Effect of carbonate content on the ESR spectrum near g=2 of carbonated calciumapatites synthesized from aqueous media

Abstract

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.

EPR dosimetry with tooth enamel: A review

“…(Vanhaelewyn et al, 2000b;Callens et al, 1989a), and the g x and g z values are averaged. In some samples, even centers with completely isotropic gtensors have been found; most probably, that was due to rapid tumbling of the radicals in the presence of water, perhaps occluded (Callens et al, 1989b;Moens et al, 1995).…”

“…When the stabilizing cation is not on the symmetry axis of the free ion, the CO 3 3-center may become orthorhombic (Table 5). In addition to the g = varieties have been reported (Table 5 and Callens et al, 1989b).…”

1H and31P ENDOR of the isotropic CO2 − signal atg=2.0007 in the EPR spectra of precipitated carbonated apatites

“…In the past twenty years, biological as well as synthetically prepared carbonated apatites have been investigated intensively with EPR [1][2][3][4][5][6][7][8]. After X-or y-irradiation, the observed EPR spectra show the so-called asymmetric signal around g = 2.00.…”

“…Although the environment certainly has an influence on the magnetic parameters characterizing the paramagnetic center, the determination of the site allocation of the radicals involved remains difficult. In the past, the site aliocation of the radicals usually was done by comparing the EPR data with results from other techniques such as InfraRed (IR) spectroscopy [6][7][8].…”

Detailed protocol for an accurate non-destructive direct dating of tooth enamel fragment using Electron Spin Resonance

“…The denomination sometimes varies from one publication to the other, and the identification and characterisation of each interfering radical falls out of the scope of this publication. For a complete description of radicals we encourage reader to refer to Callens et al, (1989 and1995), Bouchez et al (1988), Schramm and Rossi (2000), Vanhaelewyn et al (2000a and and Joannes-Boyau et al, 2010a. The influence of the main known signals can have serious repercussion on the intensity measured especially for T1-baseline and T1-B1 (Fig.…”