@misc{ErlerRiebeBeitzetal.2019, author = {Erler, Alexander and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Gebbers, Robin}, title = {Soil Nutrient Detection for Precision Agriculture Using Handheld Laser-Induced Breakdown Spectroscopy (LIBS) and Multivariate Regression Methods (PLSR, Lasso and GPR)}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {815}, issn = {1866-8372}, doi = {10.25932/publishup-44418}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-444183}, pages = {19}, year = {2019}, abstract = {Precision agriculture (PA) strongly relies on spatially differentiated sensor information. Handheld instruments based on laser-induced breakdown spectroscopy (LIBS) are a promising sensor technique for the in-field determination of various soil parameters. In this work, the potential of handheld LIBS for the determination of the total mass fractions of the major nutrients Ca, K, Mg, N, P and the trace nutrients Mn, Fe was evaluated. Additionally, other soil parameters, such as humus content, soil pH value and plant available P content, were determined. Since the quantification of nutrients by LIBS depends strongly on the soil matrix, various multivariate regression methods were used for calibration and prediction. These include partial least squares regression (PLSR), least absolute shrinkage and selection operator regression (Lasso), and Gaussian process regression (GPR). The best prediction results were obtained for Ca, K, Mg and Fe. The coefficients of determination obtained for other nutrients were smaller. This is due to much lower concentrations in the case of Mn, while the low number of lines and very weak intensities are the reason for the deviation of N and P. Soil parameters that are not directly related to one element, such as pH, could also be predicted. Lasso and GPR yielded slightly better results than PLSR. Additionally, several methods of data pretreatment were investigated.}, 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} } @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} } @misc{ZuehlkeMeilingRoderetal.2021, author = {Z{\"u}hlke, Martin and Meiling, Till Thomas and Roder, Phillip and Riebe, Daniel and Beitz, Toralf and Bald, Ilko and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Janßen, Traute and Erhard, Marcel and Repp, Alexander}, title = {Photodynamic Inactivation of E. coli Bacteria via Carbon Nanodots}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, publisher = {Universit{\"a}t Potsdam}, address = {Potsdam}, issn = {1866-8372}, doi = {10.25932/publishup-53842}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-538425}, pages = {23742 -- 23749}, year = {2021}, abstract = {The increasing development of antibiotic resistance in bacteria has been a major problem for years, both in human and veterinary medicine. Prophylactic measures, such as the use of vaccines, are of great importance in reducing the use of antibiotics in livestock. These vaccines are mainly produced based on formaldehyde inactivation. However, the latter damages the recognition elements of the bacterial proteins and thus could reduce the immune response in the animal. An alternative inactivation method developed in this work is based on gentle photodynamic inactivation using carbon nanodots (CNDs) at excitation wavelengths λex > 290 nm. The photodynamic inactivation was characterized on the nonvirulent laboratory strain Escherichia coli K12 using synthesized CNDs. For a gentle inactivation, the CNDs must be absorbed into the cytoplasm of the E. coli cell. Thus, the inactivation through photoinduced formation of reactive oxygen species only takes place inside the bacterium, which means that the outer membrane is neither damaged nor altered. The loading of the CNDs into E. coli was examined using fluorescence microscopy. Complete loading of the bacterial cells could be achieved in less than 10 min. These studies revealed a reversible uptake process allowing the recovery and reuse of the CNDs after irradiation and before the administration of the vaccine. The success of photodynamic inactivation was verified by viability assays on agar. In a homemade flow photoreactor, the fastest successful irradiation of the bacteria could be carried out in 34 s. Therefore, the photodynamic inactivation based on CNDs is very effective. The membrane integrity of the bacteria after irradiation was verified by slide agglutination and atomic force microscopy. The method developed for the laboratory strain E. coli K12 could then be successfully applied to the important avian pathogens Bordetella avium and Ornithobacterium rhinotracheale to aid the development of novel vaccines.}, language = {en} } @misc{SchultzeLemkeLoehmannsroeben2004, author = {Schultze, Rainer H. and Lemke, Matthias and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Laser-induced fluorescence (LIF) spectroscopy for the in situ analysis of petroleum product-contaminated soils}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12271}, year = {2004}, abstract = {Contents: Introduction Experimental Techniques: The LIF demonstrator unit - The LIF demonstrator unit - The mobile LIF spectrometer OPTIMOS - Investigated petroleum products and soil samples Results and Discussion: Photophysical properties of the petroleum products LIF spectroscopic investigations of oil-spiked samples LIF spectroscopic investigations of real-world soils Conclusions}, language = {en} } @misc{EngelbrechtLauSalffneretal.2006, author = {Engelbrecht, Rainer and Lau, Steffen and Salffner, Katharina and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Fasergekoppelte NIR-Diodenlaser-Spektrometer zur simultanen und isotopen-aufgel{\"o}sten Messung von CO und CO2 : Anwendungen in Plasma-Diagnostik und Bodengasanalyse}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12348}, year = {2006}, abstract = {Die Anwendung zweier {\"a}hnlicher fasergekoppelte Diodenlaser-Spektrometer-Systeme werden vorgestellt. Basis sind handels{\"u}bliche DFB-Laserdioden der optischen Kommunikationstechnik. Der faseroptische Aufbau, das Detektionsverfahren (2f Wellenl{\"a}ngenmodulations-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 Wellenl{\"a}nge von 1582 nm verwendet. Bei einem Gasdruck von 100 hPa und einer Absorptionswegl{\"a}nge von 14,9 cm wurden mit einer Laserdiode simultan CO- und CO2-Konzentrationen von 0\% bis 11\% im Gasgef{\"a}ß bei laufender Hochfrequenzgasentladung des CO2-Lasers zeitaufgel{\"o}st 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 isotopenaufgel{\"o}ster CO- und CO2-Spektroskopie k{\"o}nnen biologische Gasaustauschprozesse, z.B. in Gasen aus dem Erdboden untersucht werden. Hierzu wurde ein fasergekoppeltes feldtaugliches Diodenlaser-Spektrometer bei Wellenl{\"a}ngen um 1605 nm zur Messungder Isotopologe 12C16O, 13C16O, 12C18O und 12C16O2, 13C16O2, 12C18O16O aufgebaut. Die Messung erfolgt extraktiv in Langwegzellen mit unterschiedlichen Absorptionswegl{\"a}ngen von 100.9 m und 29.9 m. Es werden Kalibrationsmessungen zur Linearit{\"a}t und zur Pr{\"a}zision der Bestimmung der Isotopenverh{\"a}ltnisse sowie Wiederholungsmessungen zur Stabilit{\"a}t vorgestellt. Nachweisgrenzen von wenigen ppm konnten f{\"u}r die CO- und CO2-Isotopologen erhalten werden.}, language = {de} } @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} } @misc{RethfeldtBrinkmannRiebeetal.2021, author = {Rethfeldt, Nina and Brinkmann, Pia and Riebe, Daniel and Beitz, Toralf and K{\"o}llner, Nicole and Altenberger, Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Detection of Rare Earth Elements in Minerals and Soils by Laser-Induced Breakdown Spectroscopy (LIBS) Using Interval PLS}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1866-8372}, doi = {10.25932/publishup-55746}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-557469}, pages = {1 -- 17}, year = {2021}, abstract = {The numerous applications of rare earth elements (REE) has lead to a growing global demand and to the search for new REE deposits. One promising technique for exploration of these deposits is laser-induced breakdown spectroscopy (LIBS). Among a number of advantages of the technique is the possibility to perform on-site measurements without sample preparation. Since the exploration of a deposit is based on the analysis of various geological compartments of the surrounding area, REE-bearing rock and soil samples were analyzed in this work. The field samples are from three European REE deposits in Sweden and Norway. The focus is on the REE cerium, lanthanum, neodymium and yttrium. Two different approaches of data analysis were used for the evaluation. The first approach is univariate regression (UVR). While this approach was successful for the analysis of synthetic REE samples, the quantitative analysis of field samples from different sites was influenced by matrix effects. Principal component analysis (PCA) can be used to determine the origin of the samples from the three deposits. The second approach is based on multivariate regression methods, in particular interval PLS (iPLS) regression. In comparison to UVR, this method is better suited for the determination of REE contents in heterogeneous field samples. View Full-Text}, language = {en} } @misc{MorgnerLecointreCharbonniereetal.2014, author = {Morgner, Frank and Lecointre, Alexandre and Charbonni{\`e}re, Loic J. and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Detecting free hemoglobin in blood plasma and serum with luminescent terbium complexes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-99485}, pages = {6}, year = {2014}, abstract = {Hemolysis, the rupturing of red blood cells, can result from numerous medical conditions (in vivo) or occur after collecting blood specimen or extracting plasma and serum out of whole blood (in vitro). In clinical laboratory practice, hemolysis can be a serious problem due to its potential to bias detection of various analytes or biomarkers. Here we present the first ''mix-and-measure'' method to assess the degree of hemolysis in biosamples using luminescence spectroscopy. Luminescent terbium complexes (LTC) were studied in the presence of free hemoglobin (Hb) as indicators for hemolysis in TRIS-buffer, and in fresh human plasma with absorption, excitation and emission measurements. Our findings indicate dynamic as well as resonance energy transfer (FRET) between the LTC and the porphyrin ligand of hemoglobin. This transfer leads to a decrease in luminescence intensity and decay time even at nanomolar hemoglobin concentrations either in buffer or plasma. Luminescent terbium complexes are very sensitive to free hemoglobin in buffer and blood plasma. Due to the instant change in luminescence properties of the LTC in presence of Hb it is possible to access the concentration of hemoglobin via spectroscopic methods without incubation time or further treatment of the sample thus enabling a rapid and sensitive detection of hemolysis in clinical diagnostics.}, language = {en} } @misc{McQuadeO'BrienDoerretal.2013, author = {McQuade, D. Tyler and O'Brien, Alexander G. and D{\"o}rr, Markus and Rajaratnam, Rajathees and Eisold, Ursula and Monnanda, Bopanna and Nobuta, Tomoya and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Meggers, Eric and Seeberger, Peter H.}, title = {Continuous synthesis of pyridocarbazoles and initial photophysical and bioprobe characterization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95214}, pages = {4067 -- 4070}, year = {2013}, abstract = {Pyridocarbazoles when ligated to transition metals yield high affinity kinase inhibitors. While batch photocyclizations enable the synthesis of these heterocycles, the non-oxidative Mallory reaction only provides modest yields and difficult to purify mixtures. We demonstrate here that a flow-based Mallory cyclization provides superior results and enables observation of a clear isobestic point. The flow method allowed us to rapidly synthesize ten pyridocarbazoles and for the first time to document their interesting photophysical attributes. Preliminary characterization reveals that these molecules might be a new class of fluorescent bioprobe.}, language = {en} }