Fourier Transform Infrared Absorption Bands Research Articles

Characterization of yeast cells as a microencapsulation wall material by Fourier-transform infrared spectroscopy

The chemically induced structural changes of yeast cells as a wall material for the microencapsulation of chlorogenic acid (CGA) were investigated by the Fourier-transform infrared (FT-IR) spectroscopy. Results indicate that the encapsulation performance of S. cerevisiae cells was largely affected by the composition of the culture medium, and the optimal composition of the culture medium was obtained in terms of the encapsulation yield of CGA. The yeast cells cultured under optimal conditions were subject to chemical treatment by sodium chloride, cetyltrimethylammonium bromide (CTAB), Triton X-100, sodium dodecyl sulfate (SDS) or ethanol. The chemical treatments notably changed the encapsulation properties of S. cerevisiae cells for CGA, with the highest encapsulation yield in the CTAB case. All the chemical treatments decreased the FT-IR absorption bands for proteins and nucleic acids of S. cerevisiae cells but increased those for lipids and fatty acids, and it is thus rather difficult to discuss the relationship between the encapsulation yield and the wall structures derived from the original FT-IR spectra. In contrast, multivariate analyses on the second derivative transformation FT-IR spectra of the yeast cell wall materials indicate that under various culture and chemical treatment conditions, the encapsulation yield of yeast cells for CGA was positively correlated with its IR absorption ratios of 1157 cm −1 to 1043 cm −1 (D1157/D1043) and of 1537 cm −1 to 1043 cm −1 (D1537/D1043) significantly ( p < 0.05), whereas negatively correlated with those of 1080 cm −1 to 1043 cm −1 (D1080/D1043), 1458 cm −1 to 1043 cm −1 (D1458/D1043) and 1740 cm −1 to 1043 cm −1 (D1740/D1043) significantly ( p < 0.05). The five absorption ratios proposed here from the second derivative transformation FT-IR spectra may be a rapid gauge for predicting the encapsulation properties of yeast cells and screening out optimal yeast cells for encapsulation of other species.

Catalytic conversion of air–methane flow by nanostructured ruthenium dioxide: FTIR spectroscopy and modeling

Nanostructured powders of ruthenium dioxide RuO 2 were synthesized via a sol–gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO 2 nanopowders were characterized by X-ray diffraction. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range 8–16 nm, with a minimum of crystallite dimension for pH 1.5. Catalytic conversion of methane by these RuO 2 nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO 2) was maximum for sample prepared at pH 1.5, and mainly correlated to crystallite dimensions. A modeling approach of catalytic conversion is proposed for such a specific experimental configuration.

Structure, microstructure, and size dependent catalytic properties of nanostructured ruthenium dioxide

Nanostructured powders of ruthenium dioxide RuO 2 were synthesized via a sol gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO 2 nanopowders were characterized by X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Rietveld refinement of mean crystal structure was performed on RuO 2 nanopowders and crystallized standard RuO 2 sample. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range of 4–10 nm, with a minimum of crystallite dimension for pH=1.5. A good agreement between crystallite sizes calculated from Williamson Hall approach of X-ray data and from direct TEM observations was obtained. The tetragonal crystal cell parameter (a) and cell volumes of nanostructured samples were characterized by values greater than the values of standard RuO 2 sample. In addition, the [Ru–O 6] oxygen octahedrons of rutile structure also depended on crystal size. Catalytic conversion of methane by these RuO 2 nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO 2) was maximum for sample prepared at pH=1.5, and mainly correlated to crystallite dimensions. No significant catalytic effect was observed from sintered RuO 2 samples.

Combined effects of tannate and ageing on structural and surface properties of aluminum precipitates

AbstractThe influence of organics on the crystallization of Al precipitates has been well documented. However, the effects of organics and ageing on the transformation and structural configuration of Al precipitates in relation to their surface and charge properties are not fully understood. This study investigated the structural, microporous and surface properties of Al precipitates formed under the influence of tannate and ageing. The Al precipitates were synthesized at an initial Al concentration of 7 × 10−3 M, an OH/Al molar ratio (MR) of 3.0, and initial tannate/Al MRs of 0, 0.001, 0.01 and 0.1, and aged for 1, 10 and 40 days. As indicated by a decrease in gibbsite and bayerite and an increase in the oxalate-extractable Al contents, the non-crystalline precipitates increased with the increase of the initial tannate/Al MR. This observation is in accord with the X-ray diffraction and Fourier transform infrared (FTIR) data. The impact of tannic acid on the nature of the Al precipitates is also reflected in the increase of the contents of the pyrophosphate-extractable Al, which is indicative of organically bound Al. This observation is in agreement with the increase in the intensity of characteristic FTIR absorption bands of tannate and the organic C and adsorbed water contents. The decrease in the crystallinity of Al precipitates with increase in the tannate/Al MR resulted in the development of microporosity, increase in BET specific surface area and decrease of the average pore diameter and point of zero salt effect (PZSE). The FTIR absorption bands characteristic of tannate of the Al precipitates became weaker with ageing, in accord with the ageing-induced decrease in the contents of organic C and pyrophosphate-extractable Al. Ageing drastically decreased the BET specific surface area of the Al precipitates formed in the absence of tannate but this effect was less conspicuous for the products formed at the tannate/Al molar ratio of 0.1. The ageing-induced change in the PZSE of the Al precipitates formed both in the absence and presence of tannate was not significant. The results accomplished in this study are of fundamental significance to our understanding of the combined effects of organics and ageing on structural configuration of hydrolytic precipitates of Al in relation to their microporosity, surface and charge properties in the environment.

Local vibrations of interstitial carbon in SiGe alloys

The interstitial carbon impurity (C I) vibrational modes in monocrystalline Si-rich SiGe were investigated using Fourier transform infra red (FTIR) spectroscopy and density-functional modeling. For less than 4.4% Ge concentrations, the two FTIR absorption bands of C I are found to be close to those in silicon, showing shifts in opposite directions with increasing Ge content. The transversal mode band at 932 cm −1 shifts slightly to the high-frequency side, while the longitudinal mode at 922 cm −1 suffers a pronounced red- shift. Each C I-related band is found to consist of two components, and most likely correspond to different combinations of Si and Ge atoms in the neighborhood of the carbon atom. The interstitial carbon defect was modeled by a supercell density-functional pseudopotential method (AIMPRO) for alloys with 4.69% Ge concentration. From energetics, it has been found that each Ge–C bond costs at least 0.4 eV in excess of a Si–C bond. However, structures where Ge atoms are second neighbors to the C atom are marginally bound, and may explain the two-component band structure in the absorption measurements. The vibrational mode frequencies taken from several randomly generated SiGe cells produce the observed opposite shifts for the transverse and longitudinal modes. Centers with high formation energy involving Ge–C–Si and Ge–C–Ge units producing frequencies, were not seen experimentally.

Vashegyite from Gaura cu Muscă Cave (Locvei Mountains, Romania): a new and rare phosphate occurrence

This study investigated the occurrence of vashegyite from a guano-rich deposit located in the Gaura cu Muscă Cave, Romania. Analytical methods used include optical microscopy, X-ray powder diffraction (XRD), scanning electron-microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES), thermal investigations and Fourier-transform infrared (FT-IR) analyses. Vashegyite occurs as friable, chalky white, irregular nodules of up to 2.5 cm in diameter, within a 15 cm thick sequence of organic and minerogenic sediments. The chemical structural formula is: (Al10.91Fe3+0.06Na0.1Ca0.02Mg0.08)Σ=11.17[(PO4)8.78(SiO4)0.056]Σ=8.83(OH)6.17·43.79H2O. Electron microscope images show vashegyite crystals to be flattened on (001). The orthorhombic lattice constants of vashegyite determined by XRD are a = 10.766(2) Å, b = 15.00(4) Å, c = 22.661(1) Å, and V = 3660.62 Å3 (Z = 4). The major weight loss, reflected in 3 endothermic peaks, was observed between 40° and 200°C, corresponding to the removal of water molecules. Vashegyite FT-IR absorption bands are comparable in position and relative intensity to other Al-phosphates. Water percolating through guano becomes strongly acidic and reacts with the clay-rich sediment laid down by the underground stream to form vashegyite. In the lower part of the investigated profile, crandallite and ardealite were also found.

Identification of chemical compositions of skin calcified deposit by vibrational microspectroscopies

Calcinosis cutis is characterized by the deposition of calcium salts in the subcutaneous tissues. Both Fourier transform infrared (FTIR) and Raman microspectroscopic analysis have been applied to easily get the chemical compositions of the skin calcified deposit (SCD), which was surgically excised from a female patient. This SCD was cut into two parts for histopathological (H&E stain) examination and vibrational microspectroscopic study. The result indicates that the whole SCD in the skin lesion was found to be a well-developed, mature and hard mass. Several FTIR absorption bands at 873, 961 and 1,031 cm(-1) [the stretching modes of carbonate and phosphate of hydroxyapatite (HA)], 1,547 and 1,658 cm(-1) (the amide I and II bands of collagen) were detected in the IR spectrum of SCD. The Raman spectral bands at 1,665 and 1,450 cm(-1) (collagen); 1,519 and 1,156 cm(-1) (beta-carotene); and 1,072 and 958 cm(-1) (HA) were also obtained. To our knowledge, this is the first report using FTIR and Raman microspectroscopies to quickly identify and quantify three predominant components, collagen, beta-carotene and type B carbonated HA, in the SCD of a patient.

Silicon-Carbon Alloys Synthesized by Electron Cyclotron Resonance Chemical Vapor Deposition

ABSTRACTSilicon-carbon alloys were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) using either halogenated or non-halogenated precursors for the Si and C sources. Halogenated precursors were chosen for initial experiments to try to reduce the H content and to improve the microstructure of the silicon carbide (SiCx) films. While a wide range of compositions has been deposited using the halogenated precursors, only a limited range has been deposited so far with the non-halogenated precursors. Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared (FTIR) spectroscopy show that compositions ranging from near-stoichiometric SiCx to extremely C-rich can be deposited by controlling the deposition temperature, plasma power and C/Si ratio of the halogenated precursors. At the highest C/Si-precursor ratio, the deposited film is electrically conductive with a measured resistivity of 0.067ω-cm, contains only 3-atomic-percent Si and should be considered a Si-doped carbon (C:Si) film. The excellent transparency, especially that of the C:Si films, allowed the assignment of FTIR absorption bands that are usually masked by graphitic inclusions and other impurities. A weak absorption band at 1180cm−1 was found to correlate with the electrical conductivity of the films and was attributed to the asymmetric “bond-and-a-half” Si=C stretch in a Si=C=C functional group where the pi electrons are distributed equally between the three atoms. Additional results show etching of the substrate by reactive Cl from the halogenated precursors can have a dramatic effect on the microstructure, porosity and moisture stability of the films. For experiments involving halogenated precursors, the C:Si films are much more stable than the near-stoichiometric SiCx because C:Si is deposited at lower plasma powers that do not etch the Si substrate. Finally, preliminary results show that near-stoichiometric SiCx films deposited using non-halogenated precursors are much more stable with respect to moisture incorporation than those deposited with halogenated precursors.

IR-Transparent Electrically Conductive CuAlxOy Deposited by Reactive Magnetron Co-Sputtering

AbstractThis paper reports on progress in the fabrication of IR-transparent electrically conductive copper aluminum oxide (CuAlxOy) by reactive magnetron co-sputtering from high-purity-Cu and -Al targets in an argon-oxygen-gas mixture. Recent equipment modifications have resulted in much better control of deposition parameters like forward and reflected power and, consequently, much better control of film composition. Applying the correct amount of power to each target and adjusting the oxygen-partial pressure have significantly reduced the growth of surface-oxide layers on the metal targets. Equipment and process improvements have eliminated the sputterrate inconsistencies and arcing that led to lack of composition control in our earliest films. We now have much better control of film composition and are beginning to understand the relationship between the electro-optical properties and the molecular structure of the films using Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), inductively coupled plasma (ICP) emission spectroscopy, high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). A pair of weakly intense FTIR absorption bands at 1470 and 1395cm−1 is present in films that have enhanced electrical conductivity and IR transparency. Understanding the origin of these bands could speed development of CuAlO2 as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The best film to date transmits about 80% in the mid-wave IR and has a sheet resistance of 160Δ;/sq.

Electron spin resonance and fourier transform infrared study of gamma irradiated poly (phenyl methacrylate)

Radiation effects of poly (phenyl methacrylate) (PPMA) have been investigated by electron spin resonance (ESR) and Fourier Transform Infrared (FTIR) spectroscopy. The ESR spectrum observed for gamma irradiated PPMA at liquid nitrogen temperature (LNT) is a sextet (six line spectrum), while the spectrum appears to be broadened at room temperature (RT). Free radicals associated with the RT and LNT spectra are identified by the magnetic parameters employed to simulate the spectra. Thus, the ESR spectrum at LNT is found to be a superposition of components arising from the macroradicals of the type ∼CH2–Ċ(CH3)–CH2 ∼ (I) and a difference singlet spectrum due to phenoxy radicals C6H5Ȯ (II). The spectrum at RT is also simulated with the same values of magnetic parameters, employed to simulate the LNT spectrum, except for the value of the β-hyperfine splitting. Thus, the RT spectrum is thought to consist of two types of radicals I and II. The gradual decrease in intensity of the 1750 cm−1 FTIR absorption band with the increase of radiation dose indicates the cleavage of the phenoxy carbonyl (-COOC6H5) groups of PPMA.

Specific characteristics of infrared spectra of irradiated ?-polypropylene

Nonvolatile products have been identified that arise through γ-irradiation in isotactic polypropylene by Fourier transform infrared (FTIR) analysis. The γ-irradiation was performed in the air with doses varying between 20 and 1200 kGy, for a dose rate of 800 Gy/h. The contour lines of FTIR absorption bands of carbonyl groups at different region of the cross section of an irradiated sample have been determined. The carbonyl groups arise from the concentration of esters or ketones, carboxylic acids, and γ-lactones, but their structure is different for different doses. We have also investigated the degradation of irradiated polypropylene by using FTIR mappings. Dust particles of irradiated brittle polypropylene have also been studied. The gel fraction has been determined for different doses of irradiation, and the relation between the moment of the appearance of the gel and disappearance of the carbonyl groups has been made evident. © 1996 John Wiley & Sons, Inc.