Search results for "Infrared"
showing 10 items of 2110 documents
Inclusion complexes of cyclomaltooligosaccharides (cyclodextrins) with melatonin in solid phase
2005
Fourier transform infrared spectrometry (FT-IR) and X-Ray diffraction (XRD) investigations were carried out on MLT plus α-, β- and γ-CD physical mixtures and lyophilized or crystalline MLT/α-, β-, γ-CD complexes. Inclusion complexes formation between MLT and cyclodextrins in solid phase has been emphasized by the significant differences between IR and XRD spectra of physical mixtures with respect to those of the complexes. The structure of MLT CDs complexes in the solid state as well as the biochemical and pharmaceutical implications are discussed.
Toxicity of fatty acid hydroperoxides towards Yarrowia lipolytica: Implication of their membrane fluidizing action
2007
Abstract Linoleic acid hydroperoxide (HPOD), substrate of hydroperoxide lyase, an enzyme of the lipoxygenase pathway, can be transformed into many aromatic compounds, the so-called “green notes”. The presence of linoleic acid hydroperoxide in the culture medium of Yarrowia lipolytica, the yeast expressing the cloned hydroperoxide lyase of green bell pepper, undoubtedly exerted an inhibition on the growth and a toxic effect with 90% of yeast cells died after 120 min of exposition in 100 mM HPOD solution. The increase in cell membrane fluidity evaluated by measuring fluorescence generalized polarization with the increasing concentration of HPOD in the medium confirmed the fluidizing action of…
Chemistry of lanthanide–metal carbonyl systems: the ytterbium–chromium carbonyls interaction
2001
Abstract The interaction of the chromium carbonyl hydrides HCr2(CO)10− or HCr(CO)5− with Yb(acac)3·3H2O has been investigated, and the experimental conditions leading to the isolation of ytterbium–chromium carbonyl complex species are reported. Formulation of the coordination compounds produced by such interactions has been proposed on the basis of analytical data and IR spectroscopy.
Near-IR-to-visible emission in ytterbium-doped silica fiber at in-core 488-nm pumping
2008
We report near-IR-to-visible broadband emission in Ytterbium-doped silicate fiber (YF) at 488-nm in-core excitation. This emission is revealed to originate from Yb3+-Yb3+ pair clusters (900 – 1200-nm band), whose presence is proved by a separate study of cooperative processes in the fiber, and Yb2+ phototropic centers (600 – 900-nm band) provisionally accepted to be present in the YF.
Synthesis of Yb nanoparticles by laser ablation of ytterbium target in sodium bis(2-ethylhexyl)sulfosuccinate reverse micellar solution
2010
Abstract Surfactant-coated ytterbium nanoparticles were produced by Nd:YAG laser ablation of a Yb bulk target immersed in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/ n -heptane micellar solution. In our experimental conditions, as highlighted by IR spectroscopy, AOT molecules are not decomposed by the intense laser pulses but play a pivotal role in the stabilisation of Yb nanoparticles. The formation of Yb nanoparticles in the liquid phase was monitored by UV–Vis spectroscopy whereas the Yb/AOT composites obtained by evaporation of the organic solvent were characterised by XPS and TEM. Data analysis consistently shows the presence of surfactant-coated, nearly spherical and non-interacting…
ZnO – Yb2O3 composite optical ceramics: Synthesis, structure and spectral-luminescent properties
2022
International audience; Zinc oxide optical ceramics containing 0 – 2 wt% ytterbium are prepared byuniaxial hot pressing of commercial oxides at 1150 and 1180 °C. The ceramics have themain crystalline phase of hexagonal wurtzite-type ZnO. Ytterbium ions do not enter theZnO crystals but form a cubic sesquioxide phase of Yb2O3 located at the ZnO grainboundaries. Yb acts as an inhibitor for the ZnO grain growth. The ceramics exhibittransmittance up to 60% in the visible. Their transmission in the infrared is determinedby the free charge carrier absorption. The Yb3+ ions are found in C2 and C3i sites in Yb2O3crystals. Under X-ray excitation, the ceramics exhibit intense luminescence bands in the…
Determination at low ppm levels of dithiocarbamate residues in foodstuff by vapour phase-liquid phase microextraction-infrared spectroscopy
2010
Abstract A methodology based on the vapour phase (VP) generation of carbon disulphide from non-volatile dithiocarbamate compounds has been developed for determination of pesticide residues in foodstuff at low ppm levels. The method involves a selective reaction combined with liquid phase microextraction (LPME) and transmission infrared measurements. The use of a home made transmission cell improved the detection limits (LOD) compared to the use of attenuated total reflectance measurements by a factor of approximately 80. Using the most appropriate experimental conditions for the CS2 generation and LPME preconcentration, the precision of the methodology, expressed as the relative standard de…
Microstructural Evolution from Praseodymium-Containing Zircon Gels to Prx-ZrSiO4 Solid Solutions
2012
Structural evolution and coupled microstructural transformations occurred on annealing mineralizer-free Pr-containing ZrSiO4 gels up to final praseodymium-doped zircon yellow pigments are reported. Gels with nominal compositions Prx-ZrSiO4, 0 ≤ x ≤ 0.125, were prepared from mixtures of zirconium and silicon alkoxides and praseodymium acetylacetonate. Crystallization pathway and microstructural changes of thermally treated dried gels were followed by infrared spectroscopy, X-ray diffraction, field emission scanning and transmission electron microscopies, respectively. Results indicated that the crystallization pathway through the whole process of final Prx-ZrSiO4 solid solutions formation di…
Synthesis and characterization of praseodymium-containing ZrSiO4 solid solutions from gels
2011
Abstract The preparation and characterization of a series of praseodymium–zircon solid solution (Prx–ZrSiO4) materials with increasing nominal amounts of Pr is reported. Pr-doped zircon gels were prepared by gelling mixtures of zirconium n-propoxide, praseodymium acetylacetonate and tetraethylorthosilicate, and annealed over the range of temperature up to the formation of Pr–zircon solid solutions. The reaction sequence was followed by X-ray powder diffraction (XRD), ultraviolet–visible diffuse reflectance (DR) and infrared spectroscopy (IR). The first crystalline phase detected on annealing gels was a tetragonal praseodymium-containing ZrO2 phase (t-Pr–ZrO2). On further annealing, the subs…
Structural Infrared Analysis of Ultra Nanosized Crystals of Yttria-Stabilized Zirconia
2017
This paper describes the characterization of ultra nanosized crystals as monoclinic, tetragonal, cubic or mixed phases of ZrO2. Nanopowders are produced using the microwave method, which allows control of the ratio of zirconium to yttrium to yield various crystallographic structures. The synthesized ultra nanosized particles have very broad XRD peaks. In particular, the similarity of the XRD peaks of tetragonal and cubic nanocrystals makes it difficult to distinguish between these two crystals. In this paper, tetragonal and cubic nanocrystals were clearly distinguished using infrared spectroscopy (IR). An infrared spectroscopic method to quantitatively analyse the percentage distribution be…