Green synthesis of silver nanoparticles with a long lasting stability using colloidal solution of cowpea seeds (Vigna sp. L)

Silver nanoparticles (AgNPs), one of the most commercialized nanomaterials, are frequently used in various industries in medical devices to water purifiers. This study is the first to propose a low-cost and novel eco-friendly and reproducible synthesis to extract AgNPs using cowpea seeds (Vigna sp. L) with a long lasting stability. From a mixture of silver nitrate concentration of 10−3 M and 2.5 and 10 mL of seed extract, 2.19 and 1.09% spherical AgNPs were fabricated with diameters <70 nm and a maximum absorbance peak at 431 nm. The observed peaks in the extract, corresponding to carbonyl group, amide I, II and III, indicated the presence of carbohydrate and protein which stabilized the synthesized AgNPs for a period of 11 months. The carbohydrate and protein released from the aqueous extract cowpea seeds reduced the nitrate and acted as templates for silver nucleation sites to form silver nano-structures. Peptides and proteins also acted as capping agents to control the size and shape of the produced silver nanoparticles.