Pulsed laser-induced dewetting for the production of noble-metal high-entropy-alloy nanoparticles

Abstract

We report the production of quinary AgCuPdPtAu high-entropy-alloy (HEA) nanoparticles using the pulsed laser-induced dewetting (PLiD) technique, which is shown to be a facile approach applicable to both low- and high-melting-point metals. In addition, the atomic composition in the HEA nanoparticles can be controlled by varying the thickness of composite metal in the multi-layer thin films prior to dewetting. The instantaneous heating from the interaction of nanosecond laser pulse with metal and the ultrafast cooling rate involved in the PLiD process has uniquely positioned it as a non-equilibrium approach to facilitating the formation of HEA nanoparticles with the uniform atomic mixing of different metal elements. We studied the electronic structure and the charge redistribution in the produced AgCuPdPtAu HEA NPs by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES). The XPS valence band spectra with significant narrowing in the overall d band and the centroid further away from the Fermi level provide strong evidence for the d-orbital mixing and randomization of different metal components in the HEA nanoparticles. The d-charge redistributions among the constituent metal atoms of Ag, Cu, Pd, Pt, and Au have been further investigated using the XPS core-level spectra and XANES spectra of the five metals. The demonstrated viability of PLiD for the fabrication of HEA NPs and the results on the electronic structure and charge redistribution in the HEA NPs revealed by XPS/XANES would open up many opportunities for the future study of HEA NPs by X-ray spectroscopic techniques.