ZnO−Ag Hybrid Nanoparticles Used in the Antimicrobial Solvent‐Based Coatings: Antibacterial Studies in the Darkness and Under Visible‐Light Irradiation

Abstract

AbstractThis study explores how hybrid nanoparticles can be used to improve the antibacteial properties of both single nanoparticles and their polymeric nanocomposite coatings. Hybridization of two different nanoparicles, such as nano‐ZnO and silver nanoparticles (AgNPs) has been carried out to combine advantages of the individual particles. For these purposes, firstly ZnO−Ag hybrid nanoparticles were chemically fabricated by reducing Ag+ precursor on the as‐received nano‐ZnO using sodium borohydride in aqueous medium. Thereafter, these ZnO−Ag nanohybrids were introduced into the acrylic polyurethane matrix (at 2 wt.%) under sonication in xylene/toluene solvents. To reveal the effect of hybridization on the antibacterial activity against E. coli of both ZnO−Ag nanohybrids and their nanocomposite coatings, two antibacterial tests have been carrieried out in presence of visible light irradiation or without light (in dark). The agar‐well diffusion method indicated that ZnO−Ag nanohybrids exhibited high antibacterial activity against E.coli at the low concentration (8 mg/mL). In addition, their larger inhibition zones under visible light exposure were observed, when compared to the dark condition. Similarity, antibacterial test (ISO 22196 : 2007 standard) indicated that nanocomposite coating under visible light exposure had a higher antibacterial activity than that in the dark condition. Data from this antibacterial test after 24 h indicated that the visible light exposure provided more bactericidal efficiency for APU/ZnO−Ag coating (4.17 log), as compared to the dark condition (4.07 log). This increase in the bactericidal efficiency can be attributed to the hybridization of nano‐ZnO and AgNPs in their hybrid nanostructure. From the experimental data, we propose the mechanism for antibacterial activity of ZnO−Ag hybrid nanoparticles. In addition, TEM photographs indicated that AgNPs (10–30 nm) were attached to the surface of nano‐ZnO (<100 nm). Data from the diffused reflectance spectra indicated that the deposition of AgNPs on nano‐ZnO reduced its band gap energy (Eg) from 3.2 eV to 2.75 eV. In case of nanocomposite coating, addition of 2 wt.% ZnO−Ag nanohybrids into the acrylic polyurethane matrix significantly increased their impact strength and abrasion resistance.