Chemie und Prozesstechnik
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- 2020 (2) (entfernen)
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- Raman microspectroscopy (2) (entfernen)
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Dear Colleagues,
Raman spectroscopy provides vibrational fingerprints of chemical compounds, enabling their identification via a comparison with reference spectra. This analytical tool has high potential not only in the identification of minerals from natural sources but also for studying the complex microstructure and mineral distribution of both ancient and modern man-made materials, ranging from, e.g., historical ceramics and mortars to modern solar cell materials. In addition to the chemical identity of minerals, Raman spectra are affected by crystal orientations, substoichiometric to stoichiometric compositional changes (e.g., in solid solution series), traces of foreign ions, stress, strain, and crystallinity, enabling a comprehensive physicochemical characterisation of minerals. This Special Issue includes method developments and applications in the field of modern Raman spectroscopy of minerals in a broad sense, from natural mineral deposits to inorganic phases in materials; covers both spectroscopic and imaging studies; and provides a platform for discussing the possibilities and limits of the technique in the context of the existing analytical arsenal.
Thomas Schmid
Petra Dariz
Raman spectroscopy provides vibrational fingerprints of chemical compounds enabling their unambiguous identification. The assignment of Raman spectra to minerals is straightforward, if appropriate reference data is accessible. Modern couplings of Raman spectroscopy with microscopy (Raman microspectroscopy) merge the high structural specificity with down to sub-micrometre spatial resolution. This analytical tool has high potential not only in the identification of minerals from natural sources but also for studying the complex microstructure and mineral distribution of both ancient and modern man-made materials. In addition to the chemical identity of minerals, Raman spectra are affected by crystal orientations (varying relative Raman band intensities); (sub)stoichiometric compositional changes (e.g., in solid solution series), traces of foreign ions, strain (the latter three shifting Raman bands); and crystallinity (changing Raman band widths), enabling a comprehensive physico-chemical characterisation of minerals. Thus, Raman spectroscopy – including its in situ measurement capabilities – provides possibilities to study mineral paragenesis in both, natural and man-made samples at the micrometre scale. While in 1928 the first experimental evidence for inelastic light scattering was provided by C. V. Raman and K. S. Krishnan by using sunlight for excitation, filters for selecting the inelastically scattered light, and their eyes for detection (later, photographic plates for acquisition of spectra were employed), modern Raman spectrometers make use of laser excitation, dispersive spectrographs and charge coupled device (CCD) detection. This Special Issue includes technological developments and applications in the field of modern Raman spectroscopy of minerals in a broad sense, from natural mineral deposits and archaeological objects to inorganic phases in man-made materials. The studied minerals include fossil resins, typical rock-forming minerals (calcite, quartz, forsterite), iron-sulphur species (e.g., mackinawite), a range of sulphates (gypsum, bassanite, anhydrite III, anhydrite II, celestine, barite, ternesite), as well as silicate minerals like garnets (e.g., almandine).