Magnetic, Pseudocapacitive, and H₂O₂-Electrosensing Properties of Self-Assembled Superparamagnetic Co_0.3Zn_0.7Fe₂O₄...

The present work explores the structural, microstructural, optical, magnetic, and hyperfine properties of Co_0.3Zn_0.7Fe₂O₄ microspheres, which have been synthesized by a novel template-free solvothermal method. Powder X-ray diffraction, electron microscopic, and Fourier transform infrared spectroscopic techniques were employed to thoroughly investigate the structural and microstructural properties of Co_0.3Zn_0.7Fe₂O₄ microspheres. The results revealed that the microspheres (average diameter ∼121 nm) have been formed by self-assembly of nanoparticles with an average particle size of ∼12 nm. UV-vis diffuse reflectance spectroscopic and photoluminescence studies have been performed to study the optical properties of the sample. The studies indicate that Co_0.3Zn_0.7Fe₂O₄ microspheres exhibit a lower band gap value and enhanced PL intensity compared to their nanoparticle counterpart. The outcomes of dc magnetic measurement and Mössbauer spectroscopic study confirm that the sample is ferrimagnetic in nature. The values of saturation magnetization are 76 and 116 emu g^-1 at 300 and 5 K, respectively, which are substantially larger than its nanosized counterpart. The infield Mössbauer spectroscopic study and Rietveld analysis of the PXRD pattern reveal that Fe³⁺ ions have migrated from [B] to (A) sites resulting in the cation distribution: (Zn²⁺ _0.46Fe³⁺ _0.54)_A[Zn²⁺ _0.24Co²⁺ _0.3Fe³⁺ _1.46]_BO₄. Comparison of electrochemical performance of the Co_0.3Zn_0.7Fe₂O₄ microspheres to that of the Co_0.3Zn_0.7Fe₂O₄ nanoparticles reveals that the former displays greater specific capacitance (149.13 F g^-1) than the latter (80.06 F g^-1) due to its self-assembled porous structure. Moreover, it was found that Co_0.3Zn_0.7Fe₂O₄ microspheres possess a better electrochemical response toward H₂O₂ sensing than Co_0.3Zn_0.7Fe₂O₄ nanoparticles in a wide linear range.