ORCID Profile
0000-0002-1053-1273
Current Organisation
Curtin University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Electrochemistry | Analytical Chemistry | Colloid and Surface Chemistry | Electroanalytical Chemistry | Physical Chemistry (Incl. Structural) | Nanoscale Characterisation | Sensor Technology (Chemical aspects) | Microelectronics and Integrated Circuits | Photodetectors, Optical Sensors and Solar Cells | Nanochemistry and Supramolecular Chemistry | Nanomaterials | Plant Cell and Molecular Biology | Functional Materials | Compound Semiconductors | Nanotechnology | Surfaces and Structural Properties of Condensed Matter | Molecular and Organic Electronics | Nanobiotechnology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in Technology | Emerging Defence Technologies | Hydrogen Storage | Water Recycling Services (incl. Sewage and Greywater) | Biofuel (Biomass) Energy | Fuel Cells (excl. Solid Oxide) | Solid Oxide Fuel Cells | Integrated Circuits and Devices | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Electrochemically controlled cocrystallisation of caffeine:1-hydroxy-2-naphthoic acid
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1CE01281A
Abstract: The formation of caffeine and 1-hydroxy-2-naphtoic acid cocrystals at a water–oil interface was controlled by potential difference, Δwo ϕ , favouring one polymorphic form of the cocrystal.
Electrochemical Detection of Oligopeptides at Silicon-Fabricated Micro-Liquid∣Liquid Interfaces
Publisher: American Chemical Society (ACS)
Date: 25-06-2008
DOI: 10.1021/AC800089P
Abstract: The detection of peptides is an important bioanalytical challenge, as they are a generic class of potent molecules of biomedical and biopharmaceutical significance. In this work, the electrochemistry of seven oligopeptides at microscaled interfaces between two immiscible electrolyte solutions (microITIES) was investigated. Their transfer across the polarized interface was assisted by dibenzo-18-crown-6 (DB18C6). The ion transfer potentials of these oligopeptides were dependent on their hydrophobicities and their interaction with DB18C6. Micropore arrays, which were fabricated in silicon by a combination of wet and dry etch techniques, were used to enhance mass transfer and thus analytical sensitivities. The use of a gellified organic phase allowed the implementation of voltammetric stripping techniques at the liquid-organogel interface. The combination of interface miniaturization and stripping voltammetry provided limits of detection at submicromolar concentration levels. The sensitivities (calibration graph slopes) were -3205 nA microM(-1) cm(-2) for Phe-Phe, -1791 nA microM(-1) cm(-2) for Leu-Leu, -6014 nA microM(-1) cm(-2) for Lys-Lys, and -9611 nA microM(-1) cm(-2) for Lys-Lys-Lys. Mixtures of peptides were also investigated with this technique, illustrating the possibility to detect certain mixture combinations.
A lithium iron phosphate reference electrode for ionic liquid electrolytes
Publisher: Elsevier BV
Date: 08-2018
Investigation of a solvent-cast organogel to form a liquid-gel microinterface array for electrochemical detection of lysozyme
Publisher: Elsevier BV
Date: 09-2015
Apparent enhanced underpotential voltammetry of lead(II) at a spontaneously adsorbed monolayer-coated gold electrode
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A906125H
Impact of Surface Nano-textured Stainless Steel Prepared by Focused Ion Beam on Endothelial Cell Growth
Publisher: American Scientific Publishers
Date: 08-2013
Abstract: The modification of stent surfaces with nano-structures has the potential for limiting late stent restenosis. We report here the patterning of 316L austentitic stainless steel with arrays of nano-pits of two nominal diameters: 120 and 180 nm. These nano-textured surfaces were prepared by focused ion beam milling. The influence of the ion beam current on the nano-features was investigated by scanning electron and atomic force microscopies. The optimum ion beam currents were 280 pA for 120 nm nano-pits and 920 pA for 180 nm nano-pits. The depths of the nano-pits formed were (65 +/- 24) nm (120 nm) and (84 +/- 36) nm (180 nm). This wide distribution of the depths is due to the polycrystalline nature of 316 L stainless steel, which has a strong influence on the milling rates. Endothelial cells were grown in vitro on these substrates for 1, 3 and 5 days. The cells were viable for the duration of the cell culture on the nano-textured substrates. There was no significant difference in the adhesion and the proliferation based on the nano-pit diameter.
Optimisation of the conditions for stripping voltammetric analysis at liquid-liquid interfaces supported at micropore arrays: A computational simulation
Publisher: Springer Science and Business Media LLC
Date: 06-06-2010
DOI: 10.1007/S00216-010-3866-6
Abstract: Micropore membranes have been used to form arrays of microinterfaces between immiscible electrolyte solutions (µITIES) as a basis for the sensing of non-redox-active ions. Implementation of stripping voltammetry as a sensing method at these arrays of µITIES was applied recently to detect drugs and biomolecules at low concentrations. The present study uses computational simulation to investigate the optimum conditions for stripping voltammetric sensing at the µITIES array. In this scenario, the diffusion of ions in both the aqueous and the organic phases contributes to the sensing response. The influence of the preconcentration time, the micropore aspect ratio, the location of the microinterface within the pore, the ratio of the diffusion coefficients of the analyte ion in the organic and aqueous phases, and the pore wall angle were investigated. The simulations reveal that the accessibility of the microinterfaces during the preconcentration period should not be h ered by a recessed interface and that diffusional transport in the phase where the analyte ions are preconcentrated should be minimized. This will ensure that the ions are accumulated within the micropores close to the interface and thus be readily available for back transfer during the stripping process. On the basis of the results, an optimal combination of the examined parameters is proposed, which together improve the stripping voltammetric signal and provide an improvement in the detection limit.
Electrochemistry of catalase at a liquid|liquid micro-interface array
Publisher: Elsevier BV
Date: 04-2021
The performance of differential pulse stripping voltammetry at micro-liquid–liquid interface arrays
Publisher: Elsevier BV
Date: 03-2010
Fingerprinting the tertiary structure of electroadsorbed lysozyme at soft interfaces by electrostatic spray ionization mass spectrometry
Publisher: Royal Society of Chemistry (RSC)
Date: 19-08-2014
DOI: 10.1039/C4CC05545D
Abstract: Lysozyme can be electrochemically detected after adsorption at an electrified gel-water interface. Ex situ characterization by electrostatic spray ionization mass spectrometry provides insights into the interfacial detection mechanism by allowing changes to the tertiary structure of electroadsorbed lysozyme to be fingerprinted for the first time.
Electrochemical properties of polymeric nanopatterned electrodes
Publisher: Elsevier BV
Date: 07-2007
Underpotential deposition and stripping of lead at disorganized monolayer-modified gold electrodes
Publisher: Wiley
Date: 10-2005
Adsorptive stripping voltammetry of hen-egg-white-lysozyme via adsorption-desorption at an array of liquid-liquid microinterfaces
Publisher: American Chemical Society (ACS)
Date: 14-02-2012
DOI: 10.1021/AC203249P
Abstract: Electrochemical adsorption and voltammetry of hen-egg-white-lysozyme (HEWL) was studied at an array of microinterfaces between two immiscible electrolyte solutions (μITIES). Adsorption of the protein was achieved at an optimal applied potential of 0.95 V, after which it was desorbed by a voltammetric scan to lower potentials. The voltammetric peak recorded during the desorption scan was dependent on the adsorption time and on the aqueous phase concentration of HEWL. The slow approach to saturation or equilibrium indicated that protein reorganization at the interface was the rate-determining step and not diffusion to the interface. For higher concentrations and longer adsorption times, a HEWL multilayer surface coverage of 550 pmol cm(-2) was formed, on the basis of the assumption that a single monolayer corresponded to a surface coverage of 13 pmol cm(-2). Implementation of adsorption followed by voltammetric detection as an adsorptive stripping voltammetric approach to HEWL detection demonstrated a linear dynamic range of 0.05-1 μM and a limit of detection of 0.03 μM, for 5 min preconcentration in unstirred solution this is a more than 10-fold improvement over previous HEWL detection methods at the ITIES. These results provide the basis for a new analytical approach for label-free protein detection based on adsorptive stripping voltammetry.
Haemoglobin unfolding studies at the liquid-liquid interface
Publisher: Elsevier BV
Date: 07-2011
Characterization of Protein-Facilitated Ion-Transfer Mechanism at a Polarized Aqueous/Organic Interface
Publisher: American Chemical Society (ACS)
Date: 05-08-2019
Abstract: Protein electrochemistry studies at a polarized interface between two immiscible electrolyte solutions (ITIES) indicate that the detection mechanism of a protein at the interface involves a combination of protein-anion complexation and interfacial adsorption processes. A detailed characterization of the protein-facilitated mechanism of ion transfer at the ITIES will allow the development of new label-free biomolecular detection tools. Molecular dynamics simulations were performed to describe the mechanism of transfer of the hydrophobic anion tetraphenylborate (TPB
Ion-Transfer Voltammetric Behavior of Protein Digests at Liquid vertical bar Liquid Interfaces
Publisher: American Chemical Society (ACS)
Date: 10-12-2010
DOI: 10.1021/AC901909J
Abstract: The development of new methods for the detection of proteins and peptides is of widespread importance. In this work, the electrochemical behavior of peptide mixtures resulting from proteolytic digestion of proteins was investigated at the polarized liquid|liquid interface (or the interface between two immiscible electrolyte solutions, ITIES). The influence of pepsin digestion on three proteins (hemoglobin, lysozyme, and cytochrome c) was studied, and it was revealed that resulting cyclic voltammograms of the three protein digests were different due to the unique peptide mixtures for a given protein. Differential pulse stripping voltammetry of protein digests enabled the detection of digested proteins at concentrations ranging between 0.55 and 4.22 microM. A limit of detection of 0.55 microM of the initial concentration of protein was achieved, demonstrating the analytical possibilities of such an electrochemical method. These results show that ion-transfer voltammetry offers the opportunity to study and develop label-free detection of peptides resulting from enzymatic digestions of proteins and may thus have a role in development of new proteomic technologies.
Study of electrochemical phosphate sensing systems: Spectrometric, potentiometric and voltammetric evaluation
Publisher: Elsevier BV
Date: 02-2009
Secondary Structural Changes in Proteins as a Result of Electroadsorption at Aqueous-Organogel Interfaces.
Publisher: American Chemical Society (ACS)
Date: 08-04-2019
DOI: 10.1021/ACS.LANGMUIR.8B04227
Abstract: The electroadsorption of proteins at aqueous-organic interfaces offers the possibility to examine protein structural rearrangements upon interaction with lipophilic phases, without modifying the bulk protein or relying on a solid support. The aqueous-organic interface has already provided a simple means of electrochemical protein detection, often involving adsorption and ion complexation however, little is yet known about the protein structure at these electrified interfaces. This work focuses on the interaction between proteins and an electrified aqueous-organic interface via controlled protein electroadsorption. Four proteins known to be electroactive at such interfaces were studied: lysozyme, myoglobin, cytochrome c, and hemoglobin. Following controlled protein electroadsorption onto the interface, ex situ structural characterization of the proteins by FTIR spectroscopy was undertaken, focusing on secondary structural traits within the amide I band. The structural variations observed included unfolding to form aggregated antiparallel β-sheets, where the rearrangement was specifically dependent on the interaction with the organic phase. This was supported by MALDI ToF MS measurements, which showed the formation of protein-anion complexes for three of these proteins, and molecular dynamic simulations, which modeled the structure of lysozyme at an aqueous-organic interface. On the basis of these findings, the modulation of protein secondary structure by interfacial electrochemistry opens up unique prospects to selectively modify proteins.
An Electrochemical Sensing Platform Based on Liquid-Liquid Microinterface Arrays Formed in Laser-Ablated Glass Membranes
Publisher: American Chemical Society (ACS)
Date: 18-02-2016
Electrochemical immunochip sensor for aflatoxin M1 detection
Publisher: American Chemical Society (ACS)
Date: 02-06-2009
DOI: 10.1021/AC900511E
Abstract: An investigation into the fabrication, electrochemical characterization, and development of a microelectrode array (MEA) immunosensor for aflatoxin M(1) is presented in this paper. Gold MEAs (consisting of 35 microsquare electrodes with 20 microm x 20 microm dimensions and edge-to-edge spacing of 200 microm) together with on-chip reference and counter electrodes were fabricated using standard photolithographic methods. The MEAs were then characterized by cyclic voltammetry, and the behavior of the on-chip electrodes were evaluated. The microarray sensors were assessed for their applicability to the development of an immunosensor for the analysis of aflatoxin M(1) directly in milk s les. Following the sensor surface silanization, antibodies were immobilized by cross-linking with 1,4-phenylene diisothiocyanate (PDITC). Surface characterization was conducted by electrochemistry, fluorescence microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). A competitive enzyme linked immunosorbent assay (ELISA) assay format was developed on the microarray electrode surface using the 3,3,5',5'-tetramethylbenzidine dihyrochloride (TMB)/H(2)O(2) electrochemical detection scheme with horseradish peroxidase (HRP) as the enzyme label. The performance of the assay and the microarray sensor were characterized in pure buffer conditions before applying to the milk s les. With the use of this approach, the detection limit for aflatoxin M(1) in milk was estimated to be 8 ng L(-1), with a dynamic detection range of 10-100 ng L(-1), which meets present legislative limits of 50 ng L(-1). The milk interference with the sensor surface was also found to be minimal. These devices show high potential for development of a range of new applications which have previously only been detected using elaborate instrumentation.
Voltammetry of chromium(VI) at the liquid|liquid interface
Publisher: Elsevier BV
Date: 10-2005
Chapter 9: Amperometric ion sensing approaches at liquid/liquid interfaces for inorganic, organic and biological ions
Publisher: The Royal Society of Chemistry
Date: 12-10-2016
DOI: 10.1039/9781782622529-00296
Abstract: Electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) has become an invaluable tool for the selective and sensitive detection of cationic and anionic species, including charged drug molecules and proteins. In addition, neutral molecules can also be detected at the ITIES via enzymatic reactions. This chapter highlights recent developments towards creating a wide spectrum of sensing platforms involving ion transfer across the ITIES. As well as outlining the basic principles needed for performing these sensing applications, the development of ITIES-based detection strategies for inorganic, organic, and biological ions is discussed.
Sensing via Voltammetric Ion-Transfer at an Aqueous-Organogel Micro-Interface Array
Publisher: American Scientific Publishers
Date: 04-2011
DOI: 10.1166/SL.2011.1601
Study of the Effects of Nonlinear Potential Sweeps on Voltammetry
Publisher: Wiley
Date: 2009
Mechanical polishing as an improved surface treatment for platinum screen-printed electrodes
Publisher: Elsevier BV
Date: 07-2016
Reversible Integration of Microfluidic Devices with Microelectrode Arrays for Neurobiological Applications
Publisher: Springer Science and Business Media LLC
Date: 21-05-2014
Synthesis and electrochemical study of a tetra(ester thiophene)calix[4]arene: ionic recognition and electropolymerisation behaviour
Publisher: Royal Society of Chemistry (RSC)
Date: 16-07-2002
DOI: 10.1039/B204155C
Voltammetric behaviour of biological macromolecules at arrays of aqueous|organogel micro-interfaces
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C003323E
Abstract: The behaviour of two biological macromolecules, bovine pancreatic insulin and hen-egg-white lysozyme (HEWL), at aqueous-organogel interfaces confined within an array of solid-state membrane micropores was investigated via cyclic voltammetry (CV). The behaviour observed is discussed in terms of possible charge transferring species and mass transport in the interfacial reaction. Comparison of CV results for HEWL, insulin, and the well-characterised model ion tetraethylammonium cation (TEA(+)) revealed that the biomacromolecules undergo an interfacial reaction comprising biomacromolecular adsorption and facilitated transfer of electrolyte anions from the organic phase to a protein layer on the aqueous side of the interface, whereas TEA(+) undergoes a simple ion transfer process. Evidence for biomacromolecular adsorption on the aqueous side of the micro-interfaces is provided by comparison of the CVs for TEA(+) ion transfer in the presence and absence of the biomacromolecules. Similar experiments in the presence of the low generation polypropylenimine tetraamine dendrimer, (DAB-AM-4), a smaller synthetic molecule, revealed it to be non-adsorbing. The behaviour of biological macromolecules at miniaturised aqueous-organogel interfaces involves adsorption on the aqueous side of the interface and transfer of organic phase electrolyte anions across the interface to associate with the adsorbed biomacromolecule. The data presented support the previously suggested mechanism for biomacromolecular voltammetry at liquid-liquid interfaces, involving adsorption and facilitated ion-transfer of organic electrolyte anions.
Immobilisation of antibody on microporous silicon membranes
Publisher: Springer Science and Business Media LLC
Date: 19-08-2009
Performance of micromachined quartz gravimetric sensors upon electrochemical adsorption of monolayers
Publisher: IEEE
Date: 10-2008
Electroanalytical Ventures at Nanoscale Interfaces Between Immiscible Liquids
Publisher: No publisher found
Date: 2016
DOI: 10.1146/ANNUREV-ANCHEM-071015-041415
Abstract: Ion transfer at the interface between immiscible electrolyte solutions offers many benefits to analytical chemistry, including the ability to detect nonredox active ionized analytes, to detect ions whose redox electrochemistry is accompanied by complications, and to separate ions based on electrocontrolled partition. Nanoscale miniaturization of such interfaces brings the benefits of enhanced mass transport, which in turn leads to improved analytical performance in areas such as sensitivity and limits of detection. This review discusses the development of such nanoscale interfaces between immiscible liquids and examines the analytical advances that have been made to date, including prospects for trace detection of ion concentrations.
Electrochemical study of insulin at the polarized liquid-liquid interface
Publisher: American Chemical Society (ACS)
Date: 31-07-2008
DOI: 10.1021/LA800842F
Abstract: This paper reports on the electrochemical behavior of bovine insulin at the interface between two immiscible electrolyte solutions (ITIES). The voltammetric ion-transfer response obtained in the presence of insulin was dependent on the aqueous phase pH conditions and on the nature of the organic phase electrolyte employed in experiments. Optimal detection was obtained at acidic pH below the isoelectric point of insulin where it was positively charged. A shift in transfer potentials to lower potential values was observed with decreasing hydrophobicity of the anion of the organic phase electrolyte. No ion-transfer response was observed at pH values of the aqueous phase above the isoelectric point, where insulin was negatively charged. These results suggest that the voltammetric response is due to ion-pairing interactions at the ITIES between positively charged insulin and the hydrophobic anion of the organic phase electrolyte, together with adsorption of the ion-pair at the interface. The voltammetric response was obtained for insulin at concentrations down to 1 muM. These results show that electrochemistry is useful in studying the behavior of this important protein molecule at the polarized water-1,2-DCE interface and provides an alternative detection mode for bioanalytical applications.
Visualization of Diffusion within Nanoarrays
Publisher: American Chemical Society (ACS)
Date: 17-06-2016
DOI: 10.1021/ACS.ANALCHEM.6B00513
Abstract: The direct experimental characterization of diffusion processes at nanoscale remains a challenge that could help elucidate processes in biology, medicine and technology. In this report, two experimental approaches were employed to visualize ion diffusion profiles at the orifices of nanopores (radius (ra) of 86 ± 6 nm) in array format: (1) electrochemically assisted formation of silica deposits based on surfactant ion transfer across nanointerfaces between two immiscible electrolyte solutions (nanoITIES) (2) combined atomic force - scanning electrochemical microscopy (AFM-SECM) imaging of topography and redox species diffusion through the nanopores. The nature of the diffusion zones formed around the pores is directly related to the interpore distance within the array. Nanopore arrays with different ratios of pore center-to-center separation (rc) to pore radius (ra) were fabricated by focused ion beam (FIB) milling of silicon nitride (SiN) membranes, with 100 pores in a hexagonal arrangement. The ion diffusion profiles determined by the two visualization methods indicated the formation of overlapped or independent diffusion profiles at nanopore arrays with rc/ra ratios of 21 ± 2 and 91 ± 7, respectively. In particular, the silica deposition method resulted in formation of a single deposit encompassing the complete array with closer nanopore arrangement, whereas in idual silica deposits were formed around each nanopore within the more widely spaced array. The methods reveal direct experimental evidence of diffusion zones at nanopore arrays and provide practical illustration that the pore-pore separation within such arrays has a significant impact on diffusional transport as the pore size is reduced to the nanoscale. These approaches to nanoscale diffusion zone visualization open up possibilities for better understanding of molecular transport processes within miniaturized systems.
Top-Down Approaches to the Fabrication of Nanopatterned Electrodes
Publisher: Wiley
Date: 14-02-2008
Electroanalytical chemistry of per- and polyfluoroalkyl substances
Publisher: Elsevier BV
Date: 08-2023
Electrochemically Induced Formation of Cytochrome c Oligomers at Soft Interfaces
Publisher: Wiley
Date: 27-02-2017
Evaluation of interfacial sulfate complexation by a bis-thiourea ionophore at water-organic interfaces using microelectrochemistry and high resolution mass spectrometry
Publisher: Elsevier BV
Date: 03-2017
Effect of humic acid on the underpotential deposition-stripping voltammetry of copper in acetic acid soil extract solutions at mercaptoacetic acid-modified gold electrodes
Publisher: Elsevier BV
Date: 05-2004
Electrochemical oxidation of a tetraester calix[4]arene
Publisher: Elsevier BV
Date: 2001
Calixarene-facilitated transfer of alkali metal ions across the polarised liquid-liquid interface
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/A908257C
Detection of food additives by voltammetry at the liquid-liquid interface
Publisher: American Chemical Society (ACS)
Date: 31-05-2008
DOI: 10.1021/JF7035966
Abstract: Electrochemistry at the liquid-liquid interface enables the detection of nonredoxactive species with electroanalytical techniques. In this work, the electrochemical behavior of two food additives, aspartame and acesulfame K, was investigated. Both ions were found to undergo ion-transfer voltammetry at the liquid-liquid interface. Differential pulse voltammetry was used for the preparation of calibration curves over the concentration range of 30-350 microM with a detection limit of 30 microM. The standard addition method was applied to the determination of their concentrations in food and beverage s les such as sweeteners and sugar-free beverages. Selective electrochemically modulated liquid-liquid extraction of these species in both laboratory solutions and in beverage s les was also demonstrated. These results indicate the suitability of liquid-liquid electrochemistry as an analytical approach in food analysis.
Ion-transfer electrochemistry at arrays of nanoscale interfaces between two immiscible electrolyte solutions arranged in hexagonal format
Publisher: Elsevier BV
Date: 03-2022
Voltammetric studies of lead at calixarene modified screen-printed carbon electrodes and its trace determination in water by stripping voltammetry
Publisher: Elsevier BV
Date: 07-2001
Bioanalytical detection based on electrochemistry at interfaces between immiscible liquids
Publisher: Informa UK Limited
Date: 10-12-2008
Fabrication of Nanopore Array Electrodes by Focused Ion Beam Milling
Publisher: American Chemical Society (ACS)
Date: 20-03-2007
DOI: 10.1021/AC061878X
Abstract: Single nanopore electrodes and nanopore electrode arrays have been fabricated using a focused ion beam (FIB) method. High aspect ratio pores (approximately 150-400-nm diameter and 500-nm depth) were fabricated using direct-write local ion milling of a silicon nitride layer over a buried platinum electrode. This local milling results in formation of a recessed platinum electrode at the base of each nanopore. The electrochemical properties of these nanopore metal electrodes have been characterized by voltammetry. Steady-state voltammograms were obtained for a range of array sizes as well as for single nanopore electrodes. High-resolution scanning electron microscopy imaging of the arrays showed that the pores had truncated cone, rather than cylindrical, conformations. A mathematical model describing diffusion to an electrode located at the base of a truncated conical pore was developed and applied to the analysis of the electrode geometries. The results imply that diffusion to the pore mouth is the dominant mass transport process rather than diffusion to the electrode surface at the base of the truncated cone. FIB milling thus represents a simple and convenient method for fabrication of prototype nanopore electrode arrays, with scope for applications in sensing and fundamental electrochemical studies.
Collisional electrochemistry of laser-ablated gold nanoparticles by electrocatalytic oxidation of glucose
Publisher: Elsevier BV
Date: 04-2017
Electrochemical study of electroactive reagent retention in overoxidised polypyrrole films
Publisher: Elsevier BV
Date: 12-1999
Ion-Transfer Electrochemistry at Arrays of Nanointerfaces between Immiscible Electrolyte Solutions Confined within Silicon Nitride Nanopore Membranes
Publisher: American Chemical Society (ACS)
Date: 16-06-2010
DOI: 10.1021/AC1008282
Abstract: Ion transfer across interfaces between immiscible liquids provides a means for the nonredox electrochemical detection of ions. Miniaturization of such interfaces brings the benefits of enhanced mass transport. Here, the electrochemical behavior of geometrically regular arrays of nanoscale interfaces between two immiscible electrolyte solutions (nanoITIES arrays) is presented. These were prepared by supporting the two electrolyte phases within silicon nitride membranes containing engineered arrays of nanopores. The nanoITIES arrays were characterized by cyclic voltammetry of the interfacial transfer of tetraethylammonium cation (TEA(+)) between the aqueous phase and the gelled organic phase. Effects of pore radius, pore center-to-center separation, and number of pores in the array were examined. The ion transfer produced apparent steady-state voltammetry on the forward and reverse sweeps at all experimentally accessible scan rates and at all nanopore array designs. However, background-subtraction of the voltammograms revealed the evolution of a peak-shaped response on the reverse sweep with increasing scan rate, indicative of pores filled with the organic phase to a certain extent. The steady-state voltammetric behavior at the nanoITIES arrays on the forward sweep for arrays with significant diffusion zone overlap between adjacent nanoITIES is indicative of the dominance of radial diffusion to interfaces at the edge of the arrays over linear diffusion to interfaces within the arrays. This implies that nanoITIES arrays, which occupy an overall area of micrometer dimensions, behave like a single microITIES of corresponding area to the nanoITIES array.
Electrochemistry of dopamine at the polarised liquid|liquid interface facilitated by an homo-oxo-calix[3]arene ionophore
Publisher: Elsevier BV
Date: 10-2008
Electrochemically modulated liquid-liquid extraction of ions
Publisher: American Chemical Society (ACS)
Date: 10-2005
DOI: 10.1021/AC051029U
Abstract: The development of ion extraction methods under electrochemical control via electrochemistry at the interface between two immiscible electrolyte solutions is discussed. A hydrodynamic flow injection system was used for the potentiostatic extraction of non-redox-active species from a flowing aqueous phase into a stationary organogel phase. The ions tetraethylammonium, 4-octylbenzenesulfonate (4-OBSA-), and p-toluenesulfonate (p-TSA-) were studied as model analytes. The extraction study comprised examination of the influence of extraction potentials, aqueous-phase flow rate, and target species concentration. The extraction process can be monitored in situ by means of the ion-transfer current, which has opposing signs for anions and cations. Hydrodynamic voltammograms were obtained from these experiments. The selective extraction of 4-OBSA-, from its mixture with p-TSA-, as well as coextraction of both anions is shown. The results demonstrate the utility of electrochemical modulation for the controlled extraction of ions from an aqueous phase into an organogel electrolyte phase. This offers potential benefits for various analytical processes including s le preparation and cleanup.
Recent Developments in Nanozyme Based Sensors for Detection of Clinical Biomarkers—A Review
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-08-2022
Laparoscopic repair of a supravesical hernia presenting as a ‘recurrent’ inguinal hernia in a 5-year-old female
Publisher: Wiley
Date: 02-09-2018
DOI: 10.1111/ANS.13278
Interaction of surface-attached haemoglobin with hydrophobic anions monitored by on-line acoustic wave detector
Publisher: Elsevier BV
Date: 08-2010
DOI: 10.1016/J.BIOELECHEM.2009.09.012
Abstract: The behaviour of proteins on surfaces and at interfaces is an important field with applications in drug development, clinical diagnostics and studies of device biocompatibility. A key factor is the conformation of surface-bound proteins, which can affect chemical signalling and drug binding. A recent study of the interactions of haemoglobin with hydrophobic anions at a liquid-liquid interface has shown that a pH- and orientation-dependent conformational change occurs in the haemoglobin molecule upon interaction with these anions. To corroborate these results, we use an acoustic wave detector to study binding of solution-phase hydrophobic anions to surface-adhered haemoglobin. The orientation of protein is controlled by thiol chemistry, which generates hydrophilic and hydrophobic surfaces. Tetraphenylborate-based anions are introduced to the haemoglobin coated surface via an on-line flow-injection system to monitor the signal in real-time. Changes in the acoustic properties of the surface, measured piezoelectrically, are related to interactions between the protein and the anions. Signal strength is proportional to the degree of interaction between the salts and the haemoglobin, which in turn, is influenced by its conformation.
Assessment of ion transfer amperometry at liquid-liquid interfaces for detection in CE
Publisher: Wiley
Date: 10-2009
Abstract: In this research, ion transfer across the interface between two immiscible electrolyte solutions (ITIES) was used as a method of detection in a CE separation system. This method allows for the electrochemical detection of ionic analytes that cannot be easily oxidized or reduced. Method development revealed that the optimal separation conditions for three model ions (tetraethylammonium, tetrabutylammonium, and benzensulfonate) were found to be 5 mM sodium tetraborate buffer pH 9.2 with a separation voltage of 20 kV using a 40 cm, 50 microm id fused silica capillary. Constant potential erometry and pulsed erometric detection were applied at the ITIES in which the organic phase was gelled. A miniaturized ITIES within a pipette tip was investigated, which resulted in improved separation efficiency and LOD. To demonstrate the ability of the system to detect substances of bioanalytical interest, the beta-adrenergic receptor blockers timolol and propranolol were detected. The simplicity of the detection platform means that it may be useful for analytical situations not requiring trace or ultratrace detection capabilities.
Investigation of potential distribution and the influence of ion complexation on diffusion potentials at aqueous - Aqueous boundaries within a dual-stream microfluidic structure
Publisher: American Chemical Society (ACS)
Date: 21-09-2009
DOI: 10.1021/AC901061R
Abstract: The occurrence of reactions at boundaries between adjacent miscible but unmixed aqueous streams coflowing in a microfluidic channel structure has been studied by simulation of the diffusion potentials that develop between the two coflowing aqueous electrolyte streams and by measurement of the effects of aqueous ion complexation on diffusion potentials. The microfluidic structure consisted of a Y-shaped microchannel with off-chip electrodes immersed in electrolyte reservoirs connected by capillaries to the Y-microchannel. The time-dependent, one-dimensional Nernst-Planck equation employing the electroneutrality condition was solved numerically to calculate the diffusion potentials established at the boundary between the two coflowing aqueous streams. Under the experimental conditions (channel length and width, flow rate) employed, it was shown that the use of the Henderson equation was appropriate. It was also shown that the cross-channel diffusion potential remained constant from the entrance of the channel to the exit. The influence of cation complexation by a neutral ionophore was investigated by experimentally measured diffusion potentials. It was found that potassium complexation by the cyclic polyether 18-crown-6 altered the experimental diffusion potential, whereas the interaction of sodium or lithium cations with the ionophore did not perturb the diffusion potential. The results are consistent with the literature data for aqueous-phase complexation of these cations by this ionophore. The results of these investigations demonstrate that relatively simple diffusion potential measurements between coflowing streams in microchannels may be used as a basis for study of ion complexation reactions occurring at boundaries between miscible fluids.
Behavior of Lysozyme at the Electrified Water/Room Temperature Ionic Liquid Interface
Publisher: Wiley
Date: 24-07-2012
Abstract: Between the phases: The globular protein lysozyme was adsorbed and desorbed under electrochemical conditions at the water/room temperature ionic liquid microinterface array the electrochemical desorption process provides a basis for protein detection at these interfaces.
Stripping voltammetric detection of insulin at liquid-liquid microinterfaces in the presence of bovine albumin
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3AN01123B
Abstract: Electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) provides a platform for label-free detection of biomolecules. In this study, adsorptive stripping voltammetry (AdSV) was implemented at an array of microscale ITIES for the detection of the antidiabetic hormone insulin. By exploiting the potential-controlled adsorption of insulin at the ITIES, insulin was detected at 10 nM via subsequent voltammetric desorption. This is the lowest detected concentration reported to-date for a protein by electrochemistry at the ITIES. Surface coverage calculations indicate that between 0.1 and 1 monolayer of insulin forms at the interface over the 10-1000 nM concentration range of the hormone. In a step toward assessment of selectivity, the optimum adsorption potentials for insulin and albumin were determined to be 0.900 V and 0.975 V, respectively. When present in an aqueous mixture with albumin, insulin was detected by tuning the adsorption potential to 0.9 V, albeit with reduced sensitivity. This provides the first ex le of selective detection of one protein in the presence of another by exploiting optimal adsorption potentials. The results presented here provide a route to the improvement of detection limits and achievement of selectivity for protein detection by electrochemistry at the ITIES.
Ionophore-Assisted Electrochemistry of Neutral Molecules: Oxidation of Hydrogen in an Ionic Liquid Electrolyte
Publisher: American Chemical Society (ACS)
Date: 22-10-2019
DOI: 10.1021/ACS.JPCLETT.9B02666
Abstract: The electrochemical properties of gas molecules are of great interest for both fundamental and applied research. In this study, we introduce a novel concept to systematically alter the electrochemical behavior and, in particular, the redox potential of neutral gas molecules. The concept is based on the use of an ion-binding agent, or "ionophore", to bind and stabilize the ionic electrochemical reaction product. We demonstrate that the ionophore-assisted electrochemical oxidation of hydrogen in a room-temperature ionic liquid electrolyte is shifted by almost 1 V toward more negative potentials in comparison to an ionophore-free electrolyte. The altered electrochemical response in the presence of the ionophore not only yields insights into the reaction mechanism but also can be used to determine the diffusion coefficient of the ionophore species. This ionophore-modulated electrochemistry of neutral gas molecules opens up new avenues for the development of highly selective electrochemical sensors.
Research and development topics in Analytical Chemistry
Publisher: Royal Society of Chemistry (RSC)
Date: 1993
DOI: 10.1039/AP9933000129
Electroanalytical Opportunities Derived from Ion Transfer at Interfaces between Immiscible Electrolyte Solutions
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/CH15796
Abstract: This review presents an introduction to electrochemistry at interfaces between immiscible electrolyte solutions and surveys recent studies of this form of electrochemistry in electroanalytical strategies. Simple ion and facilitated ion transfers across interfaces varying from millimetre scale to nanometre scales are considered. Target detection strategies for a range of ions, inorganic, organic, and biological, including macromolecules, are discussed.
Surface chemical and physical modification in stent technology for the treatment of coronary artery disease.
Publisher: Wiley
Date: 30-07-2012
DOI: 10.1002/JBM.B.32772
Abstract: Coronary artery disease (CAD) kills millions of people every year. It results from a narrowing of the arteries (stenosis) supplying blood to the heart. This review discusses the merits and limitations of balloon angioplasty and stent implantation, the most common treatment options for CAD, and the pathophysiology associated with these treatments. The focus of the review is heavily placed on research efforts geared toward the modification of stent surfaces for the improvement of stent-vascular compatibility and the reduction in the occurrence of related pathophysiologies. Such modifications may be chemical or physical, both of which are surveyed here. Chemical modifications may be passive or active, while physical modification of stent surfaces can also provide suitable substrates to manipulate the responses of vascular cells (endothelial, smooth muscle, and fibroblast). The influence of micro- and nanostructured surfaces on the in vitro cell response is discussed. Finally, future perspectives on the combination of chemical and physical modifications of stent surfaces are also presented.
Voltammetric behaviour at gold electrodes immersed in the BCR sequential extraction scheme media
Publisher: Elsevier BV
Date: 2004
Electrochemistry of proteins at the interface between two immiscible electrolyte solutions
Publisher: Elsevier BV
Date: 12-2018
Achievement of diffusional independence at nanoscale liquid-liquid interfaces within arrays
Publisher: American Chemical Society (ACS)
Date: 15-05-2015
DOI: 10.1021/ACS.ANALCHEM.5B01162
Abstract: In this work, independent radial diffusion at arrayed nanointerfaces between two immiscible electrolyte solutions (nanoITIES) was achieved. The arrays were formed at nanopores fabricated by focused ion beam milling of silicon nitride (SiN) membranes, enabling the reproducible and systematic design of five arrays with different ratios of pore center-to-center distance (rc) to pore radius (ra). Voltammetry across water-1,6-dichlorohexane nanoITIES formed at these arrays was examined by the interfacial transfer of tetrapropylammonium ions. The diffusion-limited ion-transfer current increased with the ratio rc/ra, reaching a plateau for rc/ra ≥ 56, which was equivalent to the theoretical current for radial diffusion to an array of independent nanoITIES. As a result, mass transport to the nanoITIES arrays was greatly enhanced due to the decreased overlap of diffusion zones at adjacent nanoITIES, allowing each interface in the array to behave independently. When the rc/ra ratio increased from 13 to 56, the analytical performance parameters of sensitivity and limit of detection were improved from 0.50 (±0.02) A M(-1) to 0.76 (±0.02) A M(-1) and from 0.101 (±0.003) μM to 0.072 (±0.002) μM, respectively. These results provide an experimental basis for the design of arrayed nanointerfaces for electrochemical sensing.
Serum-protein effects on the detection of the β-blocker propranolol by ion-transfer voltammetry at a micro-ITIES array
Publisher: Elsevier BV
Date: 15-03-2010
DOI: 10.1016/J.TALANTA.2009.10.060
Abstract: In this work, the effect of the serum protein, bovine serum albumin (BSA), on the detection of propranolol in artificial serum by ion-transfer voltammetry at an array of micro-interfaces between two immiscible electrolyte solutions (microITIES) is presented. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and differential pulse stripping voltammetry (DPSV) were examined for the detection of low concentrations of propranolol. Both CV and DPV had an interference effect from BSA, manifested as lower currents in the presence of the protein. DPSV proved to be the most effective technique, enabling the detection of 0.05 microM propranolol in the presence of BSA. The DPSV method employed a preconditioning step as well as a preconcentration step followed by the analytical signal generation step. The latter was based on the back-transfer of the drug across the microITIES. The preconcentration step was crucial to prevention of the adverse effects of BSA on the voltammetric detection. These results demonstrate that serum-protein effects on drug detection at low concentrations can be eliminated by use of DPSV at arrays of microITIES. CVs of propranolol with increasing concentrations of BSA revealed the influence of the drug-protein binding interaction, with decreases in current but no change in transfer potential. Therapeutic concentrations of propranolol were detected, demonstrating the viability of this approach for bioanalytical investigations.
Reactive Conjugated Polymers: Synthesis, Modification, and Electrochemical Properties of Polypentafluorophenylacetylene (Co)Polymers
Publisher: Wiley
Date: 18-11-2017
Abstract: (Co)Polymers containing pentafluorophenylacetylene (F
Characterization of the electrochemical behavior of gastrointestinal fluids using a multielectrode sensor probe
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2011
Removal of arsenic from alkaline process waters of gold cyanidation by use of γ-Fe2O3@ZrO2 nanosorbents
Publisher: Elsevier BV
Date: 12-2017
Detection of haemoglobin using an adsorption approach at a liquid-liquid microinterface array
Publisher: Springer Science and Business Media LLC
Date: 14-12-2013
DOI: 10.1007/S00216-012-6622-2
Abstract: The behaviour of haemoglobin (Hb) at the interface between two immiscible electrolyte solutions (ITIES) has been examined for analytical purposes. When Hb is fully protonated under acidic conditions (pH <pI) in the aqueous phase, it undergoes a potential-dependent adsorption and complexation, at the interface, with the anions of the organic phase electrolyte. When utilised as a simple and fast preconcentration step, consisting of adsorbing the protein at the interface, in conjunction with voltammetric desorption, this opens up the ITIES to the adsorptive stripping voltammetry approach. Utilising a 60 s adsorption step and linear sweep voltammetry, a linear response to Hb concentration in aqueous solution over the range 0.01-0.5 μM was achieved. The equation of the best-fit straight line was I(p) = 7.46 C - 0.109, R = 0.996, where I(p) is the peak current (in nano ere) and C is haemoglobin concentration (in micromolar). The calculated detection limit (3σ) was 48 nM for a 60 s preconcentration period, while the relative standard deviation was 13.3% for six successive measurements at 0.1 μM Hb. These results illustrate the prospects for simple, portable and rapid label-free detection of biomacromolecules offered by electrochemistry at arrays of liquid-liquid microinterfaces.
Removal of arsenic from alkaline process waters of gold cyanidation by use of Fe3O4@SiO2@TiO2 nanosorbents
Publisher: Elsevier BV
Date: 08-2017
Structural Changes in Insulin at a Soft Electrochemical Interface
Publisher: American Chemical Society (ACS)
Date: 21-06-2021
Finite-element simulations of the influence of pore wall adsorption on cyclic voltammetry of ion transfer across a liquid-liquid interface formed at a micropore
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP23052F
Abstract: Adsorption onto the walls of micropores was explored by computational simulations involving cyclic voltammetry of ion transfer across an interface between aqueous and organic phases located at the micropore. Micro-interfaces between two immiscible electrolyte solutions (micro-ITIES) have been of particular research interest in recent years and show promise for biosensor and biomedical applications. The simulation model combines diffusion to and within the micropore, Butler-Volmer kinetics for ion transfer at the liquid-liquid interface, and Langmuir-style adsorption on the pore wall. Effects due to pore radius, adsorption and desorption rates, surface adsorption site density, and scan rates were examined. It was found that the magnitude of the reverse peak current decreased due to adsorption of the transferring ion on the pore wall this decrease was more marked as the scan rate was increased. There was also a shift in the half-wave potential to lower values following adsorption, consistent with a wall adsorption process which provides a further driving force to transfer ions across the ITIES. Of particular interest was the disappearance of the reverse peak from the cyclic voltammogram at higher scan rates, compared to the increase in the reverse peak size in the absence of wall adsorption. This occurred for scan rates of 50 mV s(-1) and above and may be useful in biosensor applications using micropore-based ITIES.
Determination of trace metals by underpotential deposition-stripping voltammetry at solid electrodes
Publisher: Elsevier BV
Date: 03-2005
Application of the Disorganized Monolayer Gold Electrode to Copper Determination in White Wine
Publisher: Informa UK Limited
Date: 2004
DOI: 10.1081/AL-120029738
Electrochemical strategies for the label-free detection of amino acids, peptides and proteins
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B701472D
Abstract: Electrochemical methods for the detection of amino acids, peptides, and proteins in a variety of media are reviewed. Label-free strategies in which the detection is based on the inherent electrochemical properties of the analyte are discussed. Various processes such as direct or mediated (in solution or immobilised) redox processes and interfacial ion transfers have been employed for the electrochemical detection and determination of the target analytes. The various methods covered encompass voltammetry at uncoated and modified electrodes and at immiscible liquid-liquid interfaces, potentiometry at polymer membrane electrodes and electrochemical impedance spectroscopy. The determination of the target analytes in complex biological matrices is discussed. The various approaches highlighted here illustrate the rich capabilities of electrochemical methods as simple, low-cost, sensitive tools for the determination of these important biological analytes at trace and ultra-trace levels.
Microfluidic chip for electrochemically-modulated liquid{divides}liquid extraction of ions
Publisher: Elsevier BV
Date: 2008
Paper-Based System for Ion Transfer Across the Liquid-Liquid Interface.
Publisher: American Chemical Society (ACS)
Date: 17-07-2018
DOI: 10.1021/ACS.ANALCHEM.8B02695
Abstract: While ion transfer studies were shown to be a promising method for fundamental electrochemistry, pharmacokinetic studies, and sensing, they suffer from inherent instability of the interface formed between the organic and aqueous phases. This limits to some extent the range of solvents which can be used and confines these studies to the laboratory. We propose here the use of paper, which has revolutionized the way we think of miniaturized analytical devices during the past decade, as a perfect substrate for ion transfer studies across the liquid-liquid interface. We describe the design of a simple three-phase electrode paper-based setup for redox-driven transfer of anions from an aqueous to an organic phase. Electrochemical measurements of seven different anions and concentration dependence studies are in good agreement with the results obtained with traditional setups. Additionally, we show the applicability and limitations of such setups to the analysis of anion mixtures.
Ion Transfer Voltammetry with an Electrochemical Pen
Publisher: American Chemical Society (ACS)
Date: 12-2020
Potentiometric characterisation of a dual-stream electrochemical microfluidic device
Publisher: Springer Science and Business Media LLC
Date: 20-06-2009
Comparison of Hydrothermally-Grown vs Electrodeposited Cobalt Sulfide Nanostructures as Modified Electrodes for Oxygen Evolution and Electrochemical Sensing Applications
Publisher: The Electrochemical Society
Date: 05-2022
Abstract: A wide range of electrocatalysts have been developed and implemented for electrochemical applications over the last decades, with researchers typically using either a conventional synthesis method (followed by drop-casting or spray-coating onto the electrode), or directly electrodepositing the catalyst. However, a clear comparison of the different materials synthesis techniques, and how this affects the electrochemical applications, has been less explored. Herein, we report a direct comparison of fabricated cobalt sulfide (CoS) nanostructure-based electrodes prepared by two different methods for two applications: (a) electrochemical water splitting and (b) glucose sensing. CoS is grown in the form of nanoflowers and nanosheets via facile one-pot hydrothermal (HT) and electrodeposition (ED) methods, respectively. Characterization is performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It is observed that the as-fabricated CoS-ED electrode demonstrated enhanced oxygen evolution reaction (OER) performance, a lower overpotential (∼166 mV at 10 mA cm −2 ), lower charge transfer resistance (∼372 Ω), a lower Tafel slope (86 mV dec −1 ), and better stability compared to the CoS-HT electrode. Moreover, the CoS-ED electrode-based sensor also exhibited better performance, higher sensitivity, better selectivity, and good stability for electrochemical glucose detection compared to the CoS-HT sensor.
Electrochemical ion transfer across liquid/liquid interfaces confined within solid-state micropore arrays – simulations and experiments
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B815256J
Abstract: Miniaturised liquid/liquid interfaces provide benefits for bioanalytical detection with electrochemical methods. In this work, microporous silicon membranes which can be used for interface miniaturisation were characterized by simulations and experiments. The microporous membranes possessed hexagonal arrays of pores with radii between 10 and 25 microm, a pore depth of 100 microm and pore centre-to-centre separations between 99 and 986 microm. Cyclic voltammetry was used to monitor ion transfer across arrays of micro-interfaces between two immiscible electrolyte solutions (microITIES) formed at these membranes, with the organic phase present as an organogel. The results were compared to computational simulations taking into account mass transport by diffusion and encompassing diffusion to recessed interfaces and overlapped diffusion zones. The simulation and experimental data were both consistent with the situation where the location of the liquid/liquid (l/l) interface was on the aqueous side of the silicon membrane and the pores were filled with the organic phase. While the current for the forward potential scan (transfer of the ion from the aqueous phase to the organic phase) was strongly dependent on the location of the l/l interface, the current peak during the reverse scan (transfer of the ion from the organic phase to the aqueous phase) was influenced by the ratio of the transferring ion's diffusion coefficients in both phases. The diffusion coefficient of the transferring ion in the gelified organic phase was ca. nine times smaller than in the aqueous phase. Asymmetric cyclic voltammogram shapes were caused by the combined effect of non-symmetrical diffusion (spherical and linear) and by the inequality of the diffusion coefficient in both phases. Overlapping diffusion zones were responsible for the observation of current peaks instead of steady-state currents during the forward scan. The characterisation of the diffusion behaviour is an important requirement for application of these silicon membranes in electroanalytical chemistry.
Incorporation of hydroxamic acid ligands into Nafion film electrodes
Publisher: Royal Society of Chemistry (RSC)
Date: 1993
DOI: 10.1039/AN9931800355
Recessed nanoband electrodes fabricated by focused ion beam milling
Publisher: Elsevier BV
Date: 30-01-2007
Electrochemical signature of hen egg white lysozyme at the glycerol-modified liquid-liquid interface
Publisher: Elsevier BV
Date: 12-2016
Impact of a Surfactant on the Electroactivity of Proteins at an Aqueous-Organogel Microinterface Array
Publisher: American Chemical Society (ACS)
Date: 17-01-2013
DOI: 10.1021/AC302222U
Abstract: The impact of surfactant addition to the organic phase on the electroactivity of proteins at the aqueous-organogel interface was examined by voltammetry. The presence of bis(2-ethylhexyl)sulfosuccinate (AOT) in the organogel phase, as the sodium salt, caused marked changes in the peak currents for myoglobin detection. The protein desorption voltammetric peak exhibited a 6-fold increase in the current compared to the corresponding experiment without surfactant. Interfacial coverage showed a 17-fold increase in the adsorbed protein at the interface, from 50 pmol cm(-2), in the absence of surfactant, to 850 pmol cm(-2), in the presence of 10 mM surfactant. Additionally, the presence of the surfactant resulted in a second pair of adsorption/desorption peaks at lower potentials and in a change in the capacitance of the system. The formation of surfactant-protein and surfactant-protein-organic anion deposits is proposed on the basis of these features, leading to increased voltammetric signals for myoglobin, hemoglobin, and cytochrome c. The mechanism of protein-surfactant interaction was probed by using the surfactant as the anion in the organic phase electrolyte salt. Repetitive cyclic voltammetry of cytochrome c showed that in the presence of surfactant there was an enhancement of the signal, caused by a buildup of the protein-surfactant-electrolyte anion assembly at the interface. These findings provide the basis for surfactant-modified interfaces to enhance the electroanalytical performance for protein detection.
Void-assisted ion-paired proton transfer at water-ionic liquid interfaces
Publisher: Wiley
Date: 22-10-2016
Investigation of modified nanopore arrays using FIB/SEM tomography
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8FD00019K
Abstract: FIB/SEM tomography and energy dispersive X-ray (EDX) spectroscopy are employed to study the interface between two immiscible electrolyte solutions at nanopore arrays, which were electrochemically modified by silica.
Voltammetric behavior and trace determination of cadmium at a calixarene modified screen-printed carbon electrode
Publisher: Wiley
Date: 02-2002
DOI: 10.1002/1521-4109(200202)14:3<177::AID-ELAN177>3.0.CO;2-V
Electrochemical Behavior of Chlorine on Platinum Microdisk and Screen-Printed Electrodes in a Room Temperature Ionic Liquid
Publisher: American Chemical Society (ACS)
Date: 06-10-2015
Interaction of acridine-calix[4]arene with DNA at the electrified liquid liquid interface
Publisher: Elsevier BV
Date: 03-2010
Monitoring the Dissolution and Hydrolysis of Pyrosulfate by Electrochemistry at a Liquid‐Liquid Microinterface Array
Publisher: Wiley
Date: 11-11-2022
Abstract: Dissolution and hydrolysis processes are important in a variety of settings, including industrial and environmental applications. In this work, the hydrolysis of pyrosulfate (disulfate) was investigated by ion‐transfer electrochemistry at an array of microinterfaces between two immiscible electrolyte solutions (μITIES). Current associated with pyrosulfate transfer was observed, but it decreased with time. This is due to the hydrolysis of pyrosulfate to hydrogen sulfate and sulfate. Corroborating data for the hydrolysis was obtained from pH measurements (acidification of the aqueous solution) and Raman spectroscopy (formation of sulfate and hydrogen sulfate). Measurement of the ion‐transfer potential from the voltammograms enabled estimation of pyrosulfate's Gibbs energy of transfer between the phases. Quantum mechanical calculations were employed to estimate the thermodynamics for the reactions of pyrosulfate, hydrogen sulfate and sulfate, which supported the experimentally observed trends. Altogether, these results illustrate the use of electrochemistry at the μITIES to characterise dissolution and hydrolysis processes.
Ionophore/ionomer films on glassy carbon electrodes for accumulation voltammetry. Investigation of a lead(II) IONOPHORE
Publisher: Royal Society of Chemistry (RSC)
Date: 1994
DOI: 10.1039/AN9941900287
Ion-transfer voltammetric behavior of propranolol at nanoscale liquid-liquid interface arrays
Publisher: American Chemical Society (ACS)
Date: 08-04-2015
DOI: 10.1021/ACS.ANALCHEM.5B00461
Abstract: In this work, the ion-transfer voltammetric detection of the protonated β-blocker propranolol was explored at arrays of nanoscale interfaces between two immiscible electrolyte solutions (ITIES). Silicon nitride nanoporous membranes with 400 pores in a hexagonal arrangement, with either 50 or 17 nm radius pores, were used to form regular arrays of nanoITIES. It was found that the aqueous-to-organic ion-transfer current continuously increased steadily rather than reaching a limiting current plateau after the ion-transfer wave the slope of this limiting current region was concentration dependent and associated with the high ion flux at the nanointerfaces. Electrochemical data were examined in terms of an independent nanointerface approach and an equivalent microdisc approach, supported by finite element simulation. In comparison to the larger interface configuration (50 nm radius), the array of 17 nm radius nanoITIES exhibited a 6.5-times higher current density for propranolol detection due to the enhanced ion flux arising from the convergent diffusion to smaller electrochemical interfaces. Both nanoITIES arrays achieved the equivalent limits of detection, 0.8 μM, using cyclic voltammetry. Additionally, the effect of scan rate on the charging and faradaic currents at these nanoITIES arrays, as well as their stability over time, was investigated. The results demonstrate that arrays of nanoscale liquid-liquid interfaces can be applied to study electrochemical drug transfer, and provide the basis for the development of miniaturized and integrated detection platforms for drug analysis.
Fabrication and characterization of a miniaturized planar voltammetric sensor array for use in an electronic tongue
Publisher: Elsevier BV
Date: 07-2009
Surface immobilisation of antibody on cyclic olefin copolymer for sandwich immunoassay
Publisher: Elsevier BV
Date: 04-2009
DOI: 10.1016/J.BIOS.2009.01.026
Abstract: In this work, the surface functionalisation of the commercially available cyclic olefin copolymer (COC) materials, Zeonor and Zeonex, has been studied. The methodology employed involved oxidation in oxygen plasma, functionalisation of the oxidized surface with aminopropyl triethoxy silane and, finally, attachment of antibody using covalent linker molecules. 1,4-Phenylene diisothiocyanate was selected as the most suitable cross-linker for the attachment of protein, as assessed by fluorescent intensity measurements on immobilised FITC-labelled IgG antibody. The modification method was characterised by contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. The data are consistent with the deposition of a polymeric film of the silane chemisorbed to the oxidised plastic surface. The functionalised surfaces were employed in a sandwich immunoassay format using the reagents goat anti-human IgG (G alphaHIgG) and fluorescently labelled G alphaHIgG (Cy5-G alphaHIgG) as capture and detection antibodies, respectively, and with human IgG (HIgG) as the model analyte. The lowest concentration of HIgG detected was 0.1 ng ml(-1), with a relative standard deviation of 15%. Non-specific binding effects were also assessed. The method and supporting data demonstrate that simple approaches to surface functionalisation can be adapted to plastic-based devices.
Ion-transfer voltammetric determination of the β-blocker propranolol in a physiological matrix at silicon membrane-based liquid|liquid microinterface arrays
Publisher: American Chemical Society (ACS)
Date: 12-02-2009
DOI: 10.1021/AC802644G
Abstract: In this work, the ion-transfer voltammetric detection of the protonated beta-blocker propranolol in artificial saliva is presented. Cyclic voltammetry, differential pulse voltammetry, and differential pulse stripping voltammetry (DPSV) were employed in the detection of the cationic drug based on ion-transfer voltammetry across arrays of microinterfaces between artificial saliva and an organogel phase. It was found that the artificial saliva matrix decreased the available potential window for ion-transfer voltammetry at this liquid|liquid interface but transfer of protonated propranolol was still achieved. The DPSV method employed a preconditioning step as well as a preconcentration step followed by analytical signal generation based on the back-transfer of the drug across the array of microinterfaces. The DPSV peak current response was linear with drug concentration in the artificial saliva matrix over the concentration range of 0.05-1 microM (i(p) = -8.13 (nA microM(-1))(concentration) + 0.07 (nA), R = 0.9929, n = 7), and the calculated detection limit (3s(b)) was 0.02 microM. These results demonstrate that DPSV at arrays of liquid|liquid microinterfaces is a viable analytical approach for pharmaceutical determinations in biomimetic matrixes.
Voltammetric Selectivity in Detection of Ionized Perfluoroalkyl Substances at Micro-Interfaces between Immiscible Electrolyte Solutions
Publisher: American Chemical Society (ACS)
Date: 16-09-2022
DOI: 10.1021/ACSSENSORS.2C01100
Abstract: Widespread contamination by per- and polyfluoroalkyl substances (PFAS) and concern about their health impacts require the availability of rapid sensing approaches. In this research, four PFAS, perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonic acid (PFOS), were studied at micropipette-based interfaces between two immiscible electrolyte solutions (μITIES) to assess the potentiality for their detection by ion transfer voltammetry. All four PFAS substances were detected by ion transfer voltammetry at the μITIES, with half-wave transfer potentials (
Development of surface-modified microelectrode arrays for the electrochemical detection of dihydrogen phosphate
Publisher: Wiley
Date: 03-2005
Abstract: Platinum and gold microelectrode arrays (MEAs), fabricated on silicon substrates with different geometric characteristics, were surface‐modified by the potentiostatic electropolymerization of the pyrrole‐ferrocene derivative Py(CH 2 ) 3 NHCOFc, in the case of the platinum MEAs, and chemisorption of the thiol‐functionalized ferrocene HS(CH 2 ) 6 N + (CH 3 ) 2 Fc, in the case of the gold MEAs. Cyclic voltammetry of these MEAs was typical of thin film behavior. The modified MEAs were investigated for the detection of the dihydrogen phosphate mono‐anion in non‐aqueous media via differential pulse voltammetry. This was based on electrostatic interaction and/or hydrogen‐bonding between the target anion and the amide‐ferrocene or ammonium‐ferrocene functionalized electrode surfaces. A decrease in the ferrocene (Fc) oxidation peak current with a concomitant increase in the peak current of a new peak at lower potentials was observed when the concentration of the dihydrogen phosphate was increased.
Electrochemical behaviour of myoglobin at an array of microscopic liquid-liquid interfaces
Publisher: Elsevier BV
Date: 08-2012
Enhanced Electroanalytical Sensitivity via Interface Miniaturisation: Ion Transfer Voltammetry at an Array of Nanometre Liquid–Liquid Interfaces
Publisher: Wiley
Date: 16-03-2011
Microelectrochemical systems on silicon chips for the detection of pollutants in seawater
Publisher: Wiley
Date: 07-12-2011
Selective silver ion transfer voltammetry at the polarised liquid|liquid interface
Publisher: Royal Society of Chemistry (RSC)
Date: 2003
DOI: 10.1039/B301832F
Abstract: Transfer of silver ions across the water/1,2-dichloroethane interface was studied by cyclic voltammetry (CV). In the absence of added neutral ionophore, Ag+ transferred across the interface when the organic phase contained either tetraphenylborate or tetrakis(4-chloro)phenylborate anions, but this transfer was not possible in the presence of organic phase hexafluorophosphate or perchlorate anions. The ion transfer processes observed were independent of the nature of the organic phase cation. The CV in the presence of tetraphenylborate exhibited a shape consistent with an ion transfer followed by chemical reaction the rate constant for the following chemical reaction was 0.016 s(-1). In the presence of tetrakis(4-chloro)phenylborate, a return peak equivalent in magnitude to the forward peak was observed, indicative of a simple ion transfer reaction uncomplicated by accompanying chemical reactions. The selectivity of the transfer was assessed with respect to other metal cations: no transfers for copper, cadmium, lead, bismuth, cobalt, nickel, palladium or zinc were observed. The selectivity of the transfer suggests this can form the basis of a selective voltammetric methodology for the determination of silver ions.
Calixarenes in electroanalysis
Publisher: Wiley
Date: 03-1995
Chronoamperometric response at nanoscale liquid-liquid interface arrays
Publisher: Elsevier BV
Date: 07-2013
Underpotential deposition of copper at mercaptoalkane sulfonate-coated polycrystalline gold
Publisher: Wiley
Date: 05-2001
DOI: 10.1002/1521-4109(200105)13:8/9<751::AID-ELAN751>3.0.CO;2-N
Electrochemical detection of ractopamine at arrays of micro-liquid | liquid interfaces.
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.TALANTA.2014.08.060
Abstract: The behaviour of protonated ractopamine (RacH(+)) at an array of micro-interfaces between two immiscible electrolyte solutions (micro-ITIES) was investigated via cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV). The micro-ITIES array was formed at silicon membranes containing 30 pores of radius 11.09±0.12 µm and pore centre-to-centre separation of 18.4±2.1 times the pore radius. CV shows that RacH(+) transferred across the water |1,6-dichlorohexane µITIES array at a very positive applied potential, close to the upper limit of the potential window. Nevertheless, CV was used in the estimation of some of the drug's thermodynamic parameters, such as the formal transfer potential and the Gibbs transfer energy. LSSV was implemented by pre-concentration of the drug, into the organic phase, followed by voltammetric detection, based on the back-transfer of RacH(+) from the organic to aqueous phase. Under optimised pre-concentration and detection conditions, a limit of detection of 0.1 µM was achieved. In addition, the impact of substances such as sugar, ascorbic acid, metal ions, amino acid and urea on RacH(+) detection was assessed. The detection of RacH(+) in artificial serum indicated that the presence of serum protein interferes in the detection signal, so that s le deproteinisation is required for feasible bioanalytical applications.
Electrochemical behaviour of haemoglobin at the liquid/liquid interface
Publisher: Elsevier BV
Date: 10-2008
Electrochemical Characterisation of Nanoscale Liquid jLiquid Interfaces Located at Focused Ion BeamMilled Silicon Nitride Membranes
Publisher: Wiley
Date: 14-10-2015
Detection of perfluorooctane sulfonate by ion-transfer stripping voltammetry at an array of microinterfaces between two immiscible electrolyte solutions
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0AN00884B
Abstract: An analytical approach employing ion transfer voltammetry at an array of micro-interfaces between two immiscible electrolyte solutions is presented for detection of perfluorooctane sulfonate (PFOS).
Electrodeposition of the bismuth-based superconductor Bi2 Sr2 CaCu2 O8+δ
Publisher: Elsevier BV
Date: 06-1996
Microelectrode Arrays and Microfabricated Devices in Electrochemical Stripping Analysis
Publisher: Bentham Science Publishers Ltd.
Date: 07-2008
DOI: 10.2174/157341108784911406
Abstract: In this article a comprehensive overview of the developments in the field of electrochemical stripping analysis with microelectrode arrays and microfabricated devices is presented. Due to the vastness of the topic, this mini-review deals only with the use of regular microelectrode arrays. After the description of the main fabrication methodologies employed, a large part of the review is dedicated to applications, categorised by the electrode material. Microelectrode arrays have found application in several areas of electroanalytical science including clinical and environmental analysis. They have been used for the detection of heavy metals in waters, soil extracts and blood, proving to be reliable analytical devices and bringing the advantages of low-cost, simplicity of use and easy adaptability to field measurement. In many applications, limits of detection are sub-parts per billion. Finally a short section of the review discusses miniaturised potentiostats.
Selectivity in the coextraction of cation and anion by electrochemically modulated liquid-liquid extraction
Publisher: American Chemical Society (ACS)
Date: 16-03-2006
DOI: 10.1021/AC0521192
Abstract: Electrochemistry at the interface between two immiscible electrolyte solutions has been presented as a method of electrochemically modulated liquid-liquid extraction, where ions in a mixture can be selectively partitioned as a function of the applied interfacial potential difference. In this study, a mixture comprising 4-octylbenzenesulfonate (4-OBSA-) and tetraethylammonium (TEA+) ions was evaluated. The application of negative potential differences enabled the selective extraction of 4-OBSA- into the organic phase, and more positive potential differences enabled the selective extraction of TEA+. However, intermediate potentials lead to the coextraction of both ions into the organic phase, with apparent selectivity for TEA+ over 4-OBSA-. An increased concentration of either ion in the mixture inhibited the extraction response of the other ion, but the order of the extraction at these intermediate potentials was always TEA+ followed by 4-OBSA-. The reasons for the selectivity for the cation over the anion are discussed.
A review of recent advances in electrochemically modulated extraction methods
Publisher: Springer Science and Business Media LLC
Date: 18-09-2009
DOI: 10.1007/S00216-008-2357-5
Abstract: The use of electrochemistry and electrical behavior as a control and manipulation factor in analyte extractions is reviewed. Electromodulated extractions of ionic and neutral analytes are possible using this general approach. Extractions based on solid-liquid, liquid-liquid and membrane behaviors have been demonstrated and reported together with analyte extractions from real matrices and interfacing with instrumental detection methods. The electromodulation strategy offers great opportunities for selectivity in s le preparation.
Zinc Oxide Nanoparticles as Antifouling Materials for the Electrochemical Detection of Methylparaben
Publisher: Wiley
Date: 04-01-2021
Flow-injection amperometry at microfabricated silicon-based μ-liquid–liquid interface arrays
Publisher: Elsevier BV
Date: 05-2010
Secondary Structural Changes in Proteins as a Result of Electroadsorption at Aqueous-Organogel Interfaces
Publisher: American Chemical Society (ACS)
Date: 12-03-2019
DOI: 10.26434/CHEMRXIV.7466789.V2
Abstract: The electroadsorption of proteins at aqueous-organic interfaces offers the possibility to examine protein structural rearrangements upon interaction with lipophilic phases, without modifying the bulk protein or relying on a solid support. The aqueous-organic interface has already provided a simple means of electrochemical protein detection, often involving adsorption and ion complexation however, little is yet known about the protein structure at these electrified interfaces. This work focuses on the interaction between proteins and an electrified aqueous-organic interface via controlled protein electroadsorption. Four proteins known to be electroactive at such interfaces were studied: lysozyme, myoglobin, cytochrome c, and hemoglobin. Following controlled protein electroadsorption onto the interface, ex situ structural characterization of the proteins by FTIR spectroscopy was undertaken, focusing on secondary structural traits within the amide I band. The structural variations observed included unfolding to form aggregated anti-parallel β-sheets, where the rearrangement was specifically dependent on the interaction with the organic phase. This was supported by MALDI ToF MS measurement, which showed the formation of protein-anion complexes for three of these proteins, and molecular dynamic simulations, which modelled the structure of lysozyme at an aqueous-organic interface. Based on these findings, the modulation of protein secondary structure by interfacial electrochemistry opens up unique prospects to selectively modify proteins.
Theory of electrochemistry at miniaturised interfaces between two immiscible electrolyte solutions
Publisher: Elsevier BV
Date: 02-2017
Electrochemical Characterization of an Oleyl-coated Magnetite Nanoparticle-Modified Electrode
Publisher: Wiley
Date: 19-05-2014
Oxygen reduction voltammetry on platinum macrodisk and screen-printed electrodes in ionic liquids: Reaction of the electrogenerated superoxide species with compounds used in the paste of Pt screen-printed electrodes?
Publisher: Elsevier BV
Date: 02-2097
A study of L-cysteine adsorption on gold via electrochemical desorption and copper(II) ion complexation
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A905370K
Electrochemical behaviour of hen-egg-white lysozyme at the polarised water/1, 2-dichloroethane interface
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B815589E
Abstract: The electrochemical behaviour of hen-egg-white lysozyme (HEWL) was studied at the polarized water/1,2-dichloroethane interface. The voltammetric ion-transfer response was found to be dependent on the pH and ionic strength of the aqueous phase solution and also on the nature of the organic phase electrolyte anion. The current-pH behaviour of HEWL was dominated by the charge of the biomolecule at each pH, as indicated by the close relationship between the experimental peak currents and the theoretical curve for HEWL based on its known acid-base chemistry. Three organic electrolyte anions of differing hydrophobicities were investigated (TFPB-, TPBCl- and TPB-) and it was found that the ion transfer voltammetric peaks occurred at successively higher potentials in the order of increasing hydrophobicity, Deltaphi(TPB) < Deltaphi(TPBCl) < Deltaphi(TPBF). The voltammetric response was time dependent during multi-cyclic voltammetry experiments, with the formation of a white film of precipitate at the interface. A pre-peak consistent with adsorption of the HEWL ion transfer product at the liquid/liquid interface was also observed. The results suggest that an adsorption or re-arrangement of HEWL molecules with time at the interface is taking place. A mechanism for the response on application of a triangular potential waveform with cyclic voltammetry is proposed based on an i-C-i mechanism. Our results indicate that HEWL is electroactive at the polarized liquid/liquid interface and that such electrochemical methods may provide an approach to the label-free detection and characterization of protein molecules.
Interactions of proteins with small ionised molecules: Electrochemical adsorption and facilitated ion transfer voltammetry of haemoglobin at the liquidliquid interface
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B905441N
Abstract: The interaction of proteins with interfaces and surfaces provides a basis for studying their behaviour and methods to detect them. This paper is concerned with elucidation of the mechanism of electrochemical detection of haemoglobin (Hb) at the interface between aqueous and organic electrolyte solutions. The adsorption of Hb at the interface was investigated by alternating current (AC) voltammetry. It was found that addition of Hb to the aqueous phase induced a shift of the potential of zero charge at the liquid/liquid interface, due to interfacial adsorption of Hb. The influence of the nature and the concentration of the organic phase electrolyte on the electrochemical signal was investigated by cyclic voltammetry (CV). It was found that the electrochemical signal, in the presence of aqueous phase Hb, was due to the facilitated transfer of the anion of the organic phase electrolyte to the aqueous phase. The transfer current was dependent on both the nature and concentration of the organic phase electrolyte anion. These results confirm that adsorbed Hb molecules at the liquid/liquid interface interact with small ionised molecules and facilitate their transfer across the interface. The results will provide a basis for both biomolecular detection methods and for the study of protein-small ionised molecule interactions.
Electrochemical detection of dopamine using arrays of liquid-liquid micro-interfaces created within micromachined silicon membranes
Publisher: Elsevier BV
Date: 03-2008
DOI: 10.1016/J.ACA.2008.01.077
Abstract: The detection of protonated dopamine by differential pulse voltammetry (DPV) and square wave voltammetry (SWV) at arrays of micro-interfaces between two immiscible electrolyte solutions (microITIES) is presented. Microfabricated porous silicon membranes (consisting of eight pores, 26.6 microm in radius and 500 microm pore-pore separation, in a hexagonal layout) were prepared by photolithographic and etching procedures. The membrane pores were fabricated with hydrophobic internal walls so that the organic phase filled the pores and created the liquid interface at the aqueous side of the membrane. These were used for harnessing the benefits of three-dimensional diffusion to the interface and for interface stabilisation. The liquid-liquid interface provides a simple method to overcome the major problem in the voltammetric detection of dopamine at solid electrodes due to the co-existence of ascorbate at higher concentrations. Selectivity for dopamine over ascorbate was achieved by the use of dibenzo-18-crown-6 (DB18C6) for the facilitated ion transfer of dopamine across the microITIES array. Under these conditions, the presence of ascorbate in excess did not interfere in the detection of dopamine and the lowest concentration detectable was ca. 0.5 microM. In addition, the drawback of current signal saturation (non-linear increase of the peak current with the concentration of dopamine) observed at conventional (millimetre-sized) liquid-liquid interfaces was overcome using the microfabricated porous membranes.
Electroanalytical behavior of poly-l-lysine dendrigrafts at the interface between two immiscible electrolyte solutions
Publisher: American Chemical Society (ACS)
Date: 12-06-2012
DOI: 10.1021/AC300856W
Abstract: In this work, the electrochemical behavior of nonredox-active poly-L-lysine dendrigraft molecules of four different generations was investigated at the interface between two immiscible electrolyte solutions (ITIES). The influence of the dendrigraft generation on the electrochemical response, sensitivity of the calibration curves, and limit of detection was studied. Cyclic voltammetry at the ITIES revealed that the sensitivity increased (1840 to 25 800 nA μM(-1)) and the limit of detection decreased (11.10 to 0.65 μM) as the dendrigraft generation increased from generation G2 through to generation G5, respectively. The results are compared to those for protein voltammetry at the ITIES. Our studies suggest that the sensitivity expected for a synthetic ionized macromolecule can be predicted on the basis of its net charge and its diffusion coefficient. However, electrochemistry at the ITIES demonstrates a greater sensitivity toward proteins, which is attributed to their tertiary structure.
Ionophore-Assisted Electrochemistry of Neutral Molecules: Oxidation of Hydrogen in an Ionic Liquid Electrolyte
Publisher: American Chemical Society (ACS)
Date: 22-10-2019
DOI: 10.26434/CHEMRXIV.7900943
Abstract: The electrochemical properties of gas molecules are of great interest for both fundamental and applied research. In this study, we introduce a novel concept to systematically alter the electrochemical behavior and, in particular, the redox potential of neutral gas molecules. The concept is based on the use of an ion-binding agent, or ‘ionophore’, to bind and stabilize the ionic electrochemical reaction product. We demonstrate that the ionophore-assisted electrochemical oxidation of hydrogen in a room temperature ionic liquid electrolyte is shifted by almost 1 V towards more negative potentials in comparison to an ionophore-free electrolyte. The altered electrochemical response in the presence of the ionophore not only yields insights into the reaction mechanism but can be used also to determine the diffusion coefficient of the ionophore species. This ionophore-modulated electrochemistry of neutral gas molecules opens up new avenues for the development of highly selective electrochemical sensors.
Ionophore-Assisted Electrochemistry of Neutral Molecules: Oxidation of Hydrogen in an Ionic Liquid Electrolyte
Publisher: American Chemical Society (ACS)
Date: 22-10-2019
DOI: 10.26434/CHEMRXIV.7900943.V2
Abstract: The electrochemical properties of gas molecules are of great interest for both fundamental and applied research. In this study, we introduce a novel concept to systematically alter the electrochemical behavior and, in particular, the redox potential of neutral gas molecules. The concept is based on the use of an ion-binding agent, or ‘ionophore’, to bind and stabilize the ionic electrochemical reaction product. We demonstrate that the ionophore-assisted electrochemical oxidation of hydrogen in a room temperature ionic liquid electrolyte is shifted by almost 1 V towards more negative potentials in comparison to an ionophore-free electrolyte. The altered electrochemical response in the presence of the ionophore not only yields insights into the reaction mechanism but can be used also to determine the diffusion coefficient of the ionophore species. This ionophore-modulated electrochemistry of neutral gas molecules opens up new avenues for the development of highly selective electrochemical sensors.
Ion-transfer voltammetry at silicon membrane-based arrays of micro-liquid-liquid interfaces
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B712601H
Abstract: Microporous silicon membranes, fabricated by lithographic patterning and wet and dry silicon etching processes, were used to create arrays of micro-scale interfaces between two immiscible electrolyte solutions (muITIES) for ion-transfer voltammetry. These membranes served the dual functions of interface stabilization and enhancement of the rate of mass-transport to the interface. The pore radii were 6.5 microm, 12.8 microm and 26.6 microm the pore-pore separations were ca. 20- to 40-times the pore radii and the membrane thickness was 100 microm. Deep reactive ion etching (DRIE) was used for pore drilling through the silicon, which had been previously selectively thinned by potassium hydroxide etching. DRIE produces hydrophobic fluorocarbon-coated internal pore walls. The small pore sizes and large pore-pore separations used resulted in steady-state voltammograms for the transfer of tetramethylammonium cation (TMA(+)) from the aqueous to the organic phase, whereas the reverse voltammetric sweeps were peak-shaped. These asymmetric voltammograms are consistent with the location of the ITIES at the aqueous side of the silicon membrane such that the organic phase fills the micropores. Comparison of the experimental currents to calculated currents for an inlaid disc micro-interface revealed that the interfaces were slightly recessed, up to 10 microm (or 10% of the pore length) in one case. Facilitated ion transfer, with an organic-phase ionophore, confirmed the location of the organic phase within the pores. These microporous silicon membranes offer opportunities for various analytical operations, including enhancing the rate of mass transport to ITIES-based sensing devices and stabilization of the ITIES for hydrodynamic applications.
Ionophore-Assisted Electrochemistry of Neutral Molecules: Oxidation of Hydrogen in an Ionic Liquid Electrolyte
Publisher: American Chemical Society (ACS)
Date: 27-03-2019
DOI: 10.26434/CHEMRXIV.7900943.V1
Abstract: The electrochemical properties of gas molecules are of high interest for both fundamental and applied research. In this study, we introduce a novel concept to systematically alter the electrochemical behavior and, in particular, the redox potential of neutral gas molecules. The concept is based on the use of an ionophore to bind and stabilize the ionic electrochemical reaction product. We demonstrate that the ionophore-assisted electrochemical oxidation of hydrogen in a room temperature ionic liquid electrolyte is shifted by almost 1 V towards more negative potentials in comparison to an ionophore-free electrolyte. The altered electrochemical response in the presence of the ionophore yields insights into the reaction mechanism and can be used to determine the diffusion coefficient of the ionophore species. The ionophore-modulated electrochemistry of neutral gas molecules opens new avenues for the development of selective electrochemical sensors with reduced cross-sensitivity.
DNA arrays, electronic noses and tongues, biosensors and receptors for rapid detection of toxigenic fungi and mycotoxins: A review
Publisher: Informa UK Limited
Date: 04-2005
DOI: 10.1080/02652030500070176
Abstract: This paper presents an overview of how microsystem technology tools can be applied to the development of rapid, out-of-laboratory measurement capabilities for the determinations of toxigenic fungi and mycotoxins in foodstuffs. Most of the topics discussed are all under investigation within the European Commission-sponsored project Good-Food (FP6-IST). These are DNA arrays, electronic noses and electronic tongues for the detection of fungal contaminants in feed, and biosensors and chemical sensors based on microfabricated electrode systems, antibodies and novel synthetic receptors for the detection of specific mycotoxins. The approach to resolution of these difficult measurement problems in real matrices requires a multidisciplinary approach. The technology tools discussed can provide a route to the rapid, on-site generation of data that can aid the safe production of high-quality foodstuffs.
Square-wave voltammetric transfer of silver ions across the water| 1,2-dichloroethane interface
Publisher: Wiley
Date: 08-2004
Electrochemically modulated liquid-liquid extraction of ionized drugs under physiological conditions
Publisher: American Chemical Society (ACS)
Date: 09-10-2008
DOI: 10.1021/AC800646B
Abstract: Electrochemically modulated liquid-liquid extraction (EMLLE) enables the selective extraction and separation of ions from mixtures by choice of an applied interfacial potential difference. The extraction of ionized drugs from artificial urine is reported in this paper. The artificial urine matrix was characterized by cyclic voltammetry at the interface between two immiscible electrolyte solutions (ITIES), showing that components of that aqueous phase truncate the available potential window at the ITIES. The transfer of three cationic drugs from aqueous artificial urine to the 1,2-dichloroethane organic electrolyte phase was examined. Both propranolol and timolol were found to transfer across the artificial urine-organic interface. However, sotalol transfer was not possible within the available potential window. Extraction of propranolol and timolol from artificial urine into an organogel phase, by electrochemically modulated liquid-liquid extraction, was examined. The application of potentials positive of the drugs' formal transfer potentials enabled the selective extraction of both propranolol and timolol, with a higher potential being required for timolol. This work demonstrates the practical utility of EMLLE for the selective extraction of target compounds from a complex s le matrix.
Electrochemical activity of phenolic calixarenes
Publisher: Elsevier BV
Date: 2003
Use of calixarenes as modifiers of carbon paste electrodes for voltammetric analysis
Publisher: Wiley
Date: 02-1994
Interfacial behavior of p-hexasulfonato-calix[6]arene at glassy carbon electrodes in alkaline aqueous solution studied by voltammetric methods
Publisher: American Chemical Society (ACS)
Date: 30-10-2002
DOI: 10.1021/LA0263211
Application of disorganized monolayer films on gold electrodes to the prevention of surfactant inhibition of the voltammetric detection of trace metals via anodic stripping of underpotential deposits: Detection of copper
Publisher: American Chemical Society (ACS)
Date: 17-12-2003
DOI: 10.1021/AC026093F
Abstract: Development of an approach to prevention of electrode surface fouling by surfactants in s les is demonstrated. Spontaneously adsorbed monolayer systems employing short alkyl chains and bulky end groups are used to form porous disorganized monolayers on gold electrodes. Detection of copper by stripping of underpotential deposits formed at electrodes modified with disorganized films of mercaptoethanesulfonate (MES), mercaptopropanesulfonate, mercaptoacetic acid, and mercaptopropanoic acid was possible, and to a much lesser extent at aminoethanethiol and L-cysteine films. Use of short deposition times in conjunction with linear sweep anodic stripping voltammetry allowed detection of Cu2+ ions down to 1 x 10(-6) M in sulfuric acid solution, using underpotential deposition as the deposition step of the procedure. Calibration graphs were linear in the concentration range (1-80) x 10(-6) M Cu2+ using 15-s deposition at 0.00 V versus Ag/AgCl. The surfactants Tween 20, Tween 80, and Triton X-100 were found to have no affect on detection of Cu2+ ions in the calibration curve concentration range using MES-modified gold electrodes, whereas at unmodified gold electrodes very severe attenuation of the detection capability was manifested. The average slope for all calibration curves at the MES-modified electrode in the absence and presence of the surfactants at two different concentration levels was 0.0710 +/- 0.0024 microA microM(-1) in contrast, the slope of the calibration line at uncoated gold electrodes in the presence of surfactant was 0.0268 microA microM(-1). These results indicate the excellent ability of a disorganized, porous monolayer for prevention of fouling of the electrode surface by the surfactants.
Electroactivity of Aptamer at Soft Microinterface Arrays
Publisher: American Chemical Society (ACS)
Date: 12-06-2018
DOI: 10.1021/ACS.ANALCHEM.8B01172
Abstract: The electrochemical behavior of a synthetic oligonucleotide, thrombin-binding aptamer (TBA, 15-mer), was explored at a liquid-organogel microinterface array. TBA did not display any response when only background electrolytes were present in both phases. On the basis of literature reports that surfactants can influence nucleic acid detection, the response in the presence of cetyltrimethylammonium (CTA
Investigation into the voltammetric behaviour and detection of selenium(IV) at metal electrodes in diverse electrolyte media
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.ACA.2011.05.027
Abstract: The voltammetric behaviour of selenium(IV) was studied at platinum and gold electrodes in sulphuric acid, perchloric acid and potassium chloride media as a basis for its voltammetric detection. The best voltammetric behaviour was recorded at gold electrodes with perchloric acid as the supporting electrolyte. The concomitant presence of metals, such as copper or lead, and of model biomolecules, such as bovine serum albumin, in the solution resulted in a deterioration of the electrochemical response for selenium(IV). Quantitative detection of selenium(IV) by square wave anodic stripping voltammetry at both a millimetre-sized gold disc electrode and a microband electrode array revealed linear responses to selenium concentration in the ranges 5-15 μM and 0.1-10 μM, respectively, with 60s preconcentration. The sensitivities were 6.4 μA μM(-1) cm(-2) and 100 μA μM(-1) cm(-2) at the disc and the microband array, respectively. The detection limit at the microband electrode array was 25 nM, illustrating the potentiality of such microelectrodes for the development of mercury-free analytical methods for the trace detection of selenium(IV).
Probing Interfacial Co‐Crystallisation using Simultaneous Potential and Current Measurements at Liquid‐Liquid Interfaces Polarised by Common Ion Approach
Publisher: Wiley
Date: 11-11-2022
Abstract: The simultaneous measurement of potential and current variations at the interface between two immiscible electrolyte solutions, which was polarised using tetraalkylammonium cations as a common ion, is reported here. Various concentration ratios of tetramethyl‐, tetraethyl‐, or tetrapropylammonium were dissolved in each phase. Such biphasic systems were then used to verify that the measured interfacial potential difference agreed with theory. This experimental set‐up was then used to probe the interfacial cocrystallisation process of hydrophilic, cationic caffeine with lipophilic 1‐hydroxy‐2‐naphtoic acid (1H2N). The presence of caffeine in the aqueous phase led to higher current values, caused by interfacial charge transfer. Electrochemical noise analysis suggested that a two‐step process was occurring at the ITIES (i) a potential‐driven nucleation with the transfer of caffeine from the aqueous to the organic phase (ii) a growth stage where the interfacial potential no longer plays a role.
Nanoelectrodes, nanoelectrode arrays and their applications
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B415395M
Abstract: This review deals with the topic of ultrasmall electrodes, namely nanoelectrodes, arrays of these and discusses possible applications, including to analytical science. It deals exclusively with the use of nanoelectrodes in an electrochemical context. Benefits that accrue from use of very small working electrodes within electrochemical cells are discussed, followed by a review of methods for the preparation of such electrodes. In idual nanoelectrodes and arrays or ensembles of these are addressed, as are nanopore systems which seek to emulate biological transmembrane ion transport processes. Applications within physical electrochemistry, imaging science and analytical science are summarised.
Electrochemical behaviour at a liquid-organogel microinterface array of fucoidan extracted from algae
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7AN00761B
Abstract: The electrochemical behaviour of fucoidan, a sulfated polysaccharide, was investigated, leading to a detection strategy by adsorptive stripping voltammetry.
Development of a portable electroanalytical system for the stripping voltammetry of metals: Determination of copper in acetic acid soil extracts
Publisher: Elsevier BV
Date: 11-2005
Electropolishing of medical-grade stainless steel in preparation for surface nano-texturing
Publisher: Springer Science and Business Media LLC
Date: 06-09-2012
Electrochemical overoxidation of polyindole and its cation-permselective behavior
Publisher: Wiley
Date: 06-2004
Electrochemical oxidation of a hexasulfonated calix[6]arene
Publisher: Elsevier BV
Date: 07-2001
Ion-Transfer Electrochemistry of Rat Amylin at the Water-Organogel Microinterface Array and Its Selective Detection in a Protein Mixture
Publisher: Wiley
Date: 07-06-2013
Abstract: The behavior of proteins and polypeptides at electrified aqueous-organic interfaces is of benefit in label-free detection strategies. In this work, rat amylin (or islet amyloid polypeptide) was studied at the interface formed between aqueous liquid and gelled organic phases. Amylin is a polypeptide that is co-secreted with insulin from islet beta-cells and is implicated in fibril formation. In this study, rat amylin was used, which does not undergo aggregation. The polypeptide underwent an interfacial transfer process, from water to the gelled organic phase, under applied potential stimulation. Cyclic voltammetry revealed steady-state forward and peak-shaped reverse voltammograms, which were consistent with diffusion-controlled water-to-organic transfer and thin-film stripping or desorptive back-transfer. The diffusion-controlled forward current was greater when amylin was present in an acidic aqueous phase than when it was present in an aqueous phase at physiological pH this reflects the greater charge on the polypeptide under acidic conditions. The amylin transfer current was concentration dependent over the range 2-10 μM, at both acidic and physiological pH. At physiological pH, amylin was selectively detected in the presence of a protein mixture, which illustrated the bioanalytical possibilities for this electrochemical behavior.
Dopamine voltammetry at overoxidised polyindole electrodes
Publisher: Elsevier BV
Date: 10-2004
Analysis of inorganic solids by laser ablation inductively coupled plasma spectrometry
Publisher: Royal Society of Chemistry (RSC)
Date: 1992
DOI: 10.1039/AP9922900023
Voltammetric characterisation of silicon-based microelectrode arrays and their application to mercury-free stripping voltammetry of copper ions
Publisher: Elsevier BV
Date: 28-02-2007
DOI: 10.1016/J.TALANTA.2006.05.090
Abstract: This paper describes the electrochemical characterisation of a range of gold and platinum microelectrode arrays (MEAs) fabricated by standard photolithographic methods. The inter-electrode spacing, geometry, numbers and dimensions of the electrodes in the arrays were found to influence the voltammetric behaviours obtained. Excellent correlation was found between experimental data and theoretical predictions employing published models of microelectrode behaviour. Gold MEAs were evaluated for their applicability to copper determination in a soil extract s le, where agreement was found between the standard analytical method and a method based on underpotential deposition-anodic stripping voltammetry (UPD-ASV) at the MEAs, offering a mercury-free alternative for copper sensing.
Electrochemical Behavior and Detection of Sulfated Sucrose at a Liquid|Organogel Microinterface Array
Publisher: American Chemical Society (ACS)
Date: 03-08-2018
DOI: 10.1021/ACS.ANALCHEM.8B01710
Abstract: The electrochemical behavior and detection of sulfated carbohydrates were investigated at an array of microinterfaces between two immiscible electrolyte solutions where the organic phase was gelled. It was found that the electrochemical signal was dependent on the organic phase electrolyte cation. Cyclic voltammetry (CV) of sucrose octasulfate (SOS) with bis(triphenylphosphoranylidene)ammonium BTPPA
Electrochemical behaviour and voltammetric sensitivity at arrays of nanoscale interfaces between immiscible liquids
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1AN15509A
Abstract: Arrays of nanoscale interfaces between immiscible electrolyte solutions were formed using silicon nitride nanopore array membranes. Nanopores in the range from 75 nm radius down to 17 nm radius were used to form the nano-interfaces. It was found that the liquid organic phase electrolyte solution filled the pores so that inlaid nano-interfaces were formed with the aqueous phase. Cyclic voltammetry at these nano-interface arrays demonstrated steady-state behaviour at the larger interfaces but the voltammetric wave-shape became progressively worse as the interface size decreased. It was found that the ion transfer currents were ca. 50% of those expected based on theoretical calculations, which is attributed to overlap of diffusion zones at adjacent nano-interfaces. Here, the separation between adjacent nano-interfaces was 20-times the interface radius. The analytical sensitivity for ion transfer from the aqueous to the 1,6-dichlorohexane organic phase was estimated from calibration plots of current density versus concentration of aqueous tetraethylammonium cation. The sensitivity was in the range of 65 μA cm(-2) μM(-1) (at 75 nm radius interfaces) to 265 μA cm(-2) μM(-1) (at 17 nm radius interfaces). The sensitivity depended directly on the inverse of the nano-interface radius, implying that smaller interfaces will provide better sensitivity, due to the enhanced flux of analyte arising from convergent diffusion to smaller electrochemical interfaces.
Voltammetry of proteins at liquid-liquid interfaces
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3PC90007J
Electrochemical characterization of regularly-aligned nanopore array membranes filled with electrolyte solutions and their use for detection of nucleic acid hybridization
Publisher: The Electrochemical Society
Date: 25-04-2011
DOI: 10.1149/1.3571974
Abstract: We report on the electrochemical characterization of regularly-aligned cylindrical nanopore arrays supported in silicon nitride membranes and preliminary results for the detection of nucleic acid hybridization on the nanopore walls. A range of nanopore arrays with diameters between 30 and 150 nm were examined. We tested the effect of pore diameter, number of pores, electrolyte concentration and surface chemistry on the conductance of the nanopore membranes. The pores were functionalized with single-stranded DNA and conductance measurements were performed before and after hybridization. In many cases, changes in current rectification were observed following hybridization, which is discussed as a strategy for nucleic acid hybridization and interactions.
Potentiometric evaluation of calix[4]arene anion receptors in membrane electrodes: Phosphate detection
Publisher: Elsevier BV
Date: 02-2007
DOI: 10.1016/J.ACA.2006.11.078
Abstract: Ion-selective membrane electrodes doped with the urea- or thiourea-functionalised calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-N'-(phenylureido)butyl]oxy]-26,28-dipropoxy calix[4]arene (I) and 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-(N'-phenylthioureido)-butyl]oxy]-26,28-dipropoxy calix[4]arene (II), were evaluated for anion sensing. Potentiometric results show that these calixarene ionophore-based membrane electrodes exhibit a good sensitivity to aqueous solutions of the monohydrogen orthophosphate species HPO(4)(2-) in the concentration range 5.0 x 10(-5) to 1.0 x 10(-1)M, with near-Nernstian response slopes of -33.0 and -28.0 mV dec(-1) for ionophores I and II, respectively. Selectivity coefficient values for monohydrogen orthophosphate over a range of common anions were determined by the fixed interference and matched potential methods and indicated that these membrane electrodes exhibit a good selectivity for HPO(4)(2-) with respect to the other anions, including sulfate and nitrate.
Electrochemical behaviour of denatured haemoglobin at the liquid|liquid interface
Publisher: Elsevier BV
Date: 03-2010
Cyclic and pulse voltammetric study of dopamine at the interface between two immiscible electrolyte solutions
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.BIOS.2004.08.004
Abstract: The detection of dopamine by differential pulse voltammetry (DPV) and square wave voltammetry (SWV) at the interface between two immiscible electrolyte solutions (ITIES) has been studied. Voltammetry at the liquid/liquid (water/1,2-dichloroethane) interface provides a simple method for overcoming the major problem associated with dopamine detection by voltammetry at solid electrodes: the co-existence of ascorbate at higher concentrations. Selectivity for dopamine was achieved by the use of dibenzo-18-crown-6 as an ionophore for the facilitated transfer voltammetry of protonated dopamine across the ITIES. Under these conditions, ascorbate is not transferred and hence does not interfere in the ion transfer current for dopamine. By use of DPV and SWV, the lowest concentration detectable can be lowered from ca. 0.1 mM (obtained with cyclic voltammetry) to 2 microM. Evaluation of the effect of some other physiologically important species (acetylcholine, sodium, potassium and ammonium ions) on the dopamine transfer voltammetry has been studied, indicating the need for improved ionophore designs in order to achieve practically useful selectivity.
A scanning force microscopy study of poly(phenol) films containing immobilized glucose oxidase
Publisher: Elsevier BV
Date: 03-1998
Removal of arsenic from gold processing circuits by use of novel magnetic nanoparticles
Publisher: Informa UK Limited
Date: 26-10-2017
Array of water|room temperature ionic liquid micro-interfaces
Publisher: Elsevier BV
Date: 05-2011
Pharmaceutical modulation of diffusion potentials at aqueous-aqueous boundaries under laminar flow conditions
Publisher: Wiley
Date: 16-03-2011
Abstract: In this work, the modulation of the diffusion potential formed at the microfluidic aqueous-aqueous boundary by a pharmaceutical substance is presented. Co-flowing aqueous streams in a microchannel were used to form the stable boundary between the streams. Measurement of the open circuit potential between two silver/silver chloride electrodes enabled the diffusion potential at the boundary to be determined, which is concentration dependent. Experimental results for protonated propranolol as well as tetrapropylammonium are presented. This concept may be useful as a strategy for the detection of drug substances.
Electrochemistry of Non-Redox-Active Poly(propylenimine) and Poly(amidoamine) Dendrimers at Liquid−Liquid Interfaces
Publisher: American Chemical Society (ACS)
Date: 22-05-2007
DOI: 10.1021/LA063294W
Abstract: The electrochemistry of a series of dendrimers was examined at the interface between two immiscible electrolyte solutions (ITIES), enabling study of non-redox-active dendrimers. Different generations of poly(propylenimine) (DAB-AM-n) and poly(amidoamine) (PAMAM) dendrimers were studied. In their protonated states, the dendrimers were transferred across the ITIES, with the electrochemical behavior observed depending on the dendrimer family, the generation number, and the experimental pH. The electrochemistry of the lower generations studied was characterized by well-defined peaks for both dendrimer families and with small peak-peak separations in the case of the PAMAM family. The voltammetry of the higher generations was more complex, showing distorted voltammograms and instability of the interface. The charges of the transferring dendrimers were calculated by convolution of the voltammetric data and were similar to the theoretical charges for DAB-AM-n. For PAMAM, only the lowest generation exhibited reversible behavior, with higher generations having irreversible behavior. Using cyclic voltammetry, low micromolar concentrations of the dendrimers were detected. The results show that electrochemistry at the ITIES can be a useful method for characterization of ionizable dendrimers and that voltammetry can be a simple method for detection of low concentrations of these multicharged species.
Stir-bar adsorptive extraction on a poly(tetrafluoroethylene) coated stir-bar: Preliminary evaluation using phenanthrene
Publisher: Informa UK Limited
Date: 08-05-2002
DOI: 10.1081/AL-120006678
Macromolecular sensing at the liquid-liquid interface
Publisher: IOP Publishing
Date: 17-08-2011
Potentiometric investigation of protonation reactions at aqueous-aqueous boundaries within a dual-stream microfluidic structure
Publisher: American Chemical Society (ACS)
Date: 10-11-2010
DOI: 10.1021/LA102149C
Abstract: The laminar flow regime prevailing in pressure-driven flow through a Y-shaped microfluidic channel was utilized to create a stable boundary between two aqueous liquids. Transverse transport of ions between these two liquids gave rise to a diffusion potential, which was monitored by measurement of the open circuit potential. In this report, the influence on the cross-channel potential distribution of protonation reactions occurring in the boundary zone between the two co-flowing liquids is presented. The proton source was present in one of the co-flowing streams, and an uncharged proton acceptor was present in the other aqueous stream. The time-dependent transport equation for diffusion and migration was augmented by chemical reaction terms and was solved for all species present in both streams as a theoretical basis for the analysis. Within this model, the system was assumed to be homogeneous along the channel height, and effects of nonuniform velocity profiles were neglected. A reduction in potential by several millivolts was predicted for a protonation reaction occurring close to the boundary between the two aqueous streams, provided that the mobility of the protonated species was lower than the mobility of the co-cation in the background electrolyte (alkali metal cation in this case). The magnitude of the decrease in the potential was greater for protonated molecules with lower mobility or if the mobility of the background electrolyte cation was increased. Experimental results are presented for imidazole and D-histidine as proton acceptors present in 10 mM KCl, 10 mM NaCl, or 10 mM CsCl solution and co-flowing with a stream of 10 mM hydrochloric acid, which served as the proton source. Decreases in measured potential, in line with the predicted diminished potential, were obtained.
Spontaneous formation of barium sulfate crystals at liquid–liquid interfaces
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CE01102F
Abstract: Interfacial ion transfer from organic phase to aqueous phase is employed as the basis for formation of barium sulfate crystals close to the interface.
Ion-transfer electroanalytical detection of perfluorooctanoic acid at a liquid–liquid micro-interface array
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3SD00080J
Abstract: Ion transfer voltammetry of de-ionised perfluorooctanoic acid (PFOA) was employed to achieve nanomolar detection and to assess s le matric effects.
Fabrication and electrochemical characterization of micro- and nanoelectrode arrays for sensor applications
Publisher: IOP Publishing
Date: 17-08-2011
Detection of Perfluorooctane Sulfonate by Ion-Transfer Stripping Voltammetry at an Array of Microinterfaces Between Two Immiscible Electrolyte Solutions
Publisher: American Chemical Society (ACS)
Date: 02-07-2020
DOI: 10.26434/CHEMRXIV.12236240.V2
Abstract: We present an analytical approach for the detection of perfluorooctane sulfonate (PFOS) by ion transfer stripping voltammetry at an array of micro-interfaces between two immiscible electrolyte solutions. With this approach, picomolar concentrations are detected and environmental matrix effects are evaluated.
Detection of Perfluorooctane Sulfonate by Ion-Transfer Stripping Voltammetry at an Array of Microinterfaces Between Two Immiscible Electrolyte Solutions
Publisher: American Chemical Society (ACS)
Date: 05-05-2020
DOI: 10.26434/CHEMRXIV.12236240.V1
Abstract: We present an analytical approach for the detection of perfluorooctane sulfonate (PFOS) by ion transfer stripping voltammetry at an array of micro-interfaces between two immiscible electrolyte solutions. With this approach, picomolar concentrations are detected and environmental matrix effects are evaluated.
Removal of arsenic from gold cyanidation process waters by use of cerium-based magnetic adsorbents
Publisher: Elsevier BV
Date: 06-2018
Adsorption and Unfolding of Lysozyme at a Polarized Aqueous-Organic Liquid Interface
Publisher: American Chemical Society (ACS)
Date: 18-03-2016
Abstract: The adsorption of proteins at the interface between two immiscible electrolyte solutions has been found to be key to their bioelectroactivity at such interfaces. Combined with interfacial complexation of organic phase anions by cationic proteins, this adsorption process may be exploited to achieve nanomolar protein detection. In this study, replica exchange molecular dynamics simulations have been performed to elucidate for the first time the molecular mechanism of adsorption and subsequent unfolding of hen egg white lysozyme at low pH at a polarized 1,2-dichloroethane/water interface. The unfolding of lysozyme was observed to occur as soon as it reaches the organic-aqueous interface, which resulted in a number of distinct orientations at the interface. In all cases, lysozyme interacted with the organic phase through regions rich in nonpolar amino acids, such that the side chains are directed toward the organic phase, whereas charged and polar residues were oriented toward the aqueous phase. By contrast, as expected, lysozyme in neat water at low pH does not exhibit significant structural changes. These findings demonstrate the key influence of the organic phase upon adsorption of lysozyme under the influence of an electric field, which results in the unfolding of its structure.
Ubiquinone electrochemistry in analysis and sensing
Publisher: Wiley
Date: 22-02-2023
Abstract: Ubiquinone (UQ) is a lipophilic compound present in most living organisms, where UQ's interesting but complex electrochemistry serves an important role in the transfer of electrons and protons within and across the mitochondrial membrane. We briefly review the electrochemical characteristics of UQ and its reduced state, ubiquinol, in solution and immobilized on electrodes, together with its application in electrochemical sensing and detection systems, for ex le, measuring redox status with reference to reactive oxidative species. The importance of the local environment, solvent, electrolyte, organic membrane, and pH, on the electrochemical behavior of UQ, is also discussed. We discuss techniques used for the direct detection of UQ such as liquid chromatography‐electrochemistry. Mediated electrochemistry of UQ allows for quantitative measurements of ions, small molecules, and other analytes such as glucose via chemical sensors and biosensors.
Related Organisations
University Of Southampton
Location: United Kingdom of Great Britain and Northern Ireland
University Of Salford
Location: United Kingdom of Great Britain and Northern Ireland
University College Cork National University Of Ireland
Location: Ireland
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