Synthesis and characterization of nanothermite systems with biocidal additives

The efficiency of Lactobacillus casei inactivation using nanothermites based on nAl+CuO/Fe₂O₃/MoO₃ in combination with biocidal additives such as crystalline iodine (I₂), iodoform (CHI₃) and zinc oxide (ZnO) was investigated. It was shown that the reaction products (>98%) settled within 660 s on the walls and bottom of the chamber, leaving only 1-2% of 3-4 μm aerosol particles in suspension. Among the oxidizing agents, CuO showed the most stable combustion, producing a dense aerosol cloud and achieving a bactericidal activity index of 33% at a distance of 125 mm from the explosion epicenter, compared to ~9% for Fe₂O₃ and ~3% for MoO₃. When 20 wt% I₂ was introduced, the formation of reaction products resulted in high inactivation efficiency, with a bactericidal activity index of 72% at a distance of 125 mm from the blast epicenter. However, increasing the I₂ content to 40 wt% decreased the bactericidal activity index to 50%. Similarly, 20 wt% CHI₃ enhanced inactivation through the formation of protein-complex iodine species, reaching a maximum value of 73% at 125 mm from the blast epicenter; higher concentration of CHI₃ reduced the efficiency by lowering the reaction temperature and creating biocidal reaction products. Changing the concentration of ZnO had no appreciable effect on inactivation, indicating a threshold effect in the generation of zinc biocidal compounds. For all additives, the inactivation efficiency decreased at long distances (e.g., from 125 mm to 445 mm) due to rapid dispersion of the reaction product cloud. The experimental results emphasize the importance of the balance between biocidal additive concentration and combustion efficiency. Optimal formulations incorporating 20 wt.% I₂, CHI₃ or ZnO into nAl+CuO nanothermites maintain reliable energy performance and generate biocidal reaction products that can significantly reduce the viability of Lactobacillus casei.