Bimetallic Ag@Pt core-shell nanoparticles and their catalytic activity by a green approach

In the present study, silver@platinum nanoparticles were synthesized by aqueous extract of Schinus molle L. leaves. For the preparation of the bimetallic nanoparticles, a two-step strategy was followed. First, Ag nanoparticles as seeds were obtained varying the ratio of plant extract/AgNO3-precursor salt concentration. Second, various H2PtCl6 salt concentrations were added for growing a platinum shell in the Ag seeds, with no more plant extract addition. Also, the catalytic activity of the bimetallic nanoparticles was tested against the degradation of methylene blue dye. The products derived from the synthesis of the two stages were characterized by UV-vis spectroscopy (UV-vis), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy. UV-vis spectra showed that the AgNPs-typical absorption band decreases with the addition of the H2PtCl6 precursor, which indicates the formation of Ag@PtNPs. XRD patterns prove that the Ag@PtNPs have a face-centered cubic structure. The SEM and TEM analyses showed that most of the particles obtained have an irregular dendritic-type morphology, having particle sizes in the range of 20-100 nm, with an average size of approximately 45 nm. FT-IR spectroscopy showed that the functional groups of phenolic compounds were responsible for the NPs' chemical bioreduction. In addition, the nanoparticles showed excellent catalytic activity in the degradation of the methylene blue dye.