Synthesis of zinc oxide nanoparticles from Gynostemma pentaphyllum extracts and assessment of photocatalytic properties through malachite green dye decolorization under UV illumination-A Green Approach

Abstract

Green synthesis of ZnO nanoparticles gained huge attention due to eco-friendly protocol to reduce the destructive effect of chemical synthesis mostly used in the industry. This study focused on green chemistry protocol to synthesis Gynostemma pentaphyllum zinc oxide nanoparticles (GP-ZnO-NPs) from Gynostemma plant extract using the co-precipitation method. The GP-ZnO-NPs decolorization performance was assessed by removing toxic dye Malachite Green (MG) under UV illumination. The hexagonal wurtzite structure with an average size of 35.41 nm was confirmed by X-ray powder diffraction (XRD) analysis. The FE-TEM analysis revealed the nanoparticles' hexagonal shape, and electron diffraction analysis (EDX) analyzes the percentage of Zn & oxygen of the nanostructures. The Fourier-transform infrared spectroscopy (FT-IR) analysis was revealed the functional group responsible for forming Gp-ZnO-NPs. Besides, the Photoluminescence study revealed the electron-hole pairs on the surface of the catalyst. The X-ray photoelectron spectroscopy (XPS) analysis exposed the chemical compositions (Zn, C & O) and the nanostructure's elemental state. The newly synthesized nano catalyst was applied to investigate the photocatalytic activity of Malachite Green dye under UV illumination. The photocatalyst (GP-ZnO-NPs) exhibited the decolorization of 89 % (10 mg/L) toxic MG dye within 180 min observation. The hexagonal nanoparticle structure creates a more active site to interact with the poisonous dye molecules to proceed the reaction fast. In addition, the nano catalyst can be used for five times without losing its activity. This study highly recommends the GP-ZnO-NPs to remove toxic dye for a safer environment as a greener nano catalyst.