Green synthesis, size control, and antibacterial activity of silver nanoparticles on chitosan films

Silver nanoparticles (AgNPs) synthesized on the surface of chitosan (CS) films using ultraviolet (UV) and natural light irradiation reduction methods were studied. Field-emission scanning electron microscopy revealed that the diameter of some AgNPs synthesized by the UV irradiation reduction method lay in the range of 5–15 nm. These AgNPs were isolated and dispersed on the surface of CS film. Meanwhile, some AgNPs aggregated to form larger cubic and irregular AgNPs with average size of 50–200 nm. Compared with those synthesized via the UV irradiation reduction method, AgNPs synthesized by the natural light irradiation reduction method were found to be much more individually isolated and uniformly dispersed on the CS film surface. The AgNPs synthesized using the natural light irradiation reduction method had spherical shape with average size of 10–30 nm. Thus, the size and morphology of AgNPs on the CS films (CS-AgNPs films) can be controlled by choosing an appropriate irradiation reduction method. The results of antibacterial testing illustrated that the CS-AgNPs films synthesized by both the ultraviolet and natural light irradiation reduction methods exhibited strong antibacterial activity against Escherichia coli .