Raman spectroscopy is a non-destructive, label-free technique for the analysis of molecular structure, phase and polymorphy, crystallinity, and intermolecular interactions. This spectroscopy is based on the inelastic scattering of light by matter, which known as Raman scattering. The specificity of Raman spectroscopic techniques is extremely high, although the sensitivity is low. After decades of technical development, Raman spectroscopy has become an important analytical technique in optical metrology. Raman spectroscopy-based analysis often requires small sample amounts and almost no sample preparation. Water can be readily used as a solvent in Raman spectroscopy, but hardly in infrared (IR) spectroscopy. There are now more than 25 types of known Raman spectroscopy techniques, such as coherent anti-Stokes Raman scattering (CARS), surface-enhanced Raman scattering (SERS), tip-enhanced Raman scattering (TERS), Fourier transform (FT) Raman scattering, Raman-induced Kerr effect spectroscopy (RIKE), and stimulated/coherent Raman scattering. Raman spectroscopy has potential to be a powerful analytical tool in chemical, biological, medical, pharmaceutical, and environmental applications.
A Raman spectrometer is mainly composed of light source, monochromator, sample holder and detector. Laser source is often employed as light source, either a continuous wave or pulsed laser. The continuous source of photons in the visible or IR range is commonly supplied by diode-pumped solid-state laser (DPSSL). Pulsed lasers are usually Nd:YAG or excimer lasers, and are characterized by a much higher power output. The Raman spectra collection is performed by two major technologies, dispersive Raman spectroscopy and FT Raman spectroscopy. The difference between these two technologies lies in their laser sources and Raman scattering detection and analysis methods. Both techniques have unique advantages and the method that best suit the sample should be preferred. The factors affecting the Raman spectra analysis may include high signal-to-noise ratio, instrument stability and sufficient resolution. Even though the relatively low intensity of Raman scattering, the development of highly sensitive detectors in conjunction with coupling of optical fibers and microscopes enhanced the analytical capabilities of Raman spectrometers. In addition, the combination of a Raman spectrometer and an optical microscope, known as micro-Raman spectroscopy, reaches a scanning sample depth ranging from few hundreds of nm to 1 μm by a high magnification objective.
Many useful properties of being nondestructive, noncontact, label-free, fast, and robust way of measurement reproducible and selective open new application opportunities for Raman spectroscopy. With the development of the technology, Raman spectroscopy has shown great potential in a wide range of applications from biology and medicine to forensic and archaeology. Amerigo Scientific offers affordable and ease to use Raman spectroscopy instruments to enable accurate quantitative and qualitative analysis in a variety of fields.
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