Assembly of colloidal cuprous oxide nanocrystals and study of its magnetic and electrocatalytic properties

Colloidal nanocrystal assemblies (CNAs) of cuprous oxide (CuO) are controllably synthesized by in-situ self-assembling primary CuO nanocrystals, in which CuO CNAs assemblied by nanocrystals of 8–10 nm were about 0.6 μm and CuO CNAs assemblied by nanocrystals of 32 nm were about 1.8 μm. From room temperature magnetization measurement results, both of the CNAs showed ferromagnetic behavior with very small saturation magnetization (M) values and 10 nm nanocrystal-based CNAs had the largest Ms value of about 9.2 emu/g. Electrochemical experimental results showed that submicron CuO CNAs were able to detect dopamine and uric acid quickly while micrometer CuO CNAs were not. CuO CNAs formed by 8 nm nanocrystals showed the highest electrocatalytic activity in oxygen reduction reaction and displayed the best adsorptive ability to remove Congo red in aqueous solutions, which can be recylced after a simple heat treatment. Furthermore, the formation mechanism and the relationship between crystalline size and assembly of primary nanocrystals as well as physicochemical properties of CuO CNAs have been discussed and analyzed