A green approach to synthesize Au nanoplates using Morus indica L. fruit extract and their superior activities in catalysis and surface enhanced Raman scattering

Currently, the green synthesis of nanoparticles has been considered to be a more environmentally securer and cheaper alternative to chemical and physical methods of production of nanoparticles. Herein, we have described an efficient green method for the synthesis of anisotropic gold nanoparticles using Morus indica L. fruit extract. The formation and morphology of biosynthesized nanoparticles are investigated with the help of UV–Vis spectroscopy, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy techniques. UV–Vis spectroscopy results exibit double SPR peaks with a highly intensified longitudinal SPR peak. TEM and FESEM studies reveal the formation of anisotropic Au nanoplates. Reduction and stabilization by the polyphenol-based phytochemicals of the fruit is believed to be responsible for the anisotropic growth. Experimental evidences suggest that the concentration of plant extract to metal ratio plays a key role in the shape determination of the nanoparticles. Interestingly, anisotropic AuNPs (nanoplates) showed very high catalytic activity towards the reduction of p- nitrophenol to p-aminophenol in the presence of NaBH4. The rate constant value (k) for the reduction was found to be 0.235 min−1 which is much higher than most of the previous reports of plant-extract derived AuNPs. The developed Au nanoplates showed very good surface-enhanced Raman scattering (SERS) properties which makes it potentially applicable for biomolecule detection through surface-enhanced Raman scattering.