisite for efficient control in field conditions. A number of diagnostic methods have been reported with the required level of sensitivity. Here, we propose a label free immunosensor for efficient and sensitive detection of capsicum chlorosis virus (CaCV) in bell pepper. Antigen was immobilized over the surface of gold nanoparticle/multi-walled carbon nanotube (Nano-Au/C-MWCNT) screen printed electrodes using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) cross linking chemistry followed by interaction with groundnut bud necrosis virus (GBNV)/CaCV specific polyclonal antibody. The electrochemical response was measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV) using the redox indicator. Electrode surface characterization was done by performing scanning electron microscopy (SEM). Electrochemical studies showed positive results at different antigenic dilutions ranging from 10 -2 - 8x10 -5 . The sensitivity of the immunosensor developed has been compared with direct antigen coated enzyme-linked immunosorbent assay (DAC-ELISA) and the results showed that the immunosensor developed was 800-1000 times more sensitive, when compared to DAC-ELISA for CaCV detection. The immunosensor we have developed is economical and sensitive and could be used for immediate determination of the presence of virus in extracts from bell pepper leaves.

Detection of Quinoline in G. boninense-Infected Plants Using Functionalized Multi-Walled Carbon Nanotubes: A Field Study

PubMed Central

Akanbi, Fowotade Sulayman; Yusof, Nor Azah; Abdullah, Jaafar; Sulaiman, Yusran; Hushiarian, Roozbeh

2017-01-01

Carbon nanotubes (CNTs) reinforced with gold nanoparticles (AuNPs) and chitosan nanoparticles (CTSNPs) were anchored on a screen-printed electrode to fabricate a multi-walled structure for the detection of quinoline. The surface morphology of the nanocomposites and the modified electrode was examined by an ultra-high resolution field emission scanning electron microscope (FESEM), and Fourier-transform infrared (FT-IR) spectroscopy was used to confirm the presence of specific functional groups on the multi-walled carbon nanotubes MWCNTs. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to monitor the layer-by-layer assembly of ultra-thin films of nanocomposites on the surface of the electrode and other electrochemical characterizations. Under optimized conditions, the novel sensor displayed outstanding electrochemical reactivity towards the electro-oxidation of quinoline. The linear range was fixed between 0.0004 and 1.0 μM, with a limit of detection (LOD) of 3.75 nM. The fabricated electrode exhibited high stability with excellent sensitivity and selectivity, specifically attributable to the salient characteristics of AuNPs, CTSNPs, and MWCNTs and the synergistic inter-relationship between them. The newly developed electrode was tested in the field. The Ipa increased with an increase in the amount of quinoline solution added, and the peak potential deviated minimally, depicting the real capability of the newly fabricated electrode. PMID:28671561

Sodium dodecyl sulfate-assisted hydrothermal synthesis of mesoporous nickel cobaltite nanoparticles with enhanced catalytic activity for methanol electrooxidation

NASA Astrophysics Data System (ADS)

Ding, Rui; Qi, Li; Jia, Mingjun; Wang, Hongyu

2014-04-01

Mesoporous nickel cobaltite (NiCo2O4) nanoparticles have been synthesized via a facile hydrothermal strategy with the assistance of sodium dodecyl sulfate (SDS) soft template (ST). Their physicochemical properties have been characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. Their electrocatalytic performances have been examined by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit a typical nanoscale crystalline hexagonal morphology with specific surface area (SSA) and mesopore volume of 88.63 m2 g-1 and 0.298 cm3 g-1. Impressively, the SDS-assisted NiCo2O4 electrode shows a catalytic current density of 125 mA cm-2 and 72% retention for consecutive 1000 s at 0.6 V in 1 M KOH and 0.5 M CH3OH electrolytes towards methanol (CH3OH) electrooxidation, which is better than the one without SDS assistance. The pronounced electrocatalytic activity is largely ascribed to their higher surface intensities of Co and Ni species and superior mesoporous nanostructures, which provide the richer electroactive sites and faster electrochemical kinetics, leading to the enhanced electrocatalytic activity.

Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode.

PubMed

Farahi, Abdelfettah; Achak, Mounia; El Gaini, Laila; El Mhammedi, Moulay Abderrahim; Bakasse, Mina

2015-09-01

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10 -7  mol/L to 1.0 × 10 -3  mol/L. The detection limit and quantification limit were 2.01 × 10 -8  mol/L and 6.073 × 10 -8  mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10 -5  mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures. Copyright © 2015. Published by Elsevier B.V.

Bacterial cellulose-based sheet-like carbon aerogels for the in situ growth of nickel sulfide as high performance electrode materials for asymmetric supercapacitors.

PubMed

Zuo, Lizeng; Fan, Wei; Zhang, Youfang; Huang, Yunpeng; Gao, Wei; Liu, Tianxi

2017-03-30

Electroactive materials, such as nickel sulfide (NiS), with high theoretical capacities have attracted broad interest to fabricate highly efficient supercapacitors. Preventing aggregation and increasing the conductivity of NiS particles are key challenging tasks to fully achieve excellent electrochemical properties of NiS. One effective approach to solve these problems is to combine NiS with highly porous and conductive carbon materials such as carbon aerogels. In this study, a green and facile method for the in situ growth of NiS particles on bacterial cellulose (BC)-derived sheet-like carbon aerogels (CAs) has been reported. CA prepared by the dissolution-gelation-carbonization process was used as a framework to construct NiS/CA composite aerogels with NiS uniformly decorated on the pore walls of CA. It was found that the NiS/CA composite aerogel electrodes exhibit excellent capacitive performance with high specific capacitance (1606 F g -1 ), good rate capacitance retention (69% at 10 A g -1 ), and enhanced cycling stability (91.2% retention after 10 000 continuous cyclic voltammetry cycles at 100 mV s -1 ). Furthermore, asymmetric supercapacitors (ASCs) were constructed utilizing NiS/CA composite and CA as the positive and negative electrode materials, respectively. Through the synergistic effect of three-dimensional porous structures and conductive networks derived from CA and the high capacitive performance offered by NiS, the ASC device exhibited an energy density of ∼21.5 Wh kg -1 and a power density of 700 W kg -1 at the working voltage of 1.4 V in 2 M KOH aqueous solution. The ASC device also showed excellent long-term cycle stability with ∼87.1% specific capacitance retention after 10 000 cycles of cyclic voltammetry scans. Therefore, the NiS/CA composite shows great potential as a promising alternative to high-performance electrode materials for supercapacitors.

Voltammetric behavior of Mammeisin (MA) at a glassy carbon electrode and its interaction with Bovine Serum Albumin (BSA).

PubMed

Leuna, Jules-Blaise Mabou; Sop, Sergeot Kungo; Makota, Suzanne; Njanja, Evangeline; Ebelle, Thiery Christophe; Azebaze, Anatole Guy; Ngameni, Emmanuel; Nassi, Achille

2018-02-01

The electrochemical oxidation of Mammeisin (MA) was studied in a solution containing acetone and 0.1M phosphate buffer +0.1M KCl (pH=5.3) at a glassy carbon electrode (GCE), using cyclic (CV) and square wave voltammetry (SWV). MA showed a quasi-reversible process, which is pH dependent and that involves the exchange of two electrons and two protons. The oxidation product was adsorbed by the electrode surface to form a film that blocks active sites over repetitive cyclic. Moreover, the interaction of MA and bovine serum albumin (BSA) was studied by CV and SWV at different pHs (5.4, 7.2, 9.5). As a result of the affinity binding with BSA, electrochemically inactive complex was formed. In addition, the oxidation potential of MA in the presence of BSA depends on the pH. The diffusion coefficients of both free and bound MA were estimated from the cyclic voltammetry data using the method developed by Randles-Sevich (D f =9.85×10 -5 cm 2 s -1 and D b =1.27×10 -9 cm 2 s -1 ) and the binding constant of MA-BSA complex, K=3.47×10 2 Lmol -1 , was obtained. Copyright © 2017. Published by Elsevier B.V.

Assessing the Electrochemical Behavior of Microcontact-Printed Silver Nanogrids

ERIC Educational Resources Information Center

Sanders, Wesley C.; Iles, Peter; Valcarce, Ron; Salisbury, Kyle; Johnson, Glen; Lines, Aubry; Meyers, John; Page, Cristofer; Vanweerd, Myles; Young, Davies

2018-01-01

This paper describes a laboratory exercise used to address the ongoing need for nanotechnology-related, hands-on laboratory experiences for undergraduate students. Determination of the electrochemical behavior of student-fabricated silver nanogrids is reported. Students successfully used cyclic voltammetry to analyze silver nanogrids printed using…

Voltammetric Thin-Layer Ionophore-Based Films: Part 2. Semi-Empirical Treatment.

PubMed

Yuan, Dajing; Cuartero, Maria; Crespo, Gaston A; Bakker, Eric

2017-01-03

This work reports on a semiempirical treatment that allows one to rationalize and predict experimental conditions for thin-layer ionophore-based films with cation-exchange capacity read out with cyclic voltammetry. The transition between diffusional mass transport and thin-layer regime is described with a parameter (α), which depends on membrane composition, diffusion coefficient, scan rate, and electrode rotating speed. Once the thin-layer regime is fulfilled (α = 1), the membrane behaves in some analogy to a potentiometric sensor with a second discrimination variable (the applied potential) that allows one to operate such electrodes in a multianalyte detection mode owing to the variable applied ion-transfer potentials. The limit of detection of this regime is defined with a second parameter (β = 2) and is chosen in analogy to the definition of the detection limit for potentiometric sensors provided by the IUPAC. The analytical equations were validated through the simulation of the respective cyclic voltammograms under the same experimental conditions. While simulations of high complexity and better accuracy satisfactorily reproduced the experimental voltammograms during the forward and backward potential sweeps (companion paper 1), the semiempirical treatment here, while less accurate, is of low complexity and allows one to quite easily predict relevant experimental conditions for this emergent methodology.

Electrochemical Sensor for Organophosphate Pesticides and Nerve Agents Using Zirconia Nanoparticles as Selective Sorbents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guodong; Lin, Yuehe

2005-09-15

Electrochemical sensor for detection of organophosphate (OP) pesticides and nerve agents using zirconia (ZrO₂) nanoparticles as selective sorbents is presented. Zirconia nanoparticles were electrodynamically deposited onto the polycrystalline gold electrode by cyclic voltammetry. Because of a strong affinity of zirconia to the phosphoric group, nitroaromatic OPs strongly bind to the ZrO₂ nanoparticle surface. The electrochemical characterization and anodic stripping voltammetric performance of bound OPs were evaluated using cyclic voltammetric and square-wave voltammetric (SWV) analysis. SWV was used to monitor the amount of bound OPs and provide simple, fast, and facile quantitative methods for nitroaromatic OP compounds. The sensor surface canmore » be regenerated by successively running SWV scanning. Operational parameters, including the amount of nanoparticles, adsorption time, and the pH of the reaction medium have been optimized. The stripping voltammetric response is highly linear over the 5–200 ng/mL (ppb) methyl parathion range examined (2-min adsorption), with a detection limit of 1 ng/mL (10 min accumulation), and good precision (RSD=5.3 %, n = 10). The promising stripping voltammetric performances open new opportunities for fast, simple, and sensitive analyzing of OPs in environmental and biological samples. These findings can lead to a widespread use of electrochemical sensors to detect OP contaminates.« less

Nanoscale semiconductor Pb1-xSnxSe (x = 0.2) thin films synthesized by electrochemical atomic layer deposition

NASA Astrophysics Data System (ADS)

Lin, Shaoxiong; Zhang, Xin; Shi, Xuezhao; Wei, Jinping; Lu, Daban; Zhang, Yuzhen; Kou, Huanhuan; Wang, Chunming

2011-04-01

In this paper the fabrication and characterization of IV-VI semiconductor Pb1-xSnxSe (x = 0.2) thin films on gold substrate by electrochemical atomic layer deposition (EC-ALD) method at room temperature are reported. Cyclic voltammetry (CV) is used to determine approximate deposition potentials for each element. The amperometric I-t technique is used to fabricate the semiconductor alloy. The elements are deposited in the following sequence: (Se/Pb/Se/Pb/Se/Pb/Se/Pb/Se/Sn …), each period is formed using four ALD cycles of PbSe followed by one cycle of SnSe. Then the deposition manner above is cyclic repeated till a satisfactory film with expected thickness of Pb1-xSnxSe is obtained. The morphology of the deposit is observed by field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) pattern is used to study its crystalline structure; X-ray photoelectron spectroscopy (XPS) of the deposit indicates an approximate ratio 1.0:0.8:0.2 of Se, Pb and Sn, as the expected stoichiometry for the deposit. Open-circuit potential (OCP) studies indicate a good p-type property, and the good optical activity makes it suitable for fabricating a photoelectric switch.

Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

PubMed

Hasanzadeh, Mohammad; Mokhtari, Fozieh; Jouyban-Gharamaleki, Vahid; Mokhtarzadeh, Ahad; Shadjou, Nasrin

2018-04-15

This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2 V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1 V with a low limit of quantification 5.94 nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare. Copyright © 2018 John Wiley & Sons, Ltd.

Pt/glassy carbon model catalysts prepared from PS-b-P2VP micellar templates.

PubMed

Gu, Yunlong; St-Pierre, Jean; Ploehn, Harry J

2008-11-04

Poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer was used as a micellar template to fabricate arrays of Pt nanoparticles on mica and glassy carbon (GC) supports. Polymer micellar deposition yields Pt nanoparticles with tunable particle size and surface number density on both mica and GC. After deposition of precursor-loaded micelles onto GC, oxygen plasma etching removes the polymer shell, followed by thermal treatment with H2 gas to reduce the Pt. Etching conditions were optimized to maximize removal of the polymer while minimizing damage to the GC. Arrays of Pt nanoparticles with controlled size and surface number density can be prepared on mica (for particle size characterization) and GC to make Pt/GC model catalysts. These model catalysts were characterized by tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry to measure activity for oxidation of carbon monoxide or methanol. Cyclic voltammetry results demonstrate the existence of a correlation between Pt particle size and electrocatalytic properties including onset potential, tolerance of carbonaceous adsorbates, and intrinsic activity (based on active Pt area from CO stripping voltammetry). Results obtained with Pt/GC model catalysts duplicate prior results obtained with Pt/porous carbon catalysts therefore validating the synthesis approach and offering a new, tunable platform to study catalyst structure and other effects such as aging on proton exchange membrane fuel cell (PEMFC) reactions.

The Rise of Voltammetry: From Polarography to the Scanning Electrochemical Microscope

ERIC Educational Resources Information Center

Bard, Allen J.

2007-01-01

The drooping mercury electrode (DME) was previously used to carry out electrochemical experiments but invention of polarography technique changed this. Voltammetry with DME was given the term polarography and are used in measurement of current as a function of potential at small electrodes.

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Shi, C.; Zhitomirsky, I.

2010-03-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Electrodeposition and capacitive behavior of films for electrodes of electrochemical supercapacitors.

PubMed

Shi, C; Zhitomirsky, I

2010-01-08

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Self-supported supercapacitor membrane through incorporating MnO2 nanowires into carbon nanotube networks.

PubMed

Fang, Yueping; Liu, Jianwei; Li, Jun

2010-08-01

We report on a study on the development of a self-supported membrane of carbon nanotube (CNT) mixed with MnO2 nanowires as supercapacitors. Both single-walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) have been explored to serve as the electrically conductive networks to connect redox active MnO2 nanowires. High-quality alpha-MnO2 nanowires were synthesized using bulk alpha-MnO2 crystals as the precursor by a facile hydrothermal method. The morphology and structure of the as-prepared alpha-MnO2 nanowires were characterized by X-ray and electron diffraction, transmission electron microscopy, and scanning electron microscopy. Supercapacitor membranes were prepared by filtration of mixture solutions of MnO2 nanowires and CNTs at various ratios, forming entangled networks which are self-supported and directly used as supercapacitor electrodes without binders or backing metals. Cyclic voltammetry at various scan rates and charge--discharging measurements are used to characterize the supercapacitance of the CNT-MnO2 nanowire membranes. The specific capacitance has been found to be increased by several times over that of pure CNT membranes after incorporation of MnO2 nanowires.

Symmetric redox supercapacitor based on micro-fabrication with three-dimensional polypyrrole electrodes

NASA Astrophysics Data System (ADS)

Sun, Wei; Zheng, Ruilin; Chen, Xuyuan

To achieve higher energy density and power density, we have designed and fabricated a symmetric redox supercapacitor based on microelectromechanical system (MEMS) technologies. The supercapacitor consists of a three-dimensional (3D) microstructure on silicon substrate micromachined by high-aspect-ratio deep reactive ion etching (DRIE) method, two sputtered Ti current collectors and two electrochemical polymerized polypyrrole (PPy) films as electrodes. Electrochemical tests, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatical charge/discharge methods have been carried out on the single PPy electrodes and the symmetric supercapacitor in different electrolytes. The specific capacitance (capacitance per unit footprint area) and specific power (power per unit footprint area) of the PPy electrodes and symmetric supercapacitor can be calculated from the electrochemical test data. It is found that NaCl solution is a good electrolyte for the polymerized PPy electrodes. In NaCl electrolyte, single PPy electrodes exhibit 0.128 F cm -2 specific capacitance and 1.28 mW cm -2 specific power at 20 mV s -1 scan rate. The symmetric supercapacitor presents 0.056 F cm -2 specific capacitance and 0.56 mW cm -2 specific power at 20 mV s -1 scan rate.

Reaction of Hydroquinone with Hematite I. Study of Adsorption by Electrochemical-Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stack, Andrew G; Eggleston, Carrick M; Engelhard, Mark H

2004-06-15

The reaction of hematite with quinones and the quinone moieties of larger molecules may be an important factor in limiting the rate ofreductive dissolution, especially by iron-reducing bacteria. Here, the electrochemical and physical properties of hydroquinone adsorbed on hematite surfaces at pH 2.5–3 were investigated with cyclic voltammetry (CV), electrochemical-scanning tunneling microscopy (EC-STM), and X-ray photoelectron spectroscopy (XPS). An oxidation peak for hydroquinone was observed in the CV experiments, as well as (photo)reduction of iron and decomposition of the solvent. The EC-STM results indicate that hydroquinone sometimes forms an ordered monolayer with ~1.1 H₂/nm², but can be fairly disordered (especiallymore » when viewed at larger scales). XPS results indicate that hydroquinone and benzoquinone are retained at the interface in increasing amounts as the reaction proceeds, but reduced iron is not observed. These results suggest that quinones do not adsorb by an inner-sphere complex where adsorbate–surface interactions determine the adsorbate surface structure, but rather in an outer-sphere complex where interactions among the adsorbate molecules dominate.« less

Reaction of hydroquinone with hematite I. Study of asdsorption by electrochemical-scanning tunneling microscopy and X-ray photoelectron spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stack, Andrew G; Eggleston, Carrick M; Engelhard, Mark H

2003-12-01

The reaction of hematite with quinones and the quinone moieties of larger molecules may be an important factor in limiting the rate of reductive dissolution, especially by iron-reducing bacteria. Here, the electrochemical and physical properties of hydroquinone adsorbed on hematite surfaces at pH 2.5-3 were investigated with cyclic voltammetry (CV), electrochemical-scanning tunneling microscopy (EC-STM), and X-ray photoelectron spectroscopy (XPS). An oxidation peak for hydroquinone was observed in the CV experiments, as well as (photo)reduction of iron and decomposition of the solvent. The EC-STM results indicate that hydroquinone sometimes forms an ordered monolayer with {approx}1.1 QH{sub 2}/nm{sup 2}, but can bemore » fairly disordered (especially when viewed at larger scales). XPS results indicate that hydroquinone and benzoquinone are retained at the interface in increasing amounts as the reaction proceeds, but reduced iron is not observed. These results suggest that quinones do not adsorb by an inner-sphere complex where adsorbate-surface interactions determine the adsorbate surface structure, but rather in an outer-sphere complex where interactions among the adsorbate molecules dominate.« less

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

PubMed Central

2010-01-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0–3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g−1 was observed for the sample with a specific mass of 89 μg cm−2 at a scan rate of 2 mV s−1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES). PMID:20672082

Synthesis and characterization of germa[n]pericyclynes.

PubMed

Tanimoto, Hiroki; Nagao, Tomohiko; Nishiyama, Yasuhiro; Morimoto, Tsumoru; Iseda, Fumiyasu; Nagato, Yuko; Suzuka, Toshimasa; Tsutsumi, Ken; Kakiuchi, Kiyomi

2014-06-14

The synthesis and characterization of novel pericyclynes comprising germanium atoms and acetylenes, germa[n]pericyclynes, are described. The prepared germa[4]-, [6]-, and [8]pericyclynes were compared by (13)C NMR spectroscopy, X-ray crystallography, cyclic voltammetry, UV-visible spectroscopy, fluorescence emission spectroscopy, Raman spectroscopy, and density functional theory calculation analyses.

Surface pK(sub a) of Self-Assembled Monolayers

ERIC Educational Resources Information Center

Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.

2005-01-01

The difference between solution and surface properties such as pK(sub a) is illustrated enabling students to understand the differences between nanoscale and macroscopic systems. Details regarding the usage of electrochemical instrumentation, such as a potentiostat, and of the technique such as cyclic voltammetry are given.

ON-LINE DEOXYGENATION IN REDUCTIVE (AND OXIDATIVE) AMPEROMETRIC DETECTION: ENVIRONMENTAL APPLICATIONS IN THE LIQUID CHROMATOGRAPHY OF ORGANIC PEROXIDES

EPA Science Inventory

Cyclic voltammetry was used qualitatively to characterize and determine the feasibility of the oxidation and reduction of selected organic peroxides and hydroperoxides at a glassy carbon electrode. Organic peroxides were determined using reversed-phase high-performance liquid chr...

Electrochemical detection of Hg (II) ions using EDTA-PANI/SWNTs nanocomposite modified SS electrode

NASA Astrophysics Data System (ADS)

Deshmukh, M. A.; Patil, H. K.; Shirsat, M. D.; Ramanavicius, A.

2017-05-01

Detection of Hg (II) ions using EDTA modified polyaniline (PANI) and single walled carbon nanotubes (SWNTs) nanocomposite (PANI/SWNTs) was performed electrochemically via cyclic voltammetry (CV) technique. Dodecyl benzene sulphonic next step, PANI/SWNTs nanocomposite was modified acid sodium salt (DBSA) was used as a surfactant during this synthesis to get uniform suspension SWNTs. In the by EDTA solution containing crosslinking agent 1-ethyl-3(3-(dimethylamino) propyl) - carbodiimide (EDC) utilizing dip coating technique. The sensitivity of EDTA modified PANI/SWNTs nanocomposite towards Hg (II) ions was investigated. Differential pulse voltammetry (DPV) technique was applied for the electrochemical detection of Hg (II) ions.

Synthesis and characterization of graphene quantum dots-silver nanocomposites

NASA Astrophysics Data System (ADS)

Vandana, M.; Ashokkumar, S. P.; Vijeth, H.; Niranjana, M.; Yesappa, L.; Devendrappa, H.

2018-04-01

A facile microwave assisted hydrothermal method is used to synthesise glucose derived water soluble crystalline graphene quantum dots (GQDs) andcitrate reduction method was used to synthesized silver nanoparticles (SNPs). The formation of graphene quantum dots-silver nanocomposites (GSC) was synthesized through a simple refluxing process and characterised using Fourier Transform Infrared (FT-IR) to study the chemical interaction, Surface morphology using FESEM, Optical properties were studied using UV-Visible spectroscopy. The absorption band shows at 249, 306 and 447 nm confirms the formation of GQDs and GSC. The electrochemical performance of GSC tested to determine the oxidation/reduction processes by cyclic voltammetry and linear sweep voltammetry.

Non-Kinetic Losses Caused by Electrochemical Carbon Corrosion in PEM Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Seh Kyu; Shao, Yuyan; Viswanathan, Vilayanur V.

2012-05-01

This paper presented non-kinetic losses in PEM fuel cells under an accelerated stress test of catalyst support. The cathode with carbon-supported Pt catalyst was prepared and characterized with potential hold at 1.2 V vs. SHE in PEM fuel cells. Irreversible losses caused by carbon corrosion were evaluated using a variety of electrochemical characterizations including cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, and polarization technique. Ohmic losses at the cathode with potential hold were determined using its capacitive responses. Concentration losses in PEM fuel cells were analyzed in terms of Tafel behavior and thin film/flooded-agglomerate dynamics.

Electrochemical supramolecular recognition of hemin-carbon composites

NASA Astrophysics Data System (ADS)

Le, Hien Thi Ngoc; Jeong, Hae Kyung

2018-04-01

Hemin-graphite oxide-carbon nanotube (hemin-GO-CNT) and hemin-thermally reduced graphite oxide-carbon nanotube (hemin-TRGO-CNT) composites are synthesized and investigated for the electrochemical supramolecular recognition by electron transfer between biomolecules (dopamine and hydrogen peroxide) and the composite electrodes. Redox reaction mechanisms of two composites with dopamine and hydrogen peroxide are explained in detail by using cyclic voltammetry and differential pulse voltammetry. Hemin-TRGO-CNT displays higher electrochemical detection for dopamine and hydrogen peroxide than that of hemin-GO-CNT, exhibiting enhancement of the electron transfer due to the effective immobilization of redox couple of hemin (Fe2+/Fe3+) on the TRGO-CNT surface.

Electrochemical detection and degradation of ibuprofen from water on multi-walled carbon nanotubes-epoxy composite electrode.

PubMed

Motoc, Sorina; Remes, Adriana; Pop, Aniela; Manea, Florica; Schoonman, Joop

2013-04-01

This work describes the electrochemical behaviour of ibuprofen on two types of multi-walled carbon nanotubes based composite electrodes, i.e., multi-walled carbon nanotubes-epoxy (MWCNT) and silver-modified zeolite-multi-walled carbon nanotubes-epoxy (AgZMWCNT) composites electrodes. The composite electrodes were obtained using two-roll mill procedure. SEM images of surfaces of the composites revealed a homogeneous distribution of the composite components within the epoxy matrix. AgZMWCNT composite electrode exhibited the better electrical conductivity and larger electroactive surface area. The electrochemical determination of ibuprofen (IBP) was achieved using AgZMWCNT by cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry and chronoamperometry. The IBP degradation occurred on both composite electrodes under controlled electrolysis at 1.2 and 1.75 V vs. Ag/AgCl, and IBP concentration was determined comparatively by differential-pulsed voltammetry, under optimized conditions using AgZMWCNT electrode and UV-Vis spectrophotometry methods to determine the IBP degradation performance for each electrode. AgZMWCNT electrode exhibited a dual character allowing a double application in IBP degradation process and its control.

Pulse-voltammetric glucose detection at gold junction electrodes.

PubMed

Rassaei, Liza; Marken, Frank

2010-09-01

A novel glucose sensing concept based on the localized change or "modulation" in pH within a symmetric gold-gold junction electrode is proposed. A paired gold-gold junction electrode (average gap size ca. 500 nm) is prepared by simultaneous bipotentiostatic electrodeposition of gold onto two closely spaced platinum disk electrodes. For glucose detection in neutral aqueous solution, the potential of the "pH-modulator" electrode is set to -1.5 V vs saturated calomel reference electrode (SCE) to locally increase the pH, and simultaneously, either cyclic voltammetry or square wave voltammetry experiments are conducted at the sensor electrode. A considerable improvement in the sensor electrode response is observed when a normal pulse voltammetry sequence is applied to the modulator electrode (to generate "hydroxide pulses") and the glucose sensor electrode is operated with fixed bias at +0.5 V vs SCE (to eliminate capacitive charging currents). Preliminary data suggest good linearity for the glucose response in the medically relevant 1-10 mM concentration range (corresponding to 0.18-1.8 g L(-1)). Future electroanalytical applications of multidimensional pulse voltammetry in junction electrodes are discussed.

Electrochemical methods as a tool for determining the antioxidant capacity of food and beverages: A review.

PubMed

Hoyos-Arbeláez, Jorge; Vázquez, Mario; Contreras-Calderón, José

2017-04-15

The growing interest in functional foods had led to the use of analytical techniques to quantify some properties, among which is the antioxidant capacity (AC). In order to identify and quantify this capacity, some techniques are used, based on synthetic radicals capture; and they are monitored by UV-vis spectrophotometry. Electrochemical techniques are emerging as alternatives, given some of the disadvantages faced by spectrophotometric methods such as the use of expensive reagent not environmentally friendly, undefined reaction time, long sample pretreatment, and low precision and sensitivity. This review focuses on the four most commonly used electrochemical techniques (cyclic voltammetry, differential pulse voltammetry, square wave voltammetry and chronoamperometry). Some of the applications to determine AC in foods and beverages are presented, as well as the correlation between both spectrophotometric and electrochemical techniques that have been reported. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quantitative weaknesses of the Marcus-Hush theory of electrode kinetics revealed by Reverse Scan Square Wave Voltammetry: The reduction of 2-methyl-2-nitropropane at mercury microelectrodes

NASA Astrophysics Data System (ADS)

Laborda, Eduardo; Wang, Yijun; Henstridge, Martin C.; Martínez-Ortiz, Francisco; Molina, Angela; Compton, Richard G.

2011-08-01

The Marcus-Hush and Butler-Volmer kinetic electrode models are compared experimentally by studying the reduction of 2-methyl-2-nitropropane in acetonitrile at mercury microelectrodes using Reverse Scan Square Wave Voltammetry. This technique is found to be very sensitive to the electrode kinetics and to permit critical comparison of the two models. The Butler-Volmer model satisfactorily fits the experimental data whereas Marcus-Hush does not quantitatively describe this redox system.

Electrochemical ion transfer across liquid/liquid interfaces confined within solid-state micropore arrays--simulations and experiments.

PubMed

Strutwolf, Jörg; Scanlon, Micheál D; Arrigan, Damien W M

2009-01-01

Miniaturised liquid/liquid interfaces provide benefits for bioanalytical detection with electrochemical methods. In this work, microporous silicon membranes which can be used for interface miniaturisation were characterized by simulations and experiments. The microporous membranes possessed hexagonal arrays of pores with radii between 10 and 25 microm, a pore depth of 100 microm and pore centre-to-centre separations between 99 and 986 microm. Cyclic voltammetry was used to monitor ion transfer across arrays of micro-interfaces between two immiscible electrolyte solutions (microITIES) formed at these membranes, with the organic phase present as an organogel. The results were compared to computational simulations taking into account mass transport by diffusion and encompassing diffusion to recessed interfaces and overlapped diffusion zones. The simulation and experimental data were both consistent with the situation where the location of the liquid/liquid (l/l) interface was on the aqueous side of the silicon membrane and the pores were filled with the organic phase. While the current for the forward potential scan (transfer of the ion from the aqueous phase to the organic phase) was strongly dependent on the location of the l/l interface, the current peak during the reverse scan (transfer of the ion from the organic phase to the aqueous phase) was influenced by the ratio of the transferring ion's diffusion coefficients in both phases. The diffusion coefficient of the transferring ion in the gelified organic phase was ca. nine times smaller than in the aqueous phase. Asymmetric cyclic voltammogram shapes were caused by the combined effect of non-symmetrical diffusion (spherical and linear) and by the inequality of the diffusion coefficient in both phases. Overlapping diffusion zones were responsible for the observation of current peaks instead of steady-state currents during the forward scan. The characterisation of the diffusion behaviour is an important requirement for application of these silicon membranes in electroanalytical chemistry.

Chemical synthesis and supercapacitive properties of lanthanum telluride thin film.

PubMed

Patil, S J; Lokhande, A C; Lee, D-W; Kim, J H; Lokhande, C D

2017-03-15

Lanthanum telluride (La 2 Te 3 ) thin films are synthesized via a successive ionic layer adsorption and reaction (SILAR) method. The crystal structure, surface morphology and surface wettability properties are investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and contact angle goniometer techniques, respectively. The La 2 Te 3 material exhibits a specific surface area of 51m 2 g -1 determined by Brunauer-Emmett-Teller (BET) method. La 2 Te 3 thin film electrode has a hydrophilic surface which consists of interconnected pine leaf-like flaky arrays that affect the performance of the supercapacitor. The supercapacitive performance of La 2 Te 3 film electrode is evaluated in 1M LiClO 4 /PC electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. La 2 Te 3 film electrode exhibits a specific capacitance of 194Fg -1 at a scan rate of 5mVs -1 and stored energy density of 60Whkg -1 with delivering power density of 7.22kWkg -1 . La 2 Te 3 film electrode showed capacitive retention of 82% over 1000cycles at a scan rate of 100mVs -1 . Further, flexible La 2 Te 3 |LiClO 4 -PVA|La 2 Te 3 supercapacitor cell is fabricated. Copyright © 2016 Elsevier Inc. All rights reserved.

Actinide Corroles: Synthesis and Characterization of Thorium(IV) and Uranium(IV) bis(-chloride) Dimers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Ashleigh L.; Buckley, Heather L.; Gryko, Daniel T.

2013-12-01

The first synthesis and structural characterization of actinide corroles is presented. Thorium(IV) and uranium(IV) macrocycles of Mes2(p-OMePh)corrole were synthesised and characterized by single-crystal X-ray diffraction, UV-Visible spectroscopy, variable-temperature 1H NMR, ESI mass spectrometry and cyclic voltammetry.

A Simple and Low-Cost Ultramicroelectrode Fabrication and Characterization Method for Undergraduate Students

ERIC Educational Resources Information Center

Sur, Ujjal Kumar; Dhason, A.; Lakshminarayanan, V.

2012-01-01

A laboratory experiment is described in which students fabricate disk-shaped gold and platinum microelectrodes with diameters of 10-50 [mu]m by sealing sodalime glass with metal microwires. The electrodes are characterized by performing cyclic voltammetry in aqueous and acetonitrile solution. Commercial microelectrodes are expensive (cost depends…

Fuel Cell System Contaminants Material Screening Data | Hydrogen and Fuel

Science.gov Websites

contaminants; solution conductivity; pH; total organic carbon (TOC); cyclic voltammetry (CV); membrane conductivity) and organics (measured as total organic carbon) in leachate solutions. Each plot shows the ) contaminants on voltage loss over time for each materials class. GCMS Summary: Top 4 Organic Compounds by

Discrimination of Inner- and Outer-Sphere Electrode Reactions by Cyclic Voltammetry Experiments

ERIC Educational Resources Information Center

Tanimoto, Sachiko; Ichimura, Akio

2013-01-01

A laboratory experiment for undergraduate students who are studying homogeneous and heterogeneous electron-transfer reactions is described. Heterogeneous or electrode reaction kinetics can be examined by using the electrochemical reduction of three Fe[superscript III]/Fe[superscript II] redox couples at platinum and glassy carbon disk electrodes.…

Development of Nitrogen Sensor for Determination of PN(2) in Body Tissues.

DTIC Science & Technology

1982-07-01

3) The progress of the reduction reaction (1) was followed by voltammetry. A single anodic potential sweep , starting from the open circuit...Graphite Electrode The progressive attachment of [Ru(NH3 ) 5 H2 0] +2 to PVP-coated graphite electrodes was observed by cyclic voltametry as an

A Simple and Inexpensive Function Generator and a Four-Electrode Cell for Cyclic Voltammetry.

ERIC Educational Resources Information Center

Albahadily, F. N.; Mottola, Horacio A.

1986-01-01

Describes construction and operation of an inexpensive signal generator and a four-electrode electrochemical cell for use in voltammetric experiments. Also describes construction and operation of a four-electrode electrochemical cell used to illustrate elimination (or minimization) of background currents due to electrochemical reactions by species…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, David M.; Tsang, Chu F.; Sugar, Joshua Daniel

One method for the formation of nanofilms of materials, is Electrochemical atomic layer deposition (E-ALD), one atomic layer at a time. It uses the galvanic exchange of a less noble metal, deposited using underpotential deposition (UPD), to produce an atomic layer of a more noble element by reduction of its ions. This process is referred to as surface limited redox replacement and can be repeated in a cycle to grow thicker deposits. Previously, we performed it on nanoparticles and planar substrates. In the present report, E-ALD is applied for coating a submicron-sized powder substrate, making use of a new flowmore » cell design. E-ALD is used to coat a Pd powder substrate with different thicknesses of Rh by exchanging it for Cu UPD. Furthermore, cyclic voltammetry and X-ray photoelectron spectroscopy indicate an increasing Rh coverage with increasing numbers of deposition cycles performed, in a manner consistent with the atomic layer deposition (ALD) mechanism. Cyclic voltammetry also indicated increased kinetics of H sorption and desorption in and out of the Pd powder with Rh present, relative to unmodified Pd.« less

Electrochemical separation of uranium in the molten system LiF-NaF-KF-UF4

NASA Astrophysics Data System (ADS)

Korenko, M.; Straka, M.; Szatmáry, L.; Ambrová, M.; Uhlíř, J.

2013-09-01

This article is focused on the electrochemical investigation (cyclic voltammetry and related studies) of possible reduction of U4+ ions to metal uranium in the molten system LiF-NaF-KF(eut.)-UF4 that can provide basis for the electrochemical extraction of uranium from molten salts. Two-step reduction mechanism for U4+ ions involving one electron exchange in soluble/soluble U4+/U3+ system and three electrons exchange in the second step were found on the nickel working electrode. Both steps were found to be reversible and diffusion controlled. Based on cyclic voltammetry, the diffusion coefficients of uranium ions at 530 °C were found to be D(U4+) = 1.64 × 10-5 cm2 s-1 and D(U3+) 1.76 × 10-5 cm2 s-1. Usage of the nickel spiral electrode for electrorefining of uranium showed fairly good feasibility of its extraction. However some oxidant present during the process of electrorefining caused that the solid deposits contained different uranium species such as UF3, UO2 and K3UO2F5.

Determination of the potential gold electrowinning from an ammoniacal thiosulphate solution applied to recycling of printed circuit board scraps.

PubMed

Kasper, Angela C; Carrillo Abad, Jordi; García Gabaldón, Montserrat; Veit, Hugo M; Pérez Herranz, Valentín

2016-01-01

The use of electrochemical techniques in the selective recovery of gold from a solution containing thiosulphate, ammonia, and copper, obtained from the leaching of printed circuit boards from mobile phones using ammoniacal thiosulphate, are shown in this work. First, cyclic voltammetry tests were performed to determine the potential of electrodeposition of gold and copper, and then, electrowinning tests at different potentials for checking the rates of recovery of these metals were performed. The results of the cyclic voltammetry show that copper deposition occurs at potentials more negative than -600 mV (Ag/AgCl), whereas the gold deposition can be performed at potentials more positives than -600 mV (Ag/AgCl). The results of electrowinning show that 99% of the gold present in solutions containing thiosulphate and copper can be selectively recovered in a potential range between -400 mV (vs Ag/AgCl) and -500 mV (vs Ag/AgCl). Furthermore, 99% of copper can be recovered in potentials more negative than -700 mV (vs Ag/AgCl). © The Author(s) 2015.

Formation of Gd-Al Alloy Films by a Molten Salt Electrochemical Process

NASA Astrophysics Data System (ADS)

Caravaca, Concha; De Córdoba, Guadalupe

2008-02-01

The electrochemistry of molten LiCl-KCl-GdCl3 at a reactive Al electrode has been studied at 723 to 823 K. Electrochemical techniques such as cyclic voltammetry and chronopotentiometry have been used in order to identify the intermetallic compounds formed. Cyclic voltammetry showed that, while at an inert W electrode GdCl3 is reduced to Gd metal in a single step at a potential close to the reduction of the solvent, at an Al electrode a shift towards more positive values occurs. This shift of the cathodic potential indicated a reduction of the activity of Gd in Al with respect to that ofW, due to the formation of alloys. The surface characterization of samples formed by both galvanostatic and potentiostatic electrolysis has shown the presence of two intermetallic compounds: GdAl3 and GdAl2. Using open-circuit chronopotentiometry it has been possible to measure the potentials at which these compounds are transformed into each other. The values of these potential plateaus, once transformed into e. f. m. values, allowed to determine the thermodynamic properties of the GdAl3 intermetallic compound.

Hybrid microfluidic fuel cell based on Laccase/C and AuAg/C electrodes.

PubMed

López-González, B; Dector, A; Cuevas-Muñiz, F M; Arjona, N; Cruz-Madrid, C; Arana-Cuenca, A; Guerra-Balcázar, M; Arriaga, L G; Ledesma-García, J

2014-12-15

A hybrid glucose microfluidic fuel cell composed of an enzymatic cathode (Laccase/ABTS/C) and an inorganic anode (AuAg/C) was developed and tested. The enzymatic cathode was prepared by adsorption of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Laccase on Vulcan XC-72, which act as a redox mediator, enzymatic catalyst and support, respectively. The Laccase/ABTS/C composite was characterised by Fourier Transform Infrared (FTIR) Spectroscopy, streaming current measurements (Zeta potential) and cyclic voltammetry. The AuAg/C anode catalyst was characterised by Transmission electron microscopy (TEM) and cyclic voltammetry. The hybrid microfluidic fuel cell exhibited excellent performance with a maximum power density value (i.e., 0.45 mW cm(-2)) that is the highest reported to date. The cell also exhibited acceptable stability over the course of several days. In addition, a Mexican endemic Laccase was used as the biocathode electrode and evaluated in the hybrid microfluidic fuel cell generating 0.5 mW cm(-2) of maximum power density. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural comparative studies on new Mn(II), Cr(III) and Ru(III) complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPTZ).

PubMed

Al-Assy, Waleed H; El-Askalany, Abdel Moneum H; Mostafa, Mohsen M

2013-12-01

The structure of a new Mn(II) complex, [Mn(TPTZ)Cl2(H2O)]⋅H2O, was established by a single crystal X-ray diffraction. Crystal data are as follow: monoclinic, P21/c,a = 8.7202 (3)Å, b = 11.5712 (4)Å, c = 20.8675 (9)Å, β=11 (18) × 1010, V = 2029.27 (13)Å(3), Z = 4. The HOMO, LUMO and other DFT parameters on the atoms have been calculated to confirm the geometry of the ligand and its complexes using material studio program. The complexes were characterized by elemental analyses, spectral, magnetic, thermal and cyclic voltammetry measurements. Electronic spectra and magnetic moments of the complexes suggest distorted-octahedral structures around the metal ions (Mn(II), Cr(III) and Ru(III)). The redox properties were investigated by cyclic voltammetry. Kinetic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. The results of DNA studies of the metal complexes promised to be effective in tumour treatment. Copyright © 2013 Elsevier B.V. All rights reserved.