Krisjanis Smits , Larisa Grigorjeva , Donats Millers , Karlis Kundzins , Reinis Ignatans , Janis Grabis , Claude Monty
Zirconia nanocrystals have attracted considerable interest as biolabels, which can be used as probes for
medical imaging and biosensor applications. However, zirconia particle agglomeration forms amajor limitation
to its use for biolabeling. In this backdrop, for the first time, well-separated zirconia nanocrystals
were obtained in a Heliotron reactor (PROMES CNRS, France) via the solar physical vapor deposition
(SPVD) method. As the raw material target for solar evaporation, zirconia nanopowders obtained via
the sol–gel process were used. The luminescence and upconversion luminescence properties of the Sol
Gel nanopowders were compared with those of the SPVD nanocrystals. Erbium was chosen as the luminescence
center with ytterbium as the sensitizer, and along with these two dopants, niobium was also
used. Niobium acts as a charge compensator to compensate for depletion in the charge due to the
introduction of trivalent erbium and ytterbium at tetravalent zirconium sites. Consequently, the
oxygen-vacancy concentration is reduced, and this results in a significant increase in the upconversion
luminescence.
The SPVD-prepared samples showed less agglomeration and a fine crystal structure as well as high
luminescence, and thus, such samples can be of great interest for biolabeling applications.
Optical Materials 37 (2014) 251–256
http://dx.doi.org/10.1016/j.optmat.2014.06.003
