Metal-organic frameworks (MOFs), as a new type of crystal materials, are considered a kind of promising photocatalysts. In this work, a novel Bi2S3/MIL-53(Fe) heterojunction photocatalyst was successfully prepared via a facile two-step method (hydrothermal and water bath). The characterization means, including XRD, SEM-EDS, FT-IR, XPS, PL, and UV–Vis, were employed to analyze the structural and morphological properties of Bi2S3/MIL-53(Fe). The photocatalytic performance of Bi2S3, MIL-53(Fe), and Bi2S3/MIL-53(Fe) was evaluated by the removal efficiency of the photocatalytic degradation of tetracycline (TC, 10 mg/L) under visible light irradiation (λ > 420 nm). The results show that the photocatalyst BSM-10 (the mass ratio of Bi2S3 to MIL-53(Fe) is 10:90) exhibits improved photocatalytic performance compared to Bi2S3 and MIL-53(Fe), showing the optimum photocatalytic activity (the degradation efficiency of TC is 90.9% within 120 min), and the corresponding first-order reaction rate constant is about 3 and 2 times higher than that of MIL-53(Fe) and Bi2S3, respectively. The improvement in photocatalytic activity is attributable to the efficacious separation of photogenerated electron-hole pairs and significant acceleration of charge transfer rate. Based on the free radical trapping experiment and ESR test results, combined with the band structure of MIL-53 (Fe) and Bi2S3, we speculate that a heterojunction is formed between MIL-53 (Fe) and Bi2S3, and the proposed Z scheme mechanism can well explain the enhanced catalytic activity of BSM-10. The Bi2S3/MIL-53 (Fe) heterojunction photocatalyst synthesized in this work has potential application value for removing the typical pollutant tetracycline from water.

The quantum contemplation of highly unsaturated D-π-A type renewed chromophores (TQ41-TQ45) constructed on quinoxaline core-based model TQ4 are predicted to suggest novel photovoltaic constituents for the application of organic solar cells. The model TQ4 was amended by the replacement of terminal groups with conjugated acceptors via thiophene to design five novel chromophores and their structural as well as optoelectronic attributes were calculated at selected DFT method PBEPBE/6-31G (d, p) level of theory. FMO study revealed that high charge transfer occurred between HOMO-LUMO by the reduction of energy gap up to 0.59 eV (for TQ44) which is quite low from the model TQ4 (2.04 eV). Absorption profile unveiled that the maximum absorption of all the designed chromophores in dichloromethane was in visible and near IR region exhibiting bathochromic shift up to 916 nm that is higher than the reference TQ4 (505 nm). Higher values of dipole moment by novel chromophores up to 16.85 D than reference (1.66 D) suggested good solvation and better molecular packing. ESP analysis revealed electron distribution on various parts of the molecules by colored maps that is found to be effective for better ICT. TDM plots depicted density of electron transitions on various molecular sites by the absorption of light. RE values of electron and hole for novel molecules proved to be highly efficient that enhanced the charge mobilities and prevented charge recombination. Finally, open circuit voltage of all the studied chromophores was calculated by scaling our designed donors to the well-known acceptor PC71BM that is very effective for the fabrication of elite organic solar cells.

In this study, bismuth zinc iron (BiZnFe) nanocomposites (NCs) were synthesized for the first time using a solution combustion approach and Aloe vera extract as a reducing agent. The morphology was determined for the NCs using scanning electron microscopy. X-ray diffraction and Fourier transform-infrared spectroscopy were applied to analyze the physical and chemical structures of the new NCs, and synthesis of the NCs was validated. Ultraviolet light absorption was observed in the wavelength region of 200–300nm,and the direct energy bandgap was determined as 3.06eV.The capacity of the BiZnFe NCs to shield against various types of radiation was assessed, i.e. X-rays/gamma rays, bremsstrahlung, and neutrons.In the lower energy range, the gamma shielding efficiency was equivalent to lead but lower than that of lead in the higher energy range. The bremsstrahlung exposure constant for BiZnFe NCs was comparable to those for concrete and steel, but less than that for lead. Compared with lead, the BiZnFe NCs exhibited strong radiation absorption and minimal secondary radiation emission, which are their main strengths. Furthermore, the BiZnFe NCs have been demonstrated to have much greater neutron shielding capabilities than lead, steel, and concrete in terms of scattering length, absorption, and scattering cross-sections.

Antisite disorders play a critical role in determining the magnetic ground state of the La2NiMnO6 double perovskite compounds that show multifunctional behaviours and spin-glass phases at lower temperatures. The spin-glass (SG) state and magnetization relaxation have been studied extensively; however, the polydispersity of the SG state remains elusive. Employing ac-magnetic susceptibility χ(ω,T) and temperature-dependent electron spin resonance (ESR) spectroscopy, herein, we probe the polydispersity of the SG phase in La2NiMnO6 crystallites. We employed X-ray photoelectron spectroscopy (XPS) to probe the crystallite size-dependent variable fractions of Mn3+/Mn4+ (Ni2+/Ni3+) cations and their influence on completing exchange interactions. Mn-2p core-level XPS spectra suggest a dominant Mn4+ + Ni2+→Mn3+ + Ni3+ charge transfer peak that appeared as a satellite peak at lower binding energy than the Mn core-level. The observed differences in saturation magnetization (MS) as a function of crystallite size indicate the variation in the degree of antisites disorder. Competing magnetic interactions driven by mixed valence and disorder facilitate a spin-glass (SG) phase at lower temperatures. Utilizing ESR measurement across paramagnetic → competing ferro/antiferromagnetic phase, a modified g-factor that ranges from 2.050-2.037 is observed in the paramagnetic region. The line width of the ESR signals is found to be increased across the transition suggesting spin-freezing characteristics. Cole-Cole plots obtained from χ(ω,T) data indicate collective spin relaxation dynamics in the proximity of the freezing temperature. Our findings suggest the importance of the size effect and its relation with the degree of antisites disorders in these crystallites. These experimental results enable the La2NiMnO6 compound to find its possible applications in new areas of material research.

The electronic structure and the magnetic and optical properties of a 3C–SiC system co-doped with Fe and V were systematically investigated by first-principles calculations. The origin and formation mechanism of the system's magnetism were elucidated by our analyzing the density of states of each electron orbital and calculating the magnetic moments contributed by each element. The most stable doped structure was determined by our calculating the formation energy of the system at ten different doping sites. The (5, 7) doping configuration demonstrated the greatest system stability and was used to calculate the electron spin density and optical properties. Our results showed that the co-doped 3C–SiC system exhibits better optical absorption throughout the infrared and visible regions, indicating that co-doping with Fe and V is an effective approach to improve the properties of 3C–SiC materials. We found that doping introduces magnetism to the system, generates spin polarization, and increases electrical conductivity. Furthermore, the co-doped system combines the electrical properties of semiconductors and the magnetic properties of magnets, providing a promising avenue for developing new semiconductor technology and electronic devices.

In the previous studies, the topological insulators in the half-Heusler ternary structure are assumed to be in the γ-phase having the transition metal atom at the unique middle site. In contrast, the minimum-energy half-Heusler phase can well be the β-phase with the highly electronegative anion positioned in between the electropositive metallic ions. For this subtle reason in the following a systematic study of the phase stability and the band topology of XAuZ compounds containing d0 alkaline earth atoms (X = Ca, Sr, Ba; Z = As, Sb) in their respective minimum-energy half-Heusler phases is presented. It is thus found that all the above compounds are mechanically (or dynamically) stable and have formation energies that are within a reasonable distance from the thermodynamic hull. The band structures of all compounds obtained from the more accurate TB-mBJ exchange potential with the SOC included indicate a strong band inversion such that the s-like Γ6 band falls below the p-like (Γ7+Γ8) bands. Furthermore, due to the negative spin–orbit splitting in the β-phase compounds SrAuAs and BaAuAs, the Γ8 falls below the Γ7, which opens a significant bulk insulating gap at the Fermi level. The outputs of WannierTools, such as the Z2 topological quantum numbers, surface states spectra and surface Fermi loops, indicate that the β-phase compounds SrAuAs and BaAuAs are indeed strong topological insulators with a polar character due to the lack of inversion symmetry, while non-uniform strains are needed to turn the γ-phase compounds into Weyl semimetals (ca>1) and topological insulators (ca<1).

The synthesis of bimetallic systems of ZnO/Al/Ag deposited on glass substrate was carried out by the combination of sol-gel and spin-coating methods, used as an easy and simple alternative to prepare this kind of films, in comparison with other reported methods. Structural parameters and morphology on the surface of bimetallic films were determined by analytic techniques. While band gap value was calculated by Tau graph through UV–Vis analysis. Photocatalytic and photoelectrochemical tests were also carried out to analyze the behavior of the films and the effect provided by the metallic elements. Results showed that films with bimetallic elements have an improved behavior in terms of charge transfer observed in the PEC cell, where values of up to 0.8 mA/cm2 were obtained for ZnO with 80 wt% of Al and 20 wt% of Ag (ZnO/80/20). In fact, this film produces the highest amount of hydrogen reaching 53 μmol of H2 after 3 h of reaction because of the synergy presented by the metallic elements, which increases the electron transport due to the longer service life and fast diffusion rate, but also diminish the depletion layer allowing that electrons will have to travel a smaller distance before reacting.

Light absorption and separation of photo-generated electrons and holes are important to photocatalytic hydrogen evolution of a photocatalyst. Herein, a special metal organic framework (MOFs) was fabricated by encapsulating of 2-methylimidazole and cadmium nitrate on the silica coated cuprous oxide (Cu2O/SiO2/CdIF). The structure, morphology, composition, and valence state of the obtained materials were analyzed. It was demonstrated that the core-shell Cu2O/SiO2/CdIF heterostructure was achieved. Also, the photocatalytic activity and stability of H2 generation over the Cu2O/SiO2/CdIF nanocomposite were investigated. Interestingly, the Cu2O/SiO2/CdIF nanocomposite exhibited high activity which was hardly changed after five recycles. By means of Raman spectra, solid diffuse reflection UV–vis spectra, photoelectric response, and interfacial resistance, it was shown that higher light absorption, efficient charge separation and strong synergistic effect among the components in the heterostructure were responsible to the enhanced performance in the Cu2O/SiO2/CdIF nanocomposite.

MnCr2O4 spinel is a component of the multilayered oxide film which forms atop austenitic steel alloys under high-temperature corrosion conditions. In this work, the thermodynamics and kinetics of cationic and anionic point defects in this spinel are examined through density functional theory calculations. To model the physical conditions of the corrosion process more closely, temperature is accounted for by adjusting the chemical potential of each species to fit experimentally determined values. We find that manganese is the most mobile species - migrating through the lattice via a vacancy mediated mechanism. Oxygen migration can occur via vacancy mediated or three-body interstitial mechanisms with similarly low barrier heights, highlighting the possibility of oxide growth at the film/alloy interface due to the high oxygen permeability. Furthermore, a number of more complex migration mechanisms involving substitution and antisite defects are evaluated for their potential contribution to cation mobility.

In this article, using first-principles calculations, we propose XMSiY2 (X = S, Se; M = Mo, W; and Y=N, P) monolayers as a Janus form of MA2Z4 family and investigate their electronic, spintronic, and photocatalytic properties. The obtained band structures show that XMSiY2 monolayers are semiconductors with bandgaps ranging from 1.21 eV to 2.98 eV. Considering spin-orbit coupling, we observe that broken out-of-plane symmetry in the XMSiY2 structures leads to Rashba spin-splitting at the Γ point and lack of inversion symmetry results in Zeeman spin-splitting at the K point of the valence bands. The monolayers with W atom exhibit larger Zeeman spin-splitting (up to 0.479 eV for SeWSiP2) which indicates that XWSiY2 monolayers are promising materials for spintronic and valleytronic applications. Assisted by the large work function difference (Δ&varphi) between two surfaces of the Janus XMSiY2 monolayers, all the proposed structures satisfy the band alignment requirement for overall water splitting. Benefiting from strong solar absorption, large carrier mobility (up to 104 cm2 V−1 s−1) and huge difference between electron and hole mobilities, XMSiY2 monolayers are predicted to be high performance photocatalysts. Lastly, the effect of biaxial strain on the photocatalytic properties of the proposed monolayers is comprehensively investigated and it is found that compressive strain helps XMSiY2 structures to act as great photocatalysts for overall water splitting in an expanded range of pH. In addition, tensile strain can broaden and intensify the solar light absorption spectrum of XMSiY2 monolayers to achieve high performance photocatalysts.

Transition metal oxide has been extensively investigated as a candidate for asymmetric supercapacitors based on their unique structural properties and elevated capacitance. However, the conductivity of materials such as NiCo2O4 is still not at the level of industrialization. In this work, we prepare a NiCo2-LDH-based heterostructure material via a one-step hydrothermal approach. As a result, the NiCo2-LDH/MoO2/Ti3C2 electrode material possesses a high specific capacitance (5282 mF cm−2 at 2 mA cm−2) with excellent cycling performance. Moreover, the assembled asymmetric device presents a cycling stability of 80.8% retention after 8000 cycles, and a high energy density of 5.31 Wh cm−2 as a power density of 54.0 W cm−2.

Mg2Ni is considered as one of the promising candidates of hydrogen storage materials because of its reasonable (de)hydrogenation kinetics and low costs. In view of the high operating temperature for hydrogen release due to the high thermodynamic stability of hydride, Mg2NiH4 is a serious obstacle to overcome for application usage. In this work, the crystal structure, electronic structure and thermodynamic stability of Si doped Mg2Ni and Mg2NiH4 are studied by first-principles calculations based on density functional theory. It is shown that the hydrogen desorption enthalpy can be reduced from 63.3 to 48.2 and 46.2 kJ/mol H2 with one in sixteen Mg and one in eight Ni atoms is replaced by Si, respectively. The crystal structure and electron properties of Si doped Mg2Ni and Mg2NiH4 are clarified. It is found that the weakened covalent interaction of H–Ni bonding contributes dominantly to the deteriorative thermodynamic stability of hydrides.

In this work, a numerical simulation study on cadmium telluride (CdTe)-based thin film solar cell structure utilizing CdTe as absorber layer, Cadmium sulphide (CdS) as window layer, and lead-free perovskite (CH3NH3SnBr3) as a hole transport layer (HTL) is presented for the first time. The effect of different material parameters such as shallow uniform acceptor density (NA) of absorber and HTL, thicknesses of absorber and HTL, Electron affinity of HTL, defect density of absorber layer, series and shunt resistance, back contact metal work function, and operating temperature on photovoltaic (PV) parameters such as open-circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and photo conversion efficiency (PCE) has been studied. With the introduction of perovskite as HTL, it is observed that Voc increased from 0.66 V to 1.17 V by creating a suitable band alignment with the CdTe absorber layer, causing an improvement in efficiency by preventing carrier recombination at the back contact surface. The designed solar cell has shown an enhanced PCE of 27.10% with Voc ∼1.17 V, Jsc ∼27.76 mA/cm2, and FF ∼83.40%. Thus, from the study, it is possible to achieve high-performance CdTe-based solar cells using perovskite as HTL for photovoltaic applications.

The rotational order and disorder of C60 molecules in a lattice strongly modulates the density of states at the Fermi level and exerts a large influence on electrical transport. We report herein a study of this influence at high temperatures by employing microwave conductivity and static magnetic susceptibility as the observation probes, focusing on Na2CsC60. Microwave conductivity becomes 30% higher on going from a low-temperature (LT) orientationally ordered phase (space group: Pa-3) to a freely rotational high-temperature (HT) disordered phase (space group: Fm-3m). The density of states at the Fermi level, DEF, evaluated by static magnetic susceptibility measurements, increases from 15.1 states eV−1 C60−1 for the LT ordered phase to 17.4 states eV−1 C60−1 for the HT disordered phase. Both microwave conductivity and magnetic susceptibility show that Na2CsC60 maintains its macroscopic metallicity at least up to 673 K, although local probe NMR studies suggest electron localization in the disordered state at high temperatures. The rotational disorder greatly increases the scattering of conduction electrons. Different temperature evolutions of DEF(Na2CsC60) implied by NMR spectrometry and SQUID magnetometry are discussed.

Intensively researched iron meso-tetraphenylporphyrin (FeTPP) complexes are central to the functionalities of many biological systems while at the same time they possess intriguing magnetic properties. Here we report on the synthesis and structural characterization of FeTPP complexes with axial tetrahydrofuran (THF) ligand and different non-coordinating counter anions. Structurally, the most interesting feature of these complexes is the stretching of the distance between the iron(III) and the oxygen atom of the THF ligand for different counter anions. This parameter affects the magnetic anisotropy of FeTPP as studied here with magnetic susceptibility, χm, and X-band electron paramagnetic resonance (EPR). Both magnetic probes are consistent with the iron(III) in its high-field state S = 5/2. Simulations of temperature dependencies of χm and EPR spectra show that the zero-field splitting magnetic anisotropy parameter D decreases with the tetragonal elongation of the hexa-coordinated iron(III) geometry, which is qualitatively discussed within the ligand field theory.

Our low-temperature synchrotron diffraction studies reveal an anomalous thermal expansion below ∼ 25 K (Tm). Below Tm, the Shubnikov-de Haas (SdH) oscillations are evident and anisotropic with respect to magnetic field, suggesting an anisotropic Fermi surface. Thermal variation of magnetization result shows a minimum around Tm, pointing to a significant magnetoelastic coupling. Paramagnetic singularities in the magnetization curve indicate the robust topologically-protected surface state. Careful comparison of the resistivity and magnetization results link the elastic coupling to the magnetic and electronic structure in Bi1.8Sb0.2Te3, which has not been explored in the well-studied pristine compound Bi2Te3.

In this study, the diffusion coefficient of oxygen vacancies in barium titanate doped with 2.0% Sc was calculated by using molecular dynamics. The temperature was varied from 1273 K to 2500 K, and the simulation box consisted of 10 × 10 × 10 unit cells subject to periodic boundary conditions. The Sc dopants were incorporated into the B-sublattice and compensated for by using the randomly distributed oxygen vacancies on the oxygen sublattice. The diffusivity of the vacancies was determined from the slope of the mean-squared displacement of the oxygen ions over time. The Arrhenius plot of the diffusion coefficient showed a clear linear behavior, with an activation energy of 0.84 eV. The results were interpreted by computing radial pair distribution functions for various correlations (e.g., Ti–O and Sc–O) and by static lattice (nudged elastic band) calculations of energy barriers for the migration of oxygen. While Mg-doped BaTiO3 exhibited a strong trend of the formation of defect associates between the acceptor dopant and the oxygen vacancies that lead to a clear reduction in the observed activation energy for oxygen transport with increasing temperature (non-linear Arrhenius behavior), defect-induced interactions (associates) in case of Sc doping were nearly negligibly small, and gave rise to a linear Arrhenius plot with a single activation energy.

The transformation of low-cost, renewable and eco-friendly biomass into energy conversion or storage materials with high energy density is one of the effective means to alleviate the energy crisis. In this study, a scalable route was proposed to synthesize porous, hetero-atom doped graphitized carbon nanosheets from the biomass-fish scales, and the as-prepared material was further used to construct a high-performance electrode for supercapacitor application. The synthesized N-doped graphitized carbon nanosheets (GNC-900) exhibit an average scale of 1–2 μm in size and hierarchical porous structure with a specific surface area of 1261.5 m2 g−1. The results of cyclic voltammetry (CV) and galvanostatic charge-discharge show that GNC-900 owns the quasi-electric double layer capacitance behavior in 6.0 M KOH electrolyte due to the presence of heteroatoms, and it exhibits a distinguished specific capacitance value of 448 F g−1 at a current density of 1 A g−1 in three-electrode cell. The CV curves at different scan rates reveal that this electrode has superior reversible stability and rapid response. Meanwhile, it delivers a high energy density of 57.7 Wh kg−1 at a power density of 999 W kg−1 in a two-electrode system. This novel and low-cost strategy provides an effective route to transform fish scales into highly valuable electrode materials in energy storage fields.

The ternary titanium oxide (TiO2), copper oxide (CuO), and chitosan (TiO2/CuO/Chitosan) photocatalyst (composites) for the photodegradation of synthetic methyl orange (MO) were developed by entrapping copper ions and nanosized TiO2 into chitosan thin films at room temperature. TiO2 Degussa P25 was incorporated with CuO and Chitosan (CS) solution using an ex-situ synthesis method before being immobilized onto glass plates via a dip-coating technique. This study is the first time approach for a combination of a composite comprising two metal oxides to suppress the electron-hole recombination, thus enhancing their catalytic and adsorptive properties. The morphology and surface interactions of the TiO2/CuO/Chitosan composite were determined using techniques such as XRD, FTIR, RAMAN, and SEM-EDX, respectively. The results show the anatase phase and homogenous spherical features of TiO2. The TiO2/CuO/Chitosan composites (0.5 gL-1) exhibited excellent activity for the photodegradation of MO under solar irradiation (λ > 400 nm) at different pH. The decolorization efficiency increased according to pH 9 < pH 7 < pH 6 < pH 3 with the highest degradation efficiency of 85.29% at 1 ppm MO solution, reaching two times greater than the pristine TiO2 nanoparticles (56.55%). Complete degradation of MO was attained at 240 min of solar irradiation with pH 3 using the optimum TiO2/CuO/Chitosan composites of 1:4:1 composition (5 cycles of dip coating) and the photodegradation rate constant is 0.0073 min−1. The physic-chemical study has established the structure, crystalline phase, surface contact, and stability of the catalyst. The photocatalytic improvement under visible irradiation is attributed to band-gap reduction and suspension of electron-hole recombination of the ternary catalyst system. The results of this study offer guidelines for the design of a new synthetic strategy.for the preparation of an efficient photocatalyst for the selective oxidation of synthetic azo dyes compounds.

We have investigated the effect of the substitution of iron by chromium on the structural, magnetic and magnetocaloric behaviors of Gd2Fe17-xCrx (x = 0, 0.5, 1 and 1.5). The Rietveld analysis of the X-ray powder diffraction refinement showed that this substitution leads to an increase of the unit-cell volume. All the compounds show a ferromagnetic to paramagnetic transition at the Curie temperature (TC) from the variation of magnetization vs. temperature. Upon Cr substitution, the Curie temperature decreases from 475 K for x = 0 to a value of 452 K for x = 1.5. Arrott plot analyses were applied for verifying the order of the magnetic transition in this system, which was found to be of second order. Besides, the magnetocaloric effect for the Gd2Fe17-xCrx (x = 0, 0.5, 1 and 1.5) compounds was evaluated by the magnetic entropy change and the related Relative Cooling Power (RCP). In the vicinity of TC, |-ΔSM| reached a maximum value of 1.14 J kg−1 K−1, 1.71 J kg−1 K−1, 2.45 J kg−1 K−1 and 3.40 J kg−1 K−1, although the RCP was found to be 18 J kg−1, 31.9 J kg−1, 42.5 J kg−1 and 51.2 J kg−1 for x = 0, 0.5, 1 and 0.15, respectively in a magnetic applied field of 1.56 T. These results reveal that the Gd2Fe17-xCrx (x = 0, 0.5, 1 and 1.5) compounds are attractive materials that could be used as active refrigerants for the magnetic refrigeration and heat pumping technology above room temperature.