Silver nanoparticles (NPs) / chitosan nanofibers (ChNF) composite material was fabricated with a high-pressure wet-type jet mill. A mixture comprising an aqueous silver nitrate solution and a ChNF suspension was prepared as a raw starting material. The mixture was then processed with the high-pressure wet-type jet mill at a discharge pressure of 100 MPa. An X-ray diffraction analysis of the obtained samples revealed the presence of not only chitosan crystallites, but also silver metal crystallites. According to field-emission scanning electron microscopy observation, many nano-sized silver particles were immobilized and well-dispersed on the surface of ChNF. The silver particles had a spherical shape with an average particles size of about 20 nm regardless of the number of jet milling cycles. The silver content in the composite materials increased slightly with the number of jet milling cycles. As a result of investigating the antibacterial property of the silver NPs /ChNF composite material processed five times with the high-pressure wet-type jet mill at a discharge pressure of 100 MPa, it was found that the minimum inhibitory concentration (MIC) of that for E. coli was 4.2 mg/L, although a raw ChNF had no antibacterial property.
