Cation exchange: A facile method to make NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles with a thin, tunable, and uniform shell

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DOIResolve DOI: http://doi.org/10.1021/cm2036844
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TypeArticle
Journal titleChemistry of Materials
ISSN0897-4756
1520-5002
Volume24
Issue7
Pages12971305; # of pages: 9
Subjectcation exchange; sodium lanthanide fluoride nanoparticles; core−shell nanoparticles; magnetic resonance imaging; up-conversion optical imaging
AbstractCation exchange was performed on up-conversion NaYF4:Yb,Tm nanoparticles, resulting in NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles as indicated by electron energy-loss spectroscopy 2D mapping. Results show that core–shell nanoparticles with a thin, tunable, and uniform shell of subnanometer thickness can be made via this cation exchange process. The resulting NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles have an enhanced up-conversion intensity relative to the initial core nanoparticles. As potential magnetic resonance imaging (MRI) contrast agents, they were tested for their proton relaxivities. The r1 relaxivity per Gd³⁺ ion of the nanoparticles with a thin NaGdF4 shell (ca. 0.6 nm thick) measured at 9.4 T was found to be 2.33 mM–1·s–1. This r1 relaxivity is among the highest in all the reported NaYF4–NaGdF4 core–shell nanoparticles. The r1 relaxivity per nanoparticle is 1.56 × 104 mM–1·s–1, which is over 4000 times higher than commercial Gd³⁺-complexes. The very high proton relaxivity per nanoparticle is critical for targeted MRI as such nanoparticles provide strong contrast even in low concentrations. The presented cation exchange method is a promising way to manufacture core–shell nanoparticles with up-conversion NaYF4:Yb,Tm core and paramagnetic NaGdF4 shell for bimodal imaging, i.e. MR and optical imaging.
Publication date
LanguageEnglish
AffiliationNRC Institute for Biodiagnostics; National Research Council Canada
Peer reviewedYes
NPARC number21268944
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Record identifier5c0ff6d2-44f4-4413-a129-d412b43ed7a6
Record created2013-11-27
Record modified2016-05-09
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