Formation of 1 nm-sized gold clusters with long-stability in an ionic liquid is reported. Formation via a three-stage process is suggested. Cluster growth from gold nuclei takes place according to the Lifshitz–Slyozov–Wagner (LSW) model followed by oriented attachment to form colloidal stable clusters.

Abstract

We report on gold clusters with around 62 gold atoms and a diameter of 1.15±0.10 nm. Dispersions of the clusters are long-term stable for two years at ambient conditions. The synthesis was performed by mixing tetrachloroauric acid (HAuCl₄ ⋅ 3 H₂O) with the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) at temperatures of 20 to 80 °C. Characterization was performed with small-angle X-ray scattering (SAXS), UV-Vis spectroscopy, and MALDI-TOF mass spectrometry. A three-stage model is proposed for the formation of the clusters, in which cluster growth from gold nuclei takes place according to the Lifshitz-Slyozov-Wagner (LSW) model followed by oriented attachment to form colloidal stable clusters.