Use of an aqueous plant extract in the biosynthesis of gold nanoparticles.

Aqueous extracts of stems and roots of Jatropha spp were obtained, and the foam, a component rich in surfactant compounds was mechanically separated. The extracts were characterized by phytochemical marching, UV-Vis and Raman spectroscopies. The biosynthesis of gold nanoparticles (AuNPs) was carried out using tetrachloroauric acid (HAuCl4) as precursor salt and adding different volumes of the extracts as reducing agent. By UV-Vis spectroscopy, the maximum absorption of the AuNPs was identified at 527 nm. The AuNPs biosynthesized with the root foam (ER) were smaller than those obtained from the other extracts. Using dynamic light scattering, it was measured predominant sizes of AuNPs between 11 and 43 nm in colloidal suspension. Scanning electron microscopy showed spherical nanoparticles around 20 nm, surrounded by a halo made up of the surfactant components of the ER extract. The AuNPs maintained colloidal stability both in their synthesis medium and water, after being washed and redispersed. This biotechnological approach, in addition to preserving the colloidal stability of the AuNPs, could also be useful for modulating their shape, an advantageous condition for their use in various applications. [ABSTRACT FROM AUTHOR]