Utilization of affordable nanocomposites with outstanding antimicrobial activity in waterborne coatings

Abstract This study aimed to explore the development of eco-friendly antimicrobial coatings by combining antimicrobial nanocomposites with waterborne resins. Novel nanocomposites, such as nano-ZnO/silica fume and nano-CuO/silica fume, were synthesized using the solution combustion method, along with pure nano-ZnO and nano-CuO. The nanocomposites consist of a thin layer of nanometal oxide on silica fume, aiming to enhance antimicrobial activity. These nanocomposites were incorporated into acrylic waterborne resin at two concentrations (0.4 and 0.8 wt%) to provide cost-effective alternatives to imported and expensive antimicrobial agents. Antimicrobial effectiveness was evaluated against Staphylococcus aureus, Micrococcus luteus, and Candida albicans using disc diffusion and shake flask methods. Besides, the mechanical and physical properties of the coatings were compared to the properties of a commercial coating. The findings showed that the commercial coating offered inhibition zones ranging from 16 to 21 mm. While the disc containing 0.8% nano-ZnO/silica fume offered the greatest antimicrobial activity, with inhibitory zones ranging from 17 to 26.6 mm. Additionally, the results demonstrated that discs containing nano-ZnO were better than discs containing nano-CuO. The mechanical properties indicated that the hardness of coatings with either nano-ZnO or nano-CuO is similar to the commercial coatings in group I. However, coatings with nano-ZnO/silica fume and nano-CuO/silica fume exhibited slightly higher hardness. In group II, higher ratios of nano-ZnO, nano-CuO, and their silica fume composites significantly increase hardness compared to the commercial coatings, attributed to the formation of a more compact film. Moreover, the results showed that coatings with a high ratio of pigments (0.8%) adhered better than those with 0.4% of pigments.