Synthesis of Gold Nano- and Microplates by Tryptophan and 5-Hydroxy-Tryptophan

L-Tryptophan and 5-Hydroxy-Tryptophan were used to synthesis the plate-like gold particles. The morphology of gold plates can be tunable from several nanometers to dozens of micrometers by changing reaction conditions. High temperature was not only increased the reaction ratio, but also changed the morphology of gold products. The size of gold plate was determined by the molar ratio of tryptophan to HAuCl4 . The pH value of HAuCl4 also played an important role in the formation of gold plates. One more hydroxyl group in the tryptophan enhanced the reducing ability of tryptophan, which was not suitable for the anisotropic growth.