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MICROSCOPY & IMAGING


RAMAN MICROSCOPY FOR ADVANCED R


Damon Strom provides a description of Raman microscopy and how it can be used to investigate particulate and biological samples


ANALYSIS


aman microscopy is a fast and non-destructive chemical characterisation technique. It is based on the Raman Effect, which


was discovered more than 90 years ago by Chandrasekhara Venkata Raman and documented in his paper A New Type of Secondary Radiation. Raman was later awarded the Nobel Prize in Physics for his work.


Te Raman Effect results from the inelastic scattering of excitation light by the molecules of gaseous, liquid or solid materials. Te interaction of a molecule with photons causes vibrations of its chemical bonds, leading to specific energy shifts in the scattered light that can be identified in its Raman spectrum. Any given chemical compound can be easily identified by this individual spectral ‘fingerprint’.


Less than one Raman-shifted photon is usually produced from one million incident photons. Terefore, the instruments used to acquire Raman signals should have optimised optical components, including highly sensitive detectors with low noise, and a confocal beam path to reject light from outside the focal plane and increase the signal-to-noise ratio. Tis optimisation enables the detection of Raman signals from even weak Raman scatterers and extremely low material concentrations or volumes. Measurements carried out on delicate samples also benefit from the ability to acquire Raman spectra using very low excitation energies.


RAMAN PARTICLE IDENTIFICATION AND CHARACTERISATION


High-resolution investigations of particles are of great interest in fields of application such as environmental science, microplastics research, pharmaceutical research, medical device development, life sciences and many others. Combining a particle analysis tool with Raman microscopy makes it possible to find, classify and identify particles in a sample according to their size, shape and chemical characteristics. Te physical and molecular attributes of the particles in a sample may be correlated and qualitatively and quantitatively evaluated. Te following measurement was


performed with the WITec ParticleScout particle analysis tool in conjunction with a WITec alpha300 R confocal Raman microscope. Fig. 1 shows the results of particle analysis carried out on a cosmetic peeling cream sample. Fig. 1A shows the overlay of an optical bright field microscope image


The WITec alpha300 Ri inverted confocal Raman microscope


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