Synthesis of Cu Nanoparticles: Stability and Conversion into Cu₂S Nanoparticles by Decomposition of Alkanethiolate

A lean synthesis of copper nanoparticles (Cu NP) from CuCl 2 in dodecane via formation of Cu(I)–dodecanethiolate (Cu(I)-DDT) and their decomposition paths including spontaneous C–S bond cleavage of the alkanethiol on the surface of Cu NP is presented. The reduction of Cu(I)-DDT by the tert -butylamine–borane complex (TBAB) in dodecane under N 2 at elevated temperatures leads to the formation of thiol-protected Cu NP with narrow size distribution in the size range of 3–10 nm depending on the reaction conditions. The Cu NP in the presence of excess dodecanethiol reacts further to Cu 2 S NP under decomposition of the ligand on the particle surface. The Cu 2 S formation occurs after a short time at T > 175 °C or within ∼12 h at room temperature. If excess thiol is removed immediately after the synthesis, the resulting colloid shows irreversible aggregation within days or hours. Our results suggest that alkanethiols are not long-term stable on nanocopper surfaces and that the formation of copper(I) sulfide under the cleavage of the C–S bond occurs even at room temperature.