Microbial growth inhibition caused by Zn/Ag-Y zeolite materials with different amounts of silver

Different loadings of silver exchanged on bimetallic Zn/Ag-NaY zeolite materials were studied for antimicrobial properties against four reference microorganisms. The sensitive indicator strains used were two bacteria (Escherichia coli and Bacillus subtilis) and two yeast species (Saccharomyces cerevisiae and Candida albicans). The bimetallic materials were compared with the monometallic materials prepared with the same concentrations of silver. A synergistic effect between the two metals, zinc and silver, was evidenced on the antimicrobial activity of the materials. All mono and bimetallic materials showed strong efficacy against bacteria and yeasts, although the later overall displayed lower MIC values. The results of X-ray photoelectron spectroscopy (XPS) confirm the presence of silver and zinc as ions, not homogeneously distributed throughout the zeolite framework, which implies that the metal ions are located in different sites of the faujasite structure.