Effect of storage conditions on long-term stability of Ag nanoparticles formed via green synthesis

Spherical Ag nanoparticles(AgNPs) with a diameter of 20 nm or smaller were biologically synthesized using algae Parachlorella kessleri. The effect of storage conditions on the long-term stability of AgNPs was investigated. UV/Vis spectrophotometry, transmission electron microscopy, and dynamic light scattering measurements revealed that the long-term stability of AgNPs was influenced by light and temperature conditions. The most significant loss of stability was observed for the AgNPs stored in daylight at room temperature. The AgNPs stored under these conditions began to lose their stability after approximately 30 d; after 100 d, a substantial amount of agglomerated particles settled to the bottom of the Erlenmeyer flask. The AgNPs stored in the dark at room temperature exhibited better long-term stability. Weak particle agglomeration began at approximately the 100 th day. The AgNPs stored in the dark at about 5℃ exhibited the best long-term stability; the AgNPs stored under such conditions remained spherical, with a narrow size distribution, and stable(no agglomeration) even after 6 months. Zeta-potential measurements confirmed better dispersity and stability of AgNPs stored under these conditions.

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.