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Sample records for potentiostats

  1. Instrumentation for potentiostatic corrosion studies with distilled water

    NASA Technical Reports Server (NTRS)

    Loess, R. E.; Youngdahl, C. A.

    1969-01-01

    Corrosion is studied potentiostatically in the corroding environment of distilled water with an instrument that measures the potential of the corroding specimen immediately after interruption of the polarizing current. No current is flowing. The process permits compensation for IR drops when potentiostatic control is used in high resistance systems.

  2. Wireless multichannel integrated potentiostat for distributed neurotransmitter sensing.

    PubMed

    Murari, Kartikeya; Sauer, Christian; Stanacevic, Milutin; Cauwenberghs, Gert; Thakor, Nitish

    2005-01-01

    Sensing neurotransmitters is critical in studying neural pathways and neurological disorders. An integrated device is presented which incorporates a potentiostat and a power harvesting and telemetry module. The potentiostat features 16 channels with multiple scales from microamperes to picoamperes. The wireless module is able to harvest power through inductively coupled coils and uses the same link to transmit data to and from the potentiostat. An integrated prototype is fabricated in CMOS technology, and experimentally characterized. Test results show RF powering introduces noise levels of 0.42% and 0.18% on potentiostat current scales of 500pA and 4nA respectively. Real-time multi-channel acquisition of dopamine concentration in vitro is performed with carbon fiber sensors. PMID:17281973

  3. A wireless potentiostat for mobile chemical sensing and biosensing.

    PubMed

    Steinberg, Matthew D; Kassal, Petar; Kereković, Irena; Steinberg, Ivana Murković

    2015-10-01

    Wireless chemical sensors are used as analytical devices in homeland defence, home-based healthcare, food logistics and more generally for the Sensor Internet of Things (SIoT). Presented here is a battery-powered and highly portable credit-card size potentiostat that is suitable for performing mobile and wearable amperometric electrochemical measurements with seamless wireless data transfer to mobile computing devices. The mobile electrochemical analytical system has been evaluated in the laboratory with a model redox system - the reduction of hexacyanoferrate(III) - and also with commercially available enzymatic blood-glucose test-strips. The potentiostat communicates wirelessly with mobile devices such as tablets or Smartphones by near-field communication (NFC) or with personal computers by radio-frequency identification (RFID), and thus provides a solution to the 'missing link' in connectivity that often exists between low-cost mobile and wearable chemical sensors and ubiquitous mobile computing products. The mobile potentiostat has been evaluated in the laboratory with a set of proof-of-concept experiments, and its analytical performance compared with a commercial laboratory potentiostat (R(2)=0.9999). These first experimental results demonstrate the functionality of the wireless potentiostat and suggest that the device could be suitable for wearable and point-of-sample analytical measurements. We conclude that the wireless potentiostat could contribute significantly to the advancement of mobile chemical sensor research and adoption, in particular for wearable sensors in healthcare and sport physiology, for wound monitoring and in mobile point-of-sample diagnostics as well as more generally as a part of the Sensor Internet of Things. PMID:26078146

  4. Development of a low cost potentiostat using ATXMEGA32

    NASA Astrophysics Data System (ADS)

    Muid, Abdul; Djamal, Mitra; Wirawan, Rahadi

    2014-03-01

    Potentiostat is principal devices in modern electrochemical research especially in the investigation of mechanism reaction which associated with the redox chemistry reaction and other chemical phenomena. Several applications measurement is developed based on this tool such as measurement of sample concentrations, quality test of food and medicine, environmental monitoring and biosensors or development of a protein sensor. We have developed a low cost, simple and portable potentiostat with a relatively small dimension. TLC2264 op-amp and ATMEGA32 microcontroller is used to build controller circuit system. Range potential measurement of this tool is between -1600mV and +1600mV within frequency range 1Hz - 1 kHz. The developed instrument has been tested for measuring samples using different voltammetry techniques, like cyclic, square wave, and linear sweep with relative error under 2.5%.

  5. Localized corrosion of container materials under potentiodynamic and potentiostatic controls

    SciTech Connect

    Roy, A.K.; Fleming, D.L.; Gordon, S.R.

    1996-05-01

    Potentiodynamic and potentiostatic polarization experiments were performed on ten candidate waste package container materials to evaluate their pitting tendency at ambient and elevated temperatures in aqueous environments relevant to the potential underground nuclear waste repository. Results indicate that of all the materials tested, Alloys G-30, C-4 and C-22, and Ti Gr-12 exhibited the maximum corrosion resistance, showing no pitting or observable dissolution in any environment tested. These experimental results will be used in identifying a group of potential container materials having the desired corrosion resistance.

  6. Metastable pitting of carbon steel under potentiostatic control

    SciTech Connect

    Cheng, Y.F.; Luo, J.L.

    1999-03-01

    The metastable pitting of A516-70 carbon steel was studied under potentiostatic control in solutions containing chloride ions. It was shown that there were different current fluctuation patterns and spectral slopes, that is, roll-off slopes, in passivity, general corrosion, and metastable pitting. Pits were often covered by a deposit which played an important role in the current fluctuation, with a quick current rise followed by a slow drop. There was a transitional potential (about 0 mV vs Ag/AgCl electrode) below which the metastable pitting initiation rate increased with the potential, because more sites would be activated. Above the transitional potential, the decay of the pitting occurrence rate with increased potential was due to the elimination of available pit sites. When the applied potential was between {minus}50 and 100 mV, pit growth kinetics was controlled by the potential drop through the deposit over the pit mouth. The potential dependence of repassivation time was mainly due to the effect of applied potential on the deposit over the pit mouth. There seemed to be good agreement between the calculated pit size and the measured values by optical microphotography. The assumption of hemispherical pit geometry was reasonable in calculating the pit radii.

  7. A comparison between potentiostatic circuits with grounded work or auxiliary electrode

    NASA Astrophysics Data System (ADS)

    Busoni, L.; Carlà, M.; Lanzi, L.

    2002-04-01

    Potentiostatic circuit configurations with work electrodes and auxiliary electrodes at ground potential have been reviewed and compared. Though the former is by far the best known and most used, the latter was more convenient and accurate in interfacial capacity measurements.

  8. A Glucose Biosensor Using CMOS Potentiostat and Vertically Aligned Carbon Nanofibers.

    PubMed

    Al Mamun, Khandaker A; Islam, Syed K; Hensley, Dale K; McFarlane, Nicole

    2016-08-01

    This paper reports a linear, low power, and compact CMOS based potentiostat for vertically aligned carbon nanofibers (VACNF) based amperometric glucose sensors. The CMOS based potentiostat consists of a single-ended potential control unit, a low noise common gate difference-differential pair transimpedance amplifier and a low power VCO. The potentiostat current measuring unit can detect electrochemical current ranging from 500 nA to 7 [Formula: see text] from the VACNF working electrodes with high degree of linearity. This current corresponds to a range of glucose, which depends on the fiber forest density. The potentiostat consumes 71.7 [Formula: see text] of power from a 1.8 V supply and occupies 0.017 [Formula: see text] of chip area realized in a 0.18 [Formula: see text] standard CMOS process. PMID:27337723

  9. DStat: A Versatile, Open-Source Potentiostat for Electroanalysis and Integration

    PubMed Central

    Dryden, Michael D. M.; Wheeler, Aaron R.

    2015-01-01

    Most electroanalytical techniques require the precise control of the potentials in an electrochemical cell using a potentiostat. Commercial potentiostats function as “black boxes,” giving limited information about their circuitry and behaviour which can make development of new measurement techniques and integration with other instruments challenging. Recently, a number of lab-built potentiostats have emerged with various design goals including low manufacturing cost and field-portability, but notably lacking is an accessible potentiostat designed for general lab use, focusing on measurement quality combined with ease of use and versatility. To fill this gap, we introduce DStat (http://microfluidics.utoronto.ca/dstat), an open-source, general-purpose potentiostat for use alone or integrated with other instruments. DStat offers picoampere current measurement capabilities, a compact USB-powered design, and user-friendly cross-platform software. DStat is easy and inexpensive to build, may be modified freely, and achieves good performance at low current levels not accessible to other lab-built instruments. In head-to-head tests, DStat’s voltammetric measurements are much more sensitive than those of “CheapStat” (a popular open-source potentiostat described previously), and are comparable to those of a compact commercial “black box” potentiostat. Likewise, in head-to-head tests, DStat’s potentiometric precision is similar to that of a commercial pH meter. Most importantly, the versatility of DStat was demonstrated through integration with the open-source DropBot digital microfluidics platform. In sum, we propose that DStat is a valuable contribution to the “open source” movement in analytical science, which is allowing users to adapt their tools to their experiments rather than alter their experiments to be compatible with their tools. PMID:26510100

  10. DStat: A Versatile, Open-Source Potentiostat for Electroanalysis and Integration.

    PubMed

    Dryden, Michael D M; Wheeler, Aaron R

    2015-01-01

    Most electroanalytical techniques require the precise control of the potentials in an electrochemical cell using a potentiostat. Commercial potentiostats function as "black boxes," giving limited information about their circuitry and behaviour which can make development of new measurement techniques and integration with other instruments challenging. Recently, a number of lab-built potentiostats have emerged with various design goals including low manufacturing cost and field-portability, but notably lacking is an accessible potentiostat designed for general lab use, focusing on measurement quality combined with ease of use and versatility. To fill this gap, we introduce DStat (http://microfluidics.utoronto.ca/dstat), an open-source, general-purpose potentiostat for use alone or integrated with other instruments. DStat offers picoampere current measurement capabilities, a compact USB-powered design, and user-friendly cross-platform software. DStat is easy and inexpensive to build, may be modified freely, and achieves good performance at low current levels not accessible to other lab-built instruments. In head-to-head tests, DStat's voltammetric measurements are much more sensitive than those of "CheapStat" (a popular open-source potentiostat described previously), and are comparable to those of a compact commercial "black box" potentiostat. Likewise, in head-to-head tests, DStat's potentiometric precision is similar to that of a commercial pH meter. Most importantly, the versatility of DStat was demonstrated through integration with the open-source DropBot digital microfluidics platform. In sum, we propose that DStat is a valuable contribution to the "open source" movement in analytical science, which is allowing users to adapt their tools to their experiments rather than alter their experiments to be compatible with their tools. PMID:26510100

  11. Potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries

    NASA Technical Reports Server (NTRS)

    Le Helloco, Jean-Guy; Bojkov, Hristo; Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.

    1992-01-01

    In a study of electrode activity for hydrogen evolution and hydrogen ionization, knowledge of the detailed kinetics and of the surface coverage by adsorbed hydrogen is essential. In the Ni/H2 battery, the hydrogen electrode is subjected to high hydrogen pressure; elucidation of the variation of kinetic parameters with hydrogen pressure is therefore of interest. Potentiostatic and ac impedance spectroscopic techniques were used in the present study. The equivalent circuit of the reaction, the kinetic parameters, and their pressure dependence have been determined.

  12. A cost-effective and field-ready potentiostat that poises subsurface electrodes to monitor bacterial respiration.

    PubMed

    Friedman, Elliot S; Rosenbaum, Miriam A; Lee, Alexander W; Lipson, David A; Land, Bruce R; Angenent, Largus T

    2012-02-15

    Here, we present the proof-of-concept for a subsurface bioelectrochemical system (BES)-based biosensor capable of monitoring microbial respiration that occurs through exocellular electron transfer. This system includes our open-source design of a three-channel microcontroller-unit (MCU)-based potentiostat that is capable of chronoamperometry, which laboratory tests showed to be accurate within 0.95 ± 0.58% (95% Confidence Limit) of a commercial potentiostat. The potentiostat design is freely available online: http://angenent.bee.cornell.edu/potentiostat.html. This robust and field-ready potentiostat, which can withstand temperatures of -30°C, can be manufactured at relatively low cost ($600), thus, allowing for en-masse deployment at field sites. The MCU-based potentiostat was integrated with electrodes and a solar panel-based power system, and deployed as a biosensor to monitor microbial respiration in drained thaw lake basins outside Barrow, AK. At three different depths, the working electrode of a microbial three-electrode system (M3C) was maintained at potentials corresponding to the microbial reduction of iron(III) compounds and humic acids. Thereby, the working electrode mimics these compounds and is used by certain microbes as an electron acceptor. The sensors revealed daily cycles in microbial respiration. In the medium- and deep-depth electrodes the onset of these cycles followed a considerable increase in overall activity that corresponded to those soils reaching temperatures conducive to microbial activity as the summer thaw progressed. The BES biosensor is a valuable tool for studying microbial activity in situ in remote environments, and the cost-efficient design of the potentiostat allows for wide-scale use in remote areas. PMID:22209069

  13. In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat

    PubMed Central

    Gunasekara, Dulan B.; Hulvey, Matthew K.; Lunte, Susan M.

    2012-01-01

    The combination of microchip electrophoresis (ME) with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end-channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection (ME-EC) with an electrically isolated potentiostat for the separation and in-channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (TTAB, as a buffer modifier) for the separation of nitrite (NO2-), glutathione (GSH), ascorbic acid (AA), and tyrosine (Tyr). A half-wave potential (E½) shift of approximately negative 500 mV was observed for NO2- and H2O2 standards in the in-channel configuration compared to end channel. Higher separation efficiencies were observed for both NO2- and H2O2 with the in-channel detection configuration. The limits of detection were approximately two-fold lower and the sensitivity was approximately two-fold higher for in-channel detection of nitrite when compared to end-channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described. PMID:21437918

  14. A compact hybrid-multiplexed potentiostat for real-time electrochemical biosensing applications.

    PubMed

    Ramfos, Ioannis; Vassiliadis, Nikolaos; Blionas, Spyridon; Efstathiou, Konstantinos; Fragoso, Alex; O'Sullivan, Ciara K; Birbas, Alexios

    2013-09-15

    The architecture and design of a compact, multichannel, hybrid-multiplexed potentiostat for performing electrochemical measurements on continuously-biased electrode arrays is presented. The proposed architecture utilises a combination of sequential and parallel measurements, to enable high performance whilst keeping the system low-cost and compact. The accuracy of the signal readout is maintained by following a special multiplexing approach, which ensures the continuous biasing of all the working electrodes of an array. After sampling the results, a digital calibration technique factors out errors from component inaccuracies. A prototype printed circuit board (PCB) was designed and built using off-the-shelf components for the real-time measurement of the amperometric signal of 48 electrodes. The operation and performance of the PCB was evaluated and characterised through a wide range of testing conditions, where it exhibited high linearity (R(2)>0.999) and a resolution of 400pA. The effectiveness of the proposed multiplexing scheme is demonstrated through electrochemical tests using KCl and [Fe(CN)6](3-) in KCl solutions. The applicability of the prototype multichannel potentiostat is also demonstrated using real biosensors, which were applied to the detection of IgA antibodies. PMID:23624017

  15. Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide. I. A structural and morphological study

    NASA Astrophysics Data System (ADS)

    Escudero, M. J.; Rodrigo, T.; Mendoza, L.; Cassir, M.; Daza, L.

    Porous nickel cathode was protected by potentiostatically deposited cobalt at different experimental conditions: oxidation potential and electrolysis duration. The deposition growth increased with the oxidation potential yielding a more developed granular structure with smaller grains. Thin layers of Co 3O 4 were identified by X-ray diffraction (XRD) and Raman spectroscopy. CoOOH was detected by X-ray photoelectron spectroscopy (XPS) before annealing treatment and Co 3O 4 after heating the sample at 500 °C during 4 h in air. After this treatment, some morphological changes were observed on the coated samples due to grain compaction and oxidation of the nickel substrate. The porosity of the coated samples was relatively close to that of the sole porous nickel. These coatings exhibited an appropriate dual-pore structure with macro and micro pores, a basic MCFC requirement.

  16. Distinguishing between chi and sigma phases in duplex stainless steels using potentiostatic etching

    SciTech Connect

    Jackson, E.M.L.E.M.; Visser, P.E. de . Physical Metallurgy Div.); Cornish, L.A. )

    1993-12-01

    A color interference film etching technique based on the principle of potentiostatic etching has been developed to distinguish, by optical metallography, between Cr-rich sigma and Mo-rich chi phases as well as with simultaneous identification of the ferrite and austenite phases in duplex stainless steels. The optical metallography results are confirmed by semiquantitative energy dispersive spectrometry analysis and back-scattered electron imaging. The technique is relatively simple and rapid, and makes use of low voltages and a hot etchant. Results have shown distinctively the sigma, chi, ferrite, and austenite phases, and enable observation of the microstructural development, morphology, and kinetics of formation of the phases in duplex alloys. The method, by giving excellent color contrast between sigma and chi, also facilitates quantitative image analysis of the sigma and chi volume fractions.

  17. VLSI Potentiostat Array With Oversampling Gain Modulation for Wide-Range Neurotransmitter Sensing.

    PubMed

    Stanacevic, M; Murari, K; Rege, A; Cauwenberghs, G; Thakor, N V

    2007-03-01

    A 16-channel current-measuring very large-scale integration (VLSI) sensor array system for highly sensitive electrochemical detection of electroactive neurotransmiters like dopamine and nitric-oxide is presented. Each channel embeds a current integrating potentiostat within a switched-capacitor first-order single-bit delta-sigma modulator implementing an incremental analog-to-digital converter. The duty-cycle modulation of current feedback in the delta-sigma loop together with variable oversampling ratio provide a programmable digital range selection of the input current spanning over six orders of magnitude from picoamperes to microamperes. The array offers 100-fA input current sensitivity at 3.4-muW power consumption per channel. The operation of the 3 mm times3 mm chip fabricated in 0.5-mum CMOS technology is demonstrated with real-time multichannel acquisition of neurotransmitter concentration. PMID:23851522

  18. CheapStat: An Open-Source, “Do-It-Yourself” Potentiostat for Analytical and Educational Applications

    PubMed Central

    Rowe, Aaron A.; Bonham, Andrew J.; White, Ryan J.; Zimmer, Michael P.; Yadgar, Ramsin J.; Hobza, Tony M.; Honea, Jim W.; Ben-Yaacov, Ilan; Plaxco, Kevin W.

    2011-01-01

    Although potentiostats are the foundation of modern electrochemical research, they have seen relatively little application in resource poor settings, such as undergraduate laboratory courses and the developing world. One reason for the low penetration of potentiostats is their cost, as even the least expensive commercially available laboratory potentiostats sell for more than one thousand dollars. An inexpensive electrochemical workstation could thus prove useful in educational labs, and increase access to electrochemistry-based analytical techniques for food, drug and environmental monitoring. With these motivations in mind, we describe here the CheapStat, an inexpensive (<$80), open-source (software and hardware), hand-held potentiostat that can be constructed by anyone who is proficient at assembling circuits. This device supports a number of potential waveforms necessary to perform cyclic, square wave, linear sweep and anodic stripping voltammetry. As we demonstrate, it is suitable for a wide range of applications ranging from food- and drug-quality testing to environmental monitoring, rapid DNA detection, and educational exercises. The device's schematics, parts lists, circuit board layout files, sample experiments, and detailed assembly instructions are available in the supporting information and are released under an open hardware license. PMID:21931613

  19. Fabrication of triazinedithiol functional polymeric nanofilm by potentiostatic polymerization on aluminum surface

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Wang, Yabin; Li, Yanni; Wang, Qian

    2011-01-01

    The functional polymeric nanofilm of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N) was prepared on pure aluminum surface by potentiostatic polymerization at different potentials. The thickness and weight of polymeric nanofilm increased proportionally to electro-polymerization potential following linear equation. The chemical structure of nanofilm was characterized by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Adsorption peaks in FT-IR and C1s, N1s, S2p, F1s and Al2p peaks in XPS spectra indicated that the polymeric nanofilm was poly(6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-disulfide) (PAF17). The morphologies of polymeric nanofilm were also observed by atomic force microscopy (AFM). All the results showed that the optimal electro-polymerization potential and time were 8 V and 20 s, respectively. Uniform and compact nanofilm of PAF17 could be obtained under these conditions. It is expected that this technique will be applied in the preparation of lubricating, dielectric and hydrophobic surface on aluminum substrate.

  20. Identification of the states of the processes at liquid cathodes under potentiostatic conditions using semantic diagram models

    NASA Astrophysics Data System (ADS)

    Smirnov, G. B.; Markina, S. E.; Tomashevich, V. G.

    2012-08-01

    A technique is described for constructing semantic diagram models of the electrolysis at a liquid cathode in a salt halide melt under potentiostatic conditions that are intended for identifying the static states of this system that correspond to certain combinations of the electrode processes or the processes occurring in the volumes of salt and liquid-metal phases. Examples are given for the discharge of univalent and polyvalent metals.

  1. Reprint of: Use of a mobile phone for potentiostatic control with low cost paper-based microfluidic sensors.

    PubMed

    Delaney, Jacqui L; Doeven, Egan H; Harsant, Anthony J; Hogan, Conor F

    2013-11-25

    By exploiting its ability to play sounds, a mobile phone with suitable software installed can serve the basic functions of a potentiostat in controlling an applied potential to oxidise ECL-active molecules, while the resultant photonic signal is monitored using the camera in video mode. In combination with paper microfluidic sensors this opens significant new possibilities for low-cost, instrument-free sensing. PMID:24216205

  2. Potentiostatic control of ionic liquid surface film formation on ZE41 magnesium alloy.

    PubMed

    Efthimiadis, Jim; Neil, Wayne C; Bunter, Andrew; Howlett, Patrick C; Hinton, Bruce R W; MacFarlane, Douglas R; Forsyth, Maria

    2010-05-01

    The generation of potentially corrosion-resistant films on light metal alloys of magnesium have been investigated. Magnesium alloy, ZE41 [Mg-Zn-Rare Earth (RE)-Zr, nominal composition approximately 4 wt % Zn, approximately 1.7 wt % RE (Ce), approximately 0.6 wt % Zr, remaining balance, Mg], was exposed under potentiostatic control to the ionic liquid trihexyl(tetradecyl)phosphonium diphenylphosphate, denoted [P(6,6,6,14)][DPP]. During exposure to this IL, a bias potential, shifted from open circuit, was applied to the ZE41 surface. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) were used to monitor the evolution of film formation on the metal surface during exposure. The EIS data indicate that, of the four bias potentials examined, applying a potential of -200 mV versus OCP during the exposure period resulted in surface films of greatest resistance. Both EIS measurements and scanning electron microscopy (SEM) imaging indicate that these surfaces are substantially different to those formed without potential bias. Time of flight-secondary ion mass spectrometry (ToF-SIMS) elemental mapping of the films was utilized to ascertain the distribution of the ionic liquid cationic and anionic species relative to the microstructural surface features of ZE41 and indicated a more uniform distribution compared with the surface following exposure in the absence of a bias potential. Immersion of the treated ZE41 specimens in a chloride contaminated salt solution clearly indicated that the ionic liquid generated surface films offered significant protection against pitting corrosion, although the intermetallics were still insufficiently protected by the IL and hence favored intergranular corrosion processes. PMID:20433137

  3. Wetting-in studies on alkaline-fuel-cell cathodes using a potentiostatic-galvanostatic experimental design

    SciTech Connect

    Lundblad, A.; Bjoernbom, P. . Dept. of Chemical Engineering and Technology)

    1994-06-01

    The influence of potential and current on electrolyte intrusion during the initiation phase of poly(tetrafluoroethylene)-(PTFE)-bonded carbon cathodes has been studied. A potentiostatic-galvanostatic experimental design was used. This was attained by varying the oxygen concentration using a computerized control circuit. The intrusion depth was determined by an electron microscope element-mapping method, and the amount of intruded electrolyte was determined by weighing. The wetting-in of the electrode was found to depend strongly on potential and less on applied current density. A combination of electrocapillarity and electro-osmosis is proposed as an explanation of the results. The experiments have also revealed interesting phenomena concerning electrolyte and three-dimensional current-density distribution during the initiation phase. From the results, a mechanism for the sudden failure (flooding) of PTFE-bonded carbon cathodes at the end of their service life is suggested.

  4. Identification of the states of the processes that occur on solid cathodes in the potentiostatic electrolysis mode using semantic diagram models

    NASA Astrophysics Data System (ADS)

    Smirnov, G. B.; Markina, S. E.; Tomashevich, V. G.

    2011-02-01

    A procedure is proposed to construct semantic diagram models for the electrolysis on a solid cathode in a salt halide melt under potentiostatic conditions. These models are intended to identify the static states of the system that correspond to a certain combination of the processes occurring on an electrode and in the system volume. Examples for discharging of univalent and polyvalent metals are given.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  6. Re-passivation Potential of Alloy 22 in Chloride plus Nitrate Solutions using the Potentiodynamic-Galvano-static-Potentiostatic Method

    SciTech Connect

    Evans, Kenneth J.; Rebak, Raul B.

    2007-07-01

    In general, the susceptibility of Alloy 22 to suffer crevice corrosion is measured using the Cyclic Potentiodynamic Polarization (CPP) technique. This is a fast technique that gives rather accurate and reproducible values of re-passivation potential (ER1) in most cases. In the fringes of susceptibility, when the environment is not highly aggressive, the values of re-passivation potential using the CPP technique may not be highly reproducible, especially because the technique is fast. To circumvent this, the re-passivation potential of Alloy 22 was measured using a slower method that combines Potentiodynamic-Galvano-static-Potentiostatic steps (called here the Tsujikawa-Hisamatsu Electrochemical or THE method). The THE method applies the charge to the specimen in a more controlled way, which may give more reproducible re-passivation potential values, especially when the environment is not aggressive. The values of re-passivation potential of Alloy 22 in sodium chloride plus potassium nitrate solutions were measured using the THE and CPP methods. Results show that both methods yield similar values of re-passivation potential, especially under aggressive conditions. (authors)

  7. Comparative electron microscopy (SEM) examination of Fe, Au, and Zn electrode surfaces polarized in different regions of potentiostatic E/I behavior

    SciTech Connect

    Podesta, J.J.; Arvia, A.J.; Piatti, R.C.V.

    1982-12-01

    The surface morphology of some metals (Fe, Au, and Zn) after potentiostatic polarization was studied through SEM examination. The following electrochemical systems were investigated at 25C: (1) Fe/1 M H/sub 2/SO/sub 4/; (2) Au/1 M HCl; and (3) Zn/2 M NaOH. The polarization potentials were chosen in the active dissolution region, in the passivity region, and in the potential range where periodic oscillations of the anode current are observed. The changes in the morphologies of attack on the various metals were related to the film forming species and of anion adsorption.

  8. Comparison of Galvanic Currents Generated Between Different Combinations of Orthodontic Brackets and Archwires Using Potentiostat: An In Vitro Study

    PubMed Central

    Nayak, Rabindra S; Shafiuddin, Bareera; Pasha, Azam; Vinay, K; Narayan, Anjali; Shetty, Smitha V

    2015-01-01

    Background: Technological advances in wire selection and bracket design have led to improved treatment efficiency and allowed longer time intervals between appliance adjustments. The wires remain in the mouth for a longer duration and are subjected to electrochemical reactions, mechanical forces of mastication and generalized wear. These cause different types of corrosion. This study was done to compare the galvanic currents generated between different combinations of brackets and archwires commonly used in orthodontic practices. Materials and Methods: The materials used for the study included different commercially available orthodontic archwires and brackets. The galvanic current generated by individual materials and different combinations of these materials was tested and compared. The orthodontic archwires used were 0.019″ × 0.025″ heat-activated nickel-titanium (3M Unitek), 0.019″ × 0.025″ beta-titanium (3M Unitek) and 0.019″ × 0.025″ stainless steel (3M Unitek). The orthodontic brackets used were 0.022″ MBT laser-cut (Victory Series, 3M Unitek) and metal-injection molded (Leone Company) maxillary central incisor brackets respectively. The ligature wire used for ligation was 0.009″ stainless steel ligature (HP Company). The galvanic current for individual archwires, brackets, and the different bracket-archwire-ligature combinations was measured by using a Potentiostat machine. The data were generated using the Linear Sweep Voltammetry and OriginPro 8.5 Graphing and Data Analysis Softwares. The study was conducted in two phases. Phase I comprised of five groups for open circuit potential (OCP) and galvanic current (I), whereas Phase II comprised of six groups for galvanic current alone. Results: Mean, standard deviation and range were computed for the OCP and galvanic current (I) values obtained. Results were subjected to statistical analysis through ANOVA. In Phase I, higher mean OCP was recorded in stainless steel archwire, followed by beta

  9. Investigation of the growth and local stoichiometric point group symmetry of titania nanotubes during potentiostatic anodization of titanium in phosphate electrolytes

    NASA Astrophysics Data System (ADS)

    Cummings, F. R.; Muller, T. F. G.; Malgas, G. F.; Arendse, C. J.

    2015-10-01

    Potentiostatic anodization of commercially pure, 50 μm-thick titanium (Ti) foil was performed in aqueous, phosphate electrolytes at increasing experimental timeframes at a fixed applied potential for the synthesis of titania nanotube arrays (TNAs). High resolution scanning electron microscopy images, combined with energy dispersive spectroscopy and x-ray diffraction spectra reveal that anodization of the Ti foil in a 1 M NaF+0.5 M H3PO4 electrolyte for 4 h yields a titanate surface with pore diameters ranging between 100 and 500 nm. The presence of rods on the Ti foil surface with lengths exceeding 20 μm and containing high concentrations of phosphor on the exterior was also detected at these conditions, along with micro-sized coral reef-like titanate balls. We propose that the formation of these structures play a major role during the anodization process and impedes nanotube growth during the anodization process. High spatially resolved scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) performed along the length of a single anodized TiO2 nanotube reveals a gradual evolution of the nanotube crystallinity, from a rutile-rich bottom to a predominantly anatase TiO2 structure along its length.

  10. Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations

    PubMed Central

    Meneses, Diogenes; Gunasekara, Dulan B.; Pichetsurnthorn, Pann; da Silva, José A. F.; de Abreu, Fabiane C.; Lunte, Susan M.

    2015-01-01

    In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration. PMID:25256669

  11. An investigation into factors affecting the stability of carbons and carbon supported platinum and platinum/cobalt alloy catalysts during 1.2 V potentiostatic hold regimes at a range of temperatures

    NASA Astrophysics Data System (ADS)

    Ball, S. C.; Hudson, S. L.; Thompsett, D.; Theobald, B.

    To meet automotive targets for fuel cell operation and allow higher temperature operation an understanding of the factors affecting carbon and platinum stability is critical. The stability of both carbons and carbon supported platinum and platinum/cobalt alloy catalysts was studied during 1.2 V versus RHE potentiostatic hold tests using carbon and catalyst coated electrodes in a three-chamber wet electrolyte cell at a range of temperatures. At 80 °C the wt% of carbon corroded increases with increasing BET area. Surface oxidation was followed electrochemically using the quinone/hydroquinone redox couple. Increasing temperature, time at 1.2 V and wt% platinum on the carbon increases surface oxidation. Although increasing temperature was shown to increase the extent of carbon corrosion, catalysing the carbon did not significantly change how much carbon was corroded. Platinum stability was investigated by electrochemical metal area loss (ECA). Platinum catalysts on commercial carbons lost more ECA with increasing temperature. A platinum/cobalt alloy on a low surface area carbon was demonstrated to be more stable to both carbon corrosion and metal area loss at temperatures up to 80 °C than platinum catalysts on commercial carbons, making this material an excellent candidate for higher temperature automotive operation.

  12. Communication: Coordination structure of bromide ions associated with hexyltrimethylammonium cations at liquid/liquid interfaces under potentiostatic control as studied by total-reflection X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Nagatani, Hirohisa; Harada, Makoto; Tanida, Hajime; Sakae, Hiroki; Imura, Hisanori

    2014-03-01

    Total-reflection X-ray absorption fine structure (TR-XAFS) technique was applied for the first time to an interface between two immiscible electrolyte solutions under potentiostatic control. The hydration structure of bromide ions was investigated at polarized 2-octanone/water interfaces. TR-XAFS spectra at Br K-edge measured in the presence of hexyltrimethylammonium bromide (C6TAB) were slightly modified depending on the Galvani potential difference ({Δ }_o^w φ). The extended X-ray absorption fine structure analysis exposed hydration structure changes of bromide ions at the polarized interface. The coordination structure of bromide ions at the interface could be analyzed as compared with bromide ions dissolved in aqueous solution and Br--exchanged resin having quaternary ammonium groups. The results indicated that bromide ions were associated with C6TA+ at the polarized interface. The relative contribution of ion association form of bromide ions with quaternary ammonium groups was enhanced at a potential close to the ion transfer of C6TA+, where the interfacial concentration of C6TA+ is increased as a function of {Δ }_o^w φ.

  13. Conversion of an Agilent Chip Cube System and Adaptation of a ROXY EC Potentiostat for the Analysis of Proteolytic and Non-Proteolytic Protein Samples on a Thermo Finnigan LTQ-FT Ultra Mass Spectrometer.

    PubMed Central

    Crot, C.; Helseth, L.; Xu, H.; Davis, R.; Schilling, A.

    2010-01-01

    RP-48 High resolution, high mass accuracy analysis of peptide digests and proteins using hybrid instruments such as the Thermo Finnigan LTQ-FT Ultra instrument allow for faster unambiguous computer identification of proteins from peptide digests, accurate measurement of intact protein MW and detection of post translational modifications by top down methods and the use of auxiliary dissociation methods such as ECD to study disulfide bonds and crosslinked peptides as well as post-translational modifications such as phosphorylation. User demand for these instruments remains high in shared facilities like ours and efforts are always being made to improve sample throughput to increase instrument availability. Several vendors have released microfluidic based integrated chromatographic systems in the last few years that allow for relatively easy use in nanospray mode along with reductions in delay volumes and significant improvement in sample throughput and sensitivity. The current work reports on the successful integration of one such system, the Agilent Chip Cube system, originally designed to work only on MS instruments from that manufacturer, so that it will function routinely on the LTQ-FT Ultra MS. Using the chip cube's nanocolumn cartridge “chips”, our facility has been able to significantly shorten runtimes for digest based analyses of simple and complex fractionated samples while obtaining excellent peptide detection using smaller sample injection volumes. Details of the adaptation will be provided and examples will be shown using data from both CID and ECD based proteolytic workflows. In addition, we will present data generated using an online electrochemical potentiostat, the ROXY EC system, along with the chip cube on the LTQ FT Ultra allowing the detection of electrochemically generated peptide fragments from intact proteins as an adjunct/replacement for proteolysis in specific analytical problems where the use of nano-LC/MS/MS proteolytic analysis is

  14. Intelligent potentiostat for identification of heavy metals in situ

    NASA Astrophysics Data System (ADS)

    Christidis, K.; Gow, K.; Robertson, P.; Pollard, P.

    2006-01-01

    This article presents a low-cost portable electrochemical instrument capable of on-site identification of heavy metals. The instrument acquires metal-specific voltage and current signals by the application of differential pulse anodic stripping voltammetry. This technique enhances the analytical current and rejects the background current, resulting in a higher signal-to-noise ratio for a better detection limit. The identification of heavy metals is based on an intelligent machine-based method using a multilayer perceptron neural network consisting of three layers of neurons. The neural network is implemented using a 16 bit microcontroller. The system is developed for use in the field in order to avoid expensive and time-consuming procedures and can be used in a variety of situations to help environmental assessment and control.

  15. Potentiostatic deposition of DNA for scanning probe microscopy.

    PubMed Central

    Lindsay, S M; Tao, N J; DeRose, J A; Oden, P I; Lyubchenko YuL; Harrington, R E; Shlyakhtenko, L

    1992-01-01

    We describe a procedure for reversible adsorption of DNA onto a gold electrode maintained under potential control. The adsorbate can be imaged by scanning probe microscopy in situ. Quantitative control of a molecular adsorbate for microscopy is now possible. We found a potential window (between 0 and 180 mV versus a silver wire quasi reference) over which a gold (111) surface under phosphate buffer is positively charged, but is not covered with a dense adsorbate. When DNA is present in these conditions, molecules adsorb onto the electrode and remain stable under repeated scanning with a scanning tunneling microscope (STM). They become removed when the surface is brought to a negative charge. When operated at tunnel currents below approximately 0.4 nA, the STM yields a resolution of approximately 1 nm, which is better than can be obtained with atomic force microscopy (AFM) at present. We illustrate this procedure by imaging a series of DNA molecules made by ligating a 21 base-pair oligonucleotide. We observed the expected series of fragment lengths but small fragments are adsorbed preferentially. Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 PMID:1617139

  16. A potentiostatic study of the corrosion behavior of anodized and nonanodized aluminum alloy.

    PubMed

    White, K C; Svare, C W; Taylor, T D

    1985-06-01

    The clinical implication of this study is that some improvement in the corrosion resistance of denture bases made with aluminum alloy D-214 may be obtained by anodization. However, since this study does not exactly duplicate an oral environment or take into consideration the variation in oral environments, it cannot be assumed that the additional corrosion resistance would be discernible in a particular patient. PMID:3859652

  17. Potentiostatic reversible photoelectrochromism: an effect appearing in nanoporous TiO2/Ni(OH)2 thin films.

    PubMed

    Cibrev, Dejan; Jankulovska, Milena; Lana-Villarreal, Teresa; Gómez, Roberto

    2014-07-01

    In the field of energy saving, finding composite materials with the ability of coloring upon both illumination and change of the applied electrode potential keeps on being an important goal. In this context, chemical bath deposition of Ni(OH)2 into nanoporous TiO2 thin films supported on conducting glass leads to electrodes showing both conventional electrochromic behavior (from colorless to dark brown and vice versa) together with photochromism at constant applied potential. The latter phenomenon, reported here for the first time, is characterized by fast and reversible coloration upon UV illumination. The bleaching kinetics shows first order behavior with respect to the Ni(III) centers in the film, and an order 1.2 with respect to electrons in the TiO2 film. From a more applied point of view, this study opens up the possibility of having two-mode smart windows showing not only conventional electrochromism but also reversible darkening upon illumination. PMID:24926989

  18. A potentiostatic study of oxygen transport through poly(2-ethoxyethyl methacrylate-co-2,3-dihydroxypropylmethacrylate) hydrogel membranes.

    PubMed

    Compañ, Vicente; Tiemblo, Pilar; García, F; García, J M; Guzmán, Julio; Riande, Evaristo

    2005-06-01

    The oxygen permeability and diffusion coefficients of hydrogel membranes prepared with copolymers of 2-ethoxyethyl methacrylate (EEMA)/2,3-dihydroxypropylmethacrylate (MAG) with mole fraction of the second monomer in the range between 0 and 0.75 are described. Values of the permeability and diffusion coefficients of oxygen are determined by using electrochemical procedures involving the measurement of the steady-state current in membranes prepared by radical polymerization of the monomers. The results obtained for the transport properties were analyzed taking into account the fractional free volumes, the cohesive energy densities and the glass transition temperatures of the hydrogels. PMID:15626426

  19. Potentiostatic controlled nucleation and growth modes of electrodeposited cobalt thin films on n-Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Mechehoud, Fayçal; Khelil, Abdelbacet; Eddine Hakiki, Nour; Bubendorff, Jean-Luc

    2016-08-01

    The nucleation and growth of Co electrodeposits on n-Si(1 1 1) substrate have been investigated as a function of the applied potential in a large potential range using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by atomic force microscopy (AFM). The surface preparation of the sample is crucial and we achieve a controlled n-Si(1 1 1) surface with mono-atomic steps and flat terraces. Using Scharifker-Hills models for fitting the current-time transients, we show that a transition from an instantaneous nucleation process to a progressive one occurs when the overpotential increases. A good agreement between the nucleation and growth parameters extracted from the models and the AFM data's is observed. The growth is of the Volmer-Weber type with a roughness and a spatial extension in the substrate plane of the deposited islands that increase with thickness.

  20. Aerated Shewanella oneidensis in Continuously-fed Bioelectrochemical Systems for Power and Hydrogen Production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We studied the effects of aeration of Shewanella oneidensis on potentiostatic current production, iron(III) reduction, hydrogen production in a microbial electrolysis cell, and electric power generation in a microbial fuel cell. The potentiostatic performance of aerated S. oneidensis was considerab...

  1. Electrochemical nitridation of metal surfaces

    SciTech Connect

    Wang, Heli; Turner, John A.

    2015-06-30

    Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

  2. Electrochemical Microsensors for the Detection of Cadmium(II) and Lead(II) Ions in Plants

    PubMed Central

    Krystofova, Olga; Trnkova, Libuse; Adam, Vojtech; Zehnalek, Josef; Hubalek, Jaromir; Babula, Petr; Kizek, Rene

    2010-01-01

    Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic. PMID:22219663

  3. SWEPT-POTENTIAL ELECTROCHEMICAL DETECTOR FOR FLOW STREAMS

    EPA Science Inventory

    An instrument has been designed, constructed, and evaluated for electrochemical measurements in flow streams. The instrument is basically a computer-controlled potentiostat with features that are necessary for measurements in flow streams. These features include real-time graphic...

  4. Selection of charge methods for lithium ion batteries by considering diffusion induced stress and charge time

    NASA Astrophysics Data System (ADS)

    Lu, Bo; Song, Yicheng; Zhang, Junqian

    2016-07-01

    This article demonstrates the design of charging strategies for lithium ion batteries with considering the balance between diffusion induced stress and total charge time for two- and three-stage charge methods. For the two-stage galvanostatic-potentiostatic charge method the low mechanical stress can be achieved without increasing total charge time by switching the galvanostatic to the potentiostatic at the time moment when the lithium concentration at the surface of particles reaches the limit cbarsurf = 0 . A three-stage method, which consists of an initial galvanostatic stage of high current, a galvanostatic stage of low current and a potentiostatic ending stage, is suggested. Employing the initial galvanostatic stage of high current is helpful not only in accelerating the charge process, but also in controlling the mechanical stress once the electrical current and time duration of the initial galvanostatic stage are properly designed.

  5. Plasma Arc Melting (PAM) and Corrosion Resistance of Pure NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Tuissi, A.; Rondelli, G.; Bassani, P.

    2015-03-01

    Plasma arc melting (PAM) as a suitable non-contaminating melting route for manufacturing high-quality NiTi alloy was successfully examined. The corrosion resistance of PAM Nitinol was evaluated by both potentiodynamic and potentiostatic tests and compared with lower purity NiTi produced by vacuum induction melting (VIM). For the electro-polished surfaces, excellent corrosion resistance of NiTi comparable with the Ti alloys was found with no pitting up to 800 mV versus saturated calomel electrode in simulated body fluid at 37 °C. Potentiostatic results of PAM Nitinol indicate slightly better corrosion resistance than the lower quality VIM alloy.

  6. Apparatus for use in rapid and accurate controlled-potential coulometric analysis

    DOEpatents

    Frazzini, Thomas L.; Holland, Michael K.; Pietri, Charles E.; Weiss, Jon R.

    1981-01-01

    An apparatus for controlled-potential coulometric analysis of a solution includes a cell to contain the solution to be analyzed and a plurality of electrodes to contact the solution in the cell. Means are provided to stir the solution and to control the atmosphere above it. A potentiostat connected to the electrodes controls potential differences among the electrodes. An electronic circuit connected to the potentiostat provides analog-to-digital conversion and displays a precise count of charge transfer during a desired chemical process. This count provides a measure of the amount of an unknown substance in the solution.

  7. Characterization of electrochemically deposited polypyrrole using magnetoelastic material transduction elements

    NASA Technical Reports Server (NTRS)

    Ersoz, Arzu; Ball, J. Christopher; Grimes, Craig A.; Bachas, Leonidas G.

    2002-01-01

    Magnetoelastic alloy films have been used as a working electrode in an electrochemical cell. This material allows magnetic interrogation of electrochemical deposition. This technique was used to monitor the electrochemical deposition of polypyrrole by multisweep (CV) and potentiostatic methods. Since the determination of the mass-sensitive magnetoelastic film's resonance frequency is based on magnetic transduction, an inherent advantage of this method is that it requires no electrical connections other than the working lead of the potentiostat. Increases in pyrrole deposition correlated with a decrease in the peak resonance frequency of the magnetoelastic alloy. This technique provides a novel approach by which one can monitor electrochemical processes.

  8. Overview of corrosion, corrosion protection, and stress-corrosion cracking of uranium and uranium alloys

    SciTech Connect

    Koger, J.W.

    1981-12-14

    This paper covers some basic definitions and provides some data. The 51 slides illustrates these definitions, crack initiation and propagation, sources of stress, types of specimens used for SCC, potentiostatic polarization, data for Mulberry and U-Nb alloys, effects of environment, and data for U-0.75 Ti and U-Mo alloys. (DLC)

  9. MICROFABRICATED ELECTROCHEMICAL ANALYSIS SYSTEM FOR HEAVY METAL DETECTION. (R825511C047)

    EPA Science Inventory

    A low power, hand-held system has been developed for the measurement of heavy metal ions in aqueous solutions. The system consists of an electrode array sensor, a high performance single chip potentiostat and a microcontroller circuit. The sensor is a microfabricated array of ...

  10. TiO(2) nanotube arrays: intrinsic peroxidase mimetics.

    PubMed

    Zhang, Lingling; Han, Lei; Hu, Peng; Wang, Li; Dong, Shaojun

    2013-11-18

    TiO2 nanotube arrays (NTA), prepared by potentiostatic anodization, were discovered to possess an intrinsic peroxidase-like activity. The colorimetric and electrochemical assays both demonstrated their excellent catalytic activity towards H2O2 reduction. On this basis, a simple and inexpensive electrochemical biosensor for glucose detection was developed. PMID:24084751

  11. Voltammetry at the Thin-Film Mercury Electrode (TFME).

    ERIC Educational Resources Information Center

    Pomeroy, R. S.; And Others

    1989-01-01

    Reviewed is the use of the Thin-Film Mercury Electrode for anodic stripping voltammetry, simple voltammetry of solution cations and cathodic stripping voltammetry for the determination of an environmentally important molecule, thiourea. The construction of a simple potentiostat and applications for student laboratory courses are included. (CW)

  12. Efficiencies of Bio-electrocatalytic Production of Hydrogen from Lactate Using Shewanella oneidensis MR-1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shewanella oneidensis MR-1 was grown in a chemostatic, continuously-fed bioelectrochemical cell under slightly aerated conditions. The start-up phase was controlled potentiostatically (0.4 V vs. SHE). When a stable performance was achieved, the reactor was switched to bio-electrocatalytic producti...

  13. Electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification.

    PubMed

    Jeong, Yong-Hoon; Kim, Won-Gi; Choe, Han-Cheol

    2011-02-01

    In this study, the electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification has been researched using the potentiostat equipment. Cp-Ti and Ti-6Al-4V alloy, located on X-Y motorized stage, were irradiated using femtosecond laser. The corrosion properties were examined by a potentiodynamic and AC impedance test. PMID:21456241

  14. Cybernetic Control of an Electrochemical Repertoire.

    ERIC Educational Resources Information Center

    He, Peixin; And Others

    1982-01-01

    Describes major features of a computer-operated, cybernetic potentiostat and the development, design, and operation of the software in ROM. The instrument contains control circuitry and software making it compatible with the static mercury drop electrode produced by EG&G Princeton Applied Research Corporation. Sample results using the instrument…

  15. AN ADVANCED FLUE GAS MONITOR FOR SO2 - PHASE I

    EPA Science Inventory

    The development of an instrument for continuously monitoring SO2 levels in flue gas is proposed. The SO2 will be detected by means of an electrochemical sensor cell, which operates in a three-electrode potentiostatic mode. The proposed innovation is develop-ment of an advan...

  16. Algal biosensor array on a single electrode.

    PubMed

    Tatsuma, Tetsu; Yoshida, Yutaka; Shitanda, Isao; Notsu, Hideo

    2009-02-01

    An algal array was prepared on a single transparent electrode, and photosynthetic activity of each algal channel and its inhibition by a toxin were monitored with a single-channel potentiostat by successive light irradiation with a LED array. PMID:19173040

  17. In situ monitoring of the Li-O2 electrochemical reaction on nanoporous gold using electrochemical AFM.

    PubMed

    Wen, Rui; Byon, Hye Ryung

    2014-03-11

    The lithium-oxygen (Li-O2) electrochemical reaction on nanoporous gold (NPG) is observed using in situ atomic force microscopy (AFM) imaging coupled with potentiostatic measurement. Dense Li2O2 nanoparticles form a film at 2.5 V, which is decomposed at 3.8-4.0 V in an ether-based electrolyte. PMID:24469227

  18. Surface pK(sub a) of Self-Assembled Monolayers

    ERIC Educational Resources Information Center

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.

    2005-01-01

    The difference between solution and surface properties such as pK(sub a) is illustrated enabling students to understand the differences between nanoscale and macroscopic systems. Details regarding the usage of electrochemical instrumentation, such as a potentiostat, and of the technique such as cyclic voltammetry are given.

  19. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

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

    2009-01-01

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

  20. Toward developing long-life water quality sensors for the ISS using planar REDOX and conductivity sensors

    NASA Technical Reports Server (NTRS)

    Buehler, M. G.; Kuhlman, G. M.; Keymeulen, D.; Myung, N.; Kounaves, S. P.

    2003-01-01

    REDOX and conductivity sensors are metal electrodes that are used to detect ionic species in solution by measuring the electrochemical cell current as the voltage is scanned. This paper describes the construction of the sensors, the potentiostat electronics, the measurement methodology, and applications to water quality measurements.

  1. Improvement in the Corrosion Resistance of Austenitic Stainless Steel 316L by Ion Implantation

    NASA Astrophysics Data System (ADS)

    Cai, Xun; Feng, Kai

    In the present work, austenitic stainless steel 316L (SS316L) samples were implanted with Ni and Ni-Cr. A nickel-rich layer about 100 nm in thickness and a Ni-Cr enriched layer about 60 nm thick are formed on the surface of SS316L. The effects of ion implantation on the corrosion performance of SS316L are investigated in a 0.5 M H2SO4 with 2 ppm HF solution at 80°C by open circuit potential (OCP), potentiodynamic and potentiostatic tests. The samples after the potentiostatic test are analyzed by XPS. The results indicate that the composition of the passive film change from a mixture of Fe oxides and Cr oxide to a Cr oxide dominated passive film after the potentiostatic test. The solutions after the potentiostatic test are analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results reveal that Fe is selectively dissolved in all cases and a proper Ni and Ni-Cr implant fluence can greatly improve the corrosion resistance of SS316L in the simulated polymer electrolyte membrane fuel cells (PEMFCS) environment. They are in agreement with the electrochemical test results that the bare SS316L has the highest dissolution rate in both cathode and anode environments and the Ni and Ni-Cr implantation reduce markedly the dissolution rate. After the potentiostatic test the interfacial contact resistance (ICR) values are also measured. Ni and Ni-Cr are enriched in the passive film formed in the simulated PEMFC cathode environment after ion implantation thereby providing better conductivity than that formed in the anode one. A significant improvement of ICR is achieved for the SS316L implanted with Ni and Ni-Cr as compared to the bare SS316L, which is attributed to the reduction in passive layer thickness caused by Ni and Ni-Cr implantation. The ICR values for implanted specimens increase with increasing dose.

  2. Corrosion resistance tests on NiTi shape memory alloy.

    PubMed

    Rondelli, G

    1996-10-01

    The corrosion performances of NiTi shape memory alloys (SMA) in human body simulating fluids were evaluated in comparison with other implant materials. As for the passivity current in potentiostatic conditions, taken as an index of ion release, the values are about three times higher for NiTi than for Ti6Al4V and austenitic stainless steels. Regarding the localized corrosion, while plain potentiodynamic scans indicated for NiTi alloy good resistance to pitting attack similar to Ti6Al4V, tests in which the passive film is abruptly damaged (i.e. potentiostatic scratch test and modified ASTM F746) pointed out that the characteristics of the passive film formed on NiTi alloy (whose strength can be related to the alloy's biocompatibility) are not as good as those on Ti6Al4V but are comparable or inferior to those on austenitic stainless steels. PMID:8894095

  3. Distributed effects of calcium ion contaminant on polymer electrolyte fuel cell performance

    NASA Astrophysics Data System (ADS)

    Uddin, Md Aman; Wang, Xiaofeng; Park, Jaehyung; Pasaogullari, Ugur; Bonville, Leonard

    2015-11-01

    Distributed performance of a polymer electrolyte fuel cell (PEFC) is studied both in galvanostatic and potentiostatic mode during in-situ injection of Ca2+ in the air stream using a segmented cell. In the galvanostatic mode, segments near the inlet are affected first by the contaminant resulting in decreased current density. At the same time, despite the presence of contaminants, current density for the other segments increases in order to maintain constant total current. In the potentiostatic mode, all segments are affected by the contaminants simultaneously and the current density in all segments decreases with time. The performance of the downstream segments is lower than the upstream segments. During both tests, the contaminant is found to precipitate on both the cathode flow field and the cathode GDL surface. As the test progresses, the contaminant penetrates into the GDL and deposits, causing mass transport losses.

  4. Selective dissolution in copper-tin alloys: Formation of corrosion- resistant patina on ancient Chinese bronze mirrors

    SciTech Connect

    Taube, M. |; Davenport, A.J.; King, A.H.; Chase, T. III

    1996-07-01

    Many ancient Chinese bronze mirrors have survived with a patina that leaves the delicate relief surface decorations intact. The microstructure of these ancient mirrors is two-phase and consists of acicular {alpha}-phase (Cu-rich) regions encased in a {delta}-phase (Sn-rich) matrix. At the surface, there is evidence of selective dissolution of the ct phase; the cc-phase regions are replaced pseudomorphically by a mineral product with the {delta} phase remaining metallic. Electrochemical polarization has been used to drive the copper dealloying process in modem, cast bronze. Synchrotron x-ray diffraction was employed to compare the ancient samples with those that were prepared potentiostatically. Poorly crystallized tin oxide (SnO{sub 2}) was found in the {alpha} replacement products of both sample types. The corrosion-resistance of the potentiostatically-treated bronze samples was tested by atmospheric exposure. Comparison with exposed, untreated samples indicated that the treatment was protective.

  5. A new electrochemical approach for evaluation of corrosion inhibitors in neutral aqueous solutions

    SciTech Connect

    Jovancicevic, V.; Hartwick, D.

    1997-12-01

    A new comprehensive electrochemical approach to corrosion inhibitor evaluation in neutral aqueous solutions has been developed. It consists of using concurrently three different but complementary electrochemical methods. Linear polarization resistance (LPR), concentration-step potentiostatic (CSP) and constant-concentration potentiostatic (CCP) methods are used to determine the overall corrosion rates, corrosion inhibition mechanism, and stability of the passive oxide film in the presence of corrosion inhibitors. This approach has been used successfully to evaluate corrosion inhibition of three organic inhibitor systems: a phosphonate-based corrosion inhibitor (hydroxyphosphonoacetic acid, HPA), a polymeric corrosion inhibitor (polyacrylic acid, PAA) and a non-phosphorus containing corrosion inhibitor (L-tartaric acid). Short-term CSP/CCP test results for these three inhibitors are in good agreement with long-term weight loss measurements.

  6. Electrodeposition of hafnium coatings from molten CsCl-HfCl{sub 4}

    SciTech Connect

    Kuznetsov, S.A.; Glagolevskaya, A.L.; Kuznetsova, S.V.

    1992-04-20

    The electrode processes in the CsCl-HfCl{sub 4} melt were examined by potentiodynamic and potentiostatic methods with the use of P-5827 and PI-50.1.1 potentiostats. The potential sweep rates were varied form 0.005 to 1.0 V/sec. The recorders were KSP-4 and LKD-4-003 potentiometers and a PO-5122 oscillographic polarograph. The electrochemical cell was the traditional one for electrochemical studies. The reference electrode was Ag/NaCl-KCl-AgCl (2 mass %). The mass loss in the hafnium anode was used to determine the anode current yield and the mean degree of oxidation for the hafnium ion entering the melt. The anode products were identified by X-ray methods with a DRON-2 diffractometer and also by thermographic and chemical analysis. 15 refs., 4 figs., 1 tab.

  7. Template-assisted electrodeposition of indium-antimony nanowires - Comparison of electrochemical methods

    NASA Astrophysics Data System (ADS)

    Hnida, Katarzyna; Mech, Justyna; Sulka, Grzegorz D.

    2013-12-01

    Indium antimonide (InSb) is a III-V compound semiconductor that in a form of nanowires can possess improved thermoelectrical and optical properties compared to the corresponding bulk crystal. Here, we applied three electrodeposition techniques for a fast and inexpensive template-assisted fabrication of InSb nanowires from a sodium citrate-citric acid solution at room temperature. The home-made anodic aluminum oxide (AAO) templates with the pore diameter of 100 nm were used. InSb nanowires were synthesized by potentiostatic, galvanostatic and periodic pulse reverse techniques. The morphology, composition and crystallinity of as-obtained and annealed nanowires were investigated and compared with the literature data. It was found that the potentiostatic and pulse reverse methods gave crystalline nanowires. On the other hand, the constant current density deposition results in a partially amorphous nanowire material.

  8. Nano electrode arrays for in-situ identification and quantification of chemicals in water.

    SciTech Connect

    Gurule, Natalia J.; Kelly, Michael James; Brevnov, Dmitri A.; Ashby, Carol Iris Hill; Pfeifer, Kent Bryant; Yelton, William Graham

    2004-12-01

    The nano electrode arrays for in-situ identification and quantification of chemicals in water progress in four major directions. (1) We developed and engineering three nanoelectrode array designs which operate in a portable field mode or as distributed sensor network for water systems. (2) To replace the fragile glass electrochemical cells using in the lab, we design and engineered field-ready sampling heads that combine the nanoelectrode arrays with a high-speed potentiostat. (3) To utilize these arrays in a portable system we design and engineered a light weight high-speed potentiostat with pulse widths from 2 psec. to 100 msec. or greater. (4) Finally, we developed the parameters for an analytical method in low-conductivity solutions for Pb(II) detection, with initial studies for the analysis of As(III) and As(V) analysis in natural water sources.

  9. On-line corrosion monitoring with electrochemical impedance spectroscopy

    SciTech Connect

    Roberge, P.R. . Dept. of Chemistry and Chemical Engineering); Sastri, V.S. )

    1994-10-01

    Electrochemical impedance spectroscopy (EIS) has been found to be a rapid and accurate technique for measuring corrosion rates in the most difficult situations and for yielding information concerning the occurrence of localized corrosion. When used in the absence of potentiostatic control, the technique carries less instrumental overhead, and the danger of damaging the probe by accidental polarization is reduced. Results from two field tests were presented to illustrate the advantages of using EIS for on-line monitoring of general and localized corrosion.

  10. Teorell instability in concentration polarization.

    PubMed

    Abu-Rjal, Ramadan; Prigozhin, Leonid; Rubinstein, Isaak; Zaltzman, Boris

    2015-08-01

    We investigate the development of electro-osmotic (Teorell) oscillations at a weakly charged microporous membrane without a preimposed transmembrane electrolyte concentration drop. This drop, necessary for the occurrence of oscillations, develops spontaneously as a result of concentration polarization in the solution layers adjacent to the membrane. A three-layer model comprising a membrane flanked by two diffusion layers is proposed and analyzed for galvano- and potentiostatic regimes of operation. PMID:26382404

  11. Preparation and characterisation of nearly stoichiometric CdTe films from a non-aqueous electrodeposition bath

    NASA Astrophysics Data System (ADS)

    Gore, R. B.; Pandey, Rajendra Kumar; Kumar, S. R.

    1991-06-01

    The cathodic polarisation characteristics and the growth behaviour of CdTe films in an ethylene-glycol-based bath have been studied. Conditions favouring stoichiometric deposition have been examined. The influence of the processing variables on the film properties has also been discussed with the help of the XRD, SEM and XPS studies. It has been shown that the films deposited potentiostatically at -0.8 V are stoichiometric and single phase.

  12. Teorell instability in concentration polarization

    NASA Astrophysics Data System (ADS)

    Abu-Rjal, Ramadan; Prigozhin, Leonid; Rubinstein, Isaak; Zaltzman, Boris

    2015-08-01

    We investigate the development of electro-osmotic (Teorell) oscillations at a weakly charged microporous membrane without a preimposed transmembrane electrolyte concentration drop. This drop, necessary for the occurrence of oscillations, develops spontaneously as a result of concentration polarization in the solution layers adjacent to the membrane. A three-layer model comprising a membrane flanked by two diffusion layers is proposed and analyzed for galvano- and potentiostatic regimes of operation.

  13. Proton transfer in oxidized adenosine self-aggregates.

    PubMed

    Capobianco, Amedeo; Caruso, Tonino; Celentano, Maurizio; La Rocca, Mario Vincenzo; Peluso, Andrea

    2013-10-14

    The UV-vis and the IR spectra of derivativized adenosine in dichloromethane have been recorded during potentiostatic oxidation at an optically transparent thin layer electrode. Oxidized adenosine shows a broad Zundel like absorption extending from 2800 up to 3600 cm(-1), indicating that a proton transfer process is occurring. Theoretical computations predict that proton transfer is indeed favored in oxidized 1:1 self-association complexes and allow to assign all the observed transient spectroscopic signals. PMID:24116647

  14. A Scanning Auger Microprobe analysis of corrosion products associated with sulfate reducing bacteria

    SciTech Connect

    Sadowski, R.A.; Chen, G.; Clayton, C.R.; Kearns, J.R.; Gillow, J.B.; Francis, A.J.

    1995-03-01

    A Scanning Auger Microprobe analysis was performed on the corrosion products of an austenitic AISI type 304 SS after a potentiostatic polarization of one volt for ten minutes in a modified Postgate`s C media containing sulfate reducing bacteria. The corrosion products were characterized and mapped in local regions where pitting was observed. A critical evaluation of the applicability of this technique for the examination of microbially influenced corrosion (MIC) is presented.

  15. Studying localized corrosion using liquid cell transmission electron microscopy

    SciTech Connect

    Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; Duquette, David; Ross, Frances M.; Hull, Robert

    2014-11-07

    Using liquid cell transmission electron microscopy (LCTEM), localized corrosion of Cu and Al thin films immersed in aqueous NaCl solutions was studied. We demonstrate that potentiostatic control can be used to initiate pitting and that local compositional changes, due to focused ion beam implantation of Au+ ions, can modify the corrosion susceptibility of Al films. Likewise, a discussion on strategies to control the onset of pitting is also presented.

  16. Studying localized corrosion using liquid cell transmission electron microscopy

    DOE PAGESBeta

    Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; Duquette, David; Ross, Frances M.; Hull, Robert

    2014-11-07

    Using liquid cell transmission electron microscopy (LCTEM), localized corrosion of Cu and Al thin films immersed in aqueous NaCl solutions was studied. We demonstrate that potentiostatic control can be used to initiate pitting and that local compositional changes, due to focused ion beam implantation of Au+ ions, can modify the corrosion susceptibility of Al films. Likewise, a discussion on strategies to control the onset of pitting is also presented.

  17. Electrochemical behavior of nanocrystalline Ta/TaN multilayer on 316L stainless steel: Novel bipolar plates for proton exchange membrane fuel-cells

    NASA Astrophysics Data System (ADS)

    Alishahi, M.; Mahboubi, F.; Mousavi Khoie, S. M.; Aparicio, M.; Hübner, R.; Soldera, F.; Gago, R.

    2016-08-01

    Insufficient corrosion resistance and surface conductivity are two main issues that plague large-scale application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). This study explores the use of nanocrystalline Ta/TaN multilayer coatings to improve the electrical and electrochemical performance of polished 316L SS bipolar plates. The multilayer coatings have been deposited by (reactive) magnetron sputtering and characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of bare and coated substrates has been evaluated in simulated PEMFC working environments by potentiodynamic and potentiostatic polarization tests at ambient temperature and 80 °C. The results show that the Ta/TaN multilayer coating increases the polarization resistance of 316L SS by about 30 and 104 times at ambient and elevated temperatures, respectively. The interfacial contact resistance (ICR) shows a low value of 12 mΩ × cm2 before the potentiostatic test. This ICR is significantly lower than for the bare substrate and remains mostly unchanged after potentiostatic polarization for 14 h. In addition, the high contact angle (92°) with water for coated substrates indicates a hydrophobic character, which can improve the water management within the cell in PEMFC stacks.

  18. Electrochemical sensing of nuclear matrix protein 22 in urine with molecularly imprinted poly(ethylene-co-vinyl alcohol) coated zinc oxide nanorod arrays for clinical studies of bladder cancer diagnosis.

    PubMed

    Lee, Mei-Hwa; Thomas, James L; Chang, Yu-Chia; Tsai, Yuh-Shyan; Liu, Bin-Da; Lin, Hung-Yin

    2016-05-15

    In 1996 and 2000, the US Food and Drug Administration (FDA) approved the use of Nuclear matrix protein 22 (NMP22) as a monitoring tool for predicting the recurrence/clearing of bladder cancer, and for screening undiagnosed individuals who have symptoms of, or are at risk for, that disease. The fabrication of electrodes for sensing NMP22 and their integration with a portable potentiostat in a homecare system may have great value. This work describes a sensing element comprised of molecularly imprinted polymers (MIPs) for the specific recognition of NMP22 target molecules. Zinc oxide (ZnO) nanorods (214 ± 45 nm in diameter and 1.08 ± 0.11 μm long) were hydrothermally grown on the sensing electrodes to increase the surface area to be coated with MIPs. A portable potentiostat was assembled and a data acquisition (DAQ) card and the Labview program were utilized to monitor electrochemical reaction to sense NMP22 in urine samples. Finally, in phase 0 clinical trials, measurements were made of samples from a few patients with bladder cancer using the NMP22 MIP-coated ZnO nanorods electrodes that were integrated into a portable potentiostat, revealing NMP 22 concentrations in the range 128 ± 19 to 588 ± 53 ng/mL. PMID:26774095

  19. A CMOS Amperometric System for Multi-Neurotransmitter Detection.

    PubMed

    Massicotte, Genevieve; Carrara, Sandro; Di Micheli, Giovanni; Sawan, Mohamad

    2016-06-01

    In vivo multi-target and selective concentration monitoring of neurotransmitters can help to unravel the brain chemical complex signaling interplay. This paper presents a dedicated integrated potentiostat transducer circuit and its selective electrode interface. A custom 2-electrode time-based potentiostat circuit was fabricated with 0.13 μm CMOS technology and provides a wide dynamic input current range of 20 pA to 600 nA with 56 μ W, for a minimum sampling frequency of 1.25 kHz. A multi-working electrode chip is functionalized with carbon nanotubes (CNT)-based chemical coatings that offer high sensitivity and selectivity towards electroactive dopamine and non-electroactive glutamate. The prototype was experimentally tested with different concentrations levels of both neurotransmitter types, and results were similar to measurements with a commercially available potentiostat. This paper validates the functionality of the proposed biosensor, and demonstrates its potential for the selective detection of a large number of neurochemicals. PMID:26761882

  20. A Low-Cost Smartphone-Based Electrochemical Biosensor for Point-of-Care Diagnostics

    PubMed Central

    Sun, Alexander; Wambach, Travis; Venkatesh, A. G.; Hall, Drew A.

    2015-01-01

    This paper describes the development of a smartphone-based electrochemical biosensor module. The module contains a low power potentiostat that interfaces and harvests power from a smartphone through the phone’s audio jack. A prototype with two different potentiostat designs was constructed and used to conduct proof of concept cyclic voltammetry experiments with potassium ferro-/ferricyanide (K4[Fe(CN)6] / K3[Fe(CN)6]) in a side-by-side comparison with a laboratory grade instrument. Results show that the module functions within the available power budget and that the recovered voltammogram data matches well with the data from an expensive bench top tool. Excluding the loses from supply rectification and regulation, the module consumes either 5.7 mW or 4.3 mW peak power, depending on which of the two discussed potentiostat designs is used. At single quantity pricing, the hardware for the prototype device costs less than $30. PMID:26097899

  1. Effect of chemical etching and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide resulting from manufacturing process.

    PubMed

    Shabalovskaya, S; Rondelli, G; Anderegg, J; Simpson, B; Budko, S

    2003-07-15

    The effect of chemical etching in a HF/HNO(3) acid solution and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide has been evaluated with the use of potentiodynamic, modified potentiostatic ASTM F746, and scratch tests. Scanning-electron microscopy, elemental XPS, and Auger analysis were employed to characterize surface alterations induced by surface treatment and corrosion testing. The effect of aging in boiling water on the temperatures of martensitic transformations and shape recovery was evaluated by means of measuring the wire electroresistance. After corrosion tests, as-received wires revealed uniformly cracked surfaces reminiscent of the stress-corrosion-cracking phenomenon. These wires exhibited negative breakdown potentials in potentiostatic tests and variable breakdown potentials in potentiodynamic tests (- 100 mV to + 400 mV versus SCE). Wires with treated surfaces did not reveal cracking or other traces of corrosion attacks in potentiodynamic tests up to + 900-1400-mV potentials and no pitting after stimulation at + 800 mV in potentiostatic tests. They exhibited corrosion behavior satisfactory for medical applications. Significant improvement of corrosion parameters was observed on the reverse scans in potentiodynamic tests after exposure of treated wires to potentials > 1000 mV. In scratch tests, the prepared surfaces repassivated only at low potentials, comparable to that of stainless steel. Tremendous improvement of the corrosion behavior of treated Nitinol wires is associated with the removal of defect surface material and the growth of stable TiO(2) oxide. The role of precipitates in the corrosion resistance of Nitinol-scratch repassivation capacity in particular-is emphasized in the discussion. PMID:12808592

  2. Comparative study on corrosion behaviour of Nitinol and stainless steel orthodontic wires in simulated saliva solution in presence of fluoride ions.

    PubMed

    Mirjalili, M; Momeni, M; Ebrahimi, N; Moayed, M H

    2013-05-01

    Localized corrosion and effects of pre-passivation treatment of Nitinol and SS304 orthodontic wires in simulated saliva solution in the presence and absence of fluoride ions were investigated by means of potentiodynamic and potentiostatic polarisations. Results revealed that Nitinol does not show pitting corrosion in saliva solution however, SS304 shows pitting corrosion. Meanwhile fluoride ion has deteriorative effect on pitting corrosion of Nitinol, while its effect on SS304 was marginally constructive. Additionally, the presence of artificial crevice has no effect on corrosion behaviour in the presence of fluoride. Pre-passivation treatment has positive influence on pitting corrosion of both alloys in the presence of F(-) ions. PMID:23498236

  3. Extensive study of shape and surface structure formation in the mercury beating heart system.

    PubMed

    Ramírez-Álvarez, E; Ocampo-Espindola, J L; Montoya, Fernando; Yousif, F; Vázquez, F; Rivera, M

    2014-11-13

    A phenomenological study of the mercury beating heart system in a three electrode electrochemical cell configuration forced with a harmonic perturbation is presented. The system is controlled via a potentiostat, where the mercury drop is electrically connected to a platinum wire and acts as the working electrode. This configuration exhibits geometrical shapes and complex surface structures when a harmonic signal is superimposed to the working electrode potential. This study involves a wide range of frequencies and amplitudes of the forcing signal. Differents levels of structure complexity are observed as a function of the parameters of the applied perturbation. At certain amplitudes and frequencies, rotational behavior is also observed. PMID:25343208

  4. Effect of Applied Potential on the Electrochemical Deposition of Styrene-Butadiene Co-Polymer Based Conducting Polymer Composite

    NASA Astrophysics Data System (ADS)

    Mathew, Anisha Mary; Neena, P.

    2011-10-01

    Homogeneous conducting polymer composite films with improved electrical properties are synthesized via electrochemical polymerization of polyaniline on Styrene butadiene rubber coated steel electrode. The electrochemical polymerization is carried out by potentiostatic method using an aqueous solution of 0.2 M aniline and 1.5 M sulphuric acid as electrolyte in a single compartment electrochemical cell. The optical studies show successful incorporation of polyaniline into the matrix polymer film. The effect of applied potential on the electrodeposition of composite is studied by cyclic voltammetry and by impedance spectroscopic measurements.

  5. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C.

    1994-01-01

    A process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flow cell containing flow bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flow cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flow cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  6. Novel Approach to Surface Plasmon Resonance: A Third Dimension in Data Interpretation Through Surface Roughness Changes.

    PubMed

    Manole, Claudiu Constantin; Pîrvu, C; Maury, F; Demetrescu, I

    2016-06-01

    In a Surface Plasmon Resonance (SPR) experiment two key parameters are classically recorded: the time and the angle of SPR reflectivity. This paper brings into focus a third key parameter: SPR reflectivity. The SPR reflectivity is proved to be related to surface roughness changes. Practical investigations on (i) gold anodizing and (ii) polypyrrole film growth in presence of oxalic acid is detailed under potentiostatic conditions. These experimental results reveal the potential of using the SPR technique to investigate real-time changes both on the gold surface, but also in the gold film itself. This extends the versatility of the technique in particular as sensitive in-situ diagnostic tool. PMID:27427713

  7. The Structure and Properties of Inductively Coupled Plasma Assisted Magnetron Sputtered Nanocrystalline NbN Coatings in Corrosion Protective Die Casting Molds.

    PubMed

    Chun, Sung-Yong

    2016-02-01

    Niobium nitride coatings for the surface modified die casting molds with various ICP powers have been prepared using ICP assisted magnetron sputtering. The applied ICP power was varied from 0 to 200 W. The deposited coatings were characterized post-deposition using X-ray diffractometry (XRD) and atomic force microscopy (AFM). Single NbN phased coatings with nano-grain sized (<7.6 nm) were identified. The corrosion resistance and hardness of each coating were evaluated from potentiostat and nanoindentator. Superior corrosion protective coatings in excess of 13.9 GPa were deposited with assistance of ICP plasma during sputtering. PMID:27433719

  8. Morphology, structure, and magnetism of FeCo thin films electrodeposited on hydrogen-terminated Si(111) surfaces.

    PubMed

    Zarpellon, J; Jurca, H F; Mattoso, N; Klein, J J; Schreiner, W H; Ardisson, J D; Macedo, W A A; Mosca, D H

    2007-12-15

    In this work we describe the fabrication of FeCo alloy (less than 10 at% Co) thin films from aqueous ammonium sulfate solutions onto n-type Si(111) substrates using potentiostatic electrodeposition at room temperature. The incorporation of Co into the deposits tends to inhibit Fe silicide formation and to protect deposits against oxidation under air exposure. As the incorporation of Co was progressively increased, the sizes of nuclei consisting of FeCo alloy increased, leading to films with a highly oriented body-centered cubic structure with crystalline texture, where (110) planes remain preferentially oriented parallel to the film surface. PMID:17900605

  9. Patterned electrochemical deposition of copper using an electron beam

    SciTech Connect

    Heijer, Mark den; Shao, Ingrid; Reuter, Mark C.; Ross, Frances M.; Radisic, Alex

    2014-02-01

    We describe a technique for patterning clusters of metal using electrochemical deposition. By operating an electrochemical cell in the transmission electron microscope, we deposit Cu on Au under potentiostatic conditions. For acidified copper sulphate electrolytes, nucleation occurs uniformly over the electrode. However, when chloride ions are added there is a range of applied potentials over which nucleation occurs only in areas irradiated by the electron beam. By scanning the beam we control nucleation to form patterns of deposited copper. We discuss the mechanism for this effect in terms of electron beam-induced reactions with copper chloride, and consider possible applications.

  10. Investigation of the electrochemically active surface area and lithium diffusion in graphite anodes by a novel OsO4 staining method

    NASA Astrophysics Data System (ADS)

    Pfaffmann, Lukas; Birkenmaier, Claudia; Müller, Marcus; Bauer, Werner; Mitsch, Tim; Feinauer, Julian; Krämer, Yvonne; Scheiba, Frieder; Hintennach, Andreas; Schleid, Thomas; Schmidt, Volker; Ehrenberg, Helmut

    2016-03-01

    Negative electrodes of lithium-ion batteries generally consist of graphite-based active materials. In order to realize batteries with a high current density and therefore accelerated charging processes, the intercalation of lithium and the diffusion processes of these carbonaceous materials must be understood. In this paper, we visualized the electrochemical active surface area for three different anode materials using a novel OsO4 staining method in combination with scanning electron microscopy techniques. The diffusion behavior of these three anode materials is investigated by potentiostatic intermittent titration technique measurements. From those we determine the diffusion coefficient with and without consideration of the electrochemical active surface area.

  11. The effect of potential upon the high-temperature fatigue crack growth response of low-alloy steels. Part 1: Crack growth results

    SciTech Connect

    James, L.A.; Moshier, W.C.

    1997-04-01

    Corrosion-fatigue crack propagation experiments were conducted on several low-alloy steels in elevated temperature aqueous environments, and experimental parameters included temperature, sulfur content of the steel, applied potential level, and dissolved hydrogen (and in one case, dissolved oxygen) concentration in the water. Specimen potentials were controlled potentiostatically, and the observation (or non-observation) of accelerated fatigue crack growth rates was a complex function of the above parameters. Electrochemical results and the postulated explanation for the complex behavior are given in Part II.

  12. Dynamic instabilities during the continuous electro-oxidation of CO on poly- and single crystalline Pt electrodes

    NASA Astrophysics Data System (ADS)

    Malkhandi, Sauradip; Bonnefont, Antoine; Krischer, Katharina

    2009-06-01

    Dynamic instabilities during bulk CO electro-oxidation on poly- and single crystalline rotating Pt electrodes in different electrolytes were investigated experimentally. In sulphuric and perchloric electrolytic media, only bistability is observed. The dependence of the width of the bistable regime on some parameters is discussed. The addition of small amounts of chloride ions induces current oscillations under potentiostatic conditions on polycrystalline Pt, Pt(1 1 0) and Pt(1 0 0) electrodes. Existence range, shape and mean frequency of the mainly irregular kinetic oscillations vary significantly with the crystallographic structure of the electrode surface.

  13. Convection of tin in a Bridgman system. II - An electrochemical method for detecting flow regimes

    NASA Technical Reports Server (NTRS)

    Sears, B.; Fripp, A. L.; Debnam, W. J., Jr.; Woodell, G. A.; Anderson, T. J.; Narayanan, R.

    1992-01-01

    An ampoule was designed in order to obtain local flow behavior of the flow fields for convection of tin in a vertical Bridgman configuration. Multiple electrochemical cells were located along the periphery of the ampoule. Oxygen was titrated into the ampoule at one of the cell locations using a potentiostat and the concentration of oxygen was monitored at the other cell locations by operating the cells in a galvanic mode. Onset of oscillations were detected by means of thermocouples. We conclude that the flows are generally three dimensional for an aspect ratio of 5. Results on oscillations concurred with those of earlier workers. Suggestions for improved designs were made.

  14. Calculation of mass transfer in multiphase flow

    SciTech Connect

    Wang, L.; Gopal, M.

    1998-12-31

    This paper summarizes the results of mass transfer mechanisms under disturbed liquid-gas flow in 10 cm diameter pipe using electrochemical limiting current density and potentiostatic noise technique. The solution used is potassium ferro/ferricyanide dissolve in 1.3 N sodium hydroxide system. Mass transfer coefficients in full pipe flow and slug flow are obtained. The relationship between mass transfer coefficient with full pipe flow velocities and with slug flow Froude numbers are studied. The impact of bubbles in slugs on the mass transfer coefficient is revealed, The impact of flow disturbance, including weld beads and pits, are discussed for both full pipe flow and slug flow.

  15. Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

    SciTech Connect

    Parsons-Moss, Tashi; Jones, Stephen; Wang, Jinxiu; Wu, Zhangxiong; Uribe, Eva; Zhao, Dongyuan; Nitsche, Heino

    2015-12-19

    Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat.

  16. Thin flexible intercalation anodes

    SciTech Connect

    Levy, S.C.; Cieslak, W.R.; Klassen, S.E.; Lagasse, R.R.

    1994-10-01

    Poly(acrylonitrile) fibers have been pyrolyzed under various conditions to form flexible carbon yarns capable of intercalating lithium ions. These fibers have also been formed into both woven and non woven cloths. Potentiostatic, potentiodynamic and galvanostatic tests have been conducted with these materials in several electrolytes. In some tests, a potential hold was used after each constant current charge and discharge. These tests have shown some of these flexible materials to reversibly intercalate lithium ions to levels that are suitable for use as a practical battery anode.

  17. Pitting of steam-generator tubing alloys in solutions containing thiosulfate and sulfate or chloride.

    PubMed

    Zhang, William; Carcea, Anatolie G; Newman, Roger C

    2015-01-01

    The pitting of nuclear steam generator tubing alloys 600, 690 and 800 was studied at 60 °C using dilute thiosulfate solutions containing excess sulfate or (for Alloy 600) chloride. A potentiostatic scratch method was used. In sulfate solutions, all alloys pitted at low potentials, reflecting their lack of protective Mo. The alloys demonstrated the most severe pitting at a sulfate : thiosulfate concentration ratio of ∼40. Alloy 600 pitted worst at a chloride : thiosulfate ratio of ∼2000. The results are interpreted through the mutual electromigration of differently charged anions into a pit nucleus, and differences in the major alloy component. PMID:25898311

  18. Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam.

    PubMed

    Ortendahl, T W; Högstedt, P; Odelius, H; Norén, J G

    1988-11-01

    Metallic taste has been reported from divers working with underwater electric welding and cutting. An in vitro model was designed to simulate the intraoral situation of the divers with respect to the magnetic field. Potentiostatic analyses were performed on amalgam samples exposed to AC and DC magnetic fields. Morphologic changes were analyzed using differential interference light microscopy and scanning electron microscopy. Chemical changes on the surface of the amalgam samples were analyzed with secondary ion mass spectrometry. Results demonstrated that dental amalgams exposed to a specific AC magnetic field underwent morphologic and chemical changes in the superficial amalgam layers. PMID:3227577

  19. {ital In-situ} x-ray investigation of hydrogen charging in thin film bimetallic electrodes

    SciTech Connect

    Jisrawi, N.M.; Wiesmann, H.; Ruckman, M.W.; Thurston, T.R.; Reisfeld, G.; Ocko, B.M.; Strongin, M.

    1997-08-01

    Hydrogen uptake and discharge by thin metallic films under potentiostatic control was studied using x-ray diffraction at the National Synchrotron Light Source (NSLS). The formation of metal-hydrogen phases in Pd, Pd-capped Nb and Pd/Nb multilayer electrode structures was deduced from x-ray diffraction data and correlated with the cyclic voltammetry (CV) peaks. The x-ray data was also used to construct a plot of the hydrogen concentration as a function of cell potential for a multilayered thin film. {copyright} {ital 1997 Materials Research Society.}

  20. Synthesis and characterization of porous structured ZnO thin film for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Mummoorthi, M.; Dharuman, V.

    2016-05-01

    Zinc oxide (ZnO) and zinc oxide/eosin yellow (ZnO/EY) thin films were potentiostatically deposited onto fluorine doped tin oxide (FTO) glass substrate. Effect of eosin yellow dye on structural, morphological and optical properties was studied. X-ray diffraction patterns, micro Raman spectra and photoluminescence (PL) spectra reveal hexagonal wurtzite structure with less atomic defects in 101 plane orientation of the ZnO/EY film. Scanning electron microscopy (SEM) images show flower for ZnO and porous like structure for ZnO/EY thin film, respectively. DSSC was constructed and evaluated by measuring the current density verses voltage curve.

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

    PubMed

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

    2015-08-01

    This paper presents a new microfluidic platform that can simultaneously measure and locally modulate neurotransmitter concentration in a neuron network. This work focuses on the development of a first prototype including a potentiostat and electrode functionalization to detect several neurotransmitter's simultaneously. We tested dopamine as proof of concept to validate functionality. The system is based on 320 bidirectional electrode array for dielectrophoretic manipulation and cyclic voltammetry. Each electrode is connected to a mechanical multiplexer in order to reduce noise interference and fully isolate the electrode. The multiplexing rate is 476 kHz and each electrode can drive a signal with an amplitude of 60 V pp for dielectrophoretic manipulation. PMID:26736720

  2. Corrosion resistance of stressed NiTi and stainless steel orthodontic wires in acid artificial saliva.

    PubMed

    Huang, Her-Hsiung

    2003-09-15

    The purpose of this study was to investigate the corrosion resistance of stressed NiTi and stainless steel orthodontic wires using cyclic potentiodynamic and potentiostatic tests in acid artificial saliva at 37 degrees C. An atomic force microscope was used to measure the 3-D surface topography of as-received wires. Scanning electron microscope observations were carried out before and after the cyclic potentiodynamic tests. The surface chemical analysis was characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy after the potentiostatic tests. The cyclic potentiodynamic test results showed that the pH had a significant influence on the corrosion parameters of the stressed NiTi and stainless steel wires (p < 0.05). The pitting potential, protection potential, and passive range of stressed NiTi and stainless steel wires decreased on decreasing pH, whereas the passive current density increased on decreasing pH. The load had no significant influence on the above corrosion parameters (p > 0.05). For all pH and load conditions, stainless steel wire showed higher pitting potential and wider passive range than NiTi wire (p < 0.001), whereas NiTi wire had lower passive current density than stainless steel wire (p < 0.001). The corrosion resistance of the stressed NiTi and stainless steel wires was related to the surface characterizations, including surface defect and passive film. PMID:12926035

  3. Development and application of a real-time capacitive sensor.

    PubMed

    Wongkittisuksa, Booncharoen; Limsakul, Chusak; Kanatharana, Proespichaya; Limbut, Warakorn; Asawatreratanakul, Punnee; Dawan, Supaporn; Loyprasert, Suchera; Thavarungkul, Panote

    2011-01-15

    A real-time capacitive sensor based on a potentiostatic step method was developed. It can display in real-time the evoked current waveform, capacitance and the electrical resistance of elements serially connected to the insulation layer on the electrode as a function of time as well as the ohmic resistance of the insulation layer. These features enable the user to observe the association and dissociation of the affinity binding pairs and to evaluate the insulating property of the electrode surface during measurement. The system allows the setting of potential pulse height, pulse interval, gain, filter, and sampling frequency, enabling the system to be more flexible. The performance of the system was firstly evaluated with equivalent circuits. Under suitable parameter settings it provided good accuracy of both the capacitance and resistance. Using the affinity binding pair of human serum albumin (HSA) and anti human serum albumin (anti-HSA) the measured capacitance change was used for the direct detection of HSA. The developed system provided the same sensitivity as the commercially available potentiostat (P>0.05). The proposed system was then applied to analyse HSA in real urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). The proposed system can be applied for capacitance measurement to directly detect other target analytes using different affinity binding pairs. Other applications such as kinetics analysis of the interaction between affinity bindings, thickness analysis, and the study of the insulation property of the modified layer are also promising. PMID:21087852

  4. Electrochemical extraction of neodymium by co-reduction with aluminum in LiCl-KCl molten salt

    NASA Astrophysics Data System (ADS)

    Yan, Yong-De; Xu, Yan-Lu; Zhang, Mi-Lin; Xue, Yun; Han, Wei; Huang, Ying; Chen, Qiong; Zhang, Zhi-Jian

    2013-02-01

    The electrochemical behavior of Nd(III) ions in LiCl-KCl and LiCl-KCl-AlCl3 melts on a Mo electrode at 723 K was studied by various electrochemical techniques. The results showed that Nd(III) ions are reduced to Nd(0) through two consecutive steps, and the underpotential deposition of neodymium on pre-deposited Al electrode formed two kinds of Al-Nd intermetallic compounds in LiCl-KCl-AlCl3 solutions. The electrochemical extraction of neodymium was carried out in LiCl-KCl-AlCl3 melts on a Mo electrode at 873 K by potentiostatic and galvanostatic electrolysis. The extraction efficiency was 99.25% after potentiostatic electrolysis for 30 h. Al-Li-Nd bulk alloy was obtained by galvanostatic electrolysis. X-ray diffraction (XRD) suggested that Al2Nd and Al3Nd phases were formed in Al-Li-Nd alloy. The microstructure and micro-zone chemical analysis of Al-Li-Nd alloy were characterized by scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), respectively.

  5. Electrochemical behaviour of silver in borate buffer solutions

    NASA Astrophysics Data System (ADS)

    Zaky, Ayman M.; Assaf, Fawzi H.; Abd El Rehim, Sayed S.; Mohamed, Basheer M.

    2004-01-01

    The electrochemical behaviour of Ag in aqueous 0.15 M borax and 0.15 M boric acid buffer solution was studied under various conditions using cyclic voltammetry and potentiostatic techniques. It was found that the anodic polarization curve of Ag in borate buffer solution was characterized by the appearance of two potential regions, active and passive, prior to the oxygen evolution reaction. The active potential region was characterized by the appearance of three anodic peaks, the first two peaks A 1 and A 2 correspond to the oxidation of Ag and formation of [Ag(OH) 2] - soluble compound and a passive film of Ag 2O on the electrode surface. The third anodic peak corresponds to the conversion of both [Ag(OH) 2] - and Ag 2O to Ag 2O 2. X-ray diffraction patterns confirmed the existence of Ag 2O and Ag 2O 2 passive layers on the electrode surface potentiodynamically polarized up to 800 mV. Potentiostatic current transient measurements showed that the formation of Ag 2O and Ag 2O 2 involves a nucleation and growth mechanism under diffusion control.

  6. Aqueous corrosion characteristics and corrosion-related cracking susceptibilities of Fe sub 3 Al-type iron aluminides

    SciTech Connect

    Buchanan, R.A.; Kim, J.G. . Dept. of Materials Science and Engineering)

    1991-04-01

    In certain fossil-energy applications, iron aluminides may be subjected to ambient-temperature aqueous corrosion conditions. In the present project, the aqueous corrosion characteristics and the cracking tendencies under aqueous-corrosion conditions were studied. In these studies, electrochemical, immersion and electrochemical-mechanical evaluation techniques were employed. For a range of iron-aluminide compositions, cyclic anodic polarization tests were conducted in a number of electrolytes to provide information on anodic dissolution characteristics including tendencies for either active uniform corrosion, localized corrosion, or passivation. Average corrosion penetration rates were determined by application of Tafel methods or the polarization-resistance method in combination with Faraday's law. Immersion test methods were employed to verify corrosion behavior as determined by electrochemical methods and to evaluate localized-corrosion initiation times. U-bend corrosion tests were conducted at open-circuit corrosion potentials and at potentiostatically-controlled anodic and cathodic potentials to investigate the cracking tendencies of selected iron aluminides and to provide information on the cracking mechanism. And finally, slow-strain-rate corrosion tests were conducted at open-circuit and potentiostatically-controlled cathodic potentials to study the ductility response as related to cracking tendencies and the mechanism responsible. 32 refs., 19 figs., 11 tabs.

  7. An electrochromic film device to teach polymer electrochemical physics

    NASA Astrophysics Data System (ADS)

    Huang, Mei-Rong; Tao, Tao; Li, Xin-Gui; Gong, Qian-Cheng

    2007-09-01

    We discuss the background associated with an electrochromic device that can reversibly change its color and optical density at a specific potential. We discuss the underlying science needed to make a new polyaniline (PAN)/polyvinyl alcohol(PVA) electrochromic composite film on an indium-tin oxide (ITO) conducting glass by electropolymerization and describe a reversible redox transition of the PAN. The experiment gives students an opportunity to fabricate an electrochromic device containing PAN, one of the most important conducting polymers. The experimental conditions are flexible so that each group of students can construct their own electrochromic device with particular behavior. Two techniques for polymerizing the PAN and three methods of demonstrating the electrochromism are given, depending on the available apparatus. A sophisticated three-electrode potentiostat or a crude apparatus containing a battery, wire, a variable resistor, and a voltage meter is used to synthesize the PAN deposit. The electrochromic property is repetitively observed by reversibly changing the applied potentials on the device. A potentiostatic apparatus, a single flashlight battery, or a flashlight battery accompanied by a variable resistor allows students to observe multicolor electrochromism. The experiments significantly enhance students' understanding of polymer chemicophysics principles and their appreciation of novel variable colorful films. The experiments are safe and easy to perform, provided that appropriate precautions are taken.

  8. Amperometric measurements of ethanol on paper with a glucometer.

    PubMed

    Wu, Grace; Zaman, Muhammad H

    2015-03-01

    Recent advances in electrochemical analysis on filter paper exemplify the versatility of this substrate for high performance testing. Its low-cost, light-weight, and environmentally friendly properties make it particularly attractive for applications in addressing health and environmental safety needs in low-resource settings and developing countries. However, the main drawback to sensitive electrochemical testing is the use of a potentiostat, a bench-top instrument that is extremely expensive, thereby negating the some of the benefits of paper-based devices. Hence there is a need to develop paper-devices for use with handheld, portable device readers that can extract quantitative readouts. In this study, we developed a method to use micro-paper electrochemical devices, or µPEDs, with a glucose meter, which are used for personal monitoring of blood glucose levels. Ethanol was chosen as a model target analyte due to its importance in the global issue of road safety. µPEDs were simple in design and could be tested with a potentiostat. We observed that inclusion of the stabilizer trehalose was critical to preparing µPEDs for later analysis. In addition, an NAD(+)-dependent enzyme was used to impart selectivity to the biosensor, which also represents a class of enzymes with targets relevant to the health and food industry. PMID:25618657

  9. Three-Dimensional Growth of Li2S in Lithium-Sulfur Batteries Promoted by a Redox Mediator.

    PubMed

    Gerber, Laura C H; Frischmann, Peter D; Fan, Frank Y; Doris, Sean E; Qu, Xiaohui; Scheuermann, Angelique M; Persson, Kristin; Chiang, Yet-Ming; Helms, Brett A

    2016-01-13

    During the discharge of a lithium-sulfur (Li-S) battery, an electronically insulating 2D layer of Li2S is electrodeposited onto the current collector. Once the current collector is enveloped, the overpotential of the cell increases, and its discharge is arrested, often before reaching the full capacity of the active material. Guided by a new computational platform known as the Electrolyte Genome, we advance and apply benzo[ghi]peryleneimide (BPI) as a redox mediator for the reduction of dissolved polysulfides to Li2S. With BPI present, we show that it is now possible to electrodeposit Li2S as porous, 3D deposits onto carbon current collectors during cell discharge. As a result, sulfur utilization improved 220% due to a 6-fold increase in Li2S formation. To understand the growth mechanism, electrodeposition of Li2S was carried out under both galvanostatic and potentiostatic control. The observed kinetics under potentiostatic control were modeled using modified Avrami phase transformation kinetics, which showed that BPI slows the impingement of insulating Li2S islands on carbon. Conceptually, the pairing of conductive carbons with BPI can be viewed as a vascular approach to the design of current collectors for energy storage devices: here, conductive carbon "arteries" dominate long-range electron transport, while BPI "capillaries" mediate short-range transport and electron transfer between the storage materials and the carbon electrode. PMID:26691496

  10. Metal chelate catalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Darby, R.; White, R.; Yamana, M.; Tsutsue, M.

    1981-07-01

    A variety of metal chelates were synthesized and evaluated for their activity as oxygen cathode electrocatalysts in strong acidic electrolytes. It was found that Cobalt tetraazaanulene (CoTAA) and iron phthalocyanine (FePc) exhibit the best activity of all the metal chelates synthesized, but have very limited stability. The proposed solution to this problem is the synthesis of polymeric forms of these chelates, with comparable active and considerably greater stability than the monomers. Three methods for stability testing were developed: (1) Potentiostatic, with periodic measurement of the current potential characteristic; (2) potentiostatic, with continuous monitoring of the current, and; (3) galvanostatic, with continuous monitoring of potential. Each method provides a good evaluation of activity versus time, and the method to be used depends upon the objective of the test. A polymeric form of Co(TAA) was synthesized by means of an acetylene terminated monomer, which in turn was made via a Co(TAA)Br2 intermediate. The activity of the polymer was found to be comparable to that of Co(TAA) monomer, and significantly greater than that of either the stacked or sheet polymeric forms of Cobalt tetraphenylporphrine (CoTPP) previously synthesized and tested.

  11. In situ electrochemical investigation of tungsten electrochemical behavior during chemical mechanical polishing

    SciTech Connect

    Stein, D.J.; Cecchi, J.L.; Hetherington, D.; Guilinger, T.

    1998-09-01

    The electrochemical behavior of tungsten during chemical mechanical polishing (CMP) was observed in order to investigate a proposed blanket passivation and abrasion mechanism for tungsten removal. The experiments were performed in a cell that allowed electrochemical measurements to be made during polish. Polish rates were determined from the same samples used in the cell. Alumina-based polish slurries containing potassium iodate, ferric nitrate, or ammonium persulfate were used. DC polarization experiments show no evidence of passive film formation on the tungsten during polish. Tungsten oxidation rates measured during polish account for removal rates that are 1 to 2 orders of magnitude below the measured polish rate. Values of the charge-transfer resistance (measured by ac impedance spectroscopy) during polish are 1 to 2 orders of magnitude higher than expected from the polish rate, thus corroborating the dc-based data. Polish rates under potentiostatic conditions were also measured. The current required to maintain the metal anodic of the open-circuit potential is well below the current expected from measured polish rates, assuming complete oxidation of the tungsten. The polish rate during cathodic potentiostatic conditions ({minus}0.5 V with regard to the open-circuit potential) was similar to the polish rate at open circuit. The authors conclude that the formation of a blanket passive layer does not significantly contribute to tungsten removal during CMP.

  12. Cathodic processes of neodymium(iii) in LiF-NdF3-Nd2O3 melts.

    PubMed

    Huang, Chao; Liu, Xiaolong; Gao, Yuan; Liu, Shizhe; Li, Bing

    2016-08-15

    In this paper, cyclic voltammetry and square wave voltammetry are applied to characterize the cathode processes of neodymium ions on a W electrode in LiF-NdF3 melts with or without the metal Nd. The results indicate that neodymium ions in the LiF-NdF3 (2 wt%) melt are reduced in two steps, i.e. Nd(3+) → Nd(2+) and Nd(2+) → Nd(0), corresponding to starting reduction potentials of 0.35 V vs. Li(+)/Li and 0.1 V vs. Li(+)/Li, respectively. The Nd(3+) → Nd(2+) process is controlled by mass transfer and the Nd(2+) → Nd(0) process is controlled by both an interfacial step and mass transfer. But in the LiF-NdF3 melt with excess metal Nd equilibrium, the kinetics of the above two processes are controlled by mass transfer. After potentiostatic electrolysis at 0.35 V in the LiF-NdF3-Nd2O3 melt NdF2 is formed on the Mo cathode, and metallic Nd is obtained by potentiostatic electrolysis at 0.1 V in the LiF-NdF3-Nd2O3-Nd melt, which validates the above electrochemical reduction results. PMID:27197114

  13. Miniaturized neural sensing and optogenetic stimulation system for behavioral studies in the rat

    NASA Astrophysics Data System (ADS)

    Kim, Min Hyuck; Nam, Ilho; Ryu, Youngki; Wellman, Laurie W.; Sanford, Larry D.; Yoon, Hargsoon

    2015-04-01

    Real time sensing of localized electrophysiological and neurochemical signals associated with spontaneous and evoked neural activity is critically important for understanding neural networks in the brain. Our goal is to enhance the functionality and flexibility of a neural sensing and stimulation system for the observation of brain activity that will enable better understanding from the level of individual cells to that of global structures. We have thus developed a miniaturized electronic system for in-vivo neurotransmitter sensing and optogenetic stimulation amenable to behavioral studies in the rat. The system contains a potentiostat, a data acquisition unit, a control unit, and a wireless data transfer unit. For the potentiostat, we applied embedded op-amps to build single potential amperometry for electrochemical sensing of dopamine. A light emitting diode is controlled by a microcontroller and pulse width modulation utilized to control optogenetic stimulation within a sub-millisecond level. In addition, this proto-typed electronic system contains a Bluetooth module for wireless data communication. In the future, an application-specific integrated circuit (ASIC) will be designed for further miniaturization of the system.

  14. Integrated Nanopore Detectors in a Standard Complementary Metal-Oxide-Semiconductor Process

    NASA Astrophysics Data System (ADS)

    Uddin, Ashfaque; Chen, Chin-Hsuan; Yemenicioglu, Sukru; Milaninia, Kaveh; Corigliano, Ellie; Varma, Madoo; Theogarajan, Luke

    2012-02-01

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the development of solid-state nanopore devices in a commercial CMOS potentiostat chip implemented in On-Semiconductor's 0.5 micron technology. By using post-CMOS micromachining, a free-standing oxide membrane and electrodes are fabricated utilizing the N+ polysilicon/oxide/N+ polysilicon capacitor structure available in the aforementioned process. Nanopores with sub-5 nm diameter are drilled in the membrane using a Transmission Electron Microscope. The integrity of pores is validated by measuring current-voltage and noise characteristics. DNA translocation experiments are also performed utilizing these on-chip pores. In addition, electrical tests performed on the CMOS potentiostat circuitry show that the post-CMOS micromachining process does not have any detrimental effect on the CMOS circuitry.

  15. Wearable electrochemical sensors for in situ analysis in marine environments.

    PubMed

    Malzahn, Kerstin; Windmiller, Joshua Ray; Valdés-Ramírez, Gabriela; Schöning, Michael J; Wang, Joseph

    2011-07-21

    The development of wearable screen-printed electrochemical sensors on underwater garments comprised of the synthetic rubber neoprene is reported. These wearable sensors are able to determine the presence of environmental pollutants and security threats in marine environments. Owing to its unique elastic and superhydrophobic morphology, neoprene is an attractive substrate for thick-film electrochemical sensors for aquatic environments and offers high-resolution printing with no apparent defects. The neoprene-based sensor was evaluated for the voltammetric detection of trace heavy metal contaminants and nitroaromatic explosives in seawater samples. We also describe the first example of enzyme (tyrosinase) immobilization on a wearable substrate towards the amperometric biosensing of phenolic contaminants in seawater. Furthermore, the integration of a miniaturized potentiostat directly on the underwater garment is demonstrated. The wearable sensor-potentiostat microsystem provides a visual indication and alert if the levels of harmful contaminants have exceeded a pre-defined threshold. The concept discussed here is well-suited for integration into dry- and wetsuits worn by divers and recreational surfers/swimmers, thereby providing them with the ability to continuously assess their surroundings for environmental contaminants and security hazards. PMID:21637863

  16. Simplifying microbial electrosynthesis reactor design

    PubMed Central

    Giddings, Cloelle G. S.; Nevin, Kelly P.; Woodward, Trevor; Lovley, Derek R.; Butler, Caitlyn S.

    2015-01-01

    Microbial electrosynthesis, an artificial form of photosynthesis, can efficiently convert carbon dioxide into organic commodities; however, this process has only previously been demonstrated in reactors that have features likely to be a barrier to scale-up. Therefore, the possibility of simplifying reactor design by both eliminating potentiostatic control of the cathode and removing the membrane separating the anode and cathode was investigated with biofilms of Sporomusa ovata. S. ovata reduces carbon dioxide to acetate and acts as the microbial catalyst for plain graphite stick cathodes as the electron donor. In traditional ‘H-cell’ reactors, where the anode and cathode chambers were separated with a proton-selective membrane, the rates and columbic efficiencies of microbial electrosynthesis remained high when electron delivery at the cathode was powered with a direct current power source rather than with a potentiostat-poised cathode utilized in previous studies. A membrane-less reactor with a direct-current power source with the cathode and anode positioned to avoid oxygen exposure at the cathode, retained high rates of acetate production as well as high columbic and energetic efficiencies. The finding that microbial electrosynthesis is feasible without a membrane separating the anode from the cathode, coupled with a direct current power source supplying the energy for electron delivery, is expected to greatly simplify future reactor design and lower construction costs. PMID:26029199

  17. Influence of dissolved hydrogen on aluminum-lithium alloy fracture behavior

    NASA Technical Reports Server (NTRS)

    Rivet, F. C.; Swanson, R. E.

    1989-01-01

    The objective of this work is to study the effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys. Prior to mechanical testing, potentiostatic and potentiodynamic tests were performed using NaCl/HCl solutions varying in pH from 1.5 to 7.5 (3.5 pct NaCl in deionized water). After analysis of the potentiodynamic curve for each solution, several potentiostatic experiments were conducted for various times (from 10 minutes to several hours) with a cathodic overpotential of 300 mV. These experiments were performed to select charging conditions. It is shown that the fracture of L-S and T-S orientations proceeds via slipping of layers in the S-T direction. The T-S and L-S orientations fractured with substantially higher propagation energy that the L-T and T-L orientations, due in large part to the extensive delamination propagation of the fracture.

  18. Origins of nanoscale damage to glass-sealed platinum electrodes with submicrometer and nanometer size.

    PubMed

    Nioradze, Nikoloz; Chen, Ran; Kim, Jiyeon; Shen, Mei; Santhosh, Padmanabhan; Amemiya, Shigeru

    2013-07-01

    Glass-sealed Pt electrodes with submicrometer and nanometer size have been successfully developed and applied for nanoscale electrochemical measurements such as scanning electrochemical microscopy (SECM). These small electrodes, however, are difficult to work with because they often lose a current response or give a low SECM feedback in current-distance curves. Here we report that these problems can be due to the nanometer-scale damage that is readily and unknowingly made to the small tips in air by electrostatic discharge or in electrolyte solution by electrochemical etching. The damaged Pt electrodes are recessed and contaminated with removed electrode materials to lower their current responses. The recession and contamination of damaged Pt electrodes are demonstrated by scanning electron microscopy and X-ray energy dispersive spectroscopy. The recessed geometry is noticeable also by SECM but is not obvious from a cyclic voltammogram. Characterization of a damaged Pt electrode with recessed geometry only by cyclic voltammetry may underestimate electrode size from a lower limiting current owing to an invalid assumption of inlaid disk geometry. Significantly, electrostatic damage can be avoided by grounding a Pt electrode and nearby objects, most importantly, an operator as a source of electrostatic charge. Electrochemical damage can be avoided by maintaining potentiostatic control of a Pt electrode without internally disconnecting the electrode from a potentiostat between voltammetric measurements. Damage-free Pt electrodes with submicrometer and nanometer sizes are pivotal for reliable and quantitative nanoelectrochemical measurements. PMID:23763642

  19. San copolymer membranes with ion exchangers for Cu(II) removal from synthetic wastewater by electrodialysis.

    PubMed

    Caprarescu, Simona; Corobea, Mihai Cosmin; Purcar, Violeta; Spataru, Catalin Ilie; Ianchis, Raluca; Vasilievici, Gabriel; Vuluga, Zina

    2015-09-01

    Heterogeneous membranes were obtained by using styrene-acrylonitrile copolymer (SAN) blends with low content of ion-exchanger particles (5wt.%). The membranes obtained by phase inversion were used for the removal of copper ions from synthetic wastewater solutions by electrodialytic separation. The electrodialysis was conducted in a three cell unit, without electrolyte recirculation. The process, under potentiostatic or galvanostatic control, was followed by pH and conductivity measurements in the solution. The electrodialytic performance, evaluated in terms of extraction removal degree (rd) of copper ions, was better under potentiostatic control then by the galvanostatic one and the highest (over 70%) was attained at 8V. The membrane efficiency at small ion-exchanger load was explained by the migration of resin particles toward the pores surface during the phase inversion. The prepared membranes were characterized by various techniques i.e. optical microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis and contact angle measurements. PMID:26354689

  20. Growth and Etch Rate Study of Low Temperature Anodic Silicon Dioxide Thin Films

    PubMed Central

    Ashok, Akarapu; Pal, Prem

    2014-01-01

    Silicon dioxide (SiO2) thin films are most commonly used insulating films in the fabrication of silicon-based integrated circuits (ICs) and microelectromechanical systems (MEMS). Several techniques with different processing environments have been investigated to deposit silicon dioxide films at temperatures down to room temperature. Anodic oxidation of silicon is one of the low temperature processes to grow oxide films even below room temperature. In the present work, uniform silicon dioxide thin films are grown at room temperature by using anodic oxidation technique. Oxide films are synthesized in potentiostatic and potentiodynamic regimes at large applied voltages in order to investigate the effect of voltage, mechanical stirring of electrolyte, current density and the water percentage on growth rate, and the different properties of as-grown oxide films. Ellipsometry, FTIR, and SEM are employed to investigate various properties of the oxide films. A 5.25 Å/V growth rate is achieved in potentiostatic mode. In the case of potentiodynamic mode, 160 nm thickness is attained at 300 V. The oxide films developed in both modes are slightly silicon rich, uniform, and less porous. The present study is intended to inspect various properties which are considered for applications in MEMS and Microelectronics. PMID:24672287

  1. Fabrication of the CuO/Cu2O heterojunction using an electrodeposition technique for solar cell applications

    NASA Astrophysics Data System (ADS)

    Wijesundera, R. P.

    2010-04-01

    Thin films of n-type cuprous oxide (Cu2O) were potentiostatically electrodeposited on a Ti substrate in an acetate bath. Cu2O thin films were annealed at 500 °C for 30 min in air for growing p-type cupric oxide (CuO) thin films. n-Cu2O thin films were potentiostatically electrodeposited in an acetate bath on Ti/CuO electrodes in order to fabricate the p-CuO/n-Cu2O heterojunction. The structural, morphological and optoelectronic properties of the CuO/Cu2O heterojunction were studied using x-ray diffraction (XRD), scanning electron micrographs (SEMs) and dark and light current-voltage characteristics. XRD and SEM reveal that well-covered single phase polycrystalline Cu2O thin film on the Ti/CuO electrode can be possible at the deposition potential of -550 mV versus the saturated calomel electrode (SCE) in an acetate bath. Photovoltaic characteristics further established the formation of the CuO/Cu2O heterojunction.

  2. TEM investigations on the local microstructure of electrodeposited galfenol nanowires.

    PubMed

    Pohl, D; Damm, C; Pohl, D; Schultz, L; Schlörb, H

    2016-01-22

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred 〈110〉orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces. PMID:26651087

  3. TEM investigations on the local microstructure of electrodeposited galfenol nanowires

    NASA Astrophysics Data System (ADS)

    Pohl, D.; Damm, C.; Pohl, D.; Schultz, L.; Schlörb, H.

    2016-01-01

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred <110> orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces.

  4. Facile production of thermoelectric bismuth telluride thick films in the presence of polyvinyl alcohol.

    PubMed

    Lei, C; Burton, M R; Nandhakumar, I S

    2016-06-01

    Bismuth telluride is currently the best performing thermoelectric material for room temperature operations in commercial thermoelectric devices. We report the reproducible and facile production of 600 micron thick bismuth telluride (Bi2Te3) layers by low cost and room temperature pulsed and potentiostatic electrodeposition from a solution containing bismuth and tellurium dioxide in 2 M nitric acid onto nickel in the presence of polyvinyl alcohol (PVA). This was added to the electrolyte to promote thick layer formation and its effect on the structure, morphology and composition of the electrodeposits was investigated by SEM and EDX. Well adherent, uniform, compact and stoichiometric n-type Bi2Te3 films with a high Seebeck coefficient of up to -200 μV K(-1) and a high electrical conductivity of up to 400 S cm(-1) resulting in a power factor of 1.6 × 10(-3) W m(-1) K(-2) at film growth rates of 100 μm h(-1) for potentiostatic electrodeposition were obtained. The films also exhibited a well defined hexagonal structure as determined by XRD. PMID:27166737

  5. Aerated Shewanella oneidensis in continuously fed bioelectrochemical systems for power and hydrogen production.

    PubMed

    Rosenbaum, Miriam; Cotta, Michael A; Angenent, Largus T

    2010-04-01

    We studied the effects of aeration of Shewanella oneidensis on potentiostatic current production, hydrogen production in a microbial electrolysis cell, and electric power generation in a microbial fuel cell (MFC). The potentiostatic performance of aerated S. oneidensis was considerably enhanced to a maximum current density of 0.45 A/m(2) or 80.3 A/m(3) (mean: 0.34 A/m(2), 57.2 A/m(3)) compared to anaerobically grown cultures. Biocatalyzed hydrogen production rates with aerated S. oneidensis were studied within the applied potential range of 0.3-0.9 V and were highest at 0.9 V with 0.3 m(3) H(2)/m(3) day, which has been reported for mixed cultures, but is approximately 10 times higher than reported for an anaerobic culture of S. oneidensis. Aerated MFC experiments produced a maximum power density of 3.56 W/m(3) at a 200-Omega external resistor. The main reasons for enhanced electrochemical performance are higher levels of active biomass and more efficient substrate utilization under aerobic conditions. Coulombic efficiencies, however, were greatly reduced due to losses of reducing equivalents to aerobic respiration in the anode chamber. The next challenge will be to optimize the aeration rate of the bacterial culture to balance between maximization of bacterial activation and minimization of aerobic respiration in the culture. PMID:19998276

  6. Post-CMOS fabrication of Working Electrodes for On-Chip Recordings of Transmitter Release

    PubMed Central

    Ayers, Sunitha; Berberian, Khajak; Gillis, Kevin D.; Lindau, Manfred; Minch, Bradley A.

    2010-01-01

    The release of neurotransmitters and hormones from secretory vesicles plays a fundamental role in the function of the nervous system including neuronal communication. High-throughput testing of drugs modulating transmitter release is becoming an increasingly important area in the fields of cell biology, neurobiology, and neurology. Carbon-fiber amperometry, provides high-resolution measurements of amount and time course of transmitter release from single vesicles, and their modulation by drugs and molecular manipulations. However, such methods do not allow the rapid collection of data from a large number of cells. To allow such testing, we have developed a CMOS potentiostat circuit that can be scaled to a large array. In this paper, we present two post-CMOS fabrication methods to incorporate the electrochemical electrode material. We demonstrate by proof of principle the feasibility of on-chip electrochemical measurements of dopamine, and catecholamine release from adrenal chromaffin cells. The measurement noise is consistent with the typical electrode noise in recordings with external amplifiers. The electronic noise of the potentiostat in recordings with 400 μs integration time is ~0.11 pA and is negligible compared to the inherent electrode noise. PMID:20514361

  7. Simplifying microbial electrosynthesis reactor design.

    PubMed

    Giddings, Cloelle G S; Nevin, Kelly P; Woodward, Trevor; Lovley, Derek R; Butler, Caitlyn S

    2015-01-01

    Microbial electrosynthesis, an artificial form of photosynthesis, can efficiently convert carbon dioxide into organic commodities; however, this process has only previously been demonstrated in reactors that have features likely to be a barrier to scale-up. Therefore, the possibility of simplifying reactor design by both eliminating potentiostatic control of the cathode and removing the membrane separating the anode and cathode was investigated with biofilms of Sporomusa ovata. S. ovata reduces carbon dioxide to acetate and acts as the microbial catalyst for plain graphite stick cathodes as the electron donor. In traditional 'H-cell' reactors, where the anode and cathode chambers were separated with a proton-selective membrane, the rates and columbic efficiencies of microbial electrosynthesis remained high when electron delivery at the cathode was powered with a direct current power source rather than with a potentiostat-poised cathode utilized in previous studies. A membrane-less reactor with a direct-current power source with the cathode and anode positioned to avoid oxygen exposure at the cathode, retained high rates of acetate production as well as high columbic and energetic efficiencies. The finding that microbial electrosynthesis is feasible without a membrane separating the anode from the cathode, coupled with a direct current power source supplying the energy for electron delivery, is expected to greatly simplify future reactor design and lower construction costs. PMID:26029199

  8. Preparation of corrosion-resistant and conductive trivalent Cr-C coatings on 304 stainless steel for use as bipolar plates in proton exchange membrane fuel cells by electrodeposition

    NASA Astrophysics Data System (ADS)

    Wang, Hsiang-Cheng; Sheu, Hung-Hua; Lu, Chen-En; Hou, Kung-Hsu; Ger, Ming-Der

    2015-10-01

    In this study, Cr-C-coated bipolar plates are produced by electroplating on the SS304 plates with a machined flow channel. The resulting plates were tested using potentiodynamic and potentiostatic measurements in simulated PEMFC environments, which show that the bipolar plate coated with Cr-C exhibited good anticorrosion performance. The corrosive current density of the Cr-C coating formed for a plating time of 10 min for 10 h exhibits a low stable value of 1.51 × 10-10 A/cm2 during the potentiostatic test in a 0.5 M H2SO4 + 2 ppm HF solution at 70 °C with an air purge, indicating that the Cr-C coating plated for 10 min is stable in a cathode environment. The interfacial contact resistance (ICR) of the bipolar plate with the Cr-C coating clearly improved, presenting an ICR of 19.52 mΩ cm2 at a pressure of 138 N/cm2. The results from scanning electron microscopy (SEM) and ICR before and after the corrosion tests indicate that the bipolar plate with the Cr-C coating is electrochemically stable. In this study, the maximum power density (212.41 mW/cm2) is obtained at a cell temperature of 80 °C and a gas flow rate of 300 standard cubic centimeters per minute (sccm) when Cr-C coated SS304 bipolar plates were used.

  9. Synthesis of mesoporous carbon-silica-polyaniline and nitrogen-containing carbon-silica films and their corrosion behavior in simulated proton exchange membrane fuel cells environment

    NASA Astrophysics Data System (ADS)

    Wang, Tao; He, Jianping; Sun, Dun; Guo, Yunxia; Ma, Yiou; Hu, Yuan; Li, Guoxian; Xue, Hairong; Tang, Jing; Sun, Xin

    In this study, polyaniline is deposited onto mesoporous carbon-silica-coated 304 stainless steel using electropolymerization method. Variation of the electropolymerization time and applied potential can affect the growth of polyaniline, and lead to different structural and electrochemical properties of the films. Nitrogen-containing groups are successfully introduced onto the mesoporous carbon-silica film by pyrolyzing treatment under N 2 atmosphere and the electrical conductivity is improved observably compared with the carbon-silica film. The electrochemical properties of the mesoporous carbon-silica-polyaniline films and nitrogen-containing carbon-silica composite films are examined by using potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy. The corrosion tests in 0.5 M H 2SO 4 system display that the carbon-silica-polyaniline films show the optimal protective performance. However, according to potentiostatic polarization process, nitrogen-containing carbon-silica film with a water contact angle 95° is extremely stable and better for the protection of stainless steel in simulated fuel cell environment compared to carbon-silica-polyaniline film. Therefore, the nitrogen-containing carbon-silica-coated 304 stainless steel is a promising candidate for bipolar plate materials in PEMFCs.

  10. Waste Water Derived Electroactive Microbial Biofilms: Growth, Maintenance, and Basic Characterization

    PubMed Central

    Gimkiewicz, Carla; Harnisch, Falk

    2013-01-01

    The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (jmax) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (Ep), peak current density (jp), formal potential (Ef) and peak separation (ΔEp). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis. PMID:24430581

  11. Sensitive Bioanalysis Based on in-Situ Droplet Anodic Stripping Voltammetric Detection of CdS Quantum Dots Label after Enhanced Cathodic Preconcentration.

    PubMed

    Qin, Xiaoli; Wang, Linchun; Xie, Qingji

    2016-01-01

    We report a protocol of CdS-labeled sandwich-type amperometric bioanalysis with high sensitivity, on the basis of simultaneous chemical-dissolution/cathodic-enrichment of the CdS quantum dot biolabel and anodic stripping voltammetry (ASV) detection of Cd directly on the bioelectrode. We added a microliter droplet of 0.1 M aqueous HNO₃ to dissolve CdS on the bioelectrode and simultaneously achieved the potentiostatic cathodic preconcentration of Cd by starting the potentiostatic operation before HNO₃ addition, which can largely increase the ASV signal. Our protocol was used for immunoanalysis and aptamer-based bioanalysis of several proteins, giving limits of detection of 4.5 fg·mL(-1) for human immunoglobulin G, 3.0 fg·mL(-1) for human carcinoembryonic antigen (CEA), 4.9 fg·mL(-1) for human α-fetoprotein (AFP), and 0.9 fM for thrombin, which are better than many reported results. The simultaneous and sensitive analysis of CEA and AFP at two screen-printed carbon electrodes was also conducted by our protocol. PMID:27563894

  12. A simple approach for producing colloidal noble metal nanocrystals: Alternating voltage induced electrochemical synthesis

    NASA Astrophysics Data System (ADS)

    McCann, Kevin

    Intense research has been focused on developing bottom-up nanocrystal synthesis techniques to obtain nanocrystals with sophisticated compositions and enhanced perfomances. Three popular methods are: 1) the reduction of metal complex ions or molecules with selected reducing agents, 2) the decomposition of metal compounds at elevated temperatures, and 3) the electrochemical reduction of metal ions using specialized potentiostats. The first two require expensive metal salt precursors while the last requires specialized potentiostats and either employ a single sacrificial electrode or metal salt precursors. To resolve these issues, we have focused on a facile and generic approach to generate nanocrystals by an alternating voltage induced electrochemical synthesis (AVIES) method. Nanocrystals are produced when an alternating voltage is applied by a common laboratory transformer to two sacrificial electrodes that are inserted in an electrolyte solution containing capping ligands. This work focuses on the ability of the AVIES approach to synthesize Au, Pd, and Pt noble metal nanocrystals. The nanocrystals synthesized were found to be dependent on the electrolyte identity, capping ligand, applied voltage, reaction temperature. The ability of AVIES to produce alloyed nanocrystals starting with alloyed electrodes will be discussed. The AVIES approach requires neither expensive metal compounds nor specialized instruments, is environmentally benign, and can be easily adoptable to any research lab.

  13. Electrochemical reaction of lithium with nanosized vanadium antimonate

    SciTech Connect

    Morales, Julian; Sanchez, Luis . E-mail: luis-sanchez@uco.es; Martin, Francisco; Berry, Frank

    2006-08-15

    Nanometric vanadium antimonate, VSbO{sub 4}, was prepared by mechanical milling from Sb{sub 2}O{sub 3} and V{sub 2}O{sub 5} and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbaueer spectroscopy (MS) and X-ray photoelectron spectroscopy (XPS) techniques. Its reactivity towards lithium was examined by testing Li/VSbO{sub 4} cells under galvanostatic and potentiostatic regimes. The amount of Li inserted was found to be consistent with a two-step process involving the reactions (i) VSbO{sub 4}+8 Li{sup {yields}}Sb+V+4 Li{sub 2}O and (ii) Sb+3 Li{sup {yields}}Li{sub 3}Sb, the former being virtually irreversible and the latter reversible as suggested by the shape of the anodic and cathodic curves. Ex situ XPS measurements of the discharged and charged electrode provided direct evidence of the formation of alloyed Sb and confirmed the results of the potentiostatic curves regarding the irreversible or reversible character of the previous reactions. The Li/VSbO{sub 4} cell exhibited acceptable electrochemical performance, which surpassed that of other Sb-based compounds as the likely result of the formation of V and its associated enhanced electrode conductivity. - Graphical abstract: TEM image of nanosized VSbO{sub 4} sample.

  14. Corrosion behaviour of austenitic stainless steel as a function of methanol concentration for direct methanol fuel cell bipolar plate

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Kang, Bin; Gao, Na; Du, Xiao; Jia, Linan; Sun, Juncai

    2014-05-01

    The corrosion behaviour of an AISI 304 stainless steel (304 SS) is investigated in aqueous acid methanol solutions (0.5 M H2SO4 + 2 ppm HF + x M CH3OH, x = 0, 1, 5, 10 and 20) at 50 °C to simulate the varied anodic operating conditions of direct methanol fuel cells. Electrochemical measurements including potentiodynamic polarisation, potentiostatic polarisation and electrochemical impedance spectroscopy tests, are employed to analyse the corrosion behaviour. The results reveal that the corrosion resistance of 304 SS is enhanced in solutions with higher methanol content. Scanning electron microscopy and inductively coupled plasma atomic emission spectrometry data indicate that the surface corrosion on 304 SS is alleviated when the methanol concentration is increased. According to the X-ray photoelectron spectroscopy and Mott-Schottky analyses, the passive films formed on the 304 SS after potentiostatic tests in all the test solutions are composed of a duplex electronic structure with an external n-type semiconductor layer and an internal p-type semiconductor layer. Further analyses of the surface conductivity conducted by measuring the interfacial contact resistance between the 304 SS and carbon paper reveal that the passive film formed in the solution with higher methanol content exhibits lower conductivity.

  15. Electrochemical behaviour and surface conductivity of niobium carbide-modified austenitic stainless steel bipolar plate

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Sun, Juncai; Kang, Bin; Li, Song; Ji, Shijun; Wen, Zhongsheng; Wang, Xiaochun

    2014-01-01

    A niobium carbide diffusion layer with a cubic NbC phase surface layer (∼6 μm) and a Nb and C diffusion subsurface layer (∼1 μm) is fabricated on the surface of AISI 304 stainless steel (304 SS) bipolar plate in a proton exchange membrane fuel cell (PEMFC) using plasma surface diffusion alloying. The electrochemical behaviour of the niobium carbide diffusion-modified 304 SS (Nb-C 304 SS) is investigated in simulated PEMFC environments (0.5 M H2SO4 and 2 ppm HF solution at 80 °C). Potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy measurements reveal that the niobium carbide diffusion layer considerably improves the corrosion resistance of 304 SS compared with untreated samples. The corrosion current density of Nb-C 304 SS is maintained at 0.058 μA cm-2 and 0.051 μA cm-2 under simulated anodic and cathodic conditions, respectively. The interfacial contact resistance of Nb-C 304 SS is 8.47 mΩ cm2 at a compaction force of 140 N cm-2, which is significantly lower than that of the untreated sample (100.98 mΩ cm2). Moreover, only a minor increase in the ICR of Nb-C 304 SS occurs after 10 h potentiostatic tests in both cathodic and anodic environments.

  16. Design of a miniaturized electrochemical instrument for in-situ O2 monitoring

    NASA Astrophysics Data System (ADS)

    Colomer-Farrarons, Jordi; Miribel-Català, Pedro L.; Samitier, Josep; Arundell, Martin; Rodríguez, Ivón

    2009-05-01

    The authors are working toward the design of a device for the detection of oxygen, following a discrete and an integrated instrumentation implementation. The discrete electronics are also used for preliminary analysis, to confirm the validity of the conception of system, and its set-up would be used in the characterization of the integrated device, waiting for the chip fabrication. This paper presents the design of a small and portable potentiostat integrated with electrodes, which is cheap and miniaturized, which can be applied for on-site measurements for the simultaneous detection of O2 and temperature in water systems. As a first approach a discrete PCB has been designed based on commercial discrete electronics and specific oxygen sensors. Dissolved oxygen concentration (DO) is an important index of water quality and the ability to measure the oxygen concentration and temperature at different positions and depths would be an important attribute to environmental analysis. Especially, the objective is that the sensor and the electronics can be integrated in a single encapsulated device able to be submerged in environmental water systems and be able to make multiple measurements. For our proposed application a small and portable device is developed, where electronics and sensors are miniaturized and placed in close proximity to each other. This system would be based on the sensors and electronics, forming one module, and connected to a portable notebook to save and analyze the measurements on-line. The key electronics is defined by the potentiostat amplifier, used to fix the voltage between the Working (WE) and Reference (RE) electrodes following an input voltage (Vin). Vin is a triangular signal, programmed by a LabViewinterface, which is also used to represent the CV transfers. To obtain a smaller and compact solution the potentiostat amplifier has also been integrated defining a full custom ASIC amplifier, which is in progress, looking for a point

  17. The electrochemical behaviour of 316L austenitic stainless steel in Cl- containing environment under different H2S partial pressures

    NASA Astrophysics Data System (ADS)

    Ding, Jinhui; Zhang, Lei; Lu, Minxu; Wang, Jing; Wen, Zhibin; Hao, Wenhui

    2014-01-01

    In oil-gas production environments, presence of H2S-Cl- can induce deterioration of the passive film, leading to pitting corrosion of stainless steels. In this paper, by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements (Mott-Schottky analysis), the electrochemical behaviour of AISI 316L austenitic stainless steel was investigated in Cl- solutions under different H2S partial pressures (from 0 to 1.0 bar). The results indicated that presence of H2S in Cl- solution can accelerate both the cathodic and anodic current density, leading to a metastable passive state in higher passive potential range, changing the semiconductor behaviour from p-type to n-type, increasing its susceptibility to corrosion. XPS analysis was employed to characterize the surface film after potentiostatic polarization, whose results provide good evidences for the electrochemical measurements.

  18. 3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate

    PubMed Central

    2015-01-01

    This work presents the design, fabrication, and characterization of a robust 3D printed microfluidic analysis system that integrates with FDA-approved clinical microdialysis probes for continuous monitoring of human tissue metabolite levels. The microfluidic device incorporates removable needle type integrated biosensors for glucose and lactate, which are optimized for high tissue concentrations, housed in novel 3D printed electrode holders. A soft compressible 3D printed elastomer at the base of the holder ensures a good seal with the microfluidic chip. Optimization of the channel size significantly improves the response time of the sensor. As a proof-of-concept study, our microfluidic device was coupled to lab-built wireless potentiostats and used to monitor real-time subcutaneous glucose and lactate levels in cyclists undergoing a training regime. PMID:26070023

  19. Biocompatibility of nanotube formed Ti-30Nb-7Ta alloys.

    PubMed

    Kim, Eun-Sil; Choe, Han-Cheol

    2014-11-01

    The purpose of this study was to investigate the biocompatibility of Ti-30Nb-7Ta alloy surface decorated with TiO2 nanotubes by anodization in an electrolyte containing 1 M H3PO4 and 0.8 wt.% NaF with an applied voltage of 10 V for 2 h. The anodization was carried out using a scanning potentiostat. The microstructures of alloys and morphology of the nanotubes were investigated by optical microscopy, field emission scanning electron microscopy, and X-ray diffractometry. In comparison to the Ti-30Nb-3Ta alloy, the Ti-30Nb-7Ta alloy contained a lower amount of α" phase, while the β phase was higher. In this study, we observed the formation of a spongy porous layer on the Ti-30Nb-7Ta alloy, while the Ti-30Nb and Ti-30Nb-3Ta alloys showed an absence of such a spongy layer. PMID:25958540

  20. Investigation on the Oxidation and Reduction of Titanium in Molten Salt with the Soluble TiC Anode

    NASA Astrophysics Data System (ADS)

    Wang, Shulan; Wan, Chaopin; Liu, Xuan; Li, Li

    2015-12-01

    To reveal the oxidation process of titanium from TiC anode and the reduction mechanism of titanium ions in molten NaCl-KCl, the polarization curve of TiC anode in molten NaCl-KCl and cyclic voltammograms of the molten salt after polarization were studied. Investigation on the polarization curve shows that titanium can be oxidized and dissociated from the TiC anode at very low potential. The cyclic voltammograms demonstrated that the reduction reaction of titanium ions in the molten salt is a one-step process. By potentiostatic electrolysis, dendritic titanium is obtained on the steel plate. The work promotes the understanding on the process of electrochemical oxidization/dissociation of titanium from TiC anode and the reduction mechanism of titanium ions in molten salt.

  1. Electrochemical co-deposition of magnesium with lithium from quaternary ammonium-based ionic liquid

    NASA Astrophysics Data System (ADS)

    Shimamura, Osamu; Yoshimoto, Nobuko; Matsumoto, Mami; Egashia, Minato; Morita, Masayuki

    Electrochemical deposition of magnesium (Mg) has been successfully achieved from an ionic liquid (IL) solution based on quaternary ammonium salt containing lithium (Li) salt. Irreversible electrochemical behavior was generally observed in the IL-based electrolytes containing simple Mg salt. In the IL-based electrolyte dissolving both Mg and Li salts, electrochemical reduction and oxidation of magnesium cation (Mg 2+) have become detectable. Such reversible processes correspond respectively to cathodic deposition and anodic dissolution of metallic Mg, which are accompanied by the co-deposition/co-dissolution of Li. Potentiostatic electrolysis of IL dissolving binary Mg and Li salts gave metallic deposit consisting of both elements with total current efficiency of ca. 52%.

  2. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    NASA Astrophysics Data System (ADS)

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-09-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators.

  3. High-throughput screening of thin-film semiconductor material libraries I: system development and case study for Ti-W-O.

    PubMed

    Sliozberg, Kirill; Schäfer, Dominik; Erichsen, Thomas; Meyer, Robert; Khare, Chinmay; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-04-13

    An automated optical scanning droplet cell (OSDC) enables high-throughput quantitative characterization of thin-film semiconductor material libraries. Photoelectrochemical data on small selected measurement areas are recorded including intensity-dependent photopotentials and -currents, potentiodynamic and potentiostatic photocurrents, as well as photocurrent (action) spectra. The OSDC contains integrated counter and double-junction reference electrodes and is fixed on a precise positioning system. A Xe lamp with a monochromator is coupled to the cell through a thin poly(methyl methacrylate) (PMMA) optical fiber. A specifically designed polytetrafluoroethylene (PTFE) capillary tip is pressed on the sample surface and defines through its diameter the homogeneously illuminated measurement area. The overall and wavelength-resolved irradiation intensities and the cell surface area are precisely determined and calibrated. System development and its performance are demonstrated by means of screening of a TiWO thin film. PMID:25727402

  4. Effect of annealing temperature on the pitting corrosion resistance of super duplex stainless steel UNS S32750

    SciTech Connect

    Tan Hua; Jiang Yiming; Deng Bo; Sun Tao; Xu Juliang; Li Jin

    2009-09-15

    The pitting corrosion resistance of commercial super duplex stainless steels SAF2507 (UNS S32750) annealed at seven different temperatures ranging from 1030 deg. C to 1200 deg. C for 2 h has been investigated by means of potentiostatic critical pitting temperature. The microstructural evolution and pit morphologies of the specimens were studied through optical/scanning electron microscope. Increasing annealing temperature from 1030 deg. C to 1080 deg. C elevates the critical pitting temperature, whereas continuing to increase the annealing temperature to 1200 deg. C decreases the critical pitting temperature. The specimens annealed at 1080 deg. C for 2 h exhibit the best pitting corrosion resistance with the highest critical pitting temperature. The pit morphologies show that the pit initiation sites transfer from austenite phase to ferrite phase as the annealing temperature increases. The aforementioned results can be explained by the variation of pitting resistance equivalent number of ferrite and austenite phase as the annealing temperature changes.

  5. The relationship between induction time for pitting and pitting potential for high purity aluminum.

    SciTech Connect

    Wall, Frederick Douglas; Vandenavyle, Justin J.; Martinez, Michael A.

    2003-08-01

    The objective of this study was to determine if a distribution of pit induction times (from potentiostatic experiments) could be used to predict a distribution of pitting potentials (from potentiodynamic experiments) for high-purity aluminum. Pit induction times were measured for 99.99 Al in 50 mM NaCl at potentials of -0.35, -0.3, -0.25, and -0.2 V vs. saturated calomel electrode. Analysis of the data showed that the pit germination rate generally was an exponential function of the applied potential; however, a subset of the germination rate data appeared to be mostly potential insensitive. The germination rate behavior was used as an input into a mathematical relationship that provided a prediction of pitting potential distribution. Good general agreement was found between the predicted distribution and an experimentally determined pitting potential distribution, suggesting that the relationships presented here provide a suitable means for quantitatively describing pit germination rate.

  6. Electrochemical velocimetry on centrifugal microfluidic platforms.

    PubMed

    Abi-Samra, Kameel; Kim, Tae-Hyeong; Park, Dong-Kyu; Kim, Nahui; Kim, Jintae; Kim, Hanshin; Cho, Yoon-Kyoung; Madou, Marc

    2013-08-21

    Expanding upon recent applications of interfacing electricity with centrifugal microfluidic platforms, we introduce electrochemical velocimetry to monitor flow in real-time on rotating fluidic devices. Monitoring flow by electrochemical techniques requires a simple, compact setup of miniaturized electrodes that are embedded within a microfluidic channel and are connected to a peripherally-located potentiostat. On-disc flow rates, determined by electrochemical velocimetry, agreed well with theoretically expected values and with optical measurements. As an application of the presented techniques, the dynamic process of droplet formation and release was recorded, yielding critical information about droplet frequency and volume. Overall, the techniques presented in this work advance the field of centrifugal microfluidics by offering a powerful tool, previously unavailable, to monitor flow in real-time on rotating microfluidic systems. PMID:23787459

  7. Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

    NASA Astrophysics Data System (ADS)

    Kashin, O. A.; Borisov, D. P.; Lotkov, A. I.; Abramova, P. V.; Korshunov, A. V.

    2015-10-01

    Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9-1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration.

  8. Improving the corrosion resistance of nitinol by plasma-immersion ion implantation with silicon for biomedical applications

    NASA Astrophysics Data System (ADS)

    Abramova, P. V.; Korshunov, A. V.; Lotkov, A. I.; Kashin, O. A.; Borisov, D. P.

    2015-11-01

    Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9 % NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9-1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration.

  9. Electrocatalytic activities of cathode electrodes for water electrolysis using tetra-alkyl-ammonium-sulfonic acid ionic liquid as electrolyte

    NASA Astrophysics Data System (ADS)

    Fiegenbaum, Fernanda; de Souza, Michèle O.; Becker, Márcia R.; Martini, Emilse M. A.; de Souza, Roberto F.

    2015-04-01

    The hydrogen evolution reaction (HER) performed with platinum (Pt), nickel (Ni), stainless steel 304 (SS) or glassy carbon (GC) cathodes in 0.1 M 3-triethylammonium-propanesulfonic acid tetrafluoroborate (TEA-PS.BF4) solution is studied using quasi-potentiostatic and impedance spectroscopy techniques. The objective is to compare the catalytic effect on the cathode using different materials to obtain hydrogen by water electrolysis. Furthermore, the catalytic effect of the ionic liquid (IL) on the cathode compared with that of a hydrochloric acid (HCl) solution with same pH value (0.8) is reported. A low activation energy (Ea) of 8.7 kJ mol-1 is found for the glassy carbon cathode. Tafel plots obtained with TEA-PS.BF4 IL suggest the formation of an electroactive layer of IL on the cathode, which may be responsible for the catalytically enhanced performance observed.

  10. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    NASA Astrophysics Data System (ADS)

    Zheng, Dong; Zhang, Xuran; Wang, Jiankun; Qu, Deyu; Yang, Xiaoqing; Qu, Deyang

    2016-01-01

    The polysulfide ions formed during the first reduction wave of sulfur in Li-S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfur were the S4 2 - and S5 2 - species, while the widely accepted reduction products of S8 2 - and S6 2 - for the first reduction wave were in low abundance.

  11. Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules: Correlation between inhibition efficiency and chemical structure

    SciTech Connect

    Ouici, H. B. Guendouzi, A.; Benali, O.

    2015-03-30

    The corrosion inhibition of mild steel in 5% HCl solutions by some new synthesized organic compounds namely 3-(2-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (2-MMT), 3-(3-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (3-MMT) and 3-(2-hydroxyphenyl) 5-mercapto-1. 2. 4-triazole (2-HMT) was investigated using weight loss and potentiostatic polarization techniques. These measurements reveal that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follows the order 2-MMT >3-MMT >2-HMT. Polarization studies show that these compounds are of the mixed type but dominantly act as a cathodic inhibitors for mild steel in 5% HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. Activation energy and Gibbs free energy for adsorption of inhibitors are calculated. Molecular modeling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters.

  12. A Complementary Type of Electrochromic Device by Radio Frequency Magnetron Sputtering System

    NASA Astrophysics Data System (ADS)

    Oksuz, Lutfi; Kiristi, Melek; Bozduman, Ferhat; Uygun Oksuz, Aysegul

    2014-10-01

    Electrochromic (EC) devices can change their optical properties reversibly in the visible region (400-800 nm) upon charge insertion/extraction reactions according to the applied voltage. A complementary type of EC device composes of two electrochromic layers, which is separated by an ionic conduction layer (electrolyte). In this work, the EC device was fabricated using vanadium oxide (V2O5) and titanium doped tungsten oxide (WO3-TiO2) electrodes. The EC electrodes were deposited as thin film structures by a reactive RF magnetron sputtering system in a medium of gas mixture of argon and oxygen. surface morphology of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrochemical property and durability of the EC device was investigated by a potentiostat system. Optical measurement was examined under applied voltages of +/- 2.5 V by a computer-controlled system, constantly.

  13. Electrochemical behavior of 0.2 to 3 molar ferrous chloride-ferric chloride mixtures on edge-on pyrolytic graphite rotated disk electrodes

    NASA Technical Reports Server (NTRS)

    Miller, R. O.

    1977-01-01

    Potentiostatic determinations in various mixtures of FeCl2-FeCl3 with excess HCl show rest potentials that are 0.1 V less electropositive than the theoretical values from the formulated ratios of FeII to FeIII (probably as a result of complexing). The standard rate constant sub s. ranges between 0.0001 and 0.000 cm/sec. Tafel slopes b of roughly 0.12V per decade indicate single-electron exchange kinetics. No significant trend in either b or sub s was attributed to mixture composition. The higher sub s. values occurred with and edge-on pyrolytic graphite that had undergone a permanent surface change.

  14. Simultaneous telemetric monitoring of brain glucose and lactate and motion in freely moving rats.

    PubMed

    Rocchitta, Gaia; Secchi, Ottavio; Alvau, Maria Domenica; Farina, Donatella; Bazzu, Gianfranco; Calia, Giammario; Migheli, Rossana; Desole, Maria Speranza; O'Neill, Robert D; Serra, Pier A

    2013-11-01

    A new telemetry system for simultaneous detection of extracellular brain glucose and lactate and motion is presented. The device consists of dual-channel, single-supply miniature potentiostat-I/V converter, a microcontroller unit, a signal transmitter, and a miniaturized microvibration sensor. Although based on simple and inexpensive components, the biotelemetry device has been used for accurate transduction of the anodic oxidation currents generated on the surface of implanted glucose and lactate biosensors and animal microvibrations. The device was characterized and validated in vitro before in vivo experiments. The biosensors were implanted in the striatum of freely moving animals and the biotelemetric device was fixed to the animal's head. Physiological and pharmacological stimulations were given in order to induce striatal neural activation and to modify the motor behavior in awake, untethered animals. PMID:24102201

  15. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    DOE PAGESBeta

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; Wang, Jiankun; Qu, Deyu; Qu, Deyang

    2015-10-30

    In this study, the polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfurmore » were the S42– and S52– species, while the widely accepted reduction products of S82– and S62– for the first reduction wave were in low abundance.« less

  16. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  17. An assessment of the formation of electrodeposited scales using scanning electron and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Morizot, A. P.; Neville, A.; Taylor, J. D.

    2002-04-01

    The deposition of insoluble salts onto surfaces in process systems represents an important operational problem. Mineral scale formation (e.g. CaCO 3 and BaSO 4) can result from fluid streams becoming supersaturated when incompatible waters combine (e.g. in oil recovery) or can be formed when cathodic protection is applied and electrodeposition occurs. In this study, electrodeposition is studied on metal rotating disk electrodes (RDE) in artificial seawater under static conditions and under rotation at 400 rpm. Also, a Ca-free brine and a Mg-free brine of the same dissolved solids level were used in static tests. The focus of the study is the assessment of the electrochemical response of the system under potentiostatic control and correlation of the current versus time measurements to the characteristics of the scale determined via scanning electron microscopy and atomic force microscopy analysis.

  18. An electronic pollen detection method using Coulter counting principle

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Zhe, Jiang; Chandra, Santanu; Hu, Jun

    A method for detecting and counting pollen particles based on Coulter counting principle is presented. This approach also provides information on the size and surface charges of the micro particles, allowing for preliminary differentiation of pollens from other micro particles. Three samples are studied: polymethyl methacrylate particles, tree pollens from Juniperus Scopulorum and grass pollens from Secale Cerale. The samples, suspended in diluted KCl aqueous solutions in an electrochemical cell, were allowed to pass through a microchannel and the conductance of the microchannel was sampled with a Gamry ® Potentiostat. The changes in the conductance due to the passing of the micro particles was thus recorded and analyzed. The experimental results showed that tree pollens and grass pollens display distinctive behaviors. The phenomena may be attributed to the differences in the surface characteristics of the pollens and is potentially useful for counting and differentiating different micro particles.

  19. Improvement of corrosion resistance of Nisbnd Mo alloy coatings: Effect of heat treatment

    NASA Astrophysics Data System (ADS)

    Mousavi, R.; Bahrololoom, M. E.; Deflorian, F.; Ecco, L.

    2016-02-01

    In this paper, Nisbnd Mo alloy coatings were deposited from bath containing sodium citrate, nickel sulphate, and sodium molybdate. Essentially, this work is divided into two mains parts: (i) the optimization on the coatings deposition parameters and (ii) the effect of the heat treatment. Polarization curves and electrochemical impedance spectroscopy were acquired using potentiostat/galvanostat and a frequency response analyzer, respectively. Morphology and chemical composition of the coatings were investigated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Polarization curves at different condition revealed that electroplating at temperature 40 oC, pH 9 provides a dense coating with high efficiency. Following the optimization of the deposition parameters, the coatings were annealed at 200, 400, and 600 oC for 25 min. The results showed that the coatings obtained at temperature 40 oC, pH 9, and annealing at 600 oC has the highest corrosion resistance and microhardness.

  20. Electro-active sensor, method for constructing the same; apparatus and circuitry for detection of electro-active species

    NASA Technical Reports Server (NTRS)

    Buehler, Martin (Inventor)

    2009-01-01

    An electro-active sensor includes a nonconductive platform with a first electrode set attached with a first side of a nonconductive platform. The first electrode set serves as an electrochemical cell that may be utilized to detect electro-active species in solution. A plurality of electrode sets and a variety of additional electrochemical cells and sensors may be attached with the nonconductive platform. The present invention also includes a method for constructing the aforementioned electro-active sensor. Additionally, an apparatus for detection and observation is disclosed, where the apparatus includes a sealable chamber for insertion of a portion of an electro-active sensor. The apparatus allows for monitoring and detection activities. Allowing for control of attached cells and sensors, a dual-mode circuitry is also disclosed. The dual-mode circuitry includes a switch, allowing the circuitry to be switched from a potentiostat to a galvanostat mode.

  1. In vitro biocompatibility response of Ti-Zr-Si thin film metallic glasses

    NASA Astrophysics Data System (ADS)

    Ke, J. L.; Huang, C. H.; Chen, Y. H.; Tsai, W. Y.; Wei, T. Y.; Huang, J. C.

    2014-12-01

    In this study, the bio-electrochemical response of the Ti-Zr-Si thin film metallic glasses (TFMGs) in simulated body fluid with different contents of titanium is measured via potentiostat. According to the results of bio-corrosion potential and current, as well as the polarization resistance, it is concluded that the Ti66Zr25Si9 TFMGs possess the highest bio-electrochemical resistance. With increasing content of titanium, the corrosion resistance becomes progressively higher. The passive current results reveal that amorphous alloys can form a more protective and denser passive film on the metallic glass surface than the crystalline materials. In addition, the mechanical performance of the Ti-Zr-Si TFMGs is better than the crystalline counterparts. As a result, the Ti-based TFMGs are considered to be potential materials for bio-coating applications.

  2. Relation between energetic and utilization coefficients in the positive plates of automotive lead/acid batteries

    NASA Astrophysics Data System (ADS)

    D'Alkaine, C. V.; Carubelli, A.; Fava, H. W.; Sanhueza, A. C.

    A new experimental method to distinguish between energetic and structural materials and to characterize the manufacturing technology for positive plates in lead/acid batteries is discussed. This new method proposes the evaluation of the energetic β-coefficient from plots of capacity versus very low current densities under galvanostatic conditions and using real-size positive plates in 2.3-6.9 M H 2SO 4 solutions. The results are identical to those obtained previously from potentiostatic measurements, and they fit a new equation as opposed to Peukert's equation. The independence of the β-coefficient with H 2SO 4 concentration indicates that the discharge of PbO 2 to its products proceeds via a solid-state reaction mechanism.

  3. Adhesion and proliferation of osteoblast-like cells on anodic porous alumina substrates with different morphology.

    PubMed

    Salerno, Marco; Caneva-Soumetz, Federico; Pastorino, Laura; Patra, Niranjan; Diaspro, Alberto; Ruggiero, Carmelina

    2013-06-01

    We have fabricated nanoporous alumina surfaces by means of anodization in oxalic acid in different conditions and used them as the substrates for the growth of cells from a human osteoblast-like cell line. The rough nanoporous alumina substrates have been compared both with smooth standard Petri dishes used as the control and with commercial substrates of similar material. The viability of the cells has been assessed at different culture times of 4, 11, 18, and 25 days in vitro. It turned out that the porous side of the galvanostatically fabricated alumina performed similar to the control and better than the commercial porous alumina, whereas the potentiostatically fabricated porous alumina performed better than all the other substrates at all times, and in particular at the two shortest time periods of 4 and 11 days in vitro. The best performance of the substrates is associated with intermediate surface roughness and feature spacing. PMID:23722279

  4. Corrosion behavior of sensitized duplex stainless steel.

    PubMed

    Torres, F J; Panyayong, W; Rogers, W; Velasquez-Plata, D; Oshida, Y; Moore, B K

    1998-01-01

    The present work investigates the corrosion behavior of 2205 duplex stainless steel in 0.9% NaCl solution after various heat-treatments, and compares it to that of 316L austenitic stainless steel. Both stainless steels were heat-treated at 500, 650, and 800 degrees C in air for 1 h, followed by furnace cooling. Each heat-treated sample was examined for their microstructures and Vickers micro-hardness, and subjected to the X-ray diffraction for the phase identification. Using potentiostatic polarization method, each heat-treated sample was corrosion-tested in 37 degrees C 0.9% NaCl solution to estimate its corrosion rate. It was found that simulated sensitization showed an adverse influence on both steels, indicating that corrosion rates increased by increasing the sensitization temperatures. PMID:9713683

  5. Influence of Step Annealing Temperature on the Microstructure and Pitting Corrosion Resistance of SDSS UNS S32760 Welds

    NASA Astrophysics Data System (ADS)

    Yousefieh, M.; Shamanian, M.; Saatchi, A.

    2011-12-01

    In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging from 550 to 1000 °C resulted in a precipitation of sigma phase and Cr2N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range, the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050 °C, the microstructure contains only austenite and ferrite phases. At this condition, the critical pitting temperature of samples successfully arrived to the highest value obtained in this study.

  6. Electrodeposition and Characterization of Bismuth Telluride Nanowires

    NASA Astrophysics Data System (ADS)

    Frantz, C.; Stein, N.; Gravier, L.; Granville, S.; Boulanger, C.

    2010-09-01

    In this work, we report thermoelectric measurements on electroplated bismuth telluride nanowires. Porous polycarbonate membranes, obtained by ion-track irradiation lithography, were chosen as electroplating templates. Bismuth telluride nanowires were achieved in acidic media under potentiostatic conditions at -100 mV versus saturated silver chloride electrode. The filling ratio of the pores was increased to 80% by adding dimethyl sulfoxide to the electrolyte. Whatever the experimental conditions, the nanowires were polycrystalline in the rhombohedral phase of Bi2Te3. Finally, the power output of arrays of bismuth telluride nanowires was analyzed as a function of load resistance. The results were strongly dependent on the internal resistance, which can be significantly reduced by the presence of dimethyl sulfoxide during electroplating.

  7. Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules: Correlation between inhibition efficiency and chemical structure

    NASA Astrophysics Data System (ADS)

    Ouici, H. B.; Benali, O.; Guendouzi, A.

    2015-03-01

    The corrosion inhibition of mild steel in 5% HCl solutions by some new synthesized organic compounds namely 3-(2-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (2-MMT), 3-(3-methoxyphenyl) 5-mercapto-1. 2. 4-triazole (3-MMT) and 3-(2-hydroxyphenyl) 5-mercapto-1. 2. 4-triazole (2-HMT) was investigated using weight loss and potentiostatic polarization techniques. These measurements reveal that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follows the order 2-MMT >3-MMT >2-HMT. Polarization studies show that these compounds are of the mixed type but dominantly act as a cathodic inhibitors for mild steel in 5% HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. Activation energy and Gibbs free energy for adsorption of inhibitors are calculated. Molecular modeling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters.

  8. Light addressable potentiometric sensor with an array of sensing regions

    NASA Astrophysics Data System (ADS)

    Liang, Weiguo; Han, JingHong; Zhang, Hong; Chen, Deyong

    2001-09-01

    This paper describes the mechanism of light addressable poteniometric sensors (LAPS) from the viewpoints of Semiconductor Physics, and introduces the fabrication of a multi-parameter LAPS chip. The MEMS technology is applied to produce a matrix of sensing regions on the wafer. By doing that, the cross talk among these regions is reduced, and the precision of the LAPS is increased. An IR-LED matrix is used as the light source, and the flow-injection method is used to input samples. The sensor system is compact and highly integrated. The measure and control system is composed of a personal computer, a lock-in amplifier, a potentiostat, a singlechip system, and an addressing circuit. Some experiments have been done with this device. The results show that this device is very promising for practical use.

  9. Preparation and Characterization of the Porous (TiO2) Oxide Films of Nanostructure for Biological and Medical Applications

    SciTech Connect

    Fadl-Allah, Sahar A.; El Sherief, Rabab M.; Badawy, Waheed A.

    2007-02-14

    In this paper, galvanostatically and potentiostatically formed surface oxide film on titanium in H2O2 free and H2O2 containing H2SO4 solutions were investigated. Conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) measurements beside the scanning electron microscope (SEM) were used. In absence of H2O2, the impedance response indicated a stable thin oxide film which depends on the mode of anodization of the metal. However, the introduction of H2O2 into the solution resulted in significant changes in the film characteristics, which were reflected in the EIS results. The film characteristics were found to be affected by the mode of oxide film growth and polarization time. The H2O2 addition to the solution has led to a significant decrease in the corrosion resistance of the passive film. The electrochemical and the use of equivalent circuit models have led to the understanding of the film characteristics under different conditions.

  10. Recovering Silver from Photographic Process Wastes

    NASA Astrophysics Data System (ADS)

    Sathaiyan, N.; Adaikkalam, P.; Abdul Kader, J. A. M.; Visvanathan, S.

    1990-10-01

    Spent color bleach-fix solution (CBFS), a product of photographic processing operations, is a potential source of silver. Of the extraction reactors used in recovering this silver, the rotating cylindrical electrode (RCE) has an advantage in that it provides improved mass transfer with an extended effective surface area. In addition, the application of a potentiostatic technique allows the silver deposition reaction to take place preferentially, without the formation of silver sulfide. The process consists of prior physical treatment, subsequent chemical reduction of the ferric-EDTA (ethylene diamine tetra-acetic acid) complex present in the CBFS with sodium dithionite (monitored by measuring the redox potential of Fe3+/Fe2+ couple), followed by electrodeposition of silver in a divided cell using a cation exchange membrane. The combined procedure results in increased current efficiency and reduced electrolysis time.

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

    SciTech Connect

    Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.; Abdel-Fattah, Tarek M.

    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 of 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.

  12. Li Diffusion and High-Voltage Cycling Behavior of Thin-Film LiCoO2 Cathodes

    SciTech Connect

    Jang, Y.-I.

    2001-10-02

    Mass transport and thermodynamic properties of Li{sub x}CoO{sub 2} were studied by the potentiostatic intermittent titration technique (PITT) using solid-state thin-film batteries that provide a well-defined diffusion geometry. Both the chemical diffusion coefficient and the thermodynamic factor have minima at the phase boundaries of the Li/vacancy ordered phase ''Li{sub 0.5}CoO{sub 2}''. The self-diffusion coefficient of Li has a minimum at x = 0.5 associated with the Li/vacancy ordering. As the degree of ordering increases, the nonmonotonic variations become more pronounced when approaching x = 0.5 in Li{sub x}CoO{sub 2}. We also show that thin-film LiCoO{sub 2} cathodes having grains of sub-micrometer size combined with the Li upon electrolyte exhibit excellent capacity retention when charged up to 4.5 V.

  13. Microbial characterization of anode-respiring bacteria within biofilms developed from cultures previously enriched in dissimilatory metal-reducing bacteria.

    PubMed

    Pierra, Mélanie; Carmona-Martínez, Alessandro A; Trably, Eric; Godon, Jean-Jacques; Bernet, Nicolas

    2015-11-01

    This work evaluated the use of a culture enriched in DMRB as a strategy to enrich ARB on anodes. DMRB were enriched with Fe(III) as final electron acceptor and then transferred to a potentiostatically-controlled system with an anode as sole final electron acceptor. Three successive iron-enrichment cultures were carried out. The first step of enrichment revealed a successful selection of the high current-producing ARB Geoalkalibacter subterraneus. After few successive enrichment steps, the microbial community analysis in electroactive biofilms showed a significant divergence with an impact on the biofilm electroactivity. Enrichment of ARB in electroactive biofilms through the pre-selection of DMRB should therefore be carefully considered. PMID:26182995

  14. Permeability improvements of electropolymerized polypyrrole films using dissolvable nano-CaCO3 particle templates.

    PubMed

    Popescu Mandoc, Luisa-Roxana; Gorgy, Karine; Ungureanu, Eleonora-Mihaela; Buica, George-Octavian; Holzinger, Michael; Cosnier, Serge

    2014-03-21

    The electropolymerisation of N-substituted pyrroles on a dissolvable calcium carbonate nanoparticle template was investigated in order to improve the film permeabilities in aqueous solution. After deposition of CaCO3 nanoparticles on the electrode surface, poly(pyrrole-ammonium) or poly(pyrrole-NTA) (NTA: nitrilotriacetic acid) were electrogenerated around the template structures of the electrodes using potentiostatic methods. The dissolution of nanoparticles in acidic medium leads to the formation of nano-porous structures increasing, therefore, the polypyrrole permeability in aqueous solutions. Histidine-tagged glucose oxidase, chosen as an enzyme model, was immobilised on the modified polypyrrole-NTA via the NTA-Cu(2+)-histidine interactions to validate the proposed method. The described setup led to a twofold increase in the maximum current density from 5 to 10 μA cm(-2) after template dissolution. PMID:24481549

  15. Exfoliation corrosion susceptibility and mechanisms of Al -- Li 2060 T8E30 aluminum lithium alloy in acidic media

    NASA Astrophysics Data System (ADS)

    Karayan, Ahmad Ivan

    The Al - Li 2060 aluminum lithium alloy was first launched in 2011. This alloy is a potential candidate for the use at wing/fuselage forgings, lower wing, and fuselage/pressure cabin. However, since its first launching, the corrosion properties of this alloy has not been extensively explored. There are three common laboratory tests for assessing the exfoliation corrosion (EFC) susceptibility of aluminum alloy 2XXX, namely EFC test in EXCO, modified EXCO and MASTMAASIS media. The objectives of this work is to study the susceptibility and mecahnism of corrosion of this alloy in EXCO, modified EXCO and MATSMAASIS media. These three media are acid. In the EXCO solution, this alloy suffers EFC after a 96-hour EFC test. The pH dramatically increases in the first 11 hours from 0.25 to 0.30. The pH then slightly increases and tends to remain constant at pH of 3.45 after 96 hours. The cyclic potentiodynamic polarization (CPP) test results show the presence of negative hysteresis and one breakdwon potential. This negative hysteresis suggests the absence of pitting corrosion due to the breakdown of passive film. The potentiostatic tests at potentials below and above the breakdown potential show an abrupt increase in potential in the first minutes and the presence of current transients. The scanning electron microscopy (SEM)-energy dispersive x-ray spectroscopy (EDS) examination confirms that the Al 20Cu2Mn3 particles preferentially dissolve, leaving the pitting after a potentiostatic test below the breakdown potential. From the potentiostatic test at a potential above the breakdown potential and an SEM examination after this potentiostatic test, intergranular corrosion (IGC) was observed. The electrochemical impedance spectroscopy (EIS) test and mathematical modeling indicates that the adsorption of intermediates in reduction of hydrogen ions is dominant in the first hours of immersion. The two time constants are observed when EFC occurs. The video capture microscopy

  16. Evidence of enzymatic catalysis of oxygen reduction on stainless steels under marine biofilm.

    PubMed

    Faimali, Marco; Benedetti, Alessandro; Pavanello, Giovanni; Chelossi, Elisabetta; Wrubl, Federico; Mollica, Alfonso

    2011-04-01

    Cathodic current trends on stainless steel samples with different surface percentages covered by biofilm and potentiostatically polarized in natural seawater were studied under oxygen concentration changes, temperature increases, and additions of enzymic inhibitors to the solution. The results showed that on each surface fraction covered by biofilm the oxygen reduction kinetics resembled a reaction catalyzed by an immobilised enzyme with high oxygen affinity (apparent Michaelis-Menten dissociation constant close to K(O(2))(M)  ≈ 10 μM) and low activation energy (W ≈ 20 KJ mole(-1)). The proposed enzyme rapidly degraded when the temperature was increased above the ambient (half-life time of ∼1 day at 25°C, and of a few minutes at 50°C). Furthermore, when reversible enzymic inhibitors (eg sodium azide and cyanide) were added, the cathodic current induced by biofilm growth was inhibited. PMID:21526439

  17. Some views on the erosion corrosion response of bulk chromium carbide based cermets

    NASA Astrophysics Data System (ADS)

    Stack, M. M.; Antonov, M. M.; Hussainova, I.

    2006-08-01

    Chromium carbide/nickel based composites are applicable in many environments involving tribo-corrosion due to their combined ability to resist wear and corrosion. Hence, they are candidate materials for use either in bulk as surface coatings in crude oil (offshore) or in power and marine industries. The aim of this work was to study the effect of material parameters such as composition and surface roughness, together with test conditions such as abrasive particle concentration, applied potential, temperature and time of experiment on the performance of chromium carbide based cermets. Potentiodynamic and potentiostatic tests were carried out as part of this work. SEM studies were also conducted to establish the mechanisms of the material degradation processes. Finally, erosion-corrosion maps were constructed based on the results. Material wastage, synergy and regime maps were developed for these materials and demonstrated that the performance of the cermet depends on the interplay of material and process variables.

  18. Abiotic systems for the catalytic treatment of solvent-contaminated water

    SciTech Connect

    Betterton, E.A.; Arnold, R.G.; Liu, Zhijie; Hollan, N.

    1996-12-31

    Three abiotic systems are described that catalyze the reductive dehalogenation of heavily halogenated environmental pollutants, including carbon tetrachloride, trichloroethene, and perchloroethene. These systems include (a) an electrolytic reactor in which the potential on the working electrode (cathode) is fixed by using a potentiostat, (b) a light-driven system consisting of a semiconductor and (covalently attached) macrocycle that can accept light transmitted via an optical fiber, and a light-driven, two-solvent (isopropanol/acetone) system that promotes dehalogenation reactions via an unknown mechanism. Each is capable of accelerating reductive dehalogenation reactions to very high rates under laboratory conditions. Typically, millimolar concentrations of aqueous-phase targets can be dehalogenated in minutes to hours. The description of each system includes the elements of reaction mechanism (to the extent known), typical kinetic data, and a discussion of the feasibility of applying this technology for the in situ destruction of hazardous compounds. 14 refs., 11 figs., 2 tabs.

  19. Highly sensitive DNA sensor based on polypyrrole nanowire

    NASA Astrophysics Data System (ADS)

    Mai, Anh Tuan; Duc, Thanh Pham; Thi, Xuan Chu; Nguyen, Minh Hieu; Nguyen, Hoang Hai

    2014-08-01

    This paper describes the development of a DNA sensor based on polypyrrole nanowire. By using potentiostatic technique, in the presence of gelatin as the soft mold, the polypyrrole nanowires were synthesized on the surface of the micro-sensor. The surface enhanced Raman spectroscopy shows that the Nsbnd H ends of the polypyrrole nanowires orientate upward from the surface facilitating the DNA probe immobilization through the simple linkage with the phosphate groups of the probe DNA. The label-free signal readout was carried out by lock-in amplifier technique. The response time of the DNA sensor is 10 s and the measurement time was 5 min. The lowest detectable concentration of Escherichia coli DNA was 0.1 nM.

  20. Electrochemical synthesis of core-shell magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Ovejero, Jesús G.; Bran, Cristina; Vilanova, Enrique; Kosel, Jürgen; Morales, María P.; Vazquez, Manuel

    2015-09-01

    (Fe, Ni, CoFe) @ Au core-shell magnetic nanowires have been synthesized by optimized two-step potentiostatic electrodeposition inside self-assembled nanopores of anodic aluminium templates. The optimal electrochemical parameters (e.g., potential) have been firstly determined for the growth of continuous Au nanotubes at the inner wall of pores. Then, a magnetic core was synthesized inside the Au shells under suitable electrochemical conditions for a wide spectrum of single elements and alloy compositions (e.g., Fe, Ni and CoFe alloy). Novel opportunities offered by such nanowires are discussed particularly, the magnetic behavior of (Fe, Ni, CoFe) @ Au core-shell nanowires was tested and compared with that of bare nanowires. These core-shell nanowires can be released from the template thereby opening novel opportunities for biofunctionalization of individual nanowires.

  1. Improved corrosion resistance and interfacial contact resistance of 316L stainless-steel for proton exchange membrane fuel cell bipolar plates by chromizing surface treatment

    NASA Astrophysics Data System (ADS)

    Lee, S. B.; Cho, K. H.; Lee, W. G.; Jang, H.

    The electrochemical performance and electrical contact resistance of chromized 316 stainless-steel (SS) are investigated under simulated operating condition in a proton-exchange membrane fuel cell (PEMFC). The corrosion resistance of the chromized stainless steel is assessed by potentiodynamic and potentiostatic tests and the interfacial contact resistance (ICR) is examined by measuring the electrical contact resistance as a function of the compaction force. The results show that the chromizing surface treatment improves the corrosion resistance of the stainless steel due to the high-chromium concentration in the diffuse coating layer. On the other hand, the excess Chromium content on the surface increases the contact resistance of the steel plate to a level that is excessively high for commercial applications. This study examines the root cause of the high-contact resistance after chromizing and reports the optimum process to improve the corrosion resistance without sacrificing the ICR by obtaining a chrome carbide on the outer layer.

  2. The passivity of Type 316L stainless steel in borate buffer solution

    NASA Astrophysics Data System (ADS)

    Nicic, Igor; Macdonald, Digby D.

    2008-09-01

    The passivity of Type 316 SS in borate buffer solution (pH 8.35), in the steady-state, has been explored using a variety of electrochemical techniques, including potentiostatic polarization, Mott Schottky analysis, and electrochemical impedance spectroscopy. The study shows that the passive film is an n-type semiconductor with a donor density that is essentially independent of voltage across the passive state. The passive current density is also found to be voltage-independent, but the thickness of the barrier layer depends linearly on the applied voltage. These observations are consistent with the predictions of the Point Defect Model, noting that the point defects within the barrier layer of the passive film are metal interstitials or oxygen vacancies, or both. No evidence for p-type behavior was obtained, indicating that cation vacancies do not have a significant population density in the film compared with the two donors (cation interstitials and oxygen vacancies).

  3. Electrochemical deposition and characterization of Ni-P alloy thin films

    SciTech Connect

    Mahalingam, T. . E-mail: maha51@rediffmail.com; Raja, M.; Thanikaikarasan, S.; Sanjeeviraja, C.; Velumani, S.; Moon, Hosun; Kim, Yong Deak

    2007-08-15

    Nickel phosphorus (Ni-P) alloy thin films were prepared by electrodeposition on pre-cleaned copper substrates using a potentiostatic cathodic electrodeposition method from sulfate electrolyte baths at various sodium hypophosphite (NaH{sub 2}PO{sub 2}) concentrations. X-ray diffraction studies reveal polycrystalline cubic alloys at low concentrations of phosphorus (< 13.5 at.%) and these transformed into amorphous alloys at higher concentrations. X-ray photoelectron spectra show the presence of Ni{sub 2}p and P{sub 2}p lines corresponding to their binding energies. Scanning electron microscopic studies reveal spherical shaped grains at low phosphorus contents and modules of cauliflower type morphology at higher phosphorus concentrations. The effects of phosphorus concentration on the crystal structure, composition and morphology are studied and discussed.

  4. A novel method for the modification of zinc powder by ultrasonic impregnation in cerium nitrate solution.

    PubMed

    Zhu, Liqun; Zhang, Hui

    2008-04-01

    This work is devoted to an extensive study of cerium deposits distributed directly on zinc particles by simple impregnation or ultrasonic impregnation for the modification of zinc powder. Meantime, the characterization of modified zinc powder and the influence of ultrasound parameters in the modification process upon the dendritic growth, the corrosion behavior and the cyclic performance of zinc are investigated using scanning electron microscopy, energy dispersion spectrometry, potentiostatic polarization, potentiodynamic polarization and cyclic voltammetry. Compared with simple impregnation, the assistance of ultrasonic irradiation is found to have a significant effect on the sedimentary state and favorable properties of cerium deposits in a protective way. Besides the cyclic voltammetry measurements display that the application of ultrasound also improves the cyclic performance of zinc electrode containing modified zinc powder mainly because the cerium deposits formed under ultrasonic irradiation can greatly hinder the dissolution and diffusion of the oxidation product of zinc in the electrolyte and effectively favor the capacity maintenance of zinc electrode. PMID:18024152

  5. Synthesis of gold nanowires with controlled crystallographic characteristics

    NASA Astrophysics Data System (ADS)

    Karim, S.; Toimil-Molares, M. E.; Maurer, F.; Miehe, G.; Ensinger, W.; Liu, J.; Cornelius, T. W.; Neumann, R.

    2006-09-01

    The controlled fabrication of poly- and single-crystalline Au nanowires is reported. In polycarbonate templates, prepared by heavy-ion irradiation and subsequent etching, Au nanowires with diameters down to 25 nm are electrochemically synthesized. Four-circle X-ray diffraction and transmission electron microscopy measurements demonstrate that wires deposited potentiostatically at a voltage of -1.2 V at 65 °C are single-crystalline and oriented along the [110] direction. By reverse-pulse electrodeposition, wires oriented along the [100] direction are grown. The wires are cylindrical over their whole length. The morphology of the caps growing on top of poly- and single-crystalline wires is a strong indication of the particular crystalline structure of the nanowires.

  6. Structure and dye-sensitized solar cell application of TiO2 nanotube arrays fabricated by the anodic oxidation method

    NASA Astrophysics Data System (ADS)

    Ok, Seon-Yeong; Cho, Kwon-Koo; Kim, Ki-Won; Ryu, Kwang-Sun

    2010-05-01

    Well-ordered TiO2 nanotube arrays were fabricated by the potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as an electrolyte with the small addition of NH4F and H2O. The influence of anodization temperature and time on the morphology and formation of TiO2 nanotube arrays was examined. The TiO2 nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of TiO2 nanotube arrays show a similar value, whereas the length increases with decreasing reaction temperature. The conversion efficiency is very low, which is due to a morphology breaking of the TiO2 nanotube arrays in the manufacturing process of a photoelectrode.

  7. 3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate.

    PubMed

    Gowers, Sally A N; Curto, Vincenzo F; Seneci, Carlo A; Wang, Chu; Anastasova, Salzitsa; Vadgama, Pankaj; Yang, Guang-Zhong; Boutelle, Martyn G

    2015-08-01

    This work presents the design, fabrication, and characterization of a robust 3D printed microfluidic analysis system that integrates with FDA-approved clinical microdialysis probes for continuous monitoring of human tissue metabolite levels. The microfluidic device incorporates removable needle type integrated biosensors for glucose and lactate, which are optimized for high tissue concentrations, housed in novel 3D printed electrode holders. A soft compressible 3D printed elastomer at the base of the holder ensures a good seal with the microfluidic chip. Optimization of the channel size significantly improves the response time of the sensor. As a proof-of-concept study, our microfluidic device was coupled to lab-built wireless potentiostats and used to monitor real-time subcutaneous glucose and lactate levels in cyclists undergoing a training regime. PMID:26070023

  8. A CMOS detection chip for amperometric sensors with chopper stabilized incremental ΔΣ ADC

    NASA Astrophysics Data System (ADS)

    Min, Chen; Yuntao, Liu; Jingbo, Xiao; Jie, Chen

    2016-06-01

    This paper presents a low noise complimentary metal–oxide-semiconductor (CMOS) detection chip for amperometric electrochemical sensors. In order to effectively remove the input offset of the cascaded integrators and the low frequency noise in the modulator, a novel offset cancellation chopping scheme was proposed in the Incremental ΔΣ analog to digital converter (IADC). A novel low power potentiostat was employed in this chip to provide the biasing voltage for the sensor while mirroring the sensor current out for detection. The chip communicates with FPGA through standard built in I2C interface and SPI bus. Fabricated in 0.18-μm CMOS process, this chip detects current signal with high accuracy and high linearity. A prototype microsystem was produced to verify the detection chip performance with current input as well as micro-sensors. Project supported by the State Key Development Program for Basic Research of China (No. 2015CB352100).

  9. Correlation between electronic and corrosion properties of the passive oxide film on nitinol.

    PubMed

    Katić, Jozefina; Metikoš-Huković, Mirjana

    2014-01-01

    The oxide film (TiO(2)) was formed on Nitinol potentiostatically in an acetic acid solution. Deep understanding of electronic properties of this film is needed to predict long-term corrosion properties of Nitinol implant material in simulated body fluid conditions. The capacitance measurements were performed under depletion conditions to study electronic (semiconducting) properties. The space charge, formed at the solid|liquid interface, creates the barrier for the corrosion processes in aggressive (bio)environment. According to the results of electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis (MS), the passive film on Nitinol behaves as amorphous highly-doped n-type semiconductor. The values of electronic structure parameters (the flat-band potential, E(fb) and the carrier (donor) density, N(D)) were corrected for frequency dispersion. PMID:25125118

  10. A model for pore growth in anodically etched gallium phosphide

    NASA Astrophysics Data System (ADS)

    Ricci, P. C.; Salis, M.; Anedda, A.

    2005-06-01

    The electrochemical etching process of porous gallium phosphide was studied by means of the characteristic current-potential (I-V) curves. Measurements were performed in H2SO4 0.5-M aqueous solution both in the dark and by illuminating the samples with the 351-nm line of an argon laser. Raman spectroscopy was applied to investigate the surface morphology of the samples prepared under different anodizing conditions within the potentiostatic regime. Based on a few reasonable assumptions, a simple model of pore growth is proposed. The enhancing effect in current intensity due to the branching of pores and the opposite effect due to a concomitant decrease in the effective cross area available for carrier transport are accounted for to explain the main features of the recorded I -V curves.

  11. Tribo-electrochemical characterization of hafnium multilayer systems deposited on nitride/vanadium nitride AISI 4140 steel

    NASA Astrophysics Data System (ADS)

    Mora, M.; Vera, E.; Aperador, W.

    2016-02-01

    In this work is presented the synergistic behaviour among corrosion/wear (tribocorrosion) of the multilayer coatings hafnium nitride/vanadium nitride [HfN/VN]n. The multilayers were deposited on AISI 4140 steel using the technique of physical vapor deposition PVD magnetron sputtering, the tests were performed using a pin-on-disk tribometer, which has an adapted potentiostat galvanostat with three-electrode electrochemical cell. Tribocorrosive parameters such as: Friction coefficient between the coating and the counter body (100 Cr6 steel ball); Polarization resistance by means of electrochemical impedance spectroscopy technique and corrosion rate by polarization curves were determined. It was observed an increase in the polarization resistance, a decrease in the corrosion rate and a low coefficient of friction in comparison with the substrate, due to an increase on the number of bilayers.

  12. Improvement of flexible lithium battery shelf life by pre-discharging

    NASA Astrophysics Data System (ADS)

    Lim, Seung-Gyu; Jin, En Mei; Zhao, Xing Guan; Park, Kyung-Hee; Kim, Nam-In; Gu, Hal-Bon; Park, Bok-Kee

    Poly (methyl methacrylate) (PMMA)-based gel electrolyte has been used in flexible lithium batteries. These batteries are flexible and less than 0.5 mm thick, which make them suitable as power sources for smart cards and radio frequency identification (RFID) tags. We investigated the electrochemical properties of flexible lithium batteries using an impedance analyzer and potentiostat/galvanostat to evaluate the electrical capacities. To prevent the formation of gas by decomposition of electrolyte solvent, the batteries had to be pre-discharged about 5% of theoretical MnO 2 capacity. Of the three kinds of pre-discharging methods, especially, battery two-step pre-discharging method was performed showed the best electrical properties after storage at 60 °C for 60 days.

  13. Novel integrated and portable endotoxin detection system based on an electrochemical biosensor.

    PubMed

    Zuzuarregui, Ana; Souto, David; Pérez-Lorenzo, Eva; Arizti, Fernando; Sánchez-Gómez, Susana; Martínez de Tejada, Guillermo; Brandenburg, Klaus; Arana, Sergio; Mujika, Maite

    2015-01-21

    This paper describes the design, implementation and validation of a sensitive and integral technology solution for endotoxin detection. The unified and portable platform is based on the electrochemical detection of endotoxins using a synthetic peptide immobilized on a thin-film biosensor. The work covers the fabrication of an optimized sensor, the biofunctionalization protocol and the design and implementation of the measuring and signalling elements (a microfluidic chamber and a portable potentiostat-galvanostat), framed ad hoc for this specific application. The use of thin-film technologies to fabricate the biosensing device and the application of simple immobilization and detection methods enable a rapid, easy and sensitive technique for in situ and real time LPS detection. PMID:25431806

  14. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure.

    PubMed

    May, Matthias M; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  15. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    PubMed Central

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  16. Self-organized highly ordered TiO{sub 2} nanotubes in organic aqueous system

    SciTech Connect

    Wan Jun; Yan Xia; Ding Junjie; Wang Meng; Hu Kongcheng

    2009-12-15

    A simple method to achieve self-organized, freestanding TiO{sub 2} nanotube array was constructed, free of corrosive etching process which was traditionally employed to separate TiO{sub 2} nanotubes from the metallic Ti substrate. The TiO{sub 2} nanotube arrays were constructed through potentiostatic anodization of Ti foil in aqueous electrolyte containing NH{sub 4}F and ethylene glycol. The nanotubes in the array were of 45 {mu}m lengths and 100 nm average pore diameters. The effect of NH{sub 4}F concentration on the length of the self-organized nanotube arrays was investigated. Electrochemical and spectroscopic measurements showed that the as-prepared nanotubes possessed large surface areas, good uniformity, and were ready for enzyme immobilization. The as-prepared nanotube arrays were amorphous, but crystallized with annealing at elevated temperatures, as demonstrated by X-ray diffraction (XRD).

  17. Corrosion of some chromium-nickel steels and alloys in sulfuric acid solutions of sodium sulfite

    SciTech Connect

    Kopeliovich, D.K.; Glagolenko, Yu.V.; Ermolinskii, S.P.

    1988-05-01

    Steels 12Kh18N1OT and 10Kh17N13M3T and alloys 06KhN28MDT and 46KhNM were studied in sulfuric acid solutions containing sodium sulfite and sulfur dioxide to determine the effects of different concentrations of the corrosive constituents on the anodic and cathodic active and passive corrosion behavior of the metals. Polarization curves were obtained with a P-5827 M potentiostat. Addition of sulfite facilitated both electrode processes and the region of the reactive state was broadened due to the shift of passivation potentials to more positive values. The activating effect of sulfite reduction products were confirmed by tests of alloys in spent solutions. This increased likelihood of activation and the decrease of the solutions's own corrosion potential were both attributed to retardation of the cathodic process by lower valence sulfur compounds.

  18. Corrosion characteristics of anodized Ti-(10-40wt%)Hf alloys for metallic biomaterials use.

    PubMed

    Jeong, Yong-Hoon; Choe, Han-Cheol; Brantley, William A

    2011-01-01

    The effect of anodizing on corrosion resistance of Ti-xHf alloys has been investigated. Ti-xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H(3)PO(4) solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the α' and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti-xHf alloys exhibited better corrosion resistance than non-anodized Ti-xHf alloys. PMID:21104193

  19. Tuning the characteristics of electrochemically fabricated gold nanowires.

    PubMed

    Karim, S; Ensinger, W; Cornelius, T W; Khan, E U; Neumann, R

    2008-11-01

    We have developed different electrochemical procedures for the production of gold nanowires with variable and controllable crystallographic and morphological properties using etched ion track templates. The texture of the nanowires is tuned by the variation of the electrodeposition parameters. Potentiostatic plating at low overvoltage provides strongly (110) textured wires for diameters below 100 nm. With the increase in diameter above 100 nm, this texture decreases and the signal from ({111} planes becomes more pronounced. Under reverse pulse deposition conditions, (100) textured wires are generated. The growth mechanism is discussed in detail in terms of the surface energy minimum principle. In addition, wires are shaped in a reliable way from cylindrical to conical geometry by engineering the pore structure in the template. PMID:19198285

  20. Sustainable Electrochemically-Mediated Atom Transfer Radical Polymerization with Inexpensive Non-Platinum Electrodes.

    PubMed

    Fantin, Marco; Lorandi, Francesca; Isse, Abdirisak A; Gennaro, Armando

    2016-08-01

    Electrochemically-mediated atom transfer radical polymerization (eATRP) of oligo(ethylene oxide) methyl ether methacrylate in water is investigated on glassy carbon, Au, Ti, Ni, NiCr and SS304. eATRPs are performed both in divided and undivided electrochemical cells operating under either potentiostatic or galvanostatic mode. The reaction is fast, reaching high conversions in ≈4 h, and yields polymers with dispersity <1.2 and molecular weights close to the theoretical values. Most importantly, eATRP in a highly simplified setup (undivided cell under galvanostatic mode) with inexpensive nonnoble metals, such as NiCr and SS304, as cathode is well-controlled. Additionally, these electrodes neither release harmful ions in solution nor react directly with the CX chain end and can be reused several times. It is demonstrated that Pt can be replaced with cheaper, and more readily available materials without negatively affecting eATRP performance. PMID:27333068

  1. Use of array of conducting polymers for differentiation of coconut oil products.

    PubMed

    Rañola, Rey Alfred G; Santiago, Karen S; Sevilla, Fortunato B

    2016-01-01

    An array of chemiresistors based on conducting polymers was assembled for the differentiation of coconut oil products. The chemiresistor sensors were fabricated through the potentiostatic electrodeposition of polyaniline (PANi), polypyrrole (PPy) and poly(3-methylthiophene) (P-3MTp) on the gap separating two planar gold electrodes set on a Teflon substrate. The change in electrical resistance of the sensors was measured and observed after exposing the array to the headspace of oil samples. The sensor response was found rapid, reversible and reproducible. Different signals were obtained for each coconut oil sample and pattern recognition techniques were employed for the analysis of the data. The developed system was able to distinguish virgin coconut oil (VCO) from refined, bleached & deodorised coconut oil (RBDCO), flavoured VCO, homemade VCO, and rancid VCO. PMID:26695237

  2. Dissolution of amorphous Ti-Zr-Si alloy during anodic oxidation with formation of barrier films

    SciTech Connect

    Isaev, N.I.; Yakovlev, V.B.; Iovdal'skii, A.A.; Gorshkov, T.P.

    1988-07-01

    Radiometric analysis of a solution has been used to study kinetic mechanisms for dissolution of amorphous alloy components in acid aqueous solutions with anodic oxidation in different regimes. In a galvanostatic regime for alloy and crystalline Ti, Zr, and Ta two sections are detected: an initial section of accelerated dissolution and a steady section. An increase in dissolution of zirconium from the alloy has been revealed compared with pure crystalline zirconium. Potentiostatic oxidation is accompanied by a slowdown in dissolution similar to a change in current. Current yield has been analyzed for dissolution of the main elements and nonrectifying impurities of the alloy (for example copper). Gamma spectroscopy using the gamma radiation from neutron-activated isotopes of the components and impurities was performed.

  3. Surface Morphology of Si(111) during Electrochemical Oxidation

    NASA Astrophysics Data System (ADS)

    Ando, A.; Miki, K.; Sakamoto, K.; Matsumoto, K.; Morita, Y.; Tokumoto, H.

    1997-03-01

    Topographical changes of hydrogen terminated Si(111) during electrochemical oxidation in a 0.2 M H_2SO4 aqueous solution have been investigated using atomic force microscopy (AFM). The hydrogen terminated surface with atomically flat terraces was prepared by dipping into a NH_4F aqueous solution. Electrochemical oxidation has been performed by a potentiostatic (constant potential) or a galvanostatic (constant current) method. AFM images show that the oxidation occured on the terraces and proceeded homogeneously. The surface became rough as the oxidation proceeded. However, step edges were still observed even after the charge of 50 mC/cm^2 was applied. Quantitative analysis of a relation between the charge and surface morphology will be discussed. the address below:

  4. Considerations on electrical impedance measurements of electrolyte solutions in a four-electrode cell

    NASA Astrophysics Data System (ADS)

    Chaparro, C. V.; Herrera, L. V.; Meléndez, A. M.; Miranda, D. A.

    2016-02-01

    A tetrapolar probe to measure the electrical properties of electrolyte solutions was implemented with gold electrodes according to the van der Pauw method. Electrical impedance spectroscopy (EIS) measurements of different concentrations of phosphate buffer saline (PBS) solution and an oral mucosal tissue sample dispersed in PBS were performed in the galvanostatic mode using a four-electrode cell (tetrapolar probe). Taking advantage of using a potentiostat/galvanostat for carrying out the electrical measurements, a simple and rapid method using a three-electrode electrochemical cell is described for: a) cleaning of electrodes, b) verification of surface chemical state of electrode material and c) choice of current supplied to electrodes for EIS measurements. Results of this research shown a depolarization effect due to the addition of oral mucosa tissue cells into the PBS solution.

  5. Electrochemical Behavior of CrN Coated on 316L Stainless Steel in Simulated Cathodic Environment of Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Nam, Nguyen Dang; Kim, Jung-Gu

    2008-08-01

    Four types of CrN coating were deposited on type 316L stainless steel by magnetron sputtering physical vapor deposition (PVD) for use in bipolar plates. Four samples deposited at various bias voltages were evaluated under potentiodynamic, potentiostatic, and electrochemical impedance spectroscopy (EIS) conditions. EIS data were monitored for 96 h in an aerated corrosive environment at 70 °C to determine coating performance at +600 mV application. The electrochemical behavior of the coatings was enhanced with decreasing bias voltage. The CrN films on the 316L stainless steel substrate exhibited high protective efficiency, that is, increasing corrosion resistance with decreasing bias voltage. X-ray diffraction (XRD) analysis confirmed the formation of crystalline-refined CrN(200) at a low bias voltage.

  6. Redox mechanism in the binary transition metal phosphide Cu3P

    NASA Astrophysics Data System (ADS)

    Mauvernay, B.; Doublet, M.-L.; Monconduit, L.

    2006-05-01

    The electrochemical behaviour of the binary transition metal phosphide Cu3P towards lithium is investigated through galvano- and potentiostatic measurements. Obtained through high-temperature synthesis, this system shows a better volumetric capacity than graphite and a good capacity retention. In situ X-ray diffraction and first-principles electronic structure calculations are combined with the electrochemical results to show that the complete insertion of 3Li+ in the Cu3P electrode proceeds with the formation of three intermediate phases of lithium composition LixCu(3-x)P (x=1,2,3). The extra capacity previously observed in discharge is now clearly assigned to lithium insertion into the CuP2 impurity and to SEI reactions.

  7. One-step through-mask electrodeposition of a porous structure composed of manganese oxide nanosheets with electrocatalytic activity for oxygen reduction

    SciTech Connect

    Fukuda, Masaki; Iida, Chihiro; Nakayama, Masaharu

    2009-06-03

    Potentiostatic electrolysis of a mixed aqueous solution of Bu{sub 4}NBr and MnSO{sub 4} at +1.0 V (vs. Ag/AgCl) on Pt electrode led to the oxidation of Br{sup -} and Mn{sup 2+} ions. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD) revealed that this anodic process was followed by the deposition of insulating crystals of bromide salt of Bu{sub 4}N{sup +} and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals in water left a well-dispersed porous texture composed of manganese oxide nanosheets. The resulting MnO{sub x}-modified electrode exhibited a larger catalytic current for the reduction of oxygen in alkaline solution, compared to the bare Pt electrode.

  8. A portable hypergolic oxidizer vapor sensor for NASA's Space Shuttle program

    NASA Technical Reports Server (NTRS)

    Helms, W. R.

    1978-01-01

    The design and performance characteristics of an electrochemical NO2 sensor selected by NASA for the space shuttle program is described. The instrument consists of a sample pump, an electrochemical cell, and control and display electronics. The pump pushes the sample through the electrochemical cell where the vapors are analyzed and an output proportional to the NO2 concentration is produced. The output is displayed on a panel meter, and is also available at a recorder jack. The electrochemical cell is made up of a polypropylene chamber covered with teflon membrane faceplates. Plantinum electrodes are bonded to the faceplates, and the sensing and counter electrodes are potentiostatically controlled at -200 mV with respect to the reference electrode. The cell is filled with electrolyte, consisting of 13.5 cc of 23% solution of KOH.

  9. Engineering PQS Biosynthesis Pathway for Enhancement of Bioelectricity Production in Pseudomonas aeruginosa Microbial Fuel Cells

    PubMed Central

    Cao, Bin; Seviour, Thomas; Nesatyy, Victor J.; Marsili, Enrico; Kjelleberg, Staffan; Givskov, Michael; Tolker-Nielsen, Tim; Song, Hao; Loo, Joachim Say Chye; Yang, Liang

    2013-01-01

    The biosynthesis of the redox shuttle, phenazines, in Pseudomonas aeruginosa, an ubiquitous microorganism in wastewater microflora, is regulated by the 2-heptyl-3,4-dihydroxyquinoline (PQS) quorum-sensing system. However, PQS inhibits anaerobic growth of P. aeruginosa. We constructed a P. aeruginosa strain that produces higher concentrations of phenazines under anaerobic conditions by over-expressing the PqsE effector in a PQS negative ΔpqsC mutant. The engineered strain exhibited an improved electrical performance in microbial fuel cells (MFCs) and potentiostat-controlled electrochemical cells with an approximate five-fold increase of maximum current density relative to the parent strain. Electrochemical analysis showed that the current increase correlates with an over-synthesis of phenazines. These results therefore demonstrate that targeting microbial cell-to-cell communication by genetic engineering is a suitable technique to improve power output of bioelectrochemical systems. PMID:23700414

  10. Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production.

    PubMed

    Gwak, Jieun; Choun, Myounghoon; Lee, Jaeyoung

    2016-02-19

    Ammonia is beginning to attract a great deal of attention as an alternative energy source carrier, because clean hydrogen can be produced through electrolytic processes without the emission of COx . In this study, we deposited various shapes of Pt catalysts under potentiostatic mode; the electrocatalytic oxidation behavior of ammonia using these catalysts was studied in alkaline media. The electrodeposited Pt was characterized by both qualitative and quantitative analysis. To discover the optimal structure and the effect of ammonia concentration, the bulk pH value, reaction temperature, and applied current of ammonia oxidation were investigated using potential sweep and galvanostatic methods. Finally, ammonia electrolysis was conducted using a zero-gap cell, producing highly pure hydrogen with an energy efficiency over 80 %. PMID:26530809

  11. Motion-driven electrochromic reactions for self-powered smart window system.

    PubMed

    Yeh, Min-Hsin; Lin, Long; Yang, Po-Kang; Wang, Zhong Lin

    2015-05-26

    The self-powered system is a promising concept for wireless networks due to its independent and sustainable operations without an external power source. To realize this idea, the triboelectric nanogenerator (TENG) was recently invented, which can effectively convert ambient mechanical energy into electricity to power up portable electronics. In this work, a self-powered smart window system was realized through integrating an electrochromic device (ECD) with a transparent TENG driven by blowing wind and raindrops. Driven by the sustainable output of the TENG, the optical properties, especially the transmittance of the ECD, display reversible variations due to electrochemical redox reactions. The maximum transmittance change at 695 nm can be reached up to 32.4%, which is comparable to that operated by a conventional electrochemical potentiostat (32.6%). This research is a substantial advancement toward the practical application of nanogenerators and self-powered systems. PMID:25808880

  12. A straightforward implementation of in situ solution electrochemical ¹³C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid. PMID:25868425

  13. A microfluidic paper-based electrochemical biosensor array for multiplexed detection of metabolic biomarkers

    NASA Astrophysics Data System (ADS)

    Zhao, Chen; Thuo, Martin M.; Liu, Xinyu

    2013-10-01

    Paper-based microfluidic devices have emerged as simple yet powerful platforms for performing low-cost analytical tests. This paper reports a microfluidic paper-based electrochemical biosensor array for multiplexed detection of physiologically relevant metabolic biomarkers. Different from existing paper-based electrochemical devices, our device includes an array of eight electrochemical sensors and utilizes a handheld custom-made electrochemical reader (potentiostat) for signal readout. The biosensor array can detect several analytes in a sample solution and produce multiple measurements for each analyte from a single run. Using the device, we demonstrate simultaneous detection of glucose, lactate and uric acid in urine, with analytical performance comparable to that of the existing commercial and paper-based platforms. The paper-based biosensor array and its electrochemical reader will enable the acquisition of high-density, statistically meaningful diagnostic information at the point of care in a rapid and cost-efficient way.

  14. Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy

    SciTech Connect

    Schwanke, C.; Lange, K. M.; Golnak, R.; Xiao, J.

    2014-10-15

    A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl{sub 2} aqueous solution by X-ray absorption and emission spectroscopy is presented.

  15. Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

    PubMed

    Taleatu, B A; Arbab, E A A; Omotoso, E; Mola, G T

    2014-10-01

    Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot. PMID:25088932

  16. Corrosion behavior of PIRAC nitrided Ti-6Al-4V surgical alloy.

    PubMed

    Starosvetsky, D; Shenhar, A; Gotman, I

    2001-02-01

    Hard titanium nitride (TiN) coatings were obtained on the surface of Ti-6Al-4V alloy using an original PIRAC nitriding method, based on annealing the samples under a low pressure of monatomic nitrogen created by selective diffusion of N from the atmosphere. PIRAC nitrided samples exhibited excellent corrosion resistance in Ringer's solution in both potentiodynamic and potentiostatic tests. The anodic current and metal ion release rate of PIRAC nitrided Ti-6Al-4V at the typical corrosion potential values were significantly lower than those of the untreated alloy. This, together with the excellent adhesion and high wear resistance of the TiN coatings, makes PIRAC nitriding an attractive surface treatment for Ti-6Al-4V alloy surgical implants. PMID:15348321

  17. Enhanced removal of 8-quinolinecarboxylic acid in an activated carbon cloth by electroadsorption in aqueous solution.

    PubMed

    López-Bernabeu, S; Ruiz-Rosas, R; Quijada, C; Montilla, F; Morallón, E

    2016-02-01

    The effect of the electrochemical treatment (potentiostatic treatment in a filter-press electrochemical cell) on the adsorption capacity of an activated carbon cloth (ACC) was analyzed in relation with the removal of 8-quinolinecarboxylic acid pollutant from water. The adsorption capacity of an ACC is quantitatively improved in the presence of an electric field (electroadsorption process) reaching values of 96% in comparison to 55% in absence of applied potential. In addition, the cathodic treatment results in higher removal efficiencies than the anodic treatment. The enhanced adsorption capacity has been proved to be irreversible, since the removed compound remains adsorbed after switching the applied potential. The kinetics of the adsorption processes is also improved by the presence of an applied potential. PMID:26433936

  18. Synthesis and thermoelectric/electrical characterization of electrodeposited Sb{sub x}Te{sub y} thin films

    SciTech Connect

    Lim, Jae-Hong; Park, MiYeong; Lim, Dong-Chan; Myung, Nosang V.; Lee, Jung-Ho; Jeong, Young-Keun; Yoo, Bongyoung; Lee, Kyu Hwan

    2012-10-15

    Sb{sub x}Te{sub y} films were potentiostatically electrodeposited from acidic nitric baths at room temperature by controlling the applied potential. Near-stoichiometric Sb{sub 2}Te{sub 3} thin films were obtained at applied potentials between −0.15 and −0.30 V vs. saturated calomel electrode (SCE). Post-annealing in a reducing environment resulted in an improvement in the crystal structure without the evaporation of the Te element. This result was indicated by a significant reduction in the electrical resistance and decrease in the FWHM of the main diffraction peaks. The power factor (σS{sup 2}) increased from 44.2 to 372.1 μW/m K{sup 2} after annealing at 473 K.

  19. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  20. An ultrasensitive electrochemical genosensor for Brucella based on palladium nanoparticles.

    PubMed

    Rahi, A; Sattarahmady, N; Heli, H

    2016-10-01

    Palladium nanoparticles were potentiostatically electrodeposited on a gold surface at a highly negative potential. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and the process of immobilization and hybridization was detected by electrochemical methods. The proposed method for detection of the complementary sequence and a non-complementary sequence was applied. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples with and without PCR. The genosensor could detect the complementary sequence with a sensitivity of 0.02 μA dm(3) mol(-1), a linear concentration range of 1.0 × 10(-12) to 1.0 × 10(-19) mol dm(-3), and a detection limit of 2.7 × 10(-20) mol dm(-3). PMID:27423961

  1. The alkaline zinc electrode as a mixed potential system

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.

    1979-01-01

    Cathodic and anodic processes for the alkaline zinc electrode in 0.01 molar zincate electrolyte (9 molar hydroxide) were investigated. Cyclic voltammograms and current-voltage curves were obtained by supplying pulses through a potentiostat to a zinc rotating disk electrode. The data are interpreted by treating the system as one with a mixed potential; the processes are termed The zincate and corrosion reactions. The relative proportions of the two processes vary with the supplied potential. For the cathodic region, the cathodic corrosion process predominates at higher potentials while both processes occur simultaneously at a lower potential (i.e., 50 mV). For the anodic region, the anodic zincate process predominates at higher potentials while the anodic corrosion process is dominant at lower potential (i.e., 50 mV) if H2 is present.

  2. Microfluidic in-channel multi-electrode platform for neurotransmitter sensing

    NASA Astrophysics Data System (ADS)

    Kara, A.; Mathault, J.; Reitz, A.; Boisvert, M.; Tessier, F.; Greener, J.; Miled, A.

    2016-03-01

    In this project we present a microfluidic platform with in-channel micro-electrodes for in situ screening of bio/chemical samples through a lab-on-chip system. We used a novel method to incorporate electrochemical sensors array (16x20) connected to a PCB, which opens the way for imaging applications. A 200 μm height microfluidic channel was bonded to electrochemical sensors. The micro-channel contains 3 inlets used to introduce phosphate buffer saline (PBS), ferrocynide and neurotransmitters. The flow rate was controlled through automated micro-pumps. A multiplexer was used to scan electrodes and perform individual cyclic voltammograms by a custom potentiostat. The behavior of the system was linear in terms of variation of current versus concentration. It was used to detect the neurotransmitters serotonin, dopamine and glutamate.

  3. Hydrogen storage materials, batteries, and electrochemistry; Proceedings of the Symposium, Phoenix, AZ, Oct. 14-17, 1991

    SciTech Connect

    Corrigan, D.A.; Srinivasan, S.

    1992-01-01

    Various papers on hydrogen storage materials, batteries, and electrode chemistry are presented. Individual topics addressed include: development of hydrogen-absorbing alloys for nickel metal hydride secondary batteries, capacity retention in hydrogen storage alloys, sealed metal-hydride batteries for aerospace applications, nickel-hydrogen battery self-discharge mechanism and methods for its inhibition, studies on the self-discharge mechanism of Ni/H2 cells. Also discussed are: characterization of IPV nickel electrodes by means of an integrated cycling and electrochemical impedance spectroscopy technique, characterization of IPV nickel electrodes by means of an integrated electrochemical impedance spectroscopy technique, low cost electrocatalytic gas diffusion membrane electrodes of metal-hydrogen batteries, potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries.

  4. Electrodeposition of Zn and Zn-Mn alloy coatings from an electrolytic bath prepared by recovery of exhausted zinc-carbon batteries

    NASA Astrophysics Data System (ADS)

    da Silva, Paulo Sérgio; Schmitz, Edinéia P. Sartori; Spinelli, Almir; Garcia, Jarem Raul

    2012-07-01

    The electrodeposition of galvanic coatings was performed using a chloride-based acidic electrolytic bath containing polyethylene glycol (PEG) as an additive. The electrolytic bath was prepared using Zn and Mn recovered from exhausted zinc-carbon batteries by means of acid leaching with HCl. The coatings were obtained potentiostatically at -1.2 V and -1.6 V (vs. Ag/AgCl) and galvanostatically with a current density of -10 mA cm-2. The results indicated that the presence of PEG in the bath during galvanostatic deposition favored the formation of a coating containing a mixture of Zn and Zn-Mn alloy with an Mn content of around 2 wt%.

  5. Pharmacokinetic study of medicinal polymers: models based on dextrans

    SciTech Connect

    Kulakov, V.N.; Pimenova, G.N.; Matveev, V.A.; Sedov, V.V.; Vasil'ev, A.E.

    1986-09-01

    The authors study the pharmacokinetics of dextrans with various molecular masses modified by fluorescein isothiocyanate (FITC) using a radioisotope method. The radionuclide /sup 125/I was selectively bound to a FITC residue attached to the polysaccharide by electrochemical iodination under potentiostatic conditions. In the experiments, dextrans modified by FITC were labeled with /sup 125/I (DF-/sup 125/I) by electrochemical iodination. The separation of DF-/sup 125/I and FITC from ionic forms of the radionuclide not bound to the polymer was carried out. The properties of the samples obtained are presented. The radioactivity accumulated in the rate organs and urine studied are shown. The features of DF-/sup 125/I behavior in the blood and liver are examined.

  6. The effect of deposition electrolyte on polypyrrole surface interaction with biological environment

    NASA Astrophysics Data System (ADS)

    Mîndroiu, Mihaela; Ungureanu, Camelia; Ion, Raluca; Pîrvu, Cristian

    2013-07-01

    The effects of electrolyte type used in electrodeposition of polypyrrole (PPy) films on Ti6Al7Nb alloy was studied in order to design a titanium modified surface with enhanced antibacterial activity and better biocompatibility. Therefore, the polypyrrole coatings were synthesized by potentiostatic electrochemically technique from pyrrole and lithium perchlorate (LiClO4) using aqueous and non-aqueous solutions. The both PPy films were characterized by electrochemical methods in Hank's Balanced Salt Solution (HBSS), and surface characterization by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) analysis, adhesion test and contact angle measurements. A correlation between the film stability and surface properties, synthesis parameters and the interaction with biological environment was established. The physical-chemical properties of the studied PPy films are in direct related with the doping level and have an important influence of the biocompatibility and antibacterial activity.

  7. Inhibition of mild steel corrosion by sodium dodecyl benzene sulfonate and sodium oleate in acidic solutions

    SciTech Connect

    Luo, H.; Han, K.N.; Guan, Y.C.

    1998-08-01

    Inhibition of mild steel corrosion by sodium dodecyl benzene sulfonate (C{sub 12}H{sub 25}C{sub 6}H{sub 4}SO{sub 3}Na [SDBS]) and sodium oleate (CH{sub 3}[CH{sub 2}]{sub 7}CH{double_bond}CH[CH{sub 2}]{sub 7}COONa) in acidic solutions was investigated using a potentiostat, a lock-in amplifier, a contact angle goniometer, A fourier transform infrared (FTIR) spectrometer, and an ultraviolet (UV)/visible spectrophotometer. In the presence of the organic inhibitors, the corrosion rate was reduced significantly, Anionic SDBS was adsorbed on the positively charged mild steel surface through the electrostatic attraction. However, for sodium oleate, the soluble oleic acid (CH{sub 3}[CH{sub 2}]{sub 7}CH{double_bond}CH[CH]{sub 7}COOH) chemisorbed on the steel surface at the first stage. Then, insoluble colloid adsorbed on the chemisorbed surface through van der Waals forces.

  8. Critical phenomena in magnetic nanowires.

    PubMed

    Kamalakar, M Venkata; Raychaudhuri, A K

    2009-09-01

    In this paper we report the first experimental study of critical phenomena in case of magnetic nanowires of nickel near the ferromagnetic-paramagnetic transition from the electrical transport properties. Nickel nanowire arrays, prepared by potentiostatic electrodeposition of nickel inside pores of nanoporous anodic alumina template were well characterized by X-ray Diffraction, Transmission electron microscopy and Energy dispersive Spectroscopy. Precise electrical resistance measurement of the nanowire arrays of wire diameter 20 nm have been done in the temperature range between 300 K to 700 K. We see a drop in the Curie temperature as observed from the resistivity anomaly. We analyzed the resistance data near the critical region and extracted the critical exponent alpha directly from the resistance. We observed a decrease in the critical part of the resistivity including a decrease in the magnitude of the critical exponent alpha and severe modification in the correction to scaling. PMID:19928208

  9. Modeling and analysis of a molten salt electrowinning system with liquid cadmium cathode

    SciTech Connect

    Kim, K.R.; Ahn, D.H.; Paek, S.; Kwon, S.W.; Kim, S.H.; Shim, J.B.; Chung, H.; Kim, E.H.

    2007-07-01

    In the present work, an electrowinning process in the LiCl-KCl/Cd system is considered to model and analyze the equilibrium behavior and electro-transport of the actinide and rare-earth elements. Equilibrium distributions of the actinide and rare-earth elements in a molten salt and liquid cadmium system have been estimated for an infinite potentiostatic electrolysis from the thermodynamic data and material balance. A simple dynamic modeling of this process was performed by taking into account the material balances and diffusion-controlled electrochemical reactions in a diffusion layer at an electrode interface between the molten salt and liquid cadmium cathode. This model demonstrated a prediction of the concentration behaviors, a faradic current of each element and an electrochemical potential as function of the time up to the corresponding electro-transport satisfying a given applied current based on a galvano-static electrolysis. (authors)

  10. SnO2-Based Gas (Methane) Anodes for Electrowinning of Aluminum

    NASA Astrophysics Data System (ADS)

    Xiao, S.; Mokkelbost, T.; Paulsen, O.; Ratvik, A. P.; Haarberg, Geir Martin

    2013-10-01

    SnO2-based and carbon-based gas anodes were studied in molten Na3AlF6-AlF3-Al2O3 at 1123 K (850 °C) for aluminum electrolysis. Methane was introduced to the porous anodes to take part in a three-phase (anode/electrolyte/methane) boundary reaction. Carbon was used as the cathode. It was observed that the anode potential was reduced by 0.6 V and that the current was increased up to three times in galvanostatic and potentiostatic tests after the introduction of methane on SnO2-based anodes. A measurable depolarization effect and lower consumption of carbon after the introduction of methane on carbon anodes were also demonstrated.

  11. Development of sulfur-tolerant components for the molten carbonate fuel cell

    NASA Astrophysics Data System (ADS)

    Sammells, A. F.; Nicholson, S. B.; Ang, P. G. P.

    1980-02-01

    The sulfur tolerance of candidate anode and anode current collector materials for the molten carbonate fuel cell were evaluated in an electrochemical half-cell using both steady-state and transient potentiostatic techniques. Hydrogen sulfide was introduced into the fuel at concentrations of 50 and 1000 ppm; at the higher sulfur concentration nickel and cobalt underwent a negative shift in their open-circuit potentials, and high anodic and cathodic currents were observed compared with clean fuels. Exchange currents were not greatly affected by 50 ppm H2S; but, at higher sulfur concentrations, higher apparent exchange currents were observed, indicating a probable sulfidation reaction. New anode materials including TiC showed good stability in the anodic region. Of the anode current collector materials evaluated, high stabilities were found for 410 and 310 stainless steels.

  12. Use of cyclic current reversal polarization voltammetry for investigating the relationship between corrosion resistance and heat-treatment induced variations in microstructures of 400 C martensitic stainless steels

    NASA Technical Reports Server (NTRS)

    Ambrose, John R.

    1992-01-01

    Software for running a cyclic current reversal polarization voltammagram has been developed for use with a EG&G Princeton Applied Research Model 273 potentiostat/galvanostat system. The program, which controls the magnitude, direction and duration of an impressed galvanostatic current, will produce data in ASCII spreadsheets (Lotus, Quattro) for graphical representation of CCRPV voltammograms. The program was used to determine differences in corrosion resistance of 440 C martenstic stainless steel produced as a result of changes in microstructure effected by tempering. It was determined that tempering at all temperatures above 400 F resulted in increased polarizability of the material, with the increased likelihood that pitting would be initiated upon exposure to marine environments. These results will be used in development of remedial procedures for lowering the susceptibility of these alloys toward the stress corrosion cracking experienced in bearings used in high pressure oxygen turbopumps used in the main engines of space shuttle orbiters.

  13. Synthesis of mesoporous nanocomposites for their application in solid oxide electrolysers cells: microstructural and electrochemical characterization.

    PubMed

    Torrell, M; Almar, L; Morata, A; Tarancón, A

    2015-01-01

    Fabrication routes for new SOEC mesoporous nanocomposite materials as electrodes are presented in this paper. NiO-CGO and SDC-SSC are described as possible new materials and their synthesis and the cell fabrication are discussed. The obtained materials are microstructurally characterised by SEM, TEM and XRD, where the mesoporous structures are observed and analysed. The obtained samples are electrochemically analysed by I-V polarisation curves and EIS analysis, showing a maximum current density of 330 mA cm(-2) at 1.7 V. A degradation of the cell performance is evidenced after a potentiostatic test at 1.4 V after more than 40 hours. Oxygen electrode delaminating is detected, which is most probably the main cause of ageing. Even taking into account the lack of durability of the fabricated cells, the mesoporous electrodes do not seem to be altered, opening the possibility for further studies devoted to this high stability material for SOEC electrodes. PMID:26212761

  14. Reproducible and recyclable SERS substrates: Flower-like Ag structures with concave surfaces formed by electrodeposition

    NASA Astrophysics Data System (ADS)

    Bian, Juncao; Shu, Shiwei; Li, Jianfu; Huang, Chao; Li, Yang Yang; Zhang, Rui-Qin

    2015-04-01

    Direct synthesis of three-dimensional Ag structures on solid substrates for the purposes of producing reproducible and recyclable surface-enhanced Raman scattering (SERS) applications remains challenging. In this work, flower-like Ag structures with concave surfaces (FACS) were successfully electrodeposited onto ITO glass using the double-potentiostatic method. The FACS, with an enhancement factor of the order of 108, exhibited a SERS signal intensity 3.3 times stronger than that measured from Ag nanostructures without concave surfaces. A cleaning procedure involving lengthy immersion of the sample in ethanol and KNO3 was proposed to recycle the substrate and confirmed by using rhodamine 6G, adenine, and 4-aminothiophenol as target molecules. The findings can help to advance the practical applications of Ag nanostructure-based SERS substrates.

  15. Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy.

    PubMed

    Kollender, Jan Philipp; Gasiorowski, Jacek; Sariciftci, Niyazi S; Mardare, Andrei I; Hassel, Achim Walter

    2014-07-31

    A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations. PMID:25101149

  16. Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy

    PubMed Central

    2014-01-01

    A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations. PMID:25101149

  17. Corrosion of stainless steel, nickel-titanium, coated nickel-titanium, and titanium orthodontic wires.

    PubMed

    Kim, H; Johnson, J W

    1999-02-01

    Orthodontic wires containing nickel have been implicated in allergic reactions. The potential for orthodontic wires to cause allergic reactions is related to the pattern and mode of corrosion with subsequent release of metal ions, such as nickel, into the oral cavity. The purpose of this study was to determine if there is a significant difference in the corrosive potential of stainless steel, nickel titanium, nitride-coated nickel titanium, epoxy-coated nickel titanium, and titanium orthodontic wires. At least two specimens of each wire were subjected to potentiostatic anodic dissolution in 0.9% NaCl solution with neutral pH at room temperature. Using a Wenking MP 95 potentiostat and an electrochemical corrosion cell, the breakdown potential of each wire was determined. Photographs were taken of the wire speci mens using a scanning electron microscope, and surface changes were qualitatively evaluated. The breakdown potentials of stainless steel, two nickel titanium wires, nitride-coated nickel titanium, epoxy-coated nickel titanium, and titanium were 400 mV, 300 mV, 750 mV, 300 mV, 1800 mV, and >2000 mV, respectively. SEM photographs revealed that some nickel titanium and stainless steel wires were susceptible to pitting and localized corrosion. The results indicate that corrosion occurred readily in stainless steel. Variability in breakdown potential of nickel titanium alloy wires differed across vendors' wires. The nitride coating did not affect the corrosion of the alloy, but epoxy coating decreased corrosion. Titanium wires and epoxy-coated nickel titanium wires exhibited the least corrosive potential. For patients allergic to nickel, the use of titanium or epoxy-coated wires during orthodontic treatment is recommended. PMID:10022183

  18. Electrochemically and bioelectrochemically induced ammonium recovery.

    PubMed

    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

  19. Analysis of electrochemical noise from metastable pitting in aluminum, aged Al-2%Cu, and AA 2024-T3

    SciTech Connect

    Pride, S.T.; Scully, J.R.; Hudson, J.L.

    1996-12-31

    The authors compare methods of analyzing electrochemical current (ECN) and potential (EPN) noise data associated with metastable pitting and the transition from metastable to stable pitting. Various analysis methods were applied to electrochemical noise data associated with metastable pit events on aluminum, aged Al-2%Cu, and AA 2024-T3 ST. Two experimental approaches were used. High-purity Al, roughly simulating copper-depleted grain boundary zones in aged Al-Cu alloys, was potentiostatically polarized so that current spikes associated with individual pitting events could be analyzed. Second, the coupling current between nominally identical galvanically coupled Al, aged Al-2%Cu, and AA 2024-T3 ST electrodes was recorded in conjunction with couple potential using a saturated calomel reference electrode. Pit stabilization occurred when individual pits exceeded a threshold of I{sub pit}/r{sub pit} > 10{sup {minus}2} A/cm at all times during pit growth as established from potentiostatic measurements. The magnitude of this ratio is linked directly to the concentration of the aggressive solution within pits. Two related statistical pit stabilization factors (I{sub rms}/r{sub pit total} from ECN data and the mean of (I{sub peak}-I{sub ox})/r{sub pit} values from each pit current spike) were obtained from galvanic ECN data containing a large number of pit current spikes. These parameters provided a better indication of the transition to stable pitting than the pitting index or noise resistance but also had shortcomings. Spectral analysis using current and potential spectral power density (SPD) data provided qualitative information on pit susceptibility. However, the transition to stable pitting could not be accurately defined because of a lack of information on pit sizes in spectral data.

  20. Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

    SciTech Connect

    Farmer, J C

    2003-04-15

    DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption in crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with

  1. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces

    SciTech Connect

    Gross, Benjamin J.; El-Naggar, Mohamed Y.

    2015-06-15

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions.

  2. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces

    NASA Astrophysics Data System (ADS)

    Gross, Benjamin J.; El-Naggar, Mohamed Y.

    2015-06-01

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions.

  3. Real-time telemetry system for amperometric and potentiometric electrochemical sensors.

    PubMed

    Wang, Wei-Song; Huang, Hong-Yi; Chen, Shu-Chun; Ho, Kuo-Chuan; Lin, Chia-Yu; Chou, Tse-Chuan; Hu, Chih-Hsien; Wang, Wen-Fong; Wu, Cheng-Feng; Luo, Ching-Hsing

    2011-01-01

    A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC), a microcontroller unit (MCU), a graphical user interface (GUI), and a radio frequency (RF) transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA) to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA). The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR) greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment), a small size of 5.6 cm × 8.7 cm, high portability, and high integration. PMID:22164093

  4. Enhanced performance of hexavalent chromium reducing cathodes in the presence of Shewanella oneidensis MR-1 and lactate.

    PubMed

    Xafenias, Nikolaos; Zhang, Yue; Banks, Charles J

    2013-05-01

    Biocathodes for the reduction of the highly toxic hexavalent chromium (Cr(VI)) were investigated using Shewanella oneidensis MR-1 (MR-1) as a biocatalyst and performance was assessed in terms of current production and Cr(VI) reduction. Potentiostatically controlled experiments (-500 mV vs Ag/AgCl) showed that a mediatorless MR-1 biocathode started up under aerated conditions in the presence of lactate, received 5.5 and 1.7 times more electrons for Cr(VI) reduction over a 4 h operating period than controls without lactate and with lactate but without MR-1, respectively. Cr(VI) reduction was also enhanced, with a decrease in concentration over the 4 h operating period of 9 mg/L Cr(VI), compared to only 1 and 3 mg/L, respectively, in the controls. Riboflavin, an electron shuttle mediator naturally produced by MR-1, was also found to have a positive impact in potentiostatically controlled cathodes. Additionally, a microbial fuel cell (MFC) with MR-1 and lactate present in both anode and cathode produced a maximum current density of 32.5 mA/m(2) (1000 Ω external load) after receiving a 10 mg/L Cr(VI) addition in the cathode, and cathodic efficiency increased steadily over an 8 day operation period with successive Cr(VI) additions. In conclusion, effective and continuous Cr(VI) reduction with associated current production were achieved when MR-1 and lactate were both present in the biocathodes. PMID:23517384

  5. Improved lithium storage properties of electrospun TiO2 with tunable morphology: from porous anatase to necklace rutile

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Wang, Haiying; Zhou, Qiwen; Kong, Mengqi; Ye, Haitao; Yang, Gang

    2013-10-01

    Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 °C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance.Three-dimensional TiO2 with tunable morphology and crystalline phase was successfully prepared by the electrospinning technique and subsequent annealing. Porous-shaped anatase TiO2, cluster-shaped anatase TiO2, hierarchical-shaped rutile (minor) TiO2 and nano-necklace rutile (major) TiO2 were achieved at 500, 600, 700 and 800 °C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Lithium insertion properties were evaluated by galvanostatic and potentiostatic modes in half-cell configurations. By combining the large surface area, open mesoporosity and stable crystalline phase, the porous-shaped anatase TiO2 exhibited the highest capacity, best rate and cycling performance among the four samples. The present results demonstrated the usefulness of three-dimensional TiO2 as an anode for lithium storage with improved electrode performance. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02819d

  6. Nanopore formation on the surface oxide of commercially pure titanium grade 4 using a pulsed anodization method in sulfuric acid.

    PubMed

    Williamson, R S; Disegi, J; Griggs, J A; Roach, M D

    2013-10-01

    Titanium and its alloys form a thin amorphous protective surface oxide when exposed to an oxygen environment. The properties of this oxide layer are thought to be responsible for titanium and its alloys biocompatibility, chemical inertness, and corrosion resistance. Surface oxide crystallinity and pore size are regarded to be two of the more important properties in establishing successful osseointegration. Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Research on titanium anodization using sulphuric acid has been reported in the literature as being primarily conducted in molarity levels 3 M and less using either galvanostatic or potentiostatic methods. A wide range of pore diameters ranging from a few nanometers up to 10 μm have been shown to form in sulfuric acid electrolytes using the potentiostatic and galvanostatic methods. Nano sized pores have been shown to be beneficial for bone cell attachment and proliferation. The purpose of the present research was to investigate oxide crystallinity and pore formation during titanium anodization using a pulsed DC waveform in a series of sulfuric acid electrolytes ranging from 0.5 to 12 M. Anodizing titanium in increasing sulfuric acid molarities showed a trend of increasing transformations of the amorphous natural forming oxide to the crystalline phases of anatase and rutile. The pulsed DC waveform was shown to produce pores with a size range from ≤0.01 to 1 μm(2). The pore size distributions produced may be beneficial for bone cell attachment and proliferation. PMID:23807314

  7. Statistic analysis of operational influences on the cold start behaviour of PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Oszcipok, M.; Riemann, D.; Kronenwett, U.; Kreideweis, M.; Zedda, M.

    For portable fuel cell systems a multitude of applications have been presented over the past few years. Most of these applications were developed for indoor use, and not optimised for outdoor conditions. The key problem concerning this case is the cold start ability of the polymer electrolyte membrane fuel cell (PEMFC). This topic was first investigated by the automotive industry, which has the same requirements for alternative traction systems as for conventional combustion engines. The technical challenge is the fact that produced water freezes to ice after shut-down of the PEMFC and during start-up when the temperature is below 0 °C. To investigate the basic cold start behaviour isothermal, potentiostatic single cell experiments were performed and the results are presented. The cold start behaviour is evaluated using the calculated cumulated charge transfer through the membrane which directly corresponds with the amount of produced water in the PEMFC. The charge transfer curves were mathematically fitted to obtain only three parameters describing the cold start-up with the cumulated charge transfer density and the results are analysed using the statistical software Cornerstone 4.0. The results of the statistic regression analyses are used to establish a statistic-based prediction model of the cold start behaviour which describes the behaviour of the current density during the experiment. The regression shows that the initial start current mainly depends on the membrane humidity and the operation voltage. After the membrane humidity has reached its maximum, the current density drops down to zero. The current decay also depends on the constant gas flows of the reactant gases. Ionic conductivity of the membrane and charge transfer resistance were investigated by a series of ac impedance spectra during potentiostatic operation of the single cell at freezing temperatures. Cyclic voltammetry and polarisation curves between cold start experiments show degradation

  8. Silver(I) Ions Ultrasensitive Detection at Carbon Electrodes—Analysis of Waters, Tobacco Cells and Fish Tissues

    PubMed Central

    Krizkova, Sona; Krystofova, Olga; Trnkova, Libuse; Hubalek, Jaromir; Adam, Vojtech; Beklova, Miroslava; Horna, Ales; Havel, Ladislav; Kizek, Rene

    2009-01-01

    We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 μM. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 mL) or carbon pencil was used. Limits of detection estimated by dilution of a standard were 1 (carbon tip) or 10 nM (carbon pencil). Further we employed flow injection analysis coupled with carbon tip to detect silver(I) ions released in various beverages and mineral waters. During first, second and third week the amount of silver(I) ions releasing into water samples was under the detection limit of the technique used for their quantification. At the end of a thirteen weeks long experiment the content of silver(I) ions was several times higher compared to the beginning of release detected in the third week and was on the order of tens of nanomoles. In subsequent experiments the influence of silver(I) ions (0, 5 and 10 μM) on a plant model system (tobacco BY-2 cells) during a four-day exposition was investigated. Silver(I) ions were highly toxic to the cells, which was revealed by a double staining viability assay. Moreover we investigated the effect of silver(I) ions (0, 0.3, 0.6, 1.2 and 2.5 μM) on guppies (Poecilia reticulata). Content of Ag(I) increased with increasing time of the treatment and applied concentrations in fish tissues. It can be concluded that a carbon tip or carbon pencil coupled with a miniaturized potentiostat can be used for detection of silver(I) ions in environmental samples and thus represents a small, portable, low cost and easy-to-use instrument for such purposes. PMID:22399980

  9. A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces.

    PubMed

    Gross, Benjamin J; El-Naggar, Mohamed Y

    2015-06-01

    Metal-reducing bacteria gain energy by extracellular electron transfer to external solids, such as naturally abundant minerals, which substitute for oxygen or the other common soluble electron acceptors of respiration. This process is one of the earliest forms of respiration on earth and has significant environmental and technological implications. By performing electron transfer to electrodes instead of minerals, these microbes can be used as biocatalysts for conversion of diverse chemical fuels to electricity. Understanding such a complex biotic-abiotic interaction necessitates the development of tools capable of probing extracellular electron transfer down to the level of single cells. Here, we describe an experimental platform for single cell respiration measurements. The design integrates an infrared optical trap, perfusion chamber, and lithographically fabricated electrochemical chips containing potentiostatically controlled transparent indium tin oxide microelectrodes. Individual bacteria are manipulated using the optical trap and placed on the microelectrodes, which are biased at a suitable oxidizing potential in the absence of any chemical electron acceptor. The potentiostat is used to detect the respiration current correlated with cell-electrode contact. We demonstrate the system with single cell measurements of the dissimilatory-metal reducing bacterium Shewanella oneidensis MR-1, which resulted in respiration currents ranging from 15 fA to 100 fA per cell under our measurement conditions. Mutants lacking the outer-membrane cytochromes necessary for extracellular respiration did not result in any measurable current output upon contact. In addition to the application for extracellular electron transfer studies, the ability to electronically measure cell-specific respiration rates may provide answers for a variety of fundamental microbial physiology questions. PMID:26133851

  10. Effects of Crystallographic Orientation on Corrosion Behavior of Magnesium Single Crystals

    NASA Astrophysics Data System (ADS)

    Shin, Kwang Seon; Bian, Ming Zhe; Nam, Nguyen Dang

    2012-06-01

    The corrosion behavior of magnesium single crystals with various crystallographic orientations was examined in this study. To identify the effects of surface orientation on the corrosion behavior in a systematic manner, single-crystal specimens with ten different rotation angles of the plane normal from the [0001] direction to the [ 10overline{1} 0] direction at intervals of 10° were prepared and subjected to potentiodynamic polarization and potentiostatic tests as well as electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt.% NaCl solution. Potentiodynamic polarization results showed that the pitting potential ( E pit) first decreased from -1.57 V SCE to -1.64 V SCE with an increase in the rotation angle from 0° to 40°, and then increased to -1.60 V SCE with a further increase in the rotation angle to 90°. The results obtained from potentiostatic tests are also in agreement with the trend in potentiodynamic polarization tests as a function of rotation angle. A similar trend was also observed for the depressed semicircle and the total resistances in the EIS measurements due to the facile formation of MgO and Mg(OH)2 passive films on the magnesium surface. In addition, the amount of chloride in the passive film was found first to increase with an increase in rotation angle from 0° to 40°, then decrease with a further increase in rotation angle, indicating that the tendency to form a more protective passive film increased for rotation angle near 0° [the (0001) plane] or 90° [the ( 10overline{1} 0) plane].

  11. (Titanium, chromium) nitride coatings for bipolar plate of polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Choi, H. S.; Han, D. H.; Hong, W. H.; Lee, J. J.

    (Titanium, chromium) nitride [(Ti,Cr)N] coatings are synthesized on a 316L stainless-steel substrate by inductively-coupled, plasma-assisted, reactive direct current magnetron sputtering. The chemical and electrical properties of the coating are investigated from the viewpoint of it application to bipolar plates. Nanocrystallized Cr-Ti films are formed in the absence of nitrogen gas, while a hexagonal β-(Ti,Cr) 2N phase is observed at N 2 = 1.2 sccm. Well-crystallized (Ti,Cr)N films are obtained at N 2 > 2.0 sccm. The corrosion resistance of the coating is examined by potentiodynamic and potentiostatic tests in 0.05 M H 2SO 4 + 0.2 ppm HF solution at 80 °C, which simulates the operation conditions of a polymer electrolyte membrane fuel cell. The Davies method is used to measure the interfacial contact resistance between the sample and carbon paper. The (Ti,Cr)N coating exhibits the highest corrosion potential and lowest current density. In a cathode environment, the corrosion potential and current density are 0.33 V (vs. SCE) and <5 × 10 -7 A cm -2 (at 0.6 V), respectively. In an anode environment the corresponding values are 0.16 V and <-5 × 10 -8 A cm -2 at -0.1 V. The (Ti,Cr)N coatings exhibit excellent stability during potentiostatic polarization tests in both anode and cathode environments. The interfacial contact resistance decreases with deposition of the (Ti,Cr)N film, and a minimum value of 4.5 mΩ cm 2 is obtained at a compaction force of 150 N cm -2, which indicates that the formation of oxide films can be successfully prevented by the (Ti,Cr)N film. Analysis with Auger electron spectroscopy reveals that the oxygen content at the surface decreases with increase in the nitrogen content.

  12. Effects of TiN coating on the corrosion of nanostructured Ti-30Ta-xZr alloys for dental implants

    NASA Astrophysics Data System (ADS)

    Kim, Won-Gi; Choe, Han-Cheol

    2012-01-01

    Electrochemical characteristics of a titanium nitride (TiN)-coated/nanotube-formed Ti-Ta-Zr alloy for biomaterials have been researched by using the magnetic sputter and electrochemical methods. Ti-30Ta-xZr (x = 3, 7 and 15 wt%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere and then water quenching. The formation of oxide nanotubes was achieved by anodizing a Ti-30Ta-xZr alloy in H3PO4 electrolytes containing small amounts of fluoride ions at room temperature. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. The microstructure and morphology of nanotube arrays were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The TiN coatings were obtained by the radio-frequency (RF) magnetron sputtering technique. The depositions were performed from pure Ti targets on Ti-30Ta-xZr alloys substrates. The corrosion properties of the specimens were examined using potentiodynamic test in a 0.9% NaCl solution by using potentiostat. The microstructures of Ti-30Ta-xZr alloys were changed from an equiaxed to a needle-like structure with increasing Zr content. The interspace between the nanotubes was approximately 20, 80 and 200 nm for Zr contents of 3, 7 and 15 wt%, respectively. The corrosion resistance of the TiN-coated on the anodized Ti-30Ta-xZr alloys was higher than that of the untreated Ti alloys, indicating a better protective effect.

  13. Design, Fabrication, and Characterization of Organic Electronic Devices for Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Yablonski, Joshua David

    Thermoelectric devices are an emerging application for conducting organic materials. Translating between heat and electricity, these materials could help to meet the energy needs of the future. Organic materials are advantageous because of their flexibility, processability, low toxicity, and cost. However, organic thermoelectric devices are presently lower efficiency than their inorganic counterparts, due to their lower electrical conductivities. This work seeks to progress towards higher-efficiency organic thermoelectric devices using several different approaches. First, poly(3,4-ethylenedioxythiophene) (PEDOT) thin-films were polymerized electrochemically onto a surface using galvanostatic, potentiostatic, and potentiodynamic techniques. It was determined that the surface morphologies of the potentiostatic and galvanostatic films are quite similar, but the potentiodynamic morphology is markedly different. An electrochemical dedoping process was developed for these films, and the degree of dedoping was monitored with UV-Vis and XPS. The oxidation levels in the films were found to vary between 11.7 and 33%. The electrical conductivity, Seebeck coefficient, and thermoelectric power factor of the PEDOT films were measured, and a maximum value of 13.6 microW m-1 K-2 was obtained. Second, two analogous polymers, HTAZ and FTAZ, were studied for future thermoelectric use. The polymers were chemically doped with FeCl3, the degree of doping was monitored with UV-Vis, and the doping stabilities of both polymers were recorded. The electrical conductivity was also measured and related to the doping level. Despite the space-charge limited current (SCLC) mobility of FTAZ being nearly an order of magnitude higher than HTAZ, the conductivities were nearly identical. Finally, as a way to increase mobility and conductivity in future organic thermoelectric devices, a novel metal-molecule-metal junction was designed and fabricated using an adapted transfer-printing technique

  14. Utilization of subsurface microbial electrochemical systems to elucidate the mechanisms of competition between methanogenesis and microbial iron(III)/humic acid reduction in Arctic peat soils

    NASA Astrophysics Data System (ADS)

    Friedman, E. S.; Miller, K.; Lipson, D.; Angenent, L. T.

    2012-12-01

    High-latitude peat soils are a major carbon reservoir, and there is growing concern that previously dormant carbon from this reservoir could be released to the atmosphere as a result of continued climate change. Microbial processes, such as methanogenesis and carbon dioxide production via iron(III) or humic acid reduction, are at the heart of the carbon cycle in Arctic peat soils [1]. A deeper understanding of the factors governing microbial dominance in these soils is crucial for predicting the effects of continued climate change. In previous years, we have demonstrated the viability of a potentiostatically-controlled subsurface microbial electrochemical system-based biosensor that measures microbial respiration via exocellular electron transfer [2]. This system utilizes a graphite working electrode poised at 0.1 V NHE to mimic ferric iron and humic acid compounds. Microbes that would normally utilize these compounds as electron acceptors donate electrons to the electrode instead. The resulting current is a measure of microbial respiration with the electrode and is recorded with respect to time. Here, we examine the mechanistic relationship between methanogenesis and iron(III)- or humic acid-reduction by using these same microbial-three electrode systems to provide an inexhaustible source of alternate electron acceptor to microbes in these soils. Chamber-based carbon dioxide and methane fluxes were measured from soil collars with and without microbial three-electrode systems over a period of four weeks. In addition, in some collars we simulated increased fermentation by applying acetate treatments to understand possible effects of continued climate change on microbial processes in these carbon-rich soils. The results from this work aim to increase our fundamental understanding of competition between electron acceptors, and will provide valuable data for climate modeling scenarios. 1. Lipson, D.A., et al., Reduction of iron (III) and humic substances plays a major

  15. Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy

    PubMed Central

    Ghadiri, Elham; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E.

    2016-01-01

    Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded. PMID:27095505

  16. Electrodeposited ZnO films with high UV emission properties

    SciTech Connect

    Matei, Elena; Enculescu, Ionut

    2011-11-15

    Highlights: {yields} Electrodeposition of ZnO from nitrate baths is investigated. {yields} The influence of process parameters on morphological and optical properties is studied. {yields} Experimental conditions to fabricate ZnO films with high UV emission were found. -- Abstract: We report here our results in the preparation of ZnO films with high UV band to band characteristic luminescence emission by potentiostatic electrodeposition. Zinc nitrate aqueous baths with different concentration and additives were employed for the preparation of the films on platinum substrates. We focused our research in determining how the electrodeposition bath composition, i.e. zinc nitrate concentration and addition of KCl or polyvinyl pyrolidone and applied overpotential influence the morphological and optical properties of the oxide films. Scanning electron microscopy was employed for characterizing the films in terms of morphology. Optical reflection, photoluminescence spectroscopy and cathodoluminescence were used for determining the optical characteristics of the samples. The morphology of the deposit varies from hexagonal prisms to platelets as a function of the deposition rate. This experimental parameter also influences the luminescence properties. We found that at low deposition rates high UV luminescent material is obtained.

  17. High-resolution neutron powder diffractometer SPODI at research reactor FRM II

    NASA Astrophysics Data System (ADS)

    Hoelzel, M.; Senyshyn, A.; Juenke, N.; Boysen, H.; Schmahl, W.; Fuess, H.

    2012-03-01

    SPODI is a high-resolution thermal neutron diffractometer at the research reactor Heinz Maier-Leibnitz (FRM II) especially dedicated to structural studies of complex systems. Unique features like a very large monochromator take-off angle of 155° and a 5 m monochromator-sample distance in its standard configuration achieve both high-resolution and a good profile shape for a broad scattering angle range. Two dimensional data are collected by an array of 80 vertical position sensitive 3He detectors. SPODI is well suited for studies of complex structural and magnetic order and disorder phenomena at non-ambient conditions. In addition to standard sample environment facilities (cryostats, furnaces, magnet) specific devices (rotatable load frame, cell for electric fields, multichannel potentiostat) were developed. Thus the characterisation of functional materials at in-operando conditions can be achieved. In this contribution the details of the design and present performance of the instrument are reported along with its specifications. A new concept for data reduction using a 2 θ dependent variable height for the intensity integration along the Debye-Scherrer lines is introduced.

  18. Batch-injection analysis with amperometric detection of the DPPH radical for evaluation of antioxidant capacity.

    PubMed

    Oliveira, Gracy K F; Tormin, Thiago F; Sousa, Raquel M F; de Oliveira, Alberto; de Morais, Sérgio A L; Richter, Eduardo M; Munoz, Rodrigo A A

    2016-02-01

    This work proposes the application of batch-injection analysis with amperometric detection to determine the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The efficient concentration or EC50 value corresponds to the concentration of sample or standard required to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with DPPH radical for 1h because many polyphenolic compounds typically found in plants and responsible for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 μmol L(-1)) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19 μmol L(-1) for gallic acid and butylated hydroxytoluene, respectively). Moreover, BIA methods show great promise for portable analysis because battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available. PMID:26304399

  19. Recycling of Magnesium Alloy Employing Refining and Solid Oxide Membrane (SOM) Electrolysis

    NASA Astrophysics Data System (ADS)

    Guan, Xiaofei; Zink, Peter A.; Pal, Uday B.; Powell, Adam C.

    2013-04-01

    Pure magnesium was recycled from partially oxidized 50.5 wt pct Mg-Al scrap alloy and AZ91 Mg alloy (9 wt pct Al, 1 wt pct Zn). Refining experiments were performed using a eutectic mixture of MgF2-CaF2 molten salt (flux). During the experiments, potentiodynamic scans were performed to determine the electrorefining potentials for magnesium dissolution and magnesium bubble nucleation in the flux. The measured electrorefining potential for magnesium bubble nucleation increased over time as the magnesium content inside the magnesium alloy decreased. Potentiostatic holds and electrochemical impedance spectroscopy were employed to measure the electronic and ionic resistances of the flux. The electronic resistivity of the flux varied inversely with the magnesium solubility. Up to 100 pct of the magnesium was refined from the Mg-Al scrap alloy by dissolving magnesium and its oxide into the flux followed by argon-assisted evaporation of dissolved magnesium and subsequently condensing the magnesium vapor. Solid oxide membrane electrolysis was also employed in the system to enable additional magnesium recovery from magnesium oxide in the partially oxidized Mg-Al scrap. In an experiment employing AZ91 Mg alloy, only the refining step was carried out. The calculated refining yield of magnesium from the AZ91 alloy was near 100 pct.

  20. Roles of Cationic and Elemental Calcium in the Electro-Reduction of Solid Metal Oxides in Molten Calcium Chloride

    NASA Astrophysics Data System (ADS)

    Qiu, Guohong; Jiang, Kai; Ma, Meng; Wang, Dihua; Jin, Xianbo; Chen, George Z.

    2007-06-01

    Previous work, mainly from this research group, is re-visited on electrochemical reduction of solid metal oxides, in the form of compacted powder, in molten CaCl2, aiming at further understanding of the roles of cationic and elemental calcium. The discussion focuses on six aspects: 1.) debate on two mechanisms proposed in the literature, i. e. electro-metallothermic reduction and electro-reduction (or electro-deoxidation), for the electrolytic removal of oxygen from solid metals or metal oxides in molten CaCl2; 2.) novel metallic cavity working electrodes for electrochemical investigations of compacted metal oxide powders in high temperature molten salts assisted by a quartz sealed Ag/AgCl reference electrode (650 ºC- 950 ºC); 3.) influence of elemental calcium on the background current observed during electrolysis of solid metal oxides in molten CaCl2; 4.) electrochemical insertion/ inclusion of cationic calcium into solid metal oxides; 5.) typical features of cyclic voltammetry and chronoamperometry (potentiostatic electrolysis) of metal oxide powders in molten CaCl2; and 6.) some kinetic considerations on the electrolytic removal of oxygen.

  1. Formation of Gd-Al Alloy Films by a Molten Salt Electrochemical Process

    NASA Astrophysics Data System (ADS)

    Caravaca, Concha; De Córdoba, Guadalupe

    2008-02-01

    The electrochemistry of molten LiCl-KCl-GdCl3 at a reactive Al electrode has been studied at 723 to 823 K. Electrochemical techniques such as cyclic voltammetry and chronopotentiometry have been used in order to identify the intermetallic compounds formed. Cyclic voltammetry showed that, while at an inert W electrode GdCl3 is reduced to Gd metal in a single step at a potential close to the reduction of the solvent, at an Al electrode a shift towards more positive values occurs. This shift of the cathodic potential indicated a reduction of the activity of Gd in Al with respect to that ofW, due to the formation of alloys. The surface characterization of samples formed by both galvanostatic and potentiostatic electrolysis has shown the presence of two intermetallic compounds: GdAl3 and GdAl2. Using open-circuit chronopotentiometry it has been possible to measure the potentials at which these compounds are transformed into each other. The values of these potential plateaus, once transformed into e. f. m. values, allowed to determine the thermodynamic properties of the GdAl3 intermetallic compound.

  2. Passivation Behavior of Ultrafine-Grained Pure Copper Fabricated by Accumulative Roll Bonding (ARB) Process

    NASA Astrophysics Data System (ADS)

    Fattah-alhosseini, Arash; Imantalab, Omid

    2016-01-01

    In this study, passivation behavior of ultrafine-grained (UFG) pure copper fabricated by ARB process in 0.01 M borax solution has been investigated. Before any electrochemical measurements, evaluation of microstructure was obtained by transmission electron microscopy (TEM). TEM observations revealed that with increasing the number of ARB passes, the grain size of specimens decrease. Also, TEM images showed that UFGs with average size of below 100 nm appeared after 7 passes of ARB. To investigate the passivation behavior of the specimens, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis was carried out. For this purpose, three potentials within the passive region were chosen for potentiostatic passive film growth. EIS results showed that both passive film and charge-transfer resistance increases with increasing the number of ARB passes. Moreover, Mott-Schottky analysis revealed that with increasing the number of ARB passes, the acceptor density of the passive films decreased. In conclusion, increasing the number of ARB passes offers better conditions for forming the passive films with higher protection behavior, due to the growth of a much thicker and less defective films.

  3. Role of the electrolyte in cathodic lead dioxide reduction

    SciTech Connect

    Lyamina, L.I.; Gorbunova, K.M.; Tarasova, N.I.

    1985-09-01

    The electrolyte composition and particularly the anions are thought to be important in cathodic lead dioxide reduction. Data are reported for the process in 0.1 M Na/sub 2/B/sub 4/O/sub 7/, Na/sub 2/HPO/sub 4/, KOH, and KC1 solution and in 0.3 M K/sub 2/SO/sub 4/ solution. Deposits of alpha-PbO/sub 2/ were produced electrolytically on nickel. The potentials are reported on the hydrogen scale. The electrochemical behavior of lead dioxide in said solutions was evaluated from charging curves and from potentiodynamic curves obtained with a P-5848 potentiostat. The first stage of lead dioxide reduction in all solutions results in the formation of an intermediate oxide having the composition of PbO/sub 1/ /sub 43/ to PbO/sub 1/ /sub 24/. The second stage (reduction of the intermediate oxide to metallic lead) depends on the nature of the electrolyte. An examination of the results obtained action of lead dioxide with the electrophilic component increases in the order of KOH yields KC1 yields Na/sub 2/B/sub 4/O/sub 7/ yields Na/sub 2/HPO/sub 4/ yields K/sub 2/SO/sub 4/.

  4. Carbon nanotube-based supercapacitors using low cost collectors

    NASA Astrophysics Data System (ADS)

    Amirhoseiny, Maryam; Zandi, Majid; Mosayyebi, Abolghasem; Khademian, Mehrzad

    2016-01-01

    In this work, electrochemical double layer supercapacitors were fabricated using multiwalled carbon nanotube (MWCNT) composite microfilm as electrode. To improve the electrochemical properties, MWCNTs were functionalized with -COOH by acid treatments. CNT/PVA films have been deposited on different current collectors by spin coating to drastically enhance the electrode performance. Electrode fabrication involved various stages preparing of the CNT composite, and coating of the CNT/PVA paste on different substrates which also served as current collector. Al, Ni and graphite were used and compared as current collectors. The surface morphology of the fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat analyzer. Each supercapacitor cell was subjected to charge-discharge cycling study at different current rates from 0.2Ag-1 to 1Ag-1. The results showed that graphite-based electrodes offer advantages of significantly higher conductivity and superior capacitive behavior compared to thin film electrodes formed on Ni and Al current collectors. The specific capacitance of graphite based electrode is found to be 29Fg-1.

  5. Ion and gas chromatography mass spectrometry investigations of organophosphates in lithium ion battery electrolytes by electrochemical aging at elevated cathode potentials

    NASA Astrophysics Data System (ADS)

    Weber, Waldemar; Wagner, Ralf; Streipert, Benjamin; Kraft, Vadim; Winter, Martin; Nowak, Sascha

    2016-02-01

    The electrochemical aging of commercial non-aqueous lithium hexafluorophosphate (LiPF6)/organic carbonate solvent based lithium ion battery electrolyte has been investigated in view of the formation of ionic and non-ionic alkylated phosphates. Subject was a solvent mixture of ethylene carbonate/ethyl methyl carbonate EC:EMC (1:1, by wt.) with 1 M LiPF6 (LP50 Selectilyte™, BASF). The analysis was carried out by ion chromatography coupled with electrospray ionization mass spectrometry (ESI-MS) for ionic compounds and (headspace) gas chromatography mass spectrometry ((HS)-GC-MS) for non-ionic compounds. The electrochemical aging was performed by galvanostatic charge/discharge cycling and potentiostatic experiments with LiNi0.5Mn1.5O4 (LMNO) as cathode material at increased cut-off potentials (>4.5 V vs. Li/Li+). A strong dependence of the formation of organophosphates on the applied electrode potential was observed and investigated by quantitative analysis of the formed phosphates. In addition, new possible "fingerprint" compounds for describing the electrolyte status were investigated and compared to existing compounds.

  6. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers

    NASA Astrophysics Data System (ADS)

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-02-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180o.

  7. Structural evolution, thermomechanical recrystallization and electrochemical corrosion properties of Ni-Cu-Mg amorphous coating on mild steel fabricated by dual-anode electrolytic processing

    NASA Astrophysics Data System (ADS)

    Abdulwahab, M.; Fayomi, O. S. I.; Popoola, A. P. I.

    2016-07-01

    The electrolytic Ni-Cu based alloy coating with admixed interfacial blend of Mg have been successfully prepared on mild steel substrate by dual anode electroplating processes over a range of applied current density and dwell time. The electrocodeposition of Ni-Cu-Mg coating was investigated in the presence of other bath additives. The influence of deposition current on surface morphology, adhesion behavior, preferred crystal orientation, surface topography and electrochemical activity of Ni-Cu-Mg alloy coating on mild steel were systematically examined. The thermal stability of the developed composite materials was examined via isothermal treatment. Scanning electron microscope equipped with EDS, X-ray diffraction, Atomic force microscope, micro-hardness tester and 3 μmetrohm Potentiostat/galvanostat were used to compare untreated and isothermally treated electrocodeposited composite. The induced activity of the Ni-Cu-Mg alloy changed the surface modification and results to crystal precipitation within the structural interface by the formation of Cu, Ni2Mg3 phase. The obtained results showed that the introduction of Mg particles in the plating bath generally modified the surface and brings an increase in the hardness and corrosion resistance of Ni-Cu-Mg layers fabricated. Equally, isothermally treated composites demonstrated an improved properties indicating 45% increase in the micro-hardness and 79.6% corrosion resistance which further showed that the developed composite is thermally stable.

  8. Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping.

    PubMed

    Wen, Rui-Tao; Niklasson, Gunnar A; Granqvist, Claes G

    2016-03-01

    The quest for superior and low-cost electrochromic (EC) thin films, for applications in smart windows, remains strong because of their large importance for energy-efficient buildings. Although the development of new EC materials for improved devices is important, diminishing or reversing degradation is another key issue, and electrical rejuvenation of degraded EC materials can offer new opportunities. Here we demonstrate that cathodically coloring EC thin films of TiO2, which normally suffer from ion-trapping-induced degradation of charge capacity and optical modulation upon extensive electrochemical cycling, can recover their initial EC performance by a rejuvenation procedure involving Li(+) ion detrapping. Thus, the initial performance can be regained, and refreshed TiO2 films exhibit the same degradation features as as-deposited films upon prolonged electrochemical cycling. The rejuvenation was carried out by using either galvanostatic or potentiostatic treatments. Our study may open avenues to explore the recovery not only of EC materials and devices based on those but also for other ion-exchange-based devices. PMID:26910644

  9. Electrochromic properties of electrodeposited tungsten oxide (WO3) thin film

    NASA Astrophysics Data System (ADS)

    Dalavi, D. S.; Kalagi, S. S.; Mali, S. S.; More, A. J.; Patil, R. S.; Patil, P. S.

    2012-06-01

    In this work, we report on a potentiostatic electrochemical procedure employing an ethanolic solution of peroxotungstic acid yielded tungsten oxide (WO3) films specifically for transmissive electrochromic devices (ECDs) such as "smart windows". WO3 film was confirmed from the binding energy determination by X-ray photoelectron spectroscopic studies. The diffusion coefficient during intercalation and deintercalation was found to be 2.59×10-10 and 2.40×10-10 cm2/C. Electrodeposited WO3 produce high color/bleach transmittance difference up to 74% at 630 nm. On reduction of WO3, the CIELAB 1931 2% color space coordinates show the transition from colorless to the deep blue state (L=95.18, a=2.12, b=0.3138, and L=57.78, a=-21.79, b=0.244) with steady decrease in relative luminance. The highest coloration efficiency (CE) of 92 cm2/C and good response time of 10.28 for coloration (reduction) and 3.2 s for bleaching (oxidation) was observed with an excellent reversibility of 89%.

  10. Effect of hydroxyapatite thickness on metal ion release from Ti6Al4V substrates.

    PubMed

    Sousa, S R; Barbosa, M A

    1996-02-01

    The electrochemical dissolution behaviour of Ti6Al4V alloy coated with hydroxyapatite (HA) by plasma spraying was studied in Hank's balanced salt solution (HBSS) and compared with that of polished and grit-blasted passivated surfaces. Two different nominal thicknesses of HA (50 and 200 micro m) were used. Taking a polished passivated surface as reference, grit blasting of the substrate increased the electrical charge used in the oxidation of Ti6Al4V alloy at constant potential, as a result of increased surface area. However, only HA coatings with a thickness of 200 micro m were capable of reducing the charge to values lower than those measured for polished surfaces. Electrochemical impedance spectroscopy has also shown that only 200 micro m thick coatings are effective in reducing the oxidation rate of the substrate. Furthermore, in potentiostatic experiments the 50 micro m thick coating detached from the substrate, which did not occur with the 200 micro m thick coating. However, after 6 months immersion in HBSS, detachment occurred in some regions of both coatings. No titanium, aluminium or vanadium were detected in solution by electrothermal atomic absorption spectroscopy. These data indicate that HA is an effective barrier to metal ion release, even for the thinner coatings, due to formation of metal phosphates or to incorporation of metal ions in the HA structure. PMID:8938233

  11. TiO2 membranes for concurrent photocatalytic organic degradation and corrosion protection

    NASA Astrophysics Data System (ADS)

    Liang, Robert; Hatat-Fraile, Melisa; He, Horatio; Arlos, Maricor; Servos, Mark R.; Zhou, Y. Norman

    2015-10-01

    Organic contaminants and corrosion in water treatment effluents are a current global problem and the development of effective methods to facilitate the removal of organic contaminants and corrosion control strategies are required to mitigate this problem. TiO2 nanomaterials that are exposed to UV light can generate electron-hole pairs, which undergo redox reactions to produce hydroxyl radicals from adsorbed molecular oxygen. They hydroxyl radicals are able to oxidize organic contaminants in water. This same process can be used in conjunction to protect metals from corrosion via cathodic polarization. In this work, TiO2 nanomaterials were synthesized and electrophoretically deposited on conductive substrates to serve as films or membranes. An illuminated TiO2 film on a conductive surface served as the photoanode and assisted in the cathodic protection of stainless steel (SS304) and the degradation of organic pollutants, in this case glucose. This proof-of-concept relied on photoelectrochemical experiments conducted using a potentiostat and a xenon lamp illumination source. The open-circuit potential changes that determine whether a metal is protected from corrosion under illumination was observed; and the electrical characteristics of the TiO2 film or membrane under dark and arc lamp illumination conditions were also analyzed. Furthermore, the effect of organic contaminants on the photocathodic protection mechanism and the oxidation of glucose during this process were explored.

  12. Electrochemical sensing method for point-of-care cortisol detection in human immunodeficiency virus-infected patients

    PubMed Central

    Kaushik, Ajeet; Yndart, Adriana; Jayant, Rahul Dev; Sagar, Vidya; Atluri, Venkata; Bhansali, Shekhar; Nair, Madhavan

    2015-01-01

    A novel electrochemical sensing method was devised for the first time to detect plasma cortisol, a potential psychological stress biomarker, in human immunodeficiency virus (HIV)-positive subjects. A miniaturized potentiostat (reconfigured LMP91000 chip) interfaced with a microfluidic manifold containing a cortisol immunosensor was employed to demonstrate electrochemical cortisol sensing. This fully integrated and optimized electrochemical sensing device exhibited a wide cortisol-detection range from 10 pg/mL to 500 ng/mL, a low detection limit of 10 pg/mL, and sensitivity of 5.8 μA (pg mL)−1, with a regression coefficient of 0.995. This cortisol-selective sensing system was employed to estimate plasma cortisol in ten samples from HIV patients. The electrochemical cortisol-sensing performance was validated using an enzyme-linked immunosorbent assay technique. The results obtained using both methodologies were comparable within 2%–5% variation. The information related to psychological stress of HIV patients can be correlated with disease-progression parameters to optimize diagnosis, therapeutic, and personalized health monitoring. PMID:25632229

  13. The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.

    PubMed

    Nishida, T

    1997-03-01

    Mouth-rinsing with oxydized water which contains electrolytically generated chlorine is known to hinder dental plaque formation and growth, but it also accelerates the deterioration of metallic restorations in the mouth. The present work consists of an in vitro study to elucidate the electrochemical reactions involved in the reduction of oxydized water on dental alloys through a systematic investigation of the potentiostatic polarization behavior of dental alloy electrodes. The five dental alloys selected for investigation were gold alloy, gold alloy containing platinum, silver-palladium-gold alloy, conventional amalgam and high copper amalgam. The corrosion potentials of all dental alloy electrodes were shown to be more noble in oxydized water than in 0.1N sodium chloride solution. The potential differences between the corrosion potentials were relatively small in the case of amalgam electrodes. The polarization curves for all of the dental alloy electrodes in oxydized water revealed reduction currents of chlorine, hypochlorous acid, dissolved oxygen and oxonium ion. The reduction of chlorine and hypochlorous acid started at a more noble potential than that of dissolved oxygen. The dental alloys studied, except the amalgams, did not dissolve excessively at the corrosion potentials in oxydized water. PMID:9198335

  14. Biosynthesis of Pd-Au alloys on carbon fiber paper: Towards an eco-friendly solution for catalysts fabrication

    NASA Astrophysics Data System (ADS)

    Zhuang, Zechao; Wang, Feifeng; Naidu, Ravendra; Chen, Zuliang

    2015-09-01

    Bimetallic nanomaterials with enhanced activity and stability have been extensively studied as emerging catalysts for hydrogen evolution reaction (HER). Expensive and environmentally unfriendly chemical synthesis routes inhibit their large-scale applications. In this work, we developed a facile and green synthesis of Pd-Au alloy nanoparticles (NPs) dispersed on carbon fiber paper (CFP) by plant-mediated bioreduction coupled with self-assembly. Engineering the morphology and composition of bimetallic catalysts synthesized by plant extracts on complex substrate is achieved. The resulting NPs are uniform in shape and have a spherical morphology with an average diameter of ∼180 nm, in which the molar ratio of Au/Pd is near 75:25 and the catalysts loading is about 0.5 mg cm-2. The Pd-Au/CFP hybrid electrode exhibits an excellent HER performance with a Tafel slope of 47 mV dec-1 and an exchange current density of 0.256 mA cm-2. Electrochemical stability tests through long-term potential cycles and potentiostatic electrolysis further confirm the high durability of the electrode. This development offers an efficient and eco-friendly catalysts synthesis route for constructing water-splitting cells and other electrocatalytic devices.

  15. Electrochemical formation and characterization of Au nanostructures on a highly ordered pyrolytic graphite surface

    NASA Astrophysics Data System (ADS)

    Gómez, José J. Arroyo; Zubieta, Carolina; Ferullo, Ricardo M.; García, Silvana G.

    2016-02-01

    The electrochemical formation of Au nanoparticles on a highly ordered pyrolytic graphite (HOPG) substrate using conventional electrochemical techniques and ex-situ AFM is reported. From the potentiostatic current transients studies, the Au electrodeposition process on HOPG surfaces was described, within the potential range considered, by a model involving instantaneous nucleation and diffusion controlled 3D growth, which was corroborated by the microscopic analysis. Initially, three-dimensional (3D) hemispherical nanoparticles distributed on surface defects (step edges) of the substrate were observed, with increasing particle size at more negative potentials. The double potential pulse technique allowed the formation of rounded deposits at low deposition potentials, which tend to form lines of nuclei aligned in defined directions leading to 3D ordered structures. By choosing suitable nucleation and growth pulses, one-dimensional (1D) deposits were possible, preferentially located on step edges of the HOPG substrate. Quantum-mechanical calculations confirmed the tendency of Au atoms to join selectively on surface defects, such as the HOPG step edges, at the early stages of Au electrodeposition.

  16. An Implantable RFID Sensor Tag toward Continuous Glucose Monitoring.

    PubMed

    Xiao, Zhibin; Tan, Xi; Chen, Xianliang; Chen, Sizheng; Zhang, Zijian; Zhang, Hualei; Wang, Junyu; Huang, Yue; Zhang, Peng; Zheng, Lirong; Min, Hao

    2015-05-01

    This paper presents a wirelessly powered implantable electrochemical sensor tag for continuous blood glucose monitoring. The system is remotely powered by a 13.56-MHz inductive link and utilizes an ISO 15693 radio frequency identification (RFID) standard for communication. This paper provides reliable and accurate measurement for changing glucose level. The sensor tag employs a long-term glucose sensor, a winding ferrite antenna, an RFID front-end, a potentiostat, a 10-bit sigma-delta analog to digital converter, an on-chip temperature sensor, and a digital baseband for protocol processing and control. A high-frequency external reader is used to power, command, and configure the sensor tag. The only off-chip support circuitry required is a tuned antenna and a glucose microsensor. The integrated chip fabricated in SMIC 0.13-μm CMOS process occupies an area of 1.2 mm ×2 mm and consumes 50 μW. The power sensitivity of the whole system is -4 dBm. The sensor tag achieves a measured glucose range of 0-30 mM with a sensitivity of 0.75 nA/mM. PMID:25823049

  17. Fabrication of Cu2O/γ-FeOOH heterojunction solar cells using electrodeposition

    NASA Astrophysics Data System (ADS)

    Vequizo, Junie Jhon M.; Ichimura, Masaya

    2014-04-01

    Cu2O/γ-FeOOH heterojunction solar cells were fabricated using galvanostatic-potentiostatic electrodeposition methods. The γ-FeOOH films showed n-type conductivity with a band gap of 2.2 eV. The electrodeposited Cu2O/γ-FeOOH heterojunction exhibited photovoltaic characteristics with a short-circuit current density of 0.95 mA/cm2 and open-circuit voltage of 0.11 V. Using core-level spectroscopy, it was demonstrated that the Cu2O/FeOOH heterostructure exhibited a type II junction with a valence band offset of 0.8 eV. The conduction band minimum of Cu2O was predicted to be higher than that of γ-FeOOH by 0.7 eV. This finding indicates that the γ-FeOOH material can be regarded as a suitable hetero-partner of other p-type absorbers.

  18. A Portable Luminometer with a Disposable Electrochemiluminescent Biosensor for Lactate Determination

    PubMed Central

    Martínez-Olmos, Antonio; Ballesta-Claver, Julio; Palma, Alberto J.; Valencia-Mirón, Maria del Carmen; Capitán-Vallvey, Luis Fermin

    2009-01-01

    A hand-held luminometer for measuring electrochemiluminescence (ECL) for lactate determination and based on one-shot biosensors fabricated using screen-printed electrodes is described. The lactate recognition system is based on lactate oxidase and the transduction system consists of electro-oxidation of luminol, with all the reagents immobilized in a Methocel membrane. The membrane composition and reaction conditions have been optimized to obtain adequate sensitivity. The luminometer is based on a large silicon photodiode as detector and includes a programmable potentiostat to initialize the chemical reaction and signal processing circuitry, designed to acquire a low level photocurrent with offset cancelation, low pass filtering for noise attenuation and adjustable gain up to 1012 V/A. The one-shot biosensor responds to lactate rapidly, with an acquisition time of 2.5 min, obtaining a linear dependence from 8 × 10−6 to 2 × 10−4 M, a detection limit of 2.4 × 10−6 M and a sensor-to-sensor reproducibility (relative standard deviation, RSD) of around 7–10 % at the medium level of the range. PMID:22408475

  19. Corrosion resistance, chemistry, and mechanical aspects of Nitinol surfaces formed in hydrogen peroxide solutions

    SciTech Connect

    Shabalovskay, Svetlana A.; Anderegg, James W.; Undisz, Andreas; Rettenmayr, Markus; Rondelli, Gianni C.

    2012-06-12

    Ti oxides formed naturally on Nitinol surfaces are only a few nanometers thick. To increase their thickness, heat treatments are explored. The resulting surfaces exhibit poor resistance to pitting corrosion. As an alternative approach to accelerate surface oxidation and grow thicker oxides, the exposure of Nitinol to strong oxidizing H2O2 aqueous solutions (3 and 30%) for various periods of time was used. Using X-Ray Photoelectron Spectroscopy (XPS) and Auger spectroscopy, it was found that the surface layers with variable Ti (6–15 at %) and Ni (5–13 at %) contents and the thickness up to 100 nm without Ni-enriched interfaces could be formed. The response of the surface oxides to stress in superelastic regime of deformations depended on oxide thickness. In the corrosion studies performed in both strained and strain-free states using potentiodynamic and potentiostatic polarizations, the surfaces treated in H2O2 showed no pitting in corrosive solution that was assigned to higher chemical homogeneity of the surfaces free of secondary phases and inclusions that assist better biocompatibility of Nitinol medical devices. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 1490–1499, 2012

  20. Microelectrospotting as a new method for electrosynthesis of surface-imprinted polymer microarrays for protein recognition.

    PubMed

    Bosserdt, Maria; Erdőssy, Júlia; Lautner, Gergely; Witt, Julia; Köhler, Katja; Gajovic-Eichelmann, Nenad; Yarman, Aysu; Wittstock, Gunther; Scheller, Frieder W; Gyurcsányi, Róbert E

    2015-11-15

    Here we introduce microelectrospotting as a new approach for preparation of protein-selective molecularly imprinted polymer microarrays on bare gold SPR imaging chips. During electrospotting both the gold chip and the spotting tip are electrically connected to a potentiostat as working and counter electrodes, respectively. The spotting pin encloses the monomer-template protein cocktail that upon contacting the gold surface is in-situ electropolymerized resulting in surface confined polymer spots of ca. 500 µm diameter. By repeating this procedure at preprogrammed locations for various composition monomer-template mixtures microarrays of nanometer-thin surface-imprinted films are generated in a controlled manner. We show that the removal and rebinding kinetics of the template and various potential interferents to such microarrays can be monitored in real-time and multiplexed manner by SPR imaging. The proof of principle for microelectrospotting of electrically insulating surface-imprinted films is made by using scopoletin as monomer and ferritin as protein template. It is shown that microelectrospotting in combination with SPR imaging can offer a versatile platform for label-free and enhanced throughput optimization of the molecularly imprinted polymers for protein recognition and for their analytical application. PMID:26056955

  1. Hydrometallurgical recovery of silver from waste silver oxide button cells

    NASA Astrophysics Data System (ADS)

    Sathaiyan, N.; Nandakumar, V.; Ramachandran, P.

    In recent years, recycling of household batteries has attracted much attention mainly with respect to environmental aspects in addition to the savings. Small silver oxide primary cells used in electric watches become a waste after their life is over. Recycling procedures are needed to prevent any environmental impact from these wastes and to recover the value inherent in the scrap. Smelting and electrolytic methods are discussed for silver recovery from this battery waste. Acid leaching of waste batteries and precipitation of silver as silver chloride followed by smelting at 1000 °C yields a silver recovery of about 83%. An electrolytic route is studied as an alternative to the smelting operation and involves the electrodeposition of silver with higher purity from a silver thiosulfate complex prepared from silver chloride. The electrolysis is potentiostatically controlled at a potential of -0.400 to -0.600 V (SCE) for avoiding side-reactions such as the sulfiding of silver. Although recovery methods have been identified in principle, their suitability for mixed small battery waste and economic factors have yet to be demonstrated.

  2. Electrochemical glucose oxidation on dendritic cuprous oxide film fabricated by PSS-assisted electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Jin, Xiaoqi; Huang, Qiao

    2011-02-01

    Cuprous oxides (Cu 2O) with different morphologies were deposited on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition. The as-deposited samples were characterized by XRD, BET surface area and SEM. The effects of Poly(styrene sulfonic acid) sodium salt (PSS) on the crystal morphologies of Cu 2O were studied. Different crystal morphologies of Cu 2O can be obtained by varying the concentrations of PSS in the electrolytes. The formation of dendritic microstructure in Cu 2O film depends on the concentration of PSS in the electrolyte. Dendritic Cu 2O crystals formed gradually with the increase of the concentration of PSS in the electrolyte from 0 to 4 g L -1. More symmetrical Cu 2O crystals appear when the concentration of PSS is changed from 4 to 8 g L -1. However, the Cu 2O nanoparticles formed instead of dendritic Cu 2O crystals if the concentration of PSS reaches to 12 g L -1, which is due to the slower diffusion rate of reactive species in high concentration of PSS. The as-deposited Cu 2O thin films with different morphologies all exhibit the electrochemical glucose oxidation properties. The improved performance of glucose oxidation is achieved on the dendritic Cu 2O film electrode. The result indicates that the dendritic microstructure is beneficial for decreasing the resistance and improving transportation and diffusion of reactants and products.

  3. Passivation dynamics in the anisotropic deposition and stripping of bulk magnesium electrodes during electrochemical cycling

    SciTech Connect

    Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; Nuzzo, Ralph G.

    2015-08-10

    Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.

  4. Electrochemical noise measurement: The definitive in-situ technique for corrosion applications?

    SciTech Connect

    Dawson, J.L.

    1996-12-31

    A review is presented of electrochemical noise (EN), the generic term given to fluctuations of current and potential seen in high-temperature corrosion, molten salt corrosion, and aqueous corrosion. EN levels in corrosion and particularly localized corrosion are significantly greater than EN observed in redox systems. EN associated with corrosion is the result of stochastic pulses of current generated by, for example, sudden film rupture, crack propagation, discrete events involving metal dissolution at etch pits, grain boundaries and kink sites, and hydrogen discharge with gas bubble formation and detachment. EN in corrosion includes low-frequency, nonstationary, and weakly stationary processes; transients; and cyclic or oscillatory phenomena. The use of EN, obtained either by potentiostatic/galvanostatic measurements or at freely corroding potentials, has been shown to offer advantages over conventional DC and AC techniques in research studies, testing, and corrosion monitoring. In many cases, reaction mechanisms can be elucidated and corrosion rate information can be obtained. Assessment of individual transients, use of signal analysis techniques, modeling of ensembles of transients as developed for electrocrystallization studies, and use of the chaos theory have all been used in EN evaluations.

  5. Effect of metallurgical factors on the electrochemical noise measured on AISI Type 430 stainless steels in chloride-containing media

    SciTech Connect

    Gorse, D.; Boulleret, C.; Baroux, B.

    1996-12-31

    Potentiostatic noise measurements are performed on a series of AISI 430 type ferritic stainless steels containing controlled amounts of sulfur (from 8 up to 47 ppm) and titanium (up to 0.37 wt%), in 0.02M sodium chloride (NaCl) aqueous solution (pH 6.6), in a range of potentials below the pitting potential. The authors focus on the evolution of the shape of the current transients, going from a titanium (Ti) free and 41-ppm sulfur-containing alloy to different Ti-bearing alloys with comparable amount of sulfur ({approximately}40 ppm). The results are compared to the case of a Ti-free and low sulfur (8-ppm) containing alloy. The shape of the anodic current transients obeys a power law, t{sup n}. The authors distinguish two different situations, with n either less or larger than 1, which can be associated with the Ti and sulfur content in the steel. The influence of the exposure time under polarization is also discussed. It appears that for the manganese sulfide (MnS)-containing alloys, after prolonged polarization, the shape of the metastable pitting events evolves toward that found for MnS-free alloys (Ti-bearing), or low-sulfur-containing alloys. Attention is drawn to the possible relationship between the shape of the current transients and the metallurgical defects acting as pitting initiation sites.

  6. Mitigating Electronic Current in Molten Flux for the Magnesium SOM Process

    NASA Astrophysics Data System (ADS)

    Gratz, Eric S.; Guan, Xiaofei; Milshtein, Jarrod D.; Pal, Uday B.; Powell, Adam C.

    2014-08-01

    The solid oxide membrane (SOM) process has been used at 1423 K to 1473 K (1150 °C to 1200 °C) to produce magnesium metal by the direct electrolysis of magnesium oxide. MgO is dissolved in a molten MgF2-CaF2 ionic flux. An oxygen-ion-conducting membrane, made from yttria-stabilized zirconia (YSZ), separates the cathode and the flux from the anode. During electrolysis, magnesium ions are reduced at the cathode, and Mg(g) is bubbled out of the flux into a separate condenser. The flux has a small solubility for magnesium metal which imparts electronic conductivity to the flux. The electronic conductivity decreases the process current efficiency and also degrades the YSZ membrane. Operating the electrolysis cell at low total pressures is shown to be an effective method of reducing the electronic conductivity of the flux. A two steel electrode method for measuring the electronic transference number in the flux was used to quantify the fraction of electronic current in the flux before and after SOM process operation. Potentiodynamic scans, potentiostatic electrolyses, and AC impedance spectroscopy were also used to characterize the SOM process under different operating conditions.

  7. Design and applications of an in situ electrochemical NMR cell

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaocan; Zwanziger, Josef W.

    2011-01-01

    A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5 mm NMR probe to acquire high-resolution NMR spectra while the working electrode was held at a constant electrical potential. The working electrode was a 20 nm thick gold film thermally coated on the outside of an inner 3 mm glass tube. An underlayer consisting of (3-mercaptopropyl)trimethoxy-silane was coated on the glass surface in order to improve its adhesion to gold. Tests showed prolonged life of the gold film. Details of the design and construction of the ECNMR cell are described. The ECNMR cell could be routinely used in a multi-user service high-resolution NMR instrument under oxygen-free conditions in both aqueous and non-aqueous solvents. Different approaches were applied to suppress the noise transmitted between the potentiostat and the NMR spectrometer. These approaches were shown to be effective in reducing background noise in the NMR spectra. The electrochemical and NMR performance of the ECNMR cell is presented. The reduction of 1,4-benzoquinone in both aqueous and non-aqueous solvents was used for testing. The evolution of the in situ ECNMR spectra with time demonstrated that use of the ECNMR cell was feasible. Studies of caffeic acid and 9-chloroanthracene using this ECNMR cell were undertaken to explore its applications, such as monitoring reactions and studying their reaction mechanisms.

  8. The Effect of Crystal Face of Fe2O3 on the Electrochemical Performance for Lithium-ion Batteries.

    PubMed

    Chen, Minmin; Zhao, Enyue; Yan, Qingbo; Hu, Zhongbo; Xiao, Xiaoling; Chen, Dongfeng

    2016-01-01

    Fe2O3 nanorods exposing (001) and (010) plane as well as Fe2O3 nanosheets exposing (001) plane have been successfully synthesized. Fe2O3 nanosheets exhibit better cycle performance and rate capabilities than that of Fe2O3 nanorods. The discharge capacity of Fe2O3 nanosheets can stabilize at 865 mAh/g at the rate of 0.2 C (1C = 1000 mA/g) and 570 mAh/g at the rate of 1.2 C after 80 cycles, which increased by 90% and 79% compared with 456 mAh/g and 318 mAh/g of Fe2O3 nanorods. In comparison with (010) plane, the (001) plane of hematite possesses larger packing density of Fe(3+) and O(2-), which is responsible for the superior electrochemical performances of Fe2O3 nanosheets than that of Fe2O3 nanorods. In addition, potentiostatic intermittent titration (PITT) results show the diffusion coefficients of Li(+) (DLi) of Fe2O3 nanosheets is higher than that of Fe2O3 nanorods. The higher diffusion coefficients of Li(+) is favorable for the excellent lithium-storage capabilities and rate capability of Fe2O3 nanosheets. Inspired by our results, we can design and synthesize Fe2O3 or other electrodes with high performances according to their structure features in future. PMID:27380891

  9. Pitting corrosion of iron in weakly alkaline chloride solutions

    SciTech Connect

    Makar, G.L.; Tromans, D.

    1996-04-01

    Chloride-induced pitting corrosion of iron at pH 10.5 and 25 C was examined by conducting quasi-steady-state (potentiostatic) polarization experiments in borate-buffered 0.1 M sodium chloride solutions with buffer concentrations from 0 M to 0.075 M. Values of the film breakdown potential (E{sub b}) were scattered at each buffer concentration, and the scatter band moved to higher potentials with increasing concentrations, indicating increased resistance to pitting. Consistent with this, pitting did not always occur at the higher buffer concentrations. E{sub b} measurements, optical and electron microscopy, X-ray microanalysis, and supplementary polarization experiments in lower-pH borate solutions suggested pitting in the iron -Cl{sup {minus}} system initiated within occluded regions, such as matrix-inclusion interfaces and exposed voids, where pH control was lost because of an inadequate local supply of buffer species. Pitting behavior was consistent with a mechanism dominated by mass transport, in which the presence of Cl{sup {minus}} prevented buffering of occluded regions by the borate specie H{sub 2}BO{sub 3}{sup {minus}}, allowing the ph to be driven into an acidic domain where the solubilities of ferrous hydroxide and ferric hydroxide are high.

  10. Effect of Fluoride on Nickel-Titanium and Stainless Steel Orthodontic Archwires: An In-Vitro Study

    PubMed Central

    Heravi, Farzin; Moayed, Mohamad Hadi; Mokhber, Nima

    2015-01-01

    Objectives: The commonly used Nickel-Titanium (NiTi) archwires in orthodontic treatment are often exposed to fluoride-containing mouthwashes. The aim of this in-vitro study was to evaluate and compare the corrosion resistance of three commercially available NiTi archwires exposed to 0.05 wt% and 0.2 wt% fluoride mouthwashes. Materials and Methods: Three different types of NiTi archwires, 0.016″ in diameter, from Dentaurum, Global, and GAC, and a stainless steel archwire from Dentaurum were examined to assess their corrosion resistance in Fusayama-Meyer artificial saliva and in two other artificial saliva containing 0.05 wt% and 0.2 wt% sodium fluoride (NaF). After the primary setup of wires, they were tested by potentiodynamic and potentiostatic polarization and corrosion potential/time analyses. Their surfaces were evaluated using a scanning electronic microscope (SEM). Results: The results showed that all the wires were passive in artificial saliva. In contrast, by adding fluoride ions to the solution, the decrease in the archwires’ corrosion resistance was in direct proportion to the increase in fluoride concentration. Conclusion: The NiTi wires experienced deterioration of their corrosion properties under the effect of fluoride but not as much as the stainless steel archwires. PMID:26005454

  11. Light-controlled bioelectrochemical sensor based on CdSe/ZnS quantum dots.

    PubMed

    Tanne, J; Schäfer, D; Khalid, W; Parak, W J; Lisdat, F

    2011-10-15

    This study reports on the oxygen sensitivity of quantum dot electrodes modified with CdSe/ZnS nanocrystals. The photocurrent behavior is analyzed for dependence on pH and applied potential by potentiostatic and potentiodynamic measurements. On the basis of the influence of the oxygen content in solution on the photocurrent generation, the enzymatic activity of glucose oxidase is evaluated in solution. In order to construct a photobioelectrochemical sensor which can be read out by illuminating the respective electrode area, two different immobilization methods for the fixation of the biocatalyst have been investigated. Both covalent cross-linking and layer-by-layer deposition of GOD by means of the polyelectrolyte polyallylamine hydrochloride show that a sensor construction is possible. The sensing properties of this type of electrode are drastically influenced by the amount and density of the enzyme on top of the quantum dot layer, which can be advantageously adjusted by the layer-by-layer technique. By depositing four bilayers [GOD/PAH](4) on the CdSe/ZnS electrode, a fast-responding sensor for the concentration range of 0.1-5 mM glucose can be prepared. This study opens the door to multianalyte detection with a nonstructured sensing electrode, localized enzymes, and spatial read-out by light. PMID:21870859

  12. Electrochemical behavior of gold nanoparticles modified nitrogen incorporated tetrahedral amorphous carbon and its application in glucose sensing.

    PubMed

    Liu, Aiping; Wu, Huaping; Qiu, Xu; Tang, Weihua

    2011-12-01

    Gold nanoparticles (NPs) with 10-50 nm in diameter were synthesized on nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) thin film electrode by electrodeposition. The deposition and nucleation processes of Au on ta-C:N surface were investigated by cyclic voltammetry and chronoamperometry. The morphology of Au NPs was characterized by scanned electron microscopy. The electrochemical properties of Au NPs modified ta-C:N (ta-C:N/Au) electrode and its ability to sense glucose were investigated by voltammetric and amperometric measurements. The potentiostatic current-time transients showed a progressive nucleation process and diffusion growth of Au on the surface of ta-C:N film according to the Scharifker-Hills model. The Au NPs acted as microelectrodes improved the electron transfer and electrocatalytic oxidation of glucose on ta-C:N electrode. The ta-C:N/Au electrode exhibited fast current response, a linear detection range of glucose from 0.5 to 25 mM and a detection limit of 120 microM, which hinted its potential application as a glucose biosensor. PMID:22409057

  13. Coupling Electrochemistry with Fluorescence Confocal Microscopy To Investigate Electrochemical Reactivity: A Case Study with the Resazurin-Resorufin Fluorogenic Couple.

    PubMed

    Doneux, Thomas; Bouffier, Laurent; Goudeau, Bertrand; Arbault, Stéphane

    2016-06-21

    The redox couple resazurin-resorufin exhibits electrofluorochromic properties which are investigated herein by absorption and fluorescence spectroelectrochemistry and by electrochemically coupled-fluorescence confocal laser scanning microscopy (EC-CLSM). At pH 10, the highly fluorescent resorufin dye is generated at the electrode surface by the electrochemical reduction of the poorly fluorescent resazurin. Performing EC-CLSM at electrode surfaces allows to monitor spatially resolved electrochemical processes in situ and in real time. Using a small (315 μm diameter) cylindrical electrode, a steady-state diffusion layer builds up under potentiostatic conditions at -0.45 V vs Ag|AgCl. Mapping the fluorescence intensity in 3D by CLSM enables us to reconstruct the relative concentration profile of resorufin around the electrode. The comparison of the experimental diffusion-profile with theoretical predictions demonstrates that spontaneous convection has a direct influence on the actual thickness of the diffusion layer, which is smaller than the value predicted for a purely diffusional transport. This study shows that combining fluorescence CLSM with electrochemistry is a powerful tool to study electrochemical reactivity at a spatially resolved level. PMID:27247989

  14. Effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induced stresses in spherical composition-gradient electrodes

    SciTech Connect

    Zhang, Kai; Li, Yong; Zheng, Bailin

    2015-09-14

    The composition-gradient electrode material is considered as one of the most promising materials for lithium-ion batteries because of its excellent electrochemical performance and thermal stability. In this work, the effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induce stress in the composition-gradient electrodes were studied. The coupling equations of elasticity and diffusion under both potentiostatic charging and galvanostatic charging were developed to obtain the distributions of both the Li-ions concentration and the stress. The results indicated that the effects of the concentration-dependent elastic modulus on the Li-ions diffusion and the diffusion-induce stresses are controlled by the lithiation induced stiffening factor in the composition-gradient electrodes: a low stiffening factor at the center and a high stiffening factor at the surface lead to a significant effect, whereas a high stiffening factor at the center and a low stiffening factor at the surface result in a minimal effect. The results in this work provide guidance for the selection of electrode materials.

  15. Packaged Au-PPy valves for drug delivery systems

    NASA Astrophysics Data System (ADS)

    Tsai, Han-Kuan A.; Ma, Kuo-Sheng; Zoval, Jim; Kulinsky, Lawrence; Madou, Marc

    2006-03-01

    The most common methods for the drug delivery are swallowing pills or receiving injections. However, formulations that control the rate and period of medicine (i.e., time-release medications) are still problematic. The proposed implantable devices which include batteries, sensors, telemetry, valves, and drug storage reservoirs provide an alternative method for the responsive drug delivery system [1]. Using this device, drug concentration can be precisely controlled which enhances drug efficiency and decreases the side effects. In order to achieve responsive drug delivery, a reliable release valve has to be developed. Biocompatibility, low energy consumption, and minimized leakage are the main requirements for such release method. A bilayer structure composed of Au/PPy film is fabricated as a flap to control the release valve. Optimized potentiostatic control to synthesize polypyrrole (PPy) is presented. The release of miniaturize valve is tested and showed in this paper. A novel idea to simultaneously fabricate the device reservoirs as well as protective packaging is proposed in this paper. The solution of PDMS permeability problem is also mentioned in this article.

  16. Reduction mechanism of sulfur in lithium-sulfur battery: From elemental sulfur to polysulfide

    SciTech Connect

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; Wang, Jiankun; Qu, Deyu; Qu, Deyang

    2015-10-30

    In this study, the polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfur were the S42– and S52– species, while the widely accepted reduction products of S82– and S62– for the first reduction wave were in low abundance.

  17. 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. PMID:23141325

  18. Effects of anodization growth of TiO2-nanotube array membrane on photo-conversion efficiency of dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Park, Min-Woo; Chun, Ki-Young

    2009-03-01

    Membranes of TiO2 nanotube(NT) arrays were grown by potentiostatic anodic oxidation in an ethylene glycol electrolyte with small addition of H2O and NH4F. Ti metal plate with a thickness of 0.1 mm was completely converted into ≈0.2 mm-thick TiO2 NT membrane for 24 to 96 h of anodization. Stacked NTs in membrane were separated into individual NT from the neighboring NTs as anodization continues up to 96 h. As-fabricated membrane of NTs were mechanically grinded to yield fine NT particles for the photoanode application to dye-sensitized solar cells (DSCs), in replacement of conventional TiO2 particles. Photo-conversion efficiency of the DSC using TiO2 crystalline NT particles is varying from 2.22% to 5.03%. Fine TiO2 NT particles can increase dye attachment due to high surface to volume ratio.

  19. Effects of Osseointegration by Bone Morphogenetic Protein-2 on Titanium Implants In Vitro and In Vivo

    PubMed Central

    Teng, Fu-Yuan; Chen, Wen-Cheng; Wang, Yin-Lai; Hung, Chun-Cheng; Tseng, Chun-Chieh

    2016-01-01

    This study designed a biomimetic implant for reducing healing time and achieving early osseointegration to create an active surface. Bone morphogenetic protein-2 (BMP-2) is a strong regulator protein in osteogenic pathways. Due to hardly maintaining BMP-2 biological function and specificity, BMP-2 efficient delivery on implant surfaces is the main challenge for the clinic application. In this study, a novel method for synthesizing functionalized silane film for superior modification with BMP-2 on titanium surfaces is proposed. Three groups were compared with and without BMP-2 on modified titanium surfaces in vitro and in vivo: mechanical grinding; electrochemical modification through potentiostatic anodization (ECH); and sandblasting, alkali heating, and etching (SMART). Cell tests indicated that the ECH and SMART groups with BMP-2 markedly promoted D1 cell activity and differentiation compared with the groups without BMP-2. Moreover, the SMART group with a BMP-2 surface markedly promoted early alkaline phosphatase expression in the D1 cells compared with the other surface groups. Compared with these groups in vivo, SMART silaning with BMP-2 showed superior bone quality and created contact areas between implant and surrounding bones. The SMART group with BMP-2 could promote cell mineralization in vitro and osseointegration in vivo, indicating potential clinical use. PMID:26977141

  20. Electrochemical preparation of Photosystem I-polyaniline composite films for biohybrid solar energy conversion.

    PubMed

    Gizzie, Evan A; LeBlanc, Gabriel; Jennings, G Kane; Cliffel, David E

    2015-05-13

    In this work, we report for the first time the entrapment of the biomolecular supercomplex Photosystem I (PSI) within a conductive polymer network of polyaniline via electrochemical copolymerization. Composite polymer-protein films were prepared on gold electrodes through potentiostatic electropolymerization from a single aqueous solution containing both aniline and PSI. This study demonstrates the controllable integration of large membrane proteins into rapidly prepared composite films, the entrapment of such proteins was observed through photoelectrochemical analysis. PSI's unique function as a highly efficient biomolecular photodiode generated a significant enhancement in photocurrent generation for the PSI-loaded polyaniline films, compared to pristine polyaniline films, and dropcast PSI films. A comprehensive study was then performed to separately evaluate film thickness and PSI concentration in the initial polymerization solution and their effects on the net photocurrent of this novel material. The best performing composite films were prepared with 0.1 μM PSI in the polymerization solution and deposited to a film thickness of 185 nm, resulting in an average photocurrent density of 5.7 μA cm(-2) with an efficiency of 0.005%. This photocurrent output represents an enhancement greater than 2-fold over bare polyaniline films and 200-fold over a traditional PSI multilayer film of comparable thickness. PMID:25897977

  1. Effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induced stresses in spherical composition-gradient electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Li, Yong; Zheng, Bailin

    2015-09-01

    The composition-gradient electrode material is considered as one of the most promising materials for lithium-ion batteries because of its excellent electrochemical performance and thermal stability. In this work, the effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induce stress in the composition-gradient electrodes were studied. The coupling equations of elasticity and diffusion under both potentiostatic charging and galvanostatic charging were developed to obtain the distributions of both the Li-ions concentration and the stress. The results indicated that the effects of the concentration-dependent elastic modulus on the Li-ions diffusion and the diffusion-induce stresses are controlled by the lithiation induced stiffening factor in the composition-gradient electrodes: a low stiffening factor at the center and a high stiffening factor at the surface lead to a significant effect, whereas a high stiffening factor at the center and a low stiffening factor at the surface result in a minimal effect. The results in this work provide guidance for the selection of electrode materials.

  2. Role of surfactant-mediated electrodeposited titanium oxide substrate in improving electrocatalytic features of supported platinum particles

    NASA Astrophysics Data System (ADS)

    Spătaru, Tanţa; Preda, Loredana; Osiceanu, Petre; Munteanu, Cornel; Anastasescu, Mihai; Marcu, Maria; Spătaru, Nicolae

    2014-01-01

    A new hybrid system with improved photocatalytic and electrocatalytic performances was obtained by two-step potentiostatic deposition on highly boron-doped diamond (BDD) substrate. First, hydrated TiO2 was anodically deposited from a TiCl3 aqueous solution, both in the presence and in the absence of sodium dodecyl sulfate (SDS). The study of the UV irradiation effect evidenced that titanium oxide coatings obtained by surfactant-assisted electrodeposition (TiO2:SDS) exhibit enhanced photocurrent, due to its very rough texture and presumably to better efficiency of charge carrier separation. Electrochemical deposition of platinum on the oxide-coated BDD was carried out in a second step and AFM, SEM and XPS measurements have shown that, on the TiO2:SDS substrate, Pt particles are smaller, more uniformly distributed, and tend to form clusters, leading to a specific surface area of the electrocatalyst of ca. 6.55 m2 g-1. Carbon monoxide stripping experiments demonstrated that, when deposited on TiO2:SDS, Pt particles are also less sensitive to CO-poisoning during methanol anodic oxidation.

  3. Improvement in direct methanol fuel cell performance by treating the anode at high anodic potential

    NASA Astrophysics Data System (ADS)

    Joghee, Prabhuram; Pylypenko, Svitlana; Wood, Kevin; Corpuz, April; Bender, Guido; Dinh, Huyen N.; O'Hayre, Ryan

    2014-01-01

    This work investigates the effect of a high anodic potential treatment protocol on the performance of a direct methanol fuel cell (DMFC). DMFC membrane electrode assemblies (MEAs) with PtRu/C (Hi-spec 5000) anode catalyst are subjected to anodic treatment (AT) at 0.8 V vs. DHE using potentiostatic method. Despite causing a slight decrease in the electrochemical surface area (ECSA) of the anode, associated with ruthenium dissolution, AT results in significant improvement in DMFC performance in the ohmic and mass transfer regions and increases the maximum power density by ∼15%. Furthermore, AT improves the long-term DMFC stability by reducing the degradation of the anode catalyst. From XPS investigation, it is hypothesized that the improved performance of AT-treated MEAs is related to an improved interface between the catalyst and Nafion ionomer. Among potential explanations, this improvement may be caused by incorporation of the ionomer within the secondary pores of PtRu/C agglomerates, which generates a percolating network of ionomer between PtRu/C agglomerates in the catalyst layer. Furthermore, the decreased concentration of hydrophobic CF2 groups may help to enhance the hydrophilicity of the catalyst layer, thereby increasing the accessibility of methanol and resulting in better performance in the high current density region.

  4. Poly(3,4-ethylenedioxythiophene)/multiwall carbon nanotube composite coatings for improving the stability of microelectrodes in neural prostheses applications.

    PubMed

    Zhou, Haihan; Cheng, Xuan; Rao, Li; Li, Tao; Duan, Yanwen Y

    2013-05-01

    With the purpose of improving the stability of microelectrodes under continuous high charge density stimulation, which is required for neural prostheses applications such as visual prostheses, multiwall carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite films were coated onto a platinum microelectrode by electrochemical polymerization. Galvanostatically polymerized PEDOT/MWCNT films demonstrated superior characteristics compared to polystyrene sulfonate doping and potentiostatic polymerization, including a three-dimensional cone morphology and enhanced electrochemical performance (the safe charge injection limit reached 6.2 mC cm(-2) for cathodic-first pulses). Most important of all, the improved stability of the coatings has been revealed through stimulation for 96 h using 3.0 mCc m(-2) current pulses in bicarbonate- and phosphate-buffered saline solution. Cell assays revealed that PEDOT/MWCNT films could promote the adhesion and neurite outgrowth of rat pheochromocytoma cells. Finally, platinum wires coated with PEDOT/MWCNT films were implanted into rat cortex for 6 weeks for histological evaluation. Glial fibrillary acidic protein and neuronal nuclei staining revealed that the films elicit a lower tissue response compared to platinum implants. These results suggest that the galvanostatically polymerized PEDOT/MWCNT films can improve the stability of stimulation microelectrodes and that PEDOT/MWCNT is an excellent candidate material for electrode coating for neural prostheses applications. PMID:23402765

  5. Pt-Sn/C catalysts prepared by sodium borohydride reduction for alcohol oxidation in fuel cells: Effect of the precursor addition order

    NASA Astrophysics Data System (ADS)

    López-Suárez, F. E.; Bueno-López, A.; Eguiluz, K. I. B.; Salazar-Banda, G. R.

    2014-12-01

    A series of Pt-Sn/C catalysts used as anodes during ethanol oxidation are synthesized by a deposition process using NaBH4 as the reducing agent. The order in which the precursors are added affects the electrocatalytic activity and physical-chemical characteristics of the bimetallic catalysts, where the Pt-Sn catalyst prepared by co-precipitation of both metals functions best below a potential of 0.5 V and the catalyst prepared by sequential deposition of Sn and Pt (drying after Sn addition) is most active above a potential of 0.5 V. The electrochemical behavior of catalysts during ethanol oxidation in an acidic medium are characterized and monitored in a half-cell test at room temperature by cyclic voltammetry, chronoamperometry and anode potentiostatic polarization. Catalyst structure and chemical composition are investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). This behavior presented for best Pt-Sn catalyst can be attributed to the so-called bifunctional mechanism and to the electronic interaction between Pt and Sn.

  6. Electrochemical Surface Plasmon Resonance Fiber-Optic Sensor: In Situ Detection of Electroactive Biofilms.

    PubMed

    Yuan, Yong; Guo, Tuan; Qiu, Xuhui; Tang, Jiahuan; Huang, Yunyun; Zhuang, Li; Zhou, Shungui; Li, Zhaohui; Guan, Bai-Ou; Zhang, Xuming; Albert, Jacques

    2016-08-01

    Spectroelectrochemistry has been found to be an efficient technique for revealing extracellular electron transfer (EET) mechanism of electroactive biofilms (EABs). Herein, we propose a novel electrochemical surface plasmon resonance (EC-SPR) optical fiber sensor for monitoring EABs in situ. The sensor uses a tilted fiber Bragg grating (TFBG) imprinted in a commercial single-mode fiber and coated with nanoscale gold film for high-efficiency SPR excitation. The wavelength shift of the surface plasmon resonance (SPR) over the fiber surface clearly identifies the electrochemical activity of the surface localized (adjacent to the electrode interface) bacterial cells in EABs, which differs from the "bulk" detections of the conventional electrochemical measurements. A close relationship between the variations of redox state of the EABs and the changes of the SPR under potentiostatic conditions has been achieved, pointing to a new way to study the EET mechanism of the EABs. Benefiting from its compact size, high sensitivity, and ease of use, together with remote operation ability, the proposed sensor opens up a multitude of opportunities for monitoring EABs in various hard-to-reach environments. PMID:27214753

  7. Influence of fluoride content and pH on corrosion and tribocorrosion behaviour of Ti13Nb13Zr alloy in oral environment.

    PubMed

    Golvano, I; Garcia, I; Conde, A; Tato, W; Aginagalde, A

    2015-09-01

    CpTi and Ti6Al4V alloy are the most widely used materials for implant application, but the release of toxic elements (e.g. Al and V) and the so-called stress-shielding effect are still a concern. In recent years, β and near-β titanium alloys have been developed, which overcome these issues with reduced modulus of elasticity and biocompatible alloying elements. However, literature is scarce studying the tribocorrosion behaviour of these alloys for dental implantology. The present work studies the tribocorrosion behaviour of the near-β Ti13Nb13Zr alloy in oral environment, using CpTi4 for comparison purposes. To that end, the influence of the pH and fluoride concentration in artificial saliva was analysed. Reciprocating sliding corrosion tests were carried out under open circuit potential and potentiostatic conditions. Results reveal a negative influence of the increase of fluoride concentration and the acidified artificial saliva on the material degradation. Moreover, some light has been shed on the different tribocorrosion mechanisms of Ti13Nb13Zr and CpTi4 in simulated oral environment. PMID:26042765

  8. Study of Pyridine-Mediated Electrochemical Reduction of CO2 to Methanol at High CO2 Pressure.

    PubMed

    Rybchenko, Sergey I; Touhami, Dalila; Wadhawan, Jay D; Haywood, Stephanie K

    2016-07-01

    The recently proposed highly efficient route of pyridine-catalyzed CO2 reduction to methanol was explored on platinum electrodes at high CO2 pressure. At 55 bar (5.5 MPa) of CO2 , the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yields of up to 10 % for the first 5-10 C cm(-2) of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally and was limited to sub-ppm levels irrespective of biasing conditions and pyridine concentration. This limitation cannot be removed by electrode reactivation and/or pre-electrolysis and appears to be an inherent feature of the reduction process. In agreement with bulk electrolysis findings, the CV analysis supported by simulation indicated that hydrogen evolution is still the dominant electrode reaction in pyridine-containing electrolyte solution, even with an excess CO2 concentration in the solution. No prominent contribution from either a direct or coupled CO2 reduction was found. The results obtained suggest that the reduction of CO2 to methanol is a transient process that is largely decoupled from the electrode charge transfer. PMID:27253886

  9. Electrolysis of metal oxides in MgCl2 based molten salts with an inert graphite anode.

    PubMed

    Yuan, Yating; Li, Wei; Chen, Hualin; Wang, Zhiyong; Jin, Xianbo; Chen, George Z

    2016-08-15

    Electrolysis of solid metal oxides has been demonstrated in MgCl2-NaCl-KCl melt at 700 °C taking the electrolysis of Ta2O5 as an example. Both the cathodic and anodic processes have been investigated using cyclic voltammetry, and potentiostatic and constant voltage electrolysis, with the cathodic products analysed by XRD and SEM and the anodic products by GC. Fast electrolysis of Ta2O5 against a graphite anode has been realized at a cell voltage of 2 V, or a total overpotential of about 400 mV. The energy consumption was about 1 kW h kgTa(-1) with a nearly 100% Ta recovery. The cathodic product was nanometer Ta powder with sizes of about 50 nm. The main anodic product was Cl2 gas, together with about 1 mol% O2 gas and trace amounts of CO. The graphite anode was found to be an excellent inert anode. These results promise an environmentally-friendly and energy efficient method for metal extraction by electrolysis of metal oxides in MgCl2 based molten salts. PMID:27203663

  10. Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

    PubMed

    Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

    2015-04-01

    The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

  11. Photoelectrocatalytic oxidation of glucose at a ruthenium complex modified titanium dioxide electrode promoted by uric acid and ascorbic acid for photoelectrochemical fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Shuo-Jian; Ji, Shi-Bo; Liu, Jun-Chen; Li, Hong; Li, Wei-Shan

    2015-01-01

    The simultaneous presence of uric acid (UA) and ascorbic acid (AA) is first found to largely promote the photoelectrocatalytic oxidation of glucose (GLU) at an indium-tin oxide (ITO) or TiO2 nanoparticles/ITO electrode modified with [Ru(tatp)3]2+ (tatp = 1,4,8,9-tetra-aza-triphenylene) possessing good redox activity and nanoparticle size distribution. A well-defined electrocatalytic peak for GLU oxidation is shown at 0.265 V (vs. SCE) under approximate physiological conditions upon incorporation of UA and AA. The [Ru(tatp)3]2+/ITO electrode exhibits attractive amperometric oxidation responses towards GLU, UA and AA, while controlled potentiostatically at 0.3 V, 0.7 V and 1.0 V, respectively, indicating high sensitivity and excellent reproducibility. On basis of the photoelectrocatalysis of [Ru(tatp)3]2+/TiO2/ITO anode, a GLU concentration-dependent photoelectrochemical fuel cell vs. SCE is elaborately assembled. The proposed free-enzyme photoelectrochemical fuel cell employing 0.1 M GLU associated with 0.01 M UA and 0.01 M AA as fuel shows open-circuit photovoltage of 0.608 V, short-circuit photocurrent density of 124.5 μA cm-2 and maximum power density of 21.75 μW cm-2 at 0.455 V, fill factor of 0.32 and photoenergy conversion efficiency of 36.65%, respectively.

  12. Electrooxidation of coal slurries on different electrode materials

    NASA Astrophysics Data System (ADS)

    Patil, Prashanth; De Abreu, Yolanda; Botte, Gerardine G.

    The electrochemical behavior of coal-water slurries was examined with various noble metal electrodes (i.e. Pt, Pt-Rh, Pt-Ru, Pt-Ir and plated Pt on Ti foil) using potentiostatic techniques. It was found that there was no significant difference in the performance of the electrodes in the electrooxidation of coal; except for Pt-Ir, which out performed the other electrode materials. The effect of adding iron(III) and iron(II) on the electrooxidation of coal was also tested. It was found that the presence of iron(III) and iron(II) in the coal slurry significantly increased the average current densities developed in the coal electrolytic cell. The electrolysis of pure graphite was tested and compared to the electrolysis of coal to determine if any components or impurities present in the coal affected the electrooxidation of coal. It was also found that the iridium content in the electrode affects the electrochemical performance of the coal. The maximum faradaic efficiency found for the electrooxidation of coal on a Pt-Ir (80:20) electrode was 24% for CO 2 generation with an energy consumption of 21 W h g -1 of hydrogen produced.

  13. Backside illuminated dye-sensitized solar cells based on titania nanotube array electrodes

    NASA Astrophysics Data System (ADS)

    Paulose, Maggie; Shankar, Karthik; Varghese, Oomman K.; Mor, Gopal K.; Hardin, Brian; Grimes, Craig A.

    2006-03-01

    Backside illuminated solar cells based on 6 µm long highly-ordered nanotube-array films sensitized by a self-assembled monolayer of bis(tetrabutylammonium)-cis-(dithiocyanato)- N,N'-bis(4-carboxylato-4'-carboxylic acid-2, 2'-bipyridine)ruthenium(II) (commonly called 'N719') show a short-circuit current density of 8.79 mA cm-2, 841 mV open circuit potential and a 0.57 fill factor yielding a power conversion efficiency of 4.24% under AM 1.5 sun. The solvent used to infiltrate the dye into the nanotube arrays, made by potentiostatic anodization of a titanium foil, was found to significantly influence the electrical characteristics of the resulting solar cell. A superior photoresponse was obtained with acetonitrile as the dye solvent. This is attributed to the improved wetting characteristics of the dye solution in acetonitrile enabling self-assembled monolayers with higher surface coverage to be formed inside the nanotubes. In comparison to nanocrystalline films, the nanotube-array films consistently exhibit larger open circuit photovoltage values; the origins of this enhancement are discussed.

  14. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers.

    PubMed

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180(°). PMID:26846891

  15. Electrochemical generation of oxygen. 1: The effects of anions and cations on hydrogen chemisorption and anodic oxide film formation on platinum electrode. 2: The effects of anions and cations on oxygen generation on platinum electrode

    NASA Technical Reports Server (NTRS)

    Huang, C. J.; Yeager, E.; Ogrady, W. E.

    1975-01-01

    The effects were studied of anions and cations on hydrogen chemisorption and anodic oxide film formation on Pt by linear sweep voltammetry, and on oxygen generation on Pt by potentiostatic overpotential measurement. The hydrogen chemisorption and anodic oxide film formation regions are greatly influenced by anion adsorption. In acids, the strongly bound hydrogen occurs at more cathodic potential when chloride and sulfate are present. Sulfate affects the initial phase of oxide film formation by produced fine structure while chloride retards the oxide-film formation. In alkaline solutions, both strongly and weakly bound hydrogen are influenced by iodide, cyanide, and barium and calcium cations. These ions also influence the oxide film formation. Factors considered to explain these effects are discussed. The Tafel slope for oxygen generation was found to be independent on the oxide thickness and the presence of cations or anions. The catalytic activity indicated by the exchange current density was observed decreasing with increasing oxide layer thickness, only a minor dependence on the addition of certain cations and anions was found.

  16. Development of an on-animal separation-based sensor for monitoring drug metabolism in freely roaming sheep.

    PubMed

    Scott, David E; Willis, Sean D; Gabbert, Seth; Johnson, David; Naylor, Erik; Janle, Elsa M; Krichevsky, Janice E; Lunte, Craig E; Lunte, Susan M

    2015-06-01

    The development of an on-animal separation-based sensor that can be employed for monitoring drug metabolism in a freely roaming sheep is described. The system consists of microdialysis sampling coupled to microchip electrophoresis with electrochemical detection (MD-ME-EC). Separations were accomplished using an all-glass chip with integrated platinum working and reference electrodes. Discrete samples from the microdialysis flow were introduced into the electrophoresis chip using a flow-gated injection approach. Electrochemical detection was accomplished in-channel using a two-electrode isolated potentiostat. Nitrite was separated by microchip electrophoresis using reverse polarity and a run buffer consisting of 50 mM phosphate at pH 7.4. The entire system was under telemetry control. The system was first tested with rats to monitor the production of nitrite following perfusion of nitroglycerin into the subdermal tissue using a linear probe. The data acquired using the on-line MD-ME-EC system were compared to those obtained by off-line analysis using liquid chromatography with electrochemical detection (LC-EC), using a second microdialysis probe implanted parallel to the first probe in the same animal. The MD-ME-EC device was then used on-animal to monitor the subdermal metabolism of nitroglycerin in sheep. The ultimate goal is to use this device to simultaneously monitor drug metabolism and behavior in a freely roaming animal. PMID:25697221

  17. UV/Vis/NIR Spectroelectrochemistry

    NASA Astrophysics Data System (ADS)

    Neudeck, Andreas; Marken, Frank; Compton, Richard G.

    Voltammetric techniques used in electrochemistry monitor the flow of current as a function of potential, time, and mass transport. A huge variety of different experiments are possible, giving information about reaction energies, reaction intermediates, and the kinetics of a process [1-4]. However, additional data are often required and are accessible, in particular, via in situ spectroelectrochemical approaches. By coupling a spectroscopic technique such as UV/Vis/NIR spectroscopy [5, 6] to an electrochemical experiment, a wealth of complementary information as a function of the potential, time, and mass transport is available. In a recently published book dedicated to spectroelectrochemical techniques [7] the diversity of methods and new chemical information obtained is apparent. Both spectroscopic information about short-lived unstable intermediates and spectroscopic information disentangling the composition of complex mixtures of reactants can be obtained. Figure II.6.1 shows a schematic diagram for the case of a computer-controlled potentiostat system connected to a conventional electrochemical cell (working electrode WE, reference electrode RE, counter electrode CE) and simultaneously controlling the emitter and detector of a spectrometer. This kind of experimental arrangement allows the electrochemical and the spectroscopic data to be recorded simultaneously and, therefore, in contrast to the analysis of two independent data sets, direct correlation of data as a function of time and potential is possible.

  18. Enhanced electrocatalytic activity of the Au-electrodeposited Pt nanoparticles-coated conducting oxide for the quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yoon, Yeung-Pil; Kim, Jae-Hong; Kang, Soon-Hyung; Kim, Hyunsoo; Choi, Chel-Jong; Kim, Kyong-Kook; Ahn, Kwang-Soon

    2014-08-01

    Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO2 (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Au particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of Sn2- + 2e- (CE) → Sn-12- + S2- at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, Sn2- + 2e- (TiO2 in the photoanode) → Sn-12- + S2-, and significantly improved overall energy conversion efficiency.

  19. Preparation of core/shell and hollow nanostructures of cerium oxide by electrodeposition on a polystyrene sphere template.

    PubMed

    Yamaguchi, Ippei; Watanabe, Mitsuru; Shinagawa, Tsutomu; Chigane, Masaya; Inaba, Minoru; Tasaka, Akimasa; Izaki, Masanobu

    2009-05-01

    Core/shell nanostructures of polystyrene (PS)/CeO2 have been prepared on conductive glass substrates by using a novel electrochemical route consisting of (i) the electrophoretic deposition of a PS sphere monolayer on the substrate and (ii) the following potentiostatic electrodeposition of CeO2 on the PS sphere template in Ce(NO3)3 aqueous solutions. The structural morphologies of the deposit changed drastically depending on the Ce(NO3)3 concentration; i.e., spherical and needlelike shells were deposited. The deposit was formed only on the PS sphere surface because of an interaction between cationic cerium species and a sulfate group that was immobilized on the PS sphere surface. The spherical shell layer was assigned as CeO2, and the needlelike shells were composed of Ce(OH)3 needles formed on the CeO2 layer surface, indicating that the deposit species changes from CeO2 to Ce(OH)3 during electrodeposition only in a 1 mM Ce3+ solution. Deposition of Ce(OH)3 would begin when electrogenerated hydrogen peroxide was consumed by decomposition under reductive conditions and could no longer oxidize Ce3+ ions. The corresponding CeO2 hollow shells were obtained by thermal elimination of the PS sphere core and transformation of Ce(OH)3 into CeO2 while keeping their original shapes. PMID:20355893

  20. Influences of the main anodic electroplating parameters on cerium oxide films

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Yang, Yumeng; Du, Xiaoqing; Chen, Yu; Zhang, Zhao; Zhang, Jianqing

    2014-06-01

    Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O2 and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce3+ goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce3+, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N2 or O2 purged into the bath will result in film porosities and O2 favors cerium oxide particles and film generation.

  1. Adhesion of colloidal particles on modified electrodes.

    PubMed

    Kuznetsov, Volodymyr; Papastavrou, Georg

    2012-12-01

    The adhesion between colloidal silica particles and modified electrodes has been studied by direct force measurements with the colloidal probe technique based on the atomic force microscope (AFM). The combination of potentiostatic control of gold electrodes and chemical modification of their surface with self-assembled monolayers (SAMs) allows for the decoupling of forces due to the electrical double layers and functional groups at the solid/liquid interface. Adhesion on such electrodes can be tuned over a large range using the externally applied potential and the aqueous solution's ionic strength. By utilizing cantilevers with a high force constant, it is possible to separate the various contributions to adhesion in an unambiguous manner. These contributions comprise diffuse-layer overlap, van der Waals forces, solvent exclusion, and electrocapillarity. A quantitative description of the observed adhesion forces is obtained by taking into account the surface roughness of the silica particle. The main component of the adhesion forces originates from the overlap of the electrical double layers, which is tuned by the external potential. By contrast, effects due to electrocapillarity are of only minor importance. Based on our quantitative analysis, a new approach is proposed that allows tuning of the adhesion force as a function of the externally applied potential. We expect this approach to have important applications for the design of microelectromechanical systems (MEMS), the development of electrochemical sensors, and the application of micro- and nanomanipulation. PMID:23072548

  2. Poly(3,4-ethylenedioxithiophene)/MnO 2 composite electrodes for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Rios, Emerson C.; Correa, Alessandra A.; Cristovan, Fernando H.; Pocrifka, Leandro A.; Rosario, Adriane V.

    2011-11-01

    Composite electrodes of poly(3,4-ethylenedioxithiophene) and manganese oxide (PEDOT/MnO 2) have been prepared by electrodeposition of manganese oxide over PEDOT-modified titanium substrate. The PEDOT layers are deposited on titanium by potentiostatic deposition at 1.4 V and at two different temperatures: 5 and 25 °C (named PEDOT (5) and PEDOT (25), respectively). The electrodes are characterized by field emission gun scanning electron microscopy (FEG-SEM) and their electrochemical performances are evaluated by using cyclic voltammetry (CV) in 1 molL -1 Na 2SO 4. The results show an improvement in the specific capacitance ( C s) of the oxide due to the presence of the polymer layer. Considering only the MnO 2 mass, the C s values of the electrodes Ti/MnO 2, Ti/PEDOT (5)/MnO 2 and Ti/PEDOT (25)/MnO 2, estimated by the CV technique, are 151, 159 and 199 Fg -1 at 10 mVs -1 respectively. The micrographies of electrodes show that the polymer layer leads to very significant changes in the morphology of the oxide layers, which in turn generates the improvement observed in the capacitive property.

  3. Real-time, multiplexed electrochemical DNA detection using an active complementary metal-oxide-semiconductor biosensor array with integrated sensor electronics.

    PubMed

    Levine, Peter M; Gong, Ping; Levicky, Rastislav; Shepard, Kenneth L

    2009-03-15

    Optical biosensing based on fluorescence detection has arguably become the standard technique for quantifying extents of hybridization between surface-immobilized probes and fluorophore-labeled analyte targets in DNA microarrays. However, electrochemical detection techniques are emerging which could eliminate the need for physically bulky optical instrumentation, enabling the design of portable devices for point-of-care applications. Unlike fluorescence detection, which can function well using a passive substrate (one without integrated electronics), multiplexed electrochemical detection requires an electronically active substrate to analyze each array site and benefits from the addition of integrated electronic instrumentation to further reduce platform size and eliminate the electromagnetic interference that can result from bringing non-amplified signals off chip. We report on an active electrochemical biosensor array, constructed with a standard complementary metal-oxide-semiconductor (CMOS) technology, to perform quantitative DNA hybridization detection on chip using targets conjugated with ferrocene redox labels. A 4 x 4 array of gold working electrodes and integrated potentiostat electronics, consisting of control amplifiers and current-input analog-to-digital converters, on a custom-designed 5 mm x 3 mm CMOS chip drive redox reactions using cyclic voltammetry, sense DNA binding, and transmit digital data off chip for analysis. We demonstrate multiplexed and specific detection of DNA targets as well as real-time monitoring of hybridization, a task that is difficult, if not impossible, with traditional fluorescence-based microarrays. PMID:19054661

  4. Unveiling the Hard Anodization Regime of Aluminum: Insight into Nanopores Self-Organization and Growth Mechanism.

    PubMed

    Vega, Víctor; García, Javier; Montero-Moreno, Josep M; Hernando, Blanca; Bachmann, Julien; Prida, Víctor M; Nielsch, Kornelius

    2015-12-30

    Pores growth mechanism and their self-ordering conditions are investigated for nanoporous alumina membranes synthesized by hard anodization (HA) of Al in a broad range of anodic conditions, covering oxalic acid electrolytes with concentrations from 0.300 M down to 0.075 M and potentiostatic anodization voltages between 120 and 225 V. The use of linear sweep voltammetry (LSV) and scanning and transmission electron microscopy, together with image analysis techniques allow one to characterize the intrinsic nature of the HA regime. HA of aluminum is explained on the basis of a phenomenological model taking into account the role of oxalate ions and their limited diffusion through alumina nanochannels from a bulk electrolyte. The depletion of oxalate ions at the bottom of the pores causes an increased growth of the alumina barrier layer at the oxide/electrolyte interface. Furthermore, an innovative method has been developed for the determination of the HA conditions leading to self-ordered pore growth in any given electrolyte, thus allowing one to extend the available range of interpore distances of the highly ordered hexagonal pore arrangement in a wide range of 240-507 nm, while keeping small pore diameters of 50-60 nm. PMID:26646814

  5. Effects of cooling time and alloying elements on the microstructure of the gleeble-simulated heat-affected zone of 22% Cr duplex stainless steels

    NASA Astrophysics Data System (ADS)

    Hsieh, Rong-Iuan; Liou, Horng-Yih; Pan, Yeong-Tsuen

    2001-10-01

    The effects of austenite stabilizers, such as nitrogen, nickel, and manganese, and cooling time on the microstructure of the Gleeble simulated heat-affected zone (HAZ) of 22% Cr duplex stainless steels were investigated. The submerged are welding was performed for comparison purposes. Optical microscopy (OM) and transmission electron microscopy (TEM) were used for microscopic studies. The amount of Cr2N precipitates in the simulated HAZ was determined using the potentiostatic electrolysis method. The experimental results indicate that an increase in the nitrogen and nickel contents raised the δ to transformation temperature and also markedly increased the amount of austenite in the HAZ. The lengthened cooling time promotes the reformation of austenite. An increase in the austenite content reduces the supersaturation of nitrogen in ferrite matrix as well as the precipitation tendency of Cr2N. The optimum cooling time from 800 to 500 °C (Δ t 8/5) obtained from the Gleeble simulation is between 30 and 60 s, which ensures the austenite content in HAZ not falling below 25% and superior pitting and stress corrosion cracking resistance for the steels. The effect of manganese on the formation of austenite can be negligible.

  6. Protein-Support Interactions for Rationally Designed Bilirubin Oxidase Based Cathode: A Computational Study.

    PubMed

    Matanovic, Ivana; Babanova, Sofia; Chavez, Madelaine Seow; Atanassov, Plamen

    2016-04-21

    An example of biocathode based on bilirubin oxidase (BOx) was used to demonstrate how density functional theory can be combined with docking simulations in order to study the interface interactions between the enzyme and specifically designed electrode surface. The electrode surface was modified through the adsorption of bilirubin, the natural substrate for BOx, and the prepared electrode was electrochemically characterized using potentiostatic measurements. The experimentally determined current densities showed that the presence of bilirubin led to significant improvement of the cathode operation. On the basis of the computationally calculated binding energies of bilirubin to the graphene support and BOx and the analysis of the positioning of bilirubin relative to the support and T1 Cu atom of the enzyme, we hypothesize that the bilirubin serves as a geometric and electronic extension of the support. The computational results further confirm that the modification of the electrode surface with bilirubin provides an optimal orientation of BOx toward the support but also show that bilirubin facilitates the interfacial electron transfer by decreasing the distance between the electrode surface and the T1 Cu atom. PMID:27015361

  7. Effect of an oxygen plasma treatment on the specific surface of platinum electrodeposits for fuel cells

    NASA Astrophysics Data System (ADS)

    Massoni, Nicolas; Beaumont-Martinent, Audrey; Laurent, Jean-Yves

    Fuel cells involve electrochemical reactions often catalysed by platinum whose surface has to be maximized. In this paper, platinum nano-particles are deposited onto graphite by a potentiostatic reduction of a dilute 1.0 mM solution of hexachloroplatinate acid. Some samples are pre-treated by highly dissociated oxygen plasma and exhibit an increase of their specific surface compared to the untreated ones. The gain factor on specific surface reaches 3.6 and even 4.4 when the plasma treatment is coupled with the impregnation technique. Surface functionalization made by the plasma treatment lead to denser deposits thanks to an organized nucleation and growth of platinum nuclei. XPS analyses suggest the existence of C-O bonds in the platinum clusters. Although the testing conditions were not optimized, we have measured the performances of a microfuel cell made with the optimized catalyst. The Scharifker and Hills electrocrystallisation model was used to fit the current transients. Untreated samples transients were correctly fitted by the model whereas plasma treated samples transients did not have the requested shape for this model. Hence, nucleation mechanism was determined and confirmed by observation on untreated samples only. The calculated value of the diffusion coefficient of the Pt(IV) anion PtCl 6 2- determined by the Cottrell theory was close to the literature, i.e. 2.6 ± 0.6 × 10 -6 cm 2 s -1.

  8. Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics.

    PubMed

    Kim, Jayoung; Imani, Somayeh; de Araujo, William R; Warchall, Julian; Valdés-Ramírez, Gabriela; Paixão, Thiago R L C; Mercier, Patrick P; Wang, Joseph

    2015-12-15

    This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications. PMID:26276541

  9. The Effect of Crystal Face of Fe2O3 on the Electrochemical Performance for Lithium-ion Batteries

    NASA Astrophysics Data System (ADS)

    Chen, Minmin; Zhao, Enyue; Yan, Qingbo; Hu, Zhongbo; Xiao, Xiaoling; Chen, Dongfeng

    2016-07-01

    Fe2O3 nanorods exposing (001) and (010) plane as well as Fe2O3 nanosheets exposing (001) plane have been successfully synthesized. Fe2O3 nanosheets exhibit better cycle performance and rate capabilities than that of Fe2O3 nanorods. The discharge capacity of Fe2O3 nanosheets can stabilize at 865 mAh/g at the rate of 0.2 C (1C = 1000 mA/g) and 570 mAh/g at the rate of 1.2 C after 80 cycles, which increased by 90% and 79% compared with 456 mAh/g and 318 mAh/g of Fe2O3 nanorods. In comparison with (010) plane, the (001) plane of hematite possesses larger packing density of Fe3+ and O2‑, which is responsible for the superior electrochemical performances of Fe2O3 nanosheets than that of Fe2O3 nanorods. In addition, potentiostatic intermittent titration (PITT) results show the diffusion coefficients of Li+ (DLi) of Fe2O3 nanosheets is higher than that of Fe2O3 nanorods. The higher diffusion coefficients of Li+ is favorable for the excellent lithium-storage capabilities and rate capability of Fe2O3 nanosheets. Inspired by our results, we can design and synthesize Fe2O3 or other electrodes with high performances according to their structure features in future.

  10. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples. PMID:27474318

  11. Electrochemical study of resistance to localized corrosion of stainless steels for biomaterial applications

    SciTech Connect

    Pan, J.; Karlen, C.; Ulfvin, C.

    2000-03-01

    Sandvik Bioline High-N and 316 LVM are two austenitic stainless steels especially developed for biomaterial applications. Their resistance to localized corrosion was investigated by electrochemical methods including cyclic potentiodynamic polarization and potentiostatic polarization measurements in a phosphate-buffered saline solution and in a simulated crevice solution, i.e., designed for crevice corrosion testing. Sandvik SAF 2507 (a high-performance super duplex stainless steel) was included in the tests as a reference material High-N, higher alloyed than 316 LVM, demonstrated excellent resistance to pitting initiation and a strong tendency to repassivation. High-N proved to have an equivalent or even higher resistance to localized corrosion than SAF 2507. The latter is known for its impressive corrosion properties, particularly in chloride containing environments. While 316 LVM may run the risk of crevice corrosion in implant applications, the risk seems negligible for High-N. In view of the fact that also the mechanical properties are superior to those of 316 LVM, High-N is a very attractive implant material.

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

    SciTech Connect

    Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.; Abdel-Fattah, Tarek M.

    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 electrochemical 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.

  13. Time-domain fitting of battery electrochemical impedance models

    NASA Astrophysics Data System (ADS)

    Alavi, S. M. M.; Birkl, C. R.; Howey, D. A.

    2015-08-01

    Electrochemical impedance spectroscopy (EIS) is an effective technique for diagnosing the behaviour of electrochemical devices such as batteries and fuel cells, usually by fitting data to an equivalent circuit model (ECM). The common approach in the laboratory is to measure the impedance spectrum of a cell in the frequency domain using a single sine sweep signal, then fit the ECM parameters in the frequency domain. This paper focuses instead on estimation of the ECM parameters directly from time-domain data. This may be advantageous for parameter estimation in practical applications such as automotive systems including battery-powered vehicles, where the data may be heavily corrupted by noise. The proposed methodology is based on the simplified refined instrumental variable for continuous-time fractional systems method ('srivcf'), provided by the Crone toolbox [1,2], combined with gradient-based optimisation to estimate the order of the fractional term in the ECM. The approach was tested first on synthetic data and then on real data measured from a 26650 lithium-ion iron phosphate cell with low-cost equipment. The resulting Nyquist plots from the time-domain fitted models match the impedance spectrum closely (much more accurately than when a Randles model is assumed), and the fitted parameters as separately determined through a laboratory potentiostat with frequency domain fitting match to within 13%.

  14. On the electrochemical formation of Pu-Al alloys in molten LiCl-KCl

    NASA Astrophysics Data System (ADS)

    Mendes, E.; Malmbeck, R.; Nourry, C.; Souček, P.; Glatz, J.-P.

    2012-01-01

    Properties of Pu-Al alloys were investigated in connection with development of pyrochemical methods for reprocessing of spent nuclear fuel. Electroseparation techniques in molten LiCl-KCl are being developed in ITU to group-selectively recover actinides from the mixture with fission products. In the process, actinides are electrochemically reduced on solid aluminium cathodes, forming solid actinide-aluminium alloys. This article is focused on electro-chemical characterisation of Pu-Al alloys in molten LiCl-KCl, on electrodeposition of Pu on solid Al electrodes and on determination of chemical composition and structure of the formed alloys. Cyclic voltammetry and chronopotentiometry were used to study Pu-Al alloys in the temperature range 400-550 °C. Pu is reduced to metal in one reduction step Pu 3+/Pu 0 on an inert W electrode. On a reactive Al electrode, the reduction of Pu 3+ to Pu 0 occurs at a more positive potential due to formation of Pu-Al alloys. The open circuit potential technique was used to identify the alloys formed. Stable deposits were obtained by potentiostatic electrolyses of LiCl-KCl-PuCl 3 melts on Al plates. XRD and SEM-EDX analyses were used to characterise the alloys, which were composed mainly of PuAl 4 with some PuAl 3. In addition, the preparation of PuCl 3 containing salt by carbochlorination of PuO 2 is described.

  15. Marine phototrophic consortia transfer electrons to electrodes in response to reductive stress.

    PubMed

    Darus, Libertus; Ledezma, Pablo; Keller, Jürg; Freguia, Stefano

    2016-03-01

    This work studies how extracellular electron transfer (EET) from cyanobacteria-dominated marine microbial biofilms to solid electrodes is affected by the availability of inorganic carbon (Ci). The EET was recorded chronoamperometrically in the form of electrical current by a potentiostat in two identical photo-electrochemical cells using carbon electrodes poised at a potential of +0.6 V versus standard hydrogen electrode under 12/12 h illumination/dark cycles. The Ci was supplied by the addition of NaHCO3 to the medium and/or by sparging CO2 gas. At high Ci conditions, EET from the microbial biofilm to the electrodes was observed only during the dark phase, indicating the occurrence of a form of night-time respiration that can use insoluble electrodes as the terminal electron acceptor. At low or no Ci conditions, however, EET also occurred during illumination suggesting that, in the absence of their natural electron acceptor, some cyanobacteria are able to utilise solid electrodes as an electron sink. This may be a natural survival mechanism for cyanobacteria to maintain redox balance in environments with limiting CO2 and/or high light intensity. PMID:26407568

  16. Study on Electro-polymerization Nano-micro Wiring System Imitating Axonal Growth of Artificial Neurons towards Machine Learning

    NASA Astrophysics Data System (ADS)

    Dang, Nguyen Tuan; Akai-Kasada, Megumi; Asai, Tetsuya; Saito, Akira; Kuwahara, Yuji; Hokkaido University Collaboration

    2015-03-01

    Machine learning using the artificial neuron network research is supposed to be the best way to understand how the human brain trains itself to process information. In this study, we have successfully developed the programs using supervised machine learning algorithm. However, these supervised learning processes for the neuron network required the very strong computing configuration. Derivation from the necessity of increasing in computing ability and in reduction of power consumption, accelerator circuits become critical. To develop such accelerator circuits using supervised machine learning algorithm, conducting polymer micro/nanowires growing process was realized and applied as a synaptic weigh controller. In this work, high conductivity Polypyrrole (PPy) and Poly (3, 4 - ethylenedioxythiophene) PEDOT wires were potentiostatically grown crosslinking the designated electrodes, which were prefabricated by lithography, when appropriate square wave AC voltage and appropriate frequency were applied. Micro/nanowire growing process emulated the neurotransmitter release process of synapses inside a biological neuron and wire's resistance variation during the growing process was preferred to as the variation of synaptic weigh in machine learning algorithm. In a cooperation with Graduate School of Information Science and Technology, Hokkaido University.

  17. Automated analysis of food-borne pathogens using a novel microbial cell culture, sensing and classification system.

    PubMed

    Xiang, Kun; Li, Yinglei; Ford, William; Land, Walker; Schaffer, J David; Congdon, Robert; Zhang, Jing; Sadik, Omowunmi

    2016-02-21

    We hereby report the design and implementation of an Autonomous Microbial Cell Culture and Classification (AMC(3)) system for rapid detection of food pathogens. Traditional food testing methods require multistep procedures and long incubation period, and are thus prone to human error. AMC(3) introduces a "one click approach" to the detection and classification of pathogenic bacteria. Once the cultured materials are prepared, all operations are automatic. AMC(3) is an integrated sensor array platform in a microbial fuel cell system composed of a multi-potentiostat, an automated data collection system (Python program, Yocto Maxi-coupler electromechanical relay module) and a powerful classification program. The classification scheme consists of Probabilistic Neural Network (PNN), Support Vector Machines (SVM) and General Regression Neural Network (GRNN) oracle-based system. Differential Pulse Voltammetry (DPV) is performed on standard samples or unknown samples. Then, using preset feature extractions and quality control, accepted data are analyzed by the intelligent classification system. In a typical use, thirty-two extracted features were analyzed to correctly classify the following pathogens: Escherichia coli ATCC#25922, Escherichia coli ATCC#11775, and Staphylococcus epidermidis ATCC#12228. 85.4% accuracy range was recorded for unknown samples, and within a shorter time period than the industry standard of 24 hours. PMID:26818563

  18. Evaluation of a diffusion/trapping model for hydrogen ingress in high-strength alloys. Final technical report, November 1988-November 1990

    SciTech Connect

    Pound, B.G.

    1990-11-14

    The objective of this research was to obtain the hydrogen ingress and trapping characteristics for a range of microstructures and so identify the dominant type of irreversible trap in different alloys. A diffusion/trapping model was used in conjunction with a potentiostatic pulse technique to study the ingress of hydrogen in three precipitation-hardened alloys (Inconel 718, Incoloy 925, and 18Ni maraging steel), two work-hardened alloys (Inconel 625 and Hastelloy C-276), titanium (pure and grade 2), and copper-enriched AISI 4340 steel in 1 mol/L acetic acid-1 mol/L sodium acetate containing 15 ppm arsenic oxide. In all cases except pure titanium, the data were shown to fit the interface-control form of the model and values were determined for the irreversible trapping constants (k) and the flux of hydrogen into the alloys. The density of irreversible trap defects were calculated from k and generally found to be in close agreement with the concentration of a specific heterogeneity in each alloy. Moreover, the trapping constants for the alloys were found to be consistent with their relative susceptibilities to hydrogen embrittlement.

  19. Preliminary corrosion studies of candidate materials for supercritical water oxidation reactor systems. Master's thesis

    SciTech Connect

    Orzalli, J.C.

    1994-05-01

    An experimental test facility has been designed and constructed for investigation of the corrosion behavior of candidate materials in a supercritical water oxidation environment. The high temperatures (500 deg C) and high pressures (300 atm) required in this process, made the experimental apparatus construction and control a complex engineering problem. The facility consists of two systems. The first is an exposure autoclave internal volume 850 ml, with associated monitoring and control systems for conducting long term exposure testing of test coupons and U-bends. The second is an electrochemical cell with a potentiostat and frequency response analyzer for conducting Electronic Impedance Spectroscopy (EIS) in the supercritical water environment. Exposure testing of three candidate materials; Inconel 625, Hastelloy C-276 and 316 stainless steel was conducted at three temperature regimes corresponding to three locations in a SCWO waste treatment system. Preliminary results are presented in an environment of demineralized water as a control. Experimental results indicate evidence of a film on the materials characterized by slight weight gain. Light and confocal laser light microscopic evaluations revealed the presence of localized pitting corrosion on the Inconel 625.

  20. Improvement in glucose biosensing response of electrochemically grown polypyrrole nanotubes by incorporating crosslinked glucose oxidase.

    PubMed

    Palod, Pragya Agar; Singh, Vipul

    2015-10-01

    In this paper a novel enzymatic glucose biosensor has been reported in which platinum coated alumina membranes (Anodisc™s) have been employed as templates for the growth of polypyrrole (PPy) nanotube arrays using electrochemical polymerization. The PPy nanotube arrays were grown on Anodisc™s of pore diameter 100 nm using potentiostatic electropolymerization. In order to optimize the polymerization time, immobilization of glucose oxidase (GOx) was first performed using physical adsorption followed by measuring its biosensing response which was examined amperometrically for increasing concentrations of glucose. In order to further improve the sensing performance of the biosensor fabricated for optimum polymerization duration, enzyme immobilization was carried out using cross-linking with glutaraldehyde and bovine serum albumin (BSA). Approximately six fold enhancement in the sensitivity was observed in the fabricated electrodes. The biosensors also showed a wide range of linear operation (0.2-13 mM), limit of detection of 50 μM glucose concentration, excellent selectivity for glucose, notable reliability for real sample detection and substantially improved shelf life. PMID:26117773

  1. Tyrosinase conjugated reduced graphene oxide based biointerface for bisphenol A sensor.

    PubMed

    Reza, K Kamil; Ali, Md Azahar; Srivastava, Saurabh; Agrawal, Ved Varun; Biradar, A M

    2015-12-15

    We have fabricated a nanocomposite of reduced graphene oxide (rGO) sheets and chitosan (Cn) polymer based highly sensitive electrochemical biosensor for detection of bisphenol A (BPA). The two-dimensional structure and chemical functionality of rGO and Cn provide an excellent electrode surface for loading of tyrosinase enzyme molecules. This rGO-Cn nanocomposite is capable of effectively utilizing their superior conductivity, larger effective surface area and superior electrochemical performance due to its synergistic effect between rGO and Cn. The structural, morphological and electrochemical characterizations of nanocomposite sheets have been performed by electron microscopy, X-ray diffraction, FTIR and Potentiostat/Galvanostat techniques. This fabricated biosensor is sensitive to nanomolar (0.74 nM) concentration of BPA and detection time is 10s compared to conventional BPA ELISA kit (0.3 µg/L and 2.5h). The rGO-Cn based biosensor exhibits a higher sensitivity (83.3 µA nM(-1) cm(-2)), wider linearity (0.01-50 µM) with good selectivity towards BPA. This biosensor is capable to quantify real sample of BPA using packaged drinking water bottles. This rGO-Cn nanocomposite sheets emerges as a potential electrode material for detection of other estrogenic substrate. PMID:26201981

  2. Morphological Evolution of Nanocluster Aggregates and Single Crystals in Alkaline Zinc Electrodeposition

    SciTech Connect

    Desai, D; Turney, DE; Anantharaman, B; Steingart, DA; Banerjee, S

    2014-04-24

    The morphology of Zn electrodeposits is studied on carbon-coated transmission electron microscopy grids. At low over-potentials (eta = -50 mV), the morphology develops by aggregation at two distinct length scales: similar to 5 nm diameter monocrystalline nanoclusters form similar to 50 nm diameter polycrystalline aggregates, and the aggregates form a branched network. Epitaxial (00 (0) over bar2) growth above an overpotential of vertical bar eta(c)vertical bar > 125 mV leads to the formation of hexagonal single crystals up to 2 mu m in diameter. Potentiostatic current transients were used to calculate the nucleation rate from Scharifker et al.'s model. The exp(eta) dependence of the nucleation rates indicates that atomistic nucleation theory explains the nucleation process better than Volmer-Weber theory. A kinetic model is provided using the rate equations of vapor solidification to simulate the evolution of the different morphologies. On solving these equations, we show that aggregation is attributed to cluster impingement and cluster diffusion while single-crystal formation is attributed to direct attachment.

  3. Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces.

    PubMed

    Li, Peiqiang; Wang, Huying; Xu, Jinfeng; Jing, Hua; Zhang, Jun; Han, Haixiang; Lu, Fusui

    2013-12-01

    In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L(-1) cm(-2) and 107.38 μmol L(-1) cm(-2) after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels. PMID:24121703

  4. Real-time visualization of diffusion-controlled nanowire growth in solution.

    PubMed

    Ye, Shengrong; Chen, Zuofeng; Ha, Yoon-Cheol; Wiley, Benjamin J

    2014-08-13

    This Letter shows that copper nanowires grow through the diffusion-controlled reduction of dihydroxycopper(I), Cu(OH)2(-). A combination of potentiostatic coulometry, UV-visible spectroscopy, and thermodynamic calculations was used to determine the species adding to growing Cu nanowires is Cu(OH)2(-). Cyclic voltammetry was then used to measure the diffusion coefficient of Cu(OH)2(-) in the reaction solution. Given the diameter of a Cu nanowire and the diffusion coefficient of Cu(OH)2(-), we calculated the dependence of the diffusion-limited growth rate on the concentration of copper ions to be 26 nm s(-1) mM(-1). Independent measurements of the nanowire growth rate with dark-field optical microscopy yielded 24 nm s(-1) mM(-1) for the growth rate dependence on the concentration of copper. Dependence of the nanowire growth rate on temperature yielded a low activation energy of 11.5 kJ mol(-1), consistent with diffusion-limited growth. PMID:25054865

  5. Effects of Osseointegration by Bone Morphogenetic Protein-2 on Titanium Implants In Vitro and In Vivo.

    PubMed

    Teng, Fu-Yuan; Chen, Wen-Cheng; Wang, Yin-Lai; Hung, Chun-Cheng; Tseng, Chun-Chieh

    2016-01-01

    This study designed a biomimetic implant for reducing healing time and achieving early osseointegration to create an active surface. Bone morphogenetic protein-2 (BMP-2) is a strong regulator protein in osteogenic pathways. Due to hardly maintaining BMP-2 biological function and specificity, BMP-2 efficient delivery on implant surfaces is the main challenge for the clinic application. In this study, a novel method for synthesizing functionalized silane film for superior modification with BMP-2 on titanium surfaces is proposed. Three groups were compared with and without BMP-2 on modified titanium surfaces in vitro and in vivo: mechanical grinding; electrochemical modification through potentiostatic anodization (ECH); and sandblasting, alkali heating, and etching (SMART). Cell tests indicated that the ECH and SMART groups with BMP-2 markedly promoted D1 cell activity and differentiation compared with the groups without BMP-2. Moreover, the SMART group with a BMP-2 surface markedly promoted early alkaline phosphatase expression in the D1 cells compared with the other surface groups. Compared with these groups in vivo, SMART silaning with BMP-2 showed superior bone quality and created contact areas between implant and surrounding bones. The SMART group with BMP-2 could promote cell mineralization in vitro and osseointegration in vivo, indicating potential clinical use. PMID:26977141

  6. Coupling EELS/EFTEM Imaging with Environmental Fluid Cell Microscopy

    SciTech Connect

    Unocic, Raymond R; Baggetto, Loic; Veith, Gabriel M; Dudney, Nancy J; More, Karren Leslie

    2012-01-01

    Insight into dynamically evolving electrochemical reactions and mechanisms encountered in electrical energy storage (EES) and conversion technologies (batteries, fuel cells, and supercapacitors), materials science (corrosion and oxidation), and materials synthesis (electrodeposition) remains limited due to the present lack of in situ high-resolution characterization methodologies. Electrochemical fluid cell microscopy is an emerging in-situ method that allows for the direct, real-time imaging of electrochemical processes within a fluid environment. This technique is facilitated by the use of MEMS-based biasing microchip platforms that serve the purpose of sealing the highly volatile electrolyte between two electron transparent SiNx membranes and interfacing electrodes to an external potentiostat for controlled nanoscale electrochemislly experiments [!]. In order to elucidate both stmctural and chemical changes during such in situ electrochemical experiments, it is impmtant to first improve upon the spatial resolution by utilizing energy-filtered transmission electron microscopy (EFTEM) (to minimize chromatic aben ation), then to detennine the chemical changes via electron energy loss spectroscopy (EELS). This presents a formidable challenge since the overall thickness through which electrons are scattered through the multiple layers of the cell can be on the order of hundreds of nanometers to microns, scattering through which has the deleterious effect of degrading image resolution and decreasing signal-to noise for spectroscopy [2].

  7. Variation in electrical properties of gamma irradiated cadmium selenate nanowires

    NASA Astrophysics Data System (ADS)

    Chauhan, R. P.; Rana, Pallavi; Narula, Chetna; Panchal, Suresh; Choudhary, Ritika

    2016-07-01

    Preparation of low-dimensional materials attracts more and more interest in the last few years, mainly due to the wide field of potential commercial applications ranging from life sciences, medicine and biotechnology to communication and electronics. One-dimensional systems are the smallest dimension structures that can be used for efficient transport of electrons and thus expected to be critical to the function and integration of nanoscale devices. Nanowires with well controlled morphology and extremely high aspect ratio can be obtained by replicating a nanoporous polymer ion-track membrane with cylindrical pores of controlled dimensions. With this technique, materials can be deposited within the pores of the membrane by electrochemical reduction of the desired ion. In the present study, cadmium selenate nanowires were synthesized potentiostatically via template method. These synthesized nanowires were then exposed to gamma rays by using a 60Co source at the Inter University Accelerator Centre, New Delhi, India. Structural, morphological, electrical and elemental characterizations were made in order to analyze the effect of gamma irradiation on the synthesized nanowires. I-V measurements of cadmium selenate nanowires, before and after irradiation were made with the help of Keithley 2400 source meter and Ecopia probe station. A significant change in the electrical conductivity of cadmium selenate nanowires was found after gamma irradiation. The crystallography of the synthesized nanowires was also studied using a Rigaku X-ray diffractrometer equipped with Cu-Kα radiation. XRD patterns of irradiated samples showed no variation in the peak positions or phase change.

  8. Transient non-isothermal model of a polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Shah, A. A.; Kim, G.-S.; Sui, P. C.; Harvey, D.

    In this paper we present a one-dimensional transient model for the membrane electrode assembly of a polymer-electrolyte fuel cell. In earlier work we established a framework to describe the water balance in a steady-state, non-isothermal cathode model that explicitly included an agglomerate catalyst layer component. This paper extends that work in several directions, explicitly incorporating components of the anode, including a micro-porous layer, and accounting for electronic potential variations, gas convection and time dependance. The inclusion of temperature effects, which are vital to the correct description of condensation and evaporation, is new to transient modelling. Several examples of the modelling results are given in the form of potentiostatic sweeps and compared to experimental results. Excellent qualitative agreement is demonstrated, particularly in regard to the phenomenon of hysteresis, a manifestation of the sensitive response of the system to the presence of water. Results pertaining to pore size, contact angle and the presence of a micro-porous layer are presented and future work is discussed.

  9. Influence of the cathode architecture in the frequency response of self-breathing proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ferreira-Aparicio, P.; Chaparro, A. M.

    2014-12-01

    Self-breathing proton exchange membrane fuel cells are apparently simple devices, but efficient water management is critical for their performance. The cathode configuration should guarantee balanced rates between O2 accessibility from the circumventing air and H2O removal, and a good electric contact between catalyst layers and current collectors at the same time. By applying progressive modifications to the initial concept of a conventional PEMFC, the effect of the cathode architecture on cell performance has been analyzed. Frequency response analyses of the cell during steady-state potentiostatic stepping have yielded relevant information regarding limitations originated by the cathode impedance under high current load conditions. The primitive cell design has been optimized for self-breathing operation by means of this diagnostic tool. The thickness of the perforated plate in the cathode has been found to be one of the main factors contributing to limit oxygen accessibility when a high current load is demanded. Adequate cathode architecture is critical for reducing mass transport limitations in the catalytic layer and enhancing performance under self-breathing conditions.

  10. Stretchable, multiplexed pH sensors with demonstrations on rabbit and human hearts undergoing ischemia.

    PubMed

    Chung, Hyun-Joong; Sulkin, Matthew S; Kim, Jong-Seon; Goudeseune, Camille; Chao, Hsin-Yun; Song, Joseph W; Yang, Sang Yoon; Hsu, Yung-Yu; Ghaffari, Roozbeh; Efimov, Igor R; Rogers, John A

    2014-01-01

    Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces, and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of noninvasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (-1.6 mV °C(-1) ), and minimal influence of extracellular ions (<3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants. PMID:23868871

  11. Effects of Zn amount on the properties of Zn-Zu2O composite films grown for PEC photoelectrodes by using electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Kim, Tae Gyoum; Lee, Hu Joong; Ryu, Hyukhyun; Lee, Won-Jae

    2015-10-01

    In this study, Zn-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates by using the electrochemical deposition method. Various amounts of Zinc (Zn) were added to grow the Zn-Cu2O composite films. We analyzed the morphological, structural, optical energy band gap and photocurrent density properties of the Zn-Cu2O composite films by using various measurements such as field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometry and potentiostat/galvanostat measurements, respectively. As a result, the highest photocurrent density value of -4.04 mA/cm2 was obtained for the 30-wt% sample, which had the lowest Cu2O (111)/ ZnO (101) XRD peak intensity ratio. The highest photocurrent density value from the 30-wt% sample was approximately 2.35 times higher than that from the non-composite Cu2O film (0-wt% sample). From this study, we found that adding Zn could improve the photocurrent values of Zn-Cu2O composite films.

  12. Effects of lithium (Li) on lithium-cuprous-oxide (Li-Cu2O) composite films grown by using electrochemical deposition for a PEC photoelectrode

    NASA Astrophysics Data System (ADS)

    Kim, Tae Gyoum; Ryu, Hyukhyun; Lee, Won-Jae

    2016-01-01

    In this study, Li-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates by using the electrochemical deposition method. Various amounts of lithium (Li) were added to grow the Li-Cu2O composite films. We analyzed the morphology, structure, photocurrent density and photo-stability of the Li-Cu2O composite films by using various measurements such as field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and potentiostat/galvanostat measurements, respectively. As a result, the highest XRD Cu2O (111)/ LiO (011) peak intensity ratio was obtained for the 10-wt% sample, which also had the highest photocurrent density value of -5.00 mA/cm2. The highest photocurrent density value for the 10-wt% sample was approximately 5 times greater than that of the 0-wt% sample. As shown by this result, we found that adding Li could improve the photocurrent values of Li-Cu2O composite films.

  13. Facile synthesis of polypyrrole functionalized nickel foam with catalytic activity comparable to Pt for the poly-generation of hydrogen and electricity

    NASA Astrophysics Data System (ADS)

    Tang, Tiantian; Li, Kan; Shen, Zhemin; Sun, Tonghua; Wang, Yalin; Jia, Jinping

    2016-01-01

    Polypyrrole functionalized nickel foam is facilely prepared through the potentiostatic electrodeposition. The PPy-functionalized Ni foam functions as a hydrogen-evolution cathode in a rotating disk photocatalytic fuel cell, in which hydrogen energy and electric power are generated by consuming organic wastes. The PPy-functionalized Ni foam cathode exhibits stable catalytic activities after thirteen continuous runs. Compared with net or plate structure, the Ni foam with a unique three-dimensional reticulate structure is conducive to the electrodeposition of PPy. Compared with Pt-group electrode, PPy-coated Ni foam shows a satisfactory catalytic performance for the H2 evolution. The combination of PPy and Ni forms a synergistic effect for the rapid trapping and removal of proton from solution and the catalytic reduction of proton to hydrogen. The PPy-functionalized Ni foam could be applied in photocatalytic and photoelectrochemical generation of H2. In all, we report a low cost, high efficient and earth abundant PPy-functionalized Ni foam with a satisfactory catalytic activities comparable to Pt for the practical application of poly-generation of hydrogen and electricity.

  14. 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.

  15. Bioelectrochemical treatment of table olive brine processing wastewater for biogas production and phenolic compounds removal.

    PubMed

    Marone, A; Carmona-Martínez, A A; Sire, Y; Meudec, E; Steyer, J P; Bernet, N; Trably, E

    2016-09-01

    Industry of table olives is widely distributed over the Mediterranean countries and generates large volumes of processing wastewaters (TOPWs). TOPWs contain high levels of organic matter, salt, and phenolic compounds that are recalcitrant to microbial degradation. This work aims to evaluate the potential of bioelectrochemical systems to simultaneously treat real TOPWs and recover energy. The experiments were performed in potentiostatically-controlled single-chamber systems fed with real TOPW and using a moderate halophilic consortium as biocatalyst. In conventional anaerobic digestion (AD) treatment, ie. where no potential was applied, no CH4 was produced. In comparison, Bio-Electrochemical Systems (BES) showed a maximum CH4 yield of 701 ± 13 NmL CH4·LTOPW(-1) under a current density of 7.1 ± 0.4 A m(-2) and with a coulombic efficiency of 30%. Interestingly, up to 80% of the phenolic compounds found in the raw TOPW (i.e. hydroxytyrosol and tyrosol) were removed. A new theoretical degradation pathway was proposed after identification of the metabolic by-products. Consistently, microbial community analysis at the anode revealed a clear and specific enrichment in anode-respiring bacteria (ARB) from the genera Desulfuromonas and Geoalkalibacter, supporting the key role of these electroactive microorganisms. As a conclusion, bioelectrochemical systems represent a promising bioprocess alternative for the treatment and energy recovery of recalcitrant TOPWs. PMID:27208920

  16. Towards a Multifunctional Electrochemical Sensing and Niosome Generation Lab-on-Chip Platform Based on a Plug-and-Play Concept

    PubMed Central

    Kara, Adnane; Rouillard, Camille; Mathault, Jessy; Boisvert, Martin; Tessier, Frédéric; Landari, Hamza; Melki, Imene; Laprise-Pelletier, Myriam; Boisselier, Elodie; Fortin, Marc-André; Boilard, Eric; Greener, Jesse; Miled, Amine

    2016-01-01

    In this paper, we present a new modular lab on a chip design for multimodal neurotransmitter (NT) sensing and niosome generation based on a plug-and-play concept. This architecture is a first step toward an automated platform for an automated modulation of neurotransmitter concentration to understand and/or treat neurodegenerative diseases. A modular approach has been adopted in order to handle measurement or drug delivery or both measurement and drug delivery simultaneously. The system is composed of three fully independent modules: three-channel peristaltic micropumping system, a three-channel potentiostat and a multi-unit microfluidic system composed of pseudo-Y and cross-shape channels containing a miniature electrode array. The system was wirelessly controlled by a computer interface. The system is compact, with all the microfluidic and sensing components packaged in a 5 cm × 4 cm × 4 cm box. Applied to serotonin, a linear calibration curve down to 0.125 mM, with a limit of detection of 31 μM was collected at unfunctionalized electrodes. Added sensitivity and selectivity was achieved by incorporating functionalized electrodes for dopamine sensing. Electrode functionalization was achieved with gold nanoparticles and using DNA and o-phenylene diamine polymer. The as-configured platform is demonstrated as a central component toward an “intelligent” drug delivery system based on a feedback loop to monitor drug delivery. PMID:27240377

  17. Nucleation and growth of zinc from chloride concentrated solutions

    SciTech Connect

    Trejo, G.; Ortega B, R.; Meas V, Y.; Ozil, P.; Chainet, E.; Nguyen, B.

    1998-12-01

    The electrodeposition of metals is a complex phenomenon influenced by a number of factors that modify the rates of nucleation and growth and determine the properties of the deposits. In this work the authors study the influence of the zinc chloride (ZnCl{sub 2}) concentration on the zinc nucleation process on glassy carbon, in a KCl electrolyte under conditions close to those employed in commercial acid deposition baths for zinc. The electrochemical study was performed using cyclic voltammetry and potentiostatic current-time transients. The charge-transfer coefficient and the formal potential for ZnCl{sub 2} reduction were evaluated from cyclic voltammetry experiments. The nucleation process was analyzed by comparing the transients obtained with the known dimensionless (i/i{sub m}){sup 2} vs. t/t{sub m} response for instantaneous or progressive nucleation. The results show that the nucleation process and the number density of sites are dependent on ZnCl{sub 2} concentration. Scanning electron microscopy analysis of the deposits shows that the deposits are homogeneous and compact although a change in the morphology is observed as a function of ZnCl{sub 2} concentration. Evaluation of the corrosion resistance reveals the influence of the nucleation process on the subsequent corrosion resistance of the zinc deposits.

  18. Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans.

    PubMed

    Lara, René H; García-Meza, J Viridiana; Cruz, Roel; Valdez-Pérez, Donato; González, Ignacio

    2012-08-01

    Massive pyrite (FeS₂) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)²⁻, S⁰). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S₂) to active sulfur species (e.g., Fe(1-x )S(2-y ), S⁰). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)²⁻/S⁰ speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)²⁻/S⁰ surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria. PMID:22113561

  19. Synthesis of nano-structured polypyrrole/copper electrodes for nitrate and nitrite electroreduction

    NASA Astrophysics Data System (ADS)

    Phuong Thoa Nguyen, Thi; Thinh Nguyen, Viet; Nguyen Bui, Nhat; Do, Duong Kim Bao; Pham, Anh Minh

    2010-09-01

    Nanostructured polypyrrole film was synthesized onto a copper electrode in solutions of oxalic and salicylic acids and their buffers. The electrooxidation of pyrrole to form polypyrrole film and the electroreduction of nitrate and nitrite ions at synthesized Ppy modified copper electrodes (Ppy/Cu) in potassium chloride aqueous solutions were studied using chronoamperometry. The nanoporous structure of the synthesized Ppy films was characterized by scanning electron microscopy (SEM). Nitrate and nitrite reduction were performed by an electrochemical method under potentiostatic conditions. The Ppy/Cu electrodes prepared in the oxalate buffer and salicylic acid solutions perform more stable catalytic activity for nitrate reduction; their service life is about ten times longer than that for the electrodes prepared in oxalic acid solution. After 20 h of electrolysis, the nitrite was reduced completely with 100% efficiency and the nitrate was reduced with 35% efficiency. Report submitted to the 5th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN, Hanoi, 9–12 November 2010.

  20. Pulse electrodeposition of adherent nickel coatings onto anodized aluminium surfaces

    NASA Astrophysics Data System (ADS)

    Frantz, Cédric; Vichery, Charlotte; Zechner, Johannes; Frey, Damian; Bürki, Gerhard; Cebeci, Halil; Michler, Johann; Philippe, Laetitia

    2015-03-01

    Aluminium is one of the mostly used elements in the industry because of its abundance and low weight. However, the deposition of a metallic coating requires performing the so-called zincate pre-treatment in order to allow the formation of inter-metallic bonds and thereby achieving sufficient adherence. In this work, porous anodic aluminium oxide (AAO) is used as an anchoring intermediate layer for nickel coatings. AAO is grown anodically in sulfuric acid and nickel coatings are deposited by potentiostatic reverse pulse electrodeposition onto as-anodized aluminium surfaces. The electrodeposition of nickel is initiated onto the electrochemically thinned barrier layer of AAO and pursued until the complete covering of the oxide. The electrochemical behavior of Watts and sulfamate baths is investigated by cyclic voltammetry for different barrier layer thickness, allowing to validate the thinning conditions and to determine the appropriate deposition potential of nickel. GD-OES measurements show that low duty cycles are necessary to achieve high filling ratio of the AAO. SEM micrographs show that a smooth uniform coating is obtained when nickel is deposited in presence of additives.

  1. Lab-on-a-Bird: Biophysical Monitoring of Flying Birds

    PubMed Central

    Gumus, Abdurrahman; Lee, Seoho; Ahsan, Syed S.; Karlsson, Kolbeinn; Gabrielson, Richard; Guglielmo, Christopher G.; Winkler, David W.; Erickson, David

    2015-01-01

    The metabolism of birds is finely tuned to their activities and environments, and thus research on avian systems can play an important role in understanding organismal responses to environmental changes. At present, however, the physiological monitoring of bird metabolism is limited by the inability to take real-time measurements of key metabolites during flight. In this study, we present an implantable biosensor system that can be used for continuous monitoring of uric acid levels of birds during various activities including flight. The system consists of a needle-type enzymatic biosensor for the amperometric detection of uric acid in interstitial fluids. A lightweight two-electrode potentiostat system drives the biosensor, reads the corresponding output current and wirelessly transfers the data or records to flash memory. We show how the device can be used to monitor, in real time, the effects of short-term flight and rest cycles on the uric acid levels of pigeons. In addition, we demonstrate that our device has the ability to measure uric acid level increase in homing pigeons while they fly freely. Successful application of the sensor in migratory birds could open up a new way of studying birds in flight which would lead to a better understanding of the ecology and biology of avian movements. PMID:25880904

  2. Electrochemical nucleophilic synthesis of di-tert-butyl-(4-[18F]fluoro-1,2-phenylene)-dicarbonate

    PubMed Central

    He, Qinggang; Wang, Ying; Alfeazi, Ines; Sadeghi, Saman

    2015-01-01

    An electrochemical method with the ability to conduct 18F-fluorination of aromatic molecules through direct nucleophilic fluorination of cationic intermediates is presented in this paper. The reaction was performed on a remote-controlled automatic platform. Nucleophilic electrochemical fluorination of tert-butyloxycarbonyl (Boc) protected catechol, an intermediate model molecule for the positron emission tomography (PET) probe (3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine), was performed. Fluorination was achieved under potentiostatic anodic oxidation in acetonitrile containing Et3N · 3HF and other supporting electrolytes. Radiofluorination efficiency was influenced by a number of variables, including the concentration of the precursor, concentration of Et3N · 3HF, type of supporting electrolyte, temperature and time, as well as applied potentials. Radiofluorination efficiency of 10.4 ± 0.6% (n = 4) and specific activity of up to 43 GBq/mmol was obtained after 1 h electrolysis of 0.1 M of 4-tert-butyl-diboc-catechol in the acetonitrile solution of Et3N · 3HF (0.033 M) and NBu4PF6 (0.05 M). Density functional theory (DFT) was employed to explain the tert-butyl functional group facilitation of electrochemical oxidation and subsequent fluorination. PMID:25000498

  3. Synthesis of dendritic silver nanostructures supported by graphene nanosheets and its application for highly sensitive detection of diazepam.

    PubMed

    Majidi, Mir Reza; Ghaderi, Seyran; Asadpour-Zeynali, Karim; Dastangoo, Hossein

    2015-12-01

    In this paper, preparation, characterization and application of a new sensor for fast and simple determination of trace amount of diazepam were described. This sensor is based on Ag nanodendrimers (AgNDs) supported by graphene nanosheets modified glassy carbon electrode (GNs/GCE). The AgNDs were directly electrodeposited on the surface of electrode via potentiostatic method without using any templates, surfactants, or stabilizers. The structure of the synthesized AgNDs/GNs was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. The nanodendrimers with tree-like and hierarchical structures have a fascinating structure for fabrication of effective electrocatalysts. The experimental results confirmed that AgNDs/GNs/GC electrode has good electrocatalytic activity toward the reduction of diazepam. A low detection limit of 8.56×10(-8)M and a wide linear detection range of 1.0×10(-7) to 1.0×10(-6)M and 1.0×10(-6) to 20×10(-6)M were achieved via differential pulse voltammetry (DPV). The proposed electrode displayed excellent repeatability and long-term stability and it was satisfactorily used for determination of diazepam in real samples (commercially tablet, injection and human blood plasma) with high recovery. PMID:26354262

  4. Testing various food-industry wastes for electricity production in microbial fuel cell.

    PubMed

    Cercado-Quezada, Bibiana; Delia, Marie-Line; Bergel, Alain

    2010-04-01

    Three food-industry wastes: fermented apple juice (FAJ), wine lees and yogurt waste (YW) were evaluated in combination with two sources of inoculum, anaerobic sludge and garden compost, to produce electricity in microbial fuel cells. Preliminary potentiostatic studies suggested that YW was the best candidate, able to provide up to 250 mA/m(2) at poised potential +0.3V/SCE. Experiments conducted with two-chamber MFCs confirmed that wine lees were definitely not suitable. FAJ was not able to start an MFC by means of its endogenous microflora, while YW was. Both FAJ and YW were suitable fuels when anaerobic sludge or compost leachate was used as inoculum source. Sludge-MFCs had better performance using YW (54 mW/m(2) at 232 mA/m(2)). In contrast, compost-leachate MFCs showed higher power density with FAJ (78 mW/m(2) at 209 mA/m(2)) than with YW (37 mW/m(2) at 144 mA/m(2)) but YW gave more stable production. Under optimized operating conditions, compost-leachate MFCs fueled with YW gave up to 92 mW/m(2) at 404 mA/m(2) and 44 mW/m(2) in stable conditions. PMID:20034785

  5. Dissolution and corrosion inhibition of copper, zinc, and their alloys

    SciTech Connect

    Jinturkar, P.; Guan, Y.C.; Han, K.N.

    1998-02-01

    The corrosion behavior of copper, zinc, and their alloys in sulfuric acid (H{sub 2}SO{sub 4}) solutions with oxygen and ferric ions (Fe{sup 3+}) was studied using a potentiostat. Oxygen and Fe{sup 3+} ions were shown to play an important role in corrosion of copper and copper-zinc alloys. Cathodic reduction of oxygen mainly was controlled by chemical reaction, and that of Fe{sup 3+} ions was controlled by diffusion. The overall cathodic process was the summation of the reduction of oxygen and Fe{sup 3+} ions. Corrosion of zinc was controlled mainly by reduction of water. Corrosion inhibition using benzotriazole (BTAH) also was investigated in aerated and deaerated solutions. BTAH was found to be a useful inhibitor, and the inhibition layer was shown to be stable and persistent. Morphology of the surface of copper, zinc, and brasses after corrosion in the presence and absence of BTAH was examined by scanning electron microscopy. BTAH formed a protective layer on the surface, thereby inhibiting corrosion. Solution analysis of the dissolution of brasses showed that zinc dissolved preferentially in the initial stages, followed by simultaneous dissolution of copper and zinc.

  6. The influence of Cu2O crystal structure on the Cu2O/ZnO heterojunction photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Elfadill, Nezar G.; Hashim, M. R.; Chahrour, Khaled M.; Qaeed, M. A.; Bououdina, M.

    2015-09-01

    Cuprous oxide (Cu2O) films were potentiostatically electrodeposited onto platinum (Pt) film coated onto silicon (Si) wafer from lactic solution at pH 9. The influence of applied potential on Cu2O crystal structure was carefully examined. At higher electrochemical applied potential, a polycrystalline structure was observed, and then as the applied potential decreased, a single crystalline structure oriented along (1 1 1) was obtained. Further decrease in the applied potential leads to the formation of a polycrystalline structure and finally at much lower applied potential, a single crystalline structure growing along (2 0 0) orientation (equivalent to (1 0 0) orientation) was revealed. Cu2O/ZnO heterojunction photodiodes based on these three crystal structures were fabricated and studied under dark and illuminated conditions. The best performance of the solar cell efficiency was achieved by the heterojunction based on (1 1 1) oriented Cu2O film (≈1.45%) compared to other structures (0.34% and 0.25%), which may be attributed to the formation of high quality heterojunction interface due to the heteroepitaxial-like growth of (0 0 2) oriented ZnO.

  7. Stress-corrosion behavior of aluminum-lithium alloys in aqueous environments

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1983-01-01

    The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

  8. Stress-corrosion behavior of aluminum-lithium alloys in aqueous salt environments

    NASA Technical Reports Server (NTRS)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1984-01-01

    The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg; two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

  9. Electrodeposition of polycrystalline and amorphous silicon for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Rauh, R. D.

    1980-07-01

    Plating experiments with SiHCl3 solutions in propylene carbonate with 0.1 M tetrabutylammonium tetrafluoroborate are described. Silicon was deposited on ITO glass (Nesatron) as well as Mo substrates at temperatures from 25-80 C. Both potentiostatic and galvanostatic conditions were used. The high resistance of the films limited the thickness which could be deposited by either method to less than 5 micrometers. Deposition beyond this limit resulted in a deterioration of the film quality. X-ray analysis of the films confirmed that they were amorphous. SEM analysis of the films revealed a very porous structure with nodules about 1 micrometer in diameter. Annealing the deposit at 400 C in an Ar:H2 atmosphere resulted in a slightly smoother surface but the nodules remained. The films deposited on ITO glass had a band gap of about 1.0 eV and an EO4 value of 1.5-2.0 eV. The Auger analysis of the films showed the presence of large amounts of oxygen in the samples that had been exposed to air.

  10. Entrapping cross-linked glucose oxidase aggregates within a graphitized mesoporous carbon network for enzymatic biofuel cells.

    PubMed

    Garcia-Perez, Tsai; Hong, Sung-Gil; Kim, Jungbae; Ha, Su

    2016-08-01

    This paper reports a novel method for producing glucose oxidase-nanocomposites by entrapping cross-linked glucose oxidase (GOx) aggregates within a graphitized mesoporous carbon (GMC) network. Entrapment was achieved by utilizing the strong self-aggregation tendency of GMC in aqueous buffer solution to form carbon networks. Using confocal microscopy and TEM, GOx-GMC nanocomposites were visualized. The electrochemical properties of GOx-GMC nanocomposites were studied by means of cyclic voltammograms, chronoamperometric and potentiostatic tests. Results therefrom suggested that the GOx-GMC nanocomposites offer a high electrical conductivity with the maximum electron transfer rate constant estimated at 5.16±0.61s(-1). Furthermore, thermally treating the GOx-GMC nanocomposite and GOx aggregates at 60°C for four hours, both samples maintained 99% of their initial activity, while the free GOx were completely deactivated. These performances suggested that our nanocomposite structure offered both improved electrochemical performance and stability by combining the high electrical conductivity offered by the GMC network with the high enzyme loading and stability offered by the cross-linked GOx aggregates. The GOx-GMC nanocomposite's electrochemical activity towards glucose oxidation was also investigated by using an enzymatic biofuel cell without artificial mediators, producing a power density of up to 22.4μWcm(-2) at 0.24V. PMID:27241289

  11. Quantitative DEMS study of ethanol oxidation: effect of surface structure and Sn surface modification.

    PubMed

    Mostafa, Ehab; Abd-El-Latif, Abd-El-Aziz A; Ilsley, Richard; Attard, Gary; Baltruschat, Helmut

    2012-12-14

    Using the dual thin layer flow through cell, a semi-quantitative analysis of the volatile products during the electrooxidation of adsorbed and bulk solution of 0.01 M ethanol at polycrystalline platinum, smooth, roughened and Sn modified Pt(11,1,1), Pt(311) electrodes has been done by on-line differential electrochemical mass spectroscopy (DEMS). In addition to the current efficiency of CO(2), that of acetaldehyde was determined as a function of the flow rate. At polycrystalline platinum, ethanol oxidation produces only acetaldehyde; the amount of acetaldehyde further oxidized to acetic acid is negligible due to convection conditions. For comparison and for calibration purposes, i-propanol oxidation was examined for which acetone is the only oxidation product. At Pt(11,1,1), the main oxidation product is acetaldehyde. At Pt(311), in addition to acetaldehyde, acetic acid was also formed. Surface modification with Sn did not increase the reactivity of Pt(11,1,1) instead it led to inhibition of the ethanol oxidation. In the case of Pt(311), the onset potential of oxidation was shifted negatively by 0.2 V in the presence of Sn. The results of the potentiostatic measurements showed that this shift is not associated with the production of CO(2); rather acetic acid and acetaldehyde are the main oxidation products. PMID:23108295

  12. Electrodeposited platinum thin films with preferential (100) orientation: Characterization and electrocatalytic properties for ammonia and formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Bertin, Erwan; Garbarino, Sébastien; Guay, Daniel; Solla-Gullón, José; Vidal-Iglesias, Francisco J.; Feliu, Juan M.

    2013-03-01

    The electrocatalytic activity of preferentially oriented {100} Pt electrodes for the electro-oxidation of ammonia (0.2 M NaOH + 0.1 M NH3) and formic acid (0.5 M HCOOH + 0.5 M H2SO4) was assessed. They were prepared without using any surfactant through potentiostatic deposition (Ed = -0.10 V vs RHE, [HCl] = 10 mM and [Na2PtCl6·6H2O] = 0.5 mM) and by varying the deposition charge. For comparison, polycrystalline Pt thin films were prepared using the same solution but with Ed = +0.10 V vs RHE. Quantification of the fraction of (111) and (100) sites was performed by bismuth irreversible adsorption and deconvolution of the hydrogen region, respectively. Samples with as much as 47% of (100) surface sites were obtained. The preferential orientation was further confirmed by CO stripping voltammetry that exhibits similar characteristic features, as well as a similar potential of zero total charge than those expected for a preferential (100) surface. As compared to polycrystalline Pt, the occurrence of Pt (100) surface sites leads to an electrocatalytic activity enhancement by a factor of 4.8 and 2.6 (expressed as μA cmPt-2) for the oxidation of ammonia and formic acid, respectively.

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

    PubMed Central

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

    2008-01-01

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

  14. Electrodeposition of Gold on Lignocelluloses and Graphite-Based Composite Paper Electrodes for Superior Electrical Properties

    NASA Astrophysics Data System (ADS)

    Sultana, Ishrat; Razaq, Aamir; Idrees, M.; Asif, M. H.; Ali, Hassan; Arshad, Asim; Iqbal, Shahid; Ramay, Shahid M.; Hussain, Shahzada Qamar

    2016-06-01

    Graphite-based composites are commonly used as an anode and current collector for energy storage devices; however, they have inherently limited potential for large scale rechargeable systems due to a brittle structure. In this study, flexible and light-weight graphite-based electrodes are prepared by incorporation of lignocelluloses fibers directly collected from a self-growing plant, Typha Angistifolia. Electrical properties of graphite and lignocelluloses composite sheets are enhanced by electrodeposition of gold in a three-electrode setup. Electrochemical deposition of gold on a lignocelluloses/graphite paper electrode was obtained in potentiostatic mode by the application of reduction potential -0.95 V for 2000 s, 600 s, and 100 s. The gold-deposited paper electrodes showed efficient kinetics by shifting redox peaks towards lower potentials in cyclic voltammetry measurements, whereas impedance measurements revealed seven orders of magnitude reduction in the resistive properties. Incorporated flexibility and superior electrical/electrochemical performance within presented graphite-based composites will provide cutting-edge characteristics for high-tech application of energy storage devices by keeping a focus on modern disposable technology.

  15. Nucleation and growth in electrodeposition of thin copper films on pyrolytic graphite

    SciTech Connect

    Kinaci, F.S.; Muller, R.H.

    1992-05-01

    Electrodeposition of Cu on graphite electrodes was studied, with emphasis on nucleation. Various ex-situ and in-situ methods were investigated for determining the number density of nuclei. Two direct methods were studied (scanning electron microscopy and scanning tunneling microscopy); indirect determinations included Raman spectroscopy and analysis of potentiostatic current transients. Though some of the techniques correctly predicted the nucleation densities under special conditions, SEM was the most reliable tool. The large scatter in the data necessitated steps to minimize this effect. To electrodeposit Cu on graphite, a nucleation overpotential of 250 mV was measured with cyclic voltammetry; such a large overpotential does not occur on a Pt or on a Cu-covered graphite electrode. The deposition potential is the dominant parameter governing nucleation density. There is a sharp increase in the nucleation density with applied potential. Cu can be deposited on highly oriented pyrolytic graphite only between the nucleation overpotential and the hydrogen evolution potential. To increase the Cu nucleation density, while avoiding excessive H evolution, a double pulse potential technique was used; nucleation densities on the order of 10{sup 10} nuclei/cm{sup 2} were achieved. The use of inhibitors (PVA, benzotriazole) was also investigated. Deposition on conducting polymer electrodes was also studied; initial results with polyaniline show promise. 57 figs, 6 tabs, refs. (DLC)

  16. The Prediction of Long-Term Coating Performance from Short-Term Electrochemical Data. Part 2; Comparison of Electrochemical Data to Field Exposure Results for Coatings on Steel

    NASA Technical Reports Server (NTRS)

    Contu, F.; Taylor, S. R.; Calle, L. M.; Hintze, P. E.; Curran, J. P.; Li, W.

    2009-01-01

    The pace of coatings development is limited by the time required to assess their corrosion protection properties. This study takes a step f orward from Part I in that it correlates the corrosion performance of organic coatings assessed by a series of short-term electrochemical measurement with 18-month beachside exposure results of duplicate pan els. A series of 19 coating systems on A36 steel substrates were test ed in a completely blind study using the damage tolerance test (DTT). In the DTT, a through-film pinhole defect is created, and the electro chemical characteristics of the defect are then monitored over the ne xt 4 to 7 days while immersed in 0.SM NaCl. The open circuit potentia l, anodic potentiostatic polarization tests and electrochemical imped ance spectroscopy were used to study the corrosion behavior of the co ating systems. The beachside exposure tests were conducted at the Ken nedy Space Center according to ASTM D610-01. It was found that for 79 % of the coatings systems examined, the 18 month beachside exposure r esults could be predicted by two independent laboratory tests obtained within 7 days.

  17. Quasi-in-situ single-grain photoelectron microspectroscopy of Co/PPy nanocomposites under oxygen reduction reaction.

    PubMed

    Bocchetta, Patrizia; Amati, Matteo; Bozzini, Benedetto; Catalano, Massimo; Gianoncelli, Alessandra; Gregoratti, Luca; Taurino, Antonietta; Kiskinova, Maya

    2014-11-26

    This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed ∼20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites. PMID:25369153

  18. Strong Photo-Amplification Effects in Flexible Organic Capacitors with Small Molecular Solid-State Electrolyte Layers Sandwiched between Photo-Sensitive Conjugated Polymer Nanolayers

    PubMed Central

    Lee, Hyena; Kim, Jungnam; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    We demonstrate strong photo-amplification effects in flexible organic capacitors which consist of small molecular solid-state electrolyte layers sandwiched between light-sensitive conjugated polymer nanolayers. The small molecular electrolyte layers were prepared from aqueous solutions of tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (ALQSA3), while poly(3-hexylthiophene) (P3HT) was employed as the light-sensitive polymer nanolayer that is spin-coated on the indium-tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) film substrates. The resulting capacitors feature a multilayer device structure of PET/ITO/P3HT/ALQSA3/P3HT/ITO/PET, which were mechanically robust due to good adhesion between the ALQSA3 layers and the P3HT nanolayers. Results showed that the specific capacitance was increased by ca. 3-fold when a white light was illuminated to the flexible organic multilayer capacitors. In particular, the capacity of charge storage was remarkably (ca. 250-fold) enhanced by a white light illumination in the potentiostatic charge/discharge operation, and the photo-amplification functions were well maintained even after bending for 300 times at a bending angle of 180o. PMID:26846891

  19. Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

    PubMed Central

    Lupu, Stelian; Lete, Cecilia; Balaure, Paul Cătălin; Caval, Dan Ion; Mihailciuc, Constantin; Lakard, Boris; Hihn, Jean-Yves; del Campo, Francisco Javier

    2013-01-01

    Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM. PMID:23698270

  20. The Effect of Crystal Face of Fe2O3 on the Electrochemical Performance for Lithium-ion Batteries

    PubMed Central

    Chen, Minmin; Zhao, Enyue; Yan, Qingbo; Hu, Zhongbo; Xiao, Xiaoling; Chen, Dongfeng

    2016-01-01

    Fe2O3 nanorods exposing (001) and (010) plane as well as Fe2O3 nanosheets exposing (001) plane have been successfully synthesized. Fe2O3 nanosheets exhibit better cycle performance and rate capabilities than that of Fe2O3 nanorods. The discharge capacity of Fe2O3 nanosheets can stabilize at 865 mAh/g at the rate of 0.2 C (1C = 1000 mA/g) and 570 mAh/g at the rate of 1.2 C after 80 cycles, which increased by 90% and 79% compared with 456 mAh/g and 318 mAh/g of Fe2O3 nanorods. In comparison with (010) plane, the (001) plane of hematite possesses larger packing density of Fe3+ and O2−, which is responsible for the superior electrochemical performances of Fe2O3 nanosheets than that of Fe2O3 nanorods. In addition, potentiostatic intermittent titration (PITT) results show the diffusion coefficients of Li+ (DLi) of Fe2O3 nanosheets is higher than that of Fe2O3 nanorods. The higher diffusion coefficients of Li+ is favorable for the excellent lithium-storage capabilities and rate capability of Fe2O3 nanosheets. Inspired by our results, we can design and synthesize Fe2O3 or other electrodes with high performances according to their structure features in future. PMID:27380891

  1. Non-destructive Patterning of Carbon Electrodes by Using the Direct Mode of Scanning Electrochemical Microscopy.

    PubMed

    Stratmann, Lutz; Clausmeyer, Jan; Schuhmann, Wolfgang

    2015-11-16

    Patterning of glassy carbon surfaces grafted with a layer of nitrophenyl moieties was achieved by using the direct mode of scanning electrochemical microscopy (SECM) to locally reduce the nitro groups to hydroxylamine and amino functionalities. SECM and atomic force microscopy (AFM) revealed that potentiostatic pulses applied to the working electrode lead to local destruction of the glassy carbon surface, most likely caused by etchants generated at the positioned SECM tip used as the counter electrode. By applying galvanostatic pulses, and thus, limiting the current during structuring, corrosion of the carbon surface was substantially suppressed. After galvanostatic patterning, unambiguous proof of the formation of the anticipated amino moieties was possible by modulation of the pH value during the feedback mode of SECM imaging. This patterning strategy is suitable for the further bio-modification of microstructured surfaces. Alkaline phosphatase, as a model enzyme, was locally bound to the modified areas, thus showing that the technique can be used for the development of protein microarrays. PMID:26316379

  2. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    SciTech Connect

    Lee, June Key E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok; Ryu, Sang-Wan; Jeong, Tak; Jung, Eunjin; Kim, Hyunsoo E-mail: hskim7@jbnu.ac.kr

    2015-05-14

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ∼35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  3. Fabrication of CIGS Films by Electrodeposition Method for Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Lee, Hyunju; Yoon, Hyukjoo; Ji, Changwook; Lee, Dongyun; Lee, Jae-Ho; Yun, Jae-Ho; Kim, Yangdo

    2012-12-01

    Cu(InGa)Se2 (CIGS) thin films were fabricated by electrochemical deposition in a single bath containing Cu, In, Ga, and Se ions. The electrolyte was prepared by dissolving CuCl2, InCl3, GaCl3, H2SeO3, and LiCl in deionized water. The potentiostatic deposition process was achieved by applying a voltage ranging from -0.5 V to -0.8 V versus Ag/AgCl. The effects of different chemical bath concentrations on the film composition and morphology were investigated. Stoichiometric CIGS film composition could be achieved by controlling the chemical compositions of the bath and the voltage. Gelatin was added to the solution to improve the surface and microstructures of the CIGS film. The as-deposited films were annealed at 500°C in Ar atmosphere for crystallization. The structural, morphological, and compositional properties of the CIGS thin films before and after annealing were examined by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. This study showed that the composition of the CIGS films is dependent on the bath concentration, whereas the applied potential had relatively less effect on the CIGS film composition. In addition, the use of gelatin helped in the fabrication of crack-free CIGS thin films with greatly improved surface morphology.

  4. Application of electrochemical techniques for machining titanium aluminide-based alloys

    SciTech Connect

    Ziomek-Moroz, M.; Su, W; Alman, David E.; Hawk, Jeffrey A.

    1997-01-01

    Intermetallic materials with excellent resistance to high-temperature oxidation have been considered as potential replacements for superalloys used as aerospace materials. Titanium aluminides are especially attractive for this role. However, further commercialization of titanium aluminides requires the development of non-conventional machining, such as electrochemical machining (ECM). As a first attempt in the development of the ECM process, the corrosion behavior of arc-melted gamma TiAl and alpha 2 Ti3Al was investigated along with pure titanium and aluminum in deaerated and non-deaerated solutions of sulfuric acid, sodium sulfate, and sodium hydroxide. Two types of electrochemical experiments were carried out, namely, potentiodynamic and potentiostatic. In the Na2SO4 solution, the highest current was found for Al and the lowest for TiAl. The shape of the polarization curves indicates that the intermetallics show similar behavior to that of Ti. It has been found that, in sulfuric acid, current values decrease with increasing titanium content. In the sodium sulfate and sodium hydroxide solutions, current values initially decrease with increasing titanium content and remain unchanged for higher concentrations of titanium.

  5. Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys.

    PubMed

    Ostrowski, Nicole; Lee, Boeun; Enick, Nathan; Carlson, Benjamin; Kunjukunju, Sangeetha; Roy, Abhijit; Kumta, Prashant N

    2013-11-01

    Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)2 surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2 week period and magnesium ion levels over a 1 week period indicate longer range corrosion protection and retention of the Mg(OH)2 passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation. PMID:23684762

  6. Corrosion and Fretting Corrosion Studies of Medical Grade CoCrMo Alloy in a Clinically Relevant Simulated Body Fluid Environment

    NASA Astrophysics Data System (ADS)

    Ocran, Emmanuel K.; Guenther, Leah E.; Brandt, Jan-M.; Wyss, Urs; Ojo, Olanrewaju A.

    2015-06-01

    In modular hip implants, fretting corrosion at the head/neck and neck/stem interfaces has been identified as a major cause of early revision in hip implants, particularly those with heads larger than 32 mm. It has been found that the type of fluid used to simulate the fretting corrosion of biomedical materials is crucial for the reliability of laboratory tests. Therefore, to properly understand and effectively design against fretting corrosion damage in modular hips, there is the need to replicate the human body environment as closely as possible during in vitro testing. In this work, corrosion and fretting corrosion behavior of CoCrMo in 0.14 M NaCl, phosphate buffered saline, and in a clinically relevant novel simulated body fluid was studied using a variety of electrochemical characterization techniques and tribological experiments. Electrochemical, spectroscopy and tribo-electrochemical techniques employed include Potentiodynamic polarization, Potentiostatic polarization, Electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, augur electron spectroscopy, inductively coupled plasma mass spectroscopy, and pin-on-disk wear simulation. The presence of phosphate ions in PBS accounted for the higher corrosion rate when compared with 0.14 M NaCl and the clinically relevant novel simulated body fluid. The low corrosion rates and the nature of the protective passive film formed in the clinically relevant simulated body fluid make it suitable for future corrosion and fretting corrosion studies.

  7. Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

    SciTech Connect

    T. E. Lister; R. E. Mizia; H. Tian

    2005-10-01

    The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix was executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.

  8. Phosphate Detection through a Cost-Effective Carbon Black Nanoparticle-Modified Screen-Printed Electrode Embedded in a Continuous Flow System.

    PubMed

    Talarico, Daria; Cinti, Stefano; Arduini, Fabiana; Amine, Aziz; Moscone, Danila; Palleschi, Giuseppe

    2015-07-01

    An automatable flow system for the continuous and long-term monitoring of the phosphate level has been developed using an amperometric detection method based on the use of a miniaturized sensor. This method is based on the monitoring of an electroactive complex obtained by the reaction between phosphate and molybdate that is consequently reduced at the electrode surface. The use of a screen-printed electrode modified with carbon black nanoparticles (CBNPs) leads to the quantification of the complex at low potential, because CBNPs are capable of electrocatalitically enhancing the phosphomolybdate complex reduction at +125 mV versus Ag/AgCl without fouling problems. The developed system also incorporates reagents and waste storage and is connected to a portable potentiostat for rapid detection and quantification of phosphate. Main analytical parameters, such as working potential, reagent concentration, type of cell, and flow rate, were evaluated and optimized. This system was characterized by a low detection limit (6 μM). Interference studies were carried out. Good recovery percentages comprised between 89 and 131.5% were achieved in different water sources, highlighting its suitability for field measurements. PMID:26066782

  9. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  10. Effect of Non-ionic Surfactants and Its Role in K Intercalation in Electrolytic Manganese Dioxide

    NASA Astrophysics Data System (ADS)

    Biswal, Avijit; Tripathy, B. C.; Subbaiah, T.; Meyrick, D.; Ionescu, Mihail; Minakshi, Manickam

    2014-09-01

    The effect of non-ionic surface active agents (surfactants) Triton X-100 (TX-100) and Tween-20 (Tw-20) and their role in potassium intercalation in electrolytic manganese dioxide (EMD) produced from manganese cake has been investigated. Electrosynthesis of MnO2 in the absence or presence of surfactant was carried out from acidic MnSO4 solution obtained from manganese cake under optimized conditions. A range of characterization techniques, including field emission scanning electron microscopy, transmission electron microscopy (TEM), Rutherford back scattering (RBS), and BET surface area/porosity studies, was carried out to determine the structural and chemical characteristics of the EMD. Galvanostatic (discharge) and potentiostatic (cyclic voltammetric) studies were employed to evaluate the suitability of EMD in combination with KOH electrolyte for alkaline battery applications. The presence of surfactant played an important role in modifying the physicochemical properties of the EMD by increasing the surface area of the material and hence, enhancing its electrochemical performance. The TEM and RBS analyses of the discharged EMD (γ-MnO2) material showed clear evidence of potassium intercalation or at least the formation of a film on the MnO2 surface. The extent of intercalation was greater for EMD deposited in the presence of TX-100. Discharged MnO2 showed products of Mn2+ intermediates such as MnOOH and Mn3O4.

  11. Influence of post-treatment temperature of TNTa photoelectrodes on photoelectrochemical properties and photocatalytic degradation of 4-nonylphenol

    NASA Astrophysics Data System (ADS)

    Xin, Yanjun; Liu, Huiling; Li, Junjing; Chen, Qinghua; Ma, Dong

    2013-03-01

    TiO2/Ti Nanotube array (TNTa) photoelectrodes were prepared by galvanostatic and potentiostatic anodization technique, and annealed at different temperature. The morphology and structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. Optical properties and photoelectrochemical (PECH) properties were investigated by surface photovoltage (SPV), ultra UV-vis diffuse reflectance spectra (UV/vis/DRS), open-circuit potential (OCP) and transient photocurrent. Photodecomposition performances were evaluated by the yield of •OH radicals and photocatalytic (PC) degradation rate of 4-nonylphenol (4-NP) under xenon light. The results showed that with the increase of post-treatment temperature, PECH and PC properties increased gradually and then decreased. The photocurrent densities, yield of *OH radicals and photodecomposition rates of 4-NP were following the trend of TNT-823>TNT-873>TNT-773>TNT-673>TNT-973>TNT-298. When the annealing temperature was 823 K, the photoelectrodes were composed of mixed crystal structure and ordered nanotube array, which exhibited superior PECH properties. When the annealed temperature arrived to 973 K, the nanotube collapsed and the PECH and PC properties of TNTa photoelectrodes decreased. For TNT-823 photoelectrodes, after the assistant potential was applied, the degradation rate of 4-NP increased significantly from 77% to 97% after 120 min illumination.

  12. The influence of complexing agent and proteins on the corrosion of stainless steels and their metal components.

    PubMed

    Kocijan, Aleksandra; Milosev, Ingrid; Pihlar, Boris

    2003-01-01

    The present work is devoted to the problem of biodegradation of orthopaedic implants manufactured from stainless steel. In vitro simulations of the biocompatibility of two types of stainless steel, AISI 304 and AISI 316L, and their individual metal components, i.e. iron, chromium, nickel and molybdenum, were carried out in simulated physiological solution (Hank's) containing complexing agents. Knowledge of the effects of the chemical and biological complexing agents, EDTA and proteins, respectively, on the corrosion resistance of a metal should provide a better understanding of the processes occurring in vivo on its surface. The behavior of stainless steels and metal components was studied under open circuit and under potentiostatic conditions. The concentration of dissolved corrosion products in the form of released ions was determined by differential pulse polarography (DPP) and atomic emission spectrometry using inductively coupled plasma (ICP-AES). The composition of solid corrosion products formed on the surface was analyzed by energy dispersive X-ray spectroscopy (EDS) and their morphology was viewed by scanning electron microscopy (SEM). The addition of EDTA and proteins to physiological solution increased the dissolution of pure metals and stainless steels. The effect of particular protein differs on different metals and alloys. PMID:15348541

  13. Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics

    PubMed Central

    Kim, Jayoung; Imani, Somayeh; de Araujo, William R.; Warchall, Julian; Valdés-Ramírez, Gabriela; Paixão, Thiago R.L.C.; Mercier, Patrick P.; Wang, Joseph

    2016-01-01

    This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications. PMID:26276541

  14. Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ghadiri, Elham; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E.

    2016-04-01

    Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded.

  15. An in vitro investigation of the anodic polarization and capacitance behavior of 316-L stainless steel.

    PubMed

    Sutow, E J; Pollack, S R; Korostoff, E

    1976-09-01

    Determinations were made of how the corrosion-resistant properties of the passive film on 316-L stainless steel are influenced by the material's mechanical and surface states, and the variable pH and PO2 conditions of the interstitial fluid. Cold-rolled and annealed specimens were surface-prepared, commercially and in the laboratory, respectively, as if for orthopedic implantation. Passive film behavior was studied by the anodic polarization and pulse-potentiostatic capacitance methods. The pH and PO2 of the Ringer's test solution were varied to include interstitial fluid values occurring postoperatively and onto recovery. The anodic polarization behavior of all specimens was found to be pH- and PO2-independent. Breakdown potentials of annealed specimens were 800-950 mV (SCE), in contrast to previously reported values of approximately 350 mV. This substantial increase is related to the influence of surface preparation and, in particular, to the optimization of electropolishing time which acts to produce a microscopically smooth surface, free of debris and disarrayed material. Capacitance behavior of annealed material for potentials greater than 400 mV was consistent with a model involving the entry of chloride and metal ions (mostly Fe) into the passive film. This entry is related to the onset of pitting. PMID:10307

  16. Three-Dimensionally Mesostructured Fe2O3 Electrodes with Good Rate Performance and Reduced Voltage Hysteresi

    SciTech Connect

    Wang, Junjie; Braun, Paul V.; Zhou, Hui; Nanda, Jagjit

    2015-03-26

    Ni scaffolded mesostructured 3D Fe2O3 electrodes were fabricated by colloidal templating and pulsed elec-trodeposition. The scaffold provided short pathways for both lithium ions and electrons in the active phase, enabling fast kinetics and thus a high power density. The scaffold also resulted in a reduced voltage hysteresis. The electrode showed a reversible capacity of ~1000 mA h g-1 at 0.2 A g-1 (~0.2 C) for about 20 cycles, and at a current density of 20 A g-1 (~20 C) the deliverable capacity was about 450 mA h g-1. The room temperature voltage hysteresis at 0.1 A g-1 (~0.1 C) was 0.62 V, which is significantly smaller than that normally reported in the literature. And it could be further reduced to 0.42 V when cycling at 45 ºC. Potentiostatic electrochemical impedance spectroscopy (PEIS) studies indicated the small voltage hysteresis may be due to a reduction in the Li2O/Fe interfacial area in the electrode during cycling relative to convention-al conversion systems.

  17. Experimental and Quantum Studies on Adsorption and Corrosion Inhibition Effect of Imidazole Derivatives on N80 Steel in Hydrochloric Acid

    NASA Astrophysics Data System (ADS)

    Yadav, M.; Kumar, Sumit; Sharma, Dipti; Yadav, P. N.

    2013-12-01

    The inhibition effect of synthesized N‧-(phenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, N‧-(4-methylphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, and N‧-(4-methoxyphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides on the corrosion behaviour of N80 steel in 15% hydrochloric acid solution was investigated using weight loss, potentiostatic polarization and electrochemical impedance spectroscopy methods. The inhibition efficiency increased as the concentration of the inhibitors was increased. The effect of temperature on corrosion inhibition was investigated by weight loss method and thermodynamic parameters were calculated. Potentiodynamic polarization measurements show that all the three studied inhibitors act as mixed inhibitor. The adsorption of inhibitors on N80 steel surface obeys Langmuir adsorption isotherm. The structure of inhibitors was optimized using semiemperical AM1 method. Theoretical parameters such as the highest occupied molecular orbital (EHOMO), lowest unoccupied molecular orbital (ELUMO) energy levels, energy gap (ΔE = ELUMO - EHOMO), dipole moment (μ), global hardness (γ), softness (σ), binding energy, molecular surface area and the fraction of electrons transferred (ΔN) were calculated and the adsorption mechanism was discussed. Scanning electron microscopy was used to characterize the surface marphology of the N80 steel.

  18. Affinity sensor using 3-aminophenylboronic acid for bacteria detection.

    PubMed

    Wannapob, Rodtichoti; Kanatharana, Proespichaya; Limbut, Warakorn; Numnuam, Apon; Asawatreratanakul, Punnee; Thammakhet, Chongdee; Thavarungkul, Panote

    2010-10-15

    Boronic acid that can reversibly bind to diols was used to detect bacteria through its affinity binding reaction with diol-groups on bacterial cell walls. 3-aminophenylboronic acid (3-APBA) was immobilized on a gold electrode via a self-assembled monolayer. The change in capacitance of the sensing surface caused by the binding between 3-APBA and bacteria in a flow system was detected by a potentiostatic step method. Under optimal conditions the linear range of 1.5×10(2)-1.5×10(6) CFU ml(-1) and the detection limit of 1.0×10(2) CFU ml(-1) was obtained. The sensing surface can be regenerated and reused up to 58 times. The method was used for the analysis of bacteria in several types of water, i.e., bottled, well, tap, reservoir and wastewater. Compared with the standard plate count method, the results were within one standard deviation of each other. The proposed method can save both time and cost of analysis. The electrode modified with 3-APBA would also be applicable to the detection of other cis-diol-containing analytes. The concept could be extended to other chemoselective ligands, offering less expensive and more robust affinity sensors for a wide range of compounds. PMID:20801635

  19. Compact Electrochemical System Using On-Chip Sensor Electrodes and Integrated Devices

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tomoyuki; Ikeda, Takaaki; Ishida, Makoto; Sawada, Kazuaki

    2011-04-01

    We report a compact electrochemical sensing system to implement cyclic voltammetry. This type of sensor needs a working electrode, counter electrode, and reference electrode, all of which were integrated on a single chip. The electrochemical system also needs a potentiostat and an input voltage-generating circuit, which were developed using on-chip active devices and a few discrete passive components. This is the first sensor system incorporating electrode-side input voltage generation for electrochemical measurements using an on-chip operational amplifier, which replaces a bulky external voltage controller. A continuous cyclic voltammetry measurement was conducted with a well-studied ferricyanide solution to demonstrate the operation of the intelligent sensor chip. A clear peak was observed and linearity to the target chemical concentration was obtained between the peak height and concentration of the ferricyanide solution. With potential for mass production and small size, this sensor chip could be the best candidate to realize point-of-care testing. This sensor chip is a milestone of a fully integrated electrochemical sensor chip.

  20. A new electrochemical sensor for OH radicals detection.

    PubMed

    Gualandi, Isacco; Tonelli, Domenica

    2013-10-15

    A new, cheap modified electrode for indirect detection of OH radical is described. A glassy carbon (GC) electrode was modified with a polyphenol film prepared by oxidative potentiostatic electropolymerization of 0.05 M phenol in 1M H2SO4. The film having a thickness of ~10nm perfectly covered the GC surface and inhibited the charge transfer of many redox species. The degradation of the polyphenol film, that was induced by OH radicals generated by Fenton reaction or by H2O2 photolysis, is the analytical signal and it was evaluated by cyclic voltammetry and chronoamperometry using the redox probe Ru(NH3)6(3+). Some simulations of the kinetics of the reactions occurring in the solution bulk and near the electrode surface were carried out to fully understand the processes that lead to the analytical signal. The modified electrode was used to evaluate the performances of different TiO2-based photocatalysts and the results were successfully compared with those obtained from a traditional HPLC method that is based on the determination of the hydroxylation products of salicylic acid. PMID:24054662

  1. Amperometric bienzyme screen-printed biosensor for the determination of leucine.

    PubMed

    Labroo, Pratima; Cui, Yue

    2014-01-01

    Leucine plays an important role in protein synthesis, brain functions, building muscle mass, and helping the body when it undergoes stress. Here, we report a new amperometric bienzyme screen-printed biosensor for the determination of leucine, by coimmobilizing p-hydroxybenzoate hydroxylase (HBH) and leucine dehydrogenase (LDH) on a screen-printed electrode with NADP(+) and p-hydroxybenzoate as the cofactors. The detection principle of the sensor is that LDH catalyzes the specific dehydrogenation of leucine by using NADP(+) as a cofactor. The product, NADPH, triggers the hydroxylation of p-hydroxybenzoate by HBH in the presence of oxygen to produce 3,4-dihydroxybenzoate, which results in a change in electron concentration at the working carbon electrode, which is detected by the potentiostat. The sensor shows a linear detection range between 10 and 600 μM with a detection limit of 2 μM. The response is reproducible and has a fast measuring time of 5-10 s after the addition of a given concentration of leucine. PMID:24220759

  2. Preparation of ternary Pt/Rh/SnO2 anode catalysts for use in direct ethanol fuel cells and their electrocatalytic activity for ethanol oxidation reaction

    NASA Astrophysics Data System (ADS)

    Higuchi, Eiji; Takase, Tomonori; Chiku, Masanobu; Inoue, Hiroshi

    2014-10-01

    Pt, Rh and SnO2 nanoparticle-loaded carbon black (Pt/Rh/SnO2/CB) catalysts with different contents of Pt and Rh were prepared by the modified Bönnemann method. The mean size and size distribution of Pt, Rh and SnO2 for Pt-71/Rh-4/SnO2/CB (Pt : Rh : Sn = 71 at.%: 4 at.%: 25 at.%) were 3.8 ± 0.7, 3.2 ± 0.7 and 2.6 ± 0.5 nm, respectively, indicating that Pt, Rh and SnO2 were all nanoparticles. The onset potential of ethanol oxidation current for the Pt-65/Rh-10/SnO2/CB and Pt-56/Rh-19/SnO2/CB electrodes was ca. 0.2 V vs. RHE which was ca. 0.2 V less positive than that for the Pt/CB electrode. The oxidation current at 0.6 V for the Pt/Rh/SnO2/CB electrode (ca. 2% h-1) decayed more slowly than that at the Pt/SnO2/CB electrode (ca. 5% h-1), indicating that the former was superior in durability to the latter. The main product of EOR in potentiostatic electrolysis at 0.6 V for the Pt-71/Rh-4/SnO2/CB electrode was acetic acid.

  3. Analytical detection of biological thiols in a microchip capillary channel.

    PubMed

    Chand, Rohit; Jha, Sandeep Kumar; Islam, Kamrul; Han, Dawoon; Shin, Ik-Soo; Kim, Yong-Sang

    2013-02-15

    Sulfur-containing amino acids, such as cysteine and homocysteine play crucial roles in biological systems for the diagnosis of medical states. In this regard, this paper deals with separation, aliquot and detection of amino thiols on a microchip capillary electrophoresis with electrochemical detection in an inverted double Y-shaped microchannel. Unlike the conventional capillary electrophoresis, the modified microchannel design helps in storing the separated thiols in different reservoirs for further analysis, if required; and also eliminates the need of electrodes regeneration. The device was fabricated using conventional photolithographic technique which consisted of gold microelectrodes on a soda lime glass wafer and microchannels in PDMS mold. Multiple detections were performed using in-house fabricated dual potentiostat. Based on amperometric detection, cysteine and homocysteine were analyzed in 105 s and 120 s, respectively after diverting in branched channels. Repeated experiments proved the good reproducibility of the device. The device produced a linear response for both cysteine and homocysteine in electrochemical analysis. To prove the practicality of device, we also analyzed cysteine and homocysteine in real blood samples without any pre-treatment. Upon calculation, the device showed a very low limit of detection of 0.05 μM. The modified microchip design shall find a broad range of analytical applications involving assays of thiols and other biological compounds. PMID:22940195

  4. Spatiotemporal norepinephrine mapping using a high-density CMOS microelectrode array.

    PubMed

    Wydallis, John B; Feeny, Rachel M; Wilson, William; Kern, Tucker; Chen, Tom; Tobet, Stuart; Reynolds, Melissa M; Henry, Charles S

    2015-10-21

    A high-density amperometric electrode array containing 8192 individually addressable platinum working electrodes with an integrated potentiostat fabricated using Complementary Metal Oxide Semiconductor (CMOS) processes is reported. The array was designed to enable electrochemical imaging of chemical gradients with high spatiotemporal resolution. Electrodes are arranged over a 2 mm × 2 mm surface area into 64 subarrays consisting of 128 individual Pt working electrodes as well as Pt pseudo-reference and auxiliary electrodes. Amperometric measurements of norepinephrine in tissue culture media were used to demonstrate the ability of the array to measure concentration gradients in complex media. Poly(dimethylsiloxane) microfluidics were incorporated to control the chemical concentrations in time and space, and the electrochemical response at each electrode was monitored to generate electrochemical heat maps, demonstrating the array's imaging capabilities. A temporal resolution of 10 ms can be achieved by simultaneously monitoring a single subarray of 128 electrodes. The entire 2 mm × 2 mm area can be electrochemically imaged in 64 seconds by cycling through all subarrays at a rate of 1 Hz per subarray. Monitoring diffusional transport of norepinephrine is used to demonstrate the spatiotemporal resolution capabilities of the system. PMID:26333296

  5. Effect of Fluid Flow on Zinc Electrodeposits from Acid Chloride Electrolytes. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Abdelmassir, A. A.

    1982-01-01

    Zinc was deposited potentiostatically from acid chloride baths. Once bath chemistry and electrochemistry were controlled, the study was focused on convective mass transfer at horizontal electrodes and its effect on cell performance. A laser schlieren imaging technique allowed in situ observations of flow patterns and their correlation with current transients. Convection was turbulent and mass transfer as a function of Rayleigh number was well correlated by: Sh = 0.14 R to the 1/3 power. Similarly, convection initiation time was correlated by DT/d squared = 38 Ra to the -2/3 power. Time scale of fluctuations was about half the initiation time. Taking the boundary layer thickness as a characteristic length, a critical Rayleigh number for the onset of convection was deduced: Ra sub CR = 5000. Placing the anode on the top of the cathode completely changed the flow pattern but kept the I-t curves identical whereas the use of a cathode grid doubled the limiting current. A well defined plateau in the current voltage curves suggested that hydrogen evolution has been successfully inhibited. Finally, long time deposition showed that convection at horizontal electrodes increased the induction time for dentrite growth by at least a factor of 2 with respect to a vertical wire.

  6. Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations.

    PubMed

    Sun, Bing; Mindemark, Jonas; V Morozov, Evgeny; Costa, Luciano T; Bergman, Martin; Johansson, Patrik; Fang, Yuan; Furó, István; Brandell, Daniel

    2016-03-30

    Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with ε-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li(+) and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li(+)-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments. PMID:26984668

  7. In vitro crevice corrosion behavior of implant materials.

    PubMed

    Sutow, E J; Jones, D W; Milne, E L

    1985-05-01

    The crevice corrosion susceptibility of cold-worked Type 316LVM stainless steel, cast Co-Cr-Mo, wrought Co-Cr-W-Ni, non-nitrided and nitrided Ti-6Al-4V ELI, and c.p. Ti, Grades 1 and 4, was studied in vitro by means of a crevice cell. Occlusion was created by interfacing a disc specimen and a Teflon bar. Specimens were mechanically prepared through 2-4 micron Al2O3 and passivated in 30% HNO3, followed by steam sterilization. Tests were performed in a deaerated Ringer's solution, maintained at pH = 7 and 37 degrees C. Anodic polarization was conducted potentiostatically at pre-selected levels, and resultant currents were monitored: stainless steel, 50 and 100 mV (S.C.E.), 450 min; non-stainless materials, 600 mV, 1000 min. Results for the stainless steel demonstrated that a HNO3 passivation treatment reduced its crevice corrosion susceptibility. For the non-stainless steel materials, no crevice corrosion susceptibility was observed, although a dulling and discoloration of c.p. Ti was evident. Recognizing that 600 mV is in excess of the O2 reduction potential in vivo, it was concluded that, in the absence of fretting, implants of these non-stainless steel materials would not experience significant corrosion loss under crevice conditions. PMID:3858307

  8. Corrosion of Carbon Steel and Corrosion-Resistant Rebars in Concrete Structures Under Chloride Ion Attack

    NASA Astrophysics Data System (ADS)

    Mohamed, Nedal; Boulfiza, Mohamed; Evitts, Richard

    2013-03-01

    Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., highway bridges, marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed to avoid these high-cost repairs. Thus, it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements. This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three-electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4™ potentiostat manufactured by Gamry Instruments (Warminster, PA). DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution.

  9. Kinetic features of the oxide formation on {111} polar planes upon anode treatment of n-GaAs

    NASA Astrophysics Data System (ADS)

    Orlov, A. M.; Yavtushenko, I. O.; Makhmud-Akhunov, M. Yu.

    2016-04-01

    The mechanism and kinetics of anode destruction of {111} polar planes of n-GaAs and morphological features of forming oxide films in the potentiostatic mode of polarization in weakly acid solutions of electrolytes have been studied. It has been found that anode polarization of the gallium plane (111) Ga provides the formation of a porous structure of both the single-crystal matrix and oxide film, which has a planar topology. In this case, the pore density is always commensurable with the surface dope concentration. In contrast to the gallium plane, the anode polarization of the arsenic plane overline {( {111} )} As provides the tangential mechanism of destruction of the semiconductor matrix and the island-type morphology of the oxide. Equal crystallographic orientation of islands is determined by the directive action of the family of oxidized planes { {1overline {11} } } GaAs. However, regardless of the crystallographic orientation of the polar plane, the forming oxide is represented by polycrystalline As2O3 and amorphous Ga2O3.

  10. In situ scanning tunneling microscopy studies of the SEI formation on graphite electrodes for Li(+)-ion batteries.

    PubMed

    Seidl, Lukas; Martens, Slađana; Ma, Jiwei; Stimming, Ulrich; Schneider, Oliver

    2016-08-01

    The SEI-formation on graphitic electrodes operated as an Li(+)-ion battery anode in a standard 1 M LiPF6 EC/DMC (1 : 1) electrolyte has been studied in situ by EC-STM. Two different modes of in situ study were applied, one, which allowed to follow topographic and crystallographic changes (solvent cointercalation, graphite exfoliation, SEI precipitation on the HOPG basal plane) of the graphite electrode during SEI-formation, and the second, which gave an insight into the SEI precipitation on the HOPG basal plane in real time. From the in situ EC-STM studies, not only conclusions about the SEI-topography could be drawn, but also about the formation mechanism and the chemical composition, which strongly depend on the electrode potential. It was shown that above 1.0 V vs. Li/Li(+) the SEI-formation is still reversible, since the molecular structure of the solvent molecules remains intact during an initial reduction step. During further reduction, the molecular structures of the solvents are destructed, which causes the irreversible charge loss. The STM studies were completed by electrochemical methods, like cyclic voltammetry, the potentiostatic intermittent titration technique and charge/discharge tests of MCMB electrodes. PMID:27140292

  11. A mechanistic model for oxide growth and dissolution during corrosion of Cr-containing alloys.

    PubMed

    Momeni, M; Wren, J C

    2015-01-01

    We have developed a corrosion model that can predict metal oxide growth and dissolution rates as a function of time for a range of solution conditions. Our model considers electrochemical reactions at the metal/oxide and oxide/solution interfaces, and the metal cation flux from the metal to the solution phase through a growing oxide layer, and formulates the key processes using classical chemical reaction rate or flux equations. The model imposes mass and charge balance and hence, is labeled as the Mass Charge Balance (MCB) model. Mass and charge balance dictate that at any given time the oxidation (or metal cation) flux must be equal to the sum of the oxide growth flux and the dissolution flux. For each redox reaction leading to the formation of a specific oxide, the metal oxidation flux is formulated using a modified Butler-Volmer equation with an oxide-thickness-dependent effective overpotential. The oxide growth and dissolution fluxes have a first-order dependence on the metal cation flux. The rate constant for oxide formation also follows an Arrhenius dependence on the potential drop across the oxide layer and hence decreases exponentially with oxide thickness. This model is able to predict the time-dependent potentiostatic corrosion behaviour of both pure iron, and Co-Cr and Fe-Ni-Cr alloys. PMID:25912738

  12. Miniaturized thin film glutamate and glutamine biosensors.

    PubMed

    Moser, I; Jobst, G; Aschauer, E; Svasek, P; Varahram, M; Urban, G; Zanin, V A; Tjoutrina, G Y; Zharikova, A V; Berezov, T T

    1995-01-01

    Integrated thin film biosensors were developed for the simultaneous measurement of L-glutamine and L-glutamate in a mu-flow cell. Due to a novel glutaminase with an activity optimum in the neutral pH range, direct monitoring of glutamine in a mammalian cell culture medium could be performed. The glutamine bienzyme sensor was prepared by co-immobilization of glutaminase with glutamate oxidase within a photopatterned poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel membrane. The sensor response was linear in the concentration range of 50 mumol to 10 mmol glutamine/l. Additionally, a glutamate biosensor was integrated on the sensor chip for difference measurement of possible glutamate interferences. The sensor-chip could be used for at least 300 measurements without any alteration in the performance of its sensors. A new sensor-chip with an integrated flow cell provided the possibility of simultaneous measurement of four different parameters at a cell volume of 1 microliter. In order to complete the microsystem, and in order to obtain a "lab on chip", a battery operated surface mounted device (SMD) potentiostat was developed. PMID:7612205

  13. Hydrogen trapping in high-strength steels

    SciTech Connect

    Pound, B.G.

    1998-10-09

    Hydrogen trapping in three high-strength steels -- AerMet 100 and AISI 4340 and H11 -- was studied using a potentiostatic pulse technique. Irreversible trapping constants (k) and hydrogen entry fluxes were determined for these alloys in 1 mol/1 acetic acid/1 mol/1 sodium acetate. The order of the k values for the three steels and two 18Ni maraging steels previously studies inversely parallels their threshold stress intensities for stress corrosion cracking (K{sub 1SCC}). Irreversible trapping in AerMet 100 varies with aging temperature and appears to depend on the type of carbide (Fe{sub 3}C or M{sub 2}C) present. For 4340 steel, k can be correlated with K{sub 1SCC} over a range of yield strengths. The change in k is consistent with a change in the principal type of irreversible trap from matrix boundaries to incoherent Fe{sub 3}C. The principal irreversible traps in H11 at high yield strengths are thought to be similar to those in 4340 steel.

  14. An instrument for simultaneous EQCM impedance and SECM measurements.

    PubMed

    Gollas, B; Bartlett, P N; Denuault, G

    2000-01-15

    A novel combination of an electrochemical quartz crystal microbalance (EQCM) and a scanning electrochemical microscope (SECM) has been built. Unlike conventional EQCMs, the instrument described here allows rapid in situ measurement of the modulus of the quartz crystal's transfer function. Data analysis in the complex plane for the Butterworth-Van Dyke (BVD) equivalent circuit yields the real and the imaginary components R (damping resistance) and XL (reactive inductance) of the crystal's electroacoustic impedance around its resonant frequency of 10 MHz. The influence of different tip shapes of an approaching microelectrode on the electroacoustic impedance of the quartz crystal was studied and found to be minimal for certain geometries. The capability of the EQCM/SECM instrument was tested in cyclic voltammetric plating/stripping experiments using a copper(I) chloride solution of high concentration in 1 M HCl. Four parameters, XL, R, the substrate, and the tip current, can be recorded simultaneously. Depletion layer effects were observed and could be corrected for to yield accurate current efficiencies for potentiodynamic and potentiostatic copper plating. The amperometric response of the SECM tip positioned closely to the substrate reflects the concentration changes of electroactive ions in the diffusion layer of the substrate electrode. PMID:10658330

  15. Delayed feedback induced multirhythmicity in the oscillatory electrodissolution of copper

    NASA Astrophysics Data System (ADS)

    Nagy, Timea; Verner, Erika; Gáspár, Vilmos; Kori, Hiroshi; Kiss, István Z.

    2015-06-01

    Occurrence of bi- and trirhythmicities (coexistence of two or three stable limit cycles, respectively, with distinctly different periods) has been studied experimentally by applying delayed feedback control to the copper-phosphoric acid electrochemical system oscillating close to a Hopf bifurcation point under potentiostatic condition. The oscillating electrode potential is delayed by τ and the difference between the present and delayed values is fed back to the circuit potential with a feedback gain K. The experiments were performed by determining the period of current oscillations T as a function of (both increasing and decreasing) τ at several fixed values of K. With small delay times, the period exhibits a sinusoidal type dependence on τ. However, with relatively large delays (typically τ ≫ T) for each feedback gain K, there exists a critical delay τcrit above which birhythmicity emerges. The experiments show that for weak feedback, Kτcrit is approximately constant. At very large delays, the dynamics becomes even more complex, and trirhythmicity could be observed. Results of numerical simulations based on a general kinetic model for metal electrodissolution were consistent with the experimental observations. The experimental and numerical results are also interpreted by using a phase model; the model parameters can be obtained from experimental data measured at small delay times. Analytical solutions to the phase model quantitatively predict the parameter regions for the appearance of birhythmicity in the experiments, and explain the almost constant value of Kτcrit for weak feedback.

  16. Submicron patterned metal hole etching

    DOEpatents

    McCarthy, Anthony M.; Contolini, Robert J.; Liberman, Vladimir; Morse, Jeffrey

    2000-01-01

    A wet chemical process for etching submicron patterned holes in thin metal layers using electrochemical etching with the aid of a wetting agent. In this process, the processed wafer to be etched is immersed in a wetting agent, such as methanol, for a few seconds prior to inserting the processed wafer into an electrochemical etching setup, with the wafer maintained horizontal during transfer to maintain a film of methanol covering the patterned areas. The electrochemical etching setup includes a tube which seals the edges of the wafer preventing loss of the methanol. An electrolyte composed of 4:1 water: sulfuric is poured into the tube and the electrolyte replaces the wetting agent in the patterned holes. A working electrode is attached to a metal layer of the wafer, with reference and counter electrodes inserted in the electrolyte with all electrodes connected to a potentiostat. A single pulse on the counter electrode, such as a 100 ms pulse at +10.2 volts, is used to excite the electrochemical circuit and perform the etch. The process produces uniform etching of the patterned holes in the metal layers, such as chromium and molybdenum of the wafer without adversely effecting the patterned mask.

  17. Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

    PubMed

    Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

    2016-08-01

    This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. PMID:27100467

  18. Analysis of gas products from direct utilization of carbon in a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Siengchum, Tritti; Guzman, Felipe; Chuang, Steven S. C.

    2012-09-01

    The evolution of gases from direct utilization of carbon in a solid oxide fuel cell (C-SOFC) was studied by potentiostatic/galvanostatic discharge of a fuel cell with coconut carbon, a carbonaceous material with low ash and sulfur content. Operation of C-SOFC at 750 °C produced less CO and more CO2 than those predicted by thermodynamic calculation using total Gibbs free energy minimization method. The addition of CO2 to the anode chamber increased CO formation and maximum power density from 0.09 W cm-2 to 0.13 W cm-2, indicating the occurrence of Boudouard reaction (CO2 + C ⇔ 2CO) coupling with CO electrochemical oxidation on the C-SOFC. Analysis of CO and CO2 concentration as a function of current and voltage revealed that electricity was mainly produced from the electrochemical oxidation of carbon at low current density and produced from the electrochemical oxidation of CO at high current density. The results suggest the electrochemical oxidation of solid carbon is more mass transfer limited than electrochemical oxidation of CO.

  19. Disposable electrochemical sensor to evaluate the phytoremediation of the aquatic plant Lemna minor L. toward Pb(2+) and/or Cd(2+).

    PubMed

    Neagu, Daniela; Arduini, Fabiana; Quintana, Josefina Calvo; Di Cori, Patrizia; Forni, Cinzia; Moscone, Danila

    2014-07-01

    In this work a miniaturized and disposable electrochemical sensor was developed to evaluate the cadmium and lead ion phytoremediation potential by the floating aquatic macrophyte Lemna minor L. The sensor is based on a screen-printed electrode modified "in-situ" with bismuth film, which is more environmentally friendly than the mercury-based sensor usually adopted for lead and cadmium ion detection. The sensor was coupled with a portable potentiostat for the simultaneous measurement of cadmium and lead ions by stripping analysis. The optimized analytical system allows the simultaneous detection of both heavy metals at the ppb level (LOD equal to 0.3 and 2 ppb for lead and cadmium ions, respectively) with the advantage of using a miniaturized and cost-effective system. The sensor was then applied for the evaluation of Pb(2+) or/and Cd(2+) uptake by measuring the amount of the heavy metals both in growth medium and in plant tissues during 1 week experiments. In this way, the use of Lemna minor coupled with a portable electrochemical sensor allows the set up of a model system able both to remove the heavy metals and to measure "in-situ" the magnitude of heavy metal removal. PMID:24899412

  20. Sustainable AC/AC hybrid electrochemical capacitors in aqueous electrolyte approaching the performance of organic systems

    NASA Astrophysics Data System (ADS)

    Abbas, Qamar; Babuchowska, Paulina; Frąckowiak, Elżbieta; Béguin, François

    2016-09-01

    A high energy hybrid AC/AC electrochemical capacitor has been realized in aqueous Li2SO4+KI electrolyte mixture. Owing to the redox processes associated with the 2I-/I2 system, the positive electrode operates in narrow potential range and displays high capacity. During prolonged potentiostatic floating at 1.6 V, the hybrid cell demonstrates remarkably stable capacitance and resistance. Analyses by temperature programmed desorption after floating at 1.6 V proved that oxidation of the positive AC electrode is prevented by the use of Li2SO4+KI, which enables the maximum potential of this electrode to be shifted below the water oxidation potential. When charged at 0.2 A g-1 up to U = 1.6 V, the hybrid cell displays a high capacitance of 75 F g-1 (300 F g-1 per mass of one electrode) compared to 47 F g-1 (188 F g-1 per mass of one electrode) for a symmetric cell in Li2SO4. At 0.2 A g-1 up to 1.6 V, the hybrid capacitor in Li2SO4+KI displays an energy density of 26 Wh kg-1 which approaches the energy density of 30.9 Wh kg-1 measured when the same carbon is implemented in a capacitor using TEABF4/ACN electrolyte and charged up to 2.5 V.

  1. Ultrathin, Stretchable, Multiplexing pH Sensor Arrays on Biomedical Devices With Demonstrations on Rabbit and Human Hearts Undergoing Ischemia

    PubMed Central

    Chung, Hyun-Joong; Sulkin, Matthew S.; Kim, Jong-Seon; Goudeseune, Camille; Chao, Hsin-Yun; Song, Joseph W.; Yang, Sang Yoon; Hsu, Yung-Yu; Ghaffari, Roozbeh

    2014-01-01

    Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of non-invasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In-vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (−1.6 mV/°C), and minimal influence of extracellular ions (< 3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants. PMID:23868871

  2. Long-term in vivo experience of an electrochemical sensor using the potential step technique for measurement of mixed venous oxygen pressure.

    PubMed

    Holmström, N; Nilsson, P; Carlsten, J; Bowald, S

    1998-12-01

    An implantable amperometric blood oxygen sensor was developed to improve rate adaptation of heart pacemakers. Two different working electrode materials in direct contact with the blood were tested, smooth glassy carbon and gold. Reference electrodes of Ag/AgCl and porous pyrolytic carbon were evaluated. A counter electrode being the titanium housing of the pulse generator was partly coated with carbon. An implantable pacemaker system with chronocoulometric oxygen detection was developed. Heart synchronous potential steps were periodically applied to the 7.5 mm2 working electrode in the atrium. Both single and double potential step techniques were evaluated. The oxygen diffusion limited current was used to calculate the stimulation rate. Bench tests and studies on 31 animals were performed to evaluate long-term stability and biocompatibility. In five dogs, the AV node was destroyed by RF ablation to create a realistic animal model of a pacemaker patient. Sensor stability and response to exercise was followed up to a maximum implantation time of 4 years. Post-mortem examinations of the electrode surfaces and tissue response were performed. The results show that a gold electrode is more stable than glassy carbon. The Ag/AgCl reference was found not to be biocompatible, but activated carbon was stable enough for use as reference for the potentiostat. Double potential steps stabilize the sensor response in comparison to single steps. Blood protein adsorption on the gold surface decreased the oxygen transport but not the reaction efficacy. No adverse tissue reactions were observed. PMID:9883563

  3. Fabrication of an optoelectrochemical microring array.

    PubMed

    Szunerits, Sabine; Walt, David R

    2002-04-01

    In this paper, we describe a novel approach for fabricating an optoelectrochemical microring array. The array was fabricated by coating individual optical fibers of 25-microm diameter with a 1-microm layer of gold nanoparticles via electroless gold deposition. A SAM layer around the individual gold-coated imaging fibers prevented electrical contact with neighboring ring electrodes. To achieve better mechanical stability and to make the device more practical, the electrode/fiber bundle comprising approximately 600 individual gold-coated optical fibers was dipped into epoxy. By polishing the ends of such a device, a ring microelectrode array comprising 600 individual and insulated ring electrodes was formed. To limit diffusional overlap of current, only 20-30% of the microring fiber/electrodes were wired. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 microm), while the outer radius is determined by the thickness of the deposited gold. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady-state currents at short response times. In addition, cyclic voltammetry experiments were performed using conventional potentiostats due to the amplification of current inherent in the array format. Finally, electrochemiluminescence at the ring electrode array was demonstrated through the oxidation of Ru(bpy)3(2+) in tri-n-propylamide in a pH 7 phosphate buffer solution, where the light generated was collected and detected via the fiber bundle. PMID:12033265

  4. Preparation of electrodeposited Zn-Ni-B alloy coatings

    NASA Astrophysics Data System (ADS)

    Sakai, Taro; Kamimoto, Yuki; Ichino, Ryoichi

    2016-01-01

    We prepared Zn-Ni-B alloys with high Zn content and high corrosion resistance. The composition of the alloys was controlled by potentiostatic electrolysis. In the electroplating bath, dimethylamineborane was used as the B source. The characterization of the alloys and corrosion resistance evaluation were carried out by X-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES), Tafel plots, and cyclic corrosion tests. All films were categorized into three groups on the basis of the results of XRD analysis, and it was found by TEM analysis that the Ni-B-type showed an amorphous structure. The Ni-B-type could contain up to 50.6 mol % Zn and showed similar or better anticorrosion properties than the amorphous Ni-B films. In the Ni-B-type, the higher the Zn content, the higher the corrosion resistance. The Zn-Ni-B alloys had almost the same electrochemical corrosion resistance and Zn content as the Zn-Ni-P alloys.

  5. Electrodeposition of palladium on carbon nanotubes modified nickel foam as an efficient electrocatalyst towards hydrogen peroxide reduction

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Cao, Bo; Tao, Yue; Hu, Miao; Feng, Chengcheng; Wang, Lei; Jiang, Zhao; Cao, Dianxue; Zhang, Ying

    2015-12-01

    In this article, a three-dimensional electrode (Pd-CNT/Ni foam) based on Pd nanoparticles and carbon nanotubes (CNTs) is successfully developed by a simple "dipping and drying" process and a potentiostatic deposition technology for H2O2 reduction in base medium. The composition and structure of Pd-CNT/Ni foam electrode are examined by X-ray diffractometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, respectively. The cyclic voltammetry (CV) and chronoamperometry (CA) techniques are applied to determine the electrochemical performance. The electrode exhibits a high catalytic activity for H2O2 electroreduction, and it outperforms Pd/Ni foam electrode without CNT coating. At the reduction potential of -0.8 V, the reduction currents on Pd-CNT/Ni foam electrode can reach 323 mA cm-2, however, it is only 192 mA cm-2 on Pd/Ni foam electrode, which is increased by 68.2%. The impressive electrocatalytic performance is largely attributed to the superior open structure and high electronic conductivity, which allows the high utilization of Pd surfaces and makes the electrode have higher electrochemical activity. These findings may provide the opportunity on preparing binder-free carbon-supported electrode in the application of fuel cells.

  6. Electrodeposition of Nanocrystalline Chromium Coatings Based on 1-Butyl-3-Methylimidazolium-Bromide Ionic Liquid.

    PubMed

    He, Xinkuai; Zhu, Qingyun; Hou, Bailong; Cai, Youxing; Li, Chen; Fu, Liqin; Wu, Luye

    2015-12-01

    The electrochemical behavior of trivalent chromium reduction from 1-butyl-3-methylimidazolium-bromide ([BMIM]Br) ionic liquid is studied. The result of cyclic voltammetry shows that the Cr(III) reduction is irreversible and occurs in two steps, Cr(III)to Cr(II), and Cr(II) to Cr(0), respectively. In the electrochemical impedance spectroscopy measurements, the preferable equivalent circuit is made to fit the experimental data. The effects of electroplating parameters on coating thickness and electrodepositon rate are investigated by potentiostatic method on Cu electrode from Cr(III)-[BMIM]Br solution. The results show that the temperature and depositing potential have great effect on the coating thickness and electrodeposition rate. The surface morphology and composition of deposited Cr are investigated using scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS). SEM analysis shows that chromium electrodeposits obtained on Cu electrodes present a ball-like structure. EDS analysis shows that the coatings are composed of Cr. Moreover, the corrosion resistance of the as-deposited chromium layer is evaluated using polarization curves. The results show that the corrosion resistance of the chromium coatings obtained at higher potential is better. PMID:26682363

  7. Polyaniline-coated freestanding porous carbon nanofibers as efficient hybrid electrodes for supercapacitors

    NASA Astrophysics Data System (ADS)

    Tran, Chau; Singhal, Richa; Lawrence, Daniel; Kalra, Vibha

    2015-10-01

    Three-dimensional, free-standing, hybrid supercapacitor electrodes combining polyaniline (PANI) and porous carbon nanofibers (P-CNFs) were fabricated with the aim to integrate the benefits of both electric double layer capacitors (high power, cyclability) and pseudocapacitors (high energy density). A systematic investigation of three different electropolymerization techniques, namely, potentiodynamic, potentiostatic, and galvanostatic, for electrodeposition of PANI on freestanding carbon nanofiber mats was conducted. It was found that the galvanostatic method, where the current density is kept constant and can be easily controlled facilitates conformal and uniform coating of PANI on three-dimensional carbon nanofiber substrates. The electrochemical tests indicated that the PANI-coated P-CNFs exhibit excellent specific capacitance of 366 F g-1 (vs. 140 F g-1 for uncoated porous carbon nanofibers), 140 F cm-3 volumetric capacitance, and up to 2.3 F cm-2 areal capacitance at 100 mV s-1 scan rate. Such excellent performance is attributed to a thin and conformal coating of PANI achieved using the galvanostatic electrodeposition technique, which not only provides pseudocapacitance with high rate capability, but also retains the double-layer capacitance of the underlying P-CNFs.

  8. Nanostructured silver-gold bimetallic SERS substrates for selective identification of bacteria in human blood.

    PubMed

    Sivanesan, Arumugam; Witkowska, Evelin; Adamkiewicz, Witold; Dziewit, Łukasz; Kamińska, Agnieszka; Waluk, Jacek

    2014-03-01

    Surface-enhanced Raman spectroscopy (SERS) is a potentially important tool in the rapid and accurate detection of pathogenic bacteria in biological fluids. However, for diagnostic application of this technique, it is necessary to develop a highly sensitive, stable, biocompatible and reproducible SERS-active substrate. In this work, we have developed a silver-gold bimetallic SERS surface by a simple potentiostatic electrodeposition of a thin gold layer on an electrochemically roughened nanoscopic silver substrate. The resultant substrate was very stable under atmospheric conditions and exhibited the strong Raman enhancement with the high reproducibility of the recorded SERS spectra of bacteria (E. coli, S. enterica, S. epidermidis, and B. megaterium). The coating of the antibiotic over the SERS substrate selectively captured bacteria from blood samples and also increased the Raman signal in contrast to the bare surface. Finally, we have utilized the antibiotic-coated hybrid surface to selectively identify different pathogenic bacteria, namely E. coli, S. enterica and S. epidermidis from blood samples. PMID:24419003

  9. Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy.

    PubMed

    Ghadiri, Elham; Zakeeruddin, Shaik M; Hagfeldt, Anders; Grätzel, Michael; Moser, Jacques-E

    2016-01-01

    Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and -690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded. PMID:27095505

  10. Deformation and fracture of aluminum-lithium alloys: The effect of dissolved hydrogen

    NASA Technical Reports Server (NTRS)

    Rivet, F. C.; Swanson, R. E.

    1990-01-01

    The effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys are studied. The work done during this semi-annual period consists of the hydrogen charging study and some preliminary mechanical tests. Prior to SIMS analysis, several potentiostatic and galvanostatic experiments were performed for various times (going from 10 minutes to several hours) in the cathodic zone, and for the two aqueous solutions: 0.04N of HCl and 0.1N NaOH both combined with a small amount of As2O3. A study of the surface damage was conducted in parallel with the charging experiments. Those tests were performed to choose the best charging conditions without surface damage. Disk rupture tests and tensile tests are part of the study designed to investigate the effect of temperature, surface roughness, strain rate, and environment on the fracture behavior. The importance of the roughness and environment were shown using the disk rupture test as well as the importance of the strain rate under hydrogen environment. The tensile tests, without hydrogen effects, have not shown significant differences between low and room temperature.

  11. Development of an On-animal Separation-based Sensor for Monitoring Drug Metabolism in Freely Roaming Sheep

    PubMed Central

    Scott, David E.; Willis, Sean D.; Gabbert, Seth; Johnson, Dave A.; Naylor, Erik; Janle, Elsa M.; Krichevsky, Janice E.; Lunte, Craig E.; Lunte, Susan M.

    2015-01-01

    The development of an on-animal separation-based sensor that can be employed for monitoring drug metabolism in a freely roaming sheep is described. The system consists of microdialysis sampling coupled directly to microchip electrophoresis with electrochemical detection (MD-ME-EC). Separations were accomplished using an all-glass chip with integrated platinum working and reference electrodes. Discrete samples from the microdialysis flow were introduced into the electrophoresis chip using a flow-gated injection approach. Electrochemical detection was accomplished in-channel using a two-electrode isolated potentiostat. Nitrite was separated by microchip electrophoresis using reverse polarity and a run buffer consisting of 50 mM phosphate at pH 7.4. The entire system was under telemetry control. The system was first tested with rats to monitor the production of nitrite following introduction of nitroglycerin into the subdermal tissue using a linear probe. The data acquired using the on-line MD-ME-EC system was compared to that obtained off-line analysis by liquid chromatography with electrochemical detection (LC-EC), using a second microdialysis probe implanted parallel to the first probe in the same animal. The MD-ME-EC device was then used on-animal to monitor the subdermal metabolism of nitroglycerin in sheep. The ultimate goal is to use this device to simultaneously monitor drug metabolism and behavior in a freely roaming animal. PMID:25697221

  12. Three-Dimensionally Mesostructured Fe2O3 Electrodes with Good Rate Performance and Reduced Voltage Hysteresi

    DOE PAGESBeta

    Wang, Junjie; Braun, Paul V.; Zhou, Hui; Nanda, Jagjit

    2015-03-26

    Ni scaffolded mesostructured 3D Fe2O3 electrodes were fabricated by colloidal templating and pulsed elec-trodeposition. The scaffold provided short pathways for both lithium ions and electrons in the active phase, enabling fast kinetics and thus a high power density. The scaffold also resulted in a reduced voltage hysteresis. The electrode showed a reversible capacity of ~1000 mA h g-1 at 0.2 A g-1 (~0.2 C) for about 20 cycles, and at a current density of 20 A g-1 (~20 C) the deliverable capacity was about 450 mA h g-1. The room temperature voltage hysteresis at 0.1 A g-1 (~0.1 C) wasmore » 0.62 V, which is significantly smaller than that normally reported in the literature. And it could be further reduced to 0.42 V when cycling at 45 ºC. Potentiostatic electrochemical impedance spectroscopy (PEIS) studies indicated the small voltage hysteresis may be due to a reduction in the Li2O/Fe interfacial area in the electrode during cycling relative to convention-al conversion systems.« less

  13. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    NASA Astrophysics Data System (ADS)

    Lee, June Key; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok; Ryu, Sang-Wan; Jeong, Tak; Jung, Eunjin; Kim, Hyunsoo

    2015-05-01

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ˜35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  14. Characterization of oxide layers on amorphous Zr-based alloys by Auger electron spectroscopy with sputter depth profiling

    NASA Astrophysics Data System (ADS)

    Baunack, S.; Mudali, U. Kamachi; Gebert, A.

    2005-09-01

    Amorphous Zr-Cu-Ni-Al-[Ti, Nb] ribbons prepared by melt spinning under argon atmosphere were subjected to electrochemical investigations. Passive films developed at potentiostatic anodic polarization in sulphuric acid solution were investigated by Auger electron spectroscopy (AES) and sputter depth profiling. Changes in the shape of the Auger peaks have been analyzed by factor analysis of the spectra obtained during depth profiling. Pronounced changes in shape and position occur for the Zr, Al, and Ti Auger transitions, but not for Cu and Ni. At least three different peak shapes for O(KVV) were found and attributed to different oxygen binding states. The alloy composition has no significant effect on the thickness and composition of the oxide layer. In multi-element alloys preferential sputtering is a common phenomenon. In the steady state of sputtering, a significant depletion in Cu is found. At the oxide/metal interface, a distinct enrichment of copper is found for all alloys and treatments. The degree of this Cu enrichment depends on the pretreatment. It is higher for the electrochemically-passivated samples than for samples with oxide layers grown during melt spinning.

  15. Towards a Multifunctional Electrochemical Sensing and Niosome Generation Lab-on-Chip Platform Based on a Plug-and-Play Concept.

    PubMed

    Kara, Adnane; Rouillard, Camille; Mathault, Jessy; Boisvert, Martin; Tessier, Frédéric; Landari, Hamza; Melki, Imene; Laprise-Pelletier, Myriam; Boisselier, Elodie; Fortin, Marc-André; Boilard, Eric; Greener, Jesse; Miled, Amine

    2016-01-01

    In this paper, we present a new modular lab on a chip design for multimodal neurotransmitter (NT) sensing and niosome generation based on a plug-and-play concept. This architecture is a first step toward an automated platform for an automated modulation of neurotransmitter concentration to understand and/or treat neurodegenerative diseases. A modular approach has been adopted in order to handle measurement or drug delivery or both measurement and drug delivery simultaneously. The system is composed of three fully independent modules: three-channel peristaltic micropumping system, a three-channel potentiostat and a multi-unit microfluidic system composed of pseudo-Y and cross-shape channels containing a miniature electrode array. The system was wirelessly controlled by a computer interface. The system is compact, with all the microfluidic and sensing components packaged in a 5 cm × 4 cm × 4 cm box. Applied to serotonin, a linear calibration curve down to 0.125 mM, with a limit of detection of 31 μ M was collected at unfunctionalized electrodes. Added sensitivity and selectivity was achieved by incorporating functionalized electrodes for dopamine sensing. Electrode functionalization was achieved with gold nanoparticles and using DNA and o-phenylene diamine polymer. The as-configured platform is demonstrated as a central component toward an "intelligent" drug delivery system based on a feedback loop to monitor drug delivery. PMID:27240377

  16. Wireless micropower instrumentation for multimodal acquisition of electrical and chemical neural activity.

    PubMed

    Mollazadeh, M; Murari, K; Cauwenberghs, G; Thakor, N

    2009-12-01

    The intricate coupling between electrical and chemical activity in neural pathways of the central nervous system, and the implication of this coupling in neuropathologies, such as Parkinson's disease, motivates simultaneous monitoring of neurochemical and neuropotential signals. However, to date, neurochemical sensing has been lacking in integrated clinical instrumentation as well as in brain-computer interfaces (BCI). Here, we present an integrated system capable of continuous acquisition of data modalities in awake, behaving subjects. It features one channel each of a configurable neuropotential and a neurochemical acquisition system. The electrophysiological channel is comprised of a 40-dB gain, fully differential amplifier with tunable bandwidth from 140 Hz to 8.2 kHz. The amplifier offers input-referred noise below 2 muV rms for all bandwidth settings. The neurochemical module features a picoampere sensitivity potentiostat with a dynamic range spanning six decades from picoamperes to microamperes. Both systems have independent on-chip, configurable DeltaSigma analog-to-digital converters (ADCs) with programmable digital gain and resolution. The system was also interfaced to a wireless power harvesting and telemetry module capable of powering up the circuits, providing clocks for ADC operation, and telemetering out the data at up to 32 kb/s over 3.5 cm with a bit-error rate of less than 10(-5). Characterization and experimental results from the electrophysiological and neurochemical modules as well as the full system are presented. PMID:23853286

  17. Corrosion inhibitor storage and release property of TiO{sub 2} nanotube powder synthesized by rapid breakdown anodization method

    SciTech Connect

    Arunchandran, C.; Ramya, S.; George, R.P.; Kamachi Mudali, U.

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► TiO{sub 2} nanotube powders were synthesized by rapid breakdown anodization method. ► Benzotriazole was loaded into the TiO{sub 2} nanotube powders. ► Low pH induced release of benzotriazole from TiO{sub 2} nanotube powders was proved. -- Abstract: Titanium dioxide (TiO{sub 2}) is one of the most studied substances in material science due to its versatile properties and diverse applications. In this study titanium dioxide nanotube powder were synthesized by rapid breakdown anodization (RBA) method. The synthesis involved potentiostatic anodization of titanium foil in 0.1 M HClO{sub 4} electrolyte under an applied voltage of 20 V and rapid stirring. The morphology and the phase of titanium dioxide nanotube powder were studied using field emission scanning electron microscopy, laser Raman spectroscopy and high resolution transmission electron microscopy. Benzotriazole was chosen as model inhibitor to evaluate TiO{sub 2} nanotube powder's corrosion inhibitor loading and releasing properties. The storage and release properties of TiO{sub 2} nanotube powder were studied using UV–visible spectroscopy and thermogravimetric analysis.

  18. Tribocorrosion mechanisms of Ti6Al4V biomedical alloys in artificial saliva with different pHs

    NASA Astrophysics Data System (ADS)

    Licausi, M. P.; Igual Muñoz, A.; Amigó Borrás, V.

    2013-10-01

    Titanium and its alloys has been widely used for the design of dental implants because of its biocompatibility, mechanical properties and corrosion resistance. The powder-metallurgy process is a promising alternative to the casting fabrication process of titanium alloys for bone implants design as the porous structure mimics the natural bone structures, allowing the bone to grow into the pores which results in a better fixation of the artificial implant. However, under in vivo conditions the implants are subjected to tribocorrosion phenomenon, which consists in the degradation mechanisms due to the combined effect of wear and corrosion. The aim of this study is to evaluate the tribocorrosion behaviour of cast and sintered Ti6Al4V biomedical alloy for dental applications using the cast material as reference. Titanium samples were tested in artificial human saliva solution with three different pHs (3, 6, 9) and in an acidic saliva with 1000 ppm fluorides (AS-3-1000F-) by different electrochemical techniques (potentiodynamic curves, potentiostatic tests and tribo-electrochemical tests). Cast and sintered titanium alloys exhibit the same tribocorrosion mechanisms in AS independently of the pH which consists in plastic deformation with passive dissolution, but the addition of fluorides to the acidified solution changes the degradation mechanism towards active dissolution of the titanium alloys.

  19. Enhanced pitting corrosion resistance of aluminum alloy 7075 in the presence of oxalate anions

    SciTech Connect

    Kobotiatis, L.; Tsikrikas, C.; Koutsoukos, P.G.

    1995-01-01

    The presence of oxalate in chloride-containing corrosive aqueous media was found to protect aluminum alloy AA 7075 (UNS A95075). The effect of 0.05 M sodium oxalate on induction times for the initiation of pit formation was measured on AA 7075 specimens. The variance and the mean value of the induction times measured increased with the time of specimen immersion at the open circuit potential (OCP). Statistical analysis was done by potentiostatic measurement of several specimens using electrochemical instrumentation controlled by a personal computer. Pit generation rates were found to be inversely proportional to the duration of the immersion period at OCP. Therefore, it was concluded that prolonged exposure of the tested specimens to sodium oxalate solutions enhanced their resistance to corrosion. Impedance measurements confirmed this finding. The increased resistance was attributed to the retardation of the process by which the surface protective layer would have been destroyed. This retardation may have been ascribable to the formation of surface complexes between Al{sup 3+} and oxalates from the bulk solution. Polarization of the specimens at anodic potentials reduced the corrosion resistance of AA 7075, possibly because of the destabilization of the surface complexes formed between Al and the oxalate ions.

  20. Effect of Acidified Feronia elephantum Leaf Extract on the Corrosion Behavior of Mild Steel

    NASA Astrophysics Data System (ADS)

    Muthukrishnan, Pitchaipillai; Prakash, Periakaruppan; Ilayaraja, Murugan; Jeyaprabha, Balasubramanian; Shankar, Karikalan

    2015-03-01

    Mild steel is used as a structural material for pipes, tank, reaction vessels, etc. which are known to corrode invariably in contact with various solvents. From the view point of a nation's economy and financial implications of corrosion hazard, it is necessary to adopt appropriate means and ways to reduce the losses due to corrosion. The use of eco-friendly corrosion inhibitors are increasing day by day. Feronia elephantum leaf extract (FELE) has been tested as eco-friendly corrosion inhibitor for A262 mild steel in 1 M H2SO4 and 1 M HCl solutions using non-electrochemical (Gravimetric, X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy) and electrochemical techniques (open circuit potential, potentiostatic polarization, and electrochemical impedance measurements). The protection efficiency is found to increase with increase in FELE concentration but decrease with temperature, which is suggestive of physical adsorption mechanism. The adsorption of FELE on mild steel surface obeys the Langmuir adsorption isotherm. SEM results confirm the formation of a protective layer by FELE over mild steel surface.

  1. Understanding the fundamentals of redox mediators in Li-O2 batteries: a case study on nitroxides.

    PubMed

    Bergner, Benjamin J; Hofmann, Christine; Schürmann, Adrian; Schröder, Daniel; Peppler, Klaus; Schreiner, Peter R; Janek, Jürgen

    2015-12-21

    The development of aprotic lithium-oxygen (Li-O2) batteries suffers from high charging overvoltages. Dissolved redox mediators, like nitroxides, providing increased energy efficiency and longer lifetime are promising tools to overcome this challenge. Since this auspicious concept is still in its infancy, the underlying chemical reactions as well as the impact of the different (electro)chemical parameters are poorly understood. Herein, we derive an electrochemical model for the charging reactions, which is validated by potentiostatic measurements. The model elucidates the impact of the major factors including basic cell parameters and the chemical properties of the redox mediator. The model is applied to the promising class of nitroxides, which is systematically investigated by using derivatives of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), AZADO (2-azaadamantane-N-oxyl), and an azaphenalene based nitroxide. The nitroxides are electrochemically characterized by cyclic voltammetry and their performance as redox mediators is studied in Li-O2 batteries with an ether-based electrolyte. Based on the presented model, the charging profiles of the different nitroxide redox mediators are correlated with their molecular structures. PMID:26563563

  2. Amperometric creatinine biosensor based on covalently coimmobilized enzymes onto carboxylated multiwalled carbon nanotubes/polyaniline composite film.

    PubMed

    Yadav, Sandeep; Kumar, Ashok; Pundir, C S

    2011-12-15

    A mixture of commercial creatinine amidohydrolase (CA), creatine amidinohydrolase (CI), and sarcosine oxidase (SO) was coimmobilized covalently via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry onto carboxylated multiwalled carbon nanotube (c-MWCNT)/polyaniline (PANI) nanocomposite film electrodeposited over the surface of a platinum (Pt) electrode. A creatinine biosensor was fabricated using enzyme/c-MWCNT/PANI/Pt as working electrode, Ag/AgCl as reference electrode, and Pt wire as auxiliary electrode connected through potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The biosensor detected creatinine levels as low as 0.1 μM, estimated at a signal-to-noise ratio of 3, within 5s at pH 7.5 and 35°C. The optimized biosensor showed a linear response range of 10 to 750 μM creatinine with sensitivity of 40 μA/mM/cm(2). The fabricated biosensor was successfully employed for determination of creatinine in human serum. The biosensor showed only 15% loss in its initial response after 180 days when stored at 4°C. PMID:21906581

  3. Experimental investigation of the effect of indium content on the CuIn{sub 5}S{sub 8} electrodes using electrochemical impedance spectroscopy

    SciTech Connect

    Gannouni, M. Assaker, I. Ben; Chtourou, R.

    2015-01-15

    This paper reports on the use of electrochemical impedance spectroscopy to investigate the electrochemical behavior of spinel CuIn{sub 5}S{sub 8}/electrolyte interface. The CuIn{sub 5}S{sub 8} spinel films have been potentiostatically deposited onto indium tin oxide (ITO)-coated glass substrate. CuCl{sub 2} and InCl{sub 3} mixed solutions with different [Cu]/[In] ratios were used as cation precursor and Na{sub 2}S{sub 2}O{sub 3} as the anion precursor in acidic solution and at room temperature. The effect of the [Cu]/[In] ratio in the precursor solution on the structural, chemical stoichiometry, and morphological properties of prepared samples, as well as the electrochemical behavior of the CuIn{sub 5}S{sub 8}/electrolyte interface was investigated. The electrochemical impedance spectroscopy data have been modeled using an equivalent circuit approach. Several parameters such as, flat-band potential and free carrier concentration were determined by the change in the Mott–Schottky plots.

  4. Repassivation behavior of 316L stainless steel in borate buffer solution: Kinetics analysis of anodic dissolution and film formation

    NASA Astrophysics Data System (ADS)

    Xu, Haisong; Sun, Dongbai; Yu, Hongying

    2015-12-01

    The repassivation behavior of metals or alloys after oxide film damage determines the development of local corrosion and corrosion resistance. In this work, the repassivation kinetics of 316L stainless steel (316L SS) are investigated in borate buffer solution (pH 9.1) by using the abrading electrode technique. The current densities flowing from bare 316L SS surface are measured by potentiostatic method and analyzed to characterize repassivation kinetics. The initial stages of current decay (t < 500 ms) are discussed according to a film growth model, which describes the initial current transient should be divided into substrate dissolution current and passive film formation current based on Avrami kinetics. Then the two independent components are analyzed individually. The film formation rate and the thickness of film are compared in different applied potential. It is shown that anodic dissolution dominates the repassivation for a short time during the early times, and a higher applied potential will promote the anodic dissolution of metal. The film growth rate increases slightly with increasing in potential. Correspondingly, increase in applied potential from 0 VSCE to 0.8 VSCE results in thicker monolayer, which covers the whole bare surface at the time of θ = 1. The electric field strengths through the thin passive film could reach 3.97 × 106 V cm-1.

  5. Bioactivity of self-organized TiO2 nanotubes used as surface treatment on Ti biomaterials

    NASA Astrophysics Data System (ADS)

    Souza, M. R.; Reyes, K. M.; Oliveira, N. T. C.; Kuromoto, N. K.; Marino, C. E. B.

    2016-03-01

    Titanium and its alloys are widely used as implants due to their excellent mechanical properties, corrosion resistance and biocompatibility. TiO2 nanotubes have been studied as surface treatment to increase the specific area and to improve osseointegration. However, the thermodynamic stability and bioactivity of these nanostructures must be evaluated. The objective of this research was to obtain nanotubes oxides on Ti6Al4V alloy and to analyze the electrochemical stability in physiological solution at 37 °C and the bioactive response of the biomaterial. The nanotubes were obtained by potentiostatic anodization. The morphology of the oxides was evaluated by scanning electron microscopy. The chemical characterization was analyzed by energy dispersive spectroscopy and x-ray photoelectron spectroscopy techniques. The electrochemical stability was analyzed by open circuit potential (OCP) and the bioactivity by biomimetic test in a simulated body fluid (SBF) solution. The OCP of the nanotubes oxides was shown to be more noble and stable than the compacted oxides. The biomaterial covered with theses oxides showed sealing by Ca and P after 30 d immersion in artificial blood. And after 15 d of immersion in SBF, the hydroxyapatite could be seen on the non-sealed nanotubes. TiO2 nanotube layers could improve the superficial chemical stability and also the osseointegration process.

  6. Evaluation on the Corrosion of the Three Ni-Cr Alloys with Different Composition

    PubMed Central

    Rao, Srinivasa B.; Chowdhary, Ramesh

    2011-01-01

    Dental casting alloys are widely used in contact with oral tissue for many years now. With the development of new dental alloys over the past 15 years, many questions remain unanswered about their biologic safety. Concepts and current issues concerning the response to the biologic effects of dental casting alloys are presented. In this paper, samples of three commercially available nickel-chrome (Ni-cr) casting alloys (Dentaurum, Bego, Sankin) were taken to assess their corrosion behavior, using potentiodynamic polarization method (electrochemical method) with fusayama artificial saliva as an electrolyte medium to check for their biocompatibility. The parameters for corrosion rate and corrosion resistance were obtained from computer-controlled corrosion schematic instrument, namely, potentiostat through corrosion software (power CV). The results obtained were analyzed by classic Tafel analysis. Statistical analysis was done by Student's t-test and ANOVA test. It was concluded that Dentarum and Bego showed satisfactory corrosive behavior, with exception of Sankin which depicted higher corrosion rate and least resistance to corrosion. Thus, the selection of an alloy should be made on the basis of corrosion resistance and biologic data from dental manufactures. PMID:21461232

  7. Comparison of Electrochemical Methods to Determine Crevice Corrosion Repassivation Potential of Alloy 22 in Chloride Solutions

    SciTech Connect

    K. Evans; A. Yilmaz; S. Day; L. Wong; J. Estill

    2004-08-23

    Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In some aggressive conditions of high chloride concentration, temperature and applied potential, Alloy 22 may suffer crevice corrosion, a form of localized corrosion. There are several electrochemical methods that can be used to determine localized corrosion in metallic alloys. One of the most popular for rapid screening is the cyclic potentiodynamic polarization (CPP). This work compares the repassivation potentials obtained using CPP to related repassivation potential values obtained using the Tsujikawa-Hisamatsu Electrochemical (THE) method and the potentiostatic (POT) method. Studied variables included temperature and chloride concentration. The temperature was varied from 30 C and 120 C and the chloride concentration was varied between 0.0005 M to 4 M. Results show that similar repassivation potentials were obtained for Alloy 22 using CPP and THE methods. Generally, under more aggressive conditions, the repassivation potentials were more conservative using the CPP method. POT tests confirmed the validity of the repassivation potential as a threshold below which localized corrosion does not nucleate. The mode of attack in the tested specimens varied depending if the test method was CPP or THE; however, the repassivation potential remained the same.

  8. Passivation Dynamics in the Anisotropic Deposition and Stripping of Bulk Magnesium Electrodes During Electrochemical Cycling.

    PubMed

    Wetzel, David J; Malone, Marvin A; Haasch, Richard T; Meng, Yifei; Vieker, Henning; Hahn, Nathan T; Gölzhäuser, Armin; Zuo, Jian-Min; Zavadil, Kevin R; Gewirth, Andrew A; Nuzzo, Ralph G

    2015-08-26

    Although rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. The passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte. PMID:26258957

  9. In situ electrochemical STM study of platinum nanodot arrays on highly oriented pyrolythic graphite prepared by electron beam lithography

    NASA Astrophysics Data System (ADS)

    Foelske-Schmitz, A.; Peitz, A.; Guzenko, V. A.; Weingarth, D.; Scherer, G. G.; Wokaun, A.; Kötz, R.

    2012-12-01

    Model electrodes consisting of platinum dots with a mean diameter of (30 ± 5) nm and heights of 3-5 nm upon highly oriented pyrolytic graphite (HOPG) were prepared by electron beam lithography and subsequent sputtering. The Pt nanodot arrays were stable during scanning tunnelling microscopy (STM) measurements in air and in sulphuric acid electrolyte, indicating the presence of "anchors", immobilising the dots on the HOPG surface. Electrochemical STM was used to visualise potential induced Pt, carbon and Pt-influenced carbon corrosion in situ in 0.5 M sulphuric acid under ambient conditions. Potentiostatic hold experiments show that the Pt dots start to disappear at electrode potentials of E > 1.4 V vs. SHE. With increasing time and potential a hole pattern congruent to the original dot pattern appears on the HOPG basal planes. Corrosion and peeling of the HOPG substrate could also be followed in situ. Dissolution of Pt dots appears to be accelerated for potential cycling experiments compared to the potential hold statistics.

  10. Corrosion inhibition of a mild steel by aniline and alkylamines in acidic solutions

    SciTech Connect

    Luo, H.; Han, K.N.; Guan, Y.C.

    1998-09-01

    Corrosion inhibition of a mild steel in acid solutions by alkylamines (ALK-AM) and aniline hydrochloric (ANL-HCl) salts was investigated in the presence of sodium sulfate (Na{sub 2}SO{sub 4}) and sodium chloride (NaCl) using a potentiostat, a contact-angle goniometer, a scanning electron microscope (SEM), a Fourier transform infrared spectrometer (FTIR), and an atomic force microscope (AFM). Results showed chloride ions (Cl{sup {minus}}) had a pronounced effect on inhibition of amines and ANL for corrosion of mild steel. In the presence of Cl{sup {minus}} ions, cationic types of surfactants (ALK-AM and ANL) were attached to the surface through formation of chloride precipitate at the surface. In the absence of the organic inhibitors, corrosion initiated along grain boundaries of ferrite and pearlite structures. In the presence of the organic inhibitor, however, the steel surface was covered by an organic salt precipitation, and the corrosion rate was reduced significantly.

  11. Recreation of Marine Atmospheric Corrosion Condition on Weathering Steel in Laboratory

    NASA Astrophysics Data System (ADS)

    Guchhait, S. K.; Dewan, S.; Saha, J. K.; Mitra, P. K.

    2014-04-01

    Salt spray test, autoclave corrosion test, SO2 salt spray test, and Relative humidity test are generally used to assess atmospheric corrosion in laboratories at accelerated rates. However, no test can absolutely simulate the service condition. One can get only approximate corrosion rates using the aforesaid tests which serve as an indicative of corrosion behavior of the material in a service condition. The present work is aimed at creating specific environmental condition in laboratory to get the corrosion test done in short duration to compare with on field exposure test which would otherwise take years to complete. In this work recreation of atmospheric environment of Digha was tried and it was simulated in such a manner that the results of laboratory test could be compared with long time field exposure at Digha. Weathering steel (WS) was taken for experimentations. Potentiostatic electrochemical tests route was adopted to simulate atmospheric condition of Digha. Laboratory test results compared well with 18 month field exposure data in terms of corrosion rate, SEM and Ramon Spectroscopy matching.

  12. Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms

    PubMed Central

    Bellin, Daniel L.; Sakhtah, Hassan; Rosenstein, Jacob K.; Levine, Peter M.; Thimot, Jordan; Emmett, Kevin; Dietrich, Lars E. P.; Shepard, Kenneth L.

    2014-01-01

    Despite advances in monitoring spatiotemporal expression patterns of genes and proteins with fluorescent probes, direct detection of metabolites and small molecules remains challenging. A technique for spatially resolved detection of small molecules would benefit the study of redox-active metabolites produced by microbial biofilms, which can drastically affect colony development. Here we present an integrated circuit-based electrochemical sensing platform featuring an array of working electrodes and parallel potentiostat channels. “Images” over a 3.25 × 0.9 mm area can be captured with a diffusion-limited spatial resolution of 750 μm. We demonstrate that square wave voltammetry can be used to detect, identify, and quantify (for concentrations as low as 2.6 μM) four distinct redox-active metabolites called phenazines. We characterize phenazine production in both wild-type and mutant Pseudomonas aeruginosa PA14 colony biofilms, and find correlations with fluorescent reporter imaging of phenazine biosynthetic gene expression. PMID:24510163

  13. Formation of the Microstructure of TiO2 Film Through Anodic Oxidation of Titanium

    NASA Astrophysics Data System (ADS)

    Yokogawa, Y.; Yasuki, T.; Hirotomi, T.; Nakamura, A.; Kishida, I.

    2011-04-01

    Recent titanium oxide nanotube arrays have attracted attention for their applications. Titanium oxide nanotubes were prepared under potentiostat conditions (10 - 60 V) for various times (1 min - 3 hr). SEM observations revealed that the pore sizes of the nanotubes have a tendency to increase with an increase in the applied potential in the NH4F-glycerol-H2O electrolyte. Some corrosive pores were observed on the surface of titanium substrate at 40 V for 1 minute at 40°C. The pores covered the surface of the titanium substrate after 10 minutes, and some small pores were observed in the inner part of the pores, which should correspond to the combining of some small adjacent pores into a large one. The combining of the tubes were observed after 2 h and 3 h anodization times, and the nanotube arrays seem to be formed upward from the SEM side-views. The photocatalytic activity of the titanium oxide nanotubes was evaluated according to the JIS standard (JIS R 1703-2). The R factor of the titanium oxide nanotube arrays formed at 40 V and 40°C for a 3h the anodization time was 9.71 n mol/l·min, which was twice that of the titanium oxide thin film obtained by the rf-sputtering method.

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

    PubMed Central

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

    2013-01-01

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

  15. A nanocrystalline zirconium carbide coating as a functional corrosion-resistant barrier for polymer electrolyte membrane fuel cell application

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Li, ZhengYang; Xu, Song; Munroe, Paul; Xie, Zong-Han

    2015-11-01

    A ZrC nanocrystalline coating is engineered onto a Ti-6Al-4V substrate using a double cathode glow discharge technique in order to improve the corrosion resistance and long-term stability of this alloy. The new coating exhibits an extremely dense, homogeneous microstructure composed of equiaxed grains with an average grain size of ∼12 nm and is well adhered on the surface of the substrate. The corrosion behaviour of the coating is systematically investigated using various electrochemical methods, including potentiodynamic, potentiostatic polarizations and electrochemical impedance spectroscopy (EIS), in a simulated polymer electrolyte membrane fuel cell (PEMFC) operating circumstances under different temperatures. The results show that with rising temperature, the corrosion potential (Ecorr) decreases and the corrosion current density (icorr) of the ZrC coated specimen increases, indicating that the corrosion resistance decreased with increasing temperature. However, at a given temperature, the ZrC-coated Ti-6Al-4V alloy has a higher Ecorr and lower icorr as compared to the bare substrate. The results of EIS measurements show that the values of the resistance for the ZrC coated Ti-6Al-4V alloy are three orders of magnitude larger than those of Ti-6A1-4V in the simulated PEMFC environment.

  16. Effects of passive films on corrosion resistance of uncoated SS316L bipolar plates for proton exchange membrane fuel cell application

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Ning, Xiaohui; Tang, Hongsheng; Guo, Liejin; Liu, Hongtan

    2014-11-01

    The effects of passive films on the corrosion behaviors of uncoated SS316L in anode and cathode environments of proton exchange membrane fuel cells (PEMFCs) are studied. Potentiodynamic and potentiostatic polarizations are employed to study the corrosion behavior; Mott-Schottky measurements are used to characterize the semiconductor properties of passive films; X-ray photoelectron spectroscopy (XPS) analyses are used to identify the compositions and the depth profiles of passive films. The passive films formed in the PEMFC anode and cathode environments under corresponding conditions both behave as n-type semiconductor. The passive film formed in the anode environment has a single-layer structure, Cr is the major element (Cr/Fe atomic ratio > 1), and the Cr/Fe atomic ratio decreases from the surface to the bulk; while the passive film formed in the PEMFC cathode environment has a bi-layer structure, Fe is the major element (Cr/Fe atomic ratio < 0.5), and in the external layer of the bi-layer structure Fe content increases rapidly and gradually in the internal layer. SS316L shows better corrosion resistance owing to both the high content of Cr oxide in the passive film and low band bending in normal PEMFC anode environments.

  17. Degradation of SS316L bipolar plates in simulated fuel cell environment: Corrosion rate, barrier film formation kinetics and contact resistance

    NASA Astrophysics Data System (ADS)

    Papadias, Dionissios D.; Ahluwalia, Rajesh K.; Thomson, Jeffery K.; Meyer, Harry M.; Brady, Michael P.; Wang, Heli; Turner, John A.; Mukundan, Rangachary; Borup, Rod

    2015-01-01

    A potentiostatic polarization method is used to evaluate the corrosion behavior of SS316L in simulated anode and cathode environments of polymer electrolyte fuel cells. A passive barrier oxide film is observed to form and reach steady state within ∼10 h of polarization, after which time the total ion release rates are low and nearly constant at ∼0.4 μg cm-2 h-1 for all potentials investigated. The equilibrium film thickness, however, is a function of the applied potential. The main ionic species dissolved in the liquid are predominately Fe followed by Ni, that account for >90% of the steady-state corrosion current. The dissolution rate of Cr is low but increases systematically at potentials higher than 0.8 V. The experimental ion release rates can be correlated with a point defect model using a single set of parameters over a broad range of potentials (0.2-1 V) on the cathode side. The interfacial contact resistance measured after 48 h of polarization is observed to increase with increase in applied potential and can be empirically correlated with applied load and oxide film thickness. The oxide film is substantially thicker at 1.5 V possibly because of alteration in film composition to Fe-rich as indicated by XPS data.

  18. Electrocatalytic activity and operational stability of electrodeposited Pd-Co films towards ethanol oxidation in alkaline electrolytes

    NASA Astrophysics Data System (ADS)

    Tsui, Lok-kun; Zafferoni, Claudio; Lavacchi, Alessandro; Innocenti, Massimo; Vizza, Francesco; Zangari, Giovanni

    2015-10-01

    Direct alkaline ethanol fuel cells (DEFCs) are usually run with Pd anodic catalysts, but their performance can be improved by utilizing alloys of Pd and Co. The oxyphilic Co serves to supply ample -OH to the ethanol oxidation reaction, accelerating the rate limiting step at low overpotential under alkaline conditions. Pd-Co films with compositions between 20 and 80 at% Co can be prepared by electrodeposition from a NH3 complexing electrolyte. Cyclic voltammetry studies show that the ethanol oxidation peak exhibits increasing current density with increasing Co content, reaching a maximum at 77% Co. In contrast, potentiostatic measurements under conditions closer to fuel cell operating conditions show that a 50 at% Co alloy has the highest performance. Importantly, the Co-Pd film is also found to undergo phase and morphological transformations during ethanol oxidation, resulting in a change from a compact film to high surface area flake-like structures containing Co3O4 and CoOOH; such a transformation instead is not observed when operating at a constant potential of 0.7 VRHE.

  19. Seasonal and spatial variation in soil chemistry and anaerobic processes in an Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Lipson, D.; Mauritz, M.; Bozzolo, F.; Raab, T. K.; Santos, M. J.; Friedman, E. F.; Rosenbaum, M.; Angenent, L.

    2009-12-01

    Drained thaw lake basins (DTLB) are the dominant landform in the Arctic coastal plain near Barrow, Alaska. Our previous work in a DTLB showed that Fe(III) and humic substances are important electron acceptors in anaerobic respiration, and play a significant role in the C cycle of these organic-rich soils. In the current study, we investigated seasonal and spatial patterns of availability of electron acceptors and labile substrate, redox conditions and microbial activity. Landscapes within DTLB contain complex, fine-scale topography arising from ice wedge polygons, which produce raised and lowered areas. One goal of our study was to determine the effects of microtopographic variation on the potential for Fe(III) reduction and other anaerobic processes. Additionally, the soil in the study site has a complex vertical structure, with an organic peat layer overlying a mineral layer, overlying permafrost. We described variations in soil chemistry across depth profiles into the permafrost. Finally, we installed an integrated electrode/potentiostat system to electrochemically monitor microbial activity in the soil. Topographically low areas differed from high areas in most of the measured variables: low areas had lower oxidation-reduction potential, higher pH and electrical conductivity. Soil pore water from low areas had higher concentrations of Fe(III), Fe(II), dissolved organic C (DOC), and aromaticity (UV absorbance at 260nm, “A260”). Low areas also had higher concentrations of dissolve CO2 and CH4 in soil pore water. Laboratory incubations of soil showed a trend toward higher potentials for Fe(III) reduction in topographically low areas. Clearly, ice wedge-induced microtopography exerts a strong control on microbial processes in this DTLB landscape, with increased anaerobic activity occurring in the wetter, depressed areas. Soil water extracted from 5-15 cm depth had higher concentrations of Fe(III), Fe(II), A260, and DOC compared to soil water sampled from 0-5cm

  20. Li3V2(PO4)3 encapsulated flexible free-standing nanofabric cathodes for fast charging and long life-cycle lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Sun, Pingping; Zhao, Xueying; Chen, Renpeng; Chen, Tao; Ma, Lianbo; Fan, Qi; Lu, Hongling; Hu, Yi; Tie, Zuoxiu; Jin, Zhong; Xu, Qingyu; Liu, Jie

    2016-03-01

    Lithiated transition metal phosphates with large theoretical capacities have emerged as promising cathode materials for rechargeable lithium-ion batteries. However, the poor kinetic properties caused by their low intrinsic electronic and ionic conductivity greatly hinder their practical applications. In this work, we demonstrate a novel strategy to prepare monoclinic lithium vanadium phosphate nanoparticles implanted in carbon nanofibers as the cathodes of Li-ion cells with high capacity, flexibility, long cycle stability and significantly improved high-rate performance. The composite nanofibers were obtained by electrospinning using polyacrylonitrile and Li3V2(PO4)3 nanoparticles, followed by annealing and coating with a thin layer of carbon by plasma enhanced chemical vapor deposition. The Li3V2(PO4)3 nanocrystals with the monoclinic phase were uniformly distributed in the composite nanofibers. The electrochemical performances of the as-prepared binder-free fibrous cathodes were characterized by potentiostatic and galvanostatic tests. At the rate of 0.5 C in the range of 3.0-4.3 V, the composite displayed an initial discharge capacity of 128 mA h g-1 (96.2% of the theoretical capacity). A discharge capacity of 120 mA h g-1 was observed even at a high rate of 10 C, and a capacity retention of 98.9% was maintained after 500 cycles at 5 C, indicating excellent high-rate capability and capacity retention. Compared to the control samples without a carbon outer-layer, the composite nanofibers with carbon coating demonstrated much better electrochemical performances. It indicates that the carbon coating can further protect the structural integrity of nanofabric electrodes during the charge/discharge processes without hindering the Li-ion mobility and also can prevent undesired side reactions with an electrolyte, thus greatly improving the rate performance and cyclic stability of the cathode.Lithiated transition metal phosphates with large theoretical capacities have

  1. Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces

    NASA Astrophysics Data System (ADS)

    Li, Peiqiang; Wang, Huying; Xu, Jinfeng; Jing, Hua; Zhang, Jun; Han, Haixiang; Lu, Fusui

    2013-11-01

    In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 μmol L-1 cm-2 after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels.In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L-1 cm-2 and 107.38 μmol L-1

  2. Automated Controlled-Potential Coulometer for the IAEA

    SciTech Connect

    Cordaro, J.V.; Holland, M.K.; Fields, T.

    1998-01-29

    An automated controlled-potential coulometer has been developed at the Savannah River Site (SRS) for the determination of plutonium for use at the International Atomic Energy Agency`s (IAEA) Safeguards Analytical Laboratory in Siebersdorf, Austria. The system is functionally the same as earlier systems built for use at the Savannah River Site`s Analytical Laboratory. All electronic circuits and printed circuits boards have been upgraded with state-of-the-art components. A higher amperage potentiostat with improved control stability has been developed. The system achieves electronic calibration accuracy and linearity of better than 0.01 percent, with a precision and accuracy better than 0.1 percent has been demonstrated. This coulometer features electrical calibration of the integration system, electrolysis current background corrections, and control-potential adjustment capabilities. These capabilities allow application of the system to plutonium measurements without chemical standards, achieving traceability to the international measurement system through electrical standards and Faraday`s constant. the chemist is provided with the capability to perform measurements without depending upon chemical standards, which is a significant advantage for applications such as characterization of primary and secondary standards. Additional benefits include reducing operating cost to procure, prepare and measure calibration standards and the corresponding decrease in radioactive waste generation. The design and documentation of the automated instrument are provided herein. Each individual module`s operation, wiring, layout, and alignment are described. Interconnection of the modules and system calibration are discussed. A complete set of prints and a list of associated parts are included.

  3. New Signal Readout Principle for Solid-Contact Ion-Selective Electrodes.

    PubMed

    Vanamo, Ulriika; Hupa, Elisa; Yrjänä, Ville; Bobacka, Johan

    2016-04-19

    A novel approach to signal transduction concerning solid-contact ion-selective electrodes (SC-ISE) with a conducting polymer (CP) as the solid contact is investigated. The method presented here is based on constant potential coulometry, where the potential of the SC-ISE vs the reference electrode is kept constant using a potentiostat. The change in the potential at the interface between the ion-selective membrane (ISM) and the sample solution, due to the change in the activity of the primary ion, is compensated with a corresponding but opposite change in the potential of the CP solid contact. This enforced change in the potential of the solid contact results in a transient reducing/oxidizing current flow through the SC-ISE. By measuring and integrating the current needed to transfer the CP to a new state of equilibrium, the total cumulated charge that is linearly proportional to the change of the logarithm of the primary ion activity is obtained. In this work, different thicknesses of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) were used as solid contact. Also, coated wire electrodes (CWEs) were included in the study to show the general validity of the new approach. The ISM employed was selective for K(+) ions, and the selectivity of the membrane under implementation of the presented transduction mechanism was confirmed by measurements performed with a constant background concentration of Na(+) ions. A unique feature of this signal readout principle is that it allows amplification of the analytical signal by increasing the capacitance (film thickness) of the solid contact of the SC-ISE. PMID:27018524

  4. Part I. Carbon and mercury-carbon optically transparent electrodes. Part II. Investigation of redox properties of technetium by cyclic voltammetry and thin layer spectroelectrochemistry

    SciTech Connect

    Hurst, R.W.

    1980-01-01

    A carbon optically transparent electrode (C OTE) has been prepared by vapor-deposithing a thin carbon film (150 to 310 A thick) on glass and quartz. Optical transparency is good throughout the ultraviolet-visible region. Electrochemical and spectroelectrochemical measurements were made with ferricyanide and o-tolidine respectively. The C OTE serves as a good substrate for deposition of a thin mercury film to form a mercury film transparent electrode (Hg-C OTE). The Hg-C OTE exhibits electrochemical properties of conventional mercury film electrodes as evidenced by Pb/sup 2 +/ cyclic voltammograms. The Hg-C OTE exhibits electrochemical properties of conventional mercury film electrodes as evidenced by Pb/sup 2 -/ cyclic VOHammograms. The Hg-C OTE enabled the spectrochemical characterization of cysteine oxidation, which was shown to involve the oxidation of mercury to form mercurous cysteinate. An 8080 based microcomputer has been interfaced with a Harrick oscillating mirror rapid scanning uv-visible spectrophotometer. Two different approaches are compared for controlling the galvanometer. The first utilizes the digital hardware on the Harrick processing module to derive the mirror drive waveform, while the second creates the waveform under direct software control. A potentiostat is also interfaced and the system is demonstrated by the spectroelectrochemical determination of the redox potential of o-tolidine. Redox potentials are also determined for a series of technetium complexes by the spectropotentiostatic technique. These include hexahalogens, ditertiary arsine, and 1,2-bis(diphenylphosphino) ethane complexes of technetium. Transient hexavalent technetium is produced, detected, and characterized in aqueous alkaline media by pulse radiolysis and very fast scan cyclic voltammetry. The lifetime is of the order of milliseconds. This species is potentially useful in the preparation of technetium radiopharmaceuticals.

  5. Synthesis and structural characterization of polyoxometalates incorporating with anilinium cations and facile preparation of hybrid film

    NASA Astrophysics Data System (ADS)

    Fukaya, Keisuke; Srifa, Atthapon; Isikawa, Eri; Naruke, Haruo

    2010-08-01

    The self-assembly reaction of tungstate and copper(II) in the presence of aniline (ANI) and phosphoric acid led to the formation of an anilinium (ANIH +) salt of mono-substituted Keggin-type polyoxotungstophosphate (ANIH) 5[PCu(H 2O)W 11O 39](ANI)·8H 2O ( 1), while the reaction of heptamolybdate in the coexistence of copper(II), phosphoric acid and ANI yielded an ANIH + salt of Strandberg-type pentamolybdodiphosphate, (ANIH) 2[(PO 4) 2Mo 5O 15{Cu(ANI) 2(H 2O)} 2](ANI)·2H 2O ( 2). These compounds were characterized by elemental analysis, infrared spectroscopy and X-ray single-crystal analysis. The compound 1, crystallizing in trigonal, P3¯,a = 13.883(4), c = 10.187(3) Å, Z = 1, consists of copper mono-substituted Keggin-typed [PCu(H 2O)W 11O 39] 5- anion surrounded by six ANI molecules, of which five are protonated (ANIH +). The compound 2, crystallizing in triclinic, P1¯,a = 13.98(2), b = 14.73(1), c = 16.24(1) Å, α = 111.27(3), β = 97.42(3), γ = 99.54(4)°, Z = 2, consists of Strandberg-type pentamolybdodiphospate [(PO 4) 2Mo 5O 15] 6- anions interconnected by two Cu(ANI) 2(H 2O) linkers to form a 1D-chain structure. A potentiostatic electrolysis of 1 in aqueous solution gave rise to electropolymerization of the ANIH + cations (and ANI) and deposition with the [PCu(H 2O)W 11O 39] 5- anion on an ITO electrode, forming a nano-structured polyaniline/[PCu(H 2O)W 11O 39] 5- hybrid thin film.

  6. Electrochemical Codeposition of Al-Li-Mg Alloys at Solid Aluminum Electrode from LiCl-KCl-MgCl2 Molten Salt System

    NASA Astrophysics Data System (ADS)

    Ye, Ke; Zhang, Mi Lin; Chen, Ye; Han, Wei; de Yan, Yong; Cao, Peng

    2010-06-01

    The electrochemical codeposition of Mg and Li at an aluminium electrode in LiCl-KCl (50:50 wt pct) melts containing different concentrations of MgCl2 at 893 K (620 °C) to form Al-Li-Mg alloys was investigated. Cyclic voltammograms showed that the potential of Li metal deposition at an Al electrode, before the addition of MgCl2, is more positive than that of Li metal deposition at an Mo electrode, which indicated the formation of an Al-Li alloy. The underpotential deposition of magnesium at an aluminium electrode leads to the formation of Al-Mg alloys, and the succeeding underpotential deposition of lithium on predeposited Al-Mg alloys leads to the formation of Al-Li-Mg alloys. Chronopotentiometric measurements indicated that the codeposition of Mg and Li occurs at current densities lower than -0.668 A cm-2 in LiCl-KCl-MgCl2 (8 wt pct) melts at an aluminium electrode. The chronoamperometric studies indicated that the onset potential for the codeposition of Mg and Li is -2.000 V, and the codeposition of Mg and Li at an aluminium electrode is formed into Al-Li-Mg alloys when the applied potentials are more negative than -2.000 V. X-ray diffraction and inductively coupled plasma analysis indicated that Al-Li-Mg alloys with different lithium and magnesium contents were prepared via potentiostatic and galvanostatic electrolysis. The microstructure of typical dual phases of the Al-Li-Mg alloy was characterized by an optical microscope and by scanning electron microscopy. The analysis of energy dispersive spectrometry showed that the elements of Al and Mg distribute homogeneously in the Al-Li-Mg alloy. The lithium and magnesium contents of Al-Li-Mg alloys can be controlled by MgCl2 concentrations and by electrolytic parameters.

  7. Rapid tissue dissolution efficiency of electrically-activated sodium hypochlorite on bovine muscle

    PubMed Central

    Ertugrul, Ihsan Furkan; Maden, Murat; Orhan, Ekim Onur; Ozkorucuklu, Sabriye Percin; Aglarca, Ali Vasfi

    2014-01-01

    Objective: Sodium hypochlorite (NaOCl) is a common antimicrobial and tissue-dissolving irrigant. The aim of this in vitro study is to evaluate and compare dissolution capacities of sodium hypochlorite solutions after electrically activation (E-NaOCl) on bovine muscle specimens at various time periods and concentrations. Materials and Methods: Three sodium hypochlorite solutions of 1.25%, 2.5%, and 5% were tested at 3-min. and 5-min. with and without activation by electrically. Distilled water and NaOCl solutions without electrically activation were used as controls. Pieces of bovine muscle tissue (34 ± 2 mg) were placed in 10 mL of each solution at room temperature. In the group of E-NaOCl, electrically activation was performed through the potentiostat. The tissue specimens were weighed before and after treatment, and the percentage of weight loss was calculated. Results: Weight loss of the tissue increased with the concentration of E-NaOCl and NaOCl. Higher concentration and electrically activation considerably enhanced the efficacy of sodium hypochlorite. The effect of electrically activation on tissue dissolution was much greater than that of same concentrations in the groups of NaOCl (P < 0.001). Tissue weight loss was significantly higher in 2.5% and 5% E-NaOCl at 3 min. than in 2.5% and 5% NaOCl at 5 min. (P < 0.05). There were not any significant differences between the 2.5% E-NaOCl and 5% NaOCl at 5 min. (P > 0.05). Conclusion: Electrically activation can improve the tissue-dissolving effectiveness of sodium hypochlorite. PMID:25512725

  8. PEP-on-DEP: A competitive peptide-based disposable electrochemical aptasensor for renin diagnostics.

    PubMed

    Biyani, Manish; Kawai, Keiko; Kitamura, Koichiro; Chikae, Miyuki; Biyani, Madhu; Ushijima, Hiromi; Tamiya, Eiichi; Yoneda, Takashi; Takamura, Yuzuru

    2016-10-15

    Antibody-based immunosensors are relatively less accessible to a wide variety of unreachable targets, such as low-molecular-weight biomarkers that represent a rich untapped source of disease-specific diagnostic information. Here, we present a peptide aptamer-based electrochemical sensor technology called 'PEP-on-DEP' to detect less accessible target molecules, such as renin, and to improve the quality of life. Peptide-based aptamers represent a relatively smart class of affinity binders and show great promise in biosensor development. Renin is involved in the regulation of arterial blood pressure and is an emerging biomarker protein for predicting cardiovascular risk and prognosis. To our knowledge, no studies have described aptamer molecules that can be used as new potent probes for renin. Here, we describe a portable electrochemical biosensor platform based on the newly identified peptide aptamer molecules for renin. We constructed a randomized octapeptide library pool with diversified sequences and selected renin specific peptide aptamers using cDNA display technology. We identified a few peptide aptamer sequences with a KD in the µM binding affinity range for renin. Next, we grafted the selected peptide aptamers onto gold nanoparticles and detected renin in a one-step competitive assay using our originally developed DEP (Disposable Electrochemical Printed) chip and a USB powered portable potentiostat system. We successfully detected renin in as little as 300ngmL(-1) using the PEP-on-DEP method. Thus, the generation and characterization of novel probes for unreachable target molecules by merging a newly identified peptide aptamer with electrochemical transduction allowed for the development of a more practical biosensor that, in principle, can be adapted to develop a portable, low-cost and mass-producible biosensor for point-of-care applications. PMID:26746799

  9. Preparation of Copper Telluride Films by Co-Reduction of Cu(I) and Te(IV) Ions in Choline Chloride: Ethylene Glycol Ionic Liquid

    NASA Astrophysics Data System (ADS)

    Golgovici, Florentina; Catrangiu, Adriana-Simona; Stoian, Andrei Bogdan; Anicai, Liana; Visan, Teodor

    2016-07-01

    Cathodic processes of direct co-reduction of Cu+ and Te4+ ions on Pt electrode at 60°C were investigated using cyclic voltammetry and electrochemical impedance spectroscopy techniques. The ionic liquid as background electrolyte consisted of a mixture of choline chloride and ethylene glycol (ChCl-EG 1:2 mol ratio) in which 5-20 mM CuCl and 8 mM TeO2 were dissolved. The voltammograms exhibited the following successive cathodic processes: Cu2+/Cu+ reduction, Te underpotential deposition, simultaneous deposition of Cu metal and CuTe compound, and deposition of Te-rich CuTe compound at the most negative potentials (from -0.5 V to -0.8 V). Corresponding dissolution or oxidation peaks were recorded on the anodic branch. The voltammetric results were confirmed by electrochemical impedance spectra. Copper telluride films have been synthesized on platinum substrate via potentiostatic electrodeposition at 60°C. It was found from atomic force microscopy that CuTe film samples prepared from ChCl-EG + 5 mM CuCl + 8 mM TeO2 ionic liquid have high growth rates. The x-ray diffraction patterns of the deposited films from ChCl-EG + 10 mM CuCl + 8 mM TeO2 ionic liquid indicated the presence of a Cu2Te phase for film deposited at -0.7 V and a Cu0.656Te0.344 phase for film deposited at -0.6 V.

  10. Enhanced electrochromic property of nickel hydroxide thin films prepared by anodic deposition

    SciTech Connect

    Chigane, Masaya; Ishikawa, Masami . Dept. of Inorganic Chemistry)

    1994-12-01

    Nickel hydroxide and nickel oxide thin films have received much attention as electrochromic (EC) materials, particularly as the materials for a complementary counterlayer against an EC tungsten oxide layer in smart window systems. Nickel hydroxide thin films were prepared onto transparent conductive tin oxide (NESA) substrates by potentiostatic electrolysis of a nickel amine complex solution at various potentials (0.6 to 1.5 V vs. Ag/AgCl). Nickel hydroxide thin film (F0.7) obtained at relatively lower anodic potential (0.7 V) showed enhanced electrochromism between colorless and dark brown in a sodium borate buffer solution at pH 12; the absorption spectrum in the colored (oxidized) state was broadened in the visible and near-infrared region compared with the nickel hydroxide films prepared at the higher anodic potential (1.1 V). characterization of the films revealed that crystal structure of F0.7 is assigned to [alpha]-Ni(OH)[sub 2], and that its electrochromism is based on the reversible oxidation to hexagonal [gamma][sub 2]-2NiO[sub 2] [center dot] NiOOH structure. Composite nickel hydroxide film, i.e., by the electrolytic deposition at 1.1 V followed by that at 0.7 V, showed electrochromic property similar to F0.7 and its durability in repeated redox cycles were much improved in comparison with that of F0.7. Electrochromic properties in switching performance of this composite nickel hydroxide film were investigated.

  11. Electrochemical behavior of polypyrrol/AuNP composites deposited by different electrochemical methods: sensing properties towards catechol

    PubMed Central

    García-Hernández, Celia; Medina-Plaza, Cristina; Martín-Pedrosa, Fernando; Blanco, Yolanda; de Saja, José Antonio

    2015-01-01

    Summary Two different methods were used to obtain polypyrrole/AuNP (Ppy/AuNP) composites. One through the electrooxidation of the pyrrole monomer in the presence of colloidal gold nanoparticles, referred to as trapping method (T), and the second one by electrodeposition of both components from one solution containing the monomer and a gold salt, referred to as cogeneration method (C). In both cases, electrodeposition was carried out through galvanostatic and potentiostatic methods and using platinum (Pt) or stainless steel (SS) as substrates. Scanning electron microscopy (SEM) demonstrated that in all cases gold nanoparticles of similar size were uniformly dispersed in the Ppy matrix. The amount of AuNPs incorporated in the Ppy films was higher when electropolymerization was carried out by chronopotentiometry (CP). Besides, cogeneration method allowed for the incorporation of a higher number of AuNPs than trapping. Impedance experiments demonstrated that the insertion of AuNPs increased the conductivity. As an electrochemical sensor, the Ppy/AuNp deposited on platinum exhibited a strong electrocatalytic activity towards the oxidation of catechol. The effect was higher in films obtained by CP than in films obtained by chronoamperometry (CA). The influence of the method used to introduce the AuNPs (trapping or cogeneration) was not so important. The limits of detection (LOD) were in the range from 10−5 to 10−6 mol/L. LODs attained using films deposited on platinum were lower due to a synergy between AuNPs and platinum that facilitates the electron transfer, improving the electrocatalytic properties. Such synergistic effects are not so pronounced on stainless steel, but acceptable LOD are attained with lower price sensors. PMID:26665076

  12. The role of the crystal orientation (c-axis) on switching field distribution and the magnetic domain configuration in electrodeposited hcp Co–Pt nanowires

    NASA Astrophysics Data System (ADS)

    Shahid Arshad, Muhammad; Proenca, Mariana P.; Trafela, Spela; Neu, Volker; Wolff, Ulrike; Stienen, Sven; Vazquez, Manuel; Kobe, Spomenka; Žužek Rožman, Kristina

    2016-05-01

    In this report, Co–Pt nanowires (NWs) were produced via potentiostatic electrodeposition into commonly used commercial ordered-alumina and disordered-polycarbonate membranes with similar pore diameters (≈200 nm). The pore diameter of the membranes and the deposition conditions were chosen such that the Co–Pt NWs fabricated into both membranes had a hexagonal close packed (hcp) crystal structure with a crystallographic texturing of the c-axis in the direction perpendicular to the NWs’ long axis; this effect was more pronounced in the alumina membranes. Due to the local fluctuation in electrodeposition conditions (pore diameter, pore shape), we have found a small variation in the c-axis orientations in the plane perpendicular to the NWs’ long axis. Magnetic characterizations suggested that there is uniaxial anisotropy perpendicular to the Co–Pt NWs’ long axis and the small variation in the orientation of the hcp c-axis plays an important role in the switching-field distribution and the magnetic domain structure of the Co–Pt NWs. First order reversal curves (FORCs) revealed week magnetostatic interactions between Co–Pt NWs, thus suggesting that the different pore alignments are not influencing much the magnetic properties in both membranes. The micromagnetic simulation revealed that the transverse-stripe (TS) and longitudinal stripe (LS) domains are energetically most favorable structures in such NWs. This study accentuates the influence of the crystal orientation (c-axis) of the high-anisotropy materials on their functional magnetic properties and thus is of great importance for the fabrication of nanodevices based on such NWs.

  13. Lipopolysaccharide inhibits or accelerates biomedical titanium corrosion depending on environmental acidity.

    PubMed

    Yu, Fei; Addison, Owen; Baker, Stephen J; Davenport, Alison J

    2015-09-01

    Titanium and its alloys are routinely used as biomedical implants and are usually considered to be corrosion resistant under physiological conditions. However, during inflammation, chemical modifications of the peri-implant environment including acidification occur. In addition certain biomolecules including lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls and driver of inflammation have been shown to interact strongly with Ti and modify its corrosion resistance. Gram-negative microbes are abundant in biofilms which form on dental implants. The objective was to investigate the influence of LPS on the corrosion properties of relevant biomedical Ti substrates as a function of environmental acidity. Inductively coupled plasma mass spectrometry was used to quantify Ti dissolution following immersion testing in physiological saline for three common biomedical grades of Ti (ASTM Grade 2, Grade 4 and Grade 5). Complementary electrochemical tests including anodic and cathodic polarisation experiments and potentiostatic measurements were also conducted. All three Ti alloys were observed to behave similarly and ion release was sensitive to pH of the immersion solution. However, LPS significantly inhibited Ti release under the most acidic conditions (pH 2), which may develop in localized corrosion sites, but promoted dissolution at pH 4-7, which would be more commonly encountered physiologically. The observed pattern of sensitivity to environmental acidity of the effect of LPS on Ti corrosion has not previously been reported. LPS is found extensively on the surfaces of skin and mucosal penetrating Ti implants and the findings are therefore relevant when considering the chemical stability of Ti implant surfaces in vivo. PMID:25634122

  14. Tuning the magnetic properties of multisegmented Ni/Cu electrodeposited nanowires with controllable Ni lengths.

    PubMed

    Susano, M; Proenca, M P; Moraes, S; Sousa, C T; Araújo, J P

    2016-08-19

    The fabrication of segmented Ni/Cu nanowires (NWs), with tunable structural and magnetic properties, is reported. A potentiostatic electrodeposition method with a single electrolytic bath has been used to fabricate multisegmented Ni/Cu NWs inside a highly hexagonally ordered anodic nanoporous alumina membrane, with diameters of 50 nm and Ni segment lengths (L Ni) tuned from 10 nm up to 140 nm. The x-ray diffraction results evidenced a strong dependence of the Ni NWs crystallographic face-centered-cubic (fcc) texture along the [220] direction on the aspect ratio of the NWs. The magnetic behavior of the multisegmented Ni/Cu NW arrays, as a function of the magnetic field and temperature, is also studied and correlated with their structural and morphological properties. Micromagnetic simulations, together with the experimental results, showed a dominant antiferromagnetic coupling between Ni segments along the wire length for small low aspect-ratio magnetic segments. When increasing the Ni segments' length, the magnetic interactions between these along the wire became stronger, favouring a ferromagnetic coupling. The Curie temperature of the NWs was also found to strongly depend on the Ni magnetic segment length. Particularly the Curie temperature was found to be reduced 75 K for the 20 nm Ni segments, following the finite-size scaling relation with ξ 0 = 8.1 Å and γ = 0.48. These results emphasize the advantages of using a template assisted method to electrodeposit multilayer NWs, as it allows an easy tailor of the respective morphological, chemical, structural and magnetic properties. PMID:27378738

  15. Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

    PubMed

    Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

    2012-09-01

    In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436

  16. Characterization of Nonmetallic Inclusions in High-Manganese and Aluminum-Alloyed Austenitic Steels

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun; Kim, Dong-Jin; Min, Dong Joon

    2012-07-01

    The effects of Al and Mn contents on the size, composition, and three-dimensional morphologies of inclusions formed in Fe- xMn- yAl ( x = 10 and 20 mass pct, y = 1, 3, and 6 mass pct) steels were investigated to enhance our understanding of the inclusion formation behavior in high Mn-Al-alloyed steels. By assuming that the alumina is a dominant oxide compound, the volume fraction of inclusions estimated from the chemical analysis, i.e., insoluble Al, in the Fe-Mn-3Al steels was larger than the inclusion volume fractions in the Fe-Mn-1Al and Fe-Mn-6Al steels. A similar tendency was found in the analysis of inclusions from a potentiostatic electrolytic extraction method. This finding could be explained from the terminal velocities of the compounds, which was affected by the thermophysical properties of Fe-Mn-Al steels. The inclusions formed in the Fe-Mn-Al-alloyed steels are classified into seven types according to chemistry and morphology: (1) single Al2O3 particle, (2) single AlN or AlON particle, (3) MnAl2O4 single galaxite spinel particle, (4) Al2O3(-Al(O)N) agglomerate, (5) single Mn(S,Se) particle, (6) oxide core with Mn(S,Se) skin (wrap), and (7) Mn(S,Se) core with Al2O3(-Al(O)N) aggregate (or bump). The Mn(S,Se) compounds were formed by the contamination of the steels by Se from the electrolytic Mn. Therefore, the raw materials (Mn) should be used carefully in the melting and casting processes of Fe-Mn-Al-alloyed steels.

  17. Influence of the physical, structural and chemical properties on the photoresponse property of magnetron sputtered TiO2 for the application of water splitting.

    PubMed

    Rahman, M; MacElroy, J M D; Dowling, D P

    2011-10-01

    The production of hydrogen from water (called "water splitting"), utilises sunlight as an energy source (solar-hydrogen) in a photoelectrochemical (PEC) solar cell, is a promising source of green energy. In this work, a PEC was used, for evaluating the photoactivity of a thin film TiO2 based photoanode by measuring photocurrent (which is comparable to hydrogen production rate by water splitting process in PEC). The main focus of this work is to study the effect of the TiO2 nanosurface and bulk properties on the photoresponse properties of the photoanode. The TiO2 coatings (360-400 nm) were deposited using a closed field reactive magnetron sputtering system. The structure and morphology of the TiO2 coatings were systematically altered by varying the deposition pressure between 5 x 10(-4) to 1 x 10(-2) mbar. The properties of the deposited nano-coatings were determined using Ellipsometry, SEM, AFM, profilometry, XPS, Raman and X-ray diffraction (XRD). Coating properties were correlated with the light absorption and photocurrent performance which were evaluated using UV-Vis spectroscopy and tri-electrode potentiostat measurements respectively. It was concluded from this study that the coating deposition pressure has a pronounced effect on the TiO2 photoanode properties leading to a significant enhancement in the photoactivity in PEC cell. Over a six fold increase in photocurrent at applied potential 0 V was observed for TiO2 photoanode prepared at 4 x 10(-3) mbar as compared to 5 x 10(-4) mbar. A correlation has been established between the deposition pressure, nano surface morphology and bulk properties, UV-Vis light absorbance and bandgap value, and the consequently higher (i) photocurrent density, (ii) negative flat band, and (iii) open circuit potential measured in Photoelectrochemical (PEC) cell. PMID:22400237

  18. Enhanced electrocatalytic activity of the Au-electrodeposited Pt nanoparticles-coated conducting oxide for the quantum dot-sensitized solar cells

    SciTech Connect

    Yoon, Yeung-Pil; Kim, Jae-Hong; Ahn, Kwang-Soon; Kang, Soon-Hyung; Kim, Hyunsoo; Choi, Chel-Jong; Kim, Kyong-Kook

    2014-08-25

    Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO{sub 2} (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Au particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of S{sub n}{sup 2− }+ 2e{sup −} (CE) → S{sub n−1}{sup 2−} + S{sup 2−} at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, S{sub n}{sup 2− }+ 2e{sup −} (TiO{sub 2} in the photoanode) → S{sub n-1}{sup 2−} + S{sup 2−}, and significantly improved overall energy conversion efficiency.

  19. Self-Assembled Monolayers of n-Alkanethiols Suppress Hydrogen Evolution and Increase the Efficiency of Rechargeable Iron Battery Electrodes

    SciTech Connect

    Malkhandi, S; Yang, B; Manohar, AK; Prakash, GKS; Narayanan, SR

    2013-01-09

    Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

  20. Electrochemical photovoltaic cells. Project 65021 quarterly technical progress report, October 15, 1979-January 15, 1980

    SciTech Connect

    Ang, P.G.P.; Remick, R.J.; Sammells, A.F.

    1980-03-01

    During the third quarter of this program, liquid junction devices based upon the semiconductors MoSe/sub 2/, MoS/sub 2/, GaAs, and CdSe have been evaluated. Lifetime testing of MoSe/sub 2/ and MoS/sub 2/ materials in acidic halogen electrolytes at constant current densities of 5 mA/cm/sup 2/ have shown excellent stability to date. For MoSe/sub 2/ single crystals in the electrolyte 1M HBr + 1M Br/sub 2/, short-circuit currents of 63 mA/cm/sup 2/ were achieved with a power conversion efficiency of 6.7% for 200 mW/cm/sup 2/ xenon light illumination. Transient potentiostatic measurements made on MoSe/sub 2/ in this electrolyte indicated little diffusion control, with exchange currents being of the order of 1 to 10 mA/cm/sup 2/. Good photoresponse of MoS/sub 2/ has been observed in 1M HBr + 1M Br/sub 2/. The performance of the natural crystal is comparable to the performance of a single-crystal MoS/sub 2/ in this electrolyte. CdSe thermally evaporated onto porous titanium gave efficiencies of about 4% with 100 mW/cm/sup 2/ xenon illumination. Experimental work was initiated on the dye sensitization of Fe/sub 2/O/sub 3/ and TiO/sub 2/ materials. Of the twelve dyes evaluated, little enhancement of the photoresponse of these materials was noted. Solid-state photoelectrochemical cells have been fabricated, based upon LiI. Cells of the configuration - cond. glass CdSe/LiI + PbI/sub 2//LiI/LiI + C + PbI/sub 2//cond. glass - were fabricated. Photoresponses up to 150 mV were observed.

  1. Passivation dynamics in the anisotropic deposition and stripping of bulk magnesium electrodes during electrochemical cycling

    DOE PAGESBeta

    Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; et al

    2015-08-10

    Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pitmore » densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.« less

  2. Methane Emission in a Specific Riparian-Zone Sediment Decreased with Bioelectrochemical Manipulation and Corresponded to the Microbial Community Dynamics.

    PubMed

    Friedman, Elliot S; McPhillips, Lauren E; Werner, Jeffrey J; Poole, Angela C; Ley, Ruth E; Walter, M Todd; Angenent, Largus T

    2015-01-01

    Dissimilatory metal-reducing bacteria are widespread in terrestrial ecosystems, especially in anaerobic soils and sediments. Thermodynamically, dissimilatory metal reduction is more favorable than sulfate reduction and methanogenesis but less favorable than denitrification and aerobic respiration. It is critical to understand the complex relationships, including the absence or presence of terminal electron acceptors, that govern microbial competition and coexistence in anaerobic soils and sediments, because subsurface microbial processes can effect greenhouse gas emissions from soils, possibly resulting in impacts at the global scale. Here, we elucidated the effect of an inexhaustible, ferrous-iron and humic-substance mimicking terminal electron acceptor by deploying potentiostatically poised electrodes in the sediment of a very specific stream riparian zone in Upstate New York state. At two sites within the same stream riparian zone during the course of 6 weeks in the spring of 2013, we measured CH4 and N2/N2O emissions from soil chambers containing either poised or unpoised electrodes, and we harvested biofilms from the electrodes to quantify microbial community dynamics. At the upstream site, which had a lower vegetation cover and highest soil temperatures, the poised electrodes inhibited CH4 emissions by ∼45% (when normalized to remove temporal effects). CH4 emissions were not significantly impacted at the downstream site. N2/N2O emissions were generally low at both sites and were not impacted by poised electrodes. We did not find a direct link between bioelectrochemical treatment and microbial community membership; however, we did find a correspondence between environment/function and microbial community dynamics. PMID:26793170

  3. A Wireless FSCV Monitoring IC With Analog Background Subtraction and UWB Telemetry.

    PubMed

    Dorta-Quiñones, Carlos I; Wang, Xiao Y; Dokania, Rajeev K; Gailey, Alycia; Lindau, Manfred; Apsel, Alyssa B

    2016-04-01

    A 30-μW wireless fast-scan cyclic voltammetry monitoring integrated circuit for ultra-wideband (UWB) transmission of dopamine release events in freely-behaving small animals is presented. On-chip integration of analog background subtraction and UWB telemetry yields a 32-fold increase in resolution versus standard Nyquist-rate conversion alone, near a four-fold decrease in the volume of uplink data versus single-bit, third-order, delta-sigma modulation, and more than a 20-fold reduction in transmit power versus narrowband transmission for low data rates. The 1.5- mm(2) chip, which was fabricated in 65-nm CMOS technology, consists of a low-noise potentiostat frontend, a two-step analog-to-digital converter (ADC), and an impulse-radio UWB transmitter (TX). The duty-cycled frontend and ADC/UWB-TX blocks draw 4 μA and 15 μA from 3-V and 1.2-V supplies, respectively. The chip achieves an input-referred current noise of 92 pA(rms) and an input current range of ±430 nA at a conversion rate of 10 kHz. The packaged device operates from a 3-V coin-cell battery, measures 4.7 × 1.9 cm(2), weighs 4.3 g (including the battery and antenna), and can be carried by small animals. The system was validated by wirelessly recording flow-injection of dopamine with concentrations in the range of 250 nM to 1 μM with a carbon-fiber microelectrode (CFM) using 300-V/s FSCV. PMID:26057983

  4. Bioresorbable silicon electronic sensors for the brain.

    PubMed

    Kang, Seung-Kyun; Murphy, Rory K J; Hwang, Suk-Won; Lee, Seung Min; Harburg, Daniel V; Krueger, Neil A; Shin, Jiho; Gamble, Paul; Cheng, Huanyu; Yu, Sooyoun; Liu, Zhuangjian; McCall, Jordan G; Stephen, Manu; Ying, Hanze; Kim, Jeonghyun; Park, Gayoung; Webb, R Chad; Lee, Chi Hwan; Chung, Sangjin; Wie, Dae Seung; Gujar, Amit D; Vemulapalli, Bharat; Kim, Albert H; Lee, Kyung-Mi; Cheng, Jianjun; Huang, Younggang; Lee, Sang Hoon; Braun, Paul V; Ray, Wilson Z; Rogers, John A

    2016-02-01

    Many procedures in modern clinical medicine rely on the use of electronic implants in treating conditions that range from acute coronary events to traumatic injury. However, standard permanent electronic hardware acts as a nidus for infection: bacteria form biofilms along percutaneous wires, or seed haematogenously, with the potential to migrate within the body and to provoke immune-mediated pathological tissue reactions. The associated surgical retrieval procedures, meanwhile, subject patients to the distress associated with re-operation and expose them to additional complications. Here, we report materials, device architectures, integration strategies, and in vivo demonstrations in rats of implantable, multifunctional silicon sensors for the brain, for which all of the constituent materials naturally resorb via hydrolysis and/or metabolic action, eliminating the need for extraction. Continuous monitoring of intracranial pressure and temperature illustrates functionality essential to the treatment of traumatic brain injury; the measurement performance of our resorbable devices compares favourably with that of non-resorbable clinical standards. In our experiments, insulated percutaneous wires connect to an externally mounted, miniaturized wireless potentiostat for data transmission. In a separate set-up, we connect a sensor to an implanted (but only partially resorbable) data-communication system, proving the principle that there is no need for any percutaneous wiring. The devices can be adapted to sense fluid flow, motion, pH or thermal characteristics, in formats that are compatible with the body's abdomen and extremities, as well as the deep brain, suggesting that the sensors might meet many needs in clinical medicine. PMID:26779949

  5. Mechanical properties and wear and corrosion resistance of electrodeposited Ni Co/SiC nanocomposite coating

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Sun, Chufeng; Gao, Ping; Zhou, Feng; Liu, Weimin

    2006-03-01

    Ni-Co/SiC nanocomposite coatings with various contents of SiC nano-particulates were prepared by electrodeposition in a Ni-Co plating bath containing SiC nano-particulates to be co-deposited. The influences of the nanoparticulates concentration, current density, stirring rate and temperature of the plating bath on the composition of the coatings were investigated. The shape and size of the SiC nano-particulates were observed and determined using a transmission electron microscope. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat/galvanostat device. The wear behavior of the Ni-Co/SiC nanocomposite coatings was evaluated on a ball-on-disk UMT-2MT test rig. The worn surface morphologies of the Ni-Co/SiC nanocomposite coatings were observed using a scanning electron microscope. The corrosion behavior of the nanocomposite coatings was evaluated by charting the Tafel curves of the solution of 0.5 mol L -1 NaCl at room temperature. It was found that the cathodic polarization potential of the composite electrolyte increased with increasing SiC concentration in the plating bath. The microhardness and wear and corrosion resistance of the nanocomposite coatings also increased with increasing content of the nano-SiC in the plating bath, and the morphologies of the nanocomposite coatings varied with varying SiC concentration in the plating bath as well. Moreover, the co-deposited SiC nano-particulates were uniformly distributed in the Ni-Co matrix and contributed to greatly increase the microhardness and wear resistance of the Ni-Co alloy coating.

  6. Bioresorbable silicon electronic sensors for the brain

    NASA Astrophysics Data System (ADS)

    Kang, Seung-Kyun; Murphy, Rory K. J.; Hwang, Suk-Won; Lee, Seung Min; Harburg, Daniel V.; Krueger, Neil A.; Shin, Jiho; Gamble, Paul; Cheng, Huanyu; Yu, Sooyoun; Liu, Zhuangjian; McCall, Jordan G.; Stephen, Manu; Ying, Hanze; Kim, Jeonghyun; Park, Gayoung; Webb, R. Chad; Lee, Chi Hwan; Chung, Sangjin; Wie, Dae Seung; Gujar, Amit D.; Vemulapalli, Bharat; Kim, Albert H.; Lee, Kyung-Mi; Cheng, Jianjun; Huang, Younggang; Lee, Sang Hoon; Braun, Paul V.; Ray, Wilson Z.; Rogers, John A.

    2016-02-01

    Many procedures in modern clinical medicine rely on the use of electronic implants in treating conditions that range from acute coronary events to traumatic injury. However, standard permanent electronic hardware acts as a nidus for infection: bacteria form biofilms along percutaneous wires, or seed haematogenously, with the potential to migrate within the body and to provoke immune-mediated pathological tissue reactions. The associated surgical retrieval procedures, meanwhile, subject patients to the distress associated with re-operation and expose them to additional complications. Here, we report materials, device architectures, integration strategies, and in vivo demonstrations in rats of implantable, multifunctional silicon sensors for the brain, for which all of the constituent materials naturally resorb via hydrolysis and/or metabolic action, eliminating the need for extraction. Continuous monitoring of intracranial pressure and temperature illustrates functionality essential to the treatment of traumatic brain injury; the measurement performance of our resorbable devices compares favourably with that of non-resorbable clinical standards. In our experiments, insulated percutaneous wires connect to an externally mounted, miniaturized wireless potentiostat for data transmission. In a separate set-up, we connect a sensor to an implanted (but only partially resorbable) data-communication system, proving the principle that there is no need for any percutaneous wiring. The devices can be adapted to sense fluid flow, motion, pH or thermal characteristics, in formats that are compatible with the body’s abdomen and extremities, as well as the deep brain, suggesting that the sensors might meet many needs in clinical medicine.

  7. Li3V2(PO4)3 encapsulated flexible free-standing nanofabric cathodes for fast charging and long life-cycle lithium-ion batteries.

    PubMed

    Sun, Pingping; Zhao, Xueying; Chen, Renpeng; Chen, Tao; Ma, Lianbo; Fan, Qi; Lu, Hongling; Hu, Yi; Tie, Zuoxiu; Jin, Zhong; Xu, Qingyu; Liu, Jie

    2016-04-14

    Lithiated transition metal phosphates with large theoretical capacities have emerged as promising cathode materials for rechargeable lithium-ion batteries. However, the poor kinetic properties caused by their low intrinsic electronic and ionic conductivity greatly hinder their practical applications. In this work, we demonstrate a novel strategy to prepare monoclinic lithium vanadium phosphate nanoparticles implanted in carbon nanofibers as the cathodes of Li-ion cells with high capacity, flexibility, long cycle stability and significantly improved high-rate performance. The composite nanofibers were obtained by electrospinning using polyacrylonitrile and Li3V2(PO4)3 nanoparticles, followed by annealing and coating with a thin layer of carbon by plasma enhanced chemical vapor deposition. The Li3V2(PO4)3 nanocrystals with the monoclinic phase were uniformly distributed in the composite nanofibers. The electrochemical performances of the as-prepared binder-free fibrous cathodes were characterized by potentiostatic and galvanostatic tests. At the rate of 0.5 C in the range of 3.0-4.3 V, the composite displayed an initial discharge capacity of 128 mA h g(-1) (96.2% of the theoretical capacity). A discharge capacity of 120 mA h g(-1) was observed even at a high rate of 10 C, and a capacity retention of 98.9% was maintained after 500 cycles at 5 C, indicating excellent high-rate capability and capacity retention. Compared to the control samples without a carbon outer-layer, the composite nanofibers with carbon coating demonstrated much better electrochemical performances. It indicates that the carbon coating can further protect the structural integrity of nanofabric electrodes during the charge/discharge processes without hindering the Li-ion mobility and also can prevent undesired side reactions with an electrolyte, thus greatly improving the rate performance and cyclic stability of the cathode. PMID:26990080

  8. A new electroactive paper actuator using conducting polypyrrole

    NASA Astrophysics Data System (ADS)

    Deshpande, Shripad D.; Kim, Jaehwan; Yun, Seong R.

    2004-07-01

    The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5 mA/cm2 current density or 0.7 volts applied potential. The two types of actuators were constructed namely: 1.Ppy/Cellophane bilayer 2. Ppy/ Cellophane paper /Ppy trilayer using electrochemical technique. These actuators showed a reversible and reproducible displacement in acetonitrile solution containing LiClO4 (1M). The maximum displacement of 9.1 mm was recorded for tri-layer device and 3.5 mm for bi-layer device in 1M LiClO4 acetonitrile solutions. The prepared actuator devices were investigated for their mechanical actuation in air medium. The actuation in air is comparatively less than in solution actuation, but still it showed significant movement in air also. The results obtained in acetonitrile solution containing 1M LiClO4 shows that the actuator requires very low excitation voltages of 0.2 MV m-1 at 0.5 Hz frequencies. The effect of humidity on the actuation properties was addressed. The humidity measurement was carried out between 60% to 95% humidity with the help of humidity-temperature controlled chamber. The resonating frequency of 3 Hz at 6 volts had shown 1.8 mm displacement at 95% humidity for gold-coated cellophane sample without polypyrrole.

  9. Integration of solid-state nanopores in a 0.5 μm CMOS foundry process.

    PubMed

    Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

    2013-04-19

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA-base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide-semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor's 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the n+ polysilicon/SiO2/n+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3, which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3. PMID:23519330

  10. Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium-copper alloys

    NASA Technical Reports Server (NTRS)

    Wall, Douglas; Stoner, Glenn E.

    1991-01-01

    Summary information is included for electrochemical aspects of stress corrosion cracking in alloy 2090 and an introduction to the work to be initiated on the new X2095 (Weldalite) alloy system. Stress corrosion cracking (SCC) was studied in both S-T and L-T orientations in alloy 2090. A constant load TTF test was performed in several environments with a potentiostatically applied potential. In the same environments the electrochemical behavior of phases found along subgrain boundaries was assessed. It was found that rapid failure due to SCC occurred when the following criteria was met: E(sub BR,T1) is less than E(sub applied) is less than E(sub Br, matrix phase). Although the L-T orientation is usually considered more resistant to SCC, failures in this orientation occurred when the stated criteria was met. This may be due to the relatively isotropic geometry of the subgrains which measure approximately 12 to 25 microns in diameters. Initial studies of alloy X2095 includes electrochemical characterization of three compositional variations each at three temperatures. The role of T(sub 1) dissolution in SCC behavior is addressed using techniques similar to those used in the research of 2090 described. SCC susceptibility is also studied using alternate immersion facilities at Reynolds Metals Corporation. Pitting is investigated in terms of stability, role of precipitate phases and constituent particles, and as initiation sites for SCC. In all research endeavors, attempts are made to link electrochemistry to microstructure. Previous work on 2090 provides a convenient basis for comparison since both alloys contain T(sub 1) precipitates but with different distributions. In 2090 T(sub 1) forms preferentially on subgrain boundaries whereas in X2095 the microstructure appears to be more homogeneous with finer T(sub 1) particles. Another point for comparison is the delta prime strengthening phase found in 2090 but absent in X2095.

  11. Determination of ζ-Potential and Tortuosity in Rat Organotypic Hippocampal Cultures from Electroosmotic Velocity Measurements under Feedback Control

    PubMed Central

    Guy, Yifat; Muha, Robert J.; Sandberg, Mats; Weber, Stephen G.

    2009-01-01

    Extracellular translational motion in the brain is generally considered to be governed by diffusion and tortuosity. However, the brain as a whole has a significant ζ-potential, thus translational motion is also governed by electrokinetic effects under a naturally occurring or applied electric field. We have previously measured ζ-potential and tortuosity in intact brain tissue, however the method was tedious. In this work, we use a four-electrode potentiostat to control the potential difference between two microreference electrodes in the tissue, creating a constant electric field. Additionally, some alterations have been made simplify our previous procedure. The method entails simultaneously injecting two 70 kDa dextran conjugated fluorophores into rat organotypic hippocampal cultures and observing their mobility using fluorescence microscopy. We further present two methods of data analysis: regression and two-probe analysis. Statistical comparisons are made between the previous and current methods as well as between the two data analysis methods. In comparison to the previous method, the current, simpler method with data analysis by regression gives statistically indistinguishable mean values of ζ-potential and tortuosity, with a similar variability for ζ-potential, −21.3 ± 2.8 mV, and a larger variability for the tortuosity, 1.98 ± 0.12. On the other hand, we find that the current method combined with the two-probe analysis produces accurate and more precise results, with a ζ-potential of −22.8 ± 0.8 mV and a tortuosity of 2.24 ± 0.10. PMID:19298057

  12. Microscopy of hierarchically organized TiO2 photoelectrode for dye solar cells

    NASA Astrophysics Data System (ADS)

    Eskandar, A.; Mohamed, N. M.

    2015-07-01

    Research on improving the performance of dye solar cells has various aspects of the device being investigated. This paper analyzes the deliberately hierarchized photoelectrode configuration for DSC applications to improve the performance of DSCs. Multiple layers of differently composed TiO2 particle types namely aggregates and nanoparticles were deposited to form a photoelectrode with thickness of about 12 µm. The photoelectrodes were assembled into working DSCs with an active area of 1 cm2. Measurement for solar power conversion performance was measured under 1 sun at AM1.5 spectrum simulated sunlight. Electron microscopy for photoelectrode analysis was conducted using Field Emission Scattering Electron Microscopy with enhanced resolution. External Quantum Efficiency was measured using a purpose built instrument. Kinetics were investigated using the Electrochemical Impedance Spectroscopy (EIS) measurement with a potentiostat. The best performing DSC is of the hierarchically organized photoelectrode with a photoconversion efficiency of 4.58%, an increase of 14% in comparison to the reference samples with fully aggregates configuration. Short circuit current density, Jsc increases by about 2.223 mA cm-2 relative to the blanks. The electron microscopy confirmed expected thickness at around 10 µm and layers forming the photoelectrode being hierarchically deposited with ˜20 nm TiO2 nanoparticles and 450 nm TiO2 aggregates mixture composition. EQE improved especially for visible region of 500-550 nm light wavelengths with 12 % increase in the response of in that region. Improvement to the diffusion coefficient as measured by the EIS contributed to the performance increase of the photoelectrode configuration under investigation.

  13. Identifying the microbial communities and operational conditions for optimized wastewater treatment in microbial fuel cells.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Wu, Angela; Yamanaka, Yuko; Nealson, Kenneth H; Bretschger, Orianna

    2013-12-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as "biocatalysts" to recover energy from organic matter in the form of electricity. MFCs have been explored as possible energy neutral wastewater treatment systems; however, fundamental knowledge is still required about how MFC-associated microbial communities are affected by different operational conditions and can be optimized for accelerated wastewater treatment rates. In this study, we explored how electricity-generating microbial biofilms were established at MFC anodes and responded to three different operational conditions during wastewater treatment: 1) MFC operation using a 750 Ω external resistor (0.3 mA current production); 2) set-potential (SP) operation with the anode electrode potentiostatically controlled to +100 mV vs SHE (4.0 mA current production); and 3) open circuit (OC) operation (zero current generation). For all reactors, primary clarifier effluent collected from a municipal wastewater plant was used as the sole carbon and microbial source. Batch operation demonstrated nearly complete organic matter consumption after a residence time of 8-12 days for the MFC condition, 4-6 days for the SP condition, and 15-20 days for the OC condition. These results indicate that higher current generation accelerates organic matter degradation during MFC wastewater treatment. The microbial community analysis was conducted for the three reactors using 16S rRNA gene sequencing. Although the inoculated wastewater was dominated by members of Epsilonproteobacteria, Gammaproteobacteria, and Bacteroidetes species, the electricity-generating biofilms in MFC and SP reactors were dominated by Deltaproteobacteria and Bacteroidetes. Within Deltaproteobacteria, phylotypes classified to family Desulfobulbaceae and Geobacteraceae increased significantly under the SP condition with higher current generation; however those phylotypes were not found in the OC reactor. These analyses suggest that species

  14. High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes

    NASA Astrophysics Data System (ADS)

    Markoulidis, F.; Lei, C.; Lekakou, C.; Figgemeier, E.; Duff, D.; Khalil, S.; Martorana, B.; Cannavaro, I.

    2012-09-01

    The purpose of this work was to investigate and improve the performance of supercapacitor cells with carbon-based nanocomposite electrodes. The electrode structure comprised activated carbon (AC), four types of multi-wall nanotubes (MWNTs) and two alternative polymer binders, Polyvinyl alcohol (PVA) or Polyvinylidene fluoride (PVDF). Electrode fabrication involved various stages of mixing and dispersion of the AC powder and carbon nanotubes, rolling and coating of the AC/MWNT/binder paste on an aluminium substrate which also served as current collector. The organic electrolyte utilised was 1M tetraethylammonium tetrafluoroborate (TEABF4) fully dissolved in propylene carbonate (PC). All devices were of the electrochemical double layer capacitor (EDLC) type, incorporating four layers of tissue paper as separator material. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Each supercapacitor cell was subjected to Cyclic Voltammetry (CV) at various scan rates from 0.01 V/s to 1 V/s, Charge-Discharge at a fixed current steps (2 mA) and Electrochemical Impedance Spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz. It was established that an AC-based supercapacitor with 0.15%w/w MWNT content and 30 μm roll-coated, nanocomposite electrodes provided superior energy and power and energy densities while the cells was immersed in the electrolyte; well above those generated by the AC-based EDLC cells.

  15. Effect of bicarbonate ion additives on pitting corrosion of type 316L stainless steel in aqueous 0.5 M sodium chloride solution

    SciTech Connect

    Park, J.J.; Pyun, S.I.; Lee, W.J.; Kim, H.P.

    1999-04-01

    The effect of bicarbonate ions (HCO{sub 3}{sup {minus}}) on pitting corrosion of type 316L stainless steel (SS, UNS S3 1603) was investigated in aqueous 0.5 M sodium chloride (NaCl) solution using potentiodynamic polarization, the abrading electrode technique, alternating current (AC) impedance spectroscopy combined with x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Addition of HCO{sub 3}{sup {minus}} ions to NaCl solutions extended the passive potential region in width and, at the same time, raised the pitting potential in value on the potentiodynamic polarization curve. Potentiostatic current transients obtained from the moment just after interrupting the abrading action showed the repassivation rate of propagating pits increased and that the pit growth rate decreased with increasing HCO{sub 3}{sup {minus}} ion concentration. Over the whole applied potential, the oxide film resistance was higher in the presence of HCO{sub 3}{sup {minus}} ions. The pit number density decreased with increasing HCO{sub 3}{sup {minus}} ion concentration. Moreover, addition of HCO{sub 3}{sup {minus}} ions to NaCl solutions retarded lateral pit growth, while promoting downward pit growth from the surface. The bare surface of the specimen repassivated preferentially along the pit mouth and walls, compared to the pit bottom, as a result of formation of a surface film with a high content of protective mixed ferrous-chromous carbonate ([Fe,Cr]CO{sub 3}) that formed from preferential adsorption of HCO{sub 3}{sup {minus}} ions.

  16. Electrochemical investigation of chromium oxide-coated Ti-6Al-4V and Co-Cr-Mo alloy substrates.

    PubMed

    Swaminathan, Viswanathan; Zeng, Haitong; Lawrynowicz, Daniel; Zhang, Zongtao; Gilbert, Jeremy L

    2011-08-01

    Hard coatings for articulating surfaces of total joint replacements may improve the overall wear resistance. However, any coating approach must take account of changes in corrosion behavior. This preliminary assessment analyzes the corrosion kinetics, impedance and mechanical-electrochemical stability of 100 μm thick plasma sprayed chromium oxide (Cr₂O₃) coatings on bearing surfaces in comparison to the native alloy oxide films on Co-Cr-Mo and Ti-6Al-6V. Cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and mechanical abrasion under potentiostatic conditions were performed on coated and substrate surfaces in physiological saline. SEM analysis characterized the coating morphology. The results showed that the corrosion current density values of chromium oxide coatings (0.4-1.2 μA/cm²) were of the same order of magnitude as Ti-6Al-4V alloy. Mechanical abrasion did not increase corrosion rates of chromium oxide coatings but did for uncoated Co-Cr-Mo and Ti-6Al-4V. The impedance response of chromium oxide coatings was very different than Co-Cr-Mo and Ti-6Al-4V native oxides characterized by a defected coating model. More of a frequency-independent purely resistive response was seen in mid-frequency range for the coatings (CPE(coat) : 40-280 nF/cm² (rad/s)(1-α) , α: 0.67-0.83) whereas a more capacitive character is seen for Co-Cr-Mo and Ti-6Al-4V (CPE(ox) around 20 μF/cm² (rad/s)(1-α) , α around 0.9). Pores, interparticle gaps and incomplete fusion typical for thermal spray coatings were present in these oxides which could have influenced corrosion resistance. The coating microstructure could have allowed some fluid penetration. Overall, these coatings appear to have suitable corrosion properties for wear surfaces. PMID:21648063

  17. Functionalization and Characterization of Nanomaterial Gated Field-Effect Transistor-Based Biosensors and the Design of a Multi-Analyte Implantable Biosensing Platform

    NASA Astrophysics Data System (ADS)

    Croce, Robert A., Jr.

    Advances in semiconductor research and complementary-metal-oxide semiconductor fabrication allow for the design and implementation of miniaturized metabolic monitoring systems, as well as advanced biosensor design. The first part of this dissertation will focus on the design and fabrication of nanomaterial (single-walled carbon nanotube and quantum dot) gated field-effect transistors configured as protein sensors. These novel device structures have been functionalized with single-stranded DNA aptamers, and have shown sensor operation towards the protein Thrombin. Such advanced transistor-based sensing schemes present considerable advantages over traditional sensing methodologies in view of its miniaturization, low cost, and facile fabrication, paving the way for the ultimate realization of a multi-analyte lab-on-chip. The second part of this dissertation focuses on the design and fabrication of a needle-implantable glucose sensing platform which is based solely on photovoltaic powering and optical communication. By employing these powering and communication schemes, this design negates the need for bulky on-chip RF-based transmitters and batteries in an effort to attain extreme miniaturization required for needle-implantable/extractable applications. A complete single-sensor system coupled with a miniaturized amperometric glucose sensor has been demonstrated to exhibit reality of this technology. Furthermore, an optical selection scheme of multiple potentiostats for four different analytes (glucose, lactate, O 2 and CO2) as well as the optical transmission of sensor data has been designed for multi-analyte applications. The last part of this dissertation will focus on the development of a computational model for the amperometric glucose sensors employed in the aforementioned implantable platform. This model has been applied to single-layer single-enzyme systems, as well as multi-layer (single enzyme) systems utilizing glucose flux limiting layer-by-layer assembled

  18. Real-Time Measurements of the Redox States of c-Type Cytochromes in Electroactive Biofilms: A Confocal Resonance Raman Microscopy Study

    PubMed Central

    Virdis, Bernardino; Millo, Diego; Donose, Bogdan C.; Batstone, Damien J.

    2014-01-01

    Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208±49 µA cm−2) and mature (57 days, j = 267±73 µA cm−2) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 µm from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190±37 µA cm−2) with thickness above 100 µm were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms. PMID:24587123

  19. Using anodic aluminum oxide templates and electrochemical method to deposit BiSbTe-based thermoelectric nanowires

    PubMed Central

    2014-01-01

    In this study, the cyclic voltammetry method was first used to find the reduced voltages and anodic peaks of Bi3+, Sb3+, and Te4+ ions as the judgments for the growth of the (Bi,Sb)2 - x Te3 + x-based materials. Ethylene glycol (C2H6O2) was used as a solvent, and 0.3 M potassium iodide (KI) was used to improve the conductivity of the solution. Two different electrolyte formulas were first used: (a) 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 and (b) 0.015 M Bi(NO3)3-5H2O, 0.005 M SbCl3, and 0.0075 M TeCl4. The potentiostatic deposition process was first used to find the effect of reduced voltage on the variation of compositions of the (Bi,Sb)2 - xTe3 + x-based materials. After finding the better reduced voltage, 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 were used as the electrolyte formula. The pulse deposition process was successfully used to control the composition of the (Bi,Sb)2 - xTe3 + x-based materials and grow the nanowires in anodic aluminum oxide (AAO) templates. PMID:24502697

  20. Microstructure and anodic polarization behavior of experimental Ag-18Cu-15Pd-12Au alloy in aqueous sulfide solution.

    PubMed

    Endo, Kazuhiko; Ohno, Hiroki; Asakura, Shukuji

    2003-05-01

    The anodic corrosion behavior of an experimental Ag-15Pd-18Cu-12Au alloy in 0.1% Na(2)S solution in relation to its microstructure was investigated using potentiodynamic and potentiostatic polarization techniques with analyses of corrosion products by X-ray diffractometry, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The role of Pd in improvement of the corrosion resistance was also investigated. In the potential/current density curve, three distinct current peaks, at -520 mV (peak I), -425 mV (peak II) and -175 mV (peak III), were observed. The Ag-rich alpha(2) matrix with coarse Cu and Pd-rich lamellae was the most corrosion-susceptible region, and this region was preferentially corroded at peak I with the formation of granular deposits of Ag(2)S. A small amount of Ag-Cu mixed sulfide deposited on the Cu and Pd-rich coarse particles and dissolution of Ag as AgO(-) might have occurred in parallel with Ag(2)S formation at peak II. Enrichment of Pd on the alloy surface occurred at peak III due to preferential dissolution of Ag and Cu. A high level of corrosion resistance was attained with the formation of a thin Pd-rich sulfide film, which enhanced the passivity of the alloy in an alkaline sulfide solution. It was found that passivity is an important phenomenon not only for base metal alloys but also for noble metal alloys to maintain high levels of resistance to corrosion and tarnishing in sulfide environments. PMID:15348446