Unravelling optical properties and morphology of plasmonic gold nanoparticles synthesized via a novel green route

A novel green way to synthesize plasmonic nanoparticles has been a dynamic field of research since decades as it produces ecofriendly, biocompatible, cost effective and less toxic nanoparticles. In this line, our work reports a greener route to prepare gold nanoparticles (AuNPs), by employing the bulb root segment of the banana tree. This green extract was found to possess potential application both towards reduction of the metallic ions along with proper capping of NPs. Formation of NPs in the colloidal solution was confirmed by initial colour change. The optical characteristics of the synthesized nanostructures were unravelled by investigating the spectrum obtained from UV-visible spectrophotometer. The colloidal dispersion containing AuNPs displayed a strong absorbance, approximately at around 530 nm. The average value of hydrodynamic diameter and the value of surface zeta potential of the synthesized nanoparticles were found to be approximately 44.26 nm and -22.9 mV, respectively, validating good stability of the nanoparticles. The field emission scanning electron microscope investigation disclosed the shape of the NPs to be roughly spherical. Images obtained from transmission electron microscope revealed that optimized synthesized NPs were of diameter ranging between 4 to 21 nm. X-ray diffraction pattern obtained displayed that the synthesized AuNPs possess a face-centred cubic crystalline structure. Fourier transform infrared spectroscopy analysis revealed the presence of a broad and intense peak of phenolic compounds, for both the extract and the NPs, revealing it to be the primary reducing and stabilizing group for synthesis of the nanoparticles. Further, surface plasmon resonance absorbance peak of as-synthesized AuNPs tallied with that of conventional chemical synthesis method, where the peak position of the biosynthesized nanoparticles remained almost constant with time.