LAUSR

Abstract Colloidal nanocrystal assemblies (CNAs) of cuprous oxide (Cu2O) are controllably synthesized by in-situ self-assembling primary Cu2O nanocrystals, in which Cu2O CNAs assemblied by nanocrystals of 8–10 nm were about 0.6 μm and Cu2O 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 (Ms) values and 10 nm nanocrystal-based CNAs had the largest Ms value of about 9.2 emu/g. Electrochemical experimental results showed that submicron Cu2O CNAs were able to detect dopamine and uric acid quickly while micrometer Cu2O CNAs were not. Cu2O 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 Cu2O CNAs have been discussed and analyzed.