Micro-Raman spectroscopy offers improved capability to identify and characterize natural Mn oxide phases, thereby providing a better understanding of the role of Mn oxide minerals in the environment and permitting more accurate comparisons of laboratory experiments to natural systems.  A primary advantage of the Raman technique is that the spectra provide information about local atomic coordination environments as well as longer-range structure, and therefore, it can be a useful probe even for highly disordered materials.  Modern instruments typically offer multiple laser options and high-sensitivity detectors that offer a range of data collection conditions that can be optimized for particular samples.  These micro-Raman systems have the potential to provide phase identification and structural information quickly and easily from discrete areas (~1 µm spot size) on natural or synthetic Mn oxide samples.  Moreover, high-spatial resolution Raman mapping is a standard capability in most new instruments.<br/>We present here results of a comprehensive Raman study from a large assortment of well-characterized natural and synthetic Mn oxide samples, using a variety of data collection conditions and crystal orientations.  We have demonstrated that the use of multiple lasers, especially at 785, 532, and 633 nm wavelengths, and low incident powers (30 – 500 µW, depending upon the laser light and sample), make it possible to unambiguously identify Mn oxide phases for most samples.  In addition, we explored spectral trends for some specific phases that provide insights about composition, crystal structure, symmetry, and Mn oxidation states. With our comprehensive Raman database of well-characterized Mn oxide standards and use of appropriate data collection conditions, micro-Raman is a powerful tool for identification and characterization of biotic and abiotic Mn oxide phases from diverse natural settings (including on other planets), and thereby can provide new insights into the roles of these phases in our environment. <br/>

Identification and characterization of natural and synthetic manganese oxides by Raman spectroscopy

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.