Raman techniques applications

The FT-IR technique using reflection-absorption ( RA ) and transmission spectra to quantitatively evaluate the molecular orientation in LB films is outlined. Its application to some LB films are demonstrated. In particular, the temperature dependence of the structure and molecular orientation in alternate LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid (and of their barium salts) are described in relation to its pyroelectricity. Pyroelectricity of noncentrosymmetric LB films of phenylpyrazine derivatives itself is represented, too. Raman techniques applicable to structure evaluation of pyroelectric LB films are also described. 

As the laser beam can be focused to a small diameter, the Raman technique can be used to analyze materials as small as one micron in diameter. This technique has been often used with high performance fibers for composite applications in recent years. This technique is proven to be a powerful tool to probe the deformation behavior of high molecular polymer fibers (e.g. aramid and polyphenylene benzobisthiazole (PBT) fibers) at the molecular level (Robinson et al., 1986 Day et al., 1987). This work stems from the principle established earlier by Tuinstra and Koenig (1970) that the peak frequencies of the Raman-active bands of certain fibers are sensitive to the level of applied stress or strain. The rate of frequency shift is found to be proportional to the fiber modulus, which is a direct reflection of the high degree of stress experienced by the longitudinally oriented polymer chains in the stiff fibers. 

J. J. Valentini. Laser Raman techniques, in Laser Spectroscopy and Its Applications, Optical Science and Engineering, Vol. 11, edited by L. R. Radziemsky, R. W. Solarz, J. A. Paisner (Marcel Dekker, New York, 1987), p. 507. 

The resolution of the problems outlined above will obviously require much more theoretical and experimental work before the Raman technique will become universally applicable to the study of adsorption at metal surfaces. It will be interesting to see if tuneable lasers capable of operating in the near infrared will be... 

The first part of the book is devoted to Raman techniques and methods while the second part describes applications pertinent to biomedical and... 

Future applications of the Raman technique to catalyst studies appear promising. 

The Application oi Single-Pulse Nonlinear Raman Techniques to a Liquid Photolytic Reaction... 

Thus far, we have reviewed basic theories and experimental techniques of Raman spectroscopy. In this chapter we shall discuss the principles, experimental design and typical applications of Raman spectroscopy that require special treatments. These include high pressure Raman spectroscopy, Raman microscopy, surface-enhanced Raman spectroscopy, Raman spectroelectro-chemistry, time-resolved Raman spectroscopy, matrix-isolation Raman spectroscopy, two-dimensional correlation Raman spectroscopy, Raman imaging spectrometry and non-linear Raman spectroscopy. The applications of Raman spectroscopy discussed in this chapter are brief in nature and are shown to illustrate the various techniques. Later chapters are devoted to a more extensive discussion of Raman applications to indicate the breadth and usefulness of the Raman technique. 

A typical example of the characterization of a polymorphic system by FT Raman spectroscopy has been given by Gu and Jiang (1995) while an application of the technique with near infrared excitation to the polymorphic cimetidine system has been described by Tudor et al. (1991). The FT Raman technique has been compared to infrared diffuse reflection spectroscopy in the study of the polymorphs of spironolactone (Neville et al. 1992), and the pseudopolymorphic transition of caffeine hydrate (i.e. loss of solvent) has been monitored using the technique (de Matas et al. 1996). 

Nonlinear vibrational spectroscopy provides accessibility to a range of vibrational information that is hardly obtainable from conventional linear spectroscopy. Recent progress in the pulsed laser technology has made the nonlinear Raman effect a widely applicable analytical method. In this chapter, two types of nonlinear Raman techniques, hyper-Raman scattering (HRS) spectroscopy and time-frequency two-dimensional broadband coherent anti-Stokes Raman scattering (2D-CARS) spectroscopy, are applied for characterizing carbon nanomaterials. The former is used as an alternative for IR spectroscopy. The latter is useful for studying dynamics of nanomaterials. 

Near-infrared surface-enhanced Raman spectroscopy Some of the major irritants in Raman measurements are sample fluorescence and photochemistry. However, with the help of Fourier transform (FT) Raman instruments, near-infrared (near-IR) Raman spectroscopy has become an excellent technique for eliminating sample fluorescence and photochemistry in Raman measurements. As demonstrated recently, the range of near-IR Raman techniques can be extended to include near-IR SERS. Near-IR SERS reduces the magnitude of the fluorescence problem because near-IR excitation eliminates most sources of luminescence. Potential applications of near-IR SERS are in environmental monitoring and ultrasensitive detection of highly luminescent molecules [11]. 

This book is intended to introduce a student or practitioner of analytical chemistry to the technical elements and practical benefits of the Raman revolution. It is not intended to describe high-end Raman techniques such as nonlinear or time-resolved Raman spectroscopy, nor does it attempt to describe the many theoretical treatments of Raman scattering. The book emphasizes the concepts and technology important to applications of Raman spectroscopy in chemical analysis, with attention to calibration, performance, and sampling modes. While many recent innovations in analytical Raman spectroscopy are... 

Optical activity is an old subject dating back to the early years of the last century. But it is far from exhausted. Recent developments in optical and electronic technology have led to large increases in the sensitivity of conventional optical activity measurements, and have enabled completely new optical activity phenomena to be observed. Optical activity has been traditionally associated almost exclusively with electronic transitions, but one important advance over the past decade has been the extension of optical activity measurements into the vibrational spectrum using both infrared and Raman techniques. It is now apparent that the advent of vibrational optical activity has opened up a new world of fundamental studies and practical applications. 

Neutron inelastic scattering techniques have been widely applied to the study of vibrational and rotational dynamics in hydrogenous molecular systems.1 The bulk of this research has been concerned with the study of intermolecular and interionic motions in solids, but a limited yet significant amount of effort has been directed toward the study of large-amplitude intramolecular vibrations, most notably torsional vibrations and hydrogen-bond modes.2 The present paper is restricted primarily to a discussion of the application of neutron scattering to the study of torsional vibrations and barriers to rotation of methyl groups in molecules. We will present several examples in which neutron spectra have provided information complementary to that obtained by the more widely available and applicable infrared and Raman techniques. We will also discuss in simple terms some limitations and pitfalls of the neutron technique and the interpretation of neutron spectral results. 

ETS-10 is a thermally stable titanosilicate molecular sieve with potential for application in catalysis and adsorption. The as-synthesized Si/Ti ratio is 5. Methods for modification of the Si/Ti of ETS-10 are described. The resulting materials are characterized by elemental analysis, XRD, NMR, IR and raman techniques. These modified sieves show catalytic activity for oxidation of organic substrates with peroxide. 

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