TY - JOUR A1 - Zhang, Zhiyang A1 - Gernert, U. A1 - Gerhardt, R. F. A1 - Höhn, E.-M. A1 - Belder, D. A1 - Kneipp, Janina T1 - Catalysis by Metal Nanoparticles in a Plug-In Optofluidic Platform: Redox Reactions of p-Nitrobenzenethiol and p-Aminothiophenol JF - ACS Catalysis N2 - The spectroscopic characterization by surface-enhanced Raman scattering (SERS) has shown great potential in studies of heterogeneous catalysis. We describe a plug-in multifunctional optofluidic platform that can be tailored to serve both as a variable catalyst material and for sensitive optical characterization of the respective reactions using SERS in microfluidic systems. The platform enables the characterization of reactions under a controlled gas atmosphere and does not present with limitations due to nanoparticle adsorption or memory effects. Spectra of the gold-catalyzed reduction of p-nitrothiophenol by sodium borohydride using the plug-in probe provide evidence that the borohydride is the direct source of hydrogen on the gold surface, and that a radical anion is formed as an intermediate. The in situ monitoring of the photoinduced dimerization of p-aminothiophenol indicates that the activation of oxygen is essential for the plasmon-catalyzed oxidation on gold nanoparticles and strongly supports the central role of metal oxide species. KW - Gaseous reactants KW - Heterogeneous catalysis KW - Microfluidics KW - Optofluidics KW - Radicals KW - Reusable KW - Surface-enhanced Raman scattering (SERS) PY - 2018 UR - https://pubs.acs.org/doi/10.1021/acscatal.8b00101 DO - https://doi.org/10.1021/acscatal.8b00101 VL - 8 IS - 3 SP - 2443 EP - 2449 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-44628 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeise, I. A1 - Heiner, Z. A1 - Holz, S. A1 - Joester, Maike A1 - Buttner, C. A1 - Kneipp, Janina T1 - Raman imaging of plant cell walls in sections of cucumis sativus JF - PLANTS-BASEL N2 - Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus, using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues. KW - Raman KW - Imaging KW - Pants PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474610 DO - https://doi.org/10.3390/plants7010007 SN - 2223-7747 VL - 7 IS - 1 SP - 7, 1 EP - 16 PB - MDPI, ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND AN - OPUS4-47461 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zavoiura, Oleksandr A1 - Resch-Genger, Ute A1 - Seitz, Oliver T1 - Quantum dot-PNA conjugates for target-catalyzed RNA detection JF - Bioconjugate Chemistry N2 - Detection of pathogenic nucleic acids remains one of the most reliable approaches for the diagnosis of a broad range of diseases. Current PCR-based methods require experienced personnel and cannot be easily used for point-of care diagnostics, making alternative strategies for the sensitive, reliable, and cost-efficient detection of pathogenic nucleic acids highly desirable. Here, we report an enzyme-free method for the fluorometric detection of RNA that relies on a target-induced fluorophore transfer onto a semiconductor quantum dot (QD), uses PNA probes as selective recognition elements and can be read out with simple and inexpensive equipment. For QD-PNA conjugates with optimized PNA content, limits of detection of dengue RNA in the range of 10 pM to 100 nM can be realized within 5 h in the presence of a high excess of noncomplementary RNA. KW - FRET KW - Fluorescence KW - DNA KW - Assay KW - Quantum dot KW - Nano KW - Particle KW - Synthesis KW - Ligation Assay PY - 2018 DO - https://doi.org/10.1021/acs.bioconjchem.8b00157 SN - 1043-1802 VL - 29 IS - 5 SP - 1690 EP - 1702 PB - ACS Publications AN - OPUS4-45120 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yuan, Huan A1 - Gornushkin, Igor B. A1 - Gojani, Ardian A1 - Wang, X. H. A1 - Rong, Ming Zhe T1 - Laser-induced plasma imaging for low-pressure detection JF - Optics Express N2 - A novel technique based on laser induced plasma imaging is proposed to measure residual pressure in sealed containers with transparent walls, e.g. high voltage vacuum interrupter in this paper. The images of plasma plumes induced on a copper target at pressure of ambient air between 10−2Pa and 105Pa were acquired at delay times of 200ns, 400ns, 600ns and 800ns. All the plasma images at specific pressures and delay times showed a good repeatability. It was found that ambient gas pressure significantly affects plasma shape, plasma integral intensities and expansion dynamics. A subsection characteristic method was proposed to extract pressure values from plasma images. The method employed three metrics for identification of high, intermediate and low pressures: the distance between the target and plume center, the integral intensity of the plume, and the lateral size of the plume, correspondingly. The accuracy of the method was estimated to be within 15% of nominal values in the entire pressure range between 10−2Pa and 105Pa. The pressure values can be easily extracted from plasma images in the whole pressure range, thus making laser induced plasma imaging a promising technique for gauge-free pressure detection. KW - Laser induced plasma KW - LIBS KW - Plasma modeling KW - Plasma diagnostics PY - 2018 DO - https://doi.org/10.1364/OE.26.015962 SN - 1094-4087 VL - 26 IS - 12 SP - 15962 EP - 15971 PB - Optical Society of America under the terms of the OSA Open Access Publishing Agreement AN - OPUS4-45219 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yuan, Huan A1 - Gojani, Ardian A1 - Gornushkin, Igor B. A1 - Wang, X. T1 - Investigation of laser-induced plasma at varying pressure and laser focusing JF - Spectrochimica Acta Part B N2 - Expansion dynamics of laser-induced plasma is studied for different focal positions of the ablation laser in the pressure range 10-2 - 105 Pa of the ambient air. The experimental results indicate that both the parameters significantly affect the plasma size, shape, intensity, reproducibility, and distance from the target surface. At pressures above 10 Pa, the plasma plume is confined by the ambient gas; the plumes are more compact and travel shorter distances from the target as compared to the analogous plume characteristics at pressures below 10 Pa. The pulse-to-pulse reproducibility of the integral emission intensity of the plasma is also different for different focal positions and pressures. It is found that the focal positions -1 cm and -2 cm below the target surface yield the most reproducible and intense emission signals as measured at the 600 ns delay time with the 100 ns gate. The information obtained can be of importance for pulsed laser deposition, laser welding, and analytical spectroscopy at reduced pressures. In general, a correct choice of the focal position and pressure of an ambient gas is very important for obtaining the strongest plasma emission, good reproducibility, and desired plasma plume shape. KW - Laser-induced plasma KW - Plasma expansion KW - Imaging PY - 2018 DO - https://doi.org/10.1016/j.sab.2018.10.005 SN - 0584-8547 VL - 150 SP - 33 EP - 37 PB - Elsevier AN - OPUS4-46207 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - Fischer, S. A1 - Grauel, Bettina A1 - Alivisatos, A. P. A1 - Resch-Genger, Ute T1 - Quantum Yields, Surface Quenching, and Passivation Efficiency for Ultrasmall Core/Shell Upconverting Nanoparticles N2 - We synthesized and characterized a set of ultrasmall hexagonal-phase NaGdF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles with core diameters of 3.7 ± 0.5 nm. In order to assess passivation effects and the influence of possible core−shell intermixing and to identify optimum particle structures for combined imaging in the visible and near-infrared (vis−NIR: 410−850 nm) and short-wave infrared (SWIR: 1520 nm), NaYF4 shells of varying thicknesses (monolayer to 10 nm) were introduced and the influence of this parameter on the upconversion and downshifting photoluminescence of these particles was studied at different excitation power densities. This included excitation power-dependent emission spectra, slope factors, quantum yields, and excited state decay kinetics. These measurements revealed enhancement factors of the upconversion quantum yield of >10 000 in the low power region and an excitation power density-independent quantum yield of the downshifted emission at 1520 nm between 0.1 and 14%. The optimized shell thickness for combined vis and SWIR imaging was identified as 5 nm. Moreover, lifetimes and quantum yields can be continuously tuned by shell thickness which can be exploited for lifetime multiplexing and encoding. The fact that we did not observe a saturation of the upconversion quantum yield or the excited state decay kinetics with increasing shell thickness is ascribed to a strong intermixing of the active core with the inert shell during the shelling procedure. This indicates the potential of spectroscopic tools to detect cation intermixing. KW - Nanoparticle KW - Upconversion KW - Quenching PY - 2018 DO - https://doi.org/10.1021/jacs.8b01458 IS - 140 SP - 4922 EP - 4928 PB - American Chemical Society AN - OPUS4-45378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Brandt, Guido A1 - Ehrke, Roman A1 - Nolze, Gert A1 - Schmid, Thomas A1 - Sasaki, S. A1 - Woydt, Mathias T1 - Wear behaviour of alpha-alumina in hot steam at high contact pressure JF - Wear N2 - The work examines the wear behaviour of α-aluminium oxide by combining thermodynamic modelling with advanced wear testing as well as analytical methods to get a better understanding of this structural ceramic material wear behavior and its possible use in high temperature steam environment. KW - Aluminium oxide KW - Temperature KW - Hot steam KW - Diaspore KW - Ceramic KW - Wear PY - 2018 DO - https://doi.org/10.1016/j.wear.2018.02.012 SN - 0043-1648 SN - 1873-2577 VL - 404-405 SP - 22 EP - 30 PB - Elsevier B.V. AN - OPUS4-44449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Westwood, S. A1 - Josephs, R. A1 - Choteau, T. A1 - Daireaux, A. A1 - Stoppacher, N. A1 - Wielgosz, R. A1 - Davies, S. A1 - do Rego, E. A1 - Wollinger, W. A1 - Garrido, B. A1 - Fernandes, J. A1 - Lima, J. A1 - Oliveira, R. A1 - de Sena, R. A1 - Windust, A. A1 - Huang, T. A1 - Dai, X. A1 - Quan, C. A1 - He, H. A1 - Zhang, W. A1 - Wei, C. A1 - Li, N. A1 - Gao, D. A1 - Liu, Z. A1 - Lo, M. A1 - Wong, W. A1 - Pfeifer, Dietmar A1 - Koch, Matthias A1 - Dorgerloh, Ute A1 - Rothe, Robert A1 - Philipp, Rosemarie A1 - Hanari, N. A1 - Rezali, M. A1 - Arzate, C. A1 - Berenice, M. A1 - Caballero, V. A1 - Osuna, M. A1 - Krylov, A. A1 - Kharitonov, S. A1 - Lopushanskaya, E. A1 - Liu, Q. A1 - Lin, T. A1 - Fernandes-Whaley, M. A1 - Quinn, L. A1 - Nhlapo, N. A1 - Prevoo-Franzsen, D. A1 - Archer, M. A1 - Kim, B. A1 - Baek, S. A1 - Lee, S. A1 - Lee, J. A1 - Marbumrung, S. A1 - Kankaew, P. A1 - Chaorenpornpukdee, K. A1 - Chaipet, T. A1 - Shearman, K. A1 - Gören, A. A1 - Gündüz, S. A1 - Yilmaz, H. A1 - Un, I. A1 - Bilsel, G. A1 - Clarkson, C. A1 - Bedner, M. A1 - Camara, J. A1 - Lang, B. A1 - Lippa, K. A1 - Nelson, M. A1 - Toman, B. A1 - Yu, L. T1 - Mass fraction assignment of folic acid in a high purity material - CCQM-K55.d (Folic acid) Final Report JF - Metrologia N2 - The comparison required the assignment of the mass fraction of folic acid present as the main component in the comparison sample. Performance in the comparison is representative of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molecular weight range 300–500] and high polarity (pKOW < −2). Methods used by the eighteen participating NMIs or DIs were based on a mass balance (summation of impurities) or qNMR approach, or the combination of data obtained using both methods. The qNMR results tended to give slightly lower values for the content of folic acid, albeit with larger associated uncertainties, compared with the results obtained by mass balance procedures. Possible reasons for this divergence are discussed in the report, without reaching a definitive conclusion as to their origin. The comparison demonstrates that for a structurally complex polar organic compound containing a high water content and presenting a number of additional analytical challenges, the assignment of the mass fraction content property value of the main component can reasonably be achieved with an associated relative standard uncertainty in the assigned value of 0.5% KW - CCQM key comparison KW - Purity assessment KW - Folic acid PY - 2018 UR - https://www.bipm.org/utils/common/pdf/final_reports/QM/K55/CCQM-K55.d.pdf DO - https://doi.org/10.1088/0026-1394/55/1A/08013 VL - 55 IS - Technical Supplement, 2018 SP - 08013, 1 EP - 38 PB - Institute of Physics Publishing (IOP) ; Bureau International des Poids et Mesures AN - OPUS4-44999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weller, Michael G. T1 - Ten Basic Rules of Antibody Validation JF - Analytical Chemistry Insights N2 - The quality of research antibodies is an issue for decades. Although several papers have been published to improve the situation, their impact seems to be limited. This publication makes the effort to simplify the description of validation criteria in a way that the occasional antibody user is able to assess the validation level of an immunochemical reagent. A simple, 1-page checklist is supplied for the practical application of these criteria. KW - Replication KW - Reproducibility KW - Documentation KW - Open Science KW - Quality Control KW - Biochemistry KW - Biotechnology KW - Bioanalysis PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-444322 UR - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5813849/ DO - https://doi.org/10.1177/1177390118757462 SN - 11773901 VL - 13 SP - 1 EP - 5 PB - Sage CY - Los Angeles, USA AN - OPUS4-44432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wagner, Sabine A1 - Zapata, Carlos A1 - Wan, Wei A1 - Gawlitza, Kornelia A1 - Weber, M. A1 - Rurack, Knut T1 - Role of Counterions in Molecularly Imprinted Polymers for Anionic Species JF - Langmuir N2 - Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations, and HPLC as well as MD simulations. Protected phenylalanines (Z-L/D-Phe) served as templates/analytes. While the influence of the counterion on the complex stability constants and anion-induced spectral changes shows a monotonous trend with increasing alkyl chain length at the prepolymerization stage, the cross-imprinting/rebinding studies showed a unique pattern that suggested the presence of adaptive cavities in the MIP matrix, related to the concept of induced fit of enzyme−substrate interaction. Larger cavities formed in the presence of larger counterions can take up pairs of Z-X-Phe and smaller TXA, eventually escaping spectroscopic detection. Correlation of the experimental data with the MD simulations revealed that counterion mobility, the relative distances between the three partners, and the hydrogen bond lifetimes are more decisive for the response features observed than actual distances between interacting atoms in a complex or the orientation of binding moieties. TBA has been found to yield the highest imprinting factor, also showing a unique dual behavior regarding the interaction with template and fluorescent monomer. Finally, interesting differences between both enantiomers have been observed in both theory and experiment, suggesting true control of enantioselectivity. The contribution concludes with suggestions for translating the findings into actual MIP development. KW - Anion receptors KW - Fluorescence sensing KW - Molecular dynamics simulations KW - Molecularly imprinted polymers KW - Rational design PY - 2018 DO - https://doi.org/10.1021/acs.langmuir.8b00500 SN - 0743-7463 VL - 34 IS - 23 SP - 6963 EP - 6975 PB - American Chemical Society CY - Washington, D.C. AN - OPUS4-45399 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -