Raman microscopy is the smart combination of optical confocal microscopy with Raman Spectroscopy. One big advantage of light microscopes is the ability to observe living cells. It is possible to observe a wide range of biological activity, such as the uptake of food, cell division and movement. Additionally, it is possible to use in-vivo staining techniques to observe the uptake of colored pigments by the cells. These processes can hardly be observed in real time using Raman microscopes, due to long acquisition times, and electron microscopes as the specimen has to be fixed, and dehydrated (and is therefore often dead). The low cost of optical microscopes makes them useful in a wide range of different areas, such as education, and medical applications.
The following points highlight the key Raman advantages:
Detailed Chemical/molecular Analysis
Raman spectroscopy offers very detailed sample characterization by probing individual chemical bond vibrations. As a result, a Raman spectrum is information rich, and contains data relating to the specific chemical structure of the material being analyzed. It can be used to fully characterize a material’s composition, and fast identification of unknown materials is possible with the use of extensive Raman spectral databases.
Subtle information (crystallinity, polymorphism, phase)
Beyond general material identification and characterization, Raman spectroscopy also probes more subtle chemical effects, such as crystallinity, polymorphism, phase, intrinsic stress/strain, protein folding and hydrogen bonding.
Raman spectroscopy is a very fast technique, typically requiring just a few seconds to obtain a good quality spectrum. No sample preparation is required, so sample throughput is high.
No sample preparation
Unlike many analytical techniques which require sample pre- paration (such as dissolution, grinding, glass formation, or pressing) in order to achieve results, Raman analysis can be made on ‘as received’ samples with no preparation. This is true whether a sample is a solid, liquid, powder, slurry or gas.
Raman spectroscopy is a completely non-destructive technique – it is non-contact, non-destructive, and require no sample preparation. Thus it is possible to analyze samples such as historic pigments or vital forensic evidence, and retain the sample for additional analysis by other techniques if necessary.
Microscopic spatial resolution
When performed using a confocal Raman microscope, Raman spectroscopy offers the analyst high sensitivity microscopic analysis with sub-micron spatial resolutions. Thus, individual grains and particles, and specific regions of a sample can be analyzed. Raman micro-spectroscopy retains all of the above advantages.
A true confocal Raman microscope provides full 3D spatial resolution, allowing analysis of a discrete volume in a transparent sample. This property is particularly useful for analysis of layered samples (such as polymer laminates), inclusions (such as those found in glass and minerals), thin samples on a substrate (such as cells and tissue on a microscope slide) and materials in glass/plastic containers (such as a liquid in a bottle).
Suitable for in situ, in vitro and in vivo analysis
Since Raman spectroscopy is a non-contact and non- destructive technique, it is suitable for true in situ analysis. It can be used to probe chemical reactions within a reaction vessel, without perturbing the reaction in any way. The tolerance of Raman spectroscopy to water additionally allows it to be used for in vitro and in vivo analyzes – examples include the analysis of cosmetics on skin, single cell characterization for micro-biology, and drug-cell interactions for intelligent drug design.
Raman is often compared with FTIR, which is the gold standard for molecular spectroscopy. The two techniques are complimentary.
Advantages of Raman over IR:
There are not many things that these two microscope types have in common. Both electron and light microscopes are technical devices which are used for visualizing physical and chemical structures that are too small to see with the unaided eye, and both types have relevant areas of applications in biology and the materials sciences. Generally, Raman and electron microscopes have different areas of application and they complement each other.
Raman microscope has the following advantages:
Both techniques are complimentary to assess the crystalline structure of a certain materials.
Advantages of Raman versus XRD