Manganese oxides are important geomaterials, widespread in terrestrial and Martian environments. Characterisation of the oxidation state of Mn is a central issue in science; this task has been addressed up to the present by X-ray spectroscopy or diffraction techniques. The former, however, requires access to synchrotron facilities, while the latter does not provide crystal-chemical information at the local scale. In this work, we compare a large set of Raman data from wellcharacterised samples, already published by the same authors of this paper or as found in the literature. We show a clear correlation between the oxidation state of Mn and the wavenumber of peculiar bands; octahedrally co-ordinated Mn2+ is recognised by a band around 530 cm-1, Mn3+ by a band around 580 cm-1 and Mn4+ by a band around 630 cm-1, while tetrahedrally co-ordinated Mn2+ is recognisable by a band around 650 cm-1. Strongly distorted Mn3+ octahedra are indicated by the appearance of Jahn–Teller modes. Our method allows a reliable, easily accessible tool to characterise the oxidation states of Mn in oxides, also suitable for microscale mapping. It provides a robust analytical basis for the use of these minerals as redox indicators in geology/geochemistry, in exoplanetary research or for monitoring technological processes.

Bernardini, S., Bellatreccia, F., Della Ventura, G., & Sodo, A. (2020). A Reliable Method for Determining the Oxidation State of Manganese at the Microscale in Mn Oxides via Raman Spectroscopy. GEOSTANDARDS AND GEOANALYTICAL RESEARCH [10.1111/ggr.12361].

A Reliable Method for Determining the Oxidation State of Manganese at the Microscale in Mn Oxides via Raman Spectroscopy

Bernardini, Simone
Writing – Original Draft Preparation
;
Bellatreccia, Fabio
Supervision
;
Della Ventura, Giancarlo
Writing – Review & Editing
;
Sodo, Armida
Methodology
2020

Abstract

Manganese oxides are important geomaterials, widespread in terrestrial and Martian environments. Characterisation of the oxidation state of Mn is a central issue in science; this task has been addressed up to the present by X-ray spectroscopy or diffraction techniques. The former, however, requires access to synchrotron facilities, while the latter does not provide crystal-chemical information at the local scale. In this work, we compare a large set of Raman data from wellcharacterised samples, already published by the same authors of this paper or as found in the literature. We show a clear correlation between the oxidation state of Mn and the wavenumber of peculiar bands; octahedrally co-ordinated Mn2+ is recognised by a band around 530 cm-1, Mn3+ by a band around 580 cm-1 and Mn4+ by a band around 630 cm-1, while tetrahedrally co-ordinated Mn2+ is recognisable by a band around 650 cm-1. Strongly distorted Mn3+ octahedra are indicated by the appearance of Jahn–Teller modes. Our method allows a reliable, easily accessible tool to characterise the oxidation states of Mn in oxides, also suitable for microscale mapping. It provides a robust analytical basis for the use of these minerals as redox indicators in geology/geochemistry, in exoplanetary research or for monitoring technological processes.
Bernardini, S., Bellatreccia, F., Della Ventura, G., & Sodo, A. (2020). A Reliable Method for Determining the Oxidation State of Manganese at the Microscale in Mn Oxides via Raman Spectroscopy. GEOSTANDARDS AND GEOANALYTICAL RESEARCH [10.1111/ggr.12361].
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11590/372404
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