期刊
CRYSTAL GROWTH & DESIGN
卷 18, 期 2, 页码 686-694出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.cgd.7b01050
关键词
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资金
- University of Verona
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- Fonds de recherche du Quebec Nature et technologies (FRQNT)
- Ca' Foscari University of Venice ADIR
Eu3+ doped CaF2 and SrF2 nanoparticles were synthesized through a facile hydrothermal technique, using citrate ions as capping agents and Na+ or K+ as charge compensator ions. A proper tuning of the reaction time can modulate the nanoparticle size, from few to several tens of nanometers. Analysis of EXAFS spectra indicate that the Eu3+ ions enter into the fluorite CaF2 and SrF2 structure as substitutional defects on the metal site. Laser site selective spectroscopy demonstrates that the Eu3+ ions are mainly accommodated in two sites with different symmetries. The relative site distribution for lanthanide ions depends on the nanoparticle size, and higher symmetry Eu3+ sites are prevalent for bigger nanoparticles. Eu3+ ions in high symmetry sites present lifetimes of the D-5(0) level around 27 ms, among the longest lifetimes found in the literature for Eu3+ activated materials. As a proof of concept of possible use of the Eu3+ activated alkaline-earth fluoride nanoparticles in nanomedicine, the red luminescence generated by two-photon absorption using pulsed laser excitation at 790 nm (in the first biological window) has been detected. The long Eu3+ lifetimes suggest that the present nanomaterials can be interesting as luminescent probes in time-resolved fluorescence techniques in biomedical imaging (e.g., FLIM) where fast autofluorescence is a drawback to avoid.
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