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 CTAB, CTAB, and CTAB. 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.