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DOI: 10.1039/A903185E (Paper) Reference Section for: Phys. Chem. Chem. Phys., 1999, 1, 3697-3700

An EPR study of Cd2+ incorporation in vaterite

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Vesna Nöthig-Laslo and Ljerka Brečević

Abstract

13C-vaterite, the unstable calcium carbonate polymorph, doped with Cd2+ was γ-irradiated and the stable paramagnetic centres were studied using electron paramagnetic resonance (EPR) spectroscopy. The 13C isotope has nuclear spin (I=1/2) and as a consequence hyperfine interaction with the unpaired electron occurs. This revealed all paramagnetic centres of carbonate origin, i.e. CO3- and CO2- free radicals. Two paramagnetic centres induced by cadmium doped to vaterite, one characterized by ga=1.9939 and the other by gb=1.9886, were not split by the 13C-hyperfine splitting. Therefore, these paramagnetic centres are most probably due to Cdâ†�O-. The locations of these paramagnetic centres in vaterite are determined and the role of cadmium in the formation of calcite crystals in the vaterite-precipitating system is discussed.

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