Synthesis and conversion of multi-morphology silver nanoparticles: Anisotropic growth induced by redox cycle

A well-designed strategy utilizing H2O2 as both oxidizing and reducing agent to synthesize multi-morphology silver nanoparticles (AgNPs) was developed to investigate the mechanism of anisotropic growth. At the initial stage, isotropic silver nanospheres were synthesized by pure reduction of H2O2. Then a redox cycle was established, which consisted of mutual conversion between Ag+ and Ag0 caused by reduction and oxidization of H2O2, to induce anisotropic growth of the original nanospheres into popcorn-shaped AgNPs or silver nanoplates with the presence of different concentrations of poly(vinyl pyrrolidone) (PVP). The results indicated that the redox cycle provided a driving force of anisotropic growth by inducing the formation of defects, while PVP played a key role in controlling growth direction. This work provided a high-yield method to synthesize anisotropic AgNPs by combining reduction and oxidization and suggested a hypothesis of the mechanism of anisotropic growth.