Showing papers on "Fourier transform infrared spectroscopy published in 1986"
TL;DR: This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy, which provides several advantages over conventional dispersive techniques: higher resolution, sensitivity, signal-to-noise ratio (S/N), and frequency accuracy.
Abstract: Publisher Summary This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy. Infrared spectroscopy constitutes one of the oldest methods for studying the secondary structure of polypeptides and proteins. Polypeptides and proteins exhibit a total of nine characteristic absorption bands in the infrared region. These are usually termed the amide A, B, and amide I-VII bands. The amide I (∼1630-1690 cm -1 ) band is the most useful for protein structure studies by infrared spectroscopy. The use of Fourier transform infrared spectroscopy (FTIR) has led to major improvements in this regard. In principle, FTIR provides several advantages over conventional dispersive techniques: higher (1) resolution, (2) sensitivity, (3) signal-to-noise ratio (S/N), and (4) frequency accuracy. Any one of the first three advantages can be emphasized at the expense of the other two. For protein structure studies, high sensitivity makes it possible to acquire usable infrared spectra of aqueous solutions; such spectra are always notoriously difficult to obtain.
698 citations
TL;DR: In this paper, the authors investigated the temperature evolution of the structure of silica thin films by Fourier Transform Infrared (FTIR) Spectroscopy and found that the removal of water from the pores and gel surface is easier when the gels are prepared in basic conditions.
Abstract: In this work we investigated the temperature evolution of the structure of silica thin films by Fourier Transform Infrared (FTIR) Spectroscopy. The gels, prepared by hydrolysis and polycondensation in the presence of an excess of water to tetramethoxysilane, were thin enough to be studied in transmission. It was found that the removal of water from the pores and gel surface is easier when the gels are prepared in basic conditions. During the drying heat treatment, residual methanol oxidizes and produces formaldehyde, formic acid and formates. These species are still present in the gel at 300 °C.
184 citations
TL;DR: The results show that it is necessary to be cautious in making band assignments based on exchange methods unless the extent of exchange is known, and the combination of Fourier transform infrared spectroscopy and hydrogen-deuterium exchange is a powerful technique for revealing small differences in protein secondary structure.
127 citations
TL;DR: In this paper, the influence of reaction conditions of the silylation and the effect of subsequent heat treatment and water addition were studied, and the resulting differences shed new light on the combined effects of reaction condition and silica surface structures on the course of the reactions.
110 citations
TL;DR: In this article, the melting behavior of poly(aryl-ether-etherketone) was investigated using Fourier transform infra-red (FTir) spectroscopy and differential scanning calorimetry (d.s.c.) as part of a study of a carbon fibre reinforced PEEK composite.
99 citations
TL;DR: In this paper, a quantitative evaluation of the IR spectra was in the focus of interest, where the spectra were baseline corrected in the fingerprint region and standardized in such a way that the absorption of the dominant band equalled 1.0 using the y-axis expansion algorithm.
Abstract: FTIR spectra were recorded from 44 extremely different DHP's prepared by continuous and discontinuous dehydrogenation methods. A quantitative evaluation of the IR spectra was in the focus of interest. The spectra were baseline corrected in the finger-print region and standardized in such a way that the absorption of the dominant band equalled 1.0 using the y-axis expansion algorithm of the spectrometer. Intensities of 14 bands were measured applying the baseline method. Then the absorption values were related to the intensity of the band close to 1500 cm\"\" äs it were an internal Standard. In that way an IR data set consisting of 44 X 14 numerical values was created. Hf G, and S units (in mol%) of the DHP's and their O/C^ and OMe/C^o values were determined. Each of these five analytical data sets were separately regressed against the IR data set using multiple regression analysis. Thus multiple prediction (regression) equations were obtained for analytical (experimental) data on the basis of the IR data set. The results show that analytical data can be calculated from the IR spectra with high accuracy giving high multiple regression coefficients around 0.99 and consequently low Standard deviations. The relevance of the correlation equations obtained to lignin chemistry and lignin classification is discussed. y
93 citations
TL;DR: Ion-binding ligands and the conformations of some of the acidic matrix macromolecules present in the shells of a gastroped, a bivalve, and a cephalopod, are investigated in vitro by Fourier transform infrared spectroscopy.
Abstract: Ion-binding ligands and the conformations of some of the acidic matrix macromolecules present in the shells of a gastroped, a bivalve, and a cephalopod, are investigated in vitro by Fourier transform infrared spectroscopy. The complex assemblage of matrix constituents present in the EDTA-soluble fraction is first separated into two quite different classes of macromolecules by a reversed-phase chromatographic procedure. Infrared spectra indicate that the constituents of one class, which are proteins rich in aspartic acid, adopt the β-sheet conformation upon binding calcium to the protein carboxylate groups. The second class of matrix constituents contains proteins rich in serine that appear to be associated with relatively large amounts of polysaccharide. They also bind calcium and upon doing so undergo a conformational change.
83 citations
TL;DR: In this article, neutral oxide columns which are structurally similar to γ-alumina were introduced into sheet aluminosilicate to monitor changes in structure of the host matrix following the introduction of the pillars.
Abstract: Variable-temperature powder X-ray diffractometry, Fourier-transform infrared spectroscopy and 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy have been used to elucidate both the nature of alumina pillars introduced into sheet aluminosilicate and to monitor changes in structure of the host matrix following the introduction of the pillars. The pillars are neutral oxide columns which are structurally similar to γ-alumina; they are linked through oxygen to aluminium and magnesium atoms within the octahedral layer of the clay sheet. The layer charge of the clay is balanced by protons, released during calcination, residing in the aluminosilicate structure.
81 citations
TL;DR: Polarized, low-temperature Fourier transform infrared (FTIR) difference spectroscopy has been used to investigate the structure of bacteriorhodopsin as it undergoes phototransitions from the light-adapted state, bR570, to the K630 and M412 intermediates.
Abstract: Polarized, low-temperature Fourier transform infrared (FTIR) difference spectroscopy has been used to investigate the structure of bacteriorhodopsin (bR) as it undergoes phototransitions from the light-adapted state, bR570, to the K630 and M412 intermediates. The orientations of specific retinal chromophore and protein groups relative to the membrane plane were calculated from the linear dichroism of the infrared bands, which correspond to the vibrational modes of those groups. The linear dichroism of the chromophore C=C and C-C stretching modes indicates that the long axis of the polyene chain is oriented at 20-25 degrees from the membrane plane at 250 K and that it orients more in-plane when the temperature is reduced to 81 K. The polyene plane is found to be approximately perpendicular to the membrane plane from the linear dichroism calculations of the HOOP (hydrogen out-of-plane) wags. The orientation of the transition dipole moments of chromophore vibrations in the K630 and M412 intermediates has been probed, and the dipole moment direction of the C=O bond of an aspartic acid that is protonated in the bR570----M412 transition has been measured.
80 citations
TL;DR: In this paper, the surface properties of a largely amorphous Si 3 N 4 sample prepared by nitridation with ammonia of amorphized silica at 1300°C have been studied by Fourier Transform Infrared Spectroscopy using adsorbed molecules such as water, benzene, acetonitrile, acetone, ammonia, triethylamine, chloroform, formic acid and methanol.
77 citations
TL;DR: In this paper, the IR spectra of the monomers and homopolymers of glycidyl azide (GAP), 3-azidomethyl-3-methyloxetane (AMMO), 3,3-bis(azidmethyl)oxetanes (BAMO), and 3-(2,3)-diazidopropoxymethyl)-3-moxy-mixture (DAPMMO) were assigned, and 10 scans s−1 were used to characterize the slow (5K min−1) and rapid
TL;DR: In this paper, Fourier transform infrared spectroscopy using internal reflectance elements was used to determine the degree of environmental aging of Hercules 3501−6 resins, and the results indicated that degradation occurs via hydrolysis, oxidation, and dehydration reactions at specific locations in the polymer chain.
Abstract: With the increased use of graphite-reinforced composites as replacements for metals has come concerns about durability under harsh environmental conditions. Degradation is expected to begin on the surface and progress toward the center of the resin as a function of time, and reflectance infrared techniques are ideal for monitoring structural changes on surfaces. The present paper describes the application of Fourier transform infrared spectroscopy using internal reflectance elements to the determination of the degree of environmental aging of Hercules 3501−6 resin. The results indicate that degradation occurs via hydrolysis, oxidation, and dehydration reactions at specific locations in the polymer chain. Of special interest is the unique reaction of the tertiary amine of the epoxy portion of the molecule.
TL;DR: In this article, the use of optical fibers in an attenuated total reflectance type cell with an FTIR spectrometer was demonstrated for the first time, and the spectra of acetone in water and of glycine in water were acquired with the cell.
Abstract: Silver halide (AgCl:AgBr) fibers were used as the light conductor for total internal reflection measurements in a Fourier transform infrared (FTIR) spectrometer, to obtain spectra of aqueous solutions. The use of optical fibers in an attenuated total reflectance type cell with an FTIR spectrometer was demonstrated for the first time. Spectra of acetone in water and of glycine in water were acquired with the cell.
TL;DR: In this paper, the authors investigated the usefulness of Fourier transform infrared (FT-IR) spectroscopy coupled with attenuated total reflection (ATR) optics as a method for monitoring blood-surface interactions.
TL;DR: In situ Fourier transform infrared spectroscopy was used to study the reduction of NO by H 2 on Au SiO 2 and Au MgO catalysts in this paper, and large differences in selectivity toward NO formation had been found depending on the nature of the support.
TL;DR: Infrared data suggest that the two phosphate groups of cardiolipin are conformationally non-identical when incorporated into a lipid bilayer, and controlled enzyme hydrolysis may help in the study of these complex phospholipid headgroups.
Abstract: The phosphate region (1000–1300 cm–1) of the infrared spectrum of aqueous phospholipid dispersions has been studied by the infrared Fourier transform technique. The main features of this spectral region have been described for various phospholipids, including phosphatidylcholine, phosphatidylethanolamine, cardiolipin and phosphatidylglycerophosphate (alkyl ether), the major phospholipid of Halobacterium purple membranes. No changes in the phosphate region are observed due to lipid polymorphism or as a consequence of changes in fatty acyl chain structure. Shifts in the phosphoryl stretching bands are interpreted in terms of changes in hydrogen bonding, while a contribution from R—O—P vibration is considered to reflect changes in phospholipid headgroup conformation. When added in equimolar amounts to phosphatidylcholine or phosphatidylethanolamine bilayers, surfactants (Triton X-100, sodium cholate) modify the degree of hydration and/or the orientation of the headgroup with respect to the bilayer plane. Phospholipids containing two phosphate groups give rise to more complex spectral features. Infrared data suggest that the two phosphate groups of cardiolipin are conformationally non-identical when incorporated into a lipid bilayer. Controlled enzyme hydrolysis (e.g. with phospholipase D) may help in the study of these complex phospholipid headgroups.
TL;DR: In this paper, the first time the primary reaction in green plant photosynthesis has been applied to difference spectroscopy, the spectral range investigated (between 1800 and 1000 cm−1) is tentatively attributed to changes in intensity and position of the keto and ester carbonyl vibrations of the chlorophyll or Pheo molecule(s) involved.
TL;DR: In this paper, the composition and mechanical properties of siliconoxynitride layers made by plasmaenhanced deposition, using different gas mixtures, were determined by means of Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscope (FTIR), Auger electron spectroscopic (AES), and refractive index measurements.
Abstract: We have studied the composition and mechanical properties of silicon‐oxynitride layers made by plasma‐enhanced deposition, using different gas mixtures. The composition of the as‐deposited layers was determined by means of Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR), Auger electron spectroscopy (AES), and refractive index measurements. FTIR spectra reveal the presence of Si‐H, N‐H, Si‐N, and Si‐O bonds. On the basis of the RBS and the IR data, it is concluded that all oxygen is incorporated as Si‐O‐Si groups in the films. This is confirmed by the absence of an O‐H absorption band in the IR spectra around 3620 cm−1. The mechanical stress and the etch rate in buffered HF of plasma oxynitride layers strongly depend on the amount of oxygen and hydrogen incorporated in the layer. With increasing oxygen content, the mechanical stress decreases and the etch rate increases. Heat‐treatment at temperatures higher than the deposition temperature leads to a densification of the film due to hydrogen desorption and cross‐linking.
TL;DR: The current status of reflection-absorption infrared spectroscopy (RAIRS) is reviewed with examples illustrating its application to studies of structural chemical transformations at surfaces in this article, and the prospects for the future are briefly discussed including the use of synchrotron and laser i.r. sources.
TL;DR: The experimental conditions for the microwave Fourier transform spectroscopy are given in this paper, where a typical set up of a spectrometer is presented and discussed, as well as possible extensions to the set up.
Abstract: After an introduction to the interaction of a microwave field and an ensemble of dipolar molecules the experimental conditions for the microwave Fourier transform spectroscopy are given. Specifications are derived for a spectrometer. A typical set up of a spectrometer is presented and discussed. The application to rotational spectroscopy of stable molecules is demonstrated by some examples. Possibilities for extension are mentioned.
TL;DR: In this article, it was shown that PVF2 films over PET change the thermal diffusion length such that the sample PVF 2 on PET becomes optically transparent and thermally thick.
Abstract: Photoacoustic Fourier transform infrared spectroscopy (PA/FT-IR) is used to study films of poly(vinylidine fluoride) (PVF2) and poly(ethylene terephthalate) (PET). It is shown that PVF2 films over PET change the thermal diffusion length such that the sample PVF2-on-PET becomes optically transparent and thermally thick. By changing the mirror velocity of the Michelson interferometer it is possible to obtain spectra at various sample depths. The intensity of the carbonyl band of the lower PET film changes as a function of the mirror velocity. The log-log plot of these quantities gives a slope of −3/2, which agrees with theoretical predictions for thermally thick and optically transparent samples.
TL;DR: In this paper, the surface acidity of several metathesis catalysts, Re2O7/Al2O3, Mx Oy·Re2O 7/Al 2O3(Mx Oy= V2O5, MoO3 or WO3), have been studied in situ by Fourier transform infrared spectroscopy using pyridine adsorption.
Abstract: Surface acidity of several metathesis catalysts, Re2O7/Al2O3, Mx Oy·Re2O7/Al2O3(Mx Oy= V2O5, MoO3 or WO3) and Re2O7/SiO2·Al2O3, have been studied in situ by Fourier transform infrared spectroscopy using pyridine adsorption. A distinct correlation has been found between the activity for metathesis and Bronsted acidity of the catalysts, while their Lewis acidity showed no correlation with the activity.
TL;DR: In this article, the surface properties of colloidal α-, β- and γ-ferric oxide hydroxides [Fe(O)OH], which were synthesized and aged in this laboratory, have been studied.
Abstract: Fourier-transform infrared spectra and surface properties of colloidal α-, β- and γ-ferric oxide hydroxides [Fe(O)OH], which were synthesized and aged in this laboratory, have been studied. The spectrum of the α phase has a strong absorption band at 3150 cm–1 and two weak ones at 3485 and 3661 cm–1. That of the β phase has a strong band at 3480 cm–1, a weak band at 3659 cm–1 and two very weak bands at 3686 and 3723 cm–1. That of the γ phase has a strong band at 3160 cm–1, a weak band at 3624 cm–1 and a very weak band at 3528 cm–1. The changes of these bands by the adsorption of heavy water, water and methyl iodide molecules and cupric ions have been studied in detail and the various bands were assigned to various OH groups with respect to the crystal structures of these materials.
TL;DR: In this article, the Fourier transform infrared (FTIR) difference spectroscopy was used to study the light-induced reduction of the intermediary electron acceptor I (bacteriopheophytin, BPh) in bacterial photosynthesis.
Abstract: — Molecular changes associated with the light-induced reduction of the intermediary electron acceptor I (bacteriopheophytin, BPh) in bacterial photosynthesis were studied by means of Fourier transform infrared (FTIR) difference spectroscopy. Chromatophore membranes and reconstituted reaction centers (RCs) of Rhodopseudomonas viridis were prereduced with sodium dithionite and illuminated in order to trap photochemically the state I−. Fourier transform infrared spectra of these samples were recorded before, during and after illumination, with an accuracy better than 10−3 absorbance units. Difference spectra of I− in chromatophores and in RCs closely correspond to each other. In the carbonyl stretching frequency region between 1640 and 1750 cm−1, bands are tentatively attributed to a shift (from 1713 to 1683 cm−1) of a keto carbonyl group, a change of an acetyl carbonyl grou at 1656 cm−1 and a decrease in absorbance strength of ester carbonyl groups (at 1746 and 1732 cm−P) after reduction of I. These groups likely belong to the BPh molecule, although at least one of the ester carbonyls could be assigned to an amino acid side chain. The absence of strong bands in the amide I and amide II region excludes large protein conformational changes associated with I reduction.
TL;DR: In this paper, the reaction of red phosphorus with poly(methyl methacrylate) under pyrolysis conditions was investigated with a number of physical techniques, including atatic PMMA and isotactic PMMA.
Abstract: The reaction of red phosphorus with poly(methyl methacrylate) under pyrolysis conditions was investigated with a number of physical techniques. A random methyl methacrylate/cyclic anhydride copolymer is formed from atatic PMMA, whereas a random methyl methacrylate/methacrylic acid copolymer is obtained with isotactic PMMA. The backbones of both these copolymers are more stable toward depolymerization than that of PMMA. The flame-retardant activity of red phosphorus with PMMA may arise in part from stabilization of the polymer toward depolymerization via modification of the sidechains.
TL;DR: In this article, Fourier deconvolution and second-derivative spectroscopy have been used to enhance the resolution of infrared spectra of humic acid (HA) extracted from dried municipal waste.
Abstract: Fourier deconvolution and second-derivative spectroscopy have been used to enhance the resolution of infrared spectra of humic acid (HA) extracted from dried municipal waste. The results demonstrate the extent to which the use of such resolution enhancement techniques can disclose new valuable information concerning the composition of complex heterogeneous samples. The findings are in good agreement with previously obtained solid-state NMR results.
TL;DR: In this paper, Fourier transform infrared (F.t.m.i.r.) spectra were obtained for Na +, K + and Cs + forms of iota and kappa carrageenan in water and D 2 O.
TL;DR: In this article, the photodegradation of three types of polyethylene has been studied by electron spin resonance (ESR), ultraviolet absorption (UV), Fourier transform infrared absorption (FTIR), gel fraction and mechanical properties measurements.
TL;DR: In this article, the authors used Diffuse reflectance Fourier transform infrared spectroscopy (DFTIR) to detect absorbed water hydrogen-bonded to Kevlar-49® fibers.
Abstract: Diffuse reflectance Fourier transform infrared spectroscopy has been used in order to detect absorbed water hydrogen-bonded to Kevlar-49® fibers. Varying amounts of KBr overlayers were used on the top of each sample in order to increase the surface selectivity of the technique. Three different O-H stretching vibrations of absorbed water were detected in the fibers exposed to saturated water-vapor atmosphere. Two peaks at 3640 and 3560 cm−1 are attributed to absorbed water that is weakly hydrogen-bonded to amide groups of the polymer. A broad absorption around 3450 cm−1 is characteristic of liquid-like water clustered in microvoids and other sites inside the fibers. The spectra of dried Kevlar-49® fibers show an unbonded amide N-H stretching peak at 3431 cm−1, indicative of regions with less perfect chain packing. At least part of these groups hydrogen-bond with absorbed water, depending on their availability.