Fabrication of gold nanoparticles with different morphologies in HEPES buffer

Gold nanoparticles with different morphologies, such as spindle, octahedron, and decahedron were obtained by using different molar ratios of HAuCl4/HEPES in the presence and absence of surfactants at room temperature. These nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microcopy (SEM), energy-dispersive X-rays analysis (EDX), and selected area electron diffraction (SAED). The kinetics of the formation of gold nanoparticles in HEPES buffer was studied by UV-visible spectrophotometer. The formation of gold nanoparticles was strongly dependent on the concentration of HEPES and pH value. The surfactants play a crucial role in the size and shape controlled synthesis of gold nanoparticles.