Ultrasmall, Ligand-Free Ag Nanoparticles with High Antibacterial Activity Prepared by Pulsed Laser Ablation in Liquid

Abstract

Since ancient times, silver and its compounds have been known to have a broad spectrum of antimicrobial activities for bacteria, fungi, and viruses. Due to the increasing bacterial resistance to classic antibiotics, the investigations of Ag NPs have increased. Herein, we present the preparation of ligand-free Ag NPs with 3 and 20 nm sizes by applying picosecond laser ablation in liquid at 355 and 1065 nm. Our laser processing system allows a high control on particle sizes. The produced nanoparticles were characterized by means of transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. The size effect on the antibacterial activity of Ag NPs was tested against E. coli and S. aureus. The growth curves of bacteria were monitored at 0-5 mg/L of Ag NPs by a multimode microplate reader. The size effects as well as the concentration of Ag NPs on their antibacterial activity are discussed.