Lichen biominerals: Raman spectroscopy of natural copper oxalate and synthetic analogue

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Marco E. Ciriotti
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Iscritto il: ven 25 giu, 2004 11:31
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Lichen biominerals: Raman spectroscopy of natural copper oxalate and synthetic analogue

Messaggio da Marco E. Ciriotti » sab 01 ott, 2022 11:12

Referenza:
▪ Krajanová, V., Lalinská-Voleková, B., Majzlan, J. (2022): Lichen biominerals: Raman spectroscopy of natural copper oxalate and synthetic analogue. Conference: IMA 2022: Mineralogy & Space. 23rd General Meeting of the International Mineralogical AssociationAt: Lyon, France, OL25_6, MA2022-1699.

Abstract:
Lichens (lichenized fungi) are a unique source of natural oxalates. Our work focuses on Lecidea inops Th. Fr., one of the lichen species in which the first natural copper oxalate was identified. The purpose of this study was to make Raman investigations to confirm the presence of copper oxalates in L. inops from different geographical sources (Slovak Republic, Sweden). Lichen samples were provided by Slovak National Museum - Natural History Museum in Bratislava, Slovak Republic. The purchased copper oxalate hydrate (98%, Alfa Aesar) was used as synthetic reference material for the identification of moolooite [Cu(C2O4)·0.4H2O] deposition in lichens. Raman spectra of natural and synthetic copper oxalates were obtained by DXR3xi Raman Imaging Microscope (Nicolet) equipped with 785 nm laser. Raman bands obtained from synthetic copper oxalate were: 208, 298 (lattice modes), 557 (ν (Cu–O) + ν (C–C), 584, 609 (water vibration), 831 (νs (C–O) / δ(O–C–O)), 924 (νs (C–O) + δ(O–C=O)), 1488 (νs (C–O) + ν(C–C)), and 1513 cm-1 (νa (C=O)). These bands were in good agreement with Raman bands obtained from natural copper oxalates present in lichens (210, 560, 587, 611, 836, 932, 1483, and 1512 cm-1 for the Slovak sample, and 208, 561, 590, 613, 1480, and 1514 cm-1 for Sweden sample, with weaker bands being swamped by other signals.). Small shifts in band positions were attributed to the higher hydration status of moolooite (orthorhombic), in contrast to the less hydrated synthetic analogue (monoclinic).
Marco E. Ciriotti

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