Multicore iron oxide nanostructures (“nanoflowers”) have emerged as a unique class of functional materials whose properties cannot be explained by simple extrapolation from single-core nanoparticles. Their hierarchical architecture, consisting of primary crystallites coupled into coherent multicore assemblies (Fig. 1a), enables the engineering of magnetic, structural and surface phenomena often unachievable in single-core nanoparticles. In the context of Industry 4.0, where advanced materials must integrate high performance, configurability, multifunctionality, and compatibility with digital platforms, such nanostructures offer significant potential for catalytic and environmental applications.
In a series of recent and ongoing studies, we have systematically investigated how material composition, defect structure, surface chemistry, synthesis conditions, and multicore organization govern the functional properties of iron oxide nanoflowers. By integrating structural analysis (XRD), electron microscopy (TEM), XPS spectroscopy, magnetic characterization (SQUID), and calorimetric measurements under AC magnetic fields, we have established a unified framework for the design and optimization of these materials. A particular focus of our research is the surface chemistry and ability of these nanostructures to generate heat under AC magnetic fields (magnetic hyperthermia).
The successful design of materials with well-defined surface redox pairs and high hyperthermic efficiency enables their use as heterogeneous catalysts for the degradation of emerging organic pollutants.
Our previously published work on Gd3+-doped γ-Fe2O3 nanoflowers demonstrated that even very low doping levels (≤1.7 mol%) induce pronounced surface and bulk modifications while preserving the maghemite phase and multicore morphology [1]. Gd3+ incorporation generates redox-active surface defects, increases the Fe2+ fraction, promotes oxygen-vacancy formation, enhances magnetic anisotropy, and strongly influences magnetic hyperthermia efficiency [1]. These results demonstrate that controlled defect engineering within multicore architectures enables tuning of magnetic heating and surface ionic composition, which is essential for achieving multifunctional performance. Complementary work on Zn/Mn-modified γ-Fe2O3 nanoflowers has shown that heterovalent substitution leads to vacancies at octahedral sites within the spinel lattice, resulting in pronounced local structural distortions [2]. These defect-rich multicore nanostructures exhibit exceptional magnetic heating performance, with SAR values reaching 369 W/g and ILP values up to 5.77 nH·m2/kg [2].
Our ongoing work on optimizing polyol synthesis parameters shows that the reaction duration strongly influences crystallization behavior, particle aggregation, and the resulting hyperthermic performance of iron oxides. Nanoflowers synthesized at the optimal reaction time (4 h) exhibit high crystallinity, the smallest core sizes, the lowest coercivity, and the highest SLP/ILP values (Fig. 1b,c), confirming that process engineering plays a critical role in controlling functional properties. The surface and thermal characteristics of multicore iron oxide nanostructures are particularly important for their implementation in catalytic and environmental technologies. In our ongoing studies, we employ oxone (peroxymonosulfate) as a precursor of sulfate radicals, while the high heating efficiency of the nanoflower structures under
AC magnetic fields enables rapid and selective oxone activation. This synergistic effect, combining enhanced surface redox activity with localized heating under the AC field, is expected to significantly accelerate the degradation of the model pollutant Reactive Black 5.
