Bacterially Produced Manganese Oxide and Todorokite:  UV Raman Spectroscopic Comparison

Abstract

UV Raman spectroscopic data measured at two distinct conditions, low and high laser power, establish that the manganese oxide (SP6-MnO x ) produced by the freshwater bacterium (Leptothrix discophora SP-6) closely resembles the 3 × 3-tunnel todorokite among the MnO2 materials studied. Under the two conditions, the effect of hydration/cation and the phase transition of todorokite or SP6-MnO x to Mn3O4 or birnessite will be described. A higher concentration of Mg2+ incorporated in the framework of the SP6-MnO x than in todorokite is probably responsible for the formation of a new Raman band obtained at high laser powers, matching the most intense UV Raman band of synthetic birnessite. Also, we present the assignment of Raman bands for todorokite mineral and discuss the mutual exclusion principle that should hold for all the MnO2 materials studied. These experiments provide characterization of hydrous, poorly crystalline, or nanocrystalline metal oxides, which are frequently difficult to identify.

Room temperature ferromagnetism in Mn-doped zinc oxide nanorods prepared by hybrid wet chemical route

“…Disappearance of the Raman peak at ∼577 cm −1 in the annealed films, arising due to the Zn interstitials, may be related to the substitution of Mn 2+ in the Zn 2+ site with annealing. Xu et al [29] and Kim and Stair [30] observed the existence of a weak peak at about 665 cm −1 which was ascribed to the vibration mode of Mn-O. In the present study, the observed vibrational mode at ∼660 cm −1 in Mn:ZnO nanorod samples appeared only for samples containing higher amount of Mn.…”

Raman microscopy of prehistoric paintings in French megalithic monuments

“…A(a), is frequently observed in these specimens. A study on Magdalenian pigments from Grottes de la Garenne (France) assigned this band to cryptomelane, in disagreement with UV Raman data for this mineral . This band could also be assigned to todorokite, pyrochroite and manganosite .…”

“…Raman spectra of these specimens of black paint from the chamber H, Fig. A, show broad bands in the typical spectral region of Mn–O and Mn–OH bending and stretching vibrations (450–800 cm −1 ) . This suggests the presence of Mn oxides (Mn x O y ) and oxyhydroxides (Mn x O y (OH) z ).…”

Synthesis of todorokite-type manganese oxide from Cu-buserite by controlling the pH at atmospheric pressure

“…Manganese oxide materials are a family of microporous transition metal oxides and can form mixed-valent semiconducting octahedral molecular sieves (OMS) with tunnel structures of various sizes [1][2][3][4][5][6]. Todorokite-type manganese oxide (OMS-1) is one group in the OMS family, containing 3 Â 3 tunnel structure with a pore size of 6.9 Å [7].…”