Innovative methodology for green synthesis of iridium nanoparticles of rod shapes by reduction of iridium (IV) using sustainable pectin with formation of keto-pectin derivatives

Abstract

A prospective novel technique has been developed for green synthesis of iridium nanoparticles of rod shapes for the first time with simultaneous formation of keto-derivative oxidation product with a yield of 98.3 %. This takes place by reduction of hexacholoroiridate (IV) by using sustainable pectin as a powerful reducing agent biomacromolecule in acidic media. The formation of nanoparticles (IrNPS) was identified by Fourier transform infrared (FTIR), Transmission electron microscope (TEM), X-ray diffraction (XRD), and Scanning electron microscope (SEM) investigations. The TEM morphology showed that the iridium nanoparticles were of crystalline rod shapes on contrary to the spherical shapes reported on all synthesized IrNPS earlier. The rates of nanoparticles growth were followed kinetically using a conventional spectrophotometer. The kinetic measurements revealed a unity order reaction in [IrCl6]2− as oxidant and fractional first-order in [PEC] as a reducing agent, respectively. A decrease in the reaction rates was noticed with increasing the acid concentration. Kinetic evidence reveals the creation of intermediate complex as transient species prior to the slow step. Such complex formation may be facilitated by the participation of one chloride ligand from [IrCl6]2− oxidant forming a bridge between the oxidant and reductant in such formed intermediate complex. Plausible reaction mechanisms for electron transfer pathway routes consistent with the kinetics observations were discussed.