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.