TY - GEN A1 - Lange, Ulrich A1 - Mirsky, Vladimir M. T1 - Polythiophene films on gold electrodes: A comparison of bulk and contact resistances in aqueous and organic media T2 - Journal of Solid State Electrochemistry N2 - 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. KW - Polythiophene KW - In situ conductivity measurement KW - s24-Technique KW - Spectroelectrochemistry KW - Conducting polymers Y1 - 2011 U6 - https://doi.org/10.1007/s10008-011-1450-4 SN - 1433-0768 VL - 15 IS - 11 SP - 2377 EP - 2382 ER - TY - GEN A1 - Lange, Ulrich A1 - Mirsky, Vladimir M. T1 - Integrated electrochemical transistor as a fast recoverable gas sensor T2 - Analytica Chimica Acta N2 - 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. KW - Gas sensor KW - Conducting polyme KW - Electrochemical transistor KW - Six-point resistance Measurement KW - Sensor recovery Y1 - 2011 U6 - https://doi.org/10.1016/j.aca.2010.12.008 SN - 0003-2670 VL - 687 IS - 1 SP - 7 EP - 11 ER - TY - GEN A1 - Lange, Ulrich A1 - Mirsky, Vladimir M. T1 - Chemiresistors based on conducting polymers: A review on measurement techniques T2 - Analytica Chimica Acta N2 - 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. KW - Chemiresistor KW - Chemotransistor KW - Conducting polymer KW - Chemosensor KW - Contact resistance KW - s24-Technique Y1 - 2011 U6 - https://doi.org/10.1016/j.aca.2010.11.030 SN - 0003-2670 VL - 687 IS - 2 SP - 105 EP - 113 ER - TY - GEN A1 - Lange, Ulrich A1 - Hirsch, Thomas A1 - Mirsky, Vladimir M. A1 - Wolfbeis, Otto S. T1 - Hydrogen sensor based on graphene - palladium nanocomposite T2 - Electrochimica Acta N2 - 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. KW - Graphene KW - Palladium KW - Nanoparticle KW - Sensor KW - Layer-by-layer Y1 - 2011 U6 - https://doi.org/10.1016/j.electacta.2010.10.078 SN - 0013-4686 VL - 56 IS - 10 SP - 3707 EP - 3712 ER - TY - GEN A1 - Lange, Ulrich A1 - Mirsky, Vladimir M. T1 - Chemosensitive nanocomposite for conductometric detection of hydrazine and NADH T2 - Electrochimica Acta N2 - A new chemosensitive material based on palladium nanoparticles and PEDOT-PSS is described. The composite was characterized by transmission electron microscopy, cyclic voltammetry and in situ resistance measurements. The material was applied for conductometric detection of hydrazine and NADH. Upon exposure to these analytes PEDOT is reduced leading to an increase in its conductance. This process is catalyzed by palladium. A model for description of the potential dependence of polymer conductivity was suggested, tested and applied for the development of new calibration procedure of chemiresistors based on electroactive polymers. KW - Chemosensor KW - Chemiresistor KW - Nanoparticles KW - Palladium KW - PEDOT KW - Hydrazine KW - NADH Y1 - 2011 U6 - https://doi.org/10.1016/j.electacta.2010.08.092 SN - 0013-4686 VL - 56 IS - 10 SP - 3679 EP - 3684 ER - TY - CHAP A1 - Lange, Ulrich A1 - Roznyatovskaya, Nataliya V. A1 - Hao, Qingli A1 - Mirsky, Vladimir M. ED - Mirsky, Vladimir M. ED - Yatsimirsky, Anatoly K. T1 - Conducting polymers as artificial receptors in chemical sensors T2 - Artificial receptors for chemical sensors KW - artificial receptors polyaniline KW - chemosensors KW - conducting polymers KW - polyaniline KW - transducers Y1 - 2011 SN - 978-3-527-32357-9 U6 - https://doi.org/10.1002/9783527632480.ch12 SP - 363 EP - 392 PB - Wiley-VCH CY - Weinheim ER -