Photothermal-responsive release of pesticides from sodium alginate-based composite beads: a sustainable delivery system enhanced by nanodiamonds

This investigation explores the development of a photothermal-responsive pesticide delivery system using composite beads composed of sodium alginate (SA), yeast (YS), polyvinyl alcohol (PVA), citric acid (CA), and detonation nanodiamond (DND). The beads were synthesized via ionotropic gelation and characterized for morphology, thermal stability, and functional group content. SA formed the primary biodegradable matrix, while DND significantly enhanced photothermal conversion efficiency and mechanical strength. YS mitigated drying shrinkage and improved water retention capacity, and CA enhanced structural stability. The release of fulvic acid (FA) as a model pesticide was evaluated under light exposure, demonstrating a controlled release behavior driven by the photothermal-responsive effect of DND. The release kinetics were best described by the Korsmeyer-Peppas model, which directly evidences the transition from relaxation-dominated to diffusion-relaxation-coupled release, driven by the photothermal-responsive effect of DND. This study provides a promising strategy for the controlled release of pesticides in agricultural applications, leveraging the photothermal-responsive properties of DND, the structural matrix provided by SA, the morphological stability imparted by YS, and the protective coating of CA.