The polyol process: a unique method for easy access to metal nanoparticles with tailored sizes, shapes and compositions

Abstract

After about three decades of development, the polyol process is now widely recognized and practised as a unique soft chemical method for the preparation of a large variety of nanoparticles which can be used in important technological fields. It offers many advantages: low cost, ease of use and, very importantly, already proven scalability for industrial applications. Among the different classes of inorganic nanoparticles which can be prepared in liquid polyols, metals were the first reported. This review aims to give a comprehensive account of the strategies used to prepare monometallic nanoparticles and multimetallic materials with tailored size and shape. As regards monometallic materials, while the preparation of noble as well as ferromagnetic metals is now clearly established, the scope of the polyol process has been extended to the preparation of more electropositive metals, such as post-transition metals and semi-metals. The potential of this method is also clearly displayed for the preparation of alloys, intermetallics and core-shell nanostructures with a very large diversity of compositions and architectures.

Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

“…Besides the influence of the anion on the coordination of the metal cation, the deprotonation of polyol molecules has to be considered. Deprotonation of the polyol, for example by alkalization, greatly enhances its reducing ability . The deprotonation of EG is, however, also possible by acetate ions, disregarding acid dissociation constants.…”

“…Their chelating properties due to at least two hydroxyl groups per molecule compensate to some extent the lower polarity compared to water . They can also be used as mild reducing agents to obtain a variety of metallic micro‐ or nanoparticles . In the context of this so‐called polyol process the coordination behavior of the polyalcohol plays a crucial role for the feasibility and the particulate course of reduction reactions .…”

“…They can also be used as mild reducing agents to obtain a variety of metallic micro‐ or nanoparticles . In the context of this so‐called polyol process the coordination behavior of the polyalcohol plays a crucial role for the feasibility and the particulate course of reduction reactions . Thereby, the polyol molecules compete against other ligands, especially the anions of the metal salts used as starting materials.…”

Controlled Synthesis of Surfactant‐Free Water‐Dispersible Colloidal Platinum Nanoparticles by the Co4Cat Process

“…Colloidal dispersions are obtained by reduction of a metal complex in an alkaline solution of a polyol to form NPs at high temperature (e.g., >150 °C). Surfactants or polymers such as polyvinylpyrrolidone (PVP) are typically added to avoid NP aggregation, achieve size and morphology control, or tune colloidal properties such as water‐dispersibility . The use of additives is an approach equally predominant in the preparation of metal NPs in low‐boiling‐point solvents such as water, methanol, ethanol, or mixtures of methanol and water or ethanol and water .…”

Exchange Bias in Chemically Reduced FeCo Alloy Nanostructures

“…Recently, polyol process has evolved as a cost‐effective synthesis technique and has been proved to obtain composition‐controlled FeCo alloy nanoparticles within the shortest experimental time . However, much of the endeavor was to obtain shape control and better soft magnetic properties whereas size control remains a challenge. In this study, we report the EB in size‐reduced FeCo alloy nanostructures synthesized through chemical reduction employing polyol process.…”