The Experts below are selected from a list of 4176 Experts worldwide ranked by ideXlab platform
Risto Kostiainen - One of the best experts on this subject based on the ideXlab platform.
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capillary photoionization interface for low flow rate liquid chromatography mass spectrometry
Analyst, 2019Co-Authors: Paivi Poho, Anu Vaikkinen, Markus Haapala, Petri Kylli, Risto KostiainenAbstract:This is the first report on capillary photoionization (CPI) interfacing a liquid chromatograph (LC) and mass spectrometer (MS). A new heated CPI ion source was developed, including a heated transfer capillary, a wide oval-shaped and low-depth ionization chamber with a vacuum ultraviolet (VUV) transparent Magnesium Fluoride (MgF2) window to increase the photoionization efficiency and thus the sensitivity. As both analytes and eluent are first vaporized and then photoionized inside the CPI ion source between the atmosphere and the vacuum of MS, the ion transfer efficiency into the MS and thus the sensitivity is improved. The effect of the most important operation parameters, the eluent flow rate and temperature of the CPI source, on the signal intensity was studied with selected steroids. The feasibility of LC-CPI-MS/MS for the quantitative analysis of steroids was also studied in terms of linearity, repeatability, and limits of detection. The method showed good quantitative performance and sensitivity down to the low femto-mole level.
Sinclair S. Yee - One of the best experts on this subject based on the ideXlab platform.
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Long-range surface plasmons for high-resolution surface plasmon resonance sensors
Sensors and Actuators B-chemical, 2001Co-Authors: Garet G. Nenninger, Jiřı́ Homola, P. Tobiška, Sinclair S. YeeAbstract:Abstract We present the application of long-range surface plasmons to a wavelength-modulated surface plasmon resonance sensor. Theoretical design parameters and experimental data are presented for two sensor designs, using either Magnesium Fluoride or Teflon AF-1600 as a dielectric buffer layer. The demonstrated sensitivity of the long-range surface plasmon resonance sensor in refractometric experiments is up to seven times higher than that of an equivalent conventional surface plasmon resonance (SPR) sensor, while the measured resolution is comparable. According to theoretical design calculations presented, further optimization of materials and layer thickness could reduce the resonance width while achieving even higher sensitivities, thereby creating a sensor with significantly better resolution than conventional SPR sensors.
Erhard Kemnitz - One of the best experts on this subject based on the ideXlab platform.
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Optical nanocomposites containing low refractive index MgF
'EDP Sciences', 2021Co-Authors: Leonid M. Goldenberg, Mathias Köhler, Christian Dreyer, Tohralf Krahl, Erhard KemnitzAbstract:Nanoparticles composed of Magnesium Fluoride were successfully introduced into polymer matrices used for the fabrication of planar optical waveguides. Optical layers without visible scattering were successfully prepared. The transparent nanocomposites were formulated by direct mixing of modified MgF2 nanoparticles with fluorinated co-polymer matrix or acrylate monomer mixture with a help of additional solvent. An addition of MgF2 nanoparticles results in decrease of refractive index and thermo-optic coefficient of the polymer but increases substantially the optical propagation losses for planar waveguide at 1547 nm
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Fluorolytic Sol–Gel Synthesis of Nanometal Fluorides: Accessing New Materials for Optical Applications
Inorganics, 2018Co-Authors: Kerstin Scheurell, Erhard KemnitzAbstract:The potential of fluorolytic sol–gel synthesis for a wide variety of applications in the field of optical materials is reviewed. Based on the fluorolytic sol–gel synthesis of nanometal Fluorides, sols of complex fluorometalates have become available that exhibit superior optical properties over known classical binary metal Fluorides as, for instance, Magnesium Fluoride, calcium Fluoride, or strontium Fluoride, respectively. The synthesis of transparent sols of Magnesium fluoroaluminates of the general composition MgxAlFy, and fluoroperovskites, [K1−xNax]MgF3, is reported. Antireflective coatings fabricated from MgF2, CaF2, MgxAlFy, and [K1−xNax]MgF3 sols and their relevant properties are comprehensively described. Especially the heavier alkaline earth metal Fluorides and the fluorperovskites crystallizing in a cubic crystal structure are excellent hosts for rare earth (RE) metals. Thus, the second chapter reflects the synthesis approach and the properties of luminescent systems based on RE-doped alkaline earth metal Fluorides and [K1−xNax]MgF3 phases.
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Sols of nanosized Magnesium Fluoride: formation and stabilisation of nanoparticles
Journal of Materials Chemistry, 2011Co-Authors: Johannes Noack, Franziska Emmerling, Holm Kirmse, Erhard KemnitzAbstract:The formation of Magnesium Fluoride sols and xerogels according to the fluorolytic sol–gel synthesis based on the reaction of Mg(OMe)2 with non-aqueous HF has been thoroughly investigated by X-ray scattering (WAXS/XRD), TEM, SAXS, DLS and 19F MAS NMR spectroscopy. Mechanistic insights were gained by following the reaction progress and formation of intermediate phases of the fluorination of Magnesium alkoxides. For F : Mg ratios of 0.3 and 0.4 the formation of two crystalline phases was observed containing the recently obtained compound [Mg6F2(OCH3)10(CH3OH)14] hexanuclear dicubane units. The stoichiometric reaction yields Magnesium Fluoride nanoparticles with crystallite sizes below 5 nm, which show broad reflections in the X-ray diffraction pattern. Metal Fluoride sols prepared by this way undergo tremendous changes over the first several weeks after synthesis. Immediately after the fluorination, particles of about 120 nm—probably agglomerates—are formed, which break apart in the course of about one month of ageing and low-viscous, transparent sols with particles of about 12 nm are obtained. At the same time structural re-organisation processes within the Magnesium Fluoride particles are observed by an increase of the (110) reflection in WAXS.
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a comparative study of surface acidity in the amorphous high surface area solids aluminium Fluoride Magnesium Fluoride and Magnesium Fluoride containing iron iii or aluminium iii Fluorides
Journal of Fluorine Chemistry, 2008Co-Authors: Mahmood Nickkhoamiry, Erhard Kemnitz, Stephan Rudiger, Gehan Eltanany, Stefan Wuttke, John M WinfieldAbstract:Abstract The behaviour of the sol–gel prepared, amorphous solids, high surface area (HS) aluminium Fluoride and Magnesium Fluoride in promoting room temperature dehydrochlorination of tert -butyl chloride (Bu t Cl), in their catalytic activity for the dismutation of chlorodifluoromethane and in the temperature programmed desorption of ammonia is similar, indicating that, unexpectedly, both solids exhibit significant surface Lewis acidity. Using a similar approach, it has been demonstrated that surface Lewis acidity in HS-MgF 2 is enhanced by the incorporation of amorphous iron(III) Fluoride and probably also by amorphous aluminium(III) Fluoride. A second, unexpected feature is the substantial retention of anhydrous hydrogen chloride by all the solids, which is observed by the use of chlorine-36 labelling, when they are exposed at room temperature either to Bu t Cl or to HCl directly. The detailed behaviour of H 36 Cl towards HS-AlF 3 depends on the fluorinating agent, dichlorodifluoromethane or anhydrous hydrogen Fluoride, which is used in the second stage of HS-AlF 3 synthesis. This observation and the pattern of the results obtained overall lead to the proposal that strongly adsorbed HCl behaves as an unconventional Lewis base towards these solids.
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sol gel fluorination synthesis of amorphous Magnesium Fluoride
Journal of Solid State Chemistry, 2006Co-Authors: Krishna J Murthy, Erhard Kemnitz, Udo Gros, Stephan Rudiger, John M WinfieldAbstract:Abstract The sol–gel fluorination process is discussed for the reaction of Magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized Magnesium Fluoride with high surface areas in the range of 150–350 m2/g (HS-MgF2). The H2 type hysteresis of nitrogen adsorption–desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH3 temperature-programmed desorption (NH3-TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMR- and IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal Fluoride. The preparation of complex Fluorides, M+MgF3−, by the sol–gel route is reported. From the Magnesium Fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.
Laurent Larger - One of the best experts on this subject based on the ideXlab platform.
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Magnesium Fluoride whispering gallery mode disk-resonators for microwave photonics applications
IEEE Photonics Technology Letters, 2015Co-Authors: Hervé Tavernier, Kirill Volyanskiy, Patrice Salzenstein, Yanne K Chembo, Laurent LargerAbstract:We have manufactured a high-Q whispering gallery mode resonator with Magnesium Fluoride for microwave photonics applications in the gigahertz frequency range. This crystal is scarcely used for resonator fabrication despite its numerous advantages, that are mainly high mechanical hardness, low sensitivity to water vapor pollution, and low sensitivity to photo- and thermo-refractive fluctuations at optimal temperatures. Using a customized machining procedure, we have successfully fabricated and characterized a 5-mm resonator with a surface rugosity of the order of 1 nm (from 3 to 12 atoms). Cavity ring-down measurements enabled us to determine that the resonator has a quality factor Q = 3.4 × 108 at 1550 nm.
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azimuthal turing patterns bright and dark cavity solitons in kerr combs generated with whispering gallery mode resonators
IEEE Photonics Journal, 2013Co-Authors: Aurelien Coillet, Laurent Larger, Irina Balakireva, Remi Henriet, Khaldoun Saleh, J M Dudley, C R Menyuk, Yanne K ChemboAbstract:We investigate the formation of cavity solitons in crystalline whispering-gallery-mode disk resonators that are pumped in different dispersion regimes. In the Fourier domain, these dissipative structures correspond to specific types of mode-locked Kerr optical frequency combs. Depending on the sign of the second-order chromatic dispersion and on the pumping conditions, we show that either bright or dark cavity solitons can emerge, and we show that these two regimes are associated with characteristic spectral signatures that can be discriminated experimentally. We use the Lugiato-Lefever spatiotemporal formalism to investigate the temporal dynamics leading to the formation of these azimuthal solitons, as well as the emergence of Turing patterns. The theoretical results are in excellent agreement with experimental measurements that are obtained using calcium and Magnesium Fluoride disk resonators pumped near 1550 nm.
Ehud Banin - One of the best experts on this subject based on the ideXlab platform.
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improved antibacterial and antibiofilm activity of Magnesium Fluoride nanoparticles obtained by water based ultrasound chemistry
Nanomedicine: Nanotechnology Biology and Medicine, 2012Co-Authors: Jonathan Lellouche, Alexandra Friedman, Aharon Gedanken, Ehud BaninAbstract:Antibiotic resistance has prompted the search for new agents that can inhibit bacterial growth. We recently reported on the antimicrobial and antibiofilm activities of nanosized Magnesium Fluoride (MgF2) nanoparticles (NPs) synthesized in ionic liquid using microwave chemistry. In this article, we describe a novel water-based synthesis of MgF2 NPs using sonochemistry. The sonochemical irradiation of an aqueous solution of [Mg(OAc)2⋅(H2O)4] containing acidic HF as the fluorine ion source afforded crystalline well-shaped spherical MgF2 NPs that showed much improved antibacterial properties against two common bacterial pathogens (Escherichia coli and Staphylococcus aureus). We were also able to demonstrate that the antimicrobial activity was dependent on the size of the NPs. In addition, using the described sonochemical process, we coated glass surfaces and demonstrated inhibition of bacterial colonization for 7 days. Finally, the antimicrobial activity of MgF2 NPs against established biofilms was also examined. Taken together our results highlight the potential to further develop the concept of utilizing these metal Fluoride NPs as novel antimicrobial and antibiofilm agents.
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antibiofilm surface functionalization of catheters by Magnesium Fluoride nanoparticles
International Journal of Nanomedicine, 2012Co-Authors: Jonathan Lellouche, Alexandra Friedman, Aharon Gedanken, Roxanne Lahmi, Ehud BaninAbstract:The ability of bacteria to colonize catheters is a major cause of infection. In the current study, catheters were surface-modified with MgF2 nanoparticles (NPs) using a sonochemical synthesis protocol described previously. The one-step synthesis and coating procedure yielded a homogenous MgF2 NP layer on both the inside and outside of the catheter, as analyzed by high resolution scanning electron microscopy and energy dispersive spectroscopy. The coating thickness varied from approximately 750 nm to 1000 nm on the inner walls and from approximately 450 nm to approximately 580 nm for the outer wall. The coating consisted of spherical MgF2 NPs with an average diameter of approximately 25 nm. These MgF2 NP-modified catheters were investigated for their ability to restrict bacterial biofilm formation. Two bacterial strains most commonly associated with catheter infections, Escherichia coli and Staphylococcus aureus, were cultured in tryptic soy broth, artificial urine and human plasma on the modified catheters. The MgF2 NP-coated catheters were able to significantly reduce bacterial colonization for a period of 1 week compared to the uncoated control. Finally, the potential cytotoxicity of MgF2 NPs was also evaluated using human and mammalian cell lines and no significant reduction in the mitochondrial metabolism was observed. Taken together, our results indicate that the surface modification of catheters with MgF2 NPs can be effective in preventing bacterial colonization and can provide catheters with long-lasting self-sterilizing properties.
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antibiofilm activity of nanosized Magnesium Fluoride
Biomaterials, 2009Co-Authors: Jonathan Lellouche, Aharon Gedanken, E Kahana, Sivan Elias, Ehud BaninAbstract:Abstract The ability of bacteria to develop antibiotic resistance and colonize abiotic surfaces by forming biofilms is a major cause of medical implant-associated infections and results in prolonged hospitalization periods and patient mortality. This raises the urgent need to develop compounds that can inhibit bacterial colonization of surfaces. In this study, we present an unreported microwave-based synthesis of MgF 2 nanoparticles (Nps) using ionic liquid. We demonstrate the antimicrobial activity of these Fluoride nanomaterials and their ability to restrict biofilm formation of common bacterial pathogens. Scanning and transmission electron microscopic techniques indicated that the MgF 2 ·Nps attach and penetrate into the cells. Flow cytometry analysis revealed that the Nps caused a disruption in the membrane potential. The MgF 2 ·Nps also induced membrane lipid peroxidation and once internalized can interact with chromosomal DNA. Based on these findings we further explored the possibility of using the MgF 2 ·Nps to coat surfaces and inhibit biofilm formation. A microwave synthesis and coating procedure was utilized to coat glass coupons. The MgF 2 coated surfaces effectively restricted biofilm formation of the tested bacteria. Taken together these results highlight the potential for developing MgF 2 nanoparticles in order to inhibit bacterial infections.
