Emission enhancement via local symmetry distortion in lanthanide-based upconverting nanoparticles

Lanthanide-based upconverters exhibit great potential for photovoltaic and bioimaging applications but have been traditionally plagued by prohibitively low quantum efficiencies. One reason largely responsible is the parity-forbidden nature of the electronic transitions which comprise upconversion. Ionic cosubstitution is used as a means to influence and distort the local symmetry environments of emitting ions without disturbing the global structure of the host lattice. Upconversion emission intensity is shown to increase more than 2× with a modest degree of cosubstitution. This enhancement is obtained without any changes to particle size or global structure.