Use of Alcea rosea leaf extract for biomimetic synthesis of gold nanoparticles with innate free radical scavenging and catalytic activities

Gold nanoparticles (AuNPs) are important because of their wide usages in medical applications, opto-electronic devices, biosensor, and catalysis. Here in, we have developed a low-cost, facile, eco-friendly and efficient approach for green synthesis of AuNPs by reduction of gold ions into stable AuNPs using Alcea rosea aqueous leaf extract. The synthesized A. rosea-AuNPs were characterized by different techniques such as UV-visible, TEM, SEM, EDX, XRD, FTIR and Zeta sizer. TEM images displayed that the A. rosea leaf extract could produce triangular, pentagonal, hexagonal and spherical nanoparticles with varying sizes (4-95 nm), while XRD demonstrated crystalline structure of synthesized A. rosea-AuNPs. The FTIR spectrum showed different functional groups, which may be responsible for reducing gold ions to metallic A. rosea -AuNPs. The yield of A. rosea-AuNPs synthesized by this study was around 99.99%. Such very high yield of AuNPs demonstrates the plentiful biomolecules in the A. rosea leaf extract for sufficient reduction of Au(III) ions, and the quite high efficiency of this biosynthesis methods. The as obtained AuNPs exhibited antioxidant activity against DPPH and ABTS radicals, as well as catalytic activity in degradation of 4-nitrophenol pollutant. The results represent potential applications of these nanoparticles in the biomedical and industrial applications. (C) 2018 Elsevier B.V. All rights reserved.