Synthesis and Characterization of Porous Hydrophobic and Hydrophilic Silica Microcapsules for Applications in Agriculture

Silica (SiO₂) particles are widely used in various industries due to their chemical inertness, thermal stability, and wear resistance. The present study describes the preparation and potential use of porous hydrophobic and hydrophilic SiO₂ microcapsules (MCs) of a narrow size distribution. First, various layers of SiO₂ micro/nano-particles (M/NPs) were grafted onto monodispersed polystyrene (PS) microspheres of a narrow size distribution. Hydrophobic and hydrophilic sintered SiO₂ MCs were then prepared by removing the core PS from the PS/SiO₂ core-shell microspheres by burning off under normal atmospheric conditions or organic solvent dissolution, respectively. We examined how the size and quantity of the SiO₂ M/NPs influence the MC's properties. Additionally, we utilized two forms of hollow SiO₂ MC for different applications; one form was incorporated into polymer films, and the other was free-floating. The hydrophobic microcapsules filled with 6% hydrogen peroxide were effective in killing the tomato brown rugose fruit virus (ToBRFV). The hydrophilic microcapsules filled with thymol and thin coated onto polypropylene films were successfully used to prevent mold formation for hay protection.