Copper-mediated synthesis of eugenol-based silane and its use for silica nanoparticle modification

The modified Stöber method has been used to produce silica nanoparticles with tunable chemical properties for specialized applications. In this study, we proposed a low-risk strategy to introduce eugenol into Stöber silica nanoparticles through a copper-mediated synthesis route. The goal was to produce a eugenol-based organosilane and use it as a chemical modifier agent. This approach seemed to be useful for overcoming the difficulties associated with introducing active compounds into Stöber silica nanoparticles because of their low/absent porosity, while avoiding harmful reactants. The eugenol-based organosilane was included in silica nanoparticle synthesis after a period longer than the established induction period to avoid possible disruptions in the colloidal system, which could drive noncontrolled aggregation events. According to the dynamic light scattering measurements, the particles became larger (diameter: 109.8 nm; 145.5 nm) as more eugenol-based modifier was added (1 %; 20 %), possibly due to its incorporation as hydrolyzed species onto the already-formed silica particles (from the monomer-addition perspective). In addition, thermogravimetric analysis of the modified silica nanoparticles revealed that the thermal decomposition peak, assigned to the organosilane, was more intense in formulations to which higher amounts of eugenol-based modifier were added, indicating the occurrence of the modification. Finally, the inhibitory effects of the eugenol-modified silica nanoparticles on Aspergillus niger colonies confirmed the presence of the eugenol-based organosilane in the silica nanoparticles as well as the maintenance of the antifungal properties of eugenol when supported.