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Raman spectroscopy

Raman spectroscopy is an ideal tool for the chemical analysis of samples contained in plastic bags, glass vials, and in aqueous solution of even very small sample size and is a nondestructive and noncontacting method of obtaining the fingerprint spectrum in a short time without requiring no special sample preparation. It can be used to monitor chemical reactions in real time.
Raman System

A typical laboratory Raman analyzer system consists of four major components: a strong monochromatic light excitation source, the collection device, the spectrograph, and the post-processing software. A laser is typically used as the excitation source because it can provide a coherent beam of monochromatic light with high intensity. The collection device is the fiber optic probe which collects the scattered photons, filters out the Raleigh scattering, and sends the Raman signals to the spectrograph. The spectrograph then separates the Raman signals by their wavelengths and transfers them to the light detector, which records the intensity of the accumulated photons at its own wavelength. These recorded data then are passed on to the post processing software to get a spectrum.


Many types of lasers are used as the excitation source for Raman spectroscopy. They are Ar+ ion (488.0 and 514.5 nm), Kr+ ion (530.9 and 647.1 nm),He:Ne (632.8 nm), Nd:YAG (1064 nm), and diode (630 and 980 nm) lasers. Due to recent advancements in diode laser technology, it is the best candidate to be utilized in low-cost, portable Raman analyzer systems because of its relatively low cost, compact size, high reliability (>10,000-h lifetime), and near-infrared (NIR) emission wavelength for fluorescence reduction.

Raman spectroscopy is useful in pharmaceutical, petrochemical processing, and plastic recycling applications.


Raman system is its ability to measure down to 50 cm-1 in spectral range which feature is very attractive to the pharmaceutical industry because most of the spectra of drug lattices are below 200 cm-1. Raman spectroscopy finds its application in lattice vibration study for the characterization of the solid state of a drug and especially for the investigation of polymorphism and amorphous systems, analysis and quantification of drug blends, and in the examination of drug formulations and drug excipient incompatibilities.


The gasoline has the methyl-tert-butyl ether (MTBE) content added to improve the octane number. The octane number is an experimentally determined property of petroleum fuel that defines the quality of engine ant knocking. Raman spectroscopy can be used to identify the octane level within gasoline and control of octane level in gasoline. Also, Raman systems can be used to measure and monitor oxygenates material in the gasoline during refinery process and for qualitative identification.


Plastics are common materials and consist of seven different kinds of polymers. Raman spectroscopy systems find application in real-time monitoring of polymerization reactions to control the processing time, in quantitative compositional analysis of polymer melt streams, and in plastic identification for recycling purposes.


Raman Spectroscopy has already proven to be a characterization technique suitable for characterizing nanomaterials such as nano-sized crystals and bulk homogeneous materials with a structural disorder at the nanoscale typically nanoceramics, nanocomposites, glassy materials, relaxor ferroelectrics, advanced and ancient ceramics, semiconductors and polymers developed in the form of dots, wires, films, fibers or composites for applications in the energy, electronic and aeronautics aerospace industries. Perfect control of nanoscale related properties can be achieved by correlating the parameters of the synthesis process (self-assembly, microlithography, sol-gel, polymer curing, electrochemical deposition, laser ablation, etc.) with the resulting nanostructure and this is not possible by conventional characterization techniques. Not only can it provide basic phase identification but also subtle spectra alterations can be used to assess nanoscale structural changes and characterize micromechanical behavior. It is thus a unique tool for probing or mapping nanophases dispersed in a matrix (e.g. pigments in a ceramic glaze, precipitates in a fiber coating, surface-formed nanophases (corrosion mechanisms) and solid-state devices. Some specific features can even be used to study charge transfer, film orientation, the size of clusters trapped in nano-cavities, Gru¨neisen’s parameter, configurational order (for instance the proportion of trans-gauche chains in Poly(ethylene terephtalate)-PET or intercalation, interfacial and polymerization reactions.

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