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 - 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 - 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 - Kumke, Michael Uwe A1 - Eidner, Sascha A1 - Krüger, Tobias T1 - Fluorescence quenching and luminescence sensitization in complexes of Tb3+ and Eu3+ with humic substances N2 - Intrinsic fluorescence quenching of humic substances (HS) and the sensitization of Ln(3+) luminescence (Ln3+ Tb3+, Eu3+) in HS complexes were investigated. Both measurements yielded complementary information on the complexation of metals by HS. Large differences between fulvic acids(FA)and humic acids (HA) were found. From time-resolved luminescence measurements it is concluded that a combination of energy transfer and energy back transfer between HS and Ln(3+) is responsible for the observed luminescence decay characteristics. In the case of Eu3+, an additional participation of charge-transfer states is suggested. A new concept for the evaluation of the sensitized luminescence decays of Ln(3+) was adapted Y1 - 2005 ER - TY - JOUR A1 - Roth, Martin M. A1 - Löhmannsröben, Hans-Gerd A1 - Kelz, A. A1 - Kumke, Michael Uwe T1 - innoFSPEC : fiber optical spectroscopy and sensing Y1 - 2008 SN - 978-0-819-47228-1 ER - TY - JOUR A1 - Hesse, Julia A1 - Klier, Dennis Tobias A1 - Sgarzi, Massimo A1 - Nsubuga, Anne A1 - Bauer, Christoph A1 - Grenzer, Joerg A1 - Hübner, Rene A1 - Wislicenus, Marcus A1 - Joshi, Tanmaya A1 - Kumke, Michael Uwe A1 - Stephan, Holger T1 - Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66 JF - ChemistryOpen : including thesis treasury N2 - We report a simple one-pot method for the rapid preparation of sub-10nm pure hexagonal (-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol((R))66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core-shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects. KW - core-shell materials KW - lanthanides KW - nanostructures KW - photoluminescence KW - upconversion Y1 - 2018 U6 - https://doi.org/10.1002/open.201700186 SN - 2191-1363 VL - 7 IS - 2 SP - 159 EP - 168 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Burek, Katja A1 - Eidner, Sascha A1 - Kuke, Stefanie A1 - Kumke, Michael Uwe T1 - Intramolecular deactivation processes of electronically excited Lanthanide(III) complexes with organic acids of low molecular weight JF - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy N2 - The luminescence of Lanthanide(Ill) complexes with different model ligands was studied under direct as well as sensitized excitation conditions. The research was performed in the context of studies dealing with deep-underground storages for high-level nuclear waste. Here, Lanthanide(III) ions served as natural analogues for Actinide(III) ions and the low-molecular weight organic ligands are present in clay minerals and furthermore, they were employed as proxies for building blocks of humic substances, which are important complexing molecules in the natural environment, e.g., in the far field of a repository site. Time-resolved luminescence spectroscopy was applied for a detailed characterization of Eu(III), Tb(III), Sm(III) and.Dy(III) complexes in aqueous solutions. Based on the observed luminescence the ligands were tentatively divided into two groups (A, B). The luminescence of Lanthanide(III) complexes of group A was mainly influenced by an energy transfer to OH-vibrations. Lanthanide(Ill) complexes of group B showed ligand-related luminescence quenching, which was further investigated. To gain more information on the underlying quenching processes of group A and B ligands, measurements at different temperatures (77 K <= T <= 353 K) were performed and activation energies were determined based on an Arrhenius analysis. Moreover, the influence of the ionic strength between 0 M <= 1 <= 4 M on the Lanthanide(III) luminescence was monitored for different complexes, in order to evaluate the influence of specific conditions encountered in host rocks foreseen as potential repository sites. KW - Humic substance KW - Model ligand KW - Metal complexation KW - Benzoic acids KW - Intramolecular deactivation Y1 - 2018 U6 - https://doi.org/10.1016/j.saa.2017.09.012 SN - 1386-1425 VL - 191 SP - 36 EP - 49 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Haubitz, Toni A1 - Fudickar, Werner A1 - Linker, Torsten A1 - Kumke, Michael Uwe T1 - pH-sensitive fluorescence switching of pyridylanthracenes BT - the effect of the isomeric pattern JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - 9,10-substituted anthracenes are known for their useful optical properties like fluorescence, which makes them frequently used probes in sensing applications. In this article, we investigate the fundamental photophysical properties of three pyridyl-substituted variants. The nitrogen atoms in the pyridinium six-membered rings are located in the ortho-, meta-, and para-positions in relation to the anthracene core. Absorption, fluorescence, and transient absorption measurements were carried out and were complemented by theoretical calculations. We monitored the photophysics of the anthracene derivatives in chloroform and water investigating the protonated as well as their nonprotonated forms. We found that the optical properties of the nonprotonated forms are strongly determined by the anthracene chromophore, with only small differences to other 9,10-substituted anthracenes, for example diphenyl anthracene. In contrast, protonation leads to a strong decrease in fluorescence intensity and lifetime. Transient absorption measurements and theoretical calculations revealed the formation of a charge-transfer state in the protonated chromophores, where electron density is shifted from the anthracene moiety toward the protonated pyridyl substituents. While the para- and ortho-derivatives' charge transfer is still moderately fluorescent, the meta-derivative is affected much stronger and shows nearly no fluorescence. This nitrogen-atom-position-dependent sensitivity to hydronium activity makes a combination of these fluorophores very attractive for pH-sensing applications covering a broadened pH range. KW - Absorption KW - Aromatic compounds KW - Fluorescence KW - Hydrocarbons KW - Reaction mechanisms Y1 - 2020 U6 - https://doi.org/10.1021/acs.jpca.0c09911 SN - 1089-5639 SN - 1520-5215 VL - 124 IS - 52 SP - 11017 EP - 11024 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Schott, Juliane A1 - Kretzschmar, Jerome A1 - Acker, Margret A1 - Eidner, Sascha A1 - Kumke, Michael Uwe A1 - Drobot, Björn 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 N2 - In the presence of polyborates (detected by 11B-NMR) the formation of a weak Eu(III) borate complex (lg β11 ∼ 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 277 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98774 ER - TY - JOUR A1 - Steinbrück, Dörte A1 - Rasch, Claudia A1 - Kumke, Michael Uwe T1 - Photophysics of Ochratoxin A in aqueous solution Y1 - 2008 ER -