Thanin Putjuso

Investigation of structural, morphological, optical, and magnetic properties of Sm-doped LaFeO3 nanopowders prepared by sol–gel method

Pure orthorhombic phase of La1−xSmxFeO3 (x = 0, 0.1, 0.2, and 0.3) nanoparticles can be obtained by sol–gel method after calcination at 800 °C for 3 h in air. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge spectroscopy, ultraviolet-visible spectroscopy, and vibrating sample magnetometry were used to study the crystal structure, morphology, oxidation state, functional group, optical, and magnetic properties of samples. Pure orthorhombic phase of perovskite structure is confirmed by X-ray diffraction results. Decreasing lattice parameters, crystallite sizes, and cell volumes with increasing microstrains indicate structure distortion due to the substitution of Sm ions with small ionic radius on the La sites in the orthorhombic structure. Scanning electron microscopy and transmission electron microscopy images show a homogeneous distribution of almost spherical nanoparticles with decreasing average particle sizes ranging from 56.48 ± 3.22 to 23.21 ± 4.40 nm for samples of high Sm content. Fourier transform infrared spectroscopy spectra confirm the Fe–O stretching mode in octahedral FeO6 unit of a perovskite structure. X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy results indicate the oxidation states +3 of La and Fe ions. The optical band gaps are found to decrease from 2.218 to 1.880 eV with increasing Sm content. vibrating sample magnetometry results show the antiferromagnetic behavior of undoped sample and ferromagnetic behavior for doped samples, affecting by structure distortion and particle size reduction. Interestingly, the coercive field is significantly enhanced from 95.07 Oe (x = 0.1) to 13,062.79 Oe (x = 0.3). Curie temperature (Tc) is suggested to be above 400 K.Graphical AbstractThe magnetization curves of La1-xSmxFeO3 (x = 0.0, 0.1, 0.2, and 0.3) nanoparticles prepared by the sol-gel method with the inset show the comparing coercive forces (Hc) of the present work and the previous works, La0.7M0.3FeO3 (M = Al and Ga). Sm-doped LaFeO3 nanoparticles can exhibit ferromagnetic behavior with the significant enhancement of Hc from 95.07 to 13,062.79 Oe.

Magnetic and optical properties of Cu1−xFexO nanosheets prepared by the hydrothermal method

Cu1−xFexO (x = 0, 0.025, 0.05, 0.075, and 0.1) nanosheets can be sucessfully prepared by hydrothermal method at 160 °C for 3 h in a solution of 0.5 M KOH. X–ray diffraction results indicated a monoclinic phase of crystalline CuO nanosheets. Crystallite sizes and lattice constants were determined by Rietveld refinements of the X–ray diffraction peaks. The crystallite sizes significantly decreased from 28.46 to 21.71 nm with the increase of Fe content. Scanning electron microscopy and transmission electron microscopy revealed the plate-like shapes with the estimated width and length in the range of 50–170 and 100–275 nm, respectively. The optical band gaps (Eg) studied by ultraviolet-visible spectroscopy are found to decrease from 3.625 eV for undoped sample to 3.430 eV in Fe–doped CuO sample of x = 0.1. The magnetic properties of samples studied by vibrating sample magnetometry indicated a paramagnetic behavior for CuO nanosheets and ferromagnetic behavior in Fe–doped CuO nanostructures with the magnetization strongly depended on the Fe content. The ferromagnetism of Fe-doped samples was discussed base on the F-center exchange mechanism via oxygen vacancy defects.Graphical AbstractThis figure shows the magnetization of Fe doped CuO nanosheets synthesized at 160 °C for 3 h in 0.5 M KOH with SEM micrograph, showing the plate-like morphology. It can be seen in this figure that ferromagnetic behavior of CuO nanosheets can be induced by doping with Fe ion. Moreover, the optical band gaps of Fe-doped CuO nanosheets decrease with the increase of Fe content, suggesting that Fe-doped CuO nanosheets may be applied as photocatalytic materials. Ferromagnetism is proposed to be originated from the coupling of Fe3+ with the oxygen vacancy promoted in the samples.