One-step synthesis and characterisation of chitosan-mediated micro-sized gold nanoplates through a thermal process

Most of the synthesising methods of gold nanoplates reported to date rely heavily on the use of chemical reducing agents such as N, N-dimethylformamide, sodium borohydride or other organic compounds. All of these chemicals are highly reactive and may pose potential biological risks. A simple, convenient and economical route for the mass synthesis of single-crystalline, micro-sized, polygonal gold nanoplates using chitosan as a reducing/capping agent is reported. The nanoplates possess well-defined shapes with sharp edges confirmed by scanning electron microscopy. The gold nanoplates are single crystals bound primarily by (1 1 1) lattice planes, as revealed by both selected area electron diffraction and powder X-ray diffraction. These large gold nanoplates had strong absorption in the near-infrared region. The concentration and molecular weight of chitosan are important factors for the morphology and size control of the final product. This facile approach may be extended to the synthesis of some other metal nanostructures.