Plasmonic Nanoparticle/Polymer Nanocomposites with Enhanced Photocatalytic Antimicrobial Properties

Abstract

We present a simple method of fabricating highly efficient antibacterial nanocomposite films consisting of a commercially available ethylene−vinyl alcohol copolymer (EVOH) and embedded Ag−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.

Rheological and structural details of biocidal iPP-TiO2 nanocomposites

“…This striking antimicrobial activity has been also found by using an ethylene-vinyl alcohol copolymer as polymeric matrix [6][7][8]. The existence of energy/charge transfer(s) through these polymer/oxide interfaces and the subsequent development of new electronic states within the nanocomposite system [9] are behind this optimal germicide capability.…”

Antibiofilm Activity of Epoxy/Ag-TiO2 Polymer Nanocomposite Coatings against Staphylococcus Aureus and Escherichia Coli

“…Until now, there have been very few reports that shown to resist biofilm formation on titania based polymer-nanocomposites. In one such study, Kubacka et al [52] have demonstrated photocatalysis using ethylene-vinyl alcohol copolymer (EVOH) embedded with Ag-TiO2 nanoparticles (ca. 10 −2 wt%) that showed outstanding resistance to biofilm formation by bacteria and yeast, upon ultraviolet (UV) light activation.…”

Applications of Antimicrobial Polymer Nanocomposites in Food Packaging

“…Another point of importance to improve the performance of TiO 2 -containing nanocomposite systems concerns the optimization of light absorption and the adequate handling of subsequent charge (electron-hole) pair creation and annihilation processes. This task has been typically attempted by controlling the morphological-structural-defect characteristics of the oxide and/or by extending its absorption power into the visible region through a doping process (Kubacka et al, 2009). Metal doping has long been known to be one of the most effective ways to change the intrinsic band structure of TiO 2 , and consequently, to improve its visible light sensitivity as well as increase its photocatalytic activity under UV irradiation.…”

“…A last point to mention is the concomitant degradation of the polymer matrix by effect of the charge carriers; this has been proved to be limited by addition of small amounts of titania, typically below 5 wt. % (Kubacka et al, 2009). On the other hand high release level of silver, especially for silver based bulk materials, leads to shortening the effective life of antibacterial activity.…”