Composites of Eu3+-doped calcium apatite nanoparticles and silica particles: Comparative study of two preparation methods

Ayumu Isobe, Satoru Takeshita, Tetsuhiko Isobe

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We synthesized composites of Eu3+-doped calcium apatite (CaAp:Eu3+) nanoparticles and silica particles via two methods: (i) in situ synthesis of CaAp:Eu3+ in the presence of silica particles and (ii) electrostatic adsorption of CaAp:Eu3+ nanoparticles on silica particle surfaces. In both methods, submicrometer spherical silica particles were covered with CaAp:Eu3+ nanoparticles without forming any impurity phases, as confirmed by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. In method i, part of the silica surface acted as a nucleation site for apatite crystals and silica particles were inhomogeneously covered with CaAp:Eu3+ nanoparticles. In method ii, positively charged CaAp:Eu3+ nanoparticles were homogeneously adsorbed on the negatively charged silica surface through electrostatic interactions. The bonds between the silica surface and CaAp:Eu3+ nanoparticles are strong enough not to break under ultrasonic irradiation, irrespective of the synthetic method used. The composite particles showed red photoluminescence corresponding to 4f → 4f transitions of Eu3+ under near-UV irradiation. Although the absorption coefficient of the forbidden 4f → 4f transitions of Eu3+ was small, the red emission was detectable with a commercial fluorescence microscope because the CaAp:Eu3+ nanoparticles accumulated on the silica particle surfaces.

Original languageEnglish
Pages (from-to)1811-1819
Number of pages9
Issue number5
Publication statusPublished - 2015 Feb 10

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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