A simple and effective method, UV-initiated photoreduction, has been reported for synthesis of silver NPs in the presence of citrate, polyvinylpyrrolidone, poly (acrylic acid), and collagen. For instance, Huang and Yang produced silver NPs via photoreduction of silver nitrate in layered inorganic laponite clay suspensions which served as stabilizing agent for prevention of NPs aggregation. The properties of produced NPs were studied as a function of UV irradiation time. Bimodal size distribution and relatively large silver NPs were obtained when irradiated under UV for 3 h. Further irradiation disintegrated the silver NPs into smaller sizes with a single distribution mode until a relatively stable size and size distribution was obtained (41). Silver NPs (nanosphere, nanowire, and dendrite) have been prepared by UV irradiation photoreduction technique at room temperature using poly (vinylalcohol) (as protecting and stabilizing agent). Concentration of both poly (vinylalcohol) and silver nitrate played significant role in the growth of the nanorods and dendrites (42).
Sonoelectrochemistry technique utilizes the ultrasonic power primarily to manipulate the material mechanically. Pulsed sonoelectro-chemical synthetic method involves alternating sonic and electric pulses, and electrolyte composition plays a crucial role in shape formation (43). It was reported that silver nanospheres could be prepared by sono-electrochemical reduction using a complexing agent, nitrilotriacetate to avoid aggregation (43).