Micro-FTIR spectroscopy

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. 

These experiments confirmed that IR spectroscopy indeed provides a promising means for the investigation of the uptake of binary mixtures into microporous materials and its kinetics. This successful experiment prompted us to start a systematic study on the adsorption and adsorption kinetics of some aromatics in zeolites by Fourier transform IR spectroscopy (FTIR) and FTIR microscopy or, more precisely, IR micro -spectroscopy. This topic is dealt with in Sect. 2, where the generally employed apparatuses and procedures are also described. In this context, it should be mentioned that micro-FTIR spectroscopy was also applied by Schiith and coworkers in studying the adsorption of guest molecules in microporous soHds [ 12-14]. 

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. 4 a Schematic setup for experimental studies of sorption and sorption kinetics by micro -FTIR spectroscopy (so-called FTIR microscopy), b Flow cell for micro-FTIR investigations of sorption and sorption kinetics in zeolites [30,31]... 

The diffusion of paraffins was investigated by micro-FTIR spectroscopy. In Fig. 23, spectra of the freshly activated, unloaded zeolite sample No. 7, as well as of the otherwise unchanged sample after admitting a partial pressure of 3.1 mbar of n-hexane, are presented. The experimental resolution was 2 cm ... 

Fig. 23 Monitoring the absorbance of an H-ZSM-5 sample during uptake of n-hexane at 398 K via micro-FTIR spectroscopy 3.1mbar partial pressure of n-hexane in a helium flow (100 mlmin )...

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...

Fig. 25 Uptake of n-hexane under 3.1 mbar partial pressure with helium as carrier gas at various sorption temperatures monitored via micro-FTIR spectroscopy. Solid lines calculated uptake curves symbols A = 398 K, <> = 423 K, o = 448 K, = 473 K...

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. 

Bikiahis et al (1999) Bikiaris, D. Daniilia, Sister Sotiropoulou, S. Katsimbiri, O. Pavlidou, E. Moutsatsou, A.P Chryssoulakis, Y. Ochre-differentiation through micro-Raman and micro-FTIR spectroscopies application on wall paintings at Meteora and Mount Athos, Greece SpectrochimicaActa. Part A 56 1 (1999) 3-18... 

Stehfest, K., Toepel, J., and Wilhelm, C. (2005) The application of micro-FTIR spectroscopy to analyze nutrient stress-related changes in biomass composition of phytoplankton algae. Plant Physiol. Biochenu, 43 (7), 717-726. 

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. 

Supercritical fluid extraction coupled to SFC has been used for the extraction, separation and identification of PAHs from coal. The supercritical extract was expanded with the aid of a frit restrictor accommodated in the sample cavity of a cooled micro-injector, the analytes being deposited by condensation while CO, was sent to waste through a vent valve. Subsequently, the loop contents were connected on-line to the mobile phase of the capillary chromatograph. The extracted analytes were detected by off-line FTIR spectroscopy following collection on a KBr disc and evaporation of the solvent [104]. 

Micro-Raman spectroscopy was used to characterise 4H-SiC layers grown from a variety of precursor systems.381 FTIR data were able to characterise hydrogenated amorphous silicon nitride films with embedded nanoparticles. Oxidation leads to the appearance of an Si O feature at 1070 cm 1,382 Raman spectra were used to determine the degree of micro-crystallinity of pc Si I I layers, using the intensity ratio of bands at 520 cm-1 and 480 cm-1.383 IR and Raman spectra were used to determine the effects of neutron irradiation on a-SiC H films.384 A range of a-SiCx I I and a-SiCxNy H films were studied using IR spectroscopy 385 similar experiments were carried out on a-Si i xGcx Il,F films.386... 

The FTIR spectrum of Ir02 showed a broad band near 550 cm 4 due to vlrO.339 Micro-Raman spectroscopy was used to characterise well-aligned Ir02 nanotubes.340... 

Novel chitosan based catalytic systems for hydrogenation of unsaturated compounds in the liquid phase were prepared. The catalytic performance of the obtained systems depended significantly on the chitosan forms (as the micro beads or chitosan deposited on the mineral supports), their preparation method and chemical modification of chitosan as well. The obtained chitosan based carriers and catalysts were examined by transmission and diffuse-reflectance FTIR spectroscopy. 

Song, M., Liebenberg, W. and de Villers, M.M. (2006) Comparison of high sensitivity micro differential scanning calorimetry with X-ray powder diffractometry and FTIR spectroscopy for the characterization of pharmaceutically relevant non-crystalline materials. Die Pharmazie, 61... 

Since the investigation of diffusion phenomena in zeolites by macro-FTIR and micro-FTlR spectroscopy is still not a routine technique, the experimental aspects will be described in more detail. 

More recently, essentially the same technique as proposed by Hermann et al. [944,945], viz. FTIR microscopy (Fourier transform micro-IR spectroscopy on single crystals), and by Mirth and Lercher [815], was successfully employed by Zhobolenko and Dwyer [949], who determined the transport diffusivities of a number of hydrocarbons (benzene, toluene, p-xylene, cyclohexane) in sili-calite-1 in different crystallographic directions. No significant differences of the diffusivities in the straight and sinusoidal channels of the structure were found (cf. Fig. 54), at remarkable variance to results reported by Rees et al., who used the frequency response technique [950] and found significant differences for the diffusion coefficients in both types of channels, viz. one order of magnitude smaller ones for the sinusoidal than for the straight channels. 

No.9, 1997,p.2067-75 STUDY OF THE CONFORMATIONS OF POLY(EPSILON-CAPROLACTAM) AND POLY(EPSILON-CAPROLACTAM)-POLYBUTADIENE BLOCK COPOLYMERS BY FTIR SPECTROSCOPY WITH PHOTOACOUSTIC DETECTION AND BY MICRO-RAMAN CONFOCAL SPECTROSCOPY Schmidt P Fernandez M R Pastor J M Roda J Czech Republic,Academy of Sciences ... 

FTIR spectroscopy with photoacoustic detection and micro-Raman confocal spectroscopy were used to study the conformations of poIy(epsilon caprolactam) and poly(epsilon-caprolactam)-polybutadiene block copolymers. In the block copolymers prepared by anionic polymerisation, the fraction of the planar conformation of poly(epsilon-caprolactam) chains decreased with increasing polybutadiene content. In the surface layers formed by rapid saw cutting and in the islands formed by microtome cutting, the content of the planar conformation was lowered. This was substantially increased by water treatment, especially at elevated temperatures. 15 refs. 

---