TY - JOUR A1 - Hennig, Andreas A1 - Borcherding, H. A1 - Jäger, Christian A1 - Hatami, Soheil A1 - Würth, Christian A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Scope and limitations of surface functional quantification methods: exploratory study with poly(acrylic acid)-grafted micro- and nanoparticles N2 - The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, 13C solid-state NMR, fluorophore labeling, a supramolecular assay based on high-affinity binding of cucurbit[7]uril, and two colorimetric assays based on toluidine blue and nickel complexation by pyrocatechol violet. The methods were thoroughly validated and compared with respect to reproducibility, sensitivity, and ease of use. The results demonstrate that only a small but constant fraction of the surface functional groups is accessible to covalent surface derivatization independently of the total number of surface functional groups, and different contributing factors are discussed that determine the number of probe molecules which can be bound to the polymer surface. The fluorophore labeling approach was modified to exclude artifacts due to fluorescence quenching, but absolute quantum yield measurements still indicate a major uncertainty in routine fluorescence-based surface group quantifications, which is directly relevant for biochemical assays and medical diagnostics. Comparison with results from protein labeling with streptavidin suggests a porous network of poly(acrylic acid) chains on the particle surface, which allows diffusion of small molecules (cutoff between 1.6 and 6.5 nm) into the network. KW - Polymers KW - Surface groups KW - Quantification KW - Fluorescence PY - 2012 U6 - https://doi.org/10.1021/ja302649g SN - 0002-7863 SN - 1520-5126 VL - 134 IS - 19 SP - 8268 EP - 8276 PB - American Chemical Society CY - Washington, DC AN - OPUS4-26002 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Resch-Genger, Ute A1 - Pfeifer, Dietmar A1 - Hoffmann, Katrin A1 - Flachenecker, Günter A1 - Hoffmann, Angelika A1 - Monte, C. ED - Resch-Genger, Ute ED - O.S. Wolfbeis, T1 - Linking fluorometry to radiometry with physical and chemical transfer standards: instrument characterization and traceable fluorescence measurements N2 - Problems associated with the measurement of photoluminescence are briefly reviewed, including relevant instrument parameters affecting these measurements. Procedures for the characterization of relevant instruments are discussed, focusing on spectrofluorometers, and fit-for-purpose methods including suitable standards are recommended. The aim here is to increase the awareness of the importance of reliable instrument characterization and to improve the comparability of measurements of photoluminescence. KW - Calibration KW - Emission standards KW - Fluorescence intensity standards KW - Fluorescence standards KW - Quality assurance KW - Spectral correction PY - 2008 SN - 978-3-540-75206-6 U6 - https://doi.org/10.1007/4243_2008_054 SN - 1617-1306 N1 - Serientitel: Springer Series on Fluorescence – Series title: Springer Series on Fluorescence VL - 5 IS - Part II SP - 65 EP - 99 PB - Springer AN - OPUS4-18301 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfeifer, Dietmar A1 - Hoffmann, Katrin A1 - Hoffmann, Angelika A1 - Monte, Christian A1 - Resch-Genger, Ute T1 - The Calibration Kit Spectral Fluorescence Standards - A Simple and Certified Tool for the Standardization of the Spectral Characteristics of Fluorescence Instruments N2 - With the Calibration Kit Spectral Fluorescence Standards BAM-F001–BAM-F005, we developed a simple tool for the characterization of the relative spectral responsivity and the long-term stability of the emission channel of fluorescence instruments under routine measurement conditions thereby providing the basis for an improved comparability of fluorescence measurements and eventually standardization. This first set of traceable fluorescence standards, which links fluorescence measurements to the spectral radiance scale in the spectral range of 300–770 nm and has been optimized for spectrofluorometers, can be employed for different measurement geometries and can be adapted to different fluorescence techniques with proper consideration of the underlying measurement principles. KW - Fluorescence KW - Standard KW - Spectral correction KW - Emission KW - Calibration tool PY - 2006 U6 - https://doi.org/10.1007/s10895-006-0086-8 SN - 1053-0509 SN - 1573-4994 VL - 16 IS - 4 SP - 581 EP - 587 PB - Plenum Publ. Corp. CY - New York, NY AN - OPUS4-14206 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute A1 - Hoffmann, Katrin A1 - Hoffmann, Angelika T1 - Standardization of Fluorescence Measurements - Criteria for the Choice of Suitable Standards and Approaches to Fit-for-Purpose Calibration Tools N2 - This report summarizes problems associated with the comparability of measurements of photoluminescence and procedures for the characterization of relevant instruments, focusing on physical and chemical fluorescence standards. To provide recommendations on selecting and using such standards, we derive general and scope-specific requirements and quality criteria for suitable devices and materials and briefly address metrological requirements linked to the realization of comparable measurements. Special emphasis is dedicated to liquid and solid chromophore-based fluorescence standards developed or currently tested by us. KW - Fluorescence standard KW - Fluorescence spectroscopy KW - Spectral correction KW - day-to-day intensity standard KW - Calibration KW - Metrology KW - Fluorescence microscopy PY - 2008 U6 - https://doi.org/10.1196/annals.1430.018 SN - 0077-8923 SN - 1749-6632 SN - 0094-8500 VL - 1130 SP - 35 EP - 43 PB - New York Academy of Sciences CY - New York, NY AN - OPUS4-17712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute A1 - Hoffmann, Katrin A1 - Würth, Christian A1 - Behnke, Thomas A1 - Hoffmann, Angelika A1 - Pfeifer, Dietmar A1 - Engel, A. T1 - The toolbox of fluorescence standards: Flexible calibration tools for the standardization of fluorescence-based measurements N2 - To improve the reliability of fluorescence data in the life and material sciences and to enable accreditation of fluorescence techniques, standardization concepts are required that guarantee and improve the comparability of fluorescence measurements. At the core of such concepts are simple and evaluated fluorescence standards for the consideration of instrument-specific spectral and intensity distortions of measured signals and for instrument performance validation (IPV). Similarly in need are fluorescence intensity standards for the quantification from measured intensities and for signal referencing, thereby accounting for excitation light-induced intensity fluctuations. These standards should be preferably certified, especially for use in regulated areas like medical diagnostics. This encouraged us to develop liquid and solid standards for different fluorescence parameters and techniques for use under routine measurement conditions in different formates. Special emphasis was dedicated to the determination and control of the spectral responsivity of detection systems, wavelength accuracy, homogeneity of illumination, and intensity referencing for e.g. spectrofluorometers, fluorescence sensors and confocal laser scanning fluorescence microscopes. Here, we will present design concepts and examples for mono- and multifunctional fluorescence standards that provide traceability to radiometric units and present a first step towards a toolbox of standards. KW - Fluorescence KW - Fluorescence standard KW - Calibration tool KW - Spectral fluorescence standard KW - Intensity standard KW - Instrument performance validation KW - Quality assurance KW - Traceability KW - Glass KW - Liquid standard PY - 2010 U6 - https://doi.org/10.1117/12.853133 SN - 0277-786X SN - 0038-7355 SN - 0361-0748 VL - 7666 IS - 76661J SP - 1 EP - 12 PB - Soc. CY - Redondo Beach, Calif. [u.a.] AN - OPUS4-21595 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, Katrin A1 - Dietzel, B. A1 - Schulz, B. A1 - Reck, Günter A1 - Hoffmann, Angelika A1 - Orgzall, I. A1 - Resch-Genger, Ute A1 - Emmerling, Franziska T1 - Combined structural and fluorescence studies of methyl-substituted 2,5-diphenyl-1,3,4-oxadiazoles - relation between electronic properties and packing motifs N2 - Prerequisite for the rational design of functional organic materials with tailor-made electronic properties is the knowledge of the structure–property relationship for the specific class of molecules under consideration. This encouraged us to systematically study the influence of the molecular structure and substitution pattern of aromatically substituted 1,3,4-oxadiazoles on the electronic properties and packing motifs of these molecules and on the interplay of these factors. For this purpose, seven diphenyl-oxadiazoles equipped with methyl substituents in the ortho- and meta-position(s) were synthesized and characterized. Absorption and fluorescence spectra in solution served here as tools to monitor substitution-induced changes in the electronic properties of the individual molecules whereas X-ray and optical measurements in the solid state provided information on the interplay of electronic and packing effects. In solution, the spectral position of the absorption maximum, the size of Stokes shift, and the fluorescence quantum yield are considerably affected by ortho-substitution in three or four ortho-positions. This results in blue shifted absorption bands, increased Stokes shifts, and reduced fluorescence quantum yields whereas the spectral position and vibrational structure of the emission bands remain more or less unaffected. In the crystalline state, however, the spectral position and shape of the emission bands display a strong dependence on the molecular structure and/or packing motifs that seem to control the amount of dye–dye-interactions. These observations reveal the limited value of commonly reported absorption and fluorescence measurements in solution for a straightforward comparison of spectroscopic results with single X-ray crystallography. This underlines the importance of solid state spectroscopic studies for a better understanding of the interplay of electronic effects and molecular order. KW - Diphenyl-oxadiazoles KW - X-ray structure KW - Packing motif KW - Optical properties KW - Fluorescence quantum yield PY - 2011 U6 - https://doi.org/10.1016/j.molstruc.2010.11.071 SN - 0022-2860 SN - 1872-8014 SN - 0377-046X VL - 988 IS - 1-3 SP - 35 EP - 46 PB - Elsevier CY - Amsterdam AN - OPUS4-23253 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute A1 - Behnke, Thomas A1 - Brehm, Robert A1 - Grabolle, Markus A1 - Hennig, Andreas A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Linck, Lena A1 - Lochmann, Cornelia A1 - Pauli, Jutta A1 - Spieles, Monika A1 - Würth, Christian T1 - Funktionelle Chromophor-Systeme, innovative Validierungskonzepte und rückführbare Standards für die fluoreszenzbasierte multiparametrische Bioanalytik N2 - Unter dem Motto „Innovation und Qualitätssicherung in der (Bio)Analytik“ werden in der Arbeitsgruppe Fluoreszenzspektroskopie der BAM, Bundesanstalt für Materialforschung und -prüfung, funktionelle Chromophor-Systeme, einfache Signalverstärkungs- und Multiplexingstrategien sowie innovative Validierungs- und rückführbare Standardisierungskonzepte für verschiedene fluorometrische Messgrößen und Methoden entwickelt. Im Mittelpunkt stehen dabei molekulare Fluorophore, Nanokristalle mit größenabhängigen optischen Eigenschaften (sogenannte Quantenpunkte, QDs) und fluoreszierende Partikel variabler Größe sowie Sonden und Sensormoleküle für neutrale und ionische Analyte und für die Charakterisierung von funktionellen Gruppen. Dabei erfolgen auch methodische Entwicklungen für die Fluoreszenzspektroskopie, die Fluoreszenzmikroskopie, die Milcrofluorometrie, die Sensorik und die Mikroarraytechnologie. Ziele sind u. a. das Design und die Untersuchung von multiplexfähigen selektiven und sensitiven Sonden für die Biomarkeranalytik, die Entwicklung von Methoden zur Charakterisierung der signalrelevanten Eigenschaften dieser Chromophor-Systeme und zur Charakterisierung von funktionellen Gruppen an Oberflächen und ihre Validierung sowie die Entwicklung und Bereitstellung von formatadaptierbaren, flexibel ersetzbaren Standards für die fluoreszenzbasierte Multiparameteranalytik. T2 - 5. Senftenberger Innovationsforum Multiparameteranalytik CY - Senftenberg, Deutschland DA - 10.03.2011 KW - Multiparametric KW - Multiplexing KW - Fluorescence KW - Nanoparticles KW - NIR dyes KW - Surface analysis KW - Quantum yield KW - Quantum dot KW - Lifetime PY - 2011 SP - 86 EP - 108 CY - Senftenberg AN - OPUS4-23635 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lindner, G.-G. A1 - Hoffmann, Katrin A1 - Witke, Klaus A1 - Reinen, D. A1 - Heinemann, Chr. A1 - Koch, W. T1 - Spectroscopic Properties of Se2 2- and Se2- in Cancrinite KW - Selen KW - Cancrinit PY - 1996 SN - 0022-4596 SN - 1095-726X VL - 126 IS - 1 SP - 50 EP - 54 PB - Elsevier CY - San Diego, Calif. AN - OPUS4-690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weh, K. A1 - Noack, M. A1 - Hoffmann, Katrin A1 - Schröder, K.-P. A1 - Caro, J. T1 - Change of gas permeation by photoinduced switching of zeolite-azobenzene membranes of type MFI and FAU N2 - FAU membranes of type Na–X and MFI membranes of type silicalite-1 which contain adsorbed azobenzene (AZB), have photoswitchable permeation properties due to the trans–cis photoisomerization of AZB. The change of gas permeation through these host–guest composite membranes depends on the irradiation wavelength, the quality of the membranes and the amount of adsorbed AZB. The permeances of the gases in the trans-form of the zeolite-encapsulated AZB were higher than those in the cis-form. The separation factors of equimolar mixtures of N2/CO2 and CH4/CO2 fed through the FAU–AZB membrane were higher at trans-switching than at cis-switching. The changes of the permeances of single gases and of the separation factors of equimolar gas mixtures by photoinduced trans–cis switching were found to be reversible over numerous switching cycles. The experimental results are in agreement with predictions made by Monte Carlo simulations for passing of permeant gases through these host–guest systems with the zeolite-hosted AZB in the trans- and in the cis-configuration. PY - 2002 U6 - https://doi.org/10.1016/S1387-1811(02)00331-1 SN - 1387-1811 SN - 1873-3093 VL - 54 IS - 1-2 SP - 15 EP - 26 PB - Elsevier CY - Amsterdam AN - OPUS4-1752 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hoffmann, Katrin A1 - Resch-Genger, Ute A1 - Marlow, Frank T1 - Reversible Photosensitive Refractive Index Changes of Chromophor/Zeolite Nanocomposites T2 - Abschlußkolloquium "Nanostrukturierte Wirt/Gast-Systeme" CY - Berlin, Germany DA - 2002-10-21 PY - 2002 AN - OPUS4-1753 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -