Kurt Schwabe Institute For Measuring And Sensor Technology

Markt Schwaben, Germany

Kurt Schwabe Institute For Measuring And Sensor Technology

Markt Schwaben, Germany
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Kleppisius A.,Kurt Schwabe Institute For Measuring And Sensor Technology | Kick A.,Kurt Schwabe Institute For Measuring And Sensor Technology | Mertig M.,Kurt Schwabe Institute For Measuring And Sensor Technology
Physica Status Solidi (A) Applications and Materials Science | Year: 2017

The determination of the double-layer capacitance of planar interdigitated gold electrodes in a microfluidic channel by electrical impedance spectroscopy is presented. A simple and miniaturized two-electrode setup is used to investigate electrodes coated with pH-sensitive self-assembled thiol layers of 4-mercaptopyridine (4-MP) or 4-mercaptobenzoic acid (4-MBA). The total sensing area is about 0.25mm2. Surface modifications and pH have a pronounced influence on the double-layer capacitance of the electrodes. The interfacial capacitance rises significantly at pH<3 on the 4-MP and at pH>10 on the 4-MBA layer. This effect is related to surface protonation or deprotonation of the pyridine or carboxylic moieties, respectively. It is shown that this double-layer capacitance is widely independent from the electrolyte concentration. Such electrodes can be used as pH indicators in microfluidic channels, additionally allowing the determination of the electrolyte conductivity. This kind of sensor is supposed to be used in lab-on-a-chip systems for fast readout of local chemical and physical process parameters. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wilner O.I.,Hebrew University of Jerusalem | Orbach R.,Hebrew University of Jerusalem | Henning A.,Hebrew University of Jerusalem | Henning A.,TU Dresden | And 6 more authors.
Nature Communications | Year: 2011

The synthesis of DNA nanotubes is an important area in nanobiotechnology. Different methods to assemble DNA nanotubes have been reported, and control over the width of the nanotubes has been achieved by programmed subunits of DNA tiles. Here we report the self-assembly of DNA nanotubes with controllable diameters. The DNA nanotubes are formed by the self-organization of single-stranded DNAs, exhibiting appropriate complementarities that yield hexagon (small or large) and tetragon geometries. In the presence of rolling circle amplification strands, that exhibit partial complementarities to the edges of the hexagon- or tetragon-building units, non-bundled DNA nanotubes of controlled diameters can be formed. The formation of the DNA tubes, and the control over the diameters of the generated nanotubes, are attributed to the thermodynamically favoured unidirectional growth of the sheets of the respective subunits, followed subjected to the folding of sheets by elastic-energy penalties that are compensated by favoured binding energies. © 2011 Macmillan Publishers Limited. All rights reserved.


Scharfenberg L.,Technical University Dresden01062DresdenGermany | Mertig M.,Kurt Schwabe Institute For Measuring And Sensor Technology
Physica Status Solidi (A) Applications and Materials Science | Year: 2015

Due to their intrinsic properties, single-walled carbon nanotubes (SWCNTs) are promising candidates for source-drain channels in field-effect transistors (FETs). However, their application in transistors requires semiconducting tubes, and thus, sorting of SWCNTs according to those. The basis for an efficient sorting is the dispersion of the material that usually includes but is not limited to applying tip sonication in the presence of appropriate amphiphilic molecules. We present a high semiconducting enrichment of surfactant-wrapped arc discharge SWCNTs via sorting according to electronic type by applying density gradient ultracentrifugation (DGU). We utilized a common combination of anionic surfactants, but optimized the sonication time during the dispersion step of the SWCNTs and the duration of performing DGU. Furthermore, we used UV-Vis spectroscopy to determine the differences in the content of metallic (m) and semiconducting (sc) SWCNTs of different samples. By the refinement of the conditions, we have achieved an enrichment of sc-SWCNTs up to 98% in two sorting steps. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vonau W.,Kurt Schwabe Institute For Measuring And Sensor Technology | Oelssner W.,Kurt Schwabe Institute For Measuring And Sensor Technology | Guth U.,Kurt Schwabe Institute For Measuring And Sensor Technology | Henze J.,Henze Hauck Prozessmesstechnik Analytik GmbH
Sensors and Actuators, B: Chemical | Year: 2010

Conventional liquid-filled reference electrodes are not suitable for applications where electrochemical sensors must be very robust and capable of withstanding high pressures and temperatures. This paper presents an all-solid-state reference electrode containing essentially an Ag/AgCl-reference element and a solid crystalline KCl melt, but no liquid components. Particularly with regard to the intended application in a brewery, the electrode was successfully tested in combination with a likewise all-solid-state antimony pH indicator electrode, as reference electrode in an all-solid oxygen sensor and in a potentiometric inline sensor using cyclic voltammetry. In spite of various suggestions to solve the problem, no type of all-solid-state reference electrode is available with properties completely comparable to those of conventional ones so far. © 2008 Elsevier B.V. All rights reserved.


Riedel J.,TU Dresden | Riedel J.,Kurt Schwabe Institute For Measuring And Sensor Technology | Berthold M.,Kurt Schwabe Institute For Measuring And Sensor Technology | Guth U.,TU Dresden
Electrochimica Acta | Year: 2014

Screen printed carbon electrodes (SPCE), produced close to industrial manufacturing processes as well as commercially available electrodes using nano-tubes and gold nano-particles (DRP-110CNT-GNP) were investigated with respect to the determination of nitroaromatic compounds like 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) in aqueous solution. Dynamic electrochemical measuring methods such as differential pulse voltammetry (DPV) and square wave voltammetry (SWV) are suited to measure traces of such compounds. The two peaks obtained can be separated clearly and assigned to the reduction of nitro groups. On bare carbon electrodes TNT and DNT could be determined in the concentration range between 1.2 ppb and 1500 ppb TNT (R 2 = 0.994) with high reproducibility. The coating of commercial electrodes with carbon nano-tubes and gold nano-particles provided similar results for comparison purposes. The reproducibility of the results obtained on SPCE was demonstrated over a period of up to 1.5 years. The results were verified by gas chromatography with mass spectrometry (GC-MS). © 2013 Elsevier Ltd.


Ostermaier F.,TU Dresden | Mertig M.,TU Dresden | Mertig M.,Kurt Schwabe Institute For Measuring And Sensor Technology
Physica Status Solidi (B) Basic Research | Year: 2013

We report the use of scalable gel column chromatography to sort single-walled carbon nanotubes (SWCNTs) from different production schemes according to their electronic properties. We show that this method, originally developed for HiPCO® tubes, can equally well be applied to the sorting of commercially available SWCNTs produced by CVD. We use UV-Vis spectroscopy for the quantitative characterization of the samples. It allows a fast determination of the mSWCNT and scSWCNT contents in a sample with only few preliminary information. For further prove, we assembled field-effect transistors (FETs) from enriched semiconducting suspensions by dielectrophoresis. The measurement of the I-V curves approves that FETs with reasonable electrical performance can be assembled in a single preparation step. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Schelter M.,Kurt Schwabe Institute For Measuring And Sensor Technology | Zosel J.,Kurt Schwabe Institute For Measuring And Sensor Technology | Oelssner W.,Kurt Schwabe Institute For Measuring And Sensor Technology | Guth U.,Kurt Schwabe Institute For Measuring And Sensor Technology | And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2013

Coulometric solid electrolyte sensors based on yttria-stabilized zirconia were characterized with respect to the electronic conductivity of the solid electrolyte and to their electrochemical activity of oxygen, hydrogen and hydrocarbon conversion. Sensor parameters like the temperature dependency of the electronic conductivity as well as the elevated noise of the coulometric cell at the working temperature determine the limit of detection of coulometric titration. Here we describe investigations on these parameters and approaches to shift the lower detection limit into the ppb-range. Furthermore, it is shown that a coulometric solid electrolyte sensor, positioned behind a gas chromatographic separation unit, allows simultaneous, calibration-free and long-term stable detection of different oxidizable components and oxygen. © 2012 Elsevier B.V. All rights reserved.


Posseckardt J.,Kurt Schwabe Institute For Measuring And Sensor Technology | Mertig M.,Kurt Schwabe Institute For Measuring And Sensor Technology
Physica Status Solidi (A) Applications and Materials Science | Year: 2015

Due to their capability to bind and release growth factors via electrostatic interactions, biohybrid hydrogels, formed by synthetic polymers and glycosaminoglycans, are of increasing interest for regenerative therapies. Bound to the hydrogel, growth factors are protected from diffusion and biodegradation. A sustained release of the growth factors promotes vascularization of engineered constructs. By means of impedance spectroscopy, we were able to detect the binding of biomolecules to the immobilized gel at nanomolar concentrations. Biomolecule binding causes the impedance of the gel to increase at characteristic frequencies that can be assigned to the electric properties of the gel and the electrode surface. By decreasing the dimensions of the interdigitated electrode array, the sensitivity to processes at the electrode surface can be increased. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kick A.,Kurt Schwabe Institute For Measuring And Sensor Technology | Mertig M.,Kurt Schwabe Institute For Measuring And Sensor Technology
Physica Status Solidi (A) Applications and Materials Science | Year: 2015

Layers of pH-sensitive poly(2-vinylpyridine) are immobilised on gold surfaces of surface plasmon reson-ance (SPR) or quartz crystal microbalance (QCM) sen-sors. Two different polymers are used, one (P2VP-COOH) with and another (P2VP) without a terminal carboxylic group. Swelling and stiffening are preferably observable in the low protonation state of the polymer layers by QCM. In solutions of hydrochloric acid QCM measurements reveal that P2VP-COOH forms denser and stiffer layers than P2VP. Both polymers clearly show viscoelastic properties. The SPR sensor detects dilution as well as the incorporation of hydrochloric acid into the sensing layers at lower pH, and therefore, higher protona-tion state of the polymers. SPR and QCM are complementarily used to characterise changes of the mechanical and optical properties of pH-sensitive polymer layers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vonau W.,Kurt Schwabe Institute For Measuring And Sensor Technology
Technisches Messen | Year: 2010

Numerous pH measuring problems require sensors differing from the standards. Several particular examples are described in this paper. Beside metal oxide electrodes manufactured using various fabrication steps, conventional pH glass electrodes can be miniaturized to a limited extent or the usual internal filling can be exchanged with different solid state reference systems. To establish a reversible interface to the membrane glass both compact glass electrodes and thick-film glass electrodes using zinc oxide have been used. The integration of pH sensors in multi-sensor systems is reported and procedures are presented to extend the utilisability of these systems. The importance of reference electrodes for such developments is highlighted. © Oldenbourg Wissenschaftsverlag.

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