Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates

The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3×2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25°C to 600°C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300°C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area. •Molybdenum trioxide dihydrate (MoO3×2H2O) and anhydrous MoO3 after calcination exhibit exceptional antimicrobial activities•Especially the orthorhombic samples with a large specific surface area show excellent antimicrobial properties.•The increased specific surface area is due to crack formation and to loss of hydrate water after calcination at 300°C.•Increased a local acidity as a consequence of the augmented surface area is related to the antimicrobial characteristics.