Microstructure, optical and magnetic properties of TiO2/CuO nanocomposites synthesized by a two-step method

TiO2/CuO composites in different ratios were prepared via a two-step method. X-ray diffraction and transmission electron microscopy results indicated that part of Cu2+ substituted Ti4+ in the TiO2 lattice in the composite, leading to Cu2+-substituted sites in the TiO2 lattice as well as Cu2+ species located in the CuO lattice. Scanning electron microscopy revealed a morphology change in the sample from a three-dimensional structure to a two-dimensional structure while forming an interface between TiO2 and CuO. X-ray photoelectron spectroscopy and Raman spectra showed that there are oxygen vacancies (VO) and Ti3+ in the lattice. UV-vis absorption spectra exhibited a widening of the absorption range and a decrease in the bandgap with increasing amount of CuO in the TiO2/CuO composites. Additionally, the composites exhibited room-temperature ferromagnetism (RTFM), as can be explained by the indirect double-exchange model, which is related to VO and the exchange interaction between the 3d orbitals of Ti3+ and Ti4+ at the interface.