@article{HaubitzTsushimaSteudtneretal.2018, author = {Haubitz, Toni and Tsushima, Satoru and Steudtner, Robin and Drobot, Bj{\"o}rn and Geipel, Gerhard and Stumpf, Thorsten and Kumke, Michael Uwe}, title = {Ultrafast Transient Absorption Spectroscopy of UO(2)(2+)and [UO2Cl](+)}, series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, volume = {122}, journal = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, number = {35}, publisher = {American Chemical Society}, address = {Washington}, issn = {1089-5639}, doi = {10.1021/acs.jpca.8b05567}, pages = {6970 -- 6977}, year = {2018}, abstract = {For the only water coordinated "free" uranyl (VI) aquo ion in perchlorate solution we identified and assigned several different excited states and showed that the (3)Delta state is the luminescent triplet state from transient absorption spectroscopy. With additional data from other spectroscopic methods (TRLFS, UV/vis) we generated a detailed Jablonski diagram and determined rate constants for several state transitions, like the inner conversion rate constant from the (3)Phi state to the (3)Delta state transition to be 0.35 ps(-1). In contrast to luminescence measurements, it was possible to observe the highly quenched uranyl(VI) ion in highly concentrated chloride solution by TAS and we were able to propose a dynamic quenching mechanism, where chloride complexation is followed by the charge transfer from the excited state uranyl(VI) to chloride. This proposed quenching route is supported by TD-DFT calculations.}, language = {en} } @article{HesseKlierSgarzietal.2018, author = {Hesse, Julia and Klier, Dennis Tobias and Sgarzi, Massimo and Nsubuga, Anne and Bauer, Christoph and Grenzer, Joerg and H{\"u}bner, Rene and Wislicenus, Marcus and Joshi, Tanmaya and Kumke, Michael Uwe and Stephan, Holger}, title = {Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66}, series = {ChemistryOpen : including thesis treasury}, volume = {7}, journal = {ChemistryOpen : including thesis treasury}, number = {2}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2191-1363}, doi = {10.1002/open.201700186}, pages = {159 -- 168}, year = {2018}, abstract = {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.}, language = {en} } @article{HoangHaubitzKumke2018, author = {Hoang, Hoa T. and Haubitz, Toni and Kumke, Michael Uwe}, title = {Photophysics of "Floppy" Dyadsas Potential Biomembrane Probes}, series = {Journal of fluorescence}, volume = {28}, journal = {Journal of fluorescence}, number = {5}, publisher = {Springer}, address = {New York}, issn = {1053-0509}, doi = {10.1007/s10895-018-2286-4}, pages = {1225 -- 1237}, year = {2018}, abstract = {In the study a dyad (C6 probe), constructed of two dyes with highly different hydrophobicities, was investigated by steady-state and time-resolved spectroscopic techniques in chloroform, methanol, and in phospholipid vesicles, respectively. The dyad was built on two dyes: the lipophilic benzo[a]pyrene (BaP) and the hydrophilic sulforhodamine B (SRB). The dyes were linked via a short, but flexible alkyl chain (six C-atoms). Based on their spectroscopic properties, BaP and SRB showed a very efficient non-radiative resonance energy transfer in solution. Incorporation into a lipid bilayer limited the relative flexibility (degree of freedom) between donor and acceptor and was used for the investigation of fundamental photophysical aspects (especially of FRET) as well as to elucidate the potential of the dyad to probe the interface of vesicles (or cells). The location of the two dyes in vesicles and their respective accessibility for interactions with dye-specific antibodies was investigated. Based on the alteration of the anisotropy, on the rotational correlation time as well as on the diffusion coefficient the incorporation of the C6 probe into the vesicles was evaluated. Especially the limitation in the relative movements of the two dyes was considered and used to differentiate between potential parameters, that influence the energy transfer in the dyad. Transient absorption spectroscopy (TAS) and pulsed-interleave single molecule fluorescence experiments were performed to better understand the intramolecular interactions in the dyad. Finally, in a showcase for a biosensing application of the dyads, the binding of an SRB-specific antibody was investigated when the dyad was incorporated in vesicles.}, language = {en} } @article{BurekEidnerKukeetal.2018, author = {Burek, Katja and Eidner, Sascha and Kuke, Stefanie and Kumke, Michael Uwe}, title = {Intramolecular deactivation processes of electronically excited Lanthanide(III) complexes with organic acids of low molecular weight}, series = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy}, volume = {191}, journal = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy}, publisher = {Elsevier}, address = {Oxford}, issn = {1386-1425}, doi = {10.1016/j.saa.2017.09.012}, pages = {36 -- 49}, year = {2018}, abstract = {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.}, language = {en} } @article{BurekKrauseSchwotzeretal.2018, author = {Burek, Katja and Krause, Felix and Schwotzer, Matthias and Nefedov, Alexei and S{\"u}ssmuth, Julia and Haubitz, Toni and Kumke, Michael Uwe and Thissen, Peter}, title = {Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements}, series = {ACS sustainable chemistry \& engineering}, volume = {6}, journal = {ACS sustainable chemistry \& engineering}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.8b03244}, pages = {14669 -- 14678}, year = {2018}, abstract = {In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases.}, language = {en} } @article{EisoldSellrieMemczaketal.2018, author = {Eisold, Ursula and Sellrie, Frank and Memczak, Henry and Andersson, Anika and Schenk, J{\"o}rg A. and Kumke, Michael Uwe}, title = {Dye tool box for a fluorescence enhancement immunoassay}, series = {Bioconjugate chemistry}, volume = {29}, journal = {Bioconjugate chemistry}, number = {1}, publisher = {American Chemical Society}, address = {Washington}, issn = {1043-1802}, doi = {10.1021/acs.bioconjchem.7b00731}, pages = {203 -- 214}, year = {2018}, abstract = {Immunochemical analytical methods are very successful in clinical diagnostics and are nowadays also emerging in the control of food as well as monitoring of environmental issues. Among the different immunoassays, luminescence based formats are characterized by their outstanding sensitivity making this format especially attractive for future applications. The need for multiparameter detection capabilities calls for a tool box of dye labels in order to transduce the biochemical reaction into an optically detectable signal. Here, in a multiparameter approach each analyte may be detected by a different dye with a unique emission color (covering the blue to red spectral range) or a unique luminescence decay kinetics. In the case of a competitive immunoassay format for each of the different dye labels an individual antibody would be needed. In the present paper a slightly modified approach is presented using a 7-aminocoumarin unit as the basic antigen against which highly specific antibodies were generated. Leaving the epitope region in the dyes unchanged but introducing a side group in positon 3 of the coumarin system allowed us to tune the optical properties of the coumarin dyes without the necessity of new antibody generation. Upon modification of the parent coumarin unit the full spectral range from blue to deep red was accessed. In the manuscript the photophysical characterization of the coumarin derivatives and their corresponding immunocomplexes with two highly specific antibodies is presented. The coumarin dyes and their immunocomplexes were characterized by steady-state and time-resolved absorption as well as emission spectroscopy. Moreover, fluorescence depolarization measurements were carried out to complement the data stressing the different binding modes of the two antibodies. The binding modes were evaluated using the photophysics of 7-aminocoumarins and how it was affected in the respective immunocomplexes, namely, the formation of the intramolecular charge transfer (ICT) as well as the twisted intramolecular charge transfer (TICT). In contrast to other antibody-dye pairs reported a distinct fluorescence enhancement upon formation of the antibody-dye complex up to a factor of SO was found. Because of the easy emission color tuning by tailoring the coumarin substitution for the antigen binding in nonrelevant position 3 of the parent molecule, a dye tool box is on hand which can be used in the construction of competitive multiparameter fluorescence enhancement immunoassays (FenIA).}, language = {en} } @article{HoangMertensWessigetal.2018, author = {Hoang, Hoa T. and Mertens, Monique and Wessig, Pablo and Sellrie, Frank and Schenk, J{\"o}rg A. and Kumke, Michael Uwe}, title = {Antibody Binding at the Liposome-Water Interface}, series = {ACS Omega}, volume = {3}, journal = {ACS Omega}, number = {12}, publisher = {American Chemical Society}, address = {Washington}, issn = {2470-1343}, doi = {10.1021/acsomega.8b03016}, pages = {18109 -- 18116}, year = {2018}, abstract = {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.}, language = {en} }