Thiol‐Functionalized Covalent Organic Frameworks as Thermal History Indictor for Temperature and Time History Monitoring

Abstract

Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k −20°C < k 4°C < k 20°C < k 35°C < k 55°C . The activation energy (E a ) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL −1 . The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs.

Self-Destructive Structural Color Liquids for Time–Temperature Indicating

“…Notably, the triggering agent diffusion-induced structural color destruction can be further revealed by the λ max -time–temperature relationship, which demonstrates that the self-destruction progresses within a shorter time as exposure to a higher temperature based on diffusion kinetics and Brownian motion (Figure A,B). Compared to previous material-based TTIs − , and temperature-responsive structural color materials, ,,− our structural color liquids for visibly indicating time–temperature history demonstrate outstanding overall performances in inherent irreversibility, high sensitivity, tunable self-destructive time (40 min ∼ 5 days), and wide tracking temperature range (−70 ∼ +37 °C) even at low temperatures (Figure C,D), which are critical for indicating the time–temperature history of vaccines yet is impossible for conventional TTIs (Tables S1 and S2).…”

“…Time–temperature indicators (TTIs) based on electronics and various materials have been developed to indicate the accumulated influence of time–temperature history on the quality of products. − Although electronic TTIs can monitor the time–temperature information via wireless antenna sensors, they suffer from inevitable human intervention and generate a noticeable amount of electronic waste . As a new paradigm, material-based TTIs provide convenient visual information on the time–temperature history via chemical reactions or dye diffusion of active additives (chemical reactants, microorganisms, enzymes, or dyes), raising consumers’ awareness and avoiding electronic waste. ,− However, these two material-based TTIs possess their own critical disadvantages, respectively. Chemical-reaction-based TTIs are usually activated at high-temperature ranges and thus are not applicable for vaccines that should be kept under subzero temperatures.…”

Recyclable Time–Temperature Indicator Enabled by Light Storage in Particles

“…[1][2][3] TTIs not only inform whether the products have been exposed to abnormal temperature conditions, but also suggest the quality decay and remaining service life according to the accumulative timetemperature history, thus enabling a much more reliable way of quality monitoring than conventional shelf-life labels only giving a best-before date. [4][5][6] Driven by the ever-growing demands for higher quality and safety, several types of TTIs based on different physical or chemical principles have been developed over the past few decades. [7,8] For example, the diffusion-based TTIs, having a simple structure and low cost, visualize the time-temperature history by the diffusion distance of colored substances (Figure 1a).…”

Capsule-based colorimetric temperature monitoring system for customizable cold chain management

“…There currently exist two representative indicators that are commercially available: time/temperature indicator (TTI) [12] , [13] , [14] and freeze indicator. TTIs have been studied in the past decades due to the advantage of real-time monitoring and consumer-friendliness, which has been developed mainly based on chemical, [15] , [16] , [17] , [18] , [19] , [20] biological, [21] , [22] , [23] enzymatic, [24] , [25] and electrochemical reaction [26] or mechanical deformation. [27] , [28] TTIs are potent means to monitor the time of exposure to a higher temperature, but it is difficult to monitor the exposure to a lower temperature, limiting application toward cold chain monitoring.…”