A Supraparticle‐Based Five‐Level‐Identification Tag That Switches Information Upon Readout

Abstract

Product identification tags are of great importance in a globalized world with increasingly complex trading routes and networks. Beyond currently used coding strategies, such as QR codes, higher data density, flexible application as well as miniaturization and readout indication are longed for in the next generation of security tags. In this work, micron‐sized supraparticles (SPs) with encoded information (ID) are produced that not only exhibit multiple initially covert identification levels but are also irreversibly marked as “read” upon readout. To achieve this, lanthanide doped CaF2 nanoparticles are assembled in various quantity‐weighted ratios via spray‐drying in presence of a broad‐spectrum stealth fluorophore (StFl), yielding covert spectrally encoded ID‐SPs. Using these as pigments, QR codes, initially dominated by the green fluorescence of the StFl, could be generated. Upon thermal energy input, these particle‐based tags irreversibly switch to an activated state revealing not only multiple luminescent colors but also spectral IDs. This strategy provides the next generation of material‐based security tags with a high data density and security level that switch information upon readout and can be, therefore, used as seal of quality.

Colorful Luminescent Magnetic Supraparticles: Expanding the Applicability, Information Capacity, and Security of Micrometer‐Scaled Identification Taggants by Dual‐Spectral Encoding

“…If identical information is stored in both, luminescent and magnetic codes, it will be obtained with one chosen readout option, either optically or magnetically. Thereby, the applicability is increased as the optical signal could be quickly read out from the surface of marked objects as recently demonstrated, [ 22 ] while the magnetic signal could be resolved from within materials, as it is not interferred by optical means. Thus, the optical codes could be used to identify magnetic objects such as metallic screws (Figure 4b).…”

“…Strategies that utilize designed physicochemical material properties for the spectral encoding of information have come to the forefront as they promise to achieve a plethora of encoding options and a high level of ID security. [ 20–29 ] Lately, optically resolved signals, including UV–vis, [ 30–32 ] infrared, [ 33–35 ] surface‐enhanced Raman scattering (SERS), [ 36–38 ] and fluorescence, [ 22,23,27,28,39–54 ] are considered promising for ID applications, each coming with their own merits and shortcomings. However, as the requested product information and required security steadily increases, novel design strategies for (sub)micrometer‐scaled ID taggants are demanded that expand their capabilities.…”

Hybrid Inorganic–Organic Luminescent Supraparticle Taggants with Switchable Dual‐Level ID

“…Exemplarily, wisely chosen combinations of rare‐earth‐doped CaF 2 :RE 3+ NPs, with narrow clearly distinguishable emission bands, resulted in luminescent ID SPs, as shown in our previous works. [ 36,37 ]…”

Spray‐Drying and Atomic Layer Deposition: Complementary Tools toward Fully Orthogonal Control of Bulk Composition and Surface Identity of Multifunctional Supraparticles

“…Classically, the physical properties and functionality of nanoparticles are determined by their composition, size, and morphology. Multifunctionality in one spot can be obtained by combining different nanoparticles with distinct physical properties in one entity, [ 1–4 ] so‐called supraparticles. [ 5,6 ]…”