Self-cleaning formulations of mixed metal oxide-silver micro-nano structures with spiky coronae as antimicrobial coatings for fabrics and surfaces

Abstract

Antimicrobial coatings are essential for controlling the spread of pathogens and restricting their interface with hosts. These may be applied to masks as additional security to wearers over pore filtration or applied to surfaces that are often hand-touched, as the nanocoating can deactivate viruses irreversibly. We synthesized an antimicrobial nanoformulation containing mixed metal oxides (MMOs) of TiO₂, ZnO, SiO₂, and CuO with silver nanoparticles (MMO–Ag) capped with a cationic surfactant via a hydrothermal route. The developed nanoformulation possesses a high specific surface area of 73.5 m² g⁻¹. The nanoformulation exhibits excellent antimicrobial properties against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, and bacteriophage viruses, superior to that of the spherical morphology. The minimum inhibition concentration (MIC) of the nanoformulation is 107 μg mL⁻¹ against S. aureus. The enhanced antimicrobial properties of the spiky nanoformulation are attributed to its sharp nanometric tips that can physically puncture the cell membrane of pathogens via a mechano-bactericidal effect. The net attraction between the spiky MMO particle and bacteria is 10² times when compared to smooth MMO particles, as estimated by the modified DLVO theory. The developed nanoformulation-coated fabrics exhibit self-cleaning properties upon exposure to UV light by facilitating complete degradation of the bacteria owing to the photocatalytic component present in the nanoformulation that is enhanced by the electric field intensity near the tips, augmented by silver nanoparticles.