Recently, there has been a growing concern regarding the increased contamination of water by bacteria. As a result, more attention has been paid to the potential benefits of utilizing nano adsorbents and photocatalysis for water purification. In order to better manipulate the physicochemical properties, it is crucial to gain a comprehensive understanding of the molecular behaviour between nanoparticles and pathogens. This article investigates the various interactions that can occur between Fe3O4-SiO2-TiO2 (FST) nanoparticles and bacterial cells. Moreover, it explores the impact of the SiO2 mid-layer and the governing interaction in the adhesion and degradation processes. In this regard, FST nanoparticles were prepared, and their adhesion behaviour to E. coli bacterial cells was evaluated using extended DLVO (Derjaguin- Landau-Verwey-Overbeek) theory. The following results revealed that the presence of silica transformed FST into a more hydrophobic material with a positively charged surface, thereby enhancing its affinity for bacterial adsorption. Additionally, SiO2 prevented electron/hole recombination. Amongst the various interactions, Lewis acid-base interactions had the greatest influence on the total energy and lacking energy barriers led to irreversible adhesion. Moreover, the presence of an increased number of ·OH groups on the surface resulted in enhanced bactericidal properties of FST, leading to severe damage of E. coli cells through the formation of a greater number of hydrogen bonds on the bacterial surface, which is the basis of the proposed mechanism for destruction of the bacterial structure.

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