Science.gov

Sample records for potentiostats

  1. Redox reaction rates using potentiostatic coulometry

    SciTech Connect

    Ramette, R.W.; Harris, R.Z.; Bengali, A.A.; Noll, R.J.

    1987-01-01

    A new method based on potentiostatic coulometry was used to study the kinetics of the aqueous redox reactions between the ions chlorate/iodide, bromate/iodide, and bromate/bromide. The halogen product was continuously and rapidly reduced back to halide at a large platinum gauze cathode, the current being a direct measure of reaction rate and the accumulated charge serving to measure the extent of reaction. The reactions were studied at several temperatures, and activation entropies and enthalpies were calculated.

  2. 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.

  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.

  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. 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.

  6. 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.

  7. 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

  8. An immunological interleukine-6 capacitive biosensor using perturbation with a potentiostatic step.

    PubMed

    Berggren, C; Bjarnason, B; Johansson, G

    1998-11-01

    An instrument for potentiostatic capacitance measurements, based on perturbation with a potentiostatic step was used. The capacitive sensor consisted of self-assembled sulfur compounds on gold to which antibodies towards Interleukine 6, Il-6, had been immobilized. The biosensor was part of a potentiostatic three-electrode system with an extra reference electrode. Two different methods using epoxy- or carbodiimide coupling of the polyclonal antibodies were compared. The antigen Il-6 could be detected from 5 x 10(-16) to 5 x 10(-13) M with one immobilization method and to more than 5 x 10(-9) M with the other. No labels were necessary since the binding of the antigen was detected directly. The insulating properties of the different layers of the biosensor were investigated.

  9. Potentiostatic activation of as-made graphene electrodes for high-rate performance in supercapacitors

    NASA Astrophysics Data System (ADS)

    Senthilkumar, Krishnan; Jeong, Seok; Lah, Myoung Soo; Sohn, Kee-Sun; Pyo, Myoungho

    2016-10-01

    A thermally expanded graphene oxide (EGO) electrode is electrochemically activated to simultaneously introduce electrolyte-accessible mesopores and oxygen functional groups. The former is produced via O2 evolution and the latter is incorporated by the intermediate hydroxyl radicals generated during the potentiostatic oxidation of H2O in 1 M H2SO4 at 1.2 V (vs. Ag/AgCl). When applied as a supercapacitor, the potentiostatically treated EGO (EGO-PS) shows significant enhancement in an electric-double layer (EDL) process with a noticeable Faradaic reaction and delivers high capacitance at fast charge/discharge (C/D) rates (334 F g-1 at 0.1 A g-1 and 230 F g-1 at 50 A g-1). In contrast to EGO-PS, EGO that is oxidized potentiodynamically (EGO-PD) shows negligible enhancement in EDL currents. EGO that is subjected to successive potential pulses also shows behaviors similar to EGO-PD, which indicates the importance of hydroxyl radical accumulation via a potentiostatic method for simultaneous functionalization and microstructural control of graphenes. The potentiostatic post-treatment presented here is a convenient post-treatment strategy that could be used to readily increase capacitance and simultaneously improve the high-rate performance of carbon-based electrodes.

  10. Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods

    SciTech Connect

    Molina, J.; Fernández, J.; Río, A.I. del; Bonastre, J.; Cases, F.

    2014-03-01

    Reduced graphene oxide (RGO) has been synthesized on Pt wires by means of a potentiodynamic method between + 0.6 V and − 1.4 V for 20 scans. Cyclic voltammetry characterization of the coatings showed the typical capacitative behavior of graphene. Pt nanoparticles were synthesized on Pt–RGO electrodes by means of potentiostatic methods and a comparison between different synthesis potentials (− 0.16, 0, + 0.2 and + 0.4 V) for the same synthesis charge (mC·cm{sup −2}) was established. The electrodes obtained were characterized in 0.5 M H{sub 2}SO{sub 4} solution to observe the characteristic oxidation and reduction processes of the Pt surface. A 0.5 M H{sub 2}SO{sub 4}/0.5 M CH{sub 3}OH solution was used to measure the catalytic properties of the deposits against methanol oxidation. The most appropriate potential to perform the synthesis was 0 V followed by − 0.16 V and + 0.2 V. The morphology of the coatings varied depending on the potential applied as observed by scanning electron microscopy. Alternate current methods were also used to synthesize Pt nanoparticles and compare the results with the traditional potentiostatic method. Different frequencies were used: 0.1, 1, 10, 100, 1000 and 10 000 Hz. Alternate current synthesis is more efficient than traditional potentiostatic methods, obtaining more electroactive coatings with less effective synthesis time. - Highlights: • Reduced graphene oxide has been obtained by electrochemical reduction on Pt wires. • Pt nanoparticles have been obtained potentiostatically at different potentials. • Pt nanoparticles have been obtained by ac methods with different frequencies. • ac synthesis is a better synthesis method than potentiostatic synthesis.

  11. An improved technique for dental alloy etching with a potentiostatic device.

    PubMed

    Hong, C Y

    1989-10-01

    Since a good retention of direct bonded retainers onto abutment teeth is the primary requirement for the fabrication of etched fixed partial dentures, successful formation of a micromechanical retentive architecture on the bonding surface is one of the most important procedures. For creating such a retentive dendritic pattern on nonprecious metal, a 2-electrode electrolytic method has been used. This equipment consists of a low-voltage DC power supply and two electrodes, namely, a working and a counter one. However, the current and voltage should be monitored during the entire processing time and the etching area must be pre-estimated. A potentiostat has been used to automatically stabilize the voltage across the working electrode and reference electrode by adjusting the current, as commonly employed in electro-chemical technology. A 3-electrode corrosion device originally developed for laboratory research was adapted for dental retainer etching in this study. The results revealed that the etching of dental nonprecious metal (Ni-Cr-Be alloy) could successfully be performed by using the system with a potentiostat. Moreover, the working potential was found to be approximately 1.3 volts by taking the midpoint between the breakdown and the critical potentials for passivation on the potentiostatic anode polarization curves. The optimal exposure time has been found to be in a range of 3 to 5 minutes and 4 minutes to be ideal as determined by SEM microphotographic observation which showed a uniform dendritic pattern with regular lattice form of alternating ridges and valleys.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. A low-power CMOS operational amplifier IC for a heterogeneous paper-based potentiostat

    NASA Astrophysics Data System (ADS)

    Bezuidenhout, P.; Land, K.; Joubert, T.-H.

    2016-02-01

    Electrochemical biosensing is used to detect specific analytes in fluids, such as bacterial and chemical contaminants. A common implementation of an electrochemical readout is a potentiostat, which usually includes potentiometric, amperometric, and impedimetric detection. Recently several researchers have developed small, low-cost, single-chip silicon-based potentiostats. With the advances in heterogeneous integration technology, low-power potentiostats can be implemented on paper and similar low cost substrates. This paper deals with the design of a low-power paper-based amperometric front-end for a low-cost and rapid detection environment. In amperometric detection a voltage signal is provided to a sensor system, while a small current value generated by an electrochemical redox reaction in the system is measured. In order to measure low current values, the noise of the circuit must be minimized, which is accomplished with a pre-amplification front-end stage, typically designed around an operational amplifier core. An appropriate circuit design for a low-power and low-cost amperometric front-end is identified, taking the heterogeneous integration of various components into account. The operational amplifier core is on a bare custom CMOS chip, which will be integrated onto the paper substrate alongside commercial off-the-shelf electronic components. A general-purpose low-power two-stage CMOS amplifier circuit is designed and simulated for the ams 350 nm 5 V process. After the layout design and verification, the IC was submitted for a multi-project wafer manufacturing run. The simulated results are a bandwidth of 2.4 MHz, a common-mode rejection ratio of 70.04 dB, and power dissipation of 0.154 mW, which are comparable with the analytical values.

  13. 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.

  14. 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.

  15. 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

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

    PubMed

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

    2011-04-01

    The combination of microchip electrophoresis 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 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 (as a buffer modifier) for the separation of nitrite (NO₂⁻), glutathione, ascorbic acid, and tyrosine. A half-wave potential 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.

  17. Competition between Methanogens and Acetogens in Biocathodes: A Comparison between Potentiostatic and Galvanostatic Control

    PubMed Central

    Molenaar, Sam D.; Saha, Pradip; Mol, Annemerel R.; Sleutels, Tom H. J. A.; ter Heijne, Annemiek; Buisman, Cees J. N.

    2017-01-01

    Microbial electrosynthesis is a useful form of technology for the renewable production of organic commodities from biologically catalyzed reduction of CO2. However, for the technology to become applicable, process selectivity, stability and efficiency need strong improvement. Here we report on the effect of different electrochemical control modes (potentiostatic/galvanostatic) on both the start-up characteristics and steady-state performance of biocathodes using a non-enriched mixed-culture inoculum. Based on our results, it seems that kinetic differences exist between the two dominant functional microbial groups (i.e., homoacetogens and methanogens) and that by applying different current densities, these differences may be exploited to steer product selectivity and reactor performance. PMID:28106846

  18. CheapStat: an open-source, "do-it-yourself" potentiostat for analytical and educational applications.

    PubMed

    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.

  19. Robust Functionalization of Large Microelectrode Arrays by Using Pulsed Potentiostatic Deposition

    PubMed Central

    Rothe, Joerg; Frey, Olivier; Madangopal, Rajtarun; Rickus, Jenna; Hierlemann, Andreas

    2016-01-01

    Surface modification of microelectrodes is a central step in the development of microsensors and microsensor arrays. Here, we present an electrodeposition scheme based on voltage pulses. Key features of this method are uniformity in the deposited electrode coatings, flexibility in the overall deposition area, i.e., the sizes and number of the electrodes to be coated, and precise control of the surface texture. Deposition and characterization of four different materials are demonstrated, including layers of high-surface-area platinum, gold, conducting polymer poly(ethylenedioxythiophene), also known as PEDOT, and the non-conducting polymer poly(phenylenediamine), also known as PPD. The depositions were conducted using a fully integrated complementary metal-oxide-semiconductor (CMOS) chip with an array of 1024 microelectrodes. The pulsed potentiostatic deposition scheme is particularly suitable for functionalization of individual electrodes or electrode subsets of large integrated microelectrode arrays: the required deposition waveforms are readily available in an integrated system, the same deposition parameters can be used to functionalize the surface of either single electrodes or large arrays of thousands of electrodes, and the deposition method proved to be robust and reproducible for all materials tested. PMID:28025569

  20. Synthesis and Characterization of Potentiostatically Electrodeposited Tungsten Oxide Thin Films for Smart Window Application

    NASA Astrophysics Data System (ADS)

    More, A. J.; Patil, R. S.; Dalavi, D. S.; Suryawanshi, M. P.; Burungale, V. V.; Kim, J. H.; Patil, P. S.

    2017-02-01

    Tungsten oxide (WO3) thin films have been synthesized using electrodeposition in potentiostatic mode and the effect of different deposition potentials on their structural, morphological, optical, and electrochromic (EC) properties investigated. The deposition potential versus saturated calomel electrode (SCE) was varied from -0.35 V to -0.50 V in steps of -0.05 V for 20 min each. The electrodeposited WO3 thin films were characterized using x-ray diffraction analysis, micro-Raman spectroscopy, field-emission scanning electron microscopy, and ultraviolet-visible (UV-Vis) spectrophotometry, revealing amorphous nature with nanograins having average size from 40 nm to 60 nm. The EC performance of the WO3 thin films exhibited response times of 1.35 s for bleaching ( t b) and 3.1 s for coloration ( t c) with excellent reversibility of 64.36%. The highest coloration efficiency of the electrodeposited WO3 thin films was found to be 87.95 cm2/C. The electrochemical reversibility and stability of the WO3 thin films obtained in this study make them promising for use in smart window applications.

  1. 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.

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

    PubMed

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

    2016-03-01

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

  3. Potentiostatic pulse-deposition of calcium phosphate on magnesium alloy for temporary implant applications--an in vitro corrosion study.

    PubMed

    Kannan, M Bobby; Wallipa, O

    2013-03-01

    In this study, a magnesium alloy (AZ91) was coated with calcium phosphate using potentiostatic pulse-potential and constant-potential methods and the in vitro corrosion behaviour of the coated samples was compared with the bare metal. In vitro corrosion studies were carried out using electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid (SBF) at 37 °C. Calcium phosphate coatings enhanced the corrosion resistance of the alloy, however, the pulse-potential coating performed better than the constant-potential coating. The pulse-potential coating exhibited ~3 times higher polarization resistance than that of the constant-potential coating. The corrosion current density obtained from the potentiodynamic polarization curves was significantly less (~60%) for the pulse-deposition coating as compared to the constant-potential coating. Post-corrosion analysis revealed only slight corrosion on the pulse-potential coating, whereas the constant-potential coating exhibited a large number of corrosion particles attached to the coating. The better in vitro corrosion performance of the pulse-potential coating can be attributed to the closely packed calcium phosphate particles.

  4. 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

  5. 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

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

    PubMed

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

    2015-02-01

    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.

  7. Semi-real time electrochemical monitoring for influenza virus RNA by reverse transcription loop-mediated isothermal amplification using a USB powered portable potentiostat.

    PubMed

    Nagatani, Naoki; Yamanaka, Keiichiro; Saito, Masato; Koketsu, Ritsuko; Sasaki, Tadahiro; Ikuta, Kazuyoshi; Miyahara, Toshiro; Tamiya, Eiichi

    2011-12-21

    In this paper, the semi-real time electrochemical monitoring method using a screen-printed electrode, which employs reverse transcription loop-mediated isothermal amplification (RT-LAMP) for influenza virus RNA, is presented. The amplified DNA combined with methylene blue (MB), which was used as an electroactive DNA intercalator, and the electrochemical signal was monitored using square wave voltammetry in the presence of RT-LAMP reagent components. MB molecules binding to amplified DNA caused the reduction of the peak current due to the slow diffusion of MB-amplified DNA complex to the electrode surface. We successfully monitored the amplification process of DNA on the basis of RT-LAMP by measuring and analyzing the electrochemical signal of MB with only one screen-printed electrode that connected with a USB powered portable potentiostat. The peak height of the current was related to the extent of amplification of DNA and the amount of input RNA. Since laborious probe immobilization is not required and both the amplification and the monitoring are possible in a single tube, our method does not suffer from potential cross-contamination. Furthermore, our method provides a new rote for the development of electrochemical hand held biosensors.

  8. Parallel Recording of Neurotransmitters Release from Chromaffin Cells Using a 10 × 10 CMOS IC Potentiostat Array with On-Chip Working Electrodes

    PubMed Central

    Kim, Brian Namghi; Herbst, Adam D.; Kim, Sung June; Minch, Bradley A.; Lindau, Manfred

    2012-01-01

    Neurotransmitter release is modulated by many drugs and molecular manipulations. We present an active CMOS-based electrochemical biosensor array with high throughput capability (100 electrodes) for on-chip amperometric measurement of neurotransmitter release. The high-throughput of the biosensor array will accelerate the data collection needed to determine statistical significance of changes produced under varying conditions, from several weeks to a few hours. The biosensor is designed and fabricated using a combination of CMOS integrated circuit (IC) technology and a photolithography process to incorporate platinum working electrodes on-chip. We demonstrate the operation of an electrode array with integrated high-gain potentiostats and output time-division multiplexing with minimum dead time for readout. The on-chip working electrodes are patterned by conformal deposition of Pt and lift-off photolithography. The conformal deposition method protects the underlying electronic circuits from contact with the electrolyte that covers the electrode array during measurement. The biosensor was validated by simultaneous measurement of amperometric currents from 100 electrodes in response to dopamine injection, which revealed the time course of dopamine diffusion along the surface of the biosensor array. The biosensor simultaneously recorded neurotransmitter release successfully from multiple individual living chromaffin cells. The biosensor was capable of resolving small and fast amperometric spikes reporting release from individual vesicle secretions. We anticipate that this device will accelerate the characterization of the modulation of neurotransmitter secretion from neuronal and endocrine cells by pharmacological and molecular manipulations of the cells. PMID:23084756

  9. In vivo potentiostatic studies at the electrode tissue interface: filter properties of the monophasic action potential (Ag/AgCl) electrode in living rat heart.

    PubMed

    Chou, H A; Ovadia, M; Moskowitz, M; Zavitz, D H

    2000-03-01

    The monophasic action potential (Franz) catheter is regarded as the criterion standard for high fidelity recording of a class of physiological signals. However, its signal modulation characteristics have never been reported. Broadband impedance spectroscopy was performed in perfused living rat heart in a three-electrode potentiostatic configuration to determine the filtering characteristics of the MAP and model Ag/AgCl electrode-tissue interfaces. The filter transfer function H(f) (attenuation [dB] vs log(f) [log(Hz)]) was derived for the frequency range 10 Hz-10(6) Hz. As a filter, the MAP interface is characterized by two ranges of filtering behavior. At high frequency the MAP interface is a high-pass filter with passband frequency 54 kHz-549 kHz (median 321 kHz) and with -3 dB cutoff points ranging from 10 kHz to 302 kHz. In this high frequency range the transfer function is characterized by decreasing attenuation per decade. However, in the lower frequency range relevant to physiological signals (the monophasic action potential, 0.1-40 Hz), it is a severely attenuating nondiodic high-pass filter element with an average attenuation of 16.87 dB relative to passband. In this physiological range, rolloff is nonlinear with increasing attenuation per decade. While the MAP electrode and model Ag/AgCl electrodes are high-pass filters with robust transfer functions for high frequency signals in the living heart, the attenuation of signals in a frequency range relevant to in vivo physiological recording imparts extreme attenuation that may distort physiological signals unpredictably. This disadvantage may be mitigated by amplitude scaling to a calibrated pure tone signal within the physiological frequency band to recover a reproducible signal.

  10. Potentiostat for Characterizing Microstructures at Ionic Liquid/Electrode Interfaces

    DTIC Science & Technology

    2015-10-10

    systems via simultaneous electrochemical and spectroscopic studies. These data are pertinent to understanding the microscopic (molecular and ionic...characterize ionic liquid-based (IL-based) electrolyte systems via simultaneous electrochemical and spectroscopic studies. These data are pertinent to...spectrometer to perform surface enhanced infrared absorption (SEIRA) spectroscopy with electrochemical control. The multichannel instrument has also

  11. Attofarad resolution potentiostat for electrochemical measurements on nanoscale biomolecular interfacial systems

    NASA Astrophysics Data System (ADS)

    Carminati, Marco; Ferrari, Giorgio; Sampietro, Marco

    2009-12-01

    We present an instrument that enables electrochemical measurements (cyclic voltammetry, impedance tracking, and impedance spectroscopy) on submicrometric samples. The system features a frequency range from dc to 1 MHz and a current resolution of 10 fA for a measurement time of 1 s, giving a sensitivity of few attofarads in terms of measurable capacitance with an applied voltage of only 100 mV. These performances are obtained using a low-noise wide-bandwidth integrator/differentiator stage to sense the input current and a modular approach to minimize the effect of input stray capacitances. A digitally implemented lock-in filter optimally extracts the impedance of the sample, providing time tracking and spectroscopy operating modes. This computer-based and flexible instrument is well suited for characterizing and tracking the electrical properties of biomolecules kept in the physiological solution down to the nanoscale.

  12. Study of Metal-NH[subscript 3] Interfaces (Metal= Cu, Ni, Ag) Using Potentiostatic Curves

    ERIC Educational Resources Information Center

    Nunes, Nelson; Martins, Angela; Leitao, Ruben Elvas

    2007-01-01

    Experiment is conducted to determine the kinetic parameters of metal-solution interfaces. During the experiment the kinetic parameters for the interfaces Cu-NH[subscript 3], Ag-NH[subscript 3] and Ni-NH[subscript 3] is easily determined.

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

    PubMed

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

    2014-07-09

    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.

  14. 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.

  15. Portable potentiostatic sensor integrated with neopterin-imprinted poly(ethylene-co-vinyl alcohol)-based electrode.

    PubMed

    Huang, C-Y; Hsieh, C-H; Chen, Y-L; Lee, M-H; Lin, C-F; Tsai, H-H; Juang, Y-Z; Liu, B-D; Lin, H-Y

    2011-12-01

    Neopterin is a catabolic product of guanosine triphosphate, a purine nucleotide. Measuring neopterin concentrations in biological fluids such as urine provides information about cellular immune activation in humans under control of T helper cells. A high neopterin concentration in bodily fluids, including serum and urine, indicates cellular immunity activation, which is associated with oxidative stress. In this work, neopterin is the target molecule and imprinted onto poly(ethylene-co-vinyl alcohol) via solvent evaporation. The template molecules on the thin film are then removed, and the membrane is used as a sensing element for electrochemical urinalysis. Poly(ethylene-co-vinyl alcohol) containing 27 mol% ethylene had high imprinting effectiveness and may be integrated with the proposed portable biosensor. In random urine analysis, the cyclic voltammetry measurements of neopterin with an additional recovery method achieved >95% recovery for the neopterin concentration of 15 ng/mL.

  16. 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...

  17. Electrochemical nitridation of metal surfaces

    DOEpatents

    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.

  18. 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

  19. 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.

  20. 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.

  1. Enhancement of Corrosion Resistance and Mechanical Properties of Light- Weight Metals Through the Use of Graded Nonequilibrium Microstructures

    DTIC Science & Technology

    1994-10-01

    Model 273 Potentiostat interfaced with a PC computei controlled by PAR Model 352 software, or a Gamry PC3 potentiostat controlled by CMS100 software...Submilted IL): nŘ i Ofih’e of Navel tReserch. 801) North Quimn• Street Arliug~on, VA 22217- 5000 AL October 1994 94-35250 9 111 O6!94 1 06, PENN STATE...Deposition System which was custom built by Denton Vacuum. Details concerning this system and its operation have been presented elsewhere 20 . In the

  2. 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.

  3. Characterization of Sub-Micron Sized Carbon Electrodes Insulated with a Phenol-Allylphenol Copolymer

    DTIC Science & Technology

    1992-01-15

    phosphate buffer. This solution consisted of 0 O099 M citric acid (Aldrich Chemical), and 0.181 M sodium phosphate, dibasic (Baker Scientific). Dopamine...potentiostat, and recorded on a Hewlett Packard X-Y recorder. The potentiostat was operated in the two electrode mode with a saturated sodium calomel...decade) (mV vs SSCE) Dopamine 163 ± 14 75 ± 11 12 4-methylcatechol 188 ± 14 126 ± 9 12 3,4-dihydroxy- phenylacetate 327 ± 24 155 ± 9 10 Ferrocyanide

  4. Components, Assembly and Electrochemical Properties of Three-Dimensional Battery Architectures

    DTIC Science & Technology

    2016-03-01

    density. Both potentiostatic and galvanostatic cycling experiments showed that the carbon post arrays are capable of reversibly cycling lithium with...demonstrated charge and discharge cycling in the prototype. 15. SUBJECT TERMS Three-dimensional battery (3-D battery) , 3-D electrode arrays, silicon...arrays, photopatternable materials, lithium cycling , polysulfide catholyte, SU-8 electrolyte 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF a

  5. Same-Side Platinum Electrodes for Metal Assisted Etching of Porous Silicon

    DTIC Science & Technology

    2015-11-01

    inhomogeneous PSi thickness that has been achieved using the sacrificial Pt approach .......................7 Fig. 7 Cross-sectional drawing of the...etch, which is a simplified etch procedure that does not require a potentiostat or external wires to the wafer. In this approach, a metal (e.g

  6. Electrochemical approach for passivating steel and other metals and for the simultaneous production of a biocide to render water potable

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Potentiostatic polarization curves indicated that the cathodic reactions in deaerated KI-I2 water solutions were due to iodine reduction and hydrogen evolution. In the presence of oxygen an additional reduction wave appeared. Anodic polarization curves revealed that iodine could be produced in the region of potential from +600 to +1000 nv vs. SCE.

  7. Mechanism of Stress-Corrosion Cracking.

    DTIC Science & Technology

    1977-06-01

    species ( cupric complex ions ) to the surface, and established the reversible potential, the exchange current density and the Tafel slope for the main...anodic reaction, copper dissolution. The conditions for tarnish formation and the nature of this cuprous -oxide layer were also studied. Potentiostatic

  8. 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.

  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. 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)

  11. 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…

  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. 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.

  14. Ordered and Ultra-High Aspect Ratio Nanocapillary Arrays as a Model System

    DTIC Science & Technology

    2015-10-13

    energy technologies such as photovoltaics, electrochemical capacitors and batteries, as well as a range of chemical technologies such as separations...potential distributions. Potentiostatic and linear sweep potentiometry during deep nanocapillary growth will be presented. Electrochemical impedance...during deep nanocapillary growth that exemplifies this as a model electrochemical system for porous electrodes. Particularly the EIS response of the

  15. ARO Research Instrumentation Program - IR Spectrometer Procurement

    DTIC Science & Technology

    2015-11-01

    via simultaneous electrochemical and spectroscopic studies. These studies are enabling us to understanding the microscopic (molecular and ionic...program. The instrument is being utilized to characterize ionic liquid-based (IL-based) electrolyte systems via simultaneous electrochemical and...spectrometer has been synchronized with a potentiostat to perform surface enhanced infrared absorption (SEIRA) spectroscopy during electrochemical

  16. 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…

  17. 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)

  18. 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.

  19. Measurement system for nitrous oxide based on amperometric gas sensor

    NASA Astrophysics Data System (ADS)

    Siswoyo, S.; Persaud, K. C.; Phillips, V. R.; Sneath, R.

    2017-03-01

    It has been well known that nitrous oxide is an important greenhouse gas, so monitoring and control of its concentration and emission is very important. In this work a nitrous oxide measurement system has been developed consisting of an amperometric sensor and an appropriate lab-made potentiostat that capable measuring picoampere current ranges. The sensor was constructed using a gold microelectrode as working electrode surrounded by a silver wire as quasi reference electrode, with tetraethyl ammonium perchlorate and dimethylsulphoxide as supporting electrolyte and solvent respectively. The lab-made potentiostat was built incorporating a transimpedance amplifier capable of picoampere measurements. This also incorporated a microcontroller based data acquisition system, controlled by a host personal computer using a dedicated computer program. The system was capable of detecting N2O concentrations down to 0.07 % v/v.

  20. 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.

  1. 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.

  2. Investigation of passive films on {alpha}{sub 2} and {gamma} titanium aluminides by X-ray photoelectron spectroscopy

    SciTech Connect

    Ziomek-Moroz, M.; Su, W.; Covino, B.S. Jr.

    1999-07-01

    Passive films on {alpha}{sub 2} and {gamma} titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H{sub 2}SO{sub 4}) solutions were studied by x-ray photoelectron spectroscopy (XPS). In NaOH, potentiostatic experiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al present in the outer layer of the passive films. In H{sub 2}SO{sub 4}, passive current densities increased for specimens with increasing Al content. XPS sputter depth profile showed that Al was enriched in outer layers of the passive films. These results indicated that the passive film dissolution rates increased with increasing amounts of Al in the passive film for titanium aluminides.

  3. Investigation of passive films on alpha2 and gamma titanium aluminides by X-ray photoelectron spectroscopy

    SciTech Connect

    Ziomek-Moroz, M.; Su, W.; Covino, Bernard S., Jr.

    1999-07-01

    Passive films on alpha2 and gamma titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H2SO4) solutions were studied by x-ray photoelectron microscopy (XPS). In NaOH, potentiostatic experiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al present in the outer layer of the passive films. In H2SO4, passive current densities increased for specimens with increasing Al content. XPS sputter depth profile showed that Al was enriched in outer layers of the passive films. These results indicated that the passive film dissolution rate increased with increasing amounts of Al in the passive film for titanium aluminides.

  4. Development of galvanostatic Fourier transform electrochemical impedance spectroscopy.

    PubMed

    Nam, Kwang-Mo; Shin, Dong-Hyup; Jung, Namchul; Joo, Moon G; Jeon, Sangmin; Park, Su-Moon; Chang, Byoung-Yong

    2013-02-19

    Here, we report development of the galvanostatic Fourier transform electrochemical impedance spectroscopy (FTEIS), which monitors impedance of electrochemical reactions activated by current steps. We first derive relevant relations for potential change upon application of a step current, obtain impedances theoretically from the relations by simulation, and verify them with experimental results. The validity of the galvanostatic FTEIS technique is demonstrated by measuring impedances of a semiconductive silicon wafer using the conventional frequency response analysis (FRA), the potentiostatic FTEIS, and the galvanostatic FTEIS methods, and the results are in excellent agreement with each other. This work is significant in that the galvanostatic FTEIS would allow one to record impedance changes during charge/discharge cycles of secondary batteries and fuel cells as well as electrochemically irreversible systems which may produce noise level chronoamperometric currents by potentiostatic techniques.

  5. A gold-gold oil microtrench electrode for liquid-liquid anion transfer voltammetry.

    PubMed

    Dale, Sara E C; Chan, Yohan; Bulman Page, Philip C; Barnes, Edward O; Compton, Richard G; Marken, Frank

    2013-07-01

    Two flat gold electrodes are placed vis-à-vis with an epoxy spacer layer that is etched out to give a ca. 100 μm-deep electrochemically active trench. A water-insoluble oil phase, here the redox system N,N-diethyl-N'N'-didodecyl-phenylenediamine (DDPD) in 4-(3-phenylpropyl)-pyridine (PPP), is immobilized into the trench to allow anion transfer upon oxidation of DDPD (oil) to DDP⁺ (oil). In "mono-potentiostatic mode" quantitative transfer/expulsion of anions into the trench oil phase occurs. However, in "bi-potentiostatic mode" feedback currents dominated by rapid plate-to-plate diffusion normal to the electrode surfaces are observed. Comparison of "normal" diffusion and "lateral" diffusion shows that the rate of diffusion-migration charge transport across the oil film is anion hydrophobicity dependent.

  6. 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.

  7. Origami microfluidic paper-analytical-devices (omPAD) for sensing and diagnostics.

    PubMed

    Punjiya, Meera; Chung Hee Moon; Yu Chen; Sonkusale, Sameer

    2016-08-01

    Recent research activities in the area of low-cost sensing and diagnostics that are realized on cellulosic paper substrate are presented. First a three-dimensional origami paper-based analytical device (omPAD) with multiple electrochemical sensors, an integrated sample reservoir and tight integration with a custom CMOS potentiostat is presented. Second, an optical sensor array with built-in microfluidic channel for sample delivery is presented. The sensors are fabricated using a combination of wax printing and screen-printing using a solution based approach in ambient conditions without the need for expensive fabrication equipment or a cleanroom. Readout is based on using existing consumer grade electronic devices like flatbed scanner (for optical sensor) or custom designed CMOS potentiostat (for electrochemical sensors). Together the 3D paper-based analytical device with integrated sensor, microfluidics and portable readout instrumentation demonstrates a low-cost, self-contained system suitable for sensing and point-of-care diagnostics.

  8. Titania nanotube arrays surface-modified with ZnO for enhanced photocatalytic applications

    SciTech Connect

    Nageri, Manoj; Kalarivalappil, Vijila; Vijayan, Baiju K.; Kumar, Viswanathan

    2016-05-15

    Highlights: • Heterostructures of TNA/ZnO synthesised through potentiostatic anodisation followed by hydrothermal method. • Evaluation of morphological features of the heterostructure with hydrothermal processing time. • Correlation of photocatalytic activity of the hetrostructure with its morphology and surface texture. - Abstract: Well ordered titanium dioxide nanotube arrays (TNA) of average diameter 129 nm and wall thickness of 25 nm were fabricated through potentiostatic anodisation of titanium (Ti) metal substrates. Such TNA were subsequently surface-modified with various amounts of zinc oxide (ZnO) nanopowders using hydrothermal technique to obtain heterogeneous TNA/ZnO nanostructures. The crystalline phase and surface microstructure of the heterostructures were determined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy respectively. The morphology of the heterostructures strongly depended on the hydrothermal conditions employed. The photocatalytic activity of the heterostructures have also been investigated and correlated with their surface morphology and texture.

  9. Corrosion Fatigue and Electrochemical Reactions in Modified HY130 Steel.

    DTIC Science & Technology

    1986-05-01

    techniques the current decay transient is measured under potentiostatic conditions after a clean metal surface Is suddenly exposed to an electrolyte. The...each test, the working electrode was polished with 4/0 Emery paper and was cleaned with methanol in an ultrasonic cleaner. After rinsing with distilled...specimen surface was covered with water which ensured against exposure to air during transfer from the pre-cleaning cell to the main test cell. After

  10. Dual constant composition method and its application to studies of phase transformation and crystallization of mixed phases

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, A.; Zhang, Jingwu; Nancollas, G. H.

    1991-08-01

    In a novel approach, a dual constant composition (DCC) technique has been developed for the investigation of concurrent dissolution and growth processes such as crystalline phase transformation, as well as growth of mixed crystalline phases. DCC utilizes two potentiostats and electrode sets to control simultaneous reactions in the same medium. The kinetics of concurrent dissolution or growth of dicalcium phosphate dihydrate (DCPD) and the growth of octacalcium phosphate (OCP) were studied.

  11. Characterization of p-Type CdTe Electrodes in Acetonitrile/Electrolyte Solutions. Nearly Ideal Behavior from Reductive Surface Pretreatments.

    DTIC Science & Technology

    1983-06-30

    spectra were obtained by interfacing a PAR Model 6001 photoacoustic spectrmter with a potentiostat. The photoacoustic sample cell was replaced by a single...underlying (bulk) CdTe; deconvolution of this rather broad (FHM -1.8 eV) set of bands yields two sets of bands separated by -1 eV, the difference... Code 413 Attn: Mr. Joe McCartney 800 North Quincy Street San Diego, California 92152 Arlington, Virginia 22217 2 Naval Weapons Center ONR Pasadena

  12. Effect of Temperature on the Corrosion Resistance of Nitrogen Bearing AL6X and 904L Stainless Steels

    DTIC Science & Technology

    1988-10-01

    low N alloys was performed following potentiostatic polarization in the above solutions at various solution temperatures . All XPS measurements were...the higher SN steel consistently exhibited higher breakdown potentials than the low N steel as the temperature was "raised. Below 400 C, both alloys...critical current density of the low N alloy in almost doubled that of the high N alloy. When the temperature is further raised to 400 C, the low N

  13. Demonstration of lithographic patterning in measurements of general and localized corrosion on alloy 22

    SciTech Connect

    Bedrossian, P J; Farmer, J C

    1999-07-01

    We have demonstrated a new technique capable of detecting generalized corrosion of metallographically-polished materials with nanometer-scale precision. After exposing a lithographically-patterned coupon of Alloy 22 to an electrolyte in a potentiostatically-controlled cell for twenty-four hours, we detected the loss of up to 130nm of metal. In addition, ''wormholes'' were detected at certain points of intersection of three grain boundaries.

  14. 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.

  15. Chemistry-Structure Interrelationships for Calcareous Deposits as Stand Alone Coatings.

    DTIC Science & Technology

    1986-01-01

    HY80 10/14/86 72 hrs. -0- HY8 0 10/ 14/86 168 hirs. 131 00 RPO RPA 4000 - Z (ohms) Figure 29 Nyquist plot for HY80 Steel in Seawater. Presence of...stainless steel shaft between Delrin spacers (Fig. 3). A platinized niobium mesh counter electrode encircles the steel specimen. Cell potential is...increased hydroxide production. Combined Galvanostatic/Potentiostatic Control From the previous data it can be noted that the steel surface polarized more

  16. Studying localized corrosion using liquid cell transmission electron microscopy

    DOE PAGES

    Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; ...

    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. [Use of corrosion inhibitors during the sterilization and disinfection of medical instruments].

    PubMed

    Talalina, A S; Kochanova, L G; Anan'eva, A I; Romanova, A A

    1984-01-01

    The search of corrosion inhibitors reducing the corrosive action of the sterilizing and disinfecting media has been performed in order to protect instruments made of metals against corrosion during these processes. The program of the investigations includes potentiodynamic and potentiostatic measurements and full-scale tests. The infection of the sodium benzoate or potassium gluconate into the disinfecting chloramine solution and sterilizing hydrogene peroxide solution has been shown to improve the resistance to the corrosion for medical instruments made of carbon steel.

  18. Electrochemical synthesis and characterization of Cu2Se nanowires

    NASA Astrophysics Data System (ADS)

    Kaur, Harmanmeet; Kaur, Jaskiran; Singh, Lakhwant; Singh, Surinder

    2013-12-01

    Copper Selenide (Cu2Se) nanowires were successfully fabricated via potentiostatic electrodeposition using polycarbonate membranes (Whatmann, USA) with nominal pore diameter of 100 nm. The morphology of the so fabricated nanowires was examined by field emission scanning electron microscopy (FE-SEM). Later the samples were characterized for their structural, optical and electrical properties by XRD, UV-visible spectroscopy and I-V respectively.

  19. 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.

  20. An Investigation of the Electrode Kinetics and Electrochemistry of Refractory Metal Deposition.

    DTIC Science & Technology

    1986-07-01

    can be used to generate a pulsed current waveform, as shown in Figure 8a from the Amel 551 potentiostat using a known resist- ance in the control loop...Aloa Fxdaio potentalpriroicdepition a a) I20 mA cm-2 b) -0.45 -0.05 0.35 0.75 1.15 EMV vs. REFERENCE ELECTRODE Fig. 50. Cyclic voltaxnmetric backgroun

  1. 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

  2. In vitro mechanical integrity of hydroxyapatite coated magnesium alloy.

    PubMed

    Kannan, M Bobby; Orr, Lynnley

    2011-08-01

    The mechanical integrity of resorbable implants during service, especially in load bearing orthopaedic applications, is critical. The high degradation rate of resorbable magnesium and magnesium-based implants in body fluid may potentially cause premature in-service failure. In this study, a magnesium alloy (AZ91) was potentiostatically coated with hydroxyapatite at different cathodic voltages in an attempt to enhance the mechanical integrity. The mechanical integrity of the uncoated and hydroxyapatite coated alloys was evaluated after in vitro testing of the coated samples in simulated body fluid (SBF). The uncoated alloy showed 40% loss in the mechanical strength after five days exposure to SBF. However, the hydroxyapatite coated alloy exposed to SBF showed 20% improvement in the mechanical strength as compared to that of the uncoated alloy. The alloy coated potentiostatically at -2 V performed better than the -3 V coated alloy. The cross-sectional analysis of the coatings revealed relatively uniform coating thickness for the -2 V coated alloy, whereas the -3 V coated alloy exhibited areas of uneven coating. This can be attributed to the increase in hydrogen evolution on the alloy during -3 V coating as compared to -2 V coating. The scanning electron micrographs of the in vitro tested alloy revealed that hydroxyapatite coating significantly reduced the localized corrosion of the alloy, which is critical for better in-service mechanical integrity. Thus, the study suggests that the in vitro mechanical integrity of resorbable magnesium-based alloy can be improved by potentiostatic hydroxyapatite coating.

  3. 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.

  4. Influence of cell voltage and current on sulfur poisoning behavior of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Cheng, Zhe; Zha, Shaowu; Liu, Meilin

    The sulfur poisoning behavior of nickel-yttria stabilized zirconia (YSZ) cermet anodes in solid oxide fuel cells (SOFCs) was investigated under both potentiostatic and galvanostatic conditions. While the observed relative drop in cell power output caused by sulfur poisoning decreases as the cell-terminal voltage is lowered potentiostatically (thus more current passing through the cell), it increases as more current is drawn from the cell galvanostatically (thus leading to lower terminal voltage). The apparent contradictory trends in relative performance loss due to sulfur poisoning are explained using a simple equivalent circuit analysis, which was further validated by impedance measurements of cells before and after poisoning by trace amounts of hydrogen sulfide (H 2S) under different conditions. Results suggest that the relative increase in cell internal resistance caused by sulfur poisoning is smaller when more current is drawn from the cell (or the cell-terminal voltage is lowered) under either potentiostatic or galvanostatic conditions. Thus, the increase in anode polarization resistance, not the drop in cell power output, should be used to describe the degree of sulfur poisoning in order to avoid any confusion.

  5. 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.

  6. Pulsed amperometric detection of carbohydrates at gold electrodes with a two-step potential waveform

    SciTech Connect

    Neuburger, G.G.; Johnson, D.C.

    1987-01-01

    A two-step potential waveform is demonstrated for the detection of carbohydrates at a Au electrode in alkaline solutions for application in flow injection and liquid chromatography systems. Pulsed amperometric detection of carbohydrates previously based on a three-step waveform is now extended to potentiostats capable of programming an asymmetric square waveform (e.g., normal-pulse voltammetric waveforms). Detection limits for glucose, sorbitol, and sucrose are approximately 1 nmol in a 50-..mu..L sample (i.e., ca. 200 ng of glucose and 360 ng of sucrose) in a flow injection system.

  7. Electrochemical evaluation of sensitization in austenitic stainless steels using miniaturized specimens*1

    NASA Astrophysics Data System (ADS)

    Inazumi, T.; Bell, G. E. C.; Kiuchi, K.

    1991-03-01

    An electrochemical testing system was developed to evaluate the sensitization of neutron-irradiated austenitic stainless steels using miniaturized disk-type specimens, 3 mm in diameter and 0.25 mm thick. The system consists of a specimen holder in which a miniaturized specimen is mounted as the working electrode, a test cell designed to handle radioactive materials and waste, a computer-controlled potentiostat/galvanostat and a surface preparation equipment. Sensitization of a thermally-aged Ti-modified austenitic stainless steel was successfully detected by the single-loop electrochemical potentiokinetic reactivation (SL-EPR) method.

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

    SciTech Connect

    Ortendahl, T.W.; Hoegstedt, P.O.; Odelius, H.; Noren, 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.

  9. 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.

  10. 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.

  11. Corrosion behavior and inhibitive effects on organotin compounds on nickel in formic acid

    SciTech Connect

    Singh, R.N.; Singh, V.B. . Dept. of Chemistry)

    1993-07-01

    Corrosion behavior of nickel (Ni) in different compositions of formic acid (HCOOH) at 30C was studied using the potentiostatic polarization method. The shape of the polarization curve was evaluated, and the corrosion current density, critical current density, and passive current density were determined. HCOOH solution of different composition were aggressive for the anodic dissolution of Ni, except for 20 and 30 mol/O HCOOH, in which feeble passitivity was observed. The organometallic compounds dibutyltin dichloride, phenyltin trichloride, diphenyltin dichloride, and triphenyltin chloride ([C[sub 6]H[sub 5

  12. 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.

  13. Influence of Uncompensated Solution Resistance Upon the Evaluation of Rate Constants for Rapid Electrochemical Reactions.

    DTIC Science & Technology

    1985-01-01

    1y If nece* and t entity by block numb.,) pfiC TAB u .,nounced E Tu~i’Lf icatlc ~ 1473 \\fIst\\ SECURITY CLASSIFICATION OF THIS PAGE (*%oen Dog; iteeeEo...This procedure was applied to the kinetics of Ru(N 3 )6 3 +/2+ and Ru(NH33)4(O 2)2 +/ 2+ at the mercury-aqueous interface as evaluated using a.c...employed for the a.c. polarographic measurements in ref. 1 involved using a potentiostat (PAR 173/179) featuring positive-feedback iR compensation. 3 ,4 The

  14. Behavior of alloys of the PtPd intermetallic compound with Hf and Zr in the electrosynthesis of peroxo salts

    SciTech Connect

    Toroptseva, N.T.; Vaseva, A.Yu.

    1988-08-10

    The objective of this study was to investigate the behavior of anodes made of alloys of the PtPd intermetallic compound with Hf and Zr in the synthesis of potassium peroxodicarbonates and peroxoborates. The investigations were based on polarization measurements in different regimes on stationary and rotating electrodes, the determination of the current yield of active oxygen in galvano- and potentiostatic syntheses, and the study of the kinetics of catalytic decomposition of peroxide solutions in the presence of the electrode in the range 289-308 K.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Physical and electronic properties of electrodeposited ZnO thin films: dependence on thickness

    NASA Astrophysics Data System (ADS)

    Kıcır, N.; Ozkendir, O. M.; Farha, A. H.; Kırmızıgül, F.; Tuken, T.; Gumus, C.; Çabuk, S.; Erbil, M.; Ufuktepe, Y.

    2015-10-01

    ZnO films have been prepared on indium tin oxide-coated glass substrates, with the help of a potentiostatic method in aqueous zinc nitrate solution. Dependence of crystallographic, optical and electronic properties on thickness of the film is reported and discussed. An increase in the film thickness causes an increase in the band and leads to an improvement in crystallinity and conductivity. The experimental results suggest a strong correlation between electronic and crystal structure of the polycrystalline wurtzite ZnO films. These observations can be used to establish guidelines for optimizing the thickness and orientation to increase the control of device performance based on ZnO thin films.

  20. 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.

  1. Special features in the electroreduction of oxidic molybdenum(VI) forms in tungstate melt

    SciTech Connect

    Shapoval, V.I.; Baraboshkin, A.N.; Kushkhov, K.B.; Malyshev, V.V.

    1988-01-01

    The electrochemical behavior of oxidic molybdenum in tungstate melt was studied under equilibrium and nonequilibrium conditions. Chronovoltammetry and transient polarization was used. The current-voltage curves were recorded with a pulse potentiostat and the experiments were performed in a quartz reactor with platinum and molybdenum electrodes and a platinum crucible served as the melt container and anode. The end product of the oxidic molybdenum forms were shown to depend on the acid-base properties of the melt which allows for choosing the properties and controlling the electrode process.

  2. Specific features of formation and growth mechanism of multilayered quasi-one-dimensional (Co-Ni-Fe)/Cu systems in pores of anodic alumina matrices

    NASA Astrophysics Data System (ADS)

    Trukhanov, A. V.; Grabchikov, S. S.; Vasiliev, A. N.; Sharko, S. A.; Mukhurov, N. I.; Gasenkova, I. V.

    2014-09-01

    A method for fabricating multilayered quasi-one-dimensional ferromagnet-diamagnet systems is described by the example of Co-Ni-Fe/Cu nanowires. The fabrication is implemented in a unified technological cycle from a combined electrolyte by pulsed potentiostatic electrodeposition. Regimes of the formation of layers of different systems, from pure ferromagnetic metals to alloys on their basis, are described. Mechanisms of nanowire growth are proposed. The distribution of chemical elements in the layers is investigated as a function of the electrolyte composition and the fabrication conditions. The nanowire microstructure is investigated by high-resolution scanning electron microscopy.

  3. History effects in lithium-oxygen batteries: how initial seeding influences the discharge capacity.

    PubMed

    Rinaldi, Ali; Wijaya, Olivia; Hoster, Harry E; Yu, Denis Y W

    2014-05-01

    In laboratory experiments, Li-O2 systems show "sudden death" at capacities far below the theoretical value. Identifying how discharge products limit the total capacity is crucial in Li-O2 system. We investigated the effect of Li2O2 seed layer deposited on carbon cathode under potentiostatic conditions at increasing overpotentials to the subsequent slow discharge at galvanostatic condition. The discharge capacity attainable in the second step is found to vary by more than a factor of 3 depending on the history, i.e., the seed layer. These results provide evidence that the battery history is decisive for the total discharge capacities.

  4. Detection of cadmium sulphide nanoparticles by using screen-printed electrodes and a handheld device

    NASA Astrophysics Data System (ADS)

    Merkoçi, Arben; Humberto Marcolino-Junior, Luiz; Marín, Sergio; Fatibello-Filho, Orlando; Alegret, Salvador

    2007-01-01

    A simple method based on screen-printed electrodes and a handheld potentiostatic device is reported for the detection of water soluble CdS quantum dots modified with glutathione. The detection method is based on the stripping of electrochemically reduced cadmium at pH 7.0 by using square wave voltammetry. Various parameters that affect the sensitivity of the method are optimized. QD suspension volumes of 20 µl and a number of around 2 × 1011 CdS quantum dots have been able to be detected. The proposed method should be of special interest for bioanalytical assays, where CdS quantum dots can be used as electrochemical tracers.

  5. Over 95% of large-scale length uniformity in template-assisted electrodeposited nanowires by subzero-temperature electrodeposition

    PubMed Central

    2011-01-01

    In this work, we report highly uniform growth of template-assisted electrodeposited copper nanowires on a large area by lowering the deposition temperature down to subzero centigrade. Even with highly disordered commercial porous anodic aluminum oxide template and conventional potentiostatic electrodeposition, length uniformity over 95% can be achieved when the deposition temperature is lowered down to -2.4°C. Decreased diffusion coefficient and ion concentration gradient due to the lowered deposition temperature effectively reduces ion diffusion rate, thereby favors uniform nanowire growth. Moreover, by varying the deposition temperature, we show that also the pore nucleation and the crystallinity can be controlled. PMID:21781335

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. TiC supported Pt-Ir electrocatalyst prepared by a plasma process for the oxygen electrode in unitized regenerative fuel cells

    NASA Astrophysics Data System (ADS)

    Sui, Sheng; Ma, Lirong; Zhai, Yuchun

    Unitized regenerative fuel cells (URFCs) have become more attractive for some time due to its potentially wide energy storage application such as in fields of space and renewable energy. In this study, TiC supported Pt-Ir electrocatalysts (Pt-Ir/TiC) for oxygen electrode in URFCs were synthesized, respectively, by chemical reduction process and plasma reduction process. Their physical and electrochemical properties are characterized and compared using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), cyclic voltammogram (CV), potentiostatic technique, and electrochemical impedance spectroscopy (EIS). The results from XRD, XPS and TEM demonstrate that the plasma process gives a finer metal crystals and higher metal dispersion on the TiC support. The CV, polarization, potentiostatic and EIS results show that the Pt-Ir/TiC electrocatalyst prepared by the plasma reduction process is obviously more active than that by the chemical reduction process, in agreement with the above metal-dispersion observations. The plasma process is a promising way for the preparation of supported electrocatalysts.

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

    PubMed Central

    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. 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.

  13. Waste water derived electroactive microbial biofilms: growth, maintenance, and basic characterization.

    PubMed

    Gimkiewicz, Carla; Harnisch, Falk

    2013-12-29

    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 (E(f)) 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.

  14. 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.

  15. A large format in operando wound cell for analysing the structural dynamics of lithium insertion materials

    NASA Astrophysics Data System (ADS)

    Brant, William R.; Roberts, Matthew; Gustafsson, Torbjörn; Biendicho, Jordi Jacas; Hull, Stephen; Ehrenberg, Helmut; Edström, Kristina; Schmid, Siegbert

    2016-12-01

    This paper presents a large wound cell for in operando neutron diffraction (ND) from which high quality diffraction patterns are collected every 15 min while maintaining conventional electrochemical performance. Under in operando data collection conditions the oxygen atomic displacement parameters (ADPs) and cell parameters were extracted for Li0.18Sr0.66Ti0.5Nb0.5O3. Analysis of diffraction data collected under in situ conditions revealed that the lithium is located on the (0.5 0.5 0) site, corresponding to the 3c Wyckoff position in the cubic perovskite unit cell, after the cell is discharged to 1 V. When the cell is discharged under potentiostatic conditions the quantity of lithium on this site increases, indicating a potential position where lithium becomes pinned in the thermodynamically stable phase. During this potentiostatic step the oxygen ADPs reduce significantly. On discharge, however, the oxygen ADPs were observed to increase gradually as more lithium is inserted into the structure. Finally, the rate of unit cell expansion changed by ∼44% once the lithium content approached ∼0.17 Li per formula unit. A link between lithium content and degree of mobility, disorder of the oxygen positions and changing rate of unit cell expansion at various stages during lithium insertion and extraction is thus presented.

  16. Electrodeposition synthesis and electrochemical properties of nanostructured γ-MnO 2 films

    NASA Astrophysics Data System (ADS)

    Chou, Shulei; Cheng, Fangyi; Chen, Jun

    The thin films of carambola-like γ-MnO 2 nanoflakes with about 20 nm in thickness and at least 200 nm in width were prepared on nickel sheets by combination of potentiostatic and cyclic voltammetric electrodeposition techniques. The as-prepared MnO 2 nanomaterials, which were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were used as the active material of the positive electrode for primary alkaline Zn/MnO 2 batteries and electrochemical supercapacitors. Electrochemical measurements showed that the MnO 2 nanoflake films displayed high potential plateau (around 1.0 V versus Zn) in primary Zn/MnO 2 batteries at the discharge current density of 500 mA g -1 and high specific capacitance of 240 F g -1 at the current density of 1 mA cm -2. This indicated the potential application of carambola-like γ-MnO 2 nanoflakes in high-power batteries and electrochemical supercapacitors. The growth process for the one- and three-dimensional nanostructured MnO 2 was discussed on the basis of potentiostatic and cyclic voltammetric techniques. The present synthesis method can be extended to the preparation of other nanostructured metal-oxide films.

  17. 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

  18. The corrosion behavior and microstructure of high-velocity oxy-fuel sprayed nickel-base amorphous/nanocrystalline coatings

    NASA Astrophysics Data System (ADS)

    Dent, A. H.; Horlock, A. J.; McCartney, D. G.; Harris, S. J.

    1999-09-01

    The corrosion characteristics of two Ni-Cr-Mo-B alloy powders sprayed by the high-velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5 M H2SO4. The deposits were also microstructurally characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) (utilizing both secondary electron and backscattered electron modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline face centered cubic (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallization of the amorphous matrix has also been observed in the form of cellular crystals with a fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained α-Cr2O3, though regions of the spinel oxide NiCr2O4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5 M H2SO4, as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300 mV saturated calomel electrode (SCE) and passive region current densities of ˜1 mA/cm2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit occurred.

  19. 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.

  20. Growth and etch rate study of low temperature anodic silicon dioxide thin films.

    PubMed

    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.

  1. 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.

  2. 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.

  3. Effects of sensitization and crevices on critical cracking potential for SCC of Alloy 600

    SciTech Connect

    Anzai, H.; Kuniya, J.; Shoji, T.; Yoshida, K.

    1992-12-31

    Effects of sensitization and crevices on critical cracking potential for stress corrosion cracking (SCC) of Alloy 600 were evaluated by slow strain rate tests (SSRTs). Tests were conducted under both potentiostatic controlled, and under free corrosion potential, conditions. For the former, boric acid and lithium hydroxide were added to pure water to maintain sufficient conductivity. Crevices were formed by inter-granular corrosion and wrapping stainless steel foil around the specimen. All tests were performed in 288{degrees}C water and applied strain rate was 7x10{sup {minus}7} (1/s). For the potentiostatic controlled condition, it was found that above a certain threshold potential SCC susceptibility increased with increasing applied potential. Sensitization lowered the critical cracking potential by around 200mV and inter-granular crevices shifted it even lower, by about 250mV. The critical cracking potentials obtained were not less than 200mV vs SHE, which is higher than those of sensitized stainless steel (0 to -230mV) and low alloy steel (-100 to -250mV).

  4. 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.

  5. 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.

  6. Pin-based electrochemical glucose sensor with multiplexing possibilities.

    PubMed

    Rama, Estefanía C; Costa-García, Agustín; Fernández-Abedul, M Teresa

    2017-02-15

    This work describes the use of mass-produced stainless-steel pins as low-cost electrodes to develop simple and portable amperometric glucose biosensors. A potentiostatic three-electrode configuration device is designed using two bare pins as reference and counter electrodes, and a carbon-ink coated pin as working electrode. Conventional transparency film without any pretreatment is used to punch the pins and contain the measurement solution. The interface to the potentiostat is very simple since it is based on a commercial female connection. This electrochemical system is applied to glucose determination using a bienzymatic sensor phase (glucose oxidase/horseradish peroxidase) with ferrocyanide as electron-transfer mediator, achieving a linear range from 0.05 to 1mM. It shows analytical characteristics comparable to glucose sensors previously reported using conventional electrodes, and its application for real food samples provides good results. The easy modification of the position of the pins allows designing different configurations with possibility of performing simultaneous measurements. This is demonstrated through a specific design that includes four pin working-electrodes. Different concentrations of antibody labeled with alkaline phosphatase are immobilized on the pin-heads and after enzymatic conversion of 3-indoxylphosphate and silver nitrate, metallic silver is determined by anodic stripping voltammetry.

  7. 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

  8. 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.

  9. 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

    2016-08-23

    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.

  10. 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).

  11. Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.

    PubMed

    Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

    2013-03-01

    In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples.

  12. Bioelectrochemical reduction of CO(2) to CH(4) via direct and indirect extracellular electron transfer by a hydrogenophilic methanogenic culture.

    PubMed

    Villano, Marianna; Aulenta, Federico; Ciucci, Costanza; Ferri, Tommaso; Giuliano, Antonio; Majone, Mauro

    2010-05-01

    This study describes the performance of a microbial biocathode, based on a hydrogenophilic methanogenic culture, capable of reducing carbon dioxide to methane, at high rates (up to 0.055 + or - 0.002 mmol d(-1) mgVSS(-1)) and electron capture efficiencies (over 80%). Methane was produced, at potentials more negative than -650 mV vs. SHE, both via abiotically produced hydrogen gas (i.e., via hydrogenophilic methanogenesis) and via direct extracellular electron transfer. The relative contribution of these two mechanisms was highly dependent on the set cathode potential. Both cyclic voltammetry tests and batch potentiostatic experiments indicated that the capacity for extracellular electron transfer was a constitutive trait of the hydrogenophilic methanogenic culture. In principle, both electrons and carbon dioxide required for methane production could be obtained from a bioanode carrying out the oxidation of waste organic substrates.

  13. Ion beam-assisted template synthesis of nanowires on semiconducting substrate

    NASA Astrophysics Data System (ADS)

    Kaur, Jaskiran; Singh, Surinder; Kanjilal, Dinakar

    2013-08-01

    In this paper, we have studied the electrical properties of the randomly distributed metallic (Cu, Ni and Fe) nano-/micro wires on the silicon substrate. Deposition was carried out potentiostatically into the pores of the track-etch polycarbonate membrane spin coated onto the Si substrate. Spin coated films were irradiated with 150 MeV Ni (+11) ions at a fluence of 5E8 ions/cm2, followed by Ultra-Violet (UV) irradiation and chemically etching in aqueous NaOH (6N, at room temperature). The size, shape and morphology of the synthesized nano-/micro structures is strongly dependent on the preparation conditions such as deposition potential, current density, electrolyte and etching conditions. Later, morphological and electrical properties of the so-deposited nano-/micro structures were studied.

  14. Polymer electrolyte fuel cell performance degradation at different synchrotron beam intensities.

    PubMed

    Eller, Jens; Büchi, Felix N

    2014-01-01

    The degradation of cell performance of polymer electrolyte fuel cells under monochromatic X-ray irradiation at 13.5 keV was studied in galvanostatic and potentiostatic operation modes in a through-plane imaging direction over a range of two orders of magnitude beam intensity at the TOMCAT beamline of the Swiss Light Source. The performance degradation was found to be a function of X-ray dose and independent of beam intensity, whereas the degradation rate correlates with beam intensity. The cell performance was more sensitive to X-ray irradiation at higher temperature and gas feed humidity. High-frequency resistance measurements and the analysis of product water allow conclusions to be drawn on the dominating degradation processes, namely change of hydrophobicity of the electrode and sulfate contamination of the electrocatalyst.

  15. Dissolution rate of cadmium from dental gold solder alloys.

    PubMed

    Bergman, M; Ginstrup, O

    1975-01-01

    The dissolution rate of cadmium from six different dental gold solder alloys was determined in an in vitro potentiostatic study. The measurements were made in the potential range 740--880 mV and attempts have been made to extrapolate the results to a potential region that might in reality occur in the oral cavity. For comparison the dissolution rates of copper and zinc were also determined. Electrochemically the most interesting quantity was the logarithm of the dissolution rate because it is a linear function of the applied potential. This linear relationship was given by the Tafel equation. The dissolution rate of cadmium was shown to be rather small even under circumstances which may be said to represent very unfavourable conditions within the oral cavity.

  16. 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.

  17. 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.

  18. An amperometric non-enzymatic glucose sensor by electrodepositing copper nanocubes onto vertically well-aligned multi-walled carbon nanotube arrays.

    PubMed

    Yang, Jiang; Zhang, Wei-De; Gunasekaran, Sundaram

    2010-09-15

    A non-enzymatic glucose (Glc) sensor was developed by potentiostatically electrodepositing metallic Cu nanocubes from a precursor solution onto vertically well-aligned multi-walled carbon nanotube arrays (MWCNTs). The electrochemical characteristics of the sensor were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor shows significantly higher electrocatalytic activity to the oxidation of Glc in 0.1M NaOH alkaline solution after modification of Cu nanocubes than before. The sensor response is rapid (<1s) and highly sensitive (1096 μA mM(-1) cm(-2)) with a wide linear range (up to 7.5 mM) and low detection limit (1.0 μM at signal/noise ratio (S/N)=3); it also exhibits high stability and specificity to Glc and performs very well in detecting of Glc concentration in human blood serum.

  19. Dissolution kinetics at edge dislocation site of (1 1 1) surface of copper crystals

    NASA Astrophysics Data System (ADS)

    Imashimizu, Y.

    2011-03-01

    For the study of the dissolution kinetics at dislocation site of crystal surface, copper crystals were anodically dissolved under several different conditions of potentiostatic electrolysis by using an electrolytic cell. The overpotential and temperature dependences of the dissolution rates at dislocation-free and edge dislocation sites of (1 1 1) surface were investigated. The experimental results were electrochemically analyzed, and quantitatively discussed by a nucleation model of two-dimensional pit. The critical free energy change for the formation of a two-dimensional pit at edge dislocation site as well as the activation energy at separation of an atom from the active site were estimated. It is concluded that the present estimation of the critical free energy change seems to reasonably consist with the evaluation of the precedent study and also that its value changes in different manners respectively with overpotential and temperature.

  20. Alginate electrodeposition onto three-dimensional porous Co-Ni films as drug delivery platforms.

    PubMed

    García-Torres, J; Gispert, C; Gómez, E; Vallés, E

    2015-01-21

    Three-dimensional porous Co-Ni films/alginate hybrid materials have been successfully prepared by electrodeposition to be used as a steerable magnetic device for drug delivery. Firstly, 3D porous Co-Ni films were prepared as substrates for the subsequent electrodeposition of the alginate biopolymer. Cyclic voltammetry, galvanostatic and potentiostatic studies were performed to establish the best conditions to obtain porous Co-Ni films. The electrochemical experiments were carried out in an electrolyte containing the metal salts and ammonium chloride at low pHs. In a second stage, the electrochemical deposition of alginate as a biocompatible polymer drug delivery carrier was performed. The characteristics of the alginate matrix were investigated in terms of electrochemical properties, morphology and drug release. The hybrid material obtained showed soft-magnetic behavior and drug release indicating its suitability to be used as a steerable magnetic drug delivery device.

  1. Improving the signal-to-noise ratio of an ECL-based sensor using ad hoc carbon nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Sanginario, A.; Giorcelli, M.; Tagliaferro, A.; Demarchi, D.

    2012-07-01

    In this paper, we demonstrate that mechanically modified cylinder-shaped carbon nanotube (CNT) working electrodes (WEs), combined with an averaging processing algorithm, can increase electrogenerated chemiluminescence (ECL) limit of detection by more than one order of magnitude, compared to gold electrodes. With CNT WEs, we obtained a stable light emission that lasts for hundreds of voltammetric cycles. This stability was further exploited to increase the detection limit with a simple algorithm, based on mean calculation. Ad hoc fabricated sensors are characterized with a full-custom potentiostat testbed and software platform, using tris(2,2-bipyridyl)ruthenium (II) as ECL labels. Our measurement results show that the signal-to-noise ratio (SNR) improves by a factor of larger than 20 compared to standard gold WEs to reach a detection limit up to 40 pg μl-1.

  2. 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.

  3. Al-Cd Alloy Formation by Aluminum Underpotential Deposition from AlCl3+NaCl Melts on Cadmium Substrate

    NASA Astrophysics Data System (ADS)

    Jovićević, Niko; Cvetković, Vesna S.; Kamberović, Željko J.; Jovićević, Jovan N.

    2013-02-01

    Aluminum was incorporated into a polycrystalline cadmium electrode surface by underpotential deposition from equimolar AlCl3+ NaCl melt at 473 K, 523 K, and 573 K (200 °C, 250 °C, and 300 °C). The process was studied by linear sweep voltammetry and potentiostatic deposition/galvanostatic striping. The deposits were characterized X-ray diffraction (XRD), Auger electron spectroscopy (AES), and electron probe microanalyzer (EPMA). The electrochemical measurements showed evidence of Cd-Al alloys being formed but they could not be identified. The growth kinetics of the Cd-Al layers of various proportion and depths that depended on temperature and deposition time were described.

  4. 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.

  5. Mass Spectrometry of Polymer Electrolyte Membrane Fuel Cells

    PubMed Central

    Ostroverkh, Anna; Fiala, Roman; Rednyk, Andrii; Matolín, Vladimír

    2016-01-01

    The chemical analysis of processes inside fuel cells under operating conditions in either direct or inverted (electrolysis) mode and their correlation with potentiostatic measurements is a crucial part of understanding fuel cell electrochemistry. We present a relatively simple yet powerful experimental setup for online monitoring of the fuel cell exhaust (of either cathode or anode side) downstream by mass spectrometry. The influence of a variety of parameters (composition of the catalyst, fuel type or its concentration, cell temperature, level of humidification, mass flow rate, power load, cell potential, etc.) on the fuel cell operation can be easily investigated separately or in a combined fashion. We demonstrate the application of this technique on a few examples of low-temperature (70°C herein) polymer electrolyte membrane fuel cells (both alcohol- and hydrogen-fed) subjected to a wide range of conditions. PMID:28042492

  6. Mass Spectrometry of Polymer Electrolyte Membrane Fuel Cells.

    PubMed

    Johánek, Viktor; Ostroverkh, Anna; Fiala, Roman; Rednyk, Andrii; Matolín, Vladimír

    2016-01-01

    The chemical analysis of processes inside fuel cells under operating conditions in either direct or inverted (electrolysis) mode and their correlation with potentiostatic measurements is a crucial part of understanding fuel cell electrochemistry. We present a relatively simple yet powerful experimental setup for online monitoring of the fuel cell exhaust (of either cathode or anode side) downstream by mass spectrometry. The influence of a variety of parameters (composition of the catalyst, fuel type or its concentration, cell temperature, level of humidification, mass flow rate, power load, cell potential, etc.) on the fuel cell operation can be easily investigated separately or in a combined fashion. We demonstrate the application of this technique on a few examples of low-temperature (70°C herein) polymer electrolyte membrane fuel cells (both alcohol- and hydrogen-fed) subjected to a wide range of conditions.

  7. Anticorrosion characteristics of a Zn-primer coating in a ballast tank under various chloride concentrations

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Jong; Lee, Seung-Jun

    2010-05-01

    At an open-circuit potential, the anodic polarization curves had very similar values, and no significant differences were observed among the conditions. In the cathodic polarization curves, total residual chloride (TRC) reacted with the Zn-primer coating and created a film that had anticorrosion properties. Therefore, the anticorrosion property improved. With an increase in applied potential in the potentiostatic experiment, the observed surface corrosion occurred due to the dissolution reaction. From Tafel analysis, the corrosion current density had the highest value in natural seawater and the lowest value in the 2 ppm solution. Generally, metals corrode faster with increasing TRC concentration, but with the formation of Zn(OH)2, which has anticorrosion properties, the corrosion resistance of a Zn-primer-coated specimen in seawater can be improved.

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

    PubMed

    Stević, Zoran; Andjelković, Zoran; Antić, Dejan

    2008-03-15

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

  9. 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.

  10. Elucidation of band structure of charge storage in conducting polymers using a redox reaction.

    PubMed

    Contractor, Asfiya Q; Juvekar, Vinay A

    2014-07-01

    A novel technique to investigate charge storage characteristics of intrinsically conducting polymer films has been developed. A redox reaction is conducted on a polymer film on a rotating disk electrode under potentiostatic condition so that the rate of charging of the film equals the rate of removal of the charge by the reaction. The voltammogram obtained from the experiment on polyaniline film using Fe(2+)/Fe(3+) in HCl as the redox system shows five distinct linear segments (bands) with discontinuity in the slope at specific transition potentials. These bands are the same as those indicated by electron spin resonance (ESR)/Raman spectroscopy with comparable transition potentials. From the dependence of the slopes of the bands on concentration of ferrous and ferric ions, it was possible to estimate the energies of the charge carriers in different bands. The film behaves as a redox capacitor and does not offer resistance to charge transfer and electronic conduction.

  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. 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

  13. Electrochemical removal of tannins from aqueous solutions

    SciTech Connect

    Buso, A.; Balbo, L.; Giomo, M.; Farnia, G.; Sandona, G.

    2000-02-01

    The application of electrochemical methods to remove tannins from wastewater was investigated. Gallotannic acid was used as the reference substance. Electrochemical experiments were performed using platinum electrodes. Macroscale potentiostatic or galvanostatic electrolyses were carried out with sodium sulfate or sodium chloride as supporting electrolytes, to analyze direct and indirect oxidation processes. Operating variables such as pH and chloride concentration were considered to determine their influence on the efficiency and energy consumption of the process. The simulation of a pilot plant was carried out with a mathematical model, the parameters of which were determined by fitting of experimental profiles. The results of a preliminary investigation on the oxidation-coagulation process using sacrificial electrodes are also reported.

  14. Electrochemical behaviour of Ti-Ni SMA and Co-Cr alloys in dynamic Tyrode's simulated body fluid.

    PubMed

    Liang, Chenghao; Zheng, Runfen; Huang, Naibao; Wu, Bo

    2010-05-01

    The electrochemical behaviour of Ti-Ni shape memory alloy and Co-Cr alloys were investigated in dynamic Tyrode's simulated body fluid on a Model CP6 Potentiostat/Galvanostat. The results indicated that, for all alloys, the anodic dissolution and the pitting sensitivity increased with the flow rate of the Tyrode's solution increasing while the open-circuit potentials and pitting corrosion potentials decreased with the Tyrode's solution increasing. Pitting corrosion of Ti-Ni alloy was easier than Co-Cr alloys. Since the solution's flow enhanced oxygen transform and made it easy to reach the surface of electrodes, the plateau of oxygen diffusion control was diminished. All these indicated that the cathodic reduction and the corrosion reaction, which was controlled by the electrochemical mass transport process, were all accelerated in dynamic Tyrode's simulated body fluid.

  15. Electrochemical durability of heat-treated carbon nanospheres as catalyst supports for proton exchange membrane fuel cells.

    PubMed

    Lv, Haifeng; Wu, Peng; Wan, Wei; Mu, Shichun

    2014-09-01

    Carbon nanospheres is wildly used to support noble metal nanocatalysts in proton exchange membrane (PEM) fuel cells, however they show a low resistance to electrochemical corrosion. In this study, the N-doped treatment of carbon nanospheres (Vulcan XC-72) is carried out in ammonia gas. The effect of heating treatment (up to 1000 degrees C) on resistances to electrochemical oxidation of the N-doped carbon nanospheres (HNC) is investigated. The resistance to electrochemical oxidation of carbon supports and stability of the catalysts are investigated with potentiostatic oxidation and accelerated durability test by simulating PEM fuel cell environment. The HNC exhibit a higher resistance to electrochemical oxidation than traditional Vulcan XC-72. The results show that the N-doped carbon nanospheres have a great potential application in PEM fuel cells.

  16. Electrodeposition of NiPd alloy from aqueous chloride electrolytes

    NASA Astrophysics Data System (ADS)

    Mech, K.; Wróbel, M.; Wojnicki, M.; Mech-Piskorz, J.; Żabiński, P.; Kowalik, R.

    2016-12-01

    Presented results describing properties of alloys deposited at potentiostatic conditions in Ni2+ - Pd2+ - Cl- - H2O system. Electrolysis parameters were defined based on results of thermodynamic analysis as well as voltammetry coupled with electrochemical quartz crystal microbalance (EQCM). Influence of electrode potential and electrolyte components concentration on alloy composition, morphology and its structure was investigated. Alloys were deposited at different Ni(II) and Pd(II) complexes concentrations. Results indicated possibilities of electrochemical synthesis of alloys of wide composition range. Deposits structure as well as crystallites size were discussed based on results of XRD measurements. Alloys composition was determined with the use of energy dispersive spectroscopy (EDS). Morphology of alloys was characterized with the use of scanning electron microscopy (SEM).

  17. Efficient photoelectrochemical water splitting by anodically grown WO3 electrodes.

    PubMed

    Cristino, Vito; Caramori, Stefano; Argazzi, Roberto; Meda, Laura; Marra, Gian Luigi; Bignozzi, Carlo Alberto

    2011-06-07

    The potentiostatic anodization of metallic tungsten has been investigated in different solvent/electrolyte compositions with the aim of improving the water oxidation ability of the tungsten oxide layer. In the NMF/H(2)O/NH(4)F solvent mixture, the anodization leads to highly efficient WO(3) photoanodes, which, combining spectral sensitivity, an electrochemically active surface, and improved charge-transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol-gel methods. The use of such electrodes results in high water electrolysis yields of between 70 and 90% in 1 M H(2)SO(4) under a potential bias of 1 V versus SCE and close to 100% in the presence of methanol.

  18. 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.

  19. Reduction of Tantalum Pentoxide Using Graphite and Tin-Oxide-Based Anodes via the FFC-Cambridge Process

    NASA Astrophysics Data System (ADS)

    Barnett, Roger; Kilby, Kamal Tripuraneni; Fray, Derek J.

    2009-04-01

    An investigation into the electrochemical reduction of tantalum pentoxide (Ta2O5) to tantalum metal in molten calcium chloride was performed. The oxide was made the cathode, and either graphite or tin oxide rods were selected as the anodes. The experiments were terminated after 8 hours of potentiostatic electrolysis using a two-electrode setup, with the current and anodic potential recorded. The cathode products were analyzed by means of X-ray diffraction, scanning electron microscopy (SEM), and inert-gas fusion analysis. The key result is that tantalum can be produced using either anode, but the tin oxide anode leads to greater current efficiency and a cleaner melt with no significant differences in the product microstructure.

  20. 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.

  1. Effect of microstructure and strain on the degradation behavior of novel bioresorbable iron-manganese alloy implants.

    PubMed

    Heiden, Michael; Kustas, Andrew; Chaput, Kevin; Nauman, Eric; Johnson, David; Stanciu, Lia

    2015-02-01

    Advancing the understanding of microstructural effects and deformation on the degradability of Fe-Mn bioresorbable alloys (specifically, Fe-33%Mn) will help address the current problems associated with designing degradable fracture fixation implants for hard tissues. Potentiostatic polarization tests were conducted on a wide variety of metal samples to examine how different deformation processes affect the instantaneous rate of degradation of Fe-Mn alloys. Large-strain machining (LSM), a novel severe plastic deformation (SPD) technique was utilized during these experiments to modify the degradation properties of the proposed Fe-Mn alloy. It was discovered that Fe-33%Mn after LSM with a rake angle of 0° (effective strain = 2.85) showed the most promising increase in degradation rate compared to as-cast, annealed, and additional deformation conditions (rolled and other LSM parameters) for the same alloy. The mechanisms for enhancement of the corrosion rate are discussed.

  2. Recovery of the actinides by electrochemical methods in molten chlorides using solid aluminium cathode

    SciTech Connect

    Malmbeck, R.; Mendes, E.; Serp, J.; Soucek, P.; Glatz, J.P.; Cassayre, L.

    2007-07-01

    An electrorefining process in molten chloride salts is being developed at ITU to reprocess the spent nuclear fuel. According to the thermochemical properties of the system, aluminium is the most promising electrode material for the separation of actinides (An) from lanthanides (Ln). The actinides are selectively reduced from the fission products and stabilized by the formation of solid and compact actinide-aluminium alloys with the reactive cathode material. In this work, the maximum loading of aluminium with actinides was investigated by potentiostatic and galvano-static electrorefining of U-Pu- Zr alloys. A very high aluminium capacity was achieved, as the average loading was 1.6 g of U and Pu into 1 g of aluminium and the maximum achieved loading was 2.3 g. For recovery of the actinides from aluminium, a process based on chlorination and a subsequent sublimation of AlCl{sub 3} is proposed. (authors)

  3. New Cyclic Voltammetry Method for Examining Phase Transitions on Electrodes: Simulated Results

    NASA Astrophysics Data System (ADS)

    Abou Hamad, Ibrahim; Robb, Daniel; Rikvold, Per Arne

    2007-03-01

    We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The FORC diagram for a discontinuous phase transition is characterized by a negative (unstable) region separating two positive (stable) regions, while such a negative region does not exist for continuous phase transitions. Experimental data for Electrochemical FORC (EC-FORC) analysis could easily be obtained by simple reprogramming of a potentiostat designed for conventional cyclic-voltammetry experiments.I. Abou Hamad, D.T. Robb, P.A. Rikvold, J. Electroanal. Chem., in press.

  4. 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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:27877606

  6. A wide range and high sensitivity four-channel compact electrochemical biosensor for neurotransmitter detection on a microfluidic platform.

    PubMed

    Ghodsevali, Elnaz; Landari, Hamza; Boukadoum, Mounir; Gosselin, Benoit; Miled, Amine

    2016-08-01

    We present a four-channel, high-sensitivity and linearity electrochemical biosensor for neurotransmitter (NT) detection and measurement. Using a multi-channel microfluidic platform makes this biosensor capable of detecting NT-related currents going from nanoamperes to milliamperes, with a sensitivity of the order of picoamperes. Moreover, by using a fully differential potentiostat architecture, the biosensor offers a high common-mode rejection ratio (90 dB), making it appropriate for low-noise and high-sensitive applications. The system was implemented on a 15 mm × 15 mm PCB with direct interface to the microfluidic chambers. It was calibrated with a 5 mM ferrocyanide solution and successfully tested with dopamine at three concentrations. The system shows a minimum sensistivity of 100 pA and consumes 60 mW.

  7. 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.

  8. 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

    2015-09-15

    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.

  9. 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.

  10. Corrosion resistance of polyurethane-coated nitinol cardiovascular stents.

    PubMed

    Mazumder, M M; De, S; Trigwell, S; Ali, N; Mazumder, M K; Mehta, J L

    2003-01-01

    Corrosion of metal stents implanted inside an artery can have two adverse effects: (1) tissue reaction and possible toxic effects from the metal ions leaching out of the stent, and (2) loss of mechanical strength of the stent caused by corrosion. The corrosion resistance of Nitinol (Nickel-Titanium) stents and its modulation with different film thickness of polymer coating was studied against an artificial physiological solution using a Potentiostat/Galvanostat and an electrochemical corrosion cell. The corrosion rate decreased rapidly from 275 microm/year for an uncoated surface down to less than 13 microm/year for a 30 microm thick polyurethane coating. Stainless steel (316L) and Nitinol both contain potentially toxic elements, and both are subject to stress corrosion. Minimization of corrosion can significantly reduce both tissue reaction and structural degradation.

  11. Effect of load deflection on corrosion behavior of NiTi wire.

    PubMed

    Liu, I H; Lee, T M; Chang, C Y; Liu, C K

    2007-06-01

    For dental orthodontic applications, NiTi wires are used under bending conditions in the oral environment for a long period. The purpose of this study was to investigate the effect of bending stress on the corrosion of NiTi wires using potentiodynamic and potentiostatic tests in artificial saliva. The results indicated that bending stress induces a higher corrosion rate of NiTi wires in passive regions. It is suggested that the passive oxide film of specimens would be damaged under bending conditions. Auger electron spectroscopic analysis showed a lower thickness of passive films on stressed NiTi wires compared with unstressed specimens in the passive region. By scanning electron microscopy, localized corrosion was observed on stressed Sentalloy specimens after a potentiodynamic test at pH 2. In conclusion, this study indicated that bending stress changed the corrosion properties and surface characteristics of NiTi wires in a simulated intra-oral environment.

  12. Pitting corrosion resistance of nickel-titanium rotary instruments with different surface treatments in seventeen percent ethylenediaminetetraacetic Acid and sodium chloride solutions.

    PubMed

    Bonaccorso, Antonio; Tripi, Teresa Roberta; Rondelli, Gianni; Condorelli, Guglielmo Guido; Cantatore, Giuseppe; Schäfer, Edgar

    2008-02-01

    This study evaluated the pitting corrosion resistance of nickel-titanium (NiTi) rotary instruments with different surface treatments in 17% ethylenediaminetetraacetic acid (EDTA) and NaCl solutions. Electropolished RaCe instruments were allocated to group A, non-electropolished RaCe instruments to group B, and physical vapor deposition (PVD)-coated Alpha files to group C (10 instruments per group). Electrochemical measurements were carried out by using a potentiostat for galvanic current measurements. On the basis of electrochemical tests, no localized corrosion problems are to be expected in EDTA. In NaCl, pitting potential occurred at higher values for the electropolished and PVD instruments, indicating an increased corrosion resistance. There appears to be a risk of corrosion for NiTi instruments without surface treatments in contact with NaCl. NiTi files with PVD and electropolishing surface treatments showed an increase corrosion resistance.

  13. The effect of coal syngas containing HCl on the performance of solid oxide fuel cells: Investigations into the effect of operational temperature and HCl concentration

    NASA Astrophysics Data System (ADS)

    Trembly, J. P.; Gemmen, R. S.; Bayless, D. J.

    The performance of solid oxide fuel cells (SOFCs) using simulated coal-derived syngas, with and without hydrogen chloride (HCl), was studied. Electrolyte-supported SOFCs were tested potentiostatically at 0.7 V at 800 and 900 °C with simulated coal syngas containing 0, 20, and 160 ppm HCl. The results from the tests without HCl show good performance with little degradation over 100 h of operation. Both 20 and 160 ppm HCl were shown to cause performance losses in the SOFCs after injection into the system. Although the tests presented in this paper show that HCl does cause degradation to SOFC performance, the cell performance was recoverable upon the removal of HCl from the fuel. Also recent results from anticipated Integrated Gasification Combined Cycle IGCC warm/hot-gas-cleanup technologies suggest that HCl will be removed to levels that will not cause any significant performance losses in SOFCs.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Electropolymerization molecularly imprinted polymer (E-MIP) SPR sensing of drug molecules: pre-polymerization complexed terthiophene and carbazole electroactive monomers.

    PubMed

    Pernites, Roderick; Ponnapati, Ramakrishna; Felipe, Mary Jane; Advincula, Rigoberto

    2011-01-15

    A novel chemosensitive ultrathin film with high selectivity was developed for the detection of naproxen, paracetamol, and theophylline using non-covalent electropolymerized molecular imprinted polymers (E-MIP). A series of monofunctional and bifunctional H-bonding terthiophene and carbazole monomers were compared for imprinting these drugs without the use of a separate cross-linker. A key step is the fast and efficient potentiostatic method of washing the template, which facilitated enhanced real-time sensing by surface plasmon resonance (SPR) spectroscopy. Various surface characterizations (contact angle, ellipsometry, XPS, AFM) of the E-MIP film verified the templating and release of the drug from the cross-linked conducting polymer film.

  19. 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.

  20. Electrochemical synthesis of birnessite-type layered manganese oxides for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Nakayama, Masaharu; Kanaya, Taku; Lee, Jong-Won; Popov, Branko N.

    Layered manganese dioxide (MnO 2) films intercalated with Li +, Na + or Mg 2+ ions were synthesized by a one-step electrochemical method. The electrodeposition was potentiostatically performed by applying an anodic potential of 1.0 V vs. Ag/AgCl in an aqueous MnSO 4 solution containing a perchlorate salt of the cation. The electrodeposited oxide films have a birnessite-type layered structure with alkali cations and water molecules between manganese oxide layers. The galvanostatic charge-discharge experiments performed in 1 M LiPF 6-DME/PC solution indicated that the Mg 2+-intercalated MnO 2 electrode exhibits an initial discharge capacity as large as 140 mAh g -1 and it shows a better capacity retention during cycling as compared with the Li +- or Na +-intercalated MnO 2 electrode.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. In Situ Characterization of Triboelectrochemical Effects on Topography of Patterned Copper Surfaces

    NASA Astrophysics Data System (ADS)

    Joo, Sukbae; Liang, Hong

    2013-06-01

    The topographic response of patterned copper surfaces to chemical-mechanical polishing (CMP) was investigated using a triboelectrochemical approach. Experimental methods include using a combined system containing a tribometer and a potentiostat. Results showed that more step height reduction and lower average surface roughness were obtained via CMP in acidic than in alkaline slurry. The increased contact area between wafer, pad, and abrasives was associated with the increase in friction. It was found that pH-dependent oxide formation and removal dominate the step height reduction for both acidic and alkaline slurries. The in situ approach pinpointed interactions between mechanical stimulation, chemical reaction, and electrochemical passivation. This research is beneficial to understanding triboelectrochemistry in Cu chemical-mechanical polishing of patterned wafers, an important application in semiconductor manufacturing.

  6. The resistance of high frequency inductive welded pipe to grooving corrosion in salt water

    SciTech Connect

    Duran, C.; Triess, E.; Herbsleb, G.

    1986-09-01

    When exposed to neutral, salt-containing waters, electric resistant welded pipe in carbon and low alloy steels with increased sulfur contents may suffer preferential corrosion attack in the weld area. Because of its appearance, this type of corrosion is called grooving corrosion. The susceptibility to grooving corrosion may be determined and quantitatively described by means of an accelerated potentiostatic exposure test. The importance of type, concentration, and temperature of the electrolytic solution; potential; test duration; and the sulfur content of the steel in the accelerated corrosion test and the susceptibility of steels to grooving corrosion are described. Line pipe in high frequency inductive (HFI) welded carbon and low alloy steels are resistant to grooving corrosion particularly because of their low sulfur content.

  7. On-site fuel electroanalysis: determination of lead, copper and mercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes.

    PubMed

    Almeida, Eduardo S; Richter, Eduardo M; Munoz, Rodrigo A A

    2014-07-21

    The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067 mol L(-1) HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2 μg L(-1)) for a 240 s deposition time, linear range between 5 and 300 μg L(-1), and adequate recovery values (96-104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification.

  8. Electrochemical preparation and characterization of polypyrrole/stainless steel electrodes decorated with gold nanoparticles.

    PubMed

    Gutiérrez Pineda, Eduart; Alcaide, Francisco; Rodríguez Presa, María J; Bolzán, Agustín E; Gervasi, Claudio A

    2015-02-04

    The electrosynthesis and characterization of polypyrrole(PPy)/stainless steel electrodes decorated with gold nanoparticles and the performance of the composite electrode for sensing applications is described. PPy films were grown in potassium perchlorate and sodium salicylate solutions under comparable electropolymerization conditions. Polymer films prepared in the presence of perchlorate ions exhibited worm-like structures, whereas columnar structures were obtained in salicylate-containing solutions. Voltammetric response of PPy films prepared in salicylate solutions was more reversible. PPy films were decorated with gold nanoparticles obtained by a double step potentiostatic electrodeposition routine that allowed fine control of deposit characteristics. Analysis of deposits was performed by means of SEM and confocal Raman spectroscopy. The electrocatalytic activity of the Au/PPy electrodes was assessed for the electro-oxidation of hydrazine and hydroxylamine. Results showed a successful optimization of the route of synthesis that rendered nanocomposite electrode materials with promising applications in electrochemical sensing.

  9. Electrochemical grafting of poly(3,4-ethylenedioxythiophene) into a titanium dioxide nanotube host network.

    PubMed

    Janáky, Csaba; Bencsik, Gábor; Rácz, Arpád; Visy, Csaba; de Tacconi, Norma R; Chanmanee, Wilaiwan; Rajeshwar, Krishnan

    2010-08-17

    This study focuses on electrodeposition for infiltrating in situ a conducting polymer such as poly(3,4-ethylenedioxythiophene) (PEDOT) into a host titanium dioxide (TiO(2)) nanotube array (NTA) framework. The TiO(2) NTA was electrosynthesized on titanium foil in turn by anodization in a fluoride-containing medium. The PEDOT layer was electrografted into the TiO(2) NTA framework using a two-step potentiostatic growth protocol in acetonitrile containing supporting electrolyte. The nanoscopic features of oligomer/polymer infiltration and deposition in the NTA interstitial voids were monitored by field-emission scanning electron microscopy. Systematic changes in the nanotube inner diameter and the wall thickness afforded insights into the evolution of the TiO(2)NTA/PEDOT hybrid assembly. This assembly was subsequently characterized by UV-visible diffuse reflectance, cyclic voltammetry, and photoelectrochemical measurements. These data serve as a prelude to further use of these hybrids in heterojunction solar cells.

  10. Electrochemistry of conductive polymers 38. Electrodeposited poly(3,4-ethylenedioxy-thiophene) studied by current sensing atomic force microscopy.

    PubMed

    Han, Dong-Hun; Kim, Jae-Woo; Park, Su-Moon

    2006-08-03

    Electrical and morphological properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films electrodeposited on gold-on-silicon electrodes by galvanostatic, potentiostatic, and potentiodynamic methods have been determined using current sensing atomic force microscopic experiments. Surface morphologies and vertical conductivities of PEDOT films were affected by the experimental parameters including the preparation method, the current density, the potential, and the potentiodynamic cyclic number. Band gaps obtained from current-voltage curves of dedoped PEDOT were in excellent agreement with those obtained from absorption spectra. When the film thickness was increased on the gold-on-silicon electrode, the topographic images were not very well defined due to the high roughness but conductivities increased significantly in all the galvanostatically, potetiostatically, and potentiodynamically grown PEDOT films.

  11. Microdialysis Sampling Coupled to Microchip Electrophoresis with Integrated Amperometric Detection on an All Glass Substrate

    PubMed Central

    Scott, David E.; Grigsby, Ryan; Lunte, Susan M.

    2013-01-01

    The development of an all-glass separation-based sensor using microdialysis coupled to microchip electrophoresis with amperometric detection is described. The system includes a flow-gated interface to inject discrete sample plugs from the microdialysis perfusate into the microchip electrophoresis system. Electrochemical detection was accomplished with a platinum electrode in an in-channel configuration using a wireless electrically isolated potentiostat. To facilitate bonding around the in-channel electrode, a fabrication process was employed that produced a working and a reference electrode flush with the glass surface. Both normal and reversed polarity separations were performed with this sensor. The system was evaluated in vitro for the continuous monitoring of the production of hydrogen peroxide from the reaction of glucose oxidase with glucose. Microdialysis experiments were performed using a BASi loop probe with an overall lag time of approximately five minutes and a rise time of less than 60 seconds. PMID:23794474

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  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. The Electrowetting and Corrosion Characterizations of Anodized As-Prepared Titanium Dioxide Nanotube

    NASA Astrophysics Data System (ADS)

    Dang, Trung-Dung; Bui, Thi Thanh Huyen

    2017-03-01

    Uniform titanium dioxide (TiO2) nanotube arrays were prepared via the anodizing of titanium electrodes in hydrofluoric acid containing glycerol. The relationship between the electrochemical fabrication process and nanotube formation was studied. The uniformity and diameter of the titanium dioxide nanotube can be controlled by the anodizing voltage and hydrofluoric acid and glycerol concentration. The wettability can be tuned by coating the titanium electrode with the synthesized titanium dioxide nanotube as demonstrated by the contact angle measurement. The hydrophilic characteristic of the anodized electrode surface decreases when the diameter of the titanium dioxide nanotube decreases. To evaluate the corrosion characteristic of the anodized as-prepared electrode, the electrochemical measurement (potentiostatic) was studied in a physiological saline solution. The results show high corrosion resistance of the anodized electrode. The successful preparation of these titanium dioxide nanotube electrodes offers high corrosion resistance and wetting controllability for bio-microfluidic device applications.

  18. 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.

  19. Surface enhanced Raman scattering of a lipid Langmuir monolayer at the air-water interface.

    PubMed

    Mangeney, C; Dupres, V; Roche, Y; Felidj, N; Levi, G; Aubard, J; Bernard, S

    Surface enhanced Raman spectra were recorded from a phospholipid monolayer directly at the air-water interface. We used an organized monolayer of negatively charged tetramyristoyl cardiolipins as a template for the electrochemical generation of silver deposits. This two-dimensional electrodeposition of silver under potentiostatic control was the substrate for enhancement of Raman spectra. We report the optimized conditions for the Raman enhancement, the microscopic observations of the deposits, and their characterization by atomic force microscopy. Laser excitation at 514.5 nm leads to intense and reproducible surface enhanced Raman scattering spectra recorded in situ from one monolayer of cardiolipin, using 0.5 mol % of 10N nonyl acridine orange or 5 mol % of acridine in the film, and demonstrates the possibility of estimating the pH at the metal/phospholipidic film interface.

  20. 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.

  1. 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.

  2. 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.

  3. Production of Bulk Metallic Glasses for Use in Airborne Gravity Gradiometry

    NASA Astrophysics Data System (ADS)

    Igel, Joshua

    Bulk metallic glasses (BMGs) are ideal candidates for airborne gravity gradiometer (AGG) flexures due to their unique mechanical properties. In this thesis, the role of processing variables in the production Zr-based BMGs by arc melting and suction casting was investigated and an electrochemical method for determining the degree of crystallization after electric discharge machining (EDM) was examined. Homogenization was most effectively obtained using multiple melting iterations and prolonged melting times. The difference between input and actual Zr concentration was found to be significant in arc melting and suction casting. Superior GFA was obtained using high purity argon purge gas and low purity Zr contrary to the consensus that GFA strictly increases with increasing raw material purities. The use of potentiostatic polarization in 1M NaNO3 for evaluating the degree of crystallization in Zr55Cu 30Al10Ni5 samples after EDM may be feasible due to the dependence of passivation behaviour on the degree of crystallization.

  4. Electro-Mechanical Actuation of Carbon Nanotube Yarns, Sheets, Composites

    NASA Astrophysics Data System (ADS)

    Oh, Jiyoung; Kozlov, Mikhail; Zhang, Mei; Fang, Shaoli; Baughman, Ray

    2011-03-01

    We report preparation of highly conductive carbon nanotube yarns and sheets. The materials aim at such applications as electronic textiles, electro-mechanical actuators, and conductive coatings. The electro-mechanical response of the specimens was measured using custom made force transducer operating in an isometric mode. The measurements were carried out at room temperature in aqueous and organic electrolytes; square-wave potential of variable amplitude was applied with a potentiostat. It was found that the maximum isometric stress generated by nanotube actuators could be as large as 12 MPa. This approaches the stress generation capability of commercial ferroelectrics and is significantly larger than that of natural muscles. A variety of applications of the materials is discussed.

  5. 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.

  6. Cytochrome c dynamics at gold and glassy carbon surfaces monitored by in situ scanning tunnel microscopy

    NASA Astrophysics Data System (ADS)

    Andersen, Jens E. T.; Møller, Per; Pedersen, Marianne V.; Ulstrup, Jens

    1995-02-01

    We have investigated the absorption of cytochrome c on gold and glassy carbon substrates by in situ scanning tunnel microscopy under potentiostatic control of both substrate and tip. Low ionic strength and potential ranges where no Faradaic current flows were used. Cyt c aggregates into flat composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve in time, and structures resembling individual cyt c molecules can be distinguished in the space between the 50 nm structures. Cyt c aggregates also form at glassy carbon but have a different, unbroken character where cyt c both sticks well to the surface and exhibits notable mobility. The observations suggest that characteristic surface specific, internally mobile protein aggregates are formed at both surfaces and that in situ molecular resolution of the STM pictures may have been achieved.

  7. 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 %.

  8. 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.

  9. Hierarchically structured porous cadmium selenide polycrystals using polystyrene bilayer templates.

    PubMed

    Park, Jin Young; Hendricks, Nicholas R; Carter, Kenneth R

    2012-09-18

    In this study, a novel approach is demonstrated to fabricate hierarchically structured cadmium selenide (CdSe) layers with size-tunable nano/microporous morphologies achieved using polystyrene (PS) bilayered templates (top layer: colloidal template) via potentiostatic electrochemical deposition. The PS bilayer template is made in two steps. First, various PS patterns (stripes, ellipsoids, and circles) are prepared as the bottom layers through imprint lithography. In a second step, a top template is deposited that consists of a self-assembled layer of colloidal 2D packed PS particles. Electrochemical growth of CdSe crystals in the voids and selective removal of the PS bilayered templates give rise to hierarchically patterned 2D hexagonal porous CdSe structures. This simple and facile technique provides various unconventional porous CdSe films, arising from the effect of the PS bottom templates.

  10. Detection of cadmium sulphide nanoparticles by using screen-printed electrodes and a handheld device.

    PubMed

    Merkoçi, Arben; Marcolino-Junior, Luiz Humberto; Marín, Sergio; Fatibello-Filho, Orlando; Alegret, Salvador

    2007-01-24

    A simple method based on screen-printed electrodes and a handheld potentiostatic device is reported for the detection of water soluble CdS quantum dots modified with glutathione. The detection method is based on the stripping of electrochemically reduced cadmium at pH 7.0 by using square wave voltammetry. Various parameters that affect the sensitivity of the method are optimized. QD suspension volumes of 20 microl and a number of around 2 x 10(11) CdS quantum dots have been able to be detected. The proposed method should be of special interest for bioanalytical assays, where CdS quantum dots can be used as electrochemical tracers.

  11. Inkjet printed electrode arrays for potential modulation of DNA self-assembled monolayers on gold.

    PubMed

    Li, Yunchao; Li, Paul C H; Parameswaran, M Ash; Yu, Hua-Zhong

    2008-11-15

    In this paper, we report a novel and cost-effective fabrication technique to produce electrode arrays that can be used for monitoring and electrical manipulation of the molecular orientation of DNA self-assembled monolayers (SAMs) on gold. The electrode arrays were prepared from gold coated glass sides or compact discs (CD-Rs) by using standard office inkjet printers without any hardware or software modifications. In this method, electrode arrays of varied shape and size (from submillimeter to centimeter) can be rapidly fabricated and are suitable for standard electrochemical measurements. We were able to use a dual-channel potentiostat to control the electrodes individually and a fluorescence (FL) scanner to image the electrode array simultaneously. With such an integrated modulation setup, the structural switching behavior (from "lying" to "standing" position) and the enhanced hybridization reactivity of thiolate DNA SAMs on gold under potential control have been successfully demonstrated.

  12. Distinguishing nanowire and nanotube formation by the deposition current transients

    PubMed Central

    2012-01-01

    High aspect ratio Ni nanowires (NWs) and nanotubes (NTs) were electrodeposited inside ordered arrays of self-assembled pores (approximately 50 nm in diameter and approximately 50 μm in length) in anodic alumina templates by a potentiostatic method. The current transients monitored during each process allowed us to distinguish between NW and NT formation. The depositions were long enough for the deposited metal to reach the top of the template and form a continuous Ni film. The overfilling process was found to occur in two steps when depositing NWs and in a single step in the case of NTs. A comparative study of the morphological, structural, and magnetic properties of the Ni NWs and NTs was performed using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. PMID:22650765

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

    PubMed

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

    2014-10-01

    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 CoCl2 aqueous solution by X-ray absorption and emission spectroscopy is presented.

  14. Evidence for involvement of an electron shuttle in electricity generation by Geothrix fermentans.

    PubMed

    Bond, Daniel R; Lovley, Derek R

    2005-04-01

    In experiments performed using graphite electrodes poised by a potentiostat (+200 mV versus Ag/AgCl) or in a microbial fuel cell (with oxygen as the electron acceptor), the Fe(III)-reducing organism Geothrix fermentans conserved energy to support growth by coupling the complete oxidation of acetate to reduction of a graphite electrode. Other organic compounds, such as lactate, malate, propionate, and succinate as well as components of peptone and yeast extract, were utilized for electricity production. However, electrical characteristics and the results of shuttling assays indicated that unlike previously described electrode-reducing microorganisms, G. fermentans produced a compound that promoted electrode reduction. This is the first report of complete oxidation of organic compounds linked to electrode reduction by an isolate outside of the Proteobacteria.

  15. Magnetic behavior of as-deposited and annealed CoFe and CoFeCu nanowire arrays by ac-pulse electrodeposition

    NASA Astrophysics Data System (ADS)

    Ramazani, A.; Almasi-Kashi, M.; Golafshan, E.; Arefpour, M.

    2014-09-01

    CoFe and CoFeCu self-organized alloy nanowires were grown into anodic aluminum oxide template by potentiostatic mode of ac-pulse electrodeposition technique and subsequently annealed at 580 °C. The influence of bath composition, off-time between pulses and annealing treatment on the Cu content, microstructure and magnetic properties of CoFeCu nanowire arrays have been discussed. Increasing the off-time between pulses decreased the coercivity and saturation magnetization of the CoFeCu nanowires due to substitution of Co and Fe with Cu atoms which resulted in electroless process. Coercivity and squareness of the annealed samples increased due to improvement of samples crystallinity. Magnetic measurements showed high perpendicular magnetic anisotropy of the nanowires with easy axis parallel to nanowires axis. X-ray diffraction results indicated that annealed CoFeCu nanowires were polycrystalline with two distinct CoFe and Cu phases.

  16. Virtual instrumentation for electro–analytical measurements

    PubMed Central

    Economou, A. S.; Volikakis, G. J.; Efstathiou, C. E.

    1999-01-01

    This paper deals with some applications of Virtual Instrumentation to electroanalytical measurements. Virtual Instruments (VIs) are software programmes that simulate the external appearance and functions of a real instrument on the screen of a computer. In this work, programmes have been developed to control the potential of a working electrode (through a suitable potentiostat), acquire the current response, process the acquired current signal, and control a peristaltic pump and injection valve. The sequence of operations was controlled by the VI. The programmes developed have been applied to amperometric and voltammetric measurements in static and flowing solutions. The Vl package that has been used was Lab VIEW 4.0.1 from National Instruments. PMID:18924841

  17. Lab-on-a-chip sensor for measuring Zn by stripping voltammetry

    NASA Astrophysics Data System (ADS)

    Pei, Xing; Kang, Wenjing; Yue, Wei; Bange, Adam; Wong, Hector R.; Heineman, William R.; Papautsky, Ian

    2012-03-01

    This work reports on continuing development of a lab-on-a-chip sensor for electrochemical detection of heavy metal zinc in blood serum. The sensor consists of a three electrode system, including an environmentally-friendly bismuth working electrode, a Ag/AgCl reference electrode, and a gold auxiliary electrode. By optimizing the electrodeposition of bismuth film, better control of fabrication steps and improving interface between the sensor and potentiostat, repeatability and sensitivity of the lab-on-a-chip sensor has been improved. Through optimization of electrolyte and stripping voltammetry parameters, limits of detection were greatly improved. The optimized sensor was able to measure zinc in in the physiological range of 65-95 μg/dL. Ultimately, with further development and integrated sample preparation sensor system will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for bedside monitoring.

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    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.

  19. 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

  20. Crevice corrosion products of dental amalgam

    SciTech Connect

    Sutow, E.J.; Jones, D.W.; Hall, G.C.; Owen, C.G. )

    1991-07-01

    The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of low- and high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products (Sn4(OH)6Cl2, SnO, and Cu2O) and a new product, CuCl, which formed on high-copper, {gamma} 2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam restorations and the high acidity and high chloride ion concentration associated with crevice corrosion.

  1. Bilayered nanofilm of polypyrrole and poly(DMcT) for high-performance battery cathodes

    NASA Astrophysics Data System (ADS)

    Davoglio, Rogério A.; Biaggio, Sonia R.; Rocha-Filho, Romeu C.; Bocchi, Nerilso

    Bilayered nanofilm electrodes made of polypyrrole (Ppy) and poly-2,5-dimercapto-1,3,4-thiadiazole (poly-DMcT) are produced by electrochemical means onto a carbon-fiber substrate, with the goal of preventing the loss of the electroactive mass of the disulfide and improving the electrode stability during the charge/discharge cycling process. Lightweight and high surface area composites are obtained by potentiostatically depositing a nanometric layer of Ppy onto a carbon fiber piece already supporting a layer of a potentiodynamically obtained poly(DMcT) film. The growth charge/mass ratio for the bilayered polymeric electrode is optimized, leading to a high electrochemical performance cathode with a stable specific capacity of ∼320 mA h g -1 after 100 cycles.

  2. Electron transfer mechanism in Shewanella loihica PV-4 biofilms formed at graphite electrode.

    PubMed

    Jain, Anand; Zhang, Xiaoming; Pastorella, Gabriele; Connolly, Jack O; Barry, Niamh; Woolley, Robert; Krishnamurthy, Satheesh; Marsili, Enrico

    2012-10-01

    Electron transfer mechanisms in Shewanella loihica PV-4 viable biofilms formed at graphite electrodes were investigated in potentiostat-controlled electrochemical cells poised at oxidative potentials (0.2V vs. Ag/AgCl). Chronoamperometry (CA) showed a repeatable biofilm growth of S. loihica PV-4 on graphite electrode. CA, cyclic voltammetry (CV) and its first derivative shows that both direct electron transfer (DET) mediated electron transfer (MET) mechanism contributes to the overall anodic (oxidation) current. The maximum anodic current density recorded on graphite was 90 μA cm(-2). Fluorescence emission spectra shows increased concentration of quinone derivatives and riboflavin in the cell-free supernatant as the biofilm grows. Differential pulse voltammetry (DPV) show accumulation of riboflavin at the graphite interface, with the increase in incubation period. This is the first study to observe a gradual shift from DET to MET mechanism in viable S. loihica PV-4 biofilms.

  3. Deposition of Poly(diphenylamine-co-3-aminobenzonitrile)/Palladium Nanocomposite Film and Evaluation of Electrocatalytic Activity Toward Borohydride Oxidation.

    PubMed

    Philips, M Francklin; Lee, Kwang-Pill; Gopalan, Anantha Iyengar

    2015-09-01

    New nanocomposites, poly(diphenylamine-co-3-aminobenzonitrile)/palladium (P(DPA-co-3ABN)/Pd) and poly(diphenylamine)/palladium (PDPA/Pd), have been prepared by pulse potentiostatic method and used as electrocatalysts for borohydride oxidation. Linear sweep voltammogram of P(DPA-co-3ABN)/Pd-ME exhibited the oxidation wave between -0.8 V and 0.4 V that corresponds to the direct, potentially four-electron, oxidation of borohydride ions. The peak current for borohydride oxidation is much higher at P(DPA-co-3ABN)/Pd-ME electrode as compared to PDPA/Pd-ME. The incorporation of 3ABN units augments electrocatalytic behavior and thermal stability for the P(DPA-co-3ABN)/Pd catalyst.

  4. Electrodeposited Ag nanoparticles on TiO2 nanorods for enhanced UV visible light photoreduction CO2 to CH4

    NASA Astrophysics Data System (ADS)

    Kong, Dan; Tan, Jeannie Ziang Yie; Yang, Fei; Zeng, Jieliang; Zhang, Xiwen

    2013-07-01

    We employed the double-potentiostatic methodology to electrodeposit Ag nanoparticles on oriented single-crystalline rutile TiO2 nanorods synthesized by hydrothermal method. The synthesized composites were used as the photocatalyst to reduce CO2 to CH4 under UV irradiation, and tested by SEM, XRD, TEM, XPS, UV-vis and photoluminescence. Deposition with Ag nanoparticles was observed to enhance the photocatalytic activity (≈1.5-2.64 μmol (gcatal h)-1) up to 5 times with respect to undecorated TiO2 nanorods (≈0.5 μmol (gcatal h)-1). The increase in the CH4 yield was correlated with the surface morphology and structure of TiO2 nanorods.

  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. Room temperature magnesium electrorefining by using non-aqueous electrolyte

    NASA Astrophysics Data System (ADS)

    Park, Jesik; Jung, Yeojin; Kusumah, Priyandi; Dilasari, Bonita; Ku, Heesuk; Kim, Hansu; Kwon, Kyungjung; Lee, Churl Kyoung

    2016-09-01

    The increasing usage of magnesium inevitably leads to a fast increase in magnesium scrap, and magnesium recycling appears extremely beneficial for cost reduction, preservation of natural resources and protection of the environment. Magnesium refining for the recovery of high purity magnesium from metal scrap alloy (AZ31B composed of magnesium, aluminum, zinc, manganese and copper) at room temperature is investigated with a non-aqueous electrolyte (tetrahydrofuran with ethyl magnesium bromide). A high purity (99.999%) of electrorefined magneisum with a smooth and dense surface is obtained after potentiostatic electrolysis with an applied voltage of 2 V. The selective dissolution of magnesium from magnesium alloy is possible by applying an adequate potential considering the tolerable impurity level in electrorefined magnesium and processing time. The purity estimation method suggested in this study can be useful in evaluating the maximum content of impurity elements.

  7. 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.

  8. Current-limited imposed-potential technique for inducing and monitoring metastable pitting events

    SciTech Connect

    Wall, F.D.

    1999-11-24

    A technique has been developed to selectively induce metastable pitting while preventing the transition to stable pit growth. The current-limited imposed-potential (CLIP) technique limits available cathodic current to an initiated site using a resistor in series with the working electrode to form a voltage divider. Potentiodynamic CLIP testing yields a distribution of breakdown potentials from a single experiment. Potentiostatic CLIP testing yields induction time data, which can be used as input to a calculation of germination rate. Initial data indicate that a one-to-one correlation exists between electrochemical transients and observed pitting sites. The CLIP technique provides a consistent means of gathering quantitative potential and current transients associated with localized oxide breakdown.

  9. 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).

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

    DOE PAGES

    Zheng, Dong; Yang, Xuran; Zhang, Xiaoqing; ...

    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

  11. Electrochemically and bioelectrochemically induced ammonium recovery.

    PubMed

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

    2015-01-22

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

  12. 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

  13. 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.

  14. Electrochemically and Bioelectrochemically Induced Ammonium Recovery

    PubMed Central

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

    2015-01-01

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

  15. 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.

  16. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    PubMed Central

    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

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. Corrosion Behavior of Titanium Grade 7 in Fluoride-Containing NaCl Brines

    SciTech Connect

    NA

    2004-05-18

    Titanium Grade 7 (UNS R52400) is a titanium-based alloy with 0.12-0.25% Pd. The addition of the small amount of palladium is to ennoble the corrosion potential of Ti, thus improving the corrosion resistance of titanium in reducing environments. In most aqueous environments, Ti and Ti alloys demonstrate excellent corrosion resistance due to the protective oxide film that forms spontaneously and remains stable on the surface. However, Ti and Ti alloys are susceptible to corrosion in fluoride-containing environments due to the formation of complexes such as TiF{sub 6}{sup 2-} and TiF{sub 6}{sup 3-}, which are stable and soluble in electrolyte solutions. Without the presence of fluoride, only slight effects from [Cl{sup -}], pH and temperature have been reported [1]. It has been reported that the kinetics of passive corrosion of titanium in neutral solutions and controlled by the migration of the defects in the oxide across the surface film [2]. Thus, the increase in thickness and improvement in film properties, by thermal oxidation, would lead to a significant decrease in the susceptibility to film breakdown and in the passive corrosion rate. This report summarizes recent experiment results in studies of the environmental influence on the corrosion behavior of Titanium Grade 7 (Ti-7) in NaCl brines containing fluoride. The environmental factors to be studied include temperature, pH, chloride and fluoride concentration. This report also includes the effects of oxide film, formed during an anneal treatment, on the corrosion behavior of Ti-7. Polarization measurement techniques including potentiodynamic and potentiostatic scans were use3d to characterize corrosion kinetics and susceptibility. Due to the unique alloying in Titanium Grade 7, the long-term corrosion behavior is heavily influenced by the surface enrichment of Pd. Use of electrochemical impedance spectroscopy in conjunction with a potentiostatic scan will reveal the transformation in the corrosion behavior as

  2. An evaluation of the corrosion performance of magnesium-yttrium and yttrium-magnesium nonequilibrium alloys

    NASA Astrophysics Data System (ADS)

    Heidersbach, Krista Lynn

    1998-11-01

    In an effort to develop a corrosion-resistant light-weight metallic alloy, magnetron co-sputter deposition and electron beam physical vapor deposition (EB-PVD) have been employed to deposit binary magnesium-yttrium and yttrium-magnesium alloys. Yttrium was selected because it has been shown to significantly alter the passive film of magnesium and has been used in several commercially available alloys. The binary alloys, employed in this study, were evaluated for film structure, electrochemical performance and passive film composition and structure. The film's morphology was evaluated using scanning electron microscopy (SEM). Morphologies of the sputtered alloys ranged from zones 1 to zone T. X-ray diffraction (XRD) was used as a quick check for the presence of secondary phases that are detrimental to corrosion behavior. Although secondary phases were present, MgY particles, they did not affect the corrosion performance of the alloys. Electrochemical testing included potentiodynamic polarization, potentiostatic long term testing, and electrochemical impedance spectroscopy. All studies were performed using a standard three electrode technique in one of two solutions; pH 12 buffered solution containing 0.1M NaCl and 0.05M Nasb2Bsb4Osb7 with varied chloride concentration up to 3.5sp{w}/sb{o} NaCl (pH 9.2). Corrosion rates for all four alloys were a minimum of two orders of magnitude lower than either pure Mg or pure Y. The chemical composition of the air-formed oxides, the passive formed upon immersion in the pH 12 buffered solution with no applied potential, and the passive films formed by potentiostatic polarization in the same solution were characterized using XPS. The internal structure of these surface films was identified using transmission electron microscopy. Results from XPS indicated that a bi-layer oxide-hydroxide film was present on the surface of all the sputtered alloys. The inner layer of the film was found to be Ysb2Osb3. The outer layer was a mixture

  3. 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

  4. Hybrid pulse anodization for the fabrication of porous anodic alumina films from commercial purity (99%) aluminum at room temperature.

    PubMed

    Chung, C K; Zhou, R X; Liu, T Y; Chang, W T

    2009-02-04

    Most porous anodic alumina (PAA) or anodic aluminum oxide (AAO) films are fabricated using the potentiostatic method from high-purity (99.999%) aluminum films at a low temperature of approximately 0-10 degrees C to avoid dissolution effects at room temperature (RT). In this study, we have demonstrated the fabrication of PAA film from commercial purity (99%) aluminum at RT using a hybrid pulse technique which combines pulse reverse and pulse voltages for the two-step anodization. The reaction mechanism is investigated by the real-time monitoring of current. A possible mechanism of hybrid pulse anodization is proposed for the formation of pronounced nanoporous film at RT. The structure and morphology of the anodic films were greatly influenced by the duration of anodization and the type of voltage. The best result was obtained by first applying pulse reverse voltage and then pulse voltage. The first pulse reverse anodization step was used to form new small cells and pre-texture concave aluminum as a self-assembled mask while the second pulse anodization step was for the resulting PAA film. The diameter of the nanopores in the arrays could reach 30-60 nm.

  5. Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction.

    PubMed

    Jang, Jun-Won; Park, Jae-Woo

    2014-05-30

    Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1M Na2SO4 containing 0.5wt% NH4F electrolyte, holding the potential at 20, 40, and 60V for 20min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40V for 20min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H2O2). In case of INT-40V in the presence of H2O2 3%, the first-order rate constant was found to be 1.7×10(-2)min(-1), and 1.2×10(-2)min(-1) with commercial hematite powder. Degradation of cyanide was much less with only H2O2. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction.

  6. 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.

  7. The electrocatalytic hydrogenation of glucose; 1: Kinetics of hydrogen evolution and glucose hydrogenation on Raney nickel powder

    SciTech Connect

    Anantharaman, V.; Pintauro, P.N. . Dept. of Chemical Engineering)

    1994-10-01

    The kinetics of H[sub 2] evolution and glucose reduction to sorbitol was investigated using a batch slurry reactor containing Raney nickel powder catalyst. In the presence and absence of glucose, hydrogen evolution proceeds via a Volmer-Heyrovsky mechanism, with both steps simultaneously rate controlling at low overpotentials and the Volmer reaction rate limiting at high cathodic overvoltages. A kinetic model for the electrocatalytic hydrogenation of glucose with simultaneous H[sub 2] generation was developed and tested. The model contains rate equations for the individual Volmer, Heyrovsky, and glucose hydrogenation steps, a Langmuir adsorption isotherm for glucose, an equation describing the shift in open-circuit potential due to glucose adsorption on the nickel catalyst, and steady-state atomic hydrogen and charge balance relationships. The theory accurately predicted potentiostatic polarization data and glucose hydrogenation rates. The results indicate that the mechanism for sorbitol formation with electrogenerated atomic hydrogen on Raney nickel is the same as that for the high temperature and pressure chemical catalytic hydrogenation process.

  8. 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

  9. Three-Dimensionally Mesostructured Fe2O3 Electrodes with Good Rate Performance and Reduced Voltage Hysteresi

    DOE PAGES

    Wang, Junjie; Braun, Paul V.; Zhou, Hui; ...

    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

  10. A comparison of the corrosion behaviour and surface characteristics of vacuum-brazed and heat-treated Ti6Al4V alloy.

    PubMed

    Lee, T M; Chang, E; Yang, C Y

    1998-08-01

    The corrosion characteristics of the brazed Ti6Al4V specimens were analysed and compared with respect to the conventionally heat-treated specimens by an electrochemical corrosion test. The object of this research was to explore the potentiality of the brazed titanium for biomaterials. The characteristics of the 1300 degrees C heat-treated and the 970 degrees C brazed specimens, with passivation and sterilization treatment, were evaluated by measurement of corrosion potential, Ecorr, corrosion current densities, Icorr, polarization resistance of the reacted surface films, Rp, in a potentiodynamic test. The experimental results show that the corrosion rates of the heat-treated and the brazed samples are similar at Ecorr, and the value of Ecorr for the brazed sample is noble to the heat-treated samples. The passive current density of the brazed specimen is either lower or higher than the heat-treated specimen, depending on the polarization potential. By Auger electron spectroscopic and high-resolution X-ray photoelectron spectroscopic analysis on specimens from the potentiostatic test, the elements of copper and nickel in the brazing filler were not detected while less alumina was found in the reacted film of the brazed specimens when compared with the heat-treated specimens. The implication of the results is discussed.

  11. Coatings on NiTi Alloy

    NASA Astrophysics Data System (ADS)

    Kei, C. C.; Yu, Y. S.; Racek, J.; Vokoun, D.; Šittner, P.

    2014-07-01

    Atomic layer deposition is introduced as a method suitable for preparation of Al2O3 layers on the surface of NiTi medical devices such as stents because of the excellent thickness control and conformal protective coating on complex structures. The corrosion properties of NiTi plates with Al2O3 coatings of various thicknesses in an environment similar to that occurring in the human body were studied using open circuit potential, potentiostatic electrochemical impedance spectroscopy, and cyclic polarization tests. It shows that the layer thickness plays a key role in the inhibition of corrosion. The thinner layers are more diffuse and make it easier for anodic reaction of passive NiTi with protective TiO2 underneath of Al2O3, while the thicker layers have the barrier effect with local pores initiating pitting corrosion. The results of our electrochemical experiments consistently show that corrosion properties of thick Al2O3 coatings on NiTi plate are inferior compared to the thin layers.

  12. 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.

  13. 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

  14. 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.

  15. Removal of tarnishing and roughness of copper surface by electropolishing treatment

    NASA Astrophysics Data System (ADS)

    Awad, A. M.; Ghany, N. A. Abdel; Dahy, T. M.

    2010-04-01

    Tarnishing and roughness of copper surface can be removed by electropolishing treatment (EP) imparting a bright and smooth surface at suitable conditions, e.g. current density, time, temperature, and viscosity. It was carried out by using an electrolytic cell containing phosphoric acid 55% as the electrolytic solution. Both copper working electrode and lead counter electrode, and reference electrode (SCE) were connected to a Potentiostat/Galvanostat to allow an electric current to pass through the solution. Some additives such as soluble starch, ethylene glycol, and methanol were added to reduce defects formed on the copper surface during EP process. The results showed that the highest gloss value was obtained by applying electric potential 1.5 V at the passive region of polarization curve. The surface was investigated after EP treatment, where SEM and EDX showed lower roughness in case of addition of both soluble starch and ethylene glycol more than methanol. Moreover, AFM analysis showed the lowest roughness in case of soluble starch more than other additives.

  16. Electrostatic field measurements and band flattening during electron-transfer processes at single-crystal TiO[sub 2] electrodes by electric field-induced optical second harmonic generation

    SciTech Connect

    Lantz, J.M.; Corn, R.M. )

    1994-05-05

    Optical second harmonic generation (SHG) is employed as a local, time-resolved measurement of the electrostatic fields at the surface of single-crystal TiO[sub 2] electrodes in contact with aqueous electrolyte solutions. The interfacial SHG at a fundamental wavelength of 584 nm is dominated by the electric field-induced second harmonic (EFISH) response from the first 20 nm of the space charge layer at the surface of the semiconductor. A substantial decrease in the amount of SHG from the electrode while under potentiostatic control is observed upon illumination of the surface with UV light (320 nm) whose energy is above the bandgap for TiO[sub 2] (3.0 eV or 410 nm). Comparisons of the drop in SHG upon UV illumination with photovoltage measurements for TiO[sub 2] electrodes at open circuit verify that this decrease is due to a reduction in the strength of the electrostatic fields ([open quotes]band flattening[close quotes]) within the space charge region upon UV illumination. The EFISH response from the surface decreases with increasing power of the UV illumination, corresponding to a band flattening of up to 70% for the highest power densities. Upon termination of the UV illumination, a slow (10-12 s) rise time is observed for the return of the surface SHG to its normal levels. 50 refs., 8 figs.

  17. Porphyrin-cobaloxime complexes for hydrogen production, a photo- and electrochemical study, coupled with quantum chemical calculations.

    PubMed

    Manton, Jennifer C; Long, Conor; Vos, Johannes G; Pryce, Mary T

    2014-03-07

    Two porphyrin-cobaloxime complexes; [{Co(dmgH)2Cl}{MPyTPP}] () and [{Co(dmgH)2Cl}{ZnMPyTPP}] () (dmgH = dimethylglyoxime, MPyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) have been synthesised as model systems for the generation of hydrogen from water. Although initially envisaged as photocatalytic systems neither complex catalysed the reduction of water to hydrogen following irradiation. However, both complexes are molecular precursors for hydrogen evolution under electrochemical conditions. Turnover numbers for hydrogen production of 1.8 × 10(3) and 5.1 × 10(3) were obtained for and respectively following potentiostatic electrolysis at -1.2 V vs. Ag/AgCl while cobaloxime alone produced a turnover-number of 8.0 × 10(3). The photophysical properties of and were examined to provide an explanation for the lack of photochemical activity. These results, coupled with quantum chemical calculations, confirm that porphyrins fail to act as light-harvesting units for these systems and that the lowest energy excited states are in fact cobaloxime-based rather than porphyrin based.

  18. Analyses of the genotoxic and mutagenic potential of the products formed after the biotransformation of the azo dye Disperse Red 1.

    PubMed

    Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; Marcos, Ricard; de Oliveira, Danielle Palma

    2011-12-01

    Azo dyes constitute the largest class of synthetic dyes. Following oral exposure, these dyes can be reduced to aromatic amines by the intestinal microflora or liver enzymes. This work identified the products formed after oxidation and reduction of the dye Disperse Red 1, simulating hepatic biotransformation and evaluated the mutagenic potential of the resultant solution. Controlled potential electrolysis was carried out on dye solution using a Potentiostat/Galvanostat. HPLC-DAD and GC/MS were used to determine the products generated after the oxidation/reduction process. The Salmonella/microsome assay with the strains TA98 and YG1041 without S9, and the mouse lymphoma assay (MLA) using the thymidine kinase (Tk) gene, were used to evaluate the mutagenicity of the products formed. Sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, nitrobenzene, 4-nitro-benzamine and 2-(ethylphenylamino)-ethanol were detected. This dye has already being assigned as mutagenic in different cell system. In addition, after the oxidation/reduction process the dye still had mutagenic activity for the Salmonella/microsome assay. Nevertheless, both the original dye Disperse Red 1 and its treated solutions showed negative results in the MLA. The present results suggest that the ingestion of water and food contaminated with this dye may represent human and environmental health problem, due to the generation of harmful compounds after biotransformation.

  19. Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

    SciTech Connect

    Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; Sasaki, Kotaro; Kong, Fanpeng; Du, Chunyu; Gao, Yunzhi; Yin, Geping; Adzic, Radoslav R.

    2016-04-11

    Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstrate that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OHad/Oad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.

  20. Electrodeposition technique-dependent photoelectrochemical and photocatalytic properties of an In2S3/TiO2 nanotube array.

    PubMed

    Li, Yue; Luo, Shenglian; Wei, Zhendong; Meng, Deshui; Ding, Mingyue; Liu, Chengbin

    2014-03-07

    Electrodeposition is a very versatile tool to fabricate multicomponent TiO2 nanotube array (NTA) composites. However, the understanding of the correlation between the component structure and the fabrication technique has not been clearly investigated yet, though it has been observed that the performance of composites is bound up with the component structure. In this work, the photoelectrochemical properties of In2S3-TiO2 NTA composites prepared by CV electrodeposition, potentiostatic electrodeposition and pulse electrodeposition, respectively, were investigated. The results revealed that the as-prepared photoelectrodes exhibited electrodeposition technique-dependent properties, and the pulse prepared In2S3-TiO2 yielded the highest and stable photocurrent response, consequently exhibiting a superior photocatalytic activity in the degradation of p-nitrophenol (PNP). This may be attributed to the homogeneous, ultra-fine structure of In2S3 nanoparticles (NPs), which brings about a high charge separation efficiency. Furthermore, the trapping tests showed that both radicals and holes were the main active species in the photocatalytic degradation of PNP. This work not only provided a firm basis for maximizing photocatalytic activity via tuning fabrication techniques but also gave a deep insight into the photocatalytic mechanism.

  1. 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

    2016-05-28

    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.

  2. Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms.

    PubMed

    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 that are produced by microbial biofilms and can affect their 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(2) 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.

  3. 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

  4. Corrosion behavior of Pd-Cu and Pd-Co alloys in synthetic saliva.

    PubMed

    Goehlich, V; Marek, M

    1990-04-01

    Pd-based alloys are major alternatives to gold-based alloys for PFM applications. In electrolytes simulating oral fluids, these alloys exhibit electrode behavior similar to passivity of active metals, i.e., a potential region of almost constant current density up to a critical potential, above which the current increases. The objective of this study was to correlate the electrode behavior with the results of solution analyses and changes in the surface composition of the alloys. Binary alloys Pd-15 wt% Cu and Pd-19 wt% Co, as well as the pure components, were examined. Corrosion potentials vs. time, potentiodynamic anodic polarization curves, polarization resistances vs. time, and potentiostatic anodic charges were measured with synthetic saliva used as the electrolyte. The concentrations of Pd, Cu, and Co in the solution after various exposures were determined by atomic absorption. The surfaces of the alloys were examined by x-ray photoelectron spectroscopy before and after the exposures. The results show that selective dissolution of the less-noble components occurred on the surfaces of both alloys for all the exposures, leaving the surfaces highly enriched in Pd. This enrichment contributed to the potential changes and the passive-type behavior. Copper dissolved more than cobalt at longer exposures and higher potentials, in spite of its higher nobility. Dissolution of cobalt seemed to be limited by the formation of a surface film, which may be related to the transition character of this element.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Experimental analysis of spatio-temporal behavior of anodic dead-end mode operated polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Manokaran, A.; Pushpavanam, S.; Sridhar, P.; Pitchumani, S.

    During the anodic dead-end mode operation of fuel cells, the inert gases (nitrogen and water) present in the cathode side gas channel permeate to the anode side and accumulate in the anode gas channel. The inert gas accumulation in the anode decreases the fuel cell performance by impeding the access of hydrogen to the catalyst. The performance of fuel cell under potentiostatic dead-end mode operation is shown to have three distinct regions viz. time lag region, transient current region and a steady state current region. A current distribution measurement setup is used to capture the evolution of the current distribution as a function of time and space. Co- and counter-flow operations of dead-end mode confirm the propagation of inert gas from the dead-end of anode channel to the inlet of anode. Experiments with different oxidants, oxygen and air, under dead-end mode confirm that nitrogen which permeates from cathode to anode causes the performance drop of the fuel cell. For different starting current densities of 0.15 A cm -2, 0.3 A cm -2 and 0.6 A cm -2 the inert gas occupies 35%, 45% and 57%, respectively of anode channel volume at the end of 60 min of dead-end mode operation.

  10. 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.

  11. 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.

  12. 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.

  13. Downscaled anodic oxidation process for aluminium in oxalic acid

    NASA Astrophysics Data System (ADS)

    Sieber, M.; Morgenstern, R.; Kuhn, D.; Hackert-Oschätzchen, M.; Schubert, A.; Lampke, T.

    2017-03-01

    The increasing multi-functionality of parts and assemblies in several fields of engineering demands, amongst others, highly functionalised surfaces. For the different applications, on the one hand, there is a need to scale up surface modification processes originating in the nano- and micro-scale. On the other hand, conventional macro-scale surface refinement methods offer a huge potential for application in the said nano- and micro-scale. The anodic oxidation process, which is established especially for aluminium and its alloys, allows the formation of oxide ceramic layers on the surface. The build-up of an oxide ceramic coating comes along with altered chemical, tribological and electrical surface properties. As a basis for further investigations regarding the use of the anodic oxidation process for micro-scale-manufacturing, the scale effects of oxalic acid anodising on commercially pure aluminium as well as on the AlZn5.5MgCu alloy are addressed in the present work. The focus is on the amount of oxide formed during a potentiostatic process in relation to the exchanged amount of charge. Further, the hardness of the coating as an integral measure to assess the porous oxide structure is approached by nano-indentation technique.

  14. Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte

    PubMed Central

    2010-01-01

    A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially. PMID:20596417

  15. 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.

  16. An NMR investigation of CO tolerance in a Pt/Ru fuel cell catalyst.

    PubMed

    Tong, YuYe; Kim, Hee Soo; Babu, Panakkattu K; Waszczuk, Piotr; Wieckowski, Andrzej; Oldfield, Eric

    2002-01-23

    We report the first combined application of solid-state electrochemical NMR (EC NMR), cyclic voltammetry (CV), and potentiostatic current generation to investigate the topic of the ruthenium promotion of MeOH electro-oxidation over nanoscale platinum catalysts. The CV and EC NMR results give evidence for two types of CO: CO on essentially pure Pt and CO on Pt/Ru islands. There is no NMR evidence for rapid exchange between the two CO populations. CO molecules on the primarily Pt domains behave much like CO on pure Pt, with there being little effect of Ru on the Knight shift or on Korringa relaxation. In sharp contrast, COs on Pt/Ru have highly shifted (13)C NMR resonances, much weaker Korringa relaxation, and, at higher temperatures, they undergo thermally activated surface diffusion. For CO on Pt, the correlation observed between the 2pi* Fermi level local density of states and the steady-state current suggests a role for Ru in weakening the Pt-CO bond, thereby increasing the CO oxidation rate (current). The combined EC NMR/electrochemistry approach thus provides new insights into the promotion of CO tolerance in Pt/Ru fuel cell catalysts, in addition to providing a novel route to investigating promotion in heterogeneous catalysis in general.

  17. 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.

  18. Li + ion diffusion in Li 4Ti 5O 12 thin film electrode prepared by PVP sol-gel method

    NASA Astrophysics Data System (ADS)

    Rho, Young Ho; Kanamura, Kiyoshi

    2004-06-01

    Li 4Ti 5O 12 thin films for rechargeable lithium batteries were prepared by a sol-gel method with poly(vinylpyrrolidone). Interfacial properties of lithium insertion into Li 4Ti 5O 12 thin film were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiostatic intermittent titration technique (PITT). Redox peaks in CV were very sharp even at a fast scan rate of 50 mV s -1, indicating that Li 4Ti 5O 12 thin film had a fast electrochemical response, and that an apparent chemical diffusion coefficient of Li + ion was estimated to be 6.8×10 -11 cm 2 s -1 from a dependence of peak current on sweep rates. From EIS, it can be seen that Li + ions become more mobile at 1.55 V vs. Li/Li +, corresponding to a two-phase region, and the chemical diffusion coefficients of Li + ion ranged from 10 -10 to 10 -12 cm 2 s -1 at various potentials. The chemical diffusion coefficients of Li + ion in Li 4Ti 5O 12 were also estimated from PITT. They were in a range of 10 -11-10 -12 cm 2 s -1.

  19. Analysis of tellurium thin films electrodeposition from acidic citric bath

    NASA Astrophysics Data System (ADS)

    Kowalik, Remigiusz; Kutyła, Dawid; Mech, Krzysztof; Żabiński, Piotr

    2016-12-01

    This work presents the description of the electrochemical process of formation thin tellurium layers from citrate acidic solution. The suggested methodology consists in the preparation of stable acidic baths with high content of tellurium, and with the addition of citrate acid. In order to analyse the mechanism of the process of tellurium deposition, the electroanalytical tests were conducted. The tests of cyclic voltammetry and hydrodynamic ones were performed with the use of polycrystalline gold disk electrode. The range of potentials in which deposition of tellurium in direct four-electron process is possible was determined as well as the reduction of deposited Te° to Te2- and its re-deposition as a result of the comproportionation reaction. On the basis of the obtained results, the deposition of tellurium was conducted by the potentiostatic method. The influence of a deposition potential and a concentration of TeO2 in the solution on the rate of tellurium coatings deposition was examined. The presence of tellurium was confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy.

  20. 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.

  1. 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.

  2. 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

  3. Low-melting-point titanium-base brazing alloys. Part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4V substrate

    SciTech Connect

    Chang, E.; Chen, C.H.

    1997-12-01

    Filler metal of a low-melting-point (917 C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 C for 2, 4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed {alpha} plus intergranular {beta} structure of Ti-6Al-4V substrate causes the lamellar Widmanstaetten structure to form. The intermetallic Ti{sub 2}Ni phase existing in the prior filler metal diminishes, while the Ti{sub 2}Cu phase can be identified for the metal brazed at 960 C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the {beta} phase to the substrate. In deaerated Hank`s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank`s solution, show similar corrosion behavior, irrespective of the brazing time.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. A 1000-cell SOFC reactor for domestic cogeneration

    NASA Astrophysics Data System (ADS)

    Alston, T.; Kendall, K.; Palin, M.; Prica, M.; Windibank, P.

    A cogeneration system was built using 1000 cells with the intention of supplying 30 kW of hot water and 500 W of power. The basis of the cogenerator was the small tubular SOFC design. 8Y zirconia was mixed into a plastic paste and extruded to form thin-walled tubes. The process produced a zirconia material with high strength and good electrical properties. After drying and firing to full density, electrodes were coated onto the inner and outer surfaces of the electrolyte, then sintered. Current collecting wires were wound around the tubular cells and the tubes were assembled into a reactor. Either hydrogen or a premix of natural gas and air was fed through the tubes and ignited by a hot wire. The ignition shock did not damage the cells in any way. Cycling was achieved within minutes. A steel heat exchanger/recuperator was used to feed hot air to the cell stack. The electrical output was measured via a potentiostat.

  11. Multifrequency impedance measurement technique for wireless characterization of microbiological cell cultures

    NASA Astrophysics Data System (ADS)

    Wissenwasser, J.; Vellekoop, M. J.; Kapferer, W.; Lepperdinger, G.; Heer, R.

    2011-11-01

    An impedance measurement system with probe signal frequencies up to 50 kHz with AC-probe voltages below 30 mV rms was integrated for wireless and battery-free monitoring of microbiological cell cultures. The here presented modular design and the use of state-of-the-art components greatly eases adoptions to a wide range of biotechnological applications without the need of bulky LCR-meters or potentiostats. The device had a power consumption of less than 2.5 mA at a 3.3 V single power supply and worked trouble-free within the humid environment of a cell culture incubator. Measurements on lumped RC-elements showed an error of less than 1% for absolute values and less than 1° regarding the phase of the complex impedance. The performance of sensor devices with interdigitated electrode structures for the measurement of adherent cell cultures was tested in the presence of phosphate-buffered saline solution in the humid atmosphere of an incubator for biological cell cultures.

  12. Mechanical performance of PPy helix tube microactuator

    NASA Astrophysics Data System (ADS)

    Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

    2004-02-01

    Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

  13. Assessment of corrosion rate in prestressed concrete with acoustic emission

    NASA Astrophysics Data System (ADS)

    Mangual, Jesé; ElBatanouny, Mohamed K.; Vélez, William; Ziehl, Paul; Matta, Fabio; González, Miguel

    2011-04-01

    Acoustic Emission (AE) sensing was employed to assess the rate of corrosion of steel strands in small scale concrete block specimens. The corrosion process was accelerated in a laboratory environment using a potentiostat to supply a constant potential difference with a 3% NaCl solution as the electrolyte. The embedded prestressing steel strand served as the anode, and a copper plate served as the cathode. Corrosion rate, half-cell potential measurements, and AE activity were recorded continuously throughout each test and examined to assess the development of corrosion and its rate. At the end of each test the steel strands were cleaned and re-weighed to determine the mass loss and evaluate it vis-á-vis the AE data. The initiation and propagation phases of corrosion were correlated with the percentage mass loss of steel and the acquired AE signals. Results indicate that AE monitoring may be a useful aid in the detection and differentiation of the steel deterioration phases, and estimation of the locations of corroded areas.

  14. 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.

  15. Phosphonic acid functionalized poly(pentafluorostyrene) as polyelectrolyte membrane for fuel cell application

    NASA Astrophysics Data System (ADS)

    Atanasov, Vladimir; Oleynikov, Andrey; Xia, Jiabing; Lyonnard, Sandrine; Kerres, Jochen

    2017-03-01

    In this paper we introduce polyelectrolyte membranes based on phosphonated poly(pentafluorostyrene) (PPFS) and their performances in a fuel cell. The polyelectrolytes were obtained via partial phosphonation of PPFS varying the phosphonation degree from 17 to 66%. These membranes showed a high resistance to temperature (Tdecomp. = 355-381 °C) and radical attack (96-288 h in Fenton's test). A blend membrane consisting of 82 wt% fully phosphonated PPFS and 18 wt% poly(benzimidazole) is compared to the 66% phosphonated membrane having similar ion-conductivity (σ = 57 mS cm-1 at 120 °C, 90% RH). In the fuel cell the blend showed the best performance reaching 0.40 W cm-2 against 0.34 W cm-2 for the 42 wt% phosphonated membrane and 0.35 W cm-2 for Nafion 212. Furthermore, the blend maintained its operation at potentiostatic regime (0.5 V) for 620 h without declining in its performance. The highest power density of 0.78 W cm-2 was reached for the blend with a thickness of 15 μm using humidified oxygen (RH > 90%) at the cathode side. The switch from humidified to dry gasses during operation reduced the current density down to 0.6 A cm-2, but the cell maintained under operation for 66 h.

  16. Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

    DOE PAGES

    Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; ...

    2016-04-11

    Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstratemore » that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OHad/Oad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.« less

  17. A novel open-type biosensor for the in-situ monitoring of biochemical oxygen demand in an aerobic environment

    PubMed Central

    Yamashita, Takahiro; Ookawa, Natsuki; Ishida, Mitsuyoshi; Kanamori, Hiroyuki; Sasaki, Harumi; Katayose, Yuichi; Yokoyama, Hiroshi

    2016-01-01

    Biochemical oxygen demand (BOD) is a widely used index of water-quality assessment. Since bioelectrochemical BOD biosensors require anaerobic conditions for anodic reactions, they are not directly used in aerobic environments such as aeration tanks. Normally, the BOD biosensors are closed-type, where the anode is packed inside a closed chamber to avoid exposure to oxygen. In this study, a novel bioelectrochemical open-type biosensor was designed for in-situ monitoring of BOD during intermittent aeration. The open-type anode, without any protection against exposure to oxygen, was directly inserted into an intermittently aerated tank filled with livestock wastewater. Anodic potential was controlled using a potentiostat. Interestingly, this novel biosensor generated similar levels of current under both aerating and non-aerating conditions, and showed a logarithmic correlation (R2 > 0.9) of current with BOD concentrations up to 250 mg/L. Suspended solids in the wastewater attached to and covered the whole anode, presumably leading to the production of anaerobic conditions inside the covered anode via biological oxygen removal. Exoelectrogenic anaerobes (Geobacter spp.) were detected inside the covered anode using the 16S-rRNA gene. This biosensor will have various practical applications, such as the automatic control of aeration intensity and the in-situ monitoring of natural water environments. PMID:27917947

  18. 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.

  19. LabVIEW-based sequential-injection analysis system for the determination of trace metals by square-wave anodic and adsorptive stripping voltammetry on mercury-film electrodes.

    PubMed

    Economou, Anastasios; Voulgaropoulos, Anastasios

    2003-01-01

    The development of a dedicated automated sequential-injection analysis apparatus for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) is reported. The instrument comprised a peristaltic pump, a multiposition selector valve and a home-made potentiostat and used a mercury-film electrode as the working electrodes in a thin-layer electrochemical detector. Programming of the experimental sequence was performed in LabVIEW 5.1. The sequence of operations included formation of the mercury film, electrolytic or adsorptive accumulation of the analyte on the electrode surface, recording of the voltammetric current-potential response, and cleaning of the electrode. The stripping step was carried out by applying a square-wave (SW) potential-time excitation signal to the working electrode. The instrument allowed unattended operation since multiple-step sequences could be readily implemented through the purpose-built software. The utility of the analyser was tested for the determination of copper(II), cadmium(II), lead(II) and zinc(II) by SWASV and of nickel(II), cobalt(II) and uranium(VI) by SWAdSV.

  20. Controlled electrodeposition of bismuth nanocatalysts for the solution-liquid-solid synthesis of CdSe nanowires on transparent conductive substrates.

    PubMed

    Reim, Natalia; Littig, Alexander; Behn, Dino; Mews, Alf

    2013-12-11

    Semiconductor nanowires (NWs) composed of cadmium selenide (CdSe) have been directly grown on transparent conductive substrates via the solution-liquid-solid (SLS) approach using electrodeposited bismuth nanoparticles (Bi NPs) as catalyst. Bi NPs were fabricated on indium tin oxide (ITO) surfaces from a bismuth trichloride solution using potentiostatic double-pulse techniques. The size and density of electrodeposited Bi NPs were controlled by the pulse parameters. Since the NW diameter is governed by the dimension of the Bi catalyst, the electrodeposition is a reliable method to synthesize nanowires directly on substrates with a desired size and density. We show that the density can be adjusted from individual NWs on several square micrometer to very dense NW networks. The diameter can be controlled between thick nanowires above 100 nm to very thin NW of 7 nm in diameter, which is well below the respective exciton dimension. Hence, especially the thinnest NWs exhibit diameter-dependent photoluminescence energies as a result of quantum confinement effects in the radial dimension.

  1. 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.

  2. Pulse-reverse treatment of carbon nanomaterials for the electrochemical storage of energy

    NASA Astrophysics Data System (ADS)

    Zhylinski, V. V.; Drozdovich, V. B.; Krauklis, A. V.; Zhdanok, S. A.; Zharski, I. M.

    2011-04-01

    The paper dwells upon the investigation of carbon nanomaterials synthesized by an electric arc-method from methane-air mixture under atmospheric pressure in presence of Ni catalyst. These materials may be used for the electrochemical storage of energy. According to the data of transmission electron microscopy the carbon nanomaterials are generally represented by carbon nanotubes with the diameter of 20-80 nm. The pulse-reverse treatment of carbon nanomaterials in concentrated sulphuric electrolytes with addition of fluoride and lithium ions is carried out to increase their discharge capacity in 1 M H2SO4 and 1 M KOH. The properties of carbon nanomaterials are studied using the Brunauer-Emmett-Teller method, chemical energy-dispersive X-ray analysis, potentiostatic charge method of electrochemical saturation of hydrogen and potentiodynamic discharge method. The maximum discharge capacity of 940 C g-1 in 1 M H2SO4 is revealed for CNMs subjected to pulse-reverse treatment in concentrated sulphuric electrolyte containing fluoride and lithium ions.

  3. 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.

  4. Electropolymerization of pyrrole and immobilization of glucose oxidase in a flow system: influence of the operating conditions on analytical performance.

    PubMed

    Vidal, J C; Garcia, E; Castillo, J R

    1998-03-01

    The in situ potentiostatic electropolymerization of pyrrole (Py) on a Pt electrode in a thin-layer amperometric cell and the entrapment of the enzyme glucose oxidase (GOx) for the determination of glucose are reported. Polypyrrole (PPy) is directly formed by continuous passage of a buffered solution of the monomer (0.4 M) and enzyme (250 U mL-1) at pH 7 at a flow rate of 0.05-0.1 mL min-1 under a constant applied potential of +0.85 V vs Ag/AgCl decreases. The electrosynthesis of PPy by injection of 500 microL of a Py + GOx solution in a carrier electrolyte consisting of 0.05 M phosphate buffer and 0.1 M KCl at pH 7.0 was also assayed. The influence of the electropolymerization conditions on the analytical response of the sensor to glucose was investigated. The analytical performance of the PPy/GOx sensor was also studied in terms of durability and storage life, as well as selectivity against electroactive species such as ascorbic acid and uric acid as a function of the thickness of the polymer film formed.

  5. Study of overall and local electrochemical responses of oxide films grown on CoCr alloy under biological environments.

    PubMed

    Diaz, I; Martinez-Lerma, J F; Montoya, R; Llorente, I; Escudero, M L; García-Alonso, M C

    2017-06-01

    The interaction of the physiological medium and living tissues with the implant surfaces in biological environments is regulated by biopotentials that induce changes in the chemical composition, structure and thickness of the oxide film. In this work, oxide films grown on CoCr alloys at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl have been characterized through overall and localized electrochemical techniques in a phosphate buffer solution and 0.3% hyaluronic acid. Nanopores of 10-50nm diameter are homogeneously distributed along the surface in the oxide film formed at 0.7 V vs Ag/AgCl. The distribution of the Constant Phase Element studied by local electrochemical impedance spectroscopy showed a three-dimensional (3D) model on the oxide films grown at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl. This behaviour is especially noticeable in oxide films grown at 0.7 V vs Ag/AgCl, probably due to surface inhomogeneities, and resistive properties generated by the potentiostatic growth of the oxide film.

  6. Voltammetric studies on the electrochemical determination of methylmercury in chloride medium at carbon microelectrodes.

    PubMed

    Ribeiro, F; Neto, M M M; Rocha, M M; Fonseca, I T E

    2006-10-10

    Electroanalytical techniques have been used to determine methylmercury at low levels in environmental matrices. The electrochemical behaviour of methylmercury at carbon microelectrodes in a hydrochloric acid medium using cyclic, square wave and fast-scan linear-sweep voltammetric techniques has been investigated. The analytical utility of the methylmercury reoxidation peak has been explored, but the recorded peak currents were found to be poorly reproducible. This is ascribed to two factors: the adsorption of insoluble chloromercury compounds on the electrode surface, which appears to be an important contribution to hinder the voltammetric signal of methylmercury; and the competition between the reoxidation of the methylmercury radical and its dimerization reaction, which limits the reproducibility of the methylmercury peak. These problems were successfully overcome by adopting the appropriate experimental conditions. Fast-scan rates were employed and an efficient electrochemical regeneration procedure of the electrode surface was achieved, under potentiostatic conditions in a mercury-free solution containing potassium thiocyanate--a strong complexing agent. The influence of chloride ion concentration was analysed. Interference by metals, such as lead and cadmium, was considered. Calibration plots were obtained in the micromolar and submicromolar concentration ranges, allowing the electrochemical determination of methylmercury in trace amounts. An estuarine water sample was analysed using the new method with a glassy carbon microelectrode.

  7. Study of the effect of temperature on Pt dissolution in polymer electrolyte membrane fuel cells via accelerated stress tests

    NASA Astrophysics Data System (ADS)

    Dhanushkodi, S. R.; Kundu, S.; Fowler, M. W.; Pritzker, M. D.

    2014-01-01

    Operation of polymer electrolyte membrane fuel cells (PEMFC) at higher cell temperatures accelerates Pt dissolution in the catalyst layer. In this study, a Pt dissolution accelerated stress testing protocol involving the application of a potentiostatic square-wave with 3 s at 0.6 V followed by 3 s at 1.0 V was developed to test fuel cell membrane electrode assemblies (MEAs). The use of this Pt dissolution protocol at three different temperatures (40 °C, 60 °C and 80 °C) was investigated for the same membrane electrode assembly composition. Impedance analysis of the membrane electrode assemblies showed an increase in polarization resistance during the course of the accelerated stress testing. Polarization analysis and electrochemical active surface area (ECSA) loss measurements revealed evidence of increased cathode catalyst layer (CCL) degradation due to Pt dissolution and deposition in the membrane as the cell temperature was raised. Scanning electron microscope (SEM) images confirmed the formation of Pt bands in the membrane. A diagnostic expression was developed to estimate kinetic losses due to oxygen reduction using the effective platinum surface area (EPSA) estimated from cyclic voltammograms. The results indicated that performance degradation occurred mainly due to Pt loss.

  8. A photo- and electrochemical investigation of BODIPY-cobaloxime complexes for hydrogen production, coupled with quantum chemical calculations.

    PubMed

    Manton, Jennifer C; Long, Conor; Vos, Johannes G; Pryce, Mary T

    2014-03-21

    Two BODIPY-cobaloxime complexes; [{Co(dmgH)2Cl}{3-[bis-(4-ethyl-3,5-dimethyl-1H-pyrrol-2-yl)-methyl]-pyridine-borondiflouride}] (1a) and [{Co(dmgH)2Cl}{4-[bis-(4-ethyl-3,5-dimethyl-1H-pyrrol-2-yl)-methyl]-pyridine-borondiflouride}] (2a) (BODIPY = boron dipyrromethene), (dmgH = dimethylglyoxime) have been synthesised and studied as model catalytic systems for the generation of hydrogen gas in aqueous media. Under photochemical conditions, neither complex catalysed the reduction of water to hydrogen. However, both complexes showed considerable activity under electrochemical conditions. Turn-over-numbers for hydrogen production of 1.65 × 10(4) and 1.08 × 10(4) were obtained for 1a and 2a respectively following potentiostatic electrolysis at -1.2 V vs. Ag/AgCl after 1 hour. Quantum chemical calculations were performed to provide an explanation for the lack of photochemical activity.

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

    PubMed

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

    2013-12-15

    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 × 10(20) 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).

  10. Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples.

    PubMed

    Liu, Linjie; Gou, Yuqiang; Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan; Hu, Fangdi; Li, Yingdong

    2014-09-01

    An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (ks) and electron-transfer coefficient (α) were calculated as 1.12, 1.24s(-1), and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10(-8)mol L(-1) to 3.89 × 10(-5)mol L(-1) with detection limit of 2.06 × 10(-8)mol L(-1). This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%.

  11. 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.

  12. 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.

  13. 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.

  14. Electrochemical behaviour of addition agents impregnated in cadmium hydroxide electrodes for alkaline batteries

    NASA Astrophysics Data System (ADS)

    Kalaignan, G. Paruthimal; Umaprakatheeswaran, C.; Muralidharan, B.; Gopalan, A.; Vasudevan, T.

    The development of electrode additives for the cadmium electrode of the nickel/cadmium battery is aimed mainly at increasing the discharge capacity and minimizing self-discharge. The dissolution and passivation of porous cadmium electrodes containing hydroxide and the relative stability of oxides are of importance in understanding the reversible behaviour of the cadmium electrode. Under standard conditions, the equilibrium potential of Cd(OH) 2/Cd lies above the hydrogen-evolution reaction when the cell is not in use, and the active material of the cadmium electrode undergoes self-reductive dissolution (i.e., loss of active material) accompanied by oxygen evolution. The triangular potential sweep voltammetric technique is used to determine the reversibility of the cadmium electrode in alkaline solution. The role of additives such as Ni(NO 3) 2 (0.25-0.1 M) and FeSO 4 (0.1-0.4 M), TiO 2 (0.01-0.03 M) and Na 2S (0.01-0.03 M) in Cd(NO 3) 2 on the reversibility of the electrode are discussed. The effect of discharge rate on the cyclic efficiency is also investigated. Self-discharge currents are determined by potentiostatic polarization method.

  15. Characterization of oxide layers on amorphous Mg-based alloys by Auger electron spectroscopy with sputter depth profiling.

    PubMed

    Baunack, S; Subba Rao, R V; Wolff, U

    2003-04-01

    Amorphous ribbons of Mg-Y-TM-[Ag] (TM: Cu, Ni), prepared by melt spinning, were subjected to electrochemical investigations. Oxide layers formed anodically under potentiostatic control in different electrolytes were investigated by AES and sputter depth profiling. Problems and specific features of characterization of the composition of oxide layers and amorphous ternary or quaternary Mg-based alloys have been investigated. In the alloys the Mg(KL(23)L(23)) peak exhibits a different shape compared to that in the pure element. Analysis of the peak of elastically scattered electrons proved the absence of plasmon loss features, characteristic of pure Mg, in the alloy. A different loss feature emerges in Mg(KL(23)L(23)) and Cu(L(23)VV). The system Mg-Y-TM-[Ag] suffers preferential sputtering. Depletion of Mg and enrichment of TM and Y are found. This is attributed mainly to the preferential sputtering of Mg. Thickness and composition of the formed oxide layer depend on the electrochemical treatment. After removing the oxide by sputtering the concentration of the underlying alloy was found to be affected by the treatment.

  16. 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.

  17. The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells.

    PubMed

    Eliaz, Noam; Shmueli, Sharon; Shur, Irena; Benayahu, Dafna; Aronov, Daniel; Rosenman, Gil

    2009-10-01

    This work demonstrates the effects of both surface preparation and surface post-treatment by exposure to electron beam on the surface texture, contact angle and the interaction with bone-forming cells of electrochemically deposited hydroxyapatite (HAp) coating. Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H(2)O(2) solution. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. The developed interfacial area ratio Sdr and the core fluid retention index Sci were found more reliable than the mean roughness R(a) and the root-mean-square roughness Z(rms) in correlating the adhesion of the coating to the metal substrate and the cellular response with surface texture. The NaOH pretreatment provided the highest surface area and induced the highest cell attachment, even though the H(2)O(2) treatment provided the highest hydrophilicity to the metal substrate. Electrodeposition at pH 6 was found preferable compared to electrodeposition at pH 4.2. The ability to modify the cellular response by exposure to unique electron-beam surface treatment was demonstrated. The very high hydrophilicity of the as-deposited HAp coating enhanced its bioactivity.

  18. On the correlation between the electroanalytical behavior and crystallographic features of Li-intercalation electrodes

    NASA Astrophysics Data System (ADS)

    Levi, M. D.; Levi, E.; Aurbach, D.; Schmidt, M.; Oesten, R.; Heider, U.

    The electroanalytical behavior of Li xNiO 2 and Li xCo 0.2Ni 0.8O 2 was studied by simultaneous application of slow-scan rate cyclic voltammetry (SSCV), potentiostatic and galvanostatic intermittent titration (PITT and GITT), and electrochemical impedance spectroscopy (EIS). Application of a finite-space diffusion model for treating the results obtained by these techniques allowed us to calculate the diffusion coefficient of Li ions ( D) and the differential (incremental) capacity ( Cint) as functions of the electrode's potential. Our final purpose was to compare D versus E and Cint versus E plots for both the electrodes, in order to correlate the observed difference in their electroanalytical behavior with the clear distinction in the related Li-insertion mechanisms deduced from XRD studies. While Li insertion into Li xCo 0.2Ni 0.8O 2 exhibits a single-phase reaction upon charge in the 3.0-4.08 V (versus Li/Li +) range, Li intercalation into Li xNiO 2 undergoes two-phase transitions in the same potential range. The shape of both plots, D versus E and Cint versus E for these electrodes, is discussed in the framework of a finite-space diffusion model and Li-insertion processes that can be described by Frumkin-type intercalation isotherms with short-range attraction interactions among intercalation sites.

  19. 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.

  20. 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.

  1. Surface, corrosion and biocompatibility aspects of Nitinol as an implant material.

    PubMed

    Shabalovskaya, Svetlana A

    2002-01-01

    The present review surveys studies on physical-chemical properties and biological response of living tissues to NiTi (Nitinol) carried out recently, aiming at an understanding of the place of this material among the implant alloys in use. Advantages of shape memory and superelasticity are analyzed in respect to functionality of implants in the body. Various approaches to surface treatment, sterilization procedures, and resulting surface conditions are analyzed. A review of corrosion studies conducted both on wrought and as-cast alloys using potentiodynamic and potentiostatic techniques in various corrosive media and in actual body fluids is also given. The parameters of localized and galvanic corrosion are presented. The corrosion behavior is analyzed with respect to alloy composition, phase state, surface treatment, and strain and compared to that of conventional implant alloys. Biocompatibility of porous Nitinol, Ni release and its effect on living cells are analyzed based on understanding of the surface conditions and corrosion behavior. Additionally, the paper offers a brief overview of the comparative toxicity of metals, components of commonly used medical alloys, indicating that the biocompatibility profile of Nitinol is conducive to present in vivo applications.

  2. Real-time, multiplexed electrochemical DNA detection using an active complementary metal-oxide-semiconductor biosensor array with integrated sensor electronics

    PubMed Central

    Levine, Peter M.; Gong, Ping; Levicky, Rastislav; Shepard, Kenneth L.

    2009-01-01

    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 4×4 array of gold working electrodes and integrated potentiostat electronics, consisting of control amplifiers and current-input analog-to-digital converters, on a custom-designed 5×3 mm2 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

  3. Zinc oxide nanostructures for electrochemical cortisol biosensing

    NASA Astrophysics Data System (ADS)

    Vabbina, Phani Kiran; Kaushik, Ajeet; Tracy, Kathryn; Bhansali, Shekhar; Pala, Nezih

    2014-05-01

    In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs) as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078 KΩ. M-1 for ZnO-NRs and 540 Ω. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.

  4. A Multi-Technique Reconfigurable Electrochemical Biosensor: Enabling Personal Health Monitoring in Mobile Devices.

    PubMed

    Sun, Alexander; Venkatesh, A G; Hall, Drew A

    2016-09-26

    This paper describes the design and characterization of a reconfigurable, multi-technique electrochemical biosensor designed for direct integration into smartphone and wearable technologies to enable remote and accurate personal health monitoring. By repurposing components from one mode to the next, the biosensor's potentiostat is able reconfigure itself into three different measurements modes to perform amperometric, potentiometric, and impedance spectroscopic tests all with minimal redundant devices. A [Formula: see text] PCB prototype of the module was developed with discrete components and tested using Google's Project Ara modular smartphone. The amperometric mode has a ±1 nA to [Formula: see text] measurement range. When used to detect pH, the potentiometric mode achieves a resolution of < 0.08 pH units. In impedance measurement mode, the device can measure 50 Ω-10 [Formula: see text] and has been shown to have of phase error. This prototype was used to perform several point-of-care health tracking assays suitable for use with mobile devices: 1) Blood glucose tests were conducted and shown to cover the diagnostic range for Diabetic patients (  ∼ 200 mg/dL). 2) Lactoferrin, a biomarker for urinary tract infections, was detected with a limit of detection of approximately 1 ng/mL. 3) pH tests of sweat were conducted to track dehydration during exercise. 4) EIS was used to determine the concentration of NeutrAvidin via a label-free assay.

  5. A Multi-Technique Reconfigurable Electrochemical Biosensor: Enabling Personal Health Monitoring in Mobile Devices.

    PubMed

    Sun, Alexander; Venkatesh, A G; Hall, Drew A

    2016-10-01

    This paper describes the design and characterization of a reconfigurable, multi-technique electrochemical biosensor designed for direct integration into smartphone and wearable technologies to enable remote and accurate personal health monitoring. By repurposing components from one mode to the next, the biosensor's potentiostat is able reconfigure itself into three different measurements modes to perform amperometric, potentiometric, and impedance spectroscopic tests all with minimal redundant devices. A [Formula: see text] PCB prototype of the module was developed with discrete components and tested using Google's Project Ara modular smartphone. The amperometric mode has a ±1 nA to [Formula: see text] measurement range. When used to detect pH, the potentiometric mode achieves a resolution of < 0.08 pH units. In impedance measurement mode, the device can measure 50 Ω-10 [Formula: see text] and has been shown to have of phase error. This prototype was used to perform several point-of-care health tracking assays suitable for use with mobile devices: 1) Blood glucose tests were conducted and shown to cover the diagnostic range for Diabetic patients (  ∼  200 mg/dL). 2) Lactoferrin, a biomarker for urinary tract infections, was detected with a limit of detection of approximately 1 ng/mL. 3) pH tests of sweat were conducted to track dehydration during exercise. 4) EIS was used to determine the concentration of NeutrAvidin via a label-free assay.

  6. An Efficient Power Harvesting Mobile Phone-Based Electrochemical Biosensor for Point-of-Care Health Monitoring.

    PubMed

    Sun, Alexander C; Yao, Chengyang; Venkatesh, A G; Hall, Drew A

    2016-11-01

    Cellular phone penetration has grown continually over the past two decades with the number of connected devices rapidly approaching the total world population. Leveraging the worldwide ubiquity and connectivity of these devices, we developed a mobile phone-based electrochemical biosensor platform for point-of-care (POC) diagnostics and wellness tracking. The platform consists of an inexpensive electronic module (< $20) containing a low-power potentiostat that interfaces with and efficiently harvests power from a wide variety of phones through the audio jack. Active impedance matching improves the harvesting efficiency to 79%. Excluding loses from supply rectification and regulation, the module consumes 6.9 mW peak power and can measure < 1 nA bidirectional current. The prototype was shown to operate within the available power budget set by mobile devices and produce data that matches well with that of an expensive laboratory grade instrument. We demonstrate that the platform can be used to track the concentration of secretory leukocyte protease inhibitor (SLPI), a biomarker for monitoring lung infections in cystic fibrosis patients, in its physiological range via an electrochemical sandwich assay on disposable screen-printed electrodes with a 1 nM limit of detection.

  7. 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.

  8. Doped overoxidized polypyrrole microelectrodes as sensors for the detection of dopamine released from cell populations.

    PubMed

    Sasso, Luigi; Heiskanen, Arto; Diazzi, Francesco; Dimaki, Maria; Castillo-León, Jaime; Vergani, Marco; Landini, Ettore; Raiteri, Roberto; Ferrari, Giorgio; Carminati, Marco; Sampietro, Marco; Svendsen, Winnie E; Emnéus, Jenny

    2013-07-07

    A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons.

  9. Production of Conductive PEDOT-Coated PVA-GO Composite Nanofibers

    NASA Astrophysics Data System (ADS)

    Zubair, Nur Afifah; Rahman, Norizah Abdul; Lim, Hong Ngee; Sulaiman, Yusran

    2017-02-01

    Electrically conductive nanofiber is well known as an excellent nanostructured material for its outstanding performances. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT)-coated polyvinyl alcohol-graphene oxide (PVA-GO)-conducting nanofibers were fabricated via a combined method using electrospinning and electropolymerization techniques. During electrospinning, the concentration of PVA-GO solution and the applied voltage were deliberately altered in order to determine the optimized electrospinning conditions. The optimized parameters obtained were 0.1 mg/mL of GO concentration with electrospinning voltage of 15 kV, which displayed smooth nanofibrous morphology and smaller diameter distribution. The electrospun PVA-GO nanofiber mats were further modified by coating with the conjugated polymer, PEDOT, using electropolymerization technique which is a facile approach for coating the nanofibers. SEM images of the obtained nanofibers indicated that cauliflower-like structures of PEDOT were successfully grown on the surface of the electrospun nanofibers during the potentiostatic mode of the electropolymerization process. The conductive nature of PEDOT coating strongly depends on the different electropolymerization parameters, resulting in good conductivity of PEDOT-coated nanofibers. The optimum electropolymerization of PEDOT was at a potential of 1.2 V in 5 min. The electrochemical measurements demonstrated that the fabricated PVA-GO/PEDOT composite nanofiber could enhance the current response and reduce the charge transfer resistance of the nanofiber.

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

    PubMed

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

    2012-08-01

    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 H(2)O(2) 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 H(2)O(2) 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.

  11. Niobized AISI 304 stainless steel bipolar plate for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Sun, Juncai; Li, Pengbin; Jing, Bo; Li, Song; Wen, Zhongsheng; Ji, Shijun

    2012-06-01

    AISI 304 stainless steel (SS) has been niobized by a plasma surface diffusion alloying method. A 3 μm niobized layer with dominant niobium elements has been formed on the 304 SS surface and the performances of the niobized 304 SS has been examined and evaluated as bipolar plate for proton exchange membrane fuel cell (PEMFC). Results show that the average contact angle with water for the niobized 304 SS is about 90.4°, demonstrating better hydrophobicity as compared with the untreated 304 SS (68.1°). The corrosion resistance of the 304 SS is considerably improved by the niobized layer with the corrosion current densities decreased at 0.2 and 0.4 μA cm-2 in simulated PEMFC anode purged with hydrogen and the cathode purged with air condition (0.05 M H2SO4 + 2 ppm F- solution at 70 °C), respectively. The interfacial contact resistance (ICR) for the as-prepared niobized 304 SS is 10.53 mΩ cm2 at the compaction of 140 N cm-2. Furthermore, after 4 h potentiostatic tests, the niobizied specimens exhibit much lower ICR than that for the untreated ones. Thus, the niobized layer can act as a conductively protective layer of the 304 SS bipolar plate for PEMFC.

  12. Magnetic nanowires for rapid and ultrasensitive isolation of DNA from cervical specimens for the detection of multiple human papillomaviruses genotypes.

    PubMed

    Lee, HyungJae; Hwang, Na Rae; Hwang, Sang-Hyun; Cho, Youngnam

    2016-12-15

    Detecting human papillomavirus (HPV) is central in diagnosing and monitoring HPV-related disease. However, limited sensitivity and the wide variability of the HPV genome pose challenges in the identification of HPV genes, particularly high-risk types. This study reports the development of polyethyleneimine-conjugated magnetic nanowires (PEI-MNWs) and their use in the isolation, identification, and analysis of multiple genotypes of HPV DNA from cervical cancer specimens. The nanowires are electrochemically doped with a high density of magnetic nanoparticles and biotin moieties during potentiostatic deposition, thereby allowing conjugating cationic branched polymers to direct the attachment of negatively charged DNA molecules with strong magnetic response. For proof of concept, the rapid and ultrasensitive isolation of HPV DNA is performed at concentrations as low as 10pg/mL with an efficiency of >95%. For clinical optimization, the analytical and clinical sensitivity of PEI-MNWs is compared with that of the Roche Cobas 4800 HPV Test and demonstrates excellent correlation for multiple HPV DNA genotypes with superior threshold cycle values. The high sensitivity, specificity, and good reproducibility of PEI-MNWs are particularly well suited for the recovery of DNA and provide significant and clinically meaningful evidence for the early detection and treatment of HPV-associated cancers.

  13. Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations.

    PubMed

    Sun, Bing; Mindemark, Jonas; Morozov, Evgeny V; Costa, Luciano T; Bergman, Martin; Johansson, Patrik; Fang, Yuan; Furó, István; Brandell, Daniel

    2016-04-14

    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.

  14. Charge-Transfer Dynamics of Fluorescent Dye-Sensitized Electrodes under Applied Biases.

    PubMed

    Godin, Robert; Sherman, Benjamin D; Bergkamp, Jesse J; Chesta, Carlos A; Moore, Ana L; Moore, Thomas A; Palacios, Rodrigo E; Cosa, Gonzalo

    2015-07-16

    The development of dye-sensitized solar cells requires an in-depth understanding of the interfacial charge-transfer dynamics that take place between dye sensitizers and semiconductors. Here, we describe a prototype system to probe these dynamics by monitoring in real time the fluorescence of two organic sensitizers, a perylene and a squaraine, bound to a SnO2 semiconductor thin film as a function of potentiostatic control of the Fermi level. The two different sensitizer fluorophores characterized by vastly different redox potentials undergo similar fluorescence modulation with applied bias, an indication that the density of states of the semiconductor largely influences the charge-transfer dynamics while energetics play a minimal role. We further show that the rate of photodegradation of the perylene sensitizer with applied bias provides a suitable marker to study the rate of charge injection and charge recombination. Taken together, our results demonstrate a suitable platform to visualize and study charge-transfer dynamics on films and constitute a step toward achieving single-molecule resolution in our quest to decipher the static and dynamic heterogeneity of charge-transfer dynamics in dye-sensitized photoanodes.

  15. Mobility and Oxidation of Adsorbed CO on Shape-Controlled Pt Nanoparticles in Acidic Medium.

    PubMed

    Farias, Manuel J S; Busó-Rogero, Carlos; Vidal-Iglesias, Francisco J; Solla-Gullón, José; Camara, Giuseppe A; Feliu, Juan M

    2017-01-31

    The knowledge about how CO occupies and detaches from specific surface sites on well-structured Pt surfaces provides outstanding information on both dynamics/mobility of COads and oxidation of this molecule under electrochemical conditions. This work reports how the potentiostatic growth of different coverage CO adlayers evolves with time on both cubic and octahedral Pt nanoparticles in acidic medium. Data suggest that during the growth of the CO adlayer, COads molecules slightly shift toward low coordination sites only on octahedral Pt nanoparticles, so that these undercoordinated sites are the first filled on octahedral Pt nanoparticles. Conversely, on cubic Pt nanoparticles, adsorbed CO behaves as an immobile species, and low coordinated sites as well as (100) terraces are apparently filled uniformly and simultaneously. However, once the adlayer is complete, irrespectively of whether the CO is oxidized in a single step or in a sequence of different potential steps, results suggest that COads behaves as an immobile species during its oxidation on both octahedral and cubic Pt nanoparticles.

  16. 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.

  17. Charge displacement by adhesion and spreading of a cell.

    PubMed

    Svetlicić, V; Ivosević, N; Kovac, S; Zutić, V

    2001-01-01

    The potentiostatic control of surface charge density and interfacial tension of an electrode immersed in an aqueous electrolyte solution offers a possibility for direct studies of non-specific interactions in cell adhesion. Unicellular marine alga, Dunaliella tertiolecta (Chlorophyceae) of micrometer size and flexible cell envelope was used as a model cell and 0.1 M NaCl as supporting electrolyte. The dropping mercury electrode acted as in situ adhesion sensor and the electrochemical technique of chronoamperometry allowed measurement of the spread cell-electrode interface area and the distance of the closest approach of a cell. The adhesion and spreading of a single cell at the mercury electrode causes a displacement of counter-ions from the electrical double layer over a broad range of the positive and negative surface charge densities (from +16.0 to -8.2 microC/cm2). The flow of compensating current reflects the dynamics of adhesive contact formation and subsequent spreading of a cell. The adhesion and spreading rates are enhanced by the hydrodynamic regime of electrode's growing fluid interface. The distance of the closest approach of an adherent cell is smaller or equal to the distance of the outer Helmholz plane within the electrical double layer, i.e. 0.3-0.5 nm. There is a clear evidence of cell rupture for the potentials of maximum attraction as the area of the contact interface exceeded up to 100 times the cross-section area of a free cell.

  18. Addressable nanoelectrode membrane arrays: fabrication and steady-state behavior.

    PubMed

    Zoski, Cynthia G; Yang, Nianjun; He, Peixin; Berdondini, Luca; Koudelka-Hep, Milena

    2007-02-15

    An addressable nanoelectrode membrane array (ANEMA) based on a Au-filled track-etched polycarbonate membrane was fabricated. The Au-filled membrane was secured to a lithographically fabricated addressable ultramicroelectrode (UME) array patterned with 25 regularly spaced (100 microm center to center spacing), 10 microm diameter recessed Pt UMEs to create 25 microregions of 10 microm diameter nanoelectrode ensembles (NEEs) on the membrane. The steady-state voltammetric behavior of 1.0 mM Ru(NH(3))(6)Cl(3) and 1.0 mM ferrocene methanol in 0.1 M KCl on each of the micro NEEs resulted in sigmoidal-shaped voltammograms which were reproducible across the ANEMA. This reproducibility of the steady-state current was attributed to the overlapping hemispherical diffusion layers at the Au-filled nanopores of each 10 microm diameter NEE of a ANEMA. The track-etched polycarbonate membranes were filled using a gold electroless deposition procedure into the 30 nm diameter pores in the membrane. Electrical connection between the Au-filled template array and the lithographic UME platform array was achieved by potentiostatic electrodeposition of Cu from an acidic copper solution into each of the 25 recessed Pt UMEs on the UME array platform. A multiplexer unit capable of addressing 64 individual micro NEEs on an ANEMA is described. ANEMAs have advantages of high reproducibility, facile fabrication, multitime reuse of lithographically fabricated UME arrays, and purely steady-state behavior.

  19. The effect of Fe content in electrodeposited CoFe/Cu multilayers on structural, magnetic and magnetoresistance characterizations.

    PubMed

    Tekgül, Atakan; Alper, Mürsel; Kockar, Hakan; Safak, Mürşide; Karaagac, Oznur

    2010-11-01

    A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control, but the Fe concentration in the electrolytes was changed from 0.0125 M to 0.2 M. The deposition was carried out in a three-electrode cell at room temperature. The deposition of Cu layers was made at a cathode potential of -0.3 V with respect to saturated calomel electrode (SCE), while the ferromagnetic CoFe layers were deposited at -1.5 V versus SCE. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure. The magnetic characteristics of the films were investigated using a vibrating sample magnetometer and their easy-axis was found to be in film plane. Magnetoresistance measurements were carried out using the Van der Pauw method at room temperature with magnetic fields up to +/- 12 kOe. All multilayers exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained.

  20. 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.

  1. Physical electrochemistry of nanostructured devices.

    PubMed

    Bisquert, Juan

    2008-01-07

    This Perspective reviews recent developments in experimental techniques and conceptual methods applied to the electrochemical properties of metal-oxide semiconductor nanostructures and organic conductors, such as those used in dye-sensitized solar cells, high-energy batteries, sensors, and electrochromic devices. The aim is to provide a broad view of the interpretation of electrochemical and optoelectrical measurements for semiconductor nanostructures (sintered colloidal particles, nanorods, arrays of quantum dots, etc.) deposited or grown on a conducting substrate. The Fermi level displacement by potentiostatic control causes a broad change of physical properties such as the hopping conductivity, that can be investigated over a very large variation of electron density. In contrast to traditional electrochemistry, we emphasize that in nanostructured devices we must deal with systems that depart heavily from the ideal, Maxwell-Boltzmann statistics, due to broad distributions of states (energy disorder) and interactions of charge carriers, therefore the electrochemical analysis must be aided by thermodynamics and statistical mechanics. We discuss in detail the most characteristic densities of states, the chemical capacitance, and the transport properties, specially the chemical diffusion coefficient, mobility, and generalized Einstein relation.

  2. 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.

  3. Dithionite/air direct ion liquid fuel cell

    NASA Astrophysics Data System (ADS)

    Noack, Jens; Tübke, Jens; Pinkwart, Karsten

    2015-07-01

    The feasibility of an alkaline S2O42-/air-fuel cell was evaluated at room temperature, using a cell with an anion exchange membrane and a platinum oxygen reduction reaction catalyst. The tests performed were open circuit voltage analysis, linear sweep voltammetry, discharge analysis and electrochemical impedance spectroscopy (EIS) with registration of anode half-cell potential. With 0.85 M Na2S2O4 in 2 M KOH, the cell achieved a maximum power density of 2 mW cm-2, and the open circuit cell voltage was about 0.9 V. In a potentiostatic discharging at 0.2 V cell voltage, an energy efficiency of 12.3% was achieved at an energy density of 8.6 Wh L-1. The low power density was mainly due to the low reaction kinetics of dithionite oxidation at graphite electrodes. The low energy efficiency was mainly caused by a low cathode potential, which probably resulted from mixed potential formation and the low anode kinetics.

  4. Low-melting-point titanium-base brazing alloys—part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4v substrate

    NASA Astrophysics Data System (ADS)

    Chang, E.; Chen, C.-H.

    1997-12-01

    Filler metal of a low-melting-point (917 °C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 °C for 2,4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed a plus intergranular β structure of Ti-6Al-4V substrate causes the lamellar Widmanstätten structure to form. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the metal brazed at 960 °C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the β phase to the substrate. In deaerated Hank’s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank’s solution, show similar corrosion behavior, irrespective of the brazing time.

  5. 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.

  6. 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/.

  7. 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.

  8. 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.

  9. Porous NiTi surfaces for biomedical applications

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    In this study, the NiTi shape memory alloy was surface modified by plasma electrolytic oxidation (PEO) in Na3PO4 with the aim to produce porous NiTi surfaces for biomedical applications. The oxidation was performed potentiostatically and the characteristics of the resultant surfaces were compared with those obtained in NaAlO2/NaPO2H2 under similar conditions. Surfaces with sub-micron sized pores could be produced in Na3PO4 electrolyte at 300 V. The process was accompanied by intense gas evolution and enhanced thermal effects relative to the NaAlO2/NaPO2H2 electrolyte. The EDS analyses revealed the presence of O, Ti, P, Ni, and a Ni/Ti atomic ratio of 0.4 suggesting preferential oxidation of titanium during the process and depletion of Ni from the surface. No crystalline oxide phases were detected by X-ray diffraction (XRD). By comparison, the layers formed in NaAlO2/NaPO2H2 consisted of crystalline Al2O3 and the Ni/Ti atomic ratio was 0.74. Following oxidation, the wettability and surface free energy of NiTi increased significantly. The findings of this study indicate that the PEO process shows potential for expanding the biofunctionality of NiTi.

  10. New Ni-free superelastic alloy for orthodontic applications.

    PubMed

    Arciniegas, M; Manero, J M; Espinar, E; Llamas, J M; Barrera, J M; Gil, F J

    2013-08-01

    A potential new Ni-free Ti alloy for biomedical applications was assessed in order to investigate the superelastic behavior, corrosion resistance and the biocompatibility. The alloy studied was Ti19.1Nb8.8Zr. The chemical composition was determined by X-ray microanalysis, the thermoelastic martensitic transformation was characterized by high sensitivity calorimeter. The critical stresses were determined by electromechanical testing machine and the corrosion behavior was analyzed by potentiostatic equipment in artificial saliva immersion at 37°C. The results were compared with six different NiTi orthodontic archwire brands. The biocompatibility was studied by means of cultures of MG63 cells. Ni-free Ti alloy exhibits thermoelastic martensitic transformation with Ms=45°C. The phase present at 37°C was austenite which under stress can induce martensite. The stress-strain curves show a superelastic effect with physiological critical stress (low and continuous) and a minimal lost of the recovery around 150 mechanical cycles. The corrosion resistance improves the values obtained by different NiTi alloys avoiding the problem of the Ni adverse reactions caused by Ni ion release. Cell culture results showed that adhered cell number in new substrate was comparable to that obtained in a commercially pure Ti grade II or beta-titanium alloy evaluated in the same conditions. Consequently, the new alloy presents an excellent in-vitro response.

  11. 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.

  12. Effect of chloride ions on the corrosion behavior of low-alloy steel containing copper and antimony in sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Park, Sun-Ah; Kim, Seon-Hong; Yoo, Yun-Ha; Kim, Jung-Gu

    2015-05-01

    The influence of the addition of HCl on the corrosion behavior of low-alloy steel containing copper and antimony was investigated using electrochemical (potentiodynamic and potentiostatic polarization tests, and electrochemical impedance spectroscopy) and weight loss tests in a 1.6M H2SO4 solution with different concentrations of hydrochloric acid (0.00, 0.08, 0.15 and 0.20 M HCl) at 60 °C. The result showed that the corrosion rate decreased with increasing HCl by the formation of protective layers. SEM, EDS and XPS examinations of the corroded surfaces after the immersion test indicated that the corrosion production layer formed in the solution containing HCl was highly comprised of metallic Cu, Cu chloride and metallic (Fe, Cu, Sb) compounds. The corrosion resistance was improved by the Cu-enriched layer, in which chloride ions are an accelerator for cupric ion reduction during copper deposition. Furthermore, cuprous and antimonious chloride species are complex salts for cuprous ions adsorbed on the surface during copper deposition.

  13. In-situ electrochemically active surface area evaluation of an open-cathode polymer electrolyte membrane fuel cell stack

    NASA Astrophysics Data System (ADS)

    Torija, Sergio; Prieto-Sanchez, Laura; Ashton, Sean J.

    2016-09-01

    The ability to evaluate the electrochemically active surface area (ECSA) of fuel cell electrodes is crucial toward characterising designs and component suites in-situ, particularly when evaluating component durability in endurance testing, since it is a measure of the electrode area available to take part in the fuel cell reactions. Conventional methods to obtain the ECSA using cyclic voltammetry, however, rely on potentiostats that cannot be easily scaled to simultaneously evaluate all cells in a fuel cell stack of practical size, which is desirable in fuel cell development. In-situ diagnostics of an open-cathode fuel cell stack are furthermore challenging because the cells do not each possess an enclosed cathode compartment; instead, the cathodes are rather open to the environment. Here we report on a diagnostic setup that allows the electrochemically active surface area of each cell anode or cathode in an open-cathode fuel cell stack to be evaluated in-situ and simultaneously, with high resolution and reproducibility, using an easily scalable chronopotentiometry methodology and a gas-tight stack enclosure.

  14. Sonoelectrochemical recovery of silver from photographic processing solutions

    PubMed

    Pollet; Lorimer; Phull; Hihn

    2000-04-01

    This paper describes the effect of ultrasound upon the electrochemical recovery of silver from photographic processing solutions using a newly designed electrochemical cell--SonoEcoCell. Rates of deposition of silver (obtained potentiostatically) were studied in the model 'fix' solutions (dilute aqueous Na2S2O3/NaHSO3 at a stainless steel cylinder electrode in both the absence and the presence of ultrasound. Under silent conditions, the magnitude of the cathodic potential is a major factor in the removal of silver. Under 20 kHz sonication, the rate of deposition of silver increases with increasing ultrasonic intensity. The cathode efficiency is also enhanced under insonation. The position of the ultrasonic probe with respect to the rotating cylinder electrode (RCE) was studied. It was found that for a 'face-on' geometry (probe parallel to the electrode) led to higher rate constants compared with a 'side-on' geometry (probe perpendicular to the electrode). The effect of coupling an RCE with ultrasound upon these rate constants employing the two geometry was also investigated. It was found that, employing either the face-on or the side-on geometry alone, improved rate constants were obtained below approximately 1500 and 2000 rpm, respectively.

  15. 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.

  16. Nanotube nucleation phenomena on Ti-25Ta-xZr alloys for implants using ATO technique.

    PubMed

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

    2014-10-01

    The purpose of this study was to investigate nanotube nucleation phenomena on the Ti-25Ta-xZr alloys for implant materials, using an anodic titanium oxide (ATO) technique. Ti-25Ta-(0 wt.%-15 wt.%) Zr alloys were prepared using a vacuum arc-melting furnace. The Ti-25Ta-xZr alloys were then homogenized for 12 hr at 1000 degrees C, followed by water quenching. Formation of the nanotubular oxide surface structure was achieved initially on the Ti-25Ta-xZr alloys by anodization in a 1 M H3PO4 electrolyte containing 0.8 wt.% NaF at room temperature, using a potentiostat. After the first formation of the nanotubes was achieved, this initial nanotube layer was eliminated, and further anodization was carried out repeatedly. The microstructure, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and the process of nanotube growth using this ATO method were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. Microstructures of the Ti-25Ta-xZr alloys changed from α" phase to β phase. Nanotubes formed with the ATO technique had pit-like top holes, with thinner walls and lower contact angle, compared to the initially formed nanotubes.

  17. 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.

  18. Low modulus Ti-Nb-Hf alloy for biomedical applications.

    PubMed

    González, M; Peña, J; Gil, F J; Manero, J M

    2014-09-01

    β-Type titanium alloys with a low elastic modulus are a potential strategy to reduce stress shielding effect and to enhance bone remodeling in implants used to substitute failed hard tissue. For biomaterial application, investigation on the mechanical behavior, the corrosion resistance and the cell response is required. The new Ti25Nb16Hf alloy was studied before and after 95% cold rolling (95% C.R.). The mechanical properties were determined by tensile testing and its corrosion behavior was analyzed by potentiostatic equipment in Hank's solution at 37°C. The cell response was studied by means of cytotoxicity evaluation, cell adhesion and proliferation measurements. The stress-strain curves showed the lowest elastic modulus (42GPa) in the cold worked alloy and high tensile strength, similar to that of Ti6Al4V. The new alloy exhibited better corrosion resistance in terms of open circuit potential (EOCP), but was similar in terms of corrosion current density (iCORR) compared to Ti grade II. Cytotoxicity studies revealed that the chemical composition of the alloy does not induce cytotoxic activity. Cell studies in the new alloy showed a lower adhesion and a higher proliferation compared to Ti grade II presenting, therefore, mechanical features similar to those of human cortical bone and, simultaneously, a good cell response.

  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. 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.

  1. Electrochemical nucleophilic synthesis of di-tert-butyl-(4-[18F]fluoro-1,2-phenylene)-dicarbonate.

    PubMed

    He, Qinggang; Wang, Ying; Alfeazi, Ines; Sadeghi, Saman

    2014-09-01

    An electrochemical method with the ability to conduct (18)F-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-[(18)F]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. Radio-fluorination efficiency of 10.4±0.6% (n=4) and specific activity of up to 43GBq/mmol was obtained after 1h electrolysis of 0.1M of 4-tert-butyl-diboc-catechol in the acetonitrile solution of Et3N·3HF (0.033M) and NBu4PF6 (0.05M). Density functional theory (DFT) was employed to explain the tert-butyl functional group facilitation of electrochemical oxidation and subsequent fluorination.

  2. Electrochemical oxidation of the polycyclic aromatic hydrocarbons in polluted concrete of the residential buildings.

    PubMed

    Aćimović, Danka D; Karić, Slavko D; Nikolić, Željka M; Brdarić, Tanja P; Tasić, Gvozden S; Marčeta Kaninski, Milica P; Nikolić, Vladimir M

    2017-01-01

    Polycyclic aromatic hydrocarbons (PAH) have been listed by the United States Environmental Protection Agency (US EPA) and by the European Community as priority environmental pollutants. The removal of PAHs from soils, sediments and waste water has attracted attention of scientists and engineers for several decades. Electrochemical oxidation of PAH compounds in water, is receiving increasing attention, due to its convenience and simplicity. In this study we performed electrochemical oxidation of 16 EPA PAHs mixture in 10% NaCl aqueous solution in potentiostatic conditions, at voltage 1 V. Decrease of concentration of some individual PAHs, up to 70% referred to their starting concentration, after 60 min of electrolysis, was confirmed by UPLC/PDA analysis. In further work investigation was extrapolated to in situ removal of PAHs from concrete, as the medium where, to our knowledge, such way of PAH removal has not been investigated before. High concentrations of PAH contamination occurred in the concrete structure of the residential buildings in Belgrade in 2014. Application of DC voltage of 50 V between nickel and stainless steel electrodes packed in the concrete wall, moisturized with the 10% NaCl solution, led to considerable removal of the pollutants by oxidation process throughout the concrete.

  3. 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

    2016-02-04

    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.

  4. 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.

  5. 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

  6. The Electrochemical Reduction of Chromium Sesquioxide in Molten Calcium Chloride under Cathodic Potential Control

    NASA Astrophysics Data System (ADS)

    Schwandt, Carsten; Fray, Derek J.

    2007-11-01

    Electrochemical polarization and reduction experiments are reported which were performed with a three-terminal cell and a molten salt electrolyte consisting of calcium chloride with additions of calcium oxide. Employing a metal cathode, a graphite anode and a pseudo-reference electrode also made from graphite, polarization measurements were carried out with the aim to validate the performance of the pseudo-reference electrode and to assess the stability of the electrolyte. Using a chromium sesquioxide cathode in conjunction with a graphite anode and a graphite pseudo-reference electrode, electrochemical reduction experiments were conducted under potentiostatic control. The key results are: a graphite pseudo-reference electrode has been shown to be appropriate in the present type of molten salt electrochemical experiments that take place on a time scale of many hours; the conversion of chromium oxide into chromium metal has been accomplished under cathodic potential control and in the absence of calcium metal deposition; a significant amount of calcium oxide in the calcium chloride has been found necessary to preclude anodic chlorine formation throughout the entire experiment; a considerable overpotential has been identified at the anode.

  7. 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.

  8. Crevice corrosion of nickel superalloy in deaerated chloride/sulphate solution at 90°C

    NASA Astrophysics Data System (ADS)

    Rincón Ortiz, M.; Carranza, R. M.; Rodríguez, M. A.

    2017-01-01

    Alloy 22 is a nickel base alloy highly resistant to all forms of corrosion. It was designed to resist to most aggressive environments for industrial applications. Electrochemical studies such as Potentiodynamic-Galvanostatic-Potentiostatic (PD-GS-PD) tests and Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscopy (SEM) observations were performed to determine the corrosion behaviour of alloy 22 (N06022). The effect of sulphate ion in chloride containing solutions at 90°C, were studied in this work under aggressive conditions where this material might be susceptible to crevice corrosion. The electrolyte solution, which consisted of 0.1M and 1M NaCl and different sulphate concentrations. It was observed that there were complete inhibitions of crevice corrosion for R crit =[SO4 =]/[Cl-]=1 in the 0.1mol/L NaCl solutions and R crit =2 in the 1mol/L NaCl solutions. The corrosion rate obtained was about 0.1μm/year at 24 hours of immersion.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Implementation of electrochemical elements for an alternative detection of ochratoxin A

    NASA Astrophysics Data System (ADS)

    Aristizabal, D. H.; Giraldo, D. A.; Sanchez, S.; Taborda, G.; Baeza, A.

    2017-01-01

    Ochratoxin A (OTA) is a nephrotoxic metabolite, hepatotoxic and carcinogenic produced mainly by Aspergillus and Penicillium fungi. Usually, the mycotoxin analysed through the technique of high performance liquid chromatography. This method is expensive and takes a lot of time. Therefore, expected to automate a device of low cost, minimal instrumentation micropolarographic (MIMP) for the analysis. For this purpose, the right programming environment and the manufacturing of the software for the graphical user interface selected automation of the MIMP through the design and simulation of the circuit, imprint and assembled in a container with connection ports. Lastly, validation and analysis of Ochratoxin A by cyclic voltammetry from analogous MIMP, automatic MIMP and a potentiostat, in order to corroborate the registered data. This way, voltammetry analysis of coumarin is obtained and the simulation of the MIMP electric circuit. Therefore, this are the key data during the investigation, because the molecule of OTA can be monitored through an acid hydrolysis of amides, composed by a phenylalanine and coumaric acid group, generating the significant decrease in the costs and time of analysis.

  16. Engineering bamboo-type TiO2 nanotube arrays to enhance their photocatalytic property.

    PubMed

    Guan, Dongsheng; Hymel, Paul J; Zhou, Chengjun; Wang, Ying

    2014-06-01

    Bamboo-type TiO2 nanotube arrays with high surface area can be synthesized by alternating voltage (AV) anodization for their important use as photocatalytic medium. Their morphologies are highly dependent on preparation parameters including anodization time and electrolyte composition. Minimum time of high-voltage steps required for forming desired bamboo ridge spacing on these nanotubes can be calculated from current-time profiles recorded during potentiostatic anodization at the voltage. Water content in NH4F-containing ethylene glycol (EG) electrolytes is optimized simply from analyses of current transients or current-voltage relations for anodization in EG electrolytes with different amount of water, in order to achieve efficient electrochemical growth of TiO2 nanotubes for large ridge density and long tube length. Two types of bamboo-type TiO2 nanotubes with the same length of 5.46 microm but different ridge spacing are synthesized for photocatalytic degradation of methylene blue (MB) under UV radiation. Both of the bamboo-type nanotube arrays show improved photo catalysis compared to smooth TiO2 nanotubes of the same length, due to their larger surface area favorable for heterogeneous catalytic processes. In particular, the apparent rate constant of photocatalytic degradation on bamboo-type nanotubes is up to 29.4% higher than that for degradation on smooth ones.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Repassivation Investigations on Aluminium: Physical Chemistry of the Passive State

    NASA Astrophysics Data System (ADS)

    Nagy, Tristan Oliver; Weimerskirch, Morris Jhängi Joseph; Pacher, Ulrich; Kautek, Wolfgang

    2016-09-01

    We show the temporal change in repassivation mechanism as a time-dependent linear combination of a high-field model of oxide growth (HFM) and the point defect model (PDM). The observed switch in transient repassivation current-decrease under potentiostatic control occurs independently of the active electrode size and effective repassivation time for all applied overpotentials. For that, in situ depassivation of plasma electrolytically oxidized (PEO) coatings on aluminium was performed with nanosecond laser pulses at 266 nm and the repassivation current transients were recorded as a function of pulse number. A mathematical model combines the well established theories of oxide-film formation and growth kinetics, giving insight in the non linear transient behaviour of micro-defect passivation. According to our findings, the repassivation process can be described as a charge consumption via two concurrent channels. While the major current-decay at the very beginning of the fast healing oxide follows a point-defect type exponential damping, the HFM mechanism supersedes gradually, the longer the repassivation evolves. Furthermore, the material seems to reminisce former laser treatments via defects built-in during depassivation, leading to a higher charge contribution of the PDM mechanism at higher pulse numbers.

  2. 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.

  3. 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.

  4. A novel automated electrochemical ascorbic acid assay in the 24-well microtiter plate format.

    PubMed

    Intarakamhang, Sireerat; Leson, Christian; Schuhmann, Wolfgang; Schulte, Albert

    2011-02-14

    Automatic ascorbic acid (AA) voltammetry was established in 24-well microtiter plates. The assay used a movable assembly of a pencil rod working, an Ag/AgCl reference and a Pt counter electrode with differential pulse voltammetry (DPV) for concentration-dependent current generation. A computer was in command of electrode (z) and microtiter plate (x, y) positioning and timed potentiostat operation. Synchronization of these actions supported sequential approach of all wells and subsequent execution of electrode treatment procedures or AA voltammetry at defined intervals in a measuring cycle. DPV in well solutions offered a linear current/concentration range between 0.1 and 8.0 mM, a sensitivity of about 1 μA mM(-1) AA, and a detection limit of 50 μM. When used with a calibration curve or standard addition, automated voltammetry of samples with added known amounts of AA demonstrated good recovery rates. Also, the assay achieved the accurate determination of the AA content of vitamin C tablets, a fruit juice and an herbal tea extract. Robotic AA voltammetry has the advantage of conveniently handling multiple samples in a single measuring run without the continuous attention of laboratory personnel. It is a good option when the goal is cost-effective AA screening of sample libraries and has potential for applications in health care and the food processing, cosmetic and pharmaceutical industries.

  5. Multifrequency impedance measurement technique for wireless characterization of microbiological cell cultures.

    PubMed

    Wissenwasser, J; Vellekoop, M J; Kapferer, W; Lepperdinger, G; Heer, R

    2011-11-01

    An impedance measurement system with probe signal frequencies up to 50 kHz with AC-probe voltages below 30 mV rms was integrated for wireless and battery-free monitoring of microbiological cell cultures. The here presented modular design and the use of state-of-the-art components greatly eases adoptions to a wide range of biotechnological applications without the need of bulky LCR-meters or potentiostats. The device had a power consumption of less than 2.5 mA at a 3.3 V single power supply and worked trouble-free within the humid environment of a cell culture incubator. Measurements on lumped RC-elements showed an error of less than 1% for absolute values and less than 1° regarding the phase of the complex impedance. The performance of sensor devices with interdigitated electrode structures for the measurement of adherent cell cultures was tested in the presence of phosphate-buffered saline solution in the humid atmosphere of an incubator for biological cell cultures.

  6. Simultaneous arsenite oxidation and nitrate reduction at the electrodes of bioelectrochemical systems.

    PubMed

    Nguyen, Van Khanh; Park, Younghyun; Yu, Jaecheul; Lee, Taeho

    2016-10-01

    Arsenic and nitrate contaminations in the soil and groundwater have urged the scientific community to explore suitable technologies for treatment of both contaminants. This study reports, for the first time, a novel application of bioelectrochemical systems for coupling As detoxification at the anode and denitrification at the cathode. A similar As(III) oxidation efficiency was achieved when anode potential was controlled by a potentiostat or a direct current (DC) power supply. However, a slightly lower nitrate reduction rate was obtained in reactors using DC power supply during simultaneous operation of nitrate reduction and As(III) oxidation. Microbial community analysis by denaturing gradient gel electrophoresis indicated the presence of some autotrophic As(III)-oxidizing bacteria, including Achromobacter spp., Ensifer spp., and Sinorhizobium spp., that can flexibly switch their original metabolism of using oxygen as sole electron acceptor to a new metabolism mode of using solid-state anode as sole electron acceptor driving for As(III) oxidation under anaerobic conditions. Although further research is required for validating their applicability, bioelectrochemical systems represent a brilliant technology for remediation of groundwater contaminated with nitrate and/or arsenite.

  7. Morphology and performances of the anodic oxide films on Ti6Al4V alloy formed in alkaline-silicate electrolyte with aminopropyl silane addition under low potential

    NASA Astrophysics Data System (ADS)

    Chen, Jiali; Wang, Jinwei; Yuan, Hongye

    2013-11-01

    Oxide films on Ti6Al4V alloy are prepared using sodium hydroxide-sodium silicate as the base electrolyte with addition of aminopropyl trimethoxysilane (APS) as additive by potentiostatic anodizing under 10 V. APS is incorporated into the films during anodizing and the surface morphology of the oxide films is changed from particle stacked to honeycomb-like porous surfaces as shown by scanning electron microscopy (SEM) with Energy Disperse Spectroscopy (EDX). The surface roughness and aminopropyl existence on the oxide films result in their differences in wettability as tested by the surface profile topography and contact angle measurements. The anti-abrasive ability of the anodic films is improved with the addition of APS due to its toughening effects and serving as lubricants in the ceramic oxide films as measured by ball-on-disk friction test. Also, potentiodynamic corrosion test proves that their anticorrosive ability in 3.5 wt.% NaCl is greatly improved as reflected by their much lower corrosion current (Icorr) and higher corrosion potential (Ecorr) than those of the substrate.

  8. 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.

  9. 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.

  10. Energy-efficient treatment of organic wastewater streams using a rotatable bioelectrochemical contactor (RBEC).

    PubMed

    Cheng, Ka Yu; Ho, Goen; Cord-Ruwisch, Ralf

    2012-12-01

    A membraneless bioelectrochemical system - rotatable bio-electrochemical contactor (RBEC) consists of an array of rotatable electrode disks was developed to convert the chemical energy from wastewater organics (acetate) directly into electricity. Each rotatable electrode disk had an upper-air exposing and a lower-water submerging halves. Intermittent rotation (180°) enabled each halve to alternately serve as anode and cathode. Removal of chemical oxygen demand (COD) was increased by 15% (from 0.79 to 0.91 kg COD m(-3) d(-1)) by allowing electron flow from the lower to the upper disk halves. Coupling with a potentiostat could alleviate cathodic limitation and increased COD removal to 1.32 kg COD m(-3) day(-1) (HRT 5h). About 40% of the COD removed was via current, indicating that the biofilm could use the lower half disk as electron acceptor. The RBEC removed COD more energy-efficiently than conventional activated sludge processes as active aeration is not required (0.47 vs. 0.7-2.0 kW h kg COD(-1)).

  11. 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.

  12. Amperometric Sensor for Detection of Chloride Ions†

    PubMed Central

    Trnkova, Libuse; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Kizek, Rene

    2008-01-01

    Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE) and at a CPE modified with solid AgNO3, a solution of AgNO3 and/or solid silver particles. Detection limits (3 S/N) for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO3, solution of AgNO3 and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV) we estimated the limit of detection (3 S/N) as 500 nM. PMID:27873832

  13. Electrochemical determination of arsenic in natural waters using carbon fiber ultra-microelectrodes modified with gold nanoparticles.

    PubMed

    Carrera, Patricio; Espinoza-Montero, Patricio J; Fernández, Lenys; Romero, Hugo; Alvarado, José

    2017-05-01

    We have developed an anodic stripping voltammetry method that employs carbon fiber ultra-microelectrodes modified with gold nanoparticles to determine arsenic in natural waters. Gold nanoparticles were potentiostatically deposited on carbon fiber ultra-microelectrodes at -0.90V (vs SCE) for a time of 15s, to form the carbon fiber ultra-microelectrodes modified with gold nanoparticles. Cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy coupled to an X-ray microanalysis system were used to check and confirm the presence of gold nanoparticles on the carbon fiber ultra-microelectrodes. Arsenic detection parameters such as deposition potential and deposition time were optimized allowing a detection range between 5 to 60µgL(-1). The developed modified electrodes allowed rapid As determination with improved analytical characteristics including better repeatability, higher selectivity, lower detection limit (0.9μgL(-1)) and higher sensitivity (0.0176nAμgL(-1)) as compared to the standard carbon electrodes. The analytical capability of the optimized method was demonstrated by determination of arsenic in certified reference materials (trace elements in water (NIST SRM 1643d)) and by comparison of results with those obtained by hydride generation atomic absorption spectrometry (HG-AAS) in the determination of the analyte in tap and well waters.

  14. Lab-on-a-bird: biophysical monitoring of flying birds.

    PubMed

    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.

  15. Self‐Supported Polypyrrole/Polyvinylsulfate Films: Electrochemical Synthesis, Characterization, and Sensing Properties of Their Redox Reactions

    PubMed Central

    Martinez‐Soria, Lluis X.; Schumacher, Johanna; Valero, Laura; Pascual, Victor H.

    2017-01-01

    Abstract Thick films of polypyrrole/polyvinylsulfate (PPy/PVS) blends were electrogenerated on stainless‐steel electrodes under potentiostatic conditions from aqueous solution. The best electropolymerization potential window was determined by cyclic voltammetry. After removing the film from the back metal, self‐supported electrodes were obtained. Voltammetric, coulovoltammetric, and chronoamperometric responses from a LiClO4 aqueous solution indicated the formation of an energetically stable structure beyond a reduction threshold of the material. Its subsequent oxidation required higher anodic voltammetric overpotentials or longer chronoamperometric oxidation times. This structure was attributed to the formation of lamellar or vacuolar structures. X‐ray photoelectron spectroscopy analysis of the films under different oxidations states revealed that the electrochemical reactions drive the reversible exchange of cations between the film and the electrolyte. The electrical energy and the charge consumed by the reversible reaction of the film under voltammetric conditions between the constant potential limits are a function of the potential scan rate, that is, they sense the working electrochemical conditions. PMID:28168147

  16. Ultramicroband array electrode. 1. Analysis of mercury in contaminated soils and flue gas exposed samples using a gold-plated iridium portable system by anodic stripping voltammetry.

    PubMed

    Xiao, Li; Dietze, William; Nyasulu, Frazier; Mibeck, Blaise A F

    2006-07-15

    The applicability of a gold-plated iridium Nano-Band array ultramicroelectrode (6 microm by 0.2 microm, 64-microm interspacing, 100 electrode bands) in the analysis of mercury using a portable system is demonstrated by anodic stripping voltammetry in real-life samples. Optimized measurement parameters, 0.1 M HCl electrolyte, plating potential of 0 mV, and staircase scan mode were identified. The dynamic linear range is 10-180 ppb at 5-s deposition time with 1.5 microC of gold plated. The experimental detection limit for Hg2+ in 0.1 M HCl was 0.5 ppb at a deposition time of 4 min and a scan rate of 10 V/s. Real-life samples, such as flue gas exposed samples from flue gas simulators could be analyzed within 5 min using the method of standard additions. We identified a field-portable extraction procedure for soil samples using 1:1 concentrated HNO3/30% H2O2 mixture, compatible with ASV and the iridium electrode. The detection limit for soils is 1 ppm. The results obtained using ASV are in good agreement with reference values using cold vapor atomic absorption for the sample matrixes studied here. To our knowledge, this is the first mercury application using a reusable iridium array ultramicroelectrode. The portable potentiostat is less than 500 g, and together with the portable digestion method, makes the Nano-Band Explorer system field applicable.

  17. A Portable Liquid Chromatograph with a Battery-operated Compact Electroosmotic Pump and a Microfluidic Chip Device with a Reversed Phase Packed Column.

    PubMed

    Ishida, Akihiko; Fujii, Mitsutaka; Fujimoto, Takehiro; Sasaki, Shunsuke; Yanagisawa, Ichiro; Tani, Hirofumi; Tokeshi, Manabu

    2015-01-01

    A compact and lightweight liquid chromatography system is presented with overall dimensions of 26 cm width × 18 cm length × 21 cm height and weight of 2 kg. This system comprises a battery-operated compact electroosmotic pump, a manual injector, a microfluidic chip device containing a packed column and an electrochemical detector, and a USB bus-powered potentiostat. The pumping system was designed for microfluidic-based reversed-phase liquid chromatography in which an electroosmotically generated water stream pushes the mobile phase via a diaphragm for the output. The flow rate ranged from 0 to 10 μL/min and had a high degree of precision. The pumping system operated continuously for over 24 h with dry batteries. The column formed in the microfluidic device was packed with 3-μm ODS particles with a length of 30 mm and a diameter of 0.8 mm. The results presented herein demonstrate the performance of the pumping system and the column using alkylphenols, catecholamine, catechin, and amino acids.

  18. 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

  19. Wireless powering for electrochemical sensor

    NASA Astrophysics Data System (ADS)

    Peplowski, Andrzej; Janczak, Daniel; Jakubowska, Małgorzata

    2016-09-01

    System of wireless energy supply for a electrochemical sensor is presented. As a first step, various theoretical models of the sensor were considered and a new model, proper for the application studied, was proposed to enable further design stages. In the experiment conducted, it was verified, that the sensor, working in an amperometric mode and in the presence of constant or quasi-constant voltage supply, could be electrically approximated as element of the constant impedance value. Given this, power-consumption was calculated for the sensor using Ohm's law and the proof of concept device was fabricated to evaluate performance of the sensor under theoretically calculated conditions. The results obtained were comparable to the data previously recorded using conventional laboratory potentiostat. For verification of the resistive character of the sensor, chronoamperometric method was employed, with sensor's response complying with the theoretical prediction for quasi-constant powering signal and being influenced only by major voltage changes. Calculated power consumption of the sensor was Pmax. = 18.23μW. Concerning sensor's requirement for quasiconstant voltage, simple half-wave rectifier was designed that was connected to the antenna used for powering signal reception. In the second experiment, calibration of the sensor was performed, yielding sensitivity s = 2.03 μA/μmol/L and linear correlation coefficient ρ = 0.986 and thus confirming proper operation of the device in the conditions considered.

  20. 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

  1. Printable Electrochemical Biosensors: A Focus on Screen-Printed Electrodes and Their Application

    PubMed Central

    Yamanaka, Keiichiro; Vestergaard, Mun’delanji C.; Tamiya, Eiichi

    2016-01-01

    In this review we present electrochemical biosensor developments, focusing on screen-printed electrodes (SPEs) and their applications. In particular, we discuss how SPEs enable simple integration, and the portability needed for on-field applications. First, we briefly discuss the general concept of biosensors and quickly move on to electrochemical biosensors. Drawing from research undertaken in this area, we cover the development of electrochemical DNA biosensors in great detail. Through specific examples, we describe the fabrication and surface modification of printed electrodes for sensitive and selective detection of targeted DNA sequences, as well as integration with reverse transcription-polymerase chain reaction (RT-PCR). For a more rounded approach, we also touch on electrochemical immunosensors and enzyme-based biosensors. Last, we present some electrochemical devices specifically developed for use with SPEs, including USB-powered compact mini potentiostat. The coupling demonstrates the practical use of printable electrode technologies for application at point-of-use. Although tremendous advances have indeed been made in this area, a few challenges remain. One of the main challenges is application of these technologies for on-field analysis, which involves complicated sample matrices. PMID:27775661

  2. Pt-Pd bimetallic nanoparticles on MWCNTs: catalyst for hydrogen peroxide electrosynthesis

    NASA Astrophysics Data System (ADS)

    Félix-Navarro, R. M.; Beltrán-Gastélum, M.; Salazar-Gastélum, M. I.; Silva-Carrillo, C.; Reynoso-Soto, E. A.; Pérez-Sicairos, S.; Lin, S. W.; Paraguay-Delgado, F.; Alonso-Núñez, G.

    2013-08-01

    Bimetallic nanoparticles of Pt-Pd were deposited by the microemulsion method on a multiwall carbon nanotube (MWCNTs) to obtain a Pt-Pd/MWCNTs for electrocatalytic reduction of O2 to H2O2. The activity and selectivity of the catalyst was determined qualitatively by the rotating disk electrode method in acidic medium. The catalyst was spray-coated onto a reticulated vitreous carbon substrate and quantitatively was tested in bulk electrolysis for 20 min under potentiostatic conditions (0.5 V vs Ag/AgCl) in a 0.5 M H2SO4 electrolyte using dissolved O2. The bulk electrolysis experiments show that the Pt-Pd/MWCNTs catalyst is more efficient for H2O2 electrogeneration than a MWCNTs catalyst. Nitrobenzene degradation by electrogenerated H2O2 alone and Electro-Fenton process were also tested. Our results show that both processes decompose nitrobenzene, but the Electro-Fenton process does it more efficiently. The prepared nanoparticulated catalyst shows a great potential in environmental applications.

  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.

  4. DEP-On-Go for Simultaneous Sensing of Multiple Heavy Metals Pollutants in Environmental Samples.

    PubMed

    Biyani, Madhu; Biyani, Radhika; Tsuchihashi, Tomoko; Takamura, Yuzuru; Ushijima, Hiromi; Tamiya, Eiichi; Biyani, Manish

    2016-12-27

    We describe a simple and affordable "Disposable electrode printed (DEP)-On-Go" sensing platform for the rapid on-site monitoring of trace heavy metal pollutants in environmental samples for early warning by developing a mobile electrochemical device composed of palm-sized potentiostat and disposable unmodified screen-printed electrode chips. We present the analytical performance of our device for the sensitive detection of major heavy metal ions, namely, mercury, cadmium, lead, arsenic, zinc, and copper with detection limits of 1.5, 2.6, 4.0, 5.0, 14.4, and, 15.5 μg·L(-1), respectively. Importantly, the utility of this device is extended to detect multiple heavy metals simultaneously with well-defined voltammograms and similar sensitivity. Finally, "DEP-On-Go" was successfully applied to detect heavy metals in real environmental samples from groundwater, tap water, house dust, soil, and industry-processed rice and noodle foods. We evaluated the efficiency of this system with a linear correlation through inductively coupled plasma mass spectrometry, and the results suggested that this system can be reliable for on-site screening purposes. On-field applications using real samples of groundwater for drinking in the northern parts of India support the easy-to-detect, low-cost (<1 USD), rapid (within 5 min), and reliable detection limit (ppb levels) performance of our device for the on-site detection and monitoring of multiple heavy metals in resource-limited settings.

  5. 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.

  6. 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.

  7. 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.

  8. Flow-Injection Coulometric Detection Based on Ion Transfer and Its Application to the Determination of Chlorpromazine

    PubMed Central

    Ortuño, Joaquín A.; Gil, Antonio; Sánchez-Pedreño, Concepción

    2008-01-01

    A flow-injection coulometric method for the determination of chlorpromazine based on ion transfer into a plasticized poly(vinyl chloride) (PVC) membrane, was developed. The detector used consists of a flow-through cell that incorporates a plasticized poly(vinyl chloride) (PVC) membrane which contains tetrabutylammonium tetraphenylborate as electrolyte. The membrane is located between the flowing solution and an inner aqueous electrolyte solution. Two pairs of electrodes, each pair formed by a reference electrode and a working electrode, are used, one pair in each solution. The potential between the reference electrodes was controlled by a four-electrode potentiostat with ohmic drop compensation. A potential step capable of producing the transfer of the chlorpromazine ion into the membrane was applied during the passage of a wide portion of sample plug through the cell and the corresponding quantity of the electricity was measured. In the selected conditions, a linear relationship was observed between the quantity of electricity and chlorpromazine concentrations over a range of 1×10-6 −1×10-4 M. The detection limit was 2 × 10-7 M. Good repeatability and between-day reproducibility was obtained. No interference was observed on the part of some common ions and pharmaceutical excipients. The method proposed was applied satisfactorily to the determination of chlorpromazine in pharmaceuticals and human urine. PMID:27879901

  9. Ethanol electrooxidation on a carbon-supported Pt catalyst at elevated temperature and pressure: A high-temperature/high-pressure DEMS study

    NASA Astrophysics Data System (ADS)

    Sun, S.; Halseid, M. Chojak; Heinen, M.; Jusys, Z.; Behm, R. J.

    The electrooxidation of ethanol on a Pt/Vulcan catalyst was investigated in model studies by on-line differential electrochemical mass spectrometry (DEMS) over a wide range of reaction temperatures (23-100 °C). Potentiodynamic and potentiostatic measurements of the Faradaic current and the CO 2 formation rate, performed at 3 bar overpressure under well-defined transport and diffusion conditions reveal significant effects of temperature, potential and ethanol concentration on the total reaction activity and on the selectivity for the pathway toward complete oxidation to CO 2. The latter pathway increasingly prevails at higher temperature, lower concentration and lower potentials (∼90% current efficiency for CO 2 formation at 100 °C, 0.01 M, 0.48 V), while at higher ethanol concentrations (0.1 M), higher potentials or lower temperatures the current efficiency for CO 2 formation drops, reaching values of a few percent at room temperature. These trends result in a significantly higher apparent activation barrier for complete oxidation to CO 2 (68 ± 2 kJ mol -1 at 0.48 V, 0.1 M) compared to that of the overall ethanol oxidation reaction determined from the Faradaic current (42 ± 2 kJ mol -1 at 0.48 V, 0.1 M). The mechanistic implications of these results and the importance of relevant reaction and mass transport conditions in model studies for reaction predictions in fuel cell applications are discussed.

  10. Kinetic enhancement in nanoscale electrochemical systems caused by non-normal distributions of the electrode potential

    NASA Astrophysics Data System (ADS)

    García-Morales, Vladimir; Krischer, Katharina

    2011-06-01

    We have recently shown [Proc. Natl. Acad. Sci. U.S.A. 107, 4528 (2010)] that the discreteness and stochasticity of an electron transfer event on a resistively coupled nanoelectrode causes mesoscopic fluctuations in time of the electrode potential. These fluctuations give rise to a time-average faradaic current density substantially larger than in the macroscopic limit. The deviations result to a large extent from the potentiostatic control, which imposes a constraint on the evolution of the electrode potential that leads to non-normal distributions. The degree of freedom of the electrode potential requires a resistance between nanoelectrode and metallic support. In this article, we study the dependence of the mesoscopic stochastic dynamics on this resistance (assumed to be ohmic). We show that the enhancement of the reaction rate vanishes in both limits, zero and infinite resistance. The distribution of the electrode potential continuously transforms from a normal distribution at infinite resistance (the galvanostatic limit), through a more and more peaked distribution with increasingly important rare events to the deterministic behavior at zero resistance.

  11. Multilayered Zr-C/a-C film on stainless steel 316L as bipolar plates for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Bi, Feifei; Peng, Linfa; Yi, Peiyun; Lai, Xinmin

    2016-05-01

    A multilayered zirconium-carbon/amorphous carbon (Zr-C/a-C) coating is synthesized by magnetron sputtering in order to improve the corrosion resistance and interfacial conductivity of stainless steel 316L (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs). Zr-C/a-C film contains an outmost pure amorphous carbon layer and a sub zirconium containing carbon layer. Interfacial contact resistance (ICR) between carbon paper and coated SS316L decreases to 3.63 mΩ cm2 at 1.4 MPa. Potentiodynamic polarization results reveal that the corrosion potential of Zr-C/a-C coated sample is more positive than pure a-C coated sample and the current density is only 0.49 μA cm-2 at the cathode applied potential 0.6 V. Electrochemical impendence spectroscopy also indicates that multilayered Zr-C/a-C film coated SS316L has much higher charge transfer resistance than the bare sample. After potentiostatic polarization, ICR values are 3.92 mΩ cm2 and 3.82 mΩ cm2 in the simulated PEMFCs cathode and anode environment, respectively. Moreover, XPS analysis of the coated samples before and after potential holding tests shows little difference, which disclose the chemical stability of multilayered Zr-C/a-C film. Therefore, the multilayered Zr-C/a-C coating exhibits excellent performance in various aspects and is preferred for the application of stainless steel bipolar plates.

  12. Corrosion kinetics of 316L stainless steel bipolar plate with chromiumcarbide coating in simulated PEMFC cathodic environment

    NASA Astrophysics Data System (ADS)

    Huang, N. B.; Yu, H.; Xu, L. S.; Zhan, S.; Sun, M.; Kirk, Donald W.

    Stainless steel with chromium carbide coating is an ideal candidate for bipolar plates. However, the coating still cannot resist the corrosion of a proton exchange membrane fuel cell (PEMFC) environment. In this work, the corrosion kinetics of 316L stainless steel with chromium carbide is investigated in simulated PEMFC cathodic environment by combining electrochemical tests with morphology and microstructure analysis. SEM results reveal that the steel's surface is completely coated by Cr and chromium carbide but there are pinholes in the coating. After the coated 316L stainless steel is polarized, the diffraction peak of Fe oxide is found. EIS results indicate that the capacitive resistance and the reaction resistance first slowly decrease (2-32 h) and then increase. The potentiostatic transient curve declines sharply within 2000 s and then decreases slightly. The pinholes, which exist in the coating, result in pitting corrosion. The corrosion kinetics of the coated 316L stainless steel are modeled and accords the following equation: i0 = 7.6341t-0.5, with the corrosion rate controlled by ion migration in the pinholes.

  13. Electrochemical characteristics of a carbon fibre composite and the associated galvanic effects with aluminium alloys

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Curioni, M.; Jamshidi, P.; Walker, A.; Prengnell, P.; Thompson, G. E.; Skeldon, P.

    2014-09-01

    The electrochemical behaviour of a carbon fibre reinforced epoxy matrix composite in 3.5% NaCl and 3.5% NaCl + 0.5 M CuSO4 electrolytes was examined by potentiodynamic polarisation, potentiostatic polarisation and scanning electron microscopy. Exposed carbon fibres on two defined regions (“front” and “side”) are a focus of the investigation. The large size of the exposed carbon fibres on the side region is responsible for a higher cathodic current density than the front region in the NaCl electrolyte. The deposition of copper on the front surface of composite confirmed that the significantly higher cathodic current resulted from the exposure of the fibres to the NaCl electrolyte. Galvanic coupling between the composite and individual aluminium alloys (AA7075-T6 and AA1050) was used to measure galvanic potentials and galvanic current densities. The highly alloyed AA7075-T6 alloy and its high population density of cathodic sites compared to the AA1050 acted to reduce the galvanic effect when coupled to the composite front or side regions.

  14. 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.

  15. Printable Electrochemical Biosensors: A Focus on Screen-Printed Electrodes and Their Application.

    PubMed

    Yamanaka, Keiichiro; Vestergaard, Mun'delanji C; Tamiya, Eiichi

    2016-10-21

    In this review we present electrochemical biosensor developments, focusing on screen-printed electrodes (SPEs) and their applications. In particular, we discuss how SPEs enable simple integration, and the portability needed for on-field applications. First, we briefly discuss the general concept of biosensors and quickly move on to electrochemical biosensors. Drawing from research undertaken in this area, we cover the development of electrochemical DNA biosensors in great detail. Through specific examples, we describe the fabrication and surface modification of printed electrodes for sensitive and selective detection of targeted DNA sequences, as well as integration with reverse transcription-polymerase chain reaction (RT-PCR). For a more rounded approach, we also touch on electrochemical immunosensors and enzyme-based biosensors. Last, we present some electrochemical devices specifically developed for use with SPEs, including USB-powered compact mini potentiostat. The coupling demonstrates the practical use of printable electrode technologies for application at point-of-use. Although tremendous advances have indeed been made in this area, a few challenges remain. One of the main challenges is application of these technologies for on-field analysis, which involves complicated sample matrices.

  16. Development of molten carbonate fuel cell power plant technology

    NASA Astrophysics Data System (ADS)

    Bushnell, C. L.; Davis, C. L.; Dayton, J. E.; Johnson, C. K.; Katz, M.; Krasij, M.; Kunz, H. R.; Maricle, D. L.; Meyer, A. P.; Pivar, J. C.

    1984-09-01

    A prototype molten carbonate fuel cell stack which meets the requirements of a 1990's-competitive, coal-fired electrical utility central station, or industrial cogeneration power plant was developed. Compressive creep testing of the present anode is continuedl the samples and support the earlier data showing improved creep resistance. Testing to define the operating limits that are suitable for extending the life of nickel oxide cathodes to an acceptable level is continuing. The mechanical characteristics of several one-piece cathode current collector candidates are measured for suitability. Metallographic evaluation of stack separators was initiated. Posttest characterization of surface treated INCO 825 was completed, retort corrosion testing of this material is continuing, potentiostatic immersion testing of alternative single piece cathode current collector materials is initiated. The 20-cell Stack No. 3 progressed from completion and delivery of the Test Plan through Design Review, assembly, and initial heat-up for the start of testing. Manufacture of separator plates for the upcoming 20-cell Stack No. 4 has begun. The primary objective of this follow-on test is stack cost reduction.

  17. 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.

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

    PubMed

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

    2016-12-15

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

  19. On-site in-situ determination of heavy metals in groundwater using an electrochemically-based sensor

    SciTech Connect

    Herdan, J.; Feeney, R.; Kounaves, S.P.

    1997-12-31

    An electrochemically-based probe has been developed for rapid in-situ or on-site detection of heavy metals in contaminated groundwater. The transducer consists of a microlithographically fabricated iridium ultramicroelectrode array (UMEA) which is used in conjunction with the high speed electrochemical preconcentration technique of square wave anodic stripping voltammetry (SWASV). The UMEA is connected to an integrated potentiostat which is controlled by a laptop computer. The entire probe, measuring only two inches in diameter, can be inserted downhole to measure such metal ions as Cu, Cd, Ph, and Zn, at the parts-per-billion level. The utility of this probe for rapid on site screening of metals was shown by conducting a proof-of-concept field demonstration at a metals-contaminated site at Hanscom Air Force Base in Massachusetts. Sampling was performed both, directly in-situ, and on-site by bringing the sample to the surface. Acidified samples where also taken back to the laboratory where they were measured both electrochemically using a mercury film glassy carbon electrode with SWASV, and by ICP Spectroscopy using EPA method 200.7. Excellent correlation was obtained between all of the measurement techniques, and the data for total and ionic forms was also in good agreement.

  20. Square wave anodic stripping voltammetric determination of Cd²⁺ and Pb²⁺ at bismuth-film electrode modified with electroreduced graphene oxide-supported thiolated thionine.

    PubMed

    Li, Zou; Chen, Li; He, Fang; Bu, Lijuan; Qin, Xiaoli; Xie, Qingji; Yao, Shouzhuo; Tu, Xinman; Luo, Xubiao; Luo, Shenglian

    2014-05-01

    Graphene oxide (GO)-thionine (TH) nanocomposite was prepared by π-π stacking. The nanocomposite was cast-coated on a glassy carbon electrode (GCE) to prepare an electroreduced GO (ERGO)-TH/GCE, then 2-mercaptoethanesulfonate (MES) was covalently tethered to ERGO-TH by potentiostatic anodization to form an ERGO-TH-MES/GCE. The thiolation reaction was monitored by electrochemical quartz crystal microbalance (EQCM). Square wave anodic stripping voltammetry (SWASV) was used to determine Cd(2+) and Pb(2+) at the ERGO-TH-MES/GCE further modified with Nafion and Bi. Under the optimal conditions, the linear calibration curves for Cd(2+) and Pb(2+) are from 1 to 40 μg L(-1), with limits of detection (S/N=3) of 0.1 μg L(-1) for Cd(2+) and 0.05 μg L(-1) for Pb(2+), respectively. The electrode was used for the simultaneous analysis of Cd(2+) and Pb(2+) in water samples with satisfactory recovery.

  1. 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

    2016-04-20

    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.

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

    PubMed

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

    2016-03-09

    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.

  3. Carnation-like MnO2 modified activated carbon air cathode improve power generation in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Li, Kexun; Liu, Xianhua

    2014-10-01

    Highly active and low-cost electrocatalysts are of great importance for large-scale commercial applications of microbial fuel cells (MFCs). In this work, we prepared an activated carbon (AC) air cathode containing electrodeposited γ-MnO2 using a potentiostatic method. The results indicated that carnation-like MnO2 crystals were bound to the surface of the AC air cathode after a deposition time of 10 min, which greatly improved the performance of the cathode. BET analysis results demonstrated that the electrodeposition of MnO2 decreased the micropore surface area of the cathode but increased the mesopore surface area. When compared with a bare AC air cathode, the electrodeposited MnO2 cathode exhibited higher catalytic activity for oxygen reduction reaction. The maximum power density of the MFC equipped with the electrodeposited MnO2 AC air cathode was 1554 mW m-2, which is 1.5 times higher than the control cathode.

  4. 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)

  5. Enhanced low-temperature power density of solid oxide fuel cell by nickel nanoparticle infiltration into pre-fired Ni/yttria-stabilized zirconia anode.

    PubMed

    Kang, Lee-Seung; Park, Jae Layng; Lee, Sungkyu; Jin, Yun-Ho; Hong, Hyun-Seon; Lee, Chan-Gi; Kim, Bum Sung

    2014-12-01

    The Ni/yttria-stabilized zirconia (YSZ) anode morphology of an anode-supported solid oxide fuel cell (SOFC) unit cell was improved by nickel nanoparticle infiltration. A colloidal route was selected for efficient fabrication of nickel metal nanoparticles and subsequent infiltration into the Ni/YSZ anode of a pre-fired SOFC unit cell. The power density of the anode-supported SOFC unit cell was measured by the potentiostatic method to investigate the effect of nickel nanoparticle infiltration. The increase in the power density of the Ni/YSZ anode with nickel nanoparticle infiltration became gradually less significant as the SOFC operating temperature increased from 700 to 800 degrees C. The improved performance of the Ni/YSZ anode with nickel nanoparticle infiltration compared to that of an anode without nickel nanoparticles is tentatively attributed to two factors: The discretely distributed nanoparticles on the nanostructured electrodes exhibited significant catalytic effects on the electrochemical performance of the electrodes, in addition to substantially increasing the triple phase boundary lengths.

  6. Dual-electrode oxidation used for aniline degradation in aqueous electrolyte.

    PubMed

    Yan-Yang, Chu; Ling-Ling, Li; Mao-Juan, Bai

    2011-01-01

    The electrochemical degradation of aniline in aqueous electrolyte has been studied by dual-electrode oxidation process using Ti/SnO2-Sb2O5 for anodic oxidation and graphite cathode to produce H2O2 in situ. The linear voltammograms were employed to obtain reasonable anodic and cathodic potential values for the purpose of restraining side reactions. The influence of Fe2+ on aniline degradation was investigated under potentiostatic condition with a three-electrode system. It was found that an anodic potential range of 2.0 +/- 0.1 V and a cathodic potential of -0.65 V could favor anodic oxidation and H2O2 generation. Anodic oxidation was accounted for aniline degradation in the absence of Fe2+, while in the presence of Fe2+ both electro-Fenton oxidation and anodic oxidation (dual-electrode oxidation) could degradate aniline effectively. When cathodic potential values were -0.65 and -0.80 V, the optimum Fe2+ concentration were 0.50 and 0.30 mM, respectively. 77.5% COD removal and 70.4% TOC removal with a current efficiency (CE) of 96-100% were achieved under the optimum conditions. This work indicates that dual-electrode oxidation process characterized by a high CE is feasible for the degradation of organic compounds.

  7. Active control of probability amplitudes in a mesoscale system via feedback-induced suppression of dissipation and noise

    NASA Astrophysics Data System (ADS)

    Gupta, Chaitanya; Peña Perez, Aldo; Fischer, Sean R.; Weinreich, Stephen B.; Murmann, Boris; Howe, Roger T.

    2016-12-01

    We demonstrate that a three-terminal potentiostat circuit reduces the coupling between an electronic excitation transfer (EET) system and its environment, by applying a low-noise voltage to its electrical terminals. Inter-state interference is preserved in the EET system by attenuating the dissipation in the quantum system arising from coupling to the surrounding thermodynamic bath. A classical equivalent circuit is introduced to model the environment-coupled excitation transfer for a simplified, two-state system. This model provides a qualitative insight into how the electronic feedback affects the transition probabilities and selectively reduces dissipative coupling for one of the participant energy levels EET system. Furthermore, we show that the negative feedback also constrains r.m.s. fluctuations of the energy of environmental vibrational states, resulting in persistent spectral coherence between the decoupled state and vibronic levels of the complementary state. The decoupled vibronic channel therefore can serve as a probe for characterizing the vibronic structure of the complementary channel of the EET system.

  8. Fabrication and magnetic properties of La-X (X = Co, Ni, and Fe) nanotube arrays prepared by electrodeposition methods

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Shi, D. W.; Ahmad, N.; Liu, D. P.; Zhou, W. P.; Han, X. F.

    2013-08-01

    Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of ˜200 nm, wall thicknesses of ˜40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.

  9. 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.

  10. 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.

  11. Electrochemistry combined on-line with electrospray mass spectrometry

    SciTech Connect

    Zhou, F.; Berkel, G.J.V.

    1995-10-15

    In this paper a variety of methods to couple electrochemistry on-line with electrospray mass spectrometry (EC/ES-MS) are presented, and the fundamental and analytical utility of this hybrid technique is illustrated. The major problems encountered in coupling EC and ES-MS are discussed, and means to overcome them are presented. Three types of electrochemical flow cells, viz., a thin-layer electrode flow-by cell, a tubular electrode flow-through cell, and a porous electrode flow-through cell, are discussed in regard to their suitability for this coupling. Methods for coupling each of these electrochemical cells on-line with ES-MS, either floated at or decoupled from the ES high voltage and controlled by a constant current supply, a constant potential supply, or a potentiostat are presented. Three applications are used to illustrate the utility and versatility of the EC/ES-MS combination: (1) the ionization of neutral analytes (i.e., perylene) for detection by ES-MS, (2) the study of the products of electrode reactions (i.e., nickel(II) octaethylporphyrin oxidation products), including relatively short-lived products (i.e., {Beta}-carotene oxidation products), and (3) the enhanced determination of metals (i.e., elemental silver) achieved by coupling anodic stripping voltammetry on-line with ES-MS. 52 refs., 6 figs.

  12. Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms

    NASA Astrophysics Data System (ADS)

    Bellin, Daniel L.; Sakhtah, Hassan; Rosenstein, Jacob K.; Levine, Peter M.; Thimot, Jordan; Emmett, Kevin; Dietrich, Lars E. P.; Shepard, Kenneth L.

    2014-02-01

    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 that are produced by microbial biofilms and can affect their 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 mm2 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.

  13. In situ scanning tunneling microscopy studies of the SEI formation on graphite electrodes for Li+-ion batteries

    NASA Astrophysics Data System (ADS)

    Seidl, Lukas; Martens, Slađana; Ma, Jiwei; Stimming, Ulrich; Schneider, Oliver

    2016-07-01

    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.

  14. Corrosion behavior of mild steel in acetic acid solutions

    SciTech Connect

    Singh, M.M.; Gupta, A.

    2000-04-01

    The corrosion behavior of mild steel in acetic acid (CH{sub 3}COOH) solutions was studied by weight loss and potentiostatic polarization techniques. The variation in corrosion rate of mild steel with concentrations of CH{sub 3}COOH, evaluated by weight loss and electrochemical techniques, showed marked resemblance. From both techniques, the maximum corrosion rate was observed for 20% CH{sub 3}COOH solution at all three experimental temperatures (25, 35, and 45 C). Anodic polarization curves showed active-passive behavior at each concentration, except at 80% CH{sub 3}COOH. Critical current density (i{sub c}) passive current density (I{sub n}), primary passivation potential (E{sub pp}), and potential for passivity (E{sub p}) had their highest values in 20% CH{sub 3}COOH solution. With an increase in temperature, while the anodic polarization curves shifted toward higher current density region at each concentration, the passive region became progressively less distinguishable. With the addition of sodium acetate (NaCOOCH{sub 3}) as a supporting electrolyte, the passive range was enlarged substantially. However, the transpassive region commenced at more or less the same potential. Cathodic polarization curves were almost identical irrespective of the concentration of CH{sub 3}COOH or temperature.

  15. 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%.

  16. Specific and efficient electrochemical selection of Geoalkalibacter subterraneus and Desulfuromonas acetoxidans in high current-producing biofilms.

    PubMed

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

    2015-12-01

    Two different saline sediments were used to inoculate potentiostatically controlled reactors (a type of microbial bioelectrochemical system, BES) operated in saline conditions (35 gNaCl l(-1)). Reactors were fed with acetate or a mixture of acetate and butyrate at two pH values: 7.0 or 5.5. Electroactive biofilm formation lag-phase, maximum current density production and coulombic efficiency were used to evaluate the overall performance of reactors. High current densities up to 8.5 A m(-2) were obtained using well-defined planar graphite electrodes. Additionally, biofilm microbial communities were characterized by CE-SSCP and 454 pyrosequencing. As a result of this procedure, two anode-respiring bacteria (ARB) always dominated the anodic biofilms: Geoalkalibacter subterraneus and/or Desulfuromonas acetoxidans. This suggests that a strong electrochemically driven selection process imposed by the applied potential occurs in the BES system. Moreover, the emergence of Glk. subterraneus in anodic biofilms significantly contributes to broaden the spectrum of high current producing microorganisms electrochemically isolated from environmental samples.

  17. 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.

  18. The effect of surface treatments on the fretting behavior of Ti-6Al-4V alloy.

    PubMed

    Dalmiglio, Matteo; Schaaff, Petra; Holzwarth, Uwe; Chiesa, Roberto; Rondelli, Gianni

    2008-08-01

    Stem modularity in total hip replacement introduces an additional taper joint between Ti-6Al-4V stem components with the potential for fretting corrosion processes. One possible way to reduce the susceptibility of the Ti-6Al-4V/Ti-6Al-4V interface to fretting is the surface modification of the Ti-6Al-4V alloy. Among the tested, industrially available surface treatments, a combination of two deep anodic spark deposition treatments followed by barrel polishing resulted in a four times lower material release with respect to untreated, machined fretting pad surfaces. The fretting release has been quantified by means of radiotracers introduced in the alloy surface by proton irradiation. In a simple sphere on flat geometry, the semispherical fretting pads were pressed against flat, dog-bone shaped Ti-6Al-4V fatigue samples cyclically loaded at 4 Hz. In this way a cyclic displacement amplitude along the surfaces of 20 mum has been achieved. A further simplification consisted in the use of deionized water as lubricant. A comparison of the radiotracer results with an electrochemical material characterization after selected treatments by potentiostatic tests of modular stems in 0.9% NaCl at 40 degrees C for 10 days confirmed the benefit of deep anodic spark deposition and subsequent barrel polishing for improving the fretting behavior of Ti-6Al-4V.

  19. Flow microcapillary plasma mass spectrometry-based investigation of new Al-Cr-Fe complex metallic alloy passivation.

    PubMed

    Ott, N; Beni, A; Ulrich, A; Ludwig, C; Schmutz, P

    2014-03-01

    Al-Cr-Fe complex metallic alloys are new intermetallic phases with low surface energy, low friction, and high corrosion resistance down to very low pH values (0-2). Flow microcapillary plasma mass spectrometry under potentiostatic control was used to characterize the dynamic aspect of passivation of an Al-Cr-Fe gamma phase in acidic electrolytes, allowing a better insight on the parameters inducing chemical stability at the oxyhydroxide-solution interface. In sulfuric acid pH 0, low element dissolution rates (in the µg cm(-2) range after 60 min) evidenced the passive state of the Al-Cr-Fe gamma phase with a preferential over-stoichiometric dissolution of Al and Fe cations. Longer air-aging was found to be beneficial for stabilizing the passive film. In chloride-containing electrolytes, ten times higher Al dissolution rates were detected at open-circuit potential (OCP), indicating that the spontaneously formed passive film becomes unstable. However, electrochemical polarization at low passive potentials induces electrical field generated oxide film modification, increasing chemical stability at the oxyhydroxide-solution interface. In the high potential passive region, localized attack is initiated with subsequent active metal dissolution.

  20. Combinatorial microelectrochemistry: Development and evaluation of an electrochemical robotic system

    NASA Astrophysics Data System (ADS)

    Erichsen, Thomas; Reiter, Sabine; Ryabova, Victoria; Bonsen, Eva Maria; Schuhmann, Wolfgang; Märkle, Wolfgang; Tittel, Carsten; Jung, Günther; Speiser, Bernd

    2005-06-01

    An electrochemical robotic system using standard microtiter plates as reaction wells for potentiostatic and galvanostatic electrosynthesis and high-throughput electroanalysis was conceived and realized using stepmotor driven positioning stages in combination with a flexible software. Electrode bundles specifically adapted to the experimental needs are accurately positioned in the wells of a microtiter plate followed by the automatic performance of sequences of electrosynthetic or electroanalytical techniques. The system allows us to work under inert-gas atmosphere, in aqueous and organic solvents, and to add or remove solutions by means of integrated syringe pumps. A specifically developed script language permits the user to perform very complex experimental sequences in the different wells of the microtiter plate. The hardware and software features of the developed electrochemical robotic system, the design of suitable electrode arrangements for electrosynthesis and electroanalytical techniques, as well as the reproducibility in aqueous and organic electrolytes are described. The performance of the system is demonstrated by redox screening of a Ru-complex library and by electrosynthesis with in situ analysis of a compound library.

  1. Development of amperometric biosensors based on nanostructured tyrosinase-conducting polymer composite electrodes.

    PubMed

    Lupu, Stelian; Lete, Cecilia; Balaure, Paul Cătălin; Caval, Dan Ion; Mihailciuc, Constantin; Lakard, Boris; Hihn, Jean-Yves; Javier del Campo, Francisco

    2013-05-21

    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.

  2. Development of an amperometric sulfite biosensor based on SO(x)/PBNPs/PPY modified ITO electrode.

    PubMed

    Rawal, Rachna; Pundir, C S

    2012-11-01

    A sulfite oxidase (SO(x)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SO(x)/PBNPs/PPY/ITO electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SO(x). The biosensor showed optimum response within 2s, when operated at 20 mV s⁻¹ in 0.1M Tris-HCl buffer, pH 8.5 and at 35 °C. Linear range and minimum detection limit were 0.5-1000 μM and 0.12 μM (S/N=3) respectively. There was good correlation (r=0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4 °C.

  3. Amperometric choline biosensor based on multiwalled carbon nanotubes/zirconium oxide nanoparticles electrodeposited on glassy carbon electrode.

    PubMed

    Pundir, S; Chauhan, N; Narang, J; Pundir, C S

    2012-08-01

    A bienzymatic choline biosensor was constructed by coimmobilizing acetylcholinesterase (AChE) and choline oxidase (ChO) onto nanocomposite of carboxylated multiwalled carbon nanotubes (c-MWCNTs) and zirconium oxide nanoparticles (ZrO(2)NPs) electrodeposited on the surface of a glassy carbon electrode (GCE) and using it (AChE-ChO/c-MWCNT/ZrO(2)NPs/GCE) as working electrode, Ag/AgCl as reference electrode, and Pt wire as auxiliary electrode connected through a potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and cyclic voltammetry (CV) studies, optimized, and evaluated. The biosensor exhibited optimum response within 4 s at +0.2V, pH 7.4, and 25 °C. The detection limit and working range of the biosensor were 0.01 μM and 0.05 to 200 μM, respectively. The half-life of the enzyme electrode was 60 days at 4 °C. The serum choline level, as measured by the biosensor, was 9.0 to 12.8 μmol/L (with a mean of 10.81 μmol/L) in apparently healthy persons and 5.0 to 8.4 μmol/L (with a mean of 6.53 μmol/L) in persons suffering from Alzheimer's disease. The enzyme electrode was unaffected by a number of serum substances.

  4. 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.

  5. Variation in properties of the sediment following electrokinetic treatments.

    PubMed

    Touch, Narong; Hibino, Tadashi; Nakashita, Shinya; Nakamoto, Kenji

    2017-02-01

    Many studies have reported variation in properties of the sediment within electrokinetic treatments (EKTs). However, we aim to reveal the variation in properties of the sediment following EKTs through laboratory experiments. We collected sewage-derived sediment from a littoral region, and passed it through a 2-mm sieve. We used a potentiostat to cause electrical current in EKT. We measured the sediment properties such as pH, redox potential (ORP), and hydrogen sulphide (H2S) concentration at the end of EKT and at 30 days following EKT. Results showed decreases in pH, increases in ORP, and decreases in H2S concentration at the end of EKT. Compared with the sediment without EKT, the decrease in ORP for the sediment within EKT was higher at 30 days following EKT. These suggest that anaerobic digestion of organic compounds occurs in the sediment following EKT, of which the oxidants produced by EKT serve as electron acceptors and organic compounds serve as electron donors. Furthermore, we found that EKT can remove H2S from the sediment and reduce H2S production in the sediment within EKT when compared to the case without EKT. These ensure that EKT can be used to remove H2S and control H2S production in the sediment.

  6. 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.

  7. 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.

  8. 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

    2016-10-01

    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.

  9. Production of Conductive PEDOT-Coated PVA-GO Composite Nanofibers.

    PubMed

    Zubair, Nur Afifah; Rahman, Norizah Abdul; Lim, Hong Ngee; Sulaiman, Yusran

    2017-12-01

    Electrically conductive nanofiber is well known as an excellent nanostructured material for its outstanding performances. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT)-coated polyvinyl alcohol-graphene oxide (PVA-GO)-conducting nanofibers were fabricated via a combined method using electrospinning and electropolymerization techniques. During electrospinning, the concentration of PVA-GO solution and the applied voltage were deliberately altered in order to determine the optimized electrospinning conditions. The optimized parameters obtained were 0.1 mg/mL of GO concentration with electrospinning voltage of 15 kV, which displayed smooth nanofibrous morphology and smaller diameter distribution. The electrospun PVA-GO nanofiber mats were further modified by coating with the conjugated polymer, PEDOT, using electropolymerization technique which is a facile approach for coating the nanofibers. SEM images of the obtained nanofibers indicated that cauliflower-like structures of PEDOT were successfully grown on the surface of the electrospun nanofibers during the potentiostatic mode of the electropolymerization process. The conductive nature of PEDOT coating strongly depends on the different electropolymerization parameters, resulting in good conductivity of PEDOT-coated nanofibers. The optimum electropolymerization of PEDOT was at a potential of 1.2 V in 5 min. The electrochemical measurements demonstrated that the fabricated PVA-GO/PEDOT composite nanofiber could enhance the current response and reduce the charge transfer resistance of the nanofiber.

  10. 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.

  11. Hierarchical templating in deposition of semi-covalently imprinted inverse opal polythiophene film for femtomolar determination of human serum albumin.

    PubMed

    Dabrowski, Marcin; Cieplak, Maciej; Sharma, Piyush Sindhu; Borowicz, Pawel; Noworyta, Krzysztof; Lisowski, Wojciech; D'Souza, Francis; Kuhn, Alexander; Kutner, Wlodzimierz

    2017-03-01

    Nanostructured artificial receptor materials with unprecedented hierarchical structure for determination of human serum albumin (HSA) are designed and fabricated. For that purpose a new hierarchical template is prepared. This template allowed for simultaneous structural control of the deposited molecularly imprinted polymer (MIP) film on three length scales. A colloidal crystal templating with optimized electrochemical polymerization of 2,3'-bithiophene enables deposition of an MIP film in the form of an inverse opal. Thickness of the deposited polymer film is precisely controlled with the number of current oscillations during potentiostatic deposition of the imprinted poly(2,3'-bithiophene) film. Prior immobilization of HSA on the colloidal crystal allows formation of molecularly imprinted cavities exclusively on the internal surface of the pores. Furthermore, all binding sites are located on the surface of the imprinted cavities at locations corresponding to positions of functional groups present on the surface of HSA molecules due to prior derivatization of HSA molecules with appropriate functional monomers. This synergistic strategy results in a material with superior recognition performance. Integration of the MIP film as a recognition unit with a sensitive extended-gate field-effect transistor (EG-FET) transducer leads to highly selective HSA determination in the femtomolar concentration range.

  12. 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.

  13. Kinetics and mechanism of the electrochemical formation of iron oxidation products on steel immersed in sour acid media.

    PubMed

    Hernández-Espejel, Antonio; Palomar-Pardavé, Manuel; Cabrera-Sierra, Román; Romero-Romo, Mario; Ramírez-Silva, María Teresa; Arce-Estrada, Elsa M

    2011-03-03

    From electrochemical techniques (cyclic voltammetry, potential steps, and EIS), XRD, and SEM-EDX, the kinetics and mechanism of anodic film formation applying anodic potential steps on steel immersed in sour acid media was determined. It was found, from a thermodynamic analysis, based on equilibrium phase diagrams of the system considered in this work, that iron oxidation may produce different new solid phases, depending on the applied potential, the first being the iron oxidation associated with formation of FeS((c)) species, which in turn can be reoxidized to FeS(2(c)) or even to Fe(2)O(3(c)) at higher potential values. From analysis of the corresponding experimental potentiostatic current density transients, it was concluded that the electrochemical anodic film formation involves an E(1)CE(2) mechanism, whereby the first of the two simultaneous processes were the Fe electrochemical oxidation (E(1)) followed by FeS precipitation (C) that occurs by 3D nucleation and growth limited by mass transfer reaction and FeS oxidation (E(2)) forming a mix of different stoichiometry iron sulphides and oxides. From EIS measurements, it was revealed that the anodic film's charge transfer resistance diminishes as the potential applied for its formation becomes more anodic, thus behaving poorly against corrosion.

  14. Using anodic aluminum oxide templates and electrochemical method to deposit BiSbTe-based thermoelectric nanowires

    NASA Astrophysics Data System (ADS)

    Kuo, Hsin-Hui; Kuo, Chin-Guo; Yen, Chia-Ying; Yang, Cheng-Fu

    2014-02-01

    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 - x Te3 + 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 - x Te3 + x -based materials and grow the nanowires in anodic aluminum oxide (AAO) templates.

  15. Significant different conductivities of the two grades of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), Clevios P and Clevios PH1000, arising from different molecular weights.

    PubMed

    Xia, Yijie; Ouyang, Jianyong

    2012-08-01

    Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is promising to be the next-generation transparent electrode of optoelectronic devices. This paper reports the differences between two commercially available grades of PEDOT:PSS: Clevios P and Clevios PH1000. The as-prepared PEDOT:PSS films from Clevios P and Clevios PH1000 solutions have close conductivities of 0.2-0.35 S cm(-1). Their conductivities can be enhanced to 171 and 1164 S cm(-1), respectively, through a treatment with hydrofluoroacetone trihydrate (HFA). The differences between Clevios P and Clevios PH1000 were studied by various characterizations on PEDOT:PSS aqueous solutions and PEDOT:PSS films. The gel particles are larger in Clevios PH1000 solution than in Clevios P solution as revealed by dynamic light scattering and fluorescence spectroscopy of pyrene in these solutions. These results suggest that PEDOT of Clevios PH1000 has a higher average molecular weight than that of Clevios P. The difference in the molecular weight of PEDOT for the two grades of PEDOT:PSS is confirmed by the characterizations on their polymer films, including atomic force microscopy and temperature dependences of the resistances of as-prepared and HFA-treated PEDOT:PSS films. The different molecular weights of PEDOT also gives rise to significant differences in the electrochemical behaviors of the two grades of PEDOT:PSS, as revealed by the cyclic voltammetry, in situ UV-vis-NIR absorption spectroscopy and potentiostatic transient measurements.

  16. Optical properties of electrochemically synthesized polypyrrole thin films: the electrolyte effect

    NASA Astrophysics Data System (ADS)

    Thombare, J. V.; Shinde, S. K.; Lohar, G. M.; Chougale, U. M.; Dhasade, S. S.; Dhaygude, H. D.; Relekar, B. P.; Fulari, V. J.

    2014-06-01

    Polypyrrole thin films are prepared by the potentiostatic mode of electrodeposition at +0:7 V versus a saturated calomel electrode (SCE). The polypyrrole films are prepared in the presence of different electrolytes such as: p-toluene sulphonic acid (PTS), oxalic acid and H2SO4. The prepared films are characterized by UV—vis absorption spectroscopy and normal reflectance measurements. The electrochemically synthesized films are semiconductor in nature. The band gap energy of polypyrrole thin films is found to be 1.95, 1.92 and 1.79 eV for H2SO4, oxalic acid and p-toluene sulphonic acid, respectively. The normal reflectance spectroscopy of polypyrrole films shows that the maximum reflectance is in the presence of p-toluene sulphonic acid; this is may be due to a more distinct microstructure than the others. The optical constants such as the extinction coefficient, refractive index, optical conductivity, etc. are calculated and studied with various electrolytes.

  17. Two-step electrodeposition construction of flower-on-sheet hierarchical cobalt hydroxide nano-forest for high-capacitance supercapacitors.

    PubMed

    Yang, Wanlu; Gao, Zan; Ma, Jing; Wang, Jun; Zhang, Xingming; Liu, Lianhe

    2013-11-28

    A novel flower-on-sheet hierarchical morphology of α-Co(OH)2 nanostructures was achieved via an easy two-step synthesis strategy. The method is based on first a galvanostatic electrodeposition (GE) of vertically aligned interconnected Co(OH)2 nanosheets to form a branch layer and second a potentiostatic electrodeposition (PE) of Co(OH)2 microflowers on the obtained branch layer from the secondary growth of their sheet-like precursors. The formation mechanism of this special PE time-dependent nanostructure was proposed and their morphology-dependent supercapacitor properties were also investigated. For a given areas mass loading, high specific capacitances of 1822 F g(-1) have been achieved for the electrode obtained after 200 s GE followed by a 300 s PE in a three-electrode configuration, and it maintained 91% of its initial capacity after 1000 constant-current charge/discharge cycles. Even when the discharge current density was increased from 1 to 50 mA cm(-2), the capacitance was still as high as 1499 F g(-1), indicating an excellent rate performance of the fabricated electrodes. The high performances of the electrodes are attributed to the special porous structure, 3D hierarchical morphology, vertical aligned orientation, and low contact resistance between active material and charge collector.

  18. 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.

  19. Determination of charge transfer resistance and capacitance of microbial fuel cell through a transient response analysis of cell voltage.

    PubMed

    Ha, Phuc Thi; Moon, Hyunsoo; Kim, Byung Hong; Ng, How Yong; Chang, In Seop

    2010-03-15

    An alternative method for determining the charge transfer resistance and double-layer capacitance of microbial fuel cells (MFCs), easily implemented without a potentiostat, was developed. A dynamic model with two parameters, the charge transfer resistance and double-layer capacitance of electrodes, was derived from a linear differential equation to depict the current generation with respect to activation overvoltage. This model was then used to fit the transient cell voltage response to the current step change during the continuous operation of a flat-plate type MFC fed with acetate. Variations of the charge transfer resistance and the capacitance value with respect to the MFC design conditions (biocatalyst existence and electrode area) and operating parameters (acetate concentration and buffer strength in the catholyte) were then determined to elucidate the validity of the proposed method. This model was able to describe the dynamic behavior of the MFC during current change in the activation loss region; having an R(2) value of over 0.99 in most tests. Variations of the charge transfer resistance value (thousands of Omega) according to the change of the design factors and operational factors were well-correlated with the corresponding MFC performances. However, though the capacitance values (approximately 0.02 F) reflected the expected trend according to the electrode area change and catalyst property, they did not show significant variation with changes in either the acetate concentration or buffer strength.

  20. 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

    2016-02-05

    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(°).

  1. 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.

  2. A new method for determining the acid number of biodiesel based on coulometric titration.

    PubMed

    Barbieri Gonzaga, Fabiano; Pereira Sobral, Sidney

    2012-08-15

    A new method is proposed for determining the acid number (AN) of biodiesel using coulometric titration with potentiometric detection, basically employing a potentiostat/galvanostat and an electrochemical cell containing a platinum electrode, a silver electrode, and a combination pH electrode. The method involves a sequential application of a constant current between the platinum (cathode) and silver (anode) electrodes, followed by measuring the potential of the combination pH electrode, using an isopropanol/water mixture as solvent and LiCl as the supporting electrolyte. A preliminary evaluation of the new method, using acetic acid for doping a biodiesel sample, showed an average recovery of 100.1%. Compared to a volumetric titration-based method for determining the AN of several biodiesel samples (ranging from about 0.18 to 0.95 mg g(-1)), the new method produced statistically similar results with better repeatability. Compared to other works reported in the literature, the new method presented an average repeatability up to 3.2 times better and employed a sample size up to 20 times smaller.

  3. 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.

  4. Degradation mechanisms of carbon-based electrocatalyst support materials and development of an advanced support based on electrically conducting diamond

    NASA Astrophysics Data System (ADS)

    Fischer, Anne Elizabeth

    2005-11-01

    In this dissertation, the degradation mechanisms of sp 2-bonded carbon electrocatalyst supports were studied under potential and temperature conditions relevant to the polymer electrolyte membrane fuel cell (PEMFC). In addition, an alternative support was fabricated in two forms: electrically conducting diamond powder and paper to overcome current material stability issues in the PEMFC. Two structurally well-characterized sp2-bonded carbon powders, graphite (structurally well-ordered) and glassy carbon (GC, structurally disordered) were studied under potentiostatic polarization from 1.0 to 1.6 V vs. Ag/AgCl at 25, 50, and 80°C. Characterization of the surface oxidation and microstructural changes (i.e., increase in the exposed edge plane density) provided evidence for the so-called order/disorder mechanism where structurally disordered carbons corrode more severely because of oxidation and gasification of the exposed edge plane. Microstructural changes for graphite were heterogeneously distributed across the electrode surface. This is indicative of a nucleation and growth process, where disordered regions and defects serve as active sites for electrochemical corrosion, while other, more structurally ordered regions do not corrode. Preliminary results for a high-surface-area carbon black, Vulcan XC-72, are presented that show changes in the surface oxide content and also discuss the effect of polarization potential on Pt activity. The physical and electrochemical properties of two commercial boron-doped diamond thin-film electrodes were compared with microcrystalline and nanocrystalline boron-doped diamond thin film deposited in our laboratory. The electrochemical response for Fe(CN)63-/4-, Ru(NH3)6 3+/2+, IrCl62-/3-, 4-methylcatechol, and Fe3+/2+ was quite reproducible from electrode type-to-type and from film-to-film for a given type. DeltaEp, ipox, and ip red values for Fe(CN)63-/4-, Ru(NH 3)63+/2+ on all electrodes were relatively unaffected by pH. Electrically

  5. Degradation and failure susceptibility of carbon steels in simulated Yucca Mountain nuclear repository environments

    NASA Astrophysics Data System (ADS)

    Yilmaz, Ahmet

    Environmental degradation and cracking of medium carbon steel (MCS) rock bolts and low carbon steel (LCS) I-beam have been investigated by experimental methods such as linear polarization, impedance spectroscopy, weight loss measurements, and electro-mechanical dynamic slow strain rate tensile (SSRT) tests, along with potentiostatic in-situ potential-current monitoring techniques. The experiments were conducted in concentrated aqueous environments of various temperatures, which simulated the conditions at the Yucca Mountain (YM) nuclear waste repository site, where the candidate structural materials introduced above, will be used for supporting the waste repository tunnels. MCS corroded at medium general rates approximately around 40 mum/year to 200 mum/year in de-aerated simulated YM waters of various temperatures and concentrations. Increased temperatures increased the corrosion rates in the all de-aerated waters. Increased concentrations of overall species in the simulated waters also increased the corrosion rates, but only slightly. Impedance spectroscopy revealed similar trends for temperature and concentration effects on the rates in both aerated and deaerated environments. Aeration increased corrosion rates significantly in dilute (1X) and ten times concentrated (10X) waters at all temperatures. However, inhibitive precipitates on the specimens formed by oxygen-environment reactions at higher temperatures (up to 85°C) in hundred times concentrated (100X) waters decreased corrosion rates drastically, resulting some localized corrosion and pitting. The average rates were determined to be between approximately 100 mu/year and 1000 mu/year in the entire concentration and temperature range tested. Electrochemical results showed slightly higher rates compared to the other tests because of their much shorter testing period, therefore in general they should be taken as conservative upper bounds. SSRT on LCS under various imposed metal-electrolyte interface

  6. Electrochemical properties of suprastructures galvanically coupled to a titanium implant.

    PubMed

    Oh, Keun-Taek; Kim, Kyoung-Nam

    2004-08-15

    In recent years, dental implants have been widely used for the aesthetic and functional restoration of edentulous patients. Dental implants and restorative alloys are required with high corrosion resistance. Suprastructures and implants of different compositions in electrical contact may develop galvanic or coupled corrosion problems. In addition to galvanic corrosion, crevice and pitting corrosion may occur in the marginal gap between dental implant assemblies. In this study, gold, silver-palladium, cobalt-chromium, and nickel-chromium suprastructures were used to investigate their galvanic and crevice corrosion characteristics in combination with titanium (Ti) implants. Potentiodynamic and potentiostatic testing were performed in artificial saliva at 37 degrees C. Potentiodynamic testing was carried out at the potential scan rate of 1 mV/s in the range of -600-1600 mV (SCE). Potentiostatic testing was performed with an open-circuit potential and current densities at -250, 0, and 250 mV (SCE) in artificial saliva. After electrochemical testing, surface morphologies and cross-sections were examined using micrographs of the samples. Potentiodynamic test results indicated that suprastructure/Ti implant couples produced passive current densities in the range of 0.5-12 microA/cm(2); Ti abutment/Ti implant and gold/Ti implant couples exhibited relatively low passive current densities; Co-Cr/Ti implant couples the highest. Co-Cr and Ni-Cr/Ti implant couples showed breakdown potentials of 700 and 570 mV (SCE), respectively. The open-circuit potentials of silver, Ti abutment, gold, Ni-Cr, and Co-Cr/Ti implant couples were -93.2 +/- 93.9, -123.7 +/- 58.8, -140.0 +/- 80.6, -223.5 +/- 35.1, and -312.7 +/- 29.8 mV (SCE), respectively, and did not change with immersion time. The couples exhibited cathodic current densities at -250 mV (SCE); in particular, gold and silver alloys showed high cathodic current densities of -3.18 and -6.63 microA/cm(2), respectively. At 250 mV (SCE

  7. 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

  8. 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

  9. 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

  10. Electrochemical growth and studies of CuInSe2 thin films

    NASA Astrophysics Data System (ADS)

    Prasher, Dixit; Chandel, Tarun; Rajaram, Poolla

    2014-04-01

    Thin films of CuInSe2 were grown on fluorine doped tin oxide (<10 Ω/□) coated glass using the electrodeposition technique. The electrodeposition was carried out potentiostatically using an aqueous bath consisting of solutions of CuCl2, InCl3 and SeO2 with ethylenediamine-dihydrochloride (EDC) added for complexation. CuInSe2 films were also deposited without using any complexing agent in the bath. To improve the crystallinity the CuInSe2 films were annealed in vaccum at 300 °C for one hour. The annealed films were analyzed by x-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive analysis of x-rays (EDAX), atomic force microscopy (AFM) and optical spectra. The results obtained in this work show that by adding a suitable complexing agent to the electrochemical bath, nanocrystalline CuInSe2, 20 nm to 30 nm in size, can be grown. The composition of the CuInSe2 films can be controlled by means of the bath composition and stoichiometric films can be obtained for a bath with ionic Cu:In:Se composition close to 1:4:2. AFM micrographs show that the particles are generally oval shaped for near stoichiometric compositions. However for extreme copper rich layers, the morphology is completely different, the particles in this case appearing in the form of nanoflakes. Each flake has a thickness in the nano range, but the surface extends to a length of several microns.

  11. Electrochemical synthesis and characterization of TiO(2) nanoparticles and their use as a platform for flavin adenine dinucleotide immobilization and efficient electrocatalysis.

    PubMed

    Ashok Kumar, S; Lo, Po-Hsun; Chen, Shen-Ming

    2008-06-25

    Here, we report the electrochemical synthesis of TiO(2) nanoparticles (NPs) using the potentiostat method. Synthesized particles have been characterized by using x-ray diffraction (XRD) studies, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results revealed that the TiO(2) film produced was mainly composed of rutile and that the particles are of a size in the range of 100 ± 50 nm. TiO(2) NPs were used for the modification of a screen printed carbon electrode (SPE). The resulting TiO(2) film coated SPE was used to immobilize flavin adenine dinucleotide (FAD). The flavin enzyme firmly attached onto the metal oxide surface and this modified electrode showed promising electrocatalytic activities towards the reduction of hydrogen peroxide (H(2)O(2)) in physiological conditions. The electrochemistry of FAD confined in the oxide film was investigated. The immobilized FAD displayed a pair of redox peaks with a formal potential of -0.42 V in pH 7.0 oxygen-free phosphate buffers at a scan rate of 50 mV s(-1). The FAD in the nanostructured TiO(2) film retained its bioactivity and exhibited excellent electrocatalytic response to the reduction of H(2)O(2), based on which a mediated biosensor for H(2)O(2) was achieved. The linear range for the determination of H(2)O(2) was from 0.15 × 10(-6) to 3.0 × 10(-3) M with the detection limit of 0.1 × 10(-6) M at a signal-to-noise ratio of 3. The stability and repeatability of the biosensor is also discussed.

  12. The electrochemical behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Lv, Yanzhuo; Liu, Min; Xu, Yan; Cao, Dianxue; Feng, Jing

    2013-03-01

    The electrochemical oxidation behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn electrodes in 0.7 mol L-1 NaCl solution are investigated by methods of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance spectroscopy and scanning electron microscopy. The phase composition of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn alloys is analyzed conducted by X-ray diffraction. The performances of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn as the anode of Mg-H2O2 semi fuel cells are determined. The effect of Zn content on the corrosion resistant of these Mg-Li-based alloys is studied. It is found that the Mg-8Li-3Al-0.5Zn electrode has higher discharge activity and less corrosion resistance than that of Mg-8Li-3Al-1.0Zn electrode in 0.7 mol L-1 NaCl solution. The Mg-H2O2 semi fuel cell with Mg-8Li-3Al-0.5Zn anode presents a maximum power density of 100 mW cm-2 at room temperature, which is higher than that of Mg-8Li-3Al-1.0Zn anode (80 mW cm-2). The performance of semi fuel cell with the Mg-8Li-3Al-0.5Zn electrode is better than that with Mg-8Li-3Al-1.0Zn electrode, especially at higher current density (>30 mA cm-2).

  13. Integration of solid-state nanopores in a 0.5 μm cmos foundry process

    PubMed Central

    Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

    2013-01-01

    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 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

  14. Application of the 'gate effect' of a molecularly imprinted polymer grafted on an electrode for the real-time sensing of heparin in blood.

    PubMed

    Yoshimi, Yasuo; Sato, Kuniaki; Ohshima, Masaki; Piletska, Elena

    2013-09-07

    Heparin is the most important anticoagulant drug used during surgeries and extracorporeal therapies. Although the blood levels of heparin should be monitored continuously during the procedure to ensure the safety of the patient, there is currently no technique for measuring heparin in real time. This study describes the use of a molecularly imprinted polymer (MIP) as a recognition element in the development of a heparin sensor for real-time monitoring. An indium tin oxide (ITO) electrode grafted with a heparin-specific MIP was used as a working electrode to perform cyclic voltammetry of ferrocyanide. The anodic current was found to be dependent on heparin concentration, probably due to the "gate effect", which is a change in the accessibility of the MIP-modified electrode to ferrocyanide, triggered by specific interaction between MIP and heparin. The kinetics of heparin interaction with the MIP-grafted electrode was evaluated using potentiostatic chronoamperometry of ferrocyanide in an electrochemical flow cell. The response time to stepwise changes in heparin concentration between 0 and 0.04 units per mL was estimated at 20 s, which is remarkably shorter than that achieved using conventional methods for monitoring heparin. The MIP-grafted electrode demonstrated exceptional sensitivity and could detect heparin in whole blood samples (0-6 units per mL) diluted 100-fold with physiological saline containing ferrocyanide. Therefore, the MIP-grafted electrode is suitable for real-time monitoring of heparin in blood. Another advantage is that a very small volume of blood is needed, which is very important, especially when regular measurements are required.

  15. Advanced carbon manufacturing for energy and biological applications

    NASA Astrophysics Data System (ADS)

    Turon Teixidor, Genis

    The science of miniaturization has experienced revolutionary advances during the last decades, witnessing the development of the Integrated Circuit and the emergence of MEMS and Nanotechnology. Particularly, MEMS technology has pioneered the use of non-traditional materials in microfabrication by including polymers, ceramics and composites to the well known list of metals and semiconductors. One of the latest additions to this set of materials is carbon, which represents a very important inclusion given its significance in electrochemical energy conversion systems and in applications where it is used as sensor probe material. For these applications, carbon is optimal in several counts: It has a wide electrochemical stability window, good electrical and thermal conductivity, high corrosion resistance and mechanical stability, and is available in high purity at a low cost. Furthermore carbon is biocompatible. This thesis presents several microfabricated devices that take advantage of these properties. The thesis has two clearly differentiated parts. In the first one, applications of micromachined carbon in the field of energy conversion and energy storage are presented. These applications include lithium ion micro batteries and the development of new carbon electrodes with fractal geometries. In the second part, the focus shifts to biological applications. First, the study of the interaction of living cells with micromachined carbon is presented, followed by the description of a sensor based on interdigitated nano-electrode arrays, and finally the development of the new instrumentation needed to address arrays of carbon electrodes, a multiplexed potentiostat. The underlying theme that connects all these seemingly different topics is the use of carbon microfabrication techniques in electrochemical systems.

  16. 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.

  17. 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.

  18. Experimental Study on the pH of Pore water in Compacted Bentonite under Reducing Conditions with Electromigration

    SciTech Connect

    Nessa, S.A.; Idemitsu, K.; Yamazaki, S.; Ikeuchi, H.; Inagaki, Y.; Arima, T.

    2008-07-01

    Compacted bentonite and carbon steel are considered a good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95 wt% of montmorillonite. Bentonites prominent properties of high swelling, sealing ability and cation exchange capacity provide retardation against the transport of radionuclides from the waste into the surrounding rocks in the repository and its properties determine the behavior of bentonite. In this regards, the pH of pore water in compacted bentonite is measured with pH test paper wrapped with semi-permeable membrane of collodion sheet under reducing conditions. On 30 days, the pH test paper in the experimental apparatus indicated that the pH of pore water in compacted bentonite is around 8.0 at saturated state. The carbon steel coupon is connected as the working electrode to the potentiostat and is held at a constant supplied potential between +300 and -300 mV vs. Ag/AgCl electrode for up to 7 days. During applying electromigration the pH of pore water in bentonite decreased and it reached 6.0{approx}6.0 on 7 days. The concentration of iron and sodium showed nearly complementary distribution in the bentonite specimen after electromigration. It is expected that iron could migrate as ferrous ion through the interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. Semi-permeable membrane of collodion sheet does not affect the color change of pH test paper during the experiment. (authors)

  19. 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.

  20. Angstrom-resolved real-time dissection of electrochemically active noble metal interfaces.

    PubMed

    Shrestha, Buddha R; Baimpos, Theodoros; Raman, Sangeetha; Valtiner, Markus

    2014-06-24

    Electrochemical solid|liquid interfaces are critically important for technological applications and materials for energy storage, harvesting, and conversion. Yet, a real-time Angstrom-resolved visualization of dynamic processes at electrified solid|liquid interfaces has not been feasible. Here we report a unique real-time atomistic view into dynamic processes at electrochemically active metal interfaces using white light interferometry in an electrochemical surface forces apparatus. This method allows simultaneous deciphering of both sides of an electrochemical interface-the solution and the metal side-with microsecond resolution under dynamically evolving reactive conditions that are inherent to technological systems in operando. Quantitative in situ analysis of the potentiodynamic electrochemical oxidation/reduction of noble metal surfaces shows that Angstrom thick oxides formed on Au and Pt are high-ik materials; that is, they are metallic or highly defect-rich semiconductors, while Pd forms a low-ik oxide. In contrast, under potentiostatic growth conditions, all noble metal oxides exhibit a low-ik behavior. On the solution side, we reveal hitherto unknown strong electrochemical reaction forces, which are due to temporary charge imbalance in the electric double layer caused by depletion/generation of charged species. The real-time capability of our approach reveals significant time lags between electron transfer, oxide reduction/oxidation, and solution side reaction during a progressing electrode process. Comparing the kinetics of solution and metal side responses provides evidence that noble metal oxide reduction proceeds via a hydrogen adsorption and subsequent dissolution/redeposition mechanism. The presented approach may have important implications for designing emerging materials utilizing electrified interfaces and may apply to bioelectrochemical processes and signal transmission.

  1. 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.

  2. 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.

  3. Electrocatalytic Oxidation of Alcohols on Cu2O/Cu Thin Film Electrodeposited on Titanium Substrate

    NASA Astrophysics Data System (ADS)

    Bezghiche-Imloul, T.; Hammache-Makhloufi, H.; Ait Ahmed, N.

    2016-05-01

    A novel class of nanomaterials consisting of a composite thin film of cooper metal nanoparticles and cuprous oxide (Cu2O/Cu) for the catalytic electrooxidation of methanol, ethanol and ethylene glycol is considered here. The material was prepared by electrochemical deposition under a potentiostatic condition of -250mV vs saturated calomel electrode (SCE) from acetate bath at titanium substrate. The effect of electrodeposition time on the structure, composition and morphology of the deposit was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated the formation of pure cuprous oxide Cu2O thin film at low electrodeposition time (5 min) and Cu2O oxide thin film decorated with Cu nanoparticles (Cu2O/Cu) at high electrodeposition time. The obtained Cu2O and Cu2O/Cu thin films were explored for the electrochemical oxidation of alcohols in 1 M NaOH alkaline medium using cyclic voltammetry (CV) method. The Cu2O/Cu thin film grown at electrodeposition time of 15 min shows the best electrocatalytic performance toward ethanol oxidation. The effect of concentration of alcohols on the oxidation reaction was studied by CV and chronoamperometry. It was found that the reaction is governed by an irreversible diffusion process. The promising electrocatalytic activity of the Cu2O/Cu electrode provides a new platform for the fabrication of high-performance thin films for alcohols oxidation in alkaline medium. Therefore, the Cu2O/Cu electrode is a suitable as a less expensive electrocatalyst for alcohols oxidation.

  4. Effect of the polarity reversal frequency in the electrokinetic-biological remediation of oxyfluorfen polluted soil.

    PubMed

    Barba, Silvia; Villaseñor, José; Rodrigo, Manuel A; Cañizares, Pablo

    2017-03-03

    This work studies the feasibility of the periodic polarity reversal strategy (PRS) in a combined electrokinetic-biological process for the remediation of clayey soil polluted with a herbicide. Five two-weeks duration electrobioremediation batch experiments were performed in a bench scale set-up using spiked clay soil polluted with oxyfluorfen (20 mg kg(-1)) under potentiostatic conditions applying an electric field between the electrodes of 1.0 V cm(-1) (20.0 V) and using PRS with five frequencies (f) ranging from 0 to 6 d(-1). Additionally, two complementary reference tests were done: single bioremediation and single electrokinetic. The microbial consortium used was obtained from an oil refinery wastewater treatment plant and acclimated to oxyfluorfen degradation. Main soil conditions (temperature, pH, moisture and conductivity) were correctly controlled using PRS. On the contrary, the electroosmotic flow clearly decreased as f increased. The uniform soil microbial distribution at the end of the experiments indicated that the microbial activity remained in every parts of the soil after two weeks when applying PRS. Despite the adapted microbial culture was capable of degrade 100% of oxyfluorfen in water, the remediation efficiency in soil in a reference test, without the application of electric current, was negligible. However, under the low voltage gradients and polarity reversal, removal efficiencies between 5% and 15% were obtained, and it suggested that oxyfluorfen had difficulties to interact with the microbial culture or nutrients and that PRS promoted transport of species, which caused a positive influence on remediation. An optimal f value was observed between 2 and 3 d(-1).

  5. Corrosion behavior of carbon steel in the monoethanolamine-H{sub 2}O-CO{sub 2}-O{sub 2}-SO{sub 2} system

    SciTech Connect

    Kladkaew, N.; Idem, R.; Tontiwachwuthikul, P.; Saiwan, C.

    2009-10-15

    The effects of operating parameters on the corrosion of carbon steel in the monoethanolamine (MEA)-H{sub 2}O-CO{sub 2}-O{sub 2}-SO{sub 2} system were investigated using two different corrosion measurement techniques. The corrosion studies were conducted using a 273A potentiostat using MEA, O{sub 2}, and SO{sub 2} concentrations and CO{sub 2} loading in the ranges of 1-7 kmol/m{sup 3}, 0-100%, 0-204 ppm, and 0-0.5 mol CO{sub 2}/mol MEA, respectively, at corrosion temperatures in the range of 303-353 K. The experimental results showed, for the first time, that a higher concentration of SO{sub 2} in a simulated flue gas stream induces a higher corrosion rate essentially because of the increase in the hydrogen ion concentration generated by reactions of SO{sub 2} and H{sub 2}O as well as SO{sub 2}, O{sub 2}, and H{sub 2}O. Also, an increase in oxygen concentration in the simulated flue gas stream causes a higher corrosion rate due to the increasing solubility of oxygen and, in turn, a higher amount of dissolved oxygen in the liquid phase. The results further show that an increase in the concentrations of MEA, O{sub 2}, and SO{sub 2} as well as CO{sub 2} loading will cause the generation of higher amounts of hydrogen or hydronium ions, as well as carbonic acid and bicarbonate ions, and this is what leads to a higher corrosion rate.

  6. New approach for monitoring fish stress: A novel enzyme-functionalized label-free immunosensor system for detecting cortisol levels in fish.

    PubMed

    Wu, Haiyun; Ohnuki, Hitoshi; Ota, Shirei; Murata, Masataka; Yoshiura, Yasutoshi; Endo, Hideaki

    2017-07-15

    Fishes display a wide variation in their physiological responses to stress, which is clearly evident in the plasma corticosteroid changes, chiefly cortisol levels in fish. As a well-known indicator of fish stress, a simple and rapid method for detecting cortisol changes especially sudden increases is desired. In this study, we describe an enzyme-functionalized label-free immunosensor system for detecting fish cortisol levels. Detection of cortisol using amperometry was achieved by immobilizing both anti-cortisol antibody (selective detection of cortisol) and glucose oxidase (signal amplification and non-toxic measurement) on an Au electrode surface with a self-assembled monolayer. This system is based on the maximum glucose oxidation output current change induced by the generation of a non-conductive antigen-antibody complex, which depends on the levels of cortisol in the sample. The immunosensor responded to cortisol levels with a linear decrease in the current in the range of 1.25-200ngml(-1) (R=0.964). Since the dynamic range of the sensor can cover the normal range of plasma cortisol in fish, the samples obtained from the fish did not need to be diluted. Further, electrochemical measurement of one sample required only ~30min. The sensor system was applied to determine the cortisol levels in plasma sampled from Nile tilapia (Oreochromis niloticus), which were then compared with levels of the same samples determined using the conventional method (ELISA). Values determined using both methods were well correlated. These findings suggest that the proposed label-free immunosensor could be useful for rapid and convenient analysis of cortisol levels in fish without sample dilution. We also believe that the proposed system could be integrated in a miniaturized potentiostat for point-of-care cortisol detection and useful as a portable diagnostic in fish farms in the future.

  7. Electrochemical formation of Dy alloy films in a molten LiCl-KCl-DyCl3 system

    NASA Astrophysics Data System (ADS)

    Konishi, H.; Usui, T.; Nohira, T.; Ito, Y.

    2009-05-01

    As to the electrochemical formation of Dy-Ni alloy films in a molten LiCl-KCl-DyCl3 system at 700 K, the growth of DyNi2 film and behavior of anodic dissolution of Dy from the formed DyNi2 film were investigated. The DyNi2 films were formed by potentiostatic electrolysis at 0.55, 0.62 and 0.70 V with Ni electrodes. The growth rates of DyNi2 films are higher at less noble potential, i.e., 0.47 8m min-1 at 0.55 V, 0.32 8m min-1 at 0.62 V and 0.14 8m min-1 at 0.70 V. From RBS analysis, it was suggested that the Dy-Ni alloy film was formed for 10 or 30 s during electrodepositing Dy at 0.30 V with a Ni electrode. Moreover, the growth rate of Dy-Ni alloy film was faster than that of Dy-Fe alloy film. Anodic electrolysis of the formed DyNi2 film with thickness of 15 μm was conducted at 0.90 V, 1.30 V and 1.90 V, respectively. The formed DyNi2 were transformed to other phases, i.e., DyNi3, DyNi5 and Ni, by selective anodic dissolution of Dy. The transformed Ni film was about 10 μm in thickness and had a porous structure with a pore diameter of 1~2 μm.

  8. VOLTINT: A Matlab ®-based program for semi-automated processing of geochemical data acquired by voltammetry

    NASA Astrophysics Data System (ADS)

    Bristow, Gwendolyn; Taillefert, Martial

    2008-02-01

    Recent progress has resulted in the development of advanced techniques to acquire geochemical information in situ in aquatic systems. Among these techniques, voltammetry has generated significant interest for its ability to detect several important redox-sensitive chemical species in a fast, reliable, and automated manner. Many research groups worldwide have now adopted these techniques for geochemical measurements in various marine and freshwater systems, including water column, sediment, microbial mat, and groundwater, with a high spatial and temporal resolution. Unfortunately, the ability to conduct multiple measurements with great spatial and temporal resolutions generates large data sets that are difficult to integrate manually. We report a new computer program, voltammetric integration software (VOLTINT), that can integrate large voltammetric data sets semi-automatically. This program implemented in Matlab ® is based on a graphical user interface to visualize and identify voltammetric signals. The program differentiates between voltammetric techniques and derives or integrates voltammetric signals to produce output data files containing the redox potentials, current intensities, and, when appropriate, peak surface areas of each electrochemical species that can be detected. VOLTINT was developed with the intention of integrating voltammetric data obtained with potentiostats from a specific company Analytical Instrument Systems, Inc. (AIS). However, the scripts can be easily altered to process any ASCII file containing voltammetric data. The details of the program are presented, and examples provided along with recommendations regarding the analysis of voltammetric data in the context of this program. VOLTINT is available free of charge to anyone who is interested in integrating multiple voltammetric data files in a fast and reliable manner.

  9. Electrochemical cortisol immunosensors based on sonochemically synthesized zinc oxide 1D nanorods and 2D nanoflakes.

    PubMed

    Vabbina, Phani Kiran; Kaushik, Ajeet; Pokhrel, Nimesh; Bhansali, Shekhar; Pala, Nezih

    2015-01-15

    We report on label free, highly sensitive and selective electrochemical immunosensors based on one-dimensional 1D ZnO nanorods (ZnO-NRs) and two-dimensional 2D ZnO nanoflakes (ZnO-NFs) which were synthesized on Au-coated substrates using simple one step sonochemical approach. Selective detection of cortisol using cyclic voltammetry (CV) is achieved by immobilizing anti-cortisol antibody (Anti-C(ab)) on the ZnO nanostructures (NSs). 1D ZnO-NRs and 2D ZnO-NFs provide unique sensing advantages over bulk materials. While 1D-NSs boast a high surface area to volume ratio, 2D-NSs with large area in polarized (0001) plane and high surface charge density could promote higher Anti-C(ab) loading and thus better sensing performance. Beside large surface area, ZnO-NSs also exhibit higher chemical stability, high catalytic activity, and biocompatibility. TEM studies showed that both ZnO-NSs are single crystalline oriented in (0001) plane. The measured sensing parameters are in the physiological range with a sensitivity of 11.86 µA/M exhibited by ZnO-NRs and 7.74 µA/M by ZnO-NFs with the lowest detection limit of 1 pM which is 100 times better than conventional enzyme-linked immunosorbant immunoassay (ELISA). ZnO-NSs based cortisol immunosensors were tested on human saliva samples and the performance were validated with conventional (ELISA) method which exhibits a remarkable correlation. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat for point-of-care cortisol detection and such developed protocol can be used in personalized health monitoring/diagnostic.

  10. 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.

  11. 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.

  12. Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

    NASA Astrophysics Data System (ADS)

    Jia, Hongmei; Chang, Gang; Lei, Ming; He, Hanping; Liu, Xiong; Shu, Honghui; Xia, Tiantian; Su, Jie; He, Yunbin

    2016-10-01

    Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the oxidation of glucose because of excellent synergetic effects between gold and platinum species and the increased electrochemical active area from Pt nanoparticles loading. The non-enzymatic glucose biosensor based on Pt/DGNs/GC showed a rapid respond time (within 2 s), wide linear range (from 0.1 mM to 14 mM), low detection limit (0.01 mM), supernal sensitivity (275.44 μA cm-2 mM-1, R = 0.993), satisfactory reproducibility and good stability for glucose sensing. It was demonstrated that Pt/DGNs/GC could work as promising candidate for factual non-enzymatic glucose detection.

  13. Trap-governed hydrogen diffusivity and uptake capacity in ultrahigh-strength AERMET 100 steel

    NASA Astrophysics Data System (ADS)

    Thomas, Richard L. S.; Li, Daoming; Gangloff, Richard P.; Scully, John R.

    2002-07-01

    The hydrogen-uptake capacity and mobility in ultrahigh-strength AERMET 100 are characterized for various electrochemical charging and baking conditions. From thermal desorption spectroscopy, the apparent hydrogen diffusivity ( D H < 3 × 10-8 cm2/s at 23 °C) is over tenfold less than the values typical of tempered martensitic steels such as AISI 4130. The value of D H decreases with decreasing temperature below 200 °C, with a relatively high apparent activation energy for diffusion of 17.7 to 18.8 ± 0.2 kJ/mol at the 95 pct confidence level. The value of D H also decreases with decreasing diffusible H concentration from less-severe charging or increased baking. Potentiostatic charging in saturated Ca(OH)2 produced total and diffusible H concentrations in AERMET 100 which increase with (H+/H) overpotential and are significantly higher than results for AISI 4130 steel under the same conditions. A significant H concentration was produced by zero overpotential deposition. These characteristics are explained by extensive reversible and irreversible H trapping involving at least three unique trap states in the ultrafine AERMET 100 microstructure. The former likely include coherent M2C carbides, soluble Ni, or precipitated austenite, and the latter include larger incoherent M x C y or martensite lathed-packet interfaces. Baking at 23 °C and 200 °C removes H from the lowest binding-energy sites, but results in reduced D H levels to prolong outgassing time. Additionally, substantial H was retained in stronger trap states. These trapping effects are pertinent to hydrogen embrittlement of AERMET 100 steel.

  14. A Miniaturized Transcutaneous System for Continuous Glucose Monitoring

    PubMed Central

    Croce, Robert A.; Vaddiraju, SanthiSagar; Kondo, Jun; Wang, Yan; Zuo, Liang; Zhu, Kai; Islam, Syed K.; Burgess, Diane; Papadimitrakopoulos, Fotios; Jain, Faquir C.

    2012-01-01

    Implantable sensors for continuous glucose monitoring hold great potential for optimal diabetes management. This is often undermined by a variety of issues associated with: (1) negative tissue response; (2) poor sensor performance; and (3) lack of device miniaturization needed to reduce implantation trauma. Herein, we report our initial results towards constructing an implantable device that simultaneously address all three aforementioned issues. In terms of device miniaturization, a highly miniaturized CMOS (complementary metal-oxide-semiconductor) potentiostat and signal processing unit was employed (with a combined area of 0.665 mm2). The signal processing unit converts the current generated by a transcutaneous, Clark-type amperometric sensor to output frequency in a linear fashion. The Clark-type amperometric sensor employs stratification of five functional layers to attain a well-balanced mass transfer which in turn yields a linear sensor response from 0 to 25 mM of glucose concentration, well beyond the physiologically observed (2 to 22 mM) range. In addition, it is coated with a thick polyvinyl alcohol (PVA) hydrogel with embedded poly(lactic-co-glycolic acid) (PLGA) microspheres intended to provide continuous, localized delivery of dexamethasone to suppress inflammation and fibrosis. In vivo evaluation in rat model has shown that the transcutaneous sensor system reproducibly tracks repeated glycemic events. Clarke’s error grid analysis on the as –obtained glycemic data has indicated that all of the measured glucose readings fell in the desired Zones A & B and none fell in the erroneous Zones C, D and E. Such reproducible operation of the transcutaneous sensor system, together with low power (140 μW) consumption and capability for current-to-frequency conversion renders this a versatile platform for continuous glucose monitoring and other biomedical sensing devices. PMID:22992979

  15. 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.

  16. Multiple redox states of multiheme cytochromes may enable bacterial response to changing redox environments

    NASA Astrophysics Data System (ADS)

    Arbour, T.; Wrighton, K. C.; Mullin, S. W.; Castelle, C.; Luef, B.; Gilbert, B.; Banfield, J. F.

    2013-12-01

    Multiheme c-type cytochromes (MHCs) are key components in electron-transport pathways that enable some microorganisms to transfer electron byproducts of metabolism to a variety of minerals. As a response to changes in mineral redox potential, microbial communities may shift their membership, or individual organisms may adjust protein expression. Alternatively, the ability to respond may be conferred by the innate characteristics of certain electron-transport-chain components. Here, we used potentiostat-controlled microbial fuel cells (MFCs) to measure the timescale of response to imposed changes in redox conditions, thus placing constraints on the importance of these different mechanisms. In the experiments, a solid electrode acts as an electron-accepting mineral whose redox potential can be precisely controlled. We inoculated duplicate MFCs with a sediment/groundwater mixture from an aquifer at Rifle, Colorado, supplied acetate as an electron donor, and obtained stable, mixed-species biofilms dominated by Geobacter and a novel Geobacter-related family. We poised the anode at potentials spanning the range of natural Fe(III)-reduction, then performed cyclic voltammetry (CV) to characterize the overall biofilm redox signature. The apparent biofilm midpoint potential shifted directly with anode set potential when the latter was changed within the range from about -250 to -50 mV vs. SHE. Following a jump in set potential by 200 mV, the CV-midpoint shift by ~100 mV over a timescale of ~30 minutes to a few hours, depending on the direction of the potential change. The extracellular electron transfer molecules, whose overall CV signature is very similar to those of purified MHCs, appear to span a broad redox range (~200 mV), supporting the hypothesis that MHCs confer substantial redox flexibility. This flexibility may be a principle reason for the abundance of MHCs expressed by microorganisms capable of extracellular electron transfer to minerals.

  17. Fabrication of multiwalled carbon nanotubes/polyaniline modified Au electrode for ascorbic acid determination.

    PubMed

    Chauhan, Nidhi; Narang, Jagriti; Pundir, C S

    2011-05-07

    An ascorbate oxidase (AsOx) (E.C.1.10.3.3) purified from Lagenaria siceraria fruit was immobilized covalently onto a carboxylated multiwalled carbon nanotubes and polyaniline (c-MWCNT/PANI) layer electrochemically deposited on the surface of an Au electrode. The diffusion coefficient of ascorbic acid was determined as 3.05 × 10(-4) cm(2) s(-1). The behavior of different electrolytes on electro-deposition was also studied. An ascorbate biosensor was fabricated using a AsOx/c-MWCNT/PANI/Au electrode as a working electrode, Ag/AgCl (3 M/saturated KCl) as standard and Pt wire as an auxiliary electrode connected through a potentiostat. Linear range, response time and detection limit were 2-206 μM, 2 s and 0.9 μM respectively. The biosensor showed optimum response at pH 5.8 and in a broader temperature range (30-45 °C), when polarized at +0.6 V. The biosensor was employed for determination of ascorbic acid level in sera, fruit juices and vitamin C tablets. The sensor was evaluated with 91% recovery of added ascorbic acid in sera and 6.5% and 11.4% within and between batch coefficients of variation respectively for five serum samples. There was a good correlation (r = 0.98) between fruit juice ascorbic acid values by the standard 2,6-dichlorophenolindophenol (DCPIP) method and the present method. The enzyme electrode was used 200 times over a period of two months, when stored at 4 °C. The biosensor has advantages over earlier enzyme sensors in that it has no leakage of enzyme, due to the covalent coupling of enzyme with the support, lower response time, wider working range, higher storage stability and no interference by serum substances.

  18. Microscopy of hierarchically organized TiO{sub 2} photoelectrode for dye solar cells

    SciTech Connect

    Eskandar, A.; Mohamed, N. M.

    2015-07-22

    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 TiO{sub 2} 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 cm{sup 2}. 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{sup −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 TiO{sub 2} nanoparticles and 450 nm TiO{sub 2} 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.

  19. 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.

  20. A miniaturized transcutaneous system for continuous glucose monitoring.

    PubMed

    Croce, Robert A; Vaddiraju, SanthiSagar; Kondo, Jun; Wang, Yan; Zuo, Liang; Zhu, Kai; Islam, Syed K; Burgess, Diane J; Papadimitrakopoulos, Fotios; Jain, Faquir C

    2013-02-01

    Implantable sensors for continuous glucose monitoring hold great potential for optimal diabetes management. This is often undermined by a variety of issues associated with: (1) negative tissue response; (2) poor sensor performance; and (3) lack of device miniaturization needed to reduce implantation trauma. Herein, we report our initial results towards constructing an implantable device that simultaneously address all three aforementioned issues. In terms of device miniaturization, a highly miniaturized CMOS (complementary metal-oxide-semiconductor) potentiostat and signal processing unit was employed (with a combined area of 0.665 mm(2)). The signal processing unit converts the current generated by a transcutaneous, Clark-type amperometric sensor to output frequency in a linear fashion. The Clark-type amperometric sensor employs stratification of five functional layers to attain a well-balanced mass transfer which in turn yields a linear sensor response from 0 to 25 mM of glucose concentration, well beyond the physiologically observed (2 to 22 mM) range. In addition, it is coated with a thick polyvinyl alcohol (PVA) hydrogel with embedded poly(lactic-co-glycolic acid) (PLGA) microspheres intended to provide continuous, localized delivery of dexamethasone to suppress inflammation and fibrosis. In vivo evaluation in rat model has shown that the transcutaneous sensor system reproducibly tracks repeated glycemic events. Clarke's error grid analysis on the as-obtained glycemic data has indicated that all of the measured glucose readings fell in the desired Zones A & B and none fell in the erroneous Zones C, D and E. Such reproducible operation of the transcutaneous sensor system, together with low power (140 μW) consumption and capability for current-to-frequency conversion renders this a versatile platform for continuous glucose monitoring and other biomedical sensing devices.