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Bayat A, Dondapati JS, Ahmed SR, Srinivasan S, Rajabzadeh AR. Electrochemical detection of 4(5)-methylimidazole in aqueous solutions. Food Chem 2024; 450:139320. [PMID: 38640530 DOI: 10.1016/j.foodchem.2024.139320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 03/22/2024] [Accepted: 04/08/2024] [Indexed: 04/21/2024]
Abstract
4(5)-methylimidazole (4-MeI) is a potential carcinogen widely used in food colours. EU regulations specify a maximum allowable concentration of 200 ppm for 4-MeI in caramel colours. This study reports an electrochemical determination technique for 4-MeI in caramel colours for the first time. The effect of pH and interference from air were studied to optimize the detection conditions on a glassy carbon electrode in aqueous alkaline solutions using square wave voltammetry (SWV) technique. The concentration of 4-MeI was quantitatively measured down to 10 μM (∼0.8 ppm). Traditional methods such as HPLC, GC, spectrometry and immunoassays involve either expensive instrumentation and reagents or time consuming preparation and detection processes. This study demonstrates the possibility of rapid and simple electrochemical determination of (4-MeI) in food colours with minimum workup using a portable potentiostat.
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Affiliation(s)
- Akhtar Bayat
- W. Booth School of Engineering Practice & Technology, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Jesse Smiles Dondapati
- W. Booth School of Engineering Practice & Technology, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Syed Rahin Ahmed
- W. Booth School of Engineering Practice & Technology, McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Seshasai Srinivasan
- W. Booth School of Engineering Practice & Technology, McMaster University, Hamilton, Ontario L8S 4L8, Canada.
| | - Amin Reza Rajabzadeh
- W. Booth School of Engineering Practice & Technology, McMaster University, Hamilton, Ontario L8S 4L8, Canada.
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2
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Li Z, Chande C, Cheng YH, Basuray S. Recent State and Challenges in Spectroelectrochemistry with Its Applications in Microfluidics. MICROMACHINES 2023; 14:667. [PMID: 36985074 PMCID: PMC10056660 DOI: 10.3390/mi14030667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/12/2023] [Accepted: 03/13/2023] [Indexed: 06/18/2023]
Abstract
This review paper presents the recent developments in spectroelectrochemical (SEC) technologies. The coupling of spectroscopy and electrochemistry enables SEC to do a detailed and comprehensive study of the electron transfer kinetics and vibrational spectroscopic fingerprint of analytes during electrochemical reactions. Though SEC is a promising technique, the usage of SEC techniques is still limited. Therefore, enough publicity for SEC is required, considering the promising potential in the analysis fields. Unlike previously published review papers primarily focused on the relatively frequently used SEC techniques (ultraviolet-visible SEC and surface-enhanced Raman spectroscopy SEC), the two not-frequently used but promising techniques (nuclear magnetic resonance SEC and dark-field microscopy SEC) have also been studied in detail. This review paper not only focuses on the applications of each SEC method but also details their primary working mechanism. In short, this paper summarizes each SEC technique's working principles, current applications, challenges encountered, and future development directions. In addition, each SEC technique's applicative research directions are detailed and compared in this review work. Furthermore, integrating SEC techniques into microfluidics is becoming a trend in minimized analysis devices. Therefore, the usage of SEC techniques in microfluidics is discussed.
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Affiliation(s)
- Zhenglong Li
- Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Charmi Chande
- Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Yu-Hsuan Cheng
- Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Sagnik Basuray
- Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
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3
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Swinya D, Martín-Yerga D, Walker M, Unwin PR. Surface Nanostructure Effects on Dopamine Adsorption and Electrochemistry on Glassy Carbon Electrodes. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:13399-13408. [PMID: 35983313 PMCID: PMC9377355 DOI: 10.1021/acs.jpcc.2c02801] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Dopamine (DA) adsorption and electron-transfer kinetics are strongly sensitive to the structure and composition of carbon electrodes. Activation of carbon surfaces is a popular method to improve DA detection, but the role of carbon structural features on DA behavior remains uncertain. Herein, we use scanning electrochemical cell microscopy (SECCM) for local anodization of glassy carbon (GC) electrodes in acid media followed by electrochemical imaging of DA adsorption and electrochemistry covering both unmodified and anodized GC regions of the same electrode. Electrochemical measurements of adsorbed DA involve the delivery of DA from the SECCM meniscus (30 μM) for 1 s periods followed by voltammetric analysis at a reasonable sweep rate (47 V s-1). This general approach reduces effects from interelectrode variability and allows for considerable numbers of measurements and statistical analysis of electrochemical data sets. Localized electrode activity is correlated to surface structure and chemistry by a range of characterization techniques. Anodization enhances DA electron-transfer kinetics and provides more sites for adsorption (higher specific surface area). A consequence is that adsorption takes longer to approach completion on the anodized surface. In fact, normalizing DA surface coverage by the electrochemical surface area (ECSA) reveals that adsorption is less extensive on anodized surfaces compared to as-prepared GC on the same time scale. Thus, ECSA, which has often been overlooked when calculating DA surface coverage on carbon electrodes, even where different activation methods would be expected to result in different surface roughness and nanostructure, is an important consideration. Lower graphitic and higher oxygen content on anodized GC also suggest that oxygen-containing functional groups do not necessarily enhance DA adsorption and may have the opposite effect. This work further demonstrates SECCM as a powerful technique for revealing surface structure-function relationships and correlations at heterogeneous electrodes.
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Affiliation(s)
- Dalia
L. Swinya
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Daniel Martín-Yerga
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Marc Walker
- Department
of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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4
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A simple, fast, and cost-effective analytical method for monitoring active quinones in a H2O2 production process. Microchem J 2021. [DOI: 10.1016/j.microc.2020.105861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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5
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Beall CE, Fabbri E, Schmidt TJ. Perovskite Oxide Based Electrodes for the Oxygen Reduction and Evolution Reactions: The Underlying Mechanism. ACS Catal 2021. [DOI: 10.1021/acscatal.0c04473] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Casey E. Beall
- Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Emiliana Fabbri
- Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Thomas J. Schmidt
- Paul Scherrer Institute (PSI), Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
- Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland
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6
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Pugolovkin LV, Levin EE, Arkharova NA, Orekhov AS, Presnov DE, Tsirlina GA. Cathodic deposition of birnessite from alkaline permanganate solutions: Tools to control the current efficiency, morphology and adhesion. J Electroanal Chem (Lausanne) 2020. [DOI: 10.1016/j.jelechem.2020.114521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Rahman MA, Li J, Guo SX, Kennedy G, Ueda T, Bond AM, Zhang J. Modelling limitations encountered in the thermodynamic and electrode kinetic parameterization of the α-[S2W18O62]4−/5−/6− processes at glassy carbon and metal electrodes. J Electroanal Chem (Lausanne) 2020. [DOI: 10.1016/j.jelechem.2019.113786] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Jaramillo A, Barrera-Gutiérrez R, Cortés MT. Synthesis, Follow-Up, and Characterization of Polydopamine-like Coatings Departing from Micromolar Dopamine- o-Quinone Precursor Concentrations. ACS OMEGA 2020; 5:15016-15027. [PMID: 32637775 PMCID: PMC7330902 DOI: 10.1021/acsomega.0c00676] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/01/2020] [Indexed: 06/11/2023]
Abstract
The understanding of oxidized species derived from the neurotransmitter dopamine (DA) is a relevant topic for both the medical field (Parkinson's disease) as well as for the field of materials science where the formation process of polydopamine (PDA) films is an active area of research. Polymers that interact strongly with almost all surfaces but have a low electrical conductivity have been obtained by the chemical oxidation of DA. Since electrical conductivity is a desired property for several applications, deposition alternatives such as electrochemical PDA synthesis have been proposed, but the results are still insufficient. In this context, we propose a new PDA chemical-electrochemical deposition process on glassy carbon electrodes. The chemical oxidation step that converts dopamine into dopamine-o-quinone previous to the electrochemical deposition was crucial to decrease the precursor concentration to the micromolar range. The PDA-like films synthesized by this method had high adhesion and low charge-transfer resistance, which was evidenced by impedance measurements and the successful electrodeposition of a polypyrrole coating on top of a PDA-like film. In addition, we observed that anodization of GC surfaces increases sensitivity toward six electroactive couples derived from DA oxidation in the pH regimes studied. These results show the complexity of the intermediates formed during the electrochemical polymerization of PDA.
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Affiliation(s)
- Andrés
M. Jaramillo
- Department of Chemistry, Universidad de Los Andes, Cra 1 N° 18A-12, Bogotá 111711, Colombia
| | | | - María T. Cortés
- Department of Chemistry, Universidad de Los Andes, Cra 1 N° 18A-12, Bogotá 111711, Colombia
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9
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Guerrero LA, Fernández L, González G, Montero-Jiménez M, Uribe R, Díaz Barrios A, Espinoza-Montero PJ. Peroxide Electrochemical Sensor and Biosensor Based on Nanocomposite of TiO 2 Nanoparticle/Multi-Walled Carbon Nanotube Modified Glassy Carbon Electrode. NANOMATERIALS 2019; 10:nano10010064. [PMID: 31892125 PMCID: PMC7023077 DOI: 10.3390/nano10010064] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 12/09/2019] [Accepted: 12/15/2019] [Indexed: 01/13/2023]
Abstract
A hydrogen peroxide (H2O2) sensor and biosensor based on modified multi-walled carbon nanotubes (CNTs) with titanium dioxide (TiO2) nanostructures was designed and evaluated. The construction of the sensor was performed using a glassy carbon (GC) modified electrode with a TiO2–CNT film and Prussian blue (PB) as an electrocalatyzer. The same sensor was also employed as the basis for H2O2 biosensor construction through further modification with horseradish peroxidase (HRP) immobilized at the TiO2–fCNT film. Functionalized CNTs (fCNTs) and modified TiO2–fCNTs were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray DifFraction (XRD), confirming the presence of anatase over the fCNTs. Depending on the surface charge, a solvent which optimizes the CNT dispersion was selected: dimethyl formamide (DMF) for fCNTs and sodium dodecylsulfate (SDS) for TiO2–fCNTs. Calculated values for the electron transfer rate constant (ks) were 0.027 s−1 at the PB–fCNT/GC modified electrode and 4.7 × 10−4 s−1 at the PB–TiO2/fCNT/GC electrode, suggesting that, at the PB–TiO2/fCNT/GC modified electrode, the electronic transfer was improved. According to these results, the PB–fCNT/GC electrode exhibited better Detection Limit (LD) and Quantification Limit (LQ) than the PB–TiO2/fCNT/GC electrode for H2O2. However, the PB film was very unstable at the potentials used. Therefore, the PB–TiO2/fCNT/GC modified electrode was considered the best for H2O2 detection in terms of operability. Cyclic Voltammetry (CV) behaviors of the HRP–TiO2/fCNT/GC modified electrodes before and after the chronoamperometric test for H2O2, suggest the high stability of the enzymatic electrode. In comparison with other HRP/fCNT-based electrochemical biosensors previously described in the literature, the HRP–fCNTs/GC modified electrode did not show an electroanalytical response toward H2O2.
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Affiliation(s)
- L. Andrés Guerrero
- Escuela de Ciencias Químicas, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, Quito 17-01-2184, Ecuador; (L.A.G.)
- School of Physics and Nanotechnology, Yachay Tech University, Urcuqui 100650, Ecuador;
| | - Lenys Fernández
- Escuela de Ciencias Químicas, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, Quito 17-01-2184, Ecuador; (L.A.G.)
- Departamento de Química, Universidad Simón Bolívar, Caracas 89000, Venezuela
- Correspondence: (L.F.); (G.G.); (P.J.E.-M.); Tel.: +593-2299-1700 (ext. 1929) (P.J.E.-M.)
| | - Gema González
- School of Physics and Nanotechnology, Yachay Tech University, Urcuqui 100650, Ecuador;
- Instituto Venezolano de Investigaciones Científicas, Centro de Ingeniería Materiales y Nanotecnología, Caracas 1020-A, Venezuela
- Correspondence: (L.F.); (G.G.); (P.J.E.-M.); Tel.: +593-2299-1700 (ext. 1929) (P.J.E.-M.)
| | - Marjorie Montero-Jiménez
- Escuela de Ciencias Químicas, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, Quito 17-01-2184, Ecuador; (L.A.G.)
| | - Rafael Uribe
- Departamento de Ingeniería Química, Escuela Politécnica Nacional, Quito 17-01-2759, Ecuador;
| | - Antonio Díaz Barrios
- School of Physics and Nanotechnology, Yachay Tech University, Urcuqui 100650, Ecuador;
| | - Patricio J. Espinoza-Montero
- Escuela de Ciencias Químicas, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, Quito 17-01-2184, Ecuador; (L.A.G.)
- Correspondence: (L.F.); (G.G.); (P.J.E.-M.); Tel.: +593-2299-1700 (ext. 1929) (P.J.E.-M.)
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10
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Alumina contamination through polishing and its effect on hydrogen evolution on gold electrodes. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.134915] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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11
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Rocha P, Vilas‐Boas Â, Fontes N, Geraldo D, Bento F. Evaluation of Polyphenols in Wine by Voltammetric Techniques with Screen Printed Carbon Electrodes. ELECTROANAL 2019. [DOI: 10.1002/elan.201900392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Pedro Rocha
- Centre of ChemistryUniversidade do Minho Braga Portugal
| | | | | | - Dulce Geraldo
- Centre of ChemistryUniversidade do Minho Braga Portugal
| | - Fátima Bento
- Centre of ChemistryUniversidade do Minho Braga Portugal
- Departamento de QuímicaUniversidade do Minho Campus de Gualtar 4710-057 Braga Portugal
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12
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Behan JA, Grajkowski F, Jayasundara DR, Vilella-Arribas L, García-Melchor M, Colavita PE. Influence of carbon nanostructure and oxygen moieties on dopamine adsorption and charge transfer kinetics at glassy carbon surfaces. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.02.103] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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13
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Virwani K, Ansari Y, Nguyen K, Moreno-Ortiz FJA, Kim J, Giammona MJ, Kim HC, La YH. In situ AFM visualization of Li-O 2 battery discharge products during redox cycling in an atmospherically controlled sample cell. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2019; 10:930-940. [PMID: 31165020 PMCID: PMC6541370 DOI: 10.3762/bjnano.10.94] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 03/26/2019] [Indexed: 06/09/2023]
Abstract
The in situ observation of electrochemical reactions is challenging due to a constantly changing electrode surface under highly sensitive conditions. This study reports the development of an in situ atomic force microscopy (AFM) technique for electrochemical systems, including the design, fabrication, and successful performance of a sealed AFM cell operating in a controlled atmosphere. Documentation of reversible physical processes on the cathode surface was performed on the example of a highly reactive lithium-oxygen battery system at different water concentrations in the solvent. The AFM data collected during the discharge-recharge cycles correlated well with the simultaneously recorded electrochemical data. We were able to capture the formation of discharge products from correlated electrical and topographical channels and measure the impact of the presence of water. The cell design permitted acquisition of electrochemical impedance spectroscopy, contributing information about electrical double layers under the system's controlled environment. This characterization method can be applied to a wide range of reactive surfaces undergoing transformations under carefully controlled conditions.
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Affiliation(s)
- Kumar Virwani
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | - Younes Ansari
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | - Khanh Nguyen
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | | | - Jangwoo Kim
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | | | - Ho-Cheol Kim
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | - Young-Hye La
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
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14
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Pierini GD, Robledo SN, Zon MA, Di Nezio MS, Granero AM, Fernández H. Development of an electroanalytical method to control quality in fish samples based on an edge plane pyrolytic graphite electrode. Simultaneous determination of hypoxanthine, xanthine and uric acid. Microchem J 2018. [DOI: 10.1016/j.microc.2017.12.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Carino EV, Newman DJ, Connell JG, Kim C, Brushett FR. Early Stage Anodic Instability of Glassy Carbon Electrodes in Propylene Carbonate Solvent Containing Lithium Hexafluorophosphate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11911-11918. [PMID: 28927271 DOI: 10.1021/acs.langmuir.7b02243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Irreversible changes to the morphology of glassy carbon (GC) electrodes at potentials between 3.5 and 4.5 V vs Li/Li+ in propylene carbonate (PC) solvent containing lithium hexafluorophosphate (LiPF6) are reported. Analysis of cyclic voltammetry (CV) experiments in the range of 3.0 to 6.0 V shows that the capacitance of the electrochemical double-layer increased irreversibly beginning at potentials as low as 3.5 V. These changes resulted from nonfaradaic interactions, and were not due to oxidative electrochemical decomposition of the electrode and electrolyte, anion intercalation, nor caused by the presence of water, a common impurity in organic electrolyte solutions. Atomic force microscopy (AFM) images revealed that increasing the potential of a bare GC surface from 3.0 to 4.5 V resulted in a 6× increase in roughness, in good agreement with the changes in double-layer capacitance. Treating the GC surface via exposure to trichloromethylsilane vapors resulted in a stable double-layer capacitance between 3.0 and 4.5 V, and this treatment also correlated with less roughening. These results inform future efforts aimed at controlling surface composition and morphology of carbon electrodes.
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Affiliation(s)
- Emily V Carino
- Joint Center for Energy Storage Research, Argonne National Laboratory , Argonne, Illinois 60439, United States
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Daniel J Newman
- Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Justin G Connell
- Joint Center for Energy Storage Research, Argonne National Laboratory , Argonne, Illinois 60439, United States
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Chaerin Kim
- Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Fikile R Brushett
- Joint Center for Energy Storage Research, Argonne National Laboratory , Argonne, Illinois 60439, United States
- Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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16
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Palacios-Santander J, Terzi F, Zanardi C, Pigani L, Cubillana-Aguilera L, Naranjo-Rodriguez I, Seeber R. Electrocatalytic and antifouling properties of CeO2-glassy carbon electrodes. J Solid State Electrochem 2016. [DOI: 10.1007/s10008-016-3413-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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17
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McBride NS, Hall EAH. Fe3+/Fe2+Mycobactin-Complex Electrochemistry as an Approach to Determine Mycobactin Levels in Urine. ELECTROANAL 2015. [DOI: 10.1002/elan.201400565] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Jing L, En-bo S, Quan-min L. The Influencing Mechanism of Acidity on the Oxidation Peak Currents of Uric Acid and Ascorbic Acid at the PACPE by Cyclic Voltammetry. J CHIN CHEM SOC-TAIP 2015. [DOI: 10.1002/jccs.201400136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Hernández-Cancel G, Suazo-Dávila D, Medina-Guzmán J, Rosado-González M, Díaz-Vázquez LM, Griebenow K. Chemically glycosylation improves the stability of an amperometric horseradish peroxidase biosensor. Anal Chim Acta 2015; 854:129-39. [PMID: 25479876 PMCID: PMC4292887 DOI: 10.1016/j.aca.2014.11.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 10/16/2014] [Accepted: 11/05/2014] [Indexed: 11/24/2022]
Abstract
We constructed a biosensor by electrodeposition of gold nano-particles (AuNPs) on glassy carbon (GC) and subsequent formation of a 4-mercaptobenzoic acid self-assembled monolayer (SAM). The enzyme horseradish peroxidase (HRP) was then covalently immobilized onto the SAM. Two forms of HRP were employed: non-modified and chemically glycosylated with lactose. Circular dichroism (CD) spectra showed that chemical glycosylation did neither change the tertiary structure of HRP nor the heme environment. The highest sensitivity of the biosensor to hydroquinone was obtained for the biosensor with HRP-lactose (414 nA μM(-1)) compared to 378 nA μM(-1) for the one employing non-modified HRP. The chemically glycosylated form of the enzyme catalyzed the reduction of hydroquinone more rapidly than the native form of the enzyme. The sensor employing lactose-modified HRP also had a lower limit of detection (74 μM) than the HRP biosensor (83 μM). However, most importantly, chemically glycosylation improved the long-term stability of the biosensor, which retained 60% of its activity over a four-month storage period compared to only 10% for HRP. These results highlight improvements by an innovative stabilization method when compared to previously reported enzyme-based biosensors.
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Affiliation(s)
- Griselle Hernández-Cancel
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico.
| | - Damaris Suazo-Dávila
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico.
| | - Johnsue Medina-Guzmán
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico
| | - María Rosado-González
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico.
| | - Liz M Díaz-Vázquez
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico.
| | - Kai Griebenow
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, P.O. Box 23346, San Juan 00931-3346, Puerto Rico.
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Substrate selection for fundamental studies of electrocatalysts and photoelectrodes: inert potential windows in acidic, neutral, and basic electrolyte. PLoS One 2014; 9:e107942. [PMID: 25357131 PMCID: PMC4214636 DOI: 10.1371/journal.pone.0107942] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 08/17/2014] [Indexed: 11/26/2022] Open
Abstract
The selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.
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Zebardast H, Rogak S, Asselin E. Potential of zero charge of glassy carbon at elevated temperatures. J Electroanal Chem (Lausanne) 2014. [DOI: 10.1016/j.jelechem.2014.03.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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22
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Magdić K, Kvastek K, Horvat-Radošević V. Concept of spatial surface heterogeneity in impedance modelling of electrochemically activated glass-like carbon electrode. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2013.11.065] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Fogel R, Limson JL. Electrochemically Predicting Phenolic Substrates’ Suitability for Detection by Amperometric Laccase Biosensors. ELECTROANAL 2013. [DOI: 10.1002/elan.201200642] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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Galhardo KS, Torresi RM, de Torresi SIC. Improving the performance of a glucose biosensor using an ionic liquid for enzyme immobilization. On the chemical interaction between the biomolecule, the ionic liquid and the cross-linking agent. Electrochim Acta 2012. [DOI: 10.1016/j.electacta.2011.10.088] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Electrochemical properties of nanostructured cobalt hexacyanoferrate containing K+ and Cs+ synthesized in water-in-oil AOT reverse microemulsions. J Electroanal Chem (Lausanne) 2012. [DOI: 10.1016/j.jelechem.2012.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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26
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Niland MJ, Fogel R, Flanagan SP, Limson JL. Towards Normalising Variability in Current Responses at Glassy Carbon Electrodes Using Double Layer Capacitance; a Case Study of Citrinin. ELECTROANAL 2012. [DOI: 10.1002/elan.201100645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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27
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Carino EV, Kim HY, Henkelman G, Crooks RM. Site-Selective Cu Deposition on Pt Dendrimer-Encapsulated Nanoparticles: Correlation of Theory and Experiment. J Am Chem Soc 2012; 134:4153-62. [DOI: 10.1021/ja209115e] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Emily V. Carino
- Department
of Chemistry and Biochemistry, ‡Center for Electrochemistry, §Texas Materials Institute, and ∥Institute for
Computational and Engineering Sciences, The University of Texas at Austin, 1 University Station,
A5300 Austin, Texas 78712-0165, United States
| | - Hyun You Kim
- Department
of Chemistry and Biochemistry, ‡Center for Electrochemistry, §Texas Materials Institute, and ∥Institute for
Computational and Engineering Sciences, The University of Texas at Austin, 1 University Station,
A5300 Austin, Texas 78712-0165, United States
| | - Graeme Henkelman
- Department
of Chemistry and Biochemistry, ‡Center for Electrochemistry, §Texas Materials Institute, and ∥Institute for
Computational and Engineering Sciences, The University of Texas at Austin, 1 University Station,
A5300 Austin, Texas 78712-0165, United States
| | - Richard M. Crooks
- Department
of Chemistry and Biochemistry, ‡Center for Electrochemistry, §Texas Materials Institute, and ∥Institute for
Computational and Engineering Sciences, The University of Texas at Austin, 1 University Station,
A5300 Austin, Texas 78712-0165, United States
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28
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Bae JH, Han JH, Chung TD. Electrochemistry at nanoporous interfaces: new opportunity for electrocatalysis. Phys Chem Chem Phys 2012; 14:448-63. [DOI: 10.1039/c1cp22927c] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Stevanović SI, Panić VV, Dekanski AB, Tripković AV, Jovanović VM. Relationships between structure and activity of carbon as a multifunctional support for electrocatalysts. Phys Chem Chem Phys 2012; 14:9475-85. [DOI: 10.1039/c2cp40455a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Ranganathan D, Zamponi S, Conti P, Sagratini G, Berrettoni M, Giorgetti M. Voltammetric Determination of ITX in Hydro-Alcoholic Solutions and Wine. ANAL LETT 2011. [DOI: 10.1080/00032719.2010.551692] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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31
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Carino EV, Crooks RM. Characterization of Pt@Cu core@shell dendrimer-encapsulated nanoparticles synthesized by Cu underpotential deposition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4227-4235. [PMID: 21384847 DOI: 10.1021/la2001915] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Dendrimer-encapsulated nanoparticles (DENs) containing averages of 55, 147, and 225 Pt atoms immobilized on glassy carbon electrodes served as the electroactive surface for the underpotential deposition (UPD) of a Cu monolayer. This results in formation of core@shell (Pt@Cu) DENs. Evidence for this conclusion comes from cyclic voltammetry, which shows that the Pt core DENs catalyze the hydrogen evolution reaction before Cu UPD, but that after Cu UPD this reaction is inhibited. Results obtained by in situ electrochemical X-ray absorption spectroscopy (XAS) confirm this finding.
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Affiliation(s)
- Emily V Carino
- Department of Chemistry and Biochemistry, Center for Electrochemistry, and the Texas Materials Institute, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, United States
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32
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Pande S, Weir MG, Zaccheo BA, Crooks RM. Synthesis, characterization, and electrocatalysis using Pt and Pd dendrimer-encapsulated nanoparticles prepared by galvanic exchange. NEW J CHEM 2011. [DOI: 10.1039/c1nj20083f] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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33
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Activity changes of glassy carbon electrodes caused by their exposure to OH• radicals. Electrochem commun 2010. [DOI: 10.1016/j.elecom.2010.08.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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34
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Takmakov P, Zachek MK, Keithley RB, Walsh PL, Donley C, McCarty GS, Wightman RM. Carbon microelectrodes with a renewable surface. Anal Chem 2010; 82:2020-8. [PMID: 20146453 DOI: 10.1021/ac902753x] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrode fouling decreases sensitivity and can be a substantial limitation in electrochemical experiments. In this work we describe an electrochemical procedure that constantly renews the surface of a carbon microelectrode using periodic triangle voltage excursions to an extended anodic potential at a scan rate of 400 V s(-1). This methodology allows for the regeneration of an electrochemically active surface and restores electrode sensitivity degraded by irreversible adsorption of chemical species. We show that repeated voltammetric sweeps to moderate potentials in aqueous solution causes oxidative etching of carbon thereby constantly renewing the electrochemically active surface. Oxidative etching was established by tracking surface-localized fluorine atoms with XPS, by monitoring changes in carbon surface morphology with AFM on pyrolyzed photoresist films, and also by optical and electron microscopy. The use of waveforms with extended anodic potentials showed substantial increases in sensitivity toward the detection of catechols. This enhancement arose from the adsorption of the catechol moiety that could be maintained with a constant regeneration of the electrode surface. We also demonstrate that application of the extended waveform could restore the sensitivity of carbon microelectrodes diminished by irreversible adsorption (electrode fouling) of byproducts resulting from the electrooxidation and polymerization of tyramine. Overall, this work brings new insight into the factors that affect electrochemical processes at carbon electrodes and provides a simple method to remove or reduce fouling problems associated with many electrochemical experiments.
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Affiliation(s)
- Pavel Takmakov
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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35
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36
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Hezard T, Durand G, Rakib M, Viers P, Roy S, Guigues N, Brach M, Heitzmann JP, Eberlé P, Bellouard F. Metal On-Line Voltammetric Analyzer for On-Site Monitoring of Iron Speciation in Acid Mine Drainage Waters: Development and Characterization. ELECTROANAL 2009. [DOI: 10.1002/elan.200804538] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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37
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McCreery RL. Advanced carbon electrode materials for molecular electrochemistry. Chem Rev 2008; 108:2646-87. [PMID: 18557655 DOI: 10.1021/cr068076m] [Citation(s) in RCA: 1448] [Impact Index Per Article: 90.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard L McCreery
- National Institute for Nanotechnology, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2M9, Canada.
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38
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Ledesma-García J, Escalante García IL, Rodríguez FJ, Chapman TW, Godínez LA. Immobilization of dendrimer-encapsulated platinum nanoparticles on pretreated carbon-fiber surfaces and their application for oxygen reduction. J APPL ELECTROCHEM 2007. [DOI: 10.1007/s10800-007-9466-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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39
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Awad MI, Saleh MM, Ohsaka T. Oxygen reduction on rotating porous cylinder of modified reticulated vitreous carbon. J Solid State Electrochem 2007. [DOI: 10.1007/s10008-007-0385-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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40
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Saleh MM, Awad MI, Okajima T, Suga K, Ohsaka T. Characterization of oxidized reticulated vitreous carbon electrode for oxygen reduction reaction in acid solutions. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2006.09.058] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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41
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Hermans A, Wightman RM. Conical tungsten tips as substrates for the preparation of ultramicroelectrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:10348-53. [PMID: 17129002 PMCID: PMC2515709 DOI: 10.1021/la061209e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Here we describe a simple method to prepare voltammetric microelectrodes using tungsten wires as a substrate. Tungsten wires have a high tensile modulus and enable the fabrication of electrodes that have small dimensions overall while retaining rigidity. In this work, 125 microm tungsten wires with a conical tip were employed. For the preparation of gold or platinum ultramicroelectrodes, commercial tungsten microelectrodes, completely insulated except at the tip, were used as substrates. Following removal of oxides from the exposed tungsten, platinum or gold was electroplated, yielding surfaces with an electroactive area of between 1 x 10-6 and 2 x 10-6 cm2. Carbon surfaces on the etched tip of tungsten microwires were prepared by coating with photoresist followed by pyrolysis. The entire electrode was then insulated with Epoxylite except the tip, yielding an exposed carbon surface with an area of around 4 x 10-6 to 6 x 10-6 cm2. All three types of ultramicroelectrodes fabricated on the tungsten wire had similar electrochemical behavior to electrodes fabricated from wires or fibers insulated with glass tubes.
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Affiliation(s)
| | - R. Mark Wightman
- To whom correspondence should be addressed. E-mail: Tel: +1 919 962 1472; Fax: +1 919 962 2388
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42
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Clark WJ, Park SH, Bostick DA, Duckworth DC, Van Berkel GJ. Electrochemically Modulated Separation, Concentration, and Detection of Plutonium Using an Anodized Glassy Carbon Electrode and Inductively Coupled Plasma Mass Spectrometry. Anal Chem 2006; 78:8535-42. [PMID: 17165850 DOI: 10.1021/ac061538b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plutonium is shown to be retained on anodized glassy carbon (GC) electrodes at potentials positive of +0.7 V (vs Ag/AgCl reference) and released upon potential shifts to values negative of +0.3 V. This phenomenon has been exploited for the separation, concentration, and detection of plutonium by the coupling an electrochemical flow cell on-line with an ICPMS system. The electrochemically controlled deposition and analysis of Pu improves detection limits by analyte preconcentration and by matrix and isobaric ion elimination. Information related to the parametric optimization of the technique and hypotheses regarding the mechanism of electrochemical accumulation of Pu are reported. The most likely accumulation scenario involves complexation of Pu(IV) species, produced under a controlled potential, with anions retained in the anodization film that develops during the activation of the GC electrode. The release mechanism is believed to result from the reduction of Pu(IV) in the anion complex to Pu(III), which has a lower tendency to form complexes.
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Affiliation(s)
- William J Clark
- Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6375, USA
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43
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Millo D, Ranieri A, Koot W, Gooijer C, van der Zwan G. Towards Combined Electrochemistry and Surface-Enhanced Resonance Raman of Heme Proteins: Improvement of Diffusion Electrochemistry of Cytochrome c at Silver Electrodes Chemically Modified with 4-Mercaptopyridine. Anal Chem 2006; 78:5622-5. [PMID: 16878907 DOI: 10.1021/ac060807v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To date, a successful combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry to study heme proteins is inhibited by the problems raised by the prerequisite to use silver as electrode metal. This paper indicates an approach to overcome these problems. It describes a quick and reproducible procedure to prepare silver electrodes chemically modified with 4-mercaptopyridine suitable to perform diffusion electrochemistry of cytochrome c (cyt c). The method involves the employment of a mechanical and a chemical treatment and avoids the use of alumina slurries and any electrochemical pretreatment. Cyclic voltammetry (CV) was used to test the electrochemical response of cyt c, and the CV signals were found identical with those obtained on gold electrodes under the same experimental conditions. Compared to previous literature, a significant improvement of the CV signal of cyt c at silver electrodes was achieved. Preliminary results show that this treatment can be also successfully employed for the preparation of SERRS-active electrodes.
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Affiliation(s)
- Diego Millo
- Department of Analytical Chemistry and Applied Spectroscopy, Laser Centre, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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44
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Gattrell M, Qian J, Stewart C, Graham P, MacDougall B. The electrochemical reduction of VO2+ in acidic solution at high overpotentials. Electrochim Acta 2005. [DOI: 10.1016/j.electacta.2005.05.001] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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45
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İsbіr AA, Solak AO, Üstündağ Z, Bіlge S, Natsagdorj A, Kiliç E, Kiliç Z. The electrochemical behavior of some podands at a benzo[c]cinnoline modified glassy carbon electrode. Anal Chim Acta 2005. [DOI: 10.1016/j.aca.2005.02.049] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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46
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Blackstock JJ, Rostami AA, Nowak AM, McCreery RL, Freeman MR, McDermott MT. Ultraflat Carbon Film Electrodes Prepared by Electron Beam Evaporation. Anal Chem 2004; 76:2544-52. [PMID: 15117196 DOI: 10.1021/ac035003j] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A facile method for the preparation of thin-film carbon electrodes by electron beam evaporation onto highly doped silicon is presented. The physical and electrochemical properties of these films both before and after postdeposition pyrolysis are investigated. Raman spectroscopy establishes the amorphous structure of the nonpyrolyzed carbon films and confirms the formation of graphitic carbon after pyrolysis at 1000 degrees C. Scanning force microscopy reveals the root-mean-square roughness of nonpyrolyzed films to be approximately 1 A, while pyrolyzed films exhibit an increased roughness of approximately 4 A. The electrochemical behavior of the electrodes resembles glassy carbon, with measured heterogeneous electron-transfer rate constants among the highest measured for thin carbon films. These carbon film electrodes will potentially find applications in such fields as molecular electronics and scanning probe microscopy of adsorbed species.
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