Annealing-induced highly-conductive and stable Cu–organic composite nanoparticles with hierarchical structures

Abstract To obtain high stability and electrical properties simultaneously is crucial for applications of Cu nanomaterials in microelectronics. In this work, multi-crystalline Cu nanoparticles were synthesized in the presence of PVP and SDS. Each as-grown particle was capped by a non-crystalline organic layer. The capped particles were only slightly oxidized after being stored under harsh ambient conditions for 3 months. Annealing at 250 °C and 500 °C in Ar was used to lower the electrical resistivity by five to six orders of magnitude. After being annealed at 250 °C, the original capping layer changed into a shell layer of thinner and uniform thickness. Although the electrical properties improved, oxidation of Cu into Cu 2 O was found during storage. Highly conductive and stable Cu–organic composite nanoparticles with hierarchical structures were obtained by heat treatment at 500 °C. The organics did not decompose completely but reacted with Cu to form a crystalline inner shell with a bcc structure and a non-crystalline outer shell. Small crystalline particles of 3–10 nm precipitated out within the outer shell layer and self-assembled on the surfaces of the Cu particle cores. The hierarchical Cu nanoparticles underwent no obvious enlargement and showed potential for fabricating electrical interconnections, sensors, and bionic structures.