Effect of carbonate content on the ESR spectrum near g = 2 of carbonated calciumapatites synthesized from aqueous media.
The ESR spectrum of X-irradiated carbonated apatites synthesized at low temperature was studied as a function of their carbonate content. Using 13C-enriched samples, four different carbonate-derived radicals and a surface O- ion could be identified. Isotropic CO3- and CO2- ions are present at a B site in the apatite lattice, and anisotropic CO3- and CO2- radicals are located at the surface of the crystallites. Only the isotropic ESR signals increase with increasing carbonate content. The anisotropic signal ascribed to a surface CO2- radical is mainly responsible for the so-called asymmetric ESR signal near g = 2. It is argued that this surface signal may still be composite and caused by several very similar CO2- ions. The consequences for phenomenological ESR studies of calcified tissues are discussed.
Callens
F J
FJ
Laboratory of Crystallography, State University Gent, Belgium.
Verbeeck
R M
RM
Naessens
D E
DE
Matthys
P F
PF
Boesman
E R
ER
D001031:Apatites / Q000032:analysis / Q000528:radiation effects; D002245:Carbon Dioxide / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D003743:Dental Enamel; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006801:Humans; D010100:Oxygen / Q000032:analysis; D026082:Singlet Oxygen
D001031:Apatites; D002254:Carbonates; D005609:Free Radicals; D002245:Carbon Dioxide; D026082:Singlet Oxygen; D010100:Oxygen