Biological synthesis of manganese dioxide nanoparticles by Kalopanax pictus plant extract

Manganese dioxide (MnO₂) nanoparticles were synthesised by the reduction of potassium permanganate (KMnO₄) using Kalopanax pictus leaf extract at room temperature. A transparent dark-brown colour appeared after the addition of K. pictus leaf extract to the solution of permanganate. The time course of the reduction of KMnO₄ and synthesis of MnO₂ nanoparticles was monitored by means of UV-Vis spectra. The reduction of KMnO₄ occurred after addition of plant extract with disappearance of KMnO₄ specific peaks and emergence of peak specific for MnO₂ nanoparticles. MnO₂ nanoparticles showed absorption maxima at 404 nm. The electron dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO₂ nanoparticles. Transmission electron microscopy micrographs revealed presence of uniformly dispersed spherical shaped particles with average size of 19.2 nm. The selected area electron diffraction patterns revealed the crystalline nature of MnO₂ nanoparticles. Fourier transform-infrared spectroscopy spectra of pure MnO₂ show the occurrence of O-Mn-O vibrational mode at around 518 cm^-1. The phyto-synthesised MnO₂ nanoparticles showed degradation ability of dyes (congo red and safranin O) similar to chemically synthesised MnO₂ nanoparticles. This study shows simple and eco-friendly synthesis of MnO₂ nanoparticles by plant extract and their utilisation for dye degradation for the first time.