posted on 2019-05-09, 12:40authored byKhashayar R Bajgiran, Pragathi Darapaneni, Adam T. Melvin, James A. Dorman
Tuning the luminescent
properties of nanophosphors by modifying
the energy level hybridization has been previously achieved by methods
such as heat treatments or applying strong magnetic/electric fields.
However, these methods can permanently distort the crystal geometry
or are limited to the continuous application of strong fields. This
work aims to modify the energy level hybridization of doped (Eu3+/Bi3+) YVO4 nanoparticles (NPs) via
surface functionalization with polarized molecules. Incorporating
Bi3+ into YVO4:Eu3+ core NPs resulted
in a red shift of the excitation edge by ∼30 nm and a decrease
in the Eu3+ emission lifetime. Moving the Bi3+ to the YVO4 shell layer allowed for the modification
of Bi3+/VO43– energy level
hybridization ion pairs without significant quenching of the Eu3+ ions in the core. Polarized molecules (NH2-BZA
and NO2-BZA) were used for selective tuning of the electron
density at the interface, impacting the Bi3+/VO43– energy level hybridization and the luminescent
behavior of the NPs. Higher emission lifetimes and systematic photoluminescent
response, that is, an increase or decrease in the excitation intensity
based on the direction of the dipole moment, were observed for surface-functionalized
core–shell NPs compared to the core NPs. Finally, the surface
of the core–shell NPs was decorated with d-biotin
to elucidate the effect of this biological ligand on the surface electron
density and luminescence behavior of the NPs.