Impact of microwave synthesis time on the shape of silver nanostructures and their antibacterial activity

Silver is a well-known effective antibacterial and disinfectant material with relatively few side effects. Nanosilver derived from it, have strong antibacterial, antifungal and broad-spectrum antiviral properties. This study describes how the microwave synthesis durations of silver nanoparticles affect their shape, and the effect of the shapes of these nanoparticles on their antibacterial activity. The optical properties of the nanosilver were examined through UV-Vis absorption spectroscopy. The morphology of the grain was determined by transmission electron microscopy (TEM), and the crystallinity of the nanosilver was confirmed by X-ray diffraction (XRD). The antibacterial activities were assessed using bacterial pathogens Bacillus cereus and Bacillus megaterium, and were performed using the disk diffusion method. The obtained results show that (i) the shape and size of the nanosilver change when the microwave time is increased. They are of various sizes but almost all circular in shape when microwaved for 1.5 min, of larger sizes and different non-spherical geometric shapes after 3 min of microwave, and converted to nanowires after 5 min of microwave. (ii) Bacillus cereus and Bacillus megaterium were sensitive to all nanosilver but the antibacterial activity was more potent when the nanosilver possessed a defined shape than when they were silver nanowires.