If the Raman microscope system is equipped with a motorized XY sample stage, and/or motorized Z stage, it will be capable of recording a Raman spectral image or profile.
Raman spectral imaging is a powerful technique for generating detailed chemical images based on a sample’s Raman spectrum. A complete spectrum is acquired at each and every pixel of the image, and then interrogated to generate false color images based on material composition and structure:
Thus with a single data set a wide variety of Raman spectral images can be created which take the researcher well beyond what the eye can see.
Raman profiles and images can be collected in one, two and three dimensions, including:
Raman depth profile of a layered polymer structure, showing the distribution of three chemically distinct layers from the surface (left hand side) down to 40 µm below the surface (right hand side).
A confocal Raman microscope can be used to analyze features below the sample surface provided the sample matrix is transparent to the laser. Typical examples of such analyzes include fluid/gas inclusions, contaminants in glass, and layered polymer structures.
On a basic system, manual focusing would be required to locate the required position within the sample, followed by spectral analysis. If the Raman microscope is equipped with motorized Z (focus) control, then it is possible to acquire depth (Z) profiles through the sample automatically.
75 µm multi-layered polymer of polyethylene-Nylon- polyethylene
Such a profile comprises a full Raman spectrum at each and every depth within the profile, and is then interrogated to generate intensity profiles based on material composition and structure:
A system which has additional XY motorized sample control can be used to optically slice through the sample, for example, to create an XZ or YZ Raman spectral image.
A Raman microscope can be used to analyze liquids, as well as solids, slurries, gels, gases and powders. Non-volatile liquids can be analyzed by dropping a small volume onto a microscope slide, and focusing in the normal way. Volatile (and non-volatile) liquids can be analyzed in a liquid cuvette using a simple microscope adapter with a multipass reflecting mirror which boosts the signal intensity. Alternatively, liquids can also be analyzed directly in a glass vial or bottle – a confocal Raman microscope will ensure that there is minimum interference from the glass container, and allows a good quality spectrum of the liquid inside to be collected.
Raman spectral imaging (or mapping) is a method for generating detailed chemical images based on a sample’s Raman spectrum. Raman spectral imaging allows chemical distribution to be viewed which is invisible by standard optical microscopy.
Raman spectral imaging (or mapping) is a method for generating detailed chemical images based on a sample’s Raman spectrum. A complete spectrum is acquired at each and every pixel of the image, and then interrogated to generate false color images based on material composition and structure.
A typical experiment uses sequential sample movement and spectrum acquisition, repeated hundreds, thousands or even millions of times, to collect data from the user defined image area.
Raman spectral images can be collected in two and three dimensions, to yield XY images, XZ and YZ slices, and XYZ datacubes.
Raman spectral imaging is an invaluable technique for scientists in many varied fields, since it allows chemical distribution to be viewed which is invisible by standard optical microscopy.
A Raman spectral image contains a full Raman spectrum at each and every pixel of the image. Raman spectral images provide chemical and structural information about a sample which cannot be observed using tradition light microscopy.
A Raman spectral image contains a full Raman spectrum at each and every pixel of the image - these hundreds, thousands or even millions of spectra are used to generate false color images based on material composition and structure:
Raman spectral images provide chemical and structural information about a sample which cannot be observed using tradition light microscopy.
Raman spectral images provide chemical and structural information about a sample which cannot be observed using tradition light microscopy. In particular they can be used to elucidate:
The development of ultra-fast Raman spectral imaging modules allows drastically reduced measurement times with acquisition times down to < 1ms/point.
The acquisition time for a Raman spectral image depends on many parameters, including the size of the image area, the number of pixels (data points) required, and the acquisition time per pixel (which is itself dependent on the Raman intensity of the sample’s components, and the spectral quality required). Typical Raman spectral images can contain hundreds, thousands or even millions of Raman spectra, so acquisition times can be significant.
A Raman spectral image can be acquired in any time scale from a few seconds through to several days, depending on the above requirements.
The acquisition time for a Raman spectral image depends on many parameters, including the size of the image area, the number of pixels (data points) required, and the acquisition time per pixel.
Traditional Raman spectral imaging has always been limited by relatively long acquisition times, but such methods do offer the ultimate sensitivity for materials with extremely low Raman scattering properties, and additionally allows high resolution, large spectral range measurements. Typical acquisition times for such maps can be in the order of 1s-10s per point (or longer), resulting in total measurement times in the order of hours or days.
The development of ultra-fast Raman spectral imaging modules allows drastically reduced measurement times with acquisition times down to < 1ms/point. Such speeds mean that large area survey scans and detailed Raman spectral images can be completed in seconds or minutes!
Ultra-fast Raman spectral imaging is a technique for allowing Raman spectral images to be acquired with acquisition times down to less than 5ms/point, resulting in total measurement times of seconds or minutes, even for images comprising tens or hundreds of thousands of spectra.
Ultra-fast Raman spectral imaging is a technique for allowing Raman spectral images to be acquired with acquisition times down to less than 5ms/point, resulting in total measurement times of seconds or minutes, even for images comprising tens or hundreds of thousands of spectra.
Traditional Raman spectral imaging has always been limited by long acquisition times, but such methods do offer the ultimate sensitivity for materials with extremely low Raman scattering properties, and additionally allows high resolution, large spectral range measurements. Typical acquisition times for such maps can be in the order of 1s-10s per point (or longer), resulting in total measurement times in the order of hours or days.
Raman spectral image of a 0.6 x 2.4 mm2 area of a pharmaceutical tablet, showing the distribution of aspirin (red), paracetamol (green),caffeine (blue) and cellulose (yellow).
Methods for ultra-fast Raman spectral imaging vary, but typically they coordinate sample stage movement and detector readout to minimize ‘dead time’ which occurs in standard point-by-point imaging experiments. They allow Raman spectral images to be acquired with acquisition times of 1 ms/point or less, so that large area survey scans and detailed Raman spectral images can be completed in seconds or minutes!
Ultra-fast Raman spectral imaging is not suitable for every type of sample, and its efficacy will depend on the sample’s inherent Raman intensity, and the required spectral quality necessary to create the image.
Sie haben Fragen oder Wünsche? Nutzen Sie dieses Formular, um mit unseren Spezialisten in Kontakt zu treten.
