Microwave-assisted synthesis of mesoporous high-entropy alloy and core-shell nanoparticles

Mesoporous high-entropy alloy nanoparticles (mp-HEA NPs) are an emerging class of nanostructured materials that bring together the distinctive solid-solution structure and multi-element compositions of their non-porous counterparts and highly accessible surfaces that characterize mesoporous materials. In this study, we present the facile synthesis of mp-HEA NPs (RhAgCuPdPt) via microwave-assisted heating. The structural, compositional, and morphological characteristics of the mp-HEA NPs were assessed using Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). We subsequently extended our approach to realize mesoporous Au core-HEA (RhAgCuPdPt) shell NPs (Au-HEA NPs) and investigated the thermal conversion of the Au-HEA NP to HEA NPs (AuRhAgCuPdPt) using in situ heating TEM. We determined that this conversion involves gradual grain growth at temperatures below 600 °C followed by a rapid grain growth process at elevated temperatures accompanied by the collapse of the mesostructure.