Affiliation: Department of Medicine, Harvard Medical School, 221 Longwood Ave, MA 02115, USA.
This paper describes the synthesis of gold nanorods, gold nanospheres and gold nanostars using modified versions of existing seed-mediated growth methods. The nanoparticles have been characterized on the basis of their morphology and optical properties using transmission electron microscopy (TEM) and spectrophotometry. Gold nanorods were synthesized using ascorbic acid as reducing agent, gold nanospheres were synthesized using mercaptosuccinic acid as stabilizing/ reducing agent and gold nanostars were synthesized using ascorbic acid as reducing agent and silver ion as anisotropic growth agent. Gold nanorods showed a sharp absorbance spectrum with peaks at 447 nm and 715 nm. Gold nanospheres were spherical, non porous with a diameter of 14-59 nm. The nanospheres were polycrystalline and showed variable branch length that was dependent on the relative proportions of ascorbic acid and gold salts. The spectra of gold nanostars revealed a broad absorbance pattern in the range of 660-775 nm and 930-1000 nm that may be attributed to plasmon resonance of nanostar core and plasmon resonance of nanostar branches, respectively.