Laser Raman spectroscopy
Laser Raman spectroscopy is a powerful technique for the identification of a wide range of samples – solids, liquids, and gases. It is a straightforward, non-destructive technique requiring no sample preparation. Raman spectroscopy involves illuminating the sample with monochromatic light (laser) and using a spectrometer to examine light that is scattered by the sample. Spectral composition of the scattered light carries information about different molecular or crystal vibrational modes which can serve as a unique characteristic for different materials. This makes Raman spectroscopy a useful technique for fast material identification (usually a few minutes are required) and characterisation of the content of DNA, RNA, lipids, proteins, sugars, pigments, saccharides, and amides within the sample. Typical Raman spectrometers for material identification use a microscope to focus the laser beam on a small spot so that the information about chemical composition from femtolitre volumes can be obtained. Even though the principle of this method has been known for almost a hundred years, only recently has started to be utilized in many unique applications triggered especially by the development of sensitive detectors.
The advantages and applications of Raman spectroscopy
- Raman spectroscopy is capable of rapidly identifying biological samples. For example, medically relevant bacterial strains can be detected (e.g. Staphylococcus epidermidis). Raman spectroscopy can discriminate between biofilm-positive and biofilm-negative bacterial strains in real-time. Thus, time and cost of patient treatment related to virulent infection can be reduced because an appropriate therapeutic strategy can be chosen.
- Raman spectra can serve for identification of cells in oncological applications (e.g. diagnostics for early recognition of cancerous cells in-vivo and in-vitro) and identification of cells invaded by viral infections.
- Non-destructive analysis in the pharmaceutical industry (e.g. on-line characterization of tablets) and production of chemical maps of different surfaces or identification of nano-structures are possible.
- Raman spectroscopy can be combined with optical tweezers to form so-called Raman tweezers. This powerful combination can be used for identification and sorting of microorganisms freely moving in liquids.
