From Fourier Transform Infrared Spectroscopy Research Articles

Adsorption of N2 and CO2 on Zeolite X Exchanged with Potassium, Barium, or Lanthanum

The zeolite X ion exchanged with K, Ba, or La was tested for the adsorption of N2 and CO2. The physical adsorption of N2 at 77 K confirmed that the zeolite framework remained intact after exchange and thermal treatment. The isotopic transient analysis of N2 adsorbed on the samples at 303−333 K indicated that BaX had the highest uptake of N2, with a heat of adsorption equal to 4.5 kcal mol-1. In addition, the vibrational frequency of adsorbed N2 was most perturbed by the presence of Ba cations. Results from Fourier transform infrared (FT-IR) spectroscopy showed that hydroxyl groups were associated with both the Ba and the La cations in the zeolites. FT-IR spectroscopy of adsorbed CO2 confirmed that the K form of zeolite X was the most basic with respect to forming surface carbonates.

Ageing behaviour and analytical pyrolysis characterisation of diterpenic resins used as art materials: Manila copal and sandarac

Artificial indoor and outdoor exposure conditions have been applied in order to investigate the photo-ageing behaviour of two natural resins once used as art materials. Copals and sandarac consist of free labdane diterpenoids and of a highly cross-linked fraction of polycommunic acid. To determine the nature and the composition of the cross-linked fraction, pyrolysis is required. Thermally assisted hydrolysis and methylation, coupled with gas chromatography–mass spectrometry (THM-GC/MS), has been used to identify the acidic compounds. Many secondary pyrolysis products have been recognised and distinguished from the original resin components. Further details on the composition and ageing behaviour of Manila copal and sandarac have been obtained from Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC) and direct temperature-resolved mass spectrometry (DTMS). During ageing, cross-linking and cleavage reactions were found to affect largely the chemical structure of the two resins, together with minor degradation processes such as isomerisation, defunctionalisation and oxidation.

Plasma-enhanced CVD of organosilicate glass (OSG) films deposited from octamethyltrisiloxane, bis(trimethylsiloxy)methylsilane, and 1,1,3,3-tetramethyldisiloxane

Octamethyltrisiloxane (OMTS), bis(trimethylsiloxy)methylsilane (BTMS), or 1,1,3,3-tetramethyldisiloxane (TMDS) mixed with oxygen and argon produced organosilicate glass (OSG) films having high methyl content under pulse plasma-enhanced chemical vapor deposition (PECVD). The hydrogen concentration in films deposited from OMTS, BTMS, and TMDS can exceed twice the maximum concentration in films grown from methylsilane precursors. However, the refractive indices and dielectric constants of the films grown from OMTS, BTMS, and TMDS were close to that of minimum values observed for the films grown from methylsilane precursors. This suggests that at high concentrations, methyl incorporation does not result in further reduction of film density. 29Si nuclear magnetic resonance (NMR) resolves the complex differences in the structure of the OSG films that are not apparent from Fourier transform infrared spectroscopy (FTIR) and reveals that the stability of OSG materials is improved by eliminating M groups and favoring the incorporation of T groups. These films exhibit low dielectric constants in the range of 2.4–2.6.

FTIR and SUVF spectroscopy applied to reservoir compartmentalization: a comparative study with gas chromatography fingerprints results

The purpose of this study was to evaluate reservoir continuities and geochemical evolution of oils from individual reservoirs by using gas chromatography (GC) fingerprints method and to compare the results with those obtained from Fourier transform infra red (FTIR) and synchronous ultra violet fluorescence (SUVF) spectroscopy techniques. Six crude oils which belong to different levels of exploitation were selected from Alam El Bueib (AEB) oil field (Western Desert, Egypt). The samples studied belong to three different reservoir units in different wells. The results show that the all-independent techniques provide results in good agreement and that the oils characteristics and their evolution in the reservoir can be described similarly by fingerprints GC, FTIR and SUVF spectroscopy. The FTIR and SUVF spectroscopy techniques therefore constitute a rapid and non-expensive alternative for reservoir organic geochemistry studies.

Carbon nitride films prepared by inductively coupled plasma chemical vapour deposition from a solid carbon source

Thin carbon nitride films have been prepared by inductively coupled plasma chemical vapour deposition (ICP-CVD). Instead of using conventional gaseous carbon precursors, a pure carbon mesh was used as a carbon source with nitrogen as a transport gas The basic process parameters varied were the r.f. power (up to 100 W) and the pressure in the reactor. The films were composed of nitrogen and carbon as revealed by Auger electron spectroscopy (AES), X-ray excited photoelectron spectroscopy (XPS) and heavy ion elastic recoil detection (ERD) analysis, and their nitrogen fraction N/(N+C) was at about 0.5, independent on the experimental conditions. From Fourier transform infrared spectroscopy (FTIR) and XPS data it can be concluded that carbon atoms were bonded in different ways (by triple, double and single bonds) to nitrogen atoms.

Characterization of magnetron sputtered carbon nitride films

A set of carbon nitride samples has been prepared by reactive magnetron sputtering. The only parameter varied was the nitrogen partial pressure pN2. It turns out, however, that pN2 has noticeable influence on the composition and the structure of the films only below 0.1 Pa. The composition of the bulk of the samples was investigated by elastic recoil detection (ERD), energy dispersive X-ray analysis (EDX), wavelength dispersive X-ray analysis (WDX) and Rutherford backscattering (RBS); although all of them give the same trend, some systematic differences were observed concerning the absolute values. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) measurements revealed that the surface is somewhat depleted in nitrogen. Sputter depth profiling could not be applied due to very strong preferential sputtering of nitrogen. X-ray diffraction (XRD) showed that the films are almost amorphous. Structural information was obtained from Fourier transform infrared spectroscopy (FTIR), EELS, and XPS; it turned out that the films are graphitic or paracyanogen-like with a density of approx. 2 g cm-3. All of the characterization methods applied are discussed in view of the information they yield on carbon nitride films, and problems of their application to this special type of film.

Modification of PVC/ENR blend by electron beam irradiation: effect of crosslinking agents

In order to improve the mechanical properties of PVC/ENR blends, they were irradiated by using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. Changes in mechanical properties of the blends with increasing irradiation dose were investigated. In an attempt to maximize the beneficial effect of irradiation, the influence of multifunctional acrylates (MFA) such as TMPTA, HDDA and EHA on the 70/30 PVC/ENR blend was investigated. The properties studied include hardness, gel fraction, tensile strength, elongation at break and glass transition temperature. The results revealed that all mechanical properties increased with increasing irradiation dose with exception of elongation at break. The enhancement in blend properties was further improved by addition of MFA. This is attributed to the increase in crosslink density. The steady increase in gel fraction with irradiation dose and the shifting of the irradiation those towards a lower value to achieve 70% gel fraction upon addition of MFA has provided evidence for significant increase in crosslink density. Among the MFA employed in this studies, TMPTA was found to render highest mechanical properties to the blend with irradiation. Thus, TMPTA can be useful as an efficient crosslink enhancer to PVC/ENR blends. Results from Fourier transform infrared spectroscopy (FTIR) indicated radiation-induced crosslinks formed in PVC/ENR blends sensitized by TMPTA. The single glass transition temperature obtained confirms that the blend remains miscible upon irradiation with the presence of TMPTA. The changes in blend properties upon irradiation with the addition of acrylated polyurethene (PU) oligomer are also presented in this paper.

Characterisation of Spanish coal by means of Mössbauer spectroscopy

Seven Spanish coals from lignite to semi-anthracite have been characterised by Mössbauer spectroscopy (MS) at room temperature (RT) and 80 K. The aromaticities as obtained from Fourier transform infrared spectroscopy (FTIR) varied from 0.44 to 0.96. From the analysis of the Mössbauer spectra the iron bearing minerals were found to be mainly pyrite and sulphates in all the samples. Jarosite was only found to be present in lignite, brown and sub-bituminous coal. However, iron carbonates, mainly as siderite were only detected in the bituminous and semi-anthracite that have higher aromaticities (0.71, 0.95 and 0.96).

Room-temperature backbond oxidation of the porous silicon surface by oxygen radical irradiation

Backbond oxidation of the porous silicon (PS) surface as a result of irradiation by oxygen radicals (O*) from an electron cyclotron resonance plasma has been successfully achieved at room temperature. Increasing the O* irradiation time enhances both the photoluminescence (PL) intensity, and the oxygen related absorption in the 2000–2300 cm−1 wave number range obtained from Fourier-transform infrared spectroscopy (FTIR). Analysis of the FTIR spectra correlates oxidation of the outermost backbonded Si in the form H2Si–O2, HSi–O3 bonding structures with increasing PL intensity. Furthermore, these results show that oxidation of the backbonded Si network on the PS surface is the main mechanism responsible for the enhancement of the PL intensity and suppression of the PL fatigue. This enhancement and stabilization of the PL properties of PS at such low temperatures is explained in terms of the high sticking coefficient of O* and soft O* irradiation induced oxidation.

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Mechanical and morphological properties

AbstractMiscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied by examining evidence from tensile, impact, and physical properties. The observation of synergism in tensile strength, percent elongation at break, hardness, and relative density has reaffirmed PVC/ENR blends as miscible systems. Studies of impact properties, however, revealed that the blends are microheterogeneous in nature. This could be attributed to the large sizes of polymer molecules involved and the microgel content of ENR‐50. Results from Fourier transform infrared spectroscopy (FTIR) revealed that hydrogen bonding is extensively involved in PVC/ENR systems. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence the enhanced mechanical properties of PVC/ENR blends.

Molecular Details of Anesthetic‐Lipid Interactiona

By means of isotopic labeling with deuterium (2H) and observation by nuclear magnetic resonance (NMR), it has been possible to measure the conformational ordering and dynamics of lipids and anesthetics in membranes. The local anesthetic tetracaine causes disordering in the acyl chains of the lipids, very little effect near the glyceryl residue, and minor ordering effects in the charged head group. The anesthetic itself is well ordered within the lipid matrix. The magnitudes of these effects depend upon the nature of the lipid, and upon whether or not the anesthetic is charged. A model can be constructed for the location of the anesthetic within the lipid bilayers. Confirmation of the model comes from Fourier transform infrared spectroscopy (FTIR), which also shows directly the pressure-driven exclusion of local anesthetic from lipid, and the augmentation of this effect by the presence of cholesterol. Future studies by solid-state NMR of protein, and neutron diffraction of specifically deuterated components of anesthetic-nerve systems, should reveal even more precise details of the molecular events involved in anesthesia.