Attenuated Total Reflection FTIR

Adsorption phenomena from solutions onto sohd surfaces have been one of the important subjects in colloid and surface chemistry. Sophisticated application of adsorption has been demonstrated recently in the formation of self-assembhng monolayers and multilayers on various substrates [4,7], However, only a limited number of researchers have been devoted to the study of adsorption in binary hquid systems. The adsorption isotherm and colloidal stabihty measmement have been the main tools for these studies. The molecular level of characterization is needed to elucidate the phenomenon. We have employed the combination of smface forces measmement and Fomier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR) to study the preferential (selective) adsorption of alcohol (methanol, ethanol, and propanol) onto glass surfaces from their binary mixtures with cyclohexane. Om studies have demonstrated the cluster formation of alcohol adsorbed on the surfaces and the long-range attraction associated with such adsorption. We may call these clusters macroclusters, because the thickness of the adsorbed alcohol layer is about 15 mn, which is quite large compared to the size of the alcohol. The following describes the results for the ethanol-cycohexane mixtures [10],... 

The large intrinsic birefringence of the sarcoplasmic reticulum [143] and the polarized attenuated total reflectance FTIR spectroscopy data obtained on oriented films of sarcoplasmic reticulum [144] indicate that a sizeable portion of the secondary structural elements are arranged perpendicularly to the plane of the membrane in a manner reminiscent to the structure of bacteriorhodopsin [145-148]. 

The analysis of gas plasma-modified polydimethylsiloxane elastomer surfaces using attenuated total-reflectance FTIR spectroscopy was discussed.636... 

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

Optical methods are based on fluorescence probe-labeled aptamers (fluorescence intensity, fluorescence anisotropy), or label-free aptamers can be used for detection of analyte using SPR or Fourier transform infrared attenuated total reflection (FTIR-ATR). 

Attenuated total reflection FTIR is a well-established technique for obtaining absorbance spectra of opaque samples. The mode of interaction is unique because the probing radiation is propagated in a high index-of-refraction internal reflection element (IRE). The radiation interacts with the material of interest, which is in close contact with the IRE, forming an interface across which a nonpropagating evanescent field penetrates the surface of the material of interest to a depth in the order of one wavelength of the radiation. The electric field at the interface penetrates the rarer medium in the form of an evanescent field whose amplitude decays exponentially with distance into the rarer medium. 

Tatulian SA, Hinterdorfer P, Baber G, Tamm LK. Influenza hemagglutinin assumes a tilted conformation during membrane fusion as determined by attenuated total reflection FTIR spectroscopy. EMBO. J. 1995 14 5514-5523. 

Attenuated Total Reflectance FTIR (ATR-FTIRf) is a method that has been applied by a number of workers for the study of protein conformation. ATR has been used for monitoring adsorption of proteins or blood components to sur ces (1,2), and for the structural analysis of proteins dried onto an IRE (thin film) (3,4). It has also been used for exploring the effects of solution conditions on the structure of proteins irreversibly adsorbed to an IRE (5,6,7), and has been shown to be usefel for studying the secondary structure and ligand binding properties of membrane proteins (8,9). 

Oberg and Fink (1994) The Application of Attenuated Total Reflection FTIR to the Study of Protein Structure In Solution. Ms. in preparation. 

Parker WO Jr, Millitri R, Kiricsi I (1995) Aluminum complexes in partially hydrolyzed aqueous AICI3 solutions used to prepare pillared clay catalysts. Appl Catalysis A General 121 L7-L 11 Persson P, Karlsson M., Ohman L-O. (1998) Coordination of acetate to Al(III) in aqueous solution and at the water-aluminum hydroxide interface a potentiometric and attenuated total reflectance FTIR study. Geochim Cosmochim Acta 62 3657-3668... 

The preparation of nylon-6,6 fabric containing N-chlorinated hydantoin functional groups which were covalently linked to the surface of the polyamide was outlined. The N-chlorinated hydantoin functional groups had biocidal activity against pathogenic microorganisms. Attenuated total reflectance FTIR spectroscopy studied showed that chlorination of the treated nylon-6,6 caused a blue shift of the hydantoin amide bands. This could be used as a quality control method to measure the degree of chlorination of the nylon-6,6 and hence, of the biocidal efficiency of the material. 25 refs. 

The most widely available technique for identifying mainly polymer, but also additives in plastics, is Fourier Transform Infrared (FTIR) spectroscopy. Samples are exposed to infrared light (4000-400 wavelengths per centimetre or cm ) causing chemical bonds to vibrate at specific frequencies, corresponding to particular energies. In the last 5 years, an accessory for FTIR has been developed, which enables non-destructive examination of surfaces and so is ideal for analysis of plastics in museum collections. Attenuated Total Reflection-FTIR (ATR-FTIR) requires samples to be placed on a diamond crystal with a diameter of 2 mm through which the infrared beam is reflected... 

Increasing lA concentration in copol5mierization results in lower viscosities (Fig. 1.14). lA content of copol5miers was determined using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and nuclear magnetic resonance (NMR) spectroscopies. The absoption bands at 1628 and 1730 cm due to C=0 stretching vibrations in carboxylic acid showed an increase... 

Products were characterized by Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), ultraviolet visible (UV-Vis) spectrophotometry, scanning electron microscopy (SEM), and broadband dielectric/impedance spectroscopy (BDS). New absorption bands were observed corresponding to the conjugated pol5mieric units by FTIR-ATR and UV-Vis spectrophotometric analysis. The influence of concentration of PEDOT-PSS and PEDOT on the composite electrospun nanofibers was studied by EIS. Morphologies of electrospun nanofibers were also investigated by SEM. 

The chemical polymerization of Py by CAN in PU solutions leads to the formation of PU/PPy composites. The composites were characterized by Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR], dynamic mechanical analysis (DMA], thermal gravimetric analysis (TGA], differential scanning calorimetry (DSC], X-ray photoelectron spectroscopy (XPS], and SEM measurements. The absorbances of the disordered H-bonded urethane carbonyl decrease with increasing Py concentration. The fraction of the hydrogen-bonded carbonyls is increased and the melting point increases with the increase of PPy content. These indicate the incorporation of PPy into PU may cause the complex due to the intermolecular interaction between the PPy and PU. SEM images of composite nanofibers show good distribution of the second component and the composite solution is proper to form conductive composite nanofibers. 

Specific interactions in binary blends of ethylene-vinyl acetate copolymer with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron acceptor ability of the resin, by using attenuated total reflection FTIR spectroscopy. Molecular acid-base were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and equilibrium constant of pair formation were obtained. A crystalline transition of the EVA copolymer was observed and discussed in terms of enthalpy and entropy considerations based on FTIR and calorimetric DSC investigations. Fundamental results are then summarised to predict the interfacial reactivity of such polymer blends towards acid or basic substrates. 16 refs. 

Nashville, Tn., 28th April-2nd May 1996, p.407-16. 895 ATTENUATED TOTAL REFLECTANCE FTIR MICROSCOPY AS AN ANALYTICAL PROBLEM SOLVING TOOL... 

Real-time attenuated total reflectance FTIR spectroscopy was used to follow the conversion during acrylate polymerisations by measuring the presence of functional groups at finite depths from the ciystal surface. By varying the film thickness, the reactivity of multiacrylates could be spatially resolved. These results were compared with results from different photocalorimetric studies. 22 refs. USA... 

When light traversing an optically dense medium approaches an interface with a more optically rare medium at an angle exceeding a critical value, Bent = sin (rerare/ dens), total internal reflection occurs and an evanescent wave of exponentially deca5ung intensity penetrates the rarer medium. This phenomenon is at the heart of certain spectroscopic methods used to probe biomolecules at interfaces (199). In total internal reflection fluorescence (TIRF) spectroscopy (200-202), the evanescent wave excites fluorescent probes attached to the biomolecules, and detection of the emission associated with their decay provides information on the density, composition, and conformation of adsorbed molecules. In fourier transform infrared attenuated total reflection (FTIR-ATIR) spectroscopy (203,204), the evanescent wave excites certain molecular vibrational degrees of freedom, and the detected loss in intensity due to these absorbances can provide quantitative data on density, composition, and conformation. 

In Figures 8.4 and 8.5, the attenuated total reflection FTIR (ATR-FTIR) spectra of semicrystalline PDLA2 98 and amorphous PDLA20 8o films are presented [36]. 

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