Cesium–lead–halide perovskite triggered visual platform: a disposable paper-based nano-temperature sensor for cold chain transport.

Transportation and storage of primary agricultural products, processed foods, and special items should be carried out in accordance with the requirements of cold chain transport to ensure that they are maintained within the appropriate low temperature range. Time-temperature indicators (TTIs) have proven to be an effective tool for monitoring food temperature history during the cold chain transport. Herein, a disposable paper nano-temperature sensor for color-changing temperature indicators was developed based on the strong linear photoluminescence dependence of cesium–lead–bromide perovskite nanocrystals (CsPbBr₃ NCs), where the anion-exchange reaction between Br⁻ and I⁻ can be influenced by the melting temperature from different compositions of n-hexane/1-octadecene (ODE) mixtures. The actual temperature of a mixed solvent exceeds the specified threshold temperature (T_t), causing the mixed solvent containing iodide ions to melt, flow and impregnate the film, and thus resulting in an irreversible change in the fluorescence (FL) emission wavelength of the CsPbBr₃ NCs. The FL emission wavelength is red-shifted from the original 517 nm to 650 nm, showing a large Stokes shift of more than 130 nm, which can be directly observed under a UV lamp from green to yellow, orange, and red. Accordingly, this disposable paper nano-temperature sensor with multiple color change patterns and multiple threshold temperatures of −68 °C to +4 °C is effective, portable, and stable, which provides new insights into efficient temperature monitoring for cold chain transport. [ABSTRACT FROM AUTHOR]