New Composite Nanomaterials with Antimicrobial and Photocatalytic Properties Based on Silver and Zinc Oxide

Herein we report the synthesis of composites containing nanobio silver, ZnO and phytochemicals in different Ag/Zn molar ratios. First, Ag nanoparticles were prepared using red cabbage extract and then they are covered with zinc oxide obtained also in the same extract by precipitation method. The antimicrobial activity of synthesized nanocomposites was tested against Staphylococcus aureus, Streptococcus, Escherichia coli, Pseudomonas and Candida clinical isolates and compared with that of ZnO functionalized with anthocyanins. The presence of nanobio silver into the nanocomposites enhanced the bactericidal properties demonstrated by slightly larger diameters of growth inhibition zone and lower minimal inhibitory concentrations. S. aureus and Streptococcus strains were more sensitive than the other strains and fungi both for Ag-ZnO nanocomposites and ZnO functionalized with anthocyanins. Also, the presence of silver in the nanocomposites leads to an improved photocatalytic activity (PA) confirmed in the bleaching of Congo red solution. The PA increases with silver content when Ag content is low (up to 1/12 Ag/Zn molar ratio), but decreases significantly for high silver concentration (1/7 Ag/ZnO molar ratio) in the Ag-ZnO nanocomposites.