Raman spectroscopy with the DSC

Scientific definition

Raman spectroscopy is a technique for studying molecules and for determining their structure and dynamics. It uses excitation-induced scattering of light to examine chemical bonds in a sample. The process is useful for understanding the structures and dynamics of molecules in the solid, liquid and gas phases.

Raman spectroscopy

Raman is a technique that allows the determination of molecules and molecular chain bonds. This type of spectroscopy is particularly helpful as it allows direct measurement of the chemical composition without the need to decompose a sample. Raman spectroscopy is a non-invasive technique that offers a high degree of accuracy and repeatability. The precise and fast analytical measurement enables scientists and laboratory experts to analyse a wide range of substances quickly and efficiently, thereby quickly and accurately determining the chemical composition of a sample. Due to this measurement method, qualitative and quantitative analyses can be performed during research, industrial use and medical diagnostics, among other applications. It is also very useful to support the stability of materials, process monitoring, quality control and sample identification.

A Raman spectrometer measures the Raman scattered light that occurs when light interacts with a material. This scattering changes the wavelength of the incident light and provides information about the chemical bonds within a material.

Areas of application

Raman spectroscopy can be used to measure many different materials, such as organic compounds, polymers and certain minerals. Raman spectroscopy is particularly useful in the study of samples that provide only a small amount of information, as the technique provides information not only about the chemical structure but also about the spatial arrangement of molecules (that is, crystal structure). Another advantage is that Raman spectroscopy is very sensitive and can detect even small changes in sample molecules. The technique can also be used to measure impurities and trace substances.

Raman spectroscopy can measure various molecular chain bonds, such as, for example:

• C-C (carbon-carbon) bonds in organic compounds
• C-O (carbon-oxygen) bonds in carbonyl groups
• N-H (nitrogen-hydrogen) bonds in amides
• S-O (sulfur-oxygen) bonds in thiols

It is used in a variety of applications, including:

• Quality control in the pharmaceutical and chemical industry
• Identification of materials in archaeology, art history and criminology
• Analysis of solids and liquids in materials science
• Monitoring of processes in energy and environmental technology
• Investigation of biological samples in life science research.

Raman spectrometer setup

A Raman spectrometer consists of the following main components:

• Light source: Provides incident light, usually a laser system.
• Optical components: lenses and mirrors to direct the light at the sample material and collect the Raman scattered light.
• Sample holder: holds the material to be examined.
• Detector: measures the scattered light from the sample and converts it into electrical signals.
• Electronic components: such as amplifiers and analyzers process the signals and generate the Raman spectra.

Possible combination: Raman spectrometer and a DSC

Thanks to more efficient data collection and miniaturization, Raman spectrometers have become much more affordable. For this reason, the combination of this method with other means has become more and more commercially reasonable in recent years.

For example, a Raman spectrometer can be coupled to a DSC (Differential Scanning Calorimeter). In this way, both the enthalpic effects of a sample measurement can be quantitatively displayed simultaneously and the Raman spectrum can be recorded in order to make statements about molecular chain bonds and crystallinity, among other things.

Applications

This can be beneficial in a variety of applications in materials and process development, such as the characterization of polymers, solids, battery materials and biological samples.

For example, a simple heating process of a PET (polyethylene terephthalate) sample shows various thermal effects such as a glass point (~80°C), recrystallization (~150°C) and melting of the sample (~250°C).

With the help of Raman spectroscopy, the origin of these effects can be detected by means of the Raman spectrum, for example, crystallinity: