Facile eco-friendly sol-gel synthesis of highly monodispersed Zn@silica nanospheres with dual antibacterial mechanism against multidrug-resistant bacteria

Multidrug-resistant (MDR) bacterial infections pose critical challenges to current antimicrobial therapies, necessitating the development of scalable and effective antimicrobial materials. This study presents a facile, eco-friendly sol-gel synthesis of monodispersed Zn@silica hybrid nanospheres operating through a dual antibacterial mechanism against clinically relevant MDR strains. The additive-free synthesis under ambient conditions achieved exceptional process control, yielding 1Zn@silica nanospheres with 305.06 nm diameter uniformity and 100% sphericity. Comprehensive characterization via SEM, TEM, EDS mapping, and XPS depth profiling revealed controlled zinc incorporation through iono-covalent Si-O-Zn bonding, with concentration-dependent surface enrichment (surface Zn content: 20.4 atom% for 4Zn@silica vs. 3.6 atom% for 1Zn@silica). The dual-mechanism antimicrobial action operates through: (1) sustained zinc ion release and (2) photocatalytic hydroxyl radical generation. Quantitative bioassays against four MDR strains ( E. coli , S. aureus , E. faecium , K. pneumoniae ) demonstrated significant bacterial inhibition ( p < 0.001) with concentration-dependent efficacy, achieving up to 99.9% reduction in viable cell counts. Surface area enhancement from 11.2 m 2 /g (pure silica) to 44.2 m 2 /g (4Zn@silica) optimized active site accessibility for enhanced antimicrobial performance. This scalable, environmentally sustainable approach provides a robust platform for developing next-generation antimicrobial nanomaterials with potential applications in healthcare, water treatment, and infection control systems.