Revisiting silicate substituted hydroxyapatite by solid-state NMR.
Silicon-substituted hydroxyapatite (Si-HAp) has shown promising properties such as high-bone remodeling around implants. So far, the techniques used for the structural characterization of the Si-HAp have given indirect evidence of the presence of silicon inside the structure (by X-ray and neutron diffraction). In this paper, we focus on Si-HAp derivatives obtained by a precipitation method (widely described in the literature). We demonstrate here by solid-state NMR spectroscopy that only a fraction of the silicon atoms are incorporated into the HAp lattice in the form of Q(0) (SiO(4) (4-)) species, for 4.6 wt% Si-HAp. A large amount of silicate units are located outside the HAp structure and correspond to silica-gel units. All results were established through (29)Si MAS, (1)H -->(29)Si CP MAS and T(1)rho((1)H) edited (1)H -->(29)Si CP MAS experiments. This last pulse scheme acted as a powerful editing sequence, leading to unambiguous spectroscopic conclusions, concerning the location of the SiO(4) (4-) moieties.
Gasquères
G
G
Université Pierre et Marie Curie-Paris6, UMR 7574 CNRS, Laboratoire de Chimie de la Matière Condensée de Paris, Paris, F-75005, France.
Bonhomme
C
C
Maquet
J
J
Babonneau
F
F
Hayakawa
S
S
Kanaya
T
T
Osaka
A
A
D017886:Durapatite / Q000737:chemistry*; D007554:Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008958:Models, Molecular; D033362:Powder Diffraction; D011522:Protons; D012015:Reference Standards; D017640:Silicates / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods
D007554:Isotopes; D011522:Protons; D017640:Silicates; D017886:Durapatite; D012825:Silicon