Growth-Time-Controlled CuO Nanoflower Electrodes for H2O2 Sensing and Assessment of MgO Nanoparticle-Mediated Drought Stress Mitigation in Oat (Avena sativa) and Rye (Secale cereale)

Drought stress induces the excessive accumulation of hydrogen peroxide (H2O2), leading to oxidative damage and reduced crop productivity. This study presents a dual-function nanotechnology-based strategy for monitoring and mitigating drought-induced oxidative stress in cereal crops. Hierarchical CuO nanostructures were grown directly on copper substrates by hydrothermal oxidation, and the influence of growth time on morphology and hydrogen peroxide sensing performance was systematically evaluated. An optimal growth time of 3 h produced CuO nanoflower architectures with high surface area, yielding superior electrocatalytic activity toward H2O2 detection, with a low detection limit of 1.9 µM and high sensitivity of 11.92 mA·mM−1·cm−2. The optimized sensor enabled reliable quantification of H2O2 in oat (Avena sativa) and rye (Secale cereale) under drought stress, revealing species-dependent oxidative responses. In parallel, magnesium oxide (MgO) nanoparticles effectively alleviated drought-induced oxidative damage, reducing H2O2 accumulation by up to 63% in oat and 61% in rye and significantly improving plant growth and chlorophyll content. The integration of CuO-based sensing with MgO nanoparticle-assisted stress mitigation provides a robust framework for plant stress diagnostics and intervention, highlighting the potential of nanotechnology-enabled strategies for crop stress diagnostics and precision agriculture.