Search

The utilization of lithium-ion batteries (LIBs) is increasing sharply with the increasing use of mobile phones, laptops, tablets, and electric vehicles worldwide. Technologies are required for the recycling and recovery of spent LIBs. In the context of the circular economy, it is urgent to search for new methods to recycle waste graphite that comes from the retired electrode of LIBs. The conversion of waste graphite into other products, such as new electrodes, in the field of energy devices is attractive because it reduces resource waste and processing costs, as well as preventing environmental pollution. In this paper, new electrode materials were prepared using waste anode graphite originating from a spent mobile phone battery with an xBT·0.1C12H22O11·(0.9-x)(NH4)2HPO4 composition, where x = 0–50 weight% BT from the anodic active mass of the spent phone battery (labeled as BT), using the melt quenching method. Analysis of the diffractograms shows the graphite crystalline phase with a hexagonal structure in all prepared samples. The particle sizes decrease by adding a higher BT amount in the composites. The average band gap is 1.32 eV (±0.3 eV). A higher disorder degree in the host network is the main factor responsible for lower band gap values. The prepared composites were tested as electrodes in an LIB or a fuel cell, achieving an excellent electrochemical performance. The voltammetric studies indicate that doping with 50% BT is the most suitable for applications as electrodes in LIBs and fuel cells. [ABSTRACT FROM AUTHOR]

This paper employed and developed the wave-based vibration approach to analyze the band-gap characteristics of a locally resonant (LR) beam with L-joint, which is common in engineering practices. Based on the proposed modular approach, where the discontinuities on the beam are created as modules, the design and modeling work for such an LR beam can be simplified considerably. Then, three kinds of LR beams with an L-joint suspended with transverse-force type resonators and two cells of longitudinal-force-moment type resonators are analyzed, respectively, to show their suppression ability on the axial wave's propagation and widened effect on the low-frequency band-gaps, where the longitudinal-force-moment type resonators at the 3rd–4th cells can better suppress the propagation of the axial waves. Meanwhile, the proposed analysis results are compared with the ones obtained with the finite element method and further verified the accuracy and efficiency of the wave-based vibration approach. The aim of this paper is to provide an efficient method for the analysis and design of the LR beam with L-joint for low-frequency vibration attenuation in engineering practices. [ABSTRACT FROM AUTHOR]

Photocatalysis is an energy-saving and high-efficiency green environmental technology. Because of its wide band gap and low light utilization, few studies have been conducted on ZrO2 used as a photocatalytic material. In this paper, a corrosion-resistant superhydrophobic ZrO2 coating was prepared on the surface of Zr-based bulk metallic glass by electrochemical etching. This coating not only showed a better corrosion resistance and easier collection, but also presented a stable degradation performance when combined with H2O2; these characteristics are necessary for photocatalysts to survive under harsh environments. This study provides a new direction for designing superhydrophobic surfaces on bulk metallic glass that possess a functional performance. [ABSTRACT FROM AUTHOR]

Conventional single-component quantum dots (QDs) suffer from low recombination rates of photogenerated electrons and holes, which hinders their ability to meet the requirements for LED and laser applications. Therefore, it is urgent to design multicomponent heterojunction nanocrystals with these properties. Herein, we used CdSe quantum dot nanocrystals as a typical model, which were synthesized by means of a colloidal chemistry method at high temperatures. Then, CdS with a wide band gap was used to encapsulate the CdSe QDs, forming a CdSe@CdS core@shell heterojunction. Finally, the CdSe@CdS core@shell was modified through the growth of the ZnS shell to obtain CdSe@CdS@ZnS heterojunction nanocrystal hybrids. The morphologies, phases, structures and performance characteristics of CdSe@CdS@ZnS were evaluated using various analytical techniques, including transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy, fluorescence spectroscopy and time-resolved transient photoluminescence spectroscopy. The results show that the energy band structure is transformed from type II to type I after the ZnS growth. The photoluminescence lifetime increases from 41.4 ns to 88.8 ns and the photoluminescence quantum efficiency reaches 17.05% compared with that of pristine CdSe QDs. This paper provides a fundamental study and a new route for studying light-emitting devices and biological imaging based on multicomponent QDs. [ABSTRACT FROM AUTHOR]

The enhancement of optical waves through perforated plates has received particular attention over the past two decades. This phenomenon can occur due to two distinct and independent mechanisms, namely, nanoscale enhanced optical transmission and micron-scale Fabry–Perot resonance. The aim of the present paper is to shed light on the coupling potential between two neighboring slots filled with two different materials with contrasting physical properties (air and silicon, for example). Using theoretical predictions and numerical simulations, we highlight the role of each constituent material; the low-index material (air) acts as a continuum, while the higher-index material (silicon) exhibits discrete states. This combination gives rise to the so-called Fano resonance, well known since the early 1960s. In particular, it has been demonstrated that optimized geometrical parameters can create sustainable and robust band gaps at will, which provides the scientific community with a further genuine alternative to control optical waves. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) is the main mineral component of bones and teeth. It is widely used in medicine as a bone filler and coating for implants to promote new bone growth. Ion substitutions into the HAP structure highly affect its properties. One of the most important substituents is magnesium. This paper presents new results obtained using high-precision hybrid density functional theory calculations for Mg/Ca substitutions in HAP in a wide magnesium concentration range within a 2 × 2 × 2 supercell model. Experimental data on the mechanochemical synthesis of HAP-Mg samples with different Mg concentrations are also presented. A comparison between the experiment and the theory showed good agreement: the HAP-Mg unit cell parameters and volume decreased with increasing degree of Mg/Ca substitution. The changes in the distances between the Ca and O, Ca and H, and Mg and O ions upon Mg/Ca substitution in different calcium positions was analyzed. The resulting asymmetry and distortion of the cell parameters were evaluated. It was shown that bulk modulus, energy levels, and band gap depend on the degree of Mg substitutions in the Ca1 and Ca2 positions. The formation energies of Mg/Ca substitutions showed non-monotonic behavior that was different for Ca1 and Ca2 positions. The Ca2 position had a slightly higher probability (~5 meV/f.u.) of substitution than Ca1 position at a Mg concentration x = 0.5. At x = 1, substitution in both positions can coexist. The simulated IR spectra for different Mg/Ca substitutions showed that Mg in the Ca2 position changes the IR spectrum more significantly than Mg in the Ca1 position. Similar changes were recorded in the IR spectra of the synthesized samples. The electronic structure is shown to be sensitive to the number and position of substitutions, which may be used to tweak the optical properties of the HAP-Mg material. [ABSTRACT FROM AUTHOR]

The aim of this paper is to optimize the thickness variation function of simply supported and cantilever beams, in terms of maximizing gaps between chosen neighboring frequencies, and to analyze the obtained results. The optimization results are examined in terms of achieving the objective function (related to eigenvalue problems), but also in terms of their dynamic stiffness (forced vibrations excited by a point harmonic load). In the optimization process, a genetic algorithm was used. Problems related to structural dynamics were solved by FEM implementation into the algorithm. Sample results were presented, and the developed algorithm was analyzed in terms of the results convergence by examining several variable parameters. The authors demonstrated the validity of applying the described optimization tool to the presented problems. Conclusions were drawn regarding the correlation between stiffness and mass distribution in the optimized beams and the natural frequency modes in terms of which they were optimized. [ABSTRACT FROM AUTHOR]

For the application of low-frequency vibration damping in industry, a cylindrical cavity double-layer plate-type local resonance phononic crystal structure is proposed to solve low-frequency vibration in mechanical equipment. Initially, using COMSOL 5.4 software, the bending wave band gap is calculated in conjunction with elastic dynamics theory and the BOLOCH theorem to be 127–384 Hz. Then the mechanism of bending wave gap is analyzed by combining element mode shape and an equivalent model. Subsequently, the bending vibration transmission characteristics of the crystal plate are explained, and the vibration-damping characteristics are illustrated in combination with the time–frequency domain. An experimental system is constructed to verify the vibration-damping properties of crystal plates; the experimental results and simulation results are verified with each other. Finally, the element structural parameters are optimized using the RSM. Fifty-four sets of experiments are designed based on six structural factors and three levels, and the expressions between the bending wave band gap and six structural factors are obtained. Combining the particle swarm algorithm, the optimization is performed with the band gap width as the target. This method is shown to be more accurate than the commonly used interior point method. The structure of cylindrical-cavity-type phononic crystal and the parameter optimization method proposed in this paper provide a certain reference for the design of local-resonance-type phononic crystal. [ABSTRACT FROM AUTHOR]

Inspired by classical graph neural networks, we discuss a novel quantum graph neural network (QGNN) model to predict the chemical and physical properties of molecules and materials. QGNNs were investigated to predict the energy gap between the highest occupied and lowest unoccupied molecular orbitals of small organic molecules. The models utilize the equivariantly diagonalizable unitary quantum graph circuit (EDU-QGC) framework to allow discrete link features and minimize quantum circuit embedding. The results show QGNNs can achieve lower test loss compared to classical models if a similar number of trainable variables are used, and converge faster in training. This paper also provides a review of classical graph neural network models for materials research and various QGNNs. [ABSTRACT FROM AUTHOR]

Rare earth nickel-based perovskite oxides (RENiO3) have been widely studied over recent decades because of their unique properties. In the synthesis of RENiO3 thin films, a lattice mismatch frequently exists between the substrates and the thin films, which may affect the optical properties of RENiO3. In this paper, the first-principles calculations were employed to study the electronic and optical properties of RENiO3 under strain. The results showed that with the increase in tensile strength, the band gap generally shows a widening trend. For optical properties, the absorption coefficients increase with the enhancement of photon energies in the far-infrared range. The compressive strain increases the light absorption, while the tensile strain suppresses it. For the reflectivity spectrum in the far-infrared range, a minimum reflectivity displays around the photon energy of 0.3 eV. The tensile strain enhances the reflectivity in the range of 0.05–0.3 eV, whereas it decreases it when the photon energies are larger than 0.3 eV. Furthermore, machine learning algorithms were applied and found that the planar epitaxial strain, electronegativity, volume of supercells, and rare earth element ion radius play key roles in the band gaps. Photon energy, electronegativity, band gap, the ionic radius of the rare earth element, and the tolerance factor are key parameters significantly influencing the optical properties. [ABSTRACT FROM AUTHOR]

Locally resonant phononic crystals are a kind of artificial periodic composite material/structure with an elastic wave band gap that show attractive application potential in low-frequency vibration control. For low-frequency vibration control problems of ship power systems, this paper proposes a phononic crystal board structure, and based on the Bloch theorem of periodic structure, it uses a finite element method to calculate the band structure and the displacement fields corresponding to the characteristic mode and vibration transmission curve of the corresponding finite periodic sandwich plate structure, and the band gap characteristics are studied. The mechanism of band gap formation is mainly attributed to the mode coupling of the phononic crystal plate structure. Numerical results show that the sandwich plate structure has a double periodicity, so it has a multi-stage elastic wave band gap, which can fully inhibit the transmission of flexural waves and isolate the low-frequency flexural vibration. The experimental measurements of flexural vibration transmission spectra were conducted to validate the accuracy and reliability of the numerical calculation method. On this basis, the potential application of the proposed vibration isolation method in a marine power system is discussed. A vibration isolation platform mounted on a steel plate is studied by numerical simulation, which can isolate low-frequency vibration to protect electronic equipment and precision instruments. [ABSTRACT FROM AUTHOR]

In this paper, as-synthesized and oleic acid (OA)-surface-treated zinc oxide (ZnO) nanocrystals were successfully synthesized and investigated for cool-nanopigment applications. ZnO nanocrystals were synthesized using the thermal decomposition method. The OA-surface-treated ZnO sample was obtained with an OA:ZnO ratio of 1:1. The structural, optical and morphological properties of the samples were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV-VIS-NIR diffused reflectance spectroscopy (DRS) and field-emission scanning electron microscopy (FE-SEM) techniques. ZnO nanocrystals possess a well-known zincate phase of ZnO, as confirmed for the as-synthesized sample with a reduction in the integrity of the ZnO crystalline structure upon the application of the OA coating. XRD peaks broadening and decreasing in crystallite size were obtained upon the surface modification of the ZnO by OA. The average crystallite size decreased from 31.5 to 17.4 nm, and the surface area changed from 23.37 to 7.48 m2/g upon OA treatment. These changes were attributed to the well-capping of the ZnO nanoparticles by OA, and, furthermore, OA increased the dispersion of the nanoparticles. The optical band gap of the investigated samples demonstrated a blue shift from 3.06 eV to 3.22 eV upon treatment. Both samples showed high NIR reflectance ( R N I R ∗ ) values, which makes them well qualified for use as cool nanopigments. Additionally, the as-synthesized sample showed an R N I R ∗ value higher than that of the treated sample. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the effect of variation in the component ratio of (1−x)Si3N4-xAl2O3 ceramics on the phase composition, strength and thermal properties of ceramics. To obtain ceramics and their further study, the solid-phase synthesis method combined with thermal annealing of samples at a temperature of 1500 °C typical for the initialization of phase transformation processes was used. The relevance and novelty of this study lies in obtaining new data on the processes of phase transformations with a variation in the composition of ceramics, as well as determining the effect of the phase composition on the resistance of ceramics to external influences. According to X-ray phase analysis data, it was found that an increase in the Si3N4 concentration in the composition of ceramics leads to a partial displacement of the tetragonal phase of SiO2 and Al2(SiO4)O and an increase in the contribution of Si3N4. Evaluation of the optical properties of the synthesized ceramics depending on the ratio of the components showed that the formation of the Si3N4 phase leads to an increase in the band gap and the absorbing ability of the ceramics due to the formation of additional absorption bands from 3.7–3.8 eV. Analysis of the strength dependences showed that an increase in the contribution of the Si3N4 phase with subsequent displacement of the oxide phases leads to a strengthening of the ceramic by more than 15–20%. At the same time, it was found that a change in the phase ratio leads to the hardening of ceramics, as well as an increase in crack resistance. [ABSTRACT FROM AUTHOR]

The infrared technology is entering widespread use as it starts fulfilling a growing number of emerging applications, such as smart buildings and automotive sectors. Majority of infrared photodetectors are based on interband transition, which is the energy gap between the valence band and the conduction band. As a result, infrared materials are mainly limited to semi-metal or ternary alloys with narrow-bandgap bulk semiconductors, whose fabrication is complex and expensive. Different from interband transition, intraband transition utilizing the energy gap inside the band allows for a wider choice of materials. In this paper, we mainly discuss the recent developments on intraband infrared photodetectors, including 'bottom to up' devices such as quantum well devices based on the molecular beam epitaxial approach, as well as 'up to bottom' devices such as colloidal quantum dot devices based on the chemical synthesis. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new blue-emitting material, CuCrS2/ZnS QDs (CCS QDs). To obtain bright and stable photoluminescent probes, we prepared a core/shell structure; the synthesis was conducted in a one-pot system, using 1-dodecanethiol as a sulfur source and co-ligand. The CCS QDs exhibited a semi-spherical colloidal nanocrystalline shape with an average diameter of 9.0 nm and ZnS shell thickness of 1.6 nm. A maximum photoluminescence emission peak (PL max) was observed at 465 nm with an excitation wavelength of 400 nm and PLQY was 5% at an initial [Cr3+]/[Cu+] molar ratio of one in the core synthesis. With an off-stoichiometric modification for band gap engineering, the CCS QDs exhibited slightly blue-shifted PL emission spectra and PLQY was 10% with an increase in initial molar ratio of 2.0 (462 nm PL max). However, when the initial molar ratio exceeded two, the CCS QDs exhibited a lower photoluminescence quantum yield of 4.5% with 461 nm of PL max at the initial molar ratio of four due to the formation of non-emissive Cr2S3 nanoflakes. [ABSTRACT FROM AUTHOR]

One of the topical problems of materials science is the production of van der Waals heterostructures with the desired properties. Borophene is considered to be among the promising 2D materials for the design of van der Waals heterostructures and their application in electronic nanodevices. In this paper, we considered new atomic configurations of van der Waals heterostructures for a potential application in nano- and optoelectronics: (1) a configuration based on buckled triangular borophene and gallium nitride (GaN) 2D monolayers; and (2) a configuration based on buckled triangular borophene and zinc oxide (ZnO) 2D monolayers. The influence of mechanical deformations on the electronic structure of borophene/GaN and borophene/ZnO van der Waals heterostructures are studied using the first-principles calculations based on density functional theory (DFT) within a double zeta plus polarization (DZP) basis set. Four types of deformation are considered: uniaxial (along the Y axis)/biaxial (along the X and Y axes) stretching and uniaxial (along the Y axis)/biaxial (along the X and Y axes) compression. The main objective of this study is to identify the most effective types of deformation from the standpoint of tuning the electronic properties of the material, namely the possibility of opening the energy gap in the band structure. For each case of deformation, the band structure and density of the electronic states (DOS) are calculated. It is found that the borophene/GaN heterostructure is more sensitive to axial compression while the borophene/ZnO heterostructure is more sensitive to axial stretching. The energy gap appears in the band structure of borophene/GaN heterostructure at uniaxial compression by 14% (gap size of 0.028 eV) and at biaxial compression by 4% (gap size of 0.018 eV). The energy gap appears in the band structure of a borophene/ZnO heterostructure at uniaxial stretching by 10% (gap size 0.063 eV) and at biaxial compression by 6% (0.012 eV). It is predicted that similar heterostructures with an emerging energy gap can be used for various nano- and optoelectronic applications, including Schottky barrier photodetectors. [ABSTRACT FROM AUTHOR]

Due to the low cost, light weight, semitransparency, good flexibility, and large manufacturing area of organic solar cells (OSCs), OSCs have the opportunity to become the next generation of solar cells in some specific applications. So far, the efficiency of the OSC device has been improved by more than 20%. The optical band gap between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level is an important factor affecting the performance of the device. Selenophene, a derivative of aromatic pentacyclic thiophene, is easy to polarize, its LUMO energy level is very low, and hence the optical band gap can be reduced. In addition, the selenium atoms in selenophene and other oxygen atoms or sulfur atoms can form an intermolecular interaction, so as to improve the stacking order of the active layer blend film and improve the carrier transport efficiency. This paper introduces the organic solar active layer materials containing selenium benzene in recent years, which can be simply divided into donor materials and acceptor materials. Replacing sulfur atoms with selenium atoms in these materials can effectively reduce the corresponding optical band gap of materials, improve the mutual solubility of donor recipient materials, and ultimately improve the device efficiency. Therefore, the sulfur in thiophene can be completely replaced by selenium or oxygen of the same family, which can be used in the active layer materials of organic solar cells. This article mainly describes the application of selenium instead of sulfur in OSCs. [ABSTRACT FROM AUTHOR]

In recent years, interest in the liquid-phase exfoliation (LPE) of layered crystals has been growing due to the efficiency and scalability of the method, as well as the wide range of practical applications of the obtained dispersions based on two-dimensional flakes. In this paper, we present a comparative study of as-grown and liquid-phase exfoliated GaSe1−xSx flakes. Bulk GaSe1−xSx crystals with x ~ 0, 0.25, 0.5, 0.75, 1 were synthesized by melting stoichiometric amounts of gallium, selenium, and sulfur particles in evacuated ampoules. X-ray diffraction analysis showed that the crystal structure does not change considerably after LPE, while the analysis of the Raman spectra revealed that, after liquid-phase processing in IPA, an additional peak associated with amorphous selenium is observed in selenium-rich GaSeS compounds. Nevertheless, the direct and indirect transition energies determined from the Kubelka-Munk function for LPE crystals correlate with the band gap of the as-grown bulk GaSeS crystals. This finding is also confirmed by comparison with the data on the positions of the photoluminescence peak. [ABSTRACT FROM AUTHOR]

Soft materials such as biological tissues are prone to deformation and generate different stable structures under external stimulation. This property is widely used to create tunable patterns, and the tuning of the wrinkling patterns can be applied to the control of elastic waves. In this paper, the wrinkling modes of film/substrate systems with different geometric dimensions and material parameters were studied. It is verified by numerical simulation that the elastic wave band gaps corresponding to the two wrinkling modes can be effectively superposed in one system, and the experimental samples with two wrinkling modes coexisting in one system were prepared by parameter optimization and a moisture-curing process. A vibration test showed that the hybrid system could effectively suppress the propagation of elastic waves. Combined with engineering needs, the wrinkling system under different loading conditions was studied, which provides a design guide for widening and regulating the elastic wave band gap. [ABSTRACT FROM AUTHOR]

In this study, we predicted and investigated a new light-element compound B-C-N in Pm phase, denoted as Pm-BCN, using density functional theory. Pm-BCN is mechanically, dynamically, and thermodynamically stable. The elastic moduli of Pm-BCN are larger than those of other B-C-N and light-element compounds, such as P213 BN, B2C3, P4/m BN, Pnc2 BN, and dz4 BN. By studying the mechanical anisotropy of elastic moduli, we proved that Pm-BCN is a mechanically anisotropic material. In addition, the shear anisotropy factors A2 and ABa of Pm-BCN are smaller than those of the seven B-C-N compounds mentioned in this paper. Pm-BCN is a semiconductor material with an indirect and wide band gap, suggesting that Pm-BCN can be applied in microelectronic devices. [ABSTRACT FROM AUTHOR]

Topological insulator (TI), a promising quantum and semiconductor material, has gapless surface state and narrow bulk band gap. Firstly, the properties, classifications and compounds of TI are introduced. Secondly, the preparation and doping of TI are assessed. Some results are listed. (1) Although various preparation methods are used to improve the crystal quality of the TI, it cannot reach the industrialization. Fermi level regulation still faces challenges; (2) The carrier type and lattice of TI are affected by non-magnetic impurities. The most promising property is the superconductivity at low temperature; (3) Magnetic impurities can destroy the time-reversal symmetry of the TI surface, which opens the band gap on the TI surface resulting in some novel physical effects such as quantum anomalous Hall effect (QAHE). Thirdly, this paper summarizes various applications of TI including photodetector, magnetic device, field-effect transistor (FET), laser, and so on. Furthermore, many of their parameters are compared based on TI and some common materials. It is found that TI-based devices exhibit excellent performance, but some parameters such as signal to noise ratio (S/N) are still lower than other materials. Finally, its advantages, challenges and future prospects are discussed. Overall, this paper provides an opportunity to improve crystal quality, doping regulation and application of TI. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) is recognized as a 2D wide bandgap material with unique properties, such as effective photoluminescence and diverse lattice parameters. Nitride alloys containing h-BN have the potential to revolutionize the electronics and optoelectronics industries. The energy band structures of three boron-containing nitride alloys—BxAl1−xN, BxGa1−xN, and BxIn1−xN—were calculated using standard density functional theory (DFT) with the hybrid Heyd–Scuseria–Ernzerhof (HSE) function to correct lattice parameters and energy gaps. The results for both wurtzite and hexagonal structures reveal several notable characteristics, including a wide range of bandgap values, the presence of both direct and indirect bandgaps, and phase mixing between wurtzite and hexagonal structures. The hexagonal phase in these alloys is observed at very low and very high boron concentrations (x), as well as in specific atomic configurations across the entire composition range. However, cohesive energy calculations show that the hexagonal phase is more stable than the wurtzite phase only when x > 0.5, regardless of atomic arrangement. These findings provide practical guidance for optimizing the epitaxial growth of boron-containing nitride thin films, which could drive future advancements in electronics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

Dissolved gas analysis (DGA) is a vital method for the online detection of transformer operation state. The adsorption performance of a SnP3 monolayer modified by transition metal Cr regarding six characteristic gases (CO, C2H4, C2H2, CH4, H2, C2H6) dissolved in oil was studied. The study reveals the relevant adsorption and gas-sensing response mechanisms through calculations of the adsorption energy, density of states, differential charge density, energy gap, and recovery time. The results display a considerable increase in the adsorption effect of the Cr-SnP3 monolayer on six gases. The CO, C2H2, and C2H4 gases lead to chemical adsorption, and the CH4, H2, and C2H6 gases lead to physical adsorption. Combined with the recovery time, the Cr-SnP3 monolayer has a strong adsorption effect on CO and C2H2 gases at normal temperatures and even high temperatures, and the adsorption is stable. C2H4 gas can be rapidly desorbed from the Cr-SnP3 monolayer at 398 K. Therefore, the Cr-SnP3 monolayer can be expected to serve as a CO and C2H2 gas adsorbent and a resistive gas sensor for C2H4 gas. This research offers a theoretical foundation for the development of the Cr-SnP3 monolayer in gas-sensitive materials. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA), a versatile polymer, is extensively used across many industries, such as chemicals, food, healthcare, textiles, and packaging. However, research on applying PVA to triboelectric nanogenerators (TENGs) remains limited. Consequently, we chose PVA as the primary material to explore its contact electrification mechanisms at the molecular level, alongside materials like Polyethylene (PE), Polyvinylidene fluoride (PVDF), and Polytetrafluoroethylene (PTFE). Our findings show that PVA has the highest band gap, with the smallest band gap occurring between the HOMO of PVA and the LUMO of PTFE. During molecular contact, electron transfer primarily occurs in the outermost layers of the molecules, influenced by the functional groups of the polymers. The presence of fluorine atoms enhances the electron transfer between PVA and PTFE to maximum levels. Experimental validation confirmed that PVA and PTFE contact yields the highest triboelectric performance: VOC of 128 V, ISC of 2.83 µA, QSC of 82 nC, and an output power of 384 µW. Moreover, P-TENG, made of PVA and PTFE, was successfully applied in self-powered smart devices and monitored human respiration and bodily movements effectively. These findings offer valuable insights into using PVA in triboelectric nanogenerator technologies. [ABSTRACT FROM AUTHOR]

Using a microscopic model and the Green's function theory, the size and co-doping effects on the multiferroic and optical (band gap) properties of BiFeO3 (BFO) nanoparticles are investigated. The magnetization increases, whereas the band gap energy decreases with decreasing nanoparticle size. The substitution with Co/Mn, Nd/Sm, Ce/Ni, and Cd/Ni is discussed and explained on a microscopic level. By the ion co-doping appear different strains due to the difference between the doping and host ionic radii, which leads to changes in the exchange interaction constants for tuning all properties. It is observed that by co-doping with Nd/Sm at the Bi site or with Co/Mn at the Fe site, the multiferroic properties are larger than those by doping with one ion. Moreover, by doping with Ni, the multiferroic properties are reduced. But by adding another ion (for example Ce or Cd), an increase in these properties is obtained. This shows the advantages of the co-doping, its flexibility, and its greater possibility of tuning the multiferroic properties compared to single ion substitution. The band gap energy decreases for all co-dopants. The polarization increases with increasing magnetic field. This is evidence of magnetoelectric coupling, which is enhanced by co-doping with Co/Mn. The observed theoretical results are in good qualitative agreement with the existing experimental data. [ABSTRACT FROM AUTHOR]

The FTIR absorption bands of virgin and electron-irradiated CeO2 single crystals were measured from 20 K to 500 K between 4000 cm−1 and 12,000 cm−1 (~830 nm to 2500 nm). Three broad bands centered at about 6100 cm−1 (~0.75 eV), 7000 cm−1 (~0.87 eV), and 10,500 cm−1 (~1.3 eV) were recorded above 100 K for the 2.5 MeV electron energy. Two smaller bands at about 4300 cm−1 (~0.53 eV) and 5500 cm−1 (~0.68 eV) were also recorded below 100 K. Similar broad bands centered at about 4100 cm−1 (~0.52 eV), 6400 cm−1 (~0.79 eV), 7600 cm−1 (~0.94 eV), and 10,500 cm−1 (~1.3 eV) are also found for the 1.4 MeV electron energy above 300 K. The evolution of these absorption bands was followed as a function of temperature. The plots of band intensity ratios show a thermally activated process corresponding to the ionization of the deep electronic levels of point defects in the band gap of ceria of ~26,000 cm−1 (~3.2 eV). These five bands are assigned to the different charge states (0, −1, −2, −3, −4) of the Ce vacancies produced by elastic collisions above 1.0 MeV. [ABSTRACT FROM AUTHOR]

Amorphous ZrO2 thin films with increasing Mg content were deposited on quartz substrates, by dip coating method. The films are transparent in the visible domain and absorbent in UV, with an optical band gap that decreases with the increase of Mg content, from 5.42 eV to 4.12 eV. The temperature dependent conductivity measurements showed typical semiconductor comportment. The decrease of the electrical conductivity by Mg doping was related to the increase of the OH groups (37% to 63%) as seen from X-ray Photoelectron Spectroscopy. It was found out that the electrical conductivity obeys the Meyer-Neldel rule. This rule, previously reported for different disordered material systems is obtained for ZrO2 for the first time in the literature. Exploring novel aspects of Mg-doped ZrO2, the present study underscores the origin of the Meyer-Neldel rule explained by the small-polaron hopping model in the non-adiabatic hopping regime. Determination of the presence of such a conduction mechanism in the samples hold promise for comprehending the important aspects, which might be a concern in developing various devices based on Mg-doped ZrO2. [ABSTRACT FROM AUTHOR]

Locally Resonant Acoustic Metamaterials (LRAMs) have significant application potential because they can form subwavelength band gaps. However, most current research does not involve obtaining LRAMs with specified band gaps, even though such LRAMs are significant for practical applications. To address this, we propose a parameterized level-set-based topology optimization method that can use multiple materials to design LRAMs that meet specified frequency constraints. In this method, a simplified band-gap calculation approach based on the homogenization framework is introduced, establishing a restricted subsystem and an unrestricted subsystem to determine band gaps without relying on the Brillouin zone. These subsystems are specifically tailored to model the phenomena involved in band gaps in LRAMs, facilitating the opening of band gaps during optimization. In the multi-material representation model used in this method, each material, except for the matrix material, is depicted using a similar combinatorial formulation of level-set functions. This model reduces direct conversion between materials other than the matrix material, thereby enhancing the band-gap optimization of LRAMs. Two problems are investigated to test the method's ability to use multiple materials to solve band-gap optimization problems with specified frequency constraints. The first involves maximizing the band-gap width while ensuring it encompasses a specified frequency range, and the second focuses on obtaining light LRAMs with a specified band gap. LRAMs with specified band gaps obtained in three-material or four-material numerical examples demonstrate the effectiveness of the proposed method. The method shows great promise for designing metamaterials to attenuate specified frequency spectra as required, such as mechanical vibrations or environmental noise. [ABSTRACT FROM AUTHOR]

CrSBr is a recently discovered two-dimensional anti-ferromagnet. It has attracted much attention due to its superior properties for potential optoelectronic and spintronic applications. However, its complex refractive index with layer dependence has not been systematically studied yet. In this work, we studied the room-temperature complex refractive indices of thin CrSBr flakes of different thicknesses in the visible light range. Using micro-reflectance spectroscopy, we measured the optical contrast of thin CrSBr flakes with respect to different substrates. The complex refractive index was extracted by modeling the optical contrast with the Fresnel equations. We extracted the band gap values of CrSBr in the few-layer limit. We determined the band gaps for monolayer, bilayer, and trilayer CrSBr to be 1.88 eV, 1.81 eV, and 1.77 eV, respectively. As a comparison, the band gap for multilayer CrSBr is outside our measured range, that is, below 1.55 eV. Our results suggest that the band gap of CrSBr decreases as thickness increases. [ABSTRACT FROM AUTHOR]

High-performance hydrogen sulfide (H2S) sensors are mandatory for many industrial applications. However, the development of H2S sensors still remains a challenge for researchers. In this work, we report the study of a TiO2-based conductometric sensor for H2S monitoring at low concentrations. TiO2 samples were first synthesized using the sol-gel route, annealed at different temperatures (400 and 600 °C), and thoroughly characterized to evaluate their morphological and microstructural properties. Scanning electronic microscopy, Raman scattering, X-ray diffraction, and FTIR spectroscopy have demonstrated the formation of clusters of pure anatase in the TiO2 phase. Increasing the calcination temperature to 600 °C enhanced TiO2 crystallinity and particle size (from 11 nm to 51 nm), accompanied by the transition to the rutile phase and a slight decrease in band gap (3.31 eV for 400 °C to 3.26 eV for 600 °C). Sensing tests demonstrate that TiO2 annealed at 400 °C displays good performances (sensor response Ra/Rg of ~3.3 at 2.5 ppm and fast response/recovery of 8 and 23 s, respectively) for the detection of H2S at low concentrations in air. [ABSTRACT FROM AUTHOR]

In the present work, magnesium oxide (MgO) and lead oxide (PbO) nanoparticles were prepared by the co-precipitation method. Their structural parameters and morphology were investigated using XRD, HRTEM, and FTIR. The formation of the phases was seen to have small average crystallite sizes and an orthorhombic crystal structure for both MgO and PbO nanoparticles. The results of HR-TEM showed irregularly shaped nanoparticles: quasi-spherical or rod-like shapes and spherical-like shapes for MgO and PbO nanoparticles, respectively. The produced nanoparticles' size using X-ray diffraction analysis was found to be 17 nm and 41 nm for MgO and PbO nanoparticles, respectively. On the other hand, it was observed from the calculations that the optical band gap obeys an indirect allowed transition. The calculated values of the band gap were 4.52 and 4.28 eV for MgO and PbO NPs, respectively. The MB was extracted from the wastewater using the prepared composites via absorption. Using a variety of kinetic models, the adsorptions were examined. Out of all the particles, it was discovered that the composites were best. Furthermore, of the models currently under consideration, the pseudo-second-order model best fit the degradation mechanism. The resultant composites could be beneficial for degrading specific organic dyes for water purification, as well as applications needing a wider optical band gap. [ABSTRACT FROM AUTHOR]

Honeycomb structures have attracted much attention for their excellent characteristics of reducing vibration and noise in recent years. In this study, through band analysis of different ligament structures, we aim to optimize the design of a steel structure that can isolate most of the noise in the 1500–5000 Hz range. The present study examines several different chiral structures. We calculate the band gaps of chiral structures under different geometric configurations and identify the variations in band gaps with geometric layouts. It is found that compared to other chiral structures, the triligaments chiral structure exhibits excellent band gap characteristics. The calculation results demonstrate that enhancing axial symmetry while filling central nodes can effectively enhance the structure's band gap properties. Frequency–response functions of different lattice structures are computed, and the results align with the calculations of band structures. This study then analyzes the influence of the number of periods on the magnitude of vibration attenuation, revealing that under the same number of periods, the wider the band gap of the structure, the greater the vibration attenuation. Both the triligaments chiral structure and the vertical triligaments structure possess ideal band gap widths, effectively suppressing wave propagation. Subsequently, harmonic response analyses and transient wave calculations further validate the accuracy of the band structure and frequency–response curve calculations. Our study results provide a new way to design a sound insulation structure that can isolate noise signals within the frequency range from 1500 to 5000 Hz in engineering. [ABSTRACT FROM AUTHOR]

We investigated the electronic structure of Mg-, Si-, and Zn-doped four-faceted [001]- and [110]-oriented SnO2 nanowires using first-principles calculations based on the linear combination of atomic orbitals (LCAO) method. This approach, employing atomic-centered Gaussian-type functions as a basis set, was combined with hybrid density functional theory (DFT). Our results show qualitative agreement in predicting the formation of stable point defects due to atom substitutions on the surface of the SnO2 nanowire. Doping induces substantial atomic relaxation in the nanowires, changes in the covalency of the dopant–oxygen bond, and additional charge redistribution between the dopant and nanowire. Furthermore, our calculations reveal a narrowing of the band gap resulting from the emergence of midgap states induced by the incorporated defects. This study provides insights into the altered electronic properties caused by Mg, Si, and Zn doping, contributing to the further design of SnO2 nanowires for advanced electronic, optoelectronic, photovoltaic, and photocatalytic applications. [ABSTRACT FROM AUTHOR]

The solid electrolyte Li10GeP2S12 (LGPS) plays a crucial role in the development of all-solid-state batteries and has been widely studied both experimentally and theoretically. The properties of solid electrolytes, such as thermodynamic stability, conductivity, band gap, and more, are closely related to their ground-state structures. However, the presence of site-disordered co-occupancy of Ge/P and defective fractional occupancy of lithium ions results in an exceptionally large number of possible atomic configurations (structures). Currently, the electrostatic energy criterion is widely used to screen favorable candidates and reduce computational costs in first-principles calculations. In this study, we employ the machine learning- and active-learning-based LAsou method, in combination with first-principles calculations, to efficiently predict the most stable configuration of LGPS as reported in the literature. Then, we investigate the diffusion properties of Li ions within the temperature range of 500–900 K using ab initio molecular dynamics. The results demonstrate that the atomic configurations with different skeletons and Li ion distributions significantly affect the Li ions' diffusion. Moreover, the results also suggest that the LAsou method is valuable for refining experimental crystal structures, accelerating theoretical calculations, and facilitating the design of new solid electrolyte materials in the future. [ABSTRACT FROM AUTHOR]

As a direct band gap semiconductor, perovskite has the advantages of high carrier mobility, long charge diffusion distance, high defect tolerance and low-cost solution preparation technology. Compared with traditional metal halide perovskites, which regulate energy band and luminescence by changing halogen, perovskite quantum dots (QDs) have a surface effect and quantum confinement effect. Based on the LaMer nucleation growth theory, we have synthesized CsPbBr3 QDs with high dimensional homogeneity by creating an environment rich in Br− ions based on the general thermal injection method. Moreover, the size of the quantum dots can be adjusted by simply changing the reaction temperature and the concentration of Br− ions in the system, and the blue emission of strongly confined pure CsPbBr3 perovskite is realized. Finally, optical and electrochemical tests suggested that the synthesized quantum dots have the potential to be used in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

Electric, dielectric, and optical (band gap) properties of pure multiferroic as well as La- and Ni-doped SrFe 12 O 19 (SFO) (at different sites) are investigated using a microscopic model and Green's function technique. The concentration dependence of the polarization P is considered for substitution of rare earths ions on the Sr sites. For a small La ion doping concentration, x = 0.1, La-doped SFO is ferroelectric, whereas for a larger doping concentration, for example x = 0.5, it is antiferroelectric. The real part of the dielectric constant ϵ increases with an increasing magnetic field h. ϵ decreases with an increasing frequency and La dopants. Therefore, La-doped SFO is suitable for microwave application with a low dielectric constant. The magnetic properties of pure SFO NPs are also studied. Ni doping at the Fe site of SFO leads to enhanced ferroelectric polarization and dielectric constant. The band gap decreases or increases by substitution of Ni or In ions on the Fe site, respectively. The results reveal that the tuned band gap of Ni-doped SFO makes it a crucial candidate for optoelectronic and solid oxide fuel cell applications. [ABSTRACT FROM AUTHOR]

The electronic structure of carbon nanotube bundles (CNTBs) can be a tough task for the routine first-principle calculation. The difficulty comes from several issues including the atomic structure, the boundary condition, and above all the very large number of atoms that makes the calculation quite cumbersome. In this work, we estimated the band gap of the CNTBs based on the results from single-walled carbon nanotubes (SWCNTs) under different deformations. The effects of squeezing, stretching, and torsion on the bands of SWCNTs were investigated through first-principle calculations, from which the band gaps of bundles were analyzed because the effects of these deformations were qualitatively independent when the distortions were small. Specifically, the gaps of (4,4) and (8,0) CNTBs under a reasonable torsional strength were predicted, wherein we were able to see metal–semiconductor and semiconductor–metal transitions, respectively. Such reversible mechanical modification of the conductivity may be helpful to the future band-gap engineering in nanoscale circuits. [ABSTRACT FROM AUTHOR]

In the wide group of thermoelectric compounds, the half-Heusler ZrNiSn alloy is one of the most promising materials thanks to its thermal stability and narrow band gap, which open it to the possibility of mid-temperature applications. A large variety of defects and doping can be introduced in the ZrNiSn crystalline structure, thus allowing researchers to tune the electronic band structure and enhance the thermoelectric performance. Within this picture, theoretical studies of the electronic properties of perfect and defective ZrNiSn structures can help with the comprehension of the relation between the topology of defects and the thermoelectric features. In this work, a half-Heusler ZrNiSn alloy is studied using different defective models by means of an accurate Density Functional Theory supercell approach. In particular, we decided to model the most common defects related to Ni, which are certainly present in the experimental samples, i.e., interstitial and antisite Ni and a substitutional defect consisting of the replacement of Sn with Sb atoms using concentrations of 3% and 6%. First of all, a comprehensive characterization of the one-electron properties is performed in order to gain deeper insight into the relationship between structural, topological and electronic properties. Then, the effects of the modeled defects on the band structure are analyzed, with particular attention paid to the region between the valence and the conduction bands, where the defective models introduce in-gap states with respect to the perfect ZrNiSn crystal. Finally, the electronic transport properties of perfect and defective structures are computed using semi-classical approximation in the framework of the Boltzmann transport theory as implemented in the Crystal code. The dependence obtained of the Seebeck coefficient and the power factor on the temperature and the carrier concentration shows reasonable agreement with respect to the experimental counterpart, allowing possible rationalization of the effect of the modeled defects on the thermoelectric performance of the synthesized samples. As a general conclusion, defect-free ZrNiSn crystal appears to be the best candidate for thermoelectric applications when compared to interstitial and antisite Ni defective models, and substitutional defects of Sn with Sb atoms (using concentrations of 3% and 6%) do not appreciably improve electronic transport properties. [ABSTRACT FROM AUTHOR]

Bi-based YbMg2Bi1.98 Zintl compounds represent promising thermoelectric materials. Precise composition and appropriate doping are of great importance for this complex semiconductor. Here, the influence of Zn substitution for Mg on the microstructure and thermoelectric properties of p-type YbMg1.85−xZnxBi1.98 (x = 0, 0.05, 0.08, 0.13, 0.23) was investigated. Polycrystalline samples were prepared using induction melting and densified with spark plasma sintering. X-ray diffraction confirmed that the major phase of the samples possesses the trigonal CaAl2Si2-type crystal structure, and SEM/EDS indicated the presence of minor secondary phases. The electrical conductivity increases and the lattice thermal conductivity decreases with more Zn doping in YbMg1.85−xZnxBi1.98, whereas the Seebeck coefficient has a large reduction. The band gap decreases with increasing Zn concentration and leads to bipolar conduction, resulting in an increase in the thermal conductivity at higher temperatures. Figure of merit ZT values of 0.51 and 0.49 were found for the samples with x = 0 and 0.05 at 773 K, respectively. The maximum amount of Zn doping is suggested to be less than x = 0.1. [ABSTRACT FROM AUTHOR]

This paper systematically investigated the topological design of cellular phononic crystals with a maximized gap size between two adjacent bands. Considering that the obtained structures may sustain a certain amount of static loadings, it is desirable to ensure the optimized designs to have a relatively high stiffness. To tackle this issue, we conducted a multiple objective optimization to maximize band gap size and bulk or shear modulus simultaneously with a prescribed volume fraction of solid material so that the resulting structures can be lightweight, as well. In particular, we first conducted the finite element analysis of the phononic band gap crystals and then adapted a very efficient optimization procedure to resolve this problem based on bi-directional evolutionary structure optimization (BESO) algorithm in conjunction with the homogenization method. A number of optimization results for maximizing band gaps with bulk and shear modulus constraints are presented for out-of-plane and in-plane modes. Numerical results showed that the optimized structures are similar to those obtained for composite case, except that additional slim connections are added in the cellular case to support the propagation of shear wave modes and meanwhile to satisfy the prescribed bulk or shear modulus constraints. [ABSTRACT FROM AUTHOR]

In this paper, we report on the crystal structure and the electrical and thermal transport properties of the BiCuSe1-xSxO series. From the evolution of the structural parameters with the substitution rate, we can confidently conclude that a complete solid solution exists between the BiCuSeO and BiCuSO end members, without any miscibility gap. However, the decrease of the stability of the materials when increasing the sulfur fraction, with a simultaneous volatilization, makes it difficult to obtain S-rich samples in a single phase. The band gap of the materials linearly increases between 0.8 eV for BiCuSeO and 1.1 eV in BiCuSO, and the covalent character of the Cu-Ch (Ch = chalcogen element, namely S or Se here) bond slightly decreases when increasing the sulfur fraction. The thermal conductivity of the end members is nearly the same, but a significant decrease is observed for the samples belonging to the solid solution, which can be explained by point defect scattering due to atomic mass and radii fluctuations between Se and S. When increasing the sulfur fraction, the electrical resistivity of the samples strongly increases, which could be linked to an evolution of the energy of formation of copper vacancies, which act as acceptor dopants in these materials. [ABSTRACT FROM AUTHOR]

Polymer electrolytes and composites have prevailed in the high performance and mobile marketplace during recent years. Polymer-based solid electrolytes possess the benefits of low flammability, excellent flexibility, good thermal stability, as well as higher safety. Several researchers have paid attention to the optical properties of polymer electrolytes and their composites. In the present review paper, first, the characteristics, fundamentals, advantages and principles of various types of polymer electrolytes were discussed. Afterward, the characteristics and performance of various polymer hosts on the basis of specific essential and newly published works were described. New developments in various approaches to investigate the optical properties of polymer electrolytes were emphasized. The last part of the review devoted to the optical band gap study using two methods: Tauc's model and optical dielectric loss parameter. Based on recently published literature sufficient quantum mechanical backgrounds were provided to support the applicability of the optical dielectric loss parameter for the band gap study. In this review paper, it was demonstrated that both Tauc's model and optical dielectric loss should be studied to specify the type of electron transition and estimate the optical band gap accurately. Other parameters such as absorption coefficient, refractive index and optical dielectric constant were also explored. [ABSTRACT FROM AUTHOR]

This work studies the technological preparation conditions, morphology, structural characteristics and elemental composition, and optical and photoluminescent properties of GaSe single crystals and Eu-doped β–Ga2O3 nanoformations on ε–GaSe:Eu single crystal substrate, obtained by heat treatment at 750–900 °C, with a duration from 30 min to 12 h, in water vapor-enriched atmosphere, of GaSe plates doped with 0.02–3.00 at. % Eu. The defects on the (0001) surface of GaSe:Eu plates serve as nucleation centers of β–Ga2O3:Eu crystallites. For 0.02 at. % Eu doping, the fundamental absorption edge of GaSe:Eu crystals at room temperature is formed by n = 1 direct excitons, while at 3.00 at. % doping, Eu completely shields the electron–hole bonds. The band gap of nanostructured β–Ga2O3:Eu layer, determined from diffuse reflectance spectra, depends on the dopant concentration and ranges from 4.64 eV to 4.87 eV, for 3.00 and 0.05 at. % doping, respectively. At 0.02 at. % doping level, the PL spectrum of ε–GaSe:Eu single crystals consists of the n = 1 exciton band, together with the impurity band with a maximum intensity at 800 nm. Fabry–Perrot cavities with a width of 9.3 μm are formed in these single crystals, which determine the interference structure of the impurity PL band. At 1.00–3.00 at. % Eu concentrations, the PL spectra of GaSe:Eu single crystals and β–Ga2O3:Eu nanowire/nanolamellae layers are determined by electronic transitions of Eu2+ and Eu3+ ions. [ABSTRACT FROM AUTHOR]

In this work, we investigated the MOCVD conditions to synthesize thin films with the hexagonal P63cm h-LuMnO3 phase as a potential low-band gap ferroelectric material. The main parameters investigated were the ratio of organometallic starting materials, substrate temperature, and annealing effect. Two different substrates were used in the study: fused silica (SiO2) glass and platinized silicon (Pt\Ti\SiO2\Si(100)). In order to investigate the thermodynamic stability and quality of the developed phases, a detailed analysis of the crystal structure, microstructure, morphology, and roughness of the films was performed by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy, and piezoelectric force microscopy (PFM). Molar compositions in the film within 0.93 < |Lu|/|Mn| < 1.33 were found to be suitable for obtaining a single-phase h-LuMnO3. The best films were obtained by depositions at 700 °C, followed by thermal treatments at 800 °C for long periods of up to 12 h. These films exhibited a highly crystalline hexagonal single phase with a relatively narrow direct band gap, around 1.5 eV, which is within the expected values for the h-LuMnO3 system. [ABSTRACT FROM AUTHOR]

The magnetic, electric, dielectric, and optical (band gap) properties of ion doped multiferroic KBiFe 2 O 5 (KBFO) have been systematically investigated utilizing a microscopic model and the Green's function theory. Doping with Co at the Fe site and Ru at the Bi site induces changes in magnetization, coercive field, and band gap energy. Specifically, an increase in magnetization is observed, while the coercive field and band gap energy decrease. This behavior is attributed to the distinct ionic radii of the doped and host ions, leading to alterations in the exchange interaction constants. The temperature dependence of the polarization P reveals a distinctive kink at the Neel temperature T N , which shifts to higher temperatures with an increase in the applied magnetic field h. Furthermore, doping with Ru and La leads to an increase in polarization. The temperature dependence of the dielectric constant exhibits two peaks at the Neel temperature T N and the Curie temperature T C . Notably, these peaks diminish with increasing frequency. Additionally, the dielectric constant demonstrates a decrease with the rise in the applied magnetic field h. This study sheds light on the intricate interplay between ion doping, structural modifications, and multifunctional properties in KBFO, offering valuable insights into the underlying mechanisms governing its behavior across various physical domains. [ABSTRACT FROM AUTHOR]

DyMnO3 is a p-type semiconductor oxide with two crystal systems, orthorhombic and hexagonal. This material highlights its ferroelectric and ferromagnetic properties, which have been the subject of numerous studies. Nevertheless, its photocatalytic activity has been less explored. In this work, the photocatalytic activity of DyMnO3 is evaluated through the photodegradation of MG dye. For the synthesis of this oxide, a novel and effective method was used: polymer-decomposition. The synthesized powders contain an orthorhombic phase, with a range of absorbances from 300 to 500 nm and a band gap energy of 2.4 eV. It is also highlighted that, when using this synthesis method, some of the main diffraction lines related to the orthorhombic phase appear at 100 °C. Regarding its photocatalytic activity, it was evaluated under visible light (λ = 405 nm), reaching a photodegradation of approximately 88% in a period of 30 min. Photocurrent tests reveal a charge carrier separation ( e − , h + ) at a 405 nm wavelength. The main reactive oxygen species (ROS) involved in the photodegradation process were radicals, O H • , and photo-holes ( h + ). These results stand out because it is the first time that the photodegradation capability of this oxide in the visible spectrum has been evaluated. [ABSTRACT FROM AUTHOR]

This study shows an easy way to use electrochemistry and plasma layering to make Cobalt-Blue-TiO2 nanotubes that are better at catalysing reactions. Once a titanium plate has been anodized, certain steps are taken to make oxygen vacancies appear inside the TiO2 nanostructures. To find out how the Co deposition method changed the final catalyst's properties, it was put through electrochemical tests (to find the charge transfer resistance and flat band potential) and optical tests (to find the band gap and Urbach energy). The catalysts were also described in terms of their shape, ability to stick to surfaces, and ability to inhibit bacteria. When Cobalt was electrochemically deposited to Blue-TiO2 nanotubes, a film with star-shaped structures was made that was hydrophilic and antibacterial. The band gap energy went down from 3.04 eV to 2.88 eV and the Urbach energy went up from 1.171 eV to 3.836 eV using this electrochemical deposition method. Also, photodegradation tests with artificial doxycycline (DOX) water were carried out to see how useful the study results would be in real life. These extra experiments were meant to show how the research results could be used in real life and what benefits they might have. For the bacterial tests, both gram-positive and gram-negative bacteria were used, and BT/Co-E showed the best response. Additionally, photodegradation and photoelectrodegradation experiments using artificial doxycycline (DOX) water were conducted to determine the practical relevance of the research findings. The synergistic combination of light and applied potential leads to 70% DOX degradation after 60 min of BT/Co-E irradiation. [ABSTRACT FROM AUTHOR]

Ultrathin solid slabs often have properties different from those of the bulk phase. This effect can be observed both in traditional three-dimensional materials and in van der Waals (vdW) solids in the few monolayer limit. In the present work, the band gap variation of the CdTe slabs, induced by their thickness, was studied by the density functional theory (DFT) method for the sphalerite (zinc-blende) phase and for the recently proposed inverted phase. The sphalerite phase has the Te–Cd–Te–Cd atomic plane sequence, while in the inverted phase Cd atoms are sandwiched by Te planes forming vdW blocks with the sequence Te–Cd–Cd–Te. Based on these building blocks, a bulk vdW CdTe crystal was built, whose thermodynamical stability was verified by DFT calculations. Band structures and partial densities of states for sphalerite and inverted phases were calculated. It was demonstrated for both phases that using slabs with a thickness of one to several monolayers for sphalerite phase (vdW blocks for inverted phase), structures with band gaps varying in a wide range can be obtained. The presented results allow us to argue that ultrathin CdTe can be a promising electronic material. [ABSTRACT FROM AUTHOR]

The aim of this work was to biosynthesize SnO2-decorated ZnO (ZT) nanocomposites (NCs) of different Sn content (10, 20, and 30 mol%), namely, ZT10, ZT20, and ZT30, using Olea europaea leaf aqueous extract-based phytocompounds as nanoparticle facilitating agents for application as effective photocatalyst in the removal of dyes from polluted water. The obtained ZT NCs were characterized using various techniques, including FTIR, XRD, TGA, TEM, EDS, UV–Vis, PL, and BET surface area. X-ray diffraction patterns show that rutile SnO2 and hexagonal ZnO coexist in the composites, and their crystallite size (D) is affected by the SnO2 ratio; the obtained D-values were 17.24, 19.07, 13.99, 6.45, and 12.30 nm for ZnO, SnO2, ZT10, ZT20, and ZT30, respectively. The direct band gaps of the ZT heterostructure increase with increasing SnO2 ratio (band gap = 3.10, 3.45, 3.14, 3.17, and 3.21 eV, respectively). TEM spectroscopy revealed nanorod and spherical grain morphologies of the composites, while EDS confirmed the elemental composition, the element ratio, and the composite's purity. All catalysts exhibit type III isotherm with macropore structure. The photocatalytic efficiency against cationic (methylene blue (MB), rhodamine B (RB)), and anionic (methyl orange (MO)) dyes, under sunlight, was optimal with ZT20. The results revealed almost complete degradation at 55, 65, and 55 min, respectively. Hence, it is evident that incorporating SnO2 improves the photocatalyst's performance, with an apparent optimal enhancement at 20 mol% Sn decorating ZT NCs. More interestingly, the catalyst stability and activity remained unaffected even after four activating cycles. [ABSTRACT FROM AUTHOR]

In order to shift the light emission of nitride quantum structures towards the red color, the technological problem of low In incorporation in InGaN−based heterostructures has to be solved. To overcome this problem, we consider superlattices grown on InGaN buffers with different In content. Based on the comparison of the calculated ab initio superlattice band gaps with the photoluminescence emission energies obtained from the measurements on the specially designed samples grown by metal-organic vapor phase epitaxy, it is shown that by changing the superlattice parameters and the composition of the buffer structures, the light emission can be shifted to lower energies by about 167 nm (0.72 eV) in comparison to the case of a similar type of superlattices grown on GaN substrate. The importance of using superlattices to achieve red emission and the critical role of the InGaN buffer are demonstrated. [ABSTRACT FROM AUTHOR]