N-Heterocyclic carbene-stabilized gold nanoparticles with tunable sizes

Abstract

A simple and straightforward synthesis of N-heterocyclic carbene (NHC)-protected gold nanoparticles is derived from (benz)imidazolium-AuX₄ complexes and NaBH₄ only. The proposed method allows size tuning, from 3 to 6 nm, by adding (benz)imidazolium bromide. Changing the reducing agent to tBuNH₂BH₃ shifts the size range to ca. 6–12 nm. A one pot protocol is also reported from AuCl, (benz)imidazolium bromides and NaBH₄, thereby providing an even more straightforward way of producing NHC-capped gold nanoparticles. In addition, X-ray photoelectron spectroscopy (XPS) is used to unambiguously evidence, on the nanoparticles, the covalent bond formed between the NHC and the surface gold atoms.