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

Abstract Tracking and tracing of objects are of paramount importance for realizing a Circular Economy and can be achieved by incorporating micrometer‐scaled luminescent identification (ID) taggants. While established systems are passive, displaying merely an ID feature, for monitoring a products’ life cycle, conscious taggants with stimuli‐triggered switchable ID signals, e.g., to record a recycling step, are desired. Herein, micrometer‐scaled hybrid inorganic–organic taggants with a temperature‐triggered switchable luminescent ID are reported. They are produced by assembling eight different types of organic and inorganic nanoparticles (NPs) via a two‐step spray‐drying process into supraparticles (SPs) with a core–shell structure. This hierarchical structure and well‐balanced mass‐ratios of the utilized nanosized building blocks are key to controlling the occurring coupling effects within SPs, thus, to obtain the switchable ID functionality. Initially, the temperature‐inert inorganic luminescent ID‐level, located in the core, is concealed by a mutable organic ID‐level, emitted by the shell. Upon specific heat treatment, the ID is switched by irreversible quenching of the organic ID‐level, revealing the inorganic ID‐level. Furthermore, both ID‐levels are read out ratiometrically using the same excitation wavelength for their detection. Based on the SPs’ toolbox‐like manufacturing, the ID signals are adjustable to yield the demanded code variety on both ID‐levels.