The development of multifunctional materials, which integrate multiple functional components, is a rapidly evolving field with significant implications across various technologies [1-2]. Colloidal nanocrystals are exceptional building blocks for constructing complex architectures in random or controlled assemblies [3-4]. By co-assembling different types of nanocrystals into larger colloidal particles, particularly at the mesoscale, novel supraparticles can be engineered. These supraparticles, typically micrometers in size and composed of functionalized nanoparticles and molecular building blocks [5], combine the properties of their constituent nanocrystals while maintaining their colloidal stability [6]. Recent interest in these materials stems from their versatility and broad applicability. For example, incorporating magnetic nanoparticles into supraparticles offers diverse applications, including magnetic separation, hyperthermia, drug delivery, and magnetic imaging. Furthermore, the inclusion of non-magnetic functional metal oxide ligands (e.g., Al2O3 for catalysis, ZnO for semiconductors, TiO2 for photocatalysis) can further expand the potential of these innovative supraparticle systems [7-8].
Thus, our contribution aims to comprehensively explore the impact of the Atomic Layer Deposition (ALD) process of metal oxides on the magnetic signal, structure, and composition of iron oxide supraparticles. Through detailed Mössbauer analysis, we will demonstrate the oxidation-shielding properties afforded by specific metal oxides. Finally, using the Small-Angle Neutron Scattering with incident beam Polarization (SANSPOL) we will reveal the absence of intra-supraparticle structural displacement during the ALD process, along with increased internal ordering and a significant reduction in the magnetic "dead layer" size.
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