Prolonged Antimicrobial Effects of Eucalyptus Oil via C ₈ ‐Functionalized Silica Monolith

This study presents the synthesis and characterization of a mesoporous silica‐based monolith functionalized with octyl (C 8 ) groups, developed as an absorbent for the controlled release of Eucalyptus oil (Eu‐oil). The C 8 ‐silica monolith was prepared via a two‐step acid/base‐catalyzed sol‐gel process and characterized using various analytical techniques. Chemical profiling of the Eu‐oil and Eu‐oil‐loaded monolith was conducted using gas chromatography‐mass spectrometry (GC‐MS). Evaporation tests revealed that Eu‐oil exhibited rapid volatilization within 24 h, whereas Eu‐oil‐loaded on the C 8 ‐monolith had a markedly slower release. The GC‐MS analysis confirmed that the monolith effectively retained volatile constituents, particularly eucalyptol, β ‐myrcene, and γ ‐terpinene, thereby extending the release of bioactive compounds. Antimicrobial assays showed that Eu‐oil delivered via the monolith maintained bacteriostatic activity against Escherichia coli and Staphylococcus aureus for up to 7 days, outperforming the rapid activity loss observed with Eu‐oil applied on filter discs. Similarly, antifungal tests against Aspergillus sp. isolated from garlic demonstrated prolonged suppression of fungal growth. Kinetic modeling further confirmed that the Eu‐oil release followed a concentration‐dependent, diffusion‐assisted mechanism, which was best described by the first‐order and Weibull models. These findings underscored the potential of mesoporous C 8 ‐silica monoliths as efficient carriers for volatile essential oils, offering a promising strategy for sustained antimicrobial delivery in healthcare and food preservation applications.