Electrochemical Sensors

Label-free detection of Staphylococcus aureus in skin using real-time potentiometric biosensors based on carbon nanotubes and aptamers

by Gustavo Zelada-Guillen

Published in 'Biosensors & Bioelectronics', 2011

In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of... more In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of single-walled carbon nanotubes (SWCNTs) acts as an ion-to-electron potentiometric transducer and anti-S. aureus aptamers are the recognition element. Carbon nanotubes were functionalized with aptamers using two different approaches: (1) non-covalent adsorption of drop-casted pyrenil-modified aptamers onto the external walls of the SWCNTs; and (2) covalent bond formation between amine-modified aptamers and carboxylic groups previously introduced by oxidation at the ends of the SWCNTs. Both of these approaches yielded functional biosensors but there were large differences in the minimum detectable bacteria concentration and sensitivity values. With covalent functionalization, the minimum concentration detected was 8 × 102 colony-forming units (CFU)/mL and the sensitivity was 0.36 mV/Decade. With the non-covalent approach, the sensitivity was higher (1.52 mV/Decade) but the minimum concentration detected was greatly affected (107 CFU/mL). In both cases, potential as a function of Decade of bacteria concentration was linear. Functional biosensors were used to test real samples from freshly excised pig skin, contaminated with the target microorganism, as a surrogate for human skin.

Overview of electrochemical DNA biosensors: new approaches to detect the expression of life

by Stefano Cagnin

A fully electronic sensor for the measurement of cDNA hybridization kinetics

by Stefano Cagnin

Investigating the Concept of Diffusional Independence. Potential Step Transients at Nano-and Micro-Electrode Arrays: Theory and Experiment

by Denis Menshykau

Chronoamperometry on Ring, Ring-Recessed and Disc Electrodes, and Their Arrays. The Sensitive Measurement of Diffusion Coefficients Independent of a Knowledge of …

by Denis Menshykau

Denis Menshykaua, Aoife M. O’Mahonya, Montserrat Cortina-Puigb, F. Javier del Campob, Francesc Xavier Muñozb and Richard G. Compto

Theory of chronoamperometry on ring-recessed microelectrodes and their arrays is presented. Analysis of the current... more Theory of chronoamperometry on ring-recessed microelectrodes and their arrays is presented. Analysis of the current transients measured at thin rings and their arrays shows that chronoamperometry at such devices is an excellent method of simultaneous measurement of the diffusion coefficient D and the product n[A], where n is the number of electrons transferred and [A] is the concentration of electroactive analyte. A generic, accurate and easy to use method of experimental chronoamperometric data analysis is proposed. It is shown that the method can be applied to the simultaneous measurement of D and n[A] in solution. The method is shown to be applicable to an analysis of data recorded at single disk and ring electrodes as well as arrays of these electrodes even in the case of diffusional non-independence of electrodes in the array.

Plane-recessed disk electrodes and their arrays in transient generator-collector mode: the measurement of the rate of the chemical reaction of electrochemically generated species

by Denis Menshykau

Denis Menshykau, Montserrat Cortina-Puig, F. Javier del Campo, Francesc Xavier Muñoz, Richard G. Compton

A novel electrode geometry is proposed in which a disk microelectrode is recessed below a second electrode which... more A novel electrode geometry is proposed in which a disk microelectrode is recessed below a second electrode which covers an entire plane. Potential step experiments on such plane-recessed disk electrodes and arrays of these electrodes are considered. The recessed disks act as a generator and a plane electrode above acts as a collector. Electrochemical reactions at the generator electrode are assumed to be followed by chemical reaction. Both first order (EC1) and second order (EC2) mechanisms are considered. Current transients are found to be sensitive to the diffusion coefficient of both the reduced and oxidised species as well as to the rate of the chemical reaction and its mechanism. The rate constant of the chemical reaction can be measured over a range of six orders of magnitude. The rate of the second order chemical reaction can be measured up to the limit of diffusion controlled reaction.

Influence of Electrode Roughness on Stripping Voltammetry: Mathematical Modeling and Numerical Simulation

by Denis Menshykau

Denis Menshykau and Richard G. Compton

Electrodes with rough surfaces inevitably have practical importance from both applied and fundamental points of view... more Electrodes with rough surfaces inevitably have practical importance from both applied and fundamental points of view including electroanalysis where stripping voltammetry is a popular technique due to its simplicity and high sensitivity. The diffusional domain approach is used to model stripping voltammetry at rough electrodes: two models of the electrode surface, “rough” and “scratched”, are considered. Electron transfer is described by three models which correspond to cases of stripping of a monolayer, a thin layer, and a bulk layer. The shape of the votammograms strongly depends on the model of the electron transfer but is not always sensitive to the precise model of the electrode surface; the conditions under which this is the case are identified, and generic roughness effects on stripping voltammetry are quantified. We conclude that electrode roughness can have a significant effect on the stripping of the metals from the solid electrode especially in respect of the voltammetric waveshape.

Current Collection Efficiency of Micro-and Nano-Ring-Recessed Disk Electrodes and of Arrays of These Electrodes

by Denis Menshykau

Denis Menshykaua, F. Javier del Campob, Francesc Xavier Muñoz and Richard G. Compton

Diffusional transport theory for micro- and nano-ring-recessed disc microelectrodes has been developed using finite... more Diffusional transport theory for micro- and nano-ring-recessed disc microelectrodes has been developed using finite difference methods. The device is typically operated in generator–collector mode with the disc acting as generator and the ring as the collector. The collection efficiency, defined as the ratio of the detector to generator currents under diffusion controlled conditions, is shown to depend on the depth of the recession of the disc below the ring and the radius of the ring relative to the disc radius. The latter is also the inner radius of the ring. The theory shows that collection efficiencies in excess of 90% are possible with this geometry, which is larger than most conventional hydrodynamic systems. This level of efficiency is in the same range as interdigitated microband electrodes. The diffusion domain approach is used to extend the theory to arrays of such micro- and nano-ring-recessed disc systems.

The Influence of Electrode Porosity on Diffusional Cyclic Voltammetry

by Denis Menshykau

Denis Menshykau, Richard G. Compton

A simple generic model to predict the influence of electrode porosity on the cyclic voltammetric response of an... more A simple generic model to predict the influence of electrode porosity on the cyclic voltammetric response of an electrode is presented. The conditions under which deviation from the behavior of a perfectly flat, planar electrode can be expected are predicted. The scope for misinterpretation when conventional flat electrode theory is applied to porous electrodes is highlighted, especially in respect to the extraction of electrode kinetic parameters and the influence of electrocatalysis.

Electrodes Modified With Electroinactive Layers: Distinguishing Through-Film Transport From Pinhole (Pore) Diffusion

by Denis Menshykau

Denis Menshykau and Richard G. Compton

Electrodes modified with layers, for example, of polymers or self-assembled monolayers, are of great importance from... more Electrodes modified with layers, for example, of polymers or self-assembled monolayers, are of great importance from both the fundamental and applied points of view. Two different models of electrodes covered with electroinactive layers can be proposed. First, the electrode is covered with a uniform layer into which the electroactive species dissolves and then diffuses through, or second, the layer contains pinholes that are exclusively responsible for diffusional transport to the electrode. Both models are simulated and then compared to identify conditions under which they can be distinguished. The models are studied for a broad range of parameters reflecting experimentally viable values. Different types of cyclic voltammograms can be observed in the studied models corresponding to classical Randles-Sevchik, thin layer, and steady-state behaviors. We show that the models can be distinguished experimentally through recording cyclic voltammograms over a sufficiently broad range of voltage scan rates.

Microarrays of Ring-Recessed Disk Electrodes in Transient Generator-Collector Mode: Theory and Experiment

by Denis Menshykau

Denis Menshykau, Aoife M. O’Mahony, F. Javier del Campo, Francesc Xavier Munz and Richard G. Compton

The fabrication, characterization, and use of arrays of ring-recessed disk microelectrodes are reported. These devices... more The fabrication, characterization, and use of arrays of ring-recessed disk microelectrodes are reported. These devices are operated in generator-collector mode with a disk acting as the generator and the ring as the collector. We report experiments and simulations relating to time-of-flight experiments in which material electrogenerated at a disk is diffusionally transported to the ring. Analysis of the current transient measured at the latter when it is potentiostatted at a value to ensure diffusionally controlled “collection” is shown to sensitively reflect the diffusion coefficients of the species forming the redox couple being driven at the generator electrode. The method is applied to the ferrocene/ferrocenium couple in the room temperature ionic liquid [N6,2,2,2][NTf2], and the results are found to agree with independent measurements.

Method and apparatus for providing an electrochemical sensor at an elevated temperature

by John McCaffrey

US Patent Number: 8,075,752
Inventors:  Dalmia; Avinash (Hamden, CT), Carozza; Mario (Danbury, CT), Rafa; Michael J. (Weston, CT), Groeschner; Donald L. (New Milford, CT), McCaffrey; John T. (Avon, CT) 
Assignee: PerkinElmer Health Sciences, Inc. (Waltham, MA)

The invention relates to an electrochemical sensor and method for providing the sensor having an insulator, an... more The invention relates to an electrochemical sensor and method for providing the sensor having an insulator, an electrode deposited on the insulator, an electrolytic material in contact with the electrode for providing an electrical connection, and a cooling and heating element in contact with the insulator and spaced apart from the electrode for adjusting a temperature of the sensor.

Fabrication of versatile channel flow cells for quantitative electroanalysis using prototyping

by Philip King

Published in Analytical Chemistry, 2010, 82, 3124-3131.

Here we demonstrate the use of microstereolithography (MSL), a 3D direct manufacturing technique, as a viable method... more Here we demonstrate the use of microstereolithography (MSL), a 3D direct manufacturing technique, as a viable method to produce small-scale microfluidic components for electrochemical flow detection. The flow cell is assembled simply by resting the microfabricated component on the electrode of interest and securing with thread! This configuration allows the use of a wide range of electrode materials. Furthermore, our approach eliminates the need for additional sealing methods, such as adhesives, waxes, and screws, which have previously been deployed. In addition, it removes any issues associated with compression of the cell chamber. MSL allows a reduction of the dimensions of the channel geometry (and the resultant component) and, compared to most previously produced devices, it offers a high degree of flexibility in the design, reduced manufacture time, and high reliability. Importantly, the polymer utilized does not distort so that the cell maintains well-defined geometrical dimensions after assembly. For the studies herein the channel dimensions were 3 mm wide, 3.5 mm long, and 192 or 250 μm high. The channel flow cell dimensions were chosen to ensure that the substrate electrodes experienced laminar flow conditions, even with volume flow rates of up to 64 mL min-1 (the limit of our pumping system). The steadystate transport-limited current response, for the oxidation of ferrocenylmethyl trimethylammonium hexaflorophosphate (FcTMA+), at gold and polycrystalline boron doped diamond (pBDD) band electrodes was in agreement with the Levich equation and/or finite element simulations of mass transport. We believe that this method of creating and using channel flow electrodes offers a wide range of new applications from electroanalysis to electrocatalysis.

Recent advances in the use of ionic liquids for electrochemical sensing

by Debbie Silvester

Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous... more Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous properties (e.g. high intrinsic conductivity, wide electrochemical windows, low volatility, high thermal stability and good solvating ability), which make them ideal as non-volatile electrolytes in electrochemical sensors. This mini-review article describes the recent uses of ionic liquids in electrochemical sensing applications (covering the last 3 years) in the context of voltammetric sensing at solid/liquid, liquid/liquid interfaces and carbon paste electrodes, as well as their use in gas sensing, ion- selective electrodes, and for detecting biological molecules, explosives and chemical warfare agents. A comment on the future direction and challenges in this field is also presented.

Planar Electromagnetic Sensor for the Detection of Nitrate and Contamination in Natural Water Sources Using Electrochemical Impedance Spectroscopy Approach

by Mohd Amri Bin Md Yunus

M. A. M. Yunus and S. C. Mukhopadhyay, "Planar Electromagnetic Sensor for the Detection of Nitrate and Contamination in Natural Water Sources Using Electrochemical Impedance Spectroscopy Approach," in New Developments and Applications in Sensing Technology. vol. 83, S. C. Mukhopadhyay, A. Lay-Ekuakille, and A. Fuchs, Eds., ed: Springer Berlin Heidelberg, 2011, pp. 39-63.

This paper highlights the progress of developing a low-cost system for detection of nitrate and contamination in... more This paper highlights the progress of developing a low-cost system for detection of nitrate and contamination in natural water resources based on a planar electromagnetic sensor which consists of meander and interdigital structure. The sensor has been operated and evaluated using electrochemical impedance spectroscopy (EIS) approach, based on estimated electrical model; the results obtained from the experiments were interpreted. The objectives of the present work are to conduct simulation, experiments and analysis of a new nitrate detection method using novel planar electromagnetic sensors by means of electrochemical spectroscopy analysis. The sensor was tested with two aqueous solutions of nitrates forms namely, sodium nitrates (NaNO3) and ammonium nitrates (NH4NO3), each of different concentration between 5 mg and 20 mg dissolved in 1 litre of distilled water to observe their response. Furthermore, the sensor was tested with various kinds of prepared samples and natural water samples taken from natural sources around New Zealand. The simulation results using COMSOL have assisted in understanding the characteristic and response of the sensor to the change of properties in the aqueous solution. The experimental results have authenticated the results obtained from the simulation and show the sensor can well detect the presence of nitrate added in distilled water and distinguish the concentration level from the calculated sensitivities. The experiment results with the water sample taken from various places around New Zealand show a very good correlation of contamination level, translated from the qualitative and quantitative results. The work and improvement for future consideration are also discussed in this chapter.

Electrochemistry of Hydrogen in the Room Temperature Ionic Liquid 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide: Dissolved Hydrogen “Lubricates” Diffusional Transport

by Leigh Aldous

Yao Meng, Leigh Aldous, and Richard G. Compton, J. Phys. Chem. C, 2011, 115 (29), pp 14334–14340.

http://pubs.acs.org/doi/abs/10.1021/jp205421q

We report the electrochemical characterization of bis(trifluoromethylsulfonyl)imide (H[NTf2]) and ferrocene in the... more We report the electrochemical characterization of bis(trifluoromethylsulfonyl)imide (H[NTf2]) and ferrocene in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) in the presence of dissolved hydrogen (H2). Chronoamperometric measurements in the presence of varying levels of H2 were used to determine the diffusion coefficient of H[NTf2] and ferrocene at 298 K in [C2mim][NTf2]. Upon saturation with H2 at 298 K, these were found to increase from 2.5 (±0.1) × 10–11 m2 s–1 and 4.7 (±0.1) × 10–11 m2 s–1 to 2.8 (±0.1) × 10–11 and 5.1 (±0.1) × 10–11 m2 s–1, respectively. It is believed that the physiochemical changes correspond to the H2 occupying the interstices and therefore resulting in a change in the permittivity of the space between ions of the RTIL, resulting in diminished Coulombic interactions and a net reduction in the RTILs viscosity. Even more significant changes were observed at 308 K, despite the dissolved H2 concentration being lower (4.4 mM H2 at 298 K, 4.0 mM H2 at 308 K). Arrhenius plots of the diffusion coefficient of ferrocene in the RTIL displayed a decrease in the diffusion activation energy from 29.5 kJ mol–1 in the absence of H2 to 20.5 kJ mol–1 upon saturation with H2. The activation energy of diffusion of H2 was also determined in an RTIL for the first time (13.7 kJ mol–1), and deviation of the mass transport of the small H2 molecule from the Stokes–Einstein relationship was confirmed.

http://pubs.acs.org/doi/abs/10.1021/jp205421q

Conference Paper: Portable Instrumentation for the on-site Environmental Monitoring of Heavy-metals.

by Claudius D'Silva

Conference Paper: Handheld Instrumentation for Environmental Monitoring

by Claudius D'Silva

Macrocyclic Polyether Tetralactams IV. A Potentiometric evaluation of the Ion-selective Characteristics with Alkaline-earth Cations.

by Claudius D'Silva

Analyst., 1994, 119, 2315-2318.

Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals.

by Pavel Takmakov

Pavel Takmakov, Collin J. McKinney, Regina M. Carelli, and R. Mark Wightman

Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo... more Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals.