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 2x with a modest degree of cosubstitution. This enhancement is obtained without any changes to particle size or global structure.