posted on 2021-11-18, 21:30authored byKumbam
Lingeshwar Reddy, Jikson Pulparayil Mathew, Elizabeth Shiby, Jatish Kumar
Upconversion, the process of generating
a higher-energy photon
from lower-energy photons, has captivated research interest over the
years due to its unique applications in the field of biological imaging,
light harvesting, optical devices, and anti-counterfeiting. High luminescence
efficiency and emission color tuning are key requirements for the
materials to find application in diverse fields. We have developed
a simple and facile methodology for the precise emission color tuning
in lanthanide-based upconversion nanophosphors. The use of varying
concentrations of pyroglutamic acid, an amino acid derivative, as
the capping agent led to a change in the dominant emitting state resulting
in a visual color tuning from red to green. The variation in concentration
of the surface ligand also led to a profound morphological transformation
of the nanostructures from large irregular rods to small uniform particles.
The change in morphology was accompanied by a transformation of the
crystal structure from a hexagonal to a cubic phase. This method stands
out as a one-step approach for the synthesis of hydrophilic nanophosphors
with tailored upconversion luminescence. The presence of amino acid
derivatives on the surface renders biocompatibility to the small and
uniformly sized luminescent particles. Furthermore, due to the advantages
of pyroglutamic acid based surfactants, the synthesized nanophosphors
have the potential to be developed as efficient cell-penetrating multicolor
labeling agents.