A comparative study of the catalytic activity between Ag nanoparticles and Ag flower-like particles synthesized by the Sedum praealtum aqueous extract

This work shows that using Sedum praealtum extract, silver nanoparticles (AgNPs) and flower-like silver self-assemblies (AgFLs) can be synthesized by varying only the concentration of AgNO3. In addition, the comparison of its catalytic activity on the degradation of the methylene blue dye (MB) was evaluated. SEM showed spherical AgNPs of ∼15 nm at 5 mM (AgNO3) concentration, and AgFLs are formed at 10 mM (AgNO3). XRD patterns confirmed the fcc crystal structure of the materials. FTIR spectroscopy determined that glycoside compounds are the main participants as reducing agents, stabilizers, and binders. UV-Vis spectroscopy confirmed the obtaining of Ag nanomaterials through the characteristic resonance band of the surface plasmon (RSP). In addition, the value of the band-gap was determined to measure the catalytic activity in the degradation of MB. The photocatalytic activity was mainly favored by smaller sizes of AgNPs, over the texture and surface porosity of AgFLs. However, it is independent of the morphology, and the use of an external reducing agent (NaBH4) since a 90% degradation is obtained after 24 h of reaction due to the combined action of photocatalysis and dye adsorption.