Strong Ferromagnetic, Dielectric Constant, and Photocatalytic Properties of a (Co, Mo) Modified Nanocrystalline ZnO Semiconductor

The nanocrystalline composition of Zn 0.95 Co 0.02 Mo 0.03 O revealed advanced and promising multifunctional characteristics for data and energy storage applications as well as environmental pollution treatment. Pure ZnO, Zn 0.97 Co 0.02 Mo 0.01 O, and Zn 0.95 Co 0.02 Mo 0.03 O samples were simply synthesized at 400 °C. For all samples, all X-ray diffraction (XRD) peaks were perfectly assigned to the zinc oxide (ZnO) compound with hexagonal structure. The relation between the ionic size of Zn 2+ , Co 2+ , and Mo 4+ ions, shift of XRD peaks, and variation of unit cell volume evidenced the actual substitution process. The insertion of Co 2+ and Mo 4+ ions spread the optical response of ZnO to the visible light spectrum by reducing its band gap energy from 3.25 to 2.9 and 2.8 eV. The scanning electron microscopy (SEM) micrographs of both codoped Zn 0.97 Co 0.02 Mo 0.01 O and Zn 0.95 Co 0.02 Mo 0.03 O samples display the formation of particles with sheets shaped like rose leaves and fine spherical particles. Magnetically, the composition of Zn 0.95 Co 0.02 Mo 0.03 O exhibits a strong ferromagnetic order at room temperature with perfect hysteresis loop nature and a high saturation magnetization of 1.11 emu/g. For energy storage uses, Zn 0.97 Co 0.02 Mo 0.01 O and Zn 0.95 Co 0.02 Mo 0.03 O samples exhibit a colossal dielectric constant (relative permittivity) of 11,560 and 21,019 at low frequency, respectively. The incorporation of (Co, Mo) significantly improved the sunlight-photocatalytic performance of the ZnO catalyst for depollution of stable Reactive Blue 19 (RB19) dye, leading to a total photodegradation efficiency of 98% in 75 min. In addition, the Zn 0.95 Co 0.02 Mo 0.03 O photocatalyst has a high stability for recyclability and a high ability to mineralize the RB19 dye to CO 2 and H 2 O. Graphical Abstract