Preparation of copper oxide in smectites

Copper oxide nanoparticles were prepared in the interlayer spaces of sodium- and cetyltrimethylammonium-smectites by a titration of an aqueous solution of copper nitrate at 70°C in the presence of dispersed smectites. The resulting hybrids were characterized by powder XRD, SEM, TEM, TG-DTA, as well as FT-IR and UV-visible spectroscopies. A massive blue shift (from 490nm to 232-478nm) of the UV-visible absorption observed for the hybrids confirmed the formation of nanometer-sized copper oxide (3-7nm) in the interlayer spaces. A small amount of larger CuO particle with the size of around 0.6-2.9μm formed at the external surface of clay mineral particles. The nature of the broad absorption band (at around 490nm) of pure copper oxide and the hybrids with high copper oxide loading was attributed to the overlapping of the Cu²⁺ to O^2- charge transfer as well as d-d transition of copper oxide. The interactions with smectites played a role in stabilizing and protecting the formed copper oxide nanoparticles.