Electrically controlled Michael addition: Addressing of covalent immobilization of biological receptorsPublished: 01 December 2018 by Elsevier BV in Biosensors and Bioelectronics
Electrically addressed covalent immobilization of biomolecules to the defined electrodes of an electrode array is described. It is based on Michael addition of the thiol group of biomolecules to the α,β-unsaturated carbonyl groups of benzoquinone. This “click” reaction was tested by immobilization of a number of thiolated compounds on the simplest array consisting of two gold electrodes coated by a self-assembled monolayer of benzoquinone terminated hexanethiol. Electrically controlled binding of hexanethiol, ferrocenyl-hexanethiol, human serum albumin and thiol-terminated single-stranded DNA (ssDNA) was studied. The binding was studied using cyclic voltammetry, X-ray photoelectron spectroscopy and surface plasmon resonance. The reaction requires the oxidized state of the benzoquinone moiety; this can be reached by applying of a moderate anodic potential to the electrode. Surface plasmon resonance measurements demonstrated that the thiol-modified ssDNA immobilized by this technique binds complementary synthetic oligonucleotides or PCR-amplified DNA fragments. The developed technology of electrical addressing of covalent immobilization can be applied for fabrication of sensor arrays.
Increasing energy demands of modern society requires deep understanding of the properties of energy storage materials as well as their performance tuning. We show that the capacitance of graphene oxide (GO) can be precisely tuned using a simple electrochemical reduction route. In situ resistance measurements, combined with cyclic voltammetry measurement and Raman spectroscopy, have shown that upon the reduction GO is irreversibly deoxygenated which is further accompanied with structural ordering and increasing of electrical conductivity. The capacitance is maximized when the concentration of oxygen functional groups is properly balanced with the conductivity. Any further reduction and de-oxygenation leads to the gradual loss of the capacitance. The observed trend is independent on the preparation route and on the exact chemical and structural properties of GO. It is proposed that an improvement of capacitive properties of any GO can be achieved by optimization of its reduction conditions.
Despite the history of application of surface plasmon resonance (SPR) for chemo- and biosensing being over 30 years long, the development of this technique is still in progress. This review is focused on the technological aspects of further improvement of analytical performance of SPR transducers based on Kretschmann configuration. We describe basic measurement configurations, their improvements and optimizations, and their drawbacks and limitations. An importance of referencing in SPR sensors is highlighted. The referencing approaches are classified into the following domains: (1) macroscopic spatially separated referencing, (2) self-referencing based on micro-patterning, (3) in-place referencing, (4) spatiotemporal referencing, and (5) electrochemically assisted referencing. The underlying principles of these approaches, examples of their implementation, and resulting improvements of sensor performance are described. Finally, an analysis of SPR data and an extraction of affinity properties are discussed.
Wide-Field Surface Plasmon Resonance Microscopy for In-Situ Characterization of Nanoparticle SuspensionsPublished: 25 January 2018 by Springer Nature in In-situ Characterization Techniques for Nanomaterials
During the past two decades, nanomaterials have had an enormous diversity of applications in different industrial fields and fundamental research. Some of these nanomaterials are specifically engineered to exhibit unique optical, electrical, or other physical or chemical characteristics. Owing to these attributes, the products containing various engineered nanoparticles (NP) cover large segments of the market from clothing to electronics and healthcare products . The rapid development of nanotechnologies, their industrial applications, and related nanosafety concerns demand sensitive analytical methods for the identification and analysis of nanoparticles (NPs) in very different media . In the same time, there are serious concerns on possible toxicity of nanoparticles for humans and environment . Engineered NPs (ENPs) have to be analyzed not only during their production, in pure and concentrated form, but also at trace concentrations in environment, drinking water and food, healthcare and pharmacological products, biological fluids, etc. Ideally, such a technique should provide a possibility to detect NPs at the level of single particles and deliver information on their concentration, core and surface chemical composition, size, and shape [2–4].
The capacitance of graphene oxide can be maximized by precise control of the conditions of electrochemical reduction to balance the oxygen concentration and conductivity.
Detection of Single Sub-Micrometer Objects of Biological or Technical Origin Using Wide Field Surface Plasmon MicroscopyPublished: 06 December 2017 by MDPI in Proceedings
Detection of nano- and microparticles is an important task for chemical analytics, medical
In-situ detection and characterization of nanoparticles in biological media as well as in food or other complex samples is still a big challenge for existing analytical methods. Here we describe a label-free and cost-effective analytical method for detection of nanoparticles in the concentration range 106 -1010 NPs/ml. The proposed method is based on the surface plasmon resonance microscopy (SPRM) with a large field of view (~1.3mm2 ). It is able to detect and count adsorbing nanoparticles individually, totally up to the hundreds of thousands of NPs on the sensor surface. At constant diffusion conditions the detection rate is proportional to the number concentration of NPs, this provides an approach to determine the NPs concentration. The adsorption of nanoparticle can be manipulated by the surface functionalization, pH and electrolyte concentration of suspensions. Images of detected nanoparticles can be quantified in order to characterize them individually. The image intensity grows quasi-linearly with nanoparticle size for the given material. However, the size and material of nanoparticle cannot be resolved directly from the image. For determination of chemical composition, SPRM can be assisted by electrochemical analysis. In this case, the gold sensor surface is used both as a resonant media for plasmon microscopy and as a working electrode. Under potential sweep, the adsorbed NPs can be subjected to electrochemical dissolution, which is detected optically. The potential of this conversion characterizes the material of NPs. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Wide-field surface plasmon microscopy of nano- and microparticles: features, benchmarking, limitations, and bioanalytica...Published: 16 May 2017 by SPIE-Intl Soc Optical Eng in Optical Sensors 2017
Detection of nano- and micro-particles is an important task for chemical analytics, food industry, biotechnology, environmental monitoring and many other fields of science and industry. For this purpose, a method based on the detection and analysis of minute signals in surface plasmon resonance images due to adsorption of single nanopartciles was developed. This new technology allows one a real-time detection of interaction of single nano- and micro-particles with sensor surface. Adsorption of each nanoparticle leads to characteristic diffraction image whose intensity depends on the size and chemical composition of the particle. The adsorption rate characterizes volume concentration of nano- and micro-particles. Large monitored surface area of sensor enables a high dynamic range of counting and to a correspondingly high dynamic range in concentration scale. Depending on the type of particles and experimental conditions, the detection limit for aqueous samples can be below 1000 particles per microliter. For application of method in complex media, nanoparticle images are discriminated from image perturbations due to matrix components. First, the characteristic SPRM images of nanoparticles (templates) are collected in aqueous suspensions or spiked real samples. Then, the detection of nanoparticles in complex media using template matching is performed. The detection of various NPs in consumer products like cosmetics, mineral water, juices, and wines was shown at sub-ppb level. The method can be applied for ultrasensitive detection and analysis of nano- and micro-particles of biological (bacteria, viruses, endosomes), biotechnological (liposomes, protein nanoparticles for drug delivery) or technical origin. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
The Role of Anion Adsorption in the Effect of Electrode Potential on Surface Plasmon Resonance ResponsePublished: 03 May 2017 by Wiley in ChemPhysChem
Surface plasmon resonance, being widely used in bioanalytics and biotechnology, is influenced by the electrical potential of the resonant gold layer. To evaluate the mechanism of this effect, we have studied it in solutions of various inorganic electrolytes. The magnitude of the effect decreases according to the series: KBr>KCl>KF>NaClO4. The data were treated by using different models of the interface. A quantitative description was obtained for the model, which takes into account the local dielectric function of gold being affected by the free electron charge, diffuse ionic layer near the gold/water interface, and specific adsorption of halides to the gold surface with partial charge transfer. Taking into account that most biological experiments are performed in chloride-containing solutions, detailed analysis of the model at these conditions was performed. The results indicate that the chloride adsorption is the main mechanism for the influence of potential on the surface plasmon resonance. The dependencies of surface concentration and residual charge of chloride on the applied potential were determined.
Ionic Referencing in Surface Plasmon Microscopy: Visualization of the Difference in Surface Properties of Patterned Mono...Published: 14 March 2017 by American Chemical Society (ACS) in Analytical Chemistry
An approach for visualization of patterned monomolecular layers in surface plasmon microscopy (SPM) is suggested. The development of hidden image in SPM is achieved by referencing of images obtained in the presence of electrolytes with a high molar refraction of either anions or cations. A formation of diffuse layer near the charged surface areas leads to the redistribution of ions. The ratio of SPM images allows one to visualize this redistribution and to distinguish surface areas with different properties. The approach is unobtrusive and robust; it can be used with most SPR imaging instruments.
Virtual sensor array consisting of a single sensor element with variable affinity: An application for analysis of fish f...Published: 01 March 2017 by Elsevier BV in Sensors and Actuators B: Chemical
Amino-substituted Tröger’s base: electrochemical polymerization and characterization of the polymer filmPublished: 01 January 2017 by Elsevier BV in Electrochimica Acta
Plasmonic detection and visualization of directed adsorption of charged single nanoparticles to patterned surfacesPublished: 04 October 2016 by Springer Nature in Microchimica Acta
The online version of this article (doi:10.1007/s00604-016-1956-7) contains supplementary material, which is available to authorized users.
Detection and Quantification of Single Engineered Nanoparticles in Complex Samples Using Template Matching in Wide-Field...Published: 26 September 2016 by American Chemical Society (ACS) in Analytical Chemistry
Due to constant necessity to have reliable and sensitive gas sensors in many contemporary technologies, there is a permanent need for development of new sensing platforms with good sensing properties. Here, we demonstrate a novel type of resistive gas sensors based on carbonized polyaniline/Nafion composites. The sensing mechanism of such sensors is based on the sorption of gases by the composites which induce Nafion swelling and decreasing of conductivity. Chemosensitive properties can be tuned by the (i) choice of carbon materials with different conductivities, (ii) Nafion content in the composite, and (iii) thickness of the composite layer. We have shown that the sensors respond to water, acetone, ethanol, and methanol vapors. For the last two cases, we have achieved high sensitivity, fast response, wide concentration range, and good recovery. The use of simultaneous two- and four-point techniques for these sensors provides an internal control of the sensor integrity.
A concept of virtual sensor array based on electrically controlled variation of affinity properties of the receptor layer is described. It was realized on the base of integrated electrochemical chemotransistor containing polyaniline as the receptor layer. Electrical control of the redox state of polyaniline was performed in five-electrode configuration containing four electrodes for conductivity measurements and one Ag/AgCl reference electrode. All the electrodes were integrated on the same glass chip. A room-temperature ionic liquid was used for the electrical connection between the reference electrode and chemosensitive material. Conductivity measurements demonstrated effective potential-controlled electrochemical conversions of the receptor material between different redox states. Binding of trimethylamine at three different potentials, corresponding to the different states of the receptor material, was studied. Concentration dependencies and binding kinetics were analyzed. The results demonstrated that the kinetic as well as the equilibrium binding properties of the receptor layer can be controlled by electrical potential, thus providing a possibility to form a virtual sensor array using only a single sensing element.
Einzelnachweis und elektrochemisch unterstützte Identifizierung adsorbierter Nanopartikel mit Oberflächenplasmonen-Mikro...Published: 03 May 2016 by Wiley in Angewandte Chemie
Die zunehmende Produktion und Verwendung von Nanopartikeln erfordert eine höchst empfindliche analytische Methode für die Quantifizierung und Identifizierung dieser potenziell gefährlichen Materialien. Hier beschreiben wir eine Anwendung der Oberflächenplasmonen-Mikroskopie für den Einzelnachweis jedes einzelnen adsorbierten Nanopartikels und die Sichtbarmachung seiner elektrochemischen Umsetzung. Während die Adsorptionsgeschwindigkeit die Mengenkonzentration der Nanopartikel charakterisiert, bestimmt das Oxidationspotential, bei dem die adsorbierten Nanopartikel optisch verschwinden, die Art ihres Materials. Alle adsorbierten Nanopartikel unterliegen zeitgleich dem Potentialvorschub, werden aber mithilfe ihres elektrochemischen Auflösungspotentials von einem einzelnen bis zu einer Million adsorbierter Partikel individuell identifiziert. Mit dieser Technik wurden Silber- und Kupfernanopartikel untersucht, sie kann aber auch auf viele andere elektrochemisch aktive Nanopartikel übertragen werden.
Individual Detection and Electrochemically Assisted Identification of Adsorbed Nanoparticles by Using Surface Plasmon Mi...Published: 03 May 2016 by Wiley in Angewandte Chemie International Edition
The increasing production and application of nanoparticles necessitates a highly sensitive analytical method for the quantification and identification of these potentially hazardous materials. We describe here an application of surface plasmon microscopy for the individual detection of each adsorbed nanoparticle and for visualization of its electrochemical conversion. Whereas the adsorption rate characterizes the number concentration of nanoparticles, the potential at which the adsorbed nanoparticles disappear during an anodic potential sweep characterizes the type of material. All the adsorbed nanoparticles are subjected to the potential sweep simultaneously; nevertheless, each of the up to a million adsorbed nanoparticles is identified individually by its electrochemical dissolution potential. The technique has been tested with silver and copper nanoparticles, but can be extended to many other electrochemically active nanomaterials.
Influence of synthetic conditions on the structure and electrical properties of nanofibrous polyanilines and their nanof...Published: 01 April 2016 by Elsevier BV in Synthetic Metals
Highlights•Nanofibrous polyanilines were prepared by different polymerization pathways.•Nanofibrous carbonaceous materials are produced by carbonization of polyaniline nanofibers.•Molecular structure, morphology, electrical conductivity and ζ-potential of these materials was studied. AbstractNanofibrous polyanilines (PANIs) were synthesized by several oxidative polymerization pathways that have in common the presence of excess oxidant(s) (ammonium peroxydisulfate and its mixture with hydrogen peroxide), the absence of added acid, and the absence of external template (self-assembly process). Conducting forms of the synthesized PANI nanofibers (re)doped with various acids were further used as precursors for carbonization process to obtain nanofibrous carbonaceous materials (Carb-PANIs). Morphology, molecular structure, surface properties and electrical characteristics of PANI nanofibrous precursors and their carbonized counterparts were studied by scanning electron microscopy, Raman spectroscopy, by measurements of ζ-potential and determination of isoelectric points, as well as by measurements of electrical conductivity. Graphical abstract
Computer assisted detection and quantification of single adsorbing nanoparticles by differential surface plasmon microsc...Published: 15 August 2015 by Springer Nature in Microchimica Acta
Sensitive detection of engineered nanoparticles (NPs) in air and in liquid samples is an important task and still a major challenge in analytical chemistry. Recent work demonstrated that it can be performed using surface plasmon microscopy (SPM) where binding of single NPs to a surface leads to the formation of characteristic patterns in differential SPM images. However, these patterns have to be discriminated from a noisy background. Computer-assisted recognition of nanoparticles offers a solution but requires the development of respective tools for data analysis. Hereby a numerical method for automated detection and characterization of images of single adsorbing NPs in SPM image sequences is presented. The detection accuracy of the method was validated using computer generated images and manual counting. The method was applied for detecting and imaging of gold and silver NPs adsorbing from aqueous dispersions and for soot and NaCl NPs adsorbing from aerosols. The determined adsorption rate was in range 0.1–40 NPs per (s mm2) and linearly dependent on the concentration of nanoparticles. Depending on the type of NPs and signal to noise ratio, a probability of recognition of 90–95 % can be achieved. Graphical Abstract A computer-assisted method is presented for the detection and characterization of images of single adsorbing nanoparticles in surface plasmon microscopy images. The method was validated and can be applied to detecting and imaging of nanoparticles absorbed from aqueous dispersions and aerosols.
Self-referencing SPR-sensor based on integral measurements of light intensity reflected by arbitrarily distributed sensi...Published: 01 February 2015 by Elsevier BV in Sensors and Actuators B: Chemical
Terahertz split-ring metamaterials as transducers for chemical sensors based on conducting polymers: a feasibility study...Published: 01 May 2014 by Springer Nature in Microchimica Acta
We report on the first application of terahertz metamaterials acting as transducers for chemical sensors based on conducting polymers. In our feasibility study aimed at sensing of gaseous hydrochloric and ammonia, a two-dimensional sensor metamaterial consisting of an array of split-ring resonators on the surface of undoped silicon wafer was prepared. The surface of the resonator was coated with a 150-μm layer of polyaniline. Binding of hydrogen chloride to polyaniline leads to distinct changes in the resonance frequency of the metamaterial. Measurements can be performed both in the reflection and transmission mode. A numerical simulation of the response revealed an increase of both the real and the imaginary components of the dielectric function of the polyaniline film. These changes are attributed to the transition from emaraldine base to emeraldine salt. The results demonstrate a new approach for formation of highly sensitive transducers for chemical sensors.
The edition of this Special Issue was commenced in 2013 at the occasion of the 60th anniversary of the elucidation of DNA structure. This milestone has completely changed biological and medical sciences and, more recently, has triggered the development of sophisticated instrumentation. The discovery of the polymerase chain reaction (PCR) has further promoted this trend and now allows the analysis of a DNA sequences even at a level of a single molecule. Similarly, various miniaturized chip-based approaches have been introduced in the past 10 years.
A clearing assay for lipolytic enzymes has been realized in 96-well microtiter plates. A thin layer containing emulsified tributyrin as turbidity-generating substrate was placed on a thicker supporting aqueous layer. Both layers were stabilized by a gel-forming agent. Enzyme addition leads to clearing of the emulsion detected with a standard microtiter plate reader as a decrease of extinction. Dependencies of the signal kinetics on the substrate and enzyme concentrations were studied. For 0.5–1 % tributyrin content the reaction rate is not substrate-limited. An initial slope of the signal kinetics is proportional to the lipase activity. A detailed characterization of the assay was performed. Lipolysis of tributyrin was confirmed by glycerol detection. Various gel-forming agents were compared and diffusion conditions in these gels were analyzed. Agar and agarose were found to be the most suitable gel-forming agents, which do not affect enzyme diffusion whereas polyacrylamide gels block lipase diffusion and therefore are not suitable for the assay. The optimized assay prepared from 1 % tributyrin emulsion in 2 % agar gel was tested with six microbial lipases and porcine pancreatic lipase. The detection limit is 20–60 ng/well which is equivalent to 30 μU/well for T. lanuginosus lipase.
Polyaniline doped with poly(acrylamidomethylpropanesulphonic acid): electrochemical behaviour and conductive properties ...Published: 01 January 2013 by Walter de Gruyter GmbH in Chemical Papers
Poly(2-acrylamido-2-methyl-1-propanesulphonic acid) (PAMPSA)-doped polyaniline (PANI) layers are synthesised in the presence of sulphuric and perchloric acids. The effects of the inorganic acid as well as of the electrochemical synthetic procedure (potentiostatic and potentiodynamic deposition) and thickness of the polymer layers are studied. The focus is directed towards the pH dependence of the electrochemical redox activity and conductivity of the PAMPSA-doped PANI layers obtained under different conditions. Ascorbic acid oxidation is used as a test reaction to study the electrocatalytic behaviour of various PAMPSA-doped PANI layers in neutral solution. It is found that the type of inorganic component present in the polymerisation solution has a marked effect on the extent of doping in acidic solutions as well as on the redox electroactivity in neutral solutions. A comparison between potentiostatically and potentiodynamically synthesised layers at pH 7 shows a markedly lower conductance and lower extent of redox charge preservation in the case of potentiodynamic synthesis. The PANI electrocatalytic activity for ascorbic acid oxidation is also dependent on the polymer electrodeposition procedure, with potentiostatically synthesised layers exhibiting better electrocatalytic performance.
Electroanalytical measurements without electrolytes: Conducting polymers as probes for redox titration in non-conductive...Published: 01 September 2012 by Elsevier BV in Analytica Chimica Acta
Electroanalytical methods have been applied only in conducting media. An application of conducting polymers allows to overcome this limitation. If such material is in electrochemical equilibrium with dissolved redox active species, its electrical conductivity depends on the redox potential of these species. Therefore, conductometric measurements with conducting polymers can provide about the same information as classical redox electrodes. The approach was applied for redox titration. Equivalent points obtained by this titration in aqueous and organic electrolytes were identical. Then the approach was applied for determination of bromine number by redox titration in non-conducting organic phase. Graphical Highlights► Electroanalytics in non-conducting media. ► Chemiresistors based on conducting polymers as quantitative redox sensors. ► Simultaneous conductometry with chemiresistor and redox potentiometry. ► A unique possibility to measure redox-potential in gases and nonconducting liquids. ► An application for redox-titration in non-conducting organic phase is demonstrated.
An application of terahertz metamaterials as transducer elements for chemical sensors is reported. A planar array of split-ring resonators was formed from gold on the surface of silicon wafer and coated by polyaniline. Analyte binding to polyaniline leads to well measurable changes of the resonance frequency.
SPR based biosensors register binding of analytes to the surface with immobilized receptors by measuring changes of the refractive index near this surface. An important task in the improvement of this measurement technology is a separation of signals, corresponding to the changes in the chemosensitive layer, from undesired contributions of bulk phase, for example, due to fluctuations of temperature, concentrations of solutes, pressure. The wavelength of the incident light influences strongly the penetration depth of the corresponding evanescent wave. This dependence was exploited here for compensation of the contribution of the bulk refractive index. It was performed using differential SPR measurements at two wavelengths with differing penetration depths. Theoretical analysis and numerical optimization of the suggested approach, named a Penetration Difference Self-Referencing SPR (PDSR-SPR), were performed. Experimental test was performed using 658 and 980 nm laser diodes. Over 20 times suppression of variations of bulk refractive index with magnitude up to 1000 μRIU was observed. Finally, PDSR-SPR approach was applied for monitoring of antibodies binding to the immobilized antigens.
Polythiophene films on gold electrodes: a comparison of bulk and contact resistances in aqueous and organic mediaPublished: 23 June 2011 by Springer Nature in Journal of Solid State Electrochemistry
Recently, developed technique for separated analysis of bulk and contact resistance was applied for the investigation of polythiophene films electropolymerized in boron trifluoride diethylether. Kinetics of polymer resistance and for the first time of the contact resistance during polymer oxidation and reduction were characterized. Influence of electrochemically controlled oxidation state on the polymer bulk and the polymer/metal contact resistance was measured in aqueous and organic environment. Variation of the electrical potential from −0.2 to 1.1 V vs. Ag/AgCl (sat) leads to an increase of the polymer conductivity for about three orders of magnitude and to a decrease of the contact resistance for about three orders of magnitude. The potential dependence of the two resistances was different, especially at high anodic potentials. In organic solution, the change of both resistances was more than six orders of magnitude. The results were compared with electrochemical and spectroelectrochemical data, a difference in the material behavior depending on the electrolyte solvent was observed. The influence of electrical potential on polymer resistance in aqueous solution was explained quantitatively by a three-state model with the values of oxidation potential +0.3 and +1.2 V.
A composite material was prepared from graphene and palladium nanoparticles (PdNP) by layer-by-layer deposition on gold electrodes. The material was characterized by absorption spectroscopy, scanning electron microscopy, Raman spectroscopy and surface plasmon resonance. Cyclic voltammetry demonstrated the presence of electrocatalytic centers in the palladium decorated graphene. This material can serve as a sensor material for hydrogen at levels from 0.5 to 1% in synthetic air. Pure graphene is poorly sensitive to hydrogen, but incorporation of PdNPs increases its sensitivity by more than an order of magnitude. The effects of hydrogen, nitrogen dioxide and humidity were studied. Sensor regeneration is accelerated in humid air. The sensitivity of the nanocomposite depends on the number of bilayers of graphene–PdNPs.
This review covers the development of measurement configurations for chemiresistors based on conducting polymers. The simplest chemiresistors are based on application of a two-electrode technique. Artifacts caused by contact resistance can be overcome by application of a four-electrode technique. Simultaneous application of the two- and four-electrode measurement configurations provides an internal control of sensor integrity. An incorporation of two additional electrodes controlling the redox state of chemosensitive polymers and connecting to the measurement electrodes through liquid or (quasi)solid electrolyte results in a six-electrode technique; an electrically driven regeneration of such sensors allows one to perform fast and completely reversible measurements.
A new design of conductometric chemical sensors based on conducting polymers as chemosensitive elements was suggested. The sensor includes six electrodes. Four inner electrodes coated by chemosensitive polymer are used for simultaneous two- and four-point resistance measurements thus providing information on the bulk polymer resistance and on the resistance of the polymer/electrode contacts. Two outer electrodes wired to inner electrodes by polymeric electrolyte are used for electrical control of redox state of the chemosensitive polymer. The outer electrodes are connected to potentiostat as reference and counter electrodes. It allows us to control redox state of the inner (working) electrodes. This new measurement configuration, resembling chemosensitive electrochemical transistors, provides an internal test of the sensor integrity and an electrically driven sensor regeneration. It was tested as a sensor for the detection of nitrogen dioxide. Polythiophene or polyaniline was used as receptors. Cyclic voltammograms of these polymers on the sensor surface measured in air atmosphere were very similar to that measured in aqueous electrolyte. A control of conductivity of these chemosensitive polymers by electrical potential applied vs. incorporated reference electrode was demonstrated. This effect was used for the regeneration of the chemosensitive material after exposure to nitrogen dioxide: in comparison to usual chemiresistors displaying an irreversible behavior in such test even in the time scale of hours, a completely reversible sensor regeneration within few minutes was observed.
This chapter contains sections titled: IntroductionMeasurements Under Equilibrium ConditionsKinetic MeasurementsAnalysis of Temperature DependenciesExperimental TechniquesReferences
This chapter contains sections titled: IntroductionTransducers for Artificial Receptors Based on Conducting PolymersIntrinsic Sensitivity of Conducting PolymersConducting Polymers Modified with Receptor GroupsConclusionReferences
This chapter contains sections titled: Structures of ReceptorsReferences
Electrocatalytically active nanocomposite from palladium nanoparticles and polyaniline: Oxidation of hydrazinePublished: 01 September 2010 by Elsevier BV in Sensors and Actuators B: Chemical
The layer by layer (LbL) adsorption technique was used to deposit a new electrocatalytic material consisting of palladium nanoparticles (Pd NPs) and polyaniline (PANI). As far as PANI adsorption did not affect the reactivity of the Pd NPs attached in the former adsorption step, the LbL technique offered the way of increasing the reactive Pd surface within a three-dimensional nanocomposite structure. In situ conductance measurements have shown that depending on the concentration of the PANI solution, used for the LbL adsorption, composites with either PANI-like (dependent on potential and pH) or metal-like (non-dependent on potential and pH) conductive behaviour can be obtained. Metal-like Pd NPsâPANI nanocomposites were studied as electrocatalytic materials for hydrazine oxidation. A linear concentration dependence of the voltammetric peak currents was observed in the 40â800 Î¼M hydrazine concentration range, the sensitivity increasing with the amount of adsorbed Pd NPs. Amperometric measurements showed linear response in the 10â300 Î¼M range with sensitivity 0.5 Î¼A/Î¼mol cmâ2 and a theoretical detection limit estimated to be 0.06 Î¼M.
Electroanalytical applications of nanocomposites from conducting polymers and metallic nanoparticles prepared by layer-b...Published: 08 January 2010 by International Union of Pure and Applied Chemistry (IUPAC) in Pure and Applied Chemistry
Layer-by-layer (LbL) deposition is a convenient technique for the formation of ultra-thin nanocomposite layers containing metallic nanoparticles (NPs) and conducting polymers (CPs). The advantages of this approach for producing composite layers suitable for electroanalytical applications are discussed. Examples of electroanalytical applications of LbL-deposited composites are presented. Composite layers consisting of polyaniline (PANI) and Pd NPs are used for hydrazine oxidation. The PANI–Au NPs system is applied for dopamine (DA) and uric acid (UA) oxidation.
Changes in the electrical conductance at 240 Â°C of a number of copper(I) compounds including CuI, CuBr, Cu2Te, Cu12Sb4S13, (CuI)2P14, and of NiO were measured following the exposure to the gases ammonia, nitrogen dioxide, nitrous oxide, carbon monoxide, carbon dioxide, and propane. Analytical sensitivity and kinetic parameters were compared quantitatively. The high diversity of sensitivity patterns makes these compounds promising candidates for use in sensor arrays. Principal component analysis of the data obtained with a virtual sensor array enabled highly selective sensing of five of the six analytes studied using only two principle components. Activation energies of the charge transport in the materials were determined.
Soluble neuropilin-2, a nerve repellent receptor, is increased in rheumatoid arthritis synovium and aggravates sympathet...Published: 01 October 2009 by Wiley in Arthritis & Rheumatism
In inflammatory lesions, sympathetic nerve fibers disappear soon after the start of inflammation. We identified sympathetic nerve repellents as possible causal agents in rheumatoid arthritis (RA). On nerve terminals, repellent factors bind to neuropilin‐2 and its coreceptor. The aim of this study was to investigate the role of neuropilin‐2 in the synovial tissue of patients with RA and patients with osteoarthritis (OA) and in experimental arthritis.
Voltammetric and conductometric behavior of nanocomposites of polyaniline and gold nanoparticles prepared by layer-by-la...Published: 16 September 2009 by Springer Nature in Journal of Solid State Electrochemistry
Multilayer nanocomposites from polyaniline (PANI) and gold nanoparticles (AuNPs) were formed by layer-by-layer deposition. The formation of PANI–AuNPs multilayer structures was monitored by UV-vis absorption spectroscopy and cyclic voltammetry. Each deposited bilayer of PANI–AuNPs led to a monotonous and almost linear increase in both optical absorbance and the first current peak of PANI oxidation. The prepared multilayer nanocomposites were characterized by in situ conductivity measurements at different pH and potential and by transmission electron microscopy. Finally, chemosensitive properties of the new material based on the intrinsic affinity of gold nanoparticles were studied. Changes in the film resistance on exposure to vapors of mercury and sulfur-containing compounds were observed.
The structure and the electrochemical and spectral properties of two conductive electrochemically polymerized substituted bipyrroles 4,4′-methoxy-2,2′-bipyrrole and 4,4′-buthoxy-2,2′-bipyrrole were studied and compared. The polymers were characterized by cyclic voltammetry, FT-Raman spectroscopy, scanning electron microscopy, and in situ conductivity measurements at different pH and redox state.
New sensors with improved performance characteristics are needed for applications as diverse as bedside continuous monitoring, tracking of environmental pollutants, monitoring of food and water quality, monitoring of chemical processes, and safety in industrial, consumer, and automotive settings. Typical requirements in sensor improvement are selectivity, long-term stability, sensitivity, response time, reversibility, and reproducibility. Design of new sensing materials is the important cornerstone in the effort to develop new sensors. Often, sensing materials are too complex to predict their performance quantitatively in the design stage. Thus, combinatorial and high-throughput experimentation methodologies provide an opportunity to generate new required data to discover new sensing materials and/or to optimize existing material compositions. The goal of this chapter is to provide an overview of the key concepts of experimental development of sensing materials using combinatorial and high-throughput experimentation tools, and to promote additional fruitful interactions between computational scientists and experimentalists.
Multilayer structures of conducting polymers were fabricated by a simply automated approach in flow mode. Polyaniline and poly(styrene sulfonate) were used as a model system, allowing a fast electrochemical and spectroscopic determination of the amount of deposited material. The technology was applied for layer‐by‐layer deposition of up to 100 bilayers. The results demonstrate a well reproducible and almost constant amount of the adsorbed polymer at each deposition cycle. The method can be applied for deposition of other conducting or non‐conducting polymers, biological macromolecules and composites of polyelectrolytes and nanoparticles.
Dopamine oxidation was studied on modified gold (nano-Au) electrodes obtained by Layer-by-Layer deposition of gold nanoparticles and polyacrylic acid. A gradual loss of electrochemical activity for the dopamine oxidation reaction is observed at pH 7. Simultaneous SPR spectroscopy and cyclic voltammetry indicate the formation of an adsorbed layer on the electrode surface at this pH value. Investigations, performed through electrochemical and SPR measurements at pH 4, give evidence for a reversible process. At this pH value both dopamine oxidation and reduction current peaks show linear dependence on the dopamine concentration and may be used for analytical applications. The use of the nano-Au electrode allows resolving the peaks corresponding to ascorbic acid and to dopamine oxidation by 240 mV thus providing a high selectively for dopamine detection in the presence of ascorbic acid. The detection limit of this electrode for dopamine is below 4 microM in the presence of 1 mM ascorbic acid. The sensitivity normalized to the macroscopic electrode surface is about 10 mA cm(-2) mM(-1) at sweep rate of 10 V/s.
Sensing materials play a critical role in advancing selectivity, response speed, and sensitivity of chemical and biological determinations in gases and liquids. The desirable capabilities of sensing materials originate from their numerous functional parameters, which can be tailored to meet specific sensing needs. By increasing the structural and functional complexity of sensing materials, the ability to rationally define the precise requirements that will result in desired materials properties becomes increasingly limited. Combinatorial experimentation methodologies impact all areas of sensing materials research including inorganic, organic, and biological sensing materials.
The first attempt has been made to suggest a model of influenza A virus matrix M1 protein spatial structure and molecule orientation within a virion on the basis of tritium planigraphy data and theoretical prediction results. Limited in situ proteolysis of the intact virions with bromelain and surface plasmon resonance spectroscopy study of the M1 protein interaction with lipid coated surfaces were used for independent confirmation of the proposed model.
Vladimir Mirsky participated at conference 6th International Symposium on Sensor Science and 4th SPINTECH Technology Thesis Award.
Vladimir Mirsky participated at conference 5th International Symposium on Sensor Science.
Vladimir Mirsky participated at conference 4th International Symposium on Sensor Science.