Provided are materials having antimicrobial properties. The materials include a polymer having incorporated therein a synergistic combination of at least two metal oxide powders, including a mixed oxidation state oxide of a first metal and a single oxidation state oxide of a second metal. The powders may be incorporated substantially uniformly within the polymer. Further, the powders may have substantially different specific gravities and substantially similar bulk densities. In addition, the ions of the metal powders may be in ionic contact upon exposure of the material to moisture. Also provided are methods for the preparation of the materials and uses thereof, including in combating or inhibiting the activity of microbes or microorganisms.