Biosynthesis of silver nanoparticles using aqueous bark extract of Picea abies L. and their antibacterial activity

In recent years, synthesis of nanoparticles using vegetal extract has gained much interest in nanobiotechnology. The aim of this study is the biosynthesis of silver nanoparticles (AgNPs) from silver nitrate using spruce (Picea abies L.) bark as a bioresource of cost-effective nonhazardous reducing and stabilizing compounds. The effects of various parameters such as concentration of reactants, ratio extract/silver nitrate and time of incubation on the controlled formation of AgNPs were explored. The AgNPs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible-near infrared spectroscopy and scanning electron microscopy. A stock solution of silver nitrate (0.1 M) was prepared. Different concentrations of silver nitrate (1, 2.5, 4, and 5 mM) were prepared from the above solution, then added to 5 mL of spruce bark extract. The synthesis of AgNPs was confirmed by the change in the color of the mixtures from brown to grey. It was noticed that the synthesized nanoparticles have sizes between 0.1 and 0.5 µm (100–500 nm) with an average diameter of 0.226 µm (226 nm). The antibacterial activity of synthesized AgNPs was investigated in vitro. It was found that the most potent antibacterial activity appeared in AgNPs compared to the aqueous extract or silver nitrate.