Application of microwave-assisted technology: a novel process to produce gold nanostars and their spectroscopy characterizations

Vo Ke Thanh Ngo et al 

Abstract

In this paper, we report a novel seed-mediated method for the preparation of gold nanostars using microwave irradiation. These gold nanostars are produced in different mixed solutions including anionic and zwitterionic surfactants, AgNO ₃ and ascorbic acid as reducing agent at room temperature by seed-mediated method using microwave irradiation. Moreover, microwave irradiation plays an important role in mediating the branched growth of the resultant gold nanostars by inducing anisotropic growth on the surfaces of initially formed spherical gold nanoparticles. The gold nanostars are characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and x-ray powder diffraction. It is shown that the gold nanoparticles were formed with star shape (size ranging from 50 to over 100 nm with different branches and aspect ratios (ratio of branch length to width)) and face-centered-cubic (fcc) crystalline structure. Polyethylene glycol (PEG) is used as capping agent to prevent the aggregation of gold nanostars after removing mixed surfactants.