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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.

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.

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.

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.

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.

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