Band Energy Research Articles

Impact of Au on the transition temperature and photocatalytic activity of TiO2

The effect of gold (Au) addition on the anatase to rutile transition temperature (ART) of titanium dioxide (TiO2) was investigated. Concentrations of 2, 4, 8 and 16 mol. % of Au have been synthesised via a sol–gel technique and calcined at various temperatures (500–900 °C). The inclusion of gold improves the ART at 700 °C, maintaining 44.5 % anatase content for 4 % Au. Density functional theory studies indicated that the addition of Au in the anatase phase results in considerable lattice distortions, while Au 4d states and occupied Ti 3d orbitals contribute to the valence-conduction band energy gap upon doping. However, no sign of lattice substitution was observed in the experimental analysis. Instead, we demonstrate that the actual structure is well described by gold nanoparticles deposited on anatase and present a detailed DFT description of gold-modified anatase (101). All Au-TiO2samples exhibit reduced photocatalytic degradation properties compared to the control TiO2 at 500 °C. However, after calcining at 600 °C the addition of Au increases the photocatalytic activity of TiO2 from 49 % to 61 %, at an optimal concentration of 2 % Au-TiO2. The modification of titania with gold does push the transition temperature higher. However, this comes at the cost of reduced activity for 1,4-dioxane degradation, with the unmodified titania sample having better overall photocatalytic activity.

A simulation study of transcranial magnetoacoustic stimulation of the basal ganglia thalamic neural network to improve pathological beta oscillations in Parkinson's disease

BackgroundParkinson's disease (PD) is a common neurodegenerative disease. Transcranial magnetoacoustic stimulation (TMAS) is a new therapy that combines a transcranial focused acoustic pressure field with a magnetic field to excite or inhibit neurons in targeted area, which suppresses the abnormally elevated beta band amplitude in PD states, with high spatial resolution and non-invasively. ObjectiveTo study the effective stimulation parameters of TMAS mononuclear and multinuclear stimulation for the treatment of PD with reduced beta band energy, improved abnormal synchronization, and no thermal damage. MethodsThe TMAS model is constructed based on the volunteer's computed tomography, 128 arrays of phase-controlled transducers, and permanent magnets. A basal ganglia-thalamic (BG-Th) neural network model of the PD state was constructed on the basis of the Izhikevich model and the acoustic model. An ultrasound stimulation neuron model is constructed based on the Hodgkin-Huxley model. Numerical simulations of transcranial focused acoustic pressure field, temperature field and induced electric field at single and dual targets were performed using the locations of STN, GPi, and GPe in the human brain as the main stimulation target areas. And the acoustic and electric parameters at the focus were extracted to stimulate mononuclear and multinuclear in the BG-Th neural network. ResultsWhen the stimulating effect of ultrasound is ignored, TMAS-STN simultaneously inhibits the beta-band amplitude of the GPi nucleus, whereas TMAS-GPi fails to simultaneously have an inhibitory effect on the STN. TMAS-STN&GPi can reduce the beta band amplitude. TMAS-STN&GPi&GPe suppressed the PD pathologic beta band amplitude of each nucleus to a greater extent. When considering the stimulatory effect of ultrasound, lower sound pressures of ultrasound do not affect the neuronal firing state, but higher sound pressures may promote or inhibit the stimulatory effect of induced currents. ConclusionsAt 9 T static magnetic field, 0.5–1.5 MPa and 1.5–2.0 MPa ultrasound had synergistic effects on individual STN and GPi neurons. TMAS multinuclear stimulation with appropriate ultrasound intensity was the most effective in suppressing the amplitude of pathological beta oscillations in PD and may be clinically useful.

Graphitic carbon nitride sheets sandwiched metal oxides: A novel platform for S-Scheme heterojunction generation for efficient photodegradation of volatile organics

This study reports the preparation of new kind of S-Scheme heterojunction (SSHJ) photocatalyst by distributing two semiconducting metal oxides (titanium dioxide and ZnO) onto the surface of graphitic carbon nitride (G-CN) two dimensional (2D) sheets. The composite photocatalysts, designated as T/Z@ GCN SSHJ, were prepared with different mass ratios of T,Z and G-CN.X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy were used to characterize the microstructure, morphology, chemical composition, electronic states, and optical properties of the T/Z@ GCN SSHJ composite. TEM image of the typical T/Z@ GCN SSHJ composite shows the presence of distribution of particles with sizes in the range 40–80 nm on the lamellar surface of G-CN inferring the formation of a heterostructure Z(0 D) /G-CN(2D)/T(0D) SSHJ composite. The comparison of the core level XPS spectrum of Ti 2p, Zn 2p, C1s, O1s and N1s of T/Z@ GCNSSHJ composite with the binary composites (T+G-CN and Z+G-CN) and pristine components clearly suggests that that Z, T and G-CN are kept together through van der Walls interactions. The T/Z@ GCN SSHJ composite photocatalyst with T: Z: G-CN mass ratio of 1.0: 0.80: 0.12 exhibited enhanced photocatalytic degradation (%) over binary and pristine single components for all the tested volatile organic compounds (VOCs), namely, acetaldehyde (ACD), ethyl acetate (EA), toluene (T) and benzaldehyde (BA). On comparing the % removal of VOCs after 20 minute of light irradiation, BA showed the highest removal % (94.3 %) and the others take the following order: ACD (70.9 %) >EA (56.45 %)> TL (40.12 %). The study explains the enhanced performance of T/Z@ G-CN HJ composite towards VOC photodegradation in terms of S-Scheme based charge transfer and internal electric field driven efficient charge separation. The charge transfer process of T/Z@ GCN HJ composite photocatalysts is discussed through S-Scheme HJ formation and supported with electronic states and band energy levels of the constituent components derived through the results of XPS and DRS analysis. This study gives insight into the design for regulating the hetero-interfaces for enhancing the photocatalysis and expected to further understand into charge transfer mechanism at multi-junction-based photocatalysts.

Ce-Doped SnO2 Electron Transport Layer for Minimizing Open Circuit Voltage Loss in Lead Perovskite Solar Cells.

In the planar heterostructure of perovskite-based solar cells (PSCs), tin oxide (SnO2) is a material that is often used as the electron transport layer (ETL). SnO2 ETL exhibits favorable optical and electrical properties in the PSC structures. Nevertheless, the open circuit voltage (VOC) depletion occurs in PSCs due to the defects arising from the high oxygen vacancy on the SnO2 surface and the deeper conduction band (CB) energy level of SnO2. In this research, a cerium (Ce) dopant was introduced in SnO2 (Ce-SnO2) to suppress the VOC loss of the PSCs. The CB minimum of SnO2 was shifted closer to that of the perovskite after the Ce doping. Besides, the Ce doping effectively passivated the surface defects on SnO2 as well as improved the electron transport velocity by the Ce-SnO2. These results enabled the power conversion efficiency (PCE) to increase from 21.1% (SnO2) to 23.0% (Ce-SnO2) of the PSCs (0.09 cm2 active area) with around 100 mV of improved VOC and reduced hysteresis. Also, the Ce-SnO2 ETL-based large area (1.0 cm2) PSCs delivered the highest PCE of 22.9%. Furthermore, a VOC of 1.19 V with a PCE of 23.3% was demonstrated by Ce-SnO2 ETL-based PSCs (0.09 cm2 active area) that were treated with 2-phenethylamine hydroiodide on the perovskite top surface. Notably, the unencapsulated Ce-SnO2 ETL-based PSC was able to maintain above 90% of its initial PCE for around 2000 h which was stored under room temperature condition (23-25 °C) with a relative humidity of 40-50%.

Large-area phosphorene for stable carbon-based perovskite solar cells

Carbon-based perovskite solar cells (c-PSCs) have attracted increasing attention due to their numerous advantages including ease of fabrication, the potential of assembling flexible devices, low manufacturing costs as well as large-scale production. However, c-PSCs suffer from the limited hole extraction and high charge carrier recombination due to the inadequate interface contact between the carbon electrode and perovskite film. Herein, we report the fabrication of planar c-PSCs with high efficiency and excellent stability by employing electrochemically produced large-area phosphorene flakes as a hole-transporting layer (HTL). Large-area phosphorene shows well-aligned band energy levels with the perovskite, and thus led to the efficient hole extraction and the reduced hysteresis behaviour. Consequently, while exhibiting excellent stability under various harsh testing conditions, the devices with phosphorene HTL delivered a power conversion efficiency of over 15% with an open-circuit voltage of 1.082 V, which is the highest reported value for c-PSCs without traditional hole transporting materials to date.

Structural, optoelectronic, and magnetic behaviors of Li2BeTM (TM = V, Cr, Mn, Fe) Se4 compounds using DFT investigations

In this work, we present computational investigations of the electronic, the optical and the magnetic properties of the Li2BeTMSe4(TM = V, Cr, Mn, Fe) compounds using the first-principle calculations based on the density functional theory. In this respect, we employ the generalized gradient approximation corrected by the Tran-Balaha modified Becke-Johnson exchange potential to obtain more accurate results. Among these outcomes, we first study the electronic properties such as the band energy dispersion and the state densities. Regarding this, the Li2BeTMSe4 quaternary family is found to have an indirect band gap of 1.910 eV, 1.905 eV, 2.223 eV and 1.278 eV for TM = V, Cr, Mn, and Fe, respectively. Further, an examination of the optical properties reveals that the computed optical absorption spectra cover a broad energy range in the visible and the ultraviolet spectrums. Motivated by spintronic applications, we additionally determine the total and the local magnetic moments. Then, we compute the associated Curie temperatures via a linear relation with the total magnetic moments. Among others, the Li2BeTMSe4(TM = V, Cr, Mn, Fe) materials involve acceptable temperatures showing potential applications for high temperature nano-devices activities. Comparing the obtained findings with the available ones, the acquired results indicate that the Li2BeTMSe4(TM = V, Cr, Mn, Fe) materials exhibit a wide range of applications in solar cells, optoelectronics, and other fields.

Direct probing of low-energy intra d-band transitions in gas-phase cobalt clusters

The interplay between constituent localized and itinerant electrons of metal clusters defines their physical and chemical properties. In turn, the electronic and geometrical structures are strongly entwined and exhibit strong size-dependent variations. Current understanding of low-energy excited states of metal clusters relies on stand-alone theoretical investigations and few comparisons with measured properties, since direct identification of low-lying states is lacking hitherto. Here, we report on the measurement of low-lying electronic transitions in cationic cobalt clusters using infrared photofragmentation spectroscopy. Broad and size-dependent absorption features were observed within 0.056 – 0.446 eV, well above the energies of the sharp absorption bands caused by cluster vibrations. Complementary time-dependent density functional theory calculations reproduce the main observed absorption features, providing direct evidence that they correspond to transitions between electronic states of mainly d-character, arising from the open d-shells of the Co atoms and the high spin multiplicity of the clusters.

Evidence for electron-hole crystals in a Mott insulator.

The coexistence of correlated electron and hole crystals enables the realization of quantum excitonic states, capable of hosting counterflow superfluidity and topological orders with long-range quantum entanglement. Here we report evidence for imbalanced electron-hole crystals in a doped Mott insulator, namely, α-RuCl3, through gate-tunable non-invasive van der Waals doping from graphene. Real-space imaging via scanning tunnelling microscopy reveals two distinct charge orderings at the lower and upper Hubbard band energies, whose origin is attributed to the correlation-driven honeycomb hole crystal composed of hole-rich Ru sites and rotational-symmetry-breaking paired electron crystal composed of electron-rich Ru-Ru bonds, respectively. Moreover, a gate-induced transition of electron-hole crystals is directly visualized, further corroborating their nature as correlation-driven charge crystals. The realization and atom-resolved visualization of imbalanced electron-hole crystals in a doped Mott insulator opens new doors in the search for correlated bosonic states within strongly correlated materials.

Computation of the near-infrared electro-absorption in GeSn/SiGeSn step quantum wells

In this study, we propose a theoretical simulation of the type-I step quantum well obtained from GeSn/SiGeSn to scan a wide range of telecommunication wavelengths and obtain near-infrared optical modulators. At T = 300 K, the band discontinuities and energy gap between stretched Ge1−xSnx and relaxed Si0.1Ge0.9−ySny due to the acquisition of the heterostructure were calculated.Then, optimization of this heterostructure based on (Si) GeSn was performed using the solid theory model to balance out the composition y of Si0.1Ge0.9-ySny relaxed and thickness of Ge0.91Sn0.09 QWs. The eigenenergies and their related wavefunctions are computed by solving the Schrödinger equation using the finite difference method under the framework of the effective mass approximation. Depending on the y concentration, the energy levels of the electron and the heavy hole, the change of transition energies and oscillator strength were examined for different well widths. Additionally, the absorption coefficient with y concentration and structure parameters were examined.From the findings obtained, it was determined that this material group is very important to obtain high efficiency from electro-absorption modulators covering the 1.55 μm wavelength range.

Features of the optical properties of chalcogenide glassy semiconductor Ge-As-Se(Te) systems

In this work were determined the optical band gap (Eg), packing coefficient (𝜘) and average atomic volume (Va) by conducting experiments to measure the optical transmission spectra and density (ρ) of chalcogenide glassy semiconductors of Ge-As-Se(Te) systems. Reasons of changes occurring in the band gap and in the structure of the amorphous matrix of the studied materials were suggested taking into account existing ideas about the nature of the band energy spectrum of chalcogenide glasses and analysis of experimental data. The dependence of ϰ and Va on Z and R are investigated for stoichiometric compositions of As25Ge12.5Se(Te)62.5 and the nature of these dependencies were explained in detail.

Wave-driven Friction Nanogenerator Based on PDMS/Fe3O4 Composite Nanomaterials

Wave energy is a widely available renewable energy source with a lot of potential for self-powered sensing applications. However, wave energy density is low, and most wave sources in the natural environment are low- to medium-frequency wave sources. In order to improve the collection efficiency of wave energy in low and medium frequency bands, a wave-driven overlapping cube friction nanogenerator (OC-TENG) based on polydimethylsiloxane/ triiron tetroxide (PDMS/Fe3O4) composite nanofilm materials is designed. PDMS/Fe3O4 composite nanomaterials as the negative friction layer, polyamide 11 (PA11) as the positive friction layer, and copper foil (Cu) as the electrode, combined with the overlapping cube structure. With varying wave frequencies, the OC-TENG can produce peak voltages between 57.35 and 86.32 volts as well as short-circuit currents between 4.61 and 9.83 μA, significant improvement over pure PDMS-based TENG at the same wave frequency. Due to its extremely effective wave-to-electricity conversion properties in the low and medium frequency ranges, the OC-TENG might be used as a low-power device power source.

La implanted band engineering of ZnO nanorods for enhanced photoelectrochemical water splitting performance

In the quest to improve photoelectrochemical water-splitting performance, we have doped lanthanum (La) in highly crystalline zinc oxide (ZnO) nanorods (NRs) using a facile and low-temperature hydrothermal route and successful substitution of La3+ at the Zn2+ site is confirmed from structural and chemical analysis. The tapered NRs morphology gained after La doping resulted in lower optical bandgap of 3.17 eV, enhanced visible light trapping, and multiphoton absorption, which assist in achieving good PEC activity. The La doping also offered higher Urbach energy (EU), subsidizing the number of oxygen vacancies. The UPS spectra show that La doping reduces conduction band energy level and endorses smooth charge transportation. The La-doped ZnO exhibits two times enhancement in photocurrent (1.54 mA·cm−2) compared to pristine ZnO (0.81 mA·cm−2). The higher applied bias to the photon conversion efficiency of ∼1.14% for La-doped ZnO confirms the efficient utilization of solar energy. The EIS measurements demonstrated reduction in charge transfer resistance with La-doping. Mott-Schottky analysis shows that La doping lowers the flat-band potential and enhances charge transportation, making it a potential photoanode for PEC water-splitting applications.

Study of rutile TiO2(110) single crystal by transient absorption spectroscopy in the presence of Ce4+ cations in aqueous environment. Implication on water splitting

Ce4+ cations are commonly used as electron acceptors during the water oxidation to O2 reaction over Ir- and Ru-based catalysts. They can also be reduced to Ce3+ cations by excited electrons from the conduction band of an oxide semiconductor with a suitable energy level. In this work, we have studied their interaction with a rutile TiO2(110) single crystal upon band gap excitation by femtosecond transient absorption spectroscopy (TAS) in solution in the 350–900 nm range and up to 3.5 ns. Unlike excitation in the presence of water alone the addition of Ce4+ resulted in a clear ground-state bleaching (GSB) signal at the band gap energy of TiO2 (ca. 400 nm) with a time constant t = 4–5 ps. This indicated that the Ce4+ cations presence has quenched the e-h recombination rate when compared to water alone. In addition to GSB, two positive signals are observed and are attributed to trapped holes (in the visible region, 450–550 nm) and trapped electrons in the IR region (>700 nm). Contrary to expectation, the lifetime of the positive signal between 450 and 550 nm decreased with increasing concentrations of Ce4+. We attribute the decrease in the lifetime of this signal to electrostatic repulsion between Ce4+ at the surface of TiO2(110) and positively charged trapped holes. It was also found that at the very short time scale (<2–3 ps) the fast decaying TAS signal of excited electrons in the conduction band is suppressed because of the presence of Ce4+ cations. Results point out that the presence of Ce4+ cations increases the residence time (mobility) of excited electrons and holes at the conduction band and valence band energy levels (instead of being trapped). This might provide further explanations for the enhanced reaction rate of water oxidation to O2 in the presence of Ce4+ cations.

Capture of volatile iodine by aromatic amines solutions

Abstract The presence of an excessive amount of iodine, especially radioactive iodine, is dangerous to the environment. Amine solutions are the most common and technically mature class of chemical sorption used for the capture of the pollutants. The iodine vapor diffusion and release capabilities of the aromatic amine solutions have been investigated. The iodine diffusion and release experiments were examined by UV-visible spectroscopy. Many electronic spectrophotometric studies have been reported in the coordination chemistry field on complexes. Generally, these complexes were obtained by using different electron donors with various organic or metallic electron acceptors in polar and non-polar solvents. The absorption spectra of the donor, acceptors, and the resulted complexes were carried out in methanol in the region of 200–600 nm. The correlation between the spectral characteristics of molecular complexes of iodine with various aromatic amines and the ionization potentials of the donor molecules is discussed. The concentrations of the diffused iodine and the formed complex were calculated using mathematical models and calibration curves. The values of the formation constant (k AD), molar extinction coefficient (ε AD), and absorption band energy of complexes were estimated. The ionization potential of the donor I D was calculated from the complex band energies. The kinetic of the above association and reverse reactions was studied, and some kinetic parameters have been estimated.

Energy structure of mixed halide CeF2Cl and CeFCl2 crystals

The band energy structures of CeF2Cl and CeFCl2 crystals have been calculated using the projector augmented-wave (PAW) method and the hybrid exchange-correlation functional PBE0. The valence band top consists of 2p states of F and 3p states of Cl. An energy gap is observed between the 5d states of Ce in the bottom part of the conduction band of both crystals, forming two subbands, 5d1 and 5d2, with very different effective electron masses (2.49 m0 and 0.19 m0 for CeF2Cl and 5.95 m0 and 0.84 m0 for CeFCl2, respectively). The 4f states of Ce are placed within the forbidden band. The obtained values for the band gap of CeF2Cl and CeFCl2 crystals are 6 eV and 4.6 eV, respectively.

Comparative properties of ZnO modified Au/Fe nanocomposite: electronic, dynamic, and locator annealing investigation.

A computational representation was used to model the doping and nanomodification of ZnO nanoparticles incorporated in Au/Fe nanocomposite. Au/Fe nanostructure was geometrically and discussed to investigate its electronic properties such electronic band structure and PDOS spectra. Moreover, the ZnO interacted with Au/Fe system was illustrated concerning the modified properties present on the surface of the nanocomposite as it may behave different attribution of band gap evaluated after ZnO modification included. Molecular dynamic simulation of the whole nano system was studied to predict the system stability concerning temperature and energy parameters during 100 ps simulation time. The most effective models under investigation were evaluated using adsorption annealing computations associated with the adsorption energy surface. A highly stable energetic adsorption system was anticipated by the periodic adsorption-annealing calculation. Au and Fe pure metals nanostructures were studied as a separate molecule with (0 0 1) plane surface for optimum energy minimization. Dmol3 module in/materials studio software was utilized for this protocol. The designed Au/Fe layers for nanostructure building material was computationally optimized, where DFT level was considered involving generalized gradient approximation (GGA) with Perdew-Burke-Ernzerh (PBE) exchange functional. In the computations of the structure matrix simulation, the global orbital cutoff was selected. To address the weak quantification of the standard DFT functionals, Tkatchenko-Schefer (TS) (DFT + D) was utilized to precisely correct the pairwise dispersion of the functionals. The electrical parameters were interpreted using the reciprocal space of the ultrasoft pseudopotential representation. To overcome the issues of self-electron interaction, the nonlocal hybrid functional with PBE0 method was utilized to calculate the electronic properties of the studied systems. The computations generated are predicated on a particular trajectory of the gamma k-point band energy interpolations proposed in this examination. An investigation into the position of adsorption came after geometric optimization. Adsorbed on an optimized Au/Fe surface, ZnO nanostructure was computationally explored using the Dmol3 simulation software.

Regulation on photocatalytic debromination by the reconfiguration of carbonyl groups on the covalent organic frameworks

Covalent organic frameworks (COFs) as promising organic semiconductor photocatalysts have become a research hotspot in the field of photocatalytic organic synthesis. Herein, a series of imine-linked EN-COF-x were synthesized by condensation reaction of amine monomer with triformylbenzene monomer. Then, β-ketoamine-linked KE-COF-y were obtained by the reconstruction of EN-COF-x in alkaline solution. The photocatalytic performance of COFs before and after the isomerization from enols to ketones were investigated. The characterization results and density functional theory calculations clearly demonstrated that the carbonyl groups not only make the conduction band energy level more negative, but also lead to a more inhomogeneous charge distribution in the molecule, which improved the separation efficiency of the photogenerated electrons. In addition, the increase in the number of hydroxyl groups on triformylbenzene monomer contributed to the formation of more carbonyl groups in the COF frameworks, which is beneficial to improving its photocatalytic performance. KE-COF-3 synthesized from 2,4,6-Trihydroxy-1,3,5-benzenetricarbaldehyde has more carbonyl group units and more suitable redox potential, which effectively promoted the debromination reaction with 99% yield under light irradiation. Meanwhile, it can be reused at least five times without loss of catalytic activity. This work provides insights for the rational design of functionalized β-ketoamine COFs for photocatalytic organic transformations.

Ab Initio Modeling of Mixed-Dimensional Heterostructures: A Path Forward.

Understanding the electronic structure of mixed-dimensional heterostructures is essential for maximizing their application potential. However, accurately modeling such interfaces is challenging due to the complex interplay between the subsystems. We employ a computational framework integrating first-principles methods, including GW, density functional theory (DFT), and the polarizable continuum model, to elucidate the electronic structure of mixed-dimensional heterojunctions formed by free-base phthalocyanines and monolayer molybdenum disulfide. We assess the impact of dielectric screening across various scenarios, from isolated molecules to organic films on a substrate-supported monolayer. Our findings show that while polarization effects cause significant renormalization of molecular energy levels, band energies and alignments in the most relevant setup can be accurately predicted through DFT simulations of the individual subsystems. Additionally, we analyze orbital hybridization, revealing potential pathways for interfacial charge transfer. This study offers new insights into hybrid inorganic/organic interfaces and provides a practical computational protocol suitable for scaled-up studies.

Fabrication of stannous sulfide nanoparticles for photodegradation of thiazine derivative and evaluation of its antibacterial activity

The photocatalytic degradation of environmentally harmful chemicals has been extensively explored using a variety of photocatalysts and approaches. However, achieving efficient decomposition and removal of persistent contaminants from the aquatic environment remains a challenging factor. In this study, we report stannous sulfide nanoparticles (SnS2 NPs) prepared by a simple hydrothermal technique and characterized using various analytical methods. The prepared SnS2 NPs were used for the degradation of Methylene Blue (MB) dye under visible light irradiation, which resulted in outstanding degradation compared to other photocatalysts. According to our results, the SnS2 NPs can destroy 98.4 % of MB dye (10 ppm) in 60 minutes effectively, owing to a narrowed band energy gap and photo-induced carrier separation. Based on the results of free-radical scavenging experiment, we confirmed that hydroxyl radicals (•OH) are the key reactive species, and on this basis elucidated the possible degradation mechanism. Moreover, the SnS2 NPs photocatalyst exhibited good stability in degrading MB even after four recycles. Additionally, we analyzed the antibacterial activity of the prepared SnS2 NPs against pathogenic bacteria. As a result of this research, the proposed photocatalyst shows high potential for environmental remediation of harmful contaminants.

Modeling from the first principles of the electronic properties of compositions of REE as precursors of high-temperature superconductors

Modeling of the first principles of the electronic properties of complex oxides of rare earth elements (BaY2O4, BaGd2O4, BaLu2O4) as precursors of high-temperature superconductors has been performed. The VASP software package was used as a modeling environment, in particular the method of coupled plane waves (PAW method), which allows us to obtain fairly accurate results for calculating the electron density and band structure. From the analysis of the obtained band energy structure, it follows that the studied REE oxides have a band gap width Eg = 3.29–3.84 eV, which is characteristic for dielectric materials. The studied compounds based on these rare earth elements selected from the yttrium (Y, La, Gd–Lu) and cerium (Ce–Eu) groups are characterized by an increase in Fermi energy and a decrease in the band gap as the atomic number (39, 64, 71) of the element in the periodic table increases. A method for modeling the quantum layers of the studied materials by simulating the restriction of the crystal structure along one of the coordinate axes is proposed. This representation approximates the model of the crystal lattice of REE oxides to the situation of analyzing a quantum layer whose thickness is equal to the size of the crystal cell along the specified axis. The rupture of atomic bonds in a crystal is simulated by increasing the distance between atomic layers along this axis to values at which the value of free energy is stabilized. In the quantum layer of rare earth element oxide (with its thickness close to 1 nm), a wider range of energy values is formed in which electrons are distributed than is observed in the continuous version, and the expansion of the electron distribution area extends to the energy levels of the band gap. This is explained by the fact that the geometric discretization of nanoscale structures determines the discreteness of the quantum-dimensional energy spectrum.