Gold clusters on thiol-functionalized FE3O4@SIO2 nanoparticles: a novel bioreduced catalyst for oxidation of benzyl alcohol

Abstract

Bioinspired synthesis of a magnetically recoverable gold nanoparticles (AuNPs) catalysts on Fe3O4@SiO2 support is reported. Firstly, AuNPs was prepared by using the aqueous leaf extract of Polygonum minus (kesum) as a reducing and stabilizing agent. The reduction of Au3+ ions to elemental Au was rapidly occurred and completed within 20 minutes at room temperature. The bioreduction process was monitored by UV-vis spectroscopy and the AuNPs were characterized by FTIR, XRD, TEM, and CV analyses. Then, same bioreduction process was employed in the preparation of Au catalysts supported on thiol-functionalized silica-coated magnetite nanoparticles. The supported Au catalysts were characterized by FTIR, XRD, TEM, XPS and AAS analyses. The performance of bioreduced supported Au catalysts was evaluated in the liquid phase oxidation of benzyl alcohol to benzaldehyde in water at 80o C using H2O2 as oxidant, reaction time of 6 h and 8 mg (4 µmol Au) of catalyst. Under these conditions, benzyl alcohol conversion of 58% and benzaldehyde selectivity of 100% with TON of 4,205 were achieved. The supported Au catalyst is stable and can be recovered and reused for three times without a significant loss in its activity and selectivity.