Biogenic synthesis of metal nanocatalysts using Mimosa pudica leaves for efficient reduction of aromatic nitrocompounds

Abstract

Phytochemicals present in Mimosa pudica (M.pudica) leaves extract exhibit the potential for biogenic reduction of Ni, Co and Cu ions to their respective base metal nanoparticles (NPs) in a single-step. This approach of NP synthesis mediated by plant extract is environmentally benign and totally an aqueous phase green synthetic approach. The so-synthesised metallic NPs have identical spherical shape with an average diameter of about 8 nm as determined from TEM images. The ensuing particles have been utilized as nanocatalysts for the reduction of aromatic nitro compounds, p-nitrophenol and p-nitroaniline, using sodium borohydride (NaBH₄). Both reactions are extremely slow in the absence of a catalyst. From the kinetic data, the rate constants for both the catalyzed reactions exhibit an interesting order: k_{Cu NPs} > k_{Co NPs} > k_{Ni NPs}. These variations in catalytic performance of the NPs have been attributed to the difference in their work function values.