Infrared Peak Research Articles

Effect of moisture content on solid-state interaction at the interface between magnesium stearate and captopril

A grinding process was used to accelerate the solid-state interaction at the interface between magnesium stearate (MgSt) and captopril (CAP) in the presence or absence of water. The 110 °C-preheated MgSt/CAP or MgSt/CAP ground mixture showed a 5.06% (w/w) or 6.07% (w/w) water content, respectively, which was >4.29% (w/w) for the original MgSt alone. The increased water content in each ground mixture was due to the atmospheric absorption of water caused by grinding. A small infrared (IR) peak at 1562 cm −1 appeared in the IR spectrum of the 110 °C-preheated MgSt/CAP ground mixture, whereas a stronger IR peak at 1541 cm −1 with a shoulder at 1556 cm −1 was observed for the MgSt/CAP ground mixture. These IR peaks were possibly related to the solid-state interaction at the interface between MgSt and CAP via hydrogen bonding of adsorbed water. However, an excess of water added in the MgSt/CAP ground mixture could exacerbate the solid-state interaction of MgSt and CAP to form a stearic acid as evidenced by the IR peak at 1705 cm −1. This may be due to the neutralization between basic MgSt and acidic CAP. In addition, thermal Fourier transform infrared (FTIR) microspectroscopy also confirmed that the thermal-dependent dehydration process might alter the IR peak intensity of MgSt/CAP ground mixtures.

Effects of Temperature and Pressure on ZDDP

A recent theoretical study proposed that the anti-wear property of zinc dialkyl dithio phosphate (ZDDP) is due to the formation of chemically connected networks as a result of pressure-induced cross-linkage of phosphate groups of thermally decomposed ZDDP. To investigate the initial decomposition processes and the possibility of linking of phosphate groups in the decomposed product, in-situ high-pressure and high-temperature infrared (IR) spectroscopy using synchrotron radiation were performed on the original ZDDP. At room temperature no substantial structural change was observed up to 21.2 GPa, a pressure far exceeding the predicted onset of a structural transformation for the model zinc phosphate at 7 GPa. The observed Pressure induced broadening of the IR peaks is most likely associated with structural disorder or amorphization of ZDDP which is completely reversible upon decompression. When ZDDP is heated under pressure, an irreversible transformation was observed around 225 °C and 18.4 GPa. The experimental results show that ZDDP undergoes substantial decomposition at high pressures and high temperatures but no hint of cross-linkage of phosphate groups was found.

IR-spectroscopic studies of hydrogen-bonding solutions: Lineshape analysis of ethanol + hexane system

IR (infrared) line shapes of OH stretching bands in hydrogen-bonding states of ethanol–hexane solutions have been examined using a theoretically rigorous Voigt function, instead of the commonly used empirical Lorentz–Gauss equation. An efficient and numerically-stable computer code with the Voigt function has been developed in order to analyze hydrogen-bonding effects in IR absorption spectra. Although the Voigt function is not an analytically-closed form, a numerical computer subroutine, with only three adjustable parameters for each IR band (or peak), provides a unique solution in a least-squares analysis of the line shapes. On the other hand, the Lorentz–Gauss equation is an analytical function with four adjustable parameters for each IR peak. However, this function makes non-linear least-squares analyses almost impossible due to the existence of strong correlations among the parameters. Example analyses, using the ethanol–hexane system, are given. The degree of hydrogen-bonding associations of ethanol and an effective IR-absorbance coefficient for hydrogen-bonded clusters have been estimated, and results are quite reasonable, compared with those in the literature.

Effects of UV photon irradiation on SiO x (0 < x < 2) structural properties

Thin films of a-SiO x (0 < x < 2) were prepared by reactive r.f. magnetron sputtering from a polycrystalline-silicon target in an Ar/O 2 gas mixture. The oxygen partial pressure in the deposition chamber was varied so as to obtain films with different values of x. The plasma was monitored, during depositions, by optical emission spectroscopy (OES) system. Energy dispersive X-ray (EDX) measurements and infra-red (IR) spectroscopy were used to study the compositional and structural properties of the deposited layers. Structural modifications of SiO x thin films have been induced by UV photons’ bombardment (wavelength of 248 nm) using a pulsed laser. IR spectroscopy and X-ray photoemission spectroscopy (XPS) were used to investigate the structural changes as a function of x value and incident energy. SiO x phase separation by spinodal decomposition was revealed. The IR peak position shifted towards high wavenumber values when the laser energy is increased. Values corresponding to the SiO 2 material (only Si 4+) have been found for laser irradiated samples, independently on the original x value. The phase separation process has a threshold energy that is in agreement with theoretical values calculated for the dissociation energy of the investigated material. For high values of the laser energy, crystalline silicon embedded in oxygen-rich silicon oxide was revealed by Raman spectroscopy.

Effect of through-space electron transfer on infrared spectrum of amorphous selenium

In this paper we present theoretical analyses on an infrared (IR) spectrum of amorphous selenium. The system is described by a 216-atom-chain model, and a set of molecular-dynamics simulations is performed to generate vitreous structures and vibrational modes. To describe an electronic structure of the system we employ a complete neglect of differential overlap model parametrized by ab initio cluster calculations. An IR intensity is evaluated with the Berry-phase formula for an electronic polarization. The effect of the through-space electron transfer on the IR spectrum is studied by artificially changing the magnitude of matrix elements associated with the electron transfer between nonbonded atoms in the chain. We find that the through-space electron transfer leads to (i) the enhancement of the bending IR peak at 135 cm(-1) and (ii) the appearance of a new low-frequency peak around 50 cm(-1), thus resulting in a good agreement with the experiment. The mechanism is discussed by a simple dipole model.

Electrochemical Synthesis, Crystal Structure, and Photomagnetic Properties of a Three‐Dimensional Cyano‐Bridged Copper—Molybdenum Complex.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Infrared (IR) investigation of the structural changes of silica glasses with fictive temperature

Effects of fictive temperatures on the structure of silica glass were investigated using infrared (IR) spectroscopy. From the IR peak positions of the three fundamental structural bands (asymmetric stretching, bending, and rocking vibrations), the average values of the silica structural parameters – central force constant, α, non-central force constant, β, and Si–O–Si bond angle, θ – were obtained. It was found that the Si–O–Si bond angle and the non-central force constant decreased, while the central force constant increased with increasing fictive temperature.

Electrochemical Synthesis, Crystal Structure, and Photomagnetic Properties of a Three-Dimensional Cyano-Bridged Copper−Molybdenum Complex

A single crystal of Cs(I)2Cu(II)7[Mo(IV)CN8]4.6H2O was electrochemically prepared on a Pt wire electrode with a constant potential of +500 mV vs Ag/AgCl electrode. X-ray single-crystal structural analysis showed that this compound consists of a three-dimensional cyano-bridged Cu-Mo bimetallic assembly with a tetragonal structure of I4/mmm. The coordination geometry of Mo(IV) is bicapped trigonal prism, and that of Cu(II) is five-coordinate of square pyramidal or four-coordinate of square planar. This compound was also prepared as a 0.2-3.0 microm thick film on a SnO2-coated glass in the same electrochemical manner. When the sample, which shows paramagnetism due to Cu(II) (S = 1/2), was irradiated with 450-500 nm light at 5 K, spontaneous magnetization with a Curie temperature of 23 K was observed. This photoinduced change was recovered by a thermal treatment. In the infrared (IR) and electron spin resonance (ESR) spectra after light irradiation, variations in the stretching IR peak of CN bridged to Mo(IV) and the paramagnetic ESR peak of Cu(II) were observed, respectively. The data indicate that this photomagnetism is caused by the electron transfer from Mo(IV) to Cu(II) and the ferromagnetic ordering between Cu(II) (S = 1/2) and Mo(V) (S = 1/2).

Structural, electrical and magnetic properties of polystyrene films filled with AgNO3–FeCl3 mixed fillers

The effect of various filling levels (FLs) of mixtures of two transition compounds (X)AgNO3 (10−X) FeCl3, on structural, electrical and magnetic properties of polystyrene (PS) films was investigated. The X-ray diffraction (XRD) displayed an unexpected appearance of a number of crystalline peaks beside the two main peaks characterizing the virgin film. The crystalline peaks were attributed to the cluster formation. The infrared (IR) analysis was used to detect the most notably PS peaks and to clarify the structural variations due to the filling. Certain IR peaks were taken as an evidence for the formation of polaron and/or bipolaron bound states in the polymeric matrix. The direct current (DC) electrical conduction studies revealed a linear temperature dependence of the hopping distance R0 for various FLs. This is an indication that the conduction mechanism can be attributed to one-dimensional intrachain type based on the phonon-assisted charge carrier interpolaron hopping model. The DC magnetic susceptibility results, in the temperature range 90–235K, followed the Curie–Weiss behavior. The positive and negative values of the paramagnetic Curie temperature (θp) indicate the possibility of ferromagnetic and antiferromagnetic exchange interactions between the magnetic centers at low temperatures, respectively. The electron spin resonance (ESR) spectra at the lower values of X depicted a broad signal superimposed on it a narrow one as well as a deformed signal. The ESR investigations at the lower values of X indicated the presence of aggregated Fe+3 confirming the XRD implications about the cluster formation. On the other hand and at higher values of X, an appearance of unresolved five lines of fine structure character was noticed.

Infrared absorption of a-SiC : H as a function of the annealing temperature

We performed an investigation on the origin of some temperature-reversible jumps found in the electrical conductivity of a-SiC : H alloys. The samples were grown by plasma-enhanced chemical vapor deposition using a gas mixture of SiH 4 + C 2 H 2 . An infrared (IR) analysis of the variations of the IR absorption peaks was carried out during a thermal cycle: the annealing temperature, T a , was increased from 25 °C up to 250 °C followed by cooling under identical conditions. The evolution of each IR peak was followed as a function of T a , acquiring the absorption curve with temperature steps of about 50°C. The analysis of some characteristic parameters of the IR peaks shows the reversible behavior of the IR absorption as a function of T a . An attempt is made to correlate the IR absorption peak variations with the discontinuities observed in the electrical conductivity.

High-Temperature Hydroxylation of Mullite

A plane-parallel, polished, 0.9 mm thick, single-crystal (001) plate of 2:1 mullite was treated for 6 h at 1600°C in an Ar/H2O (90/10) gas mixture at 100 kPa. Optical microscopy studies and infrared (IR) reflection spectroscopy studies of the lattice vibrations yielded no evidence for change with respect to the untreated reference crystal. However, IR absorption spectroscopy showed that structurally bound OH groups were formed by the heat treatment in the Ar/H2O gas mixture. IR absorption depth profile analysis showed a rather homogeneous OH distribution through the crystal. Five different hydroxyl groups were separated according to dipole orientations and peak positions: E‖a, ωa1= 3447 cm−1, ωa2= 3579 cm−1; E‖b, ωb1= 3456 cm−1, ωb2= 3544 cm−1; and E‖c, ωc1= 3498 cm−1. All IR peaks were strongly broadened (between 90 and 150 cm−1) because of a distribution in O-H binding distances caused by the real structure of mullite.

Preparation and performance of PVA films composited with 12-tungstogermanic heteropoly acid

PVA films containing 12-tungstogermanic heteropoly acid have been successfully prepared for the first time. Infrared (IR) spectra revealed that the Keggin structure characteristic of the GeW 12O 40 4− anion was present in the PVA films. The characteristic IR peaks have been identified and their change in wave number interpreted as a function of heteropoly acid (HPA) content. The film exhibited considerably high proton conductivity, which increased with the increase of the 12-tungstogermanic heteropoly acid content. At room temperature (20°C), the conductivity of the PVA film containing 80 wt.% 12-tungstogermanic heteropoly acid is 2.11×10 −2 S cm −1. The photochromism of the PVA film was observed. Its color changed into blue.

Fictive temperature measurement of single-mode optical-fiber core and cladding

The fictive temperatures of single-mode optical-fiber core, along with its inner and outer cladding, were measured using an infrared (IR) reflection method on the fiber cross-sectional surface. To allow for usage of a larger IR beam size than the diameter of the fiber core, the cross-sectional area of the fiber was increased by slicing the fiber at an oblique angle, along approximately 3/spl deg/ off the fiber axis direction. The magnitude of the fictive temperature was estimated from the IR peak wavenumber-fictive temperature relation obtained for bulk glasses with the same compositions. The observed fictive temperature was in the range of 1150/spl sim/1300/spl deg/C for the core, 1450/spl sim/1550/spl deg/C for the inner cladding, and 1620/spl sim/1660/spl deg/C for the outer cladding and exhibited good correlation with the fiber cooling rate.

Correlation between nitrogen concentration profile and infrared spectroscopy in silicon dioxide

There exists a strong correlation between the nitrogen concentration profile and infrared (IR) spectroscopy in gate oxynitrides for metal–oxide–Si (MOS) devices. The hot-electron hardness of the MOS device depends strongly on the nitrogen concentration profile in the gate oxide. It is experimentally found that the concentration ratios of nitrogen at SiO2/Si to the maximum amount of nitrogen in the oxide bulk ([N]int./[N]max. bulk) are proportional to the values of IR peak positions of Si–O stretching bonds. A larger value of [N]int./[N]max. bulk indicates a better hot-electron hardness of the MOS device, which can be explained by a reduction of SiO2/Si interfacial strain. The hot-electron hardness in the MOS device can be easily assessed by the IR signals of gate oxynitrides.

Infrared reflectance spectra of fayalite, and absorption datafrom assorted olivines, including pressure and isotope effects

Polarized single-crystal infrared (IR) reflectance spectra measured for synthetic fayalite (Fe2SiO4) possess all but one of the peaks mandated by symmetry plus a few weak bands attributable to overtones. Fayalite has a band at 86 cm−1, which is below the frequency range commonly examined, suggesting that vibrational spectra of ferrous minerals may need remeasuring. B2u polarizations were also measured for natural monticellite (nearly MgCaSiO4) and synthetic Mg2Si18O4. Thin film absorption data were collected for the above species, Co2SiO4, Mn2SiO4, Mg2SiO4, (Mg1.9Fe0.1)SiO4, Mg2GeO4 and Mn2GeO4. The relationships of IR peak positions (from these data and from previous single-crystal studies) with the inverse square root of the average cation mass were used to make band assignments, to estimate the positions for missing bands, and to determine which peaks are degenerate. The pressure dependencies of monticellite IR peaks were measured and resemble those of other olivines.

Structural analysis of hydrogenated carbon films obtained by reactive direct current magnetron sputtering

Amorphous hydrogenated carbon films were prepared by reactive direct current magnetron sputtering in argon plasma containing methane as the reactant gas. The films were characterized using various spectroscopic measurements such as Raman scattering, optical absorption spectroscopy in the ultraviolet–visible region, and infrared (IR) absorption spectroscopy. The spectral analyses indicated that changes in Raman spectroscopy intensity occurring with increasing methane gas content were determined to be caused by changes in optically resonant components in the films. Furthermore, a significant correlation was seen between the relative intensity of IR peaks and wear durability.

Hydrogen Passivation of HF ‐ Last Cleaned (100) Silicon Surfaces Investigated by Multiple Internal Reflection Infrared Spectroscopy

The hydrogen passivation of (100) silicon surfaces is characterized as a function of the chemical treatment by means of multiple internal reflection infrared (IR) spectroscopy using a novel sample preparation method. The samples are etched in different solutions (aqueous , , , , and buffered ) and investigated with and without DI water rinsing. The stability of the surfaces against oxidation and the buildup of a hydrocarbon contamination layer during storage in cleanroom air are examined. The IR peak at 2123 cm−1 is related to a coupling mode between dihydrides and neighboring monohydrides.

A Comparative Study of Particle Size Dependency of IR and XRD Methods for Quartz Analysis

Quartz (SiO2) is considered a probable carcinogen. In order to enforce health and safety standards, techniques that can accurately determine the quartz content of materials are necessary. Currently, two techniques dominate quartz analysis—the infrared (IR) spectrophotometry method and the X-ray diffraction (XRD) method. Unfortunately, there are problems associated with these techniques, such as sample preparation and particle size effect. This study focuses on particle size effect on quartz determination by both IR and XRD. Seven size groups of pure quartz samples, with mean diameters from 1.5 to 20 microns, were used. A set of samples with different quartz masses was prepared for each size group and subjected to both IR and XRD analysis. Two sets of calibration curves, one each from IR and XRD, were obtained. It was found that both IR and XRD methods are size-dependent but in an opposite way. As particle size increases, IR peak height decreases and XRD peak height increases for the same quartz content (mass). Since both methods are particle size-dependent, it is important that the standard quartz sample and samples of interest have similar particle size distributions. Specifically, when coal dust samples are ashed before analysis, the after-ashing particle size distribution should be used. Particle size distribution will change after ashing and it is the after-ashed particles that directly affect the IR and XRD analysis.

IR reflectance spectra of natural ilmenite: comparison with isostructural compounds and calculation of thermodynamic properties

Polarized single-crystal infrared (IR) reflectance spectra measured for natural ilmenite (FeTiO 3 ) possessed the eight peaks mandated by symmetry plus weak bands attributable to overtones. IR and Raman peaks were correlated between these data and previous polycrystalline studies of 14 isostructural compounds by comparing intensity patterns. This enabled assignment of symmetries. Frequencies for unobserved bands were estimated from relationships of IR and Raman bands with cell volume and cation mass. Different trends exist for high- and low-frequency bands indicating that the former are essentially internal motions of octahedra containing X 4+ , while the latter are translations of the M 2+ . Heat capacities calculated from vibrational spectra lie 5 % below calorimetric measurements from 150 to 1100 K. Measured entropy is bracketed by the sum of lattice entropy calculated from a Kieffer-type model plus a constant magnetic contribution and the sum S 1at plus S mag plus constant d-electron exchange and Fe-Ti charge transfer contributions. These results are consistent with electronic processes being temperature dependent, as expected for distorted octahedra. Accurate prediction of S and Cp for ferrous compounds will require knowledge of visible as well as vibrational spectra. Bulk moduli for isostructural compounds calculated from a modified Brout model lie within 5 % of experiment. K T is predicted for the eight compounds

Effects of radiation damage on infra-red and thermoluminescence properties of natural apatites

Thermoluminescence (TL) and infra-red (IR) spectra from various natural crystals of apatite have been examined. All naturally damaged samples (the amount of damaged being monitored by their fossil fission track density) were found to exhibit a reduced contribution in the thermoluminescence glow intensity relative to that of undamaged one. Annealing the samples for 1 hour at temperature above 500°C resulted in an increase in TL sensitivity. The investigation shows strong evidence that radiation damage is responsible for the reduced TL sensitivity. High uranium content in apatite sample shows an increasing IR peak intensity at 740 cm-1 with increasing annealing temperature.