Growth inhibition of Escherichia coli by zinc molybdate with different crystalline structures

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 10mm) and different crystallographic structures (a, b, hydrated, and nonhydratedmixeda- andb-phases)were obtained.Bactericidal properties of suspensions containing different concentrations (1, 5, and 10mM) of powders of a, b, and mixed a/b ZnMoO4 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 thatZnMoO4 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 electron–hole 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.