Architectural control of seeded-grown magnetic-semicondutor iron oxide-TiO(2) nanorod heterostructures: the role of seeds in topology selection.
A colloidal nonaqueous approach to semiconductor-magnetic hybrid nanocrystals (HNCs) with selectable heterodimer topologies and tunable geometric parameters is demonstrated. Brookite TiO(2) nanorods, distinguished by a curved shape-tapered profile with richly faceted terminations, are exploited as substrate seeds onto which a single spherical domain of inverse spinel iron oxide can be epitaxially grown at either one apex or any location along their longitudinal sidewalls in a hot surfactant environment. The topologically controlled arrangement of the component material lattices, the crystallographic relationships holding between them, and strain distribution across individual heterostructures have been studied by combining X-ray diffraction and absorption techniques with high-resolution transmission electron microscopy investigations. Supported by such structural knowledge, the synthetic achievements are interpreted within the frame of various mechanistic models offering complementary views of HNC formation. The different HNC architectures are concluded to be almost equivalent in terms of surface-interface energy balance associated with their formation. HNC topology selection is rationalized on the basis of a diffusion-limited mechanism allowing iron oxide heterogeneous nucleation and growth on the TiO(2) nanorods to switch from a thermodynamically controlled to a kinetically overdriven deposition regime, in which the anisotropic reactivity offered by the uniquely structured seeds is accentuated under high spatially inhomogeneous monomer fluxes. Finally, the multifunctional capabilities of the heterostructures are highlighted through illustration of their magnetic and photocatalytic properties, which have been found to diverge from those otherwise exhibited by their individual material components and physical mixture counterparts.
Buonsanti
Raffaella
R
Scuola Superiore ISUFI, Università del Salento, Distretto Tecnologico ISUFI, via per Arnesano km 5, 73100 Lecce, Italy.
Grillo
Vincenzo
V
Carlino
Elvio
E
Giannini
Cinzia
C
Gozzo
Fabia
F
Garcia-Hernandez
Mar
M
Garcia
Miguel Angel
MA
Cingolani
Roberto
R
Cozzoli
P Davide
PD