Search results for " infrared spectroscopy"
showing 10 items of 438 documents
Communication: Evidence of structural phase transitions in silicalite-1 by infrared spectroscopy
2013
The adsorption of trichloroethylene, perchloroethylene, and p-xylene on a MFI (Mobile-FIve) zeolite is studied using in situ FTIR spectroscopy at 298 K. Spectra of self-supported zeolites in contact with increasing pressures of pure gas were recorded at equilibrium in the mid-infrared domain. Analysis of the evolution of the shape and location of vibrational bands of the zeolite as a function of the amount adsorbed allowed the observation of structural modifications of the adsorbent for the first time by infrared spectroscopy.
Spectroscopic markers of the T-R quaternary transition in human hemoglobin
2004
n questo lavoro, usiamo un protocollo sol-gel per intrappolare e confrontare gli stati quaternari R e T di entrambi i deossigenati (deossiHb) ederivati di ossido di carbonio (HbCO) dell'emoglobina umana. La banda di assorbimento ottico del vicino infrarosso III e lo stretching di CO a infrarossibanda sono utilizzati per rilevare l'effetto della struttura quaternaria sulle proprietà spettrali di deoxyHb e HbCO; confronto con mioglobinaconsente una valutazione dei contributi terziari e quaternari ai turni di banda misurati. La RXLa transizione T è indicata per causare un bluspostamento della banda III di ~ 35 cm?1per deoxyHb e uno spostamento rosso della banda di allungamento CO di soli ~ 0…
Fourier transform infrared determination of CO 2 evolved from carbonate in carbonated apatites
2000
A quantitative method based on FTIR has been developed to determine carbonate in synthetic apatites. The method measures the evolved CO2 after reaction of 50 mg apatite with 2 mL of hydrochloric acid (0.5 M) in a reaction vessel, heated to 40 degrees C. The CO2 evolved was swept by a carrier of nitrogen to a laboratory-made infrared gas cell of 39 mm pathlength and 490 microL volume. The signals were recorded as a function of time and the areas of the chemigram peaks obtained from the measurements in the wavenumber range of 2,500-2,150 cm(-1), were interpolated using a calibration curve. The method can be used to study apatites with carbonate contents below 0.2% with a sampling frequency of…
Microwave, High-Resolution Infrared, and Quantum Chemical Investigations of CHBrF2: Ground and v4 = 1 States
2011
A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the…
Fourier transform infrared spectroscopy and the analytical study of sculptures and wall decoration
1997
Abstract An analytical examination of sculpture and wall painting, including several wooden polychromed carvings from Valencian churches (15th–17th centuries) using FT-IR spectroscopy is described. The organic and inorganic compounds used in the works of art and the different artistic techniques used in each historical intervention carried out in the sculptures are identified. The analytical information obtained with this technique on organic and inorganic compounds is extremely useful in the preliminary studies necessary for diagnosis and to decide on the conservation process.
Tetraallylsilane π-Complexation: Synthesis and Structure of [Cu5Cl5(CH2-CH=CH2)4Si]
2009
By alternating-current electrochemical technique, starting from CuCl2·2H2O and tetraallylsilane (TAS), crystals of the π complex [Cu5Cl5(CH2–CH=CH2)4Si] (I) were obtained, FTIR characterized and structurally investigated. The structure of I is monoclinic, space group P21/n, a = 12.292(3), b = 12.083(3), c = 13.356(3) A, β = 90.19(3)°, V = 1983.7(9) A3 [at 100(2) K], Z = 4; R1 = 0.0379, wR2 = 0.1040 for 3583 reflections. The TAS molecule behaves as a tetradentate cross-bridged ligand linking four (Cu5Cl5)∞ fragments through the C=C bonds. The influence of the inorganic part and ligand symmetries combined with their conformational abilities on the overall crystal symmetry is discussed.
Efficient Sc triflate mesoporous-based catalysts for the synthesis of 4,4′-methylenedianiline from aniline and 4-aminobenzylalcohol
2012
Abstract Sc triflate mesoporous-based catalysts have been prepared using a two-step strategy (i.e., Atrane method) based on the formation of the hierarchic bimodal porosity in the first step and the formation of Sc triflate complexes at the materials surface in the second step. All solids were analyzed by EPMA, surface area, and pore size values, XRD, TEM, FTIR, and 45Sc NMR static spectra. The catalysts have been investigated in the synthesis of 4,4′-methylenedianiline (4,4′-MDA) from aniline and 4-aminobenzylalcohol. 4,4′-MDA was obtained with selectivities over 85.0% for a conversion of aniline of 31%, at 80 °C and after 24 h. Using microwaves, selectivities of 90% in 4,4′-MDA were reach…
Study of the Interaction Mechanism in the Biosorption of Copper(II) Ions onto Posidonia oceanica and Peat
2012
A systematic approach was used to characterize the biosorption of copper(II) onto two biosorbents, Posidonia oceanica and peat, focusing on the interaction mechanisms, the copper(II) sorption–desorption process and the thermal behavior of the biosorbents. Sorption isotherms at pH 4–6 were obtained and the experimental data were fitted to the Langmuir model with a maximum uptake ( q max ) at pH 6 of 85.78 and 49.69mgg -1 , for P. oceanica and peat, respectively. A sequential desorption (SD) with water, Ca(NO 3 ) 2 , and EDTA was applied to copper-saturated biosorbents. Around 65–70% copper(II) were desorbed with EDTA, indicating that this heavy metal was strongly bound. The reversibility of …
Fast and direct analysis of oxidation levels of oil-in-water emulsions using ATR-FTIR.
2019
International audience; Oxidation of omega-3 fatty acids is a major limitation on its enrichment in food and beverages. An efficient and simple method to monitor lipid oxidation in complex systems is essential to limit lipid oxidation during formulation and processing. Fish oil-in-water emulsions (20% v/v) were exposed to iron or free radical initiated oxidation. Conjugated dienes (CDs) were rapidly measured using a previously developed fat extraction method. Fourier transform infrared (FTIR) spectroscopy has been used to directly record chemical changes occurring during oxidation. Variations were noticed in different spectral regions despite the presence of broad water bands near 3400 and …
An experimental and modeling study of the oxidation of 3-pentanol at high pressure
2019
International audience; High pressure oxidation of 3-pentanol is investigated in a jet-stirred reactor and in a shock tube. Experiments in the reactor were carried out at 10 atm, between 730 and 1180 K, for equivalence ratios of 0.35, 0.5, 1, 2, 4 and 1000 ppm fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were recorded using Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC). Ignition delay times were measured for 3-pentanol/O2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1000–1470 K and for equivalence ratios of 0.5, 1 and 2. The fuel did not show any low-temperature reactivity…