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.