Intercalation of organic compounds in layered copper-hydroxide for electrochemical sensor phytohormone in plants.

The urgent demand for precision agriculture has intensified the need for reliable sensors capable of monitoring phytohormones. To address this, we constructed a novel organic-inorganic intercalation hybrid, Cu-SDA, by embedding aromatic stilbene-4, 4'-dicarboxylate (SDA) linkers into layered copper hydroxide. This design moves beyond conventional carbon-based electrodes, leveraging the synergistic effect of π-π stacking for structural robustness and exposed copper centers for specific electrocatalytic activity. Comprehensive physicochemical characterization, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), confirmed the successful intercalation and structural integrity of the framework. Furthermore, density functional theory (DFT) calculations revealed enhanced adsorption toward salicylic acid (SA) (-1.01 eV) and indole-3-acetic acid (IAA) (-1.14 eV), accompanied by reduced bonding distances. Consequently, the Cu-SDA sensor exhibits a high electroactive surface area (0.229 cm2) and superior charge transfer efficiency compared to pristine Cu(OH)2. The platform achieves low detection limits (2.43 μM for SA, 1.15 μM for IAA) with excellent selectivity against common interferents. These detection limits are suitable for monitoring stress-induced accumulation of SA and IAA, rather than their basal physiological concentrations. Finally, the practical applicability of the proposed sensing platform was demonstrated through an on-leaf standard addition assay for SA and IAA in living peanut seedling leaves, highlighting its potential for monitoring stress-induced phytohormone variations in precision agriculture.