The nanostructured microparticles (supraparticles) can be structured to provide a specific spectral response to external magnetic excitation that contains an identifiable coding similar to a fingerprint. The iron oxide nanoparticles, wet-chemically produced for this purpose, are ecologically and economically viable building blocks for these supraparticles.
They can be added as a fine powder to plastics or adhesives and thus identify batch, material or product. This is not externally visible and cannot be destroyed.