Nowadays, it has become urgently necessary to change the traditional methods of synthesis of metallic nanoparticles, and to start using safer and more eco-friendly approaches. In the present work a green synthesis of silver nanoparticles was carried out using mint leaf extract (Mentha piperita) as the reducing and stabilizing agent. Silver nanoparticles were synthesized using a 1 mM silver nitrate solution and varying the volume of the extract (150, 250, 350 μL), at a temperature of 30 °C for 24 h. The formation of silver nanoparticles was monitored by a UV-Visible spectrophotometer which showed absorption peaks ranging from 438–470 nm. Atomic Force Microscopy and Transmission Electron Microscopy analysis showed that the silver nanoparticles presented different morphologies. For the treatment with 150 μl of extract, the silver nanoparticles were mostly spherical and for the other two treatments we observed spherical, triangular, hexagonal and irregular morphologies of the nanoparticles. Dynamic Light Scattering analysis determined a mean size of 50 nm for all of the treatments, with zeta potential values ranging from –20 to –23 mV. The results showed that the synthesized silver nanoparticles had antibacterial activity against pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. The minimum inhibitory concentration required for S. aureus was 11.1, 26.3 and 51.5 μg · ml–1, for the treatments of 150, 250 and 350 μl of extract, respectively. All of these values were higher than for E. coli, which presented a Minimum Inhibitory Concentration of 2.49 μg · ml–1. This work offers a quick, simple and non-toxic method for the synthesis of silver nanoparticles.
