IR Absorption Bands Research Articles

Correlation between the local OH stretching vibration wavenumber and the hydrogen bonding pattern of water in a condensed phase: Quantum chemical approach to analyze the broad OH band

A study of the chemical origin of the broad IR absorption band of the O–H stretching vibration (νOH) of liquid water is mentioned. The study is performed by measuring the local νOH mode of the half-deuterated water (HDO) dissolved in deuterated water (D2O) with an aid of quantum chemical calculation. The band position of a local νOH mode is analyzed as a function of hydrogen (H)-bond coordination pattern, which is taken into account by using a useful index of MOH based on the DA3 pattern method. The DA3 method focuses on a HDO–D2O (donor–accepter; DA) molecular pair, and the hydration about the DA pair is categorized into 36 patterns with respect to the H-bond coordination pattern. The MOH index summarizes the patterns by considering the positive and negative contributions of the hydration to the H-bond in the DA pair. The calculated band position of the H-bonded νOH in the pair is readily grouped by using the MOH index, which can also be used as an index for evaluating H-bonding energy. This paper demonstrates the potential of the DA3 method to analyze the νOH band and H-bonding energy of liquid water and ice by referring to QC calculation results for relatively small water clusters.

Mineral analysis of an artificial pond sediment samples from the Western Cape Province, South Africa

Mineralogical characterization was carried out to determine the major and minor constituent minerals present in sediment samples collected from five different locations at the Western Cape artificial pond sediment, South Africa by Fourier transform infrared (FT-IR) and X-ray diffractometry (XRD) techniques. The minerals were identified with the available literature from the IR absorption band of the locations of different peaks. The FT-IR technique was highly useful in identifying different minerals in sediments. The XRD analysis revealed that the minerals of artificial pond sediments in Western Cape are predominantly composed of quartz while carrolite was present in location one. The presence of pyrite could also suggest anoxia, which in turn will imply differential Fe (Iron) levels in the sediment as a function of the degree of anoxia in the sediment.

Theoretical Studies of Dynamic Interactions in Excited States of Hydrogen-Bonded Systems

Theoretical model for vibrational interactions in the hydrogen-bonded benzoic acid dimer is presented. The model takes into account anharmonic-type couplings between the high-frequency O–H and the low-frequency O⋯O stretching vibrations in two hydrogen bonds, resonance interactions between two hydrogen bonds in the dimer, and Fermi resonance between the O–H stretching fundamental and the first overtone of the O–H in-plane bending vibrations. The model is used for theoretical simulation of the O–H stretching IR absorption bands of benzoic acid dimers in the gas phase in the first excited singlet state. Ab initio CIS and CIS(D)/CIS/6-311++G(d,p) calculations have been carried out in the à state of tropolone. The grids of potential energy surfaces along the coordinates of the tunneling vibration and the low-frequency coupled vibration have been calculated. Two-dimensional model potentials have been fitted to the calculated potential energy surfaces. The tunneling splittings for vibrationally excited states have been calculated and compared with the available experimental data. The model potential energy surfaces give good estimation of the tunneling splittings in the vibrationally ground and excited states of tropolone, and explain monotonic decrease in tunneling splittings with the excitation of low-frequency out-of-plane modes and increase of the tunneling splittings with the excitation of low-frequency planar modes.

Nitrile group as infrared probe for the characterization of the conformation of bovine serum albumin solubilized in reverse micelles

Infrared spectroscopy is a powerful technique for structure characterization. For a protein hosted in a reversed micellar medium, the spectral features of the protein are always interfered by the IR absorption bands of the medium in addition to the congestion in their IR spectra. Fortunately, there is a transparent window in the 2500–2200cm−1 region. Incorporation of a vibrational probe with IR absorption frequencies in this region into proteins represents a promising strategy for the study of the conformation of a protein in a reverse micelle. In the present work, we incorporated 4-cyanobenzyl group (CN) into bovine serum albumin (BSA) via cysteine alkylation reactions under mild conditions. Circular dichroism spectroscopy showed that the CN modified BSA (CNBSA) could retain its conformation. When CNBSA was hosted in AOT reverse micelle, it was found that the nitrile group on BSA was sensitive to the conformational change of BSA induced by urea as an additive in the reverse micelle. The peak splitting of nitrile group was also observed when the size of AOT reverse micelle and the concentration of an electrolyte were varied. Obviously, the shift of the IR absorption peak and/or peak splitting of nitrile group on BSA are correlated with the change of BSA conformation in AOT reverse micelle. So we conclude that the nitrile infrared probe can be used to study protein conformation in a reverse micelle.

Simulation of the structures and calculation of IR Spectra of (22 s,23 s)-Homobrassinolide conformers

Frequencies and intensities of normal vibrations of (22 S,23 S)-homobrassinolide, a biologically active representative of steroidal phytohormones, were calculated within the framework of an original approach that combined a classical analysis of normal vibrations by a molecular mechanics method with a quantum-chemical estimation of absolute intensities. Two molecular structures with different side-chain conformations were considered. The molecular IR absorption bands in the range 1500–900 cm–1 were interpreted for the first time and the influence of the side-chain conformation on the IR spectrum was analyzed based on a comparison of the experimental and calculated spectra.

Photochemical investigation of the IR absorption bands of molecular oxygen in organic and aqueous environment

It is shown that the weak IR absorption bands corresponding to the forbidden triplet-singlet transitions in oxygen molecules can be reliably studied in air-saturated solvents under ambient conditions using measurements of the photooxygenation rates of singlet oxygen traps (1,3-diphenylisobenzofuran or uric acid) upon direct excitation of oxygen molecules by IR diode lasers. The best results were obtained from comparison of the oxygenation rates upon direct and photosensitized singlet oxygen excitation. In the present paper, this method was applied to estimation of the absorbance (A(ox)) and molar absorption coefficients (ε(ox)) corresponding to the oxygen absorption bands at 765 and 1273 nm in carbon tetrachloride, acetone, alcohols and water. In carbon tetrachloride, the band at 1073 nm was also investigated. Correlation of the obtained data with the luminescence spectra and radiative rate constants of singlet oxygen, contribution of oxygen dimols and biological significance of the studied effects are discussed.

Hydrogen-bonded supramolecular polymers containing dimethylsilane groups: Synthesis, crystal structure, and characterization

Bis[N-(4-carboxyphenyl)phtalimidyl]dimethylsilane prepared by the reaction between bis(3,4-dicarboxyphenyl)dimethylsilane anhydride and p-aminobenzoic acid has been used to built three novel hydrogen-bonded supramolecular polymers as a result of cocrystallization with pyridine derivatives: 4,4′-bipyridyl (SP1), 1,2-bis(4-pyridyl)ethylene (SP2), and 4,4′-azopyridine (SP3). The structures of the dianhydride, diacid, and derived supramolecular polymers were investigated by Fourier transform infrared (FTIR) and proton magnetic resonance (1H NMR) spectroscopy. Self-assembling was proved by the presence of the IR absorption bands around 1900 and 2400 cm−1 specific for hydrogen bond. The association constant values were estimated by using FTIR spectroscopy in solid state. According to X-ray diffraction study, the bis(3,4-dicarboxyphenyl)dimethylsilane anhydride (1) has an isolated molecular structure. Bis[N-(4-carboxyphenyl)phtalimidyl]dimethylsilane (2) molecules are associated in the crystal structure via dimeric OH…O hydrogen bonds resulting in the wavy 1D supramolecular chain. The main packing motif for SP1 and SP3 is represented by wavy chain formed by alternating sequences of 4,4′-bipyridyl or 4,4′-azopyridine and bis[N(4-carboxyphenyl)phtalimidyl]dimethylsilane molecules linked by OH…N hydrogen bonds. Thermal behavior was studied by differential scanning calorimetry and thermogravimetric analysis. The ability for the structuration in film was emphasized by atomic force microscopy. The molecular transport ability of the reversible associations was estimated by dynamic water vapor sorption (DVS) analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Effects of growth temperature on μc-Si:H films prepared by plasma assistant magnetron sputtering

Hydrogenated microcrystalline silicon thin films (μc-Si:H) were deposited by plasma assistant magnetron sputtering in Ar-H2 gas mixture. The effects of growth temperature from 150 to 450 °C on properties of deposited Si films were investigated at two different hydrogen diluted gases with [H2]/([Ar]+[H2]) of 10% and 50% at 3 Pa. The crystallinity of Si films examined by Raman scattering exhibited higher degradation by lowering growth temperature from 250 to 150 °C in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The IR absorption band around 845 and 890 cm−1 as well as calculated concentration of bonded hydrogen showed more obvious decrease of samples deposited in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The optical band gasps of both groups of samples measured by ultraviolet-visible optical absorption were decreased with increasing temperature in both gas conditions.

Synthesis and selected properties of a new solid solution in the Zn2FeV3O11–Mg2FeV3O11 system

The binary Zn2FeV3O11–Mg2FeV3O11 system has been studied by XRD, DTA, IR, and SEM methods. A new continuous substitution solid solution with the formula Zn2−x Mg x FeV3O11 has been obtained by high-temperature synthesis. The DTA investigations were used to choose the heating temperatures as well as for determination of thermal stability of the new triclinic phase. The influence of the degree of Mg2+ ion incorporation on the unit cell volume as well as on the position of the IR absorption bands of the solid solution have been determined. The morphology of crystals of the new phase is presented.

In situ Infrared Spectroscopic Study of CH4 Oxidation Over Co–ZSM-5

Surface species formed in CH4 activation over Co–ZSM-5 were monitored by in situ DRIFT spectroscopy. IR absorption bands assigned to adsorbed methoxide, formate and polyoxymethylene were detected. The similarities in the IR bands and their evolution during He purge after reactions conducted under anaerobic and aerobic conditions suggested that Cannizzaro disproportionation of formaldehyde is a significant reaction pathway. This was verified when water was found to react with a surface species to form adsorbed formate. Continued formation of surface formate was observed during purging in He which indicated substantial surface storage of formaldehyde as polyoxymethylene.

New solid solution Fe1−xCrxVSbO6 with rutile-type structure

A new solid solution with formula Fe1−xCrxVSbO6 has been prepared by the conventional solid-state reaction technique using the starting mixtures containing V2O5, α-Sb2O4, Cr2O3 and Fe2O3 as well as FeVSbO6 and CrVSbO6. Continuous substitutional solid solution of a tetragonal structure of rutile-type in the FeVSbO6–CrVSbO6 system is formed in the whole concentration range 0.0<x<1.0. The solid solution was characterised by XRD, DTA-TG, IR and SEM/EDX methods. With increasing degree of Cr3+ ion incorporation into the FeVSbO6 structure, the contraction of Fe1−xCrxVSbO6 solid solution crystal lattice increased. The temperature of its thermal stability in the solid state was established and gradual shifting of the corresponding IR absorption bands towards higher wave numbers was observed.

Origin of Saponite-Rich Clays in A Fossil Serpentinite-Hosted Hydrothermal System in The Crustal Basement of The Hyblean Plateau (Sicily, Italy)

AbstractA diapiric intrusion of clays in the Carlentini Formation (Tortonian) was discovered in a quarry at S. Demetrio High (Hyblean Plateau, Sicily, Italy). Seven clay samples were analyzed by different analytical methods, including X-ray powder diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, to determine the composition and mechanism of formation (sedimentary vs. hydrothermal) of these clays. Ferric saponite, carbonates (calcite and traces of ankerite), quartz, pyrite, and zeolites (phillipsite and harmotome) were detected using XRD and FTIR. This mineral assemblage, dominated by Fe-rich saponite, and the abundance of light rare-earth elements (LREE), Eu, fluid-mobile elements (FME &gt; 10 × primordial mantle: Li, Be, B, As, Sb, Pb, U, Ba, Sr, Cs), and other incompatible elements (Zr = 169 ppm, Nb = 46 ppm, Th = 11 ppm, on average) imply that S. Demetrio clays precipitated from a mixture of hot Si-rich hydrothermal fluids (350–400°C) and cold seawater. The evidence is in accord with the affinity of clays for hydrothermally modified mafic and ultramafic rocks, forming the Hyblean lower crust, based on multi-element comparisons, and on the occurrence of trace amounts of chrysotile 2Mc1 and sepiolite. The association of long-chain aliphatic-aromatic hydrocarbons (intensity ratios I2927/I2957 &gt; 0.5) with hydrothermal clays, the lack of fossils, and the similarity of the IR absorption bands with those of organic compounds detected previously in some metasomatized Hyblean gabbroic xenoliths suggest a possible abiogenic origin of hydrocarbons via a Fischer-Tropsch-type reaction. The S. Demetrio clay diapir was emplaced at shallow crustal levels in the Late Miocene as a consequence of the interaction, at a greater depth, of an uprising basalt magma and the products of an early, serpentinite-hosted hydrothermal system.

Fabrication and properties of acid blue 25 dye-intercalated layered double hydroxides film on an anodic alumina/aluminum substrate

The Acid Blue 25 (1-amino-9,10-dihydro-9,10-dioxo-4-(phenylamino)-2-anthracenesulphonate) anion intercalated layered double hydroxides (LDH) film was fabricated through an ion-exchange method using a ZnAl–NO3–LDH/porous anodic alumina/aluminum (PAO/Al) film as the precursor. The prepared film was investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Thermogravimetric–differential thermal analysis (TG–DTA) and the CIE 1976L⁎a⁎b⁎ color difference method. XRD patterns and FT-IR spectra confirm the successful incorporation of ADPA anions into the interlayer spacings of ZnAl–LDH with an expansion of d-spacing from 0.87nm to 2.49nm and the disappearance of characteristic IR absorption band of NO3− anions at 1384cm−1. The SEM morphologies show that the LDH films are mainly oriented with the ab face of the platelet crystallites perpendicular to the substrate surface. Additionally, the obtained results suggest that the intercalation of ADPA into ZnAl–LDH host markedly improves the thermal stability and light fastness of ADPA.

Intercalation of IR absorber into layered double hydroxides: Preparation, thermal stability and selective IR absorption

N-phosphonomethyl aminodiacetic acid (PMIDA) was intercalated into the interlayer spacing of layered double hydroxides (LDH) by an anion-exchange method. The intercalated LDHs were characterized by various techniques such as powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and simultaneous thermogravimetric and mass spectrometry (TG-MS) in details. The results show the formation of Mg2Al-PMIDA LDH based on the expansion of d-spacing from 0.89nm to 1.22nm and the disappearance of the characteristic IR absorption band at 1384cm−1 for NO3− anions. The incorporation of Mg2Al-PMIDA LDH into the low density polyethylene (LDPE) as an additive enhances the selectivity of IR absorption in the main wavelength region 9–11μm for radiant heat loss at night. Mg2Al-PMIDA LDH as a heat-retaining additive has practical application in agricultural plastic films.

Synthesis and charge-transporting properties of electron-deficient CN2–fluorene based D–A copolymers

In this paper, we report four D–A copolymers on the basis of a novel acceptor (A) unit of 9-fluorenylidene malononitrile (CN2–Fluorene) and four common donor (D) units of 9-alkylfluorene (P1), benzodithiophene (P2), bithiophene (P3), and dithienopyrrole (P4), respectively. These four copolymers were synthesized using Stille or Suzuki coupling and physicochemically characterized. Each of them exhibits a weak near IR absorption band extending down to 800 nm, due to weak intramolecular charge transfer (ICT) between the donor and CN2–Fluorene units. The LUMO energy levels of the copolymers (∼−3.70 eV) are determined mainly by the CN2–Fluorene unit, while the HOMO energy levels are finely tuned by the incorporation of donors, with the electrochemical bandgap decreasing from 2.04 eV for P1 to 1.56 eV for P2, 1.28 eV for P3, and 1.18 eV for P4. TD-DFT calculations on one repeating unit of the copolymer confirm the strong LUMO-determining ability of the CN2–Fluorene unit. The charge transport properties of the copolymers are investigated by fabricating OTFT devices with a bottom-contact configuration. The hole mobility of P3 is 1.43 × 10−3 cm2 V−1 s−1 under ambient conditions and that of P2 and P4 is 1.31 × 10−4 and 1.81 × 10−4 cm2 V−1 s−1, respectively.

Negative effect of Ni on PtHY in n-pentane isomerization evidenced by IR and ESR studies

Ni/PtHY with different Ni loadings was prepared by impregnating HY with hexachloroplatinic acid solution and Ni 2+/N, N-dimethylformamide solution. An increase in the Ni loading decreased the crystallinity, specific surface area and meso-micropores of the catalysts. Ni interacted with hydroxyl groups to produce IR absorption bands at 3740–3500 cm −1. Increasing Ni loadings resulted in a decrease in the intensities of the broad bands at 3730-3500 cm −1 and the sharp band at 3740 cm −1 with simultaneous development of new absorbance band at 3700 cm −1 that was attributed to (–OH)Ni. The acidity of the samples did not significantly change with Ni loadings up to 1.0 wt%, which indicated that Ni mostly interacts with non-acidic silanol groups (terminal- and structural-defect OH groups). The presence of Ni decreased the activity of PtHY toward the isomerization of n-pentane because of a decrease in the number of active protonic-acid sites that formed from molecular hydrogen. IR and ESR studies confirmed that Pt facilitated the formation of protonic-acid sites from molecular hydrogen, whereas Ni, even when combined with Pt, didn't exhibit such ability. The absence of protonic-acid sites from molecular hydrogen significantly decreased the yield of iso-pentane and markedly increased the cracking products.

Dimers as Fast Diffusing Species for the Aggregation of Oxygen in Boron-Doped Czochralski Silicon: Formation of New Thermal Donors

The thermal behaviors of oxygen-related complexes in boron doped Czochralski Silicon (Cz-Si) wafers at 450°C and 800°C were investigated using Fourier transform infrared spectroscopy (FTIR) and Hall mobility measurements. Activation of thermal donors (TDs) at 450°C leads to a decrease of both mobility and majority carrier concentration using the four point probes configuration of Van Der Pauw. It was found that annealing at 450°C would possibly affect the electronic properties of the Si wafers via the formation of interstitial dioxygen defects (IO2i), which exhibit an IR absorption band positioned at 545 cm–1. A strengthening of the IR bands peaking at around 1595 cm–1, 1667 cm–1, 1720 cm–1 and 1765 cm–1 occurs at 450°C, while they disappear at 800°C. At high temperatures, the precipitation of interstitial oxygen becomes predominant over all other oxygen-related reactions. The dynamic of oxygen-thermal donor generation-annihilation in Cz-Si involving the formation of small oxygen clusters is discussed.

Barioferrite BaFe12O19: A new mineral species of the magnetoplumbite group from the Haturim Formation in Israel

A new mineral barioferrite—a natural analogue of synthetic barium ferrite Ba Fe 12 3+ O19—has been identified in the central part of a metamorphosed barite nodule in the rock of the Haturim Formation (Mottled Zone) on the southern slope of Mount Ye’elim in Israel. The mineral is associated with barite, calcite, magnetite, and maghemite and occurs as tiny platy crystals up to 3 × 15 × 15 μm and their irregular aggregates. Barioferrite is black with streaks of brown, and its luster is submetallic. Its Calculated density is 5.31 g/cm3. The mineral is brittle; cleavage is absent. IR absorption bands (cm−1) are observed at 635 (shoulder), 582, 544, 433, and 405 (shoulder). Barioferrite is characterized by ferrimagnetic behavior. Under a microscope in reflected light, barioferrite is grayish white with brownish red internal reflections, the pleochroism is weak (from gray-white on R o to gray-white with a brown tint on R e), and the bireflectance is weak with distinct anisotropy. The reflectance values of R o/R e, % (λ, nm) are 24.51/22.80 (470), 24.17/22.25 (546), 23.65/21.68 (589), and 22.67/20.85 (650). The chemical composition (electron microprobe, wt %; the ranges are given in parentheses) is BaO 13.13 (12.5–13.8), Fe2O3 86.47 (85.5–87.5), and 99.60 in total. The empirical formula is Ba0.95Fe 12.03 3+ O19. Barioferrite is hexagonal with space group P63/mmc, a = 5.875 (3) A, c = 23.137 (19) A, V = 691.6 (5) A3, and Z = 2. The strongest lines of the X-ray powder diffraction pattern [d, A, (I, 5) (hkl)] are 2.938(46) (110), 2.770(100) (107), 2.624 (84) (114, 200), 2.420(44) (203), 2.225(40) (205), and 1.627(56) (304, 2.0.11). The holotype specimen of barioferrite is deposited at the Mineralogical Museum of St. Petersburg State University; its catalogue number is 1/19436.

Ionized nitrogen mono‐hydride bands are identified in the presolar and carbonado diamond spectra

Abstract– None of the well‐established nitrogen‐related IR absorption bands, common in synthetic and terrestrial diamonds, have been identified in the presolar diamond spectra. In the carbonado diamond spectra, only the single nitrogen impurity (C center) is identified and the assignments of the rest of the nitrogen‐related bands are still debated. It is speculated that the unidentified bands in the nitrogen absorption region are not induced by nitrogen, but rather by nitrogen‐hydrides because in the interstellar environment, nitrogen reacts with hydrogen and forms NH+; NH; NH2; NH3. Among these hydrides, the electronic configuration of NH+ is the closest to carbon. Thus, this ionized nitrogen‐mono‐hydride is the best candidate to substitute carbon in the diamond structure. The bands of the substitutional NH+ defect are deduced by redshifting the irradiation‐induced N+ bands due to the mass of the additional hydrogen. The six bands of the NH+ defects are identified in both the presolar and the carbonado diamond spectra. The new assignments identify all of the nitrogen‐related bands in the spectra, indicating that presolar and carbonado diamonds contain only single nitrogen impurities.

Ethylene polymerization on a SiH4-modified Phillips catalyst: detection of in situ produced α-olefins by operando FT-IR spectroscopy

Ethylene polymerization on a model Cr(II)/SiO(2) Phillips catalyst modified with gas phase SiH(4) leads to a waxy product containing a bimodal MW distribution of α-olefins (M(w) < 3000 g mol(-1)) and a highly branched polyethylene, LLDPE (M(w) ≈ 10(5) g mol(-1), T(m) = 123 °C), contrary to the unmodified catalyst which gives a linear and more dense PE, HDPE (M(w) = 86,000 g mol(-1) (PDI = 7), T(m) = 134 °C). Pressure and temperature resolved FT-IR spectroscopy under operando conditions (T = 130-230 K) allows us to detect α-olefins, and in particular 1-hexene and 1-butene (characteristic IR absorption bands at 3581-3574, 1638 and 1598 cm(-1)) as intermediate species before their incorporation in the polymer chains. The polymerization rate is estimated, using time resolved FT-IR spectroscopy, to be 7 times higher on the SiH(4)-modified Phillips catalyst with respect to the unmodified one.