Core/Frame Geometries Directly from the Gas Phase in Fe(Co)@Ag Nanocubes

The ability to engineer well-defined nanoparticles (NPs) and nanostructures in ever more complex configurations will increase functionality for nanoscale devices. However, controlling NP structure during physical synthesis, often required for CMOS-compatible electronic devices, is challenging, as it depends solely on process energetics and kinetics, and cannot be augmented by precursors or surfactants as in chemical methods. Here, we utilize a two-stage nucleation process during gas-phase condensation to control the secondary nucleation of Ag on Fe(Co) cubes, resulting in core/vertex, core/frame, and/or core/shell NPs. Τhe formation of core/frame nanostructures is attributed to the formation of two different growth zones inside a condensation chamber that contains a system with immiscible components and a stepwise nucleation process. The first nucleation event occurs inside the plasma and fosters a thermodynamically controlled growth process. The second occurs outside the plasma region where the particles grow in a more kinetically controlled environment; Ag shells/satellites form heterogeneously on already-formed Fe(Co) cubes. Our insights can help researchers optimize the design and engineering of complex nanostructures for applications in such areas as sensors, optics, magnetic recording, etc., and can create opportunities for industries dependent on high-vacuum processing that wish to incorporate NPs into devices.