PNNL

Abstract

In this report we show that the size, shape, and composition of pre-synthesized metal nanoparticles can be engineered through exploiting concurrent interparticle coalescence and interfacial copper-thiolate cleavage under a thermally-activated evolution process. This concept is demonstrated by thermally-activated processing of ultrafine (~0.5 nm) copper nanoparticles encapsulated with thiolate monolayer (Cun(SR)m) toward copper sulfide nanodiscs with controllable sizes and shapes. It involved a thermally-activated coalescence of Cun(SR)m nanoclusters accompanied by interfacial Cu-S cleavage towards the formation of Cu2S nanocrystals with well-defined nanodisc shapes with an average diameter and thickness ranging from 10.7 ±1.4 nm and 5.5 ±0.5 nm (aspect ratio ~2) to 31.2 ±4.3 nm and 3.9 ±0.4 nm (aspect ratio ~7) depending on the thermal processing parameters. These nanodiscs are stable and display remarkable ordering upon self-assembly. The abilities to create the ultrafine copper nanoclusters and to enable them to undergo a thermally-activated coalescence and a concurrent Cu-S bond cleavage toward the formation of Cu2S nanodiscs is entirely new. The viability of fine tuning the size and shape of the Cu2S nanocrystals by controlling the relative binding strength of thiolates, the C-S cleavage reactivity, and the interparticle coalescence activity, and their potential applications in electronic, sensing and photochemical devices are also discussed.