Raman Microspectroscopy and Mapping

Unfortunately, the diffraction limit does not permit spectral images to be collected from cells unless the near-field advantage is exploited. However, we have mapped mytotic cells using Raman imaging microspectroscopy, and have reported spectral images of mytotic cells in the telophase and metaphase.17... 

Confocal Raman microspectroscopy is now yielding spectra at micrometer spatial (lateral) resolution, and can be carried out in situ (Figure 6). Diffusion profiles can also be mapped. The potential for FTIR microspectroscopy is also apparent, and results have been obtained that are superior to those from OTTLE cells, with simpler cell design, thanks to the use of microelectrodes. But the discrimination against solvent absorption is poor for in situ work it is hoped that higher intensity sources, such as synchrotron sources, in conjunction with PM-IR-RAS, can overcome this problem. 

Raman microspectroscopy provides a detailed view of the three-dimensional arrangement of the molecules inside the LC droplets. Because it proves the interaction of individual bond vibrations with laser light, the method allows the mapping of segregation as a function of chemical composition. The quantitative imaging of Raman intensity reveals information about the spatial organization of the molecules and their local environment. Thus, the method maps the director fields of the liquid crystal molecules in the horizontal plane and in the vertical direction (Blach et al. 2005). 

C. Krafft, T. Knetschke, A. Siegner, R. H. W. Funk and R. Salzer, Mapping of single cells by near infrared Raman microspectroscopy, Vib. Spectrosc., 2003, 32, 75-83. 

Several modes of operation are available in state-of-the-art confocal Raman microspectroscopy, including the measurement of samples with a spatial resolution of less than 1 pm, depth profiling, and line mapping. LaPlant and Ben-Amotz have given a detailed description of the design and construction of a confocal Raman microspectrometer [34] and a number of instruments are available commercially. 

The authors stress the advantages of pre-resonance intensity enhancement effect accompanying the FT-Raman measurements allowing to detect carotenoids even in trace amounts with simultaneous elimination of background fluorescence of the plant sample. These special advantages of FT-Raman spectroscopy applied to 2D Raman mappings enabled to illustrate the distribution of individual plant carotenoids independently from each other in the same sample [4]. Furthermore, the high potential of FT-Raman microspectroscopy to obtain detailed information about microstructure and chemical composition of fennel fruits, chamomile inflorescence, and curcuma roots was demonstrated [11]. 

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