i have synthesized silver nanoparticles by green and chemical method. Silver nitrate and plant extract are used as precursor salt and reducing agent for green synthesis of silver nanoparticle, for chemical synthesis sodium citrate used as reducing and stabilizing agent .Tem image of green synthesized nanoparticles is poly dispersed,it has differnt shape and size(50-80nm) but chemically ynthesized one has almost spherical shape.why it so .poly dispersity of green synthesized particles is common?