Colloidal semiconductor/magnetic heterostructures based on iron-oxide-functionalized brookite TiO2 nanorods

Abstract

A flexible colloidal seeded-growth strategy has been developed to synthesize all-oxide semiconductor/magnetic hybrid nanocrystals (HNCs) in various topological arrangements, for which the dimensions of the constituent material domains can be controlled independently over a wide range. Our approach relies on driving preferential heterogeneous nucleation and growth of spinel cubic iron oxide (IO) domains onto brookite TiO2 nanorods (b-TiO2) with tailored geometric parameters, by means of time-programmed delivery of organometallic precursors into a suitable TiO2-loaded surfactant environment. The b-TiO2 seeds exhibit size-dependent accessibility towards IO under diffusion-controlled growth regime, which allows attainment of HNCs individually made of a single b-TiO2 section functionalized with either one or multiple nearly spherical IO domains. In spite of the dissimilarity of the respective crystal-phases, the two materials share large interfacial junctions without significant lattice strain being induced across the heterostructures. The synthetic achievements have been supported by a systematic morphological, compositional and structural characterization of the as-prepared HNCs, offering a mechanistic insight into the specific role of the seeds in the control of heterostructure formation in liquid media. In addition, the impact of the formed b-TiO2/IO heterojunctions on the magnetic properties of IO has also been assessed.

Biofunctionalization of Anisotropic Nanocrystalline Semiconductor–Magnetic Heterostructures

“…This interpretation is consistent with recent work reported by Buonsanti et al, who observed a larger anisotropic energy barrier in match-stick Fe x O y /TiO 2 nanostructures with respect to physical mixture of Fe x O y nanoparticles and TiO 2 nanorods and attributed it to the enhanced shape and surface anisotropy contribution and/or to the modification of local magnetic ordering due to interfacial strain. 27,28 Finally, it is worthwhile to note that NCs and BNCs exhibit a different approach to saturation, as clearly evidenced by the first magnetization curves normalized to the saturation value extrapolated from the fitting of high-field M vs 1/H data. As an example, although NCs are close to saturation at a relatively moderate field (M at 1 T is 0.85M s ), BNCs require fields larger than 4 T to reach the same percentage of saturation ( Figure 6).…”

Mechanochemical Synthesis and Characterization of Molybdenum Dioxide-Hematite Nanostructures with Different Molarities

“…We chose this additional system to be hematite, as hematite has various applications in scientific and industrial fields and can be used as semiconductor compound [9], magnetic material [10], catalyst [11] and gas sensor [12]. In particular, nanocrystalline hematite obtained by high-energy ball milling was found to exhibit decreased grain size, expansion of lattice parameters and two kinds of particles which coexist in the sample: Nanostructured and micrometer hematite [13].…”

Interfacial strain and defects in asymmetric Fe–Mn oxide hybrid nanoparticles

“…26,27 For example, combining iron oxide and manganese oxide into a spherical core|shell nanoparticle using a seed-growth mediated method resulted in an inorganic hybrid nanomaterial with strong antiferromagnetic (AFM) coupling. nanorods, [34][35][36][37] tetrapods, 32 branched nanomaterials 38 and other morphologies 33,39 . 24,30,31 The shape anisotropy and crystal structure 32 of the preformed seeds as well as control of the synthetic conditions 33 have been shown to direct the subsequent growth of the second phase.…”