Matched Ligands for Small, Stable Colloidal Nanoparticles of Copper, Cuprous Oxide and Cuprous Sulfide

Abstract

This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]_z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu₂ O or Cu₂ S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2 equivalents vs. [CuMes]_z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO₂ CR¹ ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO₂ CR² ) or di(thio)nonanoic acid, (HS₂ CR¹ ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu₂ O is preferentially coordinated by carboxylate ligands and Cu₂ S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection.

Keywords: colloids; copper; ligand effects; nanoparticles; organometallics.