Based on the discussed data, we proposed the growth mechanism (Figure ). The seed functioned as a core, as obtainable in other seed-mediated growth syntheses. The Ag + ions enabled the anisotropic growth of the gold nanomaterials, and the cation-π interaction between the metal ion and aromatic ring of BDAC determined the length of nanomaterials at the early stage. Afterward, the nanomaterials matured into GNBs in dozens of hours. This process is also related to the cation-π interactions between the metal ion and BDAC. We have a hypothesis that BDAC moderates the silver ion capping in the early stage to limit the anisorotopic rod-growth and in the late stage it somehow ss the GNBs wing formation, e.g., via accumulation of surfactants on the sides of nanomaterials. Silver ions induced rod shape as well known. BDAC would attract on the outer sides of maturing GNBs and prepend Ag + -Au surface interaction via cation-π interaction. Larger silver ion concentration condition and larger surfactant concentration condition, where surface micelle did not form well, resulted in relatively larger ratio of GNRs due to the lack of well obstacle of Ag+- Au interaction(Figure ) BDAC:CTAB=2:1 condition have enough amount of BDAC in first step but it was no enough to block the side of growth nanomaterial well so that some of nanomatrials had cross shapes(Figure and Figure ) The detail investigation of the GNB-formation mechanism is beneficial to the optimization of the GNB shapes for controlling the formation of LLPS droplets.