Juergen Heinze

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Name: Jürgen Heinze

Organization: Freiburg Materials Research Center (FMF) , Germany

Department: Institute for Physical Chemistry

Title: (PhD)

TOPICS

Physical Chemistry

Chemicals
References

Dependence of polypyrrole bilayer deflection upon polymerization potential

Co-reporter:Rudolf Kiefer, Daniel Georg Weis, Alvo Aabloo, Gerald Urban, Jürgen Heinze

Synthetic Metals 2013 Volume 172() pp:37-43

Publication Date(Web):15 May 2013

DOI:10.1016/j.synthmet.2013.04.003

•PPy bilayer actuation at different formation potentials.•EQCM measurements in correlation to polymerization potentials.•Model of “σ-dimerization” discussed to explain mixed ion actuation.The nature of polypyrrole (PPy) is largely influenced by the potential used for its polymerization. To investigate this influence, PPy-bilayer actuators were created using different polymerization potentials in order to examine the effect of the polymerization potential on the involvement of anions and cations in the actuation process.Cyclic voltammetry and chronoamperometry methods were used to record the ion behaviour while simultaneous measurements were made of the PPy-bilayer deflection in order to characterize the PPy-bilayer actuation properties. A polymerization potential close to 0.85 V and 1.1 V produced a PPy-bilayer actuator which managed an optimum deflection in an electrolyte consisting of TBAPF6 (tetrabutyl ammonium hexaflourophosphate) in propylene carbonate (PC).Electrochemical quartz crystal microbalance (EQCM) measurements showed the degree to which solvated cations and anions are involved in the charging and discharging processes during actuation of the PPy-bilayers. The influence of anions and cations during actuation of the PPy-bilayer at reduction and oxidation is described by the model of reversible σ-dimerization.

Nanophase separated amphiphilic polymer co-networks as efficient matrices for optical sensors: Rapid and sensitive detection of NO2

Co-reporter:Stephan Meskath, Gerald Urban, Jürgen Heinze

Sensors and Actuators B: Chemical 2013 Volume 186() pp:367-373

Publication Date(Web):September 2013

DOI:10.1016/j.snb.2013.06.007

A disposable and irreversible sensor for nitrogen dioxide detection, based on the reaction of NO2 with N,N′-diphenyl-1,4-phenylenediamine (DPPD) is described. This work focuses on the application of silicone-containing amphiphilic co-networks (APCNs) as immobilisation matrices for UV/VIS transmission spectroscopy for gas sensors. The developed flow-through gas sensor is based on a DPPD doped APCN, for real-time spectrophotometric detection of the oxidation product, and is formed in a 34 μm thin film. The measurement principle presented here describes the NO2 concentration as a function of the temporal development of absorption at 450 nm. A linear relationship between the change of absorption and the concentration of NO2 at different humidity is obtained in the range from 0.1 to 5.0 ppm at ambient temperatures. As a consequence, the sensor response is reproducible with a very low detection threshold (20 ppb) and detection times within seconds.

SECM detection of single boron doped diamond nanodes and nanoelectrode arrays using phase-operated shear force technique

Co-reporter:C. Dincer, E. Laubender, J. Hees, C.E. Nebel, G. Urban, J. Heinze

Electrochemistry Communications 2012 Volume 24() pp:123-127

Publication Date(Web):October 2012

DOI:10.1016/j.elecom.2012.08.005

Boron doped diamond (BDD) is a promising electrode material for electrochemical biosensor applications due to its low bio-fouling, chemical stability, and large potential window. For the first time, BDD nanoelectrode arrays (NEA) were studied using Scanning Electrochemical Microscopy (SECM) measurements. Using the phase-operated shear force technique and feedback mode, it was possible to scan a platinum (Pt) nanode with an active radius of 167 nm over a diamond array at a constant distance of 45 nm and to detect the electrochemical activity of single BDD nanodes in the 100 nm range.Highlights► For the first time, BDD nanoelectrode arrays were studied using SECM measurements. ► A nano-sized electrode (r = 167 nm) was employed as a SECM tip. ► A phase-based shear force regulated SECM provides a constant distance of ~ 45 nm. ► A lateral resolution within a 100 nm range was successfully achieved. ► 320 nm BDD nanodes and their arrangement in a NCD surface were clearly detected.

Electrochemically Induced Reversible and Irreversible Coupling of Triarylamines

Co-reporter:Olena Yurchenko, David Freytag, Lisa zur Borg, Rudolf Zentel, Jürgen Heinze, and Sabine Ludwigs

The Journal of Physical Chemistry B 2012 Volume 116(Issue 1) pp:30-39

Publication Date(Web):December 12, 2011

DOI:10.1021/jp208076z

The electrochemical coupling and dimerization behavior of the low molecular compounds triphenylamine (TPA) and 9-phenylcarbazole (PHC) in comparison to tri-p-tolylamine (p-TTA) with para-blocked methyl groups has been investigated in detail. In contrast to the unsubstituted radical cations of TPA and PHC, the radical cations of p-TTA are stable in the radical cation state and do not undergo any further coupling reactions. However, we found that the dicationic state of p-TTA does undergo two different competitive reaction pathways: (1) an irreversible intramolecular coupling reaction which leads to phenylcarbazole moieties and (2) a reversible intermolecular dimerization leading to charged σ-dimers. The σ-dimers become decomposed upon discharging at low potentials (Epc = −0.97 V vs Fc/Fc+) so that the starting monomer p-TTA is partially regenerated. In particular, the reversible dimerization reaction has not been described in literature so far. Polymeric systems containing para-methyl blocked triarylamines in the side chain exhibit similar coupling behavior upon electrochemical doping.

Electrochemistry with alkyl-linked oligothiophenes

Co-reporter:Markus Pagels, Günther Götz, Thomas Fischer, Peter Bäuerle, Jürgen Heinze

Electrochimica Acta 2011 Volume 56(Issue 10) pp:3419-3428

Publication Date(Web):1 April 2011

DOI:10.1016/j.electacta.2010.12.057

Two pairs of β,β′-didodecyl substituted quinquethiophenes linked via a tri- (3) and tetramethylene spacer (4) at their α-positions have been synthesized and their electrochemical behavior investigated with cyclic voltammetry in solution and in solid films. Both compounds can be charged to a tetracation in two two-electron transfer steps, which are reversible at room temperature but become partially irreversible at low temperatures. Concentration and scan rate dependent measurements support an intramolecular coupling of the oligothiophene units preferentially next to their bridging site with σ-bond formation. In solution no electropolymerization can be observed. In the solid state upon oxidation intermolecular coupling of the oligothiophene segments takes place. Conductance measurements confirm the voltammetric findings. Obviously, the mechanism of conductance is based on hopping processes within mixed valence states.

A new optochemical chlorine gas sensor based on the application of amphiphilic co-networks as matrices

Co-reporter:Stephan Meskath, Gerald Urban, Jürgen Heinze

Sensors and Actuators B: Chemical 2011 Volume 151(Issue 2) pp:327-332

Publication Date(Web):28 January 2011

DOI:10.1016/j.snb.2010.07.028

A sensor for chlorine gas detection, consisting of an amphiphilic polymer co-network with an immobilised oxidation indicator, o-tolidine, is described. Data describing gas sensing properties and long-term stability will be presented. This study focuses on APCN thin films as a matrix for indicator immobilisation.Thin films of poly(2-hydroxyethyl acrylate)-l-polydimethylsiloxane PHEA-l-PDMS were prepared as immobilisation matrices for o-tolidine.We present a simple, non-expensive, but highly sensitive optical sensor for chlorine gas detection. The thin film response is reproducible and irreversible. With our kinetic-optical method rapid response times were achieved. The determination of chlorine is performed on the basis of the oxidation of o-tolidine as the chromogenic reagent to a coloured product which can be monitored at 650 nm. The results reveal a fast response to chlorine gas down to concentrations of 0.01 ppm.

Electrochemistry of Conducting Polymers—Persistent Models and New Concepts

Co-reporter:Jürgen Heinze, Bernardo A. Frontana-Uribe and Sabine Ludwigs

Chemical Reviews 2010 Volume 110(Issue 8) pp:4724

Publication Date(Web):June 17, 2010

DOI:10.1021/cr900226k

Electrochemically Induced Formation of Independent Conductivity Regimes in Polymeric Tetraphenylbenzidine Systems

Co-reporter:Olena Yurchenko;Jürgen Heinze Dr.;Sabine Ludwigs Dr.

ChemPhysChem 2010 Volume 11( Issue 8) pp:1637-1640

Publication Date(Web):

DOI:10.1002/cphc.201000131

Generation of platinum microstructures on non-conducting surfaces by means of the scanning electrochemical microscope (SECM)

Co-reporter:Valentin Radtke, Christian Heß, Jürgen Heinze

Electrochimica Acta 2009 Volume 55(Issue 2) pp:416-422

Publication Date(Web):30 December 2009

DOI:10.1016/j.electacta.2009.03.030

The scanning electrochemical microscope (SECM) was used to form platinum microstructures. For this purpose, a thin layer of platinum dichloride was deposited as precursor on different substrates by evaporating it in high vacuum. For the reduction of this precursor the SECM provided methyl viologen radical cations locally as reducing agent. The mechanism of the reduction is discussed.

Imaging Local Proton Fluxes through a Polycarbonate Membrane by Using Scanning Electrochemical Microscopy and Functionalized Alkanethiols

Co-reporter:Norman Baltes Dr.;Jürgen Heinze Dr.

ChemPhysChem 2009 Volume 10( Issue 1) pp:174-179

Publication Date(Web):

DOI:10.1002/cphc.200800598

Abstract

A new application of scanning electrochemical microscopy (SECM) to probe the transport of protons through membranes is described. Herein, a probe ultramicroelectrode (UME) is modified with a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid to qualitatively image areas within different pH regions above a track-etched membrane. The current response of the modified electrode in the presence of potassium hexacyanoferrate as electroactive component is different in acidic and alkaline solutions. Depending on the pH value of the solution, the SAM-covered electrode exposes either a neutral or a negatively charged insulating monolayer at pH 3 or 7, respectively, which leads to an increase/decrease in the faradaic current due to electrostatic interactions between the neutral/charged surface and the charged redox mediator. Therefore, local pH changes in the close vicinity of a membrane-like substrate lead to different current responses recorded at the tip electrode when scanning above the surface.

Trinuclear Cyanines (TNCs) Revisited: A New Class of Electrochromics by Intramolecular π/σ Switching

Co-reporter:Hermann John;Christoph Briehn Dr.;Johann Schmidt;Siegfried Hünig Dr.;Jürgen Heinze Dr.

Angewandte Chemie International Edition 2007 Volume 46(Issue 3) pp:

Publication Date(Web):8 DEC 2006

DOI:10.1002/anie.200602596

The Y-shaped π systems in trinuclear cyanines can, through a formal two-electron transfer, form a core methylenecyclopropane unit with three shorter, isolated π systems (see picture). Studies of the spectroelectrochemistry verify the reversibility of this redox reaction, which has an unusually pronounced electrochromism.

Ein neuer Blick auf alte Farbstoffe: Dreikernige Cyanine (TNCs) als elektrochrome redoxschaltbare Systeme

Co-reporter:Hermann John;Christoph Briehn Dr.;Johann Schmidt;Siegfried Hünig Dr.;Jürgen Heinze Dr.

Angewandte Chemie 2007 Volume 119(Issue 3) pp:

Publication Date(Web):8 DEC 2006

DOI:10.1002/ange.200602596

Die Y-verzweigten π-Systeme in dreikernigen Cyaninen können durch formalen Zweielektronentransfer eine zentrale Methylencyclopropaneinheit mit drei kürzeren, isolierten π-Systemen bilden. Spektroelektrochemische Untersuchungen belegen die Reversibilität dieser Redoxreaktion mit ungewöhnlich großer Elektrochromie.

Disposable optochemical sensor chip for nitrogen dioxide detection based on oxidation of N,N′-diphenyl-1,4-phenylenediamine

Co-reporter:Marcin Alexy, Michael Hanko, Sara Rentmeister, Jürgen Heinze

Sensors and Actuators B: Chemical 2006 Volume 114(Issue 2) pp:916-927

Publication Date(Web):26 April 2006

DOI:10.1016/j.snb.2005.08.041

We report on a novel optochemical sensor chip for nitrogen dioxide (NO2) based on the indicator reagent N,N′-diphenyl-1,4-phenylenediamine (DPPD). The sensor chip was manufactured by immobilising DPPD in a highly permeable polymeric layer made from polydimethylsiloxane-polycarbonate block copolymer (PDMS-PC). The presence of NO2 causes oxidation of DPPD, which thereby changes its visible spectrum. The best wavelength for determining NO2 was 480 nm. To realise short measuring times (e.g. 23 s to determine 5 ppm NO2), a measuring procedure was chosen that enables a linear correlation between the rate of change of the transmission of DPPD and the concentration of NO2. A linear calibration function was obtained in the range from 0.1 to 25 ppm NO2. The limit of quantitation (LOQ) was 0.12 ppm and the accuracy exceeds 6%. The stability of the sensor chips, the effect of internal parameters (indicator reagent concentration and thickness of the polymeric layer) and the effect of external parameters (relative humidity (RH), temperature and gas flow) on the sensor chip response were investigated.No cross-sensitivities were observed at concentrations lower than 0.1 ppm ozone (O3), 0.2 ppm chlorine (Cl2) and 250 ppm nitrogen monoxide (NO).The application area of the developed sensor chips is environmental and working place analysis of NO2. For this purpose, the sensor chips will be integrated into a lightweight portable photometer made of semiconductor components.

Nanostructuring and nanoanalysis by scanning electrochemical microscopy (SECM)

Co-reporter:Joachim Ufheil, Christian Heß, Kai Borgwarth and Jürgen Heinze

Physical Chemistry Chemical Physics 2005 vol. 7(Issue 17) pp:3185-3190

Publication Date(Web):27 Jul 2005

DOI:10.1039/B505189D

The generation and application of nanodes in SECM experiments are described. Nanodes are ultramicroelectrodes with an active disk diameter in the submicrometer range. We investigated the behaviour of these electrodes by testing their properties with SECM applications which were previously performed at the micrometer scale. The active diameter of the nanodes was determined using cyclic voltammetry and SECM. The nanoanalysis was conducted at two nano interdigitated arrays. The nanostructuring was demonstrated by galvanic and electroless silver deposition from solution and from the surface, respectively. Experiments with nanodes illustrate that they exhibit the same behaviour as ultramicroelectrodes, but are more sensitive to adsorption and dirt particles in the electrolyte solution.

Investigation of carboxylic-functionalized and n-alkanethiol self-assembled monolayers on gold and their application as pH-sensitive probes using scanning electrochemical microscopy

Co-reporter:Frank-Mario Boldt, Norman Baltes, Kai Borgwarth, Jürgen Heinze

Surface Science 2005 Volume 597(1–3) pp:51-64

Publication Date(Web):15 December 2005

DOI:10.1016/j.susc.2004.04.062

We investigated the insulating properties of n-alkanethiol self-assembled monolayers (SAMs) of varying chain lengths [CH3(CH2)nSH; n = 7, 9, 11, 15] on polycrystalline gold electrodes using scanning electrochemical microscopy (SECM) and cyclic voltammetry. On the basis of SECM approach curves we examined the local ET through monolayers with increasing chain length in different redox mediators. We were able to distinguish the monolayers because of their different insulating properties and in addition, the status of SAM formation after immersion times of 2 h and 24 h, respectively, could be observed. Cyclic voltammetric measurements confirmed the SECM results and were in good agreement with other experimental data in the literature. High-resolution SECM images of hexadecanethiol SAM micropatterns down to 4 μm in diameter formed by microcontact printing (μCP) were obtained in the feedback mode. Furthermore, we studied the ET and the pH-dependent behavior of mercaptoundecanoic acid monolayers on gold at varying pH and in different redox mediator solutions to test their application as pH-sensors. An additional influence on the ET could be established based on Coulomb/ionic interactions between the charged monolayer and the redox mediator at changing pH. Therefore, we present a new approach for designing pH-sensitive SECM probes using 11-mercaptoundecanoic acid-coated 10 μm-diameter gold ultramicroelectrodes (HOOC–C11SH/Au UMEs) in aqueous solutions containing hexacyanoferrate. Voltammetric measurements at HOOC–C11SH/Au UMEs at different pH values enabled us to estimate the degree of dissociation of the carboxylic-terminated monolayers.

3D-Hybridnetzwerke aus terthiophenfunktionalisierten Polyphenylendendrimeren mit einstellbarer elektrischer Leitfähigkeit

Co-reporter:Hermann John Dipl.-Chem.;Rol Bauer Dipl.-Chem.;Pamela Espindola Lic. en Qca.;Prashant Sonar Dipl.-Chem.;Jürgen Heinze Dr.;Klaus Müllen Dr.

Angewandte Chemie 2005 Volume 117(Issue 16) pp:

Publication Date(Web):10 MAR 2005

DOI:10.1002/ange.200462378

Auffallend hoch ist die Leitfähigkeit in kovalent gebundenen dreidimensionalen Netzwerken aus geeignet funktionalisierten Dendrimeren (siehe Bild) nach elektrochemischer Dotierung. Bei Variation des Potentials für die Beladung der elektroaktiven Komponenten, die als Bausteine für den Dendrimerkern bzw. -perimeter eingesetzt wurden, treten zwei getrennte Leitfähigkeitsbereiche auf.

3D-Hybrid Networks with Controllable Electrical Conductivity from the Electrochemical Deposition of Terthiophene-Functionalized Polyphenylene Dendrimers

Co-reporter:Hermann John Dipl.-Chem.;Rol Bauer Dipl.-Chem.;Pamela Espindola Lic. en Qca.;Prashant Sonar Dipl.-Chem.;Jürgen Heinze Dr.;Klaus Müllen Dr.

Angewandte Chemie International Edition 2005 Volume 44(Issue 16) pp:

Publication Date(Web):10 MAR 2005

DOI:10.1002/anie.200462378

Unusual conductivity effects: Suitably functionalized dendrimers (see picture) are capable of forming truly covalent three-dimensional networks with remarkably high conductivity on electrochemical doping. Depending on the charging level of the electroactive components used as building blocks for the dendrimer core and the perimeter, two separated regimes of electrical conductivity can be observed.

Retrospective chemical analysis of tree rings by means of the scanning electrochemical microscopy with shear force feedback

Co-reporter:Maria Florencia Garay, Joachim Ufheil, Kai Borgwarth and Jürgen Heinze

Physical Chemistry Chemical Physics 2004 vol. 6(Issue 15) pp:4028-4033

Publication Date(Web):10 Jun 2004

DOI:10.1039/B402458C

The imaging capabilities of scanning electrochemical microscopy (SECM) were used to characterise an enzyme-modified wood surface. To avoid the convolution of effects from local electrochemical properties of the surface and variations in the distance between the tip electrode and the surface owing to the roughness of the sample, a shear force constant-distance mode was integrated into the SECM set-up. In this way, we succeeded in simultaneously measuring the topography of the wood sample and mapping the distribution of the enzymatic activity along the tree or annual rings. Glucose oxidase was used to label the amino-groups present in the wood sample. Its enzymatic activity was monitored by amperometric detection of H2O2 using the SECM in collector mode.

Darstellung von Konzentrationsprofilen redoxaktiver Spezies mittels amperometrischer Nanosonden: Einflüsse der natürlichen Konvektion auf den Massentransport bei Mikroscheibenelektroden

Co-reporter:Norman Baltes Dipl.-Chem.;Laurent Thouin Dr.;Christian Amatore Dr.;Jürgen Heinze Dr.

Angewandte Chemie 2004 Volume 116(Issue 11) pp:

Publication Date(Web):2 MAR 2004

DOI:10.1002/ange.200352662

Nanoden als Diffusionssonden: Nanometergroße Elektroden (r=80 nm) wurden hergestellt, um Konzentrationsprofile in der Diffusionsschicht von größeren Mikroelektroden (r=40 μm) in hoher Auflösung abzubilden (siehe Bild). Vergleiche mit theoretischen Rechnungen zeigen, dass entgegen bisherigen Annahmen die natürliche Konvektion signifikanten Einfluss auf die Diffusion bei Mikroelektroden hat.

Imaging Concentration Profiles of Redox-Active Species with Nanometric Amperometric Probes: Effect of Natural Convection on Transport at Microdisk Electrodes

Co-reporter:Norman Baltes Dipl.-Chem.;Laurent Thouin Dr.;Christian Amatore Dr.;Jürgen Heinze Dr.

Angewandte Chemie International Edition 2004 Volume 43(Issue 11) pp:

Publication Date(Web):2 MAR 2004

DOI:10.1002/anie.200352662

Nanoprobes for diffusion measurements: Nanometric-sized electrodes (r=80 nm) have been constructed to map concentration profiles within the diffusion layer of a larger microelectrode (r=40 μm) at high resolution (see picture). Comparisons with theoretical predictions demonstrate that, contrary to common wisdom, natural convection in the solution does, to some extent, affect diffusion at microelectrodes.

3,3′- and 4,4′-Dimethoxy-2,2′-bipyrroles: Highly Electron-Rich Model Compounds for Polypyrrole Formation.

Co-reporter:Andreas Merz Dr.;Sergiy Anikin;Bernd Lieser;Jürgen Heinze Dr.;Hermann John Dipl.-Chem.

Chemistry - A European Journal 2003 Volume 9(Issue 2) pp:

Publication Date(Web):16 JAN 2003

DOI:10.1002/chem.200390047

3,3′-Dimethoxy-2,2′-bipyrrole (1) and 4,4′-dimethoxy-2,2′-bipyrrole (2) were obtained in short sequences and good yields from N-benzyl-3-hydroxypyrrole-2,4-dicarboxylic acid. The key intermediate leading to 1 is an N-benzyl-3-methoxypyrrole, which is dimerized by lithiation and oxidation with NiCl₂. The formation of 2 is achieved by a classical Ullmann coupling of diethyl 1-benzyl-2-bromo-4-methoxypyrrole-3,5-dicarboxylate. The N-benzyl protection groups of 1 and 2 are cleaved under reducing conditions with sodium in liquid ammonia. Both isomeric bipyrroles are extremely sensitive toward air. Compound 1 has a very low oxidation potential of 0.09 V against AgCl but film formation hardly occurs. On the other hand, compound 2 with a potential of 0.35 V readily forms stable polypyrrole films with anodic waves at −0.51 and −0.35 V and a cathodic wave at −0.77 V, the lowest potential ever observed for a p-doped polymer.

Silicone Containing Amphiphilic Co-Networks as Immobilisation Matrices for Enzyme based Biosensors: Optochemical Detection of Gaseous Hydrogen Peroxide

Co-reporter:Stephan Meskath, Jürgen Heinze, Gerald Urban

Procedia Engineering (2011) Volume 25() pp:31-34

Publication Date(Web):1 January 2011

DOI:10.1016/j.proeng.2011.12.008

Silicone containing amphiphilic co-networks are used as immobilisation matrix for ABTS (chromophor) and horseradish peroxidase. The good gas diffusion properties as well as the good immobilisation properties of the silicone containing APCNs, reffered to as silicone hydrogels, makes this type of sensors suitable for fast real-time gas detection. Detection of 1 ppm of gaseous peroxide (used as explosive or precursor) is feasible within seconds.