Refine
Year of publication
Language
- English (105) (remove)
Keywords
- LIBS (10)
- Ion mobility spectrometry (9)
- ion mobility spectrometry (5)
- IR-MALDI (4)
- PCA (4)
- soil (4)
- Diodenlaserspektroskopie (3)
- Electrospray ionization (3)
- Fluorescence (3)
- Fluoreszenz-Resonanz-Energie-Transfer (3)
- HPLC (3)
- Immunoassay (3)
- Kohlendioxid (3)
- Laser (3)
- REMPI (3)
- precision agriculture (3)
- APCI (2)
- Bacteria (2)
- Base pairing (2)
- Energietransfer (2)
- FRET (2)
- Genetics (2)
- Imaging (2)
- Irradiation (2)
- Isotopenverhältnis (2)
- Lumineszenz (2)
- Mass spectrometry (2)
- OTDR (2)
- PLS regression (2)
- PLSR (2)
- Photodynamics (2)
- Quantenpunkt (2)
- UVR (2)
- atmospheric effects (2)
- carbon dioxide (2)
- carbon monoxide (2)
- copper-bearing minerals (2)
- diode laser spectroscopy (2)
- elemental composition (2)
- gas chromatography (2)
- gaussian processes (2)
- iPLS regression (2)
- instrumentation: miscellaneous (2)
- laser-induced breakdown spectroscopy (2)
- lasso (2)
- mass spectrometry (2)
- minerals (2)
- molecular oxygen (2)
- nutrients (2)
- optical sensing (2)
- proximal soil sensing (2)
- quantum dots (2)
- rare earth elements (2)
- reaction monitoring (2)
- soil nutrients (2)
- triangular-[4] phenylene (2)
- 2P cross section (1)
- 315 nm (1)
- 473 nm (1)
- 946 nm (1)
- Acoustic levitation (1)
- Ambient pressure laser ionization (1)
- Amino acids (1)
- Aptamer (1)
- Biophotonik (1)
- Bodengas (1)
- Collision cross-section (1)
- Cyclic GMP (1)
- Diode laser (1)
- ESI (1)
- Electrospray Ionization (1)
- Energy Transfer (1)
- Epithelial ion transport (1)
- Europium (1)
- Fabry-Perot etalon (1)
- Fluorescence lifetime (1)
- Fluorescence spectroscopy (1)
- Fluorescent nanoconjugate (1)
- Fluoroassay (1)
- Förster Resonanz Energie Transfer (1)
- Förster-Resonanz-Energie-Transfer (1)
- Gas chromatography (1)
- Gaseous Ions (1)
- High-resolution spectrometer (1)
- Hydrogen sulfide (1)
- IMS (1)
- Ion optics (1)
- Ionization (1)
- Ionmobility spectrometry (1)
- Isotop (1)
- Isotope detection (1)
- Isotope ratio (1)
- Kohlenmonoxid (1)
- L-selectin (1)
- Lanthanide (1)
- Lanthanoide (1)
- Laser ablation (1)
- Laser ionization (1)
- Laser-induced breakdown spectroscopy (1)
- Lucigenin (1)
- Luminescence (1)
- Luminescence spectroscopy (1)
- Mars (1)
- Methane (1)
- Methanogens (1)
- Molecular dynamics (1)
- NIR spectroscopy (1)
- Nanopartikel (1)
- Nanosensor (1)
- Naphthyridine receptor (1)
- Naphthyridines (1)
- Near infrared (1)
- Neodym-YAG-Laser (1)
- Neuroleptics (1)
- Nucleotide nanosensor (1)
- OGB-1 (1)
- OH suppression (1)
- Olefin isomerization (1)
- Optode (1)
- PAH (1)
- Peptides (1)
- Pesticides (1)
- Plume (1)
- Proton transfer reaction (1)
- Pulse duration (1)
- Quantum Dot (1)
- Quantum dots (1)
- Raman spectroscopy (1)
- Rhodamine 6G (1)
- Sauerstoff (1)
- Serum (1)
- Shadowgraphy (1)
- Sub-zero temperature (Celsius) (1)
- Subambient pressure (1)
- TCSPC (1)
- Two-dimensional separations (1)
- Two-photon excitation (1)
- Wavelength modulation gas spectroscopy (1)
- Wavelength modulation spectroscopy (laser spectroscopy) (1)
- X-ray (1)
- [N]phenylene dyads (1)
- [N]phenylenes (1)
- acceptors (1)
- alkyl nitrates (1)
- amphiphilic polymer assembly (1)
- astrophotonics (1)
- beer (1)
- bioanalysis (1)
- biomass (1)
- biophotonics (1)
- biosensor (1)
- biosensors (1)
- cGMP (1)
- complexes (1)
- continuous-flow (1)
- contrast agents (1)
- dual-frequency phase-modulation (1)
- dub-ambient (1)
- efficient (1)
- electrospray ionization (1)
- endogenous sensor proteins (1)
- europium (1)
- europium complex (1)
- explosives (1)
- feature selection (1)
- fibre Bragg gratings (1)
- fluorescence immunoassay (1)
- fluorescence quenching (1)
- fluoroimmunoassay (1)
- foam analysis (1)
- fungus (1)
- gepulster DPSS Laser (1)
- high field mobility (1)
- hydraulic oils (1)
- immunoassay (1)
- in-situ (1)
- infrared: diffuse background (1)
- infrared: general (1)
- isotope (1)
- isotope ratios (1)
- labels (1)
- lanthanide luminescence (1)
- laser induced (1)
- light (1)
- lubricants (1)
- mass (1)
- microchip (1)
- microsensors (1)
- mold (1)
- mold fungi (1)
- multivariate methods (1)
- nanobioconjugate (1)
- nanoparticles (1)
- nanosensors (1)
- neuroleptics (1)
- optical oil sensor (1)
- optode (1)
- oxygen (1)
- oxygen sensor (1)
- peptides (1)
- pesticides (1)
- phenanthrenes (1)
- phosphorescence quenching (1)
- photocatalysis (1)
- photochemical synthesis (1)
- photochemistry (1)
- photoinduced electron transfer (1)
- photoionization (1)
- photon density wave spectroscopy (1)
- plant science (1)
- pressure (1)
- process analytical technology (1)
- protein-kinase inhibitors (1)
- pulsed DPSS laser (1)
- reaction mechanisms (1)
- resonance energy-transfer (1)
- soft X-radiation (1)
- soft X-ray (1)
- soil gas (1)
- spectrometry (1)
- spectroscopy (1)
- spray imaging (1)
- surfactants (1)
- sättigbarer Absorber (1)
- time-resolved fluorescence (1)
- tunable diode laser (TDL) (1)
- volatile organic compounds (1)
Institute
The near-infrared is an important part of the spectrum in astronomy, especially in cosmology because the light from objects in the early universe is redshifted to these wavelengths. However, deep near-infrared observations are extremely difficult to make from ground-based telescopes due to the bright background from the atmosphere. Nearly all of this background comes from the bright and narrow emission lines of atmospheric hydroxyl (OH) molecules. The atmospheric background cannot be easily removed from data because the brightness fluctuates unpredictably on short timescales. The sensitivity of ground-based optical astronomy far exceeds that of near-infrared astronomy because of this long-standing problem. GNOSIS is a prototype astrophotonic instrument that utilizes "OH suppression fibers" consisting of fiber Bragg gratings and photonic lanterns to suppress the 103 brightest atmospheric emission doublets between 1.47 and 1.7 mu m. GNOSIS was commissioned at the 3.9 m Anglo-Australian Telescope with the IRIS2 spectrograph to demonstrate the potential of OH suppression fibers, but may be potentially used with any telescope and spectrograph combination. Unlike previous atmospheric suppression techniques GNOSIS suppresses the lines before dispersion and in a manner that depends purely on wavelength. We present the instrument design and report the results of laboratory and on-sky tests from commissioning. While these tests demonstrated high throughput (approximate to 60%) and excellent suppression of the skylines by the OH suppression fibers, surprisingly GNOSIS produced no significant reduction in the interline background and the sensitivity of GNOSIS+IRIS2 is about the same as IRIS2. It is unclear whether the lack of reduction in the interline background is due to physical sources or systematic errors as the observations are detector noise dominated. OH suppression fibers could potentially impact ground-based astronomy at the level of adaptive optics or greater. However, until a clear reduction in the interline background and the corresponding increasing in sensitivity is demonstrated optimized OH suppression fibers paired with a fiber-fed spectrograph will at least provide a real benefit at low resolving powers.
Continuous synthesis of pyridocarbazoles and initial photophysical and bioprobe characterization
(2013)
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.
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 Förster 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 Förster theory, Förster-radii (R0) were found to be around 60 Å for organic dyes and around 105 Å 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 Å for organic dye acceptors, while for acceptor QDs between 120 Å and 145 Å. 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.
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
Absorption and fluorescence properties of 4 hydraulic oils ( 3 biological and 1 petroleum-based) were investigated. In-situ LIF (laser-induced fluorescence) analysis of the oils on a brown sandy loam soil was performed. With calibration, quantitative detection was achieved. Estimated limits of detection were below ca. 500 mg/kg for the petroleum-based oil and ca. 2000 mg/kg for one biological oil. A semi-quantitative classification scheme is proposed for monitoring of the biological oils. This approach was applied to investigate the migration of a biological oil in soil- containing compartments, namely a soil column and a soil bed
On the basis of absorption measurements in the near-infrared (NIR) spectral range, a new method for the quantification of the ethanol content of beer is presented. Instead of the multivariate calibration models most commonly employed in NIR spectroscopic works, we use interpretive difference spectroscopy: Two wavelengths are selected according to the assignment of the absorption bands of the main substances of content of beer in the NIR region, and the difference between the absorbances at these wavelengths is used for ethanol quantification. Absorption spectra of the dominating beer ingredients are discussed and the calibration procedure with ethanol/water mixtures is shown. Robustness against the carbohydrate content of beer samples was demonstrated by analyzing solutions of ethanol and maltose in water. Validation of the method was performed with various beer samples with an ethanol concentration range between 0.5 and 7.7 vol %. The pertinent advantage of the procedure developed in this work is the indication that the results are independent from seasonal variations of the ingredients, which is of high interest for products with natural ingredients such as beer
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
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
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 Forster 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 Forster-radius, estimated from the absorption and emission bands, was ca. 77Å. 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.
The salivary glands of the blowfly were injected with luminescent oxygen-sensitive microbeads. The changes in oxygen content within individual gland tubules during hormone-induced secretory activity were quantified. The measurements are based on an upgraded phase-modulation technique, where the phase shift of the sensor phosphorescence is determined independently from concentration and background signals. We show that the combination of a lock-in amplifier with a fluorescence microscope results in a convenient setup to measure oxygen concentrations within living animal tissues at the cellular level.
Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.
Absorption and fluorescence properties of 4 hydraulic oils (3 biological and 1 petroleum-based) were investigated. In-situ LIF (laser-induced fluorescence) analysis of the oils on a brown sandy loam soil was performed. With calibration, quantitative detection was achieved. Estimated limits of detection were below ca. 500 mg/kg for the petroleum-based oil and ca. 2000 mg/kg for one biological oil. A semi-quantitative classification scheme is proposed for monitoring of the biological oils. This approach was applied to investigate the migration of a biological oil in soil-containing compartments, namely a soil column and a soil bed.
The drift time spectra of polycyclic aromatic hydrocarbons (PAH), alkylbenzenes and alkylphenylethers were recorded with a laser-based ion mobility (IM) spectrometer. The ion mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omegacalc) on the basis of the exact hard sphere scattering model (EHSSM) and their comparison with the experimentally determined diffusion cross sections (Omegaexp). These Omegaexp/Omegacalc-correlations are presented for molecules with a rigid structure like PAH and prove the reliability of the theoretical model and experimental method. The increase of the selectivity of IM spectrometry is demonstrated using resonance enhanced multiphoton ionisation (REMPI) at atmospheric pressure, realized by tuneable lasers. The REMPI spectra of nine alkylbenzenes and alkylphenylethers are investigated. On the basis of these spectra, the complete qualitative distinction of eight compounds in a mixture is shown. These experiments are extended to alkylbenzene isomer mixtures.
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 Hückel’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.
Two examples of our biophotonic research utilizing nanoparticles are presented, namely laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring. Results of the work include significantly enhanced sensitivity of a homogeneous fluorescence immunoassay and markedly improved spatial resolution of oxygen gradients in root nodules of a legume species.
Near-infrared (NIR) absorption spectroscopy with tunable diode lasers allows the simultaneous detection of the three most important isotopologues of carbon dioxide (<SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O) and carbon monoxide (<SUP>12</SUP>CO, <SUP>13</SUP>CO, <SUP>12</SUP>C<SUP>18</SUP>O). The flexible and compact fiber-optic tunable diode laser absorption spectrometer (TDLAS) allows selective measurements of CO<SUB>2</SUB> 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.