Study on the photocatalytic and antibacterial properties of silver nanoparticles synthesized by a green approach

Silver nanoparticles (AgNPs) have potential applications in several fields, mainly when they are synthesized by a green method. In the present work, the photocatalytic and antibacterial properties of silver nanoparticles biosynthesized using aqueous extracts of a variety of Eriobotrya japonica were investigated. The effects on the nanoparticles characteristics of parameters such as extract volume, stability, and reaction temperature were studied. The structural characterization showed that the synthesized nanoparticles have spherical morphology mostly with a size range of 10–60 nm. The increase of biosynthesis reaction temperature leads to an increase in the AgNPs concentration. However, the size and size distribution increased, resulting in a bimodal distribution. Therefore, the best results were obtained at room temperature with 4 ml of plant extract. According to FTIR results, the reduction of Ag ions and the subsequent nanoparticles stabilization are attributed to phenolic compounds from leaves extract. The antibacterial properties of the nanoparticles were evaluated. The bacteria analyzed were E. coli, P. aeruginosa, and S. aureus. The results demonstrate the capacity of the nanoparticles to inhibit the growth of gram-negative and gram-positive bacteria. These antibacterial properties depend on the concentration of nanoparticles. Finally, the catalytic activity of silver nanoparticles was analyzed. The results showed the excellent properties of nanoparticles to degrade methylene blue and methyl orange. Moreover, the rate and efficiency of degradation depending on the nanoparticles concentration, obtaining the best results when the highest concentration (60 μg ml⁻¹) was employed. Therefore, silver nanoparticles synthesized by green synthesis are an excellent candidate for antibacterial and catalytic applications. (paper)