Photoacoustic FTIR spectroscopy

The photoacoustic effect was first discovered by Alexander Graham Bell in the early 1880s [18], but it was not applied to Fourier transform infrared (FTIR) spectroscopy until a century later [19,20], Significant advantages of FTIR photoacoustic spectroscopy (PAS) include the following (1) Spectra may be... 

JF McClelland, S Luo, RW Jones, LM Seaverson. A tutorial on the state-of-the-art of FTIR photoacoustic spectroscopy. In D Bicanic, ed. Photoacoustic and Photother-mal Phenomena III. Berlin Springer-Verlag, 1992, pp. 113-124. 

Fourier Transform Infrared (FTIR) and FTIR Photoacoustic Spectroscopy (FTIR-PAS) - Initial rates of polymerization, photoinitiator effects and oxygen effects were evaluated using these techniques. 

FTIR photoacoustic spectroscopy was used for the study of the adsorption of poly(n-butyl methacrylate) from cyclohexane, benzene and carbon tetrachloride onto alumina. The efficiency of adsorption increased in the order cyclohexane, carbon tetrachloride, benzene, while methanol and tetrahydrofuran showed negative adsorption. Poly(n-butyl methacrylate) had a negative temperature coefficient of adsorption (126). 

New York City, 2nd-6th May 1999, p.2424-8. 012 MOLECULAR ANALYSIS OF POLYMERS BY FTIR PHOTOACOUSTIC SPECTROSCOPY McClelland J F Jones R Bajic S MTEC Photoacoustics Inc. Iowa State University (SPE)... 

FTIR photoacoustic spectroscopy (PAS) has advantages relative to conventional IR techniques (transmission, reflection and emission) because it is non-destructive, does not involve sample preparation and can probe samples with compositional gradients and layers. The theory, instrumentation, methods and applications of FTIR-PAS are discussed and results are presented on several polymer analyses based on FTIR-PAS. 4 refs. USA... 

The free radical polymerisation of 2-hydroxyethyl methacrylate was studied by FT-Raman spectroscopy and that of bisphenol-A-bis(2-hydroxypropyl methacrylate) was studied by this technique and also by FTIR photoacoustic spectroscopy. Raman spectroscopy was used to determine the conversion of C=C double bonds of the monomers exactly. 18 refs. 

Macromolecular Reports A31,Nos.3 4, 1994,p.261-70 APPLICATION OF FTIR PHOTOACOUSTIC SPECTROSCOPY IN THE DETERMINATION OF THE LEVEL OF CHEMICAL MODIFICATION OF JUTE FIBRES... 

FTIR photoacoustic spectroscopy was used to determine the extent of acylation in acetylated jute samples quantitatively and results were compared with those obtained by standard wet chemical titrimetric measurements. 12 refs. 

Transmission spectroscopy offers two significant advantages over photoacoustic spectroscopy of powders. First, transmission spectroscopy is not susceotible to external acoustic disturbances. Commercial spectrometers must be modified for vibrational isolation in order to obtain good photoacoustic spectra. Secondly, transmission spectroscopy can use solid state detectors with very fast response times, whereas photoacoustic spectroscopy is much slower, with spectra taking a few minutes to collect as compared to a few seconds for transmission spectra when both are taken with an FTIR. 

An interesting extension of this type of reaction involves the photosubstitution of the surface-confined cobalt tetracarbonyl system [S] SiCo(CO)4 (where [S] represents a high surface-area silica) and the technique of Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS) has been applied for the first time (172) to study photoreactions of a species on the surface. 

Further recent developments in DSC and IR techniques, with respect to the study of SC barrier properties, include step-scan FT-IR photoacoustic spectroscopy [195] and combined microscopic differential calorimetry-Four-ier transform infrared (DSC-FTIR) spectroscopy [196]. The former allows depth profiling of the membrane the latter enables the simultaneous detection of calorimetric and structural modifications during a thermal transition. Technological advances in DSC and IR will, no doubt, continue to expand the application of these techniques to the study of skin barrier function. 

Basically, there are two categories of FTIR spectroscopies reflection and nonreflection techniques [38], The latter class comprises either acoustic detection or emission from the sample itself. The techniques recognized here are photoacoustic spectroscopy (PAS), emission spectroscopy (EMS), and photothermal beam deflection spectroscopy (PBDS). These techniques will not be considered further in this chapter. The reader is referred to the literature [39-42], For adhesion studies the reflection techniques (SRIRS) are more important. The major classes of sampling techniques in SRIRS are ... 

FTIR step-scan photoacoustic spectroscopy was used to study the composition of thermoplastic olefin films, as a function of depth below the surface. Experiments were completed at various modulation frequencies, enabling a stratification model to be developed. The uppermost layer (0-3 im) showed large changes in talc and PP concentration, while the layer below showed a significant decrease in both the phases. In the third layer (6-9 pm), all three phases showed the maximum values. In the fourth layer (9-12 pm), the talc concentration reduced, whilst concentrations of elastomeric copolymer of ethylene and propylene (EPR) and PP were observed, decreasing with depth (44). 

Some new developments of two-dimensional spectroscopy are discussed. As a specific example, two-dimensional correlation analysis of a polymer laminate film using several different spectroscopic techniques is presented. The versatility of this technique was developed using depth-profiling photoacoustic spectroscopy, mid-and near-IR dynamic rheooptical developments, and spectroscopic imaging microscopy. Spatial and temporal variations of near-IR spectra are effectively analysed by the two-dimensional correlation technique. Step-scanning FTIR spectrometers provide an opportunity to obtain desired spectral information often difficult to obtain by the conventional rapid-scanning technique. 12 refs. 

For process control, analytical techniques such as vibrational spectroscopies, which provide information about paint composition, are important based on (1) the popularization of FT instruments, with a better signal-to-noise ratio and fast data acquisition speed (2) reflectance techniques (total attenuated and diffuse), photoacoustic spectroscopy, and the development of optical fiber-based devices that provide easy spectrometric measurements on crude samples (3) vapor-phase generation coupled with FTIR for fast analysis of the volatile paint fractions ... 

Characterization of Lignin. Lignin is characterized in the solid state by Fourier transform infrared (ftir) spectroscopy, uv microscopy, interference microscopy, cross polarization/magic angle spinning nuclear magnetic resonance (cp/mas nmr) spectroscopy, photoacoustic spectroscopy, Raman spectroscopy. 

Impurity inclusions and surface defects are a cause of many difficulties to the polymer producer and user. Equipment used for studying these phenomena discussed in Chapter 4 include electron microprobe x-ray emission/spectroscopy, NMR micro-imaging, various forms of surface infrared spectroscopy, e.g., diffusion reflection FTIR, ATR, also photoacoustic spectroscopy and x-ray diffraction - infrared microscopy of individual polymer fibres. Newer techniques such as scanning electron microscopy (SECM), transmission electron microscopy, time of flight secondary ion mass spectrometry (TOFSIMS), laser induced photoelectron ionisation with laser desorption, atomic force microscopy and microthermal analysis are discussed. 

The systems studied served as model mixtures for dielectric coatings for printed circuits. The curing behavior was monitored by FTIR spectroscopy, also in combination with photoacoustic spectroscopy. These methods provided information on the... 

In photoacoustic spectroscopy, signal amplitude increases only when absorption occurs. Thus, photoacoustic spectra will be absorption spectra as opposed to FTIR spectra which are transmission spectra. FTPAS interferograms should then show modulation at high values of retardation as well as near zero retardation. This comes about as a consequence of the properties of Fourier transforms which cause very broad general feature information to be collected at low retardation, with narrow and sharp features ("high frequency") to be collected at higher retardation. 

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