Rising Like a Phoenix from the Ashes: Fire-Proof Magnetically Retrievable Supraparticles with an Optical Fingerprint for Postmortem Identification of Products

摘要

Counterfeit electronic products not only cause financial losses but also comewith safety risks. The worst-case failure scenario certainly is a fire event.Since manufacturers are liable for damages and suffer image loss, fire-proofpostmortem taggants are needed, enabling differentiation between originalsand counterfeits even after a fire incident. This work presents such taggants:optomagnetic supraparticles (SPs), i.e., complex microscale particlescomposed of luminescent and magnetic nanoparticles (NPs) are generated.Their hybrid nature is pivotal, as magnetic separation can effectively removethe tags from light-absorbing fire debris, and a fire-proof identification (ID)fingerprint is based on ratiometric luminescence signals. To achieve thermallystable magnets, iron oxide (IO) NPs are wet-chemically coated witha SiO_2-3-aminopropyltriethoxysilane (APTES) shell. Subsequently, thesemagnetic NPs are assembled with luminescent nanophosphors (lanthanidedopedcalcium phosphate NPs with a SiO_2-core) and SiO_2-APTES spacer NPsby spray-drying to form hybrid SPs. The careful choice of type and ratios ofthe NPs and process parameters make it possible to achieve and preciselytune the desired functionality of the resulting fire-proof taggants. A proof-ofconceptis demonstrated, in which the taggants are incorporated as additivesinto coatings and subjected to real fire simulations.