Photoluminescence properties of nanoporous nanocrystalline carbonate-substituted hydroxyapatite

Luminescence characteristics of an analogue of the mineral component of dental enamel–nanocrystalline $B$-type carbonate-substituted calcium hydroxyapatite (CHAP)–with defects (nanopores $\sim$ 2–5 nm in size) on the surface of nanocrystals are studied. It is shown that laser-induced luminescence of CHAP samples synthesized by us occurs in the region of $\sim$ 515 nm ($\sim$ 2.4 eV) and is related to the existence of CO$_3$ groups substituting PO$_4$ groups in the CHAP lattice. It is determined that the luminescence intensity of the CHAP samples depends on the amount of structurally bound CO$_3$ groups and decreases with decreasing concentration of these intracenter defects in the apatite structure. The results obtained in this work are of potential importance for developing the fundamentals of precision and early detection of caries in human hard dental tissue.