Real-Time and In Situ Monitoring of Pesticide Uptake and Transportation in Plants Using Surface-Enhanced Raman...

Pesticides are essential for maintaining the global crop productivity and food security. Improving their efficiency and minimizing their environmental impact require a detailed understanding of their uptake and translocation in plants. However, existing techniques for tracking pesticides in living plants are largely destructive, ex situ, and incapable of real-time monitoring, which limits progress toward sustainable agriculture. To address this gap, we developed noninvasive, ratiometric surface-enhanced Raman scattering (SERS) nanosensors that enable in situ, real-time mapping of pesticide dynamics in plants. The nanosensors feature gap-enhanced gold nanorods (AuNNRs) with 4-mercaptobenzonitrile (4-MBN) embedded in the nanogap as a stable internal standard for ratiometric SERS quantification. Once delivered into the leaf intercellular spaces, the nanosensors create functional "sensor-equipped" plants for real-time mapping of pesticide distribution. Using this platform, we compared pesticide translocation under different application methods. The results show that root-irrigated tricyclazole moves upward in a concentration- and time-dependent manner, whereas foliar-sprayed pesticides are poorly absorbed due to the barrier posed by the leaf cuticle. Furthermore, commercial tricyclazole formulations are taken up and transported more efficiently than pure reagent-grade compounds. This SERS-based sensing strategy offers a powerful tool for optimizing pesticide delivery and supports the development of precision agriculture practices that are aimed at sustainability.