Colloidal Synthesis of Nanoparticles: from Bimetallic to High Entropy Alloys

TL;DR

This paper presents a colloidal synthesis method for creating monodisperse, multi-metallic nanoparticles, including high entropy alloys, with controlled composition and size, overcoming challenges of phase segregation in complex alloys.

Contribution

It introduces a novel colloidal route for synthesizing high entropy alloy nanoparticles with uniform composition and size, based on precursor properties and temperature-assisted reduction.

Findings

Successful synthesis of monodisperse bimetallic to pentametallic nanoparticles.

Correlation between precursor degradation temperatures and reduction potentials.

Homogeneous distribution of multiple elements within nanoparticles.

Abstract

At the nanometric scale, the synthesis of a random alloy (i.e. without phase segregation, whatever the composition) by chemical synthesis remains a not easy task, even for simple binary type systems. In this context, a unique approach based on the colloidal route is proposed enabling the synthesis of face-centred cubic and monodisperse bimetallic, trimetallic, tetrametallic and pentametallic nanoparticles with diameters around 5 nm as solid solutions. The Fe-Co-Ni-Pt-Ru alloy and its subsets are considered which is a challenging task as each element has fairly different physico-chemical properties. Nanoparticles are prepared by temperature-assisted co-reduction of metal acetylacetonate precursors in the presence of surfactants. It is highlighted how the correlation between precursors' degradation temperatures and reduction potentials values of the metal cations is the driving force to achieve a homogenous distribution of all elements within the nanoparticles.