TY  - JOUR
A1  - Müller, Katharina
A1  - Foerstendorf, Harald
A1  - Steudtner, Robin
A1  - Tsushima, Satoru
A1  - Kumke, Michael Uwe
A1  - Lefèvre, Grégory
A1  - Rothe, Jörg
A1  - Mason, Harris
A1  - Szabó, Zoltán
A1  - Yang, Ping
A1  - Adam, Christian K. R.
A1  - André, Rémi
A1  - Brennenstuhl, Katlen
A1  - Chiorescu, Ion
A1  - Cho, Herman M.
A1  - Creff, Gaëlle
A1  - Coppin, Frédéric
A1  - Dardenne, Kathy
A1  - Den Auwer, Christophe
A1  - Drobot, Björn
A1  - Eidner, Sascha
A1  - Hess, Nancy J.
A1  - Kaden, Peter
A1  - Kremleva, Alena
A1  - Kretzschmar, Jerome
A1  - Krüger, Sven
A1  - Platts, James A.
A1  - Panak, Petra
A1  - Polly, Robert
A1  - Powell, Brian A.
A1  - Rabung, Thomas
A1  - Redon, Roland
A1  - Reiller, Pascal E.
A1  - Rösch, Notker
A1  - Rossberg, André
A1  - Scheinost, Andreas C.
A1  - Schimmelpfennig, Bernd
A1  - Schreckenbach, Georg
A1  - Skerencak-Frech, Andrej
A1  - Sladkov, Vladimir
A1  - Solari, Pier Lorenzo
A1  - Wang, Zheming
A1  - Washton, Nancy M.
A1  - Zhang, Xiaobin
T1  - Interdisciplinary Round-Robin Test on molecular spectroscopy of the U(VI) Acetate System
JF  - ACS omega / American Chemical Society
N2  - A comprehensive molecular analysis of a simple aqueous complexing system. U(VI) acetate. selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated. The raw data from the different experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was high. By contrast, luminescence spectroscopic data turned out to be strongly related to the chosen acquisition parameters. Second, the potentials and limitations of coupling various spectroscopic and theoretical approaches for the comprehensive study of actinide molecular complexes were assessed. Previous spectroscopic data from the literature were revised and the benchmark data on the U(VI) acetate system provided an unambiguous molecular interpretation based on the correlation of spectroscopic and theoretical results. The multimethodologic approach and the conclusions drawn address not only important aspects of actinide spectroscopy but particularly general aspects of modern molecular analytical chemistry.
Y1  - 2019
U6  - https://doi.org/10.1021/acsomega.9b00164
SN  - 2470-1343
VL  - 4
IS  - 5
SP  - 8167
EP  - 8177
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Haubitz, Toni
A1  - John, Leonard
A1  - Wessig, Pablo
A1  - Kumke, Michael Uwe
T1  - Photophysics of Acyl- and Ester-DBD Dyes
BT  - Quadrupole-Induced Solvent Relaxation Investigated by Transient Absorption Spectroscopy
JF  - the journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - A new generation of wavelength-tunable, fluorescent dyes, so-called DBD ([1,3]dioxolo[4,5-f][1,3]benzodioxole) dyes, were developed a few years ago, and they showed great potential as probes, for example, for fluorescence microscopy. However, their photophysics is not fully explored and leaves open questions regarding their large fluorescence Stokes shifts and sensitivity to solvent conditions of differently substituted DBD dyes. To improve the understanding of the influence of the substitution pattern of the DBD dyes on their respective photophysics, transient absorption spectroscopy (TAS) was used, that is, a pump-probe experiment on the femtosecond timescale. TAS allows measurements of excited states, ground state recovery, solvent relaxation, and fluorescence properties on time scales of up to several nanoseconds. Two different DBD dye samples were investigated: aryl- and ester-substituted DBD dyes. Experiments were carried out in solvents with different polarities using different excitation energies and at different viscosities. Based on the experimental data and theoretical calculations, we were able to determine the conformational changes of the molecule due to electronic excitation and were able to investigate solvent relaxation processes for both types of DBD dyes. By generalizing the theory for quadrupole-induced solvent relaxation developed by Togashi et al., we derived quadrupole moments of both molecules in the ground and excited state. Our data showed differences in the binding of polar solvent molecules to the dyes depending on the substituent on the DBD dye. In the case of water as the solvent, an additional efficient quenching process in the electronically excited state was revealed, which was indicated by the observation of solvated electrons in the TAS signals.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.jpca.9b02973
SN  - 1089-5639
VL  - 123
IS  - 22
SP  - 4717
EP  - 4726
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hoang, Hoa T.
A1  - Mertens, Monique
A1  - Wessig, Pablo
A1  - Sellrie, Frank
A1  - Schenk, Jörg A.
A1  - Kumke, Michael Uwe
T1  - Antibody Binding at the Liposome-Water Interface
BT  - a FRET Investigation toward a Liposome-Based Assay
JF  - ACS Omega
N2  - Different signal amplification strategies to improve the detection sensitivity of immunoassays have been applied which utilize enzymatic reactions, nanomaterials, or liposomes. The latter are very attractive materials for signal amplification because liposomes can be loaded with a large amount of signaling molecules, leading to a high sensitivity. In addition, liposomes can be used as a cell-like "bioscaffold" to directly test recognition schemes aiming at cell-related processes. This study demonstrates an easy and fast approach to link the novel hydrophobic optical probe based on [1,3]dioxolo[4,5-f]-[1,3]benzodioxole (DBD dye mm239) with tunable optical properties to hydrophilic recognition elements (e.g., antibodies) using liposomes for signal amplification and as carrier of the hydrophobic dye. The fluorescence properties of mm239 (e.g., long fluorescence lifetime, large Stokes shift, high photostability, and high quantum yield), its high hydrophobicity for efficient anchoring in liposomes, and a maleimide bioreactive group were applied in a unique combination to build a concept for the coupling of antibodies or other protein markers to liposomes (coupling to membranes can be envisaged). The concept further allowed us to avoid multiple dye labeling of the antibody. Here, anti-TAMRA-antibody (DC7-Ab) was attached to the liposomes. In proof-of-concept, steady-state as well as time-resolved fluorescence measurements (e.g., fluorescence depolarization) in combination with single molecule detection (fluorescence correlation spectroscopy, FCS) were used to analyze the binding interaction between DC7-Ab and liposomes as well as the binding of the antigen rhodamine 6G (R6G) to the antibody. Here, the Forster resonance energy transfer (FRET) between mm239 and R6G was monitored. In addition to ensemble FRET data, single-molecule FRET (PIE-FRET) experiments using pulsed interleaved excitation were used to characterize in detail the binding on a single-molecule level to avoid averaging out effects.
KW  - energy-transfer
KW  - immunoassay
KW  - complexes
KW  - probes
Y1  - 2018
U6  - https://doi.org/10.1021/acsomega.8b03016
SN  - 2470-1343
VL  - 3
IS  - 12
SP  - 18109
EP  - 18116
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Alrefai, Anas
A1  - Mondal, Suvendu Sekhar
A1  - Wruck, Alexander
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Brandt, Philipp
A1  - Janiak, Christoph
A1  - Schoenfeld, Sophie
A1  - Weber, Birgit
A1  - Rybakowski, Lawrence
A1  - Herrman, Carmen
A1  - Brennenstuhl, Katlen
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Behrens, Karsten
A1  - Günter, Christina
A1  - Müller, Holger
A1  - Holdt, Hans-Jürgen
T1  - Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties
JF  - Journal of Inclusion Phenomena and Macrocyclic Chemistry
N2  - By varying reaction parameters for the syntheses of the hydrogen-bonded metal-imidazolate frameworks (HIF) HIF-1 and HIF-2 (featuring 14 Zn and 14 Co atoms, respectively) to increase their yields and crystallinity, we found that HIF-1 is generated in two different frameworks, named as HIF-1a and HIF-1b. HIF-1b is isostructural to HIF-2. We determined the gas sorption and magnetic properties of HIF-2. In comparison to HIF-1a (Brunauer-Emmett-Teller (BET) surface area of 471m(2) g(-1)), HIF-2 possesses overall very low gas sorption uptake capacities [BET(CO2) surface area=85m(2) g(-1)]. Variable temperature magnetic susceptibility measurement of HIF-2 showed antiferromagnetic exchange interactions between the cobalt(II) high-spin centres at lower temperature. Theoretical analysis by density functional theory confirmed this finding. The UV/Vis-reflection spectra of HIF-1 (mixture of HIF-1a and b), HIF-2 and HIF-3 (with 14 Cd atoms) were measured and showed a characteristic absorption band centered at 340nm, which was indicative for differences in the imidazolate framework.
KW  - Gas-sorption
KW  - Ligand design
KW  - Magnetic properties
KW  - Supramolecular chemistry
KW  - Solvothermal synthesis
Y1  - 2019
U6  - https://doi.org/10.1007/s10847-019-00926-6
SN  - 1388-3127
SN  - 1573-1111
VL  - 94
IS  - 3-4
SP  - 155
EP  - 165
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Onal, Emel
A1  - Sass, Stephan
A1  - Hurpin, Jeanne
A1  - Ertekin, Kadriye
A1  - Topal, Sevinc Zehra
A1  - Kumke, Michael Uwe
A1  - Hirel, Catherine
T1  - Lifetime-Based Oxygen Sensing Properties of palladium(II) and platinum(II) meso-tetrakis(4-phenylethynyl)phenylporphyrin
JF  - Journal of fluorescence
N2  - High oxygen permeable [poly(TMSP)] nanofibers incorporating porphyrin macrocycle as luminescence indicators were prepared by electrospinning technique. The porphyrins involves were modified by i) introducing phenylacetylide substituents on the para position of the phenyl moieties and ii) varying the metal centers [Pt(II) or Pd(II)] of the meso-tetrakisphenylporphyrins. A set of nanofibers; (Pt-TPP)NF, (Pd-TPP)NF, (Pt-TPA)NF and (Pd-TPA)NF were obtained to study their structure-activity relationship toward oxygen. The lifetime-based technique was privileged to take advantage of their long-lived phosphorescent properties. A two-fold enhancement was observed for (Pt-TPA)NF and (Pd-TPA)NF compared to (Pt-TPP)NF and (Pd-TPP)NF demonstrating the positive effect of the phenylacetylide moieties on the lifetime. Also, Silver nanoparticles were included in nanofibers to investigate their influence on lifetime-based oxygen sensitivity, showing that the presence of AgNPs only affects (Pd-TPA)NF.
KW  - Oxygen sensing
KW  - Phosphorescence lifetime
KW  - meso-tetrakisphenylporphyrins
KW  - Phenylacetylide
KW  - Nanofibers
KW  - Poly(trimethylsilylpropyne) matrix
Y1  - 2017
U6  - https://doi.org/10.1007/s10895-016-2022-x
SN  - 1053-0509
SN  - 1573-4994
VL  - 27
SP  - 861
EP  - 868
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Behrends, Nicole
A1  - Kumke, Michael Uwe
A1  - Eisold, Ursula
A1  - Meiling, Til
A1  - Hille, Carsten
T1  - Two-photon FRET pairs based on coumarin and DBD dyes
JF  - RSC Advances
N2  - The synthesis and photophysical properties of two new FRET pairs based on coumarin as a donor and DBD dye as an acceptor are described. The introduction of a bromo atom dramatically increases the two-photon excitation (2PE) cross section providing a 2PE-FRET system, which is also suitable for 2PE-FLIM.
Y1  - 2016
U6  - https://doi.org/10.1039/c6ra03983a
SN  - 2046-2069
VL  - 6
SP  - 33510
EP  - 33513
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Draffehn, Soeren
A1  - Kumke, Michael Uwe
T1  - Monitoring the Collapse of pH-Sensitive Liposomal Nanocarriers and Environmental pH Simultaneously: A Fluorescence-Based Approach
JF  - Molecular pharmaceutics
N2  - Nowadays, the encapsulation of therapeutic compounds in so-called carrier systems is a very smart method to achieve protection as well as an improvement of their temporal and spatial distribution. After the successful transport to the point of care, the delivery has to be released under controlled conditions. To monitor the triggered release from the carrier, we investigated different fluorescent probes regarding their response to the pH-induced collapse of pH-sensitive liposomes (pHSLip), which occurs when the environmental pH falls below a critical value. Depending on the probe, the fluorescence decay time as well as fluorescence anisotropy can be used equally as key parameters for monitoring the collapse. Especially the application of a fluorescein labeled fatty acid (fPA) enabled the monitoring of the pHSLips collapse and the pH of its microenvironment simultaneously without interference. Varying the pH in the range of 3 < pH < 9, anisotropy data revealed the critical pH value at which the collapse of the pHSLips occurs. Complementary methods, e.g., fluorescence correlation spectroscopy and dynamic light scattering, supported the analysis based on the decay time and anisotropy. Additional experiments with varying incubation times yielded information on the kinetics of the liposomal collapse.
KW  - pH-sensitive liposome
KW  - drug carrier system
KW  - selective drug release
KW  - intracellular pH indicator
KW  - time-resolved fluorescence spectroscopy
KW  - fluorescence anisotropy
KW  - fluorescence correlation spectroscopy
Y1  - 2016
U6  - https://doi.org/10.1021/acs.molpharmaceut.5b00064
SN  - 1543-8384
VL  - 13
SP  - 1608
EP  - 1617
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Draffehn, Soeren
A1  - Eichhorst, Jenny
A1  - Wiesner, Burkhard
A1  - Kumke, Michael Uwe
T1  - Insight into the Modification of Polymeric Micellar and Liposomal Nanocarriers by Fluorescein-Labeled Lipids and Uptake-Mediating Lipopeptides
JF  - Langmuir
N2  - Encapsulation of diagnostic and therapeutic compounds in transporters improves their delivery to the point of need. An even more efficient treatment of diseases can be achieved using carriers with targeting or protecting moieties. In the present work, we investigated micellar and liposomal nanocarriers modified with fluorescein, peptides, and polymers that are covalently bound to fatty acids or phospholipids to ensure a self-driven incorporation into the micelles or liposomes. First, we characterized the photophysics of the fluorescent probes in the absence and in the presence of nanocarriers. Changes in the fluorescence decay time, quantum yield, and intensity of a fluorescein-labeled fatty acid (fluorescein-labeled palmitic acid [fPA]) and a fluorescein-labeled lipopeptide (P2fA2) were found. By exploiting these changes, we investigated a lipopeptide (P2A2 as an uptake-mediating unit) in combination with different nanocarriers (micelles and liposomes) and determined the corresponding association constant K-ass values, which were found to be very high. In addition, the mobility of fPA was exploited using fluorescence correlation spectroscopy (FCS) and fluorescence depolarization (FD) experiments to characterize the nanocarriers. Cellular uptake experiments with mouse brain endothelial cells provided information on the uptake behavior of liposomes modified by uptake-mediating P2A2 and revealed differences in the uptake behavior between pH-sensitive and pH-insensitive liposomes.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.langmuir.6b01487
SN  - 0743-7463
VL  - 32
SP  - 6928
EP  - 6939
PB  - American Chemical Society
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Behrends, Nicole
A1  - Kumke, Michael Uwe
A1  - Eisold, Ursula
T1  - FRET Pairs with Fixed Relative Orientation of Chromophores
JF  - European journal of organic chemistry
N2  - Synthetic routes to different oligospirothioketal (OSTK) Forster resonance energy transfer (FRET) constructs are described and the photophysics of these constructs were explored in different solvents. The FRET efficiencies were determined from the experimental data and compared with theoretical values. The influence of the outstanding rigidity of the novel OSTK compounds on the FRET is discussed.
KW  - Fluorescence
KW  - Energy transfer
KW  - FRET
KW  - Chromophores
KW  - Spiro compounds
Y1  - 2016
U6  - https://doi.org/10.1002/ejoc.201600489
SN  - 1434-193X
SN  - 1099-0690
VL  - 145
SP  - 4476
EP  - 4486
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Eisold, Ursula
A1  - Behrends, Nicole
A1  - Wessig, Pablo
A1  - Kumke, Michael Uwe
T1  - Rigid Rod-Based FRET Probes for Membrane Sensing Applications
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - Oligospirothioketal (OSTK) rods are presented as an adjustable scaffold for optical membrane probes. The OSTK rods are readily incorporated into lipid bilayers due to their hydrophobic backbones. Because of their high length-over-diameter aspect ratio, only a minimal disturbance of the lipid bilayer is caused. OSTK rods show outstanding rigidity and allow defined labeling with fluorescent dyes, yielding full control of the orientation between the dye and OSTK skeleton. This. allows the construction of novel Forster resonance energy transfer probes with highly defined relative orientations of the transition dipole moments of the donor and acceptor dyes and makes the class of OSTK probes a power-fill, flexible toolbox for optical biosensing applications. Data on steady-state and time-resolved fluorescence experiments investigating the incorporation of coumarin- and [1,3]-dioxolo[4,5-f][1,3]benzo-dioxole-labeled OSTKs in large unilamellar vesicles are presented as a show case.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpcb.6b07285
SN  - 1520-6106
VL  - 120
SP  - 9935
EP  - 9943
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Burek, Katja
A1  - Dengler, Joachim
A1  - Emmerling, Franziska
A1  - Feldmann, Ines
A1  - Kumke, Michael Uwe
A1  - Stroh, Julia
T1  - Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems
JF  - ChemistryOpen
N2  - The hydration process of Portland cement in a cementitious system is crucial for development of the high‐quality cement‐based construction material. Complementary experiments of X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time‐resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time‐dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium−silicate−hydrates (C−S−H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C−S−H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process.
KW  - cement admixtures
KW  - cement hydration
KW  - Europium
KW  - luminescence
KW  - SEM
KW  - X-ray diffraction
Y1  - 2019
U6  - https://doi.org/10.1002/open.201900249
SN  - 2191-1363
VL  - 8
IS  - 12
SP  - 1441
EP  - 1452
PB  - Wiley-VCH-Verl.
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Burek, Katja
A1  - Dengler, Joachim
A1  - Emmerling, Franziska
A1  - Feldmann, Ines
A1  - Kumke, Michael Uwe
A1  - Stroh, Julia
T1  - Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The hydration process of Portland cement in a cementitious system is crucial for development of the high‐quality cement‐based construction material. Complementary experiments of X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time‐resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time‐dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium−silicate−hydrates (C−S−H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C−S−H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 808 
KW  - cement admixtures
KW  - cement hydration
KW  - Europium
KW  - luminescence
KW  - SEM
KW  - X-ray diffraction
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-442433
SN  - 1866-8372
IS  - 808
ER  - 
TY  - GEN
A1  - Wessig, Pablo
A1  - Hille, Carsten
A1  - Kumke, Michael Uwe
A1  - Meiling, Till Thomas
A1  - Behrends, Nicole
A1  - Eisold, Ursula
T1  - Two-photon FRET pairs based on coumarin and DBD dyes
N2  - The synthesis and photophysical properties of two new FRET pairs based on coumarin as a donor and DBD dye as an acceptor are described. The introduction of a bromo atom dramatically increases the two-photon excitation (2PE) cross section providing a 2PE-FRET system, which is also suitable for 2PE-FLIM.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 318 
KW  - resonance energy-tansfer
KW  - conformational-changes
KW  - microscopy
KW  - proteins
KW  - acid
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394445
SP  - 33510
EP  - 33513
ER  - 
TY  - JOUR
A1  - Mondal, Suvendu Sekhar
A1  - Behrens, Karsten
A1  - Matthes, Philipp R.
A1  - Schönfeld, Fabian
A1  - Nitsch, Jörn
A1  - Steffen, Andreas
A1  - Primus, Philipp-Alexander
A1  - Kumke, Michael Uwe
A1  - Müller-Buschbaum, Klaus
A1  - Holdt, Hans-Jürgen
T1  - White light emission of IFP-1 by in situ co-doping of the MOF pore system with Eu3+ and Tb3+
JF  - Journal of materials chemistry : C, Materials for optical and electronic devices
Y1  - 2015
U6  - https://doi.org/10.1039/c4tc02919d
SN  - 2050-7526
SN  - 2050-7534
VL  - 3
IS  - 18
SP  - 4623
EP  - 4631
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Klier, Dennis Tobias
A1  - Kumke, Michael Uwe
T1  - Upconversion NaYF4:Yb:Er nanoparticles co-doped with Gd3+ and Nd3+ for thermometry on the nanoscale
JF  - RSC Advances
N2  - In the present work, the upconversion luminescence properties of oleic acid capped NaYF4:Gd3+:Yb3+:Er3+ upconversion nanoparticles (UCNP) with pure beta crystal phase and Nd3+ ions as an additional sensitizer were studied in the temperature range of 288 K < T < 328 K. The results of this study showed that the complex interplay of different mechanisms and effects, causing the special temperature behavior of the UCNP can be developed into thermometry on the nanoscale, e.g. to be applied in biological systems on a cellular level. The performance was improved by the use of Nd3+ as an additional dopant utilizing the cascade sensitization mechanism in tri-doped UCNP.
Y1  - 2015
U6  - https://doi.org/10.1039/c5ra11502g
SN  - 2046-2069
VL  - 5
IS  - 82
SP  - 67149
EP  - 67156
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Klier, Dennis Tobias
A1  - Kumke, Michael Uwe
T1  - Analysing the effect of the crystal structure on upconversion luminescence in Yb3+, Er3+-co-doped NaYF4 nanomaterials
JF  - Journal of materials chemistry : C, Materials for optical and electronic devices
N2  - NaYF4:Yb:Er nanoparticles (UCNP) were synthesized under mild experimental conditions to obtain a pure cubic lattice. Upon annealing at different temperatures up to T-an = 700 degrees C phase transitions to the hexagonal phase and back to the cubic phase were induced. The UCNP materials obtained for different T-an were characterized with respect to the lattice phase using standard XRD and Raman spectroscopy as well as steady state and time resolved upconversion luminescence. The standard techniques showed that for the annealing temperature range 300 degrees C < T-an < 600 degrees C the hexagonal lattice phase was dominant. For T-an < 300 degrees C hardly any change in the lattice phase could be deduced, whereas for T-an > 600 degrees C a back transfer to the alpha-phase was observed. Complementarily, the luminescence upconversion properties of the annealed UCNP materials were characterized in steady state and time resolved luminescence measurements. Distinct differences in the upconversion luminescence intensity, the spectral intensity distribution and the luminescence decay kinetics were found for the cubic and hexagonal lattice phases, respectively, corroborating the results of the standard analytical techniques used. In laser power dependent measurements of the upconversion luminescence intensity it was found that the green (G1, G2) and red (R) emission of Er3+ showed different effects of T-an on the number of required photons reflecting the differences in the population routes of different energy levels involved. Furthermore, the intensity ratio of G(full)/R is highly effected by the laser power only when the beta-phase is present, whereas the G1/G2 intensity ratio is only slightly effected regardless of the crystal phase. Moreover, based on different upconversion luminescence kinetics characteristics of the cubic and hexagonal phase time-resolved area normalized emission spectra (TRANES) proved to be a very sensitive tool to monitor the phase transition between cubic and hexagonal phases. Based on the TRANES analysis it was possible to resolve the lattice phase transition in more detail for 200 degrees C < T-an < 300 degrees C, which was not possible with the standard techniques.
Y1  - 2015
U6  - https://doi.org/10.1039/c5tc02218e
SN  - 2050-7526
SN  - 2050-7534
VL  - 3
IS  - 42
SP  - 11228
EP  - 11238
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Klier, Dennis Tobias
A1  - Kumke, Michael Uwe
T1  - Upconversion Luminescence Properties of NaYF4:Yb:Er Nanoparticles Codoped with Gd3+
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - The temperature-dependent upconversion luminescence of NaYF4:Yb:Er nanoparticles (UCNP) containing different contents of Gd3+ as additional dopant was characterized. The UCNP were synthesized in a hydrothermal synthesis and stabilized with citrate in order to transfer them to the water phase. Basic characterization was carried out using TEM and DLS to determine the average size of the UCNP. The XRD technique was used to investigate the crystal lattice of the UCNP. It was found that due to the presence of Gd3+, an alteration of the lattice phase from a to beta was induced which was also reflected in the observed upconversion luminescence properties of the UCNP. A detailed analysis of the upconversion luminescence spectraespecially at ultralow temperaturesrevealed the different effects of phonon coupling between the host lattice and the sensitizer (Yb3+) as well as the activator (Er3+). Furthermore, the upconversion luminescence intensity reached a maximum between 15 and 250 K depending on Gd3+ content. In comparison to the very complex temperature behavior of the upconversion luminescence in the temperature range <273 K, the luminescence intensity ratio of H-2(11/2)-> I-4(15/2) to S-4(3/2)-> I-4(15/2) (R = G1/G2) in a higher temperature range can be described by an Arrhenius-type equation.
Y1  - 2015
U6  - https://doi.org/10.1021/jp5103548
SN  - 1932-7447
VL  - 119
IS  - 6
SP  - 3363
EP  - 3373
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Eisold, Ursula
A1  - Sellrie, Frank
A1  - Schenk, Jörg A.
A1  - Lenz, Christine
A1  - Stöcklein, Walter F. M.
A1  - Kumke, Michael Uwe
T1  - Bright or dark immune complexes of anti-TAMRA antibodies for adapted fluorescence-based bioanalysis
JF  - Analytical & bioanalytical chemistry
N2  - Fluorescence labels, for example fluorescein or rhodamin derivatives, are widely used in bioanalysis applications including lateral-flow assays, PCR, and fluorescence microscopy. Depending on the layout of the particular application, fluorescence quenching or enhancement may be desired as the detection principle. Especially for multiplexed applications or high-brightness requirements, a tunable fluorescence probe can be beneficial. The alterations in the photophysics of rhodamine derivatives upon binding to two different anti-TAMRA antibodies were investigated by absorption and fluorescence-spectroscopy techniques, especially determining the fluorescence decay time and steady-state and time-resolved fluorescence anisotropy. Two monoclonal anti-TAMRA antibodies were generated by the hybridoma technique. Although surface-plasmon-resonance measurements clearly proved the high affinity of both antibodies towards 5-TAMRA, the observed effects on the fluorescence of rhodamine derivatives were very different. Depending on the anti-TAMRA antibody either a strong fluorescence quenching (G71-DC7) or a distinct fluorescence enhancement (G71-BE11) upon formation of the immune complex was observed. Additional rhodamine derivatives were used to gain further information on the binding interaction. The data reveal that such haptens as 5-TAMRA could generate different paratopes with equal binding affinities but different binding interactions, which provide the opportunity to adapt bioanalysis methods including immunoassays for optimized detection principles for the same hapten depending on the specific requirements.
KW  - mAb
KW  - Fluorescence
KW  - Anisotropy
KW  - Exciplex
KW  - Energy-transfer probe
Y1  - 2015
U6  - https://doi.org/10.1007/s00216-015-8538-0
SN  - 1618-2642
SN  - 1618-2650
VL  - 407
IS  - 12
SP  - 3313
EP  - 3323
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Primus, Philipp-Alexander
A1  - Menski, Antonia
A1  - Yeste, Maria Pilar
A1  - Cauqui, Miguel Angel
A1  - Kumke, Michael Uwe
T1  - Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline CexZr1-xO2:Eu3+ Catalyst Materials
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Despite the wide range of industrial applications for ceria-zirconia mixed oxides (CexZr1-xO2), the complex correlation between their atomic structure and catalytic performance is still under debate. Catalytically interesting CexZr1-xO2 nanomaterials can form homogeneous solid solutions and, depending on the composition, show phase separation under the formation of small domains. The characterization of homogeneity and atomic structure of these materials remains a major challenge. High-resolution emission spectroscopy recorded under cryogenic conditions using Eu3+ as a structural probe in doped CeZrO2 nanoparticles offers an effective way to identify the different atomic environments of the Eu3+ dopants and, subsequently, to monitor structural parameters of the ceria-zirconia mixed oxides. It is found that, in stoichiometric CeZrO2:Eu3+, phase separation occurs at elevated temperatures beginning with the gradual formation of (pseudo)cubic crystallites in the amorphous materials at 500 degrees C and a sudden phase separation into tetragonal, zirconia-rich and cubic, ceria-rich domains over 900 degrees C. The presented technique allows us to easily monitor subtle changes even in amorphous, high surface area samples, yielding structural information not accessible by conventional techniques such as X-ray diffraction (XRD) and Raman. Moreover, in reference experiments investigating the reducibility of largely unordered Ce0.2Zr0.8O2:Eu3+, the main reduction peak in temperature-programmed reduction measurements appeared at exceptionally low temperatures below 200 degrees C, thus suggesting the outstanding potential of this oxide to activate catalytic oxidation reactions. This effect was found to be dependent on the amount of Eu3+ dopant introduced into the CeZrO2 matrix as well as to be connected to the atomic structure of the catalyst material.
Y1  - 2015
U6  - https://doi.org/10.1021/acs.jpcc.5b01271
SN  - 1932-7447
VL  - 119
IS  - 19
SP  - 10682
EP  - 10692
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Grunzel, Petra
A1  - Pilarek, Maciej
A1  - Steinbrueck, Doerte
A1  - Neubauer, Antje
A1  - Brand, Eva
A1  - Kumke, Michael Uwe
A1  - Neubauer, Peter
A1  - Krause, Mirja
T1  - Mini-scale cultivation method enables expeditious plasmid production in Escherichia coli
JF  - Biotechnology journal : systems & synthetic biology, nanobiotech, medicine
N2  - The standard procedure in the lab for plasmid isolation usually involves a 2-mL, 16 h over-night cultivation in 15-mL bioreaction tubes in LB medium. This is time consuming, and not suitable for high-throughput applications. This study shows that it is possible to produce plasmid DNA (pDNA) in a 1.5-mL microcentrifuge tube with only 100 L cultivation volume in less than 7 h with a simple protocol. Compared with the standard LB cultivation for pDNA production reaching a final pDNA concentration range of 1.5-4 mu g mL(-1), a 6- to 10-fold increase in plasmid concentration (from 10 up to 25 mu g mL(-1) cultivation volume) is achieved using an optimized medium with an internal substrate delivery system (EnBase (R)). Different strains, plasmids, and the applicability of different inoculation tools (i.e. different starting ODs) were compared, demonstrating the robustness of the system. Additionally, dissolved oxygen was monitored in real time online, indicating that under optimized conditions oxygen limitation can be avoided. We developed a simple protocol with a significantly decreased procedure time, enabling simultaneous handling of more samples, while a consistent quality and a higher final pDNA concentration are ensured.
KW  - Escherichia coli
KW  - High-cell-density culture
KW  - Miniaturized cultivations
KW  - Optical oxygen sensor
KW  - Plasmid DNA production
Y1  - 2014
U6  - https://doi.org/10.1002/biot.201300177
SN  - 1860-6768
SN  - 1860-7314
VL  - 9
IS  - 1
SP  - 128
EP  - 136
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mueller, Holger
A1  - Ast, Sandra
A1  - Steinbrück, Dorte
A1  - Eidner, Sascha
A1  - Geißler, Felix
A1  - Kumke, Michael Uwe
A1  - Holdt, Hans-Jürgen
T1  - Fluorescence lifetime-based sensing of sodium by an optode
JF  - Chemical communications
N2  - We report a 1,2,3-triazol fluoroionophore for detecting Na+ that shows in vitro enhancement in the Na+-induced fluorescence intensity and decay time. The Na+-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na+ in the range of 1-10 mM by measuring reversible fluorescence decay time changes.
Y1  - 2014
U6  - https://doi.org/10.1039/c4cc06112h
SN  - 1359-7345
SN  - 1364-548X
VL  - 50
IS  - 91
SP  - 14167
EP  - 14170
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Eisold, Ursula
A1  - Kupstat, Annette
A1  - Klier, Dennis Tobias
A1  - Primus, Philipp-A.
A1  - Pschenitza, Michael
A1  - Niessner, Reinhard
A1  - Knopp, Dietmar
A1  - Kumke, Michael Uwe
T1  - Probing the physicochemical interactions of 3-hydroxy-benzo[a]pyrene with different monoclonal and recombinant antibodies by use of fluorescence line-narrowing spectroscopy
JF  - Analytical & bioanalytical chemistry
N2  - Characterization of interactions between antigens and antibodies is of utmost importance both for fundamental understanding of the binding and for development of advanced clinical diagnostics. Here, fluorescence line-narrowing (FLN) spectroscopy was used to study physicochemical interactions between 3-hydroxybenzo[a]pyrene (3OH-BaP, as antigen) and a variety of solvent matrices (as model systems) or anti-polycyclic aromatic hydrocarbon antibodies (anti-PAH). We focused the studies on the specific physicochemical interactions between 3OH-BaP and different, previously obtained, monoclonal and recombinant anti-PAH antibodies. Control experiments performed with non-binding monoclonal antibodies and bovine serum albumin (BSA) indicated that nonspecific interactions did not affect the FLN spectrum of 3OH-BaP. The spectral positions and relative intensities of the bands in the FLN spectra are highly dependent on the molecular environment of the 3OH-BaP. The FLN bands correlate with different vibrational modes of 3OH-BaP which are affected by interactions with the molecular environment (pi-pi interactions, H-bonding, or van-der-Waals forces). Although the analyte (3OH-BaP) was the same for all the antibodies investigated, different binding interactions could be identified from the FLN spectra on the basis of structural flexibility and conformational multiplicity of the antibodies' paratopes.
KW  - FLNS
KW  - Antibody
KW  - Paratope
KW  - Hapten
KW  - Polycyclic aromatic hydrocarbons
Y1  - 2014
U6  - https://doi.org/10.1007/s00216-013-7584-8
SN  - 1618-2642
SN  - 1618-2650
VL  - 406
IS  - 14
SP  - 3387
EP  - 3394
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Schott, Juliane
A1  - Kretzschmar, Jerome
A1  - Acker, Margret
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Drobot, Bjoern
A1  - Barkleit, Astrid
A1  - Taut, Steffen
A1  - Brendler, Vinzenz
A1  - Stumpf, Thorsten
T1  - Formation of a Eu(III) borate solid species from a weak Eu(III) borate complex in aqueous solution
JF  - Dalton transactions : a journal of inorganic chemistry, including bioinorganic, organometallic, and solid-state chemistry
N2  - In the presence of polyborates (detected by B-11-NMR) the formation of a weak Eu(III) borate complex (lg beta(11) similar to 2, estimated) was observed by time-resolved laser-induced fluorescence spectroscopy (TRLFS). This complex is a precursor for the formation of a solid Eu(III) borate species. The formation of this solid in solution was investigated by TRLFS as a function of the total boron concentration: the lower the total boron concentration, the slower is the solid formation. The solid Eu(III) borate was characterized by IR spectroscopy, powder XRD and solid-state TRLFS. The determination of the europium to boron ratio portends the existence of pentaborate units in the amorphous solid.
Y1  - 2014
U6  - https://doi.org/10.1039/c4dt00843j
SN  - 1477-9226
SN  - 1477-9234
VL  - 43
IS  - 30
SP  - 11516
EP  - 11528
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Primus, Philipp-Alexander
A1  - Ritschel, Thomas
A1  - Sigueenza, Pilar Y.
A1  - Cauqui, Miguel Angel
A1  - Hernandez-Garrido, Juan Carlos
A1  - Kumke, Michael Uwe
T1  - High-resolution spectroscopy of europium-doped ceria as a tool to correlate structure and catalytic activity
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Site-selective emission spectra of Eu3+-doped CeO2 nanoparticles up to the D-5(0) - F-7(5) transition were recorded under cryogenic conditions to identify the local structure around the Eu3+ dopants in ceria. It is found that pretreatment conditions are crucial for the redistribution of dopants from a broad variety of environments to six well-defined lattice sites. The influence of the dopant and the host structure on the catalytic activity was investigated. A relationship between structure and reactivity is discussed. It is shown that oxygen transport is most efficient in particles with a pronounced amorphous character.
Y1  - 2014
U6  - https://doi.org/10.1021/jp505467r
SN  - 1932-7447
VL  - 118
IS  - 40
SP  - 23349
EP  - 23360
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Antoniou, Stella
A1  - Pashalidis, I.
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
T1  - The effect of humic acid on the formation and solubility of secondary solid phases (Nd(OH)CO3 and Sm(OH)CO3)
JF  - Radiochimica acta : international journal for chemical aspects of nuclear science and technology
N2  - The formation of secondary Ln(III) solid phases (e.g. Nd(OH)CO3 and Sm(OH)CO3) has been studied as a function of the humic acid (HA) concentration in 0.1 M NaClO4 aqueous solution and their solubility has been investigated in the neutral pH range (6.5-8) under normal atmospheric conditions. Nd(III) and Sm(III) were selected as analogues for trivalent lanthanide and actinide ions. The solid phases under investigation have been prepared by alkaline precipitation and characterized by TGA, ATR-FTIR, XRD, TRLFS, DR-UV-Vis and Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicate that Nd(OH)CO3 and Sm(OH)CO3 are stable and remain the solubility limiting solid phases even in the presence of increased HA concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurs, the inorganic (Ln(OH)CO3) and the organic phase (HA), which is adsorbed on the particle surface of the former. Nevertheless, HA affects the particle size of the solid phases. Increasing HA concentration results in decreasing crystallite size of the Nd(OH)CO3 and increasing crystallite size of the Sm(OH)CO3 solid phase, and affects inversely the solubility of the solid phases. However, this impact on the solid phase properties is expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere.
KW  - Lanthanide ions
KW  - Humic acid
KW  - Solid phase
KW  - Solubility
KW  - Raman
KW  - TRLFS
KW  - DR-UV-Vis
Y1  - 2011
U6  - https://doi.org/10.1524/ract.2011.1812
SN  - 0033-8230
VL  - 99
IS  - 4
SP  - 217
EP  - 223
PB  - De Gruyter
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Kupstat, Annette
A1  - Kumke, Michael Uwe
A1  - Hildebrandt, Niko
T1  - Toward sensitive, quantitative point-of-care testing (POCT) of protein markers miniaturization of a homogeneous time-resolved fluoroimmunoassay for prostate-specific antigen detection
JF  - The analyst : the analytical journal of the Royal Society of Chemistry
N2  - Point-of-care testing (POCT) systems which allow for a sensitive, quantitative detection of protein markers are extremely useful for the early detection and therapy progress monitoring of cancer. However, currently commercially available POCT devices are mainly limited to the qualitative detection of protein markers. In this study we demonstrate the successive miniaturization of a sensitive and fast assay for the quantitative detection of prostate-specific antigen (PSA) using a well established and clinically approved homogeneous time-resolved fluoroimmunoassay technology (TRACE (R)) on a commercial plate-reader system (KRYPTOR (R)). Regarding the initial requirements for the development of POCT devices we applied a 30-fold assay volume reduction (150 mu L to 5 mu L) to achieve a reasonable lab-on-a-chip volume and a 24-fold and 120-fold excitation pulse energy reduction to achieve reasonable pulse energies for low-cost miniature excitation sources. Due to highly efficient optimization of key POCT parameters our miniaturized PSA assay achieved a 30% increased sensitivity and a 2-fold improved limit of detection compared to the standard plate-reader method. Our results demonstrate the successful implementation of key parameters for a significant miniaturization and for cost reduction in the clinically approved KRYPTOR (R) platform for protein detection. The technological alterations required are easy-to-implement and can be immediately adapted for more than 30 diagnostic protein markers already available for the KRYPTOR (R) platform. These features strongly recommend our assay format to be utilized in innovative, sensitive, quantitative POCT of protein markers.
Y1  - 2011
U6  - https://doi.org/10.1039/c0an00684j
SN  - 0003-2654
VL  - 136
IS  - 5
SP  - 1029
EP  - 1035
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Antoniou, Stella
A1  - Pashalidis, Ioannis
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
T1  - Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3)
JF  - Journal of rare earths
N2  - The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere.
KW  - lanthanide ions
KW  - humic acid
KW  - solid phase
KW  - solubility
KW  - Raman
KW  - TRLFS
KW  - DR-UV-Vis
KW  - rare earths
Y1  - 2011
U6  - https://doi.org/10.1016/S1002-0721(10)60490-5
SN  - 1002-0721
VL  - 29
IS  - 6
SP  - 516
EP  - 521
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kienzler, Andrea
A1  - Flehr, Roman
A1  - Kramer, Rolf A.
A1  - Gehne, Soeren
A1  - Kumke, Michael Uwe
A1  - Bannwarth, Willi
T1  - Novel Three-Color FRET Tool Box for Advanced Protein and DNA Analysis
JF  - Bioconjugate chemistry
N2  - We report on a new three-color FRET system which we were able to verify in peptides as well as in synthetic DNA. All three chromophores could be introduced by a building block approach avoiding postsynthetic labeling. Additional features are robustness, matching spectroscopic properties, high-energy transfer, and sensitivity. The system was investigated in detail on a set of peptides as well as an array of tailored oligonucleotides. The detailed analysis of the experimental data and comparison with theoretical considerations were in excellent agreement. It is shown that in the case of polypeptides specific interaction with the fluorescence probes has to be considered. In contrast with DNA, the fluorescence probes did not show any indications of such interactions. The novel three-color FRET toolbox revealed the potential for applications studying fundamental processes of three interacting molecules in life science applications.
Y1  - 2011
U6  - https://doi.org/10.1021/bc2002659
SN  - 1043-1802
VL  - 22
IS  - 9
SP  - 1852
EP  - 1863
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Radziuk, Darya
A1  - Skirtach, Andre
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
A1  - Zhang, Wei
A1  - Möhwald, Helmuth
A1  - Shchukin, Dmitry
T1  - Ultrasonic Approach for Formation of Erbium Oxide Nanoparticles with Variable Geometries
JF  - Langmuir
N2  - Ultrasound (20 kHz, 29 W. cm(-2)) is employed to form three types of erbium oxide nanoparticles in the presence of multiwalled carbon nanotubes as a template material in water. The nanoparticles are (i) erbium carboxioxide nanoparticles deposited on the external walls of multiwalled carbon nanotubes and Er(2)O(3) in the bulk with (ii) hexagonal and (iii) spherical geometries. Each type of ultrasonically formed nanoparticle reveals Er(3+) photoluminescence from crystal lattice. The main advantage of the erbium carboxioxide nanoparticles on the carbon nanotubes is the electromagnetic emission in the visible region, which is new and not examined up to the present date. On the other hand, the photoluminescence of hexagonal erbium oxide nanoparticles is long-lived (mu s) and enables the higher energy transition ((4)S(3/2)-(4)I(15/2)), which is not observed for spherical nanoparticles. Our work is unique because it combines for the first time spectroscopy of Er(3+) electronic transitions in the host crystal lattices of nanoparticles with the geometry established by ultrasound in aqueous solution of carbon nanotubes employed as a template material. The work can be of great interest for "green" chemistry synthesis of photoluminescent nanoparticles in water.
Y1  - 2011
U6  - https://doi.org/10.1021/la203622u
SN  - 0743-7463
VL  - 27
IS  - 23
SP  - 14472
EP  - 14480
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lippold, Holger
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Lippmann-Pipke, Johanna
T1  - Diffusion, degradation or on-site stabilisation - identifying causes of kinetic processes involved in metal-humate complexation
JF  - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry
N2  - The applicability of equilibrium models for humic-bound transport of toxic or radioactive metals is affected by kinetic processes leading to an increasing inertness of metal-humic complexes. The chemical background is not yet understood. It is widely believed that bound metals undergo an in-diffusion process within the humic colloids, changing from weaker to stronger binding sites. This work is focussed on the competition effect of Al(III) on complexation of Tb(III) or Eu(III) as analogues of trivalent actinides. By using ion exchange and spectroscopic methods, their bound fractions were determined for solutions of Al and humic acid that had been pre-equilibrated for different periods of time. Whilst the amount of bound Al remained unchanged, its blocking effect was found to increase over a time frame of 2 days, which corresponds to the kinetics of the increase in complex inertness reported in most pertinent studies. Thus, the derived "diffusion theory'' turned out to be inapplicable, since it cannot explain an increase in competition for the "initial'' sites. A delayed degradation of polynuclear species (as found for Fe) does not occur. Consequently, the temporal changes must be based on structural rearrangements in the vicinity of bound Al, complicating the exchange or access. Time-dependent studies by laser fluorescence spectroscopy (steady-state and time-resolved) yielded evidence of substantial alterations, which were, however, immediately induced and did not show any significant trend on the time scale of interest, suggesting that the stabilisation process is based on comparatively moderate changes.
Y1  - 2012
U6  - https://doi.org/10.1016/j.apgeochem.2011.11.001
SN  - 0883-2927
VL  - 27
IS  - 1
SP  - 250
EP  - 256
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Xie, Zai-Lai
A1  - Xu, Hai-Bing
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
A1  - Priebe, Magdalena
A1  - Fromm, Katharina M.
A1  - Taubert, Andreas
T1  - A transparent, flexible, ion conductive, and luminescent PMMA ionogel based on a Pt/Eu bimetallic complex and the ionic liquid [Bmim][N(Tf)(2)]
JF  - Journal of materials chemistry
N2  - Transparent, ion-conducting, luminescent, and flexible ionogels based on the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide [Bmim][N(Tf)(2)], a PtEu2 chromophore, and poly(methylmethacrylate) (PMMA) have been prepared. The thermal stability of the PMMA significantly increases with IL incorporation. In particular, the onset weight loss observed at ca. 229 degrees C for pure PMMA increases to 305 degrees C with IL addition. The ionogel has a high ionic conductivity of 10(-3) S cm(-1) at 373 K and exhibits a strong emission in the red with a long average luminescence decay time of tau = 890 mu s. The resulting material is a new type of soft hybrid material featuring useful thermal, optical, and ion transport properties.
Y1  - 2012
U6  - https://doi.org/10.1039/c2jm15862k
SN  - 0959-9428
VL  - 22
IS  - 16
SP  - 8110
EP  - 8116
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Primus, Philipp-A.
A1  - Kumke, Michael Uwe
T1  - Flash photolysis study of complexes between salicylic acid and lanthanide ions in water
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - In the natural environment humic substances (HS) represent a major factor determining the speciation of metal ions, e.g., in the context of radionuclide migration. Here, due to their intrinsic sensitivity and selectivity, spectroscopic methods are often applied, requiring a fundamental understanding of the photophysical processes present in such HS-metal complexes. Complexes with different metal ions were studied using 2-hydroxybenzoic acid (2HB) as a model compound representing an important part of the chelating substructures in HS. In flash photolysis experiments under direct excitation of 2HB in the absence and the presence of different lanthanide ions, the generation and the decay of the 2HB triplet state, of the phenoxy radical, and of the solvated electron were monitored. Depending on the lanthanide ion different intracomplex processes were observed for these transient species including energy migration to and photoreduction of the lanthanide ion. The complexity of the intracomplex photophysical processes even for small molecules such as 2HB underlines the necessity to step-by-step approach the photochemical reactivity of HS by using suitable model compounds.
Y1  - 2012
U6  - https://doi.org/10.1021/jp2043575
SN  - 1089-5639
VL  - 116
IS  - 4
SP  - 1176
EP  - 1182
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kienzler, Andrea Altevogt Nee
A1  - Flehr, Roman
A1  - Gehne, Sören
A1  - Kumke, Michael Uwe
A1  - Bannwarth, Willi
T1  - Verification and biophysical characterization of a New Three-Color Forster Resonance-Energy-Transfer (FRET) System in DNA
JF  - Helvetica chimica acta
N2  - We report on a new three-color FRET system consisting of three fluorescent dyes, i.e., of a carbostyril (=quinolin-2(1H)-one)-derived donor D, a (bathophenanthroline)ruthenium complex as a relay chromophore A1, and a Cy dye as A2 (FRET=Forster resonance-energy-transfer) (cf. Fig. 1). With their widely matching spectroscopic properties (cf. Fig. 2), the combination of these dyes yielded excellent FRET efficiencies. Furthermore, fluorescence lifetime measurements revealed that the long fluorescence lifetime of the Ru complex was transferred to the Cy dye offering the possibility to measure the whole system in a time-resolved mode. The FRET system was established on double-stranded DNA (cf. Fig. 3) but it should also be generally applicable to other biomolecules.
KW  - Forster resonance energy transfer (FRET) system
KW  - DNA
KW  - Fluorescence
KW  - Ruthenium complexes
Y1  - 2012
U6  - https://doi.org/10.1002/hlca.201100460
SN  - 0018-019X
VL  - 95
IS  - 4
SP  - 543
EP  - 555
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Techen, Anne
A1  - Hille, Carsten
A1  - Dosche, Carsten
A1  - Kumke, Michael Uwe
T1  - Fluorescence study of drug-carrier interactions in CTAB/PBS buffer model systems
JF  - Journal of colloid and interface science
N2  - The well-known cationic surfactant hexadecyltrimethylammonium bromide (CTAB) was used as a model carrier to study drug-carrier interactions with fluorescence probes (5-hexadecanoylaminofluorescein (HAF) and 2,10-bis-(3-aminopropyloxy)dibenzo[aj]perylene-8,16-dione (NIR 628) by applying ensemble as well as single molecule fluorescence techniques. The impact of the probes on the micelle parameters (critical micelle concentration, average aggregation number, hydrodynamic radius) was investigated under physiological conditions. In the presence of additional electrolytes, such as buffer, the critical micelle concentration decreased by a factor of about 10. In contrast, no influence of the probes on the critical micelle concentration and on average aggregation number was observed. The results show that HAF does not affect the characteristics of CTAB micelles. Analyzing fluorescence correlation spectroscopy data and time-resolved anisotropy decays in terms of the "two-step" in combination with the "wobbling-in-cone" model, it was proven that HAF and NIR 628 are differently associated with the micelles. Based on ensemble and single molecule fluorescence experiments, intra- and intermicellar energy transfer process between the two dyes were probed and characterized.
KW  - Hexadecyltrimethylammonium bromide
KW  - 5-Hexadecanoylaminofluorescein
KW  - 2,10-Bis-(3-aminopropyloxy)dibenzo[aj]perylene-8,16-dione
KW  - Fluorescence correlation spectroscopy
KW  - Fluorescence anisotropy
KW  - Single-molecule FRET
Y1  - 2012
U6  - https://doi.org/10.1016/j.jcis.2012.03.063
SN  - 0021-9797
VL  - 377
SP  - 251
EP  - 261
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Gehne, Sören
A1  - Flehr, Roman
A1  - Kienzler, Andrea Altevogt Nee
A1  - Berg, Maik
A1  - Bannwarth, Willi
A1  - Kumke, Michael Uwe
T1  - Dye dynamics in three-color FRET samples
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - Time-resolved emission data (fluorescence decay and fluorescence depolarization) of two three-color Forster resonance energy transfer (tc-FRET) systems consisting of a carbostyril donor (D), a ruthenium complex (Ru) as relay dye, and a Cy5 derivative (Cy) or, optionally, an anthraquinone quencher (Q) were carefully analyzed using advanced distribution analysis models. Thereby, it is possible to get information on the flexibility and mobility of the chromophores which are bound to double stranded (ds) DNA. Especially the distance distribution based on the analysis of the fluorescence depolarization is an attractive approach to complement data of fluorescence decay time analysis. The distance distributions extracted from the experimental data were in excellent agreement with those determined from accessible volume (AV) simulations. Moreover, the study showed that for tc-FRET systems the combination of dyes emitting on different time scales (e.g., nanoseconds vs microseconds) is highly beneficial in the distribution analysis of time-resolved luminescence data in cases where macromolecules such as DNA are involved. Here, the short lifetimes can yield information on the rotation of the dye molecule itself and the long lifetime can give insight in the overall dynamics of the macromolecule.
Y1  - 2012
U6  - https://doi.org/10.1021/jp3064273
SN  - 1520-6106
VL  - 116
IS  - 35
SP  - 10798
EP  - 10806
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Demetriou, Antri
A1  - Pashalidis, Ioannis
A1  - Nicolaides, Athanassios V.
A1  - Kumke, Michael Uwe
T1  - Surface mechanism of the boron adsorption on alumina in aqueous solutions
JF  - Desalination and water treatment : science and engineering
N2  - The adsorption of boron (boric acid) from aqueous solutions on alumina has been investigated at pH 8.0, I=0.1M NaClO4, T=22 +/- 3 degrees C, and under normal atmospheric conditions. The characterization of the adsorbed species was performed by Raman spectroscopy and the spectroscopic speciation was assisted by theoretical DFT calculations. Evaluation of the spectroscopic data points to the formation of inner-sphere surface complexes and indicates the formation of two different types of adsorbed boron species. The theoretical calculations corroborate the spectroscopic data and indicate that at low boron concentration the monodentate surface species dominates, whereas increased boron concentration favors the formation of a bidentate surface species. Assuming low coverage, the conditional formation constant for the monodentate surface species has been evaluated to be log=4.1 +/- 0.1.
KW  - Boric acid
KW  - Alumina
KW  - Raman spectroscopy
KW  - DFT calculations
KW  - Surface complexes
KW  - Formation constant
Y1  - 2013
U6  - https://doi.org/10.1080/19443994.2013.764354
SN  - 1944-3994
SN  - 1944-3986
VL  - 51
IS  - 31-33
SP  - 6130
EP  - 6136
PB  - Taylor & Francis Group
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Techen, Anne
A1  - Czapla, Sylvia
A1  - Möllnitz, Kristian
A1  - Budach, Dennis B.
A1  - Wessig, Pablo
A1  - Kumke, Michael Uwe
T1  - Synthesis and spectroscopic characterization of fluorophore-labeled oligospiroketal rods
JF  - Helvetica chimica acta
N2  - Fluorescence probes consisting of well-established fluorophores in combination with rigid molecular rods based on spirane-type structures were investigated with respect to their fluorescence properties under different solvent conditions. The attachment of the dyes was accomplished by 1,3-dipolar cycloaddition between alkynes and azides (click' reaction) and is a prime example for a novel class of sensor constructs. Especially, the attachment of two (different) fluorophores on opposite sides of the molecular rods paves the way to new sensor systems with less bulky (compared to the conventional DNA- or protein-based concepts), nevertheless rigid spacer constructs, e.g., for FRET-based sensing applications. A detailed photophysical characterization was performed in MeOH (and in basic H2O/MeOH mixtures) for i) rod constructs containing carboxyfluorescein, ii) rod constructs containing carboxyrhodamine, iii) rod constructs containing both carboxyfluorescein and carboxyrhodamine, and iv) rod constructs containing both pyrene and perylene parts. For each dye (pair), two rod lengths with different numbers of spirane units were synthesized and investigated. The rod constructs were characterized in ensemble as well as single-molecule fluorescence experiments with respect to i) specific roddye and ii) dyedye interactions. In addition to MeOH and MeOH/NaOH, the rod constructs were also investigated in micellar systems, which were chosen as a simplified model for membranes.
KW  - Molecular rods
KW  - Forster resonance energy transfer (FRET)
KW  - Carboxyfluorescein
KW  - Carboxyrhodamine
KW  - Pyrene
KW  - Perylene
KW  - Fluorescence
Y1  - 2013
U6  - https://doi.org/10.1002/hlca.201200616
SN  - 0018-019X
SN  - 1522-2675
VL  - 96
IS  - 11
SP  - 2046
EP  - 2067
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Gehne, Sören
A1  - Sydow, Karl
A1  - Dathe, Margitta
A1  - Kumke, Michael Uwe
T1  - Characterization of cell-penetrating lipopeptide micelles by spectroscopic methods
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - The transport of bioactive compounds to the site of action is a great challenge. A promising approach to overcome application-related problems is the development of targeting colloidal transport systems, such as micelles which are equipped with uptake mediating moieties. Here, we investigated a set of novel lipopeptides which exhibit a surfactant-like structure due to attachment of two palmitoyl chains to the Nterminus of cationic or anionic amino acid sequences. We analyzed the association behavior of these lipopeptides by using 5(6)-carboxyfluorescein (CF)-labeled derivatives as a fluorescent probe and different spectroscopic methods such as fluorescence anisotropy and fluorescence correlation spectroscopy (FCS). The photophysical properties as well as the diffusion and rotational movements of the CF-labeled lipopeptides were exploited to determine the cmc and the size of the micelles consisting of lipopeptides. We could distinguish cationic and anionic lipopeptides by their association behavior and by studying the interactions with mouse brain capillary endothelial cells (b.end3). The cationic derivatives turned out to be very strong surfactants with a very low cmc in the micromolar range (0.5-14 mu M). The unique combination of micelle-forming property and cell-penetrating ability can pave the road for the development of a novel class of efficient drug carrier systems.
Y1  - 2013
U6  - https://doi.org/10.1021/jp406053g
SN  - 1520-6106
VL  - 117
IS  - 46
SP  - 14215
EP  - 14225
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Marang, Laura
A1  - Reiller, Pascal E.
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Benedetti, Marc F.
T1  - Combining spectroscopic and potentiometric approaches to characterize competitive binding to humic substances
N2  - In an area that contains high concentrations of natural organic matter, it is expected that it plays an important role on the behavior of rare earth elements (REE), like europium, and of trivalent actinides. Competitive interactions with H+, inorganic species, major cations, e.g. Ca(II) or Mg(II), could influence these metals transport and bioavailability. Competitive experiments between cations, which can bind differently to humic substances and Eu3+,will bring an improved understanding of the competitive mechanisms. The aim of this study is to acquire data for Eu(III)/Cu(II) and Eu(III)/Ca(II) competitive binding to a sedimentary originated humic acid (Gorleben, Germany). The NICA-Donnan parameters for Ca2+, Cu2+, and Eu3+ obtained from competitive binding experiments using Ca2+ or Cu2+ ion selective electrodes were used to model time-resolved laser fluorescence spectroscopy (TRLFS) measurements. Eu3+ and Cu2+ are in direct competition for the same type of sites,whereas Ca2+ has an indirect influence through electrostatic binding.
Y1  - 2008
UR  - http://pubs.acs.org/doi/full/10.1021/es702858p
U6  - https://doi.org/10.1021/Es702858p
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Lorenz-Fonfria, Victor A.
A1  - Parvulescu, Vasile Ion
A1  - Geßner, Andre
A1  - Kumke, Michael Uwe
T1  - Photoluminescence study of terbium-exchanged ultrastable Y zeolites: Number of species, photoluminescence decays and decay-associated spectra
Y1  - 2008
UR  - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=JAPIAU000104000003033530000001&idtype=cvips&doi=10.1063/1.2966304&prog=normal
U6  - https://doi.org/10.1063/1.2966304
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Kumke, Michael Uwe
A1  - Parvulescu, Vasile Ion
A1  - Geßner, Andre
A1  - Gagea, Bogdan
A1  - Martens, Johan
T1  - Europium(3+) : an efficient luminescence probe for the Si to Al ratio and silylation effect in the microporous- mesoporous Zeogrid materials
Y1  - 2008
UR  - http://pubs.acs.org/doi/pdf/10.1021/jp711337h
U6  - https://doi.org/10.1021/Jp711337h
ER  - 
TY  - JOUR
A1  - Kuke, S.
A1  - Marmodee, Bettina
A1  - Eidner, Sascha
A1  - Schilde, Uwe
A1  - Kumke, Michael Uwe
T1  - Intramolecular deactivation processes in complexes of salicylic acid or glycolic acid with Eu(III)
N2  - The complexation of Eu(III) by 2-hydroxy benzoic acid (2HB) or glycolic acid (GL) was investigated using steady- state and time-resolved laser spectroscopy. Experiments were carried out in H2O as well as in D2O in the temperature range of View the MathML source. The Eu(III) luminescence spectra and luminescence decay times were evaluated with respect to the temperature dependence of (i) the luminescence decay time ;, (ii) the energy of the View the MathML source transition, (iii) the width of the View the MathML source transition, and (iv) the asymmetry ratio calculated from the luminescence intensities of the View the MathML source and View the MathML source transition, respectively. The differences in ligand-related luminescence quenching are discussed. Based on the temperature dependence of the luminescence decay times an activation energy for the ligand-specific non-radiative deactivation in Eu(III)-2HB or Eu(III)-GL complexes was determined. It is stressed that ligand-specific quenching processes (other than OH quenching induced by water molecules) need to be determined and considered in detail, in order to extract speciation- relevant information from luminescence data (e.g., estimation of the number of water molecules nH2O in the first coordination sphere of Eu(III)). In case of 2HB, conclusions drawn from the evaluation of the Eu(III) luminescence are compared with results of a X-ray structure analysis.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/article/pii/S1386142510000144
SN  - 0584-8539
ER  - 
TY  - JOUR
A1  - Marang, Laura
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Benedetti, Marc F.
A1  - Reiller, Pascal E.
T1  - Characterization of competitive binding of Eu(III)/Cu(II) and Eu(III)/Ca(II) to Gorleben humic acid
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00167037
U6  - https://doi.org/10.1016/j.gca.2009.05.011
SN  - 0016-7037
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile Ion
A1  - Cojocaru, Bogdan
A1  - Lorenz-Fonfria, Victor A.
A1  - Kumke, Michael Uwe
A1  - Gessner, Andre
A1  - Enculescu, Ion
T1  - Polymer-microporous host interactions probed by photoluminescence spectroscopy
N2  - Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/CP/index.asp
U6  - https://doi.org/10.1039/B922591a
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile
A1  - Parvulescu, Victoria
A1  - Cotoi, Elena
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
A1  - Simon, Simion
A1  - Vasiliu, Florin
T1  - Structural and photoluminescence characterization of mesoporous silicon-phosphates
N2  - Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/10106030
U6  - https://doi.org/10.1016/j.jphotochem.2010.07.015
SN  - 1010-6030
ER  - 
TY  - JOUR
A1  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Examples of the application of optical process and quality sensing (OPQS) to beer brewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near- infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O-2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant
Y1  - 2006
UR  - http://www.springerlink.com/content/100417
U6  - https://doi.org/10.1007/s00216-005-3364-4
SN  - 1618-2642
ER  - 
TY  - JOUR
A1  - Kumke, Michael Uwe
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Trowitzsch-Kienast, Wolfram
A1  - Löhmannsröben, Hans-Gerd
T1  - Spectroscopic characterization of the artificial siderophore pyridinochelin
Y1  - 2006
UR  - http://www.znaturforsch.com/c.htm
SN  - 0939-5075
ER  - 
TY  - JOUR
A1  - Kramer, Rolf A.
A1  - Flehr, Roman
A1  - Lay, Myriam
A1  - Kumke, Michael Uwe
A1  - Bannwarth, Willi
T1  - Comparative studies of different quinoline derivatives as donors in fluorescence-resonance-energy-transfer (FRET) : systems in combination with a (Bathophenanthroline)ruthenium(II) complex as acceptor
Y1  - 2009
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/5007133/
U6  - https://doi.org/10.1002/hlca.200900235
SN  - 0018-019X
ER  - 
TY  - JOUR
A1  - Marmodée, Bettina
A1  - de Klerk, Joost
A1  - Ariese, Freek
A1  - Gooijer, Cees
A1  - Kumke, Michael Uwe
T1  - Metal binding by humic substances : characterization by high-resolution-lanthanide-ion-probe-spectroscopy (HR- LIPS)
N2  - In ultra-low-temperature experiments at 4.7 K the luminescence of Eu(III) bound to different hydroxy- and methoxybenzoic acids and to humic substances (HS) was investigated. The benzoic acid derivatives were used as simple model compounds for common metal-binding structures in HS. The Eu(III) luminescence was directly excited by means of a pulsed dye laser, scanning through the D-5(0) -> F-7(0) transition of Eu(III) and subsequently, high-resolution total luminescence spectra (TLS) were recorded. Based on the thorough analysis of the high-resolution TLS conclusions were drawn with respect to the number of different complexes formed and to the symmetry of the complexes. The crystal-field strength parameter N-nu(B-2q) was dependent on the electrostatic forces induced by the ligands as well as on the symmetry of the complexes. The formation of thermodynamically stable complexes was found to be slow even for small model ligands such its 2-hydroxybenzoic acid. Comparison between the model compounds and HS clearly revealed that the carboxylate group is the dominant binding site in HS. Indices for the formation of chelates, e.g. similar to 2- hydroxybenzoic acid, were not found for HS.
Y1  - 2009
UR  - http://www.znaturforsch.com/a.htm
SN  - 0932-0784
ER  - 
TY  - JOUR
A1  - Marang, Laura
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Benedetti, Marc F.
A1  - Reiller, Pascal E.
T1  - Spectroscopic characterization of the competitive binding of Eu(III), Ca(II) and Cu(II) to a sedimentary originated humic acid
N2  - The competition between REE, alkaline earth and d-transition metals for organic matter binding sites is still an open field of research; particularly, the mechanisms governing these phenomena need to be characterized in more detail. In this study, we examine spectroscopically the mechanisms of competitive binding of Eu(III)/Cu(II) and Eu(III)/ Ca(II) pair to Gorleben humic acid (HA), as previously proposed in the framework of the NICA-Donnan model. The evolution of time-resolved laser induced luminescence spectra of humic-complexed Eu(Ill) showed two strikingly different environments for a comparable bound proportion for Cu(II) and Ca(II). Cu(II) seems to compete more effectively with Eu(III) inducing its release into the Donnan phase, and into the bulk solution as free Eu3+. This is evidenced both by the shapes of the spectra and by the decrease in the luminescence decay times. In contrast with that, Ca(II) induces a modification of the HA structure, which enhances the luminescence of humic-bound Eu(III), and causes a minor modification of the chemical environment of the complexed rare earth ion.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00092541
U6  - https://doi.org/10.1016/j.chemgeo.2009.03.003
SN  - 0009-2541
ER  -