Seed-mediated synthesis of gold tetrahedra in high purity and with tunable, well-controlled sizes.

We report a facile synthesis of Au tetrahedra in high purity and with tunable, well-controlled sizes via seed-mediated growth. The success of this synthesis relies on the use of single-crystal, spherical Au nanocrystals as the seeds and manipulation of the reaction kinetics to induce an unsymmetrical growth pattern for the seeds. In particular, the dropwise addition of a precursor solution with a syringe pump, assisted by cetyltrimethylammonium chloride and bromide at appropriate concentrations, was found to be critical to the formation of Au tetrahedra in high purity. Their sizes could be readily tuned in the range of 30-60 nm by simply varying the amount of precursor added to the reaction solution. The current strategy not only enables the synthesis of Au tetrahedra with tunable and controlled sizes but also provides a facile and versatile approach to reducing the symmetry of nanocrystals made of a face-centered cubic lattice.