Synthesis of uniform core-shell calcium hydroxide-calcium carbonate biocidal particles via encapsulation into dry ice

This study introduces a novel synthesis method for core-shell calcium hydroxide-calcium carbonate (CSCC) biocidal particles by inducing a phase change in liquid ${\mathrm{CO}}_2$, thereby coating $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ in dry ice. Despite their benign nature, literature sources on the preparation and antimicrobial efficacy of CSCC particles is very scarce. The formation of dry ice, driven by heterogeneous nucleation, efficiently carbonates the surface of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ particles while preventing the particles from aggregation. X-ray diffraction verified the particle structure, while thermogravimetric analysis determined their bulk composition. Much higher carbonation, 55 wt.%, could be achieved relative to literature work. Fourier transform infrared spectroscopy confirmed 94 wt.% surface carbonation, suggesting a core-shell structure. Microtomy tests also revealed a core-shell structure with average sizes of 20–170 nm. CSCC particles displayed appreciable antibacterial activity, achieving complete eradication of both gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa at a concentration of 2.5 mg/mL. Additionally, surface testing revealed CSCC effectiveness in eliminating E. coli within 10 min, highlighting CSCC potential as a potent antimicrobial agent.