Micro-FTIR measurements

Fig. 5 Experimental setup for diffusion measurements in zeolites. Schematic arrangement around the IR flow-through cell (6), which for macro-FTIR measurements may be that described in Vol. 4, Chap. 1, p 42 of this series (see also [23]) or for micro-FTIR measurements the cell represented in Fig. 4b. Detailed explanation of main parts (1) ionization gauge (2) ionization gauge controller (3) baratron (4) pressure controller (5) magnetic valve (6) IR flow cell with sample (7) temperature controller (8) mass flow controllers (9) thermostatted saturators (10) four-way valves...

Structures of SA alkanethiol monolayers generated on gold substrates are better understood than the chemistries involved in their formation. Electron diffraction and FTIR measurements, together with computer simulations, have provided a picture of a SA monolayer in which the axes of the alkyl chains of the surfactants are tilted approximately 30° with respect to the surface normal of the substrate and the sulfur atoms reside in the three-fold hollows of the gold (111) surface (Fig. 25) [68, 207-210, 230, 240]. The use of scanning tunneling micro-... 

The sorption kinetics of n-hexane in MFI-type zeolites of different sizes have been measured by means of micro-FTIR spectroscopy. To check for an influence of the Si/Al ratio, nsj/Ai, on the sorption characteristics, a sample of silicalite was also investigated. The measured transport diffiisivities show ndther a dependence on the crystal size nor on the Si/Al ratio. The temperature dependence is shown to follow an Arrhenius-type law. The results of this study compare well with literature data obtained by different techniques. 

C and in order to match as closely as possible the two spectral line shapes. With hydrostatic samples one can measure pressures with a precision of slightly better than 0.01 GPa. A l/4m spectrometer (1200 grooves/mm grating) and 750 bin CCD (11 pm pixel width) gave a dispersion of 2.3 x 10 A/bin. Micro FTIR spectra were taken on a Bruker Optics vector-33 FTIR spectrometer (4cm resolution). 

Moreover, the macro - and micro -FTIR techniques enable us to obtain spectra in situ from a working catalyst, since the cells used (see Sect. 2.1.1) may be operated as flow-through reactors. Thus, coking of zeolite catalysts upon reaction of ethane or ethylbenzene was investigated in situ, and the decrease of diffusivities (e.g., of benzene) in the coking samples was measured as a function of the amount of coke deposited [15]. Similarly, the sorption of para-, meta-, and ortho-diethylbenzene from the gas phase into H-ZSM-5... 

For the FTIR microscopic diffusion measurements (micro-FTIR spectroscopy) [30-32] the same Perkin-Elmer 1800 spectrometer was used, but a so-called IR microscope (Spectra Tech model IR-Plan) and an appropriate flow-through micro-cell were attached (see Figures 4a,b). 

Fig. 24 Uptake curve of n-heptane into H-ZSM-5 at 325 K as measured via micro-FTIR spectroscopy. Solid line calculated uptake curve A experiment...

No.22, 1997, p.5699-702 EFFECTIVE WIDTH OF INTERFACE IN A STRESSED MODEL POLYMER COMPOSITE MEASURED BY MICRO-FTIR... 

The effect of mechanical deformation on a UV-cured urethane-acrylate polymer and on a silicon carbide/ urethane-acrylate model composite was studied by micro-FTIR spectroscopy. This technique was used for the first time to measure the width of the interfacial zone beyond which the fibre has no influence on the matrix, the results were discussed. 14 refs. 

A miniaturized Fourier transform spectrometer for near-infrared measurements (FTIR, 2500-8330 nm) was developed at the Forschungszentrum Karlsruhe [120], Near-infrared measurements give information, for example, about the oil, water and protein content of liquids or solids. The dimensions of the detector chip are 11.5 x 9.4 mm, the device is essentially a miniaturized Michelson interferometer and it consists of a micro optical bench with beamsplitter, ball lenses, mirrors and the detector chip. The light beam is coupled in via a glass-fiber and an electromagnetic actuator. The signal is derived from the signal response of the detector by Fourier transformation. 

FTIR spectroscopy may be applied to good advantage in such specialized areas as micro analysis where high sensitivity is required, in the analysis of aqueous solutions or dark, solid state samples that require the use of special reflectance techniques, in investigations placing emphasis on quantitative evaluation, and in experiments where analysis time is a limiting factor, e.g., in process or quality control measurements. 

Low levels of reflected energy, even from micro samples, can be measured by FTIR instruments. This method is termed diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A reflectometer design with hemiellipsoidal mirrors sliding back for sample positioning is very convenient (Fig. 4.1.4). 

Gas phase experiments of the six CWAS were performed in a Bruker Optics FTIR model IFS 66v/S spectrometer equipped with a DTGS detector and a potassium bromide (KBr) beamsplitter. A gas cell was placed in the macro compartment and adapted to a micro pump that removed background air and transferred the sample to the cell. DMMP and DIMP were used for these analyses. One gram of the CWAS was deposited on an Erlemneyer. A typical spectroscopic measurement averaged 20 scans at a resolution of 4 cm in the range of 400 - 7500 cm. Gas phase IR spectra were also acquired using Bruker Optics OPUS , Version 4.2. A background of air in the cell was recorded before each run of the CWAS experiments. 

Isomorphous substitution of boron into the MFI structure to produce [B]ZSM-5 was carried out and investigated via FTIR micro-spectroscopy ( infrared microscopy ) of single crystals by Jansen et al. [308]. Typical bands were observed at 1380 and 905 cm. The integrated band intensity of the 905 cm" band was used as a quantitative measure of the boron content, and the boron distribution in the single crystals was shown to be homogeneous. 

A newly developed thermal micro attenuated total reflection (ATR)/FTIR spectroscopic system with curve fitting program was used forthe quantitative investigation of molecular interactions in aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM). The lower critical solution temperature (LCST) in water of the PNIPAAM studied was found to be about 33C by cloud point measurement, DSC and the thermal micro ATR/FTIR spectroscopic system. The results from the new spectroscopic system with curve fitting program indicated that intermolecular interactions might predominate between PNIPAAM and water at temperatures below the LCST but above the LCST, PNIPAAM molecules in water were aggregated because of intramolecular interactions within the PNIPAAM molecules and the hydrophobic interactions in the system. 35 refs. 

PP-g-MA (0.1 mol% MA). Characterization methods included SEM, ESCA, and interfacial tension measurement. Tselios et al. (1998) have prepared compatibilized blends of LDPE and PP through inclusion of PP-g-MA (0.8 mol% MA) and EVAl (7.5 mol% vinyl alcohol). Blends were characterized using SEM, torque rheometry, mechanical properties, FTIR, and micro-Raman spectroscopy. 

Because of the very small effective source size, the spatial resolution of SR-FTIR for micro-spectroscopy is usually only limited by the wavelength, X, of the IR light [9]. Schwarzschild microscope objectives are used to focus the broad spectrum of IR light onto the sample, and these objectives typically have relatively large numerical apertures in the range 0.5-0.6. While diffraction will naturally limit the spot size on the sample [10], one can also use a single aperture before the sample to exactly define the illuminated sample region. In such a situation, the diffraction-limited spatial resolution is approximately 2X/3 [11], which corresponds to 1.7 pm (at 4000 cm ) and 13 pm (at 500 cm ) the two extremes of typical mid-IR measurements. 

Infrared synchrotron micro-spectroscopy is also an appropriate method for identifying and visualizing the existence of localized water at buried interfaces, particularly between multilayers of polymers. It was recently shown that water inclusions can be imaged at the buried interface of solid-contact-ion-selective electrodes (SC-ISEs) [22]. In this study a poly(methyl metha-crylate)-poly(decyl methacyrlate) [PMMA-PDMA] copolymer was used. Since the PMMA-PDMA copolymer is known to be water repellent and unsuitable for water sorption at measurable levels in the bulk membrane, the detection (or non-detection) of water by reflectance SR-FTIR is symbolic of the presence (or absence) of localized zones of water at the buried interface of a solid-contact ISE employing PMMA-PDMA as the sensing membrane. In fact, SR-FTIR revealed the presence of micrometer-sized inclusions of water at the gold-to-membrane interface, whereas coupling a hydrophobic solid contact of poly(3-octylthiophene 2,5-diyl) (POT) prevented the accumulation of water at the buried interface (Fig. 2) [22]. 

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