Intrinsic defect-induced magnetism and enhanced photocatalytic activity in Zn1−xZrxO (0.0 ≤ x ≤ 0.07) nanoparticles for spintronic device and photocatalytic application

Abstract

In this study, ZnO nanoparticles were synthesized by sol-gel auto combustion technique with and without Zr4+ doping. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), selected area diffraction pattern (SAED), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR). A rietveld refinement analysis was performed using fullprof software on the XRD patterns of ZnO and Zr4+ doped ZnO nanoparticles, analysis showed a hexagonal wurtzite structure with an average crystallite size between 19 and 15 nm. SEM were employed to examine the surface morphology. TEM used to determine the particle size and size distribution histogram. SAED pattern confirmed the single-crystalline wurtzite structure. The compositional stoichiometry was verified by energy dispersive spectroscopy (EDAX). The PL spectrum reveals UV emission at the near band edge, as well as defect-related blue and green emission. In the PL spectrum, the green emission of Zr doped ZnO nanoparticles correlates strongly with their magnetic properties.An oxygen vacancy defect was confirmed by EPR studies for Zr doped ZnO nanoparticles. Sample (x = 0.03) exhibited very high coercivity value due to higher oxygen vacancies (Vo). X-ray photoelectron spectroscopy showed the oxidation state of Zn and Zr4+ atoms exist as Zn2+ and Zr4+ in the ZnO structure respectively. A vibrating sample magnetometer (VSM) was used to quantify the magnetic properties. Field-dependent magnetization measurements show diamagnetic behavior for pristine and Zr (x = 0.01 mol) doped ZnO. However, other doped samples (x = 0.03, 0.05, and 0.07 mol) exhibited ferromagnetic behavior at room temperature due to intrinsic defects (Zni and Vo). A UV–visible absorption spectrum was used to determine the energy band gap. Compared with pristine ZnO nanoparticles, doped samples exhibit a redshift in absorption edge. In addition, the photocatalytic activity of synthesized samples was determined by degrading the dye methylene blue (M.B.) in the presence of sunlight. An extensive evaluation of the effect of Zr concentrations on photocatalytic degradation was conducted. Zr4+ doped ZnO nanoparticles exhibit emission peaks detected at 424, 446, and 573 nm. These emission peaks result from electron movement from the deep donor level, zinc interstitial (Zni), and oxygen vacancy(Vo), which ultimately leads to higher photocatalytic efficiency.