page_title: Raman microscope
section_title: Raman imaging
hierarchical_section_title: Raman microscope / Raman imaging
caption_attribution_description: English: Confocal Raman image of a pharmaceutical emulsion. The chemical distribution of oil (green), the active pharmaceutical ingredient (API, blue) and silicon impurities (red) are shown.
context_page_description: The Raman microscope is a laser-based microscopic device used to perform Raman spectroscopy. The term MOLE is used to refer to the Raman-based microprobe. The technique used is named after C. V. Raman who discovered the scattering properties in liquids.
context_section_description: Another tool that is becoming more popular is global Raman imaging. This technique is being used for the characterization of large scale devices, mapping of different compounds and dynamics study. It has already been used for the characterization of graphene layers, J-aggregated dyes inside carbon nanotubes and multiple other 2D materials such as MoS₂ and WSe₂. Since the excitation beam is dispersed over the whole field of view, those measurements can be done without damaging the sample.
  By using Raman microspectroscopy, in vivo time- and space-resolved Raman spectra of microscopic regions of samples can be measured. As a result, the fluorescence of water, media, and buffers can be removed. Consequently, it is suitable to examine proteins, cells and organelles.
  Raman microscopy for biological and medical specimens generally uses near-infrared (NIR) lasers (785 nm diodes and 1064 nm Nd:YAG are especially common). This reduces the risk of damaging the specimen by applying higher energy wavelengths. However, the intensity of NIR Raman scattering is low (owing to the ω⁴ dependence of Raman scattering intensity), and most detectors require very long collection times. Recently, more sensitive detectors have become available, making the technique better suited 
  to general use. Raman microscopy of inorganic specimens, such as rocks, ceramics and polymers, can use a broader range of excitation wavelengths.
  A related technique, tip-enhanced Raman spectroscopy, can produce high-resolution hyperspectral images of single molecules and DNA.
caption: Chemical image of a pharmaceutical emulsion acquired by confocal Raman microscopy (alpha300 microscope, WITec; blue: Active pharmaceutical ingredient, green: Oil, red: Silicon impurities).
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