Silver nanoparticles dispersing in chitosan solution: Preparation by γ-ray irradiation and their antimicrobial activities

Silver nanoparticles were prepared by γ-ray irradiation–reduction under simple conditions, i.e., air atmosphere, using chitosan as a stabilizer. The nanoparticles were spherical with an average size of 7–30 nm as observed from TEM. The size decreased when chitosan concentration increased, while it increased with increasing γ-ray dose and initial silver nitrate content. The obtained silver nanoparticles dispersed in a 0.5% (w/v) γ-ray irradiated chitosan–aqueous acetic acid solution were stable for more than 3 months without tendency to precipitate. The silver nanoparticles exhibited antimicrobial activities against Escherichia coli and Staphylococcus aureus. The results suggest that silver nanoparticles dispersed in chitosan solution can be directly applied in antimicrobial fields, including antimicrobial food packaging and biomedical applications.