Light microscopy fluorescence, measurement

Corrosion products should be examined for both composition and morphology. Compositional analysis can be wet chemical analysis. X-ray diffraction, high and low energy electron diffraction, X-ray fluorescence, electron probe microanalysis, or mass spectrometry. Morphology can be determined using light microscopy, hardness measurements, transmission electron microscopy, SEM, field ion microscopy, plus other techniques. For details on these methods, the reader may refer to basic texts and pertinent review articles, such as Ref 3. 

Lasers. Laser sources (discussed earlier in the Spectrophotometry section) are widely used in fluorescence applications in which highly intense, well-focused, and essentially monochromatic light is required. Examples of these applications include time-resolved fluorometry, flow cytometry, pulsed laser confocal microscopy, laser-induced fluorometry, and light-scattering measurements for particle size and shape. Several different types of lasers are available as an excitation source for fluorescence measurements (see Table 3-3). 

In addition, highly intense laser light sources with an energy output greater than 5 to 10 mW that are used for flow cytometry, fluorescence microscopy, and laser-induced fluorescence measurements will rapidly photodecompose some fluorescence analytes. This decomposition introduces nonlinear response curves and loss of the majority of the sample fluorescence. Fluorescence-based assays for analytes at ultralow concentrations require optimization of laser intensity and the use of a sensitive detector. 

Fluorescence Measurements, Fig. 2 The basic anatomy of a common fluorescence microscopy setup. LS light source, OD optical detector, ExF excitation filter, EmF emission filter, DM dichroic mirror, L lens, EM position of fluorochrome molecules... 

For fluorescence measurements in very small scales, such as the investigations performed in microfluidics and nanofluidics, an optical microscope is necessary. Among the most important elements of the setup are the set of optical filters, which separate the excitation light from the emission light. When both the excitation light path and the emission light path use the same lens near the fluorochrome molecules, the semp is termed as an epi-fluorescence microscopy semp. 

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