The quality of perishable products (such as foods, beverages, pharmaceuticals and cosmetics) strongly depends on their temperature history. Temperature abuses during the custody chain may lead to significant quality degradation, which, however, is usually not directly visible to customers. Here we developed a self-evolving color-changing smart tag to track, mimic and indicate the deteriorative processes in common perishables. The smart tag exploits the chronochromic behaviors during the Ag overgrowth on Au nanorods in aqueous solution. Under given conditions, the smart tag spontaneously changes its appearance from an initial red to a final green color, exhibiting sharp visual contrast. At room temperature, the temporal duration for this red-to-green self-evolution can be adjusted from minutes to months, and the apparent activation energy can be widely tuned from 50 to 190 kJ/mol, covering the kinetic features of almost all ambient-temperature deteriorative processes found in foods. Using E. coligrowth in milk as a model, we successfully synchronized, at multiple temperatures, the chemical evolution process in the smart tag with the microbial growth processes, implying that the �bio-chemo� correlation is temperature-independent. The smart tag is also cost-effective and eco-friendly, and well meets the ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Robust and rapid, Equipment-free, and Deliverable to end-users) proposed by WHO. We believe that this smart tag holds the promise to be further developed into a standardized protocol for the current food/beverage/pharmaceutical industries.

Self-evolving color-changing smart tags capable of quality indication for perishable products

247th National Meeting (2014)

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