Optical Signals for Quantitative and Qualitative Monitoring of Temperature-Sensitive Products

Monitoring the real-time quality and validity of thermo-sensitive foods during storage and transportation can be achieved with time-temperature indicators (TTIs). However, the available TTIs still need to be improved in terms of accuracy, recoverability, environmental tolerance, and quantitative monitoring. Here, a novel TTI based on the optical signals originating from the as-explored Sr3Y2Ge3O12: Mn2+, Er3+ (SYGO: Mn2+, Er3+) phosphor is developed. Thanks to the fact that the release of the captured carriers is tightly related to the storage time and ambient temperature, distinct optical signals of the as-obtained TTI under multi-stimulus (980 nm laser irradiation, thermal stimulation, and mechanical force) can be distinguished to judge the validity of temperature-sensitive products. This work reveals the promising potential of SYGO: Mn2+, Er3+ phosphors with cryogenic optical storage properties as advanced TTIs, especially for packaged products in cold chain logistics. A time-temperature indicator (TTI) based on the optical storage features of the Mn2+/Er3+ doped SYGO phosphors is developed, which enables obvious long persistent luminescence, photo-stimulated luminescence, mechanical stimulation, and high-temperature stimulated luminescence signals below room temperature (80-253 K) under multiple stimuli. The as-obtained TTI labels present an excellent ability for quantitative and qualitative monitoring of the storage temperature and time of the temperature-sensitive products.image