The influence of the alkyl chain length of the bis(trifluoromethylsulfonyl)imide-based ionic liquids 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-methyl-3-octylimidazolium, and 1-decyl-3-methylimidazolium cation on the potential window was investigated with low-index Au single crystal electrodes by cyclic voltammetry. The potential window of the electrical double-layer region was found to depend on the crystallographic orientation of Au, which indicated a difference in the strength of cation adsorption on the Au substrate. The potential window of the electrical double-layer region was also dependent upon the alkyl chain length of the imidazolium cation. (c) 2012 Elsevier B.V. All rights reserved.