Aluminium-based metal-organic frameworks for the colorimetric ethephon detection in fruit by paper microsensor

Ethephon (ETH) is a plant growth regulator extensively utilized in agriculture, but its overuse is associated with several health issues. However, detecting ETH sensitively and easily in the field is challenging due to the complexity and time-consuming operation of current approaches. In this study, we synthesized aluminum-based metal-organic frameworks (CAU-1) as fluorescent probes for the detection of ETH in fruit. ETH exposure enhanced and shifted the light green fluorescence of CAU-1 to blue through high absorption of phosphate by electrostatic attraction. We observed a linear correlation between fluorescent intensity and ETH concentration ranging from 2 mg/L to 400 mg/L, with the lowest detection limit at 1 mg/L. This fluorescent analysis exhibited good selectivity towards ETH. To facilitate easy identification of samples in the field, we designed a fluorescent paper-based platform with a logic gate operation, allowing visual distinction of samples containing ETH. We applied this platform to monitor ETH in various fruits, including apples, pears, and tomatoes, through fluorescent spectrum, and visual detection. The platform offered simplicity, speed, ease of use and sensitivity, providing a promising future for ETH detection in agriculture.