| abstract |
The present technology relates generally to a stable oil-in-water emulsion containing upconverting nanoparticles. In particular, the present technology relates to an ink formulation comprising a stable oil-in-water emulsion of upconverting nanoparticles useful for security printing. Preferably the upconverting nanoparticles comprise a β-Na(RE)F4 nanoparticle, wherein RE is a lanthanide, yttrium, or a combination or mixture thereof. |