Impact of Gd3+ doping on structural, electronic, magnetic, and photocatalytic properties of MnFe2O4 nanoferrites and application in dye-polluted wastewater remediation.

The present work focuses on developing Gd-doped Mn spinel nanoferrites and their potential application in the photodegradation of water pollutants. The impact of Gd3+ ion substitution on structural, electronic, and magnetic characteristics of manganese ferrites has been studied. Nanocrystalline samples of MnGdxFe2-xO4 (x = 0.0 to 0.10, in step size of 0.02) ferrites were prepared via sol-gel self-ignition route. The Rietveld, XPS, HRTEM, and SAED characterization methods confirmed the formation of phase pure ferrite nanoparticles (~ 8-22 nm) in the cubic spinel structure. The Gd3+ content in these nanoferrites responded to a systematic reduction in the size of nanocrystallites and an upsurge in the density of nanoferrites. The XPS study revealed fine assimilation of constituent elements in the fcc lattice and ruled out impurities in the nanoferrites. The Fe and the Gd ions were found to be in Fe3+ and Gd3+ states, respectively. While a major fraction of the Mn ions were found to be in the Mn2+ state, a small fraction of Mn4+ ions was observed on the surface of nanoparticles. The nanoferrites were found to exhibit a soft ferromagnetic state from 300 to 20 K limits. The highest saturation magnetization was observed for x = 0.02 (MS = 66.6 emu/g at 20 K). The observed magnetic properties can be understood with the competing (Fe3+ and Mn2+)A-O2--[Fe3+, Mn2+, and Gd3+]B superexchange interactions and magnetocrystalline anisotropy. Due to the small band gap energy of Gd-doped Mn ferrites than that of the pure Mn ferrite, they have demonstrated excellent photocatalytic activity for the degradation of methylene blue (MB) dye under visible light illumination. As much as 96.35% of the MB dye was found to get degraded in 70 min of light illumination over synthesized nanoparticles and the photodegradation reaction followed pseudo-first-order kinetics. The increased optical absorbance due to lower band gap, suppressed recombination rate of charge carriers, and enhanced charge mobility make them effective visible light active photocatalysts. This study revealed that the electronic, optical, and magnetic properties of MnFe2O4 nanoferrites could be easily tuned by varying the Gd3+ content and the prepared Gd-doped MnFe2O4 nanomaterials have boundless potential to be utilized in the future making promising active photocatalysts and degradation of harmful industrial dyes for enhanced protection in the fields of environment and health care.

Electronic, optical and magnetic properties of Cu-doped ZnO, a possible system for eco-friendly and energy-efficient spintronic applications.

Polycrystalline Zn1-xCuxO (x = 0.0, 0.02, and 0.05) samples have been prepared using the solid-state reaction procedure. The X-ray diffraction (XRD) patterns of the samples confirm that Cu ions are successfully included in the ZnO hexagonal wurtzite structure. Rietveld analysis of the XRD patterns confirms the phase purity of the synthesized samples and a slight variation in their lattice parameter upon Cu doping. The morphology study by scanning electron microscopy (SEM) depicts transfiguration with Cu doping. The existence of oxygen vacancies (Vo) in the Cu-doped samples is indicated by X-ray photoelectron spectroscopy (XPS). The magnetization measurements reveal the diamagnetic nature of pure ZnO while the Cu-doped samples depict a room-temperature ferromagnetic (RTFM) behavior. The 2% Cu-doped sample shows higher values of both the saturation magnetization and the Vo as compared to the 5% Cu-doped sample. The observed magnetization seems to show a direct relationship with the Vo. The photoluminescence (PL) and ultraviolet (UV) spectroscopic measurements were performed for their optical analysis. The presence of Vo in the Cu-doped samples is revealed by the PL findings also that is in agreement with the XPS results. The UV analysis shows that Cu doping in the ZnO influences the band gap. The observed RTFM induced by Cu doping in ZnO renders it a potential system for spintronic devices useful for energy-efficient data storage devices and energy harvesting eco-friendly applications.