Synthesis and Excellent Antibacterial Activity of Ag2O-Loaded Carboxymethyl Starch Nanocomposites

Carboxymethyl starch/silver oxide nanocomposites (CMS-Ag2O NCs) were successfully fabricated by modifying carboxymethyl starch (CMS) with Ag2O obtained from an aqueous AgNO3 solution as silver source. Ag2O nanoparticles (NPs) formed on the surface of CMS by ion exchange. Based on SEM images, the diameters of Ag2O NPs were determined to be between 50 and 100 nm. From the XRD spectra of CMS-Ag2O NCs, the new diffraction peaks appeared at 33.88 degrees and 38.08 degrees, which were attributed to the Ag2O NPs. According to the XPS analysis, Ag 3d(5/2) and Ag 3d(3/2) peaks in CMS-Ag2O NCs were fitted into two main peaks centered at 367.6 eV and 373.6 eV, which were attributed to Ag+. The antibacterial efficiencies of CMS-Ag2O NCs against Escherichia coli, Staphylococcus aureus, Pseudoalteromonas tetraodonis, Micrococcus luteus, and Shewanella putrefaciens were determined to be 99.6%, 99.7%, 99.4%, 99.5%, and 99.6%, respectively. The antibacterial efficiencies of CMS-Ag2O NCs against the bacterial species were all greater than 99%. Therefore, these results indicated that CMS-Ag2O NCs was highly effective as a bactericidal agent against multiple bacterial species. CMS-Ag2O NCs can be further applied to antifouling coating.