Microscope/microscopy Raman

There are several common configurations for Raman spectrometers. Unlike NIR, Raman can be readily done under a confocal microscope. Confocal Raman spectroscopy allows for the chemical composition of materials to be determined with micron spatial resolution including some depth profiling. Confocal Raman measurements have been shown to be useful quantitative analytical tools for the investigation of drug eluting stents [11]. Raman microscopy has been used to quantify thin... 

Fundamentals. Provided enough substance is present at the electrochemical interface in a fairly thick film of corrosion products or in a modifying layer, identification of the constituent matter is possible with (normal) Raman spectroscopy (NRS). Although this approach is not exactly surface specific, it is included because it has been applied frequently. The same argument applies to Raman spectroscopy applied with the help of a microscopy (Raman microscope). 

The evolution of Raman instrumentation has been recently reviewed (Lewis, 2001a), from the first measurements by C.V. Raman, when the spectra were excited with a mercury lamp and recorded with a small prism spectroscope equipped with a photographic plate (Raman, 1928), to the new high resolution microscopes, in Raman scanning near-field optical microscopy (Adar, 2001). This review includes Raman microscopy (Baldwin, 2001), Raman imaging (Treado, 2001), the adaptation of Raman spectrometry to industrial environment (Slater, 2001), Raman spectroscopy of catalysts (Wachs, 2001) and process Raman spectroscopy (Lewis, 2001b). 

Raman microscopy is more developed than its IR counterpart. There are several reasons for this. First, the diffraction limit for focusing a visible beam is about 10 times smaller than an IR beam. Second, Raman spectroscopy can be done in a backscattering geometry, whereas IR is best done in transmission. A microscope is most easily adapted to a backscattermg geometry, but it is possible to do it in transmission. 

A principal advantage of the Raman microprobe is that the optics are those of a conventional light microscope a wide variety of special-purpose objectives developed for materials and biological microscopy are available. The Raman microprobe also offers the advantage of fluorescence reduction owing to the high spatial resolution of the microscope if a region of low fluorescence can be chosen for observation. 

In 1994, we proposed that a metallic needle having a nano-tip at its apex be employed as a nano-light-source for microscopy attaining nanometric spatial resolution [2]. Later, we expanded the technique to Raman spectroscopy for molecular nano-identification, nano-analysis and nano-imaging. In this chapter, we give a brief introduction to local plasmons and microscopy using a metallic nano-needle to produce the local plasmons. Then, we describe the microscope that we built and... 

With regard to the confinement and enhancement ability of a metallic nano-tip, we have proposed near-field Raman microscopy using a metallic nano-tip [9]. The metallic nano-tip is able to enhance not only the illuminating light but also the Raman scattered light [9, 15, 16]. Figure 2.5 illustrates our nano-Raman microscope that mainly comprises an inverted microscope for illumination and collection of Raman... 

Similarly to FTIR spectroscopy, Raman spectroscopy is a versatile technique of analyzing both organic and inorganic materials that has experienced noticeable growth in the field of art and art conservation, in parallel to the improvement of the instrumentation [38]. In particular, the introduction of fiber optic devices has made feasible the development of mobile Raman equipments, enabling nondestructive in situ analyses [39]. On the other hand, the coupling of Raman spectroscopes with optical microscopes has given rise to Raman microscopy vide infra). 

Aerosol Heterogeneity. The variation of the chemical composition from particle to particle within an aerosol size class has been probed in a number of ways. Single-particle chemical analysis has been achieved by using the laser Raman microprobe (25) and analytical scanning electron microscopy (26). With the electron microscope techniques, the particle can be sized as well as analyzed chemically, so the need for classification prior to sample collection is reduced. Analyzing hundreds to thousands of particles provides the information necessary to track the particles back to their different sources but is extremely time consuming. 

The system components described above can be combined into a wide array of sampling configurations suitable for measurements as diverse as characterization of the effluent emitted from oceanic vents, to identification of explosives at a standoff of tens of meters, to determining the provenance of historical works of art. One of the areas of greatest Raman activity is in microscopy and microscopic imaging this will be described briefly here as an example of how the various components are integrated into a complete system. 

A more sophisticated approach uses a stack of serial sections. Three-dimensional images in all forms of light microscopy are built up as serial sections. That is, the microscope (or other device) is focused at different depths through an object, and the resulting stack of images rendered as a three-dimensional object. This technique was introduced into Raman microscopy... 

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