Green synthesis method of silver nanoparticles using starch as capping agent applied the methodology of surface response

The aim of this work was to synthesize silver nanoparticles (NPs) through a green synthesis method using starch as a capping agent. The influence of the glucose content, temperature, and pH on the size of the NPs was evaluated by means of a response surface methodology. The obtained nanomaterials were characterized by UV-Vis spectroscopy, XRD, and TEM, and the crystalline structure of the silver was determined by XRD. The optimum synthesis time was after 3 h of reaction time the colloidal solution, did not show any further significant variation in the optical absorption peak (lambda(max)). Response surface results indicate that the reducing agent (glucose) concentration was the most important factor influencing the NPs size, which ranged from 2 to 24 nm. TEM images show that NPs had predominantly spherical shapes, but also polyhedral shapes were present in smaller quantities. Analysis of Raman spectra infers that the glucose initially reduces silver ions to elemental silver. Then the starch undergoes hydrolysis providing primary hydroxyl that contributes to the reduction of silver. The carboxyl and hydroxyl groups of glucose and hydrolyzed starch stabilize the silver NPs by passivating their surface, so that they do not aggregate and remain uniformly distributed.