@misc{AstSchmaelzlinLoehmannsroebenetal.2012, author = {Ast, Cindy and Schm{\"a}lzlin, Elmar and L{\"o}hmannsr{\"o}ben, Hans-Gerd and van Dongen, Joost T.}, title = {Optical oxygen micro- and nanosensors for plant applications}, series = {Sensors}, volume = {12}, journal = {Sensors}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s120607015}, pages = {7015 -- 7032}, year = {2012}, abstract = {Pioneered by Clark's microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters.}, language = {en} } @misc{BeckHildebrandtLoehmannsroeben2006, author = {Beck, Michael and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Quantum dots as acceptors in FRET-assays containing serum}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-9504}, year = {2006}, abstract = {Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing F{\"o}rster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu3+-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37\%. The F{\"o}rster-radius, estimated from the absorption and emission bands, was ca. 77 {\AA}. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.}, subject = {Quantenpunkt}, language = {en} } @article{BeitzLaudienLoehmannsroebenetal.2006, author = {Beitz, Toralf and Laudien, Robert and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Kallies, Bernd}, title = {Ion mobility spectrometric investigation of aromatic cations in the gas phase}, issn = {1089-5639}, doi = {10.1021/Jp055335n}, year = {2006}, abstract = {In this work, ion mobility (IM) spectra of more than 50 aromatic compounds were recorded with a laser-based IM spectrometer at atmospheric pressure. IM spectra of PAH in the laser desorption experiment show a high complexity resulting from the occurrence of monomeric, dimeric, and oligomeric cluster ions. The mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omega(calc)) on the basis of the exact hard sphere scattering model and their comparison with the experimentally determined diffusion cross sections (Omega(exp)). Extended Omega(exp)/Omega(calc) and Omega(exp/)mass correlations were performed in order to gain insight into conformational properties of cationic alkyl benzenes and internal rotation of phenyl rings in aromatic ions. This is demonstrated with some examples, such as the evaluation of the dihedral angle of the ions of 9,10- diphenylanthracene, o- and m-terphenyl, and 1,2,3- and 1,3,5-triphenylbenzene. Furthermore, sandwich and T-structures of dimeric PAH cations are discussed. The analysis was extended to oligomeric ions with up to nine monomer units. Experimental evidence is presented suggesting the formation of pi-stacks with a transition toward modified pi-stacks with increasing cluster size. The distance between monomeric units in dimeric and oligomeric ions was obtained}, language = {en} } @article{BlandHawthornEllisLeonSavaletal.2011, author = {Bland-Hawthorn, Joss and Ellis, S. C. and Leon-Saval, S. G. and Haynes, R. and Roth, Martin M. and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Horton, A. J. and Cuby, J. -G. and Birks, T. A. and Lawrence, J. S. and Gillingham, P. and Ryder, S. D. and Trinh, C.}, title = {A complex multi-notch astronomical filter to suppress the bright infrared sky}, series = {Nature Communications}, volume = {2}, journal = {Nature Communications}, number = {50}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms1584}, pages = {7}, year = {2011}, abstract = {A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come.}, language = {en} } @article{BrendlerRiebeRitscheletal.2013, author = {Brendler, Christian and Riebe, Daniel and Ritschel, Thomas and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Investigation of neuroleptics and other aromatic compounds by laser-based ion mobility mass spectrometry}, series = {Analytical \& bioanalytical chemistry}, volume = {405}, journal = {Analytical \& bioanalytical chemistry}, number = {22}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-012-6654-7}, pages = {7019 -- 7029}, year = {2013}, abstract = {Laser-based ion mobility (IM) spectrometry was used for the detection of neuroleptics and PAH. A gas chromatograph was connected to the IM spectrometer in order to investigate compounds with low vapour pressure. The substances were ionized by resonant two-photon ionization at the wavelengths lambda = 213 and 266 nm and pulse energies between 50 and 300 mu J. Ion mobilities, linear ranges, limits of detection and response factors are reported. Limits of detection for the substances are in the range of 1-50 fmol. Additionally, the mechanism of laser ionization at atmospheric pressure was investigated. First, the primary product ions were determined by a laser-based time-of-flight mass spectrometer with effusive sample introduction. Then, a combination of a laser-based IM spectrometer and an ion trap mass spectrometer was developed and characterized to elucidate secondary ion-molecule reactions that can occur at atmospheric pressure. Some substances, namely naphthalene, anthracene, promazine and thioridazine, could be detected as primary ions (radical cations), while other substances, in particular acridine, phenothiazine and chlorprothixene, are detected as secondary ions (protonated molecules). The results are interpreted on the basis of quantum chemical calculations, and an ionization mechanism is proposed.}, language = {en} } @article{BrinkmannKoellnerMerketal.2023, author = {Brinkmann, Pia and K{\"o}llner, Nicole and Merk, Sven and Beitz, Toralf and Altenberger, Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Comparison of handheld and echelle spectrometer to assess copper in ores by means of laser-induced breakdown spectroscopy (LIBS)}, series = {Minerals}, volume = {13}, journal = {Minerals}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {2075-163X}, doi = {10.3390/min13010113}, pages = {19}, year = {2023}, abstract = {Its properties make copper one of the world's most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.}, language = {en} } @misc{BrinkmannKoellnerMerketal.2023, author = {Brinkmann, Pia and K{\"o}llner, Nicole and Merk, Sven and Beitz, Toralf and Altenberger, Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Comparison of handheld and echelle spectrometer to assess copper in ores by means of laser-induced breakdown spectroscopy (LIBS)}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1311}, issn = {1866-8372}, doi = {10.25932/publishup-58474}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-584742}, pages = {19}, year = {2023}, abstract = {Its properties make copper one of the world's most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.}, language = {en} } @article{CywinskiHammannHuehnetal.2014, author = {Cywinski, Piotr J. and Hammann, Tommy and Huehn, Dominik and Parak, Wolfgang J. and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing}, series = {Journal of biomedical optics}, volume = {19}, journal = {Journal of biomedical optics}, number = {10}, publisher = {SPIE}, address = {Bellingham}, issn = {1083-3668}, doi = {10.1117/1.JBO.19.10.101506}, pages = {8}, year = {2014}, abstract = {Nanobioconjugates have been synthesized using cadmium selenide quantum dots (QDs), europium complexes (EuCs), and biotin. In those conjugates, long-lived photoluminescence (PL) is provided by the europium complexes, which efficiently transfer energy via Forster resonance energy transfer (FRET) to the QDs in close spatial proximity. As a result, the conjugates have a PL emission spectrum characteristic for QDs combined with the long PL decay time characteristic for EuCs. The nanobioconjugates synthesis strategy and photo-physical properties are described as well as their performance in a time-resolved streptavidin-biotin PL assay. In order to prepare the QD-EuC-biotin conjugates, first an amphiphilic polymer has been functionalized with the EuC and biotin. Then, the polymer has been brought onto the surface of the QDs (either QD655 or QD705) to provide functionality and to make the QDs water dispersible. Due to a short distance between EuC and QD, an efficient FRET can be observed. Additionally, the QD-EuC-biotin conjugates' functionality has been demonstrated in a PL assay yielding good signal discrimination, both from autofluorescence and directly excited QDs. These newly designed QD-EuC-biotin conjugates expand the class of highly sensitive tools for bioanalytical optical detection methods for diagnostic and imaging applications. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)}, language = {en} } @article{CywinskiMoroLoehmannsroeben2014, author = {Cywinski, Piotr J. and Moro, Artur J. and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Cyclic GMP recognition using ratiometric QD-fluorophore conjugate nanosensors}, series = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, volume = {52}, journal = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, publisher = {Elsevier}, address = {Oxford}, issn = {0956-5663}, doi = {10.1016/j.bios.2013.09.002}, pages = {288 -- 292}, year = {2014}, language = {en} } @article{CywinskiMoroRitscheletal.2011, author = {Cywinski, Piotr J. and Moro, Artur J. and Ritschel, Thomas and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Sensitive and selective fluorescence detection of guanosine nucleotides by nanoparticles conjugated with a naphthyridine receptor}, series = {Analytical \& bioanalytical chemistry}, volume = {399}, journal = {Analytical \& bioanalytical chemistry}, number = {3}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-010-4420-2}, pages = {1215 -- 1222}, year = {2011}, abstract = {Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems.}, language = {en} } @article{CywinskiNonoCharbonniereetal.2014, author = {Cywinski, Piotr J. and Nono, Katia Nchimi and Charbonniere, Loic J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c3cp54883j}, pages = {6060 -- 6067}, year = {2014}, abstract = {A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Forster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surfacefunctionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Forster theory, Forsterradii (R0) were found to be around 60 angstrom for organic dyes and around 105 angstrom for QDs. The FRET efficiency (Z) reached 80\% and 25\% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 angstrom for organic dye acceptors, while for acceptor QDs between 120 angstrom and 145 angstrom. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.}, language = {en} } @article{CywinskiOlejkoLoehmannsroeben2015, author = {Cywinski, Piotr J. and Olejko, Lydia and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {A time-resolved luminescent competitive assay to detect L-selectin using aptamers as recognition elements}, series = {Analytica chimica acta : an international journal devoted to all branches of analytical chemistry}, volume = {887}, journal = {Analytica chimica acta : an international journal devoted to all branches of analytical chemistry}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0003-2670}, doi = {10.1016/j.aca.2015.06.045}, pages = {209 -- 215}, year = {2015}, abstract = {L-selectin is a protein with potential importance for numerous diseases and clinical disorders. In this paper, we present a new aptamer-based luminescent assay developed to detect L-selectin. The sensing system working principle is based on Forster Resonance Energy Transfer (FRET) from a donor terbium complex (TbC) to an acceptor cyanine dye (Cy5). In the present approach, the biotinylated aptamer is combined with Cy5-labelled streptavidin (Cy5-Strep) to yield an aptamer-based acceptor construct (Apta-Cy5-Strep), while L-selectin is conjugated using luminescent TbC. Upon aptamer binding to the TbC-labelled L-selectin (L-selectin-TbC), permanent donor-acceptor proximity is established which allows for radiationless energy transfer to occur. However, when unlabelled L-selectin is added, it competes with the L-selectin-TbC and the FRET signal decreases as the L-selectin concentration increases. FRET from the TbC to Cy5 was observed with time-gated time-resolved luminescence spectroscopy. A significant change in the corrected luminescence signal was observed in the dynamic range of 10 -500 ng/mL L-selectin, the concentration range relevant for accelerated cognitive decline of Alzheimer's disease, with a limit of detection (LOD) equal to 10 ng/mL. The aptasensor-based assay is homogeneous and can be realized within one hour. Therefore, this method has the potential to become an alternative to tedious heterogeneous analytical methods, e.g. based on enzyme-linked immunosorbent assay (ELISA). (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{CywinskiPietraszkiewiczMaciejczyketal.2016, author = {Cywinski, Piotr J. and Pietraszkiewicz, Marek and Maciejczyk, Michal and Gorski, Krzysztof and Hammann, Tommy and Liermann, Konstanze and Paulke, Bernd-Reiner and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Total protein concentration quantification using nanobeads with a new highly luminescent terbium(III) complex}, series = {RSC Advances}, volume = {6}, journal = {RSC Advances}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c6ra23207h}, pages = {115068 -- 115073}, year = {2016}, abstract = {Total protein concentration (TPC) is a key parameter in many biochemical experiments and its quantification is often necessary for isolation, separation, and analysis of proteins. A sensitive and rapid nanobead-based TPC quantification assay based on Forster Resonance Energy Transfer (FRET) has been developed. A new, highly luminescent Tb(III) complex has been synthesised and applied as donor in this FRET assay with an organic dye (Cy5) as acceptor. FRET-induced changes in luminescence have been investigated both at donor and acceptor emission wavelength using time-resolved luminescence spectroscopy with time-gated detection. In the assay, the Tb(III) complex and fine-tuned polyglycidyl methacrylate (PGMA) nanobeads ensure that an improvement in sensitivity and background reduction is achieved. Using 40 nm large PGMA nanobeads loaded with the Tb(III) complex, it is possible to determine TPC down to 50 ng mL(-1) in just 10 minutes. Through specific assay components the sensitivity has been improved when compared to existing nanobead-based assays and to currently known commercial methods. Additionally, the assay is relatively insensitive to the presence of contaminants, such as non-ionic detergents commonly found in biological samples. Due to no need for any centrifugal steps, this mix-and-measure bioassay can easily be implemented into routine TPC quantification protocols in biochemical laboratories.}, language = {en} } @misc{CywińskiNonoCharbonniereetal.2014, author = {Cywiński, Piotr J. and Nono, Katia Nchimi and Charbonni{\`e}re, Lo{\"i}c J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95390}, pages = {6060 -- 6067}, year = {2014}, abstract = {A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved F{\"o}rster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surface-functionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with F{\"o}rster theory, F{\"o}rster-radii (R0) were found to be around 60 {\AA} for organic dyes and around 105 {\AA} for QDs. The FRET efficiency (η) reached 80\% and 25\% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 {\AA} for organic dye acceptors, while for acceptor QDs between 120 {\AA} and 145 {\AA}. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.}, language = {en} } @article{DoscheKumkeLoehmannsroebenetal.2004, author = {Dosche, Carsten and Kumke, Michael Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Ariese, Freek and Bader, Arjen N. and Gooijer, Cees and Miljanic, Ognjen S. and Iwamoto, M. and Vollhardt, K. Peter C. and Puchta, Ralph and Hommes, N. J. R. V.}, title = {Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene}, issn = {1463-9076}, year = {2004}, abstract = {Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [ 4] phenylene (D-3h [4]phenylene) were studied using laser-excited Shpol'skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm(-1) and 1176 cm(-1), suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4] phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4] phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm(-1) probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state}, language = {en} } @misc{DoscheLoehmannsroebenBieseretal.2002, author = {Dosche, Carsten and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Bieser, A. and Dosa, P. I. and Han, S. and Iwamoto, M. and Schleifenbaum, A. and Vollhardt, K. Peter C.}, title = {Photophysical properties of [N]phenylenes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-11936}, year = {2002}, abstract = {In the present study, photophysical properties of [N]phenylenes were studied by means of stationary and time-resolved absorption and fluorescence spectroscopy (in THF at room temperature). For biphenylene (1) and linear [3]phenylene (2a), internal conversion (IC) with quantum yields ΦIC > 0.99 is by far the dominant mechanism of S1 state deactivation. Angular [3]phenylene (3a), the zig-zag [4]- and [5]phenylenes (3b), (3c), and the triangular [4]phenylene (4) show fluorescence emission with fluorescence quantum yieds and lifetimes between ΦF = 0.07 for (3a) and 0.21 for (3c) and τF = 20 ns for (3a) and 81 ns for (4). Also, compounds (3) and (4) exhibit triplet formation upon photoexcitation with quantum yields as high as ΦISC = 0.45 for (3c). The strong differences in the fluorescence properties and in the triplet fromation efficiencies between (1) and (2a) on one hand and (3) and (4) on the other are related to the remarkable variation of the internal conversion (IC) rate constants kIC. A tentative classification of (1) and (2a) as "fast IC compounds", with kIC > 109 s-1, and of (3) and (4) as "slow IC compounds", with kIC ≈ 107 s-1, is suggested. This classification cannot simply be related to H{\"u}ckel's rule-type concepts of aromaticity, because the group of "fast IC compounds" consists of "antiaromatic" (1) and "aromatic" (2a), and the group of "slow IC compounds" consists of "antiaromatic" (3b), (4) and "aromatic" (3a), (3c). The IC in the [N]phenylenes is discussed within the framework of the so-called energy gap law established for non-radiative processes in benzenoid hydrocarbons.}, language = {en} } @article{DoscheLoehmannsroebenBieseretal.2002, author = {Dosche, Carsten and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Bieser, A. and Dosa, P. I. and Han, S. and Iwamoto, M. and Schleifenbaum, A. and Vollhardt, K. Peter C.}, title = {Photophysical properties of [N]phenylenes}, year = {2002}, language = {en} } @misc{DoscheMicklerLoehmannsroebenetal.2007, author = {Dosche, Carsten and Mickler, Wulfhard and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Agenet, Nicolas and Vollhardt, K. Peter C.}, title = {Photoinduced electron transfer in [N]phenylenes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12463}, year = {2007}, abstract = {First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants kq and the free energy change of the electron transfer (ΔG0CS ) could be described by the Rehm-Weller equation. From the experimental results, a reorganization energy λ of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic ΔG0CS can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state.}, language = {en} } @article{DoscheMicklerLoehmannsroebenetal.2007, author = {Dosche, Carsten and Mickler, Wulfhard and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Agenet, Nicolas and Vollhardt, K. Peter C.}, title = {Photoinduced electron transfer in [N]phenylenes}, issn = {1010-6030}, doi = {10.1016/j.jphotochem.2006.12.038}, year = {2007}, abstract = {First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants k(q) and the free energy change of the electron transfer (Delta G(CS)(0)) could be described by the Rehm- Weller equation. From the experimental results, a reorganization energy lambda of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic charge separation process can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state.}, language = {en} } @misc{EichSchmaelzlinLoehmannsroeben2013, author = {Eich, Susanne and Schm{\"a}lzlin, Elmar and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Distributed fiber optical sensing of oxygen with optical time domain reflectometry}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1085}, issn = {1866-8372}, doi = {10.25932/publishup-47665}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-476659}, pages = {16}, year = {2013}, abstract = {In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.}, language = {en} }