Rapid Microwave-Assisted Synthesis of Silver Nanoparticles in a Halide-Free Deep Eutectic Solvent

Organosoluble silver nanoparticles (AgNPs) have been synthesized for the first time in a task-specific, halide-free, deep eutectic solvent (DES) using a simple and convenient wet chemical reduction route involving microwave (MW) heating with oleylamine (OAm) acting as a surfactant and reducing agent. Nanoparticle formation is extremely rapid and occurs within 30 s of microwave heating at 100 °C. The effects of various reaction parameters (e.g., synthesis temperature, MW irradiation time, maximal MW power, water content of the medium) on the size and uniformity of the prepared AgNPs have been elucidated in this study. The produced colloidal AgNPs were characterized using UV–vis spectroscopy and transmission electron microscopy (TEM), with the aim of identifying reaction parameters simultaneously achieving optimal particle yield and colloid uniformity. This work illustrates how the versatile nature of DESs can be exploited to create unconventional DESs designed for nanoscale tasks for which conventional (e.g., halide-containing) DESs may be poorly suited, further expanding the repertoire of these solvents as sustainable media for various nanoapplications.