Electrochemical sensing and biosensing platform based on chemically reduced graphene oxide.

PubMed

Zhou, Ming; Zhai, Yueming; Dong, Shaojun

2009-07-15

In this paper, the characterization and application of a chemically reduced graphene oxide modified glassy carbon (CR-GO/GC) electrode, a novel electrode system, for the preparation of electrochemical sensing and biosensing platform are proposed. Different kinds of important inorganic and organic electroactive compounds (i.e., probe molecule (potassium ferricyanide), free bases of DNA (guanine (G), adenine (A), thymine (T), and cytosine (C)), oxidase/dehydrogenase-related molecules (hydrogen peroxide (H2O2)/beta-nicotinamide adenine dinucleotide (NADH)), neurotransmitters (dopamine (DA)), and other biological molecules (ascorbic acid (AA), uric acid (UA), and acetaminophen (APAP)) were employed to study their electrochemical responses at the CR-GO/GC electrode, which shows more favorable electron transfer kinetics than graphite modified glassy carbon (graphite/GC) and glassy carbon (GC) electrodes. The greatly enhanced electrochemical reactivity of the four free bases of DNA at the CR-GO/GC electrode compared with that at graphite/GC and GC electrodes makes the CR-GO/GC electrode a better choice for the electrochemical biosensing of four DNA bases in both the single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) at physiological pH without a prehydrolysis step. This allows us to detect a single-nucleotide polymorphism (SNP) site for short oligomers with a particular sequence at the CR-GO/GC electrode without any hybridization or labeling processes in this work, suggesting the potential applications of CR-GO in the label-free electrochemical detection of DNA hybridization or DNA damage for further research. Based on the greatly enhanced electrochemical reactivity of H2O2 and NADH at the CR-GO/GC electrode, CR-GO/GC electrode-based bioelectrodes (in connection with glucose oxidase (GOD) and alcohol dehydrogenase (ADH)) show a better analytical performance for the detection of glucose and ethanol compared with graphite/GC- or GC-based bioelectrodes. By comparing the electrochemical performance of CR-GO with that of the conventional graphite and GC, we reveal that CR-GO with the nature of a single sheet showing favorable electrochemical activity should be a kind of more robust and advanced carbon electrode material which may hold great promise for electrochemical sensors and biosensors design.

A Micro-Electrochemical Study of Friction Stir Welded Aluminum 6061-T6

NASA Technical Reports Server (NTRS)

Hintze, Paul E.; Calle, Luz M.

2005-01-01

The corrosion behavior of friction stir welded Aluminum alloy 606 1-T6 was studied using a micro-electrochemical cell. The micro-electrochemical cell has a measurement area of about 0.25 square mm which allows for measurement of corrosion properties at a very small scale. The corrosion and breakdown potentials were measured at many points inside and outside the weld along lines perpendicular to the weld. The breakdown potential is approximately equal inside and outside the weld; however, it is lower in the narrow border between the weld and base material. The results of electrochemical measurements were correlated to micro-structural analysis. The corrosion behavior of the friction stir welded samples was compared to tungsten inert gas (TIG) welded samples of the same material.

Electrochemical properties of LaNi{sub 5{minus}x}Ge{sub x} alloys in Ni-MH batteries

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

Witham, C.; Hightower, A.; Fultz, B.

1997-11-01

Electrochemical studies were performed on LaNi{sub 5{minus}x}Ge{sub x} metal hydride alloys with 0 {le} x {le} 0.5. The authors carried out single-electrode studies to understand the effects of the Ge substituent on the hydrogen absorption characteristics, the electrochemical capacity, and the electrochemical kinetics of hydrogen absorption and desorption. The electrochemical characteristics of the Ge-substituted alloys are compared to those of the Sn-substituted alloys reported earlier. LaNi{sub 5{minus}x}Ge{sub x} alloys show compositional trends similar to LaNi{sub 5{minus}x}Sn{sub x} alloys, but unlike the Sn-substituted alloys, Ge-substituted alloys continue to exhibit facile kinetics for hydrogen absorption/desorption at high solute concentrations. Cycle lives ofmore » LaNi{sub 5{minus}x}Ge{sub x} electrodes were measured in 300 mAh laboratory test cells and were found to be superior to the Sn-substituted LaNi{sub 5} and comparable to a Mm(Ni, Co, Mn, Al){sub 5} alloy. The optimum Ge content for LaNi{sub 5{minus}x}Ge{sub x} metal hydride alloys in alkaline rechargeable cells is in the range 0.4 {le} x {le} 0.5.« less

The Entrance and Exit Effects in Small Electrochemical Filter-Press Reactors Used in the Laboratory

ERIC Educational Resources Information Center

Frias-Ferrer, Angel; Gonzalez-Garcia, Jose; Saez, Veronica; Exposito, Eduardo; Sanchez-Sanchez, Carlos M.; Mantiel, Vicente; Walsh, Frank C.; Aldaz, Antonio; Walsh, Frank C.

2005-01-01

A laboratory experiment designed to examine the entrance and exit effects in small electrochemical filter-press reactors used in the laboratory is presented. The single compartment of the filter-press reactor is filled with different turbulence promoters to study their influence as compared to the empty configuration.

Microfluidic electrochemical reactors

DOEpatents

Nuzzo, Ralph G [Champaign, IL; Mitrovski, Svetlana M [Urbana, IL

2011-03-22

A microfluidic electrochemical reactor includes an electrode and one or more microfluidic channels on the electrode, where the microfluidic channels are covered with a membrane containing a gas permeable polymer. The distance between the electrode and the membrane is less than 500 micrometers. The microfluidic electrochemical reactor can provide for increased reaction rates in electrochemical reactions using a gaseous reactant, as compared to conventional electrochemical cells. Microfluidic electrochemical reactors can be incorporated into devices for applications such as fuel cells, electrochemical analysis, microfluidic actuation, pH gradient formation.

An Electrochemical, Low-Frequency Seismic Micro-Sensor Based on MEMS with a Force-Balanced Feedback System

PubMed Central

Li, Guanglei; Wang, Junbo; Chen, Deyong; Chen, Lianhong; Xu, Chao

2017-01-01

Electrochemical seismic sensors are key components in monitoring ground vibration, which are featured with high performances in the low-frequency domain. However, conventional electrochemical seismic sensors suffer from low repeatability due to limitations in fabrication and limited bandwidth. This paper presents a micro-fabricated electrochemical seismic sensor with a force-balanced negative feedback system, mainly composed of a sensing unit including porous sensing micro electrodes immersed in an electrolyte solution and a feedback unit including a feedback circuit and a feedback magnet. In this study, devices were designed, fabricated, and characterized, producing comparable performances among individual devices. In addition, bandwidths and total harmonic distortions of the proposed devices with and without a negative feedback system were quantified and compared as 0.005–20 (feedback) Hz vs. 0.3–7 Hz (without feedback), 4.34 ± 0.38% (without feedback) vs. 1.81 ± 0.31% (feedback)@1 Hz@1 mm/s and 3.21 ± 0.25% (without feedback) vs. 1.13 ± 0.19% (feedback)@5 Hz@1 mm/s (ndevice = 6, n represents the number of the tested devices), respectively. In addition, the performances of the proposed MEMS electrochemical seismometers with feedback were compared to a commercial electrochemical seismic sensor (CME 6011), producing higher bandwidth (0.005–20 Hz vs. 0.016–30 Hz) and lower self-noise levels (−165.1 ± 6.1 dB vs. −137.7 dB at 0.1 Hz, −151.9 ± 7.5 dB vs. −117.8 dB at 0.02 Hz (ndevice = 6)) in the low-frequency domain. Thus, the proposed device may function as an enabling electrochemical seismometer in the fields requesting seismic monitoring at the ultra-low frequency domain. PMID:28902150

Study on electrochemical corrosion mechanism of steel foot of insulators for HVDC lines

NASA Astrophysics Data System (ADS)

Zheng, Weihua; Sun, Xiaoyu; Fan, Youping

2017-09-01

The main content of this paper is the mechanism of electrochemical corrosion of insulator steel foot in HVDC transmission line, and summarizes five commonly used artificial electrochemical corrosion accelerated test methods in the world. Various methods are analyzed and compared, and the simulation test of electrochemical corrosion of insulator steel feet is carried out by water jet method. The experimental results show that the experimental environment simulated by water jet method is close to the real environment. And the three suspension modes of insulators in the actual operation, the most serious corrosion of the V type suspension hardware, followed by the tension string suspension, and the linear string corrosion rate is the slowest.

Electrochemical oxidation coupled with liquid chromatography and mass spectrometry to study the oxidative stability of active pharmaceutical ingredients in solution: A comparison of off-line and on-line approaches.

PubMed

Torres, Susana; Brown, Roland; Zelesky, Todd; Scrivens, Garry; Szucs, Roman; Hawkins, Joel M; Taylor, Mark R

2016-11-30

Stability studies of pharmaceutical drug products and pharmaceutical active substances are important to research and development in order to fully understand and maintain product quality and safety throughout its shelf-life. Oxidative forced degradation studies are among the different types of stability studies performed by the pharmaceutical industry in order to understand the intrinsic stability of drug molecules. We have been comparing the use of electrochemistry as an alternative oxidative forced degradation method to traditional forced degradation and accelerated stability studies. Using the electrochemical degradation approach the substrate oxidation takes place in a commercially available electrochemical cell and the effluent of the cell can be either a) directly infused into the mass spectrometer or b) injected in a chromatographic column for separation of the different products formed prior to the mass spectrometry analysis. To enable the study of large numbers of different experimental conditions and molecules we developed a new dual pump automated electrochemical screening platform. This system used a HPLC pump and autosampler to load and wash the electrochemical cell and deliver the oxidized sample plug to a second injection loop. This system enabled the automatic sequential analyses of large numbers of different solutions under varied experimental conditions without need for operator intervention during the run sequence. Here we describe the system and evaluate its performance using a test molecule with well characterized stability and compare results to those obtained using an off-line electrochemistry approach. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical performance and interfacial investigation on Si composite anode for lithium ion batteries in full cell

NASA Astrophysics Data System (ADS)

Shobukawa, Hitoshi; Alvarado, Judith; Yang, Yangyuchen; Meng, Ying Shirley

2017-08-01

Lithium ion batteries (LIBs) containing silicon (Si) as a negative electrode have gained much attention recently because they deliver high energy density. However, the commercialization of LIBs with Si anode is limited due to the unstable electrochemical performance associated with expansion and contraction during electrochemical cycling. This study investigates the electrochemical performance and degradation mechanism of a full cell containing Si composite anode and LiFePO4 (lithium iron phosphate (LFP)) cathode. Enhanced electrochemical cycling performance is observed when the full cell is cycled with fluoroethylene carbonate (FEC) additive compared to the standard electrolyte. To understand the improvement in the electrochemical performance, x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) are used. Based on the electrochemical behavior, FEC improves the reversibility of lithium ion diffusion into the solid electrolyte interphase (SEI) on the Si composite anode. Moreover, XPS analysis demonstrates that the SEI composition generated from the addition of FEC consists of a large amount of LiF and less carbonate species, which leads to better capacity retention over 40 cycles. The effective SEI successively yields more stable capacity retention and enhances the reversibility of lithium ion diffusion through the interphase of the Si anode, even at higher discharge rate. This study contributes to a basic comprehension of electrochemical performance and SEI formation of LIB full cells with a high loading Si composite anode.

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.

Electrochemical Behavior of Pure Copper in Phosphate Buffer Solutions: A Comparison Between Micro- and Nano-Grained Copper

NASA Astrophysics Data System (ADS)

Imantalab, O.; Fattah-alhosseini, A.; Keshavarz, M. K.; Mazaheri, Y.

2016-02-01

In this work, electrochemical behavior of annealed (micro-) and nano-grained pure copper (fabricated by accumulative roll bonding process) in phosphate buffer solutions of various pH values ranging from 10.69 to 12.59 has been studied. Before any electrochemical measurements, evaluation of microstructure was obtained by optical microscope and transmission electron microscopy. To investigate the electrochemical behavior of the samples, the potentiodynamic polarization, Mott-Schottky analysis, and electrochemical impedance spectroscopy (EIS) were carried out. Potentiodynamic polarization plots and EIS measurements revealed that as a result of grain refinement, the passive behavior of the nano-grained sample was improved compared to that of annealed pure copper. Also, Mott-Schottky analysis indicated that the passive films behaved as p-type semiconductors and grain refinement did not change the semiconductor type of passive films.

Deterministic analysis of processes at corroding metal surfaces and the study of electrochemical noise in these systems

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

Latanision, R.M.

1990-12-01

Electrochemical corrosion is pervasive in virtually all engineering systems and in virtually all industrial circumstances. Although engineers now understand how to design systems to minimize corrosion in many instances, many fundamental questions remain poorly understood and, therefore, the development of corrosion control strategies is based more on empiricism than on a deep understanding of the processes by which metals corrode in electrolytes. Fluctuations in potential, or current, in electrochemical systems have been observed for many years. To date, all investigations of this phenomenon have utilized non-deterministic analyses. In this work it is proposed to study electrochemical noise from a deterministicmore » viewpoint by comparison of experimental parameters, such as first and second order moments (non-deterministic), with computer simulation of corrosion at metal surfaces. In this way it is proposed to analyze the origins of these fluctuations and to elucidate the relationship between these fluctuations and kinetic parameters associated with metal dissolution and cathodic reduction reactions. This research program addresses in essence two areas of interest: (a) computer modeling of corrosion processes in order to study the electrochemical processes on an atomistic scale, and (b) experimental investigations of fluctuations in electrochemical systems and correlation of experimental results with computer modeling. In effect, the noise generated by mathematical modeling will be analyzed and compared to experimental noise in electrochemical systems. 1 fig.« less

Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor

NASA Astrophysics Data System (ADS)

Cougnon, C.; Lebègue, E.; Pognon, G.

2015-01-01

Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

Electrochemical estrogen screen method based on the electrochemical behavior of MCF-7 cells.

PubMed

Li, Jinlian; Song, Jia; Bi, Sheng; Zhou, Shi; Cui, Jiwen; Liu, Jiguang; Wu, Dongmei

2016-08-05

It was an urgent task to develop quick, cheap and accurate estrogen screen method for evaluating the estrogen effect of the booming chemicals. In this study, the voltammetric behavior between the estrogen-free and normal fragmented MCF-7 cell suspensions were compared, and the electrochemical signal (about 0.68V attributed by xanthine and guanine) of the estrogen-free fragmented MCF-7 cell suspension was obviously lower than that of the normal one. The electrochemistry detection of ex-secretion purines showed that the ability of ex-secretion purines of cells sharp decreased due to the removing of endogenous estrogen. The results indicated that the electrochemical signal of MCF-7 cells was related to the level of intracellular estrogen. When the level of intracellular estrogen was down-regulated, the concentrations of the xanthine and hypoxanthine decreased, which led to the electrochemical signal of MCF-7 cells fall. Based on the electrochemical signal, the electrochemical estrogen screen method was established. The estrogen effect of estradiol, nonylphenol and bisphenol A was evaluated with the electrochemical method, and the result was accordant with that of MTT assay. The electrochemical estrogen screen method was simple, quickly, cheap, objective, and it exploits a new way for the evaluation of estrogenic effects of chemicals. Copyright © 2016. Published by Elsevier B.V.

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

Evaluation of Thymus vulgaris plant extract as an eco-friendly corrosion inhibitor for stainless steel 304 in acidic solution by means of electrochemical impedance spectroscopy, electrochemical noise analysis and density functional theory.

PubMed

Ehsani, A; Mahjani, M G; Hosseini, M; Safari, R; Moshrefi, R; Mohammad Shiri, H

2017-03-15

Inhibition performance of Thymus vulgaris plant leaves extract (thyme) as environmentally friendly (green) inhibitor for the corrosion protection of stainless steel (SS) type 304 in 1.0molL -1 HCl solution was studied by potentiodynamic polarization, electrochemical impedance (EIS) and electrochemical noise measurements (EN) techniques. The EN data were analyzed with FFT technique to make the spectral power density plots. The calculations were performed by MATLAB 2014a software. Geometry optimization and calculation of the structural and electronic properties of the molecular system of inhibitor have been carried out using UB3LYP/6-311++G ∗∗ level. Moreover, the results obtained from electrochemical noise analysis were compared with potentiodynamic polarization and electrochemical impedance spectroscopy. All of the used techniques showed positive effect of green inhibitor with increasing inhibitor concentration. Copyright © 2016 Elsevier Inc. All rights reserved.

Impact of electrolyte composition on the reactivity of a redox active polymer studied through surface interrogation and ion-sensitive scanning electrochemical microscopy.

PubMed

Burgess, Mark; Hernández-Burgos, Kenneth; Cheng, Kevin J; Moore, Jeffrey S; Rodríguez-López, Joaquín

2016-06-21

Elucidating the impact of interactions between the electrolyte and electroactive species in redox active polymers is key to designing better-performing electrodes for electrochemical energy storage and conversion. Here, we present on the improvement of the electrochemical activity of poly(para-nitrostyrene) (PNS) in solution and as a film by exploiting the ionic interactions between reduced PNS and K(+), which showed increased reactivity when compared to tetrabutylammonium (TBA(+))- and Li(+)-containing electrolytes. While cyclic voltammetry enabled the study of the effects of cations on the electrochemical reversibility and the reduction potential of PNS, scanning electrochemical microscopy (SECM) provided new tools to probe the ionic and redox reactivity of this system. Using an ion-sensitive Hg SECM tip allowed to probe the ingress of ions into PNS redox active films, while surface interrogation SECM (SI-SECM) measured the specific kinetics of PNS and a solution phase mediator in the presence of the tested electrolytes. SI-SECM measurements illustrated that the interrogation kinetics of PNS in the presence of K(+) compared to TBA(+) and Li(+) are greatly enhanced under the same surface concentration of adsorbed radical anion, exhibiting up to a 40-fold change in redox kinetics. We foresee using this new application of SECM methods for elucidating optimal interactions that enhance polymer reactivity for applications in redox flow batteries.

Performance of electrochemical oxidation and photocatalysis in terms of kinetics and energy consumption. New insights into the p-cresol degradation.

PubMed

Escudero, Carlos J; Iglesias, Olalla; Dominguez, Sara; Rivero, Maria J; Ortiz, Inmaculada

2017-06-15

This work reports the comparative performance of two Advanced Oxidation Processes (AOPs), electrochemical oxidation and photocatalysis, as individual technological alternatives for the treatment of effluents containing p-cresol. First, the influence of operating parameters in the oxidation and mineralization yield was carried out together with kinetic analysis. Boron Doped Diamond (BDD), RuO 2 and Pt as anodic materials, Na 2 SO 4 and NaCl as supporting electrolytes and different current densities were evaluated in electrochemical oxidation whereas the effect of TiO 2 concentration and radiation was studied in the photocatalytic degradation. Then, the parameter Electrical Energy per Order (E EO ) was calculated to compare the energy consumption in both AOPs, concluding that under the studied conditions the electrochemical treatment with BDD, Na 2 SO 4 and 125 A m -2 showed the best energy efficiency, with an E EO of 5.83 kW h m -3 order -1 for p-cresol and 58.05 kW h m -3 order -1 for DOC removal, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Conductivity and electrochemical stability of concentrated aqueous choline chloride solutions

NASA Astrophysics Data System (ADS)

Grishina, E. P.; Kudryakova, N. O.

2017-10-01

The conductivity and electrochemical stability of choline chloride (ChCl) solutions with water contents ranging from 20 to 39 wt % are studied. Exposing ChCl to moist ambient air yields a highly concentrated aqueous solution that, as an electrolyte, exhibits the properties and variations in conductivity with temperature and concentration characteristic of other similar systems. Its electrochemical stability window, determined by cyclic voltammetry, is comparable to that of ChCl-based deep eutectic solvents (DESs). Products of the electrolysis of ChCl‒H2O mixtures seem to be less toxic than those of Reline, Ethaline, and Maline.

Carbon-Nanotube-Based Electrochemical Double-Layer Capacitor Technologies for Spaceflight Applications

NASA Technical Reports Server (NTRS)

Arepalli, S.; Fireman, H.; Huffman, C.; Maloney, P.; Nikolaev, P.; Yowell, L.; Kim, K.; Kohl, P. A.; Higgins, C. D.; Turano, S. P.

2005-01-01

Electrochemical double-layer capacitors, or supercapacitors, have tremendous potential as high-power energy sources for use in low-weight hybrid systems for space exploration. Electrodes based on single-wall carbon nanotubes (SWCNTs) offer exceptional power and energy performance due to the high surface area, high conductivity, and the ability to functionalize the SWCNTs to optimize capacitor properties. This paper will report on the preparation of electrochemical capacitors incorporating SWCNT electrodes and their performance compared with existing commercial technology. Preliminary results indicate that substantial increases in power and energy density are possible. The effects of nanotube growth and processing methods on electrochemical capacitor performance is also presented. The compatibility of different SWCNTs and electrolytes was studied by varying the type of electrolyte ions that accumulate on the high-surface-area electrodes.

Electrochemical degradation of trichloroacetic acid in aqueous media: influence of the electrode material.

PubMed

Esclapez, M D; Díez-García, M I; Sàez, V; Bonete, P; González-García, José

2013-01-01

The electrochemical degradation of trichloroacetic acid (TCAA) in water has been analysed through voltammetric studies with a rotating disc electrode and controlled-potential bulk electrolyses. The influence of the mass-transport conditions and initial concentration of TCAA for titanium, stainless steel and carbon electrodes has been studied. It is shown that the electrochemical reduction of TCAA takes place prior to the massive hydrogen evolution in the potential window for all electrode materials studied. The current efficiency is high (> 18%) compared with those normally reported in the literature, and the fractional conversion is above 50% for all the electrodes studied. Only dichloroacetic acid (DCAA) and chloride anions were routinely detected as reduction products for any of the electrodes, and reasonable values of mass balance error were obtained. Of the three materials studied, the titanium cathode gave the best results.

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

Comparative structural and electrochemical study of high density spherical and non-spherical Ni(OH) 2 as cathode materials for Ni-metal hydride batteries

NASA Astrophysics Data System (ADS)

Shangguan, Enbo; Chang, Zhaorong; Tang, Hongwei; Yuan, Xiao-Zi; Wang, Haijiang

In this paper we compare the behavior of non-spherical and spherical β-Ni(OH) 2 as cathode materials for Ni-MH batteries in an attempt to explore the effect of microstructure and surface properties of β-Ni(OH) 2 on their electrochemical performances. Non-spherical β-Ni(OH) 2 powders with a high-density are synthesized using a simple polyacrylamide (PAM) assisted two-step drying method. X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric/differential thermal analysis (TG-DTA), Brunauer-Emmett-Teller (BET) testing, laser particle size analysis, and tap-density testing are used to characterize the physical properties of the synthesized products. Electrochemical characterization, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and a charge/discharge test, is also performed. The results show that the non-spherical β-Ni(OH) 2 materials exhibit an irregular tabular shape and a dense solid structure, which contains many overlapped sheet nano crystalline grains, and have a high density of structural disorder and a large specific surface area. Compared with the spherical β-Ni(OH) 2, the non-spherical β-Ni(OH) 2 materials have an enhanced discharge capacity, higher discharge potential plateau and superior cycle stability. This performance improvement can be attributable to a higher proton diffusion coefficient (4.26 × 10 -9 cm 2 s -1), better reaction reversibility, and lower electrochemical impedance of the synthesized material.

Synthesis of Magnetite Nanoparticles and Its Application As Electrode Material for the Electrochemical Oxidation of Methanol

NASA Astrophysics Data System (ADS)

Shah, Muhammad Tariq; Balouch, Aamna; Panah, Pirah; Rajar, Kausar; Mahar, Ali Muhammad; Khan, Abdullah; Jagirani, Muhammad Saqaf; Khan, Humaira

2018-06-01

In this study, magnetite (Fe3O4) nanoparticles were synthesized by a simple and facile chemical co-precipitation method at ambient laboratory conditions. The synthesized Fe3O4 nanostructures were characterized for their morphology, size, crystalline structure and component analysis using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, x-ray diffraction and electron dispersive x-ray spectroscopy. The Fe3O4 nanoparticles showed semi-spherical geometry with an average particle diameter up to 14 nm. The catalytic properties of Fe3O4 nanoparticles were evaluated for electrochemical oxidation of methanol. For this purpose, the magnetite NPs were coated on the surface of an indium tin oxide (ITO) electrode and used as a working electrode in the electrochemical oxidation of methanol. The effect of potential scan rate, the concentration of methanol, the volume of electrolyte and catalyst (Fe3O4 NPs) deposition volume was studied to get high peak current densities for methanol oxidation. The stability and selectivity of the fabricated electrode (Fe3O4/ITO) were also assessed during the electrochemical process. This study revealed that the Fe3O4/ITO electrode was highly stable and selective towards methanol electrochemical oxidation in basic (KOH) media. Bare ITO and Fe3O4 NPs modified glassy (Fe3O4/GCE) electrodes were also tested in the electro-oxidation study of methanol, but their peak current density responses were very low as compared to the Fe3O4/ITO electrode, which showed high electrocatalytic activity towards methanol oxidation under similar conditions. We hope that Fe3O4 nanoparticles (NPs) will be an alternative for methanol oxidation as compared to the expensive noble metals (Pt, Au, and Pd) for energy generation processes.

The application of electrochemistry to pharmaceutical stability testing--comparison with in silico prediction and chemical forced degradation approaches.

PubMed

Torres, Susana; Brown, Roland; Szucs, Roman; Hawkins, Joel M; Zelesky, Todd; Scrivens, Garry; Pettman, Alan; Taylor, Mark R

2015-11-10

The aim of this study was to evaluate the use of electrochemistry to generate oxidative degradation products of a model pharmaceutical compound. The compound was oxidized at different potentials using an electrochemical flow-cell fitted with a glassy carbon working electrode, a Pd/H2 reference electrode and a titanium auxiliary electrode. The oxidative products formed were identified and structurally characterized by LC-ESI-MS/MS using a high resolution Q-TOF mass spectrometer. Results from electrochemical oxidation using electrolytes of different pH were compared to those from chemical oxidation and from accelerated stability studies. Additionally, oxidative degradation products predicted using an in silico commercially available software were compared to those obtained from the various experimental methods. The electrochemical approach proved to be useful as an oxidative stress test as all of the final oxidation products observed under accelerated stability studies could be generated; previously reported reactive intermediate species were not observed most likely because the electrochemical mechanism differs from the oxidative pathway followed under accelerated stability conditions. In comparison to chemical degradation tests electrochemical degradation has the advantage of being much faster and does not require the use of strong oxidizing agents. Moreover, it enables the study of different operating parameters in short periods of time and optimisation of the reaction conditions (pH and applied potential) to achieve different oxidative products mixtures. This technique may prove useful as a stress test condition for the generation of oxidative degradation products and may help accelerate structure elucidation and development of stability indicating analytical methods. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparison of isothermal helicase-dependent amplification and PCR for the detection of Mycobacterium tuberculosis by an electrochemical genomagnetic assay.

PubMed

Barreda-García, Susana; Miranda-Castro, Rebeca; de-Los-Santos-Álvarez, Noemí; Miranda-Ordieres, Arturo J; Lobo-Castañón, M Jesús

2016-12-01

Methods for the early and sensitive detection of pathogenic bacteria suited to low-resource settings could impact diagnosis and management of diseases. Helicase-dependent isothermal amplification (HDA) is an ideal tool for this purpose, especially when combined with a sequence-specific detection method able to improve the selectivity of the assay. The implementation of this approach requires that its analytical performance is shown to be comparable with the gold standard method, polymerase chain reaction (PCR). In this study, we optimize and compare the asymmetric amplification of an 84-base-long DNA sequence specific for Mycobacterium tuberculosis by PCR and HDA, using an electrochemical genomagnetic assay for hybridization-based detection of the obtained single-stranded amplicons. The results indicate the generalizability of the magnetic platform with electrochemical detection for quantifying amplification products without previous purification. Moreover, we demonstrate that under optimal conditions the same gene can be amplified by either PCR or HDA, allowing the detection of as low as 30 copies of the target gene sequence with acceptable reproducibility. Both assays have been applied to the detection of M. tuberculosis in sputum, urine, and pleural fluid samples with comparable results. Simplicity and isothermal nature of HDA offer great potential for the development of point-of-care devices. Graphical Abstract Comparative evaluation of isothermal helicase-dependent amplification and PCR for electrochemical detection of Mycobacterium tuberculosis.

Electrochemical monitoring of high-temperature molten-salt corrosion

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

Gao, G.; Stott, F.H.; Dawson, J.L.

1990-02-01

Hot molten-salt corrosion can cause serious metal degradation in boiler plant, incinerators, and furnaces. In this research, electrochemical-impedance and electrochemical-noise techniques have been evaluated for the monitoring of hot-corrosion processes in such plants. Tests have been carried out on Ni-1% Co and Alloy 800, a commercial material of interest to operators of industrial plants. Electrochemical-impedance and electrochemical-noise data were compared with the results of metallographic examination of the test alloys and showed reasonable correlation between the electrochemical data and the actual degradation processes. This preliminary work indicated that the electrochemical techniques show considerable promise as instruments for the monitoring ofmore » high-temperature corrosion processes.« less

V-doped TiO2 supported Pt as a promising oxygen reduction reaction catalyst: Synthesis, characterization and in-situ evaluation in proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Bharti, Abha; Cheruvally, Gouri

2017-09-01

This study deals with the synthesis and characterization of V-doped, TiO2 supported Pt catalyst (Pt/V-TiO2) for oxygen reduction reaction (ORR) and its in-situ performance investigation in proton exchange membrane (PEM) fuel cell. Pt/V-TiO2 nanocomposite catalyst is prepared via a facile sol-gel and microwave assisted, modified chemical reduction route and its performance is compared with the undoped TiO2 supported catalyst, Pt/TiO2 prepared in an identical way. The prepared Pt/V-TiO2 and Pt/TiO2 catalysts are employed as cathode catalyst in PEM fuel cell and compared with standard Pt/C catalyst. Their comparative studies are conducted with physical and electrochemical techniques. In-situ electrochemical characterization studies show improved ORR catalytic activity of Pt/V-TiO2 compared to Pt/TiO2. Furthermore, both Pt/TiO2 and Pt/V-TiO2 are more stable than Pt/C when subjected to 6000 voltammetric cycles in the range of 0.2-1.2 V vs. standard hydrogen electrode in operating fuel cell conditions, losing only <20% of its electrochemical surface area as compared to 50% loss exhibited by Pt/C. This study thus demonstrates Pt/V-TiO2 nanocomposite material as a potential cathode catalyst for PEM fuel cell with immense scope for further investigation.

Electrochemistry-mass spectrometry for in-vitro determination of selected chemotherapeutics and their electrochemical products in comparison to in-vivo approach.

PubMed

Szultka-Mlynska, Malgorzata; Buszewski, Boguslaw

2016-11-01

Chemotherapeutics are among the most frequently prescribed medications in modern medicine. They are widely prescribed; however, problems with organisms developing resistance to these drugs means that their efficacy may be lost, so care should be taken to avoid unnecessary prescription. It is therefore of great interest to study the detailed metabolism of these biologically active compounds. This study aimed at developing an efficient analytical protocol for the determination of in-vitro electrochemical products of selected antibiotic drugs (amoxicillin, cefotaxime, fluconazole, linezolid, metronidazole and moxifloxacin). Combination of electrochemistry (EC) and mass spectrometry (MS) was applied for the in-vitro determination of the studied antibiotics and their electrochemical products. To identify the structure of the detected electrochemical products, MS/MS experiments were performed. This was one of the first applications of the EC system for generation of electrochemical products produced from antibiotic drugs. Adjustment of appropriate conditions and such parameters as the potential value, mobile phase (pH), working electrode and temperature had significant influence on electrochemical simulations and the creation of selected derivatives. Consequently, several working electrodes were evaluated for this purpose. In most of the studied cases, mainly two types of products were observed. One corresponded to an increase in mass by 14Da, which can be explained by a process consisting of oxidation (+16 m/z) and dehydrogenation (-2 m/z); The second in turn showed mass reduction by 14Da, which can be attributed to the loss of -CH2 as a result of N-demethylation. The performed experiments consisted of two stages: electrochemical oxidation of the analyzed samples (phase I of metabolic transformation), and addition of glutathione (GSH) for follow-up reactions (phase II conjunction). The electrochemical results were compared to in-vivo experiments by analyzing urine samples from patients after antibiotic drugs have been administered.. Overall, the comparison of electrochemistry to in-vivo experiments shows the high potential of EC-MS as a fast analytical tool in the prediction of electrochemical conversion that could be applied to therapeutic drug monitoring and pharmacokinetic studies as well. Copyright © 2016 Elsevier B.V. All rights reserved.

Sulfur redox reactions on nanostructured highly oriented pyrolytic graphite (HOPG) electrodes: Direct evidence for superior electrocatalytic performance on defect sites

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

Wang, Gongwei; Zheng, Dong; Liu, Dan

Fundamental research of sulfur redox reactions on well-defined controlled model electrode surfaces can provide new information to design high-performance lithium-sulfur batteries. In this paper, we study the electrochemical reduction and oxidation of sulfur on the nanostructured HOPG electrodes with pure basal planes, step plans, and pure edge planes. Finally, our results directly indicate that electrochemical reduction and oxidation of sulfur is significantly affected by the carbon surface structure, namely, the electrochemical reversibility of sulfur redox reaction is much better on edge plane, compared with basal plane and step plane.

Sulfur redox reactions on nanostructured highly oriented pyrolytic graphite (HOPG) electrodes: Direct evidence for superior electrocatalytic performance on defect sites

DOE PAGES

Wang, Gongwei; Zheng, Dong; Liu, Dan; ...

2017-04-28

Fundamental research of sulfur redox reactions on well-defined controlled model electrode surfaces can provide new information to design high-performance lithium-sulfur batteries. In this paper, we study the electrochemical reduction and oxidation of sulfur on the nanostructured HOPG electrodes with pure basal planes, step plans, and pure edge planes. Finally, our results directly indicate that electrochemical reduction and oxidation of sulfur is significantly affected by the carbon surface structure, namely, the electrochemical reversibility of sulfur redox reaction is much better on edge plane, compared with basal plane and step plane.

Electrochemical properties of titanium nitride nerve stimulation electrodes: an in vitro and in vivo study

PubMed Central

Meijs, Suzan; Fjorback, Morten; Jensen, Carina; Sørensen, Søren; Rechendorff, Kristian; Rijkhoff, Nico J. M.

2015-01-01

The in vivo electrochemical behavior of titanium nitride (TiN) nerve stimulation electrodes was compared to their in vitro behavior for a period of 90 days. Ten electrodes were implanted in two Göttingen minipigs. Four of these were used for electrical stimulation and electrochemical measurements. Five electrodes were kept in Ringer's solution at 37.5°C, of which four were used for electrical stimulation and electrochemical measurements. The voltage transients measured in vivo were 13 times greater than in vitro at implantation and they continued to increase with time. The electrochemical properties in vivo and the tissue resistance (Rtissue) followed a similar trend with time. There was no consistent significant difference between the electrochemical properties of the in vivo and in vitro electrodes after the implanted period. The differences between the in vivo and in vitro electrodes during the implanted period show that the evaluation of electrochemical performance of implantable stimulation electrodes cannot be substituted with in vitro measurements. After the implanted period, however, the performance of the in vivo and in vitro electrodes in saline was similar. In addition, the changes observed over time during the post-implantation period regarding the electrochemical properties of the in vivo electrodes and Rtissue were similar, which indicates that these changes are due to the foreign body response to implantation. PMID:26300717

Nanoparticle shape evolution and proximity effects during tip-induced electrochemical processes

DOE PAGES

Yang, Sangmo; Paranthaman, Mariappan Parans; Noh, Tae Won; ...

2016-01-08

The voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When themore » grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag +/Ag redox reaction to Ag +-ion diffusion with the increase in the applied voltage and pulse duration. Our study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.« less

Synthesis, Characterization, and Electrochemical Properties of Polyaniline Thin Films

NASA Astrophysics Data System (ADS)

Rami, Soukaina

Conjugated polymers have been used in various applications (battery, supercapacitor, electromagnetic shielding, chemical sensor, biosensor, nanocomposite, light-emitting-diode, electrochromic display etc.) due to their excellent conductivity, electrochemical and optical properties, and low cost. Polyaniline has attracted the researchers from all disciplines of science, engineering, and industry due to its redox properties, environmental stability, conductivity, and optical properties. Moreover, it is a polymer with fast electroactive switching and reversible properties displayed at low potential, which is an important feature in many applications. The thin oriented polyaniline films have been fabricated using self-assembly, Langmuir-Blodgett, in-situ self-assembly, layer-by-layer, and electrochemical technique. The focus of this thesis is to synthesize and characterize polyaniline thin films with and without dyes. Also, the purpose of this thesis is to find the fastest electroactive switching PANI electrode in different electrolytic medium by studying their electrochemical properties. These films were fabricated using two deposition techniques: in-situ self-assembly and electrochemical deposition. The characterization of these films was done using techniques such as Fourier Transform Infrared Spectroscopy (FTIR), UV-spectroscopy, Scanning Electron Microscope (SEM), and X-Ray Diffraction (XRD). FTIR and UV-spectroscopy showed similar results in the structure of the polyaniline films. However, for the dye incorporated films, since there was an addition in the synthesis of the material, peak locations shifted, and new peaks corresponding to these materials appeared. The 1 layer PANI showed compact film morphology, comparing to other PANI films, which displayed a fiber-like structure. Finally, the electrochemical properties of these thin films were studied using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in different scenarios. These scenarios included the study in different acid based electrolytes and different gel based electrolytes. The ultra-thin self-assembled PANI films were shown to have a faster switching time, especially for the 1 layer PANI, whereas the color contrast could be observed for the film containing the dye molecule. Also, HCl based electrolyte gave the best electrochemical reversibility compared to other acids used. For the gelatin and PVA based electrolytes, having the same concentration, the results were similar. Hence, the change in the electrolyte consistencies, from liquid to semi-solid, did not change the electrochemical properties of the films. Finally, in the EIS, it was shown that these PANI thin films exhibit a pseudo-capacitance behavior, and as the film thickness grew, the capacitance increased.

Entrainment in an electrochemical forced oscillator as a method of classification of chemical species-a new strategy to develop a chemical sensor

NASA Astrophysics Data System (ADS)

Nakata, S.; Yoshikawa, K.; Kawakami, H.

1992-10-01

We propose a new sensing method of varios chemical species based on information on the mode of entrainment in an electrochemically forced oscillator. It is demonstrated that the presence of one of the four basic taste compounds (salty, sweet, bitter, and sour) changes the mode of entrainment in a unique way. Thus a characteristics change of the entrainment allows us to obtain information on the properties of the electrochemical system. The response of the mode of entrainment to the taste compounds is related to the nonlinear properties of the studied electrochemical system, i.e., its voltage dependent capacitance and conductance. The experimental results are compared with computer simulations of a model system in which the capacitance is a nonlinear function of the voltage.

CMOS Electrochemical Instrumentation for Biosensor Microsystems: A Review.

PubMed

Li, Haitao; Liu, Xiaowen; Li, Lin; Mu, Xiaoyi; Genov, Roman; Mason, Andrew J

2016-12-31

Modern biosensors play a critical role in healthcare and have a quickly growing commercial market. Compared to traditional optical-based sensing, electrochemical biosensors are attractive due to superior performance in response time, cost, complexity and potential for miniaturization. To address the shortcomings of traditional benchtop electrochemical instruments, in recent years, many complementary metal oxide semiconductor (CMOS) instrumentation circuits have been reported for electrochemical biosensors. This paper provides a review and analysis of CMOS electrochemical instrumentation circuits. First, important concepts in electrochemical sensing are presented from an instrumentation point of view. Then, electrochemical instrumentation circuits are organized into functional classes, and reported CMOS circuits are reviewed and analyzed to illuminate design options and performance tradeoffs. Finally, recent trends and challenges toward on-CMOS sensor integration that could enable highly miniaturized electrochemical biosensor microsystems are discussed. The information in the paper can guide next generation electrochemical sensor design.

CMOS Electrochemical Instrumentation for Biosensor Microsystems: A Review

PubMed Central

Li, Haitao; Liu, Xiaowen; Li, Lin; Mu, Xiaoyi; Genov, Roman; Mason, Andrew J.

2016-01-01

Modern biosensors play a critical role in healthcare and have a quickly growing commercial market. Compared to traditional optical-based sensing, electrochemical biosensors are attractive due to superior performance in response time, cost, complexity and potential for miniaturization. To address the shortcomings of traditional benchtop electrochemical instruments, in recent years, many complementary metal oxide semiconductor (CMOS) instrumentation circuits have been reported for electrochemical biosensors. This paper provides a review and analysis of CMOS electrochemical instrumentation circuits. First, important concepts in electrochemical sensing are presented from an instrumentation point of view. Then, electrochemical instrumentation circuits are organized into functional classes, and reported CMOS circuits are reviewed and analyzed to illuminate design options and performance tradeoffs. Finally, recent trends and challenges toward on-CMOS sensor integration that could enable highly miniaturized electrochemical biosensor microsystems are discussed. The information in the paper can guide next generation electrochemical sensor design. PMID:28042860

Study on electrochemically deposited Mg metal

NASA Astrophysics Data System (ADS)

Matsui, Masaki

An electrodeposition process of magnesium metal from Grignard reagent based electrolyte was studied by comparing with lithium. The electrodeposition of magnesium was performed at various current densities. The obtained magnesium deposits did not show dendritic morphologies while all the lithium deposits showed dendritic products. Two different crystal growth modes in the electrodeposition process of magnesium metal were confirmed by an observation using scanning electron micro scope (SEM) and a crystallographic analysis using X-ray diffraction (XRD). An electrochemical study of the deposition/dissolution process of the magnesium showed a remarkable dependency of the overpotential of magnesium deposition on the electrolyte concentration compared with lithium. This result suggests that the dependency of the overpotential on the electrolyte concentration prevent the locally concentrated current resulting to form very uniform deposits.

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

Yang, Sangmo; Paranthaman, Mariappan Parans; Noh, Tae Won

The voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When themore » grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag +/Ag redox reaction to Ag +-ion diffusion with the increase in the applied voltage and pulse duration. Our study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.« less

Comparison of phthalic acid removal from aqueous solution by electrochemical methods: Optimization, kinetic and sludge study.

PubMed

Sandhwar, Vishal Kumar; Prasad, Basheshwar

2017-12-01

In this work, comparative study between electrochemical processes such as electrocoagulation (EC), peroxi-coagulation (PC) and peroxi-electrocoagulation (PEC) was performed for the removal of phthalic acid (PA) and chemical oxygen demand (COD) from aqueous medium. Initially, acid treatment was studied at various pH (1-3) and temperature (10-55 °C). Subsequently, the supernatant was re-treated by electrochemical processes such as EC, PC and PEC separately. Independent parameters viz. pH, current density (CD), electrolyte concentration (m), electrode gap (g), H 2 O 2 concentration and electrolysis time (t) were optimized by Central Composite Design (CCD) for these electrochemical processes. All three processes were compared based on removal, energy consumption, kinetic analysis, operating cost and sludge characteristics. In this study, PEC process was found more efficient among EC, PC and PEC processes in order to get maximum removal, minimum energy consumption and minimum operating cost. Maximum removal of PA- 68.21%, 74.36%, 82.25% & COD- 64.79%, 68.15%, 75.21% with energy consumption - 120.95, 97.51, 65.68 (kWh/kg COD removed) were attained through EC, PC and PEC processes respectively at their corresponding optimum conditions. Results indicated that PA and COD removals are in order of PEC > PC > EC under optimum conditions. First order kinetic model was found able to describe the degradation kinetics and provided best correlation for the removal rate within the acceptable error range. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction

NASA Astrophysics Data System (ADS)

Wang, Zhijuan; Wu, Shixin; Zhang, Juan; Chen, Peng; Yang, Guocheng; Zhou, Xiaozhu; Zhang, Qichun; Yan, Qingyu; Zhang, Hua

2012-02-01

The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.

Synthesis and electrochemical properties of layered structure Li[Ni{sub 0.5}Co{sub 0.25}Mn{sub 0.25}]O{sub 2} cathode material

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

Prathibha, G.; Rosaiah, P.; Reddy, B. Purusottam

Lithium ion (Li-ion) batteries are currently the energy source of choice for cell phones, laptops, and other mobile electronic devices due to their balance of high energy density with high power density compared to other electrochemical energy carriers. In the present study, mixed hydroxide method is used to prepare Li[Ni{sub 0.5}Co{sub 0.25}Mn{sub 0.25}]O{sub 2} from the precursors and analyze qualitatively and studied the electrochemical properties. The XRD spectrum exhibited predominant (003) orientation at 2θ =18.39{sup o} corresponding to hexagonal layered structure of R3m symmetry with evaluated lattice parameters are a= 2.84 Å, c= 14.43 Å. Raman measurements were performed tomore » understand the microstructure and vibrational modes of the prepared sample. From the electrochemical (EC) studies an initial discharge capacity of about 140 mAhg{sup −1} with good cyclic stability was observed for the prepared sample in the potential range 0.0 −1.0V in aqueous medium.« less

Electrochemical Implications of Defects in Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Hall, Jonathan Peter

The electrochemical behavior of carbon nanotubes (CNTs) containing both intrinsic and extrinsically introduced defects has been investigated through the study of bamboo and hollow multi-walled CNT morphologies. The controlled addition of argon, hydrogen, and chlorine ions in addition to atomic hydrogen and magnesium vapor was used for varying the charge and type of extrinsic defects. To quantify changes in the CNTs upon treatment, Raman spectroscopy and electrochemical techniques were employed. It was indicated from Raman spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and chronopotentiometric experiments that the electrochemical response of hollow type CNTs could be tailored more significantly compared to bamboo type CNTs, which have innately high reactive site densities and are less amenable to modification. Total defect density and edge-plane-like defect concentrations monitored through Raman spectroscopy were used to correlate changes in the electrochemical response of the CNT electrodes as a function of treatment. The implementation of CNT electrodes in a prototypical electrolytic capacitor device was then explored and characterized. Dependencies on source current and redox couple concentration were evaluated, as well as changes in the total capacitance as a function of treatment. Cyclability studies were also performed as a function of source current magnitude to evaluate the longevity of the faradaic currents which typically decrease over time in other similar capacitors. This thesis then concludes with an overall summary of the themes and findings of the research presented in this work.

A comparative study of electrochemical machining process parameters by using GA and Taguchi method

NASA Astrophysics Data System (ADS)

Soni, S. K.; Thomas, B.

2017-11-01

In electrochemical machining quality of machined surface strongly depend on the selection of optimal parameter settings. This work deals with the application of Taguchi method and genetic algorithm using MATLAB to maximize the metal removal rate and minimize the surface roughness and overcut. In this paper a comparative study is presented for drilling of LM6 AL/B4C composites by comparing the significant impact of numerous machining process parameters such as, electrolyte concentration (g/l),machining voltage (v),frequency (hz) on the response parameters (surface roughness, material removal rate and over cut). Taguchi L27 orthogonal array was chosen in Minitab 17 software, for the investigation of experimental results and also multiobjective optimization done by genetic algorithm is employed by using MATLAB. After obtaining optimized results from Taguchi method and genetic algorithm, a comparative results are presented.

Simulation of lubricating behavior of a thioether liquid lubricant by an electrochemical method

NASA Technical Reports Server (NTRS)

Morales, W.

1984-01-01

An electrochemical cell was constructed to explore the possible radical anion forming behavior of a thioether liquid lubricant. The electrochemical behavior of the thioether was compared with the electrochemical behavior of biphenyl, which is known to form radical anions. Under controlled conditions biphenyl undergoes a reversible reaction to a radical anion, whereas the thioether undergoes an irreversible reduction yielding several products. These results are discussed in relation to boundary lubrication.

Comparative electrochemical analysis of crystalline and amorphous anodized iron oxide nanotube layers as negative electrode for LIB.

PubMed

Pervez, Syed Atif; Kim, Doohun; Farooq, Umer; Yaqub, Adnan; Choi, Jung-Hee; Lee, You-Jin; Doh, Chil-Hoon

2014-07-23

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport.

Electrochemically exfoliated graphene anodes with enhanced biocurrent production in single-chamber air-breathing microbial fuel cells.

PubMed

Najafabadi, Amin Taheri; Ng, Norvin; Gyenge, Előd

2016-07-15

Microbial fuel cells (MFCs) present promising options for environmentally sustainable power generation especially in conjunction with waste water treatment. However, major challenges remain including low power density, difficult scale-up, and durability of the cell components. This study reports enhanced biocurrent production in a membrane-free MFC, using graphene microsheets (GNs) as anode and MnOx catalyzed air cathode. The GNs are produced by ionic liquid assisted simultaneous anodic and cathodic electrochemical exfoliation of iso-molded graphite electrodes. The GNs produced by anodic exfoliation increase the MFC peak power density by over 300% compared to plain carbon cloth (i.e., 2.85Wm(-2) vs 0.66Wm(-2), respectively), and by 90% compared to conventional carbon black (i.e., Vulcan XC-72) anode. These results exceed previously reported power densities for graphene-containing MFC anodes. The fuel cell polarization results are corroborated by electrochemical impedance spectroscopy indicating three times lower charge transfer resistance for the GN anode. Material characterizations suggest that the best performing GN samples were of relatively smaller size (~500nm), with higher levels of ionic liquid induced surface functionalization during the electrochemical exfoliation process. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectroscopic, computational and electrochemical studies on the formation of the copper complex of 1-amino-4-hydroxy-9,10-anthraquinone and effect of it on superoxide formation by NADH dehydrogenase.

PubMed

Roy, Sanjay; Mondal, Palash; Sengupta, Partha Sarathi; Dhak, Debasis; Santra, Ramesh Chandra; Das, Saurabh; Guin, Partha Sarathi

2015-03-28

A 1 : 2 copper(II) complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) having the molecular formula CuQ2 was prepared and characterized by elemental analysis, NMR, FTIR, UV-vis and mass spectroscopy. The powder diffraction of the solid complex, magnetic susceptibility and ESR spectra were also recorded. The presence of the planar anthraquinone moiety in the complex makes it extremely difficult to obtain a single crystal suitable for X-ray diffraction studies. To overcome this problem, density functional theory (DFT) was used to evaluate an optimized structure of CuQ2. In the optimized structure, it was found that there is a tilt of the two planar aromatic anthraquinone rings of the complex with respect to each other in the two planes containing the O-Cu(II)-O plane. The present study is an important addition to the understanding of the structural aspects of metal-anthracyclines because there are only a few reports on the actual structures of metal-anthracyclines. The theoretical vibrational spectrum of the complex was assigned with the help of vibrational energy distribution analysis (VEDA) using potential energy distribution (PED) and compared with experimental results. Being important in producing the biochemical action of this class of molecules, the electrochemical behavior of the complex was studied in aqueous and non-aqueous solvents to find certain electrochemical parameters. In aqueous media, reduction involves a kinetic effect during electron transfer at an electrode surface, which was characterized very carefully using cyclic voltammetry. Electrochemical studies showed a significant modification in the electrochemical properties of 1-amino-4-hydroxy-9,10-anthraquinone (QH) when bound to Cu(II) in the complex compared to those observed for free QH. This suggests that the copper complex might be a good choice as a biologically active molecule, which was reflected in the lack of stimulated superoxide generation by the complex.

Comparative study on the selective chalcopyrite bioleaching of a molybdenite concentrate with mesophilic and thermophilic bacteria.

PubMed

Romano, P; Blázquez, M L; Alguacil, F J; Muñoz, J A; Ballester, A; González, F

2001-03-01

This study evaluates different bioleaching treatments of a molybdenite concentrate using mesophilic and thermophilic bacterial cultures. Further studies on the chemical leaching and the electrochemical behavior of the MoS(2) concentrate were carried out. Bioleaching tests showed a progressive removal of chalcopyrite from the molybdenite concentrate with an increase in temperature. Chemical leaching tests support the idea of an indirect attack of the concentrate. Electrochemical tests indicate that chalcopyrite dissolution is favored when molybdenite is present. Therefore, this type of bioleaching treatment could be applied to purify molybdenite flotation concentrates by selectively dissolving chalcopyrite.

Probing the electrochemical double layer of an ionic liquid using voltammetry and impedance spectroscopy: a comparative study of carbon nanotube and glassy carbon electrodes in [EMIM](+)[EtSO(4)](-).

PubMed

Zheng, J P; Goonetilleke, P C; Pettit, C M; Roy, D

2010-05-15

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are compared as techniques for analyzing double layer capacitances of ionic liquids (ILs) at the surfaces of two carbon-based electrodes. These systems are relevant for energy storage supercapacitors and often are associated with unconventional electrochemical properties. Certain theoretical and experimental aspects of CV and EIS necessary for quantitative evaluation of the capacitance characteristics of such systems are explored. The experiments use 1-ethyl-3-methyl imidazolium ethylsulfate as a model IL electrolyte in combination with a porous electrode of carbon nanotubes (CNTs). The results are compared with those obtained with a nonporous glassy carbon (GC) electrode. The time is constant, and hence the power delivery characteristics of the experimental cell are affected by the electrolyte resistance and residual faradaic reactions of the IL, as well as by the spatially inhomogeneous electrode surfaces. It is shown that adequate characterization of these IL-electrode systems can be achieved by combining CV with EIS. A phenomenological framework for utilizing this combination is discussed.

Restructuring of an Ir(210) electrode surface by potential cycling

PubMed Central

Soliman, Khaled A; Kolb, Dieter M; Jacob, Timo

2014-01-01

Summary This study addresses the electrochemical surface faceting and restructuring of Ir(210) single crystal electrodes. Cyclic voltammetry measurements and in situ scanning tunnelling microscopy are used to probe structural changes and variations in the electrochemical behaviour after potential cycling of Ir(210) in 0.1 M H2SO4. Faceted structures are obtained electrochemically as a function of time by cycling at a scanrate of 1 V·s−1 between −0.28 and 0.70 V vs SCE, i.e., between the onset of hydrogen evolution and the surface oxidation regime. The electrochemical behaviour in sulfuric acid solution is compared with that of thermally faceted Ir(210), which shows a sharp characteristic voltammetric peak for (311) facets. Structures similar to thermally-induced faceted Ir(210) are obtained electrochemically, which typically correspond to polyoriented facets at nano-pyramids. These structures grow anisotropically in a preferred direction and reach a height of about 5 nm after 4 h of cycling. The structural changes are reflected in variations of the electrocatalytic activity towards carbon monoxide adlayer oxidation. PMID:25247118

Restructuring of an Ir(210) electrode surface by potential cycling.

PubMed

Soliman, Khaled A; Kolb, Dieter M; Kibler, Ludwig A; Jacob, Timo

2014-01-01

This study addresses the electrochemical surface faceting and restructuring of Ir(210) single crystal electrodes. Cyclic voltammetry measurements and in situ scanning tunnelling microscopy are used to probe structural changes and variations in the electrochemical behaviour after potential cycling of Ir(210) in 0.1 M H2SO4. Faceted structures are obtained electrochemically as a function of time by cycling at a scanrate of 1 V·s(-1) between -0.28 and 0.70 V vs SCE, i.e., between the onset of hydrogen evolution and the surface oxidation regime. The electrochemical behaviour in sulfuric acid solution is compared with that of thermally faceted Ir(210), which shows a sharp characteristic voltammetric peak for (311) facets. Structures similar to thermally-induced faceted Ir(210) are obtained electrochemically, which typically correspond to polyoriented facets at nano-pyramids. These structures grow anisotropically in a preferred direction and reach a height of about 5 nm after 4 h of cycling. The structural changes are reflected in variations of the electrocatalytic activity towards carbon monoxide adlayer oxidation.

Polarization Resistance Measurement in Tap Water: The Influence of Rust Electrochemical Activity

NASA Astrophysics Data System (ADS)

Vasyliev, Georgii

2017-08-01

Corrosion rate of mild steel in tap water during 4300 h was estimated by LPR and weight-loss methods coupled with OCP measurements. The LPR results were found to be overestimated compared to the weight-loss data within initial 2000 h of exposure. The electrochemical activity of the rust separated from the metal surface was studied by cycling voltammetry using a home-built powder graphite electrode. High redox currents corresponding to the initial 2000 h of exposure were detected. Rust composition was characterized with IR and XRD, and the highest amounts of electrochemically active β- and γ-FeOOH were again detected for the initial 2000 h. Current consumption in rust transformation processes during LPR measurement in the galvanostatic mode accounts for overestimation of the corrosion rate. The time dependence of rust electrochemical activity correlates with OCP variation with time. During initial 2000 h, OCP values are shifted by 50 mV to cathodic side. For the period of a higher rust electrochemical activity, the use of a reduced B is suggested to increase accuracy of LPR technique in tap water.

Ultrasensitive one-step rapid detection of ochratoxin A by the folding-based electrochemical aptasensor.

PubMed

Wu, Jingjing; Chu, Huaqin; Mei, Zhanlong; Deng, Yi; Xue, Feng; Zheng, Lei; Chen, Wei

2012-11-13

A one-step electrochemical aptasensor using the thiol- and methylene blue- (MB-) dual-labeled aptamer modified gold electrode for determination of ochratoxin A (OTA) was presented in this research. The aptamer against OTA was covalently immobilized on the surface of the electrode by the self-assembly effect and used as recognition probes for OTA detection by the binding induced folding of the aptamer. Under the optimal conditions, the developed electrochemical aptasensor demonstrated a wide linear range from 0.1 pg mL(-1) to 1000 pg mL(-1) with the limit of detection (LOD) of 0.095 pg mL(-1), which was an extraordinary sensitivity compared with other common methods for OTA detection. Moreover, as a practical application, this proposed electrochemical aptasensor was used to monitor the OTA level in red wine samples without any special pretreatment and with satisfactory results obtained. Study results showed that this electrochemical aptasensor could be a potential useful platform for on-site OTA measurement in real complex samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Carbon Nanomaterials Based Electrochemical Sensors/Biosensors for the Sensitive Detection of Pharmaceutical and Biological Compounds

PubMed Central

Adhikari, Bal-Ram; Govindhan, Maduraiveeran; Chen, Aicheng

2015-01-01

Electrochemical sensors and biosensors have attracted considerable attention for the sensitive detection of a variety of biological and pharmaceutical compounds. Since the discovery of carbon-based nanomaterials, including carbon nanotubes, C60 and graphene, they have garnered tremendous interest for their potential in the design of high-performance electrochemical sensor platforms due to their exceptional thermal, mechanical, electronic, and catalytic properties. Carbon nanomaterial-based electrochemical sensors have been employed for the detection of various analytes with rapid electron transfer kinetics. This feature article focuses on the recent design and use of carbon nanomaterials, primarily single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), SWCNTs-rGO, Au nanoparticle-rGO nanocomposites, and buckypaper as sensing materials for the electrochemical detection of some representative biological and pharmaceutical compounds such as methylglyoxal, acetaminophen, valacyclovir, β-nicotinamide adenine dinucleotide hydrate (NADH), and glucose. Furthermore, the electrochemical performance of SWCNTs, rGO, and SWCNT-rGO for the detection of acetaminophen and valacyclovir was comparatively studied, revealing that SWCNT-rGO nanocomposites possess excellent electrocatalytic activity in comparison to individual SWCNT and rGO platforms. The sensitive, reliable and rapid analysis of critical disease biomarkers and globally emerging pharmaceutical compounds at carbon nanomaterials based electrochemical sensor platforms may enable an extensive range of applications in preemptive medical diagnostics. PMID:26404304

Electrochemical DNA biosensor for bovine papillomavirus detection using polymeric film on screen-printed electrode.

PubMed

Nascimento, Gustavo A; Souza, Elaine V M; Campos-Ferreira, Danielly S; Arruda, Mariana S; Castelletti, Carlos H M; Wanderley, Marcela S O; Ekert, Marek H F; Bruneska, Danyelly; Lima-Filho, José L

2012-01-01

A new electrochemical DNA biosensor for bovine papillomavirus (BPV) detection that was based on screen-printed electrodes was comprehensively studied by electrochemical methods of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A BPV probe was immobilised on a working electrode (gold) modified with a polymeric film of poly-L-lysine (PLL) and chitosan. The experimental design was carried out to evaluate the influence of polymers, probe concentration (BPV probe) and immobilisation time on the electrochemical reduction of methylene blue (MB). The polymer poly-L-lysine (PLL), a probe concentration of 1 μM and an immobilisation time of 60 min showed the best result for the BPV probe immobilisation. With the hybridisation of a complementary target sequence (BPV target), the electrochemical signal decreased compared to a BPV probe immobilised on the modified PLL-gold electrode. Viral DNA that was extracted from cattle with papillomatosis also showed a decrease in the MB electrochemical reduction, which suggested that the decreased electrochemical signal corresponded to a bovine papillomavirus infection. The hybridisation specificity experiments further indicated that the biosensor could discriminate the complementary sequence from the non-complementary sequence. Thus, the results showed that the development of analytical devices, such as a biosensor, could assist in the rapid and efficient detection of bovine papillomavirus DNA and help in the prevention and treatment of papillomatosis in cattle. Copyright © 2012 Elsevier B.V. All rights reserved.

The negative effect of hyperbaric oxygen therapy at the acute phase of electrochemical esophageal burn induced by button battery ingestion.

PubMed

Aydin, Atakan; Aktas, Samil; Hafiz, Gunter; Kabakas, Fatih; Erer, Metin; Bilgic, Bilge

2004-07-01

Ingestion of button battery, if lodges in esophagus, causes mucosal destruction in esophagus and may damage surrounding tissues due to electrochemical reactions which may lead to esophagus perforation, tracheosefageal fistula and other serious problems. We designed an experimental study to test the effect of hyperbaric oxygen therapy on battery induced electrochemical tissue damage in the esophagus of a rabbit model and possible change with duration of contact time. Button batteries were inserted in esophagus of 40 rabbits which were divided into four groups. Groups 1 and 2 had 15 min of duration of contact time of battery in esophagus, while Groups 3 and 4 had 30 min. Groups 1 and 3 had hyperbaric oxygen therapy for 3 days; Groups 2 and 4 did not. At the end of 3rd day all animals were sacrified and samples were taken from the esophagus for determination of malondialdehyde levels and for histopathological examination to compare: mucosal destruction, muscular layer involvement, perforation and tracheal involvement between groups. Malondialdehyde levels, mucosal destruction, muscular layer involvement, perforation and tracheal involvement were significantly higher in groups which had 30 min of contact time compared to groups which had 15 min. The same assessments were significantly higher in Group 1 (15 min of contact time with hyperbaric oxygen therapy) compared to Group 2 (15 min of contact time without hyperbaric oxygen therapy). However, the difference between Group 3 (30 min of contact time with hyperbaric oxygen therapy) and Group 4 (30 min of contact time, no hyperbaric oxygen therapy) was not significant. Our study demonstrated that if contact time is 15 min HBO had an additive adverse effect to electrochemically burned esophagus by increasing free radicals and eventually tissue damage. However, if the contact time is 30 min its adverse effect is shielded by huge electrochemical destruction due to long contact time.

In situ study of LaY2Ni9 compound as Ni MH negative-electrode material

NASA Astrophysics Data System (ADS)

Latroche, M.; Isnard, O.

2008-03-01

The behavior of a Ni-MH (metal hydride) negative composite electrode made of LaY2Ni9 active material has been studied dynamically using in situ neutron diffraction during a complete charge-discharge electrochemical cycle. From the analysis of the collected diffraction patterns, the phase identity, phase amount variations and cell volume evolutions have been determined as a function of the electrochemical state of (dis)charge. The active material shows a typical two-phase behavior with equilibrium between a hydrogen-poor α phase and a hydrogen-rich β one. The lower electrochemical reversible capacity as compared to solid-gas properties has been interpreted in terms of hydrogen gas evolving during charge and kinetic limitation due to slow β to α transformation during discharge, which hinders high discharge rates.

A biofilm microreactor system for simultaneous electrochemical and nuclear magnetic resonance techniques

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

Renslow, Ryan S.; Babauta, Jerome T.; Majors, Paul D.

2014-03-01

In order to fully understand electrochemically active biofilms and the limitations to their scale-up in industrial biofilm reactors, a complete picture of the microenvironments inside the biofilm is needed. Nuclear magnetic resonance (NMR) techniques are ideally suited for the study of biofilms and for probing their microenvironments because these techniques allow for non-invasive interrogation and in situ monitoring with high resolution. By combining NMR with simultaneous electrochemical techniques, it is possible to sustain and study live electrochemically active biofilms. Here, we introduce a novel biofilm microreactor system that allows for simultaneous electrochemical and NMR techniques (EC-NMR) at the microscale. Microreactorsmore » were designed with custom radiofrequency resonator coils, which allowed for NMR measurements of biofilms growing on polarized gold electrodes. For an example application of this system, we grew Geobacter sulfurreducens biofilms. NMR was used to investigate growth media flow velocities, which were compared to simulated laminar flow, and electron donor concentrations inside the biofilms. We use Monte Carlo error analysis to estimate standard deviations of the electron donor concentration measurements within the biofilm. The EC-NMR biofilm microreactor system can ultimately be used to correlate extracellular electron transfer rates with metabolic reactions and explore extracellular electron transfer mechanisms.« less

Electrochemical studies on niobium triselenide cathode material for lithium rechargeable cells

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

Ratnakumar, B.V.; Ni, C.L.; DiStefano, S.

1989-01-01

Niobium triselenide offers promise as a high energy density cathode material for ambient temperature lithium rechargeable cells. The electrochemical behavior of NbSe/sub 3/ in the battery electrolyte, i.e., 1.5m LiAsF/sub 6//2 Me-THF is reported here. A detailed study has been carried out using various ac and dc electrochemical techniques to establish the mechanism of intercalation of three equivalents of Li with NbSe/sub 3/ as well as the rate governing processes in the reduction of NbSe/sub 3/. Based on the experimental data, an equivalent circuit has been formulated to represent the NbSe/sub 3/-solution interface. The kinetic parameters for the reduction ofmore » NbSe/sub 3/ were evaluated from the ac and dc measurements. Finally, the structural change in NbSe/sub 3/ on lithiation during initial discharge which results in higher cell voltages and different electrochemical response as compared to virgin NbSe/sub 3/ was identified to be a loss of crystallographic order, i.e., amorphous by x-ray diffraction.« less

Aerobic and Electrochemical Oxidations with N-Oxyl Reagents

NASA Astrophysics Data System (ADS)

Miles, Kelsey C.

Selective oxidation of organic compounds represents a significant challenge for chemical transformations. Oxidation methods that utilize nitroxyl catalysts have become increasingly attractive and include Cu/nitroxyl and nitroxyl/NO x co-catalyst systems. Electrochemical activation of nitroxyls is also well known and offers an appealing alternative to the use of chemical co-oxidants. However, academic and industrial organic synthetic communities have not widely adopted electrochemical methods. Nitroxyl catalysts facilitate effective and selective oxidation of alcohols and aldehydes to ketones and carboxylic acids. Selective benzylic, allylic, and alpha-heteroatom C-H abstraction can also be achieved with nitroxyls and provides access to oxygenated products when used in combination with molecular oxygen as a radical trap. This thesis reports various chemical and electrochemical oxidation methods that were developed using nitroxyl mediators. Chapter 1 provides a short review on practical aerobic alcohol oxidation with Cu/nitroxyl and nitroxyl/NO x systems and emphasizes the utility of bicyclic nitroxyls as co-catalysts. In Chapter 2, the combination of these bicyclic nitroxyls with NOx is explored for development of a mild oxidation of alpha-chiral aryl aldehydes and showcases a sequential asymmetric hydroformylation/oxidation method. Chapter 3 reports the synthesis and characterization of two novel Cu/bicyclic nitroxyl complexes and the electronic structure analysis of these complexes. Chapter 4 highlights the electrochemical activation of various nitroxyls and reports an in-depth study on electrochemical alcohol oxidation and compares the reactivity of nitroxyls under electrochemical or chemical activation. N-oxyls can also participate in selective C-H abstraction, and Chapter 5 reports the chemical and electrochemical activation of N-oxyls for radical-mediated C-H oxygenation of (hetero)arylmethanes. For these electrochemical transformations, the development of user-friendly methods and analysis techniques is emphasized.

Functionalized-graphene modified graphite electrode for the selective determination of dopamine in presence of uric acid and ascorbic acid.

PubMed

Mallesha, Malledevaru; Manjunatha, Revanasiddappa; Nethravathi, C; Suresh, Gurukar Shivappa; Rajamathi, Michael; Melo, Jose Savio; Venkatesha, Thimmappa Venkatarangaiah

2011-06-01

Graphene is chemically synthesized by solvothermal reduction of colloidal dispersions of graphite oxide. Graphite electrode is modified with functionalized-graphene for electrochemical applications. Electrochemical characterization of functionalized-graphene modified graphite electrode (FGGE) is carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of FGGE towards ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been investigated by CV, differential pulse voltammetry (DPV) and chronoamperommetry (CA). The FGGE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to that of the bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 193mv, 172mv and 264mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separations in DPV mode are 204mv, 141mv and 345mv. The FGGE is successfully used for the simultaneous detection of AA, DA and UA in their ternary mixture and DA in serum and pharmaceutical samples. The excellent electrocatalytic behavior of FGGE may lead to new applications in electrochemical analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Electrochemical performance of electrospun free-standing nitrogen-doped carbon nanofibers and their application for glucose biosensing.

PubMed

Liu, Dong; Zhang, Xueping; You, Tianyan

2014-05-14

In spite of excellent electrochemical properties, nitrogen-doped carbon nanofibers (NCNFs) have rarely been studied in the field of electroanalysis. In this work, we investigated the electrochemical properties and biosensing performance of NCNFs prepared by a newly proposed approach. The as-obtained NCNFs present a unique free-standing structure with high flexibility which could be convenient for electrode modification. Electrochemical measurements of typical redox species including [Ru(NH3)6]3+/2+, [Fe(CN)6]3-/4-, [Fe(H2O)6]3+/2+, and dopamine indicate that the NCNFs have a larger surface area and faster electron transfer rate compared with carbon nanofibers (CNFs). The presence of high content of pyrrolic-N and abundant defective sites in NCNFs leads to an obvious positive shift of peak potential for oxygen reduction at NCNFs relative to that obtained at CNFs. The unique structure and properties greatly enhance the electrochemical performance of NCNFs. The glucose biosensor based on glucose oxidase/NCNFs shows linear ranges of 0.2-1.2 mM at -0.42 V and 0.05-3 mM at 0.40 V both with high stability. These results suggest that the NCNFs could be a convenient and stable platform for electrochemical biosensors.

Enhanced Electrochemical Activity and Chromium Tolerance of the Nucleation-Agent-Free La2Ni0.9Fe0.1O4+δ Cathode by Gd0.1Ce0.9O1.95 Incorporation

NASA Astrophysics Data System (ADS)

Ling, Yihan; Xie, Huixin; Liu, Zijing; Du, Xiaoni; Chen, Hui; Ou, Xuemei; Zhao, Ling; Budiman, Riyan Achmad

2018-07-01

For the sake of improving the electrochemical activity and chromium tolerance of the K2NiF4-type oxide, La2NiO4+δ (LNO), with nonnucleation agents like Mn and Sr elements, the electrochemical performance and degradation were comparatively studied at two cathodes La2Ni0.9Fe0.1O4+δ (LNF) and LNF-40wt%Gd0.1Ce0.9O1.95 (LNF-GDC) on the GDC electrolyte, where 5wt%Cr2O3 incorporation provides Cr-containing atmosphere. Compared with non-doped LNO, LNF shows a higher interstitial oxygen concentration (δ = 0.298) and a lower electrical conductivity, where bivalent Ni ion, {Ni}_{Ni}^{ × }, and trivalent Ni ion, {Ni}_{Ni}^{ \\cdot }, and trivalent Fe ion on Ni-site, {Fe}_{Ni}^{ \\cdot }, were observed from the XPS measurements. LNF-GDC shows greatly reduced interfacial polarization resistances (Rp), which are only half of those of LNF, indicating a better electrochemical performance. More importantly, no significant degradation of LNF-GDC in performance has been observed under exposure of Cr-containing atmosphere at 700 °C for 350 h, while Rp of LNF increased by nearly 20%, suggesting LNF by GDC incorporation can enhance the electrochemical performance as well as chromium tolerance for intermediate temperature solid oxide fuel cells (IT-SOFCs).

Enhanced Electrochemical Activity and Chromium Tolerance of the Nucleation-Agent-Free La2Ni0.9Fe0.1O4+δ Cathode by Gd0.1Ce0.9O1.95 Incorporation

NASA Astrophysics Data System (ADS)

Ling, Yihan; Xie, Huixin; Liu, Zijing; Du, Xiaoni; Chen, Hui; Ou, Xuemei; Zhao, Ling; Budiman, Riyan Achmad

2018-03-01

For the sake of improving the electrochemical activity and chromium tolerance of the K2NiF4-type oxide, La2NiO4+δ (LNO), with nonnucleation agents like Mn and Sr elements, the electrochemical performance and degradation were comparatively studied at two cathodes La2Ni0.9Fe0.1O4+δ (LNF) and LNF-40wt%Gd0.1Ce0.9O1.95 (LNF-GDC) on the GDC electrolyte, where 5wt%Cr2O3 incorporation provides Cr-containing atmosphere. Compared with non-doped LNO, LNF shows a higher interstitial oxygen concentration (δ = 0.298) and a lower electrical conductivity, where bivalent Ni ion, {Ni}_{Ni}^{ × } , and trivalent Ni ion, {Ni}_{Ni}^{ \\cdot } , and trivalent Fe ion on Ni-site, {Fe}_{Ni}^{ \\cdot } , were observed from the XPS measurements. LNF-GDC shows greatly reduced interfacial polarization resistances (Rp), which are only half of those of LNF, indicating a better electrochemical performance. More importantly, no significant degradation of LNF-GDC in performance has been observed under exposure of Cr-containing atmosphere at 700 °C for 350 h, while Rp of LNF increased by nearly 20%, suggesting LNF by GDC incorporation can enhance the electrochemical performance as well as chromium tolerance for intermediate temperature solid oxide fuel cells (IT-SOFCs).

Preparation and electrochemical characterization of polymer electrolytes based on electrospun poly(vinylidene fluoride- co-hexafluoropropylene)/polyacrylonitrile blend/composite membranes for lithium batteries

NASA Astrophysics Data System (ADS)

Raghavan, Prasanth; Zhao, Xiaohui; Shin, Chorong; Baek, Dong-Ho; Choi, Jae-Won; Manuel, James; Heo, Min-Yeong; Ahn, Jou-Hyeon; Nah, Changwoon

Apart from PEO based solid polymer electrolytes, tailor-made gel polymer electrolytes based on blend/composite membranes of poly(vinylidene fluoride- co-hexafluoropropylene) and polyacrylonitrile are prepared by electrospinning using 14 wt% polymer solution in dimethylformamide. The membranes show uniform morphology with an average fiber diameter of 320-490 nm, high porosity and electrolyte uptake. Polymer electrolytes are prepared by soaking the electrospun membranes in 1 M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate. Temperature dependent ionic conductivity and their electrochemical performance are studied. The blend/composite polymer electrolytes show good ionic conductivity in the range of 10 -3 S cm -1 at ambient temperature and good electrochemical performance. All the Polymer electrolytes show an anodic stability >4.6 V with stable interfacial resistance with storage time. The prototype cell shows good charge-discharge properties and stable cycle performance with comparable capacity fade compared to liquid electrolyte under the test conditions.

Botulinum neurotoxin serotypes detected by electrochemical impedance spectroscopy.

PubMed

Savage, Alison C; Buckley, Nicholas; Halliwell, Jennifer; Gwenin, Christopher

2015-05-06

Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A-E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins.

Botulinum Neurotoxin Serotypes Detected by Electrochemical Impedance Spectroscopy

PubMed Central

Savage, Alison C.; Buckley, Nicholas; Halliwell, Jennifer; Gwenin, Christopher

2015-01-01

Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A–E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins. PMID:25954998

Electrochemical characteristics of flexible micro supercapacitors with reduced graphene oxide-carbon nanotubes composite electrodes

NASA Astrophysics Data System (ADS)

Yang, Kyungwhan; Cho, Kyoungah; Kim, Sangsig

2018-06-01

In this study, we fabricate solid-state flexible micro-supercapacitors (MSCs) with reduced graphene oxide-carbon nanotube (rGO-CNT) composite electrodes and investigate the electrochemical characteristics by comparing with those of an MSC with rGO electrodes. Regarding the resistance-capacitance time constant and IR drop, the addition of CNTs into the rGO electrodes shows a significant effect owing to both the decrease in the resistance and the increase in the permeability of the electrolytes. Compared to the rGO MSCs, the rGO-CNT MSCs show an excellent areal capacitance of 2.6 mF/cm2, a smaller IR drop of 11 mV, a lower RC time constant of 6 ms, and faster charging/discharging rates with a high scan rate ability up to 100 V/s. The mechanical stability of the flexible rGO-CNT MSCs is verified by 1000 bending cycles. In addition, the electrochemical characteristics of the flexible rGO-CNT MSCs are maintained regardless of the MSC array type.

Feasibility of an Orthogonal Redundant Sensor incorporating Optical plus Redundant Electrochemical Glucose Sensing.

PubMed

McAuley, Sybil A; Dang, Tri T; Horsburgh, Jodie C; Bansal, Anubhuti; Ward, Glenn M; Aroyan, Sarkis; Jenkins, Alicia J; MacIsaac, Richard J; Shah, Rajiv V; O'Neal, David N

2016-05-01

Orthogonal redundancy for glucose sensing (multiple sensing elements utilizing distinct methodologies) may enhance performance compared to nonredundant sensors, and to sensors with multiple elements utilizing the same technology (simple redundancy). We compared the performance of a prototype orthogonal redundant sensor (ORS) combining optical fluorescence and redundant electrochemical sensing via a single insertion platform to an electrochemical simple redundant sensor (SRS). Twenty-one adults with type 1 diabetes wore an ORS and an SRS concurrently for 7 days. Following sensor insertion, and on Day 4 with a standardized meal, frequent venous samples were collected for reference glucose measurement (laboratory [YSI] and meter) over 3 and 4 hours, respectively. Between study visits reference capillary blood glucose testing was undertaken. Sensor data were processed prospectively. ORS mean absolute relative difference (MARD) was (mean ± SD) 10.5 ± 13.2% versus SRS 11.0 ± 10.4% (P = .34). ORS values in Clarke error grid zones A and A+B were 88.1% and 97.6%, respectively, versus SRS 86.4% and 97.8%, respectively (P = .23 and P = .84). ORS Day 1 MARD (10.7 ± 10.7%) was superior to SRS (16.5 ± 13.4%; P < .0001), and comparable to ORS MARD for the week. ORS sensor survival (time-averaged mean) was 92.1% versus SRS 74.4% (P = .10). ORS display time (96.0 ± 5.8%) was equivalent to SRS (95.6 ± 8.9%; P = .87). Combining simple and orthogonal sensor redundancy via a single insertion is feasible, with accuracy comparing favorably to current generation nonredundant sensors. Addition of an optical component potentially improves sensor reliability compared to electrochemical sensing alone. Further improvement in optical sensing performance is required prior to clinical application. © 2016 Diabetes Technology Society.

SISGR-Fundamental Experimental and Theoretical Studies on a Novel Family of Oxide Catalyst Supports for Water Electrolysis

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

Kumta, Prashant

2014-10-03

Identification and development of non-noble metal based electro-catalysts or electro-catalysts with significant reduction of expensive noble metal contents (E.g. IrO2, Pt) with comparable electrochemical performance as the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a major breakthrough in the generation of hydrogen by water electrolysis. Accomplishing such a system would not only result reduction of the overall capital costs of PEM based water electrolyzers, but also help attain the targeted hydrogen production cost [< $ 3.0 / gallon gasoline equivalent (gge)] comparable to conventional liquid fuels. In line with these goals, it wasmore » demonstrated that fluorine doped IrO2 thin films and nanostructured high surface area powders display remarkably higher electrochemical activity, and comparable durability as pure IrO2 electro-catalyst for the oxygen evolution reaction (OER) in PEM based water electrolysis. Furthermore, corrosion resistant SnO2 and NbO2 support has been doped with F and coupled with IrO2 or RuO2 for use as an OER electro-catalyst. A solid solution of SnO2:F or NbO2:F with only 20 - 30 mol.% IrO2 or RuO2 yielding a rutile structure in the form of thin films and bulk nanoparticles displays similar electrochemical activity and stability as pure IrO2/RuO2. This would lead to more than 70 mol.% reduction in the noble metal oxide content. Novel nanostructured ternary (Ir,Sn,Nb)O2 thin films of different compositions FUNDAMENTAL STUDY OF NANOSTRUCTURED ELECTRO-CATALYSTS WITH REDUCED NOBLE METAL CONTENT FOR PEM BASED WATER ELECTROLYSIS 4 have also been studied. It has been shown that (Ir0.40Sn0.30Nb0.30)O2 shows similar electrochemical activity and enhanced chemical robustness as compared to pure IrO2. F doping of the ternary (Ir,Sn,Nb)O2 catalyst helps in further decreasing the noble metal oxide content of the catalyst. As a result, these reduced noble metal oxide catalyst systems would potentially be preferred as OER electro-catalysts for PEM electrolysis. The excellent performance of the catalysts coupled with its robustness would make them great candidates for contributing to significant reduction in the overall capital costs of PEM based water electrolyzers. This s.thesis provides a detailed fundamental study of the synthesis, materials, characterization, theoretical studies and detailed electrochemical response and potential mechanisms of these novel electro-catalysts for OER processes.« less

Electrochemical determination of inorganic mercury and arsenic--A review.

PubMed

Zaib, Maria; Athar, Muhammad Makshoof; Saeed, Asma; Farooq, Umar

2015-12-15

Inorganic mercury and arsenic encompasses a term which includes As(III), As(V) and Hg(II) species. These metal ions have been extensively studied due to their toxicity related issues. Different analytical methods are used to monitor inorganic mercury and arsenic in a variety of samples at trace level. The present study reviews various analytical techniques available for detection of inorganic mercury and arsenic with particular emphasis on electrochemical methods especially stripping voltammetry. A detailed critical evaluation of methods, advantages of electrochemical methods over other analytical methods, and various electrode materials available for mercury and arsenic analysis is presented in this review study. Modified carbon paste electrode provides better determination due to better deposition with linear and improved response under studied set of conditions. Biological materials may be the potent and economical alternative as compared to macro-electrodes and chemically modified carbon paste electrodes in stripping analysis of inorganic mercury and arsenic. Copyright © 2015 Elsevier B.V. All rights reserved.

In situ electrochemical and photo-electrochemical generation of the fenton reagent: a potentially important new water treatment technology.

PubMed

Peralta-Hernández, J M; Meas-Vong, Yunny; Rodríguez, Francisco J; Chapman, Thomas W; Maldonado, Manuel I; Godínez, Luis A

2006-05-01

In this work, the design and construction of an annular tube reactor for the electrochemical and photo-electrochemical in situ generation of H2O2 are described. By cathodic reduction of dissolved oxygen and the coupled oxidation of water at a UV-illuminated nanocrystalline-TiO2 semiconductor anode, it was found that the electrochemically generated H2O2 can be employed to readily oxidize the model compound Direct Yellow-52 in dilute acidic solution at high rates in the presence of small quantities of dissolved iron(II). Although, the model organic compound is chemically stable under UV radiation, its electrochemical oxidation rate increases substantially when the semiconductor anode is illuminated as compared to the same processes carried out in the dark.

Comparing electrochemical performance of transition metal silicate cathodes and chevrel phase Mo6S8 in the analogous rechargeable Mg-ion battery system

NASA Astrophysics Data System (ADS)

Chen, Xinzhi; Bleken, Francesca L.; Løvvik, Ole Martin; Vullum-Bruer, Fride

2016-07-01

Polyanion based silicate materials, MgMSiO4 (M = Fe, Mn, Co), previously reported to be promising cathode materials for Mg-ion batteries, have been re-examined. Both the sol-gel and molten salt methods are employed to synthesize MgMSiO4 composites. Mo6S8 is synthesized by a molten salt method combined with Cu leaching and investigated in the equivalent electrochemical system as a bench mark. Electrochemical measurements for Mo6S8 performed using the 2nd generation electrolyte show similar results to those reported in literature. Electrochemical performance of the silicate materials on the other hand, do not show the promising results previously reported. A thorough study of these published results are presented here, and compared to the current experimental data on the same material system. It appears that there are certain inconsistencies in the published results which cannot be explained. To further corroborate the present experimental results, atomic-scale calculations from first principles are performed, demonstrating that diffusion barriers are very high for Mg diffusion in MgMSiO4. In conclusion, MgMSiO4 (M = Fe, Mn, Co) olivine materials do not seem to be such good candidates for cathode materials in Mg-ion batteries as previously reported.

New Secondary Batteries Utilizing Electronically Conductive Polypyrrole Cathode. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Yeu, Taewhan

1991-01-01

To gain a better understanding of the dynamic behavior in electronically conducting polypyrroles and to provide guidance toward designs of new secondary batteries based on these polymers, two mathematical models are developed; one for the potentiostatically controlled switching behavior of polypyrrole film, and one for the galvanostatically controlled charge/discharge behavior of lithium/polypyrrole secondary battery cell. The first model is used to predict the profiles of electrolyte concentrations, charge states, and electrochemical potentials within the thin polypyrrole film during switching process as functions of applied potential and position. Thus, the detailed mechanisms of charge transport and electrochemical reaction can be understood. Sensitivity analysis is performed for independent parameters, describing the physical and electrochemical characteristic of polypyrrole film, to verify their influences on the model performance. The values of independent parameters are estimated by comparing model predictions with experimental data obtained from identical conditions. The second model is used to predict the profiles of electrolyte concentrations, charge state, and electrochemical potentials within the battery system during charge and discharge processes as functions of time and position. Energy and power densities are estimated from model predictions and compared with existing battery systems. The independent design criteria on the charge and discharge performance of the cell are provided by studying the effects of design parameters.

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%).

Cold pressure welding of aluminium-steel blanks: Manufacturing process and electrochemical surface preparation

NASA Astrophysics Data System (ADS)

Schmidt, Hans Christian; Homberg, Werner; Orive, Alejandro Gonzalez; Grundmeier, Guido; Hordych, Illia; Maier, Hans Jürgen

2018-05-01

In this study the manufacture of aluminium-steel blanks by cold pressure welding and their preparation for a welding process through electrochemical surface treatment are investigated and discussed. The cold pressure welding process was done with an incremental rolling tool that allows for the partial pressure welding of two blanks along a prepared path. The influence of the surface preparation by electrochemical deposition of bond promoting organosilane-based agents and roughening on a nano-scale is investigated and compared to conventional surface treatments. Coating the surfaces with a thin organosilane-based film incorporating specific functional groups should promote additional bonding between the mating oxide layers; its influence on the total weld strength is studied. Pressure welding requires suitable process strategies, and the current advances in the proposed incremental rolling process for the combination of mild steel and aluminium are presented.

Electro-synthesis of novel nanostructured PEDOT films and their application as catalyst support

PubMed Central

2011-01-01

Poly(3,4-ethylenedioxythiophene) (PEDOT) films doped with nitric and chlorine ions have been electrochemically deposited simply by a one-step electrochemical method in an aqueous media in the absence of any surfactant. The fabricated PEDOT films were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results indicate that the hierarchical structured PEDOT film doped with nitric ions displays a 'lunar craters' porous morphology consisting of PEDOT nano-sheets with a thickness of less than 2 nm. The effect of counter ions on the electro-polymerization, the electrochemistry, and the morphology of the polymer film was studied. Compared with PEDOT film doped with nitric acid, PEDOT film deposited in the presence of chlorine ions shows irregular morphology and less electrochemical activity. The specific nanostructure of the polymer was further studied as catalyst support for platinum nanoparticles to methanol electro-oxidation. PMID:21711871

Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

NASA Astrophysics Data System (ADS)

Basirun, Wan J.; Sookhakian, Mehran; Baradaran, Saeid; Mahmoudian, Mohammad R.; Ebadi, Mehdi

2013-09-01

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.

Detection of radiation-induced changes in electrochemical properties of austenitic stainless steels using miniaturized specimens and the single-loop electrochemical potentiokinetic reactivation method

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

Inazumi, T.; Bell, G.E.C.; Kenik, E.A.

1993-01-01

Single-loop electrochemical potentiokinetic reactivation testing of miniaturized (TEM) specimens can provide reliable data comparable to data obtained with larger specimens. Significant changes in electrochemical properties (increased reactivation current and Flade potential) were detected for PCA and type 316 stainless steels irradiated at 200--420[degrees]C up to 7--9 dpa. Irradiations in the FFTF Materials Open Test Assembly and in the Oak Ridge Research Reactor are reported on. 45 figs., 5 tabs., 52 refs.

Detection of radiation-induced changes in electrochemical properties of austenitic stainless steels using miniaturized specimens and the single-loop electrochemical potentiokinetic reactivation method

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

Inazumi, T.; Bell, G.E.C.; Kenik, E.A.

1993-01-01

Single-loop electrochemical potentiokinetic reactivation testing of miniaturized (TEM) specimens can provide reliable data comparable to data obtained with larger specimens. Significant changes in electrochemical properties (increased reactivation current and Flade potential) were detected for PCA and type 316 stainless steels irradiated at 200--420{degrees}C up to 7--9 dpa. Irradiations in the FFTF Materials Open Test Assembly and in the Oak Ridge Research Reactor are reported on. 45 figs., 5 tabs., 52 refs.

Electrochemical DNA biosensor for detection of porcine oligonucleotides using ruthenium(II) complex as intercalator label redox

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

Halid, Nurul Izni Abdullah; Hasbullah, Siti Aishah; Heng, Lee Yook

2014-09-03

A DNA biosensor detection of oligonucleotides via the interactions of porcine DNA with redox active complex based on the electrochemical transduction is described. A ruthenium(II) complex, [Ru(bpy){sub 2}(PIP)]{sup 2+}, (bpy = 2,2′bipyridine, PIP = 2-phenylimidazo[4,5-f[[1,10-phenanthroline]) as DNA label has been synthesized and characterized by 1H NMR and mass spectra. The study was carried out by covalent bonding immobilization of porcine aminated DNA probes sequences on screen printed electrode (SPE) modified with succinimide-acrylic microspheres and [Ru(bpy){sub 2}(PIP)]{sup 2+} was used as electrochemical redox intercalator label to detect DNA hybridization event. Electrochemical detection was performed by cyclic voltammetry (CV) and differential pulsemore » voltammetry (DPV) over the potential range where the ruthenium (II) complex was active. The results indicate that the interaction of [Ru(bpy){sub 2}(PIP)]{sup 2+} with hybridization complementary DNA has higher response compared to single-stranded and mismatch complementary DNA.« less

Electrochemical Performance of Glucose/Oxygen Biofuel Cells Based on Carbon Nanostructures.

PubMed

Koo, Min-Hye; Das, Gautam; Yoon, Hyon Hee

2016-03-01

The electrochemical performance of glucose/oxygen biofuel cells based on carbon nanostructures was investigated in the present study. Different types of carbon nanomaterials, including multi-walled carbon nanotubes (MWCNT), functionalized MWCNT (f-MWCNT), carbon nanofibers (CNF), and functionalized CNF (f-CNF) were examined for electrode fabrications. The anode for glucose/oxygen biofuel cells were prepared by sequential coating of carbon nanomaterials, charge transfer complex (CTC), glucose oxidase (GOx) and nafion membrane. The anode was then integrated with a bilirubin oxidase-immobilized cathode for the biofuel cell test. It was found that the electrochemical performance of the enzyme electrodes was remarkably enhanced by the amalgamation of carbon nanomaterials with the CTC. The biofuel cell with anode comprising of f-CNF and the cathode with MWCNT exhibited the best electrochemical performance with a maximum power density of 210 μW/cm2 at a cell voltage of 0.44 V for 20 mM glucose concentration, which is comparable with the best power density value reported earlier.

Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Wang, Rui; Feng, Lili; Yang, Wenrong; Zhang, Yinyin; Zhang, Yanli; Bai, Wei; Liu, Bo; Zhang, Wei; Chuan, Yongming; Zheng, Ziguang; Guan, Hongjin

2017-10-01

When testing the electrochemical performance of metal oxide anode for lithium-ion batteries (LIBs), binder played important role on the electrochemical performance. Which binder was more suitable for preparing transition metal oxides anodes of LIBs has not been systematically researched. Herein, five different binders such as polyvinylidene fluoride (PVDF) HSV900, PVDF 301F, PVDF Solvay5130, the mixture of styrene butadiene rubber and sodium carboxymethyl cellulose (SBR+CMC), and polyacrylonitrile (LA133) were studied to make anode electrodes (compared to the full battery). The electrochemical tests show that using SBR+CMC and LA133 binder which use water as solution were significantly better than PVDF. The SBR+CMC binder remarkably improve the bonding capacity, cycle stability, and rate performance of battery anode, and the capacity retention was about 87% after 50th cycle relative to the second cycle. SBR+CMC binder was more suitable for making transition metal oxides anodes of LIBs.

CFD analysis of a solid oxide fuel cell with internal reforming: Coupled interactions of transport, heterogeneous catalysis and electrochemical processes

NASA Astrophysics Data System (ADS)

Janardhanan, Vinod M.; Deutschmann, Olaf

Direct internal reforming in solid oxide fuel cell (SOFC) results in increased overall efficiency of the system. Present study focus on the chemical and electrochemical process in an internally reforming anode supported SOFC button cell running on humidified CH 4 (3% H 2 O). The computational approach employs a detailed multi-step model for heterogeneous chemistry in the anode, modified Butler-Volmer formalism for the electrochemistry and Dusty Gas Model (DGM) for the porous media transport. Two-dimensional elliptic model equations are solved for a button cell configuration. The electrochemical model assumes hydrogen as the only electrochemically active species. The predicted cell performances are compared with experimental reports. The results show that model predictions are in good agreement with experimental observation except the open circuit potentials. Furthermore, the steam content in the anode feed stream is found to have remarkable effect on the resulting overpotential losses and surface coverages of various species at the three-phase boundary.

Electrochemically Controlled Ion-exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

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

Choi, Daiwon; Zhu, Chengzhou; Fu, Shaofang

2016-09-15

The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structuremore » of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).« less

Fabrication of hollow boron-doped diamond nanostructure via electrochemical corrosion of a tungsten oxide template.

PubMed

Lim, Young-Kyun; Lee, Eung-Seok; Lee, Choong-Hyun; Lim, Dae-Soon

2018-08-10

In the study, a hollow boron-doped diamond (BDD) nanostructure electrode is fabricated to increase the reactive surface area for electrochemical applications. Tungsten oxide nanorods are deposited on the silicon substrate as a template by the hot filament chemical vapor deposition (HFCVD) method. The template is coated with a 100 nm BDD layer deposited by HFCVD to form a core-shell nanostructure. The WO x core is finally electrochemically dissolved to form hollow BDD nanostructure. The fabricated hollow BDD nanostructure electrode is investigated via scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The specific surface areas of the electrodes were analyzed and compared by using Brunauer-Emmett-Teller method. Furthermore, cyclic voltammetry and chronocoulometry are used to investigate the electrochemical characteristics and the reactive surface area of the as-prepared hollow BDD nanostructure electrode. A hollow BDD nanostructure electrode exhibits a reactive area that is 15 times that of a planar BDD thin electrode.

Size and ligand effects on the electrochemical and spectroelectrochemical responses of CdSe nanocrystals.

PubMed

Querner, Claudia; Reiss, Peter; Sadki, Said; Zagorska, Malgorzata; Pron, Adam

2005-09-07

The electrochemical properties of CdSe quantum dots with electrochemically inactive surface ligands (TOPO) have been investigated in comparison with the analogous nanocrystals containing electrochemically active oligoaniline ligands. The TOPO-capped nanocrystals have been studied in a wide size range (from 3 to 6.5 nm) with the goal to amplify the influence of the quantum confinement effect on the electrochemical response. The determined HOMO and LUMO levels have been found in good agreement with the ones obtained from photoluminescence studies and those predicted theoretically. Ligand exchange with aniline tetramer significantly influences the voltammetric peaks associated with the HOMO oxidation and the LUMO reduction of the quantum dots, which are shifted to higher and lower potentials, respectively. These shifts are interpreted in terms of the positive ligand charging which precedes the oxidation of the nanocrystals and the insulating nature of the ligand in the case of the nanocrystal reduction. The ligand-nanocrystal interactions have also been studied by UV-Vis-NIR and Raman spectroelectrochemistry in comparison with a specially prepared model compound which, apart from the anchoring function is identical to the grafted oligoaniline ligand. Both spectroelectrochemical techniques clearly indicate the same nature of the oxidation/reduction pathway for both the model compound and the grafted ligand. The influence of the grafting is manifested by a shift in the onset of the ligand oxidation as compared to the case of the "free" model compound. Since both components (ligands and nanocrystals) mutually influence their electrochemical and spectroelectrochemical properties, the newly developed system can be considered as a true molecular hybrid. Such hybrids are of interest because the potential zone of the ligand electroactivity is well separated from that of the nanocrystals and, as a result, the organic part can be electrochemically switched between the semiconducting and the conducting states with no change in the oxidation state of the nanocrystal. The newly developed system offers therefore the possibility of an electrical addressing of individual nanocrystals via the conducting ligands.

Porous TiO2-ZrO2 thin film formed by electrochemical technique to improve the biocompatibility of titanium alloy in physiological environment

NASA Astrophysics Data System (ADS)

Benea, L.; Dănăilă, E.; Ponthiaux, P.

2017-02-01

Porous Ti and Ti alloys have received increasing research interest for bone tissue engineering, especially for dental and orthopaedic implants because they provide cell ingrowths and vascularization, improving of adhesion and osseointegration. The tribocorrosion process is encountered in orthopaedic and dentistry applications, since it is known that the implants are often exposed to simultaneous chemical/electrochemical and mechanical stresses. The purpose of this study was to carry out a systematic investigation of the tribo-electrochemical performance of porous TiO2-ZrO2 thin film formed by anodization of Ti-10Zr alloy surface in an artificial saliva solution and to compare the resulted performance with that of the untreated Ti-10Zr alloy surface in order to be applied for biomedical use. The in situ electrochemical technique used for investigation of tribo-electrochemical degradation was the open circuit potential (OCP) measurement performed before, during and after sliding tests. The results presented herein show that controlled anodic oxidation method can significantly improve the tribocorrosion and friction performances of Ti-10Zr alloy surface intended for biomedical applications.

Electrochemical and Passive Behaviors of Pure Copper Fabricated by Accumulative Roll-Bonding (ARB) Process

NASA Astrophysics Data System (ADS)

Imantalab, O.; Fattah-alhosseini, A.

2015-07-01

In the present work, electrochemical and passive behaviors of pure copper fabricated by accumulative roll-bonding (ARB) process in 0.01 M borax solution (pH = 9.1) have been studied. Before any electrochemical measurements, evaluation of microstructure was obtained by Vickers microhardness, x-ray diffraction (XRD), and transmission electron microscopy. The results of microhardness tests revealed that microhardness values increased with the increasing number of ARB cycles. Also a sharp increase was seen in microhardness after the first ARB cycle, whereas mediocre additional increases were observed afterward up to the seven cycles. Moreover, XRD patterns showed that the mean crystallite size values decrease with the increasing number of ARB cycles. To investigate the electrochemical and passive behaviors of the samples, the potentiodynamic polarization, Mott-Schottky analysis and electrochemical impedance spectroscopy (EIS) were carried out. Polarization plots revealed that as a result of ARB, the corrosion behavior of the specimens improves compared with the annealed pure copper. Also, the Mott-Schottky analysis and EIS measurements showed that the increasing number of ARB cycles offer better conditions for forming the passive films with higher protection behavior, due to the growth of less-defective films.

Comparison of the Electrochemical Behavior of Ti and Nanostructured Ti-Coated AISI 304 Stainless Steel in Strongly Acidic Solutions

NASA Astrophysics Data System (ADS)

Attarzadeh, Farid Reza; Elmkhah, Hassan; Fattah-Alhosseini, Arash

2017-02-01

In this study, the electrochemical behaviors of pure titanium (Ti) and nanostructured (NS) Ti-coated AISI 304 stainless steel (SS) in strongly acidic solutions of H2SO4 were investigated and compared. A type of physical vapor deposition method, cathodic arc evaporation, was applied to deposit NS Ti on 304 SS. Scanning electron microscope and X-ray diffraction were used to characterize surface coating morphology. Potentiodynamic polarization, electrochemical impedance spectroscopy, and Mott-Schottky (M-S) analysis were used to evaluate the passive behavior of the samples. Electrochemical measurements revealed that the passive behavior of NS Ti coating was better than that of pure Ti in 0.1 and 0.01 M H2SO4 solutions. M-S analysis indicated that the passive films behaved as n-type semiconductors in H2SO4 solutions and the deposition method did not affect the semiconducting type of passive films formed on the coated samples. In addition, this analysis showed that the NS Ti coating had lower donor densities. Finally, all electrochemical tests showed that the passive behavior of the Ti-coated samples was superior, mainly due to the formation of thicker, yet less defective passive films.

Mathematical modeling and hydrodynamics of Electrochemical deburring process

NASA Astrophysics Data System (ADS)

Prabhu, Satisha; Abhishek Kumar, K., Dr

2018-04-01

The electrochemical deburring (ECD) is a variation of electrochemical machining is considered as one of the efficient methods for deburring of intersecting features and internal parts. Since manual deburring costs are comparatively high one can potentially use this method in both batch production and flow production. The other advantage of this process is that time of deburring as is on the order of seconds as compared to other methods. In this paper, the mathematical modeling of Electrochemical deburring is analysed from its deburring time and base metal removal point of view. Simultaneously material removal rate is affected by electrolyte temperature and bubble formation. The mathematical model and hydrodynamics of the process throw limelight upon optimum velocity calculations which can be theoretically determined. The analysis can be the powerful tool for prediction of the above-mentioned parameters by experimentation.

High performance robust F-doped tin oxide based oxygen evolution electro-catalysts for PEM based water electrolysis

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

Datta, Moni Kanchan; Kadakia, Karan; Velikokhatnyi, Oleg I

2013-01-01

Identification and development of non-noble metal based electro-catalysts or electro-catalysts comprising compositions with significantly reduced amounts of expensive noble metal contents (e.g. IrO{sub 2}, Pt) with comparable electrochemical performance to the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would signify a major breakthrough in hydrogen generation via water electrolysis. Development of such systems would lead to two primary outcomes: first, a reduction in the overall capital costs of PEM based water electrolyzers, and second, attainment of the targeted hydrogen production costs (<$3.00/gge delivered by 2015) comparable to conventional liquid fuels. In line with these goals,more » by exploiting a two-pronged theoretical first principles and experimental approach herein, we demonstrate for the very first time a solid solution of SnO{sub 2}:10 wt% F containing only 20 at.% IrO{sub 2} [e.g. (Sn{sub 0.80}Ir{sub 0.20})O{sub 2}:10F] displaying remarkably similar electrochemical activity and comparable or even much improved electrochemical durability compared to pure IrO{sub 2}, the accepted gold standard in oxygen evolution electro-catalysts for PEM based water electrolysis. We present the results of these studies.« less

Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability.

PubMed

Lee, Habeom; Hong, Sukjoon; Lee, Jinhwan; Suh, Young Duk; Kwon, Jinhyeong; Moon, Hyunjin; Kim, Hyeonseok; Yeo, Junyeob; Ko, Seung Hwan

2016-06-22

Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices.

Electrochemical biosensors for hormone analyses.

PubMed

Bahadır, Elif Burcu; Sezgintürk, Mustafa Kemal

2015-06-15

Electrochemical biosensors have a unique place in determination of hormones due to simplicity, sensitivity, portability and ease of operation. Unlike chromatographic techniques, electrochemical techniques used do not require pre-treatment. Electrochemical biosensors are based on amperometric, potentiometric, impedimetric, and conductometric principle. Amperometric technique is a commonly used one. Although electrochemical biosensors offer a great selectivity and sensitivity for early clinical analysis, the poor reproducible results, difficult regeneration steps remain primary challenges to the commercialization of these biosensors. This review summarizes electrochemical (amperometric, potentiometric, impedimetric and conductometric) biosensors for hormone detection for the first time in the literature. After a brief description of the hormones, the immobilization steps and analytical performance of these biosensors are summarized. Linear ranges, LODs, reproducibilities, regenerations of developed biosensors are compared. Future outlooks in this area are also discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Constructing the magnetic bifunctional graphene/titania nanosheet-based composite photocatalysts for enhanced visible-light photodegradation of MB and electrochemical ORR from polluted water.

PubMed

Zhang, Qian; Zhang, Yihe; Meng, Zilin; Tong, Wangshu; Yu, Xuelian; An, Qi

2017-09-25

Photocatalysis is a promising strategy to address the global environmental and energy challenges. However, the studies on the application of the photocatalytically degraded dye-polluted water and the multi-purpose use of one type of catalyst have remained sparse. In this report, we try to demonstrate a concept of multiple and cyclic application of materials and resources in environmentally relevant catalyst reactions. A magnetic composite catalyst prepared from exfoliated titania nanosheets, graphene, the magnetic iron oxide nanoparticles, and a polyelectrolyte enabled such a cyclic application. The composite catalyst decomposed a methylene blue-polluted water under visible light, and then the catalyst was collected and removed from the treated water using a magnet. The photocatalytically treated water was then used to prepare the electrolyte in electrochemical reductive reactions and presented superior electrochemical performance compared with the dye-polluted water. The composite catalyst was once again used as the cathode catalyst in the electrochemical reaction. Each component in the composite catalyst was indispensable in its catalytic activity, but each component played different roles in the photochemical, magnetic recycling, and electrochemical processes. We expect the report inspire the study on the multi-functional catalyst and cyclic use of the catalytically cleaned water, which should contribute for the environmental and energy remedy from a novel perspective.

Corrosion studies using potentiodynamic and EIS electrochemical techniques of welded lean duplex stainless steel UNS S82441

NASA Astrophysics Data System (ADS)

Brytan, Z.; Niagaj, J.; Reiman, Ł.

2016-12-01

The corrosion characterisation of lean duplex stainless steel (1.4662) UNS S82441 welded joints using the potentiodynamic test and electrochemical impedance spectroscopy in 1 M NaCl solution are discussed. The influence of autogenous TIG welding parameters (amount of heat input and composition of shielding gases like Ar and Ar-N2 and an Ar-He mixture), as well as A-TIG welding was studied. The influence of welding parameters on phase balance, microstructural changes and the protective properties of passive oxide films formed at the open circuit potential or during the anodic polarisation were studied. From the results of the potentiodynamic test and electrochemical impedance spectroscopy of TIG and A-TiG, welded joints show a lower corrosion resistance compared to non-welded parent metal, but introducing heat input properly during welding and applying shielding gases rich in nitrogen or helium can increase austenitic phase content, which is beneficial for corrosion resistance, and improves surface oxide layer resistance in 1 M NaCl solution.

[Isolation and identification of electrochemically active microorganism from micro-aerobic environment].

PubMed

Wu, Song; Xiao, Yong; Zheng, Zhi-Yong; Zheng, Yue; Yang, Zhao-Hui; Zhao, Feng

2014-10-01

Extracellular electron transfer of electrochemically active microorganism plays vital role in biogeochemical cycling of metals and carbon and in biosynthesis of bioenergy. Compared to anaerobic anode, micro-aerobic anode captures more energy from microbial fuel cell. However, most of previous researches focused on functioning bacteria in anaerobic anode, functioning bacteria in micro-aerobic anode was rarely studied. Herein, we used the traditional aerobic screening technology to isolate functioning bacteria from a micro-aerobic anode. Three pure cultures Aeromonas sp. WS-XY2, Citrobacter sp. WS-XY3 and Bacterium strain WS-XY4 were obtained. WS-XY2 and WS-XY3 were belonged to Proteobacteria, whereas WS-XY4 was possibly a new species. Cyclic voltammetry and chronoamperometry analysis demonstrated all of them showed the electrochemical activity by direct extracellular electron transfer, and micro-aerobic anode could select bacteria that have similar electrochemical activity to proliferate on the anode. We further conclude that functioning bacteria in micro-aerobic anode are more efficient than that of anaerobic anode may be the reason that micro-aerobic anode has better performance than anaerobic anode. Therefore, a thorough study of functioning bacteria in micro-aerobic anode will significantly promote the energy recovery from microbial fuel cell.

Use of a small overpotential approximation to analyze Geobacter sulfurreducens biofilm impedance

NASA Astrophysics Data System (ADS)

Babauta, Jerome T.; Beyenal, Haluk

2017-07-01

The electrochemical impedance of Geobacter sulfurreducens biofilms reflects the extracellular electron transfer mechanisms determining the rate of current output. Binned into two characteristic parameters, conductance and capacitance, biofilm impedance has received significant attention. The goal of this study was to evaluate a small overpotential approximation for extracellular electron transfer in G. sulfurreducens biofilms. Our motivation was to determine whether conductance over biofilm growth behaved linearly with respect to limiting current. Biofilm impedance was tracked during growth using electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (eQCM). We showed that normalization of the biofilm impedance is useful for characterizing the changes during growth. When the conductance and capacitance were compared to the biofilm current, we found that: 1) conductance had a linear response and 2) constant phase elements (CPE) had a saturating response that coincided with the limiting current. We provided a framework using a simple iV relationship that predicted the conductance-current slope to be 9.57 V-1. CPEs showed more variability across biofilm replicates than conductance values. Although G. sulfurreducens biofilms were used here, other electrochemically active biofilms exhibiting catalytic waves could be studied using the same methods.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

PubMed Central

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.

PubMed

Oakes, Landon; Westover, Andrew; Mares, Jeremy W; Chatterjee, Shahana; Erwin, William R; Bardhan, Rizia; Weiss, Sharon M; Pint, Cary L

2013-10-22

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite and nafion composite modified screen printed carbon electrode.

PubMed

Ku, Shuhao; Palanisamy, Selvakumar; Chen, Shen-Ming

2013-12-01

Herein, we report a highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite/nafion composite modified screen printed carbon (SPC) electrode. Electrochemically activated graphite/nafion composite was prepared by using a simple electrochemical method. Scanning electron microscope (SEM) used to characterize the surface morphology of the fabricated composite electrode. The SEM result clearly indicates that the graphitic basal planes were totally disturbed and leads to the formation of graphite nanosheets. The composite modified electrode showed an enhanced electrocatalytic activity toward the oxidation of DA when compared with either electrochemical pretreated graphite or nafion SPC electrodes. The fabricated composite electrode exhibits a good electrocatalytic oxidation toward DA in the linear response range from 0.5 to 70 μM with the detection limit of 0.023 μM. The proposed sensor also exhibits very good selectivity and stability, with the appreciable sensitivity. In addition, the proposed sensor showed satisfactory recovery results toward the commercial pharmaceutical DA samples. Copyright © 2013 Elsevier Inc. All rights reserved.

Fabrication of an electrochemical sensor based on spiropyran for sensitive and selective detection of fluoride ion.

PubMed

Tao, Jia; Zhao, Peng; Li, Yinhui; Zhao, Wenjie; Xiao, Yue; Yang, Ronghua

2016-04-28

In the past decades, numerous electrochemical sensors based on exogenous electroactive substance have been reported. Due to non-specific interaction between the redox mediator and the target, the instability caused by false signal may not be avoided. To address this issue, in this paper, a new electrochemical sensor based on spiropyran skeleton, namely SPOSi, was designed for specific electrochemical response to fluoride ions (F(-)). The breakage of Si-O induced by F(-) based on the specific nucleophilic substitution reaction between F(-) and silica would directly produce a hydroquinone structure for electrochemical signal generation. To improve the sensitivity, SPOSi probe was assembled on the single-walled carbon nanotubes (SWCNTs) modified glassy carbon electrode (GCE) through the π-π conjugating interaction. This electrode was successfully applied to monitor F(-) with a detection limit of 8.3 × 10(-8) M. Compared with the conventional F(-) ion selected electrode (ISE) which utilized noncovalent interaction, this method displays higher stability and a comparable sensitivity in the urine samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Improvement on the Repair Effect of Electrochemical Chloride Extraction Using a Modified Electrode Configuration

PubMed Central

Feng, Wei; Xu, Jinxia; Jiang, Linhua; Song, Yingbin; Cao, Yalong; Tan, Qiping

2018-01-01

To improve the repair effect of electrochemical chloride extraction, a modified electrode configuration is applied in this investigation. In this configuration, two auxiliary electrodes placed in the anodic and cathodic electrolytes were used as the anode and cathode, respectively. Besides this, the steel in the mortar was grounded to protect it from corrosion. By a comparative experiment, the potential evolution, various ions concentrations (Cl−, OH−, Na+, and K+) in different mortar depths, the corrosion potential, and the current density of the steel were measured. The results indicate that compared to electrochemical chloride extraction with the traditional electrode configuration, this electrochemical chloride extraction method with a modified electrode configuration has a similar chloride removal ratio. Besides this, potential of steel is just about 800 mV for a saturated calomel electrode (SCE) during the treatment, which did not reach the hydrogen evolution potential. The phenomenon of the accumulation of OH−, Na+, and K+ did not occur when the modified electrode configuration is applied. Additionally, higher corrosion potentials and lower corrosion current rates were measured after performing electrochemical chloride extraction with the modified electrode configuration. Additionally, it is a short period of time for the steel to go from activation to passivation. On this basis, the modified electrode configuration may overcome the drawbacks of electrochemical chloride extraction. PMID:29389855

Electrodeposition of Highly Porous Pt Nanoparticles Studied by Quantitative 3D Electron Tomography: Influence of Growth Mechanisms and Potential Cycling on the Active Surface Area.

PubMed

Ustarroz, Jon; Geboes, Bart; Vanrompay, Hans; Sentosun, Kadir; Bals, Sara; Breugelmans, Tom; Hubin, Annick

2017-05-17

Nanoporous Pt nanoparticles (NPs) are promising fuel cell catalysts due to their large surface area and increased electrocatalytic activity toward the oxygen reduction reaction (ORR). Herein, we report on the influence of the growth mechanisms on the surface properties of electrodeposited Pt dendritic NPs with large surface areas. The electrochemically active surface was studied by hydrogen underpotential deposition (H UPD) and compared for the first time to high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) quantitative 3D electron tomography of individual nanoparticles. Large nucleation overpotential leads to a large surface coverage of roughened spheroids, which provide a large roughness factor (R f ) but low mass-specific electrochemically active surface area (EASA). Lowering the nucleation overpotential leads to highly porous Pt NPs with pores stretching to the center of the structure. At the expense of smaller R f , the obtained EASA values of these structures are in the range of those of large surface area supported fuel cell catalysts. The active surface area of the Pt dendritic NPs was measured by electron tomography, and it was found that the potential cycling in the H adsorption/desorption and Pt oxidation/reduction region, which is generally performed to determine the EASA, leads to a significant reduction of that surface area due to a partial collapse of their dendritic and porous morphology. Interestingly, the extrapolation of the microscopic tomography results in macroscopic electrochemical parameters indicates that the surface properties measured by H UPD are comparable to the values measured on individual NPs by electron tomography after the degradation caused by the H UPD measurement. These results highlight that the combination of electrochemical and quantitative 3D surface analysis techniques is essential to provide insights into the surface properties, the electrochemical stability, and, hence, the applicability of these materials. Moreover, it indicates that care must be taken with widely used electrochemical methods of surface area determination, especially in the case of large surface area and possibly unstable nanostructures, since the measured surface can be strongly affected by the measurement itself.

A novel and simple cell-based electrochemical impedance biosensor for evaluating the combined toxicity of DON and ZEN.

PubMed

Gu, Wenshu; Zhu, Pei; Jiang, Donglei; He, Xingxing; Li, Yun; Ji, Jian; Zhang, Lijuan; Sun, Yange; Sun, Xiulan

2015-08-15

In this study, a novel and simple cell-based electrochemical biosensor was developed to assess the individual and combined toxicity of deoxynivalenol (DON) and zearalenone (ZEN) on BEL-7402 cells. The sensor was fabricated by modification with AuNPs, p-aminothiophenol, and folic acid in succession. The BEL-7402 cells which had a good activity were adhered on the electrode through the high affinity between the folate receptor and folic acid selectivity. We used the collagen to maintain the cell adhesion and viability. Electrochemical impedance spectroscopy (EIS) was developed to evaluate the individual and combined toxicity of DON and ZEN. Our results indicate that DON and ZEN caused a marked decrease in the cell viability in a dose-dependent manner. The value of electrochemical impedance spectroscopy decreased with the concentration of DON and ZEN in range of 0.1-20, 0.1-50 μg/ml with the detection limit as 0.03, 0.05 μg/ml, respectively, the IC50 for DON and ZEN as obtained by the proposed electrochemical method were 7.1 μg/ml and 24.6 μg/ml, respectively, and the combination of two mycotoxins appears to generate an additive response. The electrochemical cytotoxicity evaluation result was confirmed by biological assays. Compared to conventional methods, this electrochemical test is inexpensive, highly sensitive, and fast to respond, with long-term monitoring and real-time measurements. The proposed method provides a new avenue for evaluating the toxicity of mycotoxins. Copyright © 2015 Elsevier B.V. All rights reserved.

DNA interactions with a Methylene Blue redox indicator depend on the DNA length and are sequence specific.

PubMed

Farjami, Elaheh; Clima, Lilia; Gothelf, Kurt V; Ferapontova, Elena E

2010-06-01

A DNA molecular beacon approach was used for the analysis of interactions between DNA and Methylene Blue (MB) as a redox indicator of a hybridization event. DNA hairpin structures of different length and guanine (G) content were immobilized onto gold electrodes in their folded states through the alkanethiol linker at the 5'-end. Binding of MB to the folded hairpin DNA was electrochemically studied and compared with binding to the duplex structure formed by hybridization of the hairpin DNA to a complementary DNA strand. Variation of the electrochemical signal from the DNA-MB complex was shown to depend primarily on the DNA length and sequence used: the G-C base pairs were the preferential sites of MB binding in the duplex. For short 20 nts long DNA sequences, the increased electrochemical response from MB bound to the duplex structure was consistent with the increased amount of bound and electrochemically readable MB molecules (i.e. MB molecules that are available for the electron transfer (ET) reaction with the electrode). With longer DNA sequences, the balance between the amounts of the electrochemically readable MB molecules bound to the hairpin DNA and to the hybrid was opposite: a part of the MB molecules bound to the long-sequence DNA duplex seem to be electrochemically mute due to long ET distance. The increasing electrochemical response from MB bound to the short-length DNA hybrid contrasts with the decreasing signal from MB bound to the long-length DNA hybrid and allows an "off"-"on" genosensor development.

Low pCO2 Air-Polarized CO2 Concentrator Development

NASA Technical Reports Server (NTRS)

Schubert, Franz H.

1997-01-01

Life Systems completed a Ground-based Space Station Experiment Development Study Program which verifies through testing the performance and applicability of the electrochemical Air-Polarized Carbon Dioxide Concentrator (APC) process technology for space missions requiring low (i.e., less than 3 mm Hg) CO2 partial pressure (pCO2) in the cabin atmosphere. Required test hardware was developed and testing was accomplished at an approximate one-person capacity CO2 removal level. Initially, two five-cell electrochemical modules using flight-like 0.5 sq ft cell hardware were tested individually, following by their testing at the integrated APC system level. Testing verified previously projected performance and established a database for sizing of APC systems. A four person capacity APC system was sized and compared with four candidate CO2 removal systems. At its weight of 252 lb, a volume of 7 cu ft and a power consumption of 566 W while operating at 2.2 mm Hg pCO2, the APC was surpassed only by an Electrochemical Depolarized CO2 Concentrator (EDC) (operating with H2), when compared on a total equivalent basis.

Development of a novel carbon-coating strategy for producing core-shell structured carbon coated LiFePO4 for an improved Li-ion battery performance.

PubMed

Pratheeksha, Parakandy Muzhikara; Mohan, Erabhoina Hari; Sarada, Bulusu Venkata; Ramakrishna, Mantripragada; Hembram, Kalyan; Srinivas, Pulakhandam Veera Venkata; Daniel, Paul Joseph; Rao, Tata Narasinga; Anandan, Srinivasan

2016-12-21

In the present study, LiFePO 4 (LFP) has been synthesized using a flame spray pyrolysis unit followed by carbon coating on LFP using a novel strategy of dehydration assisted polymerization process (DAP) in order to improve its electronic conductivity. Characterization studies revealed the presence of a pure LFP structure and the formation of a thin, uniform and graphitic carbon layer with a thickness of 6-8 nm on the surface of the LFP. A carbon coated LFP with 3 wt% of carbon, using a DAP process, delivered a specific capacity of 167 mA h g -1 at a 0.1C rate, whereas LFP carbon coated by a carbothermal process (CLFP-C) delivered a capacity of 145 mA h g -1 at 0.1C. Further carbon coated LFP by the DAP exhibited a good rate capability and cyclic stability. The enhanced electrochemical performance of C-LFP by DAP is attributed to the presence of a uniform, thin and ordered graphitic carbon layer with a core-shell structure, which greatly increased the electronic conductivity of LFP and thereby showed an improved electro-chemical performance. Interestingly, the developed carbon coating process has been extended to synthesize a bulk quantity (0.5 kg) of carbon coated LFP under optimized experimental conditions as a part of up-scaling and the resulting material electro-chemical performance has been evaluated and compared with commercial electrode materials. Bulk C-LFP showed a capacity of 131 mA h g -1 and 87 mA h g -1 at a rate of 1C and at 10C, respectively, illustrating that the developed DAP process greatly improved the electrochemical performance of LFP in terms of rate capability and cyclic stability, not only during the lab scale synthesis but also during the large scale synthesis. Benchmark studies concluded that the electro-chemical performance of C-LFP by DAP is comparable with that of TODA LFP and better than that of UNTPL LFP. The DAP process developed in the present study can be extended to other electrode materials as well.

Enhanced hydrogen production in microbial electrolysis cell with 3D self-assembly nickel foam-graphene cathode.

PubMed

Cai, Weiwei; Liu, Wenzong; Han, Jinglong; Wang, Aijie

2016-06-15

In comparison to precious metal catalyst especially Platinum (Pt), nickel foam (NF) owned cheap cost and unique three-dimensional (3D) structure, however, it was scarcely applied as cathode material in microbial electrolysis cell (MEC) as the intrinsic laggard electrochemical activity for hydrogen recovery. In this study, a self-assembly 3D nickel foam-graphene (NF-G) cathode was fabricated by facile hydrothermal approach for hydrogen evolution in MECs. Electrochemical analysis (linear scan voltammetry and electrochemical impedance spectroscopy) revealed the improved electrochemical activity and effective mass diffusion after coating with graphene. NF-G as cathode in MEC showed a significant enhancement in hydrogen production rate compared with nickel foam at a variety of biases. Noticeably, NF-G showed a comparable averaged hydrogen production rate (1.31 ± 0.07 mL H2 mL(-1) reactor d(-1)) to Platinum/carbon (Pt/C) (1.32 ± 0.07 mL H2 mL(-1) reactor d(-1)) at 0.8 V. Profitable energy recovery could be achieved by NF-G cathode at higher applied voltage, which performed the best hydrogen yield of 3.27 ± 0.16 mol H2 mol(-1) acetate at 0.8 V and highest energy efficiency of 185.92 ± 6.48% at 0.6 V. Copyright © 2016 Elsevier B.V. All rights reserved.

Facile electrochemical pretreatment of multiwalled carbon nanotube - Polydimethylsiloxane paste electrode for enhanced detection of dopamine and uric acid

NASA Astrophysics Data System (ADS)

Buenaventura, Angelo Gabriel E.; Yago, Allan Christopher C.

2018-05-01

A facile electrochemical pretreatment via anodization was done on Carbon Paste Electrodes (CPEs) composed of Multiwalled Carbon Nanotubes (MWCNTs) and Polydimethylsiloxane (PDMS) binder to produce `anodized' CPEs (ACPE). Cyclic Voltammetry (CV) technique was used to anodize the CPEs. The anodization step, performed in various solutions (0.2 M NaOH(aq), 0.06 M BR Buffer at pH 7.0, and 0.2 M HNO3(aq)), were found to enhance the electrochemical properties of the ACPEs compared to non-anodized CPE. Electrochemical Impedance Spectroscopy (EIS) measurements revealed a significantly lower charge transfer resistance (Rct) for the ACPEs (4.01-6.25 kΩ) as compared to CPE (25.9 kΩ). Comparison of the reversibility analysis for Fe(CN)63-/4- redox couple showed that the ACPEs have peak current ratio (Ia/Ic) at range of 0.97-1.10 while 1.92 for the CPE; this result indicated better electrochemical reversible behaviors for Fe(CN)63-/4- redox couple using the ACPEs. CV Anodization process was further optimized by varying solution and CV parameters (i.e. pH, composition, number of cycles, and potential range), and the resulting optimized ACPE was used for enhanced detection of Dopamine (DA) and Uric Acid (UA) in the presence of excess Ascorbic Acid (AA). Employing Differential Pulse Voltammetry technique, enhanced voltammetric signal for DA and significant peak separation between DA and UA was obtained. The anodic peak currents for the oxidation of DA and UA appeared at 0.263V and 0.414 V, respectively, and it was observed to be linearly increasing with increasing concentrations of biomolecules (25-100 µM). The detection limit was determined to be 3.86 µM for DA and 5.61 µM for UA. This study showed a quick and cost-effective pretreatment for CPEs based on MWCNT-PDMS composite which lead to significant enhancement on its electrochemical properties.

Evaluation of a point-of-care electrochemical meter to detect subclinical ketosis and hypoglycaemia in lactating dairy cows.

PubMed

Zakian, A; Tehrani-Sharif, M; Mokhber-Dezfouli, M R; Nouri, M; Constable, P D

2017-04-01

To evaluate and validate a hand-held electrochemical meter (Precision Xtra®) as a screening test for subclinical ketosis and hypoglycaemia in lactating dairy cattle. Method comparison study using a convenience sample. Blood samples were collected into plain tubes from the coccygeal vessels of 181 Holstein cows at 2-4 weeks of lactation during summer in Iran. Blood β-hydroxybutyrate concentration (BHB) and glucose concentration were immediately measured by the electrochemical meter after applying 20 μL of blood to the reagent strip. Passing-Bablok regression and Bland-Altman plots were used to determine the accuracy of the meter against laboratory reference methods (BHB dehydrogenase and glucose oxidase). Serum BHB ranged from 0.1 to 7.3 mmol/L and serum glucose ranged from 0.9 to 5.1 mmol/L. Passing-Bablok regression analysis indicated that the electrochemical meter and reference methods were linearly related for BHB and glucose, with a slope estimate that was not significantly different from 1.00. Clinically minor, but statistically significant, differences were present for the intercept value for Passing-Bablok regression analysis for BHB and glucose, and bias estimates in the Bland-Altman plots for BHB and glucose. The electrochemical meter provided a clinically useful method to detect subclinical ketosis and hypoglycaemia in lactating dairy cows. Compared with other method validation studies using the meter, we attributed the improved performance of the electrochemical meter to application of a fixed volume of blood (20 μL) to the reagent strip, use of the meter in hot ambient conditions and use of glucose oxidase as the reference method for glucose analysis. © 2017 Australian Veterinary Association.

In operando neutron diffraction study of LaNdMgNi9H13 as a metal hydride battery anode

NASA Astrophysics Data System (ADS)

Nazer, N. S.; Denys, R. V.; Yartys, V. A.; Hu, Wei-Kang; Latroche, M.; Cuevas, F.; Hauback, B. C.; Henry, P. F.; Arnberg, L.

2017-03-01

La2MgNi9-related alloys are superior metal hydride battery anodes as compared to the commercial AB5 alloys. Nd-substituted La2-yNdyMgNi9 intermetallics are of particular interest because of increased diffusion rate of hydrogen and thus improved performance at high discharge currents. The present work presents in operando characterization of the LaNdMgNi9 intermetallic as anode for the nickel metal hydride (Ni-MH) battery. We have studied the structural evolution of LaNdMgNi9 during its charge and discharge using in situ neutron powder diffraction. The work included experiments using deuterium gas and electrochemical charge-discharge measurements. The alloy exhibited a high electrochemical discharge capacity (373 mAh/g) which is 20% higher than the AB5 type alloys. A saturated β-deuteride synthesized by solid-gas reaction at PD2 = 1.6 MPa contained 12.9 deuterium atoms per formula unit (D/f.u.) which resulted in a volume expansion of 26.1%. During the electrochemical charging, the volume expansion (23.4%) and D-contents were found to be slightly reduced. The reversible electrochemical cycling is performed through the formation of a two-phase mixture of the α-solid solution and β-hydride phases. Nd substitution contributes to the high-rate dischargeability, while maintaining a good cyclic stability. Electrochemical Impedance Spectroscopy (EIS) was used to characterize the anode electrode on cycling. A mathematical model for the impedance response of a porous electrode was utilized. The EIS showed a decreased hydrogen transport rate during the long-term cycling, which indicated a corresponding slowing down of the electrochemical processes at the surface of the metal hydride anode.

2,4-Toluene Diisocyanate Detection in Liquid and Gas Environments through Electrochemical Oxidation in an Ionic Liquid

PubMed Central

Lin, Lu; Rehman, Abdul; Chi, Xiaowei; Zeng, Xiangqun

2016-01-01

The electrochemical oxidation of 2,4-toluene diisocyanate (2,4-TDI) in an ionic liquid (IL) has been systematically characterized to determine plausible electrochemical and chemical reaction mechanisms and to define the optimal detection methods for such a highly significant analyte. It has been found that the use of an IL as the electrolyte allows the oxidation of 2,4-TDI to occur at a less positive anodic potential with no side reactions as compared to traditional acetonitrile based electrolytes. UV-Vis, FT-IR, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy (EIS) studies have revealed the unique mechanisms of dimerization of 2,4-TDI at the electrode interface by self-addition reactions, which can be utilized to improve the selectivity of detection. The study of 2,4-TDI redox chemistry further facilitates the development of a robust amperometric sensing methodology by selecting a hydrophobic IL ([C4mpy][NTf2]) and by restricting the potential window to only include the oxidation process. Thus, this innovative electrochemical sensor is capable of avoiding the two most ubiquitous interferents in ambient conditions (i.e. humidity and oxygen), thereby enhancing the sensor performance and reliability for real world applications. The method was established to detect 2,4–TDI in both liquid and gas phases. The limits of detection (LOD) values were 130.2 ppm and 0.7862 ppm, respectively, for the two phases, and are comparable to the safety standards reported by NIOSH. The as-developed 2.4-TDI amperometric sensor exhibits a sensitivity of 1.939 μA/ppm. Moreover, due to the simplicity of design and the use of an IL both as a solvent and non-volatile electrolyte, the sensor has the potential to be miniaturized for smart sensing protocols in distributed sensor applications. PMID:26763507

Electrochemical performance of CuNCN for sodium ion batteries and comparison with ZnNCN and lithium ion batteries

NASA Astrophysics Data System (ADS)

Eguia-Barrio, A.; Castillo-Martínez, E.; Klein, F.; Pinedo, R.; Lezama, L.; Janek, J.; Adelhelm, P.; Rojo, T.

2017-11-01

Transition metal carbodiimides (TMNCN) undergo conversion reactions during electrochemical cycling in lithium and sodium ion batteries. Micron sized copper and zinc carbodiimide powders have been prepared as single phase as confirmed by PXRD and IR and their thermal stability has been studied in air and nitrogen atmosphere. CuNCN decomposes at ∼250 °C into CuO or Cu while ZnNCN can be stable until 400 °C and 800 °C in air and nitrogen respectively. Both carbodiimides were electrochemically analysed for sodium and lithium ion batteries. The electrochemical Na+ insertion in CuNCN exhibits a relatively high reversible capacity (300 mAh·g-1) which still indicates an incomplete conversion reaction. This incomplete reaction confirmed by ex-situ EPR analysis, is partly due to kinetic limitations as evidenced in the rate capability experiments and in the constant potential measurements. On the other hand, ZnNCN shows incomplete conversion reaction but with good capacity retention and lower hysteresis as negative electrode for sodium ion batteries. The electrochemical performance of these materials is comparable to that of other materials which operate through displacement reactions and is surprisingly better in sodium ion batteries in comparison with lithium ion batteries.

On-line electrochemistry-bioaffinity screening with parallel HR-LC-MS for the generation and characterization of modified p38α kinase inhibitors.

PubMed

Falck, David; de Vlieger, Jon S B; Giera, Martin; Honing, Maarten; Irth, Hubertus; Niessen, Wilfried M A; Kool, Jeroen

2012-04-01

In this study, an integrated approach is developed for the formation, identification and biological characterization of electrochemical conversion products of p38α mitogen-activated protein kinase inhibitors. This work demonstrates the hyphenation of an electrochemical reaction cell with a continuous-flow bioaffinity assay and parallel LC-HR-MS. Competition of the formed products with a tracer (SKF-86002) that shows fluorescence enhancement in the orthosteric binding site of the p38α kinase is the readout for bioaffinity. Parallel HR-MS(n) experiments provided information on the identity of binders and non-binders. Finally, the data produced with this on-line system were compared to electrochemical conversion products generated off-line. The electrochemical conversion of 1-{6-chloro-5-[(2R,5S)-4-(4-fluorobenzyl)-2,5-dimethylpiperazine-1-carbonyl]-3aH-indol-3-yl}-2-morpholinoethane-1,2-dione resulted in eight products, three of which showed bioaffinity in the continuous-flow p38α bioaffinity assay used. Electrochemical conversion of BIRB796 resulted, amongst others, in the formation of the reactive quinoneimine structure and its corresponding hydroquinone. Both products were detected in the p38α bioaffinity assay, which indicates binding to the p38α kinase.

A Database for Comparative Electrochemical Performance of Commercial 18650-Format Lithium-Ion Cells

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

Barkholtz, Heather M.; Fresquez, Armando; Chalamala, Babu R.

Lithium-ion batteries are a central technology to our daily lives with widespread use in mobile devices and electric vehicles. These batteries are also beginning to be widely used in electric grid infrastructure support applications which have stringent safety and reliability requirements. Typically, electrochemical performance data is not available for modelers to validate their simulations, mechanisms, and algorithms for lithium-ion battery performance and lifetime. In this paper, we report on the electrochemical performance of commercial 18650 cells at a variety of temperatures and discharge currents. We found that LiFePO 4 is temperature tolerant for discharge currents at or below 10 Amore » whereas LiCoO 2, LiNi xCo yAl 1-x-yO 2, and LiNi 0.80Mn 0.15Co 0.05O 2 exhibited optimal electrochemical performance when the temperature is maintained at 15°C. LiNi xCo yAl 1-x-yO 2 showed signs of lithium plating at lower temperatures, evidenced by irreversible capacity loss and emergence of a high-voltage differential capacity peak. Furthermore, all cells need to be monitored for self-heating, as environment temperature and high discharge currents may elicit an unintended abuse condition. Overall, this study shows that lithium-ion batteries are highly application-specific and electrochemical behavior must be well understood for safe and reliable operation. Additionally, data collected in this study is available for anyone to download for further analysis and model validation.« less

A Database for Comparative Electrochemical Performance of Commercial 18650-Format Lithium-Ion Cells

DOE PAGES

Barkholtz, Heather M.; Fresquez, Armando; Chalamala, Babu R.; ...

2017-09-08

Lithium-ion batteries are a central technology to our daily lives with widespread use in mobile devices and electric vehicles. These batteries are also beginning to be widely used in electric grid infrastructure support applications which have stringent safety and reliability requirements. Typically, electrochemical performance data is not available for modelers to validate their simulations, mechanisms, and algorithms for lithium-ion battery performance and lifetime. In this paper, we report on the electrochemical performance of commercial 18650 cells at a variety of temperatures and discharge currents. We found that LiFePO 4 is temperature tolerant for discharge currents at or below 10 Amore » whereas LiCoO 2, LiNi xCo yAl 1-x-yO 2, and LiNi 0.80Mn 0.15Co 0.05O 2 exhibited optimal electrochemical performance when the temperature is maintained at 15°C. LiNi xCo yAl 1-x-yO 2 showed signs of lithium plating at lower temperatures, evidenced by irreversible capacity loss and emergence of a high-voltage differential capacity peak. Furthermore, all cells need to be monitored for self-heating, as environment temperature and high discharge currents may elicit an unintended abuse condition. Overall, this study shows that lithium-ion batteries are highly application-specific and electrochemical behavior must be well understood for safe and reliable operation. Additionally, data collected in this study is available for anyone to download for further analysis and model validation.« less

Electrochemical properties of Li2 FeSiO4 /C nanocomposites prepared by sol-gel and hydrothermal methods

NASA Astrophysics Data System (ADS)

Kumar, Ajay; Jayakumar, O. D.; Naik, Vaman M.; Nazri, Gholam A.; Naik, Ratna

Li2FeSiO4 is considered as potential cathode material for next generation lithium ion batteries because of its high specific theoretical capacity, low cost, and safety. However, it suffers from poor electronic conductivity and slow lithium ion diffusion in the solid phase. To address these issues, we have studied mesoporous Li2FeSiO4/C composites synthesized by sol-gel (SG) and hydrothermal (HT) methods using tri-block copolymer (P123) as carbon source and structure directing agent. The structure and morphology of the composites were characterized by XRD, SEM and TEM and the surface area and pore size distribution were measured by using N2 adsorption/desorption. Galvanostatic cycling, electrochemical impedance spectroscopy, and cyclic voltammetry were used to evaluate the electrochemical performance of the Li2FeSiO4/C composites. The Li2FeSiO4/C (HT) composites show a superior electrochemical performance compared to Li2FeSiO4/C (SG). At C/30 rate, the discharge capacity of Li2FeSiO4/C (HT) reached ~276 mAh/g in the 1.5-4.6 V window and shows better rate capability and stability at high rates. We attribute the improved electrochemical performance of Li2FeSiO4/C (HT) to its large surface area and reduced particle size. The details of the study will be presented.

Electrochemical Polishing Applications and EIS of a Vitamin B{sub 4}-Based Ionic Liquid

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

Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.

2013-01-01

Modern particle accelerators require minimal interior surface roughness for Niobium superconducting radio frequency (SRF) cavities. Polishing of the Nb is currently achieved via electrochemical polishing with concentrated mixtures of sulfuric and hydrofluoric acids. This acid-based approach is effective at reducing the surface roughness to acceptable levels for SRF use, but due to acid-related hazards and extra costs (including safe disposal of used polishing solutions), an acid-free method would be preferable. This study focuses on an alternative electrochemical polishing method for Nb, using a novel ionic liquid solution containing choline chloride, also known as Vitamin B{sub 4} (VB{sub 4}). Potentiostatic electrochemicalmore » impedance spectroscopy (EIS) was also performed on the VB4-based system. Nb polished using the VB4-based method was found to have a final surface roughness comparable to that achieved via the acid-based method, as assessed by atomic force microscopy (AFM). These findings indicate that acid-free VB{sub 4}-based electrochemical polishing of Nb represents a promising replacement for acid-based methods of SRF cavity preparation.« less

An Electrochemical Study on the Copolymer Formed from Piperazine and Aniline Monomers.

PubMed

Dkhili, Samiha; López-Bernabeu, Sara; Kedir, Chahineze Nawel; Huerta, Francisco; Montilla, Francisco; Besbes-Hentati, Salma; Morallon, Emilia

2018-06-14

A study on the electrochemical oxidation of piperazine and its electrochemical copolymerization with aniline in acidic medium is presented. It was found that the homopolymerization of piperazine cannot be achieved under electrochemical conditions. A combination of electrochemistry, in situ Fourier transform infrared (FTIR), and ex situ X-ray photoelectron spectroscopy (XPS) spectroscopies was used to characterize both the chemical structure and the redox behavior of an electrochemically synthesized piperazine⁻aniline copolymer. The electrochemical sensing properties of the deposited material were also tested against ascorbic acid and dopamine as redox probes.

Kinetic mechanism for modeling of electrochemical reactions.

PubMed

Cervenka, Petr; Hrdlička, Jiří; Přibyl, Michal; Snita, Dalimil

2012-04-01

We propose a kinetic mechanism of electrochemical interactions. We assume fast formation and recombination of electron donors D- and acceptors A+ on electrode surfaces. These mediators are continuously formed in the electrode matter by thermal fluctuations. The mediators D- and A+, chemically equivalent to the electrode metal, enter electrochemical interactions on the electrode surfaces. Electrochemical dynamics and current-voltage characteristics of a selected electrochemical system are studied. Our results are in good qualitative agreement with those given by the classical Butler-Volmer kinetics. The proposed model can be used to study fast electrochemical processes in microsystems and nanosystems that are often out of the thermal equilibrium. Moreover, the kinetic mechanism operates only with the surface concentrations of chemical reactants and local electric potentials, which facilitates the study of electrochemical systems with indefinable bulk.

Study on Microstructure and Electrochemical Corrosion Behavior of PEO Coatings Formed on Aluminum Alloy

NASA Astrophysics Data System (ADS)

Xiang, N.; Song, R. G.; Li, H.; Wang, C.; Mao, Q. Z.; Xiong, Y.

2015-12-01

Plasma electrolytic oxidation (PEO) treated 6063 aluminum alloy was applied in a silicate- and borate-based alkaline solution. The microstructure and electrochemical corrosion behavior were studied by scanning electron microscopy, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The results showed that the silicate-based PEO coating was of a denser structure compared with that of borate-based PEO coating. In addition, the silicate-based PEO coating was composed of more phased (Al9Si) than borate-based PEO coating. The results of corrosion test indicated that the silicate-based PEO coating provided a superior protection to 6063 aluminum alloy substrate, while borate-based PEO coating with a porous structure showed an inferior conservancy against corrosive electrolyte. Furthermore, the EIS tests proved that both coatings were capable to resist the aggressive erosion in 0.5 M NaCl solution after 72 h of immersion. However, the borate-based PEO coating could not provide sufficient protection to the substrate after 72-h immersion in 1 M NaCl solution.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions.

PubMed

Martins, Vitor L; Rennie, Anthony J R; Sanchez-Ramirez, Nedher; Torresi, Roberto M; Hall, Peter J

2018-02-01

Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g -1 @ 15 A g -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.

Carbohydrate-based electrochemical biosensor for detection of a cancer biomarker in human plasma.

PubMed

Devillers, Marion; Ahmad, Lama; Korri-Youssoufi, Hafsa; Salmon, Laurent

2017-10-15

Autocrine motility factor (AMF) is a tumor-secreted cytokine that stimulates tumor cell motility in vitro and metastasis in vivo. AMF could be detected in serum or urine of cancer patients with worse prognosis. Reported as a cancer biomarker, AMF secretion into body fluids might be closely related to metastases formation. In this study, a sensitive and specific carbohydrate-based electrochemical biosensor was designed for the detection and quantification of a protein model of AMF, namely phosphoglucose isomerase from rabbit muscle (RmPGI). Indeed, RmPGI displays high homology with AMF and has been shown to have AMF activity. The biosensor was constructed by covalent binding of the enzyme substrate d-fructose 6-phosphate (F6P). Immobilization was achieved on a gold surface electrode following a bottom-up approach through an aminated surface obtained by electrochemical patterning of ethylene diamine and terminal amine polyethylene glycol chain to prevent non-specific interactions. Carbohydrate-protein interactions were quantified in a range of 10 fM to 100nM. Complex formation was analyzed through monitoring of the redox couple Fe 2+ /Fe 3+ by electrochemical impedance spectroscopy and square wave voltammetry. The F6P-biosensor demonstrates a detection limit of 6.6 fM and high selectivity when compared to other non-specific glycolytic proteins such as d-glucose-6-phosphate dehydrogenase. Detection of protein in spiked plasma was demonstrated and accuracy of 95% is obtained compared to result obtained in PBS (phosphate buffered saline). F6P-biosensor is a very promising proof of concept required for the design of a carbohydrate-based electrochemical biosensor using the enzyme substrate as bioreceptor. Such biosensor could be generalized to detect other protein biomarkers of interest. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface morphology and electrochemical studies on polyaniline/CuO nano composites

NASA Astrophysics Data System (ADS)

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

2018-05-01

An electrochemically synthesized Polyaniline (PANI) and Polyaniline/copper oxide (PCN) nano composite have studied the morphology and electrochemical properties. The composite is characterized by X-ray diffraction (XRD) and surface morphology was studied using FESEM and electrochemical behavior is studied using cyclic voltammetry (CV) technique. The CV curves shows rectangular shaped curve and they have contribution to electrical double layer capacitance (EDCL).

Computational Fluid Dynamics Modeling of Nickel Hydrogen Batteries

NASA Technical Reports Server (NTRS)

Cullion, R.; Gu, W. B.; Wang, C. Y.; Timmerman, P.

2000-01-01

An electrochemical Ni-H2 battery model has been expanded to include thermal effects. A thermal energy conservation equation was derived from first principles. An electrochemical and thermal coupled model was created by the addition of this equation to an existing multiphase, electrochemical model. Charging at various rates was investigated and the results validated against experimental data. Reaction currents, pressure changes, temperature profiles, and concentration variations within the cell are predicted numerically and compared with available data and theory.

Comparative Study of the Electrochemical, Biomedical, and Thermal Properties of Natural and Synthetic Nanomaterials

NASA Astrophysics Data System (ADS)

Ghaemi, Ferial; Abdullah, Luqman Chuah; Kargarzadeh, Hanieh; Abdi, Mahnaz M.; Azli, Nur Farhana Waheeda Mohd; Abbasian, Maryam

2018-04-01

In this research, natural nanomaterials including cellulose nanocrystal (CNC), nanofiber cellulose (NFC), and synthetic nanoparticles such as carbon nanofiber (CNF) and carbon nanotube (CNT) with different structures, sizes, and surface areas were produced and analyzed. The most significant contribution of this study is to evaluate and compare these nanomaterials based on the effects of their structures and morphologies on their electrochemical, biomedical, and thermal properties. Based on the obtained results, the natural nanomaterials with low dimension and surface area have zero cytotoxicity effects on the living cells at 12.5 and 3.125 μg/ml concentrations of NFC and CNC, respectively. Meanwhile, synthetic nanomaterials with the high surface area around 15.3-21.1 m2/g and significant thermal stability (480 °C-600 °C) enhance the output of electrode by creating a higher surface area and decreasing the current flow resistance.

Comparison between Field Effect Transistors and Bipolar Junction Transistors as Transducers in Electrochemical Sensors

NASA Astrophysics Data System (ADS)

Zafar, Sufi; Lu, Minhua; Jagtiani, Ashish

2017-01-01

Field effect transistors (FET) have been widely used as transducers in electrochemical sensors for over 40 years. In this report, a FET transducer is compared with the recently proposed bipolar junction transistor (BJT) transducer. Measurements are performed on two chloride electrochemical sensors that are identical in all details except for the transducer device type. Comparative measurements show that the transducer choice significantly impacts the electrochemical sensor characteristics. Signal to noise ratio is 20 to 2 times greater for the BJT sensor. Sensitivity is also enhanced: BJT sensing signal changes by 10 times per pCl, whereas the FET signal changes by 8 or less times. Also, sensor calibration curves are impacted by the transducer choice. Unlike a FET sensor, the calibration curve of the BJT sensor is independent of applied voltages. Hence, a BJT sensor can make quantitative sensing measurements with minimal calibration requirements, an important characteristic for mobile sensing applications. As a demonstration for mobile applications, these BJT sensors are further investigated by measuring chloride levels in artificial human sweat for potential cystic fibrosis diagnostic use. In summary, the BJT device is demonstrated to be a superior transducer in comparison to a FET in an electrochemical sensor.

Comparison between Field Effect Transistors and Bipolar Junction Transistors as Transducers in Electrochemical Sensors

PubMed Central

Zafar, Sufi; Lu, Minhua; Jagtiani, Ashish

2017-01-01

Field effect transistors (FET) have been widely used as transducers in electrochemical sensors for over 40 years. In this report, a FET transducer is compared with the recently proposed bipolar junction transistor (BJT) transducer. Measurements are performed on two chloride electrochemical sensors that are identical in all details except for the transducer device type. Comparative measurements show that the transducer choice significantly impacts the electrochemical sensor characteristics. Signal to noise ratio is 20 to 2 times greater for the BJT sensor. Sensitivity is also enhanced: BJT sensing signal changes by 10 times per pCl, whereas the FET signal changes by 8 or less times. Also, sensor calibration curves are impacted by the transducer choice. Unlike a FET sensor, the calibration curve of the BJT sensor is independent of applied voltages. Hence, a BJT sensor can make quantitative sensing measurements with minimal calibration requirements, an important characteristic for mobile sensing applications. As a demonstration for mobile applications, these BJT sensors are further investigated by measuring chloride levels in artificial human sweat for potential cystic fibrosis diagnostic use. In summary, the BJT device is demonstrated to be a superior transducer in comparison to a FET in an electrochemical sensor. PMID:28134275

Effect of oxygen plasma treatment on the electrochemical performance of the rayon and polyacrylonitrile based carbon felt for the vanadium redox flow battery application

NASA Astrophysics Data System (ADS)

Dixon, D.; Babu, D. J.; Langner, J.; Bruns, M.; Pfaffmann, L.; Bhaskar, A.; Schneider, J. J.; Scheiba, F.; Ehrenberg, H.

2016-11-01

Oxygen plasma treatment was applied on commercially available graphite felt electrodes based on rayon (GFA) and polyacrylonitrile (GFD). The formation of functional groups on the surface of the felt was confirmed by X-ray photoelectron spectroscopy measurements. The BET studies of the plasma treated electrodes showed no significant increase in surface area for both the rayon as well as the PAN based felts. Both plasma treated electrodes showed significantly enhanced V3+/V2+ redox activity compared to the pristine electrodes. Since an increase of the surface area has been ruled out for plasma treated electrode the enhanced activity could be attributed to surface functional groups. Interestingly, plasma treated GFD felts showed less electrochemical activity towards V5+/V4+ compared to the pristine electrode. Nevertheless, an overall increase of the single cell performance was still observed as the negative electrode is known to be the performance limiting electrode. Thus, to a great extent the present work helps to preferentially understand the importance of functional groups on the electrochemical activity of negative and positive redox reaction. The study emphasizes the need of highly active electrodes especially at the negative electrode side as inactive electrodes can still facilitate hydrogen evolution and degrade the electrolyte in VRFBs.

Enhanced Photoelectrochemical Performance of Cuprous Oxide/Graphene Nanohybrids

PubMed Central

2017-01-01

Combination of an oxide semiconductor with a highly conductive nanocarbon framework (such as graphene or carbon nanotubes) is an attractive avenue to assemble efficient photoelectrodes for solar fuel generation. To fully exploit the possible synergies of the hybrid formation, however, precise knowledge of these systems is required to allow rational design and morphological engineering. In this paper, we present the controlled electrochemical deposition of nanocrystalline p-Cu2O on the surface of different graphene substrates. The developed synthetic protocol allowed tuning of the morphological features of the hybrids as deduced from electron microscopy. (Photo)electrochemical measurements (including photovoltammetry, electrochemical impedance spectroscopy, photocurrent transient analysis) demonstrated better performance for the 2D graphene containing photoelectrodes, compared to the bare Cu2O films, the enhanced performance being rooted in suppressed charge carrier recombination. To elucidate the precise role of graphene, comparative studies were performed with carbon nanotube (CNT) films and 3D graphene foams. These studies revealed, after allowing for the effect of increased surface area, that the 3D graphene substrate outperformed the other two nanocarbons. Its interconnected structure facilitated effective charge separation and transport, leading to better harvesting of the generated photoelectrons. These hybrid assemblies are shown to be potentially attractive candidates in photoelectrochemical energy conversion schemes, namely CO2 reduction. PMID:28460518

Corrosion of metals in wood : comparing the results of a rapid test method with long-term exposure tests across six wood treatments

Treesearch

Samuel L. Zelinka; Donald S. Stone

2011-01-01

This paper compares two methods of measuring the corrosion of steel and galvanized steel in wood: a long-term exposure test in solid wood and a rapid test method where fasteners are electrochemically polarized in extracts of wood treated with six different treatments. For traditional wood preservatives, the electrochemical extract method correlates with solid wood...

Eradication of Pseudomonas aeruginosa cells by cathodic electrochemical currents delivered with graphite electrodes.

PubMed

Niepa, Tagbo H R; Wang, Hao; Gilbert, Jeremy L; Ren, Dacheng

2017-03-01

Antibiotic resistance is a major challenge to the treatment of bacterial infections associated with medical devices and biomaterials. One important intrinsic mechanism of such resistance is the formation of persister cells that are phenotypic variants of microorganisms and highly tolerant to antibiotics. Recently, we reported a new approach to eradicating persister cells of Pseudomonas aeruginosa using low-level direct electrochemical current (DC) and synergy with the antibiotic tobramycin. To further understand the underlying mechanism and develop this technology toward possible medical applications, we investigated the electricidal activities of non-metallic biomaterial on persister and biofilm cells of P. aeruginosa using graphite-based TGON™ 805 electrodes. We employed both single and dual chamber systems to compare electrochemical factors of TGON and stainless steel 304 electrodes. The results revealed that TGON-based treatments were highly effective against P. aeruginosa persister cells. In the single chamber system, complete eradication of planktonic persister cells (corresponding to a 7-log killing) was achieved with 70μA/cm 2 DC using TGON electrodes within 40min of treatment, while the cell viability in biofilms was reduced by 2 logs within 1h. The killing effects were dose and time dependent with higher current densities requiring less time. Moreover, reduction reactions were found more effective than oxidation reactions, confirming that metal cations are not indispensable, although they may facilitate cell killing. The findings of this study can help develop electrochemical technologies to eradicate persister and biofilm cells for more effective treatment of medical device and biomaterial associated infections. Infections associated with medical devices and biomaterials present a major challenge due to high-level tolerance of microbes to conventional antibiotics. It is well established that such tolerance is due to the formation of dormant persister cells and multicellular structures known as biofilms. Recent studies have demonstrated electrochemical treatment as a promising alternative to eradicate bacterial infections, since the killing mechanism is independent of the growth phase of bacterial cells, but relies on various electrochemical species interplaying during the treatment. The current study investigated major bactericidal properties of the electrochemical currents mediated via TGON, a carbon-based electrode material. Up to total eradication of Pseudomonas aeruginosa persister cells was achieved. The new knowledge of electrochemical properties and the bioactivity of TGON may help develop new methods/devices to eradicate bacterial infections by delivering safe levels of electrochemical currents. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Computational Modeling of Electrochemical-Poroelastic Bending Behaviors of Conducting Polymer (PPy) Membranes

NASA Astrophysics Data System (ADS)

Toi, Yutaka; Jung, Woosang

The electrochemical-poroelastic bending behavior of conducting polymer actuators has an attractive feature, considering their potential applications such as artificial muscles or MEMS. In the present study, a computational modeling is presented for the bending behavior of polypyrrole-based actuators. The one-dimensional governing equation for the ionic transportation in electrolytes given by Tadokoro et al. is combined with the finite element modeling for the poroelastic behavior of polypyrroles considering the effect of finite deformation. The validity of the proposed model has been illustrated by comparing the computed results with the experimental results in the literatures.

Studies of Aqueous and Non-Aqueous Electrochemical Interface for Applications in Microelectronic and Energy Storage Systems

NASA Astrophysics Data System (ADS)

Zheng, Jianping

Various electrochemical techniques were utilized to study a wide range of electrochemical systems in this dissertation. Mainly they are grouped in three sections: 1) the conventional metal-aqueous systems for new applications in modern microelectronic devices, 2) unconventional ceramic-organic systems for applications in Li-ion batteries and 3) novel systems composed of ionic liquids and carbon series electrodes. The objects are to probe the electrochemical/chemical reactions and interfacial structures, which are the common features of the aforementioned systems. This dissertation mainly focuses on experimental aspects, however, some theories and new models used to elucidate the experiment data have also been developed and presented. Some new experimental techniques have been explored and their limitations and validity have also been discussed. Oxalic acid (OA)-based nonalkaline solutions with H2O 2 are found to support chemically mediated removal of Ta-oxide surface films on Ta. The associated surface reactions are critical for chemical mechanical planarization (CMP) of Ta barrier. In chapter 4, a Ta coupon electrode is used as a model system in abrasive-free solutions of OA and H2O 2, where the chemical component of CMP is selectively examined. In chapter 5, electrochemical impedance spectroscopy (EIS) is employed to study the competitive reactions of surface corrosion and passivating film formation on a Cu-rotating disc electrode (RDE) in pH-adjusted solutions of H2O2, acetic acid (HAc) and ammonium dodecyl sulfate (ADS). Micrometric LiMn2O4 particles are mechano-chemically modified by ball-milling to obtain a mixture of nano- and micro-scale particles. In chapter 6, this mixture is tested as a potential active cathode material for rapid-charge Li ion batteries, and also as a model system for studying the detailed kinetics of Li intercalation/de-intercalation in such electrodes. In chapter 7, cyclic voltammetry (CV) and EIS are compared as techniques for analyzing double layer capacitances of ionic liquids (ILs) at the surfaces of two carbon-based electrodes. These systems are relevant for energy storage supercapacitors and often are associated with unconventional electrochemical properties. In chapter 8, the electrochemical interfaces of a glassy carbon (GC) and a carbon nanotube (CNT) paper electrode have been studied in EmimBF 4 and BmimBF4 ILs using CV and EIS.

Comparative study for degradation of industrial dyes by electrochemical advanced oxidation processes with BDD anode in a laboratory stirred tank reactor.

PubMed

Alcocer, Salvador; Picos, Alain; Uribe, Agustín R; Pérez, Tzayam; Peralta-Hernández, Juan M

2018-08-01

Comparative degradation of the industrial dyes Blue BR, Violet SBL and Brown MF 50 mg L -1 has been studied by the electrochemical oxidation (EOx), electro-Fenton (EF), photoelectro-Fenton (PEF) process based on BDD electrode. Each dye was tested in 0.05 mM Na 2 SO 4 with 0.5 mM Fe 2+ at pH 3.0, and electrolyzed in a stirred tank reactor under galvanostatic conditions with 2.0, 5.0, 7.0, 11.0 and 18.0 mA cm -2 . Dyes were oxidized via hydroxyl radicals (OH) formed at the BDD anode from water oxidation coupled with Fenton's reaction cathodically produced hydrogen peroxide (H 2 O 2 ). Under Na 2 SO 4 medium close to 100% the decolorization was achieved. Through the color abatement rate the dyes behavior was analyzed at the beginning of the oxidation process. Dissolved Organic Carbon (DOC) was tested to evaluate the degradation. From DOC removal, it was established an increasing relative oxidation power of the EOx < EF < PEF, according with their decolorization trend. This study highlights the potential of the electrochemical/BDD process for the degradation of industrial dyes found in wastewaters under appropriate experimental conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis and electrochemical study of palladium-based nanomaterials for green energy applications

NASA Astrophysics Data System (ADS)

Ostrom, Cassandra K.

Rising global energy consumption leads to increased environmental impacts. The continued use of current energy resources, e.g. fossil fuels, will exaggerate the cumulative nature of CO2 byproduct emissions in the atmosphere. The development and implementation of a hydrogen economy, as a solution to offset degradative environmental impacts, will likely enable opportunities for maintaining or improving standards of living while significantly lowering carbon emissions. Palladium has proven to be a strong contender as an enabling material that encompasses many aspects of a prospective hydrogen economy, lending promise to applications such as hydrogen purification, storage and fuel cell catalysis. In my M.Sc. study, Pd-based nanomaterials have been synthesized and examined for their applications in hydrogen storage and fuel cell catalysis. The surface properties of synthesized Pd-based nanomaterials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), and N2 gas adsorption/desorption. Electrochemical analysis of the fabricated materials was performed using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was employed to characterize the composition of the formed samples. Hydrogen electrosorption onto activated carbon materials modified with different trimetallic dissociation catalysts (Pd-Ag-Cd) was investigated in an acidic medium. A uniform distribution of the Pd-Ag-Cd catalysts was achieved using a facile room temperature sodium borohydride reduction method. By varying the composition of the alloys, synergistic effects between the metal and carbon support resulted in drastic increases in hydrogen sorption capabilities in contrast to bi-metallic PdAg and PdCd catalysts. Utilizing electrochemical methods, the optimal composition of the Pd-Ag-Cd alloys was determined to be Pd80Ag10Cd10, with the highest hydrogen sorption capacity at a hydrogen desorption charge of 18.49 C/cm2˙mg. Further enhancement of the electroactivity of synthesized titanium dioxide nanotubes (TiO2 NTs) was achieved using UV light and electrochemical pretreatment methods. The effects of these pretreatment methods on TiO2 NTs were systematically investigated and compared. Using Pd as a dispersed catalyst, Pd/TiO2 NT electrodes were examined in acidic medium, with both UV and electrochemical pretreatment methods revealing significant enhancements in the electroactivity of the TiO2 NT substrate. The UV pretreated samples were found to dominate, when compared to those that underwent electrochemical pretreatment, in terms of overall efficacy for hydrogen sorption and the electrooxidation of formic acid. Improvements in nanotube conductivity resulted in an effective reduction of noble metal coating loads. Nanostructured PdPb electrocatalysts were loaded directly onto TiO2 NT substrates and tested for their activity towards formic acid oxidation. Comparative studies revealed the enhanced electrochemical oxidation of formic acid on Pd95Pb5/TiO2 NTs in comparison to Pd/TiO2 NTs, resulting in the successful reduction of Pd noble metal load. The work performed in this M. Sc. thesis project reveals that modifications to both Pd catalysts and their associated supports can drastically alter their geometric and electronic properties. This has a major influence on the development of more cost effective materials with enhanced activity for use towards the commercialization of fuel cells.

Solar-Electrochemical Power System for a Mars Mission

NASA Technical Reports Server (NTRS)

Withrow, Colleen A.; Morales, Nelson

1994-01-01

This report documents a sizing study of a variety of solar electrochemical power systems for the intercenter NASA study known as 'Mars Exploration Reference Mission'. Power systems are characterized for a variety of rovers, habitation modules, and space transport vehicles based on requirements derived from the reference mission. The mission features a six-person crew living on Mars for 500 days. Mission power requirements range from 4 kWe to 120 kWe. Primary hydrogen and oxygen fuel cells, regenerative hydrogen and oxygen fuel cells, sodium sulfur batteries advanced photovoltaic solar arrays of gallium arsenide on germanium with tracking and nontracking mechanisms, and tent solar arrays of gallium arsenide on germanium are evaluated and compared.

Voltammetric Sensor Based on Fe-doped ZnO and TiO2 Nanostructures-modified Carbon-paste Electrode for Determination of Levodopa

NASA Astrophysics Data System (ADS)

Anaraki Firooz, Azam; Hosseini Nia, Bahram; Beheshtian, Javad; Ghalkhani, Masoumeh

2017-10-01

In this study, undoped and 1 wt.% Fe-doped with ZnO, and TiO2 nanostructures were synthesized by a simple hydrothermal method without using templates. The influence of the Fe dopant on structural, optical and electrochemical response was studied by x-ray diffraction, scanning electron microscopy, UV-Vis spectra, photoluminescence spectra and electrochemical characterization system. The electrochemical response of the carbon paste electrode modified with synthesized nanostructures (undoped ZnO and TiO2 as well as doped with Fe ions) toward levodopa (L-Dopa) was studied. Cyclic voltammetry using provided modified electrodes showed electro-catalytic properties for electro-oxidation of L-Dopa and a significant reduction was observed in the anodic overvoltage compared to the bare electrode. The results indicated the presence of the sufficient dopants. The best response was obtained in terms of the current enhancement, overvoltage reduction, and reversibility improvement of the L-Dopa oxidation reaction under experimental conditions by the modified electrode with TiO2 nanoparticles doped with Fe ions.

Electricity generation from defective tomatoes.

PubMed

Shrestha, Namita; Fogg, Alex; Wilder, Joseph; Franco, Daniel; Komisar, Simeon; Gadhamshetty, Venkataramana

2016-12-01

The United States faces a significant burden in treating 0.61billionkg of defective tomatoes (culls) every year. We present a proof-of-concept for generating electricity from culled tomatoes in microbial-electrochemical systems (MESs). This study delineates impedance behavior of the culled tomatoes in MESs and compares its impedance spectra with that of soluble substrates (dextrose, acetate, and wastewater). A series of AC and DC diagnostic tests have revealed the superior performance of the culled tomatoes compared to the pure substrates. Cyclic voltammetry results have indicated the active role of indigenous, diffusible redox-active pigments in the culled tomatoes on overall electricity production. Electrochemical impedance spectroscopy results have elucidated the role of peel and seed on the oxidation behavior of the culled tomatoes. Copyright © 2016 Elsevier B.V. All rights reserved.

Nitrogen-based catalysts for the electrochemical reduction of CO2 to CO.

PubMed

Tornow, Claire E; Thorson, Michael R; Ma, Sichao; Gewirth, Andrew A; Kenis, Paul J A

2012-12-05

The synthesis and application of carbon-supported, nitrogen-based organometallic silver catalysts for the reduction of CO(2) is studied using an electrochemical flow reactor. Their performance toward the selective formation of CO is similar to the performance achieved when using Ag as the catalyst, but comparatively at much lower silver loading. Faradaic efficiencies of the organometallic catalyst are higher than 90%, which are comparable to those of Ag. Furthermore, with the addition of an amine ligand to Ag/C, the partial current density for CO increases significantly, suggesting a possible co-catalyst mechanism. Additional improvements in activity and selectivity may be achieved as greater insight is obtained on the mechanism of CO(2) reduction and on how these complexes assemble on the carbon support.

Investigating effectiveness of activated carbons of natural sources on various supercapacitors

NASA Astrophysics Data System (ADS)

Faisal, Md. Shahnewaz Sabit; Rahman, Muhammad M.; Asmatulu, Ramazan

2016-04-01

Activated carbon can be produced from natural sources, such as pistachio and acorn shells, which can be an inexpensive and sustainable sources of natural wastes for the energy storage devices, such as supercapacitors. The carbonaceous materials used in this study were carbonized at the temperatures of 700°C and 900°C after the stabilization process at 240°C for two hours. These shells showed approximately 60% carbon yield. Carbonized nutshells were chemically activated using1wt% potassium hydroxide (KOH). Activated carbon powders with polyvinylidene fluoride (PVdF) were used to construct carbon electrodes. A 1M of tetraethylammonium tetrafluoroborate (TEABF4) and propylene carbonate (PC) were used as electrolytes. Electrochemical techniques, such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the characterization of the supercapacitors. Scanning electron microscopy (SEM) was used to inspect the surface texture of the activated carbons. Activated pistachio shells carbonized at 700°C showed more porous surface texture than those carbonized at 900°C. Effects of the carbonization temperatures were studied for their electrochemical characteristics. The shells carbonized at 700°C showed better electrochemical characteristics compared to those carbonized at 900°C. The test results provided about 27,083 μF/g specific capacitance at a scan rate of 10mV/s. This study showed promising results for using these activated carbons produced from the natural wastes for supercapacitor applications.

In situ electrochemical assessment of cytotoxicity of chlorophenols in MCF-7 and HeLa cells.

PubMed

Qin, Hongwei; Liu, Jiguang; Zhang, Zeshi; Li, Jinlian; Gao, Guanggang; Yang, Yuxin; Yuan, Xing; Wu, Dongmei

2014-10-01

An in situ electrochemical method was used to assess the cytotoxicity of chlorophenols using human breast cancer (MCF-7) and cervical carcinoma (HeLa) cells as models. On treatment with different chlorophenols, the electrochemical responses of the selected cells, resulting from the oxidation of guanine and xanthine in the cytoplasm, indicated the cell viability. In addition, the in situ in vitro electrochemical method was further compared with the traditional MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. Although similar cytotoxicity data were obtained from both methods, the effective concentrations of chlorophenols that inhibited 50% cell growth (EC50 values) from the electrochemical method were only slightly lower than those from the MTT assay. These results indicate that the in situ in vitro electrochemical method paves a simple, rapid, strongly responsive, and label-free way to the cytotoxicity assessment of different chlorophenol pollutants. Copyright © 2014 Elsevier Inc. All rights reserved.

Electrochemical Properties of Si Film Electrodes Containing TiNi Thin-Film Current Collectors

NASA Astrophysics Data System (ADS)

Im, Yeon-min; Noh, Jung-pil; Cho, Gyu-bong; Nam, Tea-hyun

2018-03-01

A 50.3Ti-49.7Ni thin film fabricated by DC sputtering was employed as a current collector of Si film electrode. The structural and electrochemical properties of Si/TiNi film electrode were compared with those of a Si/Cu film electrode. The TiNi film with cluster-like structures composed of B2 austenitic phase at room temperature displayed the high electrochemical stability for Li ions. The amorphous Si film deposited on the TiNi film also consisted of cluster-like structures on the surface. The Si film grown on the TiNi film current collector (Si/TiNi electrode) demonstrated a high columbic efficiency of 87% at the first cycle (363 μAh/cm2 of charge capacity and 314 μAh/cm2 of discharge capacity). The Si/TiNi electrode exhibited better electrochemical properties in terms of capacity, cycle performance, and structural stability compared to the Si electrode with a conventional Cu foil current collector.

Fluorinated graphenes as advanced biosensors - effect of fluorine coverage on electron transfer properties and adsorption of biomolecules

NASA Astrophysics Data System (ADS)

Urbanová, Veronika; Karlický, František; Matěj, Adam; Šembera, Filip; Janoušek, Zbyněk; Perman, Jason A.; Ranc, Václav; Čépe, Klára; Michl, Josef; Otyepka, Michal; Zbořil, Radek

2016-06-01

Graphene derivatives are promising materials for the electrochemical sensing of diverse biomolecules and development of new biosensors owing to their improved electron transfer kinetics compared to pristine graphene. Here, we report complex electrochemical behavior and electrocatalytic performance of variously fluorinated graphene derivatives prepared by reaction of graphene with a nitrogen-fluorine mixture at 2 bars pressure. The fluorine content was simply controlled by varying the reaction time and temperature. The studies revealed that electron transfer kinetics and electrocatalytic activity of CFx strongly depend on the degree of fluorination. The versatility of fluorinated graphene as a biosensor platform was demonstrated by cyclic voltammetry for different biomolecules essential in physiological processes, i.e. NADH, ascorbic acid and dopamine. Importantly, the highest electrochemical performance, even higher than pristine graphene, was obtained for fluorinated graphene with the lowest fluorine content (CF0.084) due to its high conductivity and enhanced adsorption properties combining π-π stacking interaction with graphene regions with hydrogen-bonding interaction with fluorine atoms.Graphene derivatives are promising materials for the electrochemical sensing of diverse biomolecules and development of new biosensors owing to their improved electron transfer kinetics compared to pristine graphene. Here, we report complex electrochemical behavior and electrocatalytic performance of variously fluorinated graphene derivatives prepared by reaction of graphene with a nitrogen-fluorine mixture at 2 bars pressure. The fluorine content was simply controlled by varying the reaction time and temperature. The studies revealed that electron transfer kinetics and electrocatalytic activity of CFx strongly depend on the degree of fluorination. The versatility of fluorinated graphene as a biosensor platform was demonstrated by cyclic voltammetry for different biomolecules essential in physiological processes, i.e. NADH, ascorbic acid and dopamine. Importantly, the highest electrochemical performance, even higher than pristine graphene, was obtained for fluorinated graphene with the lowest fluorine content (CF0.084) due to its high conductivity and enhanced adsorption properties combining π-π stacking interaction with graphene regions with hydrogen-bonding interaction with fluorine atoms. Electronic supplementary information (ESI) available: SEM, HRTEM, and AFM images the sheet in pristine graphene sample, survey XPS spectrum, high resolution C 1s XPS spectrum, and Raman spectrum of pristine graphene precursor used for controlled fluorination, survey and high resolution F 1s XPS spectra of the CF0.084, CF0.158, and CF0.218 samples, EDS chemical mapping of fluorine in CF0.158, contact angle measurement of CF0.084, CF0.158, CF0.218, and HOPG, and additional electrochemical data. See DOI: 10.1039/c6nr00353b

Investigation on the electrochemical interfacial properties of 2-aminothiophenol functionalized graphene oxide modified electrode

NASA Astrophysics Data System (ADS)

Immanuel, Susan; Aparna T., K.; Sivasubramanian, R.

2018-04-01

In this paper the interfacial behavior of graphene oxide and 2-aminothiophenol functionalized graphene oxide was investigated by electrochemical method. The GO was prepared by modified Hummers method and the 2-aminothiophenol was covalently attached on the surface of GO sheets. The electrochemical properties were investigated using a redox couple and the electrokinetic parameter was inferred. It was found that the ATP-GO exhibited slow kinetics compared to GO due to the increased deformation of GO sheets after ATP functionalization.

Electrochemical Impedance Of Inorganic-Zinc-Coated Steel

NASA Technical Reports Server (NTRS)

Macdowell, Louis G.

1992-01-01

Report describes preliminary experiments to evaluate both direct-current and alternating-current electrochemical impedance measurements as candidate techniques for use in accelerated corrosion testing of mild-steel panels coated with inorganic zinc-rich primers and exposed to seaside air. Basic idea behind experiments to compare electrochemical impedance measurements with anticorrosion performances of coating materials to determine whether measurements can be used to predict performances. Part of continuing program to identify anticorrosion coating materials protecting steel panels adequately for as long as 5 years and beyond.

Feedback‐amplified electrochemical dual‐plate boron‐doped diamond microtrench detector for flow injection analysis

PubMed Central

Lewis, Grace E. M.; Gross, Andrew J.; Kasprzyk‐Hordern, Barbara; Lubben, Anneke T.

2015-01-01

An electrochemical flow cell with a boron‐doped diamond dual‐plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator‐collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is switched from an analyte consuming “external” process to an analyte regenerating “internal” process with benefits in selectivity and sensitivity. PMID:25735831

Synthetic control of manganese birnessite: Impact of crystallite size on Li, Na, and Mg based electrochemistry

DOE PAGES

Yin, Jiefu; Takeuchi, Esther S.; Takeuchi, Kenneth J.; ...

2016-08-12

We demonstrated the synthesis and characterization of Mg-birnessite (Mg xMnO 2) with different crystallite sizes, prepared though low temperature precipitation and ion exchange. The influence of crystallite size on electrochemical performance of Mg-birnessite was studied for the first time, where material with smaller crystallite size was demonstrated to have enhanced capacity and rate capability in Li ion, Na ion, and Mg ion based electrolytes. Cation diffusion using GITT type testing demonstrated the ion diffusion coefficient of Mg 2+ was ~10× lower compared with Li + and Na +. This work illustrates that tuning of inorganic materials properties can lead tomore » significant enhancement of electrochemical performance in lithium, sodium as well as magnesium based batteries for materials such as Mg-birnessite and provides a deliberate approach to improve electrochemical performance.« less

Advances of aqueous rechargeable lithium-ion battery: A review

NASA Astrophysics Data System (ADS)

Alias, Nurhaswani; Mohamad, Ahmad Azmin

2015-01-01

The electrochemical characteristic of the aqueous rechargeable lithium-ion battery has been widely investigated in efforts to design a green and safe technology that can provide a highly specific capacity, high efficiency and long life for high power applications such as the smart grid and electric vehicle. It is believed that the advantages of this battery will overcome the limitations of the rechargeable lithium-ion battery with organic electrolytes that comprise safety and create high fabrication cost issues. This review focuses on the opportunities of the aqueous rechargeable lithium-ion battery compared to the conventional rechargeable lithium-ion battery with organic-based electrolytes. Previously reported studies are briefly summarised, together with the presentation of new findings based on the conductivity, morphology, electrochemical performance and cycling stability results. The factors that influence the electrochemical performance, the challenges and potential of the aqueous rechargeable lithium-ion battery are highlighted in order to understand and maintained the excellent battery performance.

Controlling formation of single-molecule junctions by electrochemical reduction of diazonium terminal groups.

PubMed

Hines, Thomas; Díez-Pérez, Ismael; Nakamura, Hisao; Shimazaki, Tomomi; Asai, Yoshihiro; Tao, Nongjian

2013-03-06

We report controlling the formation of single-molecule junctions by means of electrochemically reducing two axialdiazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in situ between the molecule and gold electrodes. We report a yield enhancement in molecular junction formation as the electrochemical potential of both junction electrodes approach the reduction potential of the diazonium terminal groups. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond.

Microwave-assisted synthesis and electrochemical evaluation of VO 2 (B) nanostructures

DOE PAGES

Ashton, Thomas E.; Borras, David Hevia; Iadecola, Antonella; ...

2015-12-01

Understanding how intercalation materials change during electrochemical operation is paramount to optimising their behaviour and function and in situ characterisation methods allow us to observe these changes without sample destruction. Here, we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave assisted route which exhibits a larger electrochemical capacity (232 mAh g -1) compared to VO 2 (B) prepared by a solvothermal route (197 mAh g -1). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during batterymore » operation.« less

Improvement of diamond-like carbon electrochemical corrosion resistance by addition of nanocrystalline diamond.

PubMed

Marciano, F R; Almeida, E C; Bonetti, L F; Corat, E J; Trava-Airoldi, V J

2010-02-15

Nanocrystalline diamond (NCD) particles were incorporated into diamond-like carbon (DLC) films in order to investigate NCD-DLC electrochemical corrosion resistance. The films were grown over 304 stainless steel using plasma-enhanced chemical vapor deposition. NCD particles were incorporated into DLC during the deposition process. The investigation of NCD-DLC electrochemical corrosion behavior was performed using potentiodynamic polarization against NaCl. NCD-DLC films presented more negative corrosion potential and lower anodic and cathodic current densities. The electrochemical analysis indicated that NCD-DLC films present superior impedance and polarization resistance compared to the pure DLC, which indicate that they are promising corrosion protective coatings in aggressive solutions. Copyright 2009 Elsevier Inc. All rights reserved.

Carbon-Based Materials for Lithium-Ion Batteries, Electrochemical Capacitors, and Their Hybrid Devices.

PubMed

Yao, Fei; Pham, Duy Tho; Lee, Young Hee

2015-07-20

A rapidly developing market for portable electronic devices and hybrid electrical vehicles requires an urgent supply of mature energy-storage systems. As a result, lithium-ion batteries and electrochemical capacitors have lately attracted broad attention. Nevertheless, it is well known that both devices have their own drawbacks. With the fast development of nanoscience and nanotechnology, various structures and materials have been proposed to overcome the deficiencies of both devices to improve their electrochemical performance further. In this Review, electrochemical storage mechanisms based on carbon materials for both lithium-ion batteries and electrochemical capacitors are introduced. Non-faradic processes (electric double-layer capacitance) and faradic reactions (pseudocapacitance and intercalation) are generally explained. Electrochemical performance based on different types of electrolytes is briefly reviewed. Furthermore, impedance behavior based on Nyquist plots is discussed. We demonstrate the influence of cell conductivity, electrode/electrolyte interface, and ion diffusion on impedance performance. We illustrate that relaxation time, which is closely related to ion diffusion, can be extracted from Nyquist plots and compared between lithium-ion batteries and electrochemical capacitors. Finally, recent progress in the design of anodes for lithium-ion batteries, electrochemical capacitors, and their hybrid devices based on carbonaceous materials are reviewed. Challenges and future perspectives are further discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmonic Imaging of Electrochemical Reactions of Single Nanoparticles.

PubMed

Fang, Yimin; Wang, Hui; Yu, Hui; Liu, Xianwei; Wang, Wei; Chen, Hong-Yuan; Tao, N J

2016-11-15

Electrochemical reactions are involved in many natural phenomena, and are responsible for various applications, including energy conversion and storage, material processing and protection, and chemical detection and analysis. An electrochemical reaction is accompanied by electron transfer between a chemical species and an electrode. For this reason, it has been studied by measuring current, charge, or related electrical quantities. This approach has led to the development of various electrochemical methods, which have played an essential role in the understanding and applications of electrochemistry. While powerful, most of the traditional methods lack spatial and temporal resolutions desired for studying heterogeneous electrochemical reactions on electrode surfaces and in nanoscale materials. To overcome the limitations, scanning probe microscopes have been invented to map local electrochemical reactions with nanometer resolution. Examples include the scanning electrochemical microscope and scanning electrochemical cell microscope, which directly image local electrochemical reaction current using a scanning electrode or pipet. The use of a scanning probe in these microscopes provides high spatial resolution, but at the expense of temporal resolution and throughput. This Account discusses an alternative approach to study electrochemical reactions. Instead of measuring electron transfer electrically, it detects the accompanying changes in the reactant and product concentrations on the electrode surface optically via surface plasmon resonance (SPR). SPR is highly surface sensitive, and it provides quantitative information on the surface concentrations of reactants and products vs time and electrode potential, from which local reaction kinetics can be analyzed and quantified. The plasmonic approach allows imaging of local electrochemical reactions with high temporal resolution and sensitivity, making it attractive for studying electrochemical reactions in biological systems and nanoscale materials with high throughput. The plasmonic approach has two imaging modes: electrochemical current imaging and interfacial impedance imaging. The former images local electrochemical current associated with electrochemical reactions (faradic current), and the latter maps local interfacial impedance, including nonfaradic contributions (e.g., double layer charging). The plasmonic imaging technique can perform voltammetry (cyclic or square wave) in an analogous manner to the traditional electrochemical methods. It can also be integrated with bright field, dark field, and fluorescence imaging capabilities in one optical setup to provide additional capabilities. To date the plasmonic imaging technique has found various applications, including mapping of heterogeneous surface reactions, analysis of trace substances, detection of catalytic reactions, and measurement of graphene quantum capacitance. The plasmonic and other emerging optical imaging techniques (e.g., dark field and fluorescence microscopy), together with the scanning probe-based electrochemical imaging and single nanoparticle analysis techniques, provide new capabilities for one to study single nanoparticle electrochemistry with unprecedented spatial and temporal resolutions. In this Account, we focus on imaging of electrochemical reactions at single nanoparticles.

Flow Visualization of Low Prandtl Number Fluids using Electrochemical Measurements

NASA Technical Reports Server (NTRS)

Crunkleton, D.; Anderson, T.; Narayanan, R.; Labrosse, G.

2003-01-01

It is well established that residual flows exist in contained liquid metal processes. In 1-g processing, buoyancy forces often drive these flows and their magnitudes can be substantial. It is also known that residual flows can exist during microgravity processing, and although greatly reduced in magnitude, they can influence the properties of the processed materials. Unfortunately, there are very few techniques to visualize flows in opaque, high temperature liquid metals, and those available are not easily adapted to flight investigation. In this study, a novel technique is developed that uses liquid tin as the model fluid and solid-state electrochemical cells constructed from Yttria-Stabilized Zirconia (YSZ) to establish and measure dissolved oxygen boundary conditions. The melt serves as a common electrode for each of the electrochemical cells in this design, while independent reference electrodes are maintained at the outside surfaces of the electrolyte. By constructing isolated electrochemical cells at various locations along the container walls, oxygen is introduced or extracted by imposing a known electrical potential or passing a given current between the melt and the reference electrode. This programmed titration then establishes a known oxygen concentration boundary condition at the selected electrolyte-melt interface. Using the other cells, the concentration of oxygen at the electrolyte-melt interface is also monitored by measuring the open-circuit potentials developed between the melt and reference electrodes. Thus the electrochemical cells serve to both establish boundary conditions for the passive tracer and sense its path. Rayleigh-Benard convection was used to validate the electrochemical approach to flow visualization. Thus, a numerical characterization of the second critical Rayleigh numbers in liquid tin was conducted for a variety of Cartesian aspect ratios. The extremely low Prandtl number of tin represents the lowest value studied numerically. Additionally, flow field oscillations are visualized and the effect of tilt on convecting systems is quantified. Experimental studies of the effect of convection in liquid tin are presented. Three geometries are studied: (1) double electrochemical cell with vertical concentration gradients; (2) double cell with horizontal concentration gradients; and (3) multiple cells with vertical temperature gradients. The first critical Rayleigh number transition is detected with geometry (1) and it is concluded that current measurements are not as affected by convection as EMF measurements. The system is compared with numerical simulations in geometry (2), and oscillating convection is detected with geometry (3).

Electrochemical properties of TiO2-V2O5 nanocomposites as a high performance supercapacitors electrode material

NASA Astrophysics Data System (ADS)

Ray, Apurba; Roy, Atanu; Sadhukhan, Priyabrata; Chowdhury, Sreya Roy; Maji, Prasenjit; Bhattachrya, Swapan Kumar; Das, Sachindranath

2018-06-01

The individual components being ample, inexpensive and non-toxic material, TiO2-V2O5 has drawn more attention compared to other metal oxides. The cost-effective, non-toxic TiO2-V2O5 nanocomposites with various molar ratios of Ti and V have been synthesized through wet chemical method. Microstructure studies have been performed using X-ray diffraction (XRD), FESEM, HRTTEM and other spectroscopic (XPS, FTIR) techniques. The synthesized TiO2-V2O5 nanocomposite with molar ratio 10:20 exhibits 3D, mesoporous interlinked tube-like structure with excellent electrochemical properties by delivering highest specific capacitance of 310 F g-1 at 2 mV s-1 scan rate compared to individual TiO2 and V2O5 material. Increase in vanadium ratio plays a leading role to the chemical properties. The synergistic effects between TiO2 and V2O5 have also been observed in this work. Due to the excellent electrochemical as well as other acceptable performance, the porous interconnected tube like nanocomposite can be used for energy storage application mainly for pseudocapacitor electrode material.

Effects of binders on the electrochemical performance of rechargeable magnesium batteries

NASA Astrophysics Data System (ADS)

Wang, Nan; NuLi, Yanna; Su, Shuojian; Yang, Jun; Wang, Jiulin

2017-02-01

A comparative study on the effects of different binders on the electrochemical performance of rechargeable magnesium batteries with Mo6S8 cathode is conducted for the first time. The selected binders are commercial organic-soluble polyvinylidene fluoride (PVDF), water-soluble poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), gelatin, sodium alginate (SA) and Beta-cyclodextrin (β-CD). The binders significantly affect the physical properties, thus the electrochemical performance of Mo6S8 cathode. Compared with those using traditional PVDF binder, Mo6S8 electrodes with PAA and PVA exhibit enhanced cycling stabilities and rate capabilities, which are attributed to the improved cohesion among the electrode constituents and adhesion between the electrode laminate and the current collector. In addition, the anodic stability of these binders is not only related to the chemical structure of binders, but also to the uniformity of electrode surface. SA binder shows low anodic stability duo to containing easily oxidized groups. Non-uniform electrode surface decreases the anodic stability of PVDF based Mo6S8 electrode. Gelatin can be used as a binder in the formulation of high voltage cathodes for rechargeable magnesium batteries.

Pencil graphite electrodes for improved electrochemical detection of oleuropein by the combination of Natural Deep Eutectic Solvents and graphene oxide.

PubMed

Gomez, Federico J V; Spisso, Adrian; Fernanda Silva, María

2017-11-01

A novel methodology is presented for the enhanced electrochemical detection of oleuropein in complex plant matrices by Graphene Oxide Pencil Grahite Electrode (GOPGE) in combination with a buffer modified with a Natural Deep Eutectic Solvent, containing 10% (v/v) of Lactic acid, Glucose and H 2 O (LGH). The electrochemical behavior of oleuropein in the modified-working buffer was examined using differential pulse voltammetry. The combination of both modifications, NADES modified buffer and nanomaterial modified electrode, LGH-GOPGE, resulted on a signal enhancement of 5.3 times higher than the bare electrode with unmodified buffer. A calibration curve of oleuropein was performed between 0.10 to 37 μM and a good linearity was obtained with a correlation coefficient of 0.989. Detection and quantification limits of the method were obtained as 30 and 102 nM, respectively. In addition, precision studies indicated that the voltammetric method was sufficiently repeatable, %RSD 0.01 and 3.16 (n = 5) for potential and intensity, respectively. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract prepared by ultrasound-assisted extraction. The results obtained with the proposed electrochemical sensor were compared with Capillary Zone Electrophoresis analysis with satisfactory results. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploration of two-dimensional bio-functionalized phosphorene nanosheets (black phosphorous) for label free haptoglobin electro-immunosensing applications

NASA Astrophysics Data System (ADS)

Tuteja, Satish K.; Neethirajan, Suresh

2018-04-01

We report on the development of an antibody-functionalized interface based on electrochemically active liquid-exfoliated two-dimensional phosphorene (Ph) nanosheets—also known as black phosphorous nanosheets—for the label-free electrochemical immunosensing of a haptoglobin (Hp) biomarker, a clinical marker of severe inflammation. The electrodeposition has been achieved over the screen-printed electrode (SPE) using liquid-assisted ultrasonically exfoliated black phosphorus nanosheets. Subsequently, Ph-SPEs bioconjugated with Hp antibodies (Ab), using electrostatic interactions via a poly-L-lysine linker for biointerface development. Electrochemical analysis demonstrates that the Ab-modified Ph-SPEs (Ab@Ph-SPE) exhibit enhanced electroconducting behavior as compared to the pristine electrodes. This Ab-functionalized phosphorene-based electrochemical immunosensor platform has demonstrated remarkable sensitivity and specificity, having a dynamic linear response range from 0.01-10 mg ml-1 for Hp in standard and serum samples with a low detection limit (˜0.011 mg ml-1) using the label-free electrochemical technique. The sensor electrodes were also studied with other closely relative interferents to investigate cross reactivity and specificity. This strategy opens up avenues to POC (point-of-care) and on-farm livestock disease monitoring technologies for multiplexed diagnosis in complex biological samples such as serum. The technique is simple in fabrication and provides an analytical response in less than 60 s.

A time-based potential step analysis of electrochemical impedance incorporating a constant phase element: a study of commercially pure titanium in phosphate buffered saline.

PubMed

Ehrensberger, Mark T; Gilbert, Jeremy L

2010-05-01

The measurement of electrochemical impedance is a valuable tool to assess the electrochemical environment that exists at the surface of metallic biomaterials. This article describes the development and validation of a new technique, potential step impedance analysis (PSIA), to assess the electrochemical impedance of materials whose interface with solution can be modeled as a simplified Randles circuit that is modified with a constant phase element. PSIA is based upon applying a step change in voltage to a working electrode and analyzing the subsequent current transient response in a combined time and frequency domain technique. The solution resistance, polarization resistance, and interfacial capacitance are found directly in the time domain. The experimental current transient is numerically transformed to the frequency domain to determine the constant phase exponent, alpha. This combined time and frequency approach was tested using current transients generated from computer simulations, from resistor-capacitor breadboard circuits, and from commercially pure titanium samples immersed in phosphate buffered saline and polarized at -800 mV or +1000 mV versus Ag/AgCl. It was shown that PSIA calculates equivalent admittance and impedance behavior over this range of potentials when compared to standard electrochemical impedance spectroscopy. This current transient approach characterizes the frequency response of the system without the need for expensive frequency response analyzers or software. Copyright 2009 Wiley Periodicals, Inc.

Titanium is not "the most biocompatible metal" under cathodic potential: The relationship between voltage and MC3T3 preosteoblast behavior on electrically polarized cpTi surfaces.

PubMed

Ehrensberger, Mark T; Sivan, Shiril; Gilbert, Jeremy L

2010-06-15

An electrochemically controlled system has been developed which allows for cell culture directly on electrically polarized metal surfaces with simultaneous control and assessment of the electrochemical current, potential, and impedance of the interface. This system was utilized in this study to assess the interactions between electrochemically polarized commercially pure titanium (cpTi) and MC3T3 preosteoblast cells. Cells were cultured on CpTi for 24 h at static potentials between -1000 mV and +1000 mV vs. Ag/AgCl and cell morphology (SEM and cell area) and viability (MTT and Live-Dead assay) were assessed along with the electrochemical current densities and surface oxide impedance properties. The results indicate that cathodic polarization in the range of -600 mV to -1000 mV markedly reduces the spreading and viability of cells cultured directly on cpTi within 24 h, while anodic polarization (-300 mV to +1000 mV) out to 72 h shows no difference in cell behavior as compared to the OCP condition. Analysis of the relationship between the cell outcomes and the electrochemical current densities and impedance indicated the presence of voltage-dependent electrochemical thresholds (cathodic current density, i(c) > 1.0 microA/cm(2), R(p) < 10(5) Omega cm(2)) which may control the biocompatibility of cpTi. In addition, these outcomes have direct clinical significance for modular orthopedic implants whose potential can shift, via fretting corrosion, down into the range of potentials exhibiting poor cell behavior. (c) 2009 Wiley Periodicals, Inc.

Light-Regulated Electrochemical Sensor Array for Efficiently Discriminating Hazardous Gases.

PubMed

Liang, Hongqiu; Zhang, Xin; Sun, Huihui; Jin, Han; Zhang, Xiaowei; Jin, Qinghui; Zou, Jie; Haick, Hossam; Jian, Jiawen

2017-10-27

Inadequate detection limit and unsatisfactory discrimination features remain the challenging issues for the widely applied electrochemical gas sensors. Quite recently, we confirmed that light-regulated electrochemical reaction significantly enhanced the electrocatalytic activity, and thereby can potentially extend the detection limit to the parts per billion (ppb) level. Nevertheless, impact of the light-regulated electrochemical reaction on response selectivity has been discussed less. Herein, we systematically report on the effect of illumination on discrimination features via design and fabrication of a light-regulated electrochemical sensor array. Upon illumination (light on), response signal to the examined gases (C 3 H 6 , NO, and CO) is selectively enhanced, resulting in the sensor array demonstrating disparate response patterns when compared with that of the sensor array operated at light off. Through processing all the response patterns derived from both light on and light off with a pattern recognition algorithm, a satisfactory discrimination feature is observed. In contrast, apparent mutual interference between NO and CO is found when the sensor array is solely operated without illumination. The impact mechanism of the illumination is studied and it is deduced that the effect of the illumination on the discriminating features can be mainly attributed to the competition of electrocatalytic activity and gas-phase reactivity. If the enhanced electrocatalytic activity (to specific gas) dominates the whole sensing progress, enhancements in the corresponding response signal would be observed upon illumination. Otherwise, illumination gives a negligible impact. Hence, the response signal to part of the examined gases is selectively enhanced by illumination. Conclusively, light-regulated electrochemical reaction would provide an efficient approach to designing future smart sensing devices.

A New PC and LabVIEW Package Based System for Electrochemical Investigations

PubMed Central

Stević, Zoran; Andjelković, Zoran; Antić, Dejan

2008-01-01

The paper describes a new PC and LabVIEW software package based system for electrochemical research. An overview of well known electrochemical methods, such as potential measurements, galvanostatic and potentiostatic method, cyclic voltammetry and EIS is given. Electrochemical impedance spectroscopy has been adapted for systems containing large capacitances. For signal generation and recording of the response of investigated electrochemical cell, a measurement and control system was developed, based on a PC P4. The rest of the hardware consists of a commercially available AD-DA converter and an external interface for analog signal processing. The interface is a result of authors own research. The software platform for desired measurement methods is LabVIEW 8.2 package, which is regarded as a high standard in the area of modern virtual instruments. The developed system was adjusted, tested and compared with commercially available system and ORCAD simulation. PMID:27879794

The dopant type and amount governs the electrochemical performance of graphene platforms for the antioxidant activity quantification

NASA Astrophysics Data System (ADS)

Hui, Kai Hwee; Ambrosi, Adriano; Sofer, Zdeněk; Pumera, Martin; Bonanni, Alessandra

2015-05-01

Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry.Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01045d

Pencil It in: Exploring the Feasibility of Hand-Drawn Pencil Electrochemical Sensors and Their Direct Comparison to Screen-Printed Electrodes

PubMed Central

Bernalte, Elena; Foster, Christopher W.; Brownson, Dale A.C.; Mosna, Morgane; Smith, Graham C.; Banks, Craig E.

2016-01-01

We explore the fabrication, physicochemical characterisation (SEM, Raman, EDX and XPS) and electrochemical application of hand-drawn pencil electrodes (PDEs) upon an ultra-flexible polyester substrate; investigating the number of draws (used for their fabrication), the pencil grade utilised (HB to 9B) and the electrochemical properties of an array of batches (i.e, pencil boxes). Electrochemical characterisation of the PDEs, using different batches of HB grade pencils, is undertaken using several inner- and outer-sphere redox probes and is critically compared to screen-printed electrodes (SPEs). Proof-of-concept is demonstrated for the electrochemical sensing of dopamine and acetaminophen using PDEs, which are found to exhibit competitive limits of detection (3σ) upon comparison to SPEs. Nonetheless, it is important to note that a clear lack of reproducibility was demonstrated when utilising these PDEs fabricated using the HB pencils from different batches. We also explore the suitability and feasibility of a pencil-drawn reference electrode compared to screen-printed alternatives, to see if one can draw the entire sensing platform. This article reports a critical assessment of these PDEs against that of its screen-printed competitors, questioning the overall feasibility of PDEs’ implementation as a sensing platform. PMID:27589815

Organic, Organometallic and Bioorganic Catalysts for Electrochemical Reduction of CO2

PubMed Central

Schlager, Stefanie; Portenkirchner, Engelbert; Sariciftci, Niyazi Serdar

2017-01-01

Abstract A broad review of homogeneous and heterogeneous catalytic approaches toward CO2 reduction using organic, organometallic, and bioorganic systems is provided. Electrochemical, bioelectrochemical and photoelectrochemical approaches are discussed in terms of their faradaic efficiencies, overpotentials and reaction mechanisms. Organometallic complexes as well as semiconductors and their homogeneous and heterogeneous catalytic activities are compared to enzymes. In both cases, their immobilization on electrodes is discussed and compared to homogeneous catalysts in solution. PMID:28383174

Nonenzymatic electrochemical sensor based on imidazole-functionalized graphene oxide for progesterone detection.

PubMed

Gevaerd, Ava; Blaskievicz, Sirlon F; Zarbin, Aldo J G; Orth, Elisa S; Bergamini, Márcio F; Marcolino-Junior, Luiz H

2018-07-30

The modification of electrode surfaces has been the target of study for many researchers in order to improve the analytical performance of electrochemical sensors. Herein, the use of an imidazole-functionalized graphene oxide (GO-IMZ) as an artificial enzymatic active site for voltammetric determination of progesterone (P4) is described for the first time. The morphology and electrochemical performance of electrode modified with GO-IMZ were characterized by scanning electron microscopy and cyclic voltammetry, respectively. Under optimized conditions, the proposed sensor showed a synergistic effect of the GO sheets and the imidazole groups anchored on its backbone, which promoted a significant enhancement on electrochemical reduction of P4. Figures of merits such as linear dynamic response for P4 concentration ranging from 0.22 to 14.0 μmol L -1 , limit of detection of 68 nmol L -1 and limit of quantification and 210 nmol L -1 were found. In addition, presented a higher sensitivity, 426 nA L µmol -1 , when compared to the unmodified electrode. Overall, the proposed device showed to be a promising platform for a simple, rapid, and direct analysis of progesterone. Copyright © 2018 Elsevier B.V. All rights reserved.

Calendering effects on the physical and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 cathode

NASA Astrophysics Data System (ADS)

Zheng, Honghe; Tan, Li; Liu, Gao; Song, Xiangyun; Battaglia, Vincent S.

2012-06-01

Li[Ni1/3Mn1/3Co1/3]O2 cathode laminate containing 8% PVDF and 7% acetylene black is fabricated and calendered to different porosities. Calendering effects on the physical and electrochemical properties of the Li[Ni1/3Mn1/3Co1/3]O2 cathode are investigated. It is found that mechanical properties of the composite laminate strongly depend on the electrode porosity whereas the electronic conductivity is not significantly affected by calendering. Electrochemical performances including the specific capacity, the first coulombic efficiency, cycling performance and rate capability for the cathode at different porosities are compared. An optimized porosity of around 30-40% is identified. Electrochemical impedance spectroscopy (EIS) studies illustrate that calendering improves the electronic conductivity between active particles at relatively high porosities, but increases charge transfer resistance at electrode/electrolyte interface at relatively low porosities. An increase of activation energy of Li interfacial transfer for the electrode at 0% porosity indicates a relatively high barrier of activation at the electrode/electrolyte interface, which accounts for the poor rate capability of the electrode at extremely low porosity.

In vitro evaluation of the electrochemical behaviour of stainless steel and Ni-Ti orthodontic archwires at different temperatures.

PubMed

Pakshir, M; Bagheri, T; Kazemi, M R

2013-08-01

The aim of this study was to compare the electrochemical corrosion behaviour of stainless steel (SS) and nickel-titanium (Ni-Ti) orthodontic archwires in Ringer's solution at temperatures ranging from 15 to 55°C by using linear sweep voltametry and electrochemical impedance spectroscopy. Polarization curves show that the corrosion current density of SS is greater than that of Ni-Ti alloy. Since the corrosion current density is directly proportional to the corrosion rate, a great corrosion current density shows a lower resistance against corrosion. Therefore, in comparison with SS, Ni-Ti alloys have a lower corrosion rate. Results show that the temperature of the solution affects the corrosion rates of the alloys. As the temperature increases, the corrosion resistance of both of the alloys decreases, although these variations were not so large. Impedance measurements show that the electrochemical behaviour of Ni-Ti exhibits higher polarization resistance and lower capacitance, which means that passive film formed on this alloy is more homogeneous and thicker in comparison with SS. Results also show that polarization resistance of both alloys decreases slowly with increases in the temperature of the solution.

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

Dees, D. W.; Kawauchi, S.; Abraham, D. P.

Galvanostatic Intermittent Titration Technique (GITT) experiments were conducted to determine the lithium diffusion coefficient of LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}, used as the active material in a lithium-ion battery porous composite positive electrode. An electrochemical model, based on concentrated solution porous electrode theory, was developed to analyze the GITT experimental results and compare to the original GITT analytical theory. The GITT experimental studies on the oxide active material were conducted between 3.5 and 4.5 V vs. lithium, with the maximum lithium diffusion coefficient value being 10{sup -10} cm{sup 2} s{sup -1} at 3.85 V. The lithium diffusion coefficient values obtainedmore » from this study agree favorably with the values obtained from an earlier electrochemical impedance spectroscopy study.« less

Graphene-based electrochemical sensor for detection of 2,4,6-trinitrotoluene (TNT) in seawater: the comparison of single-, few-, and multilayer graphene nanoribbons and graphite microparticles.

PubMed

Goh, Madeline Shuhua; Pumera, Martin

2011-01-01

The detection of explosives in seawater is of great interest. We compared response single-, few-, and multilayer graphene nanoribbons and graphite microparticle-based electrodes toward the electrochemical reduction of 2,4,6-trinitrotoluene (TNT). We optimized parameters such as accumulation time, accumulation potential, and pH. We found that few-layer graphene exhibits about 20% enhanced signal for TNT after accumulation when compared to multilayer graphene nanoribbons. However, graphite microparticle-modified electrode provides higher sensitivity, and there was no significant difference in the performance of single-, few-, and multilayer graphene nanoribbons and graphite microparticles for the electrochemical detection of TNT. We established the limit of detection of TNT in untreated seawater at 1 μg/mL.

Interactions of doxorubicin with self-assembled monolayer-modified electrodes: electrochemical, surface plasmon resonance (SPR), and gravimetric studies.

PubMed

Nieciecka, Dorota; Krysinski, Pawel

2011-02-01

We present the results on the partitioning of doxorubicin (DOX), a potent anticancer drug, through the model membrane system, self-assembled monolayers (SAMs) on gold electrodes. The monolayers were formed from alkanethiols of comparable length with different ω-terminal groups facing the aqueous electrolyte: the hydrophobic -CH(3) groups for the case of dodecanethiol SAMs or hydrophilic -OH groups of mercaptoundecanol SAMs. The electrochemical experiments combined with the surface plasmon resonance (SPR) and gravimetric studies show that doxorubicin is likely adsorbed onto the surface of hydrophilic monolayer, while for the case of the hydrophobic one the drug mostly penetrates the monolayer moiety. The adsorption of the drug hinders further penetration of doxorubicin into the monolayer moiety.

Assessment of trends in the electrochemical CO 2 reduction and H 2 evolution reactions on metal nanoparticles

DOE PAGES

Alfonso, Dominic R.; Kauffman, Douglas R.

2017-08-14

Here, we used density functional theory to investigate the electrochemical CO 2 reduction and competing hydrogen evolution reaction on model Au, Ag, Cu, Ir, Ni, Pd, Pt, and Rh nanoparticles. On the coinage metal, the free energy of adsorbed COOH, CO, and H intermediates generally becomes more favorable with decreasing particle size. This pattern was also observed on all transition metals with the binding of the intermediates observed to be stronger on almost all of these metals. Comparative studies of the reaction profile reveal that H 2 evolution is the first reaction to be energetically allowed at zero applied bias

Assessment of trends in the electrochemical CO 2 reduction and H 2 evolution reactions on metal nanoparticles

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

Alfonso, Dominic R.; Kauffman, Douglas R.

Here, we used density functional theory to investigate the electrochemical CO 2 reduction and competing hydrogen evolution reaction on model Au, Ag, Cu, Ir, Ni, Pd, Pt, and Rh nanoparticles. On the coinage metal, the free energy of adsorbed COOH, CO, and H intermediates generally becomes more favorable with decreasing particle size. This pattern was also observed on all transition metals with the binding of the intermediates observed to be stronger on almost all of these metals. Comparative studies of the reaction profile reveal that H 2 evolution is the first reaction to be energetically allowed at zero applied bias

Application Electrochemical Impedance Spectroscopy Methods to Evaluation Corrosion Behavior of Stainless steels 304 in Nanofluids Media

NASA Astrophysics Data System (ADS)

Hadi Prajitno, Djoko; Umar, Efrizon; Gustaman Syarif, Dani

2017-01-01

Corrosion is a common problem in many engineering metals and alloys. Electrochemical methods are commonly instrument to use as tool to study the corrosion behavior of the metals and alloy. This method was examined interaction between a surface of the metals and alloys in corrosive media. The present paper, the effects of nano particle ZrO2 as an additive to aqua de mineralized on the corrosion behavior of stainless steel were investigated. Electrochemical impedance spectroscopy (EIS) testing was performed in both de mineralized water and demineralized water contain nano particle 0,01% ZrO2 as Nano fluid. Surface morphology examination of the specimens showed that microstructure of stainless steel 304 alloys relatively unchanged after corrosion and EIS testing. According to the corrosion potential examination of the stainless steel 304 in nanofluid media, it showed that stainless steel 304 actively corroded in nanofluida media. The value of anodic Tafel slope stainless steel 304 in nanofluid higher compare with in demineralized water. Tafel polarization examination show that corrosion rate of stainless steel 304 in nanofluid higher compare with corrosin rate in demineralized media.EIS technique show that impedance of stainless steel 304 in nanofluid lower compare with in demineralized media, resulting in an increase in the corrosion rates of these stainless steel 304 specimens in nano fluids

Electrochemical fabrication of capacitors

DOEpatents

Mansour, Azzam N.; Melendres, Carlos A.

1999-01-01

A film of nickel oxide is anodically deposited on a graphite sheet held in osition on an electrochemical cell during application of a positive electrode voltage to the graphite sheet while exposed to an electrolytic nickel oxide solution within a volumetrically variable chamber of the cell. An angularly orientated x-ray beam is admitted into the cell for transmission through the deposited nickel oxide film in order to obtain structural information while the film is subject to electrochemical and in-situ x-ray spectroscopy from which optimum film thickness, may be determined by comparative analysis for capacitor fabrication purposes.

Preparation and Electrochemical Properties of Graphene/Epoxy Resin Composite Coating

NASA Astrophysics Data System (ADS)

Liao, Zijun; Zhang, Tianchi; Qiao, Sen; Zhang, Luyihang

2017-11-01

The multilayer graphene powder as filler, epoxy modified silicone resin as film-forming agent, anticorrosion composite coating has been created using sand dispersion method, the electrochemical performance was compared with different content of graphene composite coating and pure epoxy resin coating. The open circuit potential (OCP), potentiodynamic polarization curves (Tafel Plot) and electrochemical impedance spectroscopy (EIS) were tested. The test results showed that the anti-corrosion performance of multilayer graphene added has improved greatly, and the content of the 5% best corrosion performance of graphene composite coating.

Electroenzymatic oxidation of veratryl alcohol by lignin peroxidase.

PubMed

Lee, KiBeom; Moon, Seung-Hyeon

2003-05-08

This paper reports the formation of veratraldehyde by electroenzymatic oxidation of veratryl alcohol (3,4-dimethoxybenzyl alcohol) hybridizing both electrochemical and enzymatic reactions and using lignin peroxidase. The novel electroenzymatic method was found to be effective for replacement of hydrogen peroxide by an electrochemical reactor, which is essential for enzyme activity of lignin peroxidase. The effects of operating parameters such as enzyme dosage, pH, and electric potential were investigated. Further, the kinetics of veratryl alcohol oxidation in an electrochemical reactor were compared to oxidation when hydrogen peroxide was supplied externally.

Extraction of Carbon Dioxide and Hydrogen from Seawater by an Electrochemical Acidification Cell. Part 3. Scaled-up Mobile Unit Studies (Calendar Year 2011)

DTIC Science & Technology

2012-05-30

Electrochemical Acidification Cell Part III: Scaled-up Mobile Unit Studies (Calendar Year 2011) May 30, 2012 Approved for public release; distribution is...Hydrogen from Seawater by an Electrochemical Acidification Cell Part III: Scaled-up Mobile Unit Studies (Calendar Year 2011) Heather D. Willauer, Dennis R...Unclassified Unlimited Unclassified Unlimited Unclassified Unlimited 41 Heather D. Willauer (202) 767-2673 Electrochemical acidification cell Carbon

Electrochemical oxidation of ciprofloxacin in two different processes: the electron transfer process on the anode surface and the indirect oxidation process in bulk solutions.

PubMed

Shen, Bo; Wen, Xianghua; Korshin, Gregory V

2018-05-14

Herein, the rotating disk electrode technique was used for the first time to investigate the effects of mass-transfer limitations and pH on the electrochemical oxidation of CPX, to determine the kinetics of CPX oxidation and to explore intrinsic mechanisms during the electron transfer process. Firstly, cyclic voltammetry revealed that an obvious irreversible CPX oxidation peak was observed within the potential window from 0.70 to 1.30 V at all pHs. Based on the Levich equation, the electrochemical oxidation of CPX in the electron transfer process was found to be controlled by both diffusion and kinetic processes when pH = 2, 5, 7 and 9; the diffusion coefficient of CPX at pH = 2 was calculated to be 1.5 × 10-7 cm2 s-1. Kinetic analysis indicated that the reaction on the electrode surface was adsorption-controlled compared to a diffusion process; the surface concentration of electroactive species was estimated to be 1.15 × 10-9 mol cm-2, the standard rate constant of the surface reaction was calculated to be 1.37 s-1, and CPX oxidation was validated to be a two-electron transfer process. Finally, a possible CPX oxidation pathway during the electron transfer process was proposed. The electrochemical degradation of CPX on a Ti-based anode was also conducted subsequently to investigate the electrochemical oxidation of CPX in the indirect oxidation process in bulk solutions. The effects of pH and current density were determined and compared to related literature results. The oxidation of CPX at different pHs is believed to be the result of a counterbalance between favorable and unfavorable factors, namely electromigration and side reactions of oxygen evolution, respectively. The effects of current density indicated a diffusion- and reaction-controlled process at low currents followed by a reaction-controlled process at high currents. The results presented in this study provide better understanding of the electrochemical oxidation of CPX and would enable the development of new treatment methods based on electrochemistry.

Electrochemical preparation of poly(methylene blue)/graphene nanocomposite thin films

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

Erçarıkcı, Elif; Dağcı, Kader; Topçu, Ezgi

2014-07-01

Highlights: • Poly(MB)/graphene thin films are prepared by a simple electrochemical approach. • Graphene layers in the film show a broad band in visible region of absorbance spectra. • Morphology of composite films indicates both disordered and ordered regions. • XRD reveals that nanocomposite films include rGO layers after electropolymerization process. • Chemically prepared graphene is better than electrochemically prepared graphene for electrooxidation of nitrite. - Abstract: Poly(methylene blue)/graphene nanocomposite thin films were prepared by electropolymerization of methylene blue in the presence of graphene which have been synthesized by two different methods of a chemical oxidation process and an electrochemicalmore » approach. Synthesized nanocomposite thin films were characterized by using cyclic voltammetry, UV–vis. absorption spectroscopy, powder X-ray diffraction, and scanning tunneling microscopy techniques. Electrocatalytical properties of prepared poly(methylene blue)/graphene nanocomposite films were compared toward electrochemical oxidation of nitrite. Under optimized conditions, electrocatalytical effect of nanocomposite films of chemically prepared graphene through electrochemical oxidation of nitrite was better than that of electrochemically prepared graphene.« less

Influence of the electrolyte's pH on the properties of electrochemically deposited hydroxyapatite coating on additively manufactured Ti64 alloy.

PubMed

Vladescu, Alina; Vranceanu, Diana M; Kulesza, Slawek; Ivanov, Alexey N; Bramowicz, Mirosław; Fedonnikov, Alexander S; Braic, Mariana; Norkin, Igor A; Koptyug, Andrey; Kurtukova, Maria O; Dinu, Mihaela; Pana, Iulian; Surmeneva, Maria A; Surmenev, Roman A; Cotrut, Cosmin M

2017-12-01

Properties of the hydroxyapatite obtained by electrochemical assisted deposition (ED) are dependent on several factors including deposition temperature, electrolyte pH and concentrations, applied potential. All of these factors directly influence the morphology, stoichiometry, crystallinity, electrochemical behaviour, and particularly the coating thickness. Coating structure together with surface micro- and nano-scale topography significantly influence early stages of the implant bio-integration. The aim of this study is to analyse the effect of pH modification on the morphology, corrosion behaviour and in vitro bioactivity and in vivo biocompatibility of hydroxyapatite prepared by ED on the additively manufactured Ti64 samples. The coatings prepared in the electrolytes with pH = 6 have predominantly needle like morphology with the dimensions in the nanometric scale (~30 nm). Samples coated at pH = 6 demonstrated higher protection efficiency against the corrosive attack as compared to the ones coated at pH = 5 (~93% against 89%). The in vitro bioactivity results indicated that both coatings have a greater capacity of biomineralization, compared to the uncoated Ti64. Somehow, the coating deposited at pH = 6 exhibited good corrosion behaviour and high biomineralization ability. In vivo subcutaneous implantation of the coated samples into the white rats for up to 21 days with following histological studies showed no serious inflammatory process.

Recent progress on the development of biofuel cells for self-powered electrochemical biosensing and logic biosensing: A review

DOE PAGES

Zhou, Ming

2015-06-12

Biofuel cells (BFCs) based on enzymes and microorganisms have been recently received considerable attention because they are recognized as an attractive type of energy conversion technology. In addition to the research activities related to the application of BFCs as power source, we have witnessed recently a growing interest in using BFCs for self-powered electrochemical biosensing and electrochemical logic biosensing applications. Compared with traditional biosensors, one of the most significant advantages of the BFCs-based self-powered electrochemical biosensors and logic biosensors is their ability to detect targets integrated with chemical-to-electrochemical energy transformation, thus obviating the requirement of external power sources. Following mymore » previous review (Electroanalysis 2012, 24, 197-209), the present review summarizes, discusses and updates the most recent progress and latest advances on the design and construction of BFCs-based self-powered electrochemical biosensors and logic biosensors. In addition to the traditional approaches based on substrate effect, inhibition effect, blocking effect and gene regulation effect for BFCs-based self-powered electrochemical biosensors and logic biosensors design, some new principles including enzyme effect, co-stabilization effect, competition effect and hybrid effect are summarized and discussed by me in details. The outlook and recommendation of future directions of BFCs-based self-powered electrochemical biosensors and logic biosensors are discussed in the end.« less

Strategies to optimize lithium-ion supercapacitors achieving high-performance: Cathode configurations, lithium loadings on anode, and types of separator

NASA Astrophysics Data System (ADS)

Cao, Wanjun; Li, Yangxing; Fitch, Brian; Shih, Jonathan; Doung, Tien; Zheng, Jim

2014-12-01

The Li-ion capacitor (LIC) is composed of a lithium-doped carbon anode and an activated carbon cathode, which is a half Li-ion battery (LIB) and a half electrochemical double-layer capacitor (EDLC). LICs can achieve much more energy density than EDLC without sacrificing the high power performance advantage of capacitors over batteries. LIC pouch cells were assembled using activated carbon (AC) cathode and hard carbon (HC) + stabilized lithium metal power (SLMP®) anode. Different cathode configurations, various SLMP loadings on HC anode, and two types of separators were investigated to achieve the optimal electrochemical performance of the LIC. Firstly, the cathode binders study suggests that the PTFE binder offers improved energy and power performances for LIC in comparison to PVDF. Secondly, the mass ratio of SLMP to HC is at 1:7 to obtain the optimized electrochemical performance for LIC among all the various studied mass ratios between lithium loading amounts and active anode material. Finally, compared to the separator Celgard PP 3501, cellulose based TF40-30 is proven to be a preferred separator for LIC.

Direct electrodeposition of porous gold nanowire arrays for biosensing applications.

PubMed

Zhang, Xinyi; Li, Dan; Bourgeois, Laure; Wang, Huanting; Webley, Paul A

2009-02-02

Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire arrays by a direct electrodeposition method. After modification with glucose oxidase, a porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose. The picture shows an SEM image of a nanowire array after removal of the alumina template by acid dissolution. We report the fabrication of porous gold nanowire arrays by means of a one-step electrodeposition method utilizing nanochannel alumina templates. The microstructure of gold nanowires depends strongly on the current density. The formation of porous gold nanowires is attributed to disperse crystallization under conditions of low nucleation rate. Interfacial electron transport through the porous gold nanowires is studied by electrochemical impedance spectroscopy. Cyclic voltammetric studies on the porous gold nanowire arrays reveal a low-potential electrocatalytic response towards hydrogen peroxide. The properties of the glucose oxidase modified porous gold nanowire array electrode are elucidated and compared with those of nonporous enzyme electrodes. The glucose oxidase modified porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose.

Experimental characterization of electrochemically polymerized polycarbazole film and study of its behavior with different metals contacts

NASA Astrophysics Data System (ADS)

Srivastava, Aditi; Chakrabarti, P.

2017-12-01

In this paper, we present the method of fabrication, experimental characterization, and comparison of electrical parameters of semiconducting polycarbazole film with different rectifying metals contacts. Electrochemical polymerization and deposition of organic semiconductor, i.e., polycarbazole on ITO-coated glass substrate, were performed using an electrochemical workstation. Experimental characterization of the prepared polymer film was done in respect of morphology, absorption, bandgap, and thickness. The stability and electro-activity of polycarbazole film were verified by the cyclic voltammetric method. Study of the behavior of prepared polycarbazole film with the different metals contacts such as Aluminum, Copper, Tungsten, and Tin has been done using semiconductor device analyzer. Various electrical parameters such as barrier height, ideality factor, and reverse saturation current have been extracted with different metal contacts, and the values were compared and contrasted. The nature of I- V characteristic of polycarbazole film in non-contact mode has also been analyzed using scanning tunneling microscope. The rectifying I- V characteristics obtained with different metals contacts have also been validated by the simulation on Deckbuild platform of the of ATLAS® software tool from Silvaco Inc.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions

PubMed Central

Martins, Vitor L.; Rennie, Anthony J. R.; Sanchez‐Ramirez, Nedher; Torresi, Roberto M.; Hall, Peter J.

2018-01-01

Abstract Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs. PMID:29577008

Effect of the Cerium Oxide (CeO2) on the Structural and Electrochemical Properties of the LaNi5Ce Metal Hydride Anode

NASA Astrophysics Data System (ADS)

Utami Hapsari, Ade; Zulfia, Anne; Raharjo, Jarot; Agustanhakri

2017-07-01

One of negative electrode, AB5-type alloy electrodes, have been extensively studied and applied in rechargeable Ni-MH batteries due to their excellent electrochemical characteristics. Some researchers have found that addition of rare earth oxides (La, Ce, Pr, Er, Tm, Yb) to AB5-type alloy (MH) electrode improves battery performance significantly. Cerium Oxide (CeO2) is a light rare earth oxide is widely obtained from the processing of tailings in mining activities. During this time, there is still little data for research applications of cerium oxide for electrode materials. In this paper, the effects of adding CeO2 on the performance metal hydride electrode were investigated. In order to study the effects of CeO2 on the performance of anode material, 1%, 2%, and 3% of weight ratio CeO2 was mixed to LaNi5 as an negative electrode. The powder mixtures were mechanically milled at a speed of rpm 240 for 2 hours using ball mill. The powder mixtures were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Electrochemical characteristics were measured using electrochemical impedance spectroscopy (EIS). The powder mixing showed the presence of Ce atom substitution into LaNi5 structures that affect the electrochemical properties of the material. The addition of cerium oxide at LaNi5 increase of the value of impedance. However, the addition of the value of impedance at 1% CeO2 is not significant when compared with the addition of 2% and 3% CeO2 that actually make the electrochemical properties of LaNi5 worst. Although the addition of 1% CeO2 also slightly increases the impedance value of LaNi5, but the addition of 1% CeO2 showed increase the corrosion resistance than without the addition of CeO2 and the addition of 2% and 3% CeO2.

Assessment of Electrochemical Concepts: A Comparative Study Involving Senior High-School Students in Indonesia and Japan

ERIC Educational Resources Information Center

Rahayu, Sri; Treagust, David F.; Chandrasegaran, A. L.; Kita, Masakazu; Ibnu, Suhadi

2011-01-01

Background and purpose: This study investigated Indonesian and Japanese senior high-school students' understanding of electrochemistry concepts. Sample: The questionnaire was administered to 244 Indonesian and 189 Japanese public senior high-school students. Design and methods: An 18-item multiple-choice questionnaire relating to five conceptual…

Electrochemical Study of Carbon Nanotubes/Nanohybrids for Determination of Metal Species Cu2+ and Pb2+ in Water Samples

PubMed Central

Oliveira Silva, Andréa Claudia; de Oliveira, Luis Carlos Ferreira; Vieira Delfino, Angladis; Meneghetti, Mario Roberto

2016-01-01

The use of nanomaterials, such as nanoparticles and nanotubes, for electrochemical detection of metal species has been investigated as a way of modifying electrodes by electrochemical stripping analysis. The present study develops a new methodology based on a comparative study of nanoparticles and nanotubes with differential pulse anodic stripping voltammetry (DPASV) and examines the simultaneous determination of copper and lead. The glassy carbon electrode modified by gold nanoparticles demonstrated increased sensitivity and decreased detection limits, among other improvements in analytical performance data. Under optimized conditions (deposition potential −0.8 V versus Ag/AgCl; deposition time, 300 s; resting time, 10 s; pulse amplitude, 50 mV; and voltage step height, 4 mV), the detection limits were 0.2279 and 0.3321 ppb, respectively, for determination of Pb2+ and Cu2+. The effects of cations and anions on the simultaneous determination of metal ions do not exhibit significant interference, thereby demonstrating the selectivity of the electrode for simultaneous determination of Pb2+ and Cu2+. The same method was also used to determine Cu2+ in water samples. PMID:27882263

Effect of nitro substituent on electrochemical oxidation of phenols at boron-doped diamond anodes.

PubMed

Jiang, Yi; Zhu, Xiuping; Li, Hongna; Ni, Jinren

2010-02-01

In order to investigate nitro-substitutent's effect on degradation of phenols at boron-doped diamond (BDD) anodes, cyclic voltammetries of three nitrophenol isomers: 2-nitrophenol (2NP), 3-nitrophenol (3NP) and 4-nitrophenol (4NP) were studied, and their bulk electrolysis results were compared with phenol's (Ph) under alkaline condition. The voltammetric study showed nitrophenols could be attacked by hydroxyl radicals and nitro-group was released from the aromatic ring. Results of bulk electrolysis showed degradation of all phenols were fit to a pseudo first-order equation and followed in this order: 2NP>4NP>3NP>Ph. Molecular structures, especially carbon atom charge, significantly influenced the electrochemical oxidation of these isomers. Intermediates were analyzed during the electrolysis process, and were mainly catechol, resorcinol, hydroquinone, and carboxylic acids, such as acetic acid and oxalic acid. A simple degradation pathway was proposed. Moreover, a linear increasing relationship between degradation rates and Hammett constants of the studied phenols was observed, which demonstrated that electrochemical oxidation of these phenols was mainly initiated by electrophilic attack of hydroxyl radicals at BDD anodes. Copyright (c) 2009 Elsevier Ltd. 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.

Synthesis and characterization of hybrid micro/nano-structured NiTi surfaces by a combination of etching and anodizing

NASA Astrophysics Data System (ADS)

Huan, Z.; Fratila-Apachitei, L. E.; Apachitei, I.; Duszczyk, J.

2014-02-01

The purpose of this study was to generate hybrid micro/nano-structures on biomedical nickel-titanium alloy (NiTi). To achieve this, NiTi surfaces were firstly electrochemically etched and then anodized in fluoride-containing electrolyte. With the etching process, the NiTi surface was micro-roughened through the formation of micropits uniformly distributed over the entire surface. Following the subsequent anodizing process, self-organized nanotube structures enriched in TiO2 could be superimposed on the etched surface under specific conditions. Furthermore, the anodizing treatment significantly reduced water contact angles and increased the surface free energy compared to the surfaces prior to anodizing. The results of this study show for the first time that it is possible to create hybrid micro/nano-structures on biomedical NiTi alloys by combining electrochemical etching and anodizing under controlled conditions. These novel structures are expected to significantly enhance the surface biofunctionality of the material when compared to conventional implant devices with either micro- or nano-structured surfaces.

Synthesis and characterization of hybrid micro/nano-structured NiTi surfaces by a combination of etching and anodizing.

PubMed

Huan, Z; Fratila-Apachitei, L E; Apachitei, I; Duszczyk, J

2014-02-07

The purpose of this study was to generate hybrid micro/nano-structures on biomedical nickel-titanium alloy (NiTi). To achieve this, NiTi surfaces were firstly electrochemically etched and then anodized in fluoride-containing electrolyte. With the etching process, the NiTi surface was micro-roughened through the formation of micropits uniformly distributed over the entire surface. Following the subsequent anodizing process, self-organized nanotube structures enriched in TiO2 could be superimposed on the etched surface under specific conditions. Furthermore, the anodizing treatment significantly reduced water contact angles and increased the surface free energy compared to the surfaces prior to anodizing. The results of this study show for the first time that it is possible to create hybrid micro/nano-structures on biomedical NiTi alloys by combining electrochemical etching and anodizing under controlled conditions. These novel structures are expected to significantly enhance the surface biofunctionality of the material when compared to conventional implant devices with either micro- or nano-structured surfaces.

Electrochemical degradation, kinetics & performance studies of solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Das, Debanjan

Linear and Non-linear electrochemical characterization techniques and equivalent circuit modelling were carried out on miniature and sub-commercial Solid Oxide Fuel Cell (SOFC) stacks as an in-situ diagnostic approach to evaluate and analyze their performance under the presence of simulated alternative fuel conditions. The main focus of the study was to track the change in cell behavior and response live, as the cell was generating power. Electrochemical Impedance Spectroscopy (EIS) was the most important linear AC technique used for the study. The distinct effects of inorganic components usually present in hydrocarbon fuel reformates on SOFC behavior have been determined, allowing identification of possible "fingerprint" impedance behavior corresponding to specific fuel conditions and reaction mechanisms. Critical electrochemical processes and degradation mechanisms which might affect cell performance were identified and quantified. Sulfur and siloxane cause the most prominent degradation and the associated electrochemical cell parameters such as Gerisher and Warburg elements are applied respectively for better understanding of the degradation processes. Electrochemical Frequency Modulation (EFM) was applied for kinetic studies in SOFCs for the very first time for estimating the exchange current density and transfer coefficients. EFM is a non-linear in-situ electrochemical technique conceptually different from EIS and is used extensively in corrosion work, but rarely used on fuel cells till now. EFM is based on exploring information obtained from non-linear higher harmonic contributions from potential perturbations of electrochemical systems, otherwise not obtained by EIS. The baseline fuel used was 3 % humidified hydrogen with a 5-cell SOFC sub-commercial planar stack to perform the analysis. Traditional methods such as EIS and Tafel analysis were carried out at similar operating conditions to verify and correlate with the EFM data and ensure the validity of the obtained information. The obtained values closely range from around 11 mA cm-2 - 16 mA cm -2 with reasonable repeatability and excellent accuracy. The potential advantages of EFM compared to traditional methods were realized and our primary aim at demonstrating this technique on a SOFC system are presented which can act as a starting point for future research efforts in this area. Finally, an approach based on in-situ State of Health tests by EIS was formulated and investigated to understand the most efficient fuel conditions for suitable long term operation of a solid oxide fuel cell stack under power generation conditions. The procedure helped to reflect the individual effects of three most important fuel characteristics CO/H2 volumetric ratio, S/C ratio and fuel utilization under the presence of a simulated alternative fuel at 0.4 A cm-2. Variation tests helped to identify corresponding electrochemical/chemical processes, narrow down the most optimum operating regimes considering practical behavior of simulated reformer-SOFC system arrangements. At the end, 8 different combinations of the optimized parameters were tested long term with the stack, and the most efficient blend was determined.

Design of titanium nitride- and wolfram carbide-doped RGO/GC electrodes for determination of gallic acid.

PubMed

Stanković, Dalibor M; Ognjanović, Miloš; Martin, Fabian; Švorc, Ľubomir; Mariano, José F M L; Antić, Bratislav

2017-12-15

In the present paper, the electrochemical behavior and the properties of two modified glassy carbon (GC) electrodes used for quantification of gallic acid in sweet wines were compared. A comparative study was conducted between titanium nitride- or wolfram carbide-doped reduced graphene oxide, labeled as TNrGO and WCrGO, respectively, modified GC electrodes, which are promising composite nanomaterials for electroanalytical applications. For the first time, WCrGO was synthesized and its electroanalytical properties compared with those of TNrGO. Results showed that the proposed materials exhibited enhanced characteristics, e.g., low limits of detection (1.1 μM and 3.1 μM for TNrGO and WCrGO, respectively), wide linear ranges (for TNrGO 4.5-76 μM and for WCrGO 10-100 μM), low adsorption, and low background current, which make them promising candidates for electrochemical sensing applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparative study of the effect of pharmaceutical additives on the elimination of antibiotic activity during the treatment of oxacillin in water by the photo-Fenton, TiO2-photocatalysis and electrochemical processes.

PubMed

Serna-Galvis, Efraim A; Silva-Agredo, Javier; Giraldo, Ana L; Flórez-Acosta, Oscar A; Torres-Palma, Ricardo A

2016-01-15

Synthetic pharmaceutical effluents loaded with the β-lactam antibiotic oxacillin were treated using advanced oxidation processes (the photo-Fenton system and TiO2 photocatalysis) and chloride mediated electrochemical oxidation (with Ti/IrO2 anodes). Combinations of the antibiotic with excipients (mannitol or tartaric acid), an active ingredient (calcium carbonate, i.e. bicarbonate ions due to the pH) and a cleaning agent (sodium lauryl ether sulfate) were considered. Additionally, urban wastewater that had undergone biological treatment was doped with oxacillin and treated with the tested systems. The evolution of antimicrobial activity was monitored as a parameter of processes efficiency. Although the two advanced oxidation processes (AOPs) differ only in the way they produce OH, marked differences were observed between them. There were also differences between the AOPs and the electrochemical system. Interestingly, each additive had a different effect on each treatment. For water loaded with mannitol, electrochemical treatment was the most suitable option because the additive did not significantly affect the efficiency of the system. Due to the formation of a complex with Fe(3+), tartaric acid accelerated the elimination of antibiotic activity during the photo-Fenton process. For TiO2 photocatalysis, the presence of bicarbonate ions contributed to antibiotic activity elimination through the possible formation of carbonate and bicarbonate radicals. Sodium lauryl ether sulfate negatively affected all of the processes. However, due to the higher selectivity of HOCl compared with OH, electrochemical oxidation showed the least inhibited efficiency. For the urban wastewater doped with oxacillin, TiO2 photocatalysis was the most efficient process. These results will help select the most suitable technology for the treatment of water polluted with β-lactam antibiotics. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrochemical Genosensor To Detect Pathogenic Bacteria (Escherichia coli O157:H7) As Applied in Real Food Samples (Fresh Beef) To Improve Food Safety and Quality Control.

PubMed

Abdalhai, Mandour H; Fernandes, António Maximiano; Xia, Xiaofeng; Musa, Abubakr; Ji, Jian; Sun, Xiulan

2015-05-27

The electrochemical genosensor is one of the most promising methods for the rapid and reliable detection of pathogenic bacteria. In a previous work, we performed an efficient electrochemical genosensor detection of Staphylococcus aureus by using lead sulfide nanoparticles (PbSNPs). As a continuation of this study, in the present work, the electrochemical genosensor was used to detect Escherichia coli O157:H7. The primer and probes were designed using NCBI database and Sigma-Aldrich primer and probe software. The capture and signalizing probes were modified by thiol (SH) and amine (NH2), respectively. Then, the signalizing probe was connected using cadmium sulfide nanoparticles (CdSNPs), which showed well-defined peaks after electrochemical detection. The genosensor was prepared by immobilization of complementary DNA on the gold electrode surface, which hybridizes with a specific fragment gene from pathogenic to make a sandwich structure. The conductivity and sensitivity of the sensor were increased by using multiwalled carbon nanotubes (MWCNT) that had been modified using chitosan deposited as a thin layer on the glass carbon electrode (GCE) surface, followed by a deposit of bismuth. The peak currents of E. coli O157:H7 correlated in a linear fashion with the concentration of tDNA. The detection limit was 1.97 × 10(-14) M, and the correlation coefficient was 0.989. A poorly defined current response was observed as the negative control and baseline. Our results showed high sensitivity and selectivity of the electrochemical DNA biosensor to the pathogenic bacteria E. coli O157:H7. The biosensor was also used to evaluate the detection of pathogen in real beef samples contaminated artificially. Compared with other electrochemical DNA biosensors, we conclude that this genosensor provides for very efficient detection of pathogenic bacteria. Therefore, this method may have potential application in food safety and related fields.

Corrosion resistance and in-vitro bioactivity of BaO containing Na2O-CaO-P2O5 phosphate glass-ceramic coating prepared on 316 L, duplex stainless steel 2205 and Ti6Al4V

NASA Astrophysics Data System (ADS)

Edathazhe, Akhila B.; Shashikala, H. D.

2018-03-01

The phosphate glass with composition 11Na2O-15BaO-29CaO-45P2O5 was coated on biomedical implant materials such as stainless steel 316 L, duplex stainless steel (DSS) 2205 and Ti6Al4V alloy by thermal enamelling method. The structural properties and composition of glass coated substrates were studied by x-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDS) analysis. The coatings were partially crystalline in nature with porous structure and pore size varied from micro to nanometer range. The polarization curve was obtained for uncoated and coated substrates from electrochemical corrosion test which was conducted at 37 °C in Hank’s balanced salt solution (HBSS). The corrosion resistance of 316 L substrate increased after coating, whereas it decreased in case of DSS 2205 and Ti6Al4V. The XRD and SEM/EDS studies indicated the bioactive hydroxyapatite (HAp) layer formation on all the coated surfaces after electrochemical corrosion test, which improved the corrosion resistance. The observed electrochemical corrosion behavior can be explained based on protective HAp layer formation, composition and diffusion of ions on glass coated surfaces. The in-vitro bioactivity test was carried out at 37 °C in HBS solution for 14 days under static conditions for uncoated and coated substrates. pH and ion release rate measurements from the coated samples were conducted to substantiate the electrochemical corrosion test. The lower ion release rates of Na+ and Ca2+ from coated 316 L supported its higher electrochemical corrosion resistance among coated samples. Among the uncoated substrates, DSS showed higher electrochemical corrosion resistance. Amorphous calcium-phosphate (ACP) layer formation on all the coated substrates after in-vitro bioactivity test was confirmed by XRD, SEM/EDS and ion release measurements. The present work is a comparative study of corrosion resistance and bioactivity of glass coated and uncoated biomedical implants such as 316 L, DSS and Ti6Al4V.

An electrochemical investigation of TMJ implant metal alloys in an artificial joint fluid environment: the influence of pH variation.

PubMed

Royhman, Dmitry; Radhakrishnan, Rashmi; Yuan, Judy Chia-Chun; Mathew, Mathew T; Mercuri, Louis G; Sukotjo, Cortino

2014-10-01

To investigate the corrosion behaviour of commonly used TMJ implants alloys (CoCrMo and Ti6Al4V) under simulated physiological conditions. Corrosion behaviour was evaluated using standard electrochemical corrosion techniques and galvanic corrosion techniques as per ASTM standards. Standard electrochemical tests (E(corr), I(corr), R(p) and C(f)) were conducted in bovine calf serum (BCS), as a function of alloys type and different pHs. Galvanic corrosion tests were conducted in BCS at a pH of 7.6. Alloy surfaces were characterized using white-light interferometry (WLI) and scanning electron microscopy (SEM). The potentiodynamic test results exhibited the enhanced passive layer growth and a better corrosion resistance of Ti6Al4V compared to CoCrMo. Electrochemical impedance spectroscopy measurements demonstrated the influence of protein as a function of pH on corrosion mechanisms/kinetics. Galvanic coupling was not a major contributor to corrosion. SEM and WLI images demonstrated a significantly higher in surface roughness in CoCrMo after corrosion. The results of this study suggest that Ti6Al4V shows superior corrosion behaviour to CoCrMo due to its strong passive layer, simulated joint fluid components can affect the electrochemical nature of the metal/electrolyte interface as a function of pH, and the galvanic effect of coupling CoCrMo and Ti6Al4V in a single joint is weak. Published by Elsevier Ltd.

Electrochemical detection of dopamine in the presence of ascorbic acid using PVP/graphene modified electrodes.

PubMed

Liu, Qin; Zhu, Xu; Huo, Zhaohui; He, Xulun; Liang, Yong; Xu, Maotian

2012-08-15

Graphene (GR) was synthesized through electrochemical reduction of graphene oxide and characterized by spectroscopic and electrochemical techniques. Polyvinylpyrrolidone (PVP)/graphene modified glassy carbon electrode (PVP/GR/GCE) was prepared and applied for the fabrication of dopamine (DA) sensors without the interference of ascorbic acid (AA). Compared to bare GCE, an increase of current signal was observed, demonstrating that PVP/GR/GCE exhibited favorable electron transfer kinetics and electrocatalytic activity towards the oxidation of dopamine. Furthermore, PVP/GR/GCE exhibited good ability to suppress the background current from large excess ascorbic acid. Amperometric response results show that the PVP based sensor displayed a wide linear range of 5×10(-10) to 1.13×10(-3) mol/L DA with a correlation coefficient of 0.9990 and a detection limit of 0.2 nM (S/N=3). The determination of dopamine in urine and human serum samples were studied. Copyright © 2012 Elsevier B.V. All rights reserved.

Chemically-modified graphenes for oxidation of DNA bases: analytical parameters.

PubMed

Goh, Madeline Shuhua; Bonanni, Alessandra; Ambrosi, Adriano; Sofer, Zdeněk; Pumera, Martin

2011-11-21

We studied the electroanalytical performances of chemically-modified graphenes (CMGs) containing different defect densities and amounts of oxygen-containing groups, namely graphite oxide (GPO), graphene oxide (GO), thermally reduced graphene oxide (TR-GO) and electrochemically reduced graphene oxide (ER-GO) by comparing the sensitivity, selectivity, linearity and repeatability towards the oxidation of DNA bases. We have observed that for differential pulse voltammetric (DPV) detection of adenine and cytosine, all CMGs showed enhanced sensitivity to oxidation, while for guanine and thymine, ER-GO and TR-GO exhibited much improved sensitivity over bare glassy carbon (GC) as well as over GPO and GO. There is also significant selectivity enhancement when using GPO for adenine and TR-GO for thymine. Our results have uncovered that the differences in surface functionalities, structure and defects of various CMGs largely influence their electrochemical behaviour in detecting the oxidation of DNA bases. The findings in this report will provide a useful guide for the future development of label-free electrochemical devices for DNA analysis.

Efficient fluorescence quenching in electrochemically exfoliated graphene decorated with gold nanoparticles

NASA Astrophysics Data System (ADS)

Hurtado-Morales, M.; Ortiz, M.; Acuña, C.; Nerl, H. C.; Nicolosi, V.; Hernández, Y.

2016-07-01

High surface area graphene sheets were obtained by electrochemical exfoliation of graphite in an acid medium under constant potential conditions. Filtration and centrifugation processes played an important role in order to obtain stable dispersions in water. Scanning electron microscopy and transmission electron microscopy imaging revealed highly exfoliated crystalline samples of ∼5 μm. Raman, Fourier transform infrared and x-ray photoelectron spectroscopy further confirmed the high quality of the exfoliated material. The electrochemically exfoliated graphene (EEG) was decorated with gold nanoparticles (AuNPs) using sodium cholate as a buffer layer. This approach allowed for a non-covalent functionalization without altering the desirable electronic properties of the EEG. The AuNP-EEG samples were characterized with various techniques including absorbance and fluorescence spectroscopy. These samples displayed a fluorescence signal using an excitation wavelength of 290 nm. The calculated quantum yield (Φ) for these samples was 40.04%, a high efficiency compared to previous studies using solution processable graphene.

Biofouling resistance of boron-doped diamond neural stimulation electrodes is superior to titanium nitride electrodes in vivo.

PubMed

Meijs, S; Alcaide, M; Sørensen, C; McDonald, M; Sørensen, S; Rechendorff, K; Gerhardt, A; Nesladek, M; Rijkhoff, N J M; Pennisi, C P

2016-10-01

The goal of this study was to assess the electrochemical properties of boron-doped diamond (BDD) electrodes in relation to conventional titanium nitride (TiN) electrodes through in vitro and in vivo measurements. Electrochemical impedance spectroscopy, cyclic voltammetry and voltage transient (VT) measurements were performed in vitro after immersion in a 5% albumin solution and in vivo after subcutaneous implantation in rats for 6 weeks. In contrast to the TiN electrodes, the capacitance of the BDD electrodes was not significantly reduced in albumin solution. Furthermore, BDD electrodes displayed a decrease in the VTs and an increase in the pulsing capacitances immediately upon implantation, which remained stable throughout the whole implantation period, whereas the opposite was the case for the TiN electrodes. These results reveal that BDD electrodes possess a superior biofouling resistance, which provides significantly stable electrochemical properties both in protein solution as well as in vivo compared to TiN electrodes.

Electrodeposition of gold nanoparticles on aryl diazonium monolayer functionalized HOPG surfaces.

PubMed

González, M C R; Orive, A G; Salvarezza, R C; Creus, A H

2016-01-21

Gold nanoparticle electrodeposition on a modified HOPG surface with a monolayer organic film based on aryl diazonium chemistry has been studied. This organic monolayer is electrochemically grown with the use of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a radical scavenger. The electrodeposition of gold on this modified surface is highly favored resulting in an AuNP surface density comparable to that found on glassy carbon. AuNPs grow only in the areas covered by the organic monolayer leaving free clean HOPG zones. A progressive mechanism for the nucleation and growth is followed giving hemispherical AuNPs, homogeneously distributed on the surface and their sizes can be well controlled by the applied electrodeposition potential. By using AFM, C-AFM and electrochemical measurements with the aid of two redox probes, namely Fe(CN)6(4-)/Fe(CN)6(3-) and dopamine, relevant results about the electrochemical modified surface as well as the gold nanoparticles electrodeposited on them are obtained.

An electrochemical ELISA-like immunosensor for miRNAs detection based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes.

PubMed

Tran, H V; Piro, B; Reisberg, S; Huy Nguyen, L; Dung Nguyen, T; Duc, H T; Pham, M C

2014-12-15

We design an electrochemical immunosensor for miRNA detection, based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes. An original immunological approach is followed, using antibodies directed to DNA.RNA hybrids. An electrochemical ELISA-like amplification strategy was set up using a secondary antibody conjugated to horseradish peroxidase (HRP). Hydroquinone is oxidized into benzoquinone by the HRP/H2O2 catalytic system. In turn, benzoquinone is electroreduced into hydroquinone at the electrode. The catalytic reduction current is related to HRP amount immobilized on the surface, which itself is related to miRNA.DNA surface density on the electrode. This architecture, compared to classical optical detection, lowers the detection limit down to 10 fM. Two miRNAs were studied: miR-141 (a prostate biomarker) and miR-29b-1 (a lung cancer biomarker). Copyright © 2014 Elsevier B.V. All rights reserved.

Electrochemical studies on the performance of SS316L electrode in electrokinetics

NASA Astrophysics Data System (ADS)

Choi, Jeong-Hee; Maruthamuthu, Sundaram; Lee, Hyun-Goo; Ha, Tae-Hyun; Bae, Jeong-Hyo

2009-10-01

Organic and trace metal pollutants are removed by employing various electrodes in an electrokinetic (EK) process. Stainless steel was used either as an anode or a cathode by various investigators in electroremediation systems. In the present study, the role of SS316L as an anode and cathode in EK system was studied by the measurements of pH, conductivity of electrolyte, and potential of the anode and cathode at different current densities. The weight loss of the anode and cathode and the leaching of chromium, iron, and nickel at different current densities were measured and discussed with an electroosmosis process. The electrochemical behavior of SS316L electrode in neutral, acidic and alkaline pH in soil environment was studied by an electrochemical technique viz. polarization study. Surface analysis of SS316L after EK was done by XPS and SEM. The higher conductivity was noticed at anolyte when compared to catholyte. The weight loss of the anode was in the following order 0.615 > 0.307 > 0.123 mA/cm2 and the cathode corrosion rate was vice versa. Peroxide production was also noticed at the anolyte, which may encourage the degradation of the total organic content (TOC) in the soil. The OCP (open circuit potential) of SS316L was about +75 mV vs SCE in the soil extract; while adding acetic acid, the potential shifted to the positive side, to about +380 mV vs SCE. The breakdown potential and the range of passivation potential were higher in acetic acid added system when compared to other systems. Pitting was observed on both the anode and cathode within 48 h during the EK process. The present study concludes that SS is not a proper electrode material for the EK process.

Performance of vegetative and fruits Zn/Cu based electrochemical cell

NASA Astrophysics Data System (ADS)

Khan, Md. Kamrul Alam, Prof. _., Dr.

2017-01-01

We have studied the performance of PKL, Aloe Vera, Tomato and Lemon juice electrochemical Cells without load condition for 1:1 Zn/Cu based electrodes. It was studied the variation of Open circuit voltage (Voc), Short current (Isc) and Maximum Power (Pmax) with the variation of time for PKL, Aloe Vera, Tomato and Lemon juice electrochemical Cells. It was seen from the research observation that the discharge characteristic of the PKL electrochemical cell was more efficient than the other three Aloe Vera, Tomato and Lemon juice electrochemical Cells. Because the Open circuit voltage (Voc), Short current (Isc) and Maximum Power (Pmax) are more stable and steady than the others three Aloe Vera, Tomato and Lemon juice electrochemical Cells. Furthermore, to enhance the performance we have also studied the secondary salt effect by using the NaCl as an electrolyte with the PKL, Aloe Vera and Lemon juice electrochemical Cells. Most of the results have been tabulated and graphically discussed. I am grateful to the authority of the Science and technology ministry,Bangladesh for financial support during the research work.

Ternary carbon composite films for supercapacitor applications

NASA Astrophysics Data System (ADS)

Tran, Minh-Hai; Jeong, Hae Kyung

2017-09-01

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1933 m2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

Fundamental Studies Connected with Electrochemical Energy Storage

NASA Technical Reports Server (NTRS)

Buck, E.; Sen, R.

1974-01-01

Papers are presented which deal with electrochemical research activities. Emphasis is placed on electrochemical energy storage devices. Topics discussed include: adsorption of dendrite inhibitors on zinc; proton discharge process; electron and protron transfer; quantum mechanical formulation of electron transfer rates; and theory of electrochemical kinetics in terms of two models of activation; thermal and electrostatic.

Spatially-resolved mapping of history-dependent coupled electrochemical and electronical behaviors of electroresistive NiO

DOE PAGES

Sugiyama, Issei; Kim, Yunseok; Jesse, Stephen; ...

2014-10-22

Bias-induced oxygen ion dynamics underpins a broad spectrum of electroresistive and memristive phenomena in oxide materials. Although widely studied by device-level and local voltage-current spectroscopies, the relationship between electroresistive phenomena, local electrochemical behaviors, and microstructures remains elusive. Here, the interplay between history-dependent electronic transport and electrochemical phenomena in a NiO single crystalline thin film with a number of well-defined defect types is explored on the nanometer scale using an atomic force microscopy-based technique. A variety of electrochemically-active regions were observed and spatially resolved relationship between the electronic and electrochemical phenomena was revealed. The regions with pronounced electroresistive activity were furthermore » correlated with defects identified by scanning transmission electron microscopy. Using fully coupled mechanical-electrochemical modeling, we illustrate that the spatial distribution of strain plays an important role in electrochemical and electroresistive phenomena. In conclusion, these studies illustrate an approach for simultaneous mapping of the electronic and ionic transport on a single defective structure level such as dislocations or interfaces, and pave the way for creating libraries of defect-specific electrochemical responses.« less

Aptamer based electrochemical sensor for detection of human lung adenocarcinoma A549 cells

NASA Astrophysics Data System (ADS)

Sharma, Rachna; Varun Agrawal, Ved; Sharma, Pradeep; Varshney, R.; Sinha, R. K.; Malhotra, B. D.

2012-04-01

We report results of the studies relating to development of an aptamer-based electrochemical biosensor for detection of human lung adenocarcinoma A549 cells. The aminated 85-mer DNA aptamer probe specific for the A549 cells has been covalently immobilized onto silane self assembled monolayer (SAM) onto ITO surface using glutaraldehyde as the crosslinker. The results of cyclic voltammetry and differential pulse voltammetry studies reveal that the aptamer functionalized bioelectrode can specifically detect lung cancer cells in the concentration range of 103 to 107 cells/ml with detection limit of 103 cells/ml within 60 s. The specificity studies of the bioelectrode have been carried out with control KB cells. No significant change in response is observed for control KB cells as compared to that of the A549 target cells.

Electrochemical Properties of LaNi(sub 5-x)Ge(sub x) Alloys in Ni-MH Batteries

NASA Technical Reports Server (NTRS)

Bowman, R. C., Jr.; Witham, C.

1997-01-01

Electrochemical studies were performed on LaNi(sub 5-x)Ge(sub x) metal hydride alloys with 0 <= x <= 0.5. We carried out single-electrode studies to understand the effects of the Ge substituent on the hydrogen absorption characteristics, the electrochemical capacity, and the electrochemical kinetics of hydrogen absorption and desorption.

Immobilization free electrochemical biosensor for folate receptor in cancer cells based on terminal protection.

PubMed

Ni, Jiancong; Wang, Qingxiang; Yang, Weiqiang; Zhao, Mengmeng; Zhang, Ying; Guo, Longhua; Qiu, Bin; Lin, Zhenyu; Yang, Huang-Hao

2016-12-15

The determination of folate receptor (FR) that over expressed in vast quantity of cancerous cells frequently is significant for the clinical diagnosis and treatment of cancers. Many DNA-based electrochemical biosensors have been developed for FR detection with high selectivity and sensitivity, but most of them need complicated immobilization of DNA on the electrode surface firstly, which is tedious and therefore results in the poor reproducibility. In this study, a simple, sensitive, and selective electrochemical FR biosensor in cancer cells has been proposed, which combines the advantages of the convenient immobilization-free homogeneous indium tin oxide (ITO)-based electrochemical detection strategy and the high selectivity of the terminal protection of small molecule linked DNA. The small molecule of folic acid (FA) and an electroactive molecule of ferrocence (Fc) were tethered to 3'- and 5'-end of an arbitrary single-stranded DNA (ssDNA), respectively, forming the FA-ssDNA-Fc complex. In the absence of the target FR, the FA-ssDNA-Fc was degraded by exonuclease I (Exo I) from 3'-end and produced a free Fc, diffusing freely to the ITO electrode surface and resulting in strong electrochemical signal. When the target FR was present, the FA-ssDNA-Fc was bound to FR through specific interaction with FA anchored at the 3'-end, effectively protecting the ssDNA strand from hydrolysis by Exo I. The FR-FA-ssDNA-Fc could not diffuse easily to the negatively charged ITO electrode surface due to the electrostatic repulsion between the DNA strand and the negatively charged ITO electrode, so electrochemical signal reduced. The decreased electrochemical signal has a linear relationship with the logarithm of FR concentration in range of 10fM to 10nM with a detection limit of 3.8fM (S/N=3). The proposed biosensor has been applied to detect FR in HeLa cancer cells, and the decreased electrochemical signal has a linear relationship with the logarithm of cell concentration ranging from 100-10000cell/mL. Compared with the traditional heterogeneous electrochemical FR biosensors, the proposed biosensor owns the merits of the simplicity and high specificity, presenting the great potential application in the area of early diagnosis of cancers. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical characterization of bulk and thin film copper in ammonia- and nitric acid-based slurries for chemical mechanical planarization of interconnects

NASA Astrophysics Data System (ADS)

Sainio, Carlyn Anne

Copper will be replacing aluminum as the interconnect material in silicon integrated circuits. Chemical mechanical planarization (CMP) in combination with an inlaid metal interconnection scheme has been utilized to pattern copper interconnects. The thesis describes an attempt to understand the electrochemistry of copper in slurries used for CMP. Steady-state electrochemical potential measurements, linear polarization resistance determinations, and potentiodynamic and potentiostatic polarization scans have been used in order to characterize the mechanism by which copper is removed during CMP. Electrochemical measurements were implemented on a rotating disk assembly to simulate conditions during CMP. Experiments were performed on both bulk copper samples and blanket copper thin films sputter deposited onto silicon wafers. Electrochemical potential measurements have been used in conjunction with potential-pH diagrams to determine the possible copper species which are stable during CMP. Electrochemical results were correlated to CMP experiments to determine slurry compositions with optimum potential-pH ranges for copper planarization. The results indicate that such studies present an opportunity to isolate the electrochemical and chemical effects from the mechanical effects in the CMP of metals and to determine the dependencies of each of these effects on the other. CMP of copper was controlled by the removal of native or non-native surface films. High CMP rates were achieved by matching the rates of film formation and copper and film dissolution. During CMP, surface films are abraded, allowing increased dissolution of copper until the surface film reforms. When the surface was indented by abrasive particles, the corrosion rate of the exposed copper increased by two orders of magnitude. Etchants (i.e. ammonia or nitric acid) were necessary for high CMP rates (120-240 nm/min) and to minimize scratching. CMP rates of copper in 1 volume percent NHsb4OH and 0.7 volume percent HNOsb3 with 0.0016 weight percent KMnOsb4 were comparable. Electrochemical characterization can narrow the possible slurry compositions that may be used for polishing. Also, the possibility of implementing electrochemical techniques to detect the endpoint of polishing was investigated. Although electrochemical measurements in ammonia-based slurries did not indicate when tantalum was exposed, similar measurements may be used to determine when polishing pads should be replaced.

The electrochemical Evaluation of a Zr-Based Bulk Metallic Glass in a Phosphate-Buffered Saline Electrolyte

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

Morrison, M. L.; Buchanan, R. A.; Leon, R. V.

2005-01-01

Bulk metallic glasses (BMGs) represent an emerging class of materials with an amorphous structure and a unique combination of properties. The objectives of this investigation were to define the electrochemical behavior of a specific Zr-based BMG alloy in a physiologically relevant environment and to compare these properties to standard, crystalline biomaterials as well as other Zr-based BMG compositions. Cyclic-anodic-polarization studies were conducted with a Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10.0}Ti{sub 5.0} (at %) BMG in a phosphate-buffered saline electrolyte with a physiologically relevant oxygen content at 37 C. The results were compared to three common, crystalline biomaterials: CoCrMo, 316L stainless steel,more » and Ti-6Al-4V. The BMG alloy was found to have a lower corrosion penetration rate (CPR), as compared to the 316L stainless steel, and an equivalent CPR, as compared to the CoCrMo and Ti-6Al-4V alloys. Furthermore, the BMG alloy demonstrated better localized corrosion resistance than the 316L stainless steel. However, the localized corrosion resistance of the BMG alloy was not as high as those of the CoCrMo and Ti-6Al-4V alloys in the tested environment. The excellent electrochemical properties demonstrated by the BMG alloy are combined with a low modulus and unparalleled strength. This unique combination of properties dramatically demonstrates the potential for amorphous alloys as a new generation of biomaterials.« less

Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors

NASA Astrophysics Data System (ADS)

Mandon, Julien; Högman, Marieann; Merkus, Peter J. F. M.; van Amsterdam, Jan; Harren, Frans J. M.; Cristescu, Simona M.

2012-01-01

Fractional exhaled nitric oxide (FENO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring FENO. It consists of a quantum cascade laser (QCL) combined with a multi-pass cell and wavelength modulation spectroscopy for the detection of NO at the sub-part-per-billion by volume (ppbv, 1∶10-9) level. The characteristics and diagnostic performance of the sensor were assessed. A detection limit of 0.5 ppbv was demonstrated with a relatively simple design. The QCL-based sensor was compared with two market sensors, a chemiluminescent analyzer (NOA 280, Sievers) and a portable hand-held electrochemical analyzer (MINO®, Aerocrine AB, Sweden). FENO from 20 children diagnosed with asthma and treated with inhaled corticosteroids were measured. Data were found to be clinically acceptable within 1.1 ppbv between the QCL-based sensor and chemiluminescent sensor and within 1.7 ppbv when compared to the electrochemical sensor. The QCL-based sensor was tested on healthy subjects at various expiratory flow rates for both online and offline sampling procedures. The extended NO parameters, i.e. the alveolar region, airway wall, diffusing capacity, and flux were calculated and showed a good agreement with the previously reported values.

Carbon Nanotube Thread Electrochemical Cell: Detection of Heavy Metals.

PubMed

Zhao, Daoli; Siebold, David; Alvarez, Noe T; Shanov, Vesselin N; Heineman, William R

2017-09-19

In this work, all three electrodes in an electrochemical cell were fabricated based on carbon nanotube (CNT) thread. CNT thread partially insulated with a thin polystyrene coating to define the microelectrode area was used as the working electrode; bare CNT thread was used as the auxiliary electrode; and a micro quasi-reference electrode was fabricated by electroplating CNT thread with Ag and then anodizing it in chloride solution to form a layer of AgCl. The Ag|AgCl coated CNT thread electrode provided a stable potential comparable to the conventional liquid-junction type Ag|AgCl reference electrode. The CNT thread auxiliary electrode provided a stable current, which is comparable to a Pt wire auxiliary electrode. This all-CNT thread three electrode cell has been evaluated as a microsensor for the simultaneous determination of trace levels of heavy metal ions by anodic stripping voltammetry (ASV). Hg 2+ , Cu 2+ , and Pb 2+ were used as a representative system for this study. The calculated detection limits (based on the 3σ method) with a 120 s deposition time are 1.05, 0.53, and 0.57 nM for Hg 2+ , Cu 2+ , and Pb 2+ , respectively. These electrodes significantly reduce the dimensions of the conventional three electrode electrochemical cell to the microscale.

Impact of isoelectric points of nanopowders in electrolytes on electrochemical characteristics of dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Mohanty, Shyama Prasad; Bhargava, Parag

2012-11-01

Nanoparticle loaded quasi solid electrolytes are important from the view point of developing electrolytes for dye sensitized solar cells (DSSCs) having long term stability. The present work shows the influence of isoelectric point of nanopowders in electrolyte on the photoelectrochemical characteristics of DSSCs. Electrolytes with nanopowders of silica, alumina and magnesia which have widely differing isoelectric points are used in the study. Adsorption of ions from the electrolyte on the nanopowder surface, characterized by zeta potential measurement, show that cations get adsorbed on silica, alumina surface while anions get adsorbed on magnesia surface. The electrochemical characteristics of nanoparticulate loaded electrolytes are examined through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DSSCs fabricated using liquid, silica or alumina loaded electrolytes exhibit almost similar performance. But interestingly, the magnesia loaded electrolyte-based cell show lower short circuit current density (JSC) and much higher open circuit voltage (VOC), which is attributed to adsorption of anions. Such anionic adsorption prevents the dark reaction in magnesia loaded electrolyte-based cell and thus, enhances the VOC by almost 100 mV as compared to liquid electrolyte based cell. Also, higher electron life time at the titania/electrolyte interface is observed in magnesia loaded electrolyte-based cell as compared to others.

Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors.

PubMed

Mandon, Julien; Högman, Marieann; Merkus, Peter J F M; van Amsterdam, Jan; Harren, Frans J M; Cristescu, Simona M

2012-01-01

Fractional exhaled nitric oxide (F(E)NO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring F(E)NO. It consists of a quantum cascade laser (QCL) combined with a multi-pass cell and wavelength modulation spectroscopy for the detection of NO at the sub-part-per-billion by volume (ppbv, 110(-9)) level. The characteristics and diagnostic performance of the sensor were assessed. A detection limit of 0.5 ppbv was demonstrated with a relatively simple design. The QCL-based sensor was compared with two market sensors, a chemiluminescent analyzer (NOA 280, Sievers) and a portable hand-held electrochemical analyzer (MINO, Aerocrine AB, Sweden). F(E)NO from 20 children diagnosed with asthma and treated with inhaled corticosteroids were measured. Data were found to be clinically acceptable within 1.1 ppbv between the QCL-based sensor and chemiluminescent sensor and within 1.7 ppbv when compared to the electrochemical sensor. The QCL-based sensor was tested on healthy subjects at various expiratory flow rates for both online and offline sampling procedures. The extended NO parameters, i.e. the alveolar region, airway wall, diffusing capacity, and flux were calculated and showed a good agreement with the previously reported values.

Static and Dynamic Measurement of Dopamine Adsorption in Carbon Fiber Microelectrodes Using Electrochemical Impedance Spectroscopy.

PubMed

Rivera-Serrano, Nilka; Pagan, Miraida; Colón-Rodríguez, Joanisse; Fuster, Christian; Vélez, Román; Almodovar-Faria, Jose; Jiménez-Rivera, Carlos; Cunci, Lisandro

2018-02-06

In this study, electrochemical impedance spectroscopy was used for the first time to study the adsorption of dopamine in carbon fiber microelectrodes. In order to show a proof-of-concept, static and dynamic measurements were taken at potentials ranging from -0.4 to 0.8 V versus Ag|AgCl to demonstrate the versatility of this technique to study dopamine without the need of its oxidation. We used electrochemical impedance spectroscopy and single frequency electrochemical impedance to measure different concentrations of dopamine as low as 1 nM. Moreover, the capacitance of the microelectrodes surface was found to decrease due to dopamine adsorption, which is dependent on its concentration. The effect of dissolved oxygen and electrochemical oxidation of the surface in the detection of dopamine was also studied. Nonoxidized and oxidized carbon fiber microelectrodes were prepared and characterized by optical microscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Optimum working parameters of the electrodes, such as frequency and voltage, were obtained for better measurement. Electrochemical impedance of dopamine was determined at different concentration, voltages, and frequencies. Finally, dynamic experiments were conducted using a flow cell and single frequency impedance in order to study continuous and real-time measurements of dopamine.

Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) in chloride medium at boron doped diamond (BDD) and platinum anodes.

PubMed

Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens

2015-02-01

For electrochemical oxidation to become applicable in water treatment outside of laboratories, a number of challenges must be elucidated. One is the formation and fate of degradation intermediates of targeted organics. In this study the degradation of the pesticide residue 2,6-dichlorobenzamide, an important groundwater pollutant, was investigated in a chloride rich solution with the purpose of studying the effect of active chlorine on the degradation pathway. To study the relative importance of the anodic oxidation and active chlorine oxidation in the bulk solution, a non-active BDD and an active Pt anode were compared. Also, the effect of the active chlorine oxidation on the total amount of degradation intermediates was investigated. We found that for 2,6-dichlorobenzamide, active chlorine oxidation was determining for the initial step of the degradation, and therefore yielded a completely different set of degradation intermediates compared to an inert electrolyte. For the Pt anode, the further degradation of the intermediates was also largely dependent on active chlorine oxidation, while for the BDD anode anodic oxidation was most important. It was also found that the presence of active chlorine led to fewer degradation intermediates compared to treatment in an inert electrolyte. Copyright © 2014 Elsevier Ltd. All rights reserved.

Structure, temperature and frequency dependent electrical conductivity of oxidized and reduced electrochemically exfoliated graphite

NASA Astrophysics Data System (ADS)

Radoń, Adrian; Włodarczyk, Patryk; Łukowiec, Dariusz

2018-05-01

The article presents the influence of reduction by hydrogen in statu nascendi and modification by hydrogen peroxide on the structure and electrical conductivity of electrochemically exfoliated graphite. It was confirmed that the electrochemical exfoliation can be used to produce oxidized nanographite with an average number of 25 graphene layers. The modified electrochemical exfoliated graphite and reduced electrochemical exfoliated graphite were characterized by high thermal stability, what was associated with removing of labile oxygen-containing groups. The presence of oxygen-containing groups was confirmed using Fourier-transform infrared spectroscopy. Influence of chemical modification by hydrogen and hydrogen peroxide on the electrical conductivity was determined in wide frequency (0.1 Hz-10 kHz) and temperature range (-50 °C-100 °C). Material modified by hydrogen peroxide (0.29 mS/cm at 0 °C) had the lowest electrical conductivity. This can be associated with oxidation of unstable functional groups and was also confirmed by analysis of Raman spectra. The removal of oxygen-containing functional groups by hydrogen in statu nascendi resulted in a 1000-fold increase in the electrical conductivity compared to the electrochemical exfoliated graphite.

The nanostructure of microbially-reduced graphene oxide fosters thick and highly-performing electrochemically-active biofilms

NASA Astrophysics Data System (ADS)

Virdis, Bernardino; Dennis, Paul G.

2017-07-01

Biofilms of electrochemically-active organisms are used in microbial electrochemical technologies (METs) to catalyze bioreactions otherwise not possible at bare electrodes. At present, however, achievable current outputs are still below levels considered sufficient for economic viability of large-scale METs implementations. Here, we report three-dimensional, self-aggregating biofilm composites comprising of microbial cells embedded with microbially-reduced graphene oxide (rGO) nanoparticles to form a thick macro-porous network with superior electrochemical properties. In the presence of metabolic substrate, these hybrid biofilms are capable of producing up to five times more catalytic current than the control biofilms. Cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy, show that in spite of the increased thickness, the biofilms amended with GO display lower polarization/charge transfer resistance compared to the controls, which we ascribe to the incorporation of rGO into the biofilms, which (1) promotes fast electron transfer, yet conserving a macroporous structure that allows free diffusion of reactants and products, and (2) enhances the interfacial dynamics by allowing a higher load of microbial cells per electrode surface area. These results suggest an easy-to-apply and cost-effective method to produce high-performing electrochemically-active biofilms in situ.

Electrochemical sensor for terbutaline sulfate based on a glassy carbon electrode modified with grapheme and multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Li, Zhou; Hua, Xin; Pei, Hongying; Shen, Yuan; Shen, Guijun

2017-12-01

A glass carbon electrode was prepared that coated with a composite film containing grapheme and multi-walled carbon nanotubes. It was used to study the electrochemical response of terbutaline sulfate. Under the optimized conditions, the oxidation peak current was found to be proportional to its concentration in the range of 0.2-5 μmol·L-1 and 5-40 μmol·L-1).Compared with the bare GC electrode, the GN-MWNTs-modified GC (GN-MWNTs/GC) had many advantages such as relatively high sensitivity, good stability and long life time. The modified electrode was used to determine the TES tablets with satisfactory results.

Electrochemical study of aluminum corrosion in boiling high purity water

NASA Technical Reports Server (NTRS)

Draley, J. E.; Legault, R. A.

1969-01-01

Electrochemical study of aluminum corrosion in boiling high-purity water includes an equation relating current and electrochemical potential derived on the basis of a physical model of the corrosion process. The work involved an examination of the cathodic polarization behavior of 1100 aluminum during aqueous oxidation.

Elucidation of the Biological Redox Chemistry of Purines Using Electrochemical Techniques.

ERIC Educational Resources Information Center

Dryhurst, Glenn; And Others

1983-01-01

Electrochemical studies can give insights into the chemical aspects of enzymatic and in vivo redox reactions of naturally occurring organic compounds. This is illustrated by studies of the electrochemical oxidation of the purinem uric acid. The discussion is limited to information at pH 7 or greater. (JN)

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

DOE PAGES

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.; ...

2018-01-01

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

Using sewage sludge pyrolytic gas to modify titanium alloy to obtain high-performance anodes in bio-electrochemical systems

NASA Astrophysics Data System (ADS)

Gu, Yuan; Ying, Kang; Shen, Dongsheng; Huang, Lijie; Ying, Xianbin; Huang, Haoqian; Cheng, Kun; Chen, Jiazheng; Zhou, Yuyang; Chen, Ting; Feng, Huajun

2017-12-01

Titanium is under consideration as a potential stable bio-anode because of its high conductivity, suitable mechanical properties, and electrochemical inertness in the operating potential window of bio-electrochemical systems; however, its application is limited by its poor electron-transfer capacity with electroactive bacteria and weak ability to form biofilms on its hydrophobic surface. This study reports an effective and low-cost way to convert a hydrophobic titanium alloy surface into a hydrophilic surface that can be used as a bio-electrode with higher electron-transfer rates. Pyrolytic gas of sewage sludge is used to modify the titanium alloy. The current generation, anodic biofilm formation surface, and hydrophobicity are systematically investigated by comparing bare electrodes with three modified electrodes. Maximum current density (15.80 A/m2), achieved using a modified electrode, is 316-fold higher than that of the bare titanium alloy electrode (0.05 A/m2) and that achieved by titanium alloy electrodes modified by other methods (12.70 A/m2). The pyrolytic gas-modified titanium alloy electrode can be used as a high-performance and scalable bio-anode for bio-electrochemical systems because of its high electron-transfer rates, hydrophilic nature, and ability to achieve high current density.

Computer Aided Battery Engineering Consortium

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

Pesaran, Ahmad

A multi-national lab collaborative team was assembled that includes experts from academia and industry to enhance recently developed Computer-Aided Battery Engineering for Electric Drive Vehicles (CAEBAT)-II battery crush modeling tools and to develop microstructure models for electrode design - both computationally efficient. Task 1. The new Multi-Scale Multi-Domain model framework (GH-MSMD) provides 100x to 1,000x computation speed-up in battery electrochemical/thermal simulation while retaining modularity of particles and electrode-, cell-, and pack-level domains. The increased speed enables direct use of the full model in parameter identification. Task 2. Mechanical-electrochemical-thermal (MECT) models for mechanical abuse simulation were simultaneously coupled, enabling simultaneous modelingmore » of electrochemical reactions during the short circuit, when necessary. The interactions between mechanical failure and battery cell performance were studied, and the flexibility of the model for various batteries structures and loading conditions was improved. Model validation is ongoing to compare with test data from Sandia National Laboratories. The ABDT tool was established in ANSYS. Task 3. Microstructural modeling was conducted to enhance next-generation electrode designs. This 3- year project will validate models for a variety of electrodes, complementing Advanced Battery Research programs. Prototype tools have been developed for electrochemical simulation and geometric reconstruction.« less

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

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

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

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.

Electrochemical Study of Polymer and Ceramic-Based Nanocomposite Coatings for Corrosion Protection of Cast Iron Pipeline

PubMed Central

Ammar, Ameen Uddin; Shahid, Muhammad; Ahmed, Muhammad Khitab; Khan, Munawar; Khalid, Amir

2018-01-01

Coating is one of the most effective measures to protect metallic materials from corrosion. Various types of coatings such as metallic, ceramic and polymer coatings have been investigated in a quest to find durable coatings to resist electrochemical decay of metals in industrial applications. Many polymeric composite coatings have proved to be resistant against aggressive environments. Two major applications of ferrous materials are in marine environments and in the oil and gas industry. Knowing the corroding behavior of ferrous-based materials during exposure to these aggressive applications, an effort has been made to protect the material by using polymeric and ceramic-based coatings reinforced with nano materials. Uncoated and coated cast iron pipeline material was investigated during corrosion resistance by employing EIS (electrochemical impedance spectroscopy) and electrochemical DC corrosion testing using the “three electrode system”. Cast iron pipeline samples were coated with Polyvinyl Alcohol/Polyaniline/FLG (Few Layers Graphene) and TiO2/GO (graphene oxide) nanocomposite by dip-coating. The EIS data indicated better capacitance and higher impedance values for coated samples compared with the bare metal, depicting enhanced corrosion resistance against seawater and “produce water” of a crude oil sample from a local oil rig; Tafel scans confirmed a significant decrease in corrosion rate of coated samples. PMID:29495339

Electrochemical Study of Polymer and Ceramic-Based Nanocomposite Coatings for Corrosion Protection of Cast Iron Pipeline.

PubMed

Ammar, Ameen Uddin; Shahid, Muhammad; Ahmed, Muhammad Khitab; Khan, Munawar; Khalid, Amir; Khan, Zulfiqar Ahmad

2018-02-25

Coating is one of the most effective measures to protect metallic materials from corrosion. Various types of coatings such as metallic, ceramic and polymer coatings have been investigated in a quest to find durable coatings to resist electrochemical decay of metals in industrial applications. Many polymeric composite coatings have proved to be resistant against aggressive environments. Two major applications of ferrous materials are in marine environments and in the oil and gas industry. Knowing the corroding behavior of ferrous-based materials during exposure to these aggressive applications, an effort has been made to protect the material by using polymeric and ceramic-based coatings reinforced with nano materials. Uncoated and coated cast iron pipeline material was investigated during corrosion resistance by employing EIS (electrochemical impedance spectroscopy) and electrochemical DC corrosion testing using the "three electrode system". Cast iron pipeline samples were coated with Polyvinyl Alcohol/Polyaniline/FLG (Few Layers Graphene) and TiO₂/GO (graphene oxide) nanocomposite by dip-coating. The EIS data indicated better capacitance and higher impedance values for coated samples compared with the bare metal, depicting enhanced corrosion resistance against seawater and "produce water" of a crude oil sample from a local oil rig; Tafel scans confirmed a significant decrease in corrosion rate of coated samples.

Electrochemical Performance of Ni-MOFs for Supercapacitors

NASA Astrophysics Data System (ADS)

Li, Yujuan; Song, Lili; Han, Yinghui; Wang, Guangyou

2018-03-01

In this work, the Ni-MOFs of electrode material has been synthesized, characterized and studied for the electrochemical properties of electrode materials. The effects of the doping amount of Ni, calcination temperature and time were studied in detail. The results suggested that the electrochemical properties were obviously improved by the Ni-MOFs of electrode material and the best preparation conditions can also improve the electrochemical properties of electrode materials. These results open a way for the design of tailored MOFs as electrode materials for supercapacitors.

Enhanced electrochemical performance of in situ reduced graphene oxide-polyaniline nanotubes hybrid nanocomposites using redox-additive aqueous electrolyte

NASA Astrophysics Data System (ADS)

Devi, Madhabi; Kumar, A.

2018-02-01

Reduced graphene oxide (RGO)-polyaniline nanotubes (PAniNTs) nanocomposites have been synthesized by in situ reduction of GO. The morphology and structure of the nanocomposites are characterized by HRTEM, XRD and micro-Raman spectroscopy. The electrical and electrochemical performances of the nanocomposites are investigated for different RGO concentrations by conductivity measurements, cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy. Highest gravimetric specific capacitance of 448.71 F g-1 is obtained for 40 wt.% of RGO-PAniNTs nanocomposite as compared to 194.92 F g-1 for pure PAniNTs in 1 M KCl electrolyte. To further improve the electrochemical performance of the nanocomposite electrode, KI is used as redox-additive with 1 M KCl electrolyte. Highest gravimetric specific capacitance of 876.43 F g-1 and an improved cyclic stability of 91% as compared to 79% without KI after 5000 cycles is achieved for an optimized 0.1 M KI concentration. This is attributed to the presence of different ionic species of I- ions that give rise to a number of possible redox reactions improving the pseudocapacitance of the electrode. This improved capacitive performance is compared with that of catechol redox-additive in 1 M KCl electrolyte, and that of KI and catechol redox-additives added to 1 M H2SO4 electrolyte.

Electrochemically and Bioelectrochemically Induced Ammonium Recovery

PubMed Central

Gildemyn, Sylvia; Luther, Amanda K.; Andersen, Stephen J.; Desloover, Joachim; Rabaey, Korneel

2015-01-01

Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems. PMID:25651406

Electrochemically and bioelectrochemically induced ammonium recovery.

PubMed

Gildemyn, Sylvia; Luther, Amanda K; Andersen, Stephen J; Desloover, Joachim; Rabaey, Korneel

2015-01-22

Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems.

On the electrochemical deposition of metal–organic frameworks

DOE PAGES

Campagnol, Nicolo; Van Assche, Tom R. C.; Li, Minyuan; ...

2016-02-11

In this paper we study and compare the anodic and cathodic electrodeposition of Metal–Organic Frameworks (MOFs) and suggest guidelines for the electrodeposition of new MOFs with this technique. KHUST-1 was electrodeposited both anodically and cathodically and a four step mechanism is proposed to explain the anodic synthesis.

Creating an Electronic Reference and Information Database for Computer-aided ECM Design

NASA Astrophysics Data System (ADS)

Nekhoroshev, M. V.; Pronichev, N. D.; Smirnov, G. V.

2018-01-01

The paper presents a review on electrochemical shaping. An algorithm has been developed to implement a computer shaping model applicable to pulse electrochemical machining. For that purpose, the characteristics of pulse current occurring in electrochemical machining of aviation materials have been studied. Based on integrating the experimental results and comprehensive electrochemical machining process data modeling, a subsystem for computer-aided design of electrochemical machining for gas turbine engine blades has been developed; the subsystem was implemented in the Teamcenter PLM system.

Chemical splitting of multiwalled carbon nanotubes to enhance electrochemical capacitance for supercapacitors

NASA Astrophysics Data System (ADS)

Li, Xinlu; Li, Tongtao; Zhang, Xinlin; Zhong, Qineng; Li, Hongyi; Huang, Jiamu

2014-06-01

Multiwalled carbon nanotubes (MWCNTs) were chemically split and self-assembled to a flexible porous paper made of graphene oxide nanoribbons (GONRs). The morphology and microstructure of the pristine MWCNTs and GONRs were analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. And the specific surface area and porosity structure were measured by N2 adsorption-desorption. The longitudinally split MWCNTs show an enhancement in specific capacitance from 21 F g-1 to 156 F g-1 compared with the pristine counterpart at 0.1 A g-1 in a 6 M KOH aqueous electrolytes. The electrochemical experiments prove that the chemical splitting of MWCNTs will make inner carbon layers opened and exposed to electrochemical double layers, which can effectively improve the electrochemical capacitance for supercapacitors.

Microstructures and electrochemical behaviors of the friction stir welding dissimilar weld.

PubMed

Shen, Changbin; Zhang, Jiayan; Ge, Jiping

2011-06-01

By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

A New PC and LabVIEW Package Based System for Electrochemical Investigations.

PubMed

Stević, Zoran; Andjelković, Zoran; Antić, Dejan

2008-03-15

The paper describes a new PC and LabVIEW software package based system forelectrochemical research. An overview of well known electrochemical methods, such aspotential measurements, galvanostatic and potentiostatic method, cyclic voltammetry andEIS is given. Electrochemical impedance spectroscopy has been adapted for systemscontaining large capacitances. For signal generation and recording of the response ofinvestigated electrochemical cell, a measurement and control system was developed, basedon a PC P4. The rest of the hardware consists of a commercially available AD-DA converterand an external interface for analog signal processing. The interface is a result of authorsown research. The software platform for desired measurement methods is LabVIEW 8.2package, which is regarded as a high standard in the area of modern virtual instruments. Thedeveloped system was adjusted, tested and compared with commercially available systemand ORCAD simulation.

A new self-assembled layer-by-layer glucose biosensor based on chitosan biopolymer entrapped enzyme with nitrogen doped graphene.

PubMed

Barsan, Madalina M; David, Melinda; Florescu, Monica; Ţugulea, Laura; Brett, Christopher M A

2014-10-01

The layer-by-layer (LbL) technique has been used for the construction of a new enzyme biosensor. Multilayer films containing glucose oxidase, GOx, and nitrogen-doped graphene (NG) dispersed in the biocompatible positively-charged polymer chitosan (chit(+)(NG+GOx)), together with the negatively charged polymer poly(styrene sulfonate), PSS(-), were assembled by alternately immersing a gold electrode substrate in chit(+)(NG+GOx) and PSS(-) solutions. Gravimetric monitoring during LbL assembly by an electrochemical quartz microbalance enabled investigation of the adsorption mechanism and deposited mass for each monolayer. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the LbL modified electrodes, in order to establish the contribution of each monolayer to the overall electrochemical properties of the biosensor. The importance of NG in the biosensor architecture was evaluated by undertaking a comparative study without NG in the chit layer. The GOx biosensor's analytical properties were evaluated by fixed potential chronoamperometry and compared with similar reported biosensors. The biosensor operates at a low potential of -0.2V vs., Ag/AgCl, exhibiting a high sensitivity of 10.5 μA cm(-2) mM(-1), and a detection limit of 64 μM. This study shows a simple approach in developing new biosensor architectures, combining the advantages of nitrogen-doped graphene with the LbL technique for enzyme immobilization. Copyright © 2014 Elsevier B.V. All rights reserved.

Nonlinear dielectric thin films for high-power electric storage with energy density comparable with electrochemical supercapacitors.

PubMed

Yao, Kui; Chen, Shuting; Rahimabady, Mojtaba; Mirshekarloo, Meysam Sharifzadeh; Yu, Shuhui; Tay, Francis Eng Hock; Sritharan, Thirumany; Lu, Li

2011-09-01

Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.

Electrochemical Characterization of a Low Modulus Ti-35.5Nb-7.3Zr-5.7Ta Alloy in a Simulated Body Fluid Using Eis for Biomedical Applications

NASA Astrophysics Data System (ADS)

Bhola, R.; Bhola, S. M.; Mishra, B.; Ayers, R. A.; Olson, D. L.

2011-06-01

Electrochemical characterization of the low modulus Ti-35.5Nb-7.3Zr-5.7Ta beta alloy (TNZT) has been performed in phosphate buffer saline solution at 37 °C using the non destructive electrochemical impedance spectroscopy technique. Measurements were performed at various immersion intervals at the open circuit potential (OCP), which was also monitored with time. Results obtained for TNZT alloy have been compared with those for the commercially used Ti-6Al-4V mixed alloy (Ti64) and the commercially pure titanium (Ti2) alpha alloy. Potentiodynamic polarization was performed to supplement the data obtained from EIS analysis. The TNZT alloy exhibits a two time constant impedance response, whereas the Ti64 and Ti2 alloys display a one time constant behavior. Human fetal osteoblast cells show a better adhesion and a higher cell count for the TNZT alloy compared to the other two alloys. The present investigation is an effort to understand the correlation between the electrochemical, morphological and cellular characteristics of titanium alloys to qualify them for implant applications.

Effect of morphology and defect density on electron transfer of electrochemically reduced graphene oxide

NASA Astrophysics Data System (ADS)

Zhang, Yan; Hao, Huilian; Wang, Linlin

2016-12-01

Electrochemically reduced graphene oxide (ERGO) is widely used to construct electrochemical sensors. Understanding the electron transfer behavior of ERGO is essential for its electrode material applications. In this paper, different morphologies of ERGO were prepared via two different methods. Compared to ERGO/GCEs prepared by electrochemical reduction of pre-deposited GO, more exposed edge planes of ERGO are observed on the surface of ERGO-GCE that was constructed by electrophoretic deposition of GO. The defect densities of ERGO were controlled by tuning the mass or concentration of GO. The electron transfer kinetics (k0) of GCE with different ERGOs was comparatively investigated. Owing to increased surface areas and decreased defect density, the k0 values of ERGO/GCE initially increase and then decrease with incrementing of GO mass. When the morphology and surface real areas of ERGO-GCE are the same, an increased defect density induces an accelerated electron transfer rate. k0 valuesof ERGO-GCEs are about 1 order of magnitude higher than those of ERGO/GCEs due to the difference in the amount of edge planes. This work demonstrates that both defect densities and edge planes of ERGO play crucial roles in electron transfer kinetics.

Insulated InP (100) semiconductor by nano nucleus generation in pure water

NASA Astrophysics Data System (ADS)

Ghorab, Farzaneh; Es'haghi, Zarrin

2018-01-01

Preparation of specified designs on optoelectronic devices such as Light-Emitting Diodes (LEDs) and Laser Diodes (LDs) by using insulated thin films is very important. InP as one of those semiconductors which is used as optoelectronic devices, have two different kinds of charge carriers as n-InP and p-InP in the microelectronic industry. The surface preparation of this kind of semiconductor can be accomplished with individually chemical, mechanical, chemo - mechanical and electrochemical methods. But electrochemical method can be suitably replaced instead of the other methods, like CMP (Chemical Mechanical Polishing), because of the simplicity. In this way, electrochemically formation of insulated thin films by nano nucleus generation on semiconductor (using constant current density of 0.07 mA /cm2) studied in this research. Insulated nano nucleus generation and their growth up to thin film formation on semiconductor single crystal (100), n-InP, inpure water (0.08 µs/cm,25°c) characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Four-point probe and Styloprofilometer techniques. The SEM images show active and passive regions on the n-InP surface and not uniform area on p-InP surface by passing through the passive condition. So the passive regions were nonuniform, and only the active regions were uniform and clean. The various semiconducting behavior in electrochemical condition, studied and compared with structural specification of InP type group (III-V).

Study on the Carbonation Behavior of Cement Mortar by Electrochemical Impedance Spectroscopy

PubMed Central

Dong, Biqin; Qiu, Qiwen; Xiang, Jiaqi; Huang, Canjie; Xing, Feng; Han, Ningxu

2014-01-01

A new electrochemical model has been carefully established to explain the carbonation behavior of cement mortar, and the model has been validated by the experimental results. In fact, it is shown by this study that the electrochemical impedance behavior of mortars varies in the process of carbonation. With the cement/sand ratio reduced, the carbonation rate reveals more remarkable. The carbonation process can be quantitatively accessed by a parameter, which can be obtained by means of the electrochemical impedance spectroscopy (EIS)-based electrochemical model. It has been found that the parameter is a function of carbonation depth and of carbonation time. Thereby, prediction of carbonation depth can be achieved. PMID:28788452

Study on the Carbonation Behavior of Cement Mortar by Electrochemical Impedance Spectroscopy.

PubMed

Dong, Biqin; Qiu, Qiwen; Xiang, Jiaqi; Huang, Canjie; Xing, Feng; Han, Ningxu

2014-01-03

A new electrochemical model has been carefully established to explain the carbonation behavior of cement mortar, and the model has been validated by the experimental results. In fact, it is shown by this study that the electrochemical impedance behavior of mortars varies in the process of carbonation. With the cement/sand ratio reduced, the carbonation rate reveals more remarkable. The carbonation process can be quantitatively accessed by a parameter, which can be obtained by means of the electrochemical impedance spectroscopy (EIS)-based electrochemical model. It has been found that the parameter is a function of carbonation depth and of carbonation time. Thereby, prediction of carbonation depth can be achieved.

Electrochemical reduction of carbon dioxide. Final report

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

LaConti, A.B.; Molter, T.M.; Zagaja, J.A.

1986-05-01

Many researchers have studied the electrochemical reduction of carbon dioxide and related organic species to form concentrated liquid/gaseous products in laboratory-scale hardware. Hamilton Standard has developed a high pressure SPE electrolysis cell capable of reducing carbon dioxide streams to form pure, concentrated alcohols, carboxylic acids, and other hydrocarbons. The process is unique in that the byproducts of reaction include oxygen and, under some test conditions water. In addition, a relatively simple test system was designed and constructed permitting both batch and semibatch type electrochemical reduction studies. In this study, cathode materials were developed which 1) had a characteristic high hydrogenmore » overvoltage, and 2) possessed the intrinsic affinity for electrochemical reduction of the carbon dioxide species. In addition, suitable anode electrocatalyst materials were identified. Studies involving the electrochemical reduction of carbon dioxide required the ability to identify and quantify reaction products obtained during cell evaluation. Gas chromatographic techniques were developed along with the establishment of ion chromatographic methods permitting the analysis of organic reaction products. Hamilton Standard has evaluated electrochemical carbon dioxide reduction cells under a variety of test conditions.« less

A ratiometric strategy -based electrochemical sensing interface for the sensitive and reliable detection of imidacloprid.

PubMed

Li, Xueyan; Kan, Xianwen

2018-04-30

In this study, a ratiometric strategy-based electrochemical sensor was developed by electropolymerization of thionine (THI) and β-cyclodextrin (β-CD) composite films on a glassy carbon electrode surface for imidacloprid (IMI) detection. THI played the role of an inner reference element to provide a built-in correction. In addition, the modified β-CD showed good selective enrichment for IMI to improve the sensitivity and anti-interference ability of the sensor. The current ratio between IMI and THI was calculated as the detected signal for IMI sensing. Compared with common single-signal sensing, the proposed ratiometric strategy showed a higher linear range and a lower limit of detection of 4.0 × 10-8-1.0 × 10-5 mol L-1 and 1.7 × 10-8 mol L-1, respectively, for IMI detection. On the other hand, the ratiometric strategy endowed the sensor with good accuracy, reproducibility, and stability. The sensor was also used for IMI determination in real samples with satisfactory results. The simple, effective, and reliable way reported in this study can be further used to prepare ratiometric strategy-based electrochemical sensors for the selective and sensitive detection of other compounds with good accuracy and stability.

Toxicological characterization of the landfill leachate prior/after chemical and electrochemical treatment: a study on human and plant cells.

PubMed

Garaj-Vrhovac, Vera; Oreščanin, Višnja; Gajski, Goran; Gerić, Marko; Ruk, Damir; Kollar, Robert; Radić Brkanac, Sandra; Cvjetko, Petra

2013-10-01

In this research, toxicological safety of two newly developed methods for the treatment of landfill leachate from the Piškornica (Croatia) sanitary landfill was investigated. Chemical treatment procedure combined chemical precipitation with CaO followed by coagulation with ferric chloride and final adsorption by clinoptilolite. Electrochemical treatment approach included pretreatment with ozone followed by electrooxidation/electrocoagulation and final polishing by microwave irradiation. Cell viability of untreated/treated landfill leachate was examined using fluorescence microscopy. Cytotoxic effect of the original leachate was obtained for both exposure periods (4 and 24 h) while treated samples showed no cytotoxic effect even after prolonged exposure time. The potential DNA damage of the untreated/treated landfill leachate was evaluated by the comet assay and cytokinesis-block micronucleus (CBMN) assay using either human or plant cells. The original leachate exhibited significantly higher comet assay parameters compared to negative control after 24 h exposure. On the contrary, there was no significant difference between negative control and chemically/electrochemically treated leachate for any of the parameters tested. There was also no significant increase in either CBMN assay parameter compared to the negative control following the exposure of the lymphocytes to the chemically or electrochemically treated landfill leachate for both exposure periods while the original sample showed significantly higher number of micronuclei, nucleoplasmic bridges and nuclear buds for both exposure times. Results suggest that both methods are suitable for the treatment of such complex waste effluent due to high removal efficiency of all measured parameters and toxicological safety of the treated effluent. Copyright © 2013 Elsevier Ltd. All rights reserved.

Interesting electrochemical properties of novel three-dimensional Ag3PO4 tetrapods as a new super capacitor electrode material

NASA Astrophysics Data System (ADS)

Li, Shouguang; Teng, Fei; Chen, Mindong; Li, Na; Hua, Xia; Wang, Kai; Li, Min

2014-05-01

The novel three-dimensional (3D) silver phosphate tetrapods (TA) are synthesized and employed as a super capacitor electrode material. The electrochemical properties are investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). It is interesting that compared with irregular silver phosphate particles (IA), TA shows a higher capacitance (250 vs. 160 F g-1), and a higher coulombic efficiency (80% vs. 74%), which is mainly ascribed to the 3D microstructure and its high conductivity. To the best of our knowledge, this is the first report on silver phosphate as a super capacitor material.

Electrochemical Impedance Analysis of β-TITANIUM Alloys as Implants in Ringers Lactate Solution

NASA Astrophysics Data System (ADS)

Bhola, Rahul; Bhola, Shaily M.; Mishra, Brajendra; Olson, David L.

2010-02-01

Commercially pure titanium and two β-titanium alloys, TNZT and TMZF, have been characterized using various electrochemical techniques for their corrosion behavior in Ringers lactate solution. The variation of corrosion potential and solution pH with time has been discussed. Electrochemical Impedance Spectroscopy has been used to fit the results into a circuit model. The stability of the oxides formed on the surface of these alloys has been correlated with impedance phase angles. Cyclic Potentiodynamic Polarization has been used to compute the corrosion parameters for the alloys. TMZF is found to be a better β-alloy as compared to TNZT.

Electrochemical determination of hydroquinone using hydrophobic ionic liquid-type carbon paste electrodes

PubMed Central

2010-01-01

Three types of carbon paste electrodes (CPEs) with different liquid binders were fabricated, and their electrochemical behavior was characterized via a potassium hexacyanoferrate(II) probe. 1-Octyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) as a hydrophobic conductive pasting binder showed better electrochemical performance compared with the commonly employed binder. The IL-contained CPEs demonstrated excellent electroactivity for oxidation of hydroquinone. A diffusion control mechanism was confirmed and the diffusion coefficient (D) of 5.05 × 10-4 cm2 s-1 was obtained. The hydrophobic IL-CPE is promising for the determination of hydroquinone in terms of high sensitivity, easy operation, and good durability. PMID:20977733

Chemical Oxidation of a Redox-Active, Ferrocene-Containing Cationic Lipid: Influence on Interactions with DNA and Characterization in the Context of Cell Transfection

PubMed Central

Aytar, Burcu S.; Muller, John P. E.; Golan, Sharon; Kondo, Yukishige; Talmon, Yeshayahu; Abbott, Nicholas L.; Lynn, David M.

2012-01-01

We report an approach to the chemical oxidation of a ferrocene-containing cationic lipid [bis(11-ferrocenylundecyl)dimethylammonium bromide, BFDMA] that provides redox-based control over the delivery of DNA to cells. We demonstrate that BFDMA can be oxidized rapidly and quantitatively by treatment with Fe(III)sulfate. This chemical approach, while offering practical advantages compared to electrochemical methods used in past studies, was found to yield BFDMA/DNA lipoplexes that behave differently in the context of cell transfection from lipoplexes formed using electrochemically oxidized BFDMA. Specifically, while lipoplexes of the latter do not transfect cells efficiently, lipoplexes of chemically oxidized BFDMA promoted high levels of transgene expression (similar to levels promoted by reduced BFDMA). Characterization by SANS and cryo-TEM revealed lipoplexes of chemically and electrochemically oxidized BFDMA to both have amorphous nanostructures, but these lipoplexes differed significantly in size and zeta potential. Our results suggest that differences in zeta potential arise from the presence of residual Fe2+ and Fe3+ ions in samples of chemically oxidized BFDMA. Addition of the iron chelating agent EDTA to solutions of chemically oxidized BFDMA produced samples functionally similar to electrochemically oxidized BFDMA. These EDTA-treated samples could also be chemically reduced by treatment with ascorbic acid to produce samples of reduced BFDMA that do promote transfection. Our results demonstrate that entirely chemical approaches to oxidation and reduction can be used to achieve redox-based ‘on/off’ control of cell transfection similar to that achieved using electrochemical methods. PMID:22980739

Immunosensor based on electrodeposition of gold-nanoparticles and ionic liquid composite for detection of Salmonella pullorum.

PubMed

Wang, Dan; Dou, Wenchao; Zhao, Guangying; Chen, Yan

2014-11-01

In order to increase the reproducibility and stability of electrochemical immunosensor, which is a key issue for its application and popularization, an accurate and stable immunosensor for rapid detection of Salmonella pullorum (S. pullorum) was proposed in this study. The immunosensor was fabricated by modifying Screen-printed Carbon Electrode (SPCE) with electrodeposited gold nanoparticles (AuNPs), HRP-labeled anti-S. pullorum and ionic liquids (ILs) (AuNP/HRP/IL). AuNPs are electrodeposited on the working electrode surface to increase the amount of antibodies that bind to the electrode and then modified with ILs to protect the antibodies from being inactivated in the test environment and maintain their biological activity and the stability of the detection electrode. The electrochemical characteristics of the stepwise modified electrodes and the detection of S. pullorum were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As shown in the results of the experiments, AuNPs with unique electrochemical properties as well as biocompatibility characteristics have been proven to be able to strengthen the antibody combination effectively and to increase the electrochemical response signal. In addition, a crucial assessment regarding implementation of stability and reproducibility analysis of a range of immunosensors is provided. We found that application of AuNPs/ILs in the immune modified electrodes showed obvious improvement when compared with other groups. Given their high levels of reproducibility, stability, target specificity and sensitivity, AuNPs and ILs were considered to be excellent elements for electrode modification. Copyright © 2014 Elsevier B.V. All rights reserved.

Integration of thermocouple microelectrode in the scanning electrochemical microscope at variable temperatures: simultaneous temperature and electrochemical imaging and its kinetic studies.

PubMed

Pan, He; Zhang, Hailing; Lai, Junhui; Gu, Xiaoxin; Sun, Jianjun; Tang, Jing; Jin, Tao

2017-03-24

We describe herein a method for the simultaneous measurement of temperature and electrochemical signal with a new type of thermocouple microelectrode. The thermocouple microelectrode can be used not only as a thermometer but also as a scanning electrochemical microscope (SECM) tip in the reaction between tip-generated bromine and a heated Cu sample. The influence of temperature on the SECM imaging process and the related kinetic parameters have been studied, such as kinetic constant and activation energy.

Integration of thermocouple microelectrode in the scanning electrochemical microscope at variable temperatures: simultaneous temperature and electrochemical imaging and its kinetic studies

PubMed Central

Pan, He; Zhang, Hailing; Lai, Junhui; Gu, Xiaoxin; Sun, Jianjun; Tang, Jing; Jin, Tao

2017-01-01

We describe herein a method for the simultaneous measurement of temperature and electrochemical signal with a new type of thermocouple microelectrode. The thermocouple microelectrode can be used not only as a thermometer but also as a scanning electrochemical microscope (SECM) tip in the reaction between tip-generated bromine and a heated Cu sample. The influence of temperature on the SECM imaging process and the related kinetic parameters have been studied, such as kinetic constant and activation energy. PMID:28338002

Poly(3,4-ethylenedioxythiophene)/reduced graphene oxide composites as counter electrodes for high efficiency dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Ma, Jinfu; Yuan, Shenghua; Yang, Shaolin; Lu, Hui; Li, Yingtao

2018-05-01

A facile, low cost, easy-controllable method to prepare Poly(3,4-ethylenedioxythiophene) (PEDOT)/reduced graphene oxide (rGO) composites by electrochemical deposition onto fluorinated tin oxide (FTO) as counter electrodes (CEs) in high performance dye-sensitized solar cells (DSSCs) is reported. The electro-deposition process was accomplished by electro-polymerization of graphene oxide (GO)/PEDOT composites onto FTO substrates followed by electrochemical reduction of the GO component. Electrochemical measurements show that the I-/I3- catalytic activity of the as-prepared PEDOT/rGO CE is improved compared with that of the pure PEDOT and PEDOT/GO electrode. Through the analysis of photoelectric properties, the performance of the electrodes fabricated with different polymerization times are compared, and the optimal preparation condition is determined. The photoelectric conversion efficiency (PCE) of the DSSC assembled with PEDOT/rGO electrode reaches 7.79%, close to 8.33% of the cell with Platinum (Pt) electrode, and increases by 13.2% compared with 6.88% of the device with the PEDOT electrode.

A new electrocatalyst and its application method for vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Wei, Guanjie; Jing, Minghua; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

2015-08-01

The edge plane in carbon structure has good electrocatalytic activity toward vanadium redox reaction. To apply it in vanadium redox flow battery (VRFB) practically, the graphite nanopowders (GNPs) containing amounts of edge planes are used as electrocatalyst and embedded in the electrospun carbon nanofibers (ECNFs) by different mass ratios to make composite electrodes. The morphology and electrochemical activity of the GNPs and the composite electrodes containing them are characterized. Compared with the pristine ECNFs, the composite electrodes show much higher electrochemical activity. With the increase of GNPs content in composite electrodes, the electrochemical reversibility of the vanadium redox couples also increases. It proves the addition of GNPs can surely improve the electrochemical activity of ECNFs. Among the composite electrodes, the ECNFs containing 30 nm GNP by mass ratio of 1:50 show the best electrochemical activity, largest active surface area and excellent stability. Due to the high performance of GNP/ECNFs composite electrode and its relatively low cost preparation process, the GNPs are expected to be used as electrocatalyst in VRFB on a large scale to improve the cell performance.

Reduced Graphene Oxides: Influence of the Reduction Method on the Electrocatalytic Effect towards Nucleic Acid Oxidation

PubMed Central

Báez, Daniela F.; Pardo, Helena; Laborda, Ignacio; Marco, José F.; Yáñez, Claudia; Bollo, Soledad

2017-01-01

For the first time a critical analysis of the influence that four different graphene oxide reduction methods have on the electrochemical properties of the resulting reduced graphene oxides (RGOs) is reported. Starting from the same graphene oxide, chemical (CRGO), hydrothermal (hTRGO), electrochemical (ERGO), and thermal (TRGO) reduced graphene oxide were produced. The materials were fully characterized and the topography and electroactivity of the resulting glassy carbon modified electrodes were also evaluated. An oligonucleotide molecule was used as a model of DNA electrochemical biosensing. The results allow for the conclusion that TRGO produced the RGOs with the best electrochemical performance for oligonucleotide electroanalysis. A clear shift in the guanine oxidation peak potential to lower values (~0.100 V) and an almost two-fold increase in the current intensity were observed compared with the other RGOs. The electrocatalytic effect has a multifactorial explanation because the TRGO was the material that presented a higher polydispersity and lower sheet size, thus exposing a larger quantity of defects to the electrode surface, which produces larger physical and electrochemical areas. PMID:28677654

Construction of self-supported porous TiO2/NiO core/shell nanorod arrays for electrochemical capacitor application

NASA Astrophysics Data System (ADS)

Wu, J. B.; Guo, R. Q.; Huang, X. H.; Lin, Y.

2013-12-01

High-quality metal oxides hetero-structured nanoarrays have been receiving great attention in electrochemical energy storage application. Self-supported TiO2/NiO core/shell nanorod arrays are prepared on carbon cloth via the combination of hydrothermal synthesis and electro-deposition methods. The obtained core/shell nanorods consist of nanorod core and interconnected nanoflake shell, as well as hierarchical porosity. As cathode materials for pseudo-capacitors, the TiO2/NiO core/shell nanorod arrays display impressive electrochemical performances with both high capacitance of 611 F g-1 at 2 A g-1, and pretty good cycling stability with a retention of 89% after 5000 cycles. Besides, as compared to the single NiO nanoflake arrays on carbon cloth, the TiO2/NiO core/shell nanorod arrays exhibit much better electrochemical properties with higher capacitance, better electrochemical activity and cycling life. This enhanced performance is mainly due to the core/shell nanorods architecture offering fast ion/electron transfer and sufficient contact between active materials and electrolyte.

Binder-free carbon nanotube electrode for electrochemical removal of chromium.

PubMed

Wang, Haitao; Na, Chongzheng

2014-11-26

Electrochemical treatment of chromium-containing wastewater has the advantage of simultaneously reducing hexavalent chromium (CrVI) and reversibly adsorbing the trivalent product (CrIII), thereby minimizing the generation of waste for disposal and providing an opportunity for resource reuse. The application of electrochemical treatment of chromium is often limited by the available electrochemical surface area (ESA) of conventional electrodes with flat surfaces. Here, we report the preparation and evaluation of carbon nanotube (CNT) electrodes consisting of vertically aligned CNT arrays directly grown on stainless steel mesh (SSM). We show that the 3-D organization of CNT arrays increases ESA up to 13 times compared to SSM. The increase of ESA is correlated with the length of CNTs, consistent with a mechanism of roughness-induced ESA enhancement. The increase of ESA directly benefits CrVI reduction by proportionally accelerating reduction without compromising the electrode's ability to adsorb CrIII. Our results suggest that the rational design of electrodes with hierarchical structures represents a feasible approach to improve the performance of electrochemical treatment of contaminated water.

A review on various electrochemical techniques for heavy metal ions detection with different sensing platforms.

PubMed

Bansod, BabanKumar; Kumar, Tejinder; Thakur, Ritula; Rana, Shakshi; Singh, Inderbir

2017-08-15

Heavy metal ions are non-biodegradable and contaminate most of the natural resources occurring in the environment including water. Some of the heavy metals including Lead (Pb), Mercury (Hg), Arsenic (As), Chromium (Cr) and Cadmium (Cd) are considered to be highly toxic and hazardous to human health even at trace levels. This leads to the requirement of fast, accurate and reliable techniques for the detection of heavy metal ions. This review presents various electrochemical detection techniques for heavy metal ions those are user friendly, low cost, provides on-site and real time monitoring as compared to other spectroscopic and optical techniques. The categorization of different electrochemical techniques is done on the basis of different types of detection signals generated due to presence of heavy metal ions in the solution matrix like current, potential, conductivity, electrochemical impedance, and electrochemiluminescence. Also, the recent trends in electrochemical detection of heavy metal ions with various types of sensing platforms including metals, metal films, metal oxides, nanomaterials, carbon nano tubes, polymers, microspheres and biomaterials have been evoked. Copyright © 2017 Elsevier B.V. All rights reserved.

Regulation of the discharge reservoir of negative electrodes in Ni-MH batteries by using Ni(OH) x (x = 2.10) and γ-CoOOH

NASA Astrophysics Data System (ADS)

Shangguan, Enbo; Chang, Zhaorong; Tang, Hongwei; Yuan, Xiao-Zi; Wang, Haijiang

In this paper, a novel strategy to regulate the discharge reservoir of negative electrodes in Ni-MH batteries is introduced by using Ni(OH) x (x = 2.10) and γ-CoOOH. The electrochemical measurements of these batteries demonstrate that the use of Ni(OH) x (x = 2.10) and γ-CoOOH can not only successfully regulate the discharge reservoir of negative electrodes in Ni-MH batteries to an adequate quantity, but also effectively improve the electrochemical performance of the batteries. Compared with normal batteries, the in-house prepared batteries with a lower discharge reservoir exhibit an enhanced discharge capacity, improved high-rate discharge ability, higher discharge potential plateau and superior cycle stability. The effect of Ni(OH) x (x = 2.10) and γ-CoOOH on the electrochemical performance of nickel electrode is also investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results suggest that the new method is simple and effective for cost reduction of Ni-MH batteries with improved electrochemical performance.

Detection of Hepatitis C core antibody by dual-affinity yeast chimera and smartphone-based electrochemical sensing.

PubMed

Aronoff-Spencer, Eliah; Venkatesh, A G; Sun, Alex; Brickner, Howard; Looney, David; Hall, Drew A

2016-12-15

Yeast cell lines were genetically engineered to display Hepatitis C virus (HCV) core antigen linked to gold binding peptide (GBP) as a dual-affinity biobrick chimera. These multifunctional yeast cells adhere to the gold sensor surface while simultaneously acting as a "renewable" capture reagent for anti-HCV core antibody. This streamlined functionalization and detection strategy removes the need for traditional purification and immobilization techniques. With this biobrick construct, both optical and electrochemical immunoassays were developed. The optical immunoassays demonstrated detection of anti-HCV core antibody down to 12.3pM concentrations while the electrochemical assay demonstrated higher binding constants and dynamic range. The electrochemical format and a custom, low-cost smartphone-based potentiostat ($20 USD) yielded comparable results to assays performed on a state-of-the-art electrochemical workstation. We propose this combination of synthetic biology and scalable, point-of-care sensing has potential to provide low-cost, cutting edge diagnostic capability for many pathogens in a variety of settings. Copyright © 2016 Elsevier B.V. All rights reserved.

Colonization of Bacteria on the Surfaces of Cold-Sprayed Copper Coatings Alters Their Electrochemical Behaviors

NASA Astrophysics Data System (ADS)

Suo, Xinkun; Abdoli, Leila; Liu, Yi; Xia, Peng; Yang, Guanjun; Li, Hua

2017-04-01

Copper coatings were fabricated on stainless steel plates by cold spraying. Attachment and colonization of Bacillus sp. on their surfaces in artificial seawater were characterized, and their effects on anticorrosion performances of the coatings were examined. Attached bacteria were observed using field emission scanning electron microscopy. Electrochemical behaviors including potentiodynamic polarization and electrochemical impedance spectroscopy with/without bacterial attachment were evaluated using commercial electrochemical analysis station Modulab. Results show that Bacillus sp. opt to settle on low-lying spots of the coating surfaces in early stage, followed by recruitment and attachment of extracellular polymeric substances (EPS) secreted through metabolism of Bacillus sp. The bacteria survive with the protection of EPS. An attachment model is proposed to illustrate the bacterial behaviors on the surfaces of the coatings. Electrochemical data show that current density under Bacillus sp. environment decreases compared to that without the bacteria. Charge-transfer resistance increases markedly in bacteria-containing seawater, suggesting that corrosion resistance increases and corrosion rate decreases. The influencing mechanism of bacteria settlement on corrosion resistance of the cold-sprayed copper coatings was discussed and elucidated.

Corrosion Behavior of Stainless Steels in Neutral and Acidified Sodium Chloride Solutions by Electrochemical Impedance Spectroscopy

NASA Technical Reports Server (NTRS)

Calle, L. M.; Kolady, M. R.; Vinje, R. D.

2004-01-01

The objective of this work was to evaluate the corrosion performance of three alloys by Electrochemical Impedance Spectroscopy (EIS) and to compare the results with those obtained during a two-year atmospheric exposure study.' Three alloys: AL6XN (UNS N08367), 254SM0 (UNS S32154), and 304L (UNS S30403) were included in the study. 304L was included as a control. The alloys were tested in three electrolyte solutions which consisted of neutral 3.55% NaC1, 3.55% NaC1 in 0.lN HC1, and 3.55% NaC1 in 1.ON HC1. These conditions were expected to be less severe, similar, and more severe respectively than the conditions at NASA's Kennedy Space Center launch pads.

Electrochemical Polishing Applications and EIS of a Novel Choline Chloride-Based Ionic Liquid

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

Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.

2013-06-01

Minimal surface roughness is a critical feature for high-field superconducting radio frequency (SRF) cavities used to engineer particle accelerators. Current methods for polishing Niobium cavities typically utilize solutions containing a mixture of concentrated sulfuric and hydrofluoric acid. Polishing processes such as these are effective, yet there are many hazards and costs associated with the use (and safe disposal) of the concentrated acid solutions. An alternative method for electrochemical polishing of the cavities was explored using a novel ionic liquid solution containing choline chloride. Potentiostatic electrochemical impedance spectroscopy (EIS) was used to analyze the ionic polishing solution. Final surface roughness ofmore » the Nb was found to be comparable to that of the acid-polishing method, as assessed by atomic force microscopy (AFM). This indicates that ionic liquid-based electrochemical polishing of Nb is a viable replacement for acid-based methods for preparation of SRF cavities.« less

Electrochemical Detection in Stacked Paper Networks.

PubMed

Liu, Xiyuan; Lillehoj, Peter B

2015-08-01

Paper-based electrochemical biosensors are a promising technology that enables rapid, quantitative measurements on an inexpensive platform. However, the control of liquids in paper networks is generally limited to a single sample delivery step. Here, we propose a simple method to automate the loading and delivery of liquid samples to sensing electrodes on paper networks by stacking multiple layers of paper. Using these stacked paper devices (SPDs), we demonstrate a unique strategy to fully immerse planar electrodes by aqueous liquids via capillary flow. Amperometric measurements of xanthine oxidase revealed that electrochemical sensors on four-layer SPDs generated detection signals up to 75% higher compared with those on single-layer paper devices. Furthermore, measurements could be performed with minimal user involvement and completed within 30 min. Due to its simplicity, enhanced automation, and capability for quantitative measurements, stacked paper electrochemical biosensors can be useful tools for point-of-care testing in resource-limited settings. © 2015 Society for Laboratory Automation and Screening.

Binder-induced surface structure evolution effects on Li-ion battery performance

NASA Astrophysics Data System (ADS)

Rezvani, S. J.; Pasqualini, M.; Witkowska, A.; Gunnella, R.; Birrozzi, A.; Minicucci, M.; Rajantie, H.; Copley, M.; Nobili, F.; Di Cicco, A.

2018-03-01

A comparative investigation on binder induced chemical and morphological evolution of Li4Ti5O12 electrodes was performed via X-ray photoemission spectroscopy, scanning electron microscopy, and electrochemical measurements. Composite electrodes were obtained using three different binders (PAA, PVdF, and CMC) with 80:10:10 ratio of active material:carbon:binder. The electrochemical performances of the electrodes, were found to be intimately correlated with the evolution of the microstructure of the electrodes, probed by XPS and SEM analysis. Our analysis shows that the surface chemistry, thickness of the passivation layers and the morphology of the electrodes are strongly dependent on the type of binders that significantly influence the electrochemical properties of the electrodes. These results point to a key role played by binders in optimization of the battery performance and improve our understanding of the previously observed and unexplained electrochemical properties of these electrodes.

The edge- and basal-plane-specific electrochemistry of a single-layer graphene sheet

PubMed Central

Yuan, Wenjing; Zhou, Yu; Li, Yingru; Li, Chun; Peng, Hailin; Zhang, Jin; Liu, Zhongfan; Dai, Liming; Shi, Gaoquan

2013-01-01

Graphene has a unique atom-thick two-dimensional structure and excellent properties, making it attractive for a variety of electrochemical applications, including electrosynthesis, electrochemical sensors or electrocatalysis, and energy conversion and storage. However, the electrochemistry of single-layer graphene has not yet been well understood, possibly due to the technical difficulties in handling individual graphene sheet. Here, we report the electrochemical behavior at single-layer graphene-based electrodes, comparing the basal plane of graphene to its edge. The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane. A convergent diffusion effect was observed at the sub-nanometer thick graphene edge-electrode to accelerate the electrochemical reactions. Coupling with the high conductivity of a high-quality graphene basal plane, graphene edge is an ideal electrode for electrocatalysis and for the storage of capacitive charges. PMID:23896697

Electrochemical comparison of nickel and nickel hydroxide nanoparticles composited with reduced graphene oxide and polyaniline for their supercapacitor application

NASA Astrophysics Data System (ADS)

Viswanthan, Aranganathan; Shetty, Adka Nityananda

2018-04-01

The reduced graphene oxide/polyaniline/Ni(OH)2 (GP-Ni(OH)2) and reduced graphene oxide/polyaniline/Ni (GP-Ni) nanocomposites were synthesized by facile in situ single step chemical method. The constituents were confirmed by powder-XRD, and the electrochemical characterizations were carried out using cyclic voltammetry(CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The electrochemical contribution of Ni(OH)2 and Ni to their supercapacitance along with reduced graphene oxide and polyaniline was compared. The GP-Ni nanocomposite exhibited a specific capacitance of 266.66 F g-1, energy density of 53.33 W h kg-1 and power density of 1385 W kg-1 at a current density of 0.25 A g-1 and the results were enhanced to 21% and more promising than that of nanocomposite GP-Ni(OH)2.

Novel nanoarchitectures for electrochemical biosensing

NASA Astrophysics Data System (ADS)

Archibald, Michelle M.

Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point-of-care (POC) technologies. Current methods, while sensitive, do not adequately allow for POC applications due to several limitations, including complex instrumentation, high reagent consumption, and cost. We have investigated two novel nanoarchitectures, the nanocoax and the nanodendrite, as electrochemical biosensors towards the POC detection of infectious disease biomarkers to overcome these limitations. The nanocoax architecture is composed of vertically-oriented, nanoscale coaxial electrodes, with coax cores and shields serving as integrated working and counter electrodes, respectively. The dendritic structure consists of metallic nanocrystals extending from the working electrode, increasing sensor surface area. Nanocoaxial- and nanodendritic-based electrochemical sensors were fabricated and developed for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). Both nanoarchitectures exhibited levels of sensitivity that are comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, these electrochemical nanosensors provide a simple electrochemical readout and a miniaturized platform with multiplexing capabilities toward POC implementation. Further development as suggested in this thesis may lead to increases in sensitivity, enhancing the attractiveness of the architectures for future POC devices.

Solar Thermo-coupled Electrochemical Oxidation of Aniline in Wastewater for the Complete Mineralization Beyond an Anodic Passivation Film.

PubMed

Yuan, Dandan; Tian, Lei; Li, Zhida; Jiang, Hong; Yan, Chao; Dong, Jing; Wu, Hongjun; Wang, Baohui

2018-02-15

Herein, we report the solar thermal electrochemical process (STEP) aniline oxidation in wastewater for totally solving the two key obstacles of the huge energy consumption and passivation film in the electrochemical treatment. The process, fully driven by solar energy without input of any other energies, sustainably serves as an efficient thermoelectrochemical oxidation of aniline by the control of the thermochemical and electrochemical coordination. The thermocoupled electrochemical oxidation of aniline achieved a fast rate and high efficiency for the full minimization of aniline to CO 2 with the stability of the electrode and without formation of polyaniline (PAN) passivation film. A clear mechanism of aniline oxidation indicated a switching of the reactive pathway by the STEP process. Due to the coupling of solar thermochemistry and electrochemistry, the electrochemical current remained stable, significantly improving the oxidation efficiency and mineralization rate by apparently decreasing the electrolytic potential when applied with high temperature. The oxidation rate of aniline and chemical oxygen demand (COD) removal rate could be lifted up to 2.03 and 2.47 times magnification compared to conventional electrolysis, respectively. We demonstrate that solar-driven STEP processes are capable of completely mineralizing aniline with high utilization of solar energy. STEP aniline oxidation can be utilized as a green, sustainable water treatment.

Preparation and characterizations of activated carbon monolith from rubber wood and its effect on supercapacitor performances

NASA Astrophysics Data System (ADS)

Taer, E.; Taslim, R.; Deraman, M.

2016-02-01

Preparation of activated carbon monolith (ACM) from rubber wood was investigated. Two kind of preparation method were carried out by pre-carbonized of rubber wood saw dust and rubber wood material as it is naturally. The samples were prepared with pelletizing method and small cutting of rubber wood in cross sectional method. Both of samples were characterized by physical and electrochemical technique. The physical properties such as morphology and porosity were investigated. The electrochemical properties of both samples such as equivalent series resistances (ESR) and specific capacitances were also compared. In conclusion, this study showed that both of different preparation method would propose a simple method of ACM electrode preparation technique for supercapacitor applications.

Ultrasonic modification of carbon materials for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Rachiy, Bogdan I.; Nykoliuk, Marian O.; Budzulyak, Ivan M.; Kachmar, Andrii I.

2017-01-01

The paper is devoted to study the ultrasonic impact on the biomass of natural raw materials, which were used for the creation a nanoporous carbon material (NCM), which was used as electrode material for electrochemical capacitors (EC). The dry shells of apricot seeds were a feedstock, which were modified by the chemical treatment in the phosphoric acid and part of them were impacted by ultrasonic waves for 25 minutes. The NCM, which were obtained by carbonization at 550 °C, were modified by chemical treatment in the nitric acid. Thus, the different of modification NCM was obtained to compare their capacitance characteristics for EC. From experimental data we can do a conclusion, that ultrasonic modification and chemical treatment in nitric acidare improvecapacitance characteristics of NCM for EC.

PILOT SCALE REACTOR FOR ELECTROCHEMICAL DECHLORINATION OF MODEL CHLORINATED CONTAMINANTS

EPA Science Inventory

Electrochemical degradation (ECD) is a promising technology for in-situ remediation of diversely contaminated submarine matrices, by the application of low level DC electric fields. This study, prompted by successful bench-scale electrochemical dechlorination of Trichloroe...

Characterization of Copper Corrosion Products in Drinking Water by Combining Electrochemical and Surface Analyses

EPA Science Inventory

This study focuses on the application of electrochemical approaches to drinking water copper corrosion problems. Applying electrochemical approaches combined with copper solubility measurements, and solid surface analysis approaches were discussed. Tafel extrapolation and Electro...

Characterization of Copper Corrosion Products Formed in Drinking Water by Combining Electrochemical and Surface Analyses

EPA Science Inventory

This study focuses on the application of electrochemical approaches to drinking water copper corrosion problems. Applying electrochemical approaches combined with copper solubility measurements, and solid surface analysis approaches were discussed. Tafel extrapolation and Electro...

Electrochemistry at Nanometer-Scaled Electrodes

ERIC Educational Resources Information Center

Watkins, John J.; Bo Zhang; White, Henry S.

2005-01-01

Electrochemical studies using nanometer-scaled electrodes are leading to better insights into electrochemical kinetics, interfacial structure, and chemical analysis. Various methods of preparing electrodes of nanometer dimensions are discussed and a few examples of their behavior and applications in relatively simple electrochemical experiments…

Sm@C2v(3)-C80: site-hopping motion of endohedral Sm atom and metal-induced effect on redox profile

NASA Astrophysics Data System (ADS)

Xu, Wei; Niu, Ben; Shi, Zujin; Lian, Yongfu; Feng, Lai

2012-10-01

A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles. CCDC reference number 894168. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr32193a

Cost and size estimates for an electrochemical bulk energy storage concept

NASA Technical Reports Server (NTRS)

Warshay, M.; Wright, L. O.

1975-01-01

Preliminary capital cost and size estimates were made for a titanium trichloride, titanium tetrachloride, ferric chloride, ferrous chloride redox-flow-cell electric power system. On the basis of these preliminary estimates plus other important considerations, this electrochemical system emerged as having great promise as a bulk energy storage system for power load leveling. The size of this system is less than two per cent of that of a comparable pumped hydroelectric plant. The estimated capital cost of a 10 MW, 60- and 85-MWh redox-flow system compared well with that of competing systems.

Electrolysis Performance Improvement Concept Study (EPICS) flight experiment phase C/D

NASA Technical Reports Server (NTRS)

Schubert, F. H.; Lee, M. G.

1995-01-01

The overall purpose of the Electrolysis Performance Improvement Concept Study flight experiment is to demonstrate and validate in a microgravity environment the Static Feed Electrolyzer concept as well as investigate the effect of microgravity on water electrolysis performance. The scope of the experiment includes variations in microstructural characteristics of electrodes and current densities in a static feed electrolysis cell configuration. The results of the flight experiment will be used to improve efficiency of the static feed electrolysis process and other electrochemical regenerative life support processes by reducing power and expanding the operational range. Specific technologies that will benefit include water electrolysis for propulsion, energy storage, life support, extravehicular activity, in-space manufacturing and in-space science in addition to other electrochemical regenerative life support technologies such as electrochemical carbon dioxide and oxygen separation, electrochemical oxygen compression and water vapor electrolysis. The Electrolysis Performance Improvement Concept Study flight experiment design incorporates two primary hardware assemblies: the Mechanical/Electrochemical Assembly and the Control/Monitor Instrumentation. The Mechanical/Electrochemical Assembly contains three separate integrated electrolysis cells along with supporting pressure and temperature control components. The Control/Monitor Instrumentation controls the operation of the experiment via the Mechanical/Electrochemical Assembly components and provides for monitoring and control of critical parameters and storage of experimental data.

Study of lipid peroxidation and ascorbic acid protective role in large unilamellar vesicles from a new electrochemical performance.

PubMed

Barroso, M Fátima; Luna, M Alejandra; Moyano, Fernando; Delerue-Matos, Cristina; Correa, N Mariano; Molina, Patricia G

2018-04-01

In this contribution an electrochemical study is described for the first time of lipid peroxidation and the role of antioxidant on lipid protection using large unilamellar vesicles (LUVs). In order to simulate the cell membrane, LUVs composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were used. A vesicle-modified electrode was constructed by immobilizing DOPC LUVs onto carbon paste electrodes (CPEs). Lipid peroxidation was studied electrochemically by incubating the vesicle-modified electrodes with hydroxyl (HO) radicals generated via the Fenton reaction. Oxidative damage induced by HO was verified by using square wave voltammetry (SWV) and was indirectly measured by the increase of electrochemical peak current to [Fe(CN) 6 ] 4- which was used as the electrochemical label. Ascorbic acid (AA) was used as the antioxidant model in order to study its efficacy on free radical scavenging. The decrease of the electrochemical signal confirms the protective key role promoted by AA in the prevention of lipid peroxidation in vesicles. Through microscopy, it was possible to observe morphologic modification on vesicle structures after lipid peroxidation in the presence or absence of AA. Copyright © 2017 Elsevier B.V. All rights reserved.

Microelectrode array fabrication for electrochemical detection with carbon nanotubes

NASA Astrophysics Data System (ADS)

Clark, James

Understanding how the brain works remains one of the key challenges for scientists. To further this understanding a wide variety of technologies and research methods have been developed. One such technology is conductive electrodes, used to measure the electrical signals elicited from neuronal cells and tissues. These electrodes can be fabricated as a singular electrode or as a multi-electrode array (MEA). This permits bio-electrical measurements from one particular area or simultaneous measurements from multiple areas, respectively. Studying electrical and chemical signals of individual cells in situ requires the use of electrodes with ≤20 µm diameter. However, electrodes of this size generally produce high impedance, perturbing recording of the small signals generated from individual cells. Nanomaterials, such as carbon nanotubes (CNTs), can be deposited to increase the real surface area of these electrodes, producing higher sensitivity measurements. This thesis investigates the potential for using photo-thermal chemical vapour deposition grown CNTs as the electrode material for a de novo fabricated MEA. This device aimed to measure electrochemical signals in the form of dopamine, an important mammalian neurotransmitter, as well as conventional bio-electrical signals that the device is designed for. Realising this aim began with improving CNT aqueous wetting behaviour via oxygen plasma functionalisation. This procedure demonstrated grafting of oxygen functional groups to the CNT structure, and dramatic improvements in aqueous wetting behaviour, with CNTs attached to the device. Subsequently, oxygen plasma functionalised CNT-based MEAs were fabricated and tested, allowing comparisons with a non-functionalised CNT MEA and a state-of-the-art commercial MEA. The functionalised CNT MEA demonstrated an order of magnitude improvement compared to commercial MEAs (2.75 kΩ vs. 25.6 kΩ), at the biologically relevant frequency of 1 kHz. This was followed by measurement of one of the best sensitivity density values, compared to the available literature, for the electrochemical detection of dopamine (9.48 µA µM-1 mm-2). The functionalised CNT MEA then illustrated some selectivity compared to common interferents, i.e. ascorbic acid, of a higher concentration. Nonetheless, imaging of the MEA revealed CNTs were being removed from the electrode areas due to extensive use. Therefore, the final results chapter aimed to develop a novel fabrication route for CNT-based MEAs that produced improved CNT retention on the electrodes. This next-generation functionalised CNT-based MEA displayed improved CNT retention, whilst also producing competitive electrochemical impedance values at 1 kHz (17.8 kΩ) and excellent electrochemical selectivity for dopamine vs. ascorbic acid. Overall, this thesis demonstrates the potential for using MEAs as electrochemical detectors of biological molecules, specifically when using functionalised CNTs as the electrode material.

Electrochemical decolorization of dye wastewater by surface-activated boron-doped nanocrystalline diamond electrode.

PubMed

Chen, Chienhung; Nurhayati, Ervin; Juang, Yaju; Huang, Chihpin

2016-07-01

Complex organics contained in dye wastewater are difficult to degrade and often require electrochemical advanced oxidation processes (EAOPs) to treat it. Surface activation of the electrode used in such treatment is an important factor determining the success of the process. The performance of boron-doped nanocrystalline diamond (BD-NCD) film electrode for decolorization of Acid Yellow (AY-36) azo dye with respect to the surface activation by electrochemical polarization was studied. Anodic polarization found to be more suitable as electrode pretreatment compared to cathodic one. After anodic polarization, the originally H-terminated surface of BD-NCD was changed into O-terminated, making it more hydrophilic. Due to the oxidation of surface functional groups and some portion of sp(2) carbon in the BD-NCD film during anodic polarization, the electrode was successfully being activated showing lower background current, wider potential window and considerably less surface activity compared to the non-polarized one. Consequently, electrooxidation (EO) capability of the anodically-polarized BD-NCD to degrade AY-36 dye was significantly enhanced, capable of nearly total decolorization and chemical oxygen demand (COD) removal even after several times of re-using. The BD-NCD film electrode favored acidic condition for the dye degradation; and the presence of chloride ion in the solution was found to be more advantageous than sulfate active species. Copyright © 2016. Published by Elsevier B.V.

Towards an Electrochemical Immunosensor System with Temperature Control for Cytokine Detection.

PubMed

Metzner, Julia; Luckert, Katrin; Lemuth, Karin; Hämmerle, Martin; Moos, Ralf

2018-04-24

The cytokine interleukin-13 (IL-13) plays a major role in airway inflammation and is a target of new anti-asthmatic drugs. Hence, IL-13 determination could be interesting in assessing therapy success. Thus, in this work an electrochemical immunosensor for IL-13 was developed and integrated into a fluidic system with temperature control for read-out. Therefore, two sets of results are presented. First, the sensor was set up in sandwich format on single-walled carbon nanotube electrodes and was read out by applying the hydrogen peroxide⁻hydroquinone⁻horseradish peroxidase (HRP) system. Second, a fluidic system was built up with an integrated heating function realized by Peltier elements that allowed a temperature-controlled read-out of the immunosensor in order to study the influence of temperature on the amperometric read-out. The sensor was characterized at the temperature optimum of HRP at 30 °C and at 12 °C as a reference for lower performance. These results were compared to a measurement without temperature control. At the optimum operation temperature of 30 °C, the highest sensitivity (slope) was obtained compared to lower temperatures and a limit of detection of 5.4 ng/mL of IL-13 was calculated. Taken together, this approach is a first step towards an automated electrochemical immunosensor platform and shows the potential of a temperature-controlled read-out.

A Study of the Mechanism of the Hydrogen Evolution Reaction on Nickel by Surface Interrogation Scanning Electrochemical Microscopy.

PubMed

Liang, Zhenxing; Ahn, Hyun S; Bard, Allen J

2017-04-05

The hydrogen evolution reaction (HER) on Ni in alkaline media was investigated by scanning electrochemical microscopy under two operating modes. First, the substrate generation/tip collection mode was employed to extract the "true" cathodic current associated with the HER from the total current in the polarization curve. Compared to metallic Ni, the electrocatalytic activity of the HER is improved in the presence of the low-valence-state oxide of Ni. This result is in agreement with a previous claim that the dissociative adsorption of water can be enhanced at the Ni/Ni oxide interface. Second, the surface-interrogation scanning electrochemical microscopy (SI-SECM) mode was used to directly measure the coverage of the adsorbed hydrogen on Ni at given potentials. Simulation indicates that the hydrogen coverage follows a Frumkin isotherm with respect to the applied potential. On the basis of the combined analysis of the Tafel slope and surface hydrogen coverage, the rate-determining step is suggested to be the adsorption of hydrogen (Volmer step) in the investigated potential window.

Electrochemical Study of Hydrocarbon-Derived Electrolytes for Supercapacitors

NASA Astrophysics Data System (ADS)

Noorden, Zulkarnain A.; Matsumoto, Satoshi

2013-10-01

In this paper, we evaluate the essential electrochemical properties - capacitive and resistive behaviors - of hydrocarbon-derived electrolytes for supercapacitor application using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrolytes were systematically prepared from three hydrocarbon-derived compounds, which have different molecular structures and functional groups, by treatment with high-concentration sulfuric acid (H2SO4) at room temperature. Two-electrode cells were assembled by sandwiching an electrolyte-containing glass wool separator with two active electrodes of activated carbon sheets. The dc electrical properties of the tested cells in terms of their capacitive behavior were investigated by CV, and in order to observe the frequency characteristics of the constructed cells, EIS was carried out. Compared with the tested cell with only high-concentration H2SO4 as the electrolyte, the cell with the derived electrolytes exhibit a capacitance as high as 135 F/g with an improved overall internal resistance of 2.5 Ω. Through the use of a simple preparation method and low-cost precursors, hydrocarbon-derived electrolytes could potentially find large-scale and higher-rating supercapacitor applications.

Development of electrochemical based sandwich enzyme linked immunosensor for Cryptosporidium parvum detection in drinking water.

PubMed

Thiruppathiraja, Chinnasamy; Saroja, Veerappan; Kamatchiammal, Senthilkumar; Adaikkappan, Periyakaruppan; Alagar, Muthukaruppan

2011-10-01

Cryptosporidium parvum is one of the most important biological contaminants in drinking water and generates significant risks to public health. Due to low infectious dose of C. parvum, remarkably sensitive detection methods are required for water and food industry analysis. This present study describes a simple, sensitive, enzyme amplified sandwich form of an electrochemical immunosensor using dual labeled gold nanoparticles (alkaline phosphatase and anti-oocysts monoclonal antibody) in indium tin oxide (ITO) as an electrode to detect C. parvum. The biosensor was fabricated by immobilizing the anti-oocysts McAb on a gold nanoparticle functionalized ITO electrode, followed by the corresponding capture of analytes and dual labeled gold nanoparticle probe to detect the C. parvum target. The outcome shows the sensitivity of electrochemical immune sensor enhanced by gold nanoparticles with a limit of detection of 3 oocysts/mL in a minimal processing period. Our results demonstrated the sensitivity of the new approach compared to the customary method and the immunosensors showed acceptable precision, reproducibility, stability, and could be readily applied to multi analyte determination for environmental monitoring.

Sensing Properties of Multiwalled Carbon Nanotubes Grown in MW Plasma Torch: Electronic and Electrochemical Behavior, Gas Sensing, Field Emission, IR Absorption

PubMed Central

Majzlíková, Petra; Sedláček, Jiří; Prášek, Jan; Pekárek, Jan; Svatoš, Vojtěch; Bannov, Alexander G.; Jašek, Ondřej; Synek, Petr; Eliáš, Marek; Zajíčková, Lenka; Hubálek, Jaromír

2015-01-01

Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 μm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‐modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures. PMID:25629702

Substituent Inductive Effects on the Electrochemical Oxidation of Flavonoids Studied by Square Wave Voltammetry and Ab Initio Calculations.

PubMed

Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo

2016-10-27

Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.

Short communication: simultaneous analysis of reducing sugars and 5-hydroxymethyl-2-furaldehyde at a low concentration by high performance anion exchange chromatography with electrochemical detector, compared with HPLC with refractive index detector.

PubMed

Guan, Y-G; Yu, P; Yu, S-J; Xu, X-B; Wu, X-L

2012-11-01

A simultaneous analysis of reducing sugars and 5-hydroxymethyl-2-furaldehyde of the Maillard reaction products was detailed. It was based on a high performance anion exchange chromatography with electrochemical detector system and an HPLC with refractive index detector. Results showed that high performance anion exchange chromatography with electrochemical detector using a CarboPac PA-1 column (Dionex Corp., Sunnyvale, CA) was more suitable for reducing sugars and 5-hydroxymethyl-2-furaldehyde determination, especially for trace analysis. The lowest detectable limit of reducing sugars and 5-hydroxymethyl-2-furaldehyde was 0.00005 mol/L in this experiment. However, HPLC with a refractive index detector always produces a tailing peak for 5-hydroxymethyl-2-furaldehyde, and mannose and fructose cannot be absolutely separated. The results of the present study could provide a more sensitive means for 5-hydroxymethyl-2-furaldehyde and reducing sugar detection. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Lipoxygenase-modified Ru-bpy/graphene oxide: Electrochemical biosensor for on-farm monitoring of non-esterified fatty acid.

PubMed

Veerapandian, Murugan; Hunter, Robert; Neethirajan, Suresh

2016-04-15

Elevated concentrations of non-esterified fatty acids (NEFA) in biological fluids are recognized as critical biomarkers for early diagnosis of dairy cow metabolic diseases. Herein, a cost-effective, electrochemically active, and bio-friendly sensor element based on ruthenium bipyridyl complex-modified graphene oxide nanosheets ([Ru(bpy)3](2+)-GO) is proposed as a biosensor platform for NEFA detection. Electrochemical analysis demonstrates that the [Ru(bpy)3](2+)-GO electrodes exhibit superior and durable redox properties compared to the pristine carbon and GO electrodes. Target specificity is accomplished through immobilization of the enzyme, lipoxygenase, which catalyzes the production of redox active species from NEFA. Lipoxygenases retain their catalytic ability upon immobilization and exhibit changes to amperometric signals upon interaction with various concentrations of standard NEFA and serum samples. Our study demonstrates that the [Ru(bpy)3](2+)-GO electrode has the potential to serve as a biosensor platform for developing a field deployable, rapid, and user-friendly detection tool for on-farm monitoring of dairy cow metabolic diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

Characteristics of Zinc Phosphate Coating Activated by Different Concentrations of Nickel Acetate Solution

NASA Astrophysics Data System (ADS)

Abdalla, Khalid; Zuhailawati, H.; Rahmat, Azmi; Azizan, A.

2017-02-01

Activation pretreatment with nickel acetate solution at various concentrations was performed prior to the phosphating step to enhance the corrosion resistance of carbon steel substrates. The activation solution was studied over various concentrations: 10, 50, and 100 g/L. The effects of these concentrations on surface characteristics and microstructural evolution of the coated samples were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The electrochemical behavior was evaluated using potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion test in a 3.5 pct NaCl solution. Significant increases in the nucleation sites and surface coverage of zinc phosphate coating were observed as the concentration of activation solution reached 50 g/L. The electrochemical analysis revealed that the activation treatment with 50 g/L nickel acetate solution significantly improved the protection ability of the zinc phosphate coating. The corrosion current density of activated phosphate coating with 50 g/L was reduced by 64.64 and 13.22 pct, compared to the coatings obtained with activation solutions of 10 and 100 g/L, respectively.

Electrochemical Migration Behavior of Copper-Clad Laminate and Electroless Nickel/Immersion Gold Printed Circuit Boards under Thin Electrolyte Layers

PubMed Central

Yi, Pan; Xiao, Kui; Ding, Kangkang; Dong, Chaofang; Li, Xiaogang

2017-01-01

The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed. PMID:28772497

Determining the inertial states of low Prandtl number fluids using electrochemical cells

NASA Astrophysics Data System (ADS)

Crunkleton, Daniel Wray

The quality of crystals grown from the melt is often deteriorated by the presence of buoyancy-induced convection, produced by temperature or concentration inhomogenities. It is, therefore, important to develop techniques to visualize such flows. In this study, a novel technique is developed that uses solid-state electrochemical cells to establish and measure dissolved oxygen boundary conditions. To visualize convection, a packet of oxygen is electrochemically introduced at a specific location in the melt. As the fluid convects, this oxygen packet follows the flow, acting as a tracer. Electrochemical sensors located along the enclosure then detect the oxygen as it passes. Over sufficiently long times, oxygen diffusion is important; consequently, the oxygen diffusivity in the fluid is measured. This diffusivity is determined using both transient and steady state experiments with tin and tin-lead alloys as model fluids. It is concluded that the presence of convection due to solutal gradients and/or tilt increases the measured diffusivity by one-half to one order of magnitude. The oxygen diffusivity in tin-lead alloys is measured and the results show that the alloy diffusivities are lower than those of the corresponding pure metals. This concentration functionality is explained with a multicomponent diffusion model and shows good agreement. Rayleigh-Benard convection was used to validate the electrochemical approach to flow visualization. Thus, a numerical characterization of the second critical Rayleigh numbers in liquid tin was conducted for a variety of Cartesian aspect ratios. The extremely low Prandtl number of tin represents the lowest value studied numerically. Additionally, flow field oscillations are visualized and the effect of tilt on convecting systems is quantified. Finally, experimental studies of the effect of convection in liquid tin are presented. Three geometries are studied: (1) double cell with vertical concentration gradients; (2) double cell with horizontal concentration gradients; and (3) multiple cell with vertical temperature gradients. The first critical Rayleigh number transition is detected with geometry (1) and it is concluded that current measurements are not as affected by convection as EMF measurements. The system is compared with numerical simulations in geometry (2), and oscillating convection is detected with geometry (3).

MnO2 prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery.

PubMed

Feng, Lili; Xuan, Zhewen; Zhao, Hongbo; Bai, Yang; Guo, Junming; Su, Chang-Wei; Chen, Xiaokai

2014-01-01

Two α-MnO2 crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO2 prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO2 crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO2 crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO2 material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO2 material has better electrochemical performance.

Mechanisms for sodium insertion in carbon materials

NASA Astrophysics Data System (ADS)

Stevens, David Andrew

2000-12-01

This thesis details the mechanisms for sodium insertion into different carbons using both electrochemical and vapour techniques. Room temperature electrochemical measurements were completed to examine the insertion and removal of sodium from soft (graphitizable) and nanoporous hard (non-graphitizable) carbons prepared by the heat treatment of organic precursors to a range of temperatures. The mechanisms identified from these studies were further investigated through a series of in situ x-ray scattering studies on operating electrochemical cells. The results obtained were then compared with x-ray scattering measurements on carbons after exposure to sodium vapour at 890C. This work is primarily driven by the aluminium industry's need to understand how sodium insertion causes carbon cathode blocks in aluminium reduction cells to swell. The results obtained are also of relevance to the lithium-ion battery field as they help to verify mechanisms proposed in the literature for lithium insertion into carbon hosts. Some carbons were also identified that could accommodate large amounts of sodium, making them attractive candidates for anodes in rechargeable sodium ion batteries. For soft carbons, the results showed that both sodium and lithium insert between approximately parallel carbon layers along the sloping voltage region of the electrochemical curves, increasing the average interlayer spacing. The sodium and lithium capacities decreased with increasing carbon heat treatment temperature. For the soft carbons studied, the sodium capacity was found to be consistently lower than the lithium capacity, implying that some lithium-accessible sites were unavailable for sodium insertion. The electrochemical profiles for the hard carbons also contained capacity along a sloping voltage region and, as with the soft carbons, this was shown to result from the insertion of sodium and lithium between approximately parallel carbon layers. In contrast to the soft carbons, however, the electrochemical profiles for the hard carbons also exhibited significant capacity along low voltage plateaus at chemical potentials close to the chemical potential of the metal. An in situ small angle x-ray scattering experimental method was therefore developed to examine changes in scattering from the nanopores during sodium and lithium insertion/removal. The results from this technique clearly showed that the low voltage plateau capacity resulted from the insertion of sodium and lithium into nanopores in the carbon.

Subcellular mechanism of Escherichia coli inactivation during electrochemical disinfection with boron-doped diamond anode: A comparative study of three electrolytes.

PubMed

Long, Yujiao; Ni, Jinren; Wang, Zuhui

2015-11-01

Although the identification of effective oxidant species has been extensively studied, yet the subcellular mechanism of bacterial inactivation has never been clearly elucidated in electrochemical disinfection processes. In this study, subcellular mechanism of Escherichia coli inactivation during electrochemical disinfection was revealed in terms of comprehensive factors such as cell morphology, total organic components, K(+) leakage, membrane permeability, lipid peroxidation, membrane potential, membrane proteins, intracellular enzyme, cellular ATP level and DNA. The electrolysis was conducted with boron-doped diamond anode in three electrolytes including chloride, sulfate and phosphate. Results demonstrated that cell inactivation was mainly attributed to damage to the intracellular enzymatic systems in chloride solution. In sulfate solution, certain essential membrane proteins like the K(+) ion transport systems were eliminated. Thus, the pronounced K(+) leakage from cytosol resulted in gradual collapse of the membrane potential, which would hinder the subcellular localization of cell division-related proteins as well as ATP synthesis and thereby lead to the bacterial inactivation. Remarkable lipid peroxidation was observed, while the intracellular damage was negligible. In phosphate solution, the cells sequentially underwent overall destruction as a whole cell with no captured intermediate state, during which the organic components of the cells were mostly subjected to mineralization. This study provided a thorough insight into the bacterial inactivation mechanism on the subcellular level. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrophoretic nanotechnology of graphene-carbon nanotube and graphene-polypyrrole nanofiber composites for electrochemical supercapacitors.

PubMed

Shi, Kaiyuan; Zhitomirsky, Igor

2013-10-01

Thin films of multiwalled carbon nanotubes (MWCNT), graphene and polypyrrole (PPy) nanofibers were prepared by cathodic electrophoretic deposition (EPD) from aqueous suspensions, containing safranin (SAF) as a new dispersant. The results of Fourier transform infrared spectroscopy, UV-Vis spectroscopy studies and sedimentation tests, coupled with deposition yield and electron microscopy data showed that SAF adsorbed on MWCNT, graphene and PPy, provided their dispersion and charging in the suspensions and allowed efficient EPD. The deposition yield can be controlled by the variation of SAF concentration in the suspensions and deposition time. The use of SAF as a co-dispersant for MWCNT, graphene and PPy, allowed controlled EPD of composite graphene-MWCNT and graphene-PPy films. The proposed approach for the deposition of PPy paves the way for EPD of neutral polymers using organic dyes as dispersing and charging agents. The composite films were investigated for application in electrochemical supercapacitors (ES). The graphene-MWCNT and graphene-PPy films showed significant increase in capacitance, decrease in resistance and increase in capacitance retention at high charge-discharge rates compared to the films of individual components. The analysis of electrochemical testing results and electron microscopy data provided an insight into the influence of composite microstructure on electrochemical performance. The composites, prepared by EPD are promising materials for electrodes of ES. Copyright © 2013 Elsevier Inc. All rights reserved.

Improvement in low-temperature and instantaneous high-rate output performance of Al-free AB5-type hydrogen storage alloy for negative electrode in Ni/MH battery: Effect of thermodynamic and kinetic regulation via partial Mn substituting

NASA Astrophysics Data System (ADS)

Zhou, Wanhai; Zhu, Ding; Tang, Zhengyao; Wu, Chaoling; Huang, Liwu; Ma, Zhewen; Chen, Yungui

2017-03-01

A series of Al-free Mn-modified AB5-type hydrogen storage alloys have been designed and the effects of thermodynamic stability and electrochemical kinetics on electrochemical performance via Mn substituting have been investigated. Compared with high-Al alloys, the Al-free alloys in this study have better low-temperature performance and instantaneous high-rate output because of the higher surface catalytic ability. After partial substitution of Ni by Mn, both the hydrogen desorption capacity and plateau pressure decrease, and correspondingly results in an improved thermodynamic stability which is adverse to low-temperature delivery. Additionally, with the improvement of charge acceptance ability and anti-corrosion property via Mn substitution, the room-temperature discharge capacity and cycling stability increase slightly. However, Mn adversely affects the electrochemical kinetics and deteriorates both the surface catalytic ability and the bulk hydrogen diffusion ability, leading to the drop of low-temperature dischargeability, high-rate dischargeability and peak power (Ppeak). Based on the thermodynamic and kinetic regulation and overall electrochemical properties, the optimal composition is obtained when x = 0.2, the discharge capacity is 243.6 mAh g-1 at -40 °C with 60 mA g-1, and the Ppeak attains to 969.6 W kg-1 at -40 °C.

Highly sensitive detection of cancer cells with an electrochemical cytosensor based on boronic acid functional polythiophene.

PubMed

Dervisevic, Muamer; Senel, Mehmet; Sagir, Tugba; Isik, Sevim

2017-04-15

The detection of cancer cells through important molecular recognition target such as sialic acid is significant for the clinical diagnosis and treatment. There are many electrochemical cytosensors developed for cancer cells detection but most of them have complicated fabrication processes which results in poor reproducibility and reliability. In this study, a simple, low-cost, and highly sensitive electrochemical cytosensor was designed based on boronic acid-functionalized polythiophene. In cytosensors fabrication simple single-step procedure was used which includes coating pencil graphite electrode (PGE) by means of electro-polymerization of 3-Thienyl boronic acid and Thiophen. Electrochemical impedance spectroscopy and cyclic voltammetry were used as an analytical methods to optimize and measure analytical performances of PGE/P(TBA 0.5 Th 0.5 ) based electrode. Cytosensor showed extremely good analytical performances in detection of cancer cells with linear rage of 1×10 1 to 1×10 6 cellsmL -1 exhibiting low detection limit of 10 cellsmL -1 and incubation time of 10min. Next to excellent analytical performances, it showed high selectivity towards AGS cancer cells when compared to HEK 293 normal cells and bone marrow mesenchymal stem cells (BM-hMSCs). This method is promising for future applications in early stage cancer diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Flat Graphene-Enhanced Electron Transfer Involved in Redox Reactions.

PubMed

Pan, Meilan; Zhang, Yanyang; Shan, Chao; Zhang, Xiaolin; Gao, Guandao; Pan, Bingcai

2017-08-01

Graphene is easily warped in the out-of-plane direction because of its high in-plane Young's modulus, and exploring the influence of wrinkled graphene on its properties is essential for the design of graphene-based materials for environmental applications. Herein, we prepared wrinkled graphene (WGN-1 and WGN-2) by thermal treatment and compared their electrochemical properties with those of flat graphene nanosheets (FGN). FGN exhibit activities that are much better than those of wrinkled graphene nanosheets (WGN), not only in the electrochemical oxidation of methylene blue (MB) but also in the electrochemical reduction of nitrobenzene (NB). Transformation ratios of MB and NB in FGN, WGN-1, and WGN-2 were 97.5, 80.1, and 57.9% and 94.6, 92.1, and 81.2%, respectively. Electrochemical impedance spectroscopy and the surface resistance of the graphene samples increased in the following order: FGN < WGN-1 < WGN-2. This suggests that the reaction charges transfer faster across the reaction interfaces and along the surface of FGN than that of WGN, and wrinkles restrict reaction charge transfer and reduce the reaction rates. This study reveals that the morphology of the graphene (flat or wrinkle) greatly affects redox reaction activities and may have important implications for the design of novel graphene-based nanostructures and for our understanding of graphene wrinkle-dependent redox reactions in environmental processes.

Corrosion barriers processed by Al electroplating and their resistance against flowing Pb-15.7Li

NASA Astrophysics Data System (ADS)

Krauss, Wolfgang; Konys, Jürgen; Wulf, Sven-Erik

2014-12-01

In the HCLL blanket design, ferritic-martensitic steels are in direct contact with the flowing liquid breeder Pb-15.7Li and have to withstand severe corrosion attack. Beyond corrosion, T-permeation from the breeder into the RAFM-steels is also an important issue and has to be reduced significantly. Earlier work showed that Al-based coatings can act as barriers for both, however, applied processes e.g. HDA or VPS exhibited strong drawbacks in the past. Meanwhile new industrial relevant coating processes, using electroplating technology are under development and called ECA (electrochemical aluminization) and ECX (electrochemical deposition from ionic liquids) process. In this study electrochemically Al-coated and heat-treated Eurofer samples were tested in PICOLO loop for exposure times up to 12,000 h (ECA) and 2000 h (first results ECX) respectively to determine corrosion properties in flowing Pb-15.7Li (550 °C, 0.1 m/s). Cross section analysis afterward corrosion testing proved the ability of thin Al-based barriers made by electrochemical techniques to protect the bare Eurofer from corrosion attack even at exposure times of 12,000 h. Determined radial corrosion rates lay between 10 and 20 μm/a. First results for ECX coated samples (2000 h) revealed more homogeneous corrosion behavior of the barrier layer itself compared to ECA.

Synthesis and characterization of manganese diselenide nanoparticles (MnSeNPs): Determination of capsaicin by using MnSeNP-modified glassy carbon electrode.

PubMed

Sukanya, Ramaraj; Sakthivel, Mani; Chen, Shen-Ming; Chen, Tse-Wei; Al-Hemaid, Fahad M A; Ajmal Ali, M; Elshikh, Mohamed Soliman

2018-06-02

A new type of manganese diselenide nanoparticles (MnSeNPs) was synthesized by using a hydrothermal method. Their surface morphology, crystallinity and elemental distribution were characterized by using transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy which scrutinize the formation of the NPs. The NPs were coated on a glassy carbon electrode (GCE), and electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were applied to study the electroanalytical properties towards the oxidation of the food additive capsaicin. The modified GCE displays lower charge transfer resistance (R ct  = 29.52 Ω), a larger active surface area (0.089 cm 2 /g, and more efficient electrochemical oxidation of capsaicin compared to a MnS 2 /GCE and a bare GCE. The oxidation peak potential is 0.43 V (vs. Ag/AgCl) which is lower than that of previously reported GCEs. The sensor has a detection limit as low as 0.05 μM and an electrochemical sensitivity of 2.41 μA μM -1  cm -2 . The method was applied to the determination of capsaicin in pepper samples. Graphical abstract Electrochemical determination of capsaicin in pepper extract by using MnSeNPs modified electrode.

Electrochemical sensing platform based on the highly ordered mesoporous carbon-fullerene system.

PubMed

Zhou, Ming; Guo, Jidong; Guo, Li-ping; Bai, Jing

2008-06-15

In this paper, we report a novel all-carbon two-dimensionally ordered nanocomposite electrode system on the basis of the consideration of host-guest chemistry, which utilizes synergistic interactions between a nanostructured matrix of ordered mesoporous carbon (OMC) and an excellent electron acceptor of nanosized fullerene (C 60) to facilitate heterogeneous electron-transfer processes. The integration of OMC-C 60 by covalent interaction, especially its electrochemical applications for electrocatalysis, has not been explored thus far. Such integration may even appear to be counterintuitive because OMC and C 60 provide opposite electrochemical benefits in terms of facilitating heterogeneous electron-transfer processes. Nevertheless, the present work demonstrates the integration of OMC and C 60 can provide a remarkable synergistic augmentation of the current. To illuminate the concept, eight kinds of inorganic and organic electroactive compounds were employed to study the electrochemical response at an OMC-C 60 modified glassy carbon (OMC-C 60/GC) electrode for the first time, which shows more favorable electron-transfer kinetics than OMC/GC, carbon nanotube modified GC, C 60/GC, and GC electrodes. Such electrocatalytic behavior at OMC-C 60/GC electrode could be attributed to the unique physicochemical properties of OMC and C 60, especially the unusual host-guest synergy of OMC-C 60, which induced a substantial decrease in the overvoltage for NADH oxidation compared with GC electrode. The ability of OMC-C 60 to promote electron transfer not only suggests a new platform for the development of dehydrogenase-based bioelectrochemical devices but also indicates a potential of OMC-C 60 to be of a wide range of sensing applications because the electrocatalysis of different electroactive compounds at the OMC-C 60/GC electrode in this work should be a good model for constructing a novel and promising electrochemical sensing platform for further electrochemical detection of other biomolecules.

Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst

NASA Astrophysics Data System (ADS)

Nouralishahi, Amideddin; Rashidi, Ali Morad; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Choolaei, Mohammadmehdi

2015-04-01

The electro-catalytic behavior of Pt-CoOx/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH4 as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoOx, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of COads on Pt active sites by the participation of CoOx. Compared to Pt/MWCNTs, Pt-CoOx/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoOx/MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups controls the total rate of MOR process.

Electrochemical CO2 and O2 separation for crew and plant environments

NASA Technical Reports Server (NTRS)

Lee, M. G.; Grigger, David J.; Foerg, Sandra L.

1992-01-01

The study describes a closed ecosystem concept that includes electrochemical CO2 and O2 separators and a moisture condenser/separator for maintaining CO2, O2, and humidity levels in the crew and plant habitats at their respective optimal conditions. The key processes of this concept are aqueous electrolyte-based electrochemical CO2 and O2 separations. The principles and cell characteristics of these electrochemical gas separation processes are described. Also presented are descriptions of test hardware and the test results of the Electrochemical CO2 Separator (ECS) and the Electrochemical O2 Separator (EOS), and the combination of the ECS and the EOS. The test results proved that the ECS and EOS processes for the combined concept are viable.

Catalytic activity of platinum on ruthenium electrodes with modified (electro)chemical states.

PubMed

Park, Kyung-Won; Sung, Yung-Eun

2005-07-21

Using Pt on Ru thin-film electrodes with various (electro)chemical states designed by the sputtering method, the effect of Ru states on the catalytic activity of Pt was investigated. The chemical and electrochemical properties of Pt/Ru thin-film samples were confirmed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In addition, Pt nanoparticles on Ru metal or oxide for an actual fuel cell system showed an effect of Ru states on the catalytic activity of Pt in methanol electrooxidation. Finally, it was concluded that such an enhancement of methanol electrooxidation on the Pt is responsible for Ru metallic and/or oxidation sites compared to pure Pt without any Ru state.

Electrochemical behavior of adrenaline at the carbon atom wire modified electrode

NASA Astrophysics Data System (ADS)

Xue, Kuan-Hong; Liu, Jia-Mei; Wei, Ri-Bing; Chen, Shao-Peng

2006-09-01

Electrochemical behavior of adrenaline at an electrode modified by carbon atom wires (CAWs), a new material, was investigated by cyclic voltammetry combined with UV-vis spectrometry, and forced convection method. As to the electrochemical response of redox of adrenaline/adrenalinequinone couple in 0.50 M H 2SO 4, at a nitric acid treated CAW modified electrode, the anodic and cathodic peak potentials Epa and Epc shifted by 87 mV negatively and 139 mV in the positive direction, respectively, and standard heterogeneous rate constant k0 increased by 16 times compared to the corresponding bare electrode, indicating the extraordinary activity of CAWs in electrocatalysis for the process.

3D printed graphene-based electrodes with high electrochemical performance

NASA Astrophysics Data System (ADS)

Vernardou, D.; Vasilopoulos, K. C.; Kenanakis, G.

2017-10-01

Three-dimensional (3D) printed graphene pyramids were fabricated through a dual-extrusion FDM-type 3D printer using a commercially available PLA-based conductive graphene. Compared with flat printed graphene, a substantial enhancement in the electrochemical performance was clearly observed for the case of 3D printed graphene pyramids with 5.0 mm height. Additionally, the charge transfer of Li+ across the graphene pyramids/electrolyte interface was easier enhancing its performance presenting a specific discharge capacity of 265 mAh g-1 with retention of 93% after 1000 cycles. The importance of thickness control towards the printing of an electrode with good stability and effective electrochemical behavior is highlighted.

Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries

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

Weinrich, Henning; Come, Jérémy; Tempel, Hermann

Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topographymore » changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here in this paper, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.« less

Modeling the hydrodynamic and electrochemical efficiency of semi-solid flow batteries

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

Brunini, VE; Chiang, YM; Carter, WC

2012-05-01

A mathematical model of flow cell operation incorporating hydrodynamic and electrochemical effects in three dimensions is developed. The model and resulting simulations apply to recently demonstrated high energy-density semi-solid flow cells. In particular, state of charge gradients that develop during low flow rate operation and their effects on the spatial non-uniformity of current density within flow cells are quantified. A one-dimensional scaling model is also developed and compared to the full three-dimensional simulation. The models are used to demonstrate the impact of the choice of electrochemical couple on flow cell performance. For semi-solid flow electrodes, which can use solid activemore » materials with a wide variety of voltage-capacity responses, we find that cell efficiency is maximized for electrochemical couples that have a relatively flat voltage vs. capacity curve, operated under slow flow conditions. For example, in flow electrodes limited by macroscopic charge transport, an LiFePO4-based system requires one-third the polarization to reach the same cycling rate as an LiCoO2-based system, all else being equal. Our conclusions are generally applicable to high energy density flow battery systems, in which flow rates can be comparatively low for a given required power. (C) 2012 Elsevier Ltd. All rights reserved.« less

Relation Between Crystal Structure and Electrochemical Performance of LiNi1/3Zn x Co1/3-xMn1/3O₂ (0.000 ≤ x ≤ 0.133).

PubMed

Wang, Xujun; Wan, Yong; Wang, Ruiqi; Xu, Xiantang; Wang, He; Chang, Mingning; Yuan, Feng; Ge, Xiaohui; Shao, Weiquan; Xu, Sheng

2018-04-01

LiNi1/3ZnxCo1/3-xMn1/3O2 (0.000 ≤ x ≤ 0.133) hollow microspheres are synthesized using MnO2 hollow microspheres both as a self-template and Mn source. These hollow microspheres, ~4 μm in diameter, are composed of approximately 300 nm basic nanoparticles. The XRD patterns of LiNi1/3ZnxCo1/3-xMn1/3O2 were analyzed by the RIETAN-FP program, and the obtained samples have a layered α-NaFeO2 structure. Electrochemical performances of the samples were carried out between 2.5 V and 4.5 V. The behavior of the lattice parameters is consistent with Cycling performance and rate performance change with increase of x. Compared with the others, the sample of x = 0.133 exhibits a relatively superior electrochemical performance. The specific capacity of x = 0.133 was increased by 10.7% than no-doped. In addition, the cyclic voltammograms curves of the second cycle show no significant alteration compared with the first cycle and the electrochemical impedance of zinc doping sample showed smaller transfer resistance than the no-doping sample.

Comparing the Properties of Electrochemical-Based DNA Sensors Employing Different Redox Tags

PubMed Central

Kang, Di; Zuo, Xiaolei; Yang, Renqiang; Xia, Fan; Plaxco, Kevin W.; White, Ryan J.

2009-01-01

Many electrochemical biosensor approaches developed in recent years utilize redox labeled (most commonly methylene blue or ferrocene) oligonucleotide probes site-specifically attached to an interrogating electrode. Sensors in this class have been reported employing a range of probe architectures, including single- and double-stranded DNA, more complex DNA structures, DNA and RNA aptamers and, most recently, DNA-small molecule chimeras. Signaling in this class of sensors is generally predicated on binding-induced changes in the efficiency with which the covalently attached redox label transfers electrons with the interrogating electrode. Here we have investigated how the properties of the redox tag affect the performance of such sensors. Specifically, we compare the differences in signaling and stability of electrochemical DNA sensors (E-DNA sensors) fabricated using either ferrocene or methylene blue as the signaling redox moiety. We find that while both tags support efficient E-DNA signaling, ferrocene produces slightly improved signal gain and target affinity. These small advantages, however, come at a potentially significant price: the ferrocene-based sensors are far less stable than their methylene blue counterparts, particularly with regards to stability to long-term storage, repeated electrochemical interrogations, repeated sensing/regeneration iterations, and employment in complex sample matrices such as blood serum. PMID:19810694

A perspective on the structural studies of inner membrane electrochemical potential-driven transporters.

PubMed

Lemieux, M Joanne

2008-09-01

Electrochemical potential-driven transporters represent a vast array of proteins with varied substrate specificities. While diverse in size and substrate specificity, they are all driven by electrochemical potentials. Over the past five years there have been increasing numbers of X-ray structures reported for this family of transporters. Structural information is available for five subfamilies of electrochemical potential-driven transporters. No structural information exists for the remaining 91 subfamilies. In this review, the various subfamilies of electrochemical potential-driven transporters are discussed. The seven reported structures for the electrochemical potential-driven transporters and the methods for their crystallization are also presented. With a few exceptions, overall crystallization trends have been very similar for the transporters despite their differences in substrate specificity and topology. Also discussed is why the structural studies on these transporters were successful while others are not as fruitful. With the plethora of transporters with unknown structures, this review provides incentive for crystallization of transporters in the remaining subfamilies for which no structural information exists.

Aptamer-conjugated silver nanoparticles for electrochemical dual-aptamer-based sandwich detection of staphylococcus aureus.

PubMed

Abbaspour, Abdolkarim; Norouz-Sarvestani, Fatemeh; Noori, Abolhassan; Soltani, Noushin

2015-06-15

Staphylococcus aureus (S. aureus) is one of the most important human pathogens and causes numerous illnesses. In this study, we report a sensitive and highly selective dual-aptamer-based sandwich immunosensor for the detection of S. aureus. In this bioassay system, a biotinylated primary anti-S.aureus aptamer was immobilized on streptavidin coated magnetic beads (MB), which serves as a capture probe. A secondary anti-S.aureus aptamer was conjugated to silver nanoparticles (Apt-AgNP) that sensitively reports the detection of the target. In the presence of target bacterium, an Apt/S.aureus/apt-AgNP sandwich complex is formed on the MB surface and the electrochemical signal of AgNPs followed through anodic stripping voltammetry. The proposed sandwich assay benefits from advantageous of a sandwich assay for increased specificity, MB as carriers of affinity ligands for solution-phase recognition and fast magnetic separation, AgNPs for signal amplification, and an electrochemical stripping voltammetry read-out as a simple and sensitive detection. The electrochemical immunosensor shows an extended dynamic range from 10 to 1×10(6) cfu/mL with a low detection limit of 1.0 cfu/mL (S/N=3). Furthermore, the possible interference of other analog bacteria was studied. To assess the general applicability of this sensor, we investigated the quantification of S. aureus in real water samples. The results were compared to the experimental results obtained from a plate counting method, which demonstrated an acceptable consistency. Copyright © 2014 Elsevier B.V. All rights reserved.

Studying the reducing potencies of antioxidants with the electrochemistry inherently present in electrospray ionization-mass spectrometry.

PubMed

Plattner, Sabine; Erb, Robert; Chervet, Jean-Pierre; Oberacher, Herbert

2014-01-01

In this proof-of-principle study, the applicability of electrospray ionization-mass spectrometry (ESI-MS) to characterize the reducing potencies of natural antioxidants is demonstrated. The ESI source represents a controlled-current electrochemical cell. The interfacial potential at the emitter electrode will be at or near the electrochemical potential of those reactions that sufficiently supply all the required current for the ESI circuit. Indicator molecules prone to oxidation in ESI such as amodiaquine were used to visualize the impact of reducing compounds on the interfacial potential. The extent of inhibition of the oxidation of the indicator molecule was found to be dependent on the kind and amount of antioxidant added. Concentration-inhibition curves were constructed and used to compare reducing potencies and to rank antioxidants. This ranking was found to be dependent on the electrode material-indicator molecule combination applied. For fast and automated characterization of the reducing potencies of electrochemically active molecules, a flow-injection system was combined with ESI-MS. Liquid chromatography was used to process complex biological samples, such as red and white wine. Due to their high content of different polyphenols, red wine fractions were found to exhibit higher reducing potencies than the corresponding white wine fractions. Furthermore, for 14 important natural antioxidants, the results obtained with the controlled-current EC-ESI-MS assay were compared to those obtained with chemical antioxidant assays. Irrespectively of the kind of assay used to test the reducing potency, gallic acid, quercetin, and epicatechin were found to be potent reductants. Other antioxidants performed well in one particular assay only. This observation suggests that different kinds of redox and antioxidant chemistry were assessed with each of the assays applied. Therefore, several assays should be used to comprehensively study antioxidants and their reducing potencies.

Screen-Printed Graphite Electrodes as Low-Cost Devices for Oxygen Gas Detection in Room-Temperature Ionic Liquids

PubMed Central

Lee, Junqiao

2017-01-01

Screen-printed graphite electrodes (SPGEs) have been used for the first time as platforms to detect oxygen gas in room-temperature ionic liquids (RTILs). Up until now, carbon-based SPEs have shown inferior behaviour compared to platinum and gold SPEs for gas sensing with RTIL solvents. The electrochemical reduction of oxygen (O2) in a range of RTILs has therefore been explored on home-made SPGEs, and is compared to the behaviour on commercially-available carbon SPEs (C-SPEs). Six common RTILs are initially employed for O2 detection using cyclic voltammetry (CV), and two RTILs ([C2mim][NTf2] and [C4mim][PF6]) chosen for further detailed analytical studies. Long-term chronoamperometry (LTCA) was also performed to test the ability of the sensor surface for real-time gas monitoring. Both CV and LTCA gave linear calibration graphs—for CV in the 10–100% vol. range, and for LTCA in the 0.1–20% vol. range—on the SPGE. The responses on the SPGE were far superior to the commercial C-SPEs; more instability in the electrochemical responses were observed on the C-SPEs, together with some breaking-up or dissolution of the electrode surface materials. This study highlights that not all screen-printed ink formulations are compatible with RTIL solvents for longer-term electrochemical experiments, and that the choice of RTIL is also important. Overall, the low-cost SPGEs appear to be promising platforms for the detection of O2, particularly in [C4mim][PF6]. PMID:29186869

On the reasons for low sulphur utilization in the lithium-sulphur batteries

NASA Astrophysics Data System (ADS)

Kolosnitsyn, V. S.; Kuzmina, E. V.; Karaseva, E. V.

2015-01-01

This work is to study the reasons for the relatively low efficiency of sulphur reduction (about 75%) in lithium-sulphur batteries. The two main reasons for that are suggested to be: the relatively low electrochemical activity of low order lithium polysulphides and blocking of the carbon framework of the sulphur electrode by insoluble products of electrochemical reactions - sulphur and lithium sulphide. The electrochemical activity of lithium polysulphides with different composition (Li2Sn, n = 2-6) has been studied in 1 M solutions of CF3SO3Li in sulfolane. It is shown that lithium polysulphides including lithium disulphide are able to electrochemically reduce with efficiency close to 100%. The electrochemical activity of lithium polysulphides decreases with the order. The order of lithium polysulphides affects the value of voltage of discharge plateaus but not the efficiency of sulphur reducing in the lithium polysulphides species. The relatively low efficiency of sulphur reduction in the lithium-sulphur batteries is more likely caused by blocking of carbon particles in the sulphur electrode by insoluble products of electrochemical reactions (sulphur and lithium sulphide). This prevents the electrochemical reduction of low order lithium polysulphides and especially lithium disulphide.

Nature of the Electrochemical Properties of Sulphur Substituted LiMn2O4 Spinel Cathode Material Studied by Electrochemical Impedance Spectroscopy

PubMed Central

Bakierska, Monika; Świętosławski, Michał; Dziembaj, Roman; Molenda, Marcin

2016-01-01

In this work, nanostructured LiMn2O4 (LMO) and LiMn2O3.99S0.01 (LMOS1) spinel cathode materials were comprehensively investigated in terms of electrochemical properties. For this purpose, electrochemical impedance spectroscopy (EIS) measurements as a function of state of charge (SOC) were conducted on a representative charge and discharge cycle. The changes in the electrochemical performance of the stoichiometric and sulphur-substituted lithium manganese oxide spinels were examined, and suggested explanations for the observed dependencies were given. A strong influence of sulphur introduction into the spinel structure on the chemical stability and electrochemical characteristic was observed. It was demonstrated that the significant improvement in coulombic efficiency and capacity retention of lithium cell with LMOS1 active material arises from a more stable solid electrolyte interphase (SEI) layer. Based on EIS studies, the Li ion diffusion coefficients in the cathodes were estimated, and the influence of sulphur on Li+ diffusivity in the spinel structure was established. The obtained results support the assumption that sulphur substitution is an effective way to promote chemical stability and the electrochemical performance of LiMn2O4 cathode material. PMID:28773819

Design of aqueous redox-enhanced electrochemical capacitors with high specific energies and slow self-discharge.

PubMed

Chun, Sang-Eun; Evanko, Brian; Wang, Xingfeng; Vonlanthen, David; Ji, Xiulei; Stucky, Galen D; Boettcher, Shannon W

2015-08-04

Electrochemical double-layer capacitors exhibit high power and long cycle life but have low specific energy compared with batteries, limiting applications. Redox-enhanced capacitors increase specific energy by using redox-active electrolytes that are oxidized at the positive electrode and reduced at the negative electrode during charging. Here we report characteristics of several redox electrolytes to illustrate operational/self-discharge mechanisms and the design rules for high performance. We discover a methyl viologen (MV)/bromide electrolyte that delivers a high specific energy of ∼14 Wh kg(-1) based on the mass of electrodes and electrolyte, without the use of an ion-selective membrane separator. Substituting heptyl viologen for MV increases stability, with no degradation over 20,000 cycles. Self-discharge is low, due to adsorption of the redox couples in the charged state to the activated carbon, and comparable to cells with inert electrolyte. An electrochemical model reproduces experiments and predicts that 30-50 Wh kg(-1) is possible with optimization.

Design of aqueous redox-enhanced electrochemical capacitors with high specific energies and slow self-discharge

PubMed Central

Chun, Sang-Eun; Evanko, Brian; Wang, Xingfeng; Vonlanthen, David; Ji, Xiulei; Stucky, Galen D.; Boettcher, Shannon W.

2015-01-01

Electrochemical double-layer capacitors exhibit high power and long cycle life but have low specific energy compared with batteries, limiting applications. Redox-enhanced capacitors increase specific energy by using redox-active electrolytes that are oxidized at the positive electrode and reduced at the negative electrode during charging. Here we report characteristics of several redox electrolytes to illustrate operational/self-discharge mechanisms and the design rules for high performance. We discover a methyl viologen (MV)/bromide electrolyte that delivers a high specific energy of ∼14 Wh kg−1 based on the mass of electrodes and electrolyte, without the use of an ion-selective membrane separator. Substituting heptyl viologen for MV increases stability, with no degradation over 20,000 cycles. Self-discharge is low, due to adsorption of the redox couples in the charged state to the activated carbon, and comparable to cells with inert electrolyte. An electrochemical model reproduces experiments and predicts that 30–50 Wh kg−1 is possible with optimization. PMID:26239891

Enhancing the sensitivity of needle-implantable electrochemical glucose sensors via surface rebuilding.

PubMed

Vaddiraju, Santhisagar; Legassey, Allen; Qiang, Liangliang; Wang, Yan; Burgess, Diane J; Papadimitrakopoulos, Fotios

2013-03-01

Needle-implantable sensors have shown to provide reliable continuous glucose monitoring for diabetes management. In order to reduce tissue injury during sensor implantation, there is a constant need for device size reduction, which imposes challenges in terms of sensitivity and reliability, as part of decreasing signal-to-noise and increasing layer complexity. Herein, we report sensitivity enhancement via electrochemical surface rebuilding of the working electrode (WE), which creates a three-dimensional nanoporous configuration with increased surface area. The gold WE was electrochemically rebuilt to render its surface nanoporous followed by decoration with platinum nanoparticles. The efficacy of such process was studied using sensor sensitivity against hydrogen peroxide (H2O2). For glucose detection, the WE was further coated with five layers, namely, (1) polyphenol, (2) glucose oxidase, (3) polyurethane, (4) catalase, and (5) dexamethasone-releasing poly(vinyl alcohol)/poly(lactic-co-glycolic acid) composite. The amperometric response of the glucose sensor was noted in vitro and in vivo. Scanning electron microscopy revealed that electrochemical rebuilding of the WE produced a nanoporous morphology that resulted in a 20-fold enhancement in H2O2 sensitivity, while retaining >98% selectivity. This afforded a 4-5-fold increase in overall glucose response of the glucose sensor when compared with a control sensor with no surface rebuilding and fittable only within an 18 G needle. The sensor was able to reproducibly track in vivo glycemic events, despite the large background currents typically encountered during animal testing. Enhanced sensor performance in terms of sensitivity and large signal-to-noise ratio has been attained via electrochemical rebuilding of the WE. This approach also bypasses the need for conventional and nanostructured mediators currently employed to enhance sensor performance. © 2013 Diabetes Technology Society.

Optimization on electrochemical synthesis of HKUST-1 as candidate catalytic material for Green diesel production

NASA Astrophysics Data System (ADS)

Lestari, W. W.; Nugraha, R. E.; Winarni, I. D.; Adreane, M.; Rahmawati, F.

2016-04-01

In the effort to support the discovery of new renewable energy sources in Indonesia, biofuel is one of promising options. The conversion of vegetable oil into ready-biofuel, especially green diesel, needs several steps, one of which is a hydrogenation or hydro-deoxygenation reaction. In this case, the catalyst plays a very important role regarding to its activity and selectivity, and Metal-Organic Frameworks (MOFs) becoming a new generation of heterogeneous catalyst in this area. In this research, a preliminary study to optimize electrochemical synthesis of the catalytic material based on MOFs, namely HKUST-1 [Cu3(BTC)2], has been conducted. Some electrochemical reaction parameters were tested, for example by modifying the electrochemical synthetic conditions, i.e. by performing variation of voltages (12, 13, 14, and 15 Volt), temperatures (RT, 40, 60, and 80 °C) and solvents (ethanol, water, methanol and dimethyl-formamide (DMF)). Material characterization was carried out by XRD, SEM, FTIR, DTA/TG and SAA. The results showed that the optimum synthetic conditions of HKUST-1 are performed at room temperature in a solvent combination of water: ethanol (1: 1) and a voltage of 15 Volt for 2 hours. The XRD-analysis revealed that the resulted peaks are identical to the simulated powder pattern generated from single crystal data and comparable to the peaks of solvothermal method. However, the porosity of the resulting material through electrochemical method is still in the range of micro-pore according to IUPAC and 50% smaller than the porosity resulted from solvothermal synthesis. The corresponding compounds are thermally stable until 300 °C according to TG/DTA.

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.

Performance of an electrochemical carbon monoxide monitor in the presence of anesthetic gases.

PubMed

Dunning, M; Woehlck, H J

1997-11-01

The passage of volatile anesthetic agents through accidentally dried CO2 absorbents in anesthesia circuits can result in the chemical breakdown of anesthetics with production of greater than 10000 ppm carbon monoxide (CO). This study was designed to evaluate a portable CO monitor in the presence of volatile anesthetic agents. Two portable CO monitors employing electrochemical sensors were tested to determine the effects of anesthetic agents, gas sample flow rates, and high CO concentrations on their electrochemical sensor. The portable CO monitors were exposed to gas mixtures of 0 to 500 ppm CO in either 70% nitrous oxide, 1 MAC concentrations of contemporary volatile anesthetics, or reacted isoflurane or desflurane (containing CO and CHF3) in oxygen. The CO measurements from the electrochemical sensors were compared to simultaneously obtained samples measured by gas chromatography (GC). Data were analyzed by linear regression. Overall correlation between the portable CO monitors and the GC resulted in an r2 value >0.98 for all anesthetic agents. Sequestered samples produced an exponential decay of measured CO with time, whereas stable measurements were maintained during continuous flow across the sensor. Increasing flow rates resulted in higher CO readings. Exposing the CO sensor to 3000 and 19000 ppm CO resulted in maximum reported concentrations of approximately 1250 ppm, with a prolonged recovery. Decrease in measured concentration of the sequestered samples suggests destruction of the sample by the sensor, whereas a diffusion limitation is suggested by the dependency of measured value upon flow. Any value over 500 ppm must be assumed to represent dangerous concentrations of CO because of the non-linear response of these monitors at very high CO concentrations. These portable electrochemical CO monitors are adequate to measure CO concentrations up to 500 ppm in the presence of typical clinical concentrations of anesthetics.

In situ electrochemical detection of embryonic stem cell differentiation.

PubMed

Yea, Cheol-Heon; An, Jeung Hee; Kim, Jungho; Choi, Jeong-Woo

2013-06-20

Stem cell sensors have emerged as a promising technique to electrochemically monitor the functional status and viability of stem cells. However, efficient electrochemical analysis techniques are required for the development of effective electrochemical stem cell sensors. In the current study, we report a newly developed electrochemical cyclic voltammetry (CV) system to determine the status of mouse embryonic stem (ES) cells. 1-Naphthly phosphate (1-NP), which was dephosphorylated by alkaline phosphatase into a 1-naphthol on an undifferentiated mouse ES cell, was used as a substrate to electrochemically monitor the differentiation status of mouse ES cells. The peak current in the cyclic voltammetry of 1-NP increased linearly with the concentration of pure 1-NP (R(2)=0.9623). On the other hand, the peak current in the electrochemical responses of 1-NP decreased as the number of undifferentiated ES cells increased. The increased dephosphorylation of 1-NP to 1-naphthol made a decreased electrochemical signal. Non-toxicity of 1-NP was confirmed. In conclusion, the proposed electrochemical analysis system can be applied to an electrical stem cell chip for diagnosis, drug detection and on-site monitoring. Copyright © 2013 Elsevier B.V. All rights reserved.

A comparative study on the electrochemical corrosion behavior of iron and X-65 steel in 4.0 wt % sodium chloride solution after different exposure intervals.

PubMed

Sherif, El-Sayed M

2014-07-09

In this work, the results obtained from studying the anodic dissolution of pure iron and API X-65 5L pipeline steel after 40 min and 12 h exposure period in 4.0 wt % NaCl solutions at room temperature were reported. Potential-time, electrochemical impedance spectroscopy, potentiodynamic polarization, and chronoamperometric current-time at constant potential techniques were employed. It has been found that the iron electrode corrodes in the chloride test solutions faster than the API X-65 5L steel does under the same conditions. Increasing the exposure period for the electrodes from 40 min to 12 h showed a significant reduction in the corrosion parameters for both iron and steel in the 4.0 wt % NaCl solution. Results together confirmed clearly that the X-65 steel is superior to iron against corrosion in sodium chloride solutions.

Determination of antioxidant power of red and white wines by a new electrochemical method and its correlation with polyphenolic content.

PubMed

Alonso, Angeles M; Domínguez, Cristina; Guillén, Dominico A; Barroso, Carmelo G

2002-05-22

A new method for measuring the antioxidant power of wine has been developed based on the accelerated electrochemical oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The calibration (R = 0.9922) and repeatability study (RSD = 7%) have provided good statistical parameters. The method is easy and quick to apply and gives reliable results, requiring only the monitoring of time and absorbance. It has been applied to various red and white wines of different origins. The results have been compared with those obtained by the total antioxidant status (TAS) method. Both methods reveal that the more antioxidant wines are those with higher polyphenolic content. From the HPLC study of the polyphenolic content of the same samples, it is confirmed that there is a positive correlation between the resveratrol content of a wine and its antioxidant power.

Interfacial chemistry of zinc anodes for reinforced concrete structures

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

Covino, B.S. Jr.; Bullard, S.J.; Cramer, S.D.

1997-12-01

Thermally-sprayed zinc anodes are used in both galvanic and impressed current cathodic protection systems for reinforced concrete structures. The Albany Research Center, in collaboration with the Oregon Department of Transportation, has been studying the effect of electrochemical aging on the bond strength of zinc anodes for bridge cathodic protection systems. Changes in anode bond strength and other anode properties can be explained by the chemistry of the zinc-concrete interface. The chemistry of the zinc-concrete interface in laboratory electrochemical aging studies is compared with that of several bridges with thermal-sprayed zinc anodes and which have been in service for 5 tomore » 10 years using both galvanic and impressed current cathodic protection systems. The bridges are the Cape Creek Bridge on the Oregon coast and the East Camino Undercrossing near Placerville, CA. Also reported are interfacial chemistry results for galvanized steel rebar from the 48 year old Longbird Bridge in Bermuda.« less

Fundamental Investigation of Si Anode in Li-Ion Cells

NASA Technical Reports Server (NTRS)

Wu, James J.; Bennett, William R.

2012-01-01

Silicon is a promising and attractive anode material to replace graphite for high capacity lithium ion cells since its theoretical capacity is approximately 10 times of graphite and it is an abundant element on earth. However, there are challenges associated with using silicon as Li-ion anode due to the significant first cycle irreversible capacity loss and subsequent rapid capacity fade during cycling. In this paper, cyclic voltammetry and electrochemical impedance spectroscopy are used to build a fundamental understanding of silicon anodes. The results show that it is difficult to form the SEI film on the surface of Si anode during the first cycle, the lithium ion insertion and de-insertion kinetics for Si are sluggish, and the cell internal resistance changes with the state of lithiation after electrochemical cycling. These results are compared with those for extensively studied graphite anodes. The understanding gained from this study will help to design better Si anodes.

A Mini-Electrochemical System with Integrated Micropipet Tip and Pencil Graphite Electrode for Measuring Cytotoxicity.

PubMed

Wu, Dong-Mei; Guo, Xiao-Ling; Wang, Qian; Li, Jin-Lian; Cui, Ji-Wen; Zhou, Shi; Hao, Su-E

2017-01-01

A novel mini-electrochemical system has been developed for evaluating cytotoxicity of anticancer drugs based on trace cell samples. The mini-electrochemical system was integrated by using pencil graphite modified with threonine as working electrode, an Ag/AgCl reference electrode and a micropipet tip as electrochemical cell. The mini-electrochemical system dramatically reduces sample volumes from 500 μL in a traditional electrochemical system to 10 μL, and exhibits excellent electrocatalytic activity toward oxidation of purine from MCF-7 cells due to increased sensitivity provided by threonine. Moreover, the relationship between peak current and the cell concentration in the range from 3.0 × l0 3 to 7.0 × l0 6 cells/mL was studied, and a nonlinear exponential relationship between them was established over a wide concentration range. In evaluating the effect of anticancer drugs on cell viability, the results of drug cytotoxicity test based on cyclophosphamide were in close agreement with classical 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assays. The proposed device is so simple, cheap, and easy to operate that it could be applied to single-use applications. The mini-electrochemical system proved to be a useful tool and can be applied to electrochemical studies of cancer cells as well as other biological samples such as proteins and DNA.

The corrosion protection of several aluminum alloys by chromic acid and sulfuric acid anodizing

NASA Technical Reports Server (NTRS)

Danford, M. D.

1994-01-01

The corrosion protection afforded 7075-T6, 7075-T3, 6061-T6, and 2024-T3 aluminum alloys by chromic acid and sulfuric acid anodizing was examined using electrochemical techniques. From these studies, it is concluded that sulfuric acid anodizing provides superior corrosion protection compared to chromic acid anodizing.

Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

EPA Science Inventory

Multi-anode microbial electrochemical cells (MXCs) are considered as one of the most promising configurations for scale-up of MXCs, but fundamental understanding of anode kinetics governing current density is limited in the MXCs. In this study we first assessed microbial communi...

The possibility of multi-layer nanofabrication via atomic force microscope-based pulse electrochemical nanopatterning

NASA Astrophysics Data System (ADS)

Kim, Uk Su; Morita, Noboru; Lee, Deug Woo; Jun, Martin; Park, Jeong Woo

2017-05-01

Pulse electrochemical nanopatterning, a non-contact scanning probe lithography process using ultrashort voltage pulses, is based primarily on an electrochemical machining process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through non-contact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration. Additionally, protruding nanoscale oxides were removed completely by simple chemical etching, showing a depressed pattern on the sample substrate surface. Nanoscale two-dimensional oxides, prepared by a localized electrochemical reaction, can be defined easily by controlling physical and electrical variables, before proceeding further to a layer-by-layer nanofabrication process.

Beyond graphene: Electrochemical sensors and biosensors for biomarkers detection.

PubMed

Bollella, Paolo; Fusco, Giovanni; Tortolini, Cristina; Sanzò, Gabriella; Favero, Gabriele; Gorton, Lo; Antiochia, Riccarda

2017-03-15

Graphene's success has stimulated great interest and research in the synthesis and characterization of graphene-like 2D materials, single and few-atom-thick layers of van der Waals materials, which show fascinating and technologically useful properties. This review presents an overview of recent electrochemical sensors and biosensors based on graphene and on graphene-like 2D materials for biomarkers detection. Initially, we will outline different electrochemical sensors and biosensors based on chemically derived graphene, including graphene oxide and reduced graphene oxide, properly functionalized for improved performances and we will discuss the various strategies to prepare graphene modified electrodes. Successively, we present electrochemical sensors and biosensors based on graphene-like 2D materials, such as boron nitride (BN), graphite-carbon nitride (g-C 3 N 4 ), transition metal dichalcogenides (TMDs), transition metal oxides and graphane, outlining how the new modified 2D nanomaterials will improve the electrochemical performances. Finally, we will compare the results obtained with different sensors and biosensors for the detection of important biomarkers such as glucose, hydrogen peroxide and cancer biomarkers and highlight the advantages and disadvantages of the use of graphene and graphene-like 2D materials in different sensing platforms. Copyright © 2016 Elsevier B.V. All rights reserved.

Probing the characteristics of casein as green binder for non-aqueous electrochemical double layer capacitors' electrodes

NASA Astrophysics Data System (ADS)

Varzi, Alberto; Raccichini, Rinaldo; Marinaro, Mario; Wohlfahrt-Mehrens, Margret; Passerini, Stefano

2016-09-01

Casein from bovine milk is evaluated in this work as binding agent for electrochemical double layer capacitors (EDLCs) electrodes. It is demonstrated that casein provides excellent adhesion strength to the current collector (1187 kPa compared to 51 kPa achieved with PVdF), thus leading to mechanically stable electrodes. At the same time, it offers high thermal stability (above 200 °C) and electrochemical stability in organic electrolytes. Apparently though, the casein-based electrodes offer lower electronic conductivity than those based on other state-of-the-art binders, which can limit the rate performance of the resulting EDLC. In the attempt of improving the electrochemical performance, it is found that the application of a pressing step can solve this issue, leading to excellent rate capability (up to 84% capacitance retention at 50 mA cm-2) and cycling stability (96.8% after 10,000 cycles at 10 mA cm-2) in both PC- and ACN-based electrolytes. Although the adhesive power casein is known since ancient times, this report presents the first proof of concept of its employment in electrochemical power sources.

Electrochemical detection of Piscirickettsia salmonis genomic DNA from salmon samples using solid-phase recombinase polymerase amplification.

PubMed

Del Río, Jonathan Sabaté; Svobodova, Marketa; Bustos, Paulina; Conejeros, Pablo; O'Sullivan, Ciara K

2016-12-01

Electrochemical detection of solid-phase isothermal recombinase polymerase amplification (RPA) of Piscirickettsia salmonis in salmon genomic DNA is reported. The electrochemical biosensor was constructed by surface functionalization of gold electrodes with a thiolated forward primer specific to the genomic region of interest. Solid-phase RPA and primer elongation were achieved in the presence of the specific target sequence and biotinylated reverse primers. The formation of the subsequent surface-tethered duplex amplicons was electrochemically monitored via addition of streptavidin-linked HRP upon completion of solid-phase RPA. Successful quantitative amplification and detection were achieved in less than 1 h at 37 °C, calibrating with PCR-amplified genomic DNA standards and achieving a limit of detection of 5 · 10 -8  μg ml -1 (3 · 10 3 copies in 10 μl). The presented system was applied to the analysis of eight real salmon samples, and the method was also compared to qPCR analysis, observing an excellent degree of correlation. Graphical abstract Schematic of use of electrochemical RPA for detection of Psiricketessia salmonis in salmon liver.

Studies of electrode structures and dynamics using coherent X-ray scattering and imaging

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

You, H.; Liu, Y.; Ulvestad, A.

2017-08-01

Electrochemical systems studied in situ with advanced surface X-ray scattering techniques are reviewed. The electrochemical systems covered include interfaces of single-crystals and nanocrystals with respect to surface modification, aqueous dissolution, surface reconstruction, and electrochemical double layers. An emphasis will be given on recent results by coherent X-ray techniques such as X-ray photon correlation spectroscopy, Bragg coherent diffraction imaging, and surface ptychography.

Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process.

PubMed

Naja, Ghinwa; Mustin, Christian; Volesky, Bohumil; Berthelin, Jacques

2006-01-01

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared. The resin stabilized the initial electrochemical potential to -405+/-5 mV corresponding to 2 micro gl(-1) of lead concentration in solution. The amounts of lead sorbed by R. arrhizus biomass and diatomite were 0.9 mmol g(-1) (C(e)=5.16 x 10(-2)mM) and 0.052 mmol g(-1) (C(e)=5.97 x 10(-2) mM), respectively. Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites. The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity.

Electrochemical Corrosion and In Vitro Bioactivity of SiO2:ZrO2-Coated 316L Stainless Steel in Simulated Body Fluid

NASA Astrophysics Data System (ADS)

Srinivasan, A.; Rajendran, N.

2015-08-01

The effect of Si:Zr ratio on the in vitro bioactivity and electrochemical corrosion behavior of SiO2:ZrO2-mixed oxide-coated 316L stainless steel (SS) was evaluated in simulated body fluid (SBF) solution for 72, 120, and 168 h. Growth of Hydroxyapatite (HAp) was accelerated when Si content in the coating was increased. The Zr content in the coating improved the corrosion resistance of 316L SS rather than accelerating the HAp growth. When the Si:Zr ratio was 50:50, the coating exhibited significant improvement in corrosion resistance as well as HAp growth. The mechanism of HAp growth was proposed based on the change in surface zeta potential values of the coatings. Potentiodynamic polarization studies revealed about 10 and 5 times reduction in corrosion current density ( i corr) values for SiO2:ZrO2 (50:50)-coated 316L SS after 168 h of immersion compared to SiO2, ZrO2, and Si:Zr (70:30) coatings in SBF solutions thus confirming the superior corrosion resistance. The equivalent circuit parameters derived from electrochemical impedance spectroscopy studies further confirmed significant improvement in charge transfer resistance value even after 168 h of exposure.

Advanced Anticorrosion Coating Materials Derived from Sunflower Oil with Bifunctional Properties.

PubMed

Balakrishnan, Thiruparasakthi; Sathiyanarayanan, Sadagopan; Mayavan, Sundar

2015-09-09

High-performance barrier films preventing permeation of moisture, aggressive chloride ions, and corrosive acids are important for many industries ranging from food to aviation. In the current study, pristine sunflower oil was used to form uniform adherent films on iron (Fe) via a simple single-step thermal treatment (without involving any initiator/mediator/catalyst). Oxidation of oil on heating results in a highly conjugated (oxidized) crystalline lamellar network with interlayer separation of 0.445 nm on Fe. The electrochemical corrosion tests proved that the coating exhibits superior anticorrosion performance with high coating resistance (>10(9) ohm cm2) and low capacitance values (<10(-10) F cm(-2)) as compared to bare Fe, graphene, and conducting polymer based coatings in 1 M hydrochloric acid solutions. The electrochemical analyses reveal that the oil coatings developed in this study provided a two-fold protection of passivation from the oxide layer and barrier from polymeric films. It is clearly observed that there is no change in structure, morphology, or electrochemical properties even after a prolonged exposure time of 80 days. This work indicates the prospect of developing highly inert, environmentally green, nontoxic, and micrometer level passivating barrier coatings from more sustainable and renewable sources, which can be of interest for numerous applications.

Electrochemical Interfaces and Electrode Processes: Electrochemical Oxidation of Small Organisms

DTIC Science & Technology

1994-09-01

temperatures up to I 50°C. The electrode kinetics have been compared with methane and other small hydrocarbons in acid media. The formation of strongly...methanol, ethanol ). Bridge bonded CO(ads) is also observed in some instances with FTIR. The adsorbed CO is very strongly adsorbed on the platinum...research has demonstrated, however, that this problem is substantially lessened at higher temperatures (>I 50’C). The use of platinum alloy catalysts

MnO2 prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery

PubMed Central

2014-01-01

Two α-MnO2 crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO2 prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO2 crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO2 crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO2 material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO2 material has better electrochemical performance. PMID:24982603

Corrosion properties of powder bed fusion additively manufactured 17-4 PH stainless steel

DOE PAGES

Schaller, Rebecca; Taylor, Jason; Rodelas, Jeffrey; ...

2017-02-20

The corrosion susceptibility of a laser powder bed fusion (LPBF) additively manufactured alloy, UNS S17400 (17-4 PH), was explored compared to conventional wrought material. Microstructural characteristics were characterized and related to corrosion behavior in quiescent, aqueous 0.6 M NaCl solutions. Electrochemical measurements demonstrated that the LPBF 17-4 PH alloy exhibited a reduced passivity range and active corrosion compared to its conventional wrought counterpart. Lastly, a micro-electrochemical cell was employed to further understand the effects of the local scale and attributed the reduced corrosion resistance of the LPBF material to pores with diameters ≥ 50 µm.

Corrosion properties of powder bed fusion additively manufactured 17-4 PH stainless steel

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

Schaller, Rebecca; Taylor, Jason; Rodelas, Jeffrey

The corrosion susceptibility of a laser powder bed fusion (LPBF) additively manufactured alloy, UNS S17400 (17-4 PH), was explored compared to conventional wrought material. Microstructural characteristics were characterized and related to corrosion behavior in quiescent, aqueous 0.6 M NaCl solutions. Electrochemical measurements demonstrated that the LPBF 17-4 PH alloy exhibited a reduced passivity range and active corrosion compared to its conventional wrought counterpart. Lastly, a micro-electrochemical cell was employed to further understand the effects of the local scale and attributed the reduced corrosion resistance of the LPBF material to pores with diameters ≥ 50 µm.

Semi-conducting single-walled carbon nanotubes are detrimental when compared to metallic single-walled carbon nanotubes for electrochemical applications.

PubMed

Dong, Qi; Nasir, Muhammad Zafir Mohamad; Pumera, Martin

2017-10-18

As-synthetized single walled carbon nanotubes (SWCNTs) contain both metallic and semiconducting nanotubes. For the electronics, it is desirable to separate semiconducting SWCNTs (s-SWCNTs) from the metallic ones as s-SWCNTs provide desirable electronic properties. Here we test whether ultrapure semi-conducting single-walled carbon nanotubes (s-SWCNTs) provide advantageous electrochemical properties over the as prepared SWCNTs which contain a mixture of semiconducting and metallic CNTs. We test them as a transducer platform which enhanced the detection of target analytes (ascorbic acid, dopamine, uric acid) when compared to a bare glassy carbon (GC) electrode. Despite that, the two materials exhibit significantly different electrochemical properties and performances. A mixture of m-SWCNTs and s-SWCNTs demonstrated superior performance over ultrapure s-SWCNTs with greater peak currents and pronounced shift in peak potentials to lower values in cyclic and differential pulse voltammetry for the detection of target analytes. The mixture of m- and s-SWCNTs displayed about a 4 times improved heterogeneous electron transfer rate as compared to bare GC and a 2 times greater heterogeneous electron transfer rate than s-SWCNTs, demonstrating that ultrapure SWCNTs do not provide any major enhancement over the as prepared SWCNTs.

Comparative studies of structural, thermal, optical, and electrochemical properties of azines with different end groups with their azomethine analogues toward application in (opto)electronics.

PubMed

Sek, Danuta; Siwy, Mariola; Bijak, Katarzyna; Grucela-Zajac, Marzena; Malecki, Grzegorz; Smolarek, Karolina; Bujak, Lukasz; Mackowski, Sebastian; Schab-Balcerzak, Ewa

2013-10-10

Two series of azines and their azomethine analogues were prepared via condensation reaction of benzaldehyde, 2-hydroxybenzaldehyde, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 4-(diphenylamino)benzaldehyde with hydrazine monohydrate and 1,4-phenylenediamine, respectively. The structures of given compounds were characterized by FTIR, (1)H NMR, and (13)C NMR spectroscopy as well as elemental analysis. Optical, electrochemical, and thermal properties of all compounds were investigated by means of differential scanning calorimetry (DSC), UV-vis spectroscopy, stationary and time-resolved photoluminescence spectroscopy, and cycling voltammetry (CV). Additionally, the electronic properties, that is, orbital energies and resulting energy gap were calculated theoretically by density functional theory (DFT). Influence of chemical structure of the compounds on their properties was analyzed.

Defect engineering of the electrochemical characteristics of carbon nanotube varieties

NASA Astrophysics Data System (ADS)

Hoefer, Mark A.; Bandaru, Prabhakar R.

2010-08-01

The electrochemical behavior of carbon nanotubes (CNTs) containing both intrinsic and extrinsically introduced defects has been investigated through the study of bamboo and hollow multiwalled CNT morphologies. The controlled addition of argon ions was used for varying the charge and type of extrinsic defects. It was indicated from Raman spectroscopy and voltammetry that the electrocatalytic response of hollow type CNTs could be tailored more significantly, compared to bamboo type CNTs which have innately high reactive site densities and are less amenable to modification. An in-plane correlation length parameter was used to understand the variation of the defect density as a function of argon ion irradiation. The work has implications in the design of nanotube based chemical sensors, facilitated through the introduction of suitable reactive sites.

Highly specific and reversible fluoride sensor based on an organic semiconductor.

PubMed

Aboubakr, Hecham; Brisset, Hugues; Siri, Olivier; Raimundo, Jean-Manuel

2013-10-15

A novel sulfonamide-conjugated benzo-[2,1-b:3,4-b']bithiophene semiconductor has been designed and synthetized in order to develop a probe for specific detection of anions both in the homogeneous (solution) and heterogeneous phase. Its photophysical and electrochemical data were reported in this study. On the basis of the optical and NMR titrations analysis, the chelator was found to be highly selective for fluoride compared to others anions (Ka = 1.6 × 10(4) M(-1) in dimethyl sulfoxide (DMSO)). In addition, from an intricate sample, the novel chelator shows exceptional specificity toward fluoride and reveals a complete reversibility after addition of trifluoroacetic acid (TFA). Sensing films were obtained by electrochemical polymerization of the probe on an electrode surface, which clearly show effective detection of fluoride.

Ultrasonic modification of carbon materials for electrochemical capacitors.

PubMed

Rachiy, Bogdan I; Nykoliuk, Marian O; Budzulyak, Ivan M; Kachmar, Andrii I

2017-12-01

The paper is devoted to study the ultrasonic impact on the biomass of natural raw materials, which were used for the creation a nanoporous carbon material (NCM), which was used as electrode material for electrochemical capacitors (EC). The dry shells of apricot seeds were a feedstock, which were modified by the chemical treatment in the phosphoric acid and part of them were impacted by ultrasonic waves for 25 minutes. The NCM, which were obtained by carbonization at 550 °C, were modified by chemical treatment in the nitric acid. Thus, the different of modification NCM was obtained to compare their capacitance characteristics for EC. From experimental data we can do a conclusion, that ultrasonic modification and chemical treatment in nitric acidare improvecapacitance characteristics of NCM for EC.

The effect of metallic oxide deposition on the electrochemical behaviour of Al-Zn-Mg-Sn alloy in natural tropical seawater

NASA Astrophysics Data System (ADS)

Din Yati, M. S.; Nazree Derman, Mohd; Isa, M. C.; Y Ahmad, M.; Yusoff, N. H. N.; Muhammad, M. M.; Nain, H.

2014-06-01

The potential of aluminium alloys as anode materials in cathodic protection system has been explored and a significant improvement has been achieved. However, for marine application, it is quite difficult to maintain continuous activation process due to passivation behavior of aluminum alloys. Therefore, to choose the best activation mechanism for aluminium alloy in marine environment, it has to be considered from various points such as alloy composition and surface treatment. This paper report the effect of metallic ruthenium oxide (RuO2) deposition on the surface of as-cast Al-Zn-Mg-Sn alloy and to study the effect of its presence on the electrochemical behavior using direct current (DC) electrochemical polarization and current capacity measurement. The morphology and topography of corroded surface were studied by the aid of scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) respectively. Results from this study showed that the presence of intermetallic compound (Mg2Sn) and also mixed metal oxide compound (Al2O3 and RuO2) on the alloy surface has been very useful in improving electrochemical reaction and charge transfer activities in chloride containing solution. This study also showed that RuO2 catalytic coating applied on the surface of Al-Zn-Mg-Sn alloy has slightly increased the corrosion current density compared to Al-Zn-Mg-Sn without RuO2. The corrosion morphology and topography of corroded surface of Al-Zn-Mg-Sn alloy deposited with RuO2 was found more uniform corrosion attack with the formation of porous and fibrous mud-like crack on outer layer. Based on surface morphology and 3D topographic studies, these features were believed to facilitate ionic species adsorption and diffusion through corrosion product layer at solution-alloy interface. Deposited RuO2 films also was found to increase of current efficiency by more than 10%.

Electrochemical Cathodic Polarization, a Simplified Method That Can Modified and Increase the Biological Activity of Titanium Surfaces: A Systematic Review

PubMed Central

2016-01-01

Background The cathodic polarization seems to be an electrochemical method capable of modifying and coat biomolecules on titanium surfaces, improving the surface activity and promoting better biological responses. Objective The aim of the systematic review is to assess the scientific literature to evaluate the cellular response produced by treatment of titanium surfaces by applying the cathodic polarization technique. Data, Sources, and Selection The literature search was performed in several databases including PubMed, Web of Science, Scopus, Science Direct, Scielo and EBSCO Host, until June 2016, with no limits used. Eligibility criteria were used and quality assessment was performed following slightly modified ARRIVE and SYRCLE guidelines for cellular studies and animal research. Results Thirteen studies accomplished the inclusion criteria and were considered in the review. The quality of reporting studies in animal models was low and for the in vitro studies it was high. The in vitro and in vivo results reported that the use of cathodic polarization promoted hydride surfaces, effective deposition, and adhesion of the coated biomolecules. In the experimental groups that used the electrochemical method, cellular viability, proliferation, adhesion, differentiation, or bone growth were better or comparable with the control groups. Conclusions The use of the cathodic polarization method to modify titanium surfaces seems to be an interesting method that could produce active layers and consequently enhance cellular response, in vitro and in vivo animal model studies. PMID:27441840

Electrochemical Studies on Minoxidil and Its Determination in Tablets by Differential-Pulse Polarography.

DTIC Science & Technology

1984-01-16

AD-R76 981 ELECTROCHEMICAL STUDIES ON MINOXIDIL AND ITS j/j IDETERMINATION IN TABLETS BY..(U) UTAH UNIV SALT LAKE AS CITY DEPT OF CHEMISTRY L...INSTRUCTIONES 2. QVT CCESSIN ". 3 krCIPII-.,n I CATALOG Numtnk 22 ’TTE(d.t8v . TYPE OF R4EPORT a PERIOD COEd Electrochemical Studies on Minoxidil and... minoxidil in pharmaceutical dosage forms. The extracting . solvent was methani and the supporting electrolyte was 1.0 N sulphuric acid. L. An excellent

Analysis of electrochemical noise (ECN) data in time and frequency domain for comparison corrosion inhibition of some azole compounds on Cu in 1.0 M H2SO4 solution

NASA Astrophysics Data System (ADS)

Ramezanzadeh, B.; Arman, S. Y.; Mehdipour, M.; Markhali, B. P.

2014-01-01

In this study, the corrosion inhibition properties of two similar heterocyclic compounds namely benzotriazole (BTA) and benzothiazole (BNS) inhibitors on copper in 1.0 M H2SO4 solution were studied by electrochemical techniques as well as surface analysis. The results showed that corrosion inhibition of copper largely depends on the molecular structure and concentration of the inhibitors. The effect of DC trend on the interpretation of electrochemical noise (ECN) results in time domain was evaluated by moving average removal (MAR) method. Accordingly, the impact of square and Hanning window functions as drift removal methods in frequency domain was studied. After DC trend removal, a good trend was observed between electrochemical noise (ECN) data and the results obtained from EIS and potentiodynamic polarization. Furthermore, the shot noise theory in frequency domain was applied to approach the charge of each electrochemical event (q) from the potential and current noise signals.

Electrochemical Deposition of High Purity Silicon from Molten Salts

NASA Astrophysics Data System (ADS)

Haarberg, Geir Martin

Several approaches were tried in order to develop an electrochemical route for producing high purity silicon from molten salts. SiO2, K2SiF6 and metallurgical silicon were used as the source of silicon. Molten electrolytes based on chloride (CaCl2-NaCl) and fluoride (LiF-KF) at temperatures from 550 - 900 oC were used. Transient electrochemical techniques were used to study the electrochemical behaviour of dissolved silicon species. Electrolysis experiments were carried out to deposit silicon.

Electrochemical Deposition of High Purity Silicon in Molten Salts

NASA Astrophysics Data System (ADS)

Haarberg, Geir Martin

Several approaches were tried in order to develop an electrochemical route for producing high purity silicon from molten salts. SiO2, K2SiF6 and metallurgical silicon were used as the source of silicon. Molten electrolytes based on chloride (CaCl2-NaCl) and fluoride (LiF-KF) at temperatures from 550 - 900 °C were used. Transient electrochemical techniques were used to study the electrochemical behaviour of dissolved silicon species. Electrolysis experiments were carried out to deposit silicon.

Electrochemical Corrosion of Stainless Steel in Thiosulfate Solutions Relevant to Gold Leaching

NASA Astrophysics Data System (ADS)

Choudhary, Lokesh; Wang, Wei; Alfantazi, Akram

2016-01-01

This study aims to characterize the electrochemical corrosion behavior of stainless steel in the ammoniacal thiosulfate gold leaching solutions. Electrochemical corrosion response was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy, while the semi-conductive properties and the chemical composition of the surface film were characterized using Mott-Schottky analysis and X-ray photoelectron spectroscopy, respectively. The morphology of the corroded specimens was analyzed using scanning electron microscopy. The stainless steel 316L showed no signs of pitting in the ammoniacal thiosulfate solutions.

Electrochemical performances of Al-0.5Mg-0.1Sn-0.02In alloy in different solutions for Al-air battery

NASA Astrophysics Data System (ADS)

Jingling, Ma; Jiuba, Wen; Hongxi, Zhu; Quanan, Li

2015-10-01

In this research, the corrosion behavior and the electrochemical performances of Al-0.5Mg-0.1Sn-0.02In (wt.%) alloy have been investigated in 2 M NaCl, 4 M NaOH ethanol-10% water, 4 M NaOH solutions. The results show that the optimal electrochemical properties are obtained in 4 M NaOH ethanol-water solutions, and the alloy has higher anodic utilization and lower self-corrosion rate in the solutions compared to 2 M NaCl or 4 M aqueous NaOH. SEM and EIS results of the alloy are in good agreement with corrosion characteristics. By comparison with the electrochemical performance of Zn in 4 M NaOH solutions, the feasibility of using Al-0.5Mg-0.1Sn-0.02In alloy as anode material for a high power density Al-air battery in 4 M NaOH ethanol-water solutions is demonstrated.

Enhanced electrochemical performance of monoclinic WO3 thin film with redox additive aqueous electrolyte.

PubMed

Shinde, Pragati A; Lokhande, Vaibhav C; Chodankar, Nilesh R; Ji, Taeksoo; Kim, Jin Hyeok; Lokhande, Chandrakant D

2016-12-01

To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices. Copyright © 2016 Elsevier Inc. All rights reserved.

A label-free electrochemical sensor for detection of mercury(II) ions based on the direct growth of guanine nanowire.

PubMed

Huang, Yan Li; Gao, Zhong Feng; Jia, Jing; Luo, Hong Qun; Li, Nian Bing

2016-05-05

A simple, sensitive and label-free electrochemical sensor is developed for detection of Hg(2+) based on the strong and stable T-Hg(2+)-T mismatches. In the presence of Mg(2+), the parallel G-quadruplex structures could be specifically recognized and precipitated in parallel conformation. Therefore, the guanine nanowire was generated on the electrode surface, triggering the electrochemical H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). In this research, a new method of signal amplification for the quantitative detection of Hg(2+) was described based on the direct growth of guanine nanowire via guanine nanowire. Under optimum conditions, Hg(2+) was detected in the range of 100 pM-100 nM, and the detection limit is 33 pM. Compared to the traditional single G-quadruplex label unit, this electrochemical sensor showed high sensitivity and selectivity for detecting Hg(2+). Copyright © 2016 Elsevier B.V. All rights reserved.

Recent Progress in the Development of Conducting Polymer-Based Nanocomposites for Electrochemical Biosensors Applications: A Mini-Review.

PubMed

Naseri, Maryam; Fotouhi, Lida; Ehsani, Ali

2018-06-01

Among various immobilizing materials, conductive polymer-based nanocomposites have been widely applied to fabricate the biosensors, because of their outstanding properties such as excellent electrocatalytic activity, high conductivity, and strong adsorptive ability compared to conventional conductive polymers. Electrochemical biosensors have played a significant role in delivering the diagnostic information and therapy monitoring in a rapid, simple, and low cost portable device. This paper reviews the recent developments in conductive polymer-based nanocomposites and their applications in electrochemical biosensors. The article starts with a general and concise comparison between the properties of conducting polymers and conducting polymer nanocomposites. Next, the current applications of conductive polymer-based nanocomposites of some important conducting polymers such as PANI, PPy, and PEDOT in enzymatic and nonenzymatic electrochemical biosensors are overviewed. This review article covers an 8-year period beginning in 2010. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical detection of dopamine in the presence of ascorbic acid using graphene modified electrodes.

PubMed

Kim, Yang-Rae; Bong, Sungyool; Kang, Yeon-Joo; Yang, Yongtak; Mahajan, Rakesh Kumar; Kim, Jong Seung; Kim, Hasuck

2010-06-15

Dopamine plays a significant role in the function of human metabolism. It is important to develop sensitive sensor for the determination of dopamine without the interference by ascorbic acid. This paper reports the synthesis of graphene using a modified Hummer's method and its application for the electrochemical detection of dopamine. Electrochemical measurements were performed at glassy carbon electrode modified with graphene via drop-casting method. Cyclic voltammogram of ferri/ferrocyanide redox couple at graphene modified electrode showed an increased current intensity compared with glassy carbon electrode and graphite modified electrode. The decrease of charge transfer resistance was also analyzed by electrochemical impedance spectroscopy. The capacity of graphene modified electrode for selective detection of dopamine was confirmed in a sufficient amount of ascorbic acid (1 mM). The observed linear range for the determination of dopamine concentration was from 4 microM to 100 microM. The detection limit was estimated to be 2.64 microM. Copyright 2010 Elsevier B.V. All rights reserved.

Force modulation and electrochemical gating of conductance in a cytochrome

NASA Astrophysics Data System (ADS)

Davis, Jason J.; Peters, Ben; Xi, Wang

2008-09-01

Scanning probe methods have been used to measure the effect of electrochemical potential and applied force on the tunnelling conductance of the redox metalloprotein yeast iso-1-cytochrome c (YCC) at a molecular level. The interaction of a proximal probe with any sample under test will, at this scale, be inherently perturbative. This is demonstrated with conductive probe atomic force microscopy (CP-AFM) current-voltage spectroscopy in which YCC, chemically adsorbed onto pristine Au(111) via its surface cysteine residue, is observed to become increasingly compressed as applied load is increased, with concomitant decrease in junction resistance. Electrical contact at minimal perturbation, where probe-molecule coupling is comparable to that in scanning tunnelling microscopy, brings with it the observation of negative differential resistance, assigned to redox-assisted probe-substrate tunnelling. The role of the redox centre in conductance is also resolved in electrochemical scanning tunnelling microscopy assays where molecular conductance is electrochemically gateable through more than an order of magnitude.

Effect of electrochemical redox reaction on growth and metabolism of Saccharomyces cerevisiae as an environmental factor.

PubMed

Na, Kwan Byung; Hwang, Tae Sik; Lee, Sung Hun; Ahn, Dae Hee; Park, Doo Hyun

2007-03-01

The effect of an electrochemically generated oxidation-reduction potential and electric pulse on ethanol production and growth of Saccharomyces cerevisiae ATCC 26603 was experimented and compared with effects of electron mediators (neutral red, benzyl viologen, and thionine), chemical oxidants (hydrogen peroxide and hypochlorite), chemical reductants (sulfite and nitrite), oxygen, and hydrogen. The oxidation (anodic) and reduction (cathodic) potential and electric pulse activated ethanol production and growth, and changed the total soluble protein pattern of the test strain. Neutral red electrochemically reduced activated ethanol production and growth of the test strain, but benzyl viologen and thionine did not. Nitrite inhibited ethanol production but did not influence growth of the test strain. Hydrogen peroxide, hypochlorite, and sulfite did not influence ethanol production and growth of the test strain. Hydrogen and oxygen also did not influence the growth and ethanol production. It shows that the test strain may perceive electrochemically generated oxidation-reduction potential and electric pulse as an environmental factor.

Removal of arsenic, phosphates and ammonia from well water using electrochemical/chemical methods and advanced oxidation: a pilot plant approach.

PubMed

Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Halkijevic, Ivan; Kuspilic, Marin; Findri Gustek, Stefica

2014-01-01

The purpose of this work was to develop a pilot plant purification system and apply it to groundwater used for human consumption, containing high concentrations of arsenic and increased levels of phosphates, ammonia, mercury and color. The groundwater used was obtained from the production well in the Vinkovci County (Eastern Croatia). Due to a complex composition of the treated water, the purification system involved a combined electrochemical treatment, using iron and aluminum electrode plates with simultaneous ozonation, followed by a post-treatment with UV, ozone and hydrogen peroxide. The removal of the contaminant with the waste sludge collected during the electrochemical treatment was also tested. The combined electrochemical and advanced oxidation treatment resulted in the complete removal of arsenic, phosphates, color, turbidity, suspended solids and ammonia, while the removal of other contaminants of interest was up to 96.7%. Comparable removal efficiencies were obtained by using waste sludge as a coagulant.

Electrochemical product detection of an asymmetric convective polymerase chain reaction.

PubMed

Duwensee, Heiko; Mix, Maren; Stubbe, Marco; Gimsa, Jan; Adler, Marcel; Flechsig, Gerd-Uwe

2009-10-15

For the first time, we describe the application of heated microwires for an asymmetric convective polymerase chain reaction (PCR) in a modified PCR tube in a small volume. The partly single-stranded product was labeled with the electrochemically active compound osmium tetroxide bipyridine using a partially complementary protective strand with five mismatches compared to the single-stranded product. The labeled product could be successfully detected at a gold electrode modified with a complementary single-stranded capture probe immobilized via a thiol-linker. Our simple thermo-convective PCR yielded electrochemically detectable products after only 5-10 min. A significant discrimination between complementary and non-complementary target was possible using different immobilized capture probes. The total product yield was approx. half the amount of the classical thermocycler PCR. Numerical simulations describing the thermally driven convective PCR explain the received data. Discrimination between complementary capture probes and non-complementary capture probes was performed using square-wave voltammetry. The coupling of asymmetric thermo-convective PCR with electrochemical detection is very promising for future compact DNA sensor devices.

A comparison of electrochemically pre-treated and spark-platinized carbon fiber microelectrode. Measurement of 8-oxo-7,8-dihydro-2'-deoxyguanosine in human urine and plasma.

PubMed

Bartosova, Z; Riman, D; Halouzka, V; Vostalova, J; Simanek, V; Hrbac, J; Jirovsky, D

2016-09-07

A novel method of carbon fiber microelectrode activation using spark discharge was demonstrated and compared to conventional electrochemical pretreatment by potential cycling. The spark discharge was performed at 800 V between the microelectrode connected to positive pole of the power supply and platinum counter electrode. Spark discharge led both to trimming of the fiber tip into conical shape and to the modification of carbon fiber microelectrode with platinum, as proven by scanning electron microscopy and electron dispersive X-ray spectroscopy. After the characterization of electrochemical properties using ferricyanide voltammetry, the activated electrodes were used for electrochemical analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative stress marker. Subnanomolar detection limits (0.55 nmol L(-1)) in high-performance liquid chromatography were achieved for spark platinized electrodes incorporated into the flow detection cell. Copyright © 2016 Elsevier B.V. All rights reserved.

Flow-injection analysis with electrochemical detection of reduced nicotinamide adenine dinucleotide using 2,6-dichloroindophenol as a redox coupling agent.

PubMed

Tang, H T; Hajizadeh, K; Halsall, H B; Heineman, W R

1991-01-01

The determination of reduced nicotinamide adenine dinucleotide (NADH) by electrochemical oxidation requires a more positive potential than is predicted by the formal reduction potential for the NAD+/NADH couple. This problem is alleviated by use of 2,6-dichloroindophenol (DCIP) as a redox coupling agent for NADH. The electrochemical characteristics of DCIP at the glassy carbon electrode are examined by cyclic voltammetry and hydrodynamic voltammetry. NADH is determined by reaction with DCIP to form NAD+ and DCIPH2. DCIPH2 is then quantitated by flow-injection analysis with electrochemical detection by oxidation at a detector potential of +0.25 V at pH 7. NADH is determined over a linear range of 0.5 to 200 microM and with a detection limit of 0.38 microM. The lower detection potential for DCIPH2 compared to NADH helps to minimize interference from oxidizable components in serum samples.

Surface Modifications of Materials by Electrochemical Methods to Improve the Properties for Industrial and Medical Applications

NASA Astrophysics Data System (ADS)

Benea, Lidia

2018-06-01

There are two applied electrochemical methods in our group in order to obtain advanced functional surfaces on materials: (i) direct electrochemical synthesis by electro-codeposition process and (ii) anodization of materials to form nanoporous oxide layers followed by electrodeposition of hydroxyapatite or other bioactive molecules and compounds into porous film. Electrodeposition is a process of low energy consumption, and therefore very convenient for the surface modification of various types of materials. Electrodeposition is a powerful method compared with other methods, which led her to be adopted and spread rapidly in nanotechnology to obtain nanostructured layers and films. Nanoporous thin oxide layers on titanum alloys as support for hydroxyapatite or other biomolecules electrodeposition in view of biomedical applications could be obtained by electrochemical methods. For surface modification of titanium or titanium alloys to improve the biocompatibility or osseointegration, the two steps must be fulfilled; the first is controlled growth of oxide layer followed by second being biomolecule electrodeposition into nanoporous formed titanium oxide layer.

Solution Processed PEDOT Analogues in Electrochemical Supercapacitors.

PubMed

Österholm, Anna M; Ponder, James F; Kerszulis, Justin A; Reynolds, John R

2016-06-01

We have designed fully soluble ProDOTx-EDOTy copolymers that are electrochemically equivalent to electropolymerized PEDOT without using any surfactants or dispersants. We show that these copolymers can be incorporated as active layers in solution processed thin film supercapacitors to demonstrate capacitance, stability, and voltage similar to the values of those that use electrodeposited PEDOT as the active material with the added advantage of the possibility for large scale, high-throughput processing. These Type I supercapacitors provide exceptional cell voltages (up to 1.6 V), highly symmetrical charge/discharge behavior, promising long-term stability exceeding 50 000 charge/discharge cycles, as well as energy (4-18 Wh/kg) and power densities (0.8-3.3 kW/kg) that are comparable to those of electrochemically synthesized analogues.

Electrochemical sensing of bisphenol using a multilayer graphene nanobelt modified photolithography patterned platinum electrode

NASA Astrophysics Data System (ADS)

Karthick Kannan, Padmanathan; Hu, Chunxiao; Morgan, Hywel; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

2016-09-01

An electrochemical sensor has been developed for the detection of Bisphenol-A (BPA) using photolithographically patterned platinum electrodes modified with multilayer graphene nanobelts (GNB). Compared to bare electrodes, the GNB modified electrode exhibited enhanced BPA oxidation current, due to the high effective surface area and high adsorption capacity of the GNB. The sensor showed a linear response over the concentration range from 0.5 μM-9 μM with a very low limit of detection = 37.33 nM. In addition, the sensor showed very good stability and reproducibility with good specificity, demonstrating that GNB is potentially a new material for the development of a practical BPA electrochemical sensor with application in both industrial and plastic industries.

Evaluation of Carbon Anodes for Rechargeable Lithium Cells

NASA Technical Reports Server (NTRS)

Huang, C-K.; Surampudi, S.; Attia, A.; Halpert, G.

1993-01-01

Both liquid phase intercalation technique and electrochemical intercalation technique were examined for the Li-carbon material preparation. The electrochemical techniques include a intermittent discharge method and a two step method. These two electrochemical techniques can ensure to achieve the maximum reversible Li capacity for common commercially available carbon materials. The carbon materials evaluated by the intercalacation method includes: pitch coke, petroleum cole, PAN fiber and graphite materials. Their reversible Li capacity were determined and compared. In this paper, we also demonstrate the importance of EPDM binder composition in the carbon electrode. Our results indicated that it can impact the Li intercalation and de-intercalation capacity in carbon materials. Finally, two possibilities that may help explain the capacity degradation during practical cell cycling were proposed.

Development of paper-based electrochemical sensors for water quality monitoring

NASA Astrophysics Data System (ADS)

Smith, Suzanne; Bezuidenhout, Petroné; Mbanjwa, Mesuli; Zheng, Haitao; Conning, Mariette; Palaniyandy, Nithyadharseni; Ozoemena, Kenneth; Land, Kevin

2016-02-01

We present a method for the development of paper-based electrochemical sensors for detection of heavy metals in water samples. Contaminated water leads to serious health problems and environmental issues. Paper is ideally suited for point-of-care testing, as it is low cost, disposable, and multi-functional. Initial sensor designs were manufactured on paper substrates using combinations of inkjet printing and screen printing technologies using silver and carbon inks. Bismuth onion-like carbon nanoparticle ink was manufactured and used as the active material of the sensor for both commercial and paper-based sensors, which were compared using standard electrochemical analysis techniques. The results highlight the potential of paper-based sensors to be used effectively for rapid water quality monitoring at the point-of-need.

Structure-function study of Poly(sulfobetaine 3,4-ethylenedioxythiophene) (PSBEDOT) and its derivatives.

PubMed

Lee, Chen-Jung; Wang, Huifang; Young, Megan; Li, Shengxi; Cheng, Fang; Cong, Hongbo; Cheng, Gang

2018-06-04

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been widely studied in recent decades due to its high stability, biocompatibility, low redox potential, moderate band gap, and optical transparency in its conducting state. However, for its long-term in vivo applications, the biocompatibility of PEDOT still need to be improved. To address this challenge, zwitterionic Poly(sulfobetaine 3,4-ethylenedioxythiophene) (PSBEDOT) that contains EDOT backbone with sulfobetaine functional side chains were developed in our previous study. Although PSBEDOT showed great resistance to proteins, cells, and bacteria, it is still not clear how the zwitterionic sulfobetaine side chain affects the electrochemical properties of the polymer and reactivity of the monomer. To have better understanding on the structure-function relationship of zwitterionic conducting polymer, we synthesized two derivatives of PSBEDOT, PSBEDOT-4 and PSBEDOT-5, by introducing the alkoxyl spacer between EDOT and sulfobetaine. The interfacial impedance of PSBEDOT-4 and PSBEDOT-5 was examined by electrochemical impedance spectroscopy and showed significant improvement which is about 20 times lower than PSBEDOT on both gold and indium tin oxide substrates at 1 Hz. In the protein adsorption test, PSBEDOT, PSBEDOT-4 and PSBEDOT-5 exhibited comparable resistance to the fibrinogen solution. All three polymers had low protein adsorption around 3%-5% comparing to the control sample, PEDOT, which was normalized to 100%. Additionally, the morphology of PSBEDOT, PSBEDOT-4 and PSBEDOT-5 with different synthesis parameter have been investigated by scanning electron microscope. We believe that these stable and biocompatible materials can be good candidates for developing long-term bioelectronics devices. To address the challenges associated existing conducting materials for bioelectronics, we developed a versatile and high performance zwitterionic conducting material platform with excellent stability, electrochemical, antifouling and controllable antimicrobial/antifouling properties. In this work, we developed two high-performance conducting polymers and systematically investigated how its structure affect their properties. Our study shows we can accurately tune the molecular structure of the monomer to dramatically improve the performance of zwitterionic conducting polymer. This zwitterionic conducting polymer platform may dramatically increase the performance and service life of electrochemical devices for many long-term applications, such as implantable biosensing, tissue engineering, wound healing, robotic prostheses, biofuel cell etc., which all require high performance conducting materials with excellent antifouling/biocompatibility at complex biointerfaces. Copyright © 2018. Published by Elsevier Ltd.

Electrochemical method for measuring corrosion of metals in wood

Treesearch

Samuel L. Zelinka; Douglas Rammer

2006-01-01

Preliminary studies have shown that electrochemical methods, especially Electrochemical Impedance Spectroscopy (EIS), appear to have great promise for measuring the corrosion rate of metals in wood. One of the major reasons for using these techniques is the ability to maintain moisture content and temperature at conditions encountered in service while measuring the...

New insights into the electrochemical behavior of acid orange 7: Convergent paired electrochemical synthesis of new aminonaphthol derivatives

NASA Astrophysics Data System (ADS)

Momeni, Shima; Nematollahi, Davood

2017-02-01

Electrochemical behavior of acid orange 7 has been exhaustively studied in aqueous solutions with different pH values, using cyclic voltammetry and constant current coulometry. This study has provided new insights into the mechanistic details, pH dependence and intermediate structure of both electrochemical oxidation and reduction of acid orange 7. Surprisingly, the results indicate that a same redox couple (1-iminonaphthalen-2(1H)-one/1-aminonaphthalen-2-ol) is formed from both oxidation and reduction of acid orange 7. Also, an additional purpose of this work is electrochemical synthesis of three new derivatives of 1-amino-4-(phenylsulfonyl)naphthalen-2-ol (3a-3c) under constant current electrolysis via electrochemical oxidation (and reduction) of acid orange 7 in the presence of arylsulfinic acids as nucleophiles. The results indicate that the electrogenerated 1-iminonaphthalen-2(1 H)-one participates in Michael addition reaction with arylsulfinic acids to form the 1-amino-3-(phenylsulfonyl)naphthalen-2-ol derivatives. The synthesis was carried out in an undivided cell equipped with carbon rods as an anode and cathode.

Electrochemically active biofilms: facts and fiction. A review

PubMed Central

Babauta, Jerome; Renslow, Ryan; Lewandowski, Zbigniew; Beyenal, Haluk

2014-01-01

This review examines the electrochemical techniques used to study extracellular electron transfer in the electrochemically active biofilms that are used in microbial fuel cells and other bioelectrochemical systems. Electrochemically active biofilms are defined as biofilms that exchange electrons with conductive surfaces: electrodes. Following the electrochemical conventions, and recognizing that electrodes can be considered reactants in these bioelectrochemical processes, biofilms that deliver electrons to the biofilm electrode are called anodic, ie electrode-reducing, biofilms, while biofilms that accept electrons from the biofilm electrode are called cathodic, ie electrode-oxidizing, biofilms. How to grow these electrochemically active biofilms in bioelec-trochemical systems is discussed and also the critical choices made in the experimental setup that affect the experimental results. The reactor configurations used in bioelectrochemical systems research are also described and the authors demonstrate how to use selected voltammetric techniques to study extracellular electron transfer in bioelectrochemical systems. Finally, some critical concerns with the proposed electron transfer mechanisms in bioelectrochemical systems are addressed together with the prospects of bioelectrochemical systems as energy-converting and energy-harvesting devices. PMID:22856464

BF 3-promoted electrochemical properties of quinoxaline in propylene carbonate

DOE PAGES

Carino, Emily V.; Diesendruck, Charles E.; Moore, Jeffrey S.; ...

2015-02-04

Electrochemical and density functional studies demonstrate that coordination of electrolyte constituents to quinoxalines modulates their electrochemical properties. Quinoxalines are shown to be electrochemically inactive in most electrolytes in propylene carbonate, yet the predicted reduction potential is shown to match computational estimates in acetonitrile. We find that in the presence of LiBF 4 and trace water, an adduct is formed between quinoxaline and the Lewis acid BF3, which then displays electrochemical activity at 1–1.5 V higher than prior observations of quinoxaline electrochemistry in non-aqueous media. Direct synthesis and testing of a bis-BF 3 quinoxaline complex further validates the assignment of themore » electrochemically active species, presenting up to a ~26-fold improvement in charging capacity, demonstrating the advantages of this adduct over unmodified quinoxaline in LiBF 4-based electrolyte. The use of Lewis acids to effectively “turn on” the electrochemical activity of organic molecules may lead to the development of new active material classes for energy storage applications.« less

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.

A PVC/polypyrrole sensor designed for beef taste detection using electrochemical methods and sensory evaluation.

PubMed

Zhu, Lingtao; Wang, Xiaodan; Han, Yunxiu; Cai, Yingming; Jin, Jiahui; Wang, Hongmei; Xu, Liping; Wu, Ruijia

2018-03-01

An electrochemical sensor for detection of beef taste was designed in this study. This sensor was based on the structure of polyvinyl chloride/polypyrrole (PVC/PPy), which was polymerized onto the surface of a platinum (Pt) electrode to form a Pt-PPy-PVC film. Detecting by electrochemical methods, the sensor was well characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor was applied to detect 10 rib-eye beef samples and the accuracy of the new sensor was validated by sensory evaluation and ion sensor detection. Several cluster analysis methods were used in the study to distinguish the beef samples. According to the obtained results, the designed sensor showed a high degree of association of electrochemical detection and sensory evaluation, which proved a fast and precise sensor for beef taste detection. Copyright © 2017 Elsevier Ltd. 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

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.

Electrochemical Dissolution of Iridium and Iridium Oxide Particles in Acidic Media: Transmission Electron Microscopy, Electrochemical Flow Cell Coupled to Inductively Coupled Plasma Mass Spectrometry, and X-ray Absorption Spectroscopy Study.

PubMed

Jovanovič, Primož; Hodnik, Nejc; Ruiz-Zepeda, Francisco; Arčon, Iztok; Jozinović, Barbara; Zorko, Milena; Bele, Marjan; Šala, Martin; Šelih, Vid Simon; Hočevar, Samo; Gaberšček, Miran

2017-09-13

Iridium-based particles, regarded as the most promising proton exchange membrane electrolyzer electrocatalysts, were investigated by transmission electron microscopy and by coupling of an electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometry. Additionally, studies using a thin-film rotating disc electrode, identical location transmission and scanning electron microscopy, as well as X-ray absorption spectroscopy have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that Ir particles dissolve well below oxygen evolution reaction (OER) potentials, presumably induced by Ir surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile-type IrO 2 particles are substantially more stable and less active in comparison to as-prepared metallic and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER-relevant conditions, E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism, where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low-temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyzer.

Synthesis, Optical and Electrochemical Properties of Y2O3 Nanoparticles Prepared by Co-Precipitation Method.

PubMed

Saravanan, Thulasingam; Raj, Srinivasan Gokul; Chandar, Nagamuthu Raja Krishna; Jayavel, Ramasamy

2015-06-01

Y2O3 nanoparticles were synthesized by co-precipitation route using yttrium nitrate hexahydrate and ammonium hydroxide as precursors. The prepared sample was calcined at 500 degrees C and subjected to various characterization studies like thermal analysis (TG/DTA), X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The XRD pattern showed the cubic fluorite structure of Y2O3 without any impurity peaks, revealing high purity of the prepared sample. TEM images revealed that the calcined Y2O3 nanoparticles consist of spherical-like morphology with an average particle size of 12 nm. The absorption spectrum of calcined samples shows blue-shift compared to the as-prepared sample, which was further confirmed by PL studies. The possible formation mechanism of Y2O3 nanoparticles has been discussed based on the experimental results. Electrochemical behavior of Y2O3 nanoparticles was studied by cyclic voltammetry to assess their suitability for supercapacitor applications.

X-ray and Electrochemical Impedance Spectroscopy Diagnostic Investigations of Liquid Water in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

NASA Astrophysics Data System (ADS)

Antonacci, Patrick

In this thesis, electrochemical impedance spectroscopy (EIS) and synchrotron x-ray radiography were utilized to characterize the impact of liquid water distributions in polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs) on fuel cell performance. These diagnostic techniques were used to quantify the effects of liquid water visualized on equivalent resistances measured through EIS. The effects of varying the thickness of the microporous layer (MPL) of GDLs were studied using these diagnostic techniques. In a first study on the feasibility of this methodology, two fuel cell cases with a 100 microm-thick and a 150 microm-thick MPL were compared under constant current density operation. In a second study with 10, 30, 50, and 100 microm-thick MPLs, the liquid water in the cathode substrate was demonstrated to affect mass transport resistance, while the liquid water content in the anode (from back diffusion) affected membrane hydration, evidenced through ohmic resistance measurements.

Reserve lithium-thionyl chloride battery for missile applications

NASA Astrophysics Data System (ADS)

Planchat, J. P.; Descroix, J. P.; Sarre, G.

A comparative performance study has been conducted for silver-zinc, thionyl chloride, and thermal batteries designed for such missile applications as ICBM guidance system power supplies. Attention is given to each of the three candidates' conformity to requirements concerning mechanical configuration, electrochemical design, electrolyte reservoir, external case, and gas generator. The silver-zinc and Li-SOCl2 candidates employ similar cell configurations and yield comparable performance. The thermal battery is found to be incapable of meeting battery case temperature-related requirements.

Effects of Salts and Metal Oxides on Electrochemical and Optical Properties of Streptococcus mutans

NASA Astrophysics Data System (ADS)

Kawai, Tsuyoshi; Nagame, Seigo; Kambara, Masaki; Yoshino, Katsumi

1994-10-01

The effects of calcium salts and metal oxide powders on electrochemical, optical and biological properties of Streptococcus mutans have been studied as a novel method to determine the strain. Electrochemical signals of Streptococcus mutans show remarkable decrease in the presence of saturated calcium salts such as CaHPO4, Ca3(PO4)2, and Ca5(PO4)3OH depending on the strains of Streptococcus mutans: Ingbritt, NCTC-10449, or GS-5. The number of viable cells also decreases upon addition of these powders. The effects of metal oxides such as ZnO and BaTiO3 on the electrochemical characteristics and photoluminescence of Streptococcus mutans have also been studied.

High-capacity nanostructured germanium-containing materials and lithium alloys thereof

DOEpatents

Graetz, Jason A.; Fultz, Brent T.; Ahn, Channing; Yazami, Rachid

2010-08-24

Electrodes comprising an alkali metal, for example, lithium, alloyed with nanostructured materials of formula Si.sub.zGe.sub.(z-1), where 0

Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

PubMed

Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

2014-02-14

Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.

Multilayer poly(3,4-ethylenedioxythiophene)-dexamethasone and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate-carbon nanotubes coatings on glassy carbon microelectrode arrays for controlled drug release.

PubMed

Castagnola, Elisa; Carli, Stefano; Vomero, Maria; Scarpellini, Alice; Prato, Mirko; Goshi, Noah; Fadiga, Luciano; Kassegne, Sam; Ricci, Davide

2017-07-13

The authors present an electrochemically controlled, drug releasing neural interface composed of a glassy carbon (GC) microelectrode array combined with a multilayer poly(3,4-ethylenedioxythiophene) (PEDOT) coating. The system integrates the high stability of the GC electrode substrate, ideal for electrical stimulation and electrochemical detection of neurotransmitters, with the on-demand drug-releasing capabilities of PEDOT-dexamethasone compound, through a mechanically stable interlayer of PEDOT-polystyrene sulfonate (PSS)-carbon nanotubes (CNT). The authors demonstrate that such interlayer improves both the mechanical and electrochemical properties of the neural interface, when compared with a single PEDOT-dexamethasone coating. Moreover, the multilayer coating is able to withstand 10 × 10 6 biphasic pulses and delamination test with negligible change to the impedance spectra. Cross-section scanning electron microscopy images support that the PEDOT-PSS-CNT interlayer significantly improves the adhesion between the GC substrate and PEDOT-dexamethasone coating, showing no discontinuities between the three well-interconnected layers. Furthermore, the multilayer coating has superior electrochemical properties, in terms of impedance and charge transfer capabilities as compared to a single layer of either PEDOT coating or the GC substrate alone. The authors verified the drug releasing capabilities of the PEDOT-dexamethasone layer when integrated into the multilayer interface through repeated stimulation protocols in vitro, and found a pharmacologically relevant release of dexamethasone.

Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

DOE PAGES

Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; ...

2015-10-23

Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediatemore » ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.« less

The electrochemical behavior of poly 1-pyrenemethyl methacrylate binder and its effect on the interfacial chemistry of a silicon electrode

NASA Astrophysics Data System (ADS)

Haregewoin, Atetegeb Meazah; Terborg, Lydia; Zhang, Liang; Jurng, Sunhyung; Lucht, Brett L.; Guo, Jinghua; Ross, Philip N.; Kostecki, Robert

2018-02-01

The physico-chemical properties of poly (1-pyrenemethyl methacrylate) (PPy) are presented with respect to its use as a binder in a Si composite anode for Li-ion batteries. PPy thin-films on Si(100) wafer and Cu model electrodes are shown to exhibit superior adhesion as compared to conventional polyvinylidene difluoride (PVdF) binder. Electrochemical testing of the model bi-layer PPy/Si(100) electrodes in a standard organic carbonate electrolyte reveal higher electrolyte reduction current and an overall irreversible cathodic charge consumption during initial cycling versus the uncoated Si electrode. The PPy thin-film is also shown to impede lithiation of the underlying Si. XAS, AFM, TGA and ATR-FTIR analysis indicated that PPy binder is both chemically and electrochemically stable in the cycling potential range however significant swelling is observed due to a selective uptake of diethyl carbonate (DEC) from the electrolyte. The increased concentration of DEC and depletion of ethylene carbonate (EC) at the Si/PPy interface leads to continuous decomposition of the electrolyte and results in non-passivating behavior of the Si(100)/PPy electrode as compared to pristine silicon. Consequently, PPy binder improves the mechanical integrity of composite Si anodes but it influences mass transport at the Si(100)/PPy interface and alters electrochemical response of silicon during cycling in an adverse manner.

Direct Investigation of Mg Intercalation into the Orthorhombic V 2O 5 Cathode Using Atomic-Resolution Transmission Electron Microscopy [Direct Investigation of Mg intercalation into orthorhombic V 2O 5 cathode using Atomic Resolution Electron Microscopy Methods

DOE PAGES

Mukherjee, Arijita; Sa, Niya; Phillips, Patrick J.; ...

2017-02-13

Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V 2O 5, combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electronmore » energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V 2O 5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV 2O 5 sample. Results suggest that the electrochemically cycled orthorhombic V 2O 5 cathode shows a local formation of the theoretically predicted ϵ-Mg0.5V2O5 phase; however, the intercalation levels of Mg are lower than predicted. Lastly, this phase is different from the chemically synthesized sample, which is found to represent the δ-MgV 2O 5 phase.« less

Terpolymer polyrotaxanes: a promising supramolecular system as electron-transporting materials for optoelectronics

NASA Astrophysics Data System (ADS)

Farcas, A.; Resmerita, A.-M.; Farcas, F.

2016-12-01

Optical, electrochemical and surface-morphological properties of three terpolymer polyrotaxanes (1a, 1b and 1c) composed of 2,7-dibromo-9,9-dicyanomethylenefluorene encapsulated into γ-cyclodextrin (γCD), β- or γ-persilylated cyclodextrin (PS-γCD, PS-γCD) cavities (acceptor) and 4,4'-dibromo-4''-methyltriphenylamine (donor) randomly distributed into 9,9-dioctylfluorene conjugated chains have been evaluated and compared to those of the reference 1. The role of the encapsulation on the thermal stability, solubility, film forming ability and transparency was also investigated. High fluorescence efficiency, almost identical normalized absorbance maximum in solution and solid-states of 1a, 1b and 1c provides the lower aggregation tendency. The fluorescence lifetimes (τ) of 1a, 1b and 1c follow a mono-exponential decay with a value τ = 1.11, 1.03 and 1.14 ns, compared with the neat 1, where a bi-exponential decay was identified. AFM studies reveal a smooth and homogenous surface morphology for polyrotaxanes than that of the reference. The electrochemical data provided that the investigated compounds exhibited n- and p-doping processes. The HOMO/LUMO energy levels 1a, 1b, 1c and 1 and in combination with the work function of anodic ITO glass substrates coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (-5.2 eV) and cathodic Ca (-2.8 eV) or Al (-2.2 eV) indicate that the compounds are electrochemically accessible as electron-transporting materials.

Enhanced Intrinsic Catalytic Activity of λ-MnO2 by Electrochemical Tuning and Oxygen Vacancy Generation.

PubMed

Lee, Sanghan; Nam, Gyutae; Sun, Jie; Lee, Jang-Soo; Lee, Hyun-Wook; Chen, Wei; Cho, Jaephil; Cui, Yi

2016-07-18

Chemically prepared λ-MnO2 has not been intensively studied as a material for metal-air batteries, fuel cells, or supercapacitors because of their relatively poor electrochemical properties compared to α- and δ-MnO2 . Herein, through the electrochemical removal of lithium from LiMn2 O4 , highly crystalline λ-MnO2 was prepared as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of the material was further improved by introducing oxygen vacancies (OVs) that could be achieved by increasing the calcination temperature during LiMn2 O4 synthesis; a concentration of oxygen vacancies in LiMn2 O4 could be characterized by its voltage profile as the cathode in a lithiun-metal half-cell. λ-MnO2-z prepared with the highest OV exhibited the highest diffusion-limited ORR current (5.5 mA cm(-2) ) among a series of λ-MnO2-z electrocatalysts. Furthermore, the number of transferred electrons (n) involved in the ORR was >3.8, indicating a dominant quasi-4-electron pathway. Interestingly, the catalytic performances of the samples were not a function of their surface areas, and instead depended on the concentration of OVs, indicating enhancement in the intrinsic catalytic activity of λ-MnO2 by the generation of OVs. This study demonstrates that differences in the electrochemical behavior of λ-MnO2 depend on the preparation method and provides a mechanism for a unique catalytic behavior of cubic λ-MnO2 . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SWCNT Supercapacitor Electrode Fabrication Methods

DTIC Science & Technology

2011-02-01

supercapacitor electrodes out of single-wall carbon nanotubes (SWCNT). We have found that it is best to use SWCNT solutions free from additives that...effect on the resulting specific capacitance, as did the deposition methods compared here. 15. SUBJECT TERMS Carbon nanotube , electrochemical...area may increase the capacitance of supercapacitors. Two materials being studied for this are carbon nanotubes (CNTs) and graphene. Graphene is a

Comparing aging of graphite/LiFePO4 cells at 22 °C and 55 °C - Electrochemical and photoelectron spectroscopy studies

NASA Astrophysics Data System (ADS)

Hellqvist Kjell, Maria; Malmgren, Sara; Ciosek, Katarzyna; Behm, Mårten; Edström, Kristina; Lindbergh, Göran

2013-12-01

Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 °C and 55 °C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process-specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.

Fundamentals, achievements and challenges in the electrochemical sensing of pathogens.

PubMed

Monzó, Javier; Insua, Ignacio; Fernandez-Trillo, Francisco; Rodriguez, Paramaconi

2015-11-07

Electrochemical sensors are powerful tools widely used in industrial, environmental and medical applications. The versatility of electrochemical methods allows for the investigation of chemical composition in real time and in situ. Electrochemical detection of specific biological molecules is a powerful means for detecting disease-related markers. In the last 10 years, highly-sensitive and specific methods have been developed to detect waterborne and foodborne pathogens. In this review, we classify the different electrochemical techniques used for the qualitative and quantitative detection of pathogens. The robustness of electrochemical methods allows for accurate detection even in heterogeneous and impure samples. We present a fundamental description of the three major electrochemical sensing methods used in the detection of pathogens and the advantages and disadvantages of each of these methods. In each section, we highlight recent breakthroughs, including the utilisation of microfluidics, immunomagnetic separation and multiplexing for the detection of multiple pathogens in a single device. We also include recent studies describing new strategies for the design of future immunosensing systems and protocols. The high sensitivity and selectivity, together with the portability and the cost-effectiveness of the instrumentation, enhances the demand for further development in the electrochemical detection of microbes.

Surface morphology and surface energy of anode materials influence power outputs in a multi-channel mediatorless bio-photovoltaic (BPV) system.

PubMed

Bombelli, Paolo; Zarrouati, Marie; Thorne, Rebecca J; Schneider, Kenneth; Rowden, Stephen J L; Ali, Akin; Yunus, Kamran; Cameron, Petra J; Fisher, Adrian C; Ian Wilson, D; Howe, Christopher J; McCormick, Alistair J

2012-09-21

Bio-photovoltaic cells (BPVs) are a new photo-bio-electrochemical technology for harnessing solar energy using the photosynthetic activity of autotrophic organisms. Currently power outputs from BPVs are generally low and suffer from low efficiencies. However, a better understanding of the electrochemical interactions between the microbes and conductive materials will be likely to lead to increased power yields. In the current study, the fresh-water, filamentous cyanobacterium Pseudanabaena limnetica (also known as Oscillatoria limnetica) was investigated for exoelectrogenic activity. Biofilms of P. limnetica showed a significant photo response during light-dark cycling in BPVs under mediatorless conditions. A multi-channel BPV device was developed to compare quantitatively the performance of photosynthetic biofilms of this species using a variety of different anodic conductive materials: indium tin oxide-coated polyethylene terephthalate (ITO), stainless steel (SS), glass coated with a conductive polymer (PANI), and carbon paper (CP). Although biofilm growth rates were generally comparable on all materials tested, the amplitude of the photo response and achievable maximum power outputs were significantly different. ITO and SS demonstrated the largest photo responses, whereas CP showed the lowest power outputs under both light and dark conditions. Furthermore, differences in the ratios of light : dark power outputs indicated that the electrochemical interactions between photosynthetic microbes and the anode may differ under light and dark conditions depending on the anodic material used. Comparisons between BPV performances and material characteristics revealed that surface roughness and surface energy, particularly the ratio of non-polar to polar interactions (the CQ ratio), may be more important than available surface area in determining biocompatibility and maximum power outputs in microbial electrochemical systems. Notably, CP was readily outperformed by all other conductive materials tested, indicating that carbon may not be an optimal substrate for microbial fuel cell operation.

Kelvin Probe Force Microscopy in liquid using Electrochemical Force Microscopy

DOE PAGES

Collins, Liam; Jesse, Stephen; Kilpatrick, J.; ...

2015-01-19

Conventional closed loop-Kelvin probe force microscopy (KPFM) has emerged as a powerful technique for probing electric and transport phenomena at the solid-gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe-sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present). Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q watermore » and aqueous NaCl) and ionically-inactive (non-polar decane) liquids by electrochemical force microscopy (EcFM), a multidimensional (i.e., bias- and time-resolved) spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids), KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD) values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions). EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid–liquid interface.« less

Scanning electrochemical microscopy of graphene/polymer hybrid thin films as supercapacitors: Physical-chemical interfacial processes

NASA Astrophysics Data System (ADS)

Gupta, Sanju; Price, Carson

2015-10-01

Hybrid electrode comprising an electric double-layer capacitor of graphene nanosheets and a pseudocapacitor of the electrically conducting polymers namely, polyaniline; PAni and polypyrrole; PPy are constructed that exhibited synergistic effect with excellent electrochemical performance as thin film supercapacitors for alternative energy. The hybrid supercapacitors were prepared by layer-by-layer (LbL) assembly based on controlled electrochemical polymerization followed by reduction of graphene oxide electrochemically producing ErGO, for establishing intimate electronic contact through nanoscale architecture and chemical stability, producing a single bilayer of (PAni/ErGO)1, (PPy/ErGO)1, (PAni/GO)1 and (PPy/GO)1. The rationale design is to create thin films that possess interconnected graphene nanosheets (GNS) with polymer nanostructures forming well-defined tailored interfaces allowing sufficient surface adsorption and faster ion transport due to short diffusion distances. We investigated their electrochemical properties and performance in terms of gravimetric specific capacitance, Cs, from cyclic voltammograms. The LbL-assembled bilayer films exhibited an excellent Cs of ≥350 F g-1 as compared with constituents (˜70 F g-1) at discharge current density of 0.3 A g-1 that outperformed many other hybrid supercapacitors. To gain deeper insights into the physical-chemical interfacial processes occurring at the electrode/electrolyte interface that govern their operation, we have used scanning electrochemical microscopy (SECM) technique in feedback and probe approach modes. We present our findings from viewpoint of reinforcing the role played by heterogeneous electrode surface composed of nanoscale graphene sheets (conducting) and conducting polymers (semiconducting) backbone with ordered polymer chains via higher/lower probe current distribution maps. Also targeted is SECM imaging that allowed to determine electrochemical (re)activity of surface ion adsorption sites density at solid/liquid interface.

Highly labeled methylene blue-ds DNA silica nanoparticles for signal enhancement of immunoassays: application to the sensitive detection of bacteria in human platelet concentrates.

PubMed

Bonnet, Romaric; Farre, Carole; Valera, Lionel; Vossier, Ludivine; Léon, Fanny; Dagland, Typhaine; Pouzet, Agnès; Jaffrézic-Renault, Nicole; Fareh, Jeannette; Fournier-Wirth, Chantal; Chaix, Carole

2018-05-15

A nanoparticle-based electrochemical sandwich immunoassay was developed for bacteria detection in platelet concentrates. For the assay, magnetic beads were functionalized with antibodies to allow the specific capture of bacteria from the complex matrix, and innovative methylene blue-DNA/nanoparticle assemblies provided the electrochemical response for amplified detection. This nanoparticular system was designed as a temperature-sensitive nano-tool for electrochemical detection. First, oligonucleotide-functionalized nanoparticles were obtained by direct synthesis of the DNA strands on the nanoparticle surface using an automated oligonucleotide synthesizer. Densely packed DNA coverage was thus obtained. Then, DNA duplexes were constructed on the NP surface with a complementary strand bearing a 3 methylene blue tag. This strategy ultimately produced highly functionalized nanoparticles with electrochemical markers. These assemblies enabled amplification of the electrochemical signal, resulting in a very good sensitivity. A proof-of-concept was carried out for E. coli detection in human platelet concentrates. Bacterial contamination of this complex biological matrix is the highest residual infectious risk in blood transfusion. The development of a rapid assay that could reach 10-102 CFU mL-1 sensitivity is a great challenge. The nanoparticle-based electrochemical sandwich immunoassay carried out on a boron doped diamond electrode proved to be sensitive for E. coli detection in human platelets. Two antibody pairs were used to develop either a generic assay against certain Gram negative strains or a specific assay for E. coli. The methylene blue-DNA/nanoparticles amplify sensitivity ×1000 compared with the assay run without NPs for electrochemical detection. A limit of detection of 10 CFU mL-1 in a biological matrix was achieved for E. coli using the highly specific antibody pair.

Enhancement of the electrochemical performance of hydrothermally prepared anatase nanoparticles for optimal use as high capacity anode materials in lithium ion batteries (LIBs)

NASA Astrophysics Data System (ADS)

Sanad, M. M. S.; Rashad, M. M.; Powers, K.

2015-02-01

Mesoporous TiO2 nanoparticles have been synthesized via facile hydrolytic hydrothermal technique without incorporation any template. The precious metallic nanoparticles; Ag, Pt and Pd have been embedded between the anatase particles using in situ reduction step. The structural properties of the as-synthesized samples were investigated by X-ray diffraction, transmission electron microscopic and N2 adsorption-desorption isotherm ( S BET). The electrochemical studies for the as-prepared anode materials including, cyclic voltammetry and electrochemical impedance spectroscopy indicated a significant improvement in the electronic conductivity of the lithium-TiO2 cells. Therefore, the charge-discharge rates were noticeably promoted as a result of the enhancement of Li-ion diffusion and charge transfer. The cycling results of Pd-TiO2 revealed a marvelous improvement in both charge and discharge capacities by 89.4 and 88 % after 10 cycles at C/5 rate. Generally, all the as-prepared TiO2 nanocomposites showed enhanced specific capacity, cycling stability and rate capability compared to the pure TiO2, providing a promising behavior for use as anodes in lithium ion batteries (LIBs).

Real-time mapping of salt glands on the leaf surface of Cynodon dactylon L. using scanning electrochemical microscopy.

PubMed

Parthasarathy, Meera; Pemaiah, Brindha; Natesan, Ravichandran; Padmavathy, Saralla R; Pachiappan, Jayaraman

2015-02-01

Salt glands are specialized organelles present in the leaf tissues of halophytes, which impart salt-tolerance capability to the plant species. These glands are usually identified only by their morphology using conventional staining procedures coupled with optical microscopy. In this work, we have employed scanning electrochemical microscopy to identify the salt glands not only by their morphology but also by their salt excretion behavior. Bermuda grass (Cynodon dactylon L.) species was chosen for the study as they are known to be salt-tolerant and contain salt glands on leaf surfaces. Scanning electrochemical microscopy performed in sodium chloride medium in the presence and absence of potassium ferrocyanide as redox mediator, reveals the identity of salt glands. More insight into the ion expulsion behavior of these glands was obtained by mapping lateral and vertical variations in ion concentrations using surface impedance measurements which indicated five times higher resistance over the salt glands compared to the surrounding tissues and bulk solution. The protocol could be used to understand the developmental processes in plants grown in different soil/water conditions in order to improve salt tolerance of food crops by genetic engineering and hence improve their agricultural productivity.

Electrochemical lithiation performance and characterization of silicon-graphite composites with lithium, sodium, potassium, and ammonium polyacrylate binders.

PubMed

Han, Zhen-Ji; Yamagiwa, Kiyofumi; Yabuuchi, Naoaki; Son, Jin-Young; Cui, Yi-Tao; Oji, Hiroshi; Kogure, Akinori; Harada, Takahiro; Ishikawa, Sumihisa; Aoki, Yasuhito; Komaba, Shinichi

2015-02-07

Poly(acrylic acid) (PAH), which is a water soluble polycarboxylic acid, is neutralized by adding different amounts of LiOH, NaOH, KOH, and ammonia (NH4OH) aqueous solutions to fix neutralization degrees. The differently neutralized polyacid, alkali and ammonium polyacrylates are examined as polymeric binders for the preparation of Si-graphite composite electrodes as negative electrodes for Li-ion batteries. The electrode performance of the Si-graphite composite depends on the alkali chemicals and neutralization degree. It is found that 80% NaOH-neutralized polyacrylate binder (a pH value of the resultant aqueous solution is ca. 6.7) is the most efficient binder to enhance the electrochemical lithiation and de-lithiation performance of the Si-graphite composite electrode compared to that of conventional PVdF and the other binders used in this study. The optimum polyacrylate binder highly improves the dispersion of active material in the composite electrode. The binder also provides the strong adhesion, suitable porosity, and hardness for the composite electrode with 10% (m/m) binder content, resulting in better electrochemical reversibility. From these results, the factors of alkali-neutralized polyacrylate binders affecting the electrode performance of Si-graphite composite electrodes are discussed.

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices.

PubMed

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J; Grant, Patrick S

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

A nanocomposite-based electrochemical sensor for non-enzymatic detection of hydrogen peroxide

PubMed Central

Du, Xin; Chen, Yuan; Dong, Wenhao; Han, Bingkai; Liu, Min; Chen, Qiang; Zhou, Jun

2017-01-01

Hydrogen peroxide (H2O2) plays important signaling roles in normal physiology and disease. However, analyzing the actions of H2O2 is often impeded by the difficulty in detecting this molecule. Herein, we report a novel nanocomposite-based electrochemical sensor for non-enzymatic detection of H2O2. Graphene oxide (GO) was selected as the dopant for the synthesis of polyaniline (PANI), leading to the successful fabrication of a water-soluble and stable GO-PANI composite. GO-PANI was subsequently subject to cyclic voltammetry to generate reduced GO-PANI (rGO-PANI), enhancing the conductivity of the material. Platinum nanoparticles (PtNPs) were then electrodeposited on the surface of the rGO-PANI-modified glassy carbon electrode (GCE) to form an electrochemical H2O2 sensor. Compared to previously reported sensors, the rGO-PANI-PtNP/GCE exhibited an expanded linear range, higher sensitivity, and lower detection limit in the quantification of H2O2. In addition, the sensor displayed outstanding reproducibility and selectivity in real-sample examination. Our study suggests that the rGO-PANI-PtNP/GCE may have broad utility in H2O2 detection under physiological and pathological conditions. PMID:28035076

High surface area synthesis, electrochemical activity, and stability of tungsten carbide supported Pt during oxygen reduction in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Chhina, H.; Campbell, S.; Kesler, O.

The oxidation of carbon catalyst supports to carbon dioxide gas leads to degradation in catalyst performance over time in proton exchange membrane fuel cells (PEMFCs). The electrochemical stability of Pt supported on tungsten carbide has been evaluated on a carbon-based gas diffusion layer (GDL) at 80 °C and compared to that of HiSpec 4000™ Pt/Vulcan XC-72R in 0.5 M H 2SO 4. Due to other electrochemical processes occurring on the GDL, detailed studies were also performed on a gold mesh substrate. The oxygen reduction reaction (ORR) activity was measured both before and after accelerated oxidation cycles between +0.6 V and +1.8 V vs. RHE. Tafel plots show that the ORR activity remained high even after accelerated oxidation tests for Pt/tungsten carbide, while the ORR activity was extremely poor after accelerated oxidation tests for HiSpec 4000™. In order to make high surface area tungsten carbide, three synthesis routes were investigated. Magnetron sputtering of tungsten on carbon was found to be the most promising route, but needs further optimization.

Nanokit for single-cell electrochemical analyses.

PubMed

Pan, Rongrong; Xu, Mingchen; Jiang, Dechen; Burgess, Jame D; Chen, Hong-Yuan

2016-10-11

The development of more intricate devices for the analysis of small molecules and protein activity in single cells would advance our knowledge of cellular heterogeneity and signaling cascades. Therefore, in this study, a nanokit was produced by filling a nanometer-sized capillary with a ring electrode at the tip with components from traditional kits, which could be egressed outside the capillary by electrochemical pumping. At the tip, femtoliter amounts of the kit components were reacted with the analyte to generate hydrogen peroxide for the electrochemical measurement by the ring electrode. Taking advantage of the nanotip and small volume injection, the nanokit was easily inserted into a single cell to determine the intracellular glucose levels and sphingomyelinase (SMase) activity, which had rarely been achieved. High cellular heterogeneities of these two molecules were observed, showing the significance of the nanokit. Compared with the current methods that use a complicated structural design or surface functionalization for the recognition of the analytes, the nanokit has adapted features of the well-established kits and integrated the kit components and detector in one nanometer-sized capillary, which provides a specific device to characterize the reactivity and concentrations of cellular compounds in single cells.

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.

PubMed

Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

2013-12-15

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. © 2013 Elsevier B.V. All rights reserved.

Comparison of TiO2 photocatalysis, electrochemically assisted Fenton reaction and direct electrochemistry for simulation of phase I metabolism reactions of drugs.

PubMed

Ruokolainen, Miina; Gul, Turan; Permentier, Hjalmar; Sikanen, Tiina; Kostiainen, Risto; Kotiaho, Tapio

2016-02-15

The feasibility of titanium dioxide (TiO2) photocatalysis, electrochemically assisted Fenton reaction (EC-Fenton) and direct electrochemical oxidation (EC) for simulation of phase I metabolism of drugs was studied by comparing the reaction products of buspirone, promazine, testosterone and 7-ethoxycoumarin with phase I metabolites of the same compounds produced in vitro by human liver microsomes (HLM). Reaction products were analysed by UHPLC-MS. TiO2 photocatalysis simulated the in vitro phase I metabolism in HLM more comprehensively than did EC-Fenton or EC. Even though TiO2 photocatalysis, EC-Fenton and EC do not allow comprehensive prediction of phase I metabolism, all three methods produce several important metabolites without the need for demanding purification steps to remove the biological matrix. Importantly, TiO2 photocatalysis produces aliphatic and aromatic hydroxylation products where direct EC fails. Furthermore, TiO2 photocatalysis is an extremely rapid, simple and inexpensive way to generate oxidation products in a clean matrix and the reaction can be simply initiated and quenched by switching the UV lamp on/off. Copyright © 2015 Elsevier B.V. All rights reserved.

Facile and efficient electrochemical enantiomer recognition of phenylalanine using β-Cyclodextrin immobilized on reduced graphene oxide.

PubMed

Zaidi, Shabi Abbas

2017-08-15

This work demonstrates the facile and efficient preparation protocol of β-Cyclodextrin-reduced graphene oxide modified glassy carbon electrode (β-CD/RGO/GCE) sensor for an impressive chiral selectivity analysis for phenylalanine enantiomers. In this work, the immobilization of β-CD over graphene sheets allows the excellent enantiomer recognition due to the large surface area and high conductivity of graphene sheets and extraordinary supramolecular (host-guest interaction) property of β-CD. The proposed sensor was well characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS) techniques. The analytical studies demonstrated that the β-CD/RGO/GCE exhibit superior chiral recognition toward L-phenylalanine as compared to D-phenylalanine. Under optimum conditions, the developed sensor displayed a good linear range from 0.4 to 40µM with the limit of detection (LOD) values of 0.10µM and 0.15µM for l- and D-phenylalanine, respectively. Furthermore, the proposed sensor exhibits good stability and regeneration capacity. Thus, the as-synthesized material can be exploited for electrochemical enantiomer recognition successfully. Copyright © 2017 Elsevier B.V. All rights reserved.

Photo-Electrochemical Treatment of Reactive Dyes in Wastewater and Reuse of the Effluent: Method Optimization

PubMed Central

Sala, Mireia; López-Grimau, Víctor; Gutiérrez-Bouzán, Carmen

2014-01-01

In this work, the efficiency of a photo-electrochemical method to remove color in textile dyeing effluents is discussed. The decolorization of a synthetic effluent containing a bi-functional reactive dye was carried out by applying an electrochemical treatment at different intensities (2 A, 5 A and 10 A), followed by ultraviolet irradiation. The combination of both treatments was optimized. The final percentage of effluent decolorization, the reduction of halogenated organic volatile compound and the total organic carbon removal were the determinant factors in the selection of the best treatment conditions. The optimized method was applied to the treatment of nine simulated dyeing effluents prepared with different reactive dyes in order to compare the behavior of mono, bi, and tri-reactive dyes. Finally, the nine treated effluents were reused in new dyeing processes and the color differences (DECMC (2:1)) with respect to a reference were evaluated. The influence of the effluent organic matter removal on the color differences was also studied. The reuse of the treated effluents provides satisfactory dyeing results, and an important reduction in water consumption and salt discharge is achieved. PMID:28788251

Refined method for predicting electrochemical windows of ionic liquids and experimental validation studies.

PubMed

Zhang, Yong; Shi, Chaojun; Brennecke, Joan F; Maginn, Edward J

2014-06-12

A combined classical molecular dynamics (MD) and ab initio MD (AIMD) method was developed for the calculation of electrochemical windows (ECWs) of ionic liquids. In the method, the liquid phase of ionic liquid is explicitly sampled using classical MD. The electrochemical window, estimated by the energy difference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), is calculated at the density functional theory (DFT) level based on snapshots obtained from classical MD trajectories. The snapshots were relaxed using AIMD and quenched to their local energy minima, which assures that the HOMO/LUMO calculations are based on stable configurations on the same potential energy surface. The new procedure was applied to a group of ionic liquids for which the ECWs were also experimentally measured in a self-consistent manner. It was found that the predicted ECWs not only agree with the experimental trend very well but also the values are quantitatively accurate. The proposed method provides an efficient way to compare ECWs of ionic liquids in the same context, which has been difficult in experiments or simulation due to the fact that ECW values sensitively depend on experimental setup and conditions.

Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Diethelm, Stefan; Van herle, Jan

This study investigates the performance of a standard Ni-YSZ anode supported cell under ethanol steam reforming operating conditions. Therefore, the fuel cell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also used for comparison to check the conversion of ethanol and of reformate gases (H 2, CO) in the fuel cell. The electrochemical properties of the fuel cell fed with four different fuel compositions were characterized between 710 and 860 °C by I- V and EIS measurements at OCV and under polarization. In order to elucidate the limiting processes, impedance spectra obtained with different gas compositions were compared using the derivative of the real part of the impedance with respect of the natural logarithm of the frequency. Results show that internal steam reforming of ethanol takes place significantly on Ni-YSZ anode only above 760 °C. Comparisons of results obtained with reformate gas showed that the electrochemical cell performance is dominated by the conversion of hydrogen. The conversion of CO also occurs either directly or indirectly through the water-gas shift reaction but has a significant impact on the electrochemical performance only above 760 °C.

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices

NASA Astrophysics Data System (ADS)

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J.; Grant, Patrick S.

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

Extracting cancer cell line electrochemical parameters at the single cell level using a microfabricated device.

PubMed

Alqabandi, Jassim A; Abdel-Motal, Ussama M; Youcef-Toumi, Kamal

2009-02-01

Cancer cells have distinctive electrochemical properties. This work sheds light on the system design aspects and key challenges that should be considered when experimentally analyzing and extracting the electrical characteristics of a tumor cell line. In this study, we developed a cellularbased functional microfabricated device using lithography technology. This device was used to investigate the electrochemical parameters of cultured cancer cells at the single-cell level. Using impedance spectroscopy analyses, we determined the average specific capacitance and resistance of the membrane of the cancer cell line B16-F10 to be 1.154 +/- 0.29 microF/cm(2), and 3.9 +/- 1.15 KOmega.cm(2) (mean +/- SEM, n =14 cells), respectively. The consistency of our findings via different trails manifests the legitimacy of our experimental procedure. Furthermore, the data were compared with a proposed constructed analytical-circuit model. The results of this work may greatly assist researchers in defining an optimal procedure while extracting electrical properties of cancer cells. Detecting electrical signals at the single cell level could lead to the development of novel approaches for analysis of malignant cells in human tissues and biopsies.

Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.

PubMed

Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

2012-10-15

In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 μM to 1 mM with a detection limit of 0.1 μM and high sensitivity of 1.1 μA μM(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other. Copyright © 2012 Elsevier B.V. All rights reserved.

Self-discharge of electrochemical capacitors based on soluble or grafted quinone.

PubMed

Shul, Galyna; Bélanger, Daniel

2016-07-28

The self-discharge of hybrid electrochemical capacitors based on the redox activity of electrolyte additives or grafted species to the electrode material is investigated simultaneously for the cell and each individual electrode. Electrochemical capacitors using a redox-active electrolyte consisting in hydroquinone added to the electrolyte solution and a redox-active electrode based on anthraquinone-grafted carbon as a negative electrode are investigated. The results are analyzed by using Conway kinetic models and compared to those of a common electrochemical double layer capacitor. The self-discharge investigation is complemented by charge/discharge cycling and it is shown that processes affecting galvanostatic charge/discharge cycling and the self-discharge rate occurring at each electrode of an electrochemical capacitor are different but related to each other. The electrochemical capacitor containing hydroquinone in the electrolyte exhibits a much quicker self-discharge rate than that using a negative electrode based on grafted anthraquinone with a 50% decay of the cell voltage of the fully charged device in 0.6 and 6 h, respectively. The fast self-discharge of the former is due to the diffusion of benzoquinone molecules (formed at the positive electrode during charging) to the negative electrode, where they are reduced, causing a quick depolarization. The grafting of anthraquinone molecules on the carbon material of the negative electrode led to a much slower self-discharge, which nonetheless occurred, by the reaction of the reduced form of the grafted species with electrolyte species.

A study for hypergolic vapor sensor development

NASA Technical Reports Server (NTRS)

Stetter, J. R.

1977-01-01

The use of an electrochemical technique for MMH and N02 measurement was investigated. Specific MMH and N02 electrochemical sensors were developed. Experimental techniques for preparation, handling, and analysis of hydrazine's vapor mixtures at ppb and ppm levels were developed. Two approaches to N02 instrument design were evaluated including specific adsorption and specific electrochemical reduction. Two approaches to hydrazines monitoring were evaluated including catalytic conversion to N0 with subsequent N0 detection and direct specific electrochemical oxidation. Two engineering prototype MMH/N02 monitors were designed and constructed.

Application of electrochemically formed polyazulene to rechargeable lithium battery

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

Osaka, T.; Naoi, K.; Hirabayashi, T.

1987-11-01

An electrochemically formed polyazulene(PAz), one of the electroconductive polycyclic hydrocarbons, was studied for its electrochemical properties in order to examine the possibility of utilizing it as a cathode active material of rechargeable lithium battery. The electrode kinetics of PAz film electrode, especially the anion doping-undoping process, were investigated mainly with cyclic voltammetry and FFT impedance method. The cyclic voltammetric results of PAz film showed a highly reversible redox process. Cole-Cole plots for PAz electrode obtained by impedance measurements as a function of doping potential were also found to offer an indication that PAz can be an excellent battery material. Themore » charging-discharging property, and the cyclability of a Li/LiClO/sub 4/-PC(propylene carbonate)/PAz battery were then studied as a function of the film thickness of PAz cathode. The charging-discharging behavior of Li/LiClO/sub 4/-PC/PAz was also compared with those of Li/LiClO/sub 4/--PC/polypyrrole and Li/LiClO/sub 4/-PC/polyaniline batteries, which had been examined earlier. When compared with Li/LiClO/sub 4/-PC/polypyrrole or Li/LiClO/sub 4/-PC/polyaniline batteries, a Li/LiClO/sub 4//PAz battery showed fully-high and constant discharge voltage (ca. 3.2V), while keeping 100% of coulombic yield. Inspection by SEM showed that the surface condition of PAz film greatly resembled that of polypyrrole, however, a 10 C cm/sup -2/ PAz film was prepared with thicker than polypyrrole formed with the same amount of charge of 10 C cm/sup -2/.« less

Comparative studies in electrochemical degradation of sulfamethoxazole and diclofenac in water by using various electrodes and phosphate and sulfate supporting electrolytes.

PubMed

Sifuna, Fred W; Orata, Francis; Okello, Veronica; Jemutai-Kimosop, Selly

2016-09-18

In this study, the electro-oxidation capacities of Na2SO4 and potassium phosphate buffer supporting electrolytes were tested and compared for destruction of the sulfamethoxazole (SMX) and diclofenac (DCF) on platinum (Pt) electrode and graphite carbon electrode in aqueous medium. The suitability of pharmaceutical active compounds (PhACs) for electrochemical oxidation was tested by cyclic voltammetry (CV) technique performed in the potential range -1.5 to +1.5 V versus Ag/AgCl, which confirmed the electro-activity of the selected PhACs. The degradation and mineralization were monitored by ultraviolet (UV)-Vis spectrophotometry and HPLC. 0.1 M Na2SO4 supporting electrolyte was found to be more effective for mineralization of SMX and DCF, with efficiency of 15-30% more than the 0.1 M phosphate buffer supporting electrolyte on the platinum (Pt) and carbon electrodes. The Pt electrode showed better performance in the degradation of the two PhACs while under the same conditions than the carbon electrode for both 0.1 M Na2SO4 and 0.1 M potassium phosphate buffer supporting electrolytes. The SMX and DCF degradation kinetics best fitted the second-order reaction, with rate constants ranging between 0.000389 and 0.006 mol(2) L(-2) min(-1) and correlation coefficient (R(2)) above 0.987. The second-order degradation kinetics indicated that the rate-determining step in the degradation could be a chemical process, thus suggesting the active involvement of electrolyte radical species in the degradation of SMX and DCF. Results obtained from a real field sample showed a more than 98% removal of the PhACs from the wastewater by electrochemical degradation.

Anodic electrochemical performances of MgCo{sub 2}O{sub 4} synthesized by oxalate decomposition method and electrospinning technique for Li-ion battery application

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

Darbar, Devendrasinh; Department of Mechanical Engineering, National University of Singapore, 117576; Department of Physics, National University of Singapore, 117542

2016-01-15

Highlights: • MgCo{sub 2}O{sub 4} was prepared by oxalate decomposition method and electrospinning technique. • Electrospun MgCo{sub 2}O{sub 4} shows the reversible capacity of 795 and 227 mAh g{sup −1} oxalate decomposition MgCo{sub 2}O{sub 4} after 50 cycle. • Electrospun MgCo{sub 2}O{sub 4} show good cycling stability and electrochemical performance. - Abstract: Magnesium cobalt oxide, MgCo{sub 2}O{sub 4} was synthesized by oxalate decomposition method and electrospinning technique. The electrochemical performances, structures, phase formation and morphology of MgCo{sub 2}O{sub 4} synthesized by both the methods are compared. Scanning electron microscope (SEM) studies show spherical and fiber type morphology, respectively for themore » oxalate decomposition and electrospinning method. The electrospun nanofibers of MgCo{sub 2}O{sub 4} calcined at 650 °C, showed a very good reversible capacity of 795 mAh g{sup −1} after 50 cycles when compared to bulk material capacity of 227 mAh g{sup −1} at current rate of 60 mA g{sup −1}. MgCo{sub 2}O{sub 4} nanofiber showed a reversible capacity of 411 mAh g{sup −1} (at cycle) at current density of 240 mA g{sup −1}. Improved performance was due to improved conductivity of MgO, which may act as buffer layer leading to improved cycling stability. The cyclic voltammetry studies at scan rate of 0.058 mV/s show main cathodic at around 1.0 V and anodic peaks at 2.1 V vs. Li.« less

Reclamation of niobium compounds from ionic liquid electrochemical polishing of superconducting radio frequency cavities

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

Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.

2013-06-01

Recent research has shown that choline chloride (vitamin B4)-based solutions can be used as a greener alternative to acid-based electrochemical polishing solutions. This study demonstrated a successful method for electrochemical deposition of niobium compounds onto the surface of copper substrates using a novel choline chloride-based ionic liquid. Niobium ions present in the ionic liquid solution were dissolved into the solution prior to deposition via electrochemical polishing of solid niobium. A black coating was clearly visible on the surface of the Cu following deposition. This coating was analyzed using scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), atomic force microscopymore » (AFM), and X-ray fluorescence spectroscopy (XRF). This ionic liquid-based electrochemical deposition method effectively recycles previously dissolved niobium from electrochemical polishing of superconducting radio frequency (SRF) cavities.« less

Development of a system for treatment of coconut industry wastewater using electrochemical processes followed by Fenton reaction.

PubMed

Gomes, Lúcio de Moura; Duarte, José Leandro da Silva; Pereira, Nathalia Marcelino; Martínez-Huitle, Carlos A; Tonholo, Josealdo; Zanta, Carmen Lúcia de Paiva E Silva

2014-01-01

The coconut processing industry generates a significant amount of liquid waste. New technologies targeting the treatment of industrial effluents have emerged, including advanced oxidation processes, the Fenton reaction, and electrochemical processes, which produce strong oxidizing species to remove organic matter. In this study we combined the Fenton reaction and electrochemical process to treat wastewater generated by the coconut industry. We prepared a synthetic wastewater consisting of a mixture of coconut milk and water and assessed how the Fenton reagents' concentration, the cathode material, the current density, and the implementation of associated technologies affect its treatment. Electrochemical treatment followed by the Fenton reaction diminished turbidity and chemical oxygen demand (COD) by 85 and 95%, respectively. The Fenton reaction followed by the electrochemical process reduced turbidity and COD by 93 and 85%, respectively. Therefore, a combination of the Fenton and electrochemical technologies can effectively treat the effluent from the coconut processing industry.

Unravelling the electrochemical double layer by direct probing of the solid/liquid interface

PubMed Central

Favaro, Marco; Jeong, Beomgyun; Ross, Philip N.; Yano, Junko; Hussain, Zahid; Liu, Zhi; Crumlin, Ethan J.

2016-01-01

The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential. PMID:27576762

The mechanical and electrochemical properties of bulk metallic glasses

NASA Astrophysics Data System (ADS)

Morrison, Mark Lee

The objectives of this study were to define and model the electrochemical and mechanical behaviors of BMGs, in addition to the interactions between these. The electrochemical behaviors of Zr-, Ti-, and Ca-based BMGs have been studied in various environments. Moreover, the electrochemical behaviors of several common, crystalline materials have also been characterized in the same environments to facilitate comparisons. Mechanical characterization of the Vitreloy 105 alloy was conducted through four-point bend fatigue testing, as well as tensile testing with in situ thermography. After the electrochemical and mechanical behaviors of the Vit 105 BMG alloy were defined separately, the corrosion-fatigue behavior of this alloy was studied. Corrosion-fatigue tests were conducted in a 0.6 M NaCl electrolyte, identical to one of the environments in which the electrochemical behavior was previously defined. The environmental effect was found to be significant at most stress levels, with decreasing effects at higher stress levels due to decreasing time in the detrimental environment, and severely depressed the corrosion-fatigue endurance limit. Cyclic-anodic-polarization tests were conducted during cyclic loading to elucidate the effect of cyclic stresses on the electrochemical behavior. It was found that a stress range of 900 MPa resulted in active pitting at the open-circuit potentials. The degradation mechanism was determined to be stress-assisted dissolution, not hydrogen embrittlement. Finally, tensile tests were conducted with the Vit 105 BMG alloy with in situ infrared (IR) thermography to observe the evolution of shear bands during deformation. More importantly, the length, location, sequence, temperature evolution, and velocity of individual shear bands have been quantified through the use of IR thermography. Based upon all of these studies on a variety of BMG alloy systems, the most important factor in the mechanical and electrochemical behavior was found to be material quality and homogeneity. Therefore, future research on the improvement of BMG alloys should be focused on this area.

A Nanocoaxial-Based Electrochemical Sensor for the Detection of Cholera Toxin

NASA Astrophysics Data System (ADS)

Archibald, Michelle M.; Rizal, Binod; Connolly, Timothy; Burns, Michael J.; Naughton, Michael J.; Chiles, Thomas C.

2015-03-01

Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications. Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications. This work was supported by the National Institutes of Health (National Cancer Institute award No. CA137681 and National Institute of Allergy and Infectious Diseases Award No. AI100216).

Optically transparent FTO-free cathode for dye-sensitized solar cells.

PubMed

Kavan, Ladislav; Liska, Paul; Zakeeruddin, Shaik M; Grätzel, Michael

2014-12-24

The woven fabric containing electrochemically platinized tungsten wire is an affordable flexible cathode for liquid-junction dye-sensitized solar cells with the I3(-)/I(-) redox mediator and electrolyte solution consisting of ionic liquids and propionitrile. The fabric-based electrode outperforms the thermally platinized FTO in serial ohmic resistance and charge-transfer resistance for triiodide reduction, and it offers comparable or better optical transparency in the visible and particularly in the near-IR spectral region. The electrode exhibits good stability during electrochemical loading and storage at open circuit. The dye-sensitized solar cells with a C101-sensitized titania photoanode and either Pt-W/PEN or Pt-FTO cathodes show a comparable performance.

Corrosion of NiTi Wires with Cracked Oxide Layer

NASA Astrophysics Data System (ADS)

Racek, Jan; Šittner, Petr; Heller, Luděk; Pilch, Jan; Petrenec, Martin; Sedlák, Petr

2014-07-01

Corrosion behavior of superelastic NiTi shape memory alloy wires with cracked TiO2 surface oxide layers was investigated by electrochemical corrosion tests (Electrochemical Impedance Spectroscopy, Open Circuit Potential, and Potentiodynamic Polarization) on wires bent into U-shapes of various bending radii. Cracks within the oxide on the surface of the bent wires were observed by FIB-SEM and TEM methods. The density and width of the surface oxide cracks dramatically increase with decreasing bending radius. The results of electrochemical experiments consistently show that corrosion properties of NiTi wires with cracked oxide layers (static load keeps the cracks opened) are inferior compared to the corrosion properties of the straight NiTi wires covered by virgin uncracked oxides. Out of the three methods employed, the Electrochemical Impedance Spectroscopy seems to be the most appropriate test for the electrochemical characterization of the cracked oxide layers, since the impedance curves (Nyquist plot) of differently bent NiTi wires can be associated with increasing state of the surface cracking and since the NiTi wires are exposed to similar conditions as the surfaces of NiTi implants in human body. On the other hand, the potentiodynamic polarization test accelerates the corrosion processes and provides clear evidence that the corrosion resistance of bent superelastic NiTi wires degrades with oxide cracking.

Formation of Sn–M (M=Fe, Al, Ni) alloy nanoparticles by DC arc-discharge and their electrochemical properties as anodes for Li-ion batteries

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

Gao, Song; Huang, Hao, E-mail: huanghao@dlut.edu.cn; Wu, Aimin

2016-10-15

A direct current arc-discharge method was applied to prepare the Sn–M (M=Fe, Al, Ni) bi-alloy nanoparticles. Thermodynamic is introduced to analyze the energy circumstances for the formation of the nanoparticles during the physical condensation process. The electrochemical properties of as-prepared Sn–M alloy nanoparticles are systematically investigated as anodes of Li-ion batteries. Among them, Sn–Fe nanoparticles electrode exhibits high Coulomb efficiency (about 71.2%) in the initial charge/discharge (257.9 mA h g{sup −1}/366.6 mA h g{sup −1}) and optimal cycle stability (a specific reversible capacity of 240 mA h g{sup −1} maintained after 20 cycles) compared with others. Large differences in themore » electrochemical behaviors indicate that the chemical composition and microstructure of the nanoparticles determine the lithium-ion storage properties and the long-term cyclic stability during the charge/discharge process. - Graphical abstract: The growth mechanism and electrochemical performance of Sn-based alloy nanoparticles. - Highlights: • Thermodynamic analyses of oxides on Sn-M nanoparticles surface. • The relationship between chemical components and electrochemical responses. • Sn-Fe nanoparticles show excellent electrode performance.« less

Improvement of electrochemical performance of nickel rich LiNi0.6Co0.2Mn0.2O2 cathode active material by ultrathin TiO2 coating.

PubMed

Qin, CanCan; Cao, JiaLi; Chen, Jun; Dai, GaoLe; Wu, TongFu; Chen, Yanbin; Tang, YueFeng; Li, AiDong; Chen, Yanfeng

2016-06-21

LiNi0.6Co0.2Mn0.2O2 cathode material has been surface-modified by coating with ultrathin TiO2via atomic layer deposition (ALD) technology to improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathodes for lithium ion batteries. Within the cut-off voltage of 2.5-4.3 V, the coated sample delivers an initial discharge capacity of 187.7 mA h g(-1) at 0.1 C and with a capacity retention about 85.9% after 100 cycles at 1 C, which provides a significant improvement in terms of discharge capacity and cyclability, as compared with those of the bare one. Such enhanced electrochemical performance of the coated sample is ascribed to its high-quality ultrathin coating of amorphous TiO2, which can protect the active material from HF attack, withstand the dissolution of metal ions in the electrode and favor the lithium diffusion of oxide as proved by electrochemical impedance spectroscopy (EIS) tests. TiO2 coating via the ALD process provides a potential approach for battery factories to surface-modify Ni-rich electrode materials so as to realize improvements in electrochemical performance.

Solar-driven thermo- and electrochemical degradation of nitrobenzene in wastewater: Adaptation and adoption of solar STEP concept.

PubMed

Gu, Di; Shao, Nan; Zhu, Yanji; Wu, Hongjun; Wang, Baohui

2017-01-05

The STEP concept has successfully been demonstrated for driving chemical reaction by utilization of solar heat and electricity to minimize the fossil energy, meanwhile, maximize the rate of thermo- and electrochemical reactions in thermodynamics and kinetics. This pioneering investigation experimentally exhibit that the STEP concept is adapted and adopted efficiently for degradation of nitrobenzene. By employing the theoretical calculation and thermo-dependent cyclic voltammetry, the degradation potential of nitrobenzene was found to be decreased obviously, at the same time, with greatly lifting the current, while the temperature was increased. Compared with the conventional electrochemical methods, high efficiency and fast degradation rate were markedly displayed due to the co-action of thermo- and electrochemical effects and the switch of the indirect electrochemical oxidation to the direct one for oxidation of nitrobenzene. A clear conclusion on the mechanism of nitrobenzene degradation by the STEP can be schematically proposed and discussed by the combination of thermo- and electrochemistry based the analysis of the HPLC, UV-vis and degradation data. This theory and experiment provide a pilot for the treatment of nitrobenzene wastewater with high efficiency, clean operation and low carbon footprint, without any other input of energy and chemicals from solar energy. Copyright © 2016 Elsevier B.V. All rights reserved.

Real-time electrochemical monitoring of isothermal helicase-dependent amplification of nucleic acids.

PubMed

Kivlehan, Francine; Mavré, François; Talini, Luc; Limoges, Benoît; Marchal, Damien

2011-09-21

We described an electrochemical method to monitor in real-time the isothermal helicase-dependent amplification of nucleic acids. The principle of detection is simple and well-adapted to the development of portable, easy-to-use and inexpensive nucleic acids detection technologies. It consists of monitoring a decrease in the electrochemical current response of a reporter DNA intercalating redox probe during the isothermal DNA amplification. The method offers the possibility to quantitatively analyze target nucleic acids in less than one hour at a single constant temperature, and to perform at the end of the isothermal amplification a DNA melt curve analysis for differentiating between specific and non-specific amplifications. To illustrate the potentialities of this approach for the development of a simple, robust and low-cost instrument with high throughput capability, the method was validated with an electrochemical system capable of monitoring up to 48 real-time isothermal HDA reactions simultaneously in a disposable microplate consisting of 48-electrochemical microwells. Results obtained with this approach are comparable to that obtained with a well-established but more sophisticated and expensive fluorescence-based method. This makes for a promising alternative detection method not only for real-time isothermal helicase-dependent amplification of nucleic acid, but also for other isothermal DNA amplification strategies.

Electrochemical Evaluation of Stainless Steels in Acidified Sodium Chloride Solutions

NASA Technical Reports Server (NTRS)

Calle, L. M.; MacDowell, L. G.; Vinje, R. D.

2004-01-01

This paper presents the results of an investigation in which several 300-series stainless steels (SS): AISI S30403 SS (UNS S30403), AISI 316L SS (UNS S31603), and AISI 317L SS (LINS S31703), as well as highly-alloyed: SS 254-SMO (UNS S32154), AL-6XN (N08367) and AL29-4C (UNS S44735), were evaluated using DC electrochemical techniques in three different electrolyte solutions. The solutions consisted of neutral 3.55% NaCl, 3.55% NaCl in 0.1N HCl, and 3.55% NaCl in 1.0N HCl. These solutions were chosen to simulate environments that are less, similar, and more aggressive, respectively, than the conditions at the Space Shuttle launch pads. The electrochemical test results were compared to atmospheric exposure data and evaluated for their ability to predict the long-term corrosion performance of the subject alloys. The electrochemical measurements for the six alloys indicated that the higher-alloyed SS 254-SMO, AL29-4C, and AL-6XN exhibited significantly higher resistance to localized corrosion than the 300-series SS. There was a correlation between the corrosion performance of the alloys during a two-year atmospheric exposure and the corrosion rates calculated from electrochemical (polarization resistance) measurements.

A novel strategy for screening-out raw milk contaminated with Mycobacterium bovis on dairy farms by double-tagging PCR and electrochemical genosensing.

PubMed

Lermo, Anabel; Liébana, Susana; Campoy, Susana; Fabiano, Silvia; García, M Inés; Soutullo, Adriana; Zumárraga, Martín J; Alegret, Salvador; Pividori, M Isabel

2010-06-01

A highly sensitive assay for rapidly screening-out Mycobacterium bovis in contaminated samples was developed based on electrochemical genosensing. The assay consists of specific amplification and double-tagging of the IS6110 fragment, highly related to M. bovis, followed by electrochemical detection of the amplified product. PCR amplification was carried out using a labeled set of primers and resulted in a amplicon tagged at each terminus with both biotin and digoxigenin. Two different electrochemical platforms for the detection of the double-tagged amplicon were evaluated: (i) an avidin biocomposite (Av-GEB) and (ii) a magneto sensor (m-GEC) combined with streptavidin magnetic beads. In both cases, the double- tagged amplicon was immobilized through its biotinylated end and electrochemically detected, using an antiDig-HRP conjugate, through its digoxigenin end. The assay was determined to be highly sensitive, based on the detection of 620 and 10 fmol of PCR amplicon using the Av-GEB and m-GEC strategies, respectively. Moreover, the m-GEC assay showed promising features for the detection of M. bovis on dairy farms by screening for the presence of the bacterium's DNA in milk samples. The obtained results are discussed and compared with respect to those of inter-laboratory PCR assays and tuberculin skin testing.

Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

NASA Astrophysics Data System (ADS)

Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

2015-12-01

Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

Nano-Electrochemistry and Nano-Electrografting with an Original Combined AFM-SECM

PubMed Central

Ghorbal, Achraf; Grisotto, Federico; Charlier, Julienne; Palacin, Serge; Goyer, Cédric; Demaille, Christophe; Ben Brahim, Ammar

2013-01-01

This study demonstrates the advantages of the combination between atomic force microscopy and scanning electrochemical microscopy. The combined technique can perform nano-electrochemical measurements onto agarose surface and nano-electrografting of non-conducting polymers onto conducting surfaces. This work was achieved by manufacturing an original Atomic Force Microscopy-Scanning ElectroChemical Microscopy (AFM-SECM) electrode. The capabilities of the AFM-SECM-electrode were tested with the nano-electrografting of vinylic monomers initiated by aryl diazonium salts. Nano-electrochemical and technical processes were thoroughly described, so as to allow experiments reproducing. A plausible explanation of chemical and electrochemical mechanisms, leading to the nano-grafting process, was reported. This combined technique represents the first step towards improved nano-processes for the nano-electrografting. PMID:28348337

Preparation of Nickel Cobalt Sulfide Hollow Nanocolloids with Enhanced Electrochemical Property for Supercapacitors Application

PubMed Central

Chen, Zhenhua; Wan, Zhanghui; Yang, Tiezhu; Zhao, Mengen; Lv, Xinyan; Wang, Hao; Ren, Xiuli; Mei, Xifan

2016-01-01

Nanostructured functional materials with hollow interiors are considered to be good candidates for a variety of advanced applications. However, synthesis of uniform hollow nanocolloids with porous texture via wet chemistry method is still challenging. In this work, nickel cobalt precursors (NCP) in sub-micron sized spheres have been synthesized by a facile solvothermal method. The subsequent sulfurization process in hydrothermal system has changed the NCP to nickel cobalt sulfide (NCS) with porous texture. Importantly, the hollow interiors can be tuned through the sulfurization process by employing different dosage of sulfur source. The derived NCS products have been fabricated into supercapacitor electrodes and their electrochemical performances are measured and compared, where promising results were found for the next-generation high-performance electrochemical capacitors. PMID:27114165

Preparation of AAO-CeO2 nanotubes and their application in electrochemical oxidation desulfurization of diesel

NASA Astrophysics Data System (ADS)

Du, Xiaoqing; Yang, Yumeng; Yi, Chenxi; Chen, Yu; Cai, Chao; Zhang, Zhao

2017-02-01

The coaxial arrays of AAO-CeO2 NTs have been successfully galvanostatically deposited on an anode, characterized and adopted as a catalyst for removing organic sulfurs from diesel. The influence of the main electrochemical oxidation factors on the efficiency of desulfurization have also been investigated. The results show that the fabrication process of AAO-CeO2 NTs is accompanied by the formation of a new phase, namely Al3Ce, and the main oxidation products of the diesel are soluble inorganic sulphides, especially Ce2(SO4)3. When compared with dibenzothiophene and 4, 6-dimethyldibenzothiophene, benzothiophene is much more easily removed, with a removal efficiency that reaches 87.2%. Finally, a possible electrochemical oxidation desulfurization pathway for diesel is proposed.

Conducting Polymer 3D Microelectrodes

PubMed Central

Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi; Castillo-León, Jaime; Emnéus, Jenny; Svendsen, Winnie E.

2010-01-01

Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements. PMID:22163508

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases.

PubMed

Rauf, Abdur; Shah, Afzal; Abbas, Saghir; Rana, Usman Ali; Khan, Salah Ud-Din; Ali, Saqib; Zia-Ur-Rehman; Qureshi, Rumana; Kraatz, Heinz-Bernhard; Belanger-Gariepy, Francine

2015-03-05

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms. Copyright © 2014 Elsevier B.V. All rights reserved.

A graphene-based electrochemical sensor for sensitive detection of paracetamol

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

Kang, Xinhuang; Wang, Jun; Wu, Hong

2010-05-15

An electrochemical sensor based on the electrocatalytic activity of functionalized graphene for sensitive detection of paracetamol is presented. The electrochemical behaviors of paracetamol on graphene-modified glassy carbon electrodes (GCEs) were investigated by cyclic voltammetry and square-wave voltammetry. The results showed that the graphene-modified electrode exhibited excellent electrocatalytic activity to paracetamol. A quasi-reversible redox process of paracetamol at the modified electrode was obtained, and the over-potential of paracetamol decreased significantly compared with that at the bare GCE. Such electrocatalytic behavior of graphene is attributed to its unique physical and chemical properties, e.g., subtle electronic characteristics, attractive π–π interaction, and strong adsorptivemore » capability. The sensor shows great promise for simple, sensitive, and quantitative detection of paracetamol.« less

Active control of methanol carbonylation selectivity over Au/carbon anode by electrochemical potential.

PubMed

Funakawa, Akiyasu; Yamanaka, Ichiro; Otsuka, Kiyoshi

2005-05-12

Electrochemical oxidative carbonylation of methanol was studied over Au supported carbon anode in CO. The major carbonylation products were dimethyl oxalate (DMO) and dimethyl carbonate (DMC). The minor oxidation products were dimethoxy methane (DMM) and methyl formate (MF) from methanol and CO(2). Influences of various reaction conditions were studied on carbonylation activities and selectivities. The selectivities to DMO and DMC can be controlled by the electrochemical potential. Electrocatalysis of Au/carbon anode was studied by cyclic voltammetry (CV), stoichiometric reactions among Au(3+), methanol, and CO, and UV-vis spectra. The Au/carbon anode was characterized by XRD, SEM, and BE images before and after the carbonylation. These experimental facts strongly suggest that transition of oxidation states of Au affects changing of the carbonylation selectivities to DMO and DMC. Au(0) is the active species for the selective DMO formation by direct electrochemical carbonylation at low potentials (<+1.2 V (Ag/AgCl)). On the other hand, Au(3+) is the active spices for the selective DMC formation by indirect electrochemical carbonylation through Au(3+)/Au(+) redox at high potentials (>+1.3 V).

An Audio Jack-Based Electrochemical Impedance Spectroscopy Sensor for Point-of-Care Diagnostics.

PubMed

Jiang, Haowei; Sun, Alex; Venkatesh, A G; Hall, Drew A

2017-02-01

Portable and easy-to-use point-of-care (POC) diagnostic devices hold high promise for dramatically improving public health and wellness. In this paper, we present a mobile health (mHealth) immunoassay platform based on audio jack embedded devices, such as smartphones and laptops, that uses electrochemical impedance spectroscopy (EIS) to detect binding of target biomolecules. Compared to other biomolecular detection tools, this platform is intended to be used as a plug-and-play peripheral that reuses existing hardware in the mobile device and does not require an external battery, thereby improving upon its convenience and portability. Experimental data using a passive circuit network to mimic an electrochemical cell demonstrate that the device performs comparably to laboratory grade instrumentation with 0.3% and 0.5° magnitude and phase error, respectively, over a 17 Hz to 17 kHz frequency range. The measured power consumption is 2.5 mW with a dynamic range of 60 dB. This platform was verified by monitoring the real-time formation of a NeutrAvidin self-assembled monolayer (SAM) on a gold electrode demonstrating the potential for POC diagnostics.

Glutamate biosensors based on diamond and graphene platforms.

PubMed

Hu, Jingping; Wisetsuwannaphum, Sirikarn; Foord, John S

2014-01-01

l-Glutamate is one of the most important neurotransmitters in the mammalian central nervous system, playing a vital role in many physiological processes and implicated in several neurological disorders, for which monitoring of dynamic levels of extracellular glutamate in the living brain tissues may contribute to medical understanding and treatments. Electrochemical sensing of glutamate has been developed recently mainly using platinum, carbon fibre and carbon nanotube electrodes. In the present work, we explore the fabrication and properties of electrochemical glutamate sensors fabricated on doped chemical vapour deposition diamond electrodes and graphene nanoplatelet structures. The sensors incorporate platinum nanoparticles to catalyse the electrooxidation of hydrogen peroxide, glutamate oxidase to oxidise glutamate, and a layer of poly-phenylenediamine to impart selectivity. The performance of the devices was compared to a similar sensor fabricated on glassy carbon. Both the diamond and the graphene sensor showed very competitive performance compared to the majority of existing electrochemical sensors. The graphene based sensor showed the best performance of the three investigated in terms of sensitivity, linear dynamic range and long term stability, whereas it was found that the diamond device showed the best limit of detection.

Biodegradability engineering of biodegradable Mg alloys: Tailoring the electrochemical properties and microstructure of constituent phases

PubMed Central

Cha, Pil-Ryung; Han, Hyung-Seop; Yang, Gui-Fu; Kim, Yu-Chan; Hong, Ki-Ha; Lee, Seung-Cheol; Jung, Jae-Young; Ahn, Jae-Pyeong; Kim, Young-Yul; Cho, Sung-Youn; Byun, Ji Young; Lee, Kang-Sik; Yang, Seok-Jo; Seok, Hyun-Kwang

2013-01-01

Crystalline Mg-based alloys with a distinct reduction in hydrogen evolution were prepared through both electrochemical and microstructural engineering of the constituent phases. The addition of Zn to Mg-Ca alloy modified the corrosion potentials of two constituent phases (Mg + Mg2Ca), which prevented the formation of a galvanic circuit and achieved a comparable corrosion rate to high purity Mg. Furthermore, effective grain refinement induced by the extrusion allowed the achievement of much lower corrosion rate than high purity Mg. Animal studies confirmed the large reduction in hydrogen evolution and revealed good tissue compatibility with increased bone deposition around the newly developed Mg alloy implants. Thus, high strength Mg-Ca-Zn alloys with medically acceptable corrosion rate were developed and showed great potential for use in a new generation of biodegradable implants. PMID:23917705

Epoxy-encapsulated ceramic superconductor microelectrodes

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

Gollmor, R.O.; McDevitt, J.T.; Murray, R.W.

1989-12-01

A procedure is outlined for fabricating well-behaved microelectrodes from ceramic pellets of YBa{sub 2}CU{sub 3}O{sub 7} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} which involves systematic polishing of an epoxy-encapsulated superconductror chip, under Et{sub 4}NCIO{sub 4}/acetonitrile solution, to a potentiometric end point. Voltammetry of the resulting microelectrodes in acetronitrile is illustrated and compared to that arising from alternative superconductor electrode geometries. The microelectrodes have active electrode surface areas ranging from 2 {times} 10 {sup {minus} sup 6} to 3 {times} 10 {sup {minus} sup 4}cm{sup 2}, as characterized electrochemically and microscopically. The results discussed herein are steps toward developing the methodologymore » necessary to study the electrochemical response of high temperature superconductor phases at temperatures below theirtheir superconductor critical temperature.« less

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).

Aptamer-based electrochemical sensors with aptamer-complementary DNA oligonucleotides as probe.

PubMed

Lu, Ying; Li, Xianchan; Zhang, Limin; Yu, Ping; Su, Lei; Mao, Lanqun

2008-03-15

This study describes a facile and general strategy for the development of aptamer-based electrochemical sensors with a high specificity toward the targets and a ready regeneration feature. Very different from the existing strategies for the development of electrochemical aptasensors with the aptamers as the probes, the strategy proposed here is essentially based on the utilization of the aptamer-complementary DNA (cDNA) oligonucleotides as the probes for electrochemical sensing. In this context, the sequences at both ends of the cDNA are tailor-made to be complementary and both the redox moiety (i.e., ferrocene in this study) and thiol group are labeled onto the cDNA. The labeled cDNA are hybridized with their respective aptamers (i.e., ATP- and thrombin-binding aptamers in this study) to form double-stranded DNA (ds-DNA) and the electrochemical aptasensors are prepared by self-assembling the labeled ds-DNA onto Au electrodes. Upon target binding, the aptamers confined onto electrode surface dissociate from their respective cDNA oligonucleotides into the solution and the single-stranded cDNA could thus tend to form a hairpin structure through the hybridization of the complementary sequences at both its ends. Such a conformational change of the cDNA resulting from the target binding-induced dissociation of the aptamers essentially leads to the change in the voltammetric signal of the redox moiety labeled onto the cDNA and thus constitutes the mechanism for the electrochemical aptasensors for specific target sensing. The aptasensors demonstrated here with the cDNA as the probe are readily regenerated and show good responses toward the targets. This study may offer a new and relatively general approach to electrochemical aptasensors with good analytical properties and potential applications.

Electrochemistry for the Generation of Renewable Chemicals: One-Pot Electrochemical Deoxygenation of Xylose to δ-Valerolactone.

PubMed

James, Olusola O; Sauter, Waldemer; Schröder, Uwe

2017-05-09

In this study, the electrochemical conversion of xylose to δ-valerolactone via carbonyl intermediates is demonstrated. The conversion was achieved in aqueous media and at ambient conditions. This study also demonstrates that the feedstock for production of renewable chemicals and biofuels through electrochemistry can be extended to primary carbohydrate molecules. This is the first report on a one-pot electrochemical deoxygenation of xylose to δ-valerolactone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CO oxidation on stepped-Pt(111) under electrochemical conditions: insights from theory and experiment.

PubMed

Busó-Rogero, C; Herrero, E; Bandlow, J; Comas-Vives, A; Jacob, Timo

2013-11-14

The co-adsorption of CO and OH on two Pt stepped surfaces vicinal to the (111) orientation has been evaluated by means of density functional theory (DFT) calculations. Focusing on Pt(533) and Pt(221), which contain (100) and (111)-steps, respectively, we find that (111)-steps should be more reactive towards CO oxidation than surfaces containing (100)-steps. The DFT results are compared with electrochemical experiments on the CO adsorption and oxidation on these vicinal surfaces.

High Power Density Electrochemical Thermocells for Inexpensively Harvesting Low-Grade Thermal Energy.

PubMed

Zhang, Long; Kim, Taewoo; Li, Na; Kang, Tae June; Chen, Jun; Pringle, Jennifer M; Zhang, Mei; Kazim, Ali H; Fang, Shaoli; Haines, Carter; Al-Masri, Danah; Cola, Baratunde A; Razal, Joselito M; Di, Jiangtao; Beirne, Stephen; MacFarlane, Douglas R; Gonzalez-Martin, Anuncia; Mathew, Sibi; Kim, Yong Hyup; Wallace, Gordon; Baughman, Ray H

2017-03-01

Continuously operating thermo-electrochemical cells (thermocells) are of interest for harvesting low-grade waste thermal energy because of their potentially low cost compared with conventional thermoelectrics. Pt-free thermocells devised here provide an output power of 12 W m -2 for an interelectrode temperature difference (ΔT) of 81 °C, which is sixfold higher power than previously reported for planar thermocells operating at ambient pressure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel metal-filled polyimide electrodes

NASA Technical Reports Server (NTRS)

Furtsch, T. A.; Finklea, H. O.; Taylor, L. T.

1984-01-01

Palladium-coated polyimide films are evaluated as electrochemical electrodes. The film electrodes exhibit essentially identical behavior compared to bulk palladium electrodes. In aqueous 0.5M H2SO4, current peaks due to oxide formation, oxide stripping, hydrogen adsorption, and H2 oxidation are observed. The ferri/ferrocyanide redox couple is grossly irreversible in the same electrolyte. Reversible electrochemical behavior is obtained for Fe(EDTA)(1-/2-) in 1M KCl/H2O, and for ferrocene/ferricenium in 0.1M TEAP/dimethylacetamide.

Comparative analysis of single-walled and multi-walled carbon nanotubes for electrochemical sensing of glucose on gold printed circuit boards.

PubMed

Alhans, Ruby; Singh, Anukriti; Singhal, Chaitali; Narang, Jagriti; Wadhwa, Shikha; Mathur, Ashish

2018-09-01

In the present work, a comparative study was performed between single-walled carbon nanotubes and multi-walled carbon nanotubes coated gold printed circuit board electrodes for glucose detection. Various characterization techniques were demonstrated in order to compare the modified electrodes viz. cyclic voltammetry, electrochemical impedance spectroscopy and chrono-amperometry. Results revealed that single-walled carbon nanotubes outperformed multi-walled carbon nanotubes and proved to be a better sensing interface for glucose detection. The single-walled carbon nanotubes coated gold printed circuit board electrodes showed a wide linear sensing range (1 mM to 100 mM) with detection limit of 0.1 mM with response time of 5 s while multi-walled carbon nanotubes coated printed circuit board gold electrodes showed linear sensing range (1 mM to 100 mM) with detection limit of 0.1 mM with response time of 5 s. This work provided low cost sensors with enhanced sensitivity, fast response time and reliable results for glucose detection which increased the affordability of such tests in remote areas. In addition, the comparative results confirmed that single-walled carbon nanotubes modified electrodes can be exploited for better amplification signal as compared to multi-walled carbon nanotubes. Copyright © 2018. Published by Elsevier B.V.

Studies of electrochemical interfaces by TOF neutron reflectometry at the IBR-2 reactor

NASA Astrophysics Data System (ADS)

Petrenko, V. I.; Gapon, I. V.; Rulev, A. A.; Ushakova, E. E.; Kataev, E. Yu; Yashina, L. V.; Itkis, D. M.; Avdeev, M. V.

2018-03-01

The operation performance of electrochemical energy conversion and storage systems such as supercapacitors and batteries depends on the processes occurring at the electrochemical interfaces, where charge separation and chemical reactions occur. Here, we report about the tests of the neutron reflectometry cells specially designed for operando studies of structural changes at the electrochemical interfaces between solid electrodes and liquid electrolytes. The cells are compatible with anhydrous electrolytes with organic solvents, which are employed today in all lithium ion batteries and most supercapacitors. The sensitivity of neutron reflectometry applied at the time-of-flight (TOF) reflectometer at the pulsed reactor IBR-2 is discussed regarding the effect of solid electrolyte interphase (SEI) formation on metal electrode surface.

Electrochemical performance of MXenes as K-ion battery anodes

DOE PAGES

Naguib, Michael; Adams, Ryan A.; Zhao, Yunpu; ...

2017-05-31

In this paper, we report on the electrochemical performance of two-dimensional transition metal carbonitrides as novel promising electrode materials in K-ion batteries. Titanium carbonitride, Ti 3CNT z, was investigated in detail using electrochemical galvanostatic cycling at various current densities. Finally, X-ray diffraction and X-ray photoelectron spectroscopy were used to study the potassiation mechanism and its structural changes.

Study of electrochemical reduced graphene oxide and MnO2 heterostructure for supercapacitor application

NASA Astrophysics Data System (ADS)

Jana, S. K.; Rao, V. P.; Banerjee, S.

2013-02-01

In this paper we have shown enhanced supercapacitive property of electrochemically reduced graphene oxide (ERGO) and manganese dioxide (MnO2) based heterostructure over single MnO2 thin film grown by electrochemical deposition on indium tin oxide (ITO). ERGO improves the electrical conduction leading to decrease of the internal resistance of the heterostructure.

Characteristics for electrochemical machining with nanoscale voltage pulses.

PubMed

Lee, E S; Back, S Y; Lee, J T

2009-06-01

Electrochemical machining has traditionally been used in highly specialized fields, such as those of the aerospace and defense industries. It is now increasingly being applied in other industries, where parts with difficult-to-cut material, complex geometry and tribology, and devices of nanoscale and microscale are required. Electric characteristic plays a principal function role in and chemical characteristic plays an assistant function role in electrochemical machining. Therefore, essential parameters in electrochemical machining can be described current density, machining time, inter-electrode gap size, electrolyte, electrode shape etc. Electrochemical machining provides an economical and effective method for machining high strength, high tension and heat-resistant materials into complex shapes such as turbine blades of titanium and aluminum alloys. The application of nanoscale voltage pulses between a tool electrode and a workpiece in an electrochemical environment allows the three-dimensional machining of conducting materials with sub-micrometer precision. In this study, micro probe are developed by electrochemical etching and micro holes are manufactured using these micro probe as tool electrodes. Micro holes and microgroove can be accurately achieved by using nanoscale voltages pulses.

Atomistic Simulation and Electronic Structure of Lithium Doped Ionic Liquids: Structure, Transport, and Electrochemical Stability

NASA Technical Reports Server (NTRS)

Haskins, Justin B.; Bauschlicher, Charles W.; Lawson, John W.

2015-01-01

Zero-temperature density functional theory (DFT), density functional theory molecular dynamics (DFT-MD), and classical molecular dynamics using polarizable force fields (PFF-MD) are employed to evaluate the influence of Lithium ion on the structure, transport, and electrochemical stability of three potential ionic liquid electrolytes: N--methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([pyr14][TFSI]), N--methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ([pyr13][FSI]), and 1-ethyl-3--methylimidazolium boron tetrafluoride ([EMIM][BF4]). We characterize the Lithium ion solvation shell through zero-temperature DFT simulations of [Li(Anion)sub n](exp n-1) -clusters, DFT-MD simulations of isolated lithium ions in small ionic liquid systems, and PFF-MD simulations with high Li-doping levels in large ionic liquid systems. At low levels of Li-salt doping, highly stable solvation shells having 2-3 anions are seen in both [pyr14][TFSI] and [pyr13][FSI], while solvation shells with 4 anions dominate in [EMIM][BF sub 4]. At higher levels of doping, we find the formation of complex Li-network structures that increase the frequency of 4 anion-coordinated solvation shells. A comparison of computational and experimental Raman spectra for a wide range of [Li(Anion) sub n](exp n -1) - clusters shows that our proposed structures are consistent with experiment. We estimate the ion diffusion coefficients and quantify both size and simulation time effects. We find estimates of lithium ion diffusion are a reasonable order of magnitude and can be corrected for simulation time effects. Simulation size, on the other hand, is also important, with diffusion coefficients from long PFF-MD simulations of small cells having 20-40% error compared to large-cell values. Finally, we compute the electrochemical window using differences in electronic energy levels of both isolated cation/anion pairs and small ionic liquid systems with Li-salt doping. The single pair and liquid-phase systems provide similar estimates of electrochemical window, while Li-doping in the liquid-phase systems results in electrochemical windows little changed from the neat systems. Pure and hybrid functionals systematically provide an upper and lower bound, respectively, to the experimental electrochemical window for the systems studied here.

Cyclodextrins Based Electrochemical Sensors for Biomedical and Pharmaceutical Analysis.

PubMed

Lenik, Joanna

2017-01-01

Electrochemical sensors are very convenient devices, as they may be used in a lot of fields starting from the food industry to environmental monitoring and medical diagnostics. They offer the values of simple design, reversible and reproducible measurements, as well as ensuring precise and accurate analytical information. Compared with other methods, electrochemical sensors are relatively simple as well as having low costs, which has led to intensive development, especially in the field of medicine and pharmaceuticals within the last decade. Recently, the number of publications covering the determination of aminoacids, dopamine, cholesterol, uric acid, biomarkers, vitamins and other pharmaceutical and biological compounds has significantly increased. Many possible types of such sensors and biosensors have been proposed: owing to the kind of the detection-potentiometric voltametric, amperometry, and the materials that can be used for, e.g. designing molecular architecture of the electrode/solution interface, carbon paste, carbon nanotubes, glass carbon, graphite, graphene, PVC, conductive polymers and/or nanoparticles. The active compounds which provide the complex formation with analyte (in the case of non-current techniques) or activate biomolecules electrochemically by particle recognition and selective preconcentration of analyte on the electrode surface (in the case of current techniques) are the most recently used cyclodextrins. These macrocyclic compounds have the ability to interact with a large diversity of guest particles to form complexes of the type of guest host, for example, with particles from drugs, biomolecules, through their hydrophilic outer surface and lipophilic inner cavities. Cyclodextrins have been the subject of frequent electrochemical studies that focused mostly on both their interactions in a solid state and in solution. The process of preparing of CDs modified electrodes would, consequently, open new avenues for new electrochemical sensors and, therefore, widen their use in biomedical and drug analysis. This review presents information on manufacturing techniques and performances of these sensors and biosensors. The opportunities for these sensors to carry out biomedical and pharmaceutical researches are demonstrated. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

A Flexible Sensing Unit Manufacturing Method of Electrochemical Seismic Sensor

PubMed Central

Li, Guanglei; Sun, Zhenyuan; Wang, Junbo; Chen, Deyong; Chen, Lianhong; Xu, Chao; Qi, Wenjie; Zheng, Yu

2018-01-01

This paper presents an electrochemical seismic sensor in which paraylene was used as a substrate and insulating layer of micro-fabricated electrodes, enabling the detection of seismic signals with enhanced sensitivities in comparison to silicon-based counterparts. Based on microfabrication, paralene-based electrochemical seismic sensors were fabricated in which the thickness of the insulating spacer was 6.7 μm. Compared to silicon-based counterparts with ~100 μm insulating layers, the parylene-based devices produced higher sensitivities of 490.3 ± 6.1 V/(m/s) vs. 192.2 ± 1.9 V/(m/s) at 0.1 Hz, 4764.4 ± 18 V/(m/s) vs. 318.9 ± 6.5 V/(m/s) at 1 Hz, and 4128.1 ± 38.3 V/(m/s) vs. 254.5 ± 4.2 V/(m/s) at 10 Hz. In addition, the outputs of the parylene vs. silicon devices in response to two transit inputs were compared, producing peak responses of 2.97 V vs. 0.22 V and 2.41 V vs. 0.19 V, respectively. Furthermore, the self-noises of parylene vs. silicon-based devices were compared as follows: −82.3 ± 3.9 dB vs. −90.4 ± 9.4 dB at 0.1 Hz, −75.7 ± 7.3 dB vs. −98.2 ± 9.9 dB at 1 Hz, and −62.4 ± 7.7 dB vs. −91.1 ± 8.1 dB at 10 Hz. The developed parylene-based electrochemical seismic sensors may function as an enabling technique for further detection of seismic motions in various applications. PMID:29641455

Real-Time Evaluation of Live Cancer Cells by an in Situ Surface Plasmon Resonance and Electrochemical Study.

PubMed

Wu, Changyu; Rehman, Fawad Ur; Li, Jingyuan; Ye, Jing; Zhang, Yuanyuan; Su, Meina; Jiang, Hui; Wang, Xuemei

2015-11-11

This work presents a new strategy of the combination of surface plasmon resonance (SPR) and electrochemical study for real-time evaluation of live cancer cells treated with daunorubicin (DNR) at the interface of the SPR chip and living cancer cells. The observations demonstrate that the SPR signal changes could be closely related to the morphology and mass changes of adsorbed cancer cells and the variation of the refractive index of the medium solution. The results of light microscopy images and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide studies also illustrate the release or desorption of HepG2 cancer cells, which were due to their apoptosis after treatment with DNR. It is evident that the extracellular concentration of DNR residue can be readily determined through electrochemical measurements. The decreases in the magnitudes of SPR signals were linearly related to cell survival rates, and the combination of SPR with electrochemical study could be utilized to evaluate the potential therapeutic efficiency of bioactive agents to cells. Thus, this label-free, real-time SPR-electrochemical detection technique has great promise in bioanalysis or monitoring of relevant treatment processes in clinical applications.

Design of electrical stimulation bioreactors for cardiac tissue engineering.

PubMed

Tandon, N; Marsano, A; Cannizzaro, C; Voldman, J; Vunjak-Novakovic, G

2008-01-01

Electrical stimulation has been shown to improve functional assembly of cardiomyocytes in vitro for cardiac tissue engineering. Carbon electrodes were found in past studies to have the best current injection characteristics. The goal of this study was to develop rational experimental design principles for the electrodes and stimulation regime, in particular electrode configuration, electrode ageing, and stimulation amplitude. Carbon rod electrodes were compared via electrochemical impedance spectroscopy (EIS) and we identified a safety range of 0 to 8 V/cm by comparing excitation thresholds and maximum capture rates for neonatal rat cardiomyocytes cultured with electrical stimulation. We conclude with recommendations for studies involving carbon electrodes for cardiac tissue engineering.

Comparative studies of electrochemical properties of carbon nanotubes and nanostructured boron carbide

NASA Astrophysics Data System (ADS)

Singh, Paviter; Kaur, Gurpreet; Singh, Kulwinder; Singh, Bikramjeet; Kaur, Manjot; Kumar, Manjeet; Bala, Rajni; Kumar, Akshay

2018-05-01

Boron carbide (B4C) and carbon nanotubes (CNTs) have the potential to act as electrocatalyst as these material show bifunctional behavior. B4C and CNTs were synthesized using solvothermal method. B4C display great catalytic activity as compared to CNTs. Raman spectra confirmed the formation of nanostructured carbon nanotubes. The observed onset potential was smaller 1.58 V in case of B4C as compared to CNTs i.e. 1.96 V in cyclic voltammetry. B4C material can emerge as a promising bifunctional electrocatalyst for battery applications.

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

Prabhakaran, Venkateshkumar; Johnson, Grant E.; Wang, Bingbing

Molecular-level understanding of electrochemical processes occurring at electrode-electrolyte interfaces (EEI) is key to the rational development of high-performance and sustainable electrochemical technologies. This article reports the development and first application of solid-state in situ electrochemical probes to study redox and catalytic processes occurring at well-defined EEI generated using soft-landing of mass- and charge-selected cluster ions (SL). In situ electrochemical probes with excellent mass transfer properties are fabricated using carefully-designed nanoporous ionic liquid membranes. SL enables deposition of pure active species that are not obtainable with other techniques onto electrode surfaces with precise control over charge state, composition, and kinetic energy.more » SL is, therefore, a unique tool for studying fundamental processes occurring at EEI. For the first time using an aprotic electrochemical probe, the effect of charge state (PMo12O403-/2-) and the contribution of building blocks of Keggin polyoxometalate (POM) clusters to redox processes are characterized by populating EEI with novel POM anions generated by electrospray ionization and gas phase dissociation. Additionally, a proton conducting electrochemical probe has been developed to characterize the reactive electrochemistry (oxygen reduction activity) of bare Pt clusters (Pt40 ~1 nm diameter), thus demonstrating the capability of the probe for studying reactions in controlled gaseous environments. The newly developed in situ electrochemical probes combined with ion SL provide a versatile method to characterize the EEI in solid-state redox systems and reactive electrochemistry at precisely-defined conditions. This capability will advance molecular-level understanding of processes occurring at EEI that are critical to many energy-related technologies.« less

Electrochemical studies of Copper, Tantalum and Tantalum Nitride surfaces in aqueous solutions for applications in chemical-mechanical and electrochemical-mechanical planarization

NASA Astrophysics Data System (ADS)

Sulyma, Christopher Michael

This report will investigate fundamental properties of materials involved in integrated circuit (IC) manufacturing. Individual materials (one at a time) are studied in different electrochemical environmental solutions to better understand the kinetics associated with the polishing process. Each system tries to simulate a real CMP environment in order to compare our findings with what is currently used in industry. To accomplish this, a variety of techniques are used. The voltage pulse modulation technique is useful for electrochemical processing of metal and alloy surfaces by utilizing faradaic reactions like electrodeposition and electrodissolution. A theoretical framework is presented in chapter 4 to facilitate quantitative analysis of experimental data (current transients) obtained in this approach. A typical application of this analysis is demonstrated for an experimental system involving electrochemical removal of copper surface layers, a relatively new process for abrasive-free electrochemical mechanical planarization of copper lines used in the fabrication of integrated circuits. Voltage pulse modulated electrodissolution of Cu in the absence of mechanical polishing is activated in an acidic solution of oxalic acid and hydrogen peroxide. The current generated by each applied voltage step shows a sharp spike, followed by a double-exponential decay, and eventually attains the rectangular shape of the potential pulses. For the second system in chapter 5, open-circuit potential measurements, cyclic voltammetry and Fourier transform impedance spectroscopy have been used to study pH dependent surface reactions of Cu and Ta rotating disc electrodes (RDEs) in aqueous solutions of succinic acid (SA, a complexing agent), hydrogen peroxide (an oxidizer), and ammonium dodecyl sulfate (ADS, a corrosion inhibitor for Cu). The surface chemistries of these systems are relevant for the development of a single-slurry approach to chemical mechanical planarization (CMP) of Cu lines and Ta barriers in the fabrication of semiconductor devices. It is shown that in non-alkaline solutions of H2O2, the SA-promoted surface complexes of Cu and Ta can potentially support chemically enhanced material removal in low-pressure CMP of surface topographies overlying fragile low-k dielectrics. ADS can suppress Cu dissolution without significantly affecting the surface chemistry of Ta. Chapter 6 discusses anodic corrosion of Ta, which is examined as a possible route to voltage induced removal of Ta for potential applications in electrochemical mechanical planarization (ECMP) of diffusion barriers. This strategy involves electro-oxidation of Ta in the presence of NO3- anions to form mechanically weak surface oxide films, followed by removal of the oxide layers by moderate mechanical abrasion. This NO3 - system is compared with a reference solution of Br -. In both electrolytes, the voltammetric currents of anodic oxidation exhibit oscillatory behaviors in the initial cycles of slow (5 mV s-1) voltage scans. The frequencies of these current oscillations are show signature attributes of localized pitting or general surface corrosion caused by Br- or NO3 -, respectively. Scanning electron microscopy, cyclic voltammetry, polarization resistance measurements, and time resolved Fourier transform impedance spectroscopy provide additional details about these corrosion mechanism. Apart from their relevance in the context of ECMP, the results also address certain fundamental aspects of pitting and general corrosions. The general protocols necessary to combine and analyze the results of D.C. and A.C. electrochemical measurements involving such valve metal corrosion systems are discussed in detail. In chapter 7 potassium salts of certain oxyanions (nitrate, sulfate and phosphate in particular) are shown to serve as effective surface-modifying agents in chemically enhanced, low-pressure chemical mechanical planarization (CMP) of Ta and TaN barrier layers for interconnect structures. The surface reactions that form the basis of this CMP strategy are investigated here in detail using the electrochemical techniques of cyclic voltammetry, open circuit potential analysis, polarization resistance measurements, and Fourier transform impedance spectroscopy. The results suggest that forming structurally weak oxide layers on the CMP samples is a key to achieving the goal of chemically controlled CMP of Ta/TaN at low down-pressures. (Abstract shortened by UMI.)

Electrochemical regeneration of phenol-saturated activated carbon - proposal of a reactor.

PubMed

Zanella, Odivan; Bilibio, Denise; Priamo, Wagner Luiz; Tessaro, Isabel Cristina; Féris, Liliana Amaral

2017-03-01

An electrochemical process was used to investigate the activated carbon regeneration efficiency (RE) saturated with aromatics. For this purpose, an electrochemical reactor was developed and the operational conditions of this equipment were investigated, which is applied in activated carbon regeneration process. The influence of regeneration parameters such as processing time, the current used, the polarity and the processing fluid (electrolyte) were studied. The performance of electrochemical regeneration was evaluated by adsorption tests, using phenol as adsorbate. The increase in current applied and the process time was found to enhance the RE. Another aspect that indicated a better reactor performance was the type of electrolyte used, showing best results for NaCl. The polarity showed the highest influence on the process, when the cathodic regeneration was more efficient. The electrochemical regeneration process developed in this study presented regeneration capacities greater than 100% when the best process conditions were used, showing that this form of regeneration for activated carbon saturated with aromatics is very promising.

Effect of uniaxial stress on the electrochemical properties of graphene with point defects

NASA Astrophysics Data System (ADS)

Szroeder, Paweł; Sagalianov, Igor Yu.; Radchenko, Taras M.; Tatarenko, Valentyn A.; Prylutskyy, Yuriy I.; Strupiński, Włodzimierz

2018-06-01

We report a calculational study of electron states and the resulting electrochemical properties of uniaxially strained graphene with point defects. For this study the reduction of ferricyanide to ferrocyanide serves as a benchmark electrochemical reaction. We find that the heterogeneous electron transfer activity of the perfect graphene electrode rises under uniaxial strain. However, evolution of the cathodic reaction rate depends on the direction of strain. For moderate lattice deformations, the zigzag strain improves electrochemical performance better than the armchair strain. Standard rate constant increases by 50% at the zigzag strain of 10%. Vacancies, covalently bonded moieties, charged adatoms and substitutional impurities in the zigzag strained graphene induce changes in the shape of the curve of the cathodic reaction rate. However, this changes do not translate into the electrocatalytic activity. Vacancies and covalently bonded moieties at concentration of 0.1% do not affect the electrochemical performance. Charged adatoms and substitutional impurities give a slight increase in the standard rate constant by, respectively, 2.2% and 3.4%.

Pitting Corrosion Behaviour of New Corrosion-Resistant Reinforcement Bars in Chloride-Containing Concrete Pore Solution

PubMed Central

Liu, Yao; Chu, Hong-yan; Wang, Danqian; Ma, Han; Sun, Wei

2017-01-01

In this study, the pitting behaviour of a new corrosion-resistant alloy steel (CR) is compared to that of low-carbon steel (LC) in a simulated concrete pore solution with a chloride concentration of 5 mol/L. The electrochemical behaviour of the bars was characterised using linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS). The pitting profiles were detected by reflective digital holographic microscopy (DHM), scanning electron microscopy (SEM), and the chemical components produced in the pitting process were analysed by X-ray energy dispersive spectroscopy (EDS). The results show that the CR bars have a higher resistance to pitting corrosion than the LC bars. This is primarily because of the periodic occurrence of metastable pitting during pitting development. Compared to the pitting process in the LC bars, the pitting depth grows slowly in the CR bars, which greatly reduces the risk of pitting. The possible reason for this result is that the capability of the CR bars to heal the passivation film helps to restore the metastable pits to the passivation state. PMID:28777327

Comparing Triflate and Hexafluorophosphate Anions of Ionic Liquids in Polymer Electrolytes for Supercapacitor Applications.

PubMed

Liew, Chiam-Wen; Ramesh, S

2014-05-21

Two different ionic liquid-based biopolymer electrolyte systems were prepared using a solution casting technique. Corn starch and lithium hexafluorophosphate (LiPF₆) were employed as polymer and salt, respectively. Additionally, two different counteranions of ionic liquids, viz. 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF₆) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (also known as 1-butyl-3-methylimidazolium triflate) (BmImTf) were used and studied in this present work. The maximum ionic conductivities of (1.47 ± 0.02) × 10 -4 and (3.21 ± 0.01) × 10 -4 S∙cm -1 were achieved with adulteration of 50 wt% of BmImPF₆ and 80 wt% of BmImTf, respectively at ambient temperature. Activated carbon-based electrodes were prepared and used in supercapacitor fabrication. Supercapacitors were then assembled using the most conducting polymer electrolyte from each system. The electrochemical properties of the supercapacitors were then analyzed. The supercapacitor containing the triflate-based biopolymer electrolyte depicted a higher specific capacitance with a wider electrochemical stability window compared to that of the hexafluorophosphate system.