Phase-Dependent Morphological Response of TiO 2 Nanorod Arrays to Nb Doping: Interplay of Surface Energetics and Adsorbate-Controlled Growth

The morphology of nanostructured TiO 2 is highly sensitive to surface energetics and adsorption during solution-phase growth, yet dopant-induced morphological changes are often interpreted solely in terms of surface energy modifications. Here, we systematically observed the effect of Nb doping on TiO 2 nanorod arrays by directly comparing rutile and anatase phases grown under adsorption-controlled conditions. Nb doping induces pronounced morphological changes in rutile TiO 2 nanorod arrays, including enhanced lateral growth and densification, whereas the corresponding effect in anatase TiO 2 nanorod arrays is markedly weaker. These contrasting responses cannot be fully explained by surface energy considerations alone. Additional experiments indicate that morphology is determined by the interplay between dopant-induced surface-energy modification and phase-specific adsorbate-controlled growth and nanocrystal assembly. This study shows that the morphological response of TiO 2 nanorod arrays to Nb doping is strongly phase dependent and provides a framework for interpreting dopant-induced morphological changes in nanostructured oxides.