Platanus orientalis Leaf Mediated Rapid Synthesis of Catalytic Gold and Silver Nanoparticles

In an attempt to synthesize novel catalytic gold (AuNPs) and silver nanoparticles (AgNPs) we have used Platanus orientalis leaf extract for both reduction and capping. The synthesis was rapid which completed by 5 h as indicated by change in colour and development of prominent peak at 540 nm for AuNPs and 440 nm for AgNPs, as revealed by UV-visible spectroscopy. The phytogenic nanoparticles showed exotic shapes which included triangles, spheres, hexagons and pentagons as analyzed by high resolution transmission electron microscopy. The optimized processing parameters like salt concentration (1 mM concentration of HAuCl4 and 4 mM of AgNO3) and the reaction temperature (50°C) led to faster nanoparticles synthesis. Energy dispersive spectra and X-ray diffraction studies confirmed the elemental gold and silver in AuNPs and AgNPs. Detailed phytochemical characterization using biochemical techniques and gas chromatography mass spectrometry indicated the predominance of ascorbic acid, citric acid, reducing sugars and even starch which may together lead to simultaneous synthesis and capping. Further, AuNPs and AgNPs catalyzed the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH4 with apparent rate constants of 1.908 × 10-4 min-1 and 3.071 × 10-4 min-1, respectively.