Direct Gap Research Articles

Structural Evolution and Magnetic, Optical, and Optoelectronic Properties Changes in Annealed Co0.5Sr0.5Fe2O4 Nanoparticles: A Comprehensive Study

A sample of Co0.5Sr0.5Fe2O4 nanoparticles was synthesized by the coprecipitation technique to explore the effect of annealing on the structure and some physical properties of the produced material. The coprecipitated sample consists of an orthorhombic strontium carbonate phase and the required cubic Co0.5Sr0.5Fe2O4. Annealing at elevated temperatures (900 °C) leads to the formation of cubic and hexagonal phases. This crystal structure was confirmed by X-ray diffraction analysis (XRD). The accuracy of the cation distribution of the cubic phase determined from the Rietveld analysis of XRD patterns is demonstrated by matching the experimental and theoretical lattice constants. There are several noticeable changes in aspects as the annealing temperature goes up. The transmission electron microscopy (TEM) images indicated that heating substantially affects the growth and densification of the smaller nanoparticles. There is a drop in the longitudinal and transverse wave velocities, bulk, rigidity, Young's moduli, Poisson ratio (σ), and Debye temperature (θD) with annealing and grain growth. The saturation magnetization and coercive field are enhanced with annealing. The particle size distribution calculated from TEM is confirmed and supported by the switching field distribution. The indirect optical bandgap energy (Eg) decreased with annealing. The present study concentrated on the thermal treatment impacts on various optical parameters, such as the refractive index and extinction coefficient. The optoelectrical parameters, such as the dielectric constant, dielectric loss, and optical and electrical conductivity, were extensively investigated, giving valuable insights, and their results were interpreted. These findings suggest potential applications in magnetic storage, sensors, and optoelectronics fields.

Tuning the optical and photophysical characteristics of DR1 through mixing with JGB

A dye mixture of Disperse red1 (DR1) and Janus green B (JGB) was prepared with different concentrations of the two dyes. The optical properties were studied for the two dyes and their mixtures in terms of the absorbance spectra. The direct optical energy gap in addition to the refractive index, extinction coefficient, dielectric constant and optical conductivity were estimated to the two dyes and their mixtures. The experimental energy gap was found to be 2.234 and 1.666 eV for DR1 and JGB respectively, while the values of the energy gaps for the mixtures were found to be ranging between these two values. On the other hand, the refractive index was found to be changed in a systematic way by changing the contents of the dye mixture. The same behavior was also observed for the dielectric constant and optical conductivity. The emission of the two dyes and their mixtures was studied in terms of fluorescence spectra using excitation wavelength of 300 nm where a change in the fluorescence intensity was observed by changing the contents of the mixture. Finally, TD-DFT simulations were performed for the two dyes and their mixture to study the electron density, electrostatic potential, energy gap and optical absorption spectrum and found to be compatible with the experimental measurements.

Synthesis, Spectral Analysis, and DFT Studies of the Novel Pyrano[3,2-c] quinoline-based 1,3,4-thiadiazole for Enhanced Solar Cell Performance

In this study, we synthesized a novel compound, 3-(5-amino-1,3,4-thiadiazol-2-yl)-6-ethyl-4-hydroxy-2H-pyrano[3,2-c]quinoline-2,5(6H)-dione (ATEHPQ), through a condensation reaction between 6-ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinoline-3-carboxaldehyde and thiosemicarbazide, followed by oxidative cyclization. We characterized ATEHPQ using elemental analysis, IR, 1H and 13C NMR spectroscopy, and mass spectrometry. Density Functional Theory (DFT) calculations with the B3LYP/6-311++G(d,p) basis set were employed to optimize the molecular geometry and analyze global reactivity descriptors, including HOMO-LUMO energies. The Molecular Electrostatic Potential (MEP) map was used to identify reactive sites, and drug-likeness studies indicated potential pharmaceutical applications. Notably, ATEHPQ showed a higher first hyperpolarizability (βtot) compared to urea, suggesting its suitability for nonlinear optical applications. We also determined the Miller indices for ATEHPQ’s preferred orientations using a specialized program. Williamson–Hall analysis revealed an average crystal size of 26.08 nm and a lattice strain of 6.3 × 10−3. The thin films exhibited three distinct absorption peaks at 2.8, 3.41, and 4.21 eV, with a direct energy gap of 2.43 eV. Dispersion parameters from the single oscillator model provided oscillator and dispersion energies of 3.12 eV and 14.21 eV, respectively, with a high-frequency dielectric constant of 4.71. The ATEHPQ thin films, when combined with n-Si, demonstrated significant improvements in photovoltaic performance: the open-circuit voltage (Voc) rose from 0.13 V to 0.521 V, the short-circuit current (Isc) increased from 0.253 mA to 2.94 mA, the fill factor (FF) improved from 0.238 to 0.33, and the efficiency (η) grew from 0.71% to 4.64% with increased illumination intensity. These results highlight the excellent photovoltaic and photodetection capabilities of ATEHPQ thin films, underscoring their potential for advanced optoelectronic and solar cell applications.

The impact of social comparison on self-deception: An event-related potentials study.

Self-deception refers to an individual holding inflated beliefs about their abilities, and it plays a crucial role in human behavior and decision-making. The present study employed event-related potentials (ERPs) technique to explore the neural responses to the impacts of social comparison direction and comparison gap on self-deceptive behavior. They were instructed to predict their performance in the forward-looking paradigm. Behavioral responses and neural reactions during the decision-making process were documented. The behavioral results indicated that, in contrast to the downward comparison condition, participants engaged in upward comparison exhibited more occurrences of self-deception. However, within the context of upward comparison, participants demonstrated a higher frequency of self-deception in the large gap condition compared with the small gap condition. The ERP results showed that induced self-deception under conditions with a large comparative gap between participants and their paired counterparts stimulated larger P300 and smaller N400 amplitude than under conditions with a small gap. However, when participants were in the upward comparison situation, the late positive potential (LPP) amplitude induced by self-deception behavior in the condition of a large comparison gap between participants and paired opponents was larger than that in the condition of a small comparison gap. These results indicated that individuals in the large gap group feel strong unfairness and negative emotions. More importantly, the self-deception induced by the large gap group in the upward comparison situation used fewer cognitive resources than the small gap condition, whereas the individuals in the downward comparison situation did not show the difference in cognitive resources.

Modulation of photoluminescence properties of transition metal dichalcogenides through temperature and Au/Ag nanoparticles

Abstract Transition metal dichalcogenides (TMDCs) attract significant attention because of their remarkable optical properties. Nowadays, the light emission efficiency of TMDCs is still inferior. Temperature and plasma resonance effects can be important approaches in the modulation of their luminescence performance. Here, multilayer WSe2 and monolayer MoSe2 were synthesized. Under the temperature control system, two photoluminescence (PL) peaks are observed from multilayer WSe2. The higher-energy PL peak results from K-Γ indirect band gap transition, which is then demonstrated by the first principle calculation. Otherwise, PL enhancement is realized on monolayer MoSe2 decorated with Au nanoparticles. The PL of WS2 is inhibited by hybridization with Ag nanoparticles.

A comprehensive DFT Study of the electronic structure and optical properties of Iodine-based halide double perovskites for photovoltaic applications

This study aims to explore the electronic structure, thermodynamic, mechanical stability, and optical response of Iodine-based ordered vacancy double halide perovskite compounds through the application of density functional theory. The two compounds Cs2ZrI6 and Rb2ZrI6 exhibit thermodynamic stability, with displaying particularly notable. Moreover, analysis of the calculated coefficients of elastic stiffness confirms the mechanical stability of all materials under ambient pressure conditions. By using the Density Functional Theory with Spin-Orbit Coupling (SOC), it was observed that Cs2TeI6 and Rb2TeI6 possess an indirect band gap located between the X and L high-symmetry points, this show that Cs2TeI6, Rb2ZrI6, Cs2HfI6, and Rb2HfI6 are identified as direct semiconductor compounds. Moreover, the band gap values of X2YI6 (where X = Cs, Rb, and Y = Te, Zr, and Hf) exhibit an increasing trend as we progress along the alkali and transition metal elements in the periodic table, ranging from 1.422 eV for Cs2TeI6 to 2.465 eV for Rb2TeI6. Besides, the optical behavior of the visible light show that X2YI6 compounds have a high absorption of about 70%, reflectance of 30%, and a low transmittance. Thanks to their advantageous bandgap, enduring stabilities, and effective absorption of visible light, Cs2TeI6 and Rb2TeI6 hold significant promise for a wide range of electronic and optoelectronic applications, particularly in photovoltaics.

First Principle Investigations of Structural, Electronic and Thermal Properties of Pristine, Metal and Non-Metal Doped Silicene for Thermoelectric Applications

Silicene, a two-dimensional hexagonal silicon layer, exhibits exceptional electronic and thermoelectric properties. However, its application in semiconductors is hindered by its zeroband gap, which could be overcome by modifying its electronic properties through doping. In this paper, Density Functional Theory (DFT) calculations were performed to investigate the band gap opening in silicene by studying the effect of magnesium and sulphur doping on its electronic, structural and thermal properties. Pristine silicene has a lattice constant of 3.86 Å and a zero-band gap. Upon doping with 12.5% S and Mg atoms, the lattice constant modifies to 3.45 Å and 3.93 Å, respectively, resulting in a direct band gap opening. For 25% Mg and S doping, the result shows that Mg and S effectively alter the band structure and the band gap of silicene monolayer at various configurations. The maximum band gap was 0.98 eV and 1.22 eV for Mg and S doping into the meta position to the reference point R, respectively. The power factor significantly increases with doping, reaching 1.20 x 1011 WK-2m-1 and 1.40 x 1011 WK- 2 m-1 for 12.5% Mg and S doping compared to 7.4 x 1010 WK-2m-1 for pristine silicene. This substantial enhancement indicates improved thermoelectric performance, making silicene a promising candidate for thermoelectric applications. Results demonstrate that tuning the band gap through doping can simultaneously enhance the power factor, highlighting the potential of Mg/S-doped silicene for efficient energy harvesting and conversion.

Nonlinear optical parameters and electronic properties of plasma polymerized methyl acrylate thin films

Plasma polymerized methyl acrylate (PPMA) thin films were fabricated on a borosilicate glass substrate at a plasma power of 28 W to study nonlinear optical parameters and electronic properties. X-ray Diffraction analysis confirmed the amorphous nature of the PPMA films, while Attenuated total reflectance Fourier transform infrared spectroscopy indicated monomer fragmentation due to plasma polymerization. Field emission scanning electron microscope images of the films display a water wave-like structure. PPMA films demonstrated thermal stability up to approximately 574 K in both N2 and air environments. The values of direct band gap energies increase from 3.30 to 3.41 eV with increasing film thicknesses, whereas the Urbach energy values show in an opposite manner. The Wemple-DiDomenico model was employed to analyze both the oscillator energies ranging from 5.54 to 6.44 eV and the dispersion energies ranging from 10.56 to 12.89 eV. The static linear refractive index showed typical dispersion behavior, with film thickness conforming to Moss's rule. The nonlinear refractive index and 2nd and 3rd order nonlinear susceptibilities decrease with increasing the studied films. The lattice dielectric constant values exceeded the high-frequency dielectric constant, indicating the presence of lattice vibrations and free carriers. Electronic parameters are fluctuating with increasing film thickness. The observed changes in nonlinear optical parameters and electronic properties highlight the potential of PPMA films for applications in photovoltaic and optoelectronics.

Biocompatible 2D SnSe Nanoflake Employed Enhanced Photocatalytic Degradation of Rhodamine B

AbstractIn this article, we report the results of the photocatalytic effect of the cost effective grown SnSe nanoparticles (NPs), nanoflakes (NFs), nanoflowers (NFLs) on the toxic water contaminant dye of Rhodamine B (RhB) under visible light irradiation different duration time. The results showed that for the degradation of 99 %, 96 % and 94 % of the RhB have been occurred in presence of NFs, NFLs, NPs, respectively for the irradiation time of 30 min, 45 min, 65 min, respectively. Before photocatalytic test, the grown SnSe were characterised optically and structurally. The nanoparticles, nano flakes, nanoflowers morphology along with atomic composition of Sn and Se were observed from FESEM images and EDAX analysis. The direct band gap of the NPs, NFs, NFLs was calculated from UV‐VIS spectrum and found to be 1.89 eV, 1.78 eV, 1.7 eV, respectively. The crystal structure showed orthorhombic crystal phase with nanocrystal sizes varies from 22 nm to 31 nm. The Scavenger test in presence of the scavenging elements BQ, IPA, ethanol and EDTA have been discussed. The stability test showed that SnSe NFs is a good and stable catalysis for practical applications. The effect of the NFs, NPs, NFLs on red blood cell showed that all the tested SnSe nanostructures had <2 % hemolysis, suggesting their hemocompatible nature.

Modulation of electronic and thermal properties of boron phosphide nanotubes under electric and magnetic fields

This work theoretically investigates the thermoelectric properties of boron phosphide nanotubes (BPNTs) using the tight-binding model, Green function method, and Kubo formalism, focusing on a zigzag BPNT with indices (20, 0). The tight binding parameters obtained by matching its band structure with calculated density functional theory band structure. The study examines the effects of transverse electric fields and axial magnetic fields on various physical properties, such as band structure, density of states (DOS), heat capacity, magnetic susceptibility, and other thermoelectric properties. BPNTs consistently show semiconducting properties with a nearly 1 eV direct band gap. The electronic properties of BPNTs are significantly affected by applied electric field, which at very strong strengths can induce a semiconducting to metallic phase transition. In contrast, the magnetic field leads to the splitting of energy bands, especially around the Fermi level. The DOS also changes with the electric field, including variations in the position, intensity, and number of DOS peaks. The thermal properties and thermoelectric performance of BPNTs are temperature-dependent. Increasing of excited electrons thermal energy cause more occupation of high energy levels in the conduction bands. The electric field further enhances the thermal properties of BPNTs by modifying their electronic properties and reducing the band gap. Stronger electric fields cause a noticeable enhancement in the BPNTs thermal properties because it is increasing the concentration of excited charge carriers. This aspect is crucial for improving the thermoelectric efficiency of BPNTs, making them more competitive for practical applications.

Structural, electronic, optical and thermoelectric properties of FrSnI3-xClx (X=0, 1, 2, 3) perovskites using the TB-mBJ approach

Mixed halide inorganic perovskites represent a significant advance in energy conversion materials, with research on these materials paving the way for more sustainable and accessible energy solutions. In this work we investigated the effects of chlorine atom substitution on the structural, electronic, optical and thermoelectric properties of mixed halide perovskites FrSnI3-xClx (x=0, 1, 2, 3). The FP-LAPW approach within the Wien2k package has been employed, using the modified Becke-Johnson potential (TB-mBJ) for the exchange correlation functionals. For FrSnI3 and FrSnCl3 the calculated lattice parameters are in good agreement with theoretical results.The formation energies calculated for FrSnI3-x Clx (x = 0, 1, 2, 3) confirm the thermodynamic stability of all these materials. Analysis of the electronic properties, including partial density of states (PDOS), total density of states (TDOS) and band structures, indicates that these materials exhibit p-type semiconductor behaviour with direct band gaps ranging from 1.169 to 1.953 eV. In terms of optical properties, the FrSnI3-xClx compounds exhibit high optical absorption (α(ω) > 104 cm−1) in the visible region. The broad absorption range extends from visible to ultraviolet energy. The low reflectivity values observed (below 30%) and their minimal energy loss suggest potential applications in optoelectronic devices. The thermoelectric properties of these materials were also studied over a temperature range of 100 to 950 K. They exhibit high Seebeck coefficients, high electrical conductivity, and low thermal conductivity. Notably, at room temperature, FrSnI2Cl and FrSnICl2 show the highest figures of merit, reaching 1.31 and 0.61, respectively, demonstrating their high efficiency for thermoelectric devices

Investigating optical, structural and morphological properties of CuxZn1-xS thin films

Abstract CuxZn1-xS (CZS) Nano crystallized thin films with (x=0.25,0.5,0.75) were grown from alloy by thermal evaporation technique on glasses substrates at room temperature in a vacuum ∼ 2 × 10 −5 mbar with 450±20 nm thickness. The Cu content concentration effects on structure, morphology besides optically property of these films were investigated. X-ray diffraction (XRD) technique and Atomic force microscopy (AFM) were used to investigation the structural and morphological properties of CuxZn1-xS films. XRD analysis offered that these films had poly crystalline hexagonal structure with preferred orientation along (201) plane and mixed of of CuS-ZnS structure. The crystallites size changing with Cu concentration were found as (4.12, 5.5, 8.4) nm respectively. Using AFM measurements to investigate morphological properties of these films, the grain size for CuxZn1-xS films differs with Cu content thru uniform distribution. UV-Vis absorption spectroscopy was used to investigation the optical characterization of CuxZn1-xS films as a function of Cu content. The direct band gap values of these films were found decrease with increasing Cu content as (2.45, 2.4, and 2.3) eV respectively and the optical constant affected with Cu content. The CuxZn1-xS films have suitable optical characteristics which can used it for solar cell applications.

Insights into the pressure-dependent physical properties of cubic Ca3MF3 (M = As and Sb): First-principles calculations

Here, first-principles calculations have been employed to make a comparative study on structural, mechanical, electronic, and optical properties of new Ca3MF3 (M = As and Sb) photovoltaic compounds under pressure. The findings disclose that these two systems possess a direct band gap, showcasing a large tunable range under pressure, effectively encompassing the visible light spectrum. Adjusting various levels of hydrostatic pressure has effectively tuned both the band alignment and the effective masses of electrons and holes. Both compounds were initially identified as brittle materials at 0 GPa pressure; however, as the pressure increases, they transform, becoming highly anisotropic and ductile. Due to the material's mechanical robustness and enhanced ductility, as evidenced by its stress-induced mechanical properties, the Ca3MF3 (M = As and Sb) material shows potential for use in solar energy applications. Furthermore, as the influence of external pressure increases, the absorption edge seems to move slightly towards lower energy region. Optical properties show that the materials studied might be used from several optoelectronic devices in the visible and ultraviolet range area. Our findings show that pressure considerably influences the physicochemical properties of Ca3MF3 (M = As and Sb) compounds, which is a promising feature that can be useful for optoelectronic and photonic applications, for instance, light-emitting diodes, photodetectors, and solar cells.

First-principles investigation of Rb2NaXCl6 (X = In, Tl) compounds for energy harvesting applications

Lead free halide double perovskites (HDPs) have attracted significant interest of the scientific community owing to their better stability, low cost, and eco-friendly nature, and high power conversion efficiency for optoelectronic, and thermoelectric usages. Herein, the physical properties of two novel Rb2NaInCl6 and Rb2NaTlCl6 HDPs are reported via first principles methods. Both HDPs are found to be stable thermodynamically and geometrically, supported by negative formation enthalpies, and structural optimization. Electronic properties analysis revealed direct band gap values of 4.88 and 3.13 eV for respective Rb2NaInCl6 and Rb2NaTlCl6 structures. Corresponding to these band gap values, both HDPs are optically active in the ultraviolet (UV) region of light. Static dielectric constant (Ɛ1 (0)) is consistent with Penn's model. Maximum polarization is achieved at 7.1/5.16 eV for Rb2Na(In/Tl)Cl6, respectively. Maximum absorption peaks occurred in UV region, predicting their suitability for high energy optoelectronic applications. The optical conductivity revealed the highest intensity of 3049.72 (at 5.4 eV) for Rb2NaTlCl6 and 2632.08 Ω−1cm−1 (at 7.4 eV) for Rb2NaInCl6. Moreover, our analysis of thermoelectric parameters revealed that Rb2NaInCl6 and Rb2NaTlCl6 have figure of merit (ZT) values of 0.73/0.75, respectively. High ZT values and greater absorption in the UV region suggest that Rb2Na(In/Tl)Cl6 are suitable for TE and optoelectronic usages.

Fabrication, Physical, Structural, Optical Properties, and γ‐Ray Attenuation Attributes of Germanate Borosilicate Glasses: Role of GeO2

AbstractSamples of germanium borosilicate glasses with chemical formula 50.5B2O3 + 0.5CeO2 + 10SiO2 + (20‐x) CaO + 19Na2O + XGeO2 with 0 (GeO0) ≤ X ≤ 5 (GeO5) mol% were fabricated by using the melt quenching technique. Structure, physical, and optical properties as well as radiation attenuation capacity was examined. XRD data confirmed that GeOX samples were in amorphous state. The density (ρ) of the prepared glass samples increased from 2.24 to 2.55 g/cm3, while the molar volume (Vm) slightly declined from 26.8 to 26.42 cm3/mol. The UV absorption edge shifted to a higher wavelength as the concentration of GeO2 increased. The values of direct band gap ranged from 3.36 to 2.91 eV, and the indirect ranged from 3.12 to 2.75 eV. Urbach energy (Eu) values fluctuated between 0.65 to 0.16 eV. As the Ge4+ ion increased, the glass sample's refractive index enhanced. Mass attenuation coefficients (MACs) of GeOX samples increased from 6.788 to 10.381 cm2/g at 0.015 MeV. The GeO5 sample possessed the lowest half value layer (HVL) and mean free path (MFP). Effective atomic number (Zeff) of GeOX possessed the same trend of MAC. Results confirmed that the suggested GeOX glasses can be applied in different optical and radiation attenuation applications.

A Janus WSi2P2As2 monolayer: A promising material for detecting NO2 with excellent sensitivity, selectivity, reversibility, and humidity resistance

Realizing highly sensitive, selective, humidity-resistant, and reversible detection of hazardous gas molecules with low detection limit in the air environment at room temperature is essential. Herein, we predict a novel two-dimensional Janus WSi2P2As2 material and propose a NO2 gas sensor with excellent response, selectivity, humidity resistance, and reversibility based on WSi2P2As2, by employing density functional theory, statistical thermodynamic modeling, and the non-equilibrium Green’s function approach. The Janus WSi2P2As2 monolayer is a stable semiconductor with a direct band gap of 0.85 eV and an intrinsic out-of-plane dipole moment. We study the sensing properties of the Janus WSi2P2As2 monolayer towards several typical toxic gases (NO, NO2, NH3, SO2, and H2S). All the gas molecules are physically adsorbed on the surface. Different adsorption energies and electronic structures are found for the top- and bottom-surface adsorptions due to the intrinsic dipole of the Janus WSi2P2As2. The experimental viability is characterized by the adsorption density and the recovery time. The statistical estimation of the adsorption density shows that the oxide gases can be adsorbed practically even at ultra-low concentration of part per billion (ppb) at room temperature. The rapid natural desorption of these toxic gases at 300 K indicates the recyclability of the WSi2P2As2 material. Furthermore, we evaluate the sensing performance of the WSi2P2As2-based gas sensor by the conductance change. The sensor exhibits ultra-response of 374 % and excellent selectivity towards NO2 molecules. Importantly, the sensor remains operating with high performance in the humid environment and air environment. These results demonstrate that the Janus WSi2P2As2 is a promising gas-sensing material for the NO2 detection.

Structural and Optical Characterization of Cu2Se0.8S0.2 Thin Films Deposited by Thermal Evaporation

Abstract A simple cost thermal evaporation deposition technique was used to prepare of Cu2SeS thin films on the substrates made of glass at RT with thickness ( 500 + − 20 ) nm . Structural, and optical properties of these films were investigated. The films were structurally characterized using X-ray diffraction XRD analyses, the film samples were morphologically characterized using atomic force microscopy (AFM), and optical UV-Vis spectroscopy was also to characterize the samples. The films have been treated at deferent temperatures (403, 453 &503) K for 1 hour, X-ray diffraction (XRD-with wavelength 1.54 A) study the structure properties of this films suggest a cubic structure and have prominent (111) orientation. AFM analysis, it is evident that Cu2SeS film is polycrystalline in nature, and that crystallite size and average grain size for films after annealing were increasing. The optical absorption coefficient (α) of the film was evaluated using absorbance spectra in the wavelength range (400-1100) nm. The direct band gap of about 2.2 eV, decrease by increasing annealing temperature, The structure and the optical characteristics of these films may have practical applications in renewable energy.

Investigation of Annealing Temperature Effect on Structural, Morphological, Optical, Magnetic, and Dielectric Properties of Cobalt-Doped Manganese Ferrites

Spinel ferrite Mn0.95Co0.05Fe2O4 was prepared via chemical co-precipitation routes and annealed at four distinct temperatures of 600°C, 650°C, 700°C, and 750°C. The XRD peak confirmed a single-phase cubic spinel structure, with an increasing crystallite size of 21.64–23.98nm by the annealing effect. The TEM images show an increase in particle size with rising annealing temperature and indicate well-defined nanocrystalline Mn-Co ferrite. FT-IR spectra detected two vibrational modes at interstitial sub-lattice sites, identifying Co-O, Mn-O, and Fe-O bonds with the spinel structure of Mn-Co ferrite. UV-vis-NIR reflectance revealed an optimal direct band gap of 3.76–4.70eV, indicating a scope of semiconducting behaviors in the nanocatalysts. In the magnetic hysteresis curve, saturation magnetization decreased while coercivity increased with rising annealing and crystallite size. The M-T loop reveals the Curie temperature of Mn-Co ferrite decreases from 533.84°C to 382.74°C. Frequency-dependent complex permeability at different annealing temperatures shows stable initial permeability over a wide frequency range (1kHz to 100MHz) and a quality factor several times higher due to reduced magnetic tangent loss. The real dielectric constant and losses decline in rising alternating fields (100Hz to 1MHz) and stabilize at higher frequencies following Maxwell-Wagner-type polarization. Eventually, structural, morphological, and magnetic properties are performed relatively well at higher annealing temperatures, and optical and dielectric properties are performed at lower annealing temperatures.

Theoretical study on arsenene as anode material for magnesium ion battery in rail transit

The development and regulation of high-performance anode materials contribute to the rapid development of ion batteries in rail transit. In this paper, based on the first-principles calculation method of density functional theory, the properties of two-dimensional arsenene materials are regulated by torsional deformation, and the feasibility of torsionally deformed arsenene as an electrode material for magnesium ion batteries is studied. The results show that the arsenene monolayer remains stable after being adsorbed by a single Mg ion. The properties of arsenene are indirect bandgap semiconductors with a band gap of 1.60 eV. In the current research scope, deformation does not change the semiconductor properties of intrinsic arsenene. As the torsion angle increases, the band gap gradually decreases. The Mg-adsorbed arsenene system exhibits quasi-metallic properties with a band gap of 0.07 eV. The torsional deformation transforms the adsorption system into a small band gap semiconductor. The torsion deformation makes the diffusion energy barrier of magnesium ions on the arsenene monolayer only 0.09 eV, which ensures an excellent charge–discharge rate. The research results provide a theoretical basis for the design of magnesium ion batteries in rail transit.

Electronic and optical properties of Cr-Mn co-doped in monolayer MoS2: A first-principles study

The effects of Cr-Mn co-doping of neighboring and spacer sites on the electronic and optical properties of monolayer molybdenum disulfide (ML-MoS2) are investigated using a first-principles plane-wave pseudopotential method based on density-functional theory (DFT). The results show that the band structure (BS) and the bandgap of pristine ML-MoS2 are in good agreement with the available experimental and theoretical data. Electronic analysis implies that the bandgap of Cr-Mn co-doped ML-MoS2 is smaller than that of the pristine ML-MoS2 and the bandgap of Cr-Mn co-doped ML-MoS2 at spacer sites is the smallest. Moreover, the ML-MoS2 changes from a direct bandgap to an indirect bandgap semiconductor, which facilitates electron-hole pair transfer. In addition, pristine ML-MoS₂ has no magnetism, while Cr-Mn co-doped ML-MoS2 at neighboring and spacer sites present ferromagnetism. Studies of optical properties have shown that doped ML-MoS2 systems, especially Cr-Mn co-doped at spacer sites, exhibit higher sensitivity to visible and ultraviolet (UV) light along the x-axis as well as to UV light along the z-axis. This suggests the possibility of applications in photodetectors, solar cells, and photocatalysis. It is noteworthy that Cr-Mn co-doping at the spacer sites significantly improves the photovoltaic performance and light utilization efficiency of ML-MoS2 by increasing the dielectric tensor, absorption coefficient, and photoconductivity while decreasing the extinction coefficient compared with pristine ML-MoS2.