Effect of Calcination on Structural and Magnetic Properties of Co-Doped ZnO Nanostructures

Abstract

Diluted magnetic semiconductors have gained much interest in spintronics due to the involvement of both spin and charge. Among various diluted magnetic semiconductors ZnO, lightly doped with transition metals (Mn, Fe, Co, Ni, In, V, and Cr), has gained interest due to the presence of room temperature ferromagnetism. Amongst various dopants, cobalt is a potential candidate because its ionic radius (Co 2+ =0.58Å) is extremely close to zinc (Zn 2+ =0.6Å). Zinc acetate dihydrate and cobalt nitrate are used as precursor materials. Nanostructures are synthesized at a low temperature of 70˚C. The dopant concentration is varied as 1, 3, 5, 7 and 9wt. %. XRD results indicate formation of hexagonal wurtzite structure even under as-synthesized conditions. Crystallite size decreases from 22.7nm to 17.8nm as dopant concentration was increased in the range 0-7wt%. XRD of the samples with 7wt% Co concentration is calcined in the temperature range of 100-500°C. SEM images show nanostructures with grain size less than 50nm. Saturation magnetization increases from 5.07emu/g to 6.4emu/g as dopant concentration was increased to 7wt% under as synthesized conditions. Nanostructures calcined at 400˚C show highest saturation magnetization of 9.9emu/g. Magnetic hysteresis equivalent to that of multilayered structure is obtained after calcination of Co doped ZnO nanoparticles at 300 °C. Single layer of these synthesized Co doped ZnO can be used instead of complex structures in spintronic devices.

Synthesis and characterization of silver nanoparticle-decorated cobalt nanocomposites (Co@AgNPs) and their density-dependent antibacterial activity

“…Perhaps due to overlapping of both peaks, the cobalt peak could not be distinguished. The increased intensity ( I S3 > I S2 > I S1 ) of the major silver peak (111) reflected the improvement in crystallinity of the deposited material which might be due to the enhanced density of decorated crystalline AgNPs on the Co-cores [39,40]. Thus, XRD results confirmed the bimetallic (cobalt and silver) crystalline nature of our fabricated hetero-structured nanocomposites.…”

Bimetallic Copper–Iron Oxide Nanoparticle-Coated Leathers for Lighting Applications

“…The HRSEM micrograph of the calcined bimetallic Cu-IO NPs displays a similar spherical morphology with an average particle size of 54 ± 9 nm (Figure c). It should be noted that the nanoparticles seem to be agglomerated due to the heat treatment and lack of surface coating agents. , The results also show that the calcined bimetallic nanoparticles appear to be in contact aggregation form without the core–shell structures. The hydrodynamic particle size distributions of calcined IO NPs, Cu NPs, and Cu-IO NPs are shown in Figure d–f.…”

Ex Situ and In Situ Analyses of the Mechanism of Electrocatalytic Hydrogen Peroxide Production by CoxZn1–xO (0 < x < 0.018) Materials in Alkaline Media

“…This effect has been observed in Co-doped zinc oxide. − Zinc oxide (ZnO) is an n-type direct semiconductor with a wide band gap energy of 3.37 eV at room temperature and large exciton energy of 60 meV . Doping of Co 2+ in ZnO has been shown to produce an intense UV absorption peak at 3.84 eV and weak bands in the visible region (1.8–2.4 eV) owing to the incorporation of cobalt into the tetrahedral sites. ,, Furthermore, Co-doped ZnO has been reported to catalyze the oxygen reduction reaction (ORR) in alkaline media when combined with reduced graphene oxide …”

“…11 Doping of Co 2+ in ZnO has been shown to produce an intense UV absorption peak at 3.84 eV and weak bands in the visible region (1.8−2.4 eV) owing to the incorporation of cobalt into the tetrahedral sites. 9,12,13 Furthermore, Co-doped ZnO has been reported to catalyze the oxygen reduction reaction (ORR) in alkaline media when combined with reduced graphene oxide. Herein, we study the electrocatalytic activity of carbon-free Co x Zn 1−x O (0 < x < 0.018) materials toward the two-electron ORR pathway to produce hydrogen peroxide (H 2 O 2 ).…”