Synthesis and characterization of Nd3+-Yb3+ doped hydroxyapatite nanoparticles

The present work focuses on Nd3+-Yb3+ co-doping of bare and Sr-substituted hydroxyapatite nanoparticles and their chemical, structural and optical characterization. An energy transfer between Nd3+ and Yb3+ centers was found, generating an efficient down-shifting process, where Nd3+ absorbs at a low near-infrared wavelength and Yb3+ emits at its characteristic 2F7/2 → 2F5/2 transition. The energy transfer was found to be more efficient in Sr-substituted than in bare hydroxyapatite nanoparticles. The synthesized Nd3+-Yb3+ doped hydroxyapatite nanoparticles can potentially find applications not only as diagnostic near-infrared down-shifting agent but also as nanosystem for near-infrared photoactivated treatment.