The interesting electrochemical, solubilizing, and complexing features of deep eutectic solvents (DESs) make them fascinating media for tailored nanoparticle synthesis. In this work, we demonstrate the utility of task-specific DESs as designer solvents for the scaled-up synthesis of high-quality coinage metal nanoparticles using both batch and continuous flow approaches. Oleylamine as cosolvent, reductant, and colloid capping agent has been used to produce large amounts of high-quality monodispersed metal nanocrystals using both conventional heating and simple microwave-mediated reduction. A silver-based deep eutectic solvent containing silver triflate as the metal precursor resulted in a high colloidal concentration of 500 mM. Similarly, concentration as high as 1000 mM for Ag and 400 mM for Au was achieved with dimethylammonium nitrate−polyol deep eutectic solvents with their extraordinary metal dissolution properties. When translated to a continuous flow millifluidic synthesis at a moderate flow rate of 0.24 mL min<sup>−1</sup>, a 1000 mM AgNO<sub>3</sub> reaction mixture produced 26 mg of silver nanoparticles per minute. Surprisingly, a “size-focusing” effect was observed in the highly concentrated regime producing nanocrystals with RDS as low as 8.8%. A full preservation of nanoparticle size, morphology, monodispersity, and colloidal stability was observed after an efficient phase transfer of the oleylamine-capped gold and silver nanocrystals from nonpolar solvent (toluene) into aqueous solution by applying a ligand-exchange reaction using 11-mercaptoundecanoic acid. This work highlights the utility of DESs as high-performance media to further push colloidal nanocrystal output in future nanomanufacturing efforts.

Colloidal metal nanoparticle synthesis in deep eutectic solvents

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.