Optical and Spectroscopic Techniques

Other optical and spectroscopic techniques are also important, particularly with regard to segmental orientation. Some examples are fluorescence polarization, deuterium nuclear magnetic resonance (NMR), and polarized IR spectroscopy [4,246,251]. Also relevant here is some work indicating that microwave techniques can be used to image elastomeric materials, for example, with regard to internal damage [252,253]. 

Other optical and spectroscopic techniques are also important, including positron annihilation lifetime spectroscopy, spectroscopic ellip-sometry, confocal Raman spectroscopy, and photoluminescence spectroscopy. Surface-enhanced Raman spectroscopy has been made tunable using gold nanorods and strain control on elastomeric PDMS substrates. ... 

A. Schulte, M. Nebel and W. Schuhmann, in Imaging and Spectroscopic Analysis of Living Cells Optical and Spectroscopic Techniques, ed. P. M. Conn, 2012, vol. 504, pp. 237-254. 

COMBINATION OF SECM WITH OPTICAL AND SPECTROSCOPIC TECHNIQUES... 

Structural investigations into the degree of branching and into the position and nature of glycosidic bonds and of non-carbohydrate residues in polysaccharides may include periodate oxidation and other procedures such as exhaustive methylation. X-ray diffraction and spectroscopic techniques such as nuclear magnetic resonance and optical rotatory dispersion also give valuable information especially relating to the three-dimensional structures of these polymers. 

However, in an attempt to integrate the SFA and spectroscopic techniques, the use of silver for optical interferometry has been seen as a drawback due to the fact that it precluded sufficient excitation source intensity to illuminate the buried interface. In order to circumvent this problem Mukhopadhyay and co-workers in an experimental set-up where the SFA was combined with fluorescence correlation spectroscopy (FCS) used, instead of silver, multilayer dielectric coatings that allowed simultaneous interferometry and fluorescence measurements in different regions of the optical spectrum [75]. Using this set-up they succeeded in measuring diffusion in molecularly thin films with singlemolecule sensitivity. 

To resolve the difficulties described above, spectroelectrochemistry is used for monitoring redox processes in proteins. The method combines optical and electrochemical techniques, allowing the electrochemical signals (current, charge, etc.) and spectroscopic responses (UV-VIS, IR) to be obtained simultaneously. As a result, more information about the oxidation or reduction mechanisms of redox proteins can be acquired than with traditional electrochemical methods. Among the various spectroelec-trochemical techniques, in situ UV-VIS absorption spectroelectrochemistry in an optically transparent thin-layer cell has become one of the most useful methods for studying the direct electrochemistry of redox proteins. 

The main objective of this chapter is to illustrate how fundamental aspects behind catalytic two-phase processes can be studied at polarizable interfaces between two immiscible electrolyte solutions (ITIES). The impact of electrochemistry at the ITIES is twofold first, electrochemical control over the Galvani potential difference allows fine-tuning of the organization and reactivity of catalysts and substrates at the liquid liquid junction. Second, electrochemical, spectroscopic, and photoelectrochemical techniques provide fundamental insights into the mechanistic aspects of catalytic and photocatalytic processes in liquid liquid systems. We shall describe some fundamental concepts in connection with charge transfer at polarizable ITIES and their relevance to two-phase catalysis. In subsequent sections, we shall review catalytic processes involving phase transfer catalysts, redox mediators, redox-active dyes, and nanoparticles from the optic provided by electrochemical and spectroscopic techniques. This chapter also features a brief overview of the properties of nanoparticles and microheterogeneous systems and their impact in the fields of catalysis and photocatalysis. 

Polymers are at best semi-crystalline and in many cases amorphous. The crystalline regions can be studied by X-ray diffraction techniques, but the non-crystalline or amorphous regions are mostly studied by optical and spectroscopic methods. The details of these techniques are discussed in later chapters. A few general points are, however, worth emphasising at this juncture. 

Interferences are physical or chemical processes that cause the signal from the analyte in the sample to be higher or lower than the signal from an equivalent standard. Interferences can therefore cause positive or negative errors in quantitative analysis. There are two major classes of interferences in AAS, spectral interferences and nonspectral interferences. Nonspectral interferences are those that affect the formation of analyte free atoms. Nonspectral interferences include chemical interference, ionization interference, and solvent effects (or matrix interference). Spectral interferences cause the amount of light absorbed to be erroneously high due to absorption by a species other than the analyte atom. While all techniques suffer from interferences to some extent, AAS is much less prone to spectral interferences and nonspectral interferences than atomic anission spectrometry and X-ray fluorescence (XRF), the other major optical atomic spectroscopic techniques. 

Detection methods applied in ion chromatography (IC) can be divided into electrochemical and spectrometric methods. Electrochemical detection methods include conductometric, amperometric, and potentiometric methods, while spectroscopic methods include molecular techniques (UVA is, chemiluminescence, fluorescence, and refractive index methods), and spectroscopic techniques such as atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and mass spectrometry (MS). ... 

There are several excellent and more detailed presentations of special instruments and spectroscopic techniques, such as spectrometers, interferometry, and Fourier spectroscopy. Besides the references given in the various sections, several series on optics [4.2], optical engineering [4.1], advanced optical techniques [4.154], and the monographs [4.4,4.6,4.153. 158 may help to give more extensive information about special problems. Useful practical hints can be found in the handbook [4.159]. 

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