Green synthesis of Ag nanoparticles: Effect of algae life cycle on Ag nanoparticle production and long-term stability

Spherical Ag nanoparticles (AgNPs) were biologically synthesized using four different extracts prepared from Parachlorella kessleri algae cultivated for 1, 2, 3 and 4 weeks. The influence of algae life cycle on AgNPs formation and effect of different storage conditions on AgNPs long-term stability were investigated. The age of algae influenced the rate of AgNPs synthesis and amount of AgNPs in solution. The age of algae did not influence the AgNPs long-term stability. UV–vis and TEM observation revealed that long-term stability of AgNPs can be influenced by storage temperatures, and low temperature positively influences the AgNPs stability. AgNPs stored at dark and at temperature of ～5 °C showed the best long-term stability regardless of the culture age. Such AgNPs remained spherical, fine (5–20 nm) and stable (no agglomeration) even after 6 months.