Luminescent Supraparticles Based on CaF₂–Nanoparticle Building Blocks as Code Objects with Unique IDs

In the course of globalization, tracking of material supply chains and product protection against counterfeiting is a topic of increasing relevance. The labeling of raw materials or product components with encoded microstructures may therefore ensure their reliable and tamper-proof identification. In this work, luminescent lanthanide doped calcium fluoride nanoparticles with characteristic optical properties are assembled to micrometer-sized supraparticles via spray-drying. By wise selection of these nanoscale building blocks, it is possible to create spectrally encoded microparticles. Their code relies on the relative emission intensities of the different luminescent nanoparticles and their concentration ratios within the supraparticle. Due to this strategy, we offer a nanoscale modular approach for an easily adjustable and simple creation of ratiometric luminescence-encoded microparticles for the tamper-proof marking of objects.