Photocatalytic study and superparamagnetic nature of Zn-doped MgFe₂O₄ colloidal size nanocrystals prepared by...

Biocompatible Mg_1-xZn_xFe₂O₄ (x=0.2, 0.4, 0.5, 0.6 & 0.8) nanoparticles were synthesized by solvothermal reflux method. All compounds were crystallized in cubic spinel structure with slightly enhance of lattice parameter with biocompatible substituent Zn²⁺ concentration. All compounds were shown spherical geometry with average particle diameter is around 12nm (colloidal size). The spinel structure formation was confirmed by X-ray diffraction,electron diffraction, infrared, Raman shift measurements. Infrared analysis shows oleic acid coating on the surface of nanoparticles and TGA analysis shows that oleic acid desorbs from nanoparticle by decomposition at around 400°C. UV-Vis-NIR spectra show all the compounds show energy band gap in the semiconductor range (≈ 1.9eV). All compounds show superparamagnetic characteristics at room temperature with enhanced saturated mass magnetization (M_s) with Zn²⁺ concentration up to x=0.5 and then reduces with further enhance of x up to 0.8. The M_s changes were ascribed to occupation of Zn²⁺ at tetrahedral sites and proportional enhance of Fe³⁺ at octahedral sites. The enhanced Fe³⁺ concentration at octahedral sublattice leads to formation Fe³⁺-O^2--Fe³⁺ networks which favor antiferromagnetic interactions due to superexchange phenomenon. Photocatalytic activity of all compounds were studied through methylene blue (MB) degradation analysis. All compounds show ≈ 96% degradation of MB upon 70min irradiation of light on photoreactor vessel. In addition, photocatalytic activity (degradation efficiency) enhances with Zn²⁺ concentration in MgFe₂O₄. The Zn²⁺ substitution enhances both M_s and photocatalytic activity biocompatible of MgFe₂O₄ nanoparticles.