Hybrid Inorganic-Organic Luminescent Supraparticle Taggants with Switchable Dual-Level ID

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.