Reflection IR spectrum

Multiple internal reflection IR spectra (ATR- IR) to measure e.g. the relative absorption of C00H, NH2 and CH2 bands at 1730,... 

For the two methods, the resulting grafting of functional monomers, e.g. acrylic acid and acrylamide, has been measured by multiple reflection IR spectra, ESCA spectra, and dye adsorption from an aqueous solution of crystal violet. The measurements indicate that the inert surfaces of the polymer substrates are modified by a complete surface layer of the grafted monomers. 

As mentioned before, fosinopril sodium is known to be capable of existing in two polymorphic forms, and the diffuse reflectance IR spectra of the two forms indicated that the two structures differed in the conformation of one sidechain. The solid state 13C NMR spectra obtained on both forms were found to confirm this hypothesis [19]. As may be seen in Fig. 3, the significant spectral differences were all associated with nuclei contained within the acetal sidechain. 

The utilization of IR spectroscopy is very important in the characterization of pseudopolymorphic systems, especially hydrates. It has been used to study the pseudopolymorphic systems SQ-33600 [36], mefloquine hydrochloride [37], ranitidine HC1 [38], carbovir [39], and paroxetine hydrochloride [40]. In the case of SQ-33600 [36], humidity-dependent changes in the crystal properties of the disodium salt of this new HMG-CoA reductase inhibitor were characterized by a combination of physical analytical techniques. Three crystalline solid hydrates were identified, each having a definite stability over a range of humidity. Diffuse reflectance IR spectra were acquired on SQ-33600 material exposed to different relative humidity (RH) conditions. A sharp absorption band at 3640 cm-1 was indicative of the OH stretching mode associated with either strongly bound or crystalline water (Fig. 5A). The sharpness of the band is evidence of a bound species even at the lowest levels of moisture content. The bound nature of this water contained in low-moisture samples was confirmed by variable-temperature (VT) diffuse reflectance studies. As shown in Fig. 5B, the 3640 cm-1 peak progressively decreased in intensity upon thermal... 

Fig. 5 A, diffuse reflectance IR spectra of SQ-33600 displaying the absorption band due to bound water of hydration after exposure to different relative humidity conditions of (a) initial sample containing 3.5% water, (b) 6%, (c) 15%, (d) 31%, (e) 43%, (f) 52%, (g) 70%, and (h) 84%. B, variable-temperature diffuse reflectance IR spectra of SQ-33600 initially containing 3.5% water.

Figure 8.9 shows the diffuse reflectance IR spectra of Ti02 samples after the photoreaction. The band due to the hydroxyl groups is observed at 3,665 cm-1 for the fresh Ti02 (a), consistent with that for anataseT The band at 3.630 cm-1 is assignable to the adsorbed water,7) which may originate from the ambient air... 

Figure 4. Variation in the specular reflectance IR spectra of films of different thicknesses of silane A187 on aluminium mirror surfaces. The sensitivity used for the monolayer is ten times that used for the other spectra.

The reflection technique has not been used as extensively as transmission. Its slow development may be attributed to several factors. It is used primarily on highly polished metal surfaces including those involved in fundamental studies of single crystals. The theoretical framework for reflection IR spectra has been developed only recently. Ultrahigh-vacuum techniques are required and modifications are needed for standard IR spectrometers. Since the reflection technique can be used with single crystals of metals, it is a bridge between the more sophisticated surface techniques used in surface science and the IR studies of the more practical catalysts. 

Figure 1. Difference reflection IR spectra of air surface of Avcothane intraaortic baloon pump with KRS-5 reflection plate (a) without a barrier film, (b) with a barrier film of thickness 0.65 /x (19)...

Thin layers (100-1000 A) of polyimide on the substrate were prepared for external reflectance IR spectra and to measure the average depth of modification, which will be discussed in detail. Figure 2 displays the ER IR spectra of the 870-A-thick polyimide and the modified samples in the range of 1900-1300 cm-1 which provide the most useful information for this re-... 

Figure 2. External reflectance IR spectra (a) PMDA-ODA polyimide, (b) potassium polyamate and (c) polyamic acid. The starting polyimide is 870 A thick and the whole layer is modified. The IR incidence angle is 37° from the sample surface.

Mitchell, et al. described the diffuse reflectance IR spectra of silica-supported Cu(acac)2 forming prepared by extended refluxing of the acetonitrile solvent containing silica and the metal complexes. They attempted to prepare samples showing both monolayers and multiple layers of Cu(acac)2 on the surface of this solid and showed that for metal complex loadings less than a monolayer (Fig. 13, 1.42 x lO " molecules/cm ) the DRIFT spectra were missing one vibration that was present in the samples containing more than a monolayer and also present in the spectrum of the polycrystalline metal complex. 

Figure 16 Diffuse reflectance IR spectra of a) Zr(acac)4 b) Fe(acac)s c) Zr02jFe(acac)s and d) Zr02lHacac...

Figure 4. Internal reflection IR spectra of the surface zones of cold water cast rat skin collagen films (top) and hot water cast (i.e., gelatinized) films from the same original sample (bottom)...

Figure 7. Internal reflection IR spectra revealing the variety of structures dominating the surface zones of six different gelatin preparations cast from hot water into thin, smooth films...

Figure 3. Internal reflection IR spectra characterizing the equilibrium surface layers coating plastic (top) and steel (bottom) intrauterine foreign bodies, each...

Figure 4. Internal reflection IR spectra illustrating the similarity of the coating acquired in utero on the surfaces of various intrauterine foreign bodies that were in place for various lengths of time...

Diffuse-reflectance IR spectra were measured in the spectral range of 4000 -1800 cm l using a Perkin-Elmer 580 B spectrophotometer supplied with a diffuse-reflectance attachment [10]. Trifluoromethane, chloroform, acetylene, methylacetylene, phenylacetylene, diethylacetal of propargylaldehyde were used as probe-molecules for basic centers in the zeolites under study. The substances were adsorbed at room temperature either from the gas phase at a pressure of 1-30 torr or from the vapor phase at a pressure of saturated vapors. 

Diffuse-reflectance IR-spectra of CO adsorbed on Pd/chitosan/ZrOz catalyst are presented in Fig 4. Two characteristic adsorption bands (AB) at 2070 cm and 1900 cm, corresponded to the vibrations of CO. adsorbed on Pd" in the linear and in the bridge (three-fold coordinated) form, respectively, arc presented in the IR spectrum of the System. The presence of bridged or three-fold coordinated CO points to the formation of Pd" metal clusters. Noteworthy is that frequencies of linear and bridged forms of CO are shifted toward lower wave numbers compared to conventional Pd/support systems (e. g. 2070 vs 2100 cm" for linear form) [6, 7], This is indicative of negative charging of Pd clusters. 

Figure 1. Attenuated total reflectance IR spectra of poly-(phenylene oxide) film before and after Pyrex-filtered Hg lamp irradiation.

Reflection IR spectra were obtained with a Perkin-Elmer computerized spectrometer 580B using a micro MIR accessory at a crystal angle of 45 incidence. The absorbance values have been normalized by using the IR band for Cl groups at 2930 cm as a standard in order to overcome variations in optical density resulting from differences in contact between the polymer films and the ATR crystal. 

The above discussion suggests a two-dimensional spiral on the surface, with attractive energy between polymeric segments, which agrees satisfactorily with the a-helical form. This has been demonstrated by others for this and other macromolecules (25, 26, 30, 31, 32, 33). To confirm further the a-helical form on the surface, we recorded multiple reflection IR spectra at surface pressures both less than and greater than the plateau pressure (Figure 4, part 1). The band characteristic of the... 

Finally, the multiple reflection IR spectra, obtained on the mono-molecular films from solvent II and transferred at constant pressure in the zone of condensed film, are shown in Figure 4, part 2. The band at 1630 cm"1 is characteristic of the ft form (33, 39). Thus, the surface contains two-dimensional films of ft helixes in the case of pyridine-rich spreading solvents. This agrees with the results of others for different polymers (33). The f3 helixes for the same polymer in monolayer are present (40) because the sample had a low molecular weight. 

The multiple reflection IR spectra are identical for films transferred above or below the plateau pressure (Figure 8). The surface entropies corresponding to the plateau pressure of —0.15 erg/cm2 K and the value of AH of transition (monomolecular film — b imolecular film), calculated at about 70 ergs/cm2, agree well with the corresponding values necessary for the a form to pass from the mono- to the bilayer (30, 31), Therefore, the plateau represents collapse, and the isotherm curves at pressures greater than the collapse pressure pertain to films which are not homogeneous monolayers. 

Figure 6.36 Reflection IR-spectra of adamantanone (bottom) and of an oxidized diamond film (top) ( ACS 2003).

Figure 6.42 The reaction of diamond surfaces with 1,3-butadiene (a) reflection IR-spectra of a reacted diamond and, for comparison, of physisorbed cyclohexene ( ...

Borovkov V Yu, Serykh AI and Kazansky V B (2000), Diffuse reflectance IR spectra of orf/to-hydrogen and para-hydrogen adsorbed on zeolite BaX at 77 K and their interpretation in terms of the Stark effect , Kinet Catal., 41, 787. 

Diffuse reflectance IR-spectra were measured using Bedtman Acta M-VII" and "Perkin-Elmer 580B" spectrophotometers [5]. CO, Hg, CDgCN and were... 

Fig. 12. Multi-internal reflection IR spectra of an iron layer on a germanium crystal at various potentials. Scan rate, 2mV s 1. All spectra are on the same absorbance scale. The spectra number indicates the potential at the end of the sampling of 10 single interferograms in a time range of approximately 5 s (corresponding to a potential range of 10 mV). The time between two samplings is necessary for the storage of the interferograms in the computer equipment.

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