Spectroscopic Insights into Controlling Sidewall Faceting of TiO₂ 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.