DENDRITIC UNIMOLECULAR MICELLE STABILIZED Au/Pd BIMETALLIC NANOPARTICLES: SYNTHESIS AND AQUEOUS PHASE CATALYSIS

摘要

The present study investigates the synthesis of amphiphilic poly(propyleneimine) dendrimer generation-2 with peripheral quaternary ammonium head and dodecane tail protected Au/Pd bimetallic nanoparticles. The dendrimer has been designed to accomplish the micelle structure, which in turn accompanies the organic substrates to the aqueous phase. The typical investigation deals the stabilization tendency of the amphiphilic dendrimer toward the metal nanoparticles in an aqueous medium. The dendrimer protected bimetallic nanoparticles, namely gold-palladium, were synthesized in a simplified procedure. The nanocomposite was characterized by using plasmon resonance absorbance and high-resolution transmission electron microscopy. In UV-Vis spectra, dendrimer with Au NP showed the surface plasmon resonance absorption at 530 nm and after interaction with Pd NPs, the SPR of Au NP was altered and observed the blueshift. The high resolution transmission electron microscope images showed different types of bimetallic nanoparticles, viz., core-shell, random alloy, and cluster in cluster with the mean particle size of 30 nm. The type and structures of bimetallic nanoparticles obtained between gold and palladium were discussed. Afterward, the synergetic catalytic ability of the amphiphilic dendrimer-bimetallic nanoparticles composite was experimented through the aqueous phase reduction of nitrobenzene reaction. Remarkably, it was found that the amphiphilic dendrimer protected Au-Pd bimetallic nanoparticles are more efficient catalysts for aqueous phase reactions. Therefore, the catalyst plays a pivotal role in the aqueous phase organic reactions.