application of raman
- 1. APPLICATIONS OF RAMAN SPECTROSCOPY By Sher Muhammad Fida Hussain Roll NO 21 Date 20/4/2016
- 2. Raman Spectra of Inorganic Species The Raman technique is often superior to infrared for spectroscopy investigating inorganic systems because aqueous solutions can be employed. In addition, the vibrational energies of metal-ligand bonds are generally in the range of 100 to 700 cm-1, a region of the infrared that is experimentally difficult to study. These vibrations are frequently Raman active, however, and peaks with values in this range are readily observed. Raman studies are potentially useful sources of information concerning the composition, structure, and stability of coordination compounds.
- 3. Raman Spectra of Organic Species Raman spectra are similar to infrared spectra in that they have regions that are useful for functional group detection and fingerprint regions that permit the identification of specific compounds. Raman spectra yield more information about certain types of organic compounds than do their infrared counterparts. Biological Applications of Raman Spectroscopy Raman spectroscopy has been applied widely for the study of biological systems. The advantages of his technique include the small sample requirement, the minimal sensitivity toward interference by water, the spectral detail, and the conformational and environmental sensitivity.
- 4. Quantitative applications Raman spectra tend to be less cluttered with peaks than infrared spectra. As a consequence, peak overlap in mixtures is less likely, and quantitative measurements are simpler. In addition, Raman sampling devices are not subject to attack by moisture, and small amounts of water in a sample do not interfere. Despite these advantages, Raman spectroscopy has not yet been exploited widely for quantitative analysis. This lack of use has been due largely to the rather high cost of Raman spectrometers relative to that of absorption instrumentation.
- 5. Resonance Raman Spectroscopy Resonance Raman scattering refers to a phenomenon in which Raman line intensities are greatly enhanced by excitation with wavelengths that closely approach that of an electronic absorption peak of an analyte. Under this circumstance, the magnitudes of Raman peaks associated with the most symmetric vibrations are enhanced by a factor of 102 to 106. As a consequence, resonance Raman spectra have been obtained at analyte concentrations as low as 10-8 M.
- 7. Resonance Raman Spectroscopy The most important application of resonance Raman spectroscopy has been to the study of biological molecules under physiologically significant conditions; that is , in the presence of water and at low to moderate concentration levels. As an example, the technique has been used to determine the oxidation state and spin of iron atoms in hemoglobin and cytochrome-c. In these molecules, the resonance Raman bands are due solely to vibrational modes of the tetrapyrrole chromophore. None of the other bands associated with the protein is enhanced, and at the concentrations normally used these bands do not interfere as a consequence.
- 8. Surface-Enhanced Raman Spectroscopy (SERS) Surface enhanced Raman spectroscopy involves obtaining Raman spectra in the usual way on samples that are adsorbed on the surface of colloidal metal particles (usually silver, gold, or copper) or on roughened surfaces of pieces of these metals. For reasons that are not fully understood, the Raman lines of the adsorbed molecule are often enhanced by a factor of 103 to 106. When surface enhancement is combined with the resonance enhancement technique discussed in the previous section, the net increase in signal intensity is roughly the product of the intensity produced by each of the techniques. Consequently, detection limits in the 10-9 to 10-12 M range have been observed.
- 9. Applications in Real Life • Identify Molecules • Environmental Monitoring • Explosives/Contraband • Quality Control/Commercial Industry • Biochemistry/Medical Applications • Art Examination and Preservation • Electronics and Semiconductors
- 10. 10 General Applications of Raman Spectroscopy • Structural chemistry • Solid state • Analytical chemistry • Applied materials analysis • Process control • Microspectroscopy/imaging • Environmental monitoring • Biomedical