Applications of Optical Microscopy

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Applications of Optical Microscopy in Analysis of Asbestos and Quartz... 

The general importance of microscopy for surface investigations is reflected in the in situ applications of optical microscopy, scanning tunneling microscopy (STM), and atomic force microscopy (AFM) to oxide and semiconductor electrodes. The methods were described in Chapter 4. Of equal importance for oxide and semiconductor electrodes is the application of ex situ methods like scanning electron microscopy (SEM). 

Dixon, W.C., Applications of Optical Microscopy in Analysis of Asbestos and Quartz, Analytical Techniques in Occupational Health Chemistry, edited by D.D. Dollberg and A.W. Verstuyft. Wash. D.C. American Chemical Society, (ACS Symposium Series 120) 1980. pp. 13-41. 

The paper by Pis et al provides a good example of the application of optical microscopy. In this case, image-analysis has been used to provide a quantitative evaluation of the number, size and shape of pores in cokes produced by progressive oxidation. The results are compared with the mercury intrusion data and the two techniques shown to be complementary. 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

In condensed-phase CARS, the effects of the nonresonant susceptibility x(3)nr are most profound when a sample with weak Raman modes is embedded in a nonlinear medium. The nonresonant background of the latter can be easily comparable to or larger than the resonant contribution from the sample of interest. This is a situation commonly encountered in biological applications of CARS microscopy. Depending on the experimental situation, the CARS detection sensitivity to weak resonances can then be restricted either by the nonresonant background or by the photon shot-noise [62]. To maximize either the relative or the absolute CARS intensity, nonresonant background suppression schemes [44, 60, 61, 63, 64] and optical heterodyne detection (OHD) techniques [65-67] have been developed during recent years. 

A limiting factor in electron microscopy is the quality of the electron beam. Aberrations introduced by the optics limit both spatial resolution and analytical capabilities. There is a need to correct for the spherical and chromatic aberrations introduced by the electron optics. This will result in improved coherence of the beam and improved imaging and diffraction. In particular, these advances will permit the analysis of amorphous samples. Smaller beam sizes can also be achieved, allowing for sub-Angstrom resolution chemical analysis of samples. Development of higher-quality electron beams and short pulses of electron beams would broaden and deepen the application of electron microscopy. 

In this paper we shall describe how high resolution electron microscopy (HREM) can be used in conjunction with selected area electron diffraction (SAED) to probe the local structure of zeolitic solids (2, 5 8) which are often microcrystalline, multi-phasic or twinned. We shall also refer to the application of optical diffractometry (4, 9-11) as a supplemental procedure either for interpretation of electron micrographs, or for analogue diffraction studies of model systems. 

Although some principles of optics may be applied to both LM and TEM, image formation in a TEM is fundamentally different than that of either a LM or LSM. An understanding of the process of image formation is essential for illustrating the specific applications of such microscopy to biochemical research. 

With respect to other major literature on or related to XRE, are chapters in various analytical series and individual books. Two chapters are in the first edition of the famous Treatise on Analytical Chemistry. Comprehensive coverage of X-ray methods absorption, diffraction, and emission is provided by Liebhafsky et al. (1964) in a 90-page chapter in the section on Optical methods of analysis (E. J. Meehan, section advisor). This is immediately followed by the chapter by Wittry (1964) on X-ray microanalysis by means of electron probes. Chapters on relevant topics appearing in the other well known series on analytical chemistry. Comprehensive Analytical Chemistry, are by Beretka (1975) (Analytical applications of electron microscopy) with a brief mention of the XRF-based technique electron probe... 

It is assumed that the reader is familiar with the techniques of optical microscopy. There are, however, a number of other specialized techniques, which are useful for examining various features of oxidation morphologies. These techniques mainly generate information from interactions between the specimen and an incident beam of electrons, photons, or ions. The basis for the various techniques will be described here. Examples of their application will be presented in subsequent chapters. 

Kino, G. S. (1989). Intermediate optics in Nipkow disk microscopes. In The Handbook of Biological Confocal Microscopy (J. Pawley, ed.), 1st ed., pp 105-126. IMR Press, Madison, WI. Matsumoto, B. (1993). Cell biological applications of confocal microscopy. Methods Cell Biol. 38, 1-380. 

Hargave,R. V. Venkateswaran, D and Chatterjee, A.K., "Application of Optical Microscope as Quality Control Tool in Some Indian Cement Plants," Proceedings of the 9th International Conference on Cement Microscopy, International Cement Microscopy Association, Reno, Nevada, 1987, pp. 148-164. 

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