Ultrasmall Cu2O nanocrystals: facile synthesis, controllable assembly and photocatalytic properties

In this work, we have successfully synthesized ultrasmall Cu2O nanocrystals with uniform sizes through a solution-based method. By virtue of the ideal Cu2O building blocks, 2D or 3D Cu2O superstructures can be easily achieved by tailoring the assembly process. The results indicate that diethyl carbonate (DEC) plays a crucial role for controlled self-assembly of Cu2O nanoparticles into a range of superstructures. Interestingly, the aggregative growths of Cu2O nanocrystals in the self-assembly process are accompanied by oriented attachment and Ostwald ripening. Furthermore, Cu2O and Cu2O–Au 3D colloidal spheres can be also obtained by an emulsion-based bottom-up self-assembly strategy. The results show that, compared with pure Cu2O nanospheres, the as-obtained Cu2O–Au nanospheres exhibit remarkable photocatalytic activities in the photodegradation of methyl orange (MO).