Biophysical Insights into ZnO and Carbon Nanodot-Plant Interactions through Impedance Spectroscopy of Crassula ovata

Abstract

Abstract Insertion of nanoparticles (NPs) in plants induce various biophysical changes as well as modulate ion channels and transporters, resulting in improved water and nutrient uptake. High concentration of NPs has toxic effect like excessive production of reactive oxygen species, hormonal imbalances and impaired cellular processes. These biophysical changes also change the complex impedance of plant leaves. Here, we use impedance spectroscopy to probe, for the first time, the electrochemical response of the succulent Crassula ovata leaves following exposure to water-soluble carbon nanodots (CNDs) and zinc oxide (ZnO) nanoparticles. Nanoparticles were introduced through static root immersion in aqueous suspensions at varying concentrations (1, 5, and 10 mg L-1). Quantitative analysis revealed strikingly different dielectric signatures. CND treatment caused grain boundary (gb) resistance to rise from ~256 Ω in the control sample to ~27.6 kΩ at 10 mg L-1 accompanied by a consistent suppression of permittivity, reflecting progressive obstruction of ionic pathways and space-charge accumulation, on NP insertion. ZnO NPs, in contrast, showed a saturation effect: gb resistance peaked at ~14.6 kΩ at 5 mg L-1 but declined to ~7.3 kΩ at 10 mg L-1, where conductivity and dielectric relaxation partially recovered through Zn2+-mediated defect pathways. Equivalent-circuit modelling and Jonscher analysis corroborated these concentration-dependent shifts, revealing nanomaterial-specific modulation of ionic mobility and capacitive behaviour. Together, these findings establish a mechanistic contrast between carbon-based and metal-oxide nanomaterials in plant systems, underscoring nanoparticle chemistry as a key determinant of electrochemical response. This comparative framework advances plant nanobionics by linking material composition to bioelectrical function, with implications for bioelectronics, sensing, and sustainable energy interfaces.

Plant phenotyping relevance

植物葉の電気化学的・生理状態をインピーダンス分光で定量抽出し、等価回路モデル等で検証する測定法が研究の中心であるため、植物フェノタイピング手法として採用。

Code and data availability

The paper reports impedance spectroscopy measurements of Crassula ovata leaves treated with CNDs and ZnO nanoparticles, but no public phenotype dataset, image/sensor data, analysis code, or trained model is deposited. The only availability statement directs readers to contact the corresponding author.

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