TY - JOUR A1 - Schenk, Jonas A1 - Batzdorf, Lisa A1 - Emmerling, Franziska A1 - Kneipp, Janina A1 - Panne, Ulrich A1 - Buurman, Merwe T1 - Simultaneous UV/Vis spectroscopy and surface enhanced raman scattering of nanoparticle formation and aggregation in levitated droplets N2 - The formation and growth of hydroxylamine reduced silver nanoparticles were investigated by simultaneous Raman and UV/Vis spectroscopy coupled to an acoustic levitator as a sample holder. Based on the UV/Vis spectra, a two step particle formation mechanism with fast initial formation and adjacent coalescence can be proposed for the reduction of silver nitrate with hydroxylamine. The presence of the analyte adenine during particle formation resulted in differences in the adenine SERS signature compared to experiments, where adenine was added after particle synthesis. It was possible to monitor the adenine and sodium chloride induced aggregation of the nanoparticles and its dynamics based on both the extinction spectra and the SERS data. Correlating the information from the extinction spectra with the SERS intensity, the maximum SERS signals were observed at maximum extinction of the aggregated nanoparticle solution at the Raman excitation wavelength. PY - 2012 U6 - https://doi.org/10.1039/c2ay05744a SN - 1759-9660 SN - 1759-9679 N1 - Geburtsname von Batzdorf, Lisa: Tröbs, L. - Birth name of Batzdorf, Lisa: Tröbs, L. N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 4 IS - 5 SP - 1252 EP - 1258 PB - RSC Publ. CY - Cambridge AN - OPUS4-25742 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Suhm, M.A. A1 - Buurman, Merwe T1 - Comment on 'theoretical investigations into the enantiomeric and racemic forms of alpha-(trifluoromethyl)lactic acid' by R. Tonner, V.A. Soloshonok and P. Schwerdtfeger, Phys. Chem. Chem. Phys., 2011, 13, 811-817 N2 - It is argued that differences between homo- and heterochiral dimers of the title compound in the gas phase cannot be responsible for the different sublimation behaviour of racemic and enantiomerically pure crystals near room temperature. KW - Chirality recognition KW - Sublimation PY - 2011 U6 - https://doi.org/10.1039/c0cp02455d SN - 1463-9076 SN - 1463-9084 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 13 IS - 9 SP - 4159 EP - 4160 PB - The Royal Soc. of Chemistry CY - Cambridge AN - OPUS4-25001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schenk, Jonas A1 - Panne, Ulrich A1 - Buurman, Merwe T1 - Interaction of levitated ionic liquid droplets with water N2 - The influence of a humid or dry atmosphere on acoustically levitated ionic liquid droplets was studied by volumetric analysis and vibrational spectroscopy. Imidazolium-based ionic liquids with two types of anions, fluorinated (BF4 and PF6) and alkylsulfate anions, were investigated. The amount of absorbed water was correlated with structural differences of the ionic liquids and analyzed in terms of equilibrium mole fraction as well as absorption rate. The type of anion had the most significant influence on the amount of adsorbed water from the atmosphere. Furthermore, spectral changes in the in situ Raman spectra due to absorbed water were studied for all investigated ionic liquids. For 1-ethyl-3-methylimidazolium ethylsulfate, an exemplary detailed analysis of the intermolecular interactions between cations, anions and water was carried out based on the spectroscopic data. The observed band shifts were explained with a hydrogen bond between the anion and water. KW - Ionic liquids KW - Levitated droplets KW - Raman spectroscopy PY - 2012 U6 - https://doi.org/10.1021/jp309661p SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 116 IS - 48 SP - 14171 EP - 14177 PB - Soc. CY - Washington, DC AN - OPUS4-27427 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stindt, Arne A1 - Buurman, Merwe A1 - Panne, Ulrich A1 - Riedel, Jens T1 - CO2 laser ionization of acoustically levitated droplets N2 - For many analytical purposes, direct laser ionization of liquids is desirable. Several studies on supported droplets, free liquid jets, and ballistically dispensed microdroplets have been conducted, yet detailed knowledge of the underlying mechanistics in ion formation is still missing. This contribution introduces a simple combination of IR-MALDI mass spectrometry and an acoustical levitation device for contactless confinement of the liquid sample. The homebuilt ultrasonic levitator supports droplets of several millimeters in diameter. These droplets are vaporized by a carbon dioxide laser in the vicinity of the atmospheric pressure interface of a time of flight mass spectrometer. The evaporation process is studied by high repetition rate shadowgraphy experiments elucidating the ballistic evaporation of the sample and revealing strong confinement of the vapor by the ultrasonic field of the trap. Finally, typical mass spectra for pure glycerol/water matrix and lysine as an analyte are presented with and without the addition of trifluoracetic acid, and the ionization mechanism is briefly discussed. The technique is a promising candidate for a reproducible mass spectrometric detection scheme for the field of microfluidics. KW - Ambient mass spectrometry KW - Levitated droplets KW - IR-MALDI PY - 2012 UR - http://link.springer.com/content/pdf/10.1007%2Fs00216-012-6500-y U6 - https://doi.org/10.1007/s00216-012-6500-y SN - 1618-2642 SN - 1618-2650 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. SP - 1 EP - 6(?) PB - Springer CY - Berlin AN - OPUS4-27429 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lee, J.J. A1 - Buurman, Merwe A1 - Rice, C.A. A1 - Suhm, M.A. A1 - Stamm, A. A1 - Zimmer, M. A1 - Gerhards, M. T1 - Adaptive aggregation of peptide model systems N2 - Jet-cooled infrared spectra of acetylated glycine, alanine, and dialanine esters and their dimers are reported in the amide A and amide I–III regions. They serve as particularly simple peptide aggregation models and are found to prefer a single backbone conformation in the dimer that is different from the most stable monomer backbone conformation. In the case of alanine, evidence for topology-changing chirality discrimination upon dimer formation is found. The jet spectroscopic results are compared to gas phase spectra and quantum chemical calculations. They provide reliable benchmarks for the evaluation of the latter in the field of peptide interactions. KW - Jet-cooled infrared spectra KW - Peptide aggregation KW - Quantum chemical calculations PY - 2013 U6 - https://doi.org/10.1021/jp400056n SN - 1089-5639 SN - 1520-5215 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 117 IS - 32 SP - 7050 EP - 7063 PB - Soc. CY - Washington, DC AN - OPUS4-29025 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buurman, Merwe A1 - Stindt, Arne A1 - Panne, Ulrich A1 - Riedel, Jens T1 - CO2-Laser Atmospheric Pressure Ionization of Acoustically Levitated Droplets T2 - SCIX CY - Kansas City, MO, USA DA - 2012-09-29 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27332 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buurman, Merwe A1 - Schenk, Jonas A1 - Stindt, Arne A1 - Riedel, Jens A1 - Panne, Ulrich T1 - Acoustically levitated droplets as containerless microreactors T2 - Microfluids 2012 CY - Heidelberg, Germany DA - 2012-07-25 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27334 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buurman, Merwe A1 - Schenk, Jonas A1 - Stindt, Arne A1 - Riedel, Jens A1 - Panne, Ulrich T1 - Spectroscopic analysis in acoustically levitated droplets T2 - SciX 2012 (FACSS) CY - Kansas City, MO, USA DA - 2012-09-30 PY - 2012 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-27335 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buurman, Merwe A1 - Schenk, Jonas A1 - Panne, Ulrich T1 - Spectroscopic analysis in acoustically levitated dropletz T2 - ANAKON 2013 CY - Essen, Germany DA - 2013-03-04 PY - 2013 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. AN - OPUS4-30344 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Buurman, Merwe A1 - Schenk, J. A. A1 - Schulz, Katrin A1 - Panne, Ulrich T1 - Raman spectroscopic analysis in microfluidic systems T2 - ICORS 2014 CY - Jena DA - 2014-08-10 PY - 2014 AN - OPUS4-32300 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bolz, Axel A1 - Panne, Ulrich A1 - Rurack, Knut A1 - Buurman, Merwe T1 - Glass fibre paper-based test strips for sensitive SERS sensing N2 - We present paper-based test strips for chemical sensing with surface enhanced Raman scattering as detection method. The test strips are prepared on glass fibre paper with silver nanoparticles and a spray method with an airbrush spray setup as a low cost fabrication approach. The properties of the test strips are investigated with three classical Raman analytes rhodamine 6G, 4-aminothiophenol and adenine and optimized for a good reproducibility of the intensity measurements. All test analytes can be identified at low concentrations. For adenine, a concentration series from 10⁻⁴ M to 10⁻⁸ M is measured and the calibration data can be fitted and evaluated with a Langmuir isotherm model. The optimized test strips are applied for the identification of two antibiotics enoxacin and enrofloxacin. KW - surface enhanced Raman scattering KW - glass fibre paper KW - sensing KW - spray KW - Langmuir isotherm PY - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-354878 SN - 1759-9660 VL - 8 IS - 6 SP - 1313 EP - 1318 PB - The Royal Society of Chemistry AN - OPUS4-35487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bell, Jérémy A1 - Climent Terol, Estela A1 - Hecht, Mandy A1 - Buurman, Merwe A1 - Rurack, Knut T1 - Combining a droplet-based microfluidic tubing system with gated indicator releasing nanoparticles for mercury trace detection N2 - A droplet-based microfluidic sensor was developed for the detection of Hg2+ traces in water. The approach uses gated mesoporous nanoparticles loaded with a fluorescent BODIPY dye. The squaraine-based gating mechanism is highly selective for Hg2+ and the indicator release mechanism ensures sensitive detection. The microfluidic system is modular and was assembled from simple PTFE/PFA tubes, while detection was realized with standard optomechanic, optic, and electronic parts. The sensor shows a stable response without memory effects and allows the detection of Hg2+ in water down to 20 ppt. KW - Microfluidic sensor KW - Gated delivery system KW - Fluorescence KW - Mercury KW - Hybrid nanoparticles PY - 2016 U6 - https://doi.org/10.1021/acssensors.5b00303 SN - 2379-3694 VL - 1 IS - 4 SP - 334 EP - 338 PB - American Chemical Society CY - Washington, DC AN - OPUS4-35831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stindt, Arne A1 - Andrade, M. A. B. A1 - Buurman, Merwe A1 - Adamowski, J. C. A1 - Panne, Ulrich A1 - Riedel, Jens T1 - Experimental and numerical characterization of the sound pressure in standing wave acoustic levitators N2 - A novel method for predictions of the sound pressure distribution in acoustic levitators is based on a matrix representation of the Rayleigh integral. This method allows for a fast calculation of the acoustic field within the resonator. To make sure that the underlying assumptions and simplifications are justified, this approach was tested by a direct comparison to experimental data. The experimental sound pressure distributions were recorded by high spatially resolved frequency selective microphone scanning. To emphasize the general applicability of the two approaches, the comparative studies were conducted for four different resonator geometries. In all cases, the results show an excellent agreement, demonstrating the accuracy of the matrix method. KW - Acoustic levitation KW - Matrix calculation KW - Microphony KW - Noncontact ultrasonic transportation KW - Small objects KW - Matrix-method KW - Droplets KW - Air KW - Manipulation KW - Simulation KW - Fields KW - Water PY - 2014 U6 - https://doi.org/10.1063/1.4861197 SN - 0034-6748 SN - 1089-7623 N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M. VL - 85 IS - 015110 SP - 1 EP - 6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-30405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ashokkumar, Pichandi A1 - Bell, Jérémy A1 - Buurman, Merwe A1 - Rurack, Knut T1 - Analytical platform for sugar sensing in commercial beverages using a fluorescent BODIPY "light-up" probe N2 - Because of the globally increasing prevalence of diabetes, the need for accurate, efficient and at best miniaturized automated analytical systems for sugar detection in medical diagnostics and the food industry is still urgent. The development of molecular probes for sugars based on boronic acid receptors offers an excellent alternative to the kinetically slow enzyme-based sugar sensors. Moreover, by coupling such chelating units with dye scaffolds like BODIPYs (boron–dipyrromethenes), highly fluorescent sugar sensing schemes can be realized. In this work, a boronic acid-functionalized BODIPY probe was developed, which binds selectively to fructose’s adjacent diols to form cyclic boronate esters. Placement of an amino group in direct neighborhood of the boronic acid moiety allowed us to obtain a broad working range at neutral pH, which distinguishes the probe from the majority of systems working only at pH > 8, while still meeting the desired sensitivity in the micro-molar range due to a pronounced analyte-induced fluorescence increase. To enhance the applicability of the test in the sense described above, integration with a microfluidic chip was achieved. Here, fructose was selectively detected by fluorescence with similar sensitivity in real time on chip, and an assay for the straightforward detection of sugar in (colored) sodas without sample clean-up was established. KW - BODIPY dyes KW - Boronic acid KW - Fluorescence KW - Microfluidics KW - Sugars PY - 2018 U6 - https://doi.org/10.1016/j.snb.2017.09.201 SN - 0925-4005 VL - 256 SP - 609 EP - 615 PB - Elsevier CY - Amsterdam AN - OPUS4-43102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -