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

Abstract

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 (Eg) of Zn0.97Gd0.03O was higher than the Eg 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.

Evaluation of the optical and magnetic properties of novel Nd0.9Zn0.1FeO3 perovskite nanoparticles and their adsorption of Pb2+ ions from water

“…The optical band gap (E g ) of Zn-doped NdFeO 3 can be determined using the Tauc plot. Equation ( 12 ) represents the Tauc equation 18 , 35 . where A is a constant.…”

“…The adsorption process is affected by many parameters, such as contact time, the surface area of the nanoparticles, the porosity of the samples, the pH value, and the function groups on the surface of the adsorbent materials. The good adsorbent materials of heavy metals are characterized by their thermal stability, such as zeolites 11 , graphene 12 , activated carbon 13 , zero-valent iron 14 , agricultural waste 15 , magnetic materials 16 , 17 , ZnO 18 , chitosan derivatives 19 – 22 , BaTi 0.8 Zr 0.2 O 3 23 , and pectin‑ based biohydrogels 24 . Also, ferrite materials have received great attention from scientists for the removal of HMs from water 25 , 26 due to their properties, such as being easy to prepare, thermal stability, and magnetic properties, which allow them to be extracted from the water by an external magnet and regenerated another time.…”

Highly efficient lead removal from water by Nd0.90Ho0.10FeO3 nanoparticles and studying their optical and magnetic properties

“…The average crystallite size (L) of the sample was estimated from all peaks using the Scherer formula, which is represented by the following equation 30 : where λ denotes the X-ray wavelength, β is the full width at half maximum, and θ is the Bragg angle. The value of L is 39.136 nm, which indicates the sample was prepared at the nanoscale.…”