Surfactant-Free Colloidal Syntheses of Gold-Based Nanomaterials in Alkaline Water and Mono-alcohol Mixtures

Gold nanoparticles (Au NPs) and gold-based nano materials combine unique properties relevant for medicine, imaging, optics, sensing, catalysis, and energy conversion. While the Turkevich-Frens and Brust-Schiffrin methods remain the state-ofthe-art colloidal syntheses of Au NPs, there is a need for more sustainable and tractable synthetic strategies leading to new model systems. In particular, stabilizers are almost systematically used in colloidal syntheses, but they can be detrimental for fundamental and applied studies. Here, a surfactant-free synthesis of size-controlled colloidal Au NPs stable for months is achieved by the simple reduction of HAuCl4 at room temperature in alkaline solutions of low-viscosity mono-alcohols such as ethanol or methanol and water, without the need for any other additives. Palladium (Pd) and bimetallic AuxPdy NPs, nanocomposites and multimetallic samples, are also obtained and are readily active (electro)catalysts. The multiple benefits over the state-of-the-art syntheses that this simple synthesis bears for fundamental and applied research are highlighted.

Automated summary

This article introduces a surfactant-free synthesis method for gold nanoparticles, which can achieve stable and size-controlled colloidal gold nanoparticles for months by reducing HAuCl4 with low-viscosity mono-alcohols and water at room temperature in alkaline solutions, without the need for other additives. Pd and bimetallic AuxPdy NPs, nanocomposites, and multimetallic samples can also be obtained and act as active (electro)catalysts. This simple synthesis method has multiple advantages over the state-of-the-art syntheses in fundamental and applied research.