Role of Gd3+ and Ho3+ doping on the structure, physical properties and applications of ZnO

ZnO, Zn0.97Gd0.03O and Zn0.97Ho0.03O were prepared via a citrate auto-combustion method. X-ray diffraction (XRD) demonstrated that the investigated nanoparticles were prepared in a hexagonal structure, with crystallite sizes averaging between 12 and 60 nm. The morphology of the samples is illustrated by the field emission scanning electron microscope (FESEM) images. The paramagnetic behavior of the investigated nanoparticles is demonstrated by VSM. The value of the optical band gap (E-g) of Zn0.97Gd0.03O was higher than the E-g of ZnO due to the Moss-Burstein effect. Heavy metal Cd2+ ions from water are effectively adsorbed by rare earth-doped ZnO. At pH = 8, Zn0.97Ho0.03O exhibits a maximum removal efficiency of 91%. The Freundlich isotherm model fits the experimental results well.

Automated summary

ZnO, Zn0.97Gd0.03O, and Zn0.97Ho0.03O nanoparticles were prepared via a citrate auto-combustion method, exhibiting a hexagonal structure with crystallite sizes ranging from 12 to 60 nm according to X-ray diffraction. The morphology of the samples was observed using field emission scanning electron microscopy (FESEM). VSM revealed the paramagnetic behavior of the nanoparticles. The optical band gap (E-g) of Zn0.97Gd0.03O was higher than that of ZnO due to the Moss-Burstein effect, and rare earth-doped ZnO demonstrated effective adsorption of Cd2+ ions from water. At pH = 8, Zn0.97Ho0.03O achieved a maximum removal efficiency of 91%, and the Freundlich isotherm model provided a good fit to the experimental results.