Plasma-assisted modification of micronutrient-embedded PVA/PVP blend films for sustained nutrient delivery in agricultural applications

Abstract

Sustained and controlled delivery of micronutrients remains a critical challenge in agricultural systems, largely due to the high solubility and uncontrolled release of conventional polymer-based nutrient carriers. In this work, we report for the first time the use of non-thermal Dielectric Barrier Discharge (DBD) plasma to modify PVA/PVP-based films embedded with CuSO₄ and FeSO₄, aiming to enhance their performance for controlled nutrient release applications. The composite films synthesized by the solution casting method were subjected to argon plasma treatment at 25 kV for various exposure durations. Physicochemical characterization and mechanical properties confirmed the notable surface changes after plasma exposure such as increased roughness, formation of oxygen functional groups, plasma-induced crosslinking and increased tensile strength. These modifications contributed to the formation of a denser film network, effectively slowing ion diffusion. In vitro nutrient release studies showed a reduction in the release rate of Cu²⁺ ions, decreasing from 85.4 ± 1.8% to 49.4 ± 1.4% after plasma treatment. Kinetic modeling indicated that the release behavior followed the Higuchi model, suggesting a diffusion-controlled mechanism influenced by the altered film structure. This work presents a novel and eco-friendly approach for engineering polymer–metal salt films via plasma technology, demonstrating strong potential for sustained micronutrient delivery in agricultural applications.