Urea-assisted fabrication of Fe₃O₄@ZnO@Au composites for the catalytic photodegradation of Rhodamine-B

Abstract

A new chemical approach for the fabrication of Fe₃O₄ embedded ZnO magnetic semicondutctor composite is reported. The method consists in increasing the pH of the synthesis solution by the thermal decomposition of urea instead of using common alkaline agents, such as NaOH and NH₄OH. The material (Fe₃O₄@ZnO) was used as a platform for the fabrication of highly dispersed gold nanoparticles (~5 nm). The catalytic efficiency of the material, Fe₃O₄@ZnO@Au, was tested in the photodegradation of Rhodamine-B solutions, and prominent catalytic efficiency, stability, and recycling were achieved. A single portion of the catalyst could be used up to five times without significant loss of activity and its photodegradation efficiency was considered high even after the 12th cycle (56%). Catalyst separation after each batch could be easily achieved because of the intrinsic magnetic property of the material. Leaching monitoring of free Zn species during the fabrication of the catalyst suggests that the use of urea decreased substantially the formation of non-magnetic-semiconducting species and provided a higher mass yield of the magnetic composite compared to an analogous protocol using NaOH. The catalyst was also characterized by detailed structural and chemical analyses, such as transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and vibration sample magnetometer (VSM).