R. Zellner

University of Duisburg-Essen, Essen, North Rhine-Westphalia, Germany

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Publications (141)188.46 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Whilst the physical and chemical properties of nanoparticles in the gas or idealized solvent phase can nowadays be characterized with sufficient accuracy, this is no longer the case for particles in the presence of a complex biological environment. Interactions between nanoparticles and biomolecules are highly complex on a molecular scale. The detailed characterization of nanoparticles under these conditions and the mechanistic knowledge of their molecular interactions with the biological world is, however, needed for any solid conclusions with regards to the relationship between the biological behavior of such particles and their physicochemical properties. In the present article we discuss some of the challenges with characterization and behavior of nanoparticles that are associated with their presence in chemically complex biological environments. Our focus is on the stability of colloids as well as on the formation and characteristics of protein coronae that have recently been shown to significantly modify the properties of pristine particles. Finally, we discuss the perspectives that may be expected from an improved understanding of nanoparticles in biological media.
    Physical Chemistry Chemical Physics 06/2014; · 4.20 Impact Factor
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    ABSTRACT: PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm, a hydrodynamic diameter of 120 nm and a zeta potential of -20 mV were prepared and investigated with regard to their biological activity. This review summarizes the physicochemical properties (dissolution, protein adsorption, dispersability) of these nanoparticles and the cellular consequences of the exposure of a broad range of biological test systems to this defined type of silver nanoparticles. Silver nanoparticles dissolve in water in the presence of oxygen. In addition, in biological media (i.e., in the presence of proteins) the surface of silver nanoparticles is rapidly coated by a protein corona that influences their physicochemical and biological properties including cellular uptake. Silver nanoparticles are taken up by cell-type specific endocytosis pathways as demonstrated for hMSC, primary T-cells, primary monocytes, and astrocytes. A visualization of particles inside cells is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM analysis. By staining organelles, their localization inside the cell can be additionally determined. While primary brain astrocytes are shown to be fairly tolerant toward silver nanoparticles, silver nanoparticles induce the formation of DNA double-strand-breaks (DSB) and lead to chromosomal aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo induced a moderate pulmonary toxicity, however, only at rather high concentrations. The same was found in precision-cut lung slices of rats in which silver nanoparticles remained mainly at the tissue surface. In a human 3D triple-cell culture model consisting of three cell types (alveolar epithelial cells, macrophages, and dendritic cells), adverse effects were also only found at high silver concentrations. The silver ions that are released from silver nanoparticles may be harmful to skin with disrupted barrier (e.g., wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the data obtained on the effects of this well-defined type of silver nanoparticles on various biological systems clearly demonstrate that cell-type specific properties as well as experimental conditions determine the biocompatibility of and the cellular responses to an exposure with silver nanoparticles.
    Beilstein J Nanotechnol. 01/2014; 5:1944-65.
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    ABSTRACT: The interfacing of colloidal nanoparticles with mammalian cells is now well into its second decade. In this review our goal is to highlight the more generally accepted concepts that we have gleaned from nearly twenty years of research. While details of these complex interactions strongly depend, amongst others, upon the specific properties of the nanoparticles used, the cell type, and their environmental conditions, a number of fundamental principles exist, which are outlined in this review.
    Beilstein Journal of Nanotechnology 01/2014; 5:1477-90. · 2.37 Impact Factor
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    ABSTRACT: The deliquescence behavior of ternary inorganic (ammonium sulfate and ammonium nitrate)/organic (glutaric acid and malonic acid)/water aerosol particles has been investigated at 293 K using a novel surface aerosol microscopy (SAM) technique. The results obtained for the deliquescence relative humidities (DRH) for particles of variable inorganic/organic contents show a eutectic behavior with the mixed particles showing deliquescence at lower DRH compared to the pure inorganic and organic components, respectively. This behavior has been quantitatively modeled using the extended aerosol inorganics (E-AIM) thermodynamic model of Clegg et al. in combination with the UNIFAC group activity approach to account for organic molecular solutes. In addition, we have investigated the crystallization behavior of supersatured and formerly deliquesced ternary solution droplets using space resolved Raman spectroscopy. It is found that such droplets produce solid particles in which the inorganic and organic phases show some spatial separation with the organic component being predominantly found at the outer part of the particle. Independent measurements of the contact angles of such ternary droplets reveal that their angles are within experimental error identical to those of the purely organic/water solutions.
    The Journal of Physical Chemistry A 04/2012; 116(24):6199-210. · 2.77 Impact Factor
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    ABSTRACT: In biological fluids, proteins associate with nanoparticles, leading to a protein "corona" defining the biological identity of the particle. However, a comprehensive knowledge of particle-guided protein fingerprints and their dependence on nanomaterial properties is incomplete. We studied the long-lived ("hard") blood plasma derived corona on monodispersed amorphous silica nanoparticles differing in size (20, 30, and 100 nm). Employing label-free liquid chromatography mass spectrometry, one- and two-dimensional gel electrophoresis, and immunoblotting the composition of the protein corona was analyzed not only qualitatively but also quantitatively. Detected proteins were bioinformatically classified according to their physicochemical and biological properties. Binding of the 125 identified proteins did not simply reflect their relative abundance in the plasma but revealed an enrichment of specific lipoproteins as well as proteins involved in coagulation and the complement pathway. In contrast, immunoglobulins and acute phase response proteins displayed a lower affinity for the particles. Protein decoration of the negatively charged particles did not correlate with protein size or charge, demonstrating that electrostatic effects alone are not the major driving force regulating the nanoparticle-protein interaction. Remarkably, even differences in particle size of only 10 nm significantly determined the nanoparticle corona, although no clear correlation with particle surface volume, protein size, or charge was evident. Particle size quantitatively influenced the particle's decoration with 37% of all identified proteins, including (patho)biologically relevant candidates. We demonstrate the complexity of the plasma corona and its still unresolved physicochemical regulation, which need to be considered in nanobioscience in the future.
    ACS Nano 08/2011; 5(9):7155-67. · 12.03 Impact Factor
  • Lennart Treuel, Alice Sandmann, Reinhard Zellner
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    ABSTRACT: This work examines the crystals resulting from the efflorescence of internally mixed aqueous aerosols comprising ammonium sulphate and different dicarboxylic acids. Most studies on the deliquescence of aerosols use previously effloresced aerosols in their experiments. However, during efflorescence a highly supersaturated solution crystallises in a kinetically controlled way unlike the case of thermodynamically controlled crystallisation. Herein the distribution of individual substances within the effloresced crystals is investigated using Raman scanning experiments. The data presented show an intriguingly complex behaviour of these ternary and quarternary aerosols. A spatial separation of substances in the crystals resulting from the efflorescence of previously internally mixed ternary salt/dicarboxylic acid/water aerosol droplets is demonstrated and mechanistic aspects are discussed.
    ChemPhysChem 04/2011; 12(6):1109-17. · 3.35 Impact Factor
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    ABSTRACT: Interactions between differently functionalised silver and gold nanoparticles (NPs) as well as polystyrene nanoparticles with bovine serum albumin (BSA) are studied using circular dichroism (CD) spectroscopy. It is found that the addition of NPs to the protein solution destroys part of the helical secondary structure of the protein as a result of surface adsorption. From the loss of free protein and hence the extent of their structural change adsorption equilibrium constants are derived. The results reveal that citrate-coated gold and silver NPs exhibit much stronger interactions with BSA than polymeric or polymer-coated metallic NPs. It is therefore concluded that for the particles considered, the influence of surface composition on the interaction behaviour dominates that of the core.
    ChemPhysChem 10/2010; 11(14):3093-9. · 3.35 Impact Factor
  • Reinhard Zellner
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    ABSTRACT: Das Verständnis und die Bedeutung des Verhaltens von Spurenstoffen in der Atmosphäre sind innerhalb der letzten 20 Jahre stark gewachsen. Dies ist darauf zurückzuführen, daß die Grundlagenforschung an Breite und Tiefe zugenommen hat. Allerdings zeigt die wissenschaftliche Deutung drohender regionaler und globaler Umweltveränderungen, daß Politik und Gesellschaft handeln müssen.
    Nachrichten aus der Chemie 07/2010; 47(7):790-792. · 0.20 Impact Factor
  • H. Hein, A. Hoffmann, R. Zellner
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    ABSTRACT: Reactions of 2-butoxy radicals have been investigated using time-resolved measurements of NO2 and OH concentration profiles in the flash initiated oxidation of 2-bromobutane and subsequent numerical simulation. 2-butoxy radicals were produced selectively by the excimer-laser photolysis of 2-bromobutane at 193 or 248 nm followed by the reaction of 2-butyl radicals with O2 and NO. Whereas NO2 was detected by cw-LIF, detection of OH was achieved by laser long-path absorption at 308 nm. All experiments were performed at 293 K and a total pressure of 50 mbar. The rate coefficients of the O2 reaction (kO2) and of unimolecular decomposition (kdecomp) have been varied, using the FACSIMILE code, until best fits were obtained. The following rate coefficients were derived: kO2 = (6.5±2) × 10−15 cm3-molecule−1·s−1 and kdecomp = (3.5±2) × 10−3 s−1.
    Berichte der Bunsengesellschaft für physikalische Chemie. 06/2010; 102(12):1840 - 1849.
  • Ch. Mund, Ch. Fockenberg, R. Zellner
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    ABSTRACT: Fluorescence excitation spectra of CH3CH2CH2O (n-propoxy) and (CH3)2CHO (i-propoxy) radicals were obtained using a combined laser photolysis/laser-induced fluorescence (LIF) technique and the kinetics of reactions of these radicals with (1) O2 as a function of temperature and with (2) NO2 as a function of pressure have been determined.Propoxy radicals were produced by excimer laser photolysis of the appropriate propyl nitrites at λ = 351 nm. The spectra of the (Ã←X̃) transitions show progressions of the CO-stretching vibration in the electronically excited states with spacings of the bands of (560±10) cm−1 for i-propoxy and (580±10) cm−1 for n-propoxy. Fluorescence spectra taken after excitation in the (4,0) band at λ = 340.1 nm (i-propoxy) and in the (1,0) band at λ = 342.4nm (n-propoxy) show progressions of the CO-stretching vibration in the electronic ground state of (900±60) cm−1 for i-propoxy and (1000±50) cm−1 for n-propoxy.The Arrhenius expressions for the ractions of n-propoxy and i-propoxy with O2 have been determined to be k1 (n) = (1.4±0.6)×10−14 exp (0.9±0.5) kJ mol−1/RT) cm3 s−1 and k1 (i) = (1.0±0.3)×10−14 exp (-(1.8±0.4) kJ mol−1/RT) cm3 s−1 in me range 218–313 K. The rate coefficients for the reactions of NO2 with n-propoxy and i-propoxy at T = 296 K were found to be independent of total pressure with k2(n) = (3.6±0.4)×10−11 cm3 s−1 (6.7–53 mbar) and k2(i)=(3.3±0.3)×10−11 cm3 s−1 (6.7–106 mbar).
    Berichte der Bunsengesellschaft für physikalische Chemie. 06/2010; 102(5):709 - 715.
  • Berichte der Bunsengesellschaft für physikalische Chemie. 06/2010; 102(5):716 - 722.
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    ABSTRACT: The rate coefficient for the reaction of Cl atoms with (1) H2O and of Cl2− radical anions with (2) H2O and (3) OH− have been determined using laser photolysis for the generation of Cl/Cl2− and long path laser absorption for the time resolved detection of Cl2−. The following results were obtained: k1 = (2.3 + 0.6)· 105 s−1, k2 < 610s−1 and k3 = (4.0 + 0.6)· 106M−1s−1. It is concluded that the lifetime of Cl/Cl2− in aqueous solution strongly depends on the Cl− content and on pH.
    Berichte der Bunsengesellschaft für physikalische Chemie. 06/2010; 101(12):1909 - 1913.
  • M. Exner, H. Herrmann, R. Zellner
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    ABSTRACT: A new experimental technique for temperature dependent studies of the kinetics of the nitrate radical (NO3) in aqueous solution has been developed. In this technique NO3 is produced by excimer laser photolysis of peroxodisulfate anions at 351 nm in the presence of excess nitrate and detected by time-resolved long-path laser absorption using the 632.8 nm line of a HeNe-laser. — For the generation reaction of NO3, viz. (1) SO4− + NO3− SO42- + NO3 a rate constant of k1 = (5.0 ± 0.5) · 104 l mol · s at T = 298 K and zero ionic strength was found. For the reactions (2) NO3 + OH− NO3− OH and (3) NO3 + Cl− NO3− + Cl rate coefficients of k2 = (8.2 ± 0.9) · 107 and k3. = (1.0 ± 0.2) · 107 l/mol · s were determined at T = 298 K. In temperature dependent experiments the Arrhenius expressions k2(T) = (8.1 ± 0.4) · 1011 exp[-(2700 ± 400)K/T] l/mol · s and k3(T) = (1.9 ± 0.2) · 1013 exp[-(4300 ± 500) K/T] l/mol · s were derived. - The rate constant of the reaction of NO3 with dissolved sulfur (IV) has been studied over a range of pH-values and temperature. For the reactions with SO2(aq) (4). and HSO3− (5) rate coefficients of k4 = (2.3 ± 0.5) · 108 and k5 = (1.4 ± 0.1) · 109 l/mol · s, respectively, at 298 K were obtained. The corresponding temperature dependences are described by: k4(T) = (5.6 ± 0.7) · 1013 exp[-(3700 ± 1100)K/T] l/mol · s and k5(T) = (1.1 ± 0.2) · 1012 exp[-(2000 ± 400)K/T] l mol · s. For the reaction of NO3 with SO32- (6) a rate constant of k6 = (3.0 ± 0.4) · 108 l/mol · s was derived at T = 278 K.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 96(3):470 - 477.
  • V. Mörs, A. Hoffmann, W. Malms, R. Zellner
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    ABSTRACT: The oxidative degradation of HCFC 141 b (CFCl2CH3) and HCFC 142 b (CF2ClCH3) in the presence of NO at T = 293 K and p = 50 mbar has been studied using laser pulse initiation combined with cw laser long path absorption/LiF for the detection of OH and NO2. The absolute yield and temporal behaviour of these products have been found to be sensitive indicators for the reaction behaviour of the alkoxy radicals CFCl2CH2O and CF2ClCH2O, respectively. The rate coefficients for the reactions of the alkoxy radicals with O2 were determined to be k(CFCl2CH2O+O2→CFCl2CHO+HO2) = (2.0±1.0)×10−15 cm3/s and k(CF2ClCH2O+O2→CF2ClCHO+HO2) = (2.5±1.5)×10−15 cm3/s. Upper limits for the rate coefficients for unimolecular decomposition of the alkoxy radicals by C-C-bond fission of k(CFCl2CH2O+M→CFCl2+CH2O+M)×1.0±103 s−1 and k(CF2ClCH2O+M→CF2Cl+CH2O+M)≤1.5 T≤ 103 s−1 were derived. We conclude from these data that CFCl2CHO and CF2ClCHO will be formed as the dominant primary carbonyl products in the oxidation of HCFC 141 b and 142 b throughout the troposphere. Moreover, the rate coefficients for the reactions of the HCFCs with OH radicals at T = 293 K have been measured. The values k(CFCl2CH3+OH→CFCl2CH2+H2O) = (4.6±0.8)×10−15 cm3/s and k(CF2ClCH3+OH→CF2ClCH2+H2O) = (2.6±0.4)×10−15 cm3/s were obtained.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 100(5):540 - 552.
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    ABSTRACT: The atmospheric chemical behaviour of 2H-Heptafluoropropane (CF3CHFCF3, HFC-227) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of HFC-227 with OH radicals has been determined in direct time resolved experiments using a combination of laser-pulse initiation and LIF. In the temperature range T=298-463 K the Arrhenius expression k(T) = (3.8±0.8) 10−13 exp(-1596±77K/T) cm3/s, which corresponds to k (298 K) = (1.8±0.3) 10−15cm3/s, was found. The mechanism of the atmospheric degradation of HFC-227 has been investigated using both, laser-pulse initiated/time resolved and UV photolysis/FTIR product studies. It is concluded that the major carbonyl products are CF3COF and CF2O which result from the decomposition of the oxy radical CF3CF(O)CF3 by C-C bond fission. The rate coefficient for this decomposition process has been determined to be k = (2±1) 103s−1 at 298K. Based on the reactivity of HFC-227 with respect to the reaction with OH radicals, the atmospheric lifetime and the GWP value for HFC-227 are estimated to be ∼40 years and 0.6±0.2, respectively.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 98(2):141 - 146.
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    ABSTRACT: Steady-state photolysis of oxalylfluoride (FC(O)C(O)F) together with FTIR-spectroscopy has been used to investigate the reactions of FCO and FC(O)OO radicals in the presence of O2 and NO2. Formation of FCO radicals has been identified as the main photodissociation process of oxalylfluoride at λ = 254 nm. However, a quantum yield of ø = 0.11±0.02 was attributed to the direct formation of CF2O and CO in this process. In the presence of O2, the products of reactions of FC(O)Ox(x = 0, 1, 2) radicals were bis-fluoroformylperoxide (FC(O)OOC(O)F) and bis-fluoroformyltrioxide (FC(O)OOOC(O)F), as well as CF2O, CO and CO2. Addition of NO2 to the reaction system led to the formation of fluoroformylperoxynitrate (FC(O)OONO2). The rate constant for the thermal decomposition of fluoroformylperoxynitrate in the temperature range 275–307 K was measured to be k(T) = 3.5 × 1016 exp (-13 900+1700−2600/T) s−1. For bis-fluoroformyltrioxide, a rate constant for thermal decomposition of 6.0×10−4 s−1 was measured at temperatures around 250 K. The thermal stability of bisfluoroformyltrioxide and fluoroformylperoxynitrate is discussed in terms of a comparison with the stability of similar molecules.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 100(4):445 - 454.
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    ABSTRACT: The atmospheric chemical behaviour of 1,1,1,2-tetrafluoroethane (CF3CFH2, HFC-134a) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of (1 a) CF3CFH2 + OH→CF3CFH + H2O has been determined in direct time-resolved experiments using laser-pulse initiation and laser long-path absorption. A value of k1a = (4.6±0.5)×10−15 cm3/s at T = 295K has been found. The ratio of the rate coefficients for the reactions of the CF3CFHO-radical with O2, (4) CF3CFHO + O2→CF3CFO + HO2, and C-C bond fission, (5) CF3CFHO + M→CFHO + CF3 + M, for T = 295 K and ptotal = 50 mbar (O2) has been obtained to be k4/(k5 [M]) = 1.5×10−19 cm3, with the individual values being k4 = 2.7×10−15 cm3/s and k5 [M] = 1.8×104 s−1. The mechanism of the atmospheric degradation of HFC-134a has been investigated in the temperature range 244-295 K and ptotal = 1000 mbar using UV photolysis/FTIR product studies. From these experiments the Arrhenius expression k4/(k5 [M]) = 8.7±10−25 exp ((3240+990−610) K/T) cm3 was determined. Moreover, it is concluded that the major carbonyl products are CF3CFO, CFHO and CF2O which result from the two possible reactions of the oxy radical CF3CFHO. As a consequence the yield of these carbonyl products is dependent on temperature, O2 partial pressure and total pressure. For the reaction of CFHO with Cl atoms the Arrhenius expression k18 = 5.7×10−14exp (−(1130 ± 160) K/T) cm3/s was determined in the temperature range 244-298 K.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 100(5):528 - 539.
  • H. Herrmann, M. Exner, R. Zellner
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    ABSTRACT: Absorption coefficients for the nitrate (NO3) radical in aqueous solution have been determined using multichannel optical absorption in the range λ = 540 – 760 nm. NO3 radicals were generated by excimer laser photolysis of (NH4)2[Ce(NO3)6] at 351 nm. For the quantum yield of NO3 formation from this process a value of ϕ(NO3) = (0.85 ± 0.09) has been determined using a Br− scavenging technique. With this value the absolute absorption coefficient of NO3 at the maximum of its absorption at 635 nm was found as ϵ = (527 ± 105) l/mol · cm (base 10). Absorption coefficient data for the range 540–760 nm are presented in 2 nm intervals. The oscillator strength of the (0-0) band transition near 665 nm has been calculated to be (1.6 ± 0.5) · 10−3 in reasonable agreement with the gas phase value.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 95(5):598 - 604.
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    ABSTRACT: Since chemical and radiative effects of atmospheric aerosols are size and phase related, they are strongly influenced by the ambient relative humidity (RH) due to water absorbing hygroscopic components, changing both particle diameter and wavelength dependent refractive indices. Therefore, the assessment of the net effect on chemistry and/or climate for a given atmospheric particle load will critically depend on the level of scientific understanding regarding the phase behaviour of complex organic/ inorganic aerosols. The influence of organic substances such as dicarboxylic acids on the deliquescence behaviour has been subject of numerous studies over the past years. In this work a number of different mixtures comprising ammonium sulphate (AS) and different dicarboxylic acids (glutaric acid, maleic acid, malonic acid, succinic acid, and oxalic acid) have been used in Raman scanning experiments to study the spacial distribution of substances in the crystalline aerosol formed from the efflorescence process of internally mixed ternary ammonium sulphate / dicarboxylic acid / water aerosols. The results give intriguing insights into the complexity of the behaviour of highly supersaturated ternary organic/inorganic solutions and reveal substantial differences in the spacial distributions of organic and inorganic crystalline substances resulting from the efflorescence of these originally internally mixed systems. The relevance of these findings for the interpretations of the complex, concentration dependent phase behaviour of organic/ inorganic aerosols will be discussed. Modelling the behaviour of these complex solution aerosols frequently involves calculations of interactions between individual ionic components. In order to quantify these impacts the ammonium salts for a number of dicarboxylic acids have been synthesised and their thermodynamic behaviour has been elucidated with the surface aerosol microscope (SAM) setup. The results have been used to test and validate critical parameters of the aerosol inorganics model (AIM). In this work we present activity measurements for aqueous aerosols containing these organic ammonium salts as well as a comparison of AIM model data and experimental results.

Publication Stats

743 Citations
188.46 Total Impact Points


  • 1994–2014
    • University of Duisburg-Essen
      • Physical Chemistry
      Essen, North Rhine-Westphalia, Germany
    • HagaZiekenhuis van Den Haag
      's-Gravenhage, South Holland, Netherlands
    • University of Leipzig
      Leipzig, Saxony, Germany
  • 2006
    • Bulgarian Academy of Sciences
      Ulpia Serdica, Sofia-Capital, Bulgaria
  • 1999
    • Klinikum Karlsruhe
      Carlsruhe, Baden-Württemberg, Germany
  • 1990–1999
    • Georg-August-Universität Göttingen
      • Institute of Physical Chemistry
      Göttingen, Lower Saxony, Germany
    • Klinikum Darmstadt
      Darmstadt, Hesse, Germany
  • 1990–1998
    • Klinikum Garmisch-Partenkirchen
      Markt Garmisch-Partenkirchen, Bavaria, Germany
  • 1997
    • ETH Zurich
      Zürich, Zurich, Switzerland
  • 1996
    • New York State
      New York City, New York, United States
  • 1995
    • IHU de Strasbourg
      Strasburg, Alsace, France
  • 1993
    • SH-Gen Wiesbaden
      Wiesbaden, Hesse, Germany
  • 1991
    • Hochschule Bochum
      Bochum, North Rhine-Westphalia, Germany
  • 1988
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
    • University of East Anglia
      • School of Environmental Sciences
      Norwich, England, United Kingdom
  • 1987
    • Bergische Universität Wuppertal
      • Physical and Theoretical Chemistry
      Wuppertal, North Rhine-Westphalia, Germany