Development of a novel silver ions-nanosilver complementary composite as antimicrobial additive for powder coating

Applying silver into coatings has become a prevalent method in fabricating antimicrobial surfaces. However, the concerns about durability always exist and limit its applications. Here, a highly inhibitory, active, durable, and easy-to-use silver ions-nanosilver antimicrobial additive for powder coatings was fabricated in this study. Silver nanoparticles were chemically bonded to the Ag, Cu, and Zn-ternary ion-exchanged zeolite by α -lipoic acid, which was then encapsulated by hydrophilic polymers. The fabricated silver ions and silver nanoparticles (Ag + -AgNPs) complementary structure provides a synergistic effect. Ag + is the main antimicrobial agent, while AgNPs act as a supplementary reservoir of Ag + . As well, the formed thin layer of silver nanoparticles and hydrophilic film prolongs the release of active Ag + from zeolite, and Ag + facilitates the activation of AgNPs. The results show that this additive indicates excellent antimicrobial activity to E. coli , S. aureus , P. aeruginosa , and C. albicans , and that the coatings with the additive exhibit over 99.99% reduction rate for the tested bacteria and fungi. The coating film is able to maintain over 99% antimicrobial reduction even after 1200 repeated solution wipings, or over 30 wash cycles of artificial sweat solution, indicating high durability. Furthermore, the yellowness of the coating is not evident (Δb < 2) despite the high loading of silver, and the silver nanoparticles have little impact on gloss, haze, and distinctness of the coating film image.