This project aims to examine the structure of microemulsions formed by water and 1-methyl-3-ethylimidazolium-based ionic liquids with the acetate or octanoate anion. These systems have previously been studied as media for in situ CuO nanoparticles (NP) formation, but the resulting NP have distinctly differing sizes. It is believed that the size of the NP formed is a result of the presence of polar domains formed in the IL/water mixture, and are clearly driven by the contrasting properties of the anion. We propose to examine the differences in liquid structure between the two IL/water systems to determine important factors relevant to the control of the size of NP formed in the relevant processes. Such information would permit rational design and tailoring of ionic liquid-based systems which provide specific NP sizes for use in varied applications such as gas sensing and semiconductors.