FT-IR measurements

The FT-IR measurements were carried out in a Nicolet IRTF spectrometer. Samples (self-supported discs) were activated in situ under vacuum (10 6 mbar) at 450°C before adsorption of probe molecules. Adsorption was carried out at room temperature the physisorbed species were removed at RT (C02) and 150°C (2,6-dimethylpyridine) under vacuum. 

Complex formation between Co and chelating agents was investigated by FT-IR spectroscopy after the second impregnation followed by drying. The dried sample was diluted with KBr powder and then formed into a self-supporting wafer. FT-IR measurements were carried out in a transmittance mode on an FTS6000 FT-IR spectrometer (Varian) with spectral resolution and accumulation time of 4 cm 1 and 1,024, respectively. 

For Fourier transform infrared (FT-IR) measurement, thin films of polymers were cast from 0.5 wt% distilled-deionized water onto CaF2 plates at room temperature. Most of the water in the films was removed by evaporation at 50°C in a vacuum oven for 24 h. FT-IR spectra of the dried film were... 

Dr Cristina Flego from EniTecnologie SpA is gratefully acknowledged for performing FT-IR measurements. 

The peptide subunit was easily incorporated into lipid bilayers of liposome, as confirmed by absorption and fluorescence spectroscopy. Formation of H-bonded transmembrane channel structure was confirmed by FT IR measurement, which suggests the formation of a tight H-bond network in phosphatidylcholine liposomes. Liposomes were first prepared to make the inside pH 6.5 and the outside pH 5.5. Then the addition of the peptide to such liposomal suspensions caused a rapid collapse of the pH gradient. The proton transport activity was comparable to that of antibiotics gramicidin A and amphotericin B. 

The redox protein cytochrome c dissolved in both [BMPrl][H2P04] and [H0EtMe3N][H2P04] [87] indicating that a hydrogen-bonding capability of the cation is not required, in contrast with the above example. FT-IR measurements showed that cyt c maintained its native secondary structure upon dissolution in these ionic liquids. 

This multiplex advantage in FT-IR is easiest to understand with respect to the speed of the measurement. For a resolution of 1 cm-1 and frequency range of 400 to 4,000, the FT-IR measurement time is 3,600 times faster than with a dispersive instrument. Consequently, when the time of measurement is limited, the FT-IR has an advantage of two orders of magnitude in speed. For studies of the curing of epoxies this time advantage can be extremely valuable 9). 

A series of papers have rqwrted FT-IR studies of the thermal degradation of polyacrylonitrile 22S-226,227 228, 229, 230>. These FT-IR measurements indicate that the nitrile groups play an important role in the degradation process even in the initial stages and show a steady decrease in nitrile with time both in air and under reduced pressure. These results are contrary to previous dispersive infrared measurements... 

In a previous publication [2], the authors have demonstrated that excellent quantitative FT-IR measurements could be made on various silanized kaolin clays. Figure 1, for example, shows superimposed calibration spectra at various concentrations of vinyl silanized clay from [2], and Fig. 2, the corresponding least squares fit (LSF) plot showing a correlation coefficient of 0.9951 which is comparable to the Kubelka-Munk (KM) corrected LSF data shown in Fig. 3 since the Alog (1/R) values are small. 

Fourier Transform Infrared Spectroscopy (FT-IR) measurements were made using a Nicolet Instruments 740 FT-IR spectrometer. A horizontal attenuated toted reflectance cell equipped with a 45° zinc-selenide crystal trough wets used. Spectra of neat solutions were obtained by co-addition of 256 scans at 4 cm- resolution. 

It has been shown by FT-IR measurements that perchlorate which is normally thought to be innocent , forms inner-sphere complexes with lanthanides. Most of the bound perchlorate is a monodentate. In the case of Eu3+ and Tb3+ bidentate disposition of perchlorate was also observed. The value of association constants of perchlorate with lanthanides are given in Table 7.10. 

Resolution errors occuring in FT-IR measurements of peak absorbances have been investigated experimentally by Jalsovszky (1984) for unapodized spectra as well as for triangular and Happ-Genzel apodization. 

At the same time isomerization of 53b to 52b took place at the radical anion stage. From FT-IR measurements in MeOH (NaOAc) it was found that the amount of 52b present in the solution increased during the electrolysis, and it was estimated that 30% of the 53b initially reduced was converted to 52b [131]. 

The Test Systems In order to demonstrate the spatial resolution achieved in practical measurements, two test sample systems were investigated by FT-IR imaging measurements in the ATR mode and in transmission. The sizes of the imaging areas were 50 X 50 pm for the micro ATR FT-IR measurements (20x objective) and 260x260pm for the micro FT-IR transmission measurements (15x objective). 

The results for the experimental determination of spatial resolution for the polymer laminate (PE/PC) and the laser-imprinted grid on the aluminum-coated PET film are summarized in Table 9.4. Whereas, a good agreement between the experimental and the theoretical (2r) values (in parentheses) was obtained for the transmission measurement and the aluminum-coated PET film, relatively large deviations were observed for the ATR FT-IR measurements and the theoretical values of the PE/PC laminate. This discrepancy can most likely be attributed to the thickness step along the borderline between the PC/PE dual layer and the PE monolayer film, and to the resultant nonoptimum contact of the polymer film and the reflection element in this area. 

Figure 10.5 ATR-FT-IR image of mineral oil measured with a ZnSe ATR accessory showing the integrated absorbance at 1480-1420cm. The histogram showing the number of detector pixels for different values of the integrated absorbance at the same range for the ATR-FT-IR measurement.

IR source. A 1 mm aperture was placed in front of the silicon wafer, and 200 scans were taken for each data point. Unfortunately, this degree of reproducibility only demonstrates the potential precision of FT-IR measurements. In fact, variations of up to 20% have been reported (60-62). These variations can occur in the measurement of the same specimen by different laboratories or in the analysis of a given specimen before and after it has undergone different back-surface treatments. Experiences of this kind have caused a lack of confidence in the precision of the IR method for the determination of the oxygen content of production silicon wafers. This problem has been ascribed to differences among the wide variety of instrument models and computer software packages used in the measurements (61). Variations in the specimen condition, i.e., dopant level, back-surface treatment or oxygen distribution have also been a source of poor reproducibility (8,9,52,53,63). 

From pyridine poisoning experiments and FT/IR measurements it can be concluded that this increased activity stems from the increased acidity of the resulting NiSMM (Ni-synthetic mica montmorillonite) clay, due to reduction of Ni. 

FT/IR measurements of adsorbed NH3 on NiSMM catalysts have shown that the number of sites, most probably Bronsted sites, increases due to Ni reduction ( ). This suggests that the newly formed acidic sites are responsible for the increased activity of NiSMM compared with e.g., beidellite, in which no Ni is substituted for Al in the octahedral sites. The newly formed sites should then be highly acidic. In order to verify this statement we have studied the thermal desorption of pyridine from Pd-NiSMM before and after reduction, by means of FT/IR spectroscopy. For comparison, the same study was made with Pd-exchanged synthetic beidellite. 

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