TY - JOUR A1 - Löhmannsröben, Hans-Gerd A1 - Lau, Steffen T1 - Isotope selectivity in environmental monitoring : NIR diode laser spectroscopy for isotope-selective sensing of soil-respired carbon dioxide Y1 - 2005 ER - TY - JOUR A1 - Horner, G. A1 - Lau, Steffen A1 - Kantor, Z. A1 - Löhmannsröben, Hans-Gerd T1 - Isotope selective analysis of CO2 with tunable diode laser (TDL) spectroscopy in the NIR N2 - The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (3001)(III) <-- (000) band of (CO2)-C-12 around 1.6 mum, the dominating isotope species (CO2)-C-12, (CO2)-C-13, and (COO)-C-12-O-18-O-16 were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision-typically +/-1% and +/-6% for 3% and 0.7% of CO2, respectively-renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate (CO2)-C-12 line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements Y1 - 2004 SN - 0003-2654 ER - TY - GEN A1 - Lau, Steffen A1 - Salffner, Katharina A1 - Löhmannsröben, Hans-Gerd T1 - Isotopic resolution of carbon monoxide and carbon dioxide by NIR diode laser spectroscopy N2 - Near-infrared (NIR) absorption spectroscopy with tunable diode lasers allows the simultaneous detection of the three most important isotopologues of carbon dioxide (¹²CO₂, ¹³CO₂, ¹²C¹⁸O¹⁶O) and carbon monoxide (¹²CO, ¹³CO, ¹²C¹⁸O). The flexible and compact fiber-optic tunable diode laser absorption spectrometer (TDLAS) allows selective measurements of CO₂ and CO with high isotopic resolution without sample preparation since there is no interference with water vapour. For each species, linear calibration plots with a dynamic range of four orders of magnitude and detection limits (LOD) in the range of a few ppm were obtained utilizing wavelength modulation spectroscopy (WMS) with balanced detection in a Herriott-type multipass cell. The high performance of the apparatus is illustrated by fill-evacuation-refill cycles. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 017 KW - Isotop KW - Kohlenmonoxid KW - Kohlendioxid KW - Diodenlaserspektroskopie KW - isotope KW - carbon monoxide KW - carbon dioxide KW - diode laser spectroscopy Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10135 ER - TY - GEN A1 - Hörner, Gerald A1 - Lau, Steffen A1 - Löhmannsröben, Hans-Gerd T1 - NIR-diode laser spectroscopy for isotope-selective sensing of soil-respired carbon dioxide N2 - The performance of a home-built tunable diode laser (TDL) spectrometer has been optimized regarding multi-line detection of carbon dioxide in natural gases. In the regime of the (30⁰1)_III ← (000) band of ¹²CO₂ around 1.6 μm, the dominating isotope species ¹²CO₂, ¹³CO₂, and ¹²C¹⁸O¹⁶O were detected simultaneously. In contrast to most established techniques, selective measurements are performed without any sample preparation. This is possible since the CO₂ detection is free of interference from water, ubiquitous in natural gases. Detection limits in the range of a few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. Linear calibration plots cover a dynamic range of four orders of magnitude, allowing for quantitative CO₂ detection in various samples, like soil and breath gas. High isotopic resolution enables the excellent selectivity, sensitivity, and stability of the chosen analytical concept. The obtained isotopic resolution of typically ± 1.0 ‰ and ± 1.5 ‰ (for 3 vol. % and 0.7 vol. % of CO₂, respectively) offers a promising analytical tool for isotope-ratio determination of carbon dioxide in soil gas. Preliminary experiments on soil respiration for the first time combine the on-line quantification of the overall carbon dioxide content with an optode sensor and isotopic determination (TDL system) of natural gas species. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 021 KW - Kohlendioxid KW - Isotopenverhältnis KW - Bodengas KW - Diodenlaserspektroskopie KW - tunable diode laser (TDL) KW - carbon dioxide KW - isotope ratios KW - soil gas Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10148 ER - TY - GEN A1 - Hörner, Gerald A1 - Lau, Steffen A1 - Kantor, Zoltan A1 - Löhmannsröben, Hans-Gerd T1 - Isotope selective analysis of CO2 with tunable diode laser (TDL) spectroscopy in the NIR N2 - The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (30⁰1)_III / (000) band of ¹²CO₂ around 1.6 μm, the dominating isotope species ¹²CO₂, ¹³CO₂, and ¹²C¹⁸O¹⁶O were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision —typically ±1‰ and ±6‰ for 3% and 0.7% of CO₂, respectively— renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate ¹²CO₂ line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 020 KW - Isotopenverhältnis KW - Kohlendioxid KW - Diodenlaserspektroskopie KW - Isotope ratio KW - carbon monoxide KW - diode laser spectroscopy Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10167 ER - TY - GEN A1 - Engelbrecht, Rainer A1 - Lau, Steffen A1 - Salffner, Katharina A1 - Löhmannsröben, Hans-Gerd T1 - Fasergekoppelte NIR-Diodenlaser-Spektrometer zur simultanen und isotopen-aufgelösten Messung von CO und CO2 : Anwendungen in Plasma-Diagnostik und Bodengasanalyse N2 - Die Anwendung zweier ähnlicher fasergekoppelte Diodenlaser-Spektrometer-Systeme werden vorgestellt. Basis sind handelsübliche DFB-Laserdioden der optischen Kommunikationstechnik. Der faseroptische Aufbau, das Detektionsverfahren (2f Wellenlängenmodulations-Spektroskopie mit Balanced Receiver), Rauschverhalten und Detektionslimit werden diskutiert. Zur in-situ Plasma-Diagnostik von CO- und CO2-Konzentrationen in industriellen CO2-Lasern der Materialbearbeitung wurde eine Wellenlänge von 1582 nm verwendet. Bei einem Gasdruck von 100 hPa und einer Absorptionsweglänge von 14,9 cm wurden mit einer Laserdiode simultan CO- und CO2-Konzentrationen von 0% bis 11% im Gasgefäß bei laufender Hochfrequenzgasentladung des CO2-Lasers zeitaufgelöst gemessen. Vorgestellt und diskutiert werden Aufbau und Eigenschaften des Spektrometers sowie die Ergebnisse der dynamischen Gasanalysen, die zu einer Verbesserung der Katalysator-Technik im CO2-Laser beigetragen haben.Mit isotopenaufgelöster CO- und CO2-Spektroskopie können biologische Gasaustauschprozesse, z.B. in Gasen aus dem Erdboden untersucht werden. Hierzu wurde ein fasergekoppeltes feldtaugliches Diodenlaser-Spektrometer bei Wellenlängen um 1605 nm zur Messungder Isotopologe 12C16O, 13C16O, 12C18O und 12C16O2, 13C16O2, 12C18O16O aufgebaut. Die Messung erfolgt extraktiv in Langwegzellen mit unterschiedlichen Absorptionsweglängen von 100.9 m und 29.9 m. Es werden Kalibrationsmessungen zur Linearität und zur Präzision der Bestimmung der Isotopenverhältnisse sowie Wiederholungsmessungen zur Stabilität vorgestellt. Nachweisgrenzen von wenigen ppm konnten für die CO- und CO2-Isotopologen erhalten werden. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 13 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12348 ER - TY - JOUR A1 - Schwarze, Martin A1 - Schellhammer, Karl Sebastian A1 - Ortstein, Katrin A1 - Benduhn, Johannes A1 - Gaul, Christopher A1 - Hinderhofer, Alexander A1 - Toro, Lorena Perdigon A1 - Scholz, Reinhard A1 - Kublitski, Jonas A1 - Roland, Steffen A1 - Lau, Matthias A1 - Poelking, Carl A1 - Andrienko, Denis A1 - Cuniberti, Gianaurelio A1 - Schreiber, Frank A1 - Neher, Dieter A1 - Vandewal, Koen A1 - Ortmann, Frank A1 - Leo, Karl T1 - Impact of molecular quadrupole moments on the energy levels at organic heterojunctions JF - Nature Communications N2 - The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the p-p-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor-acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers. Y1 - 2019 U6 - https://doi.org/10.1038/s41467-019-10435-2 SN - 2041-1723 VL - 10 PB - Nature Publ. Group CY - London ER - TY - THES A1 - Lau, Steffen T1 - Djodenlaser-Absorptionsspektroskopie (DLAS) zur isotopenselektiven Gasanalye von Kohlenmonoxid, Kohlendioxide und Methan Y1 - 2009 CY - Potsdam ER - TY - JOUR A1 - Lau, Skadi A1 - Maier, Anna A1 - Braune, Steffen A1 - Gossen, Manfred A1 - Lendlein, Andreas T1 - Effect of endothelial culture medium composition on platelet responses to polymeric biomaterials JF - International journal of molecular sciences N2 - Near-physiological in vitro thrombogenicity test systems for the evaluation of blood-contacting endothelialized biomaterials requires co-cultivation with platelets (PLT). However, the addition of PLT has led to unphysiological endothelial cell (EC) detachment in such in vitro systems. A possible cause for this phenomenon may be PLT activation triggered by the applied endothelial cell medium, which typically consists of basal medium (BM) and nine different supplements. To verify this hypothesis, the influence of BM and its supplements was systematically analyzed regarding PLT responses. For this, human platelet rich plasma (PRP) was mixed with BM, BM containing one of nine supplements, or with BM containing all supplements together. PLT adherence analysis was carried out in six-channel slides with plasma-treated cyclic olefin copolymer (COC) and poly(tetrafluoro ethylene) (PTFE, as a positive control) substrates as part of the six-channel slides in the absence of EC and under static conditions. PLT activation and aggregation were analyzed using light transmission aggregometry and flow cytometry (CD62P). Medium supplements had no effect on PLT activation and aggregation. In contrast, supplements differentially affected PLT adherence, however, in a polymer- and donor-dependent manner. Thus, the use of standard endothelial growth medium (BM + all supplements) maintains functionality of PLT under EC compatible conditions without masking the differences of PLT adherence on different polymeric substrates. These findings are important prerequisites for the establishment of a near-physiological in vitro thrombogenicity test system assessing polymer-based cardiovascular implant materials in contact with EC and PLT. KW - cyclic olefin copolymer KW - poly(tetrafluoroethylene) KW - endothelial cells KW - platelets KW - in vitro thrombogenicity testing Y1 - 2021 U6 - https://doi.org/10.3390/ijms22137006 SN - 1422-0067 SN - 1661-6596 VL - 22 IS - 13 PB - Molecular Diversity Preservation International CY - Basel ER -