Plasmonic Nanoparticle/Polymer Nanocomposites with Enhanced Photocatalytic Antimicrobial Properties

We present a simple method of fabricating highly efficient antibacterial nanocomposite films consisting of a commercially available ethylene-vinyl alcohol copolymer (EVOH) and embedded A-TiO2 nanoparticles. These systems display potent antimicrobial activity toward Gram-negative, Gram-positive bacteria/cocci (Escherichia coli 1337-H; Pseudomonas putida KT2440, Staphylococcus aureus 1341-H), and yeasts (Pichia jadini) and, moreover, show outstanding resistance to biofilm formation. These nanocomposites differ from known and similar TiO2-EVOH systems by the presence of small quantities (in the 10(-2) wt. % level) of silver. Through a plasmonic effect, the presence of the noble metal significantly enhances the antimicrobial power of TiO2-EVOH systems upon ultraviolet (UV) light and opens the fruitful use of visible-light excitation sources. A joint UV-visible and photoluminescence optical characterization of the films allows an understanding of the behavior upon both UV and visible light excitations and provides evidence that the biocidal action comes from the inorganic-organic interface and takes place on the whole nanocomposite surface. These properties indicate that the films are potentially useful as antimicrobial materials in a wide variety of packaging, biomedical, and general use applications.