High-Yield Synthesis of Tetrahedral-Like Gold Nanotripods Using an Aqueous Binary Mixture of Cetyltrimethylammonium Bromide and Hexamethylenetetramine

We present an effective strategy to grow the uncommon highly anisotropic shape of tribranched gold nanoparticles (nanotripods) via the reduction of tetrachloroaurate ions (AuCl 4 − ) in an aqueous mixture of cetyltrimethylammonium bromide (CTAB) and hexamethylenetetramine (HMT) at room temperature. By simply optimizing the concentrations of HAuCl 4, NaOH, CTAB, and HMT, gold nanotripods with a dominant Y-shape tetrahedral-like morphology could be obtained in high yield (∼80%). While the in-plane growth to form gold nanotripods or branched gold nanocrystals with tips has been reported up to now, the present result exhibited three-dimensional nanostructural growth to form the tetrahedral-like shape of gold nanocrystals. The surface plasmon absorption of the formed gold nanotripods showed a strong peak around 670−800 nm depending on the size of nanotripods. The formation and transformation processes of gold nanotripods are discussed on the basis of the changes in absorption spectra.