Showing papers on "Fourier transform infrared spectroscopy published in 1988"
TL;DR: In this paper, the clean surface of a silicon single crystal was prepared with ultraviolet cleaning followed by HF dipping with low concentration HF obtained by dilution by organic free ultrapure water, at room temperature under the atmospheric condition.
Abstract: We have tried to develop a new procedure to prepare the clean surface of a silicon single crystal. We successfully prepared the contamination free bare silicon surface with ultraviolet cleaning followed by HF dipping with low concentration HF obtained by dilution by organic free ultrapure water, at room temperature under the atmospheric condition. X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet photoelectron spectroscopy measurements proved thus prepared surface has a hydrogen monoatomic layer terminating the dangling bonds of silicon. The hydrogen termination was found to have remarkable passivation effect against surface oxidation reaction. A silicon thin‐film epitaxially grown on the prepared surface was confirmed to have perfect crystal structure and high‐purity level by scanning electron microscopy, reflection high‐energy electron diffraction, Raman spectroscopy and secondary ion mass spectroscopy.
451 citations
TL;DR: The method developed allowed samples of light-cured composite to be made with controlled conversion for parameter testing, and eliminated effects of resin lost to slurry during polishing or an increase in conversion as a result of heat generated during grinding.
Abstract: The sensitivities of Fourier transform infrared spectroscopy, Knoop hardness, water sorption, and resin leaching were compared for their ability to distinguish differences between composite samples cured through different thicknesses of overlying resin. The method developed allowed samples of light-cured composite to be made with controlled conversion for parameter testing, and eliminated effects of resin lost to slurry during polishing or an increase in conversion as a result of heat generated during grinding. Sensitivity to differences was greatest and equal for FTIR spectroscopy and Knoop hardness, while resin leaching proved to have moderate sensitivity, and water sorption none. The ability of these parameters to predict monomer conversion as measured by FTIR spectroscopy was also determined. Knoop hardness proved the best conversion predictor, resin leaching the next best, and water sorption the worst. Water sorption values did not vary with changes in specimen conversion.
432 citations
TL;DR: FT-IR spectra of 13C-labeled phospholipids show that the vibrational bands of both, thesn-1 as well as the sn-2 C = O group, are clearly superpositions of at least two underlying components of different frequency and intensity.
Abstract: Fourier transform infrared spectroscopy has been used to characterize the carbonyl stretching vibration of DMPC, DMPE, DMPG, and DMPA, all labeled with 13C at the carbonyl group of the sn-2 chain. Due to the vibrational isotope effect, the 13C = O and the 12C = O vibrational bands are separated by ca. 40-43 cm-1. This frequency difference does not change when the labeling is reversed with the 13C = O group at the sn-1 chain. For lipids in organic solvents possible conformational differences between the sn-1 and sn-2 ester groups have no effect on the vibrational frequency of the C = O groups. In aqueous dispersion unlabeled phospholipids always show a superposition of two bands for the C = O vibration located at ca. 1740 and 1727 cm-1. These two bands have previously been assigned to the sn-1 and sn-2 C = O groups. FT-IR spectra of 13C-labeled phospholipids show that the vibrational bands of both, the sn-1 as well as the sn-2 C = O group, are clearly superpositions of at least two underlying components of different frequency and intensity. Band frequencies were determined by Fourier self-deconvolution and second-derivative spectroscopy. The difference between the component bands is ca. 11-17 cm-1. Again, the conformational effect as shown by reversed labeling is negligible with only 1-2 cm-1. The splitting of the C = O vibrational bands in H2O and D2O is caused by hydrogen bonding of water molecules to both C = O groups as shown by a comparison with spectra of model ester compounds in different solvents. To extract quantitative information about changes in hydration, band profiles were stimulated with Gaussian-Lorentzian functions. The chemical nature of the head group and its electronic charge have distinctive effects on the extent of hydration of the carbonyl groups. In the gel and liquid-crystalline phase of DMPC the sn-2 C = O group is more hydrated than the sn-1 C = O. This is accord with the conformation determined by X-ray analysis. In DMPG the sn-1 C = O group seems to be more accessible to water, indicating a different conformation of the glycerol backbone.
427 citations
TL;DR: In this paper, two surface sulfate species were formed after oxidation of between 10 and about 250 μmol g−1, and although the extent of formation of each was dependent on the quantity oxidized, the total band area between 1400-1350 cm−1 was a linear function of the quantity of H2S or SO2 introduced into the infrared cell.
221 citations
TL;DR: Spectrometrie FTIR des melanges du copolymere ethylene/acide methacrylique avec le polymethylvinylether ou le copolyme oxyde d'ethylene/oxyde de propene as mentioned in this paper.
Abstract: Spectrometrie FTIR des melanges du copolymere ethylene/acide methacrylique avec le polymethylvinylether ou le copolymere oxyde d'ethylene/oxyde de propene
141 citations
TL;DR: La miscibilite de ces melanges provient d'interactions intermoleculaires specifiques mettant en jeu des groupes >NH et carbonyl.
Abstract: La miscibilite de ces melanges provient d'interactions intermoleculaires specifiques mettant en jeu des groupes >NH et carbonyl
111 citations
TL;DR: A model for the packing of beta-strands in porin is proposed which satisfies both IR and x-ray requirements and indicates that the plane of the beta-sheets is approximately perpendicular to the bilayer.
90 citations
IBM1
89 citations
TL;DR: In this paper, Fourier transform infrared (FTIR) spectroscopy has been used as a modern analytical tool to elucidate the structure of urea-formaldehyde (UF) resins.
Abstract: Fourier transform infrared (FTIR) spectroscopy has been used as a modern analytical tool to elucidate the structure of urea—formaldehyde (UF) resins. Several low molecular weight condensation products of urea and formaldehyde were synthesized and characterized. Structural differences were observed for prepolymers prepared in alkaline and acidic media. Plausible mechanistic routes are proposed to explain the prepolymer structural differences prepared in different experimental conditions. The structural elucidation of the UF resins is considerably increased and improved by using absorbance magnification to further enhance the observed signals.
88 citations
01 Nov 1988
TL;DR: The adsorbate formed during ethanol oxidation in acidic solutions is studied by Fourier transform infrared reflection-absorption spectroscopy (FTIR) at constant potential, on-line (DEMS) and thermal desorption mass spectrograms (ECTDMS).
Abstract: The adsorbate formed during ethanol oxidation in acidic solutions is studied by Fourier transform infrared reflection-absorption spectroscopy (FTIR) at constant potential, on-line (DEMS) and thermal desorption mass spectroscopy (ECTDMS). – As in the case of methanol adsorbate COad was identified by FTIR and in addition COHad by ECTDMS. On-line MS experiments showed the formation of methane during the cathodic sweep of the voltammogram. Main products of ethanol oxidation from the bulk are carbon dioxide and acetaldehyde.
77 citations
TL;DR: In this article, surface-enhanced Raman spectra of pyridine on copper and gold electrodes in the near-infrared were obtained with a Fourier transform Raman Spectrometer.
Abstract: Surface-enhanced Raman spectra of pyridine on copper and gold electrodes in the near-infrared were obtained with a Fourier transform Raman spectrometer. Surface-enhanced Raman spectra were observed for pyridine adsorbed on copper and gold electrodes while a Nd:YAG laser (1.064 μm) was used for excitation. Good-quality spectra were recorded for 0.08 mM pyridine on a copper electrode with a single oxidation-reduction cycle, whereas for a gold electrode, several ORCs were necessary. A very intense low-energy Raman band was observed on both metals at positive potentials, which may be due to a metal-oxide vibrational mode.
TL;DR: In this article, the Kitt Peak Fourier transform spectrometer was used to record the infrared emission spectrum of the Rydberg molecule XeH in a hollow cathode discharge of 2·2 torr H2 and 0·1 torr Xe.
Abstract: The infrared emission spectrum of the Rydberg molecule XeH was recorded with the Kitt Peak Fourier transform spectrometer. XeH was made in a hollow cathode discharge of 2·2 torr H2 and 0·1 torr Xe. The 0-0 bands of the C 2Π-B 2Σ+ and the D 2Σ+-C 2Π transitions were observed near 3250 cm−1 and 4420 cm−1, respectively. A rotational analysis provides spectroscopic constants for these states.
TL;DR: In this paper, the interface of a two-dimensional computer-controlled stepper-motor-driven microscope stage with an infrared microspectroscopy system is explained in terms of its usefulness in performing microscopic imaging.
Abstract: The interface of a two-dimensional computer-controlled stepper-motor-driven microscope stage with an infrared microspectroscopy system is explained in terms of its usefulness in performing microscopic imaging. Images are obtained by reducing spatially specific infrared spectra to functional group maps. The maps are constructed at a given infrared absorption frequency and are a function of the intensity versus × and y spatial coordinates. The use of the technique is demonstrated through two examples of polymer characterization. Transmittance infrared spectra reduced to five images based on absorptions at 1735, 1241, 1016 (ester functionalities), 1892 (crystalline band), and 908 (vinyl unsaturation) cm−1 show that a polyethylene film contains an inclusion of an acetate-containing material. Reflectance infrared spectra reduced to an image based on a ratio of the absorptions at 1738 cm−1 (ester carbonyl) and 1705 cm−1 (acid carbonyl) show that the streak in a film of an ethylene-acrylic acid/ethylene-methacrylate copolymer blend on aluminum foil contains more of the ester component of the blend.
TL;DR: Amorphous calcium-magnesium phosphates were prepared by precipitation from moderately supersaturated aqueous solutions at pH 7.5 and showed that up to 50% of the phosphate ions were protonated, the proportion increasing with the magnesium to calcium ion activity ratio in the solution as mentioned in this paper.
TL;DR: FTIR spectra of alamethicin have been obtained in KBr disk, methanol and in aqueous lipid dispersion (above and below the lipid phase transition) and a comparison of the spectra with that obtained with bacteriorhodopsin shows spectral similarities, e.g. the presence of a high-frequency amide I maximum at 1661-1663 cm- 1 and shoulders near 1640 cm-1 and 1620cm-1.
01 Jan 1988
TL;DR: In this article, the Fourier Transform Infrared Infrared (FT-IR) spectrometer has been extended to include measurements on particles, as well as gases and soot particles.
Abstract: An infrared emission/transmission (E/T) technique, (a method previously used as an in-situ diagnostic for gases and soot particles using dispersive infrared) has been implemented with a Fourier Transform Infrared Infrared (FT-IR) spectrometer and extended to include measurements on particles, as well as gases (CO2, H2O, ethylene, methane, butane, and acetylene) and soot particles. The method can measure both the concentration and temperature of each of the phases. This paper presents the applications of FT-IR E/T spectroscopy to gases and soot particles in reacting flows. Several examples are presented including a coannular laminar ethylene diffusion flame. The results for soot particle temperature and concentration in this flame are in good agreement with measurements reported by other investigators.
TL;DR: In this paper, the effect of surface-adsorbed water and postreaction curing temperature on relative surface silane concentration and extent of methoxy group hydrolysis was investigated.
TL;DR: In this article, an external reflection Fourier transform infrared spectroscopy was applied to the in situ measurement of the infrared spectra of insoluble phospholipid monolayer films that were spread at the air/water interface.
Abstract: External reflection Fourier transform infrared spectroscopy has been applied to the in situ measurement of the infrared spectra of insoluble phospholipid monolayer films that were spread at the air/water interface. The spreading conditions for the phospholipids [1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)] were chosen to mimic those of liquid-condensed and liquid-expanded surface films, respectively. It is shown that the infrared reflection spectra can identify vibrations due to the hydrocarbon acyl chains, carbonyl ester, and phosphate groups for these monolayer films on water. Detailed examination of the frequencies and polarization properties of the C-H stretching region shows that the liquid-condensed DSPC acyl chains are in a rigid, mostly all-trans configuration, while the liquid-expanded DMPC acyl chains are highly fluid. The spectra demonstrate that the external reflection FT-IR experiment can differentiate between the physical conformation of monomolecular films when water is used as a reflective substrate.
TL;DR: In this article, a commercial Fourier transform infrared (FT-IR) spectrometer was modified for remote near-IR Raman spectroscopy, where a single optical fiber was used to guide the excitation light to the specimen and to collect scattered light from the specimen.
Abstract: A commercial Fourier transform infrared (FT-IR) spectrometer was modified for remote near-IR Raman spectroscopy. In one configuration, a single optical fiber was used to guide the excitation light to the specimen and to collect scattered light from the specimen. In an alternative configuration, separate fibers were used for excitation and collection. The optical fiber probes were used to record the Raman spectra of both liquid and solid specimens. The Raman scattering of the optical fibers interfered with the analyte signal. This fiber interference was affected by the optical properties of the specimen and the optical sampling configuration. These interferences were partially removed by subtracting a background spectrum. Potential applications and improvements are discussed.
TL;DR: In this paper, the pure rotational spectrum of s -trans-1,3-butadiene 1,1-d 2 has been observed with a pulsed microwave Fourier transform spectrometer between 12 and 18 GHz.
TL;DR: In this paper, the adsorption of NO on Ni(111) at 85 K has been studied by Fourier transform infrared spectroscopy, and two NO stretching modes are observed, typically at 1508 and 1543 cm −1.
TL;DR: In this article, the design of a spectrometer for the observation of infrared vibrational circular dichroism (VCD) is reported. This instrument utilizes f/4 aperture, a minimum of optical elements, and a new electronic data acquisition method to improve the sensitivity of previous dispersive units.
Abstract: The design of a spectrometer for the observation of infrared vibrational circular dichroism (VCD) is reported. This instrument utilizes f/4 aperture, a minimum of optical elements, and a new electronic data acquisition method to improve the sensitivity of previous dispersive units. The instrument described exhibits a level of sensitivity comparable to that of present Fourier transform (FT) VCD instruments, while avoiding some problems which still persist in FT-VCD.
TL;DR: In this paper, a Fourier transform infrared (FTIR) isotopic matrix study of the C2H3 vinyl radical produced by the vacuum UV photolysis of ethylene has been carried out in the midinfrared from 250 to 4800 cm−1.
Abstract: A Fourier transform infrared (FTIR) isotopic matrix study of the C2H3 vinyl radical produced by the vacuum UV photolysis of ethylene has been carried out in the midinfrared from 250 to 4800 cm−1. A variety of carbon‐13 and deuterium substituted ethylene parent molecules were used to form various isotopomers of C2H3. On the basis of its isotopic behavior and by comparison with Dupuis and Wendoloski’s GVB ab initio calculations, an absorption at 900 cm−1 has been assigned to the ν7, out‐of‐plane bending mode of C2H3. The following values for ν7 have been obtained for vinyl isotopomers: 887 cm−1 for 12CH2=12CD; 797 cm−1 for 12CD2=12CH; 704 cm−1 for 12CD2=12CD; 889 cm−1 for 13CH2=12CH; 895 cm−1 for 12CH2=13CH; and 894 cm−1 for 13CH2=13CH.
TL;DR: In this article, a Fourier transform infrared spectroscopic study of Sphagnum peat, Carex peat and mixtures of these peat types is reported, where intensity values from selected wavenumber regions of the infrared spectra were correlated with calorific value, degree of decomposition, carbon, and nitrogen content, and content of amino acids and amino sugars, with the use of the method of partial least squares modelling with latent variables.
Abstract: A Fourier transform infrared spectroscopic study of Sphagnum peat, Carex peat, and mixtures of these peat types is reported. Intensity values from selected wavenumber regions of the infrared spectra were correlated with calorific value, degree of decomposition, carbon, and nitrogen content, and content of amino acids and amino sugars, with the use of the method of partial least-squares modelling with latent variables (PLS). The application of this method is shown to give valuable information about properties of peat which have no easily measured quantitative relationship to the infrared spectrum.
LGC1
TL;DR: Using Fourier transform infrared spectroscopy, it is shown that the fully hardened cement is bonded predominantly by zinc carboxylate complexes, rather than by associations of purely ionic character as had previously been supposed.
Abstract: The formation and structure of zinc polyacrylate has been studied by Fourier transform infrared spectroscopy (FTIR). Using this technique we have shown that the fully hardened cement is bonded predominantly by zinc carboxylate complexes, rather than by associations of purely ionic character as had previously been supposed. Ionic bonds are formed in the initial stages of the reaction but are gradually converted to complex forms. This bond rearrangement appears partly responsible for physical changes that occur during gelation, setting, and hardening.
TL;DR: In this article, Fourier transform infrared (FT-IR) spectra of an α-gliadin protein fraction from wheat endosperm were analyzed in terms of secondary structure and conformation.
TL;DR: In this article, fine-particle (3,mu,m) aerosol sample organics were characterized in terms of their molecular functionalities, to quantify chemical classes, and the derived weight yields account for a substantial part of the organic fineparticle aerosol.
Abstract: Complete analysis of urban aerosol samples has been difficult because of the complexity of the organic portion. Previous techniques have seldom accounted for more than a few percent of the total mass of the organic matter because they determine individual components, of which there are hundreds in urban aerosol. We have instead characterized fine-particle (<3 ..mu..m) aerosol sample organics in terms of their molecular functionalities, to quantify chemical classes. Aerosol extracts were fractionated by liquid adsorption chromatography (LC) and high-performance liquid chromatography (HPLC). Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) using a diamond powder matrix was applied to the HPLC subfractions on non-hydrocarbon polar fractions. Calibration was carried out with mixtures of reference compounds. The derived weight yields account for a substantial part (from 17% to 100% for various LC fractions) of the organic fine-particle aerosol.
TL;DR: Difference spectra showed that the largest differences were observed between confluent cells and cells in early growth stages, which may reflect cell morphological changes, biochemical activity, and degree of ATR crystal exposure to the bulk medium.
TL;DR: In this paper, the rotational temperature and dissociation information of N2 O in a radio-frequency (RF) glow discharge were estimated based on analysis of P branch rotational lines of the 2ν1 harmonic and ν1 +ν3 combination band of the molecule.
Abstract: The technique of in situ Fourier transform infrared (FTIR) absorption spectroscopy has been used to determine rotational temperatures and the extent of dissociation of N2 O in a radio‐frequency (rf) glow discharge. Measurements were made at 0.65 cm−1 resolution on 13.56‐MHz plasmas at 500 mTorr, with an input flowrate of 40 sccm, and powers of 10 and 30 W. Temperature and dissociation information estimates are based upon analysis of P branch rotational lines of the 2ν1 harmonic and ν1 +ν3 combination band of the molecule. Line intensities are corrected for instrument‐induced distortion. Under the conditions investigated, rotational temperatures are between 335 and 420 K, and dissociation ranges from 45% to 75%. Both rotational temperature and dissociation increase with rf power.