Biobased green method to synthesise palladium and iron nanoparticles using Terminalia chebula aqueous extract

There are many methods to synthesise metal and metal oxide nanoparticles (NPs) using different reducing agents which are hazardous in nature. Although some researchers have used biobased materials for synthesis of these NPs, further research is needed in this area. To explore the scope of bio-extract for the synthesis of transition metal NPs, the present paper synthesises metal NPs replacing hazardous traditional reducing agents. This paper reports the synthesis of palladium and iron NPs, using aqueous extract of Terminalia chebula fruit. Reduction potential of aqueous extract of polyphenolic rich T. chebula was 0.63 V vs. SCE by cyclic voltammetry study which makes it a good green reducing agent. This helps to reduce palladium and iron salts to palladium and iron NPs respectively. Powder X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) analyses revealed that amorphous iron NPs were within the size less than 80 nm and cubic palladium NPs were within the size less than 100 nm. The synthesised nanomaterials were remarkably stable for a long period and synthesis of stable metal NPs will need to be explored using biobased materials as reducing agents.

Graphical abstractUnder mild acidic conditions, the polyphenols present in extract in the form of tannins hydrolyses to give gallic acid, ellagic acid, glucose, etc. Transformation of phenolics to quinone form enables the reduction of metal ions to metal nanoparticles. Oxidised polyphenols acts as stabilising agents. Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► First report using aq. Terminalia chebula extracts to synthesise FeO and Pd nanoparticles. ► Polyphenols act as reducing and capping agents. ► Formation of FeO and Pd NPs were rapid and stable.