Laser-assisted nanofabrication of multielement complex oxide core–shell nanoparticles

[Display omitted] •Synthesis of Cr2O3-Fe2O3 core-shell nanoparticles by nanosecond pulsed laser-induced dewetting of alloyed thin films.•The contact angle and shell thickness of nanoparticles remain almost consistent regardless of the nanoparticle size.•Core-shell formation is governed by the differences in cooling rate, surface energy, and mixing enthalpy of Cr2O3 and Fe2O3. Nanoparticles with core–shell motifs are of particular interest because they enable combining multiple functionalities at nanoscale. However, a key challenge in designing such novel structures is to phase-separate the constituents at the core and shell regions, especially in thermodynamically miscible systems. In this study, we report the successful formation of self-organized Cr2O3-Fe2O3 core–shell nanoparticles by adopting a non-equilibrium route of pulsed laser-induced dewetting of an alloyed thin film. In this process, the evolution of nanoparticles takes place from the rupture of the initially flat liquid-phase alloyed film under laser irradiation. A continued laser pulsing results in the ripening of the morphologies at different stages eventually leading to a final droplet shape nanoparticle. Using highly sensitive 3D chemical mapping of individual nanoparticles and thermal simulations, we reveal that thermodynamically-soluble Cr2O3 and Fe2O3 phase-segregate in the core and shell regions, respectively, within ∼ 100 ns during a fast solidification process, leveraging the difference in the cooling rates, surface energies and enthalpy of mixing at high-temperatures. With these results, we present a non-equilibrium laser-assisted pathway that can be used to create core–shell nanostructures with dissimilar characteristics.