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Articles 1 - 30 of 132
Full-Text Articles in Physical Sciences and Mathematics
Experimental Manipulation Of Interfacial Molecular Assemblies: Using Macroscopic Processes To Create Defined Interfacial Structure And Properties, Mark Anderson
Mark R. Anderson
No abstract currently available.
Experimental Manipulation Of Interfacial Molecular Assemblies, Mark Anderson
Experimental Manipulation Of Interfacial Molecular Assemblies, Mark Anderson
Mark R. Anderson
No abstract currently available.
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 …
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 …
Impedance Of Contact-Printed Alkanethiol Self-Assembled Monolayers On Gold, Leslie Adamczyk, Mark Anderson
Impedance Of Contact-Printed Alkanethiol Self-Assembled Monolayers On Gold, Leslie Adamczyk, Mark Anderson
Mark R. Anderson
Contact printing (CP) is a common method for creating modified interfaces having two-dimensional patterns. The popularity of this method is due to the ease and low cost of this method. When printing an interfacial pattern with n-alkanethiols, the desired properties are those of a homogeneous, solution deposited monolayer. Patterning a surface, however, may cause defects to occur within the monolayer where two thiol domains meet. If large enough, the activity of these areas can dominate the electrochemical response. Creating patterned monolayer modified interfaces, therefore, may generate vast user defined domain boundaries that impact the electrochemical behavior of the modified interface …
Potential Driven Polyelectrolyte Adsorption Onto Monolayer Modified Electrodes, Mark Anderson, Weslie Sanders
Potential Driven Polyelectrolyte Adsorption Onto Monolayer Modified Electrodes, Mark Anderson, Weslie Sanders
Mark R. Anderson
Preparation of interfacial structures by molecular self-assembly has been actively studied for many years. Well-defined modified interfaces can be used to study fundamental interfacial properties, or they can be used in different practical applications. To broaden the utility of interfaces prepared by molecular self-assembly, monolayers containing terminal functionality are frequently used. These interfaces have structural and physical properties that can be controlled by both the identity of the functionalization as well as the ensemble structure of the modified interface. This suggests that the chemical and physical properties of an interface can be designed and/or controlled to some extent by altering …
Potential Driven Polyelectrolyte Adsorptoin Onto Monolayer Modified Electrodes, Mark Anderson
Potential Driven Polyelectrolyte Adsorptoin Onto Monolayer Modified Electrodes, Mark Anderson
Mark R. Anderson
No abstract currently available.
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 …
Manipulating Interfacial Structure And Properties, Mark Anderson
Manipulating Interfacial Structure And Properties, Mark Anderson
Mark R. Anderson
No abstract is available at this time.
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 …
Differences In Electrochemical Properties Of Contact Printed And Solution Adsorbed Alkanehtiol Self-Assembled Monolayers On Gold, Leslie Adamczyk, Mark Anderson
Differences In Electrochemical Properties Of Contact Printed And Solution Adsorbed Alkanehtiol Self-Assembled Monolayers On Gold, Leslie Adamczyk, Mark Anderson
Mark R. Anderson
No abstract is currently available.
Effects Of Potential On Ionic Self-Assembly Of Carboxylic Acid Terminated Monolayers, Wesley Sanders, Mark Anderson
Effects Of Potential On Ionic Self-Assembly Of Carboxylic Acid Terminated Monolayers, Wesley Sanders, Mark Anderson
Mark R. Anderson
No abstract is currently available.
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- …
Generation Of An On-Capillary Enzyme Reactor Coupled To Capillary Electrophoresis For The Selective Detection Of The Enzyme Substrate, Stephanie Hooper, Mark Anderson
Generation Of An On-Capillary Enzyme Reactor Coupled To Capillary Electrophoresis For The Selective Detection Of The Enzyme Substrate, Stephanie Hooper, Mark Anderson
Mark R. Anderson
No abstract is currently available.
Electrochemical Impedance Spectroscopy To Evalutate The Effects Of Ph Variations And Ionic Self-Assembly On Undecanoic Acid Monolayers Immobilized On Gold, Mark Anderson, Wesley Sanders
Electrochemical Impedance Spectroscopy To Evalutate The Effects Of Ph Variations And Ionic Self-Assembly On Undecanoic Acid Monolayers Immobilized On Gold, Mark Anderson, Wesley Sanders
Mark R. Anderson
No abstract is currently available.
Analytical Chemistry: Theoretical And Metrological Fundamentals, Mark Anderson
Analytical Chemistry: Theoretical And Metrological Fundamentals, Mark Anderson
Mark R. Anderson
Review of the book "Analytical Chemistry: Theoretical and Metrological Fundamentals," by K. Danzer. Springer: Berlin, Heidelberg, New York. 2007.
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 …
Synthesis And Characterization Of Regio-Interconvertible N-Tritylpyrrolidino Derivatives Of Sc3na@C80 Ihisomer, Ting Cai, Liaosa Xu, Mark Anderson, S. Carla, Alan Balch, Marilyn Olmstead, Harry Gibson, Harry Dorn
Synthesis And Characterization Of Regio-Interconvertible N-Tritylpyrrolidino Derivatives Of Sc3na@C80 Ihisomer, Ting Cai, Liaosa Xu, Mark Anderson, S. Carla, Alan Balch, Marilyn Olmstead, Harry Gibson, Harry Dorn
Mark R. Anderson
No abstract is currently available.
Site-Selective Reductive Desorption Used For Interfacial Patterning Of Substrates, Mark Anderson, David Roach
Site-Selective Reductive Desorption Used For Interfacial Patterning Of Substrates, Mark Anderson, David Roach
Mark R. Anderson
No abstract is currently available.
An Electronic And Vibrational Study Of Sc3n@C68, Liaosa Xu, Ting Cai, Mark Anderson, Harry Dorn
An Electronic And Vibrational Study Of Sc3n@C68, Liaosa Xu, Ting Cai, Mark Anderson, Harry Dorn
Mark R. Anderson
No abstract is currently available.
Ionic Self-Assembly Of An On-Column Enzyme Reactor For Capillary Separations: Detection Of Glucose And Glutamate, Stephanie Hooper, Mark Anderson
Ionic Self-Assembly Of An On-Column Enzyme Reactor For Capillary Separations: Detection Of Glucose And Glutamate, Stephanie Hooper, Mark Anderson
Mark R. Anderson
No abstract is currently available.
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. …