cm9b01155_si_002.mpg (333.62 kB)
Morphology Control of Lanthanide Doped NaGdF4 Nanocrystals via One-Step Thermolysis
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posted on 2019-06-03, 00:00 authored by Miao Wang, Yu Zhang, Qiaofeng Yao, Michael Ng, Ming Lin, Xu Li, Kishore Kumar Bhakoo, Alex Y. Chang, Federico Rosei, Fiorenzo Vetroneβ-phase
NaGdF4 nanocrystals doped with Er3+ and Yb3+ possessing diverse morphologies were
synthesized from the thermolysis of trifluoroacetate precursors in
1-octadecene and oleic acid by modifying the hot-injection strategy.
Modulation of the injection temperature during the hot-injection step
was an effective approach to control the size and shape of the prepared
nanocrystals and allowed for the direct synthesis of nanorods. Here,
we report for the first time the fabrication of monodispersed uniform
nanorods through a one-step thermolysis approach. The different supersaturation
caused by the different temperatures could directly manipulate the
nucleation and growth of α-phase nanoparticles before the α
→ β phase transition, subsequently influences the Ostwald
ripening mode during the α → β phase transition,
and consequently affects their morphology (i.e., nanorods, nanospheres,
nanoprisms, nanoplates, and nanodisks), uniformity, and monodispersity.
The upconversion luminescence intensity decreased with increase of
the surface to volume ratio of the upconverting nanocrystals, and
a higher ratio of green to red emission was observed when the aspect
ratio was close to 1. The negative contrast enhancement on T2-weighted magnetic resonance images caused
by the upconverting nanocrystals was increased with increasing size
with the exception of the nanorods, which performed the best as T2 contrast agents despite being smaller compared
to the nanoplates. Our work provided strong evidence for the use of
morphology controlled synthesis in NaGdF4 based upconverting
nanocrystals and their implementation in multifunctional nanoplatforms
for future biomedical applications.