• Spectroscopy and Spectral Analysis
  • Vol. 39, Issue 4, 997 (2019)
ZHU Ting1, LIU Yang2、3, WU Jun2、4, WANG En-liang1, and XUE Feng5
Author Affiliations
  • 1[in Chinese]
  • 2[in Chinese]
  • 3[in Chinese]
  • 4[in Chinese]
  • 5[in Chinese]
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    DOI: 10.3964/j.issn.1000-0593(2019)04-0997-08 Cite this Article
    ZHU Ting, LIU Yang, WU Jun, WANG En-liang, XUE Feng. Development and Application of Spatially Offset Raman Spectroscopy[J]. Spectroscopy and Spectral Analysis, 2019, 39(4): 997 Copy Citation Text show less

    Abstract

    The traditional Raman spectroscopy can only detect the surface information of the sample, or can only through the transparent surface detect the inner information of the sample, and it has same problems to get information of multilayer opaque sample or opaque packaging sample, such as searching for hidden explosives, identifying fake medicine with opaque package and non-invasive detection of bone disease, etc.. Spatially offset Raman Spectroscopy (SORS) is a new type of spectral detection technique, which can get information from opaque package non-invasively or gain information through surface layer to inner of the sample directly. This technology solves the problems mentioned above. Firstly, this paper introduced the principle of SORS in detail. The fundamental principle lies in the theory of photon migration. Between the focus point of the incident laser light source and the focus point of the collect lens there is a certain spatial distance offset ΔS from surface of the sample. When the laser light incident into the surface of sample, it will be stimulated or scatter broadband fluorescence by the surface of sample. One part of scattered light will reach to the inner of sample, and the photons of Raman scattered light from inner sample is easier to migrate than the photons of the surface of sample. The photons of Raman scattered light are returned to the surface of sample and collected by optical system after multiple scattering. Scattered light from different depths ΔH have different spatial distance offset ΔS after returning to the surface of sample.When the spatial distance offset ΔS is zero, the focus point of the incident laser light and the focus point of the collect lens are coincided where the density of photons is maximum, and the Raman signal collected by optical system are mostly from the surface of sample, and Raman signal of inner sample is submerged. When the spatial distance offset ΔS is not zero, the Raman signal from the surface of sample collected by optical system is attenuated quickly, but Raman signal of inner sample is attenuated more slowly than that from the sample surface, and this makes the proportion of inner sample more larger, so as to realize the Raman spectral separation. Then optical system will show us the Raman spectral from different depths of inner sample with multivariate data analysis method, and this Raman spectral is the Spatially offset Raman Spectroscopy(SORS). SORS has a good ability to suppress the interference of Raman and fluorescence spectra of surface materials, especially for the extraction of Raman spectra from substances under opaque packaging materials, so as to identify the target components quickly and non-invasively. Secondly, the characteristics of SORS technology are introduced. It is the derivative of Raman spectroscopy. Besides it has all the advantages of Raman spectroscopy, such as simple sample making, less water interference, less sample consumption, high sensitivity, etc.. It also has the special advantages of effectively suppressing the fluorescence, deep detection, non-invasive characteristics of nondestructive detecting and remote detection. These special advantages improved the intensity of Raman spectra effectively, reduced the user’s detection and production costs and also improved the personal safety of the inspectors. At the same time, this paper summarized and compared three existing working methods of SORS technology, standard SORS, inverse SORS and tilted SORS. The standard SORS technology can be used in non-contact remote sensing detection, and inverse SORS compared with the standard SORS has higher sensitivity and potential anti spectral distortion, and the incident light face and the effective spatial distance offset ΔS is controllable, and also avoid the sample overheating. Tilted SORS has a higher detection sensitivity of SORS, and the experimental device is easy to achieve. Then, based on a large number of research papers, the development and application of SORS technology combined with other technologies in chemical production, security inspection, biomedicine, archaeology, food safety, inspection and counterfeiting and national defense safety in recent years were reviewed. Finally, the existing problems of SORS technology are pointed out and the future prospects of the technology are also prospected.
    ZHU Ting, LIU Yang, WU Jun, WANG En-liang, XUE Feng. Development and Application of Spatially Offset Raman Spectroscopy[J]. Spectroscopy and Spectral Analysis, 2019, 39(4): 997
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