Raman spectroscopy study of manganese oxides: Layer structures

Abstract

Raman spectra were collected for an extensive set of well-characterized layer-structure Mn oxide mineral species (phyllomanganates) employing a range of data collection conditions. We show that the application of a variety of laser wavelengths, such as 785, 633, and 532 nm, at low power levels (30-500 µW) in conjunction with the comprehensive database of standard spectra presented here, makes it possible to distinguish and identify the various phyllomanganate minerals. The Raman mode relative intensities can vary significantly as a function of crystal orientation relative to the incident laser light polarization direction as well as incident laser light wavelength. Consequently, phase identification success is enhanced when using a standards database that includes multiple spectra collected for different crystal orientations and with different laser light wavelengths. The position of the highest frequency Raman mode near 630-665 cm-1 shows a strong linear correlation with the fraction of Mn 3+ in the octahedral Mn sites. With the comprehensive Raman database of well-characterized Mn oxide standards provided here (and available online as supplemental materials), 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, as well as for laboratory and industrial materials.

Unusually High Electron Affinity Enables the High Oxidizing Power of Layered Birnessite

“…The XRD patterns of all other powders (Figure S1 in the Supporting Information, SI) conformed to the standard pattern of pure crystalline phases of the respective oxides . Raman spectroscopy has been shown to be a sensitive tool for probing lattices lacking long-range order, especially birnessite-type structures. − Figure B shows the Raman spectra of the cation-exchanged birnessites. All spectra match the spectra of the pure birnessite-type lattice with two prominent bands: one near 560 cm –1 corresponding to an in-plane Mn–O stretching vibration along the basal planes of MnO 6 sheets and the other near 650 cm –1 , which is associated with the out-of-plane vibration perpendicular to the basal plane.…”

Micro‐Raman spectroscopy on pigments of painted pre‐Islamic ceramics from the Kur River Basin (Fars Province, Iran): The case of manganese oxides identification

“…Research on the characterization of manganese oxide phases [30][31][32][33][34][35][36] is not only done due to their importance in the archaeological field but also related to the role that manganese has in biological processes, catalysis and water-splitting reactions [37]. Identification of these mineral species is possible by multiple techniques, such as X-ray diffractometry (XRD) [30,31,33,38], infrared spectroscopy (IR) [30][31][32], electrochemical characterization [30,33] and scanning electron microscopy (SEM) [33].…”

Formation of the Metastable MnIII Water Oxidation Intermediate in Birnessite is Controlled by a Dissolution‐Deposition Process Involving Labile MnII

“…In general, the interlayer spacing appears to increase with an increase in the ionic radius of the interlayer cation, which is 0.69 Å, 1.38 Å, 1.7 Å [23] for Li + , K + , and Cs + ions, respectively. The crystallographic structure of birnessite films was confirmed through Raman spectroscopy (Figure 1A), which showed two prominent bands that are consistent with patterns of birnessite lattices [24–26] . The vibration peak at 570 cm −1 corresponds to an in‐plane Mn−O stretching vibration along the basal planes of MnO 6 sheets, and the other near 650 cm −1 is associated with out‐of‐plane vibration perpendicular to the basal plane.…”

“…The crystallographic structure of birnessite films was confirmed through Raman spectroscopy (Figure 1A), which showed two prominent bands that are consistent with patterns of birnessite lattices. [24][25][26] The vibration peak at 570 cm À 1 Figure 1. A) Raman spectra of Cs + -, K + -, and Li + -birnessite thin films on FTO.…”