A mini-review on AFe2O4 (A = Zn, Mg, Mn, Co, Cu, and Ni) nanoparticles: Photocatalytic, magnetic hyperthermia and cytotoxicity study

We report on the performance of density functional theory (DFT) with the Tran–Blaha modified Becke–Johnson exchange potential and the random phase approximation dielectric function for optical constants of semiconductors in the ultraviolet–visible (UV-Vis) light region. We calculate optical bandgaps Eg, refractive indices n, and extinction coefficients k of 70 semiconductors listed in the Handbook of Optical Constants of Solids [(Academic Press, 1985), Vol. 1; (Academic Press, 1991), Vol. 2; and (Academic Press, 1998), Vol. 3] and compare the results with experimental values. The results show that the calculated bandgaps and optical constants agree well with the experimental values to within 0.440 eV for Eg, 0.246–0.299 for n, and 0.207–0.598 for k in root mean squared error (RMSE). The small values of the RMSEs indicate that the optical constants of semiconductors in the UV-Vis region can be quantitatively predicted even by a low-cost DFT calculation of this type.

Assessing the performance of the Tran-Blaha modified Becke-Johnson exchange potential for optical constants of semiconductors in the ultraviolet-visible light region

Elaboration and Experimental Investigation of Zn-Ni-Co Spinel Ferrite Multi-doped Rare-Earth (Gd, Er, and Sm) Prepared by Coprecipitation Method

Investigation of the electronic structure of contending battery electrode materials is an essential step for developing a detailed mechanistic understanding of charge-discharge properties. Herein, we use synchrotron soft X-ray absorption spectroscopy (XAS) in combination with complementary experiments and density functional theory calculations to map the electronic structure, band positioning, and band gap of prototype vanadium(III) phosphate cathode materials, Na3V2(PO4)3, Li3V2(PO4)3, and K3V3(PO4)4·H2O, for alkali-ion rechargeable batteries. XAS fluorescence yield and electron yield measurements reveal substantial variation in surface-to-bulk atomic structure, vanadium oxidation states, and density of oxygen hole states across all samples. We attribute this variation to an intrinsic alkali metal surface depletion identified across these alkali metal vanadium(III) phosphates. We propose that an alkali-depleted surface provides a beneficial interface with the bulk structure(s) that raises the Fermi level and improves surface charge transfer kinetics. Furthermore, we discuss how this effect can play a significant role in reducing the electronic and ionic diffusion limitations of alkali vanadium phosphates in alkali-ion rechargeable batteries. These findings clarify the electronic structure and properties of alkali metal vanadium phosphates and offer guidance on future strategies to improve vanadium phosphate battery performance.

Validating the Electronic Structure of Vanadium Phosphate Cathode Materials.

ZnFe2-x-yGdxSmyO4 (x = y = 0.01) ferrite nanoparticles with average size of 5 nm are synthesized by the co-precipitation method for the first time. X-Ray Diffractometer (XRD) revealed the formation of single-phase spinel with a high crystallinity. Fourier Transform Infrared (FTIR) confirmed the formation of spinel matrix crystallographic sites and Transmission Electron Microscopy (TEM) confirmed the formation of agglomerated spherical particles with nanometric sizes. The analysis of magnetic properties indicates a week ferrimagnetic behavior at low temperatures, while a superparamagnetic behavior is observed at high temperatures. The blocking temperature value is 55 K. A DFT study was performed on the normal, mixed and Sm–Gd co-doped spinel zinc ferrite using the GGA + U method to evaluate their ground state magnetic spin configuration and the effect of Sm3+ and Gd3+ doping on the structural, magnetic and electronic properties of zinc ferrite nanoparticles. It is found that the nanomaterial is most likely to adopt a ferrimagnetic spin arrangement with a degree of inversion close to 0.5. These results suggest that this material has significant function in the industry, which could be beneficial in point of view for telecommunication applications.

New nanosized (Gd3+, Sm3+) co-doped zinc ferrite: Structural, magnetic and first-principles study

Monoclinic α‐NaVOPO4 as cathode materials for sodium‐ions batteries: Experimental and DFT investigation

Monoclinic lithium vanadium phosphate Li3V2(PO4)3 is a very promising cathode candidate for applications in Li-ion batteries, with a high operational voltage (~ 4 V vs. Li+/Li) and a high theoretical capacity of 197 mAh/g. However, the underlying electrochemical mechanism of monoclinic Li3V2(PO4)3 is not yet fully understood, due to its complexity. To gain more knowledge about the electrochemical performance of the monoclinic Li3V2(PO4)3, we perform density functional calculations of structural, electrochemical, electronic, and magnetic properties of LixV2(PO4)3 for x = 3, 2, 1, based on the full-potential linearized augmented plane wave (FP-LAPW) method. The generalized gradient approximation corrected with the present work self-consistently calculated Hubbard parameter U (GGA+U method) shows that it can successfully reproduce the experimental average lithium intercalation voltage for the redox couple V4+/V3+ within 7% error, and within 2% error for the transition x: 3 ➔ 2. The present work method is fully ab initio and without any arbitrary parameters. In the literature, the existence of charge ordering in Li2V2(PO4)3 is subject to discrepancy. By analyzing the present calculated structural, magnetic, and electronic properties of Li2V2(PO4)3, the existence of charge ordering had been confirmed. The present work method sets the path for accurately predicting the redox potential of future lithium and sodium phosphate compounds for the next-generation batteries technology.

https://link.springer.com/content/pdf/10.1007/s10008-020-04808-7.pdf

Structural, electrochemical, electronic, and magnetic properties of monoclinic LixV2(PO4)3 for x = 3, 2, 1 using first-principles calculations

For the time we investigated the structural, optical and magnetic properties of (Sm, Gd) co-doped TiO2 anatase nanoparticles, in addition to Sm-doped TiO2 anatase nanoparticles using sol–gel method. The X-ray diffraction confirmed the single phase of tetragonal anatase with space group I41/amd, where the crystallite size was found 7.2 nm and 8.8 nm for Ti0.99Sm0.01O2 and Ti0.99Sm0.005Gd0.005O2, respectively. The Fourier-transform infrared spectra showed the basic absorption bands in tetragonal anatase structure with a stretching vibration around 500 cm−1 assigned to Ti–O–M, M = (Gd, Sm). Raman spectroscopy demonstrated the presence of the six active vibrational modes for anatase TiO2. Scanning electron microscopy analysis revealed that the particles are spherical in nature and agglomerated. Energy-dispersive X-ray spectroscopy confirmed the high purity of the as-prepared materials. The UV–VIS analysis showed absorption in visible range, due to the electronic transition, which has been confirmed theoretically, also a slight decrease in the band gap was noticed compared to the pure TiO2 anatase. The magnetic measurements reveal the existence of weak ferro or ferrimagnetic behavior. In this work, it is the first time that experimental and theoretical results prove that rare earth ions are incorporated into the sites of the TiO2 lattice without the formation of separate phases. In addition, the experimental work carried out has revealed the importance of surface area, crystallinity, light absorption, the presence of oxygen vacancies and structural defects on the magnetic and more particularly optical properties with the highlighting of the intermediate energy level between the valence and conduction bands. This study was complemented by first-principles calculations to investigate the effects of doping anatase TiO2 with the rare-earth elements Sm and Gd on its structural, optical and magnetic properties.

New investigation of nanosized co-doped Gd-Sm anatase TiO 2 structural, magnetic, optical, and first-principles study

Effect of heating temperature on structural and magnetic properties of zinc ferrite nanoparticles synthesized for the first time in presence of Moroccan reagents

Investigation of Tetravalent Cation Doping with (M = Sn4+, Zr4+, and Ge4+) on the Electrochemical Properties of Monoclinic Li3V2(PO4)3 Using First-Principles Calculations

Chouaib Ahmani Ferdi

Papers

Monoclinic α‐NaVOPO4 as cathode materials for sodium‐ions batteries: Experimental and DFT investigation

Structural, electrochemical, electronic, and magnetic properties of monoclinic LixV2(PO4)3 for x = 3, 2, 1 using first-principles calculations

New investigation of nanosized co-doped Gd-Sm anatase TiO 2 structural, magnetic, optical, and first-principles study

Effect of heating temperature on structural and magnetic properties of zinc ferrite nanoparticles synthesized for the first time in presence of Moroccan reagents

Investigation of Tetravalent Cation Doping with (M = Sn4+, Zr4+, and Ge4+) on the Electrochemical Properties of Monoclinic Li3V2(PO4)3 Using First-Principles Calculations