Synthesis of Surface-Enhanced Raman Scattering-Active Gold Nanoflowers by 5-Hydroxytryptophan in Acidic Solution

We demonstrated a one-step synthesis of gold nanoflowers by 5-hydroxytryptophan (5-HTP) in acidic solutions at room temperature. The synthesized nanoflowers are 400 nm in dimension consisting of a solid core and many small petal-like nanoparticles (30-50 nm) in various directions. The shape, size and surface morphology of the gold nanostructure could be tuned by controlling the molar ratio of 5-HTP to HAuCl4 and HCl concentration. Examination of the nanoparticles at different reaction stages with transmission electron microscopy (TEM) reveals the shape evolutionary process of the nanoflowers to get a better understanding on their possible formation mechanism. Additionally, these gold nanoflowers exhibit a high SERS performance because of textured surface which is expected to provide many active sites.