Stretching Mode Vibrations Research Articles

Live-cell ATR-FTIR spectroscopy as a novel bioanalytical tool for cell glucose metabolism research

Current novel drug developments for the treatment of diabetes require multiple bioanalytical assays to interrogate the cellular metabolism, which are costly, laborious and time-consuming. Fourier-transform infrared (FTIR) spectroscopy is a nondestructive, label-free, sensitive and low-cost technique that is recently found to be suitable for studying living cells. The aim of this study is to demonstrate that live-cell FTIR can be applied to study the differences in glucose metabolism in cells in normal culturing medium and cells treated in high glucose (a diabetes model) in order to highlight the potential of the technique in diabetes research. Live HepG2 cells were treated in normal glucose (3.8 mM; control) or high glucose (25 mM) medium and were measured directly using the FTIR approach. Principal component analysis was used to highlight any possible correlated changes 24, 48 and 72 h after treatments. FTIR spectra of live cell treated in normal and high glucose medium have shown significant differences (p < 0.05) for all treatment time. The control cells have seen an increased in the absorbance at 1088, 1240 and 1400 cm−1, which are associated with phosphate stretching mode vibrations from phosphorylated proteins and DNA back bone; and symmetric stretching mode vibration of COO- from fatty acids, amino acids, lipids and carbohydrate metabolites. However, the high glucose treated cells have shown a different changes in the 1000–1200 cm−1 region, which is linked to the glycogen and ATP:ADP ratio. In conclusion, live-cell FTIR can be a low-cost method for the studies of metabolic changes in cells.

Microwave-assisted V2O5 nanoflowers for efficient lithium-ion battery

ABSTRACT A facile approach to synthesise V2O5 nanoflowers are adopted through the microwave-assisted method. The as-prepared V2O5 was characterised by the X-ray diffraction, scanning electron microscopy analyses. The X-ray diffraction spectra confirmed the formation of the orthorhombic crystal structure of V2O5 nanoflowers with an average crystallite size of 20 nm. FTIR results showed the V-O-V stretching mode vibration at 442 cm−1. The above material has studied as cathode material for lithium-ion batteries (LIB) at C/10 rate and the results showed, V2O5 nanoflowers delivered the specific capacity of 241 mAh g−1 than the commercial V2O5 of 98 mAh g−1 at 1.5–4.0 V apart from this, better cycle stability over 100 charge-discharge cycles and reasonable discharge capacities obtained at high C-rates. These results suggest enhancement of LIB capacity due to high surface area and good porosity of mesoporous V2O5 nanoflowers.

Utilization of Nkpuma-Akpatakpa clay in ceramics: characterization and microstructural studies

Nkpuma – Akpatakpa clay was analysed for its ceramics suitability. Chemical, mechanical and spectral characterization of the clay was carried out to obtain more information from this clay found in commercial quantity at Ebonyi State Nigeria. The XRD analysis showed that the principal minerals in the clay are quartz, qandilite, aragonite, Muscovite and anatase. FTIR showed the stretching vibrations for Si – O at 685.8cm –1 showing the presence of Quartz. The frequency at 1431cm-1 is due to (CO3)2- stretching mode vibration or C – O stretching of Aragonite and the band at 2467.6 is due to OH- stretching. Bands observed at 984.7 and 987.7cm –1 correspond to Al – O bending vibrations which suggest the presence of muscovite in the clay and SEM studies were also carried out and reported. Porosity of the clay was 0.88% considered too small for refractory, thermal insulation and other high porosity desired ceramics applications. Value obtained for Fe2O3 was &gt; 1.7% which accounted for why the clay did not fire white. The values for M.O.R was &gt;40KgF/cm2. The refractoriness was &lt;13400C. Chemical characterization showed the presence of fluxing oxides at elevated levels which are responsible for the poor refractoriness and limits the utilization of the clay to low or mid-temperature ceramics products.Keywords: Nkpuma-Akpatakpa clay, Ceramics, Characterization, Qandilite, FTIR, Bulk density

1D coordination polymers with polychalcogenides as linkers between metal atoms

Abstract The reactions of zinc metal with elemental selenium and selenium/sulfur mixtures in liquid ammonia or methylamine under solvothermal conditions in closed glass ampoules at 50 °C lead within some days specifically to [Zn(NH 3 ) 2 Se 4 ] n ( 1 ), [Zn(MeNH 2 ) 2 Se 4 ] n ( 2 ), [Zn(NH 3 ) 2 Se 2.23 S 1.77 ] n ( 3 ). From MnCl 2 , Rb 2 Se and excess Se in n -butylamine [Mn( n BuNH 2 ) 4 Se 6 ] n ( 4 ) is obtained after prolonged reaction time at ambient temperature. The compounds are sensitive towards air and loss of NH 3 or the amine ligands. The crystal structures were determined by single crystal diffraction at low temperatures. As a common structural feature, all compounds represent 1D coordination polymers with polychalcogenide chains as linkers between the metal atoms and consist of infinite [ M – Ch m –] n chains ( M =Zn, Mn; Ch m =Se 4 , (S/Se) 4 , Se 6 ). The Zn central atoms in 1 – 3 have tetrahedral coordination with two amine ligands, the Mn atoms in 4 have octahedral coordination with four amine ligands and cis position of the two Se atoms. Raman spectra of 1 – 3 show the stretching mode vibrations of the Ch 4 groups. The observation of S–S, S–Se, and Se–Se vibration bands in the spectrum of 3 indicates the presence of mixed S/Se polyanions. An optical band gap of 1.86(5) eV was determined for 2 by diffuse reflectance spectroscopy.

Formation dynamics of hexadecanethiol self-assembled monolayers on (001) GaAs observed with photoluminescence and Fourier transform infrared spectroscopies

The dynamics of hexadecanethiol (HDT) [HS(CH2)15CH3] chemisorption and the formation of a self-assembled monolayer (SAM) on the GaAs(001) surface was studied in situ by monitoring the photoluminescence (PL) intensity over a 20 h period. Comparing the PL time series in HDT solution with that of the bare GaAs surface similarly exposed to the ethanol solvent, we observed a two-phased evolution of the associated PL enhancement. Time-commensurate changes in the absorption frequency and intensity of the C–H stretching mode vibrations were then recorded using Fourier transform infrared spectroscopy, supporting that the PL enhancement corresponds directly with known mechanisms of ordered SAM formation. These results highlight the sensitivity with which in situ PL monitoring can reflect surface processes and underscores its potential for use in sensor applications.

Hydrocarbons on Saturn's satellites Iapetus and Phoebe

Material of low geometric albedo ( p V ⩽ 0.1 ) is found on many objects in the outer Solar System, but its distribution in the saturnian satellite system is of special interest because of its juxtaposition with high-albedo ice. In the absence of clear, diagnostic spectral features, the composition of this low-albedo (or “dark”) material is generally inferred to be carbon-rich, but the form(s) of the carbon is unknown. Near-infrared spectra of the low-albedo hemisphere of Saturn's satellite Iapetus were obtained with the Visible–Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft at the fly-by of that satellite of 31 December 2004, yielding a maximum spatial resolution on the satellite's surface of ∼65 km. The spectral region 3–3.6 μm reveals a broad absorption band, centered at 3.29 μm, and concentrated in a region comprising about 15% of the low-albedo surface area. This is identified as the C H stretching mode vibration in polycyclic aromatic hydrocarbon (PAH) molecules. Two weaker bands attributed to CH 2 stretching modes in aliphatic hydrocarbons are found in association with the aromatic band. The bands most likely arise from aromatic and aliphatic units in complex macromolecular carbonaceous material with a kerogen- or coal-like structure, similar to that in carbonaceous meteorites. VIMS spectra of Phoebe, encountered by Cassini on 11 June 2004, also show the aromatic hydrocarbon band, although somewhat weaker than on Iapetus. The origin of the PAH molecular material on these two satellites is unknown, but PAHs are found in carbonaceous meteorites, cometary dust particles, circumstellar dust, and interstellar dust.

Characterization of Undoped, N- and P-Type Hydrogenated Nanocrystalline Silicon Carbide Films Deposited by Hot-Wire Chemical Vapor Deposition at Low Temperatures

Undoped, n- and p-type hydrogenated nanocrystalline cubic silicon carbide (nc-3C–SiC:H) films were successfully deposited on glass and silicon substrates at a low substrate temperature of about 300 °C by hot-wire chemical vapor deposition. The structural, optical, and electrical properties of the films were investigated by X-ray diffraction (XRD), Fourier transform infrared absorption (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry, photothermal deflection spectroscopy (PDS), and conductivity measurements. The XRD and FTIR measurements revealed a clear correlation between the average grain size and width of the SiC stretching mode vibration of the films. The dark conductivity of the films was increased from 5.8×10-11 to 6.2×10-6 S/cm with increasing the grain size from 6.4 to 16.6 nm. The detailed analysis of the dark conductivity indicates that the Fermi level position is affected by the grain size of the films. Spectroscopic ellipsometry measurements showed that the dielectric functions of the films are strongly affected by the grain size. The n- and p-type nc-3C–SiC:H films were also successfully deposited using phosphine, hexamethyldisilazane, and dimethylaluminumhydride as dopants. For the n- and p-type films, the dark conductivities of 5.32×10-0 and 7.67×10-4 S/cm were achieved, respectively. The optical absorption spectra of the doped films indicate that p-type doping significantly affects absorption coefficients above the bandgap of nc-3C–SiC:H compared with n-type doping. For the n-type films, the absorption coefficients below the bandgap are affected by free carrier absorption as well as by localized states within the bandgap.

Two-Dimensional Correlation Study of Uniaxially Drawn Poly(Ethylene Terephthalate) Films by Using Attenuated Total Reflection Based Dynamic Compression Modulation Step-Scan Fourier Transform Infrared in Combination with Spectral Simulation Analysis by Density Functional Theory

Attenuated total reflection (ATR) based dynamic compression modulation two-dimensional (2D) correlation studies of uniaxially drawn poly(ethylene terephthalate) (PET) films have been performed in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of the CCO stretching mode vibrations show four distinct correlation peaks located around 1290, 1265, 1248, and 1234 cm(-1). These bands can be clearly assigned to the combination bands or coupling modes of the CH in-plane bend of the benzene ring or the CH(2) deformation of the ethylene glycol unit, as well as CCO stretching vibrations, which are gauche conformer's characteristic bands, by DFT analysis. The sequential analysis of 2D correlation data shows that, upon applying the dynamic compression, the response of the side chain regions (ester groups) occurs first, followed by that of the backbone regions (benzene rings). The ATR based dynamic compression modulation 2D correlation spectroscopy in combination with DFT analysis can be a powerful tool for various polymer characterizations.

Formation of wide and narrow optical-band-gap amorphous-CN x:H films using i-C 4H 10/N 2 supermagnetron plasma

Amorphous-CN x :H films were formed using supermagnetron plasma CVD. In this experiment, the rf powers supplied to the upper electrode (UPRF) and lower electrode (LORF) were controlled to 10 and 5–800 W, respectively. The optical band gap of the a-CN x :H film was found to decrease largely from 2.6 to 0.22 eV with the increase of LORF from 5 to 800 W. The hardness increased from 5.9 to 27.5 GPa with the increase of LORF from 5 to 200 W, and then it decreased gradually to 10.7 GPa with the further increase of LORF to 800 W. FT-IR absorption spectrum showed strong C H stretching mode vibration at low LORF, i.e., films formed at low LORF included many hydrogens bonded to carbons. The photoluminescence (PL) was measured, and it was found that the wide optical-band-gap a-CN x :H film formed at UPRF/LORF of 10/10 W showed broad white PL.

Infrared absorption and Raman scattering ofOH−andOD−stretching-mode vibrations in alkali fluorides: Isolated defects

The stretching-mode (SM) of ${\mathrm{OH}}^{\ensuremath{-}}$ and ${\mathrm{OD}}^{\ensuremath{-}}$ defects in LiF, NaF, and KF hosts has been studied with Raman scattering and Fourier transform infrared (FTIR) absorption spectroscopy, at temperatures from 4 K to 500 K. In all three hosts the $〈111〉$ orientation of the ${\mathrm{OH}}^{\ensuremath{-}}$ molecular axis is confirmed both by polarized Raman spectra and by stress-induced FTIR dichroism. The latter technique also yields the values of the disc-shaped elastic dipole tensor, aligning the ${\mathrm{OH}}^{\ensuremath{-}}$ parallel to an applied $〈111〉$ uniaxial stress with a Curie law. Accurate band-shape analysis of low-temperature FTIR absorption and ${T}_{2g}$ Raman spectra yields for low concentrations of ${\mathrm{OH}}^{\ensuremath{-}}$ in LiF and KF consistent values of their nearest-neighbor reorientational tunneling parameters $(\ensuremath{\Delta}=1.2$ and $0.6{\mathrm{cm}}^{\ensuremath{-}1},$ respectively). For ${\mathrm{OH}}^{\ensuremath{-}}$ in NaF and for ${\mathrm{OD}}^{\ensuremath{-}}$ in all three hosts spectral substructure from tunneling is undetectable in the narrow Lorentzian-shaped SM lines. The strong temperature broadening that occurs for the SM absorption and ${T}_{2g}$ Raman bands and the smaller broadening of the ${A}_{1g}$ line can be fitted with models for the dephasing of the transition by phonons, considering the presence of isotropic and anisotropic dephasing components. In spite of the very different amplitudes of the ${\mathrm{OH}}^{\ensuremath{-}}$ and ${\mathrm{OD}}^{\ensuremath{-}}$ SM vibrations, their relative infrared absorption and Raman intensities are found to be very similar; the only exception is an extremely weak oscillator strength of the ${\mathrm{OD}}^{\ensuremath{-}}$ absorption in KF.

Laser Raman spectroscopic study of water in gelatin-surfactant solutions and gels

A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol (40–60 °C) states at various concentrations (0.5, 1, 5, 10 and 15 mM) of anionic surfactant, sodium dodecyl sulfate (SDS). The in-phase collective stretching mode vibration of hydrogen-bonded -OH oscillators, centered around 3250 cm−1 in a tetrahedral network of water molecules, was observed to be significantly affected by temperature and the presence of SDS. According to our observation this may be due to the thinning of the hydration water around the gelatin molecules due to strong thermal agitation. The peak center of the collective bands of water decreased linearly with SDS concentration in the gel state which implied that with the increase in concentration of SDS, the -OH oscillators gradually lost their attachment to gelatin chains and were replaced by SDS molecules. Ultimately this resulted in a thinning of the hydration layer around the gelatin and the oscillation frequency of -OH oscillators moved towards 3250 cm−1 at 1 mM SDS concentration resulting in increased coupling of -OH oscillators to form the tetrahedral network at the critical micelle concentration (cmc) of SDS. The variation in the peak amplitudes and the systematic reversal of their trend about the cmc axis was surprising. At 40 °C the amplitude of the peak at 3250 cm−1 increased drastically due to a possible coil expansion by about 7–8% which accommodated more interstitial water into the pseudonetwork leading to an increase in the number of nearest neighbors and for about 6% increase in the C value. However, at the cmc the peak amplitude was observed to be independent of temperature. Continuous shifting of the peak center and full width at half-maxima towards lower values was observed with increasing SDS concentrations in the gel state.

Relaxation phenomena in keV-ion implanted hydrogenated amorphous silicon carbide

Infrared spectroscopy was used in order to monitor the relaxation phenomena in amorphous silicon carbide induced by hydrogen introduction. Amorphous silicon carbide (a-SiC) thin films (90 nm) were prepared by high fluence implantation (3×1017 ions cm−2) of C ions in silicon. To obtain hydrogenated (a-SiC:Hx) films hydrogen ions were also implanted at different fluences and the hydrogen fraction ranges from x=0.1 to x=1.0. The bonding structure was studied by infrared spectrometry, following the stretching mode vibration of Si–C, Si–H and CHn bonds. Hydrogen introduction in amorphous silicon carbide produces a decrease of width and of IR absorption cross section of Si–C mode, both effects being related to a decrease of disorder of the amorphous phase. The main role of hydrogen is the rearrangement of bonds, the saturation of dangling bonds and the reduction in the number of defects, which relax the structure of the amorphous material.

Pressure and Temperature Effects on Conformational and Hydrational Properties of Lamellar and Bicontinuous Cubic Phases of the Fully Hydrated Monoacylglyceride MonoelaidinA Fourier Transform-Infrared Spectroscopy Study Using the Diamond Anvil Technique

We report on the effects of pressure and temperature on the phase behavior and structural properties of aqueous dispersions of monoelaidin (ME) using Fourier transform−infrared spectroscopy (FT-IR) in combination with the diamond anvil technique. The IR spectral parameters, such as frequencies, intensities, band shapes, and band splittings, were used to detect structural and dynamic changes upon change of pressure and temperature. Analysis of these spectral parameters yields information on conformer population, reorientational fluctuations, interchain interaction, hydrogen bonding, and phase transformations. The monoacyglyceride ME was chosen for investigation because it exhibits various mesomorphic liquid−crystalline phases of different dimensionality, including lamellar, a cubic-primitive (QIID), and a body-centered cubic phase (QIIP). The latter two are inverse bicontinuous cubic phases. We have established the excess water p,T-phase diagram of ME over the 1−23-kbar range at ∼15−95 °C. In the high-pressure region, enhanced interchain interaction leads to a correlation field splitting of the CH2 bending and rocking modes, which is expected when entering the lamellar crystalline Lc phase that has the smallest partial molar volume. As revealed by the phase diagram, the energetic degeneracy of the cubic phases is broken. With increasing temperature or decreasing pressure, the cubic phases QIIP and QIID are formed. Interpretation of the CH2 stretching and wagging modes for evaluation of conformational states in the fluidlike disordered (Lα, QIIP, and QIID) phases reveals different populations of gauche conformers and kinks in these fluidlike phases. From the analysis of the carbonyl stretching mode vibrations we have been also able to detect small but marked differences in the level of hydration of different bicontinuous cubic phases. Compared with the QIID phase of ME, the lipid chains of the body-centered cubic phase QIIP seem to contain a slightly higher population of gauche sequences and a slightly lower level of hydration of the carbonyl group. The results are compared with recent energetic models for intercubic phase transitions.

A study of anthracene–Arn (n=0–5) in the ground cationic state by laser threshold photoelectron spectroscopy: Selective ionization of complex isomers formed in the free jet expansion

The van der Waals complexes formed between anthracene and argon in a free jet expansion are studied using laser resonance enhanced multiphoton ionization (REMPI) threshold photoelectron spectroscopy with the aim of selectively ionizing specific isomers of small- to medium-sized clusters for which discrete absorption peaks exist in the excitation spectrum. Two-color (1+1′) REMPI threshold photoelectron spectra of a number of isomers of anthracene–Arn (n=1–5) have been recorded in addition to that of anthracene itself. The following adiabatic ionization energies (Ia) have been obtained to within ±5 cm−1: 59 872 (n=0), 59 807 and 59 825 (n=1), 59 757 and 59 774 (n=2), 59 695 (n=3), 59 606 and 59 660 (n=4), and 59 565 cm−1 (n=5). For n=1–3, detailed van der Waals cation vibrational structure was observed, showing progressions in both bending and stretching mode vibrations. The resulting vibrational information together with the ionization energy red shifts has helped in assigning bands observed in the threshold photoelectron spectra to particular geometric isomers some of which were not necessarily observed in the excitation spectrum.

Low Temperature Deposition of SiO2 by Distributed Electron Cyclotron Resonance Plasma‐Enhanced Chemical Vapor Deposition

Silicon dioxide thin films have been deposited at low substrate temperatures using a microwave plasma. A new type of microwave excitation, the distributed electron cyclotron resonance (DECR), which provides high density plasma (≈ 1011 cm−3) of low‐energy ions, has been used. Pure and are mixed in the discharge. At constant pressure (0.1 pa), the ratio of flow to flow was varied from 1–9. We have studied the effects of the gas phase composition at two different microwave powers (800 and 1200 W) on the refractive index, atomic composition, infrared absorption bands, etch rate, and electrical properties of the films. For ratio larger than 4, near‐stoichiometric films are obtained, with N and H atomic contaminations below 2 and 5 atomic percent (a/o), respectively, even at low temperature and without post deposition annealing. For , the films have physical and chemical properties similar to those obtained by RF plasma enhanced chemical vapor deposition at 350°C, in terms of refractive index in the range of 1.47–1.48, etch rate in “P‐etch” (6 Å/s), and Si‐O‐Si stretching mode vibration (1058 cm−1). These films exhibit, at and 1200 W, electrical resistivity of 1015 Ω cm and critical field larger than 3.5 MV cm−1, without post‐deposition annealing.

Light-induced degradation of hydrogenated amorphous silicon films deposited at different rf powers

Light-induced degradation has been investigated in glow-discharge deposited hydrogenated amorphous silicon (a-Si:H) films (≊1 μm), deposited at different rf powers by glow-discharge decomposition of pure silane. Changes in electrical, ellipsometric, and infrared parameters have been observed by exposing the films to white light of intensity 350 mW/cm2 for 4 h. The initial dangling bond density increases and the rate of change of the dangling bond density decreases in films successively deposited at higher powers up to 50 W. However, at still higher power (75 W), a reverse behavior has been observed. Spectroscopic ellipsometry shows maximum void fraction in films deposited at 50 W. Light soaking results in an increase in void fraction and hence, the dangling bond density. The unaltered position of ε2 max suggests that the tetrahedral coordination of the silicon network remains unchanged on light exposure. The IR transmittance difference curves indicate changes on light soaking in the stretching mode vibrations only in 50-W deposited film and in the rocking mode for all films except that deposited at 5 W. A greater change (maximum change for 50-W film) in the state of bonds has been observed for samples having a greater initial void fraction.

Application of Laser-Excited Raman Spectroscopy to Organic Chemistry I. Raman Spectra of Some Acyclic Monoterpenes

Laser-Raman spectra of 12 acyclic terpenoids has been recorded. Assignments were made for stretching mode vibrations of carbon-carbon double bonds by comparison with infrared spectra. The results of intensity and depolarization studies are discussed.