Substrate-Mediated Growth of Au Nanowires Under Weak CTAB Control and Rapid Au Deposition

The selective Au deposition at the Au-substrate interface is known to give ultrathin Au nanowires and the synthesis usually employs strong thiol-based ligands. It is shown that, by increasing the rate of Au deposition, weak cetyltrimethylammonium bromide (CTAB) can be made to behave like a strong ligand, so that it induces Active Surface Growth and gives Au nanowires. The ligand strength also depends on the packing interactions in the ligand layer, in the order of C₁₄TAB, C₁₆TAB, and C₁₈TAB. The substrate-mediated growth under weak CTAB control is different in many ways from the previous studies, in terms of the huge imbalance in the inter-particle competition among the active sites, and the formation of nanosheets/nanobelts in defiance of Rayleigh instability of the active sites. With a small amount of chiral thiol-based ligand (glutathione), the strengthened control by mixed ligands gives orderly bifurcated nanowires, with a clear-cut transition from the initial nanosheets/nanobelts.