Synthesis and physical and chemical characterization of CaAg(PO)(OH) apatites

Cationic and Anionic Substitutions in Hydroxyapatite

“…By FT-IR and XRD analyses, it was demonstrated that Ag + ions substitute for Ca 2+ ions within the apatite lattice [141,161,181,186,187,189,199,[204][205][206]. Indeed, the effective Ag + incorporation within apatite lattice was testified by the identification of CaO, whose formation was ascribed to the oxidation of the free Ca 2+ ions, available in consequence of Ag + substitution for Ca 2+ within apatite lattice, during the thermal treatments [141].…”

“…In particular, it has been reported that Ag + ions substitution takes place for Ca 2+ preferentially in Ca(I) site of HAp, leading to an increase in the lattice parameters [161,187,189,192,206], due to the bigger Ag + ionic radius (0.128 nm vs 0.099 nm).…”

Crystallographic Aspects Regarding the Insertion of Ag+ Ions into a Hydroxyapatite Structure

“…(1-y/6)Ca 10 (PO 4 ) 6 (OH) 2 + (x+y)CO 2 + yCaO + yAg (6) After CO 3 2-is released from the HA structure, the excess Ca 2+ tends to form CaO, the inserted silver tends to form metallic silver 8,25 , and the remainder generates a stoichiometric hydroxyapatite. Thus, after calcination, the vibrational modes from OH -groups may be remarkably enhanced because of the better lattice organization and release of CO 3 2-from the structure.…”

“…Rameshbabu et al 5 and Badrour et al 6 reported that the insertion of Ag + into the HA structure occurred preferentially at the Ca I site, which is the only site in which Ca 2+ ions are Figure 6. X-ray diffraction pattern of the HA-Ag sample after calcination at 1000 °C/2 h. The phases hydroxyapatite (HAp) and calcium oxide (CaO) were identified and quantified by Rietveld refinement.…”

“…Problems related to chemical and thermal stability, denaturation, and storage conditions make common antibiotics considerably more complex in terms of synthesis and handling than silver and its compounds. Consequently, several attempts have been made to associate silver and its compounds with biomaterials and implantable devices [4][5][6] . Implantable devices composed of hydroxyapatite (HA), particularly those used in ostomies, are constantly exposed to bacteria, which can use these devices as body-invasion gateways.…”