Raman Spectrometers

 

How To Choose Raman Spectrometer Types

Raman spectroscopy provides rapid and reliable non-destructive chemical analysis of aqueous solutions, powders, tablets, gels and surfaces. Raman scattering is a phenomenon that when a laser beam hits on a material, causing its molecules to vibrate, resulting in light-emitting with shifted wavelength related to the molecule energy levels.     Raman spectroscopy is thus used to identify molecules with their structural fingerprint.   To find out how strong the Raman signal for the material of your interest, please search the scientific literature.  If the signal is strong, then select the low cost uncooled spectrometer-PeakSeeker, if the signal is weak, then select the more expensive cooled spectrometer – PeakSeeker Pro.

Many materials have weak Raman signals.  To detect these chemicals, a high sensitivity spectrometer is needed.  There are two known methods to achieve high sensitivity Raman detection: surface-enhanced Raman spectroscopy (SERS) and cooled detectors.  Analyzers based on SERS have shown sensitivity amplifications. However, since SERS is a surface plasmonic effect, all demonstrated approaches require a nanostructured substrate that is prone to environmental variations.  Consequently, the inconvenience and uncertainty of SERS render it less desirable for general use. Conversely, cooled spectrometers are proven to achieve high sensitivity in the detection of weak Raman emissions. At the heart of a spectrometer is a photodetector that generates electron current upon light illumination. But under weak illumination, such as weak Raman emission, the electron carriers are mainly generated from random thermal excitation in the semiconductor, and this degrades performance through increased dark current and noise.  An effective way to reduce these effects is to reduce the detector’s operating temperature and integrate the photons over a period of time during the collection.  Therefore, if one needs to identify a substance with weak Raman signals, a cooled Raman spectrometer must be selected.  Raman spectrum for most chemicals can be found in publications.  Please check the related literature to make your buying decision.

FAQ
Q: How should a sample be prepared for analysis?
A: In general, solid samples don’t need special care. Liquid samples will need a glass or quartz container.

Q: How should the machine be set up for different types of measurements. Does it require calibration?
A: Calibration is not necessary. There are no moving parts inside the optical benchtop device. But if you think the spectrometer needs to be recalibrated, please refer to user manual pages 31~34.

Q: How should results be interpreted?
A: Different chemicals have different peaks. We use the distribution of peaks to identify the chemical.

Q: How is the material looked up based upon our results.
A: Through libraries; either our standard library or you can build you own. Please refer to user manual pages 37~40 and the chemicals list.

Q: Are there different libraries available? How do we get access?
A: There is only 1 library at this point, and it’s included in each order. Please refer to user manual pages 37~40.

Q: What is the proper way to care for the unit?
A: Raman spectrometers don’t typically need special care. Just make sure the lens on the probe is clean before every scan.