A flexible and wearable chemiresistive ethylene gas sensor modified with PdNPs-SWCNTs@Cu-MOF-74 nanocomposite: a targeted strategy for the dynamic monitoring of fruit freshness

A chemiresistive ethylene gas sensor was fabricated for fruit wearable based on SWCNTs/PdNPs/Cu-MOF-74 (SPM) nanocomposite which was attached to a flexible PET substrate (AIEFP) for dynamic monitoring of the freshness of Kiwi at room temperature (25 °C). The electrodes are printed on PET substrate by laser direct writing method, which makes the SPM/AIEFP sensor wearable to be attached to the target and achieve accurate in-situ online detection. The sensing mechanism depends on the widely recognized theory of adsorbed oxygen, in which SWCNTs provide a path for charge transfer between materials, PdNPs improve the response by catalyzing the cracking of ethylene double bond and the formation of adsorbed oxygen, and the selective bonding of Cu-MOF-74 and ethylene provides selectivity. The selectivity of the proposed SPM/AIEFP sensor has been proved. Besides, the key parameters of the sensor fabrication were optimized, and the sensing performance was investigated. Finally, the SPM/AIEFP sensor was successfully utilized to determine the ripeness and corruption of kiwifruit in real-time, indicating that the SPM/AIEFP sensor is a good candidate tool for detecting fruit freshness during transportation and storage.