Biosynthesis of Platinum Nanoparticles Using Centella Asiatica Aqueous Leaf Extract and Its Catalytic Activity in Reduction of 4-nitrophenol

Abstract

Platinum nanoparticles (PtNPs) have been regarded as important catalyst in various organic reactions. In this research, a rapid and environmentally friendly method to prepare PtNPs using Centella Asiatica aqueous leaf extract is reported. The biomolecules found in Centella Asiatica aqueous leaf extract such as flavonoids are believed to act as reducing and capping agent. The formation of PtNPs is monitored by UV-Vis spectroscopy. The disappearance of a Pt(IV) ions absorption peak at 260 nm strongly suggested a complete reduction of Pt(IV) ions to Pt(0). The FTIR spectrum of PtNPs showed similar absorption bands with the spectrum of the Centella Asiatica leaf powder, suggesting the presence of biomolecules from as capping agent on PtNPs. HRTEM image analysis revealed that the PtNPs are mostly spherical with mean particle size of 10.62 nm ± 1.92. The catalytic activity of the biosynthesized PtNPs in the reduction of aqueous 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as reducing agent was also investigated. Results obtained showed the PtNPs is catalytically active achieving 86.6% conversion, follows a pseudo-first order reaction with rate constant value at 1.86×10-2 min-1.