Plasma electrochemistry in ionic liquids: deposition of copper nanoparticles

We report on the synthesis of copper nanoparticles in two different water- and air-stable ionic liquids using plasma electrochemical deposition. The copper nanoparticles were deposited in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py-1,Py-4]Tf2N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf2N). To get information on the dimensions of the particles made, we have applied in situ transmission electron microscopy (TEM) (particles in ionic liquid). The chemical composition was investigated by ex situ X-ray photoelectron spectroscopy (XPS). We found that the copper particles produced in [Py-1,Py-4]Tf2N were larger in size compared to the particles obtained in [EMIm]Tf2N (roughly 20 vs. 10 nm). The chemical composition of the particle surface differs too. In both cases the particles are partly oxidised leading to a CuO shell, but the particles obtained in [Py-1,Py-4]Tf2N carry a lot of residues from the ionic liquid.