Adhesive Conductive Hydrogel Interface for Noninvasive Electrochemical Sensing of Nitric Oxide in Plant Leaves and Fruits

Real-time, noninvasive monitoring of nitric oxide (NO) on intact plant and fruit tissues is limited by NO's short lifetime and the lack of soft, conductive, adhesive interfaces for irregular surfaces. A detachable electrode-tissue bridge is introduced by integrating a catechol-functionalized carbon-nanotube polyacrylamide hydrogel (CNT-DA-PAM) with a commercial screen-printed carbon electrode, enabling on-demand electrochemical NO sensing on leaves and fruit peels. The hydrogel provides reversible adhesion, mechanical robustness, and a percolating CNT network for efficient charge transfer. The modified electrode exhibits characteristic NO oxidation signals, a broad linear range (0.1 μM-10 mM), a detection limit of 0.49 μM, good selectivity, and 14-day storage stability. On living leaves, thermal and mechanical stimuli induce graded, minute-scale NO responses, whereas on fruit peels, NO signals increase over 0-48 h and scale with damage severity. This soft, reversible interface enables minimally perturbative NO sensing across organs and time scales without invasive probes.