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- Electrochemistry (8)
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Articles 1 - 30 of 40
Full-Text Articles in Physical Sciences and Mathematics
Potential Driven Deposition Of Polyelectrolytes Onto The Surface Of Cysteine Monolayers Assembled On Gold, Wesley Sanders, Mark Anderson
Potential Driven Deposition Of Polyelectrolytes Onto The Surface Of Cysteine Monolayers Assembled On Gold, Wesley Sanders, Mark Anderson
Mark R. Anderson
Electrochemical impedance spectroscopy and the quartz crystal microbalance measurements are used to examine the ability of potential applied to a substrate to create, in situ, conditions favorable for the electrostatic deposition of polyelectrolytes onto a gold substrate modified by the self-assembly of cysteine. Cysteine is a zwitterionic compound that, when confined to a substrate, has the ability to establish either a net positive or a net negative interfacial charge, depending on the conditions. As such, cysteine modified interfaces could possibly be used as a versatile substrate for deposition of either cationic or anionic polyelectrolytes. The potential of zero charge of …
Electrochemical Glucose Sensors—Developments Using Electrostatic Assembly And Carbon Nanotubes For Biosensor Construction, Alice Harper, Mark Anderson
Electrochemical Glucose Sensors—Developments Using Electrostatic Assembly And Carbon Nanotubes For Biosensor Construction, Alice Harper, Mark Anderson
Mark R. Anderson
In 1962, Clark and Lyons proposed incorporating the enzyme glucose oxidase in the construction of an electrochemical sensor for glucose in blood plasma. In their application, Clark and Lyons describe an electrode in which a membrane permeable to glucose traps a small volume of solution containing the enzyme adjacent to a pH electrode, and the presence of glucose is detected by the change in the electrode potential that occurs when glucose reacts with the enzyme in this volume of solution. Although described nearly 50 years ago, this seminal development provides the general structure for constructing electrochemical glucose sensors that is …
The Effect Of Ion-Pairing On The Open Circuit Potential Of 3-Mercaptoproprionic Acid Modified Gold Electrodes, Mark Anderson, Alice Harper
The Effect Of Ion-Pairing On The Open Circuit Potential Of 3-Mercaptoproprionic Acid Modified Gold Electrodes, Mark Anderson, Alice Harper
Mark R. Anderson
Open circuit potential (OCP) measurement is used to monitor the charge of a monolayer of 3-mercaptopropionic acid. OCP is determined by the concentrations of the reduced and oxidized forms of a redox couple in the solution adjacent to the modified interface. OCP values were monitored in the presence of the one-electron redox couple Fe(CN)63-/4- as a function of solution pH. The OCP measured at basic pHs was different from the acidic OCP due to differences in electrostatic interactions between the interface and the redox species as described by the Nernst equation. The influence of ion-pairing with the monolayer is studied …
Impedance Differences Found With N-Alkanethiol Monolayers Prepared By Contact Printing And Solution Adsorption, Leslie Adamczyk, Mark Anderson
Impedance Differences Found With N-Alkanethiol Monolayers Prepared By Contact Printing And Solution Adsorption, Leslie Adamczyk, Mark Anderson
Mark R. Anderson
Self-assembled monolayers (SAMs) of n-octadecanethiol, n-dodecanethiol and n-pentanethiol formed by contact printing and solution adsorption are characterized by electrochemical impedance spectroscopy (EIS). Impedance measurements show that monolayers prepared by contact printing are on the order of 5 times less resistive to charge transfer and have greater defect density than monolayers prepared by solution adsorption. Modeling of the average defect size and density show that the size of monolayer defects stays relatively constant independent of the monolayer preparation conditions; however, the density of defects decreases with increasing concentration for the contact printed monolayers. The impedance data also show that monolayers prepared …
Electrostatic Deposition Of Polycations And Polyanions Onto Cysteine Monolayers, Mark Anderson
Electrostatic Deposition Of Polycations And Polyanions Onto Cysteine Monolayers, Mark Anderson
Mark R. Anderson
Electrochemical impedance spectroscopy and the quartz crystal microbalance are used to monitor the deposition of polyelectrolytes onto an interface modified with a monolayerofcysteine. When using an anionic redox probe, Fe(CN)−46, the impedance of the cysteine modified electrode is a function of the solution pH; the charge-transfer resistance being higher at basic pH, and smaller under acidic conditions relative to the value found when the solution is buffered near the pI for cysteine. This behavior is consistent with the electrostatic interaction between the anionic redox probe and the net charge of the interface. After exposure of the cysteine-modified interface to 0.10 …
Potential Driven Deposition Of Poly(Diallyldimethylammonium Chloride) Onto The Surface Of 3-Mercaptopropionic Acid Monolayers Assembled On Gold, Wesley Sanders, Mark Anderson
Potential Driven Deposition Of Poly(Diallyldimethylammonium Chloride) Onto The Surface Of 3-Mercaptopropionic Acid Monolayers Assembled On Gold, Wesley Sanders, Mark Anderson
Mark R. Anderson
Electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM) measurements are used to examine the ability of applied potential to drive the ionic self-assembly of poly(diallyldimethylammonium) chloride (PDDA) onto a substrate modified with a monolayer of 3-mercaptopropionic acid (3-MPA). The potential of zero charge (PZC) of the gold electrode modified with a monolayer of 3-MPA was found by differential capacitance measurements to be −0.12 (±0.01) V versus Ag−AgCl. Changing the substrate potential to values positive (−0.01 V vs Ag−AgCl) of the PZC induces interfacial conditions that are favorable for the electrostatic deposition of cationic polymers onto the surface of 3-MPA …
Characterization Of Carboxylic Acid-Terminated Self-Assembled Monolayers By Electrochemical Impedance Spectroscopy And Scanning Electrochemical Microscopy, Wesley Sanders, Ricardo Vargas, Mark Anderson
Characterization Of Carboxylic Acid-Terminated Self-Assembled Monolayers By Electrochemical Impedance Spectroscopy And Scanning Electrochemical Microscopy, Wesley Sanders, Ricardo Vargas, Mark Anderson
Mark R. Anderson
Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are used to monitor changes in the ionization of monolayers of 11-mercaptoundecanoic acid. When using an anionic redox probe, Fe(CN)6−4, the charge-transfer resistance of the 11-mercaptoundecanoic acid monolayer-modified interface increases in a sigmoidal fashion as the solution is made basic. The opposite effect is observed when using a cationic redox probe. The inflection points of these two titration curves, however, differ when using the different redox probes. This result is taken as being characteristic of the influence that applied potential has on the ionization of the monolayer. The role of substrate …
Simultaneous Determination Of Glucose And L‐Glutamate Using A Capillary Enzyme Reactor With Electrochemical Detection, Stephanie Hooper, Mark Anderson
Simultaneous Determination Of Glucose And L‐Glutamate Using A Capillary Enzyme Reactor With Electrochemical Detection, Stephanie Hooper, Mark Anderson
Mark R. Anderson
An electrophoresis capillary that incorporates two enzymes for the simultaneous determination of glucose and l-glutamate is described. The enzymes deposited along the separation capillary walls react with their respective substrate as they are separated during the electrophoresis to produce hydrogen peroxide that is detected by amperometry as the hydrogen peroxide zone emerges from the end of the capillary. Even though both enzyme reactions produce a common product, hydrogen peroxide, the hydrogen peroxide produced by each enzyme reaction stays in narrow zones that migrate the length of the capillary at different rates. The rate of migration for the individual H2O2 zones …
Selective Formation Of A Symmetric Sc3n@C78 Bisadduct: Adduct Docking Controlled By An Internal Trimetallic Nitride Cluster, Ting Cai, Liaosa Xu, Chunying Shu, Hunter Champion, Jonathan Reid, Clemins Anklin, Mark Anderson, Harry Gibson, Harry Dorn
Selective Formation Of A Symmetric Sc3n@C78 Bisadduct: Adduct Docking Controlled By An Internal Trimetallic Nitride Cluster, Ting Cai, Liaosa Xu, Chunying Shu, Hunter Champion, Jonathan Reid, Clemins Anklin, Mark Anderson, Harry Gibson, Harry Dorn
Mark R. Anderson
In this paper we report a regioselective Bingel−Hirsch reaction of Sc3N@C78 yielding a single mono- and a dominate bis-ethyl malonate derivative for the first time. The Cs-symmetric monoadduct 1 and C2v-symmetric bisadduct 2 were isolated by HPLC and characterized by MS, UV−vis, and NMR spectroscopy. The symmetric bisadduct 2 clearly demonstrate the remarkable regioselectivity control exerted by the encapsulated Sc3N cluster. We have employed a LUMO electron density surface computational approach to predict multiadduct docking sites on the ellipsoidal fullerene cage surface.
Application Of A Square‐Wave Potential Program For Time‐Dependent Amperometric Detection In Capillary Electrophoresis, Stephanie Hooper, David Roach, Mark Anderson
Application Of A Square‐Wave Potential Program For Time‐Dependent Amperometric Detection In Capillary Electrophoresis, Stephanie Hooper, David Roach, Mark Anderson
Mark R. Anderson
Use of a square-wave potential program for time-dependent amperometric detection of analyte zones in capillary electrophoresis (CE) is described. Electrochemical detection for CE requires that the separation field be isolated from that of the electrochemical detection. This is generally done by physically separating the CE separation field from that of the detection. By applying a time variant potential program to the detection electrode, the detector current has a time dependence that can be used to help isolate the electrochemical detection current from that of the separation. When using a 20 μm inner-diameter capillary, we find that a square-wave potential program …
Modification Of A Capillary For Electrophoresis By Electrostatic Self-Assembly Of An Enzyme For Selective Determination Of The Enzyme Substrate, Stephanie Hooper, Mark Anderson
Modification Of A Capillary For Electrophoresis By Electrostatic Self-Assembly Of An Enzyme For Selective Determination Of The Enzyme Substrate, Stephanie Hooper, Mark Anderson
Mark R. Anderson
The integration of a separation capillary for capillary electrophoresis (CE) with an on-column enzyme reaction for selective determination of the enzyme substrate is described. Enzyme immobilization is achieved by electrostatic assembly of poly(diallydimethylammonium chloride) (PDDA) followed by adsorption of a mixture of the negatively charged enzyme glucose oxidase (GOx) and anionic poly(styrenesulfonate) (PSS). The reaction of glucose with the GOx produces hydrogen peroxide which migrates the length of the capillary and is detected amperometrically at the capillary outlet. The enzyme reaction occurs during a capillary separation, allowing selective determination of the substrate in complex samples without the need for pre- …
Electrostatic Assembly Of A Redox Catalysis System For Detection Of Glutamate, Alice Harper, Mark Anderson
Electrostatic Assembly Of A Redox Catalysis System For Detection Of Glutamate, Alice Harper, Mark Anderson
Mark R. Anderson
Interfacial assemblies capable of determining glutamate by redox catalysis are prepared by electrostatic assembly of alternating layers of ferrocene poly(allylamine) polymer and glutamate oxidase on a gold electrode. Deposition of the polymer was confirmed in cyclic voltammetry measurements by the presence of a surface wave corresponding to the oxidation of the ferrocene group. In the presence of glutamate in the adjacent electrolyte solution, the current increases and approaches a pseudosteady state, consistent with redox catalysis. Electrodes modified with glutamate oxidase had a linear response to glutamate up to 0.0045 M with sensitivity of 20 μA/cm2 and a limit of detection …
Structure And Enhanced Reactivity Rates Of The D 5 H Sc3n@ C80 And Lu3n@ C80 Metallofullerene Isomers: The Importance Of The Pyracylene Motif, Ting Cai, Liaosa Xu, Mark Anderson, Zhongxin Ge, Tianming Zuo, Xuelei Wang, Marilyn Olmstead, Alan Balch, Harry Gibson, Harry Dorn
Structure And Enhanced Reactivity Rates Of The D 5 H Sc3n@ C80 And Lu3n@ C80 Metallofullerene Isomers: The Importance Of The Pyracylene Motif, Ting Cai, Liaosa Xu, Mark Anderson, Zhongxin Ge, Tianming Zuo, Xuelei Wang, Marilyn Olmstead, Alan Balch, Harry Gibson, Harry Dorn
Mark R. Anderson
In this paper we report enhanced reactivity of the D5h isomers in comparison with the more common Ih isomers of Sc3N@C80 and Lu3N@C80 toward Diels−Alder and 1,3-dipolar tritylazomethine ylide cycloaddition reactions. Also, the structure of the D5h isomer of Sc3N@C80 has been determined through single-crystal X-ray diffraction on D5h-Sc3N@C80·Ni(OEP)·2benzene (OEP = octaethylporphyrin). The Sc3N portion of D5h-Sc3N@C80 is strictly planar, but the plane of these four atoms is tipped out of the noncrystallographic, horizontal mirror plane of the fullerene by 30°. The combination of short bond length and high degree of pyramidization for the central carbon atoms of the pyracylene …
Optimization Of Electrode Alignment For Electrochemical Detection In Capillary Electrophoresis Using A Scanning Electrochemical Microscope, David Roach, Stephanie Hooper, Mark Anderson
Optimization Of Electrode Alignment For Electrochemical Detection In Capillary Electrophoresis Using A Scanning Electrochemical Microscope, David Roach, Stephanie Hooper, Mark Anderson
Mark R. Anderson
Electrochemical detection in capillary electrophoresis requires decoupling the voltage applied to the working electrode from the separation voltage applied across the capillary. End-capillary electrochemical detection achieves this by placing the electrode just outside the ground end of the separation capillary. Obtaining adequate signal-to-noise in this arrangement requires using small inner diameter capillaries. Decreasing the inner diameter of the separation capillary, however, increases the difficulty of aligning the microelectrode with the open end of the capillary. Using scanning electrochemical microscopy (SECM), the position of the capillary opening is determined while electroactive material is continuously emerging from the end of the capillary. …
Reductivedesorption Of 11-Mercaptoundecanoic Acid Monolayers Modified By Covalent Attachment Of 1,3- And 1,4-Phenylenediamine, Mark Anderson, Richard Baltzersen
Reductivedesorption Of 11-Mercaptoundecanoic Acid Monolayers Modified By Covalent Attachment Of 1,3- And 1,4-Phenylenediamine, Mark Anderson, Richard Baltzersen
Mark R. Anderson
1,3- and 1,4-phenylenediamine were covalently attached to a self-assembled monolayer of 11-mercaptoundecanoic acid by formation of an amide bond. Bonding of the phenylenediamine isomers was confirmed by the presence of infrared features attributable to ring vibrational modes, the amide I vibration, and the amide II vibration in the reflection–absorption infrared spectrum of the modified interface. Reductivedesorption peak potentials were shifted by 120 mV for the monolayer modified by 1,4-phenylenediamine and by 90 mV for the monolayer modified by 1,3-phenylenediamine relative to the desorption potential of the unmodified 11-mercaptoundecanoic acid monolayer. These potential shifts represent 23 and 17 kJ/mol stabilization of …
Thin Polyimide Films Prepared By Ionic Self-Assembly, Mark Anderson, Richey Davis, C. Douglas Taylor, Michiaiah Parker, Spencer Clark, Daniela Marciu, Michael Miller
Thin Polyimide Films Prepared By Ionic Self-Assembly, Mark Anderson, Richey Davis, C. Douglas Taylor, Michiaiah Parker, Spencer Clark, Daniela Marciu, Michael Miller
Mark R. Anderson
Layer-by-layer electrostatic deposition of polyelectrolytes was used to modify a gold substrate with polydiallyl dimethylammonium chloride and an Ultem-type poly(amic acid) salt. Following deposition, heat treatment converted the poly(amic acid) salt into a polyimide. A decrease in the thin film thickness and a substantial increase in the interfacial contact angle accompanied thermal treatment. Results from cyclic voltammetry measurements also show that the imidized surface had a decreased dielectric constant relative to an unmodified or a poly(amic acid)-modified interface. Each of these results is consistent with formation of the polyimide. Infrared spectra of the thin films formed by the electrostatic deposition …
Dopamine Adsorption At Surface Modified Carbon-Fiber Electrodes, Bradley Bath, Heidi Martin, R. Mark Wightman, Mark Anderson
Dopamine Adsorption At Surface Modified Carbon-Fiber Electrodes, Bradley Bath, Heidi Martin, R. Mark Wightman, Mark Anderson
Mark R. Anderson
Fast-scan cyclic voltammetry at high repetition rates was used to characterize adsorptive properties of dopamine (DA) at native and modified carbon-fiber microelectrode surfaces. Disk electrodes were fabricated from Thornel P55 fibers, and cylindrical electrodes, from Thornel T650 fibers. Their surfaces were modified by physisorption of 2,6-anthraquinone disulfonic acid (2,6-AQDS) or chemisorption of 4-carboxyphenyl or catechols. Chemisorption was accomplished via electrochemical reduction of diazonium salts. The degree of DA adsorption and its oxidation kinetics were found to vary for the two types of native carbon fiber electrodes and with the different chemical overlayers on the carbon surfaces. 2,6-AQDS measurably increased DA …
Infrared Spectro-Electrochemistry, Mark Anderson, C. Douglas Taylor
Infrared Spectro-Electrochemistry, Mark Anderson, C. Douglas Taylor
Mark R. Anderson
The combination of infrared (IR) spectroscopy and electrochemistry in a single measurement has been an area of active research interest since the late 1960s. IR spectroelectrochemical experiments provide insight about interfacial electrochemical phenomena and/or oxidation–reduction reaction mechanisms that cannot be obtained using either technique individually. The power of the measurement is in the complementary nature of the spectroscopic and electrochemical information available when obtained simultaneously. The combination of measurements, however, requires compromise between the IR spectroscopy and the electrochemistry because of their different sampling requirements. The need for compromise illustrates the unique strengths and weaknesses of the combined spectroelectrochemical measurement. …
Making Connections Between Metallofullerenes And Fullerenes: Electrochemical Investigations, Mark Anderson, Harry Dorn, Steven Stevenson
Making Connections Between Metallofullerenes And Fullerenes: Electrochemical Investigations, Mark Anderson, Harry Dorn, Steven Stevenson
Mark R. Anderson
The square-wave voltammetry for a series of related fullerenes and metallofullerenes measured in pyridine solutions containing 0.10 M tetra-n-butylammonium perchlorate is reported. Several dimetallic metallofullerenes, M2@Cx (where M=Sc or Er, and x=82 or 84), are found to have similar voltammetric responses regardless of metal identity or carbon number. Assignment of formal charges to the fullerene cage suggests that these metallofullerenes are isoelectronic and have related molecular orbital structures. The voltammetry of the empty C82 and D2d-C84 cages are also alike, but are different from the square-wave voltammetry of the C60, C70, and D2-C84. The similarity of the voltammetry for C82 …
The Voltammetry Of C84 Isomers, Mark Anderson, Harry Dorn, Steven Stevenson, Susanne Dana
The Voltammetry Of C84 Isomers, Mark Anderson, Harry Dorn, Steven Stevenson, Susanne Dana
Mark R. Anderson
The square-wave voltammetry of isolated isomers of C84 is reported. Based on their relative abundance, the isomers are assumed to have D2 and D2d symmetry. The D2 isomer has four reversible reductions at −0.65, −0.98, −1.34, and −1.75 V versus Fc/Fc+ prior to electrolyte decomposition. This behavior is consistent with previous reports, and is similar to the voltammetry of C60 and C70 (e.g. sequential reductions spaced at slightly increasing intervals). The D2d isomer has five reversible reductions at −0.46, −0.77, −1.58, −1.98, and −2.27 V versus Fc/Fc+ prior to the onset of electrolyte decomposition. The large potential difference separating the …
The Voltammetry Of Sc3@C82, Mark Anderson, Harry Dorn, Paul Burbank, Steven Stevenson, James Gibson
The Voltammetry Of Sc3@C82, Mark Anderson, Harry Dorn, Paul Burbank, Steven Stevenson, James Gibson
Mark R. Anderson
Many endohedral metallofullerenes have a C82 cage surrounding the metals, even though the normal arc-vaporization method of fullerene preparation does not generate C82 in significant abundance.1-10Manolopous et al.11-13attribute the low abundance of empty-cage C82 to the unfavorable electron configuration of this species. Consequently, the prevalence of C82 in metallofullerenes may be the result of an electron transfer from the encapsulated metal atoms to the fullerene cage.10-13 The extent of this charge transfer also contributes to the properties (e.g. catalytic, superconductive, nonlinear optical, and ferromagnetic) that are attributed to the endohedral metallofullerenes.14,15Because of the importance of the charge transfer reaction, characterization …
Electrochemistry Of C82: Relationship To Metallofullerene Electrochemistry, Paul Burbank, James Gibson, Harry Dorn, Mark Anderson
Electrochemistry Of C82: Relationship To Metallofullerene Electrochemistry, Paul Burbank, James Gibson, Harry Dorn, Mark Anderson
Mark R. Anderson
Square-wave voltammetry of C82 in pyridine solutions containing 0.10 M tetra-n-butyl ammonium perchlorate indicates that C82 is reduced in four one-electron steps prior to the onset of electrolyte decomposition. The first reduction occurs at potentials positive of the reported first reduction potentials of other empty cage fullerenes, and at approximately the same reported potential for the first reduction of the endohedral metallofullerenes La@C82 and Y@C82. No oxidations were observed for the C82 under these conditions.
Influence Of Solvent On The Interfacial Structure Of Self-Assembled Alkanethiol Monolayers, Mark Anderson, Mark Evaniak, Minhui Zhang
Influence Of Solvent On The Interfacial Structure Of Self-Assembled Alkanethiol Monolayers, Mark Anderson, Mark Evaniak, Minhui Zhang
Mark R. Anderson
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) is used to study the structure of octadecanethiol, tetradecanethiol, and decanethiol monolayers in the presence of air, deuterium oxide, and acetonitrile-d3. It is found that the structure of the monolayer is dependent on both the adjacent environment and the initial structural order of the monolayer. In the D2O solutions, spectral changes are similar for the three monolayers and are characteristic of interaction predominantly between the solvent and the terminal portion of the monolayers. This correlates with electrochemical capacitance measurements that indicate little permeation of the aqueous electrolyte in the monolayer, even with the …
Development And Evaluation Of Internet-Based Hypermedia Chemistry Tutorials, Brian Tissue, Ronald Earp, Ching-Wan Yip, Mark Anderson
Development And Evaluation Of Internet-Based Hypermedia Chemistry Tutorials, Brian Tissue, Ronald Earp, Ching-Wan Yip, Mark Anderson
Mark R. Anderson
This progress report describes the development and student use of World-Wide-Web-based prelaboratory exercises in senior-level Instrumental Analysis during the 1995 Fall semester. The laboratory preparation exercises contained hypermedia tutorials and multiple-choice questions that were intended to familiarize the students with the experiments and instrumentation before their laboratory session. The overall goal of our work is to explore ways in which computer and network technology can be applied in education to improve the cost-effectiveness and efficacy of teaching. The course material can be accessed at http://www.chem.vt.edu/chem-ed/4114/Fall1995.html.
Investigation Of The Charge Transfer Properties Of Electrodes Modified By The Spontaneous Adsorption Of Unsymmetrical Dialkyl Sulfides, Minhui Zhang, Mark Anderson
Investigation Of The Charge Transfer Properties Of Electrodes Modified By The Spontaneous Adsorption Of Unsymmetrical Dialkyl Sulfides, Minhui Zhang, Mark Anderson
Mark R. Anderson
Electrodes modified by the spontaneous adsorption of unsymmetrical dialkyl sulfides are used to investigate two monolayer properties, structural disorder and solvent compatibility, that may be of importance in determining the ability for faradaic charge transport to occur in the presence of the monolayer. Two groups of dialkyl sulfides are prepared and studied: a purely hydrocarbon dialkyl sulfide with the structure CH3(CH2)17S(CH2)nCH3, where n, = 7,9, and 17, and an acid containing dialkyl sulfide with the structure CH3(CH2)17S(CH2)mCOOH, where m = 7, 10, and 15. Reflection infrared spectroscopy of the hydrocarbon dialkyl sulfide reveals that the monolayer structure is disordered, when …
Effect Of Applied Potential Upon The In Situ Structure Of Self-Assembled Monolayers On Gold Electrodes, Mark Anderson, Marilyn Gatin
Effect Of Applied Potential Upon The In Situ Structure Of Self-Assembled Monolayers On Gold Electrodes, Mark Anderson, Marilyn Gatin
Mark R. Anderson
Polarization modulation Fourier transform infrared reflection absorption spectroscopy (PM-FTIRRAS) has been utilized to study the in situ structure of octadecanethiol when adsorbed to gold electrode surfaces and with the application of potential to the substrate. It is found that applied potential has little effect upon the spectrum of the monolayer in the presence of D2O solutions containing 0.10 M NaClO4. The presence of an acetonitrile solution contacting the monolayer leads to small changes in the infrared spectrum relative to that seen in D2O solutions, suggestive of some small disordering of the monolayer caused by the presence of the acetonitrile. With …
Application Of The Quartz Crystal Microbalance To Characterize The Interaction Of Solutes With Modified Interfaces, John Roush, David Thacker, Mark Anderson
Application Of The Quartz Crystal Microbalance To Characterize The Interaction Of Solutes With Modified Interfaces, John Roush, David Thacker, Mark Anderson
Mark R. Anderson
Piezoelectric quartz crystals, modified by the spontaneous adsorption of either 4-aminothiophenol or octadecanethiol, were utilized to investigate the selective interactions that exist between solutes and the surface modification layer. It is found that the exposed amine functionality of the 4-aminothiophenol monolayer increases the sensitivity of the quartz crystal microbalance to phenols relative to the response found at either a crystal modified with an octadecanethiol monolayer or an unmodified quartz crystal. Protonation of the amino group decreases the sensitivity of the 4-aminothiophenol modified crystal toward the phenol solutes, to a level approximately the same as seen for the octadecanethiol monolayer and …
Quantitative Determination Of Surface Excess By The Semiintegral Method, Susanne Dana, Mathew Jablonski, Mark Anderson
Quantitative Determination Of Surface Excess By The Semiintegral Method, Susanne Dana, Mathew Jablonski, Mark Anderson
Mark R. Anderson
In 1988 Bowling and McCreery reported that the semiintegral of voltammetric data provided an excellent method for the qualitative diagnosis of weak adsortpion of material upon an electrode. This report was important to electroanalytical chemistry because of the difficulty often encountered when trying to identify the presence of weakly adsorbed material and because of the impact that weak adsorption has upon voltammetric response. Many electrochemical analyses are dependent upon the evaluation of voltammetric wave shape, particularly kinetic analyses. Unlike strong adsorption, the presence of weakly adsorbed material does not dramatically and obviously perturb the shape of the voltammetric response; consequently, …
Application Of Square Wave Voltammetry For Electrochemical Detection In Gradient Elution Hplc, John Roush, Mark Anderson
Application Of Square Wave Voltammetry For Electrochemical Detection In Gradient Elution Hplc, John Roush, Mark Anderson
Mark R. Anderson
The utility of square-wave voltammetry with a conventionally sized indicator electrode for use in the detection of gradient elution HPLC applications is demonstrated. A redesigned electrochemical detector cell, based upon a type of wall-jet design, provides more efficient potential control and allows the voltammetric detection. The minimum detectable quantity and linear dynamic range for the new detector design were found to be 13pg and 5 orders of magnitude, respectively, comparable to other electrochemical detectors. In the separation of a test mixture containing hydroquinone. bromohydroquinone, catechol, resorcinol, and phenylhydroquinone baseline resolution of all five components is obtained in 12 minutes using …
The Influence Of Cation Size Upon The Infrared Spectrum Of Carbon Monoxide Adsorbed On Platinum Electrodes, Mark Anderson, Jimin Huang
The Influence Of Cation Size Upon The Infrared Spectrum Of Carbon Monoxide Adsorbed On Platinum Electrodes, Mark Anderson, Jimin Huang
Mark R. Anderson
The infrared spectrum of carbon monoxide adsorbed on polycrystalline platinum electrodes in the presence of acetonitrile solutions is examined. Acetonitrile solutions provide a wide double layer region (approximately 4 V) in which to investigate the observed potential dependence of the infrared peak position. The wider window allows for better comparisons of experimental data with theoretical predictions than those which are available from measurements conducted in aqueous solutions. It is found that (i) near-monolayer surface coverage can be obtained from solutions saturated with CO, (ii) the coverage stays constant over roughly the entire double layer region, (iii) the CO adsorbs to …