Analytical Chemistry Commons^™

Electrochemical Surface-Enhanced Raman Spectroscopy—Current Status And Perspective, Bin Ren, Jian-Feng Li, Yi-Fan Huang, Zhi-Cong Zeng, Zhong-Qun Tian

Journal of Electrochemistry

Electrochemical interface is a very important interface closely related to various energy and life processes. Surface-enhanced Raman scattering was widely used in electrochemistry soon after its discovery to understand the surface bonding,configuration,and orientation of the surface species. In recent 10 years,the fast development of nanoscience and nanotechnology has offered SERS with abundant substrates and characterization methods,which has allowed impressive development of electrochemical SERS. This articles will follow the time line to make systematically overview of SERS on Au and Ag,thin-layer transition-metal SERS,pure transition metal SERS,core-shell SERS and those methods for studying single crystal surfaces,including gap-mode SERS, TERS and SHINERS. Emphasis …

Fabrication Of Electrochemically Activated Glassy Carbon/Bismuth Film Electrodes For Sensitive Analysis Of Pb(2+) And Cd(2+), Kang Shi, Wen-Jing Wang, Kun Hu

Journal of Electrochemistry

The application of electrochemically activated glassy carbon (GC) in the in-situ preparing of bismuth film electrodes (BiFEs) to analyze Pb^{2 +} and Cd^{2 +} was investigated. The glassy carbon electrodes were electrochemically activated by either potentiostic or cyclic polarization in 1 mol·L^-1 NaOH solution. Experimental results show that employment of HCl solution as the analytical solution not only can reproducibly renew the electrochemically activated GC electrode surface with an electrochemical clear procedure, but also can greatly enhance the sensitivity of BiFes method for analysis of Pb^{2 +} and Cd^{2 +}. The test range thus …

Synthesis And Electrochemical Studies In Microstructured Media, Jamie Norton

All Dissertations

In-situ electrochemical methods involving both oxidative and reductive mediators were employed to modify the oxidation state (doping level) of PEDOT polymers in colloidal PEDOT-coated silica core-shell particles that were prepared as a dispersion encapsulated in a hydrogel matrix. The modifications of the redox states of the PEDOT coating induced a change in the absorbance characteristics. A mediated electron transfer system was employed to ferry charge from the electrodes of the cell to the isolated particles. The mediator diffuses between the electrode surface and the PEDOT-coated particles to accomplish (de)doping. The developed system was a fully self-contained and electrically driven device. …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective was to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in RTIL solutions, and use this data to effectively separate species with very similar chemical properties.

In consultation with a DOE collaborator, electrochemical methods and materials were evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing the ability to selectively target and sequester individual species from mixtures. This project, in its third year, successfully completed phases 1, 2. Phase 3 was partially completed. The project expanded to include phase 4.

The following were specific goals for 2007-2008:

• To …

F-Element Electrochemistry In Rtil Solutions: Electrochemical Separation Of Lanthanides And Actinides, David W. Hatchett

Separations Campaign (TRP)

Electrochemical methods can be used to effectively separate actinide and lanthanide species from complex mixtures. This is based on the unique electrochemical properties of each specific target species. In studies it has been found that, with the exception of Ce, aqueous solutions provide unsuitable electrochemical windows to effectively evaluate the thermodynamic properties that are useful for chemical separations. Therefore, a more novel approach was examined which eliminated the aqueous solution with a room temperature ionic liquid (RTIL) solution. RTIL solutions do not suffer from the side reactions that are prominent in aqueous environments. In addition, the potential window is much …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objectives of this project are to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in RTIL solution, and to use this data to effectively separate species with very similar chemical properties. In consultation with a national laboratory collaborator, electrochemical methods and materials will be evaluated and used to exploit the thermodynamic differences between similar chemical species, enhancing the ability to selectively target and sequester individual species from mixtures. This project is in its third year and has successfully completed phases 1 and 2. Phase 3 has been partially completed. The tasks have been expanded …

F-Element Electrochemistry In Room Temperature Ionic Liquids, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This proposal focuses on f-element electrochemistry in room temperature ionic liquids (RTILs). The ultimate goal is to fully characterize the oxidation/reduction of elements in RTILs to establish the baseline thermodynamic and kinetic data for these systems. The data will be used to critically evaluate the ability to use electrochemical methods for controlled, potential mediated, separation off-elements by electroplating on electrodes surfaces. Factors that will influence the ability to measure the redox processes in f-elements in RTIL solutions and electroplating on electrode surfaces include the structure, solubility, and stability of the target species in these solutions. These factors will be addressed …

The Electrochemical Separation Of Curium And Americium: Quaterly Report January - March, 2006, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium. For two and a half years, research has been actively performed on this project, and is currently on schedule for the proposed timelines.

Progress:

• The electrochemical characterization of Ce and Eu complexed with EDTA, NTA, and Citrate has been completed.

• Synthesis of the polymer substrate and the chelating ligand is underway. Approximately 50 grams of disulfide has been produced to produce the chelating thiol group required for the last set of studies.

• Gold substrates have been prepared to perform …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in aqueous solution and use this data to effectively separate species with very similar chemical properties. In consultation with a national laboratory collaborators, electrochemical methods and materials will be evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing the ability to selectively target and sequester individual species from mixtures. This project is in its third year and has successfully completed Phases 1 and 2.

The following were specific goals for this year:

• To develop a fundamental …

The Electrochemical Separation Of Curium And Americium: Quaterly Report April - June, 2005, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Results

• We have completed the electrochemical investigation in of the Ce³⁺/Ce⁴⁺ redox couple and have determined the optimum experimental conditions.

• Computer modeling of the cerium using the JChess speciation-modeling program has been completed for the Ce redox couple. Traditional complexing ligands such as EDTA, oxalate, NTA, phosphate, acetate, and sulfate have been purchased and will be used to initiate the complexation and electrochemical characterization.

• Electrochemical investigations have continued on the Eu²⁺/Eu³⁺ redox …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in aqueous solution and use this data to effectively separate species with very similar chemical properties. In consultation with our DOE collaborator, electrochemical methods and materials will be evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing our ability to selectively target and sequester individual species from mixtures.

The following were specific goals for this year:

• To develop a fundamental understanding of the thermodynamic properties of actinide and lanthanide species such as Cm, Am, Ce, Nd, …

The Electrochemical Separation Of Curium And Americium: Quaterly Report August-December 2004, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium. The following pages outline the progress on our project to date. We have been actively performing research on this project for three months and are currently on schedule in terms of the proposed timelines.

The initial focus of the project involved setting up the laboratories for the studies outlined in the grant proposal. The instrumentation needed included an electrochemical work station that will perform the bulk of the electrochemical studies. This instrument will complement the electrochemical instrumentation in Dr. Hatchett’s laboratory and …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to develop a method for the separation of Am from Cm based on electrochemical techniques. Electrochemical systems that allow the thermodynamics of actinide and lanthanide complexes to be systematically evaluated and tuned will be examined. The influence of complex formation on the ability to selectively isolate a given species electrochemically will be evaluated. Metal-ligand complex formation provides a useful derivation technique to increase solubility in solution environments that favor precipitation. In addition, the thermodynamic properties of a complex relative to the isolated species may be shifted to more suitably measurable electrochemical separation regimes. Electrochemical …

The Electrochemical Separation Of Curium And Americium: Quaterly Report January - March 2004, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Data collection and analysis of the Ce³⁺/Ce⁴⁺ redox couple in various supporting electrolytes has continued. All electrolyte systems were investigated at Pt, Au, and Glassy Carbon working electrodes. Analysis of these data was accomplished by performing appropriate background subtractions to reveal net peaks due to Ce redox behavior. Successful identification of the Ce redox couple was achieved with all electrolyte/electrode systems, although a decline in peak resolution was observed with increasing acid concentration. Optimal conditions in this experiment were …

The Activity Of Silicon Carbide Particles In Al-Based Metal Matrix Composites Revealed By Scanning Electrochemical Microscopy, David O. Wipf, L. Díaz-Ballote, L. Veleva, M. A. Pech-Canul, M. I. Pech-Canul

CAS Publications

Scanning electrochemical microscopy (SECM) is used to image variations in electrochemical activity over the surface of an aluminum-based metal matrix composite (MMC) in contact with buffered or unbuffered neutral solutions. The composite consists of an Al - 13.5% Si - 9% Mg alloy matrix and reinforcing silicon carbide particles (SiC_p). Feedback mode SECM imaging using ferrocenemethanol as a redox mediator in 0.1 M NaCl solution and in buffer solution (pH 6.8) revealed that the SiC particles are electrochemically active. The data suggest that the electronic conductivity at these sites is higher than that of the Al₂O …

Fabricating And Imaging Carbon-Fiber Immobilized Enzyme Ultramicroelectrodes With Scanning Electrochemical Microscopy, David O. Wipf, Fuyun Ge, Robert C. Tenent

Publications

The scanning electrochemical microscope (SECM) is used to image the activity of enzymes immobilized on the surfaces of disk-shaped carbon-fiber electrodes. SECM was used to map the concentration of enzymatically produced hydroquinone or hydrogen peroxide at the surface of a 33-mm diameter disk-shaped carbon-fiber electrode modified by an immobilized glucose-oxidase layer. Sub-monolayer coverage of the enzyme at the electrode surface could be detected with micrometer resolution. The SECM was also employed as a surface modification tool to produce microscopic regions of enzyme activity by using a variety of methods. One method is a gold-masking process in which microscopic gold patterns …

Impedance Feedback Control For Scanning Electrochemical Microscopy, David O. Wipf, Mario A. Apuche-Avlles

CAS Publications

A new constant-distance imaging method based on the relationship between tip impedance and tip-substrate separation has been developed for the scanning electrochemical microscope (SECM). The tip impedance is monitored by application of a high frequency ac voltage bias between the tip and auxiliary electrode. The high frequency ac current is easily separated from the dc level faradaic electrochemistry with a simple RC filter, which allows impedance measurements during feedback or generation/collection experiments. By employing a piezo-based feedback controller we are able to maintain the impedance at a constant value and, thus, maintain a constant tip-substrate separation. Application of the method …

Construction Of Gold Micro-Bead Ultramicroelectrodes, Deon T. Miles, Andrew Knedlik, David O. Wipf

CAS Publications

A new way to construct small electrodes by the use of metal micro-beads is described. Gold beads of 1.5 to 3.0 mm diameter were used to construct inexpensive and disposable microelectrodes with overall structural diameters of £ 6 mm and electrode diameters of £ 5 mm. The voltammetric response of these electrodes is consistent with existing theory and the electrodes exhibited the sigmoidal waves expected at ultramicroelectrodes.

Ohmic Drop Compensation In Voltammetry:  Iterative Correction Of The Applied Potential, David O. Wipf

CAS Publications

A new method of ohmic potential drop correction for use with potential step and sweep voltammetric methods is described. The method, iterative correction of the applied potential (ICAP), essentially replaces an electronic positive feedback correction with a digital positive feedback correction. This paper will present one form of the ICAP procedure, in which voltammetric current data acquired by a high-speed digital oscilloscope are used to iteratively generate a compensating potential waveform that is then synthesized by an arbitrary waveform generator. The ICAP method is advantageous for high-speed measurements, since many of the difficulties caused by electronic positive feedback compensation are …