The morphology of nanostructured TiO2 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 TiO2 nanorod arrays by directly comparing rutile and anatase phases grown under adsorption-controlled conditions. Nb doping induces pronounced morphological changes in rutile TiO2 nanorod arrays, including enhanced lateral growth and densification, whereas the corresponding effect in anatase TiO2 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 TiO2 nanorod arrays to Nb doping is strongly phase dependent and provides a framework for interpreting dopant-induced morphological changes in nanostructured oxides.
Kimura et al. (2026) studied this question.