Spectroscopic Insights into Controlling Sidewall Faceting of TiO ₂ Nanowires via Au–Ag Bimetallic Seeds

Precisely controlling the morphology and crystallographic features of single-crystalline, defect-free nanowires is key to advancing their applications. This study demonstrates that the local compositional heterogeneity within Au-Ag bimetallic seeds─specifically the presence of Ag-rich domains at a particular corner of the seed-nanowire interface─drives a transition from ⟨110⟩-oriented bead-like TiO₂ nanowires to ⟨111⟩-oriented prismatic nanowires during vapor-phase growth. The strong affinity between Ag and oxygen-containing growth species, as identified through X-ray absorption spectroscopy and electron energy loss spectroscopy, facilitates site-specific nucleation and lateral growth across the hexagonal seed-nanowire interface for prismatic nanowires. These findings underscore the critical role of localized seed composition at the seed-nanowire interface in governing nucleation behavior and enabling controlled nanowire morphology through seed engineering.