Nha Tran Thi Ngoc, Prakash Sankar Hari, Mohana Roopan Selvaraj, Samuel James Jebaseelan, Toan Dang Ngoc, Khan Dinh Thanh, Bich Do Danh, Thanh Tran Dang, Ngan Le Thi Tuyet, Manh Do Hung, Phong Pham Thanh
Graduate University of Science and Technology, Vietnam Academy of Science and Technology 18 Hoang Quoc Viet Hanoi Vietnam.
Chemistry of Heterocycles & Natural Product Research Laboratory, Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology Vellore Tamil Nadu India.
RSC Adv. 2025 Aug 21;15(36):29571-29592. doi: 10.1039/d5ra04897d. eCollection 2025 Aug 18.
MFeO (M = Co and Mn) nanoparticles were synthesized from coconut coir extract using a microwave-assisted co-precipitation method, representing a green and sustainable approach for ferrite nanomaterial preparation. The physical properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, photoluminescence, Raman spectroscopy, and vibrating sample magnetometry. Scanning electron micrographs revealed nanoscale morphology with evidence of polymorphism. Rietveld refinement confirmed the formation of single-phase spinel ferrites with lattice constants ranging from 8.4224 Å to 8.4782 Å for CoFeO and MnFeO, respectively. The distribution of metal cations at the tetrahedral and octahedral sites in the ABO spinel lattice was found to depend on the synthesis route and significantly influenced the magnetic and optical behaviors of the materials. Raman spectra exhibited characteristic peaks corresponding to a mixed spinel structure. The optical band gaps estimated from the UV-vis spectra were 2.66 eV for CoFeO and 2.64 eV for MnFeO. PL spectra showed four distinct emission peaks at 458, 692, 758, and 871 nm. Based on UV-vis and photoluminescence spectral results, a schematic energy band structure was constructed. Magnetic measurements, analyzed using the "law of approach" to saturation, revealed saturation magnetizations of 70 emu g (CoFeO) and 49 emu g (MnFeO) at 55 K-values that are among the highest reported for these systems; the squareness ratios were 0.58 and 0.12, respectively. The CoFeO sample exhibited high effective anisotropy due to surface spin contributions, resulting in high coercivity and squareness. In contrast, the enhanced dipolar interactions in MnFeO reduced coercivity and squareness. These magnetic behaviors were interpreted within the frameworks of the Stoner-Wohlfarth and superparamagnetic models that account for interparticle interactions.
采用微波辅助共沉淀法从椰壳提取物中合成了MFeO（M = Co和Mn）纳米颗粒，这是一种绿色可持续的铁氧体纳米材料制备方法。使用X射线衍射、扫描电子显微镜、紫外可见光谱、光致发光、拉曼光谱和振动样品磁强计对样品的物理性质进行了表征。扫描电子显微镜照片显示出纳米级形态并有多晶型的证据。Rietveld精修证实形成了单相尖晶石铁氧体，CoFeO和MnFeO的晶格常数分别为8.4224 Å至8.4782 Å。发现ABO尖晶石晶格中四面体和八面体位点上金属阳离子的分布取决于合成路线，并显著影响材料的磁性和光学行为。拉曼光谱显示出对应于混合尖晶石结构的特征峰。由紫外可见光谱估计的光学带隙，CoFeO为2.66 eV，MnFeO为2.64 eV。PL光谱在458、692、758和871 nm处显示出四个不同的发射峰。基于紫外可见光谱和光致发光光谱结果，构建了示意性能带结构。使用“趋近饱和定律”分析的磁性测量结果表明，在55 K时，CoFeO的饱和磁化强度为70 emu g，MnFeO的饱和磁化强度为49 emu g，这些值是这些体系中报道的最高值之一；矩形比分别为0.58和0.12。由于表面自旋贡献，CoFeO样品表现出高有效各向异性，导致高矫顽力和矩形比。相比之下，MnFeO中增强的偶极相互作用降低了矫顽力和矩形比。这些磁性行为在考虑颗粒间相互作用的斯托纳 - 沃尔法特和超顺磁模型框架内进行了解释。
