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

Abstract

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.

Keywords

• Nanosecond pulsed laser deposition
• Multielement oxide
• Dewetting phenomenon
• Core–shell nanoparticles
• Atom probe tomography