ZnO nanoparticle induced electrical modulation and charge storage in Aloe vera leaves

This study investigates the influence of zinc oxide (ZnO) nanoparticles on the electrical transport and charge storage behavior of living Aloe vera leaves. Defect-rich ZnO nanoparticles (∼25.5 nm, wurtzite structure) were introduced via root-mediated exposure at concentrations of 1, 5, and 10 mg L^-1. Electrochemical impedance spectroscopy (20 Hz to 5 MHz) revealed a concentration-dependent modulation of the electrical response of leaf tissues. The phase angle increased from ∼65° (control) to ∼83° (10 mg L^-1), indicating enhanced capacitive behavior and interfacial polarization. Equivalent circuit analysis showed a significant rise in grain boundary resistance (∼100 Ω to >10 k Ω), suggesting restricted ionic transport across intercellular interfaces. Concurrently, grain and grain boundary capacitances decreased by nearly two orders of magnitude, indicating reduced polarization and charge storage. Dielectric analysis showed suppressed permittivity and energy dissipation with increasing ZnO concentration. AC conductivity results revealed a transition from long-range ionic conduction (s ≈ 0.0066) to localized hopping transport (s ≈ 0.98). Electric modulus analysis confirmed non-Debye relaxation behavior in treated samples. These findings demonstrate that ZnO uptake significantly alters the internal electrical properties of Aloe vera in a concentration-dependent manner, highlighting the potential of plant-nanomaterial systems for bioelectrical and sensing applications.