Developing novel compounds with antimicrobial properties can be an effective approach to decreasing the number of healthcare-associated infections, particularly in the context of medical devices and touch surfaces. A variety of molybdate powders (AgMoO, CaMoO, CuMoO and CuMoO) were synthesized and characterized, and Escherichia coli was used as a model gram-negative bacterium to demonstrate their antimicrobial properties. Optical density measurements, bacterial colony growth, and stained gel images for protein expression clearly showed that silver- and copper molybdates inhibit bacterial growth, whereas CaMoO exhibited no bactericidal effect. All tests were performed in both daylight and darkness to assess the possible contribution of a photocatalytic effect on the activity observed. The main mechanism responsible for the antibacterial effect observed for AgMoO is related to Ag release in combination with medium acidification, whereas for compounds containing copper, leaching of Cu ions is proposed. All these effects are known to cause damage at the cellular level. A photocatalytic contribution to the antibacterial activity was not clearly observable. Based on the pH and solubility measurements performed for powders in contact with various media (ultrapure water and bacterial growth medium), silver molybdate (AgMoO) was identified as the best antibacterial candidate. This compound has great potential for further use in hybrid powder-polymer/varnish systems for touch surfaces in healthcare settings.

Zinc molybdate powders were synthesized by hydrothermal methods using different salt precursors, and in the presence (or absence) of citric acid as surfactant. As a function of precursors, synthesis conditions and post-synthesis annealing, powders with various sizes (from tens of nm up to 10 mm) and different crystallographic structures (a, b, hydrated, and nonhydrated mixed aand b-phases) were obtained. Bactericidal properties of suspensions containing different concentrations (1, 5, and 10 mM) of powders of a, b, and mixed a/b ZnMoO 4 phases were tested against Escherichia coli. Optical density measurements and the results obtained from the observation of cultures growth on agar petri dishes clearly showed that ZnMoO 4 possesses antibacterial properties. The antibacterial efficiency was dependent on the concentration of powders in suspension, as well as on the crystalline structure in relation to the crystals size/surface structuring. The intrinsic semiconducting properties of this material, together with the defect states present in the bandgap which hindered the recombination of electronhole pairs produced under visible light, as well as electronic transitions were factors proposed as being responsible for the observed antibacterial activity by the creation of reactive oxygen species and hydrogen peroxide.