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

Abstract Colloidal nanocrystal assemblies (CNAs) of cuprous oxide (Cu 2 O) are controllably synthesized by in-situ self-assembling primary Cu 2 O nanocrystals, in which Cu 2 O CNAs assemblied by nanocrystals of 8–10 nm were about 0.6 μm and Cu 2 O 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 s ) values and 10 nm nanocrystal-based CNAs had the largest Ms value of about 9.2 emu/g. Electrochemical experimental results showed that submicron Cu 2 O CNAs were able to detect dopamine and uric acid quickly while micrometer Cu 2 O CNAs were not. Cu 2 O 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 Cu 2 O CNAs have been discussed and analyzed.