Facile and Green Synthesis of Monodisperse Sub-10 nm Copper and Tin Nanoparticles Using L-ascorbic Acid as a Reducing Agent

We report a simple, low-cost procedure for the synthesis of stable, monodisperse colloidal nanoparticles of copper and tin (Cu NPs and Sn NPs), with average sizes below 10 nm and a narrow size distribution. In the modified polyol method employed in this study, Cu2+ and Sn2+ ions in concentrated solutions are efficiently reduced to their zerovalent form (Cu0 and Sn0), by L-ascorbic acid at a mild reaction temperature (80 °C) under air without the need of additional surface protective agents or operating under an inert atmosphere. Inexpensive commercial metal precursors (CuCl2 and SnCl2) and solvents (water, ethylene glycol or diethylene glycol) were used. The resulting nanoparticles- Cu (FCC) and unconventional α-Sn phase- exhibit excellent chemical stability against oxidation and good colloidal stability over extended periods under air. They can therefore be safely further processed for various potential applications. The as-synthesized Cu NPs and Sn NPs were characterized by several techniques including transmission electron microscopy (TEM), UV-visible spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS).