TY - JOUR A1 - Rietsch, P. A1 - Zeyat, M. A1 - Hübner, Oskar A1 - Hoffmann, Katrin A1 - Resch-Genger, Ute A1 - Kutter, M. A1 - Paskin, A. A1 - Uhlig, J. A1 - Lentz, D. A1 - Eigler, S. T1 - Substitution Pattern-Controlled Fluorescence Lifetimes of Fluoranthene Dyes N2 - The absorption and emission properties of organic dyes are generally tuned by altering the substitution pattern. However, tuning the fluorescence lifetimes over a range of several 10 ns while barely affecting the spectral features and maintaining a moderate fluorescence quantum yield is challenging. Such properties are required for lifetime multiplexing and barcoding applications. Here, we show how this can be achieved for the class of fluoranthene dyes, which have substitution-dependent lifetimes between 6 and 33 ns for single wavelength excitation and emission. We explore the substitution-dependent emissive properties in the crystalline solid state that would prevent applications. Furthermore, by analyzing dye mixtures and embedding the dyes in carboxyfunctionalized 8 μm-sized polystyrene particles, the unprecedented potential of these dyes as labels and encoding fluorophores for time-resolved fluorescence detection techniques is demonstrated. KW - Fluorescence KW - Label KW - Fluoranthene KW - Quantum yield KW - Reporter KW - Crystal KW - Encoding KW - Multiplexing KW - Particle KW - Bead KW - Lifetime KW - Dye KW - Barcoding PY - 2021 DO - https://doi.org/10.1021/acs.jpcb.0c08851 SN - 1520-5207 VL - 125 IS - 4 SP - 1207 EP - 1213 PB - American Chemical Society AN - OPUS4-52087 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engel, A. A1 - Ottermann, C. A1 - Klahn, J. A1 - Korb, T. A1 - Resch-Genger, Ute A1 - Hoffmann, Katrin A1 - Kynast, U. A1 - Rupertus, V. ED - Dan V. Nicolau, ED - Daniel L. Farkas, ED - Robert C. Leif, T1 - Anorganic fluorescence reference materials for decay time of fluorescence emission N2 - Fluorescence techniques are known for their high sensitivity and are widely used as analytical tools, detection methods and imaging applications for product and process control, material sciences, environmental and bio-technical analysis, molecular genetics, cell biology, medical diagnostics, and drug screening. According to DIN/ISO 17025 certified standards are used for steady state fluorescence diagnostics, a method having the drawback of giving relative values for fluorescence intensities only. Therefore reference materials for a quantitative characterization have to be related directly to the materials under investigation. In order to evaluate these figures it is necessary to calculate absolute numbers such as absorption/excitation cross sections and quantum yield. This has been done for different types of dopands in different materials such as glass, glass ceramics, crystals or nano crystalline material embedded in polymer matrices. Samples doped with several fluophores of different emission wavelengths and decay times are required for fluorescent multiplexing applications. Decay times shorter than 100 ns are of special interest. In addition, a proper knowledge is necessary of quantum efficiency in highly scattering media. Recently, quantum efficiency in YAG:Ce glass ceramics has been successfully investigated. Glass and glass ceramics doped with threefold charged rare earth elements are available. However, these samples have the disadvantage of emission decay times much longer than 1 microsecond, due to the excitation and emission of their optical forbidden electronic transitions. Therefore first attempts have been made to produce decay-time standards based on organic and inorganic fluophores. Stable LUMOGEN RED pigments and YAG:Ce phosphors are diluted simultaneously in silicone matrices using a wide range of concentrations between 0.0001 and 2 wt%. Organic LUMOGEN RED has decay times in the lower nanosecond range with a slight dependency on concentration and temperature. In addition, the well-known decay properties of inorganic YAG:Ce are observed also embedded in silicone matrix. Luminescent silicone layers are obtained with thicknesses between 150 and 300 m and no change of decay time, which has been determined to be between 60 and 62 ns. Finally, first results are shown for fluorescent CaF2:Pb glass ceramics embedded in a silicate glass matrix. Wavelength accuracy and lifetime are characterized for different environmental conditions such as temperature treatment and UV irradiation. Moreover, intensity patterns, e.g. line profiles and results, are discussed on homogeneity and photo and thermal stability, respectively. Fluorescence (steady state, decay time) and absorption (remission, absorption) spectroscopy are employed as diagnostic methods to get a microscopic view of the relevant physical processes. The work is funded by BMBF under project number 13N8849. KW - Fluorescence KW - Reference material KW - Glass KW - Glass ceramic KW - Phosphor KW - Doped glass and glass ceramics PY - 2008 SN - 978-0-8194-7034-8 DO - https://doi.org/10.1117/12.767633 VL - 6859 SP - 68591A-1 - 68591A-10 PB - SPIE, the International Society for Optical Engineering CY - Bellingham, Wash. AN - OPUS4-19800 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute A1 - Hoffmann, Katrin A1 - Nietfeld, W. A1 - Engel, A. A1 - Neukammer, J. A1 - Nitschke, R. A1 - Ebert, B. A1 - Macdonald, R. T1 - How to Improve Quality Assurance in Fluorometry: Fluorescence-Inherent Sources of Error and Suited Fluorescence Standards N2 - The scope of this paper is to illustrate the need for an improved quality assurance in fluorometry. For this purpose, instrumental sources of error and their influences on the reliability and comparability of fluorescence data are highlighted for frequently used photoluminescence techniques ranging from conventional macro- and microfluorometry over fluorescence microscopy and flow cytometry to microarray technology as well as in vivo fluorescence imaging. Particularly, the need for and requirements on fluorescence standards for the characterization and performance validation of fluorescence instruments, to enhance the comparability of fluorescence data, and to enable quantitative fluorescence analysis are discussed. Special emphasis is dedicated to spectral fluorescence standards and fluorescence intensity standards. KW - Fluorescence KW - Standard KW - Calibration KW - Microarray KW - In vivo imaging KW - Flow cytometry PY - 2005 DO - https://doi.org/10.1007/s10895-005-2630-3 SN - 1053-0509 SN - 1573-4994 VL - 15 IS - 3 SP - 337 EP - 362 PB - Plenum Publ. Corp. CY - New York, NY AN - OPUS4-10823 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Behnke, Thomas A1 - Laux, Eva-Maria A1 - Hoffmann, Katrin A1 - Peters, S. A1 - Haueisen, J. A1 - Klemm, M. A1 - Resch-Genger, Ute T1 - Simple approaches to fluorescence lifetime standards using dye-quencher pairs N2 - Photoluminescence techniques are amongst the most widely used tools in the material and life sciences, with new and exciting applications continuously emerging. Advantages include their comparative ease of use, unique sensitivity, non-invasive character, and potential for multiplexing, remote sensing, and miniaturization. Increasing applications of fluorescence techniques in the life sciences and emerging medical applications of fluorescence microscopic techniques including 1P and 2P fluorescence microscopy combined with fluorescence lifetime imaging (FLIM) in e.g. in vivo eye diagnostics boosted the demand for robust, easy-to-use, and reliable fluorescence standards to ensure the reliability and comparability of fluorescence data. This includes fluorescence standards for the consideration of instrument-specific spectral and intensity distortions of measured signals and instrument performance validation, fluorescence intensity standards for the quantification of measured intensities and for signal referencing, and lately, also fluorescence lifetime standards. T2 - BMT 2012 - 46. DGBMT Jahrestagung CY - Jena, Germany DA - 16.09.2012 PY - 2012 DO - https://doi.org/10.1515/bmt-2012-4499 SN - 0013-5585 SN - 1862-278X VL - 57 IS - Suppl. 1 SP - 613 PB - De Gruyter CY - Berlin AN - OPUS4-27682 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Angeli, J. A1 - Bengtson, A. A1 - Bogaerts, A. A1 - Hoffmann, V. A1 - Hodoroaba, Vasile-Dan A1 - Steers, E. T1 - Glow discharge optical emission spectrometry: moving towards reliable tion film analysis - a short review N2 - Glow discharge optical emission spectroscopy (GD-OES) is briefly reviewed, with particular reference to topics relevant to the application field of near surface and thin film analysis. The special needs and requirements for thin film analysis, in contrast to coating and bulk analysis, are pointed out. A task list is developed which shows the requirements of further developments to the technique and the fundamentals. The state-of-the-art is presented in measurement technique, GD source control and design, the effect of traces of molecular gases, correction and quantification procedures, contributions of modelling and, finally, reference materials for thin film analysis. PY - 2003 DO - https://doi.org/10.1039/b301293j SN - 0267-9477 SN - 1364-5544 VL - 18 IS - 6 SP - 670 EP - 679 PB - Royal Society of Chemistry CY - London AN - OPUS4-2533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hodoroaba, Vasile-Dan A1 - Klemm, D. A1 - Reinholz, Uwe A1 - Strub, E. A1 - Röhrich, J. A1 - Bohne, W. A1 - Hoffmann, V. A1 - Wetzig, K. T1 - Potential candidates of certified reference material for determination of hydrogen concentration with glow discharge optical emission spectrometry (GD-OES) - a feasibility study N2 - Three different coatings/layers have been found in a feasibility study as potential candidates for certified reference materials for the determination of hydrogen concentration by GD-OES: (i) electroplated zinc, (ii) carbon-rich coatings and (iii) amorphous silicon layers. KW - CRM KW - Hydrogen KW - GDS PY - 2008 DO - https://doi.org/10.1039/b717924c SN - 0267-9477 SN - 1364-5544 VL - 23 SP - 460 EP - 462 PB - Royal Society of Chemistry CY - London AN - OPUS4-17335 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferreira da Silva, F. A1 - do N. Varella, M. T. A1 - Jones, N. C. A1 - Vrönning Hoffmann, S. A1 - Denifl, S. A1 - Bald, Ilko A1 - Kopyra, J. T1 - Electron-Induced Reactions in 3-Bromopyruvic Acid N2 - 3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour Radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of Cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br@ close to 0 eV and within several resonant features at 1.9 and 3–8 eV. At low electron energies, Br@ formation proceeds through s* and p* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser. KW - Density functional calculations KW - Dissociative electron attachment KW - Drug discovery KW - Gas-phase reactions KW - Sensitizers PY - 2019 DO - https://doi.org/10.1002/chem.201806132 SN - 0947-6539 VL - 25 IS - 21 SP - 5498 EP - 5506 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-48003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Carl, Peter A1 - Sarma, Dominik A1 - Gregório, Bruno J. R. A1 - Hoffmann, Kristin A1 - Lehmann, Andreas A1 - Rurack, Knut A1 - Schneider, Rudolf T1 - Wash-Free Multiplexed Mix-and-Read Suspension Array Fluorescence Immunoassay for Anthropogenic Markers in Wastewater N2 - Pharmaceuticals, certain food ingredients, and mammalian endogenous metabolic products in wastewater are mostly of human origin. They are anthropogenic markers. Proper knowledge of their levels in wastewater helps to track sources of pollutants in natural waters and allows for calculation of removal efficiencies in wastewater Treatment plants. Here, we describe the development and application of an indirect competitive, multiplexing suspension Array fluorescence immunoassay (SAFIA) for the detection of carbamazepine (CBZ), diclofenac (DCF), caffeine (CAF), and isolithocholic acid (ILA) in wastewater, covering those classes of anthropogenic markers. The assay consists of haptens covalently conjugated to fluorescence-encoded polystyrene core/silica shell microparticles to create a site for competitive binding of the antibodies (Abs). Bound Abs are then stained with fluorophore-labeled Abs. Encoding and signaling fluorescence of the particles are determined by an automated flow cytometer. For compatibility of the immunoassay with the 96-well microtiter plate format, a stop reagent, containing formaldehyde, is used. This enables a wash-free procedure while decreasing time-to-result. Detection limits of 140 ± 40 ng/L for CBZ, 180 ± 110 ng/L for CAF, 4 ± 3 ng/L for DCF, and 310 ± 70 ng/L for ILA are achieved, which meet the sensitivity criteria of wastewater analysis. We demonstrate the applicability of SAFIA to real wastewater samples from three different wastewater Treatment plants, finding the results in good agreement with LC-MS/MS. Moreover, the accuracy in general exceeded that from classical ELISAs. We therefore propose SAFIA as a quick and reliable approach for wastewater analysis meeting the requirements for process analytical technology. KW - Suspension Array KW - Immunoassay KW - Carbamazepine KW - Caffeine KW - Diclofenac KW - SAFIA PY - 2019 DO - https://doi.org/10.1021/acs.analchem.9b03040 SN - 0003-2700 VL - 91 IS - 20 SP - 12988 EP - 12966 PB - ACS Publications AN - OPUS4-49305 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bruna, F. G. A1 - Prokop, M. A1 - Bystron, T. A1 - Loukrakpam, R. A1 - Melke, J. A1 - Lobo, C. M. S. A1 - Fink, M. A1 - Zhu, M. A1 - Voloshina, E. A1 - Kutter, M. A1 - Hoffmann, H. A1 - Yusenko, Kirill A1 - de Oliveira Guilherme Buzanich, Ana A1 - Röder, B. A1 - Bouzek, K. A1 - Paulus, B. A1 - Roth, C. T1 - Following adsorbed intermediates on a platinum gas diffusion electrode in H3PO3‑containing electrolytes using in situ X‑ray absorption spectroscopy N2 - One of the challenges of high-temperature polymer electrolyte membrane fuel cells is the poisoning of the Pt catalyst with H3PO4. H3PO4 is imbibed into the routinely used polybenzimidazole-based membranes, which facilitate proton conductivity in the temperature range of 120−200 °C. However, when leached out of the membrane by water produced during operation, H3PO4 adsorbs on the Pt catalyst surface, blocking the active sites and hindering the oxygen reduction reaction (ORR). The reduction of H3PO4 to H3PO3, which occurs at the anode due to a combination of a low potential and the presence of gaseous H2, has been investigated as an additional important contributing factor to the observed poisoning effect. H3PO3 has an affinity toward adsorption on Pt surfaces even greater than that of H2PO4 −. In this work, we investigated the poisoning effect of both H3PO3 and H3PO4 using a half-cell setup with a gas diffusion electrode under ambient conditions. By means of in situ X-ray absorption spectroscopy, it was possible to follow the signature of different species adsorbed on the Pt nanoparticle catalyst (H, O, H2PO4 −, and H3PO3) at different potentials under ORR conditions in various electrolytes (HClO4, H3PO4, and H3PO3). It was found that H3PO3 adsorbs in a pyramidal configuration P(OH)3 through a Pt−P bond. The competition between H3PO4 and H3PO3 adsorption was studied, which should allow for a better understanding of the catalyst poisoning mechanism and thus assist in the development of strategies to mitigate this phenomenon in the future by minimizing H3PO3 generation by, for example, improved catalyst design or adapted operation conditions or changes in the electrolyte composition. KW - H3PO4 life cycle KW - XAS KW - In situ coupling KW - High-temperature fuel cells KW - Δμ XANES KW - H3PO3 PY - 2022 DO - https://doi.org/10.1021/acscatal.2c02630 SN - 2155-5435 VL - 12 IS - 18 SP - 11472 EP - 11484 PB - ACS CY - Washington, DC AN - OPUS4-55815 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Appelhans, Dietmar A1 - Oertel, U. A1 - Mazzeo, R. A1 - Komber, H. A1 - Hoffmann, J. A1 - Weidner, Steffen A1 - Brutschy, B. A1 - Voit, B. A1 - Ottaviani, M.F. T1 - Dense-shell glycodendrimers: UV/Vis and electron paramagnetic resonance study of metal ion complexation N2 - The development of dendritic metal ion carrier systems for use in a biological environment is a challenging task as the carrier system must possess multiple features (e.g. a protective shell for metal decomplexation, targeting functions, metal-intradendrimer complexes, etc.) to substitute for the function of metal proteins in processes such as copper metabolism. Thus, Cu(II) complexation by a series of poly(propyleneimine) glycodendrimers ranging up to the fifth generation that have either a dense maltose or maltotriose shell was investigated by UV/Vis spectroscopy and electron paramagnetic resonance (EPR). As a necessary step towards potential biological application, we elucidated the complexation capacity, location of the Cu(II)-dendrimer complexes and the Cu(II) coordination sphere in the dendritic environment. A generation-dependent Cu(II) complexation was found. Furthermore, analysis of the EPR spectra revealed that internal and external Cu(II) coordination and the symmetry (axial and rhombic) of the generated complexes depend on the oligosaccharide shell, dendrimer generation and the relative concentrations of Cu(II) and the dendrimers. Both axial and rhombic symmetries are generation dependent, but also distort with increasing generation number. External coordination of Cu(II) is supported by sugar groups and water molecules. Finally, a third-generation dendrimer with a maltose shell was used to explore the general complexation behaviour of the dendritic poly(propyleneimine) scaffold towards different metal ions [Cu(II), Ag(I), VO(IV), Ni(II), Eu(III) and UO2(VI)]. KW - Glycodendrimers KW - Metal ion complexation KW - Metal ion-intradendrimer complexes KW - Electron paramagnetic resonance study PY - 2010 DO - https://doi.org/10.1098/rspa.2009.0107 SN - 1364-5021 SN - 0962-8444 SN - 0080-4630 SN - 0950-1207 SN - 1471-2946 VL - 466 SP - 1489 EP - 1513 CY - London, UK AN - OPUS4-21622 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kuhne, Maren A1 - Dippong, Martin A1 - Flemig, Sabine A1 - Hoffmann, Katrin A1 - Petsch, K. A1 - Schenk, J.A. A1 - Kunte, Hans-Jörg A1 - Schneider, Rudolf T1 - Comparative characterization of mAb producing hapten-specific hybridoma cells by flow cytometric analysis and ELISA N2 - A novel method that optimizes the screening for antibody-secreting hapten-specific hybridoma cells by using flow cytometry is described. Cell clones specific for five different haptens were analyzed. We selectively double stained and analyzed fixed hybridoma cells with fluorophore-labeled haptens to demonstrate the target-selectivity, and with a fluorophore-labeled anti-mouse IgG antibody to characterize the level of surface expression of membrane-bound IgGs. ELISA measurements with the supernatants of the individual hybridoma clones revealed that antibodies from those cells, which showed the highest fluorescence intensities in the flow cytometric analysis, also displayed the highest affinities for the target antigens. The fluorescence intensity of antibody-producing cells corresponded well with the produced antibodies' affinities toward their respective antigens. Immunohistochemical staining verified the successful double labeling of the cells. Our method makes it possible to perform a high-throughput screening for hybridoma cells, which have both an adequate IgG production rate and a high target affinity. KW - Immunization KW - Hapten KW - Monoclonal antibodies KW - Hybridoma KW - Flow cytometry KW - ELISA KW - Estradiol KW - Estrone KW - Digoxigenin KW - Zearalenone KW - Aflatoxin KW - CLSM PY - 2014 DO - https://doi.org/10.1016/j.jim.2014.07.004 SN - 0022-1759 SN - 1872-7905 VL - 413 SP - 45 EP - 56 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-32322 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perez, R.M. A1 - Sandler, J.K.W. A1 - Altstädt, V. A1 - Hoffmann, T. A1 - Pospiech, D. A1 - Ciesielski, M. A1 - Döring, M. A1 - Braun, Ulrike A1 - Knoll, Uta A1 - Schartel, Bernhard T1 - Effective halogen-free flame retardants for carbon fibre-reinforced epoxy composites N2 - DOPO-based flame retardants with tailored chemical structures are proposed for carbon fibre reinforced epoxy composites. Critical properties related to the fracture toughness are maintained, effectively allowing the use of such compounds in composites for demanding applications. KW - Fire retardancy KW - DOPO KW - Epoxy resin KW - LOI KW - UL94 PY - 2006 DO - https://doi.org/10.1007/s10853-006-0134-4 SN - 0022-2461 SN - 1573-4803 VL - 41 IS - 15 SP - 4981 EP - 4984 PB - Springer Science + Business Media B.V. CY - New York, USA AN - OPUS4-12641 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perez, R.M. A1 - Sandler, J.K.W. A1 - Altstädt, V. A1 - Hoffmann, T. A1 - Pospiech, D. A1 - Ciesielski, M. A1 - Döring, M. A1 - Braun, Ulrike A1 - Balabanovich, Aliaksandr A1 - Schartel, Bernhard T1 - Novel phosphorus-modified polysulfone as a combined flame retardant and toughness modifier for epoxy resins N2 - A novel phosphorus-modified polysulfone (P-PSu) was employed as a combined toughness modifier and a source of flame retardancy for a DGEBA/DDS thermosetting system. In comparison to the results of a commercially available polysulfone (PSu), commonly used as a toughness modifier, the chemorheological changes during curing measured by means of temperature-modulated DSC revealed an earlier occurrence of mobility restrictions in the P-PSu-modified epoxy. A higher viscosity and secondary epoxy-modifier reactions induced a sooner vitrification of the reacting mixture; effects that effectively prevented any phase separation and morphology development in the resulting material during cure. Thus, only about a 20% increase in fracture toughness was observed in the epoxy modified with 20 wt.% of P-PSu, cured under standard conditions at 180 °C for 2 h. Blends of the phosphorus-modified and the standard polysulfone (PSu) were also prepared in various mixing ratios and were used to modify the same thermosetting system. Again, no evidence for phase separation of the P-PSu was found in the epoxy modified with the P-PSu/PSu blends cured under the selected experimental conditions. The particular microstructures formed upon curing these novel materials are attributed to a separation of PSu from a miscible P-PSu–epoxy mixture. Nevertheless, the blends of P-PSu/PSu were found to be effective toughness/flame retardancy enhancers owing to the simultaneous microstructure development and polymer interpenetration. KW - Flame retardants KW - Phosphorus-modified polysulfone KW - Fracture toughness PY - 2007 SN - 0032-3861 SN - 1873-2291 VL - 48 IS - 3 SP - 778 EP - 790 PB - Springer CY - Berlin AN - OPUS4-14515 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mix, Renate A1 - Hoffmann, Katrin A1 - Buschmann, H.-J. A1 - Friedrich, Jörg Florian A1 - Resch-Genger, Ute T1 - Anbindung von Fluoreszenzfarbstoffen an plasmachemisch funktionalisierte und Cucurbituril-modifizierte Oberflächen N2 - Plasmapolymerisierte Allylaminschichten (50 nm) wurden auf Polypropylenfolien abgeschieden. Die auf diese Weise generierte NH2-funktionalisierte Polymeroberfläche wurde mit Xanthen-Fluorophoren chemisch umgesetzt. Da die Farbstoff-gekoppelten Folien nur geringe Fluoreszenz aufwiesen, wurden zwei Wege zur möglichen Entkopplung der Farbstoffe von der Oberfläche und damit zur Erhöhung der Fluoreszenzintensität getestet. Als erstes wurde ein Spacer durch die Umsetzung der primären Aminogruppen mit Glutaraldehyd und der nachfolgenden Kettenverlängerung mit Diaminohexan eingeführt. Diese nachfolgende Reaktion ergab eine spacergebundene NH2-Oberfläche, die analog der Allylaminschicht mit den Farbstoffen umgesetzt wurde. Als weiterer Weg wurde der Zusatz einer geeigneten Käfigverbindung, des Cucurbit[6]urils, getestet. Die spacergebundenen und zusätzlich mit Cucurbituril modifizierten aminofunktionellen Oberflächen zeigten nach der Farbstoffankopplung eine verbesserte Fluoreszenzintensität. KW - Fluoreszenz KW - Spacer KW - Cucurbituril PY - 2007 DO - https://doi.org/10.1002/vipr.200700329 SN - 0947-076X SN - 1522-2454 VL - 19 IS - 5 SP - 31 EP - 37 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-16000 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, Katrin A1 - Mix, Renate A1 - Friedrich, Jörg Florian A1 - Buschmann, H.-J. A1 - Resch-Genger, Ute T1 - Anchoring of Fluorophores to plasma-chemically modified polymer surfaces and the effect of Cucurbit[6]uril on dye emission N2 - Polypropylene supports were functionalized by plasma-deposition of polymeric allylamine layers. The surface amino groups generated were wet-chemically reacted with xanthene dyes resulting in fluorescent polymer films. The effect of polymer-attachment of the dyes on their emission features was studied fluorometrically and different methods were tested to improve the fluorescence properties of the films. Modification with cucurbit[6]uril (CB6) yields a moderately enhanced fluorescence as well as an improved photostability. The observed effect is most likely due to CB6-induced rigidization of the linker molecules which seems to reduce fluorescence quenching dye–dye and fluorophore–surface interactions. KW - Fluorescence KW - Cucurbituril KW - Surface modification KW - Plasma functionalization KW - Polymer surface KW - Xanthene dyes PY - 2009 DO - https://doi.org/10.1007/s10895-008-0407-1 SN - 1053-0509 SN - 1573-4994 VL - 19 SP - 229 EP - 237 PB - Plenum Publ. Corp. CY - New York, NY AN - OPUS4-19154 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, H A1 - Paulisch, M C A1 - Gebhard, M A1 - Osiewacz, J A1 - Kutter, M A1 - Hilger, A A1 - Arlt, T A1 - Kardjilov, N A1 - Ellendorff, B A1 - Beckmann, F A1 - Markötter, Henning A1 - Luik, M A1 - Turek, T A1 - Manke, I A1 - Roth, C T1 - Development of a Modular Operando Cell for X-ray Imaging of Strongly Absorbing Silver-Based Gas Diffusion Electrodes N2 - Metal-based gas diffusion electrodes are utilized in chlor-alkali electrolysis or electrochemical reduction of carbon dioxide, allowing the reaction to proceed at high current densities. In contrast to planar electrodes and predominantly 2D designs, the industrially required high current densities can be achieved by intense contact between the gas and liquid phase with the catalytically active surfaces. An essential asset for the knowledge-based design of tailored electrodes is therefore in-depth information on electrolyte distribution and intrusion into the electrode’s porous structure. Lab-based and synchrotron radiography allow for monitoring this process operando. Herein, we describe the development of a cell design that can be modularly adapted and successfully used to monitor both the oxygen reduction reaction and the electrochemical reduction of CO2 as exemplary and currently very relevant examples of gas-liquid reactions by only minor modifications to the cell set-up. With the reported cell design, we were able to observe the electrolyte distribution within the gas diffusion electrode during cell operation in realistic conditions. KW - X-Ray imaging KW - Gas diffusion electrodes KW - Operando cell PY - 2022 DO - https://doi.org/10.1149/1945-7111/ac6220 VL - 169 IS - 4 SP - 044508 PB - IOP science AN - OPUS4-55027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Descalzo López, Ana Belén A1 - Xu, H.-J. A1 - Xue, Z.-L. A1 - Hoffmann, Katrin A1 - Shen, Z. A1 - Weller, Michael G. A1 - You, X.-Z. A1 - Rurack, Knut T1 - Phenanthrene-Fused Boron-Dipyrromethenes as Bright Long-Wavelength Fluorophores N2 - A new class of boron-dipyrromethene (BDP or BODIPY) dyes was obtained by phenanthrene fusion to the β-pyrrole positions, absorbing in the wavelength range of important laser sources. Despite a 'propeller-like' distorted structure in the crystalline state, the chromophore absorbs (log ε ≥ 5) and fluoresces (Φf ≥ 0.8) strongly and can be easily turned into a fluorescence light-up probe. Incorporation into latex beads produces bright and photostable single-dye and Förster Resonance Energy Transfer (FRET) particles for microscopy applications. KW - Fluoreszenz KW - Absorption KW - BODIPY-Farbstoffe KW - Ladungstransfer KW - NIR-Farbstoffe PY - 2008 DO - https://doi.org/10.1021/ol800271e SN - 1523-7060 SN - 1523-7052 VL - 10 IS - 8 SP - 1581 EP - 1584 PB - American Chemical Society CY - Washington, DC AN - OPUS4-17511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wolf, S. E. A1 - Müller, L. A1 - Barrea, R. A1 - Kampf, C.J. A1 - Leiterer, Jork A1 - Panne, Ulrich A1 - Hoffmann, T. A1 - Emmerling, Franziska A1 - Tremel, W. T1 - Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates N2 - During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. PY - 2011 DO - https://doi.org/10.1039/c0nr00761g SN - 2040-3364 SN - 2040-3372 IS - 3 SP - 1158 EP - 1165 PB - RSC Publ. CY - Cambridge AN - OPUS4-23355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -