Stretching Vibration Mode Research Articles

Control of vibrational distribution functions in nonequilibrium molecular plasmas and high-speed flows

The control of the vibrational distribution of nitrogen by energy transfer to CO2 is studied in two closely related experiments. In the first experiment, the time-resolved N2(v = 0–3) vibrational level populations and temperature in the afterglow of a diffuse filament nanosecond pulse discharge are measured using broadband coherent anti-Stokes Raman spectroscopy. The rotational–translational temperature in the afterglow is inferred from the partially rotationally resolved structure of the N2(v = 0) band. The measurements are performed in nitrogen, dry air, and their mixtures with CO2. N2 vibrational excitation in the discharge occurs by electron impact, with subsequent vibration–vibration (V–V) energy transfer within the N2 vibrational manifold, vibration–translation (V–T) relaxation, and near-resonance V–V′ energy transfer from the N2 to CO2 asymmetric stretch vibrational mode. The results show that rapid V–V′ energy transfer to CO2, followed by collisional intramolecular energy redistribution to the symmetric stretch and bending modes of CO2 and their V–T relaxation, accelerate the net rate of energy thermalization and temperature increase in the afterglow. In the second experiment, injection of CO2 into a supersonic flow of vibrationally excited nitrogen demonstrates the effect of accelerated vibrational relaxation on a supersonic shear layer. The nitrogen flow is vibrationally excited in a repetitive nanosecond pulse/DC sustainer electric discharge in the plenum of a nonequilibrium flow supersonic wind tunnel. A transient pressure increase as well as an upward displacement of the shear layer between the supersonic N2 flow and the subsonic CO2 injection flow are detected when the source of N2 vibrational excitation is turned on. CO2 injection leads to the reduction of the N2 vibrational temperature in the shear layer, demonstrating that its displacement is caused by accelerated N2 vibrational relaxation by CO2, which produces a static temperature and a pressure increase in the test section. This demonstrates the significant potential of accelerated vibrational relaxation for nonequilibrium flow control, by injection of rapid ‘relaxer’ species at a desired location, resulting in the rapid thermalization of vibrational energy in nitrogen and air flows, and producing a significant effect on the flow field.

Investigation of organo-carbonate associations in carbonaceous chondrites by Raman spectroscopy

Carbonates record information regarding the timing, nature and conditions of the fluids circulating through asteroid parent bodies during aqueous alteration events. Determining carbonate abundances and their relationships with organic matter improves our understanding of the genesis of major carbonaceous components in chondritic materials. In this study, five CM2 carbonaceous chondrites (CM2.2 Nogoya, CM2.3 Jbilet Winselwan, CM2.5 Murchison, CM2 Santa Cruz, and CM2TII Wisconsin Range 91600) were studied with Raman spectroscopy. Carbonates were identified in these meteorite samples by the distinctive Raman band in the ∼1100cm−1 region, representing the symmetric stretching vibration mode (ν1) of the (CO3)2− anion. Carbonates identified in the meteorite samples are all calcite, with the exception of a single dolomite grain in Nogoya. The v1 positions of the CM calcites are 2–3cm−1 higher than in pure calcite, which suggests that they contain significant impurity cations. Typical graphitic first-order D and G bands were identified in the meteorite matrix as well as in ∼25% of the analyzed carbonate grains. From the Raman results, we postulate that the carbonates might not have formed under equilibrium conditions from a single fluid. The first generation of carbonate is interpreted to have formed from highly oxidized fluids that led to the oxidation of organic matter (OM) and produced carbonates that are OM-barren. The second generation of carbonate was formed from a more evolved aqueous fluid with the presence of OM. The Raman parameters of the organics in carbonates clearly deviate from the matrix OM which suggests that the carbonate organics contain very different carbonaceous components that are distinct from the typical amorphous OM of the CM matrix. The occurrence of different generations of carbonate in close proximity may be partly responsible for the wide range in estimated ages of carbonates in carbonaceous chondrites reported in previous studies.

토실 활성화된 폴리스티렌 마이크로구체 자성 입자 표면의 화학적 변형에 대한 적외선 연구

입자 표면에 고분자를 화학적으로 접목하는 것은 수용성 액체 이상 시스템(ATPS)과 같이 분리된 액체 층에서 마이크로/나노입자를 선택적으로 분배시키는데 중요한 구실을 한다. 본 연구에서는 덱스트란, 폴리에틸렌 글리콜, 알부민을 화학적으로 폴리스티렌 자성 마이크로입자 표면에 화학적으로 부착시켰다. 분배 현상을 역전시킬 수 있는 긴 고분자 사슬의 부착은 일차 아민 작용기를 가진 다양한 고분자를 p-톨루엔술폰산(토실)기를 부착시킨 폴리스티렌 자성 마이크로입자와의 S_N2 치환에 의해 간단히 수행될 수 있었다. 이 후 적외선 현미경을 사용하여 마이크로입자의 표면 변화의 유무를 검사하였다. 반응 후 입자들은 세 가지 폴리머 모두 N-H 신축 진동 피크를 보였으며 대부분의 주요 피크들의 위치는 반응 전후에 유사하였으나 지문 영역에서 구별 가능한 차이를 보였다. The chemical engrafting of polymers on particle surface, plays an important role on selective partitioning of micro/nano-particles in the separated layers of liquid media, such as aqueous two phase systems (ATPSs). Three polymers, dextran, poly (ethylene glycol) and albumin were chosen and chemically conjugated to the polystyrene (PS) magnetic microparticle surface. The attachment of long-chained polymer chains which may switch the partition behavior, can be simply performed by S_N2 substitution of various polymers having primary amine functional groups, with p-toluenesulfonyl (tosyl)-activated polystyrene magnetic micro-particles. The surface modification of microparticle was probed by infrared microscopy. The distinctive peak represents N-H stretching vibration mode for microparticles after the reaction and it is common for all three polymers examined. The locations of main peaks are similar for all micro-particles but different and distinguishable in fingerprint region.

Development of hierarchical layered nanostructured α-MoO3 thin films using dc magnetron sputtering

The synthesis of environmentally friendly, catalyst free, hierarchical molybdenum oxide nanostructured thin films of different morphologies by a DC magnetron sputtering technique is reported. With increase in the annealing temperature, the spherical molybdenum nanoparticles arrange themselves in the form of vertically aligned nanorods and platelets stacked over one another. The preliminary phase analysis was carried out using x-ray diffraction. The sample annealed at 600 °C shows the formation of highly crystalline orthorhombic α-MoO3. Field emission scanning electron microscopy and transmission electron microscopy images confirm the formation of a layered structure at higher annealing temperatures, while the Raman spectroscopy revealed the stretching vibration modes of Mo–O bonds in the formation of the orthorhombic α-MoO3 layered structure. The Raman peaks at 667, 820 and 995 cm−1 correspond to the layered structure of orthorhombic α-MoO3. The electrical properties and possible growth mechanism of the as-prepared samples at different annealing temperatures are also discussed.

The discovery of the hydrogen bond from p-Nitrothiophenol by Raman spectroscopy: Guideline for the thioalcohol molecule recognition tool.

Inter- and intra- molecular hydrogen bonding plays important role in determining molecular structure, physical and chemical properties, which may be easily ignored for molecules with a non-typical hydrogen bonding structure. We demonstrated in this paper that the hydrogen bonding is responsible for the different Raman spectra in solid and solution states of p-Nitrothiophenol (PNTP). The consistence of the theoretical calculation and experiment reveals that the intermolecular hydrogen bonding yields an octatomic ring structure (8) of PNTP in the solid state, confirmed by the characteristic S-H---O stretching vibration mode at 2550 cm−1; when it comes to the solution state, the breakage of hydrogen bond of S-H---O induced the S-H stretching vibration at 2590 cm−1. Our findings may provide a simple and fast method for identifying the intermolecular hydrogen bonding.

A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in the Nickel-Catalyzed Amination of Arenes.

The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]2 B10 H10 (termed SiCCSi) is reported (NHSi=N-heterocyclic silylene; L=PhC(NtBu)2 ). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the Si(II) atoms in the SiCCSi ligand are even stronger σ donors than the P(III) atoms in phosphines and C(II) atoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1-10 mol %).

A Bis(silylene)‐Substituted ortho‐Carborane as a Superior Ligand in the Nickel‐Catalyzed Amination of Arenes

AbstractThe synthesis and structure of the first 1,2‐bis(NHSi)‐substituted ortho‐carborane [(LSi:)C]2B10H10 (termed SiCCSi) is reported (NHSi=N‐heterocyclic silylene; L=PhC(NtBu)2). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the SiII atoms in the SiCCSi ligand are even stronger σ donors than the PIII atoms in phosphines and CII atoms in N‐heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni‐based precatalysts (1–10 mol %).

Raman spectroscopy of proton-irradiated K(H1−xDx)2PO4

We have employed Raman spectroscopy in order to study the mechanism of the significantly increased ferroelectric phase transition temperatures in proton-irradiated K(H1−x Dx)2PO4 crystals. Prominent changes occurred in the asymmetric stretching vibration mode frequency of D2PO4 molecules in the proton-irradiated crystals, thus stating the role of the lattice coupled to H/D.

Identification of intracellular squalene in living algae, Aurantiochytrium mangrovei with hyper‐spectral coherent anti‐Stokes Raman microscopy using a sub‐nanosecond supercontinuum laser source

We applied hyper‐spectral coherent anti‐Stokes Raman scattering imaging to intracellular lipid identification in living microalgae, Aurantiochytrium mangrovei 18W‐13a. Two different lipids, squalene and triacylglycerol, were found inside living cells with clear vibrational contrast. Based on the endogenous lipid band as a result of the cis CC stretch vibrational mode, squalene and triacylglycerol were clearly distinguished in different intracellular areas. In particular, squalene was detected solely in vacuoles as lipid particles, which was also supported by electron microscopy. Copyright © 2016 John Wiley & Sons, Ltd.

Picosecond pulsed infrared laser tuned to amide I band dissociates polyglutamine fibrils in cells.

Amyloid fibrils are causal substances for serious neurodegenerative disorders and amyloidosis. Among them, polyglutamine fibrils seen in multiple polyglutamine diseases are toxic to neurons. Although much efforts have been made to explore the treatments of polyglutamine diseases, there are no effective drugs to block progression of the diseases. We recently found that a free electron laser (FEL), which has an oscillation wavelength at the amide I band (C = O stretch vibration mode) and picosecond pulse width, was effective for conversion of the fibril forms of insulin, lysozyme, and calcitonin peptide into their monomer forms. However, it is not known if that is also the case in polyglutamine fibrils in cells. We found in this study that the fibril-specific β-sheet conformation of polyglutamine peptide was converted into nonfibril form, as evidenced by the infrared microscopy and scanning-electron microscopy after the irradiation tuned to 6.08μm. Furthermore, irradiation at this wavelength also changed polyglutamine fibrils to their nonfibril state in cultured cells, as shown by infrared mapping image of protein secondary structure. Notably, infrared thermography analysis showed that temperature increase of the cells during the irradiation was within 1K, excluding thermal damage of cells. These results indicate that the picosecond pulsed infrared laser can safely reduce amyloid fibril structure to the nonfibril form even in cells.

Methylsilsesquioxane-Based Aerogel Systems-Insights into the Role of the Formation of Molecular Clusters.

Condensed clusters of hydrolyzed methyltrimethoxysilane (MTMS) were studied using two complementary approaches: (i) Fourier transform infrared (FTIR) spectroscopy was applied along with the hydrolysis and condensation stages of a sol-gel process from the condensation of colloidal suspension of nanoparticles to the solid phase of bulk material; (ii) density functional theory calculations of energies, structural and vibrational data of pertinent MTMS hydrolysis products, specifically, methylsilanetriol-based species with different number of silicon atoms (from two to eight atoms) and different structures/conformations (linear, cyclic, and cage, in a total of 13 structures), were performed at B3LYP/6-311+G(d,p) level of theory. The calculated infrared spectra show two distinct Si-O-Si stretch vibration bands for models of caged structures. The higher-frequency IR band at ca. 1120 cm(-1) is derived from the antisymmetric Si-O-Si stretch vibration mode, while the lower-frequency band at 1035 cm(-1) is due to the symmetric Si-O-Si stretch and is characteristic of the cyclic clusters, being absent in highly symmetric cage structures. The calculated versus the experimental FTIR spectra of poly(methylsilsesquioxane) (PMSQ) dried aerogel in KBr pellet show that cage/cyclic-like structures prevail over ladder structures (linear) in actual PMSQ.

Structural Changes of Cu(110) and Cu(110)-(2 × 1)-O Surfaces under Carbon Monoxide in the Torr Pressure Range Studied with Scanning Tunneling Microscopy and Infrared Reflection Absorption Spectroscopy

The atomic structure of the clean Cu(110) and the oxygen covered Cu(110) surfaces in the presence of carbon monoxide (CO) gas in the Torr pressure range at 298 K is studied using scanning tunneling microscopy (STM) and infrared reflection adsorption spectroscopy (IRRAS). We found that the initially clean surface reconstructs to form short rows of Cu atoms along the [1–10] direction separated by missing rows. The adsorbed CO molecules show two different C–O stretch vibration modes originating from molecules bound to Cu atoms with different coordination numbers, in the middle and at the end of the atomic rows. On the oxygen covered p(2 × 1) surface, adsorbed CO is observed only after removal of surface O atoms by reaction with CO. In the presence of 1:5 and 1:1 mixtures of O2 and CO at 298 K, the p(2 × 1)-O reconstructed surface transforms into Cu2O, instead of reducing to metallic Cu.

Corrosion, ion release and Mott–Schottky probe of chromium oxide coatings in saline solution with potential for orthopaedic implant applications

We report our investigation on chromium oxide thin film coatings that show a negligible ion release during electrochemical corrosion testing in saline solution. The chemical constituents of the films prepared by reactive magnetron sputtering were identified to be predominantly Cr2O3 based on Raman spectroscopy anti-symmetric stretching vibration modes for CrIII–O and other peaks and an FTIR spectroscopy Eu vibrational mode at 409 cm−1. X-ray photoelectron spectroscopy, multiplet fitting for 2P3/2 and 2P1/2 states also confirmed the predominantly Cr2O3 stoichiometry in the films. The prepared chromium oxide coatings showed superior pitting corrosion resistance compared to the native chromium oxide films on bare uncoated stainless steel when tested under open circuit potential, potentiodynamic polarisation and cyclic voltammetry in saline solution. The chromium ion released into solution during the corrosion testing of stainless steel substrates coated with chromium oxide coatings was found to be negligibly small based on atomic absorption spectroscopy measurements. Our Mott–Schottky analysis investigation showed that the negligibly small ion release from the chromium oxide coated steel substrates is most likely due to a much lower defect density on the surface of the deposited coatings compared to the native oxide layer on the uncoated steel substrates. This opens up the opportunity for using chromium oxide surface coatings in hip, knee and other orthopaedic implants where possible metal ion release in vivo still poses a great challenge.

Effects of single bond-ion and single bond-diradical form on the stretching vibration of C[dbnd]N bridging bond in 4,4′-disubstituted benzylidene anilines

Fifty-seven samples of model compounds, 4,4′-disubstituted benzylidene anilines, p-X-ArCH=NAr-p-Y were synthesized. Their infrared absorption spectra were recorded, and the stretching vibration frequencies νCN of the CN bridging bond were determined. New stretching vibration mode was proposed by means of the analysis of the factors affecting νCN, that is there are mainly three modes in the stretching vibration of CN bond: (I) polar double bond form CN, (II) single bond-ion form C+–N− and (III) single bond-diradical form C–N. The contributions of the forms (I) and (II) to the change of νCN can be quantified by using Hammett substituent constant (including substituent cross-interaction effects between X and Y groups), whereas the contribution of the form (III) can be quantified by employing the excited-state substituent constant. The most contribution of these three forms is the form (III), the next is the form (II), whose contribution difference was discussed with the viewpoint of energy requirements in vibration with the form (III) and form (II).

Impact of post deposition annealing in O2 ambient on structural properties of nanocrystalline hafnium oxide thin film

In the present work, HfO2 thin film (100 nm) has been deposited by sputtering technique and annealed at various temperatures ranging from 400 to 1000 °C (in step of 200 °C) in O2 ambient for 10 min. The samples have been characterized using XRD, FTIR, EDAX, AFM and Laser Ellipsometer. The impact of annealing temperatures in O2 ambient on structural properties such as crystallite size, phase, orientation, stress have been studied using XRD. The Hf–O phonon peaks in the infrared absorption spectrum are detected at 512, 412 cm−1. The stretching vibration modes at 720 and 748 cm−1 correspond to HfO2. AFM data show mean grain size in the range of 38–67 nm. The film reveals variation in structural properties, which appears to be responsible for variation in oxygen percentage, refractive index (1.96–2.01) at 632 nm wavelength and roughness (6.13–16.40 nm). Annealing temperature as well as ambient condition has significant effects on stress, crystal size and thus the arrangement of atoms. For good quality film, annealing temperature larger than 600 °C is desired.

Study of the dehydroxylation of kaolinite and alunite from a Mexican clay with DRIFTS-MS

AbstractFew reports exist on the use of Diffuse Reflectance Infrared Fourier Transform Spectrometry coupled with Mass Spectrometry (DRIFTS-MS) in situ to monitor the dehydroxylation of kaolinitic clays. The use of DRIFTS-MS in situ allows study of the effect of heat treatment on the dehydroxylation, identifying intensities and temperatures at which the hydroxyl groups are released, forming metakaolinite and meta-alunite. The effluent gases from the infrared cell were analysed by mass spectrometry. The decrease in intensity of the bands at 3694, 3669, 3650 and 3621 cm−1 associated with the −OH stretching vibration modes of AlVI−OH−AlVI of kaolinite began at 450°C. Two additional bands at 3513 and 3485 cm−1 are associated with the vibration of AlVI−OH of alunite that also began to disappear during thermal treatment. Monitoring of the fractions m/e 17 and 18 using a mass spectrometer revealed that the intensity of these fractions increased starting at 450°C. Therefore, it is possible to study the dehydroxylation process of clays during thermal treatment.Chemical and mineralogical characterization of a kaolinitic clay (KN) fromMexico showed that the clay consists of 64.8% kaolinite, 11.0% alunite and 24.4% quartz based on PXRD, EDS, TG/DTA, TEM and FTIR results, and suggested that the material might have potential for use in the manufacture of ceramics, refractory bricks or geopolymers.

Intensification phenomenon of weak ionic interactions of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid macro-dispersed in poly(methyl methacrylate): FTIR spectroscopic evidence

Phase separated heterogeneous conducting films of poly(methyl methacrylate) PMMA/1-butyl-3-methylimidazolium hexafluorophosphate BMIPF6 have been prepared using solution cast technique and investigated by means of FT-IR spectroscopy. Based on the shifts of specific frequencies the intra- and inter molecular interactions have been estimated. To accurate determine of shifts value the Gaussian fitting of ring C–H and F–P stretching vibration modes of BMIPF6 has been applied. It was found that BMIPF6 interacts with PMMA mainly via the hydrogen atom on the second carbon of imidazolium cation and carboxylic oxygen of polymer. In addition, in BMIPF6 captured by PMMA as a liquid macro-dispersed phase the interaction between BMI+ cation and PF6− anion was found to be more intensive than a weak one in a bulk pure ionic liquid.

Synthesis and Evaluation of Thiocyanate and Selenocyanate Derivatives of Adenosine and Phenylalanine as Vibrational Reporters

Two novel modified 2’-deoxyadenosine (dA) molecules, Si2-dA-SCN and Si2-dA-SeCN, and two novel modified phenylalanine (Phe) molecules, Boc-Me-PheCH2SCN and Boc-Me-PheCH2SeCN have been synthesized and the -SCN and -SeCN functional groups evaluated as vibrational reporters. The syntheses of Si2-dA-SCN and Si2-dA-SeCN were accomplished in three steps in 16% and 32% overall yields, respectively, from commercially available adenine 9-β-D-arabinofuranoside. Similarly, the syntheses of Boc-Me-PheCH2SCN and Boc-Me-PheCH2SeCN were completed in four steps in 8.9% and 2.3% overall yields, respectively, using commercially available N-(tert-Butoxycarbonyl)-4-iodo-L-phenylalanine as the starting material. The absorbance bands resulting from the -SCN and -SeCN stretch vibrational modes are in a clear region of the IR spectrum, and are narrow and symmetrical suggesting that they are not complicated by anharmonic coupling. These stretch vibrational modes are also sensitive to local environment as shown by change in position and full width half maximum (fwhm) of the absorbance bands in different solvents, including tetrahydrofuran (THF), H2O/THF mixtures, and ethanol (EtOH). For example, the -SeCN absorbance band of Boc-Me-PheCH2SeCN shifted from 2151.2 to 2150.7 cm−1, and broadened from 7.1 to 11.0 cm−1, going from 0-40% (v/v) H2O/THF. In addition, the same band in ethanol shifted to 2154.1 cm−1 and the fwhm increased to 12.7 cm−1. These reporters also have longer vibrational lifetimes than other commonly used probes as determined by two-dimensional infrared spectroscopy (2D IR) experiments using Si2-dA-SCN and Si2-dA-SeCN. The increased lifetimes and the solvent sensitivity make -SCN and -SeCN moieties highly promising for their utility in studying several processes, including protein and nucleic acid hydration dynamics.

Suitability of Malaysian Fly Ash for Geopolymer Synthesis

Fly ash is a pozzolanic material which is produced during coal combustion in thermal power plants. This paper investigates the suitability of Malaysian fly ash for geopolymer synthesis. Chemical composition analysis, particle size analysis, amorphous and crystalline phases present, bonding nature, and microstructural behavior are used to determine the suitability of fly ash for geopolymer synthesis. The results showed that fly ash contains silica, alumina, ferrous oxide, and calcium oxide in major proportions which are the main ingredients required for geopolymer synthesis. Higher portion of particles having size in the range of 1-15 µm. Fly ash contains quartz, mullite, and ferrite as the crystalline compounds while the major portion of fly ash is in amorphous form. The band due to asymmetric stretching vibration mode of Si-O-T appears at 1095 cm-1 which is the main band used to follow geopolymer formation. Microstructure of fly ash shows that the higher portion of fly ash is in amorphous form while it contains cenospheres, magnetic spheres, carbon, and a large number of small particles. Malaysian fly ash is a suitable material for geopolymer and it can be used for geopolymer synthesis.

Structural and optical characteristics of SnS thin film prepared by SILAR

AbstractSnS thin films were grown on glass substrates by a simple route named successive ion layer adsorption and reaction (SILAR) method. The films were prepared using tin chloride as tin (Sn) source and ammonium sulfide as sulphur (S) source. The structural, optical and morphological study was done using XRD, FESEM, FT-IR and UV-Vis spectrophotometer. XRD measurement confirmed the presence of orthorhombic phase. Particle size estimated from XRD was about 45 nm which fitted well with the FESEM measurement. The value of band gap was about 1.63 eV indicating that SnS can be used as an important material for thin film solar cells. The surface morphology showed a smooth, homogenous film over the substrate. Characteristic stretching vibration mode of SnS was observed in the absorption band of FT-IR spectrum. The electrical activation energy was about 0.306 eV.