Pd/his@SiO₂ colourimetric sensor array for ethylene monitoring under variable temperature and humidity conditions

The monitoring of ethylene continues to pose significant challenges for conventional sensors, primarily due to their instability when subjected to environmental fluctuations. Consequently, in the study, a coordination-stabilized Pd(II)/His@SiO₂ nanocomposite was engineered through the optimization of the histidine (His)-Pd(II) molar ratio (Pd-His-1-0.8). This was achieved by suppressing the hydrolysis/thermal decomposition of Pd(NO₃)₂ to ensure uniform dispersion of Pd(II) via His-SiO₂ hydrogen bonding. A 4 × 4 colourimetric sensor array, based on the Pd-His-1-0.8 and integrated with pH-responsive dyes, was constructed. This array generated unique fingerprints mediated by the Wacker reaction, facilitating the quantification of ethylene. The stability experiment proved that the sensor exhibited negligible signal drift across harsh conditions (25-70 °C, 43-81 % RH) and 21 d storage. Furthermore, some postharvest storage experiments using bananas as a representative fruit demonstrated that results obtained from the colourimetric sensor array were in good agreement with those from commercial detectors. This indicates the considerable potential of the sensors for applications in food and agricultural detection.