FTIR transmission spectra

Disc shaped samples similar to those used in the CO2 equipment were exposed to irradiation by UVA-340 tubes in a QUV Accelerated Weathering unit (Q-Panel Company). A constant temperature of 40°C was used. The samples were removed from the exposure chamber periodically to record FTIR transmission spectra in the 1700-1800 cm region. 

Fig. 29 Typical FTIR transmission spectra of the PTFE films deposited on Si(100) substrates at Ts=RT by SR etching (bottom trace) and laser ablation (top trace). In the bottom trace, in contrast with the perpendicular bands detected at 556 and 1156 cm-1, the parallel bands at 513 and 640 cm-1 appeared very small. Since the intense band at ca. 1210 cm-1 with a shoulder at ca. 1250 cm-1 could not be uniquely assigned, it is not used for the discussion...

Fig. 31 Typical changes in the FTIR transmission spectra of the PTFE films deposited on Si(100) substrates at a higher substrate temperature Ts=265 °C by thermal evaporation. The bottom trace is for the normal incidence and the top trace for the oblique incidence. Here, similar behaviors to the SR case (cf., Fig. 30a) can be observed in the spectral change...

Figure 5.7. FTIR transmission spectra of LPDFxSiOy oxide at different annealing temperatures. Reprinted, by permission, from C.-F. Yeh and C.-L. Chen, J. Electrochem. Soc. 142, 3579 (1995). Copyright 1995 Electrochemical Society, Inc.

For spectral analysis below 2000cm , FTIR transmission spectra were obtained. A small amount of sample (approximately 10-20 mg) was placed between two NaCl plates, which were then rotated to disperse the particles. Spectra were obtained at 4 cm nominal resolution with a DTGS detector by co-addition of 16 scans. 

FTIR transmission spectra of pristine and irradiated PoT-PVC blend films are shown in Figurel4.30. After irradiation the overall transmission intensity of the polymer blend decreases which indicates some distuibance in the structure of polymer blend films due to the chain scissoring and bond breaking in the polymer chains. The C-Cl stretch intensity at 625 cm", the intensity of substituted benzene ring vibration at 680 cm, and the C-N stretch intensity at 971 cm" decreases. The intensity of ring vibrations of benzenoid and quinoid groups at 1602 and 1427 cm decreases, which may be due to the deformation in ring stracture of polymer blend after irradiation. The C-H stretch vibration at 2850-3000 cm" deforms after irradiation. 

Figure 23 HPTLC-FTIR transmission spectra (A) and chromatogram (B) of cobaIt(III)-EDTA (edetic acid) complex AMD (automated multiple development) chamber (CAMAG) with ammontacal methanol-dichloromethane solvent gradient.

Fig. 4.22. FTIR transmission spectra of 50 50 PVFi-PVAc (a), PVF2 (b), PVAc (c), and the interaction spectrum of the 50 50 PVF2-PVAC blend obtained from the subtraction a — b - c. The spectra were collected immediately after heat treatment at 75°C for 1 h. (Source Ref. [24].)...

Fig. 9 FTIR transmission spectrum of a free standing diamond film obtained by HFCVD. ...

The magnetron sputtered film s polymer layer and A1 layer were 50 pm and 185 nm, respectively. This film was nearly three times thicker than commercial film 1 and commercial film 2. The absorbance values of this film in transmission mode were too high, since both the A1 layer and polypropylene layer were thicker. The FTIR transmission spectrum of this thick film coated by magnetron sputtering had very high absorbance values indicating it was also a good shield for infrared radiation. 

Figure 5 FTIR transmission image of a PA/PTFE blend (left) and SEM image from the same area (right). PTFE distribution was calculated from the 1,210 cm 1 C-F absorption (intensity cf. color scale in the middle). The arrow indicates from where on the image the IR spectrum was extracted. The orange ovals show identical PTFE clusters as detected by FTIR and SEM, respectively. (See Color Plate Section at the end of this book.)...

The ATR technique is a commonly used infrared internal reflection sampling technique. It samples only the surface layer in contact with the ATR element the sampling depth probed is typically of the order of 0.3-3 pm [1]. Unless software corrected, compared with a transmission spectrum, the relative intensity of bands within an ATR spectrum increase in intensity with decreasing wavenumber. Several FTIR instrument companies now supply "ATR-correction" software developed to correct for the different relative intensities of bands observed between ATR and transmission spectra, so that ATR spectra can be more easily compared to and searched against transmission spectra. 

Figu re 3.1 (a) FTIR reflectance spectrum of a MgO monocrystal (incidence angle 26.5°, face [001]). (b) FTIR and FTFIR absorption / transmission spectra of MgO powder (reprinted with permission from G. Busca... 

In ATR-FTIR excitation occurs only in the immediate vicinity of the surface ol the reflection element, in an evanescent wave resulting from total internal reflection. The intensity of the evanescent field decays exponentially in the direction normal to the interface with a penetration depth given by (1.7.10.121, which for IR radiation is of the order of a few hundreds of nm. Absorption leads to an attenuation of the totally reflected beam. The ATR spectrum is similar to the IR transmission spectrum. Only for films with a thickness comparable to, or larger than, the penetration depth of the evanescent field, do the band intensities depend on the film thickness. Information on the orientation of defined structural units can be obtained by measuring the dichroic ratio defined as R = A IA, where A and A are the band absorbances for radiation polarized parallel and perpendicular with respect to the plane of incidence, respectively. From this ratio the second-order parameter of the orientation distribution (eq. [3.7.13]) can be derived ). ATR-FTIR has been extensively used to study the conformation and ordering in LB monolayers, bilayers and multilayers of fatty acids and lipids. Examples of various studies can be found... 

The FTIR spectrum of the PTFE film deposited by laser ablation was identical to that of the target [54], but that of the film produced by SR etching showed some visible differences (see Fig. 29). Obviously, the C-F2 deformation bands at 640 and 513 cm-1 appear much smaller in the bottom trace. To understand why these 640 and 513 cm-1 bands were so small in the SR case, we measured both normal and oblique transmission of FTIR with an incident angle of 0 and 80° [58]. Two FTIR spectrometers (PERKIN-ELMER and JASCO) were used to measure spectra in the range 400-3000 cm-1. For a cross-check, the film was also deposited on a metallic surface and infrared reflection absorption spectroscopy [62] was carried out to confirm our oblique transmission measurements. Typical changes in the FTIR transmission... 

All spectra were run on a Digilab FTS-10 FTIR system equipped with fast-scan capabilities, a Hycomp 32 data array processor, and a nitrogen-cooled mercury-cad-mium-telluride detector. Transmission spectra were obtained using CaF2 windows with a 6- xm spacer. For each transmission spectrum, 500 scans were co-added at 4-cm-1 resolution. Smoothing was not needed on these spectra. All the spectra in this chapter (both transmission and ATR) are subtracted spectra, that is, they are the resultof subtracting a saline (H20) spectrum from the spectra of the aqueous protein solutions. 

Fig. 14. Infrared spectra of carbon fiber (A) transmission spectrum without water interferenr (B) transmission spectrum with water interferenr (C) transmission spectrum with water interference in the tockground KBr pellet (D) PAS -FTIR sttectrnm (E) DRIFT spectrum [2441. Reprinted with permission from C.Q. Yang and J. R. Simms, Fuel, 74 (1995) 543. CoRTight (1995) American Chemical Society...

Plasticizers are attached to the polymer by weak physical bonds rather than chemical ones, so can be separated readily by solvent extraction. A suitable solvent should selectively dissolve the plasticizer from the polymer. Methanol is frequently employed. Excess methanol should be dried off at 105°C. Infrared spectroscopy can be used to identify plasticizers by smearing the sample on one side of a KBr tablet and running a transmission spectrum or by examining the neat extract by ATR-FTIR spectroscopy. The resulting spectra can be compared with those in a specialized database of additives (Scholl, 1981). 

Spectra collected by these fom methods of an oxidized layer on 50-70-p,m galena particles (natural PbS, n 4) using the same number of scans (100) and resolution (4 cm ) and a Perkin-Ehner 1760X FTIR spectrometer equipped with a mercury-cadmium-teUmium detector are shown in Fig. 2.51. Because of strong backscattering by the PbS particles and, as a result, a small penetration depth of radiation, the transmission spectrum obtained from the powder squeezed between two plane-parallel KBr plates represents mainly the component /q that has passed by the particles (Fig. 1.22) and, hence, bears no information on the sample absorption. The DRIFTS and DTIFTS spectra of the PbS powder and the transmission spectrum of a mixture of PbS and KBr spectra are more informative. The distinct absorption bands of surface oxidation products at 1440, 1400, and 1200-1100 cm are assigned to lead carbonate, hydroxide, and sulfoxide [109],... 

Figure 7. FTIR spectra of DNA layer formed on a Au surface a) reflection absorption (RA) spectrum of Au treated with native DNA b) RA spectrum of Au treated with disuliide-terminated DNA c) transmission spectrum of DNA (cast film on CaF2)-...

If a sample absorbs IR radiation at characteristic wavenumbers, it is capable of emitting radiation at these wavenumbers. A thin sample of a material will emit radiation with a spectrum very similar to its absorption spectrum. By ratioing the emitted radiation from the thin film to that from a black body at the same temperature, an emissivity spectrum is obtained which generally has the appearance of an inverted transmission spectrum. Emission spectra used to be collected from samples heated well above r.t., typically to 40-100°C (to minimise sample degradation), with a black-body source (e.g. graphite) at the same temperature as a reference. With FTIR instruments, emission spectra can also be recorded at room temperature. 

Fig. 18. FTIR spectra of ammonium, C9F19 -COC>H3N+-Ci8F37. (a)RAS spectra of adsorbed film (b)RAS spectra of adsorbed film after friction test (c) Transmission spectrum of bulk material.

Transmission/wavenumber (cm) Figure D 8. FTIR spectrum of cyclosarin - GF... 

FTIR Microspectroscopy.3 A microscope accessory coupled to a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector can be used to obtain an IR spectrum. This is possible in both the transmission and reflectance modes. Several beads are spread on an IR-transparent window (NaCl, KBr, diamond) and possibly flattened via a hand-press or a compression cell. The IR beam is focused on a single bead using the view mode of the microscope. The blank area surrounding the bead is isolated using an adjustable aperture, and a spectrum is recorded using 32 scans (<1 min). A nearby blank area of the same size on the IR transparent window is recorded as the background. 

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