We
report on the potential of BaLiF3 as a host matrix
for the upconversion sensitizer (Yb3+)-activator (Er3+) pairs as prepared by ball milling. Specifically, the infrared
(980 nm)-excited upconversion luminescence (UCL) of BaLiF3:Yb3+, Er3+ samples before and after annealing
in air is reported, and it is demonstrated that the upconversion efficiency
is enhanced by ∼2 orders of magnitude via a postannealing treatment.
The UCL of BaLiF3:Yb3+, Er3+ compared
favorably with that of the efficient NaYF4:Yb3+, Er3+ UCL nanophosphors. In addition, the X-ray storage
capability of BaLiF3:Yb3+, Er3+ was
explored. It was observed that the photoluminescence intensities of
Yb3+ (∼980 nm) and Er3+ (∼650
nm) ions decrease gradually with cumulative X-ray doses due to X-ray-induced
reduction of Yb3+ to Yb2+ and Er3+ to Er2+, and as a result, the upconversion luminescence
decreases. The Yb2+ photoluminescence spectrum upon X-irradiation
was observed at 480 nm in accord with earlier reports for the BaLiF3 host. In a unique development, 2D X-ray imaging based on
the UCL signal is reported for the first time. These results demonstrate
the X-ray recording capability of mechanochemically synthesized BaLiF3:Yb3+, Er3+ nanocrystals and point to
possible applications in combining X-ray dosimetry and bioimaging.
In
recent decades, storage phosphors have found widespread applications
in the fields of dosimetry and computed radiography due to their impressive
properties, including large dynamic ranges and passive storage modalities.
Despite this success, further development of highly efficient X-ray-
and UV-sensitive
luminescent materials is still desirable, in particular for applications
in dosimetry. In this article, we report X-ray and UV storage properties
of nanocrystalline barium lithium fluoride (BaLiF3) doped
with Sm3+. Nanocrystalline BaLiF3:Sm3+ was prepared mechanochemically by ball milling and the resulting
product was characterized by powder X-ray diffraction and transmission
electron microscopy. The response of the phosphor to X-ray and UV
radiation was investigated by measuring room temperature photoluminescence
spectra before and after irradiation for a wide range of doses. The
lifetime of the Sm2+ emission at 694 nm was determined
for both the X-ray and UV irradiated powder samples. The results indicate
a potential for Sm3+-activated nanocrystalline BaLiF3 to be used in dosimetry applications.
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