Electron-electron Interaction Research Articles

Министерство внутренних дел Российской Федерации как субъект предоставления государственных услуг

The article reveals the features of the provision of public services as an institution of administrative law. The author paid attention to the study of the Russian Ministry of Internal Affairs as the subject of their provision. The types and features of the provision of public services to the population by this department are analyzed, the basics of interdepartmental electronic interaction in the course of their provision are considered. The author also examines current problems in the provision of public services to the Ministry of Internal Affairs of Russia and offers recommendations for their resolution. Possible trends and prospects for the transition to a full electronic format have been identified in relation to all types of public services provided by the law enforcement agency in question.

In-plane anisotropic dispersion property and second-harmonic generation of violet phosphorus with two-dimensional nano-interlocking structure

The unique one-dimensional chain structure of violet phosphorus provides an ideal platform for the study of second-order nonlinear optical properties. This also offers more possibilities for the further development of novel two-dimensional layered nanomaterials in the frequency domain. The research suggest that the highest occupied molecular orbital of monolayer phosphorene is characterized by a small effective mass and high hole mobility, while the lowest unoccupied molecular orbital exhibits opposite properties. This may be attributed to increased lattice scattering or electron-electron interactions in the conduction band. Monolayer violet phosphorus exhibits strong absorption capabilities in the near-ultraviolet light range, which can be utilized in UV spectroscopy technology for detecting harmful substances in water and air. Besides, its second harmonic generation response is also very strong within the visible light spectrum, and this response significantly varies with changes in angle. This provides theoretical guidance for optimizing the different stacking directions and heterojunction structures of violet phosphorus, more importantly, the sensitivity and directional selectivity of sensors can be improved. The work not only deepens the understanding of the electro-optical performance of violet phosphorus materials but also lays a theoretical foundation and guidance for the design and application of devices based on violet phosphorus.

Recent Advances on Two-Dimensional Nanomaterials Supported Single-Atom for Hydrogen Evolution Electrocatalysts.

Water electrolysis has been recognized as a promising technology that can convert renewable energy into hydrogen for storage and utilization. The superior activity and low cost of catalysis are key factors in promoting the industrialization of water electrolysis. Single-atom catalysts (SACs) have attracted attention due to their ultra-high atomic utilization, clear structure, and highest hydrogen evolution reaction (HER) performance. In addition, the performance and stability of single-atom (SA) substrates are crucial, and various two-dimensional (2D) nanomaterial supports have become promising foundations for SA due to their unique exposed surfaces, diverse elemental compositions, and flexible electronic structures, to drive single atoms to reach performance limits. The SA supported by 2D nanomaterials exhibits various electronic interactions and synergistic effects, all of which need to be comprehensively summarized. This article aims to organize and discuss the progress of 2D nanomaterial single-atom supports in enhancing HER, including common and widely used synthesis methods, advanced characterization techniques, different types of 2D supports, and the correlation between structural hydrogen evolution performance. Finally, the latest understanding of 2D nanomaterial supports was proposed.

Insights into the Synergistic Catalytic Effect of TiO2 Supported V-W Oxides for Selective C-H Bond Oxidation of Cyclohexane to KA Oil.

It is urgent to develop an efficient and stable non-noble metal catalyst for selective C-H bond oxidation of cyclohexane. Herein, a series of V-W oxides supported on TiO2catalysts (V-W/TiO2) were fabricated. The V-W/TiO2catalysts exhibited much higher catalytic activity for the selective oxidation of cyclohexane to KA oil, compared to that of V/TiO2and W/TiO2catalysts. The good distribution of active metals and the synergistic effect were responsible for the enhanced catalytic activity. H2-TPR results disclosed that the presence of V inV-W/TiO2 affected the reducibility of W6+species, and XPS verified that an electronic interaction was formed between them. Such results led to good catalytic reusability of V-W/TiO2catalyst during the reactions, and no obvious activity loss was found after six runs. The reaction mechanism was investigated, and the results verified that hydroxyl radicals generated from H2O2homolysis were the main active oxidative species. Theoretical study revealed that V dopant could regulate electronic structure of adjacent O atom, facilitating the adsorption of cyclohexane, and lower energy was needed for the rate-limiting step over V-W/TiO2during the whole oxidation reaction. This work developed an efficient V-W/TiO2catalyst for the selective oxidation of cyclohexane via a synergistic effect.

Steady and transient modeling of dye-sensitive solar cells: The impact of electrode thickness and dye specifications

Investigating the impact of dye compounds on cell performance is crucial for advancing dye-sensitized solar cells (DSSCs). This research focuses on the sensitivity analysis of the effect of critical parameters to enhance DSSC efficiency using a thermo-electric numerical model. These parameters include dye types, trapping parameters, diffusion coefficients, and photoanode thickness. When the type of dye changes, in fact, both physical and chemical properties (molar absorption coefficient, etc.) Change, but to avoid the complexity of solving the equations and only to evaluate the effect of the absorption wavelength range on the cell performance only changes in physical properties are considered. The model calculates steady and transient currents under actual weather conditions and sunlight. It incorporates time/space-dependent relationships for increased accuracy and examines electron, iodide, and triiodide ion interactions under varying environmental conditions. Key concepts include the quasi-Fermi level and the multiple trap model, assuming that trapping processes are faster than electron transport and recombination. The results showed that increasing the trapping parameter can affect the transient current behavior, also increasing the thickness of the photoanode and the wavelength range of the dye increases the efficiency of the cell, so that the N749-BD provides the best performance. The findings provide insights into current–voltage characteristics, electron production, and the effects of photoanode thickness and dye types on cell performance, offering pathways for optimizing DSSC technology.

Electronic States of Single Perovskite Quantum Dots in Weak and Strong Interaction Regimes: Implications in Electrically Pumped Quantum Emitters.

We investigate the effect of Coulomb interactions on the electronic states of a single perovskite quantum dot (PQD), CsPbBr3, through scanning tunneling microscopy/spectroscopy (STM/S). Under a weak interaction regime, where the time-averaged occupation of electrons in a PQD remains zero, the peaks observed in the differential tunneling conductance (dI/dV) spectrum correspond to the single-particle density of states (DOS) without any electron-electron correlation. However, with a shorter tunnel distance between the STM tip and PQD, additional electrons are trapped in the QD, leading to a strong interaction regime with well-defined electronic fine structures due to the lifting of spin degeneracy in the conduction bands. Interestingly, we observe that the strong Coulomb interaction can modify the spin-orbit coupling (SOC) strength in the PQDs. We have concluded that the energy levels under a strong electron-electron interaction regime are of utmost importance since they will be applicable to electrically pumped PQD-based single photon quantum emitters.

Rethinking Electron Statistics Rules

The Fermi–Dirac and Bose–Einstein statistics are considered to be key concepts in quantum mechanics, and they are used to explain the occupancy limit of electron orbitals. We investigate the physical origin of these two statistics and uncover that the key determining factor is whether an individual electron spin is measurable or not. Microscopically, a system with individually measurable electron spins corresponds to the presence of Larmor spin precession in electron–electron interactions, while the non-measurability of individual electron spins corresponds to the absence of Larmor spin precession. Both interaction types are possible, and the favored interaction type is thermodynamically determined. The absence of Larmor spin precession is realized in coherent electron states, and coherent electrons therefore obey Bose–Einstein statistics.

Nature of electrically detected magnetic resonance in highly nitrogen-doped 6H -SiC single crystals

This work focuses on unraveling electron paramagnetic resonance (EPR) and electrically detected magnetic resonance (EDMR) properties of n-type 6H silicon carbide (SiC) single crystals with high concentrations of uncompensated nitrogen (N) donors, which is essential for fundamental understanding of spin-related phenomena, developing spin-based devices, optimizing materials and devices, and advancing research in quantum information and spintronics. Utilizing low-temperature multifrequency EPR spectroscopy (9.4–395.12 GHz), we identified two intense signals labeled as S line and S1 line in the 6H-SiC crystals with ND–NA≈8×1018 and 4×1019cm−3. In addition, in 6H-SiC crystals with ND–NA≈8×1018cm−3, a low-intensity triplet from N donors substituting the quasicubic “k2” nonequivalent position (Nk2) was observed. The S line [g⊥=2.0029(2),g∥=2.0038(2)] was assigned to the exchange interaction of conduction electrons and Nk2, while the S1 line [g⊥=2.0030(2),g∥=2.0040(2)] is caused by the exchange spin coupling of localized N donors at the “k1” and “k2” positions. The S1 line was observed in high-frequency EDMR spectra of 6H-SiC with ND–NA≈8×1018cm−3, and its emergence was explained by an enhancement of the hopping conductivity due to the EPR-induced temperature increase mechanism. No EDMR spectra were found to occur in the 6H-SiC crystals with ND–NA≈4×1019cm−3, which is close to the critical donor concentration value for a semiconductor-metal transition. Thus it can be concluded that this N donor concentration is too high for the appearance of spin-dependent scattering and too low for the emergence of EPR-induced hopping mechanisms in 6H-SiC. Published by the American Physical Society 2024

Selective hydrogenation of acetylene over Pd/β-Mo2C catalyst: Experimental and theoretical studies

Molybdenum carbide is a promising support to tune the metal reactivity, which originates from the interaction between metal and support. In this work, Pd/β-Mo2C was prepared using a deposition-precipitation method for selective hydrogenation of acetylene. The high temperature calcination is employed to modulate the interaction between Pd and β-Mo2C. The Pd/β-Mo2C catalyst calcined at 600 °C exhibits significant promotion in selective hydrogenation, which shows 100 % acetylene conversion and 81.4 % ethylene selectivity at 160 °C. The activity promotion originates from the enhanced electronic metal-support interaction, which induces a shift of Pd 3d to higher binding energy. Besides, the Pd species become atomically dispersed after calcination. The changes in geometric and electronic structure suppress the formation of Pd hydrides, which consequently inhibits the excessive hydrogenation capacity of Pd. The structure variation also affects the adsorption of ethylene. No strong adsorbed ethylene (di-σ bonded ethylene) can be identified, which is conducive to the improvement of ethylene selectivity. Density functional theoretical (DFT) calculations confirm that Pd on β-Mo2C is positively charged. The desorption energy of C2H4* (0.78 eV) is significantly lower than that of further hydrogenation (1.45 eV), which explains the improved ethylene selectivity of the calcinated catalyst. The present study indicates calcination is an effective method to tune the activity of Pd/β-Mo2C for reactions beyond selective hydrogenation of acetylene.

Spatially Confined Alloying of Pt Accelerates Mass Transport for Fuel Cell Oxygen Reduction.

Pt-based alloy with high mass activity and durability is highly desired for proton exchange membrane fuel cells, yet a great challenge remains due to the high mass transport resistance near catalysts with lowering Pt loading. Herein, an extensible approach employing atomic layer deposition to accurately introduce a gas-phase metal precursor into platinum nanoparticles (NPs) pre-filled mesoporous channels is reported, achieved by controlling both the deposition site and quantity. Following the spatially confined alloying treatment, the prepared PtSn alloy catalyst within mesopores demonstrates a small size and homogeneous distribution (2.10 ± 0.53nm). The membrane electrode assembly with mesoporous carbon-supported PtSn alloy catalyst achieves a high initial mass activity of 0.85 A at 0.9V, which is attributed to the smallest local oxygen transport resistance (3.68 S m-1) ever reported. The mass activity of the catalyst only decreases by 11% after 30000 cycles of accelerated durability test, representing superior full-cell durability among the reported Pt-based alloy catalysts. The enhanced activity and durability are attributed to the decreased adsorption energy of oxygen intermediates on Pt surface and the strong electronic interaction between Pt and Sn inhibiting Pt dissolution.

Constructing ultralow-loading Cu single atoms/Fe2O3 particles on Nb2C MXenes for efficient utilization of atomic H to boost electrochemical debromination

Bromate is a commonly identified carcinogenic and genotoxic disinfection byproduct in water. Electrochemical debromination is an environmentally friendly and effective approach but it often suffers the limited reducing atomic H (H*) ability and high metal catalyst dosage. In this study, a unique composite catalyst comprised of ultra-low loading Cu single atoms (0.016 wt%) and Fe2O3 nanoparticles supported on a Nb2C MXene (denoted as Cu0.2/Fe0.1/Nb2C) was synthesized by one-step high-temperature molten salt method. The Cu0.2/Fe0.1/Nb2C significantly outperformed the Nb2C, Cu0.2/Nb2C and Fe0.1/Nb2C counterparts in the electrochemical debromination with a 94.2 % removal efficiency of bromate. It is revealed that the introducing of Cu single atoms, efficiently promotes the adsorption of H* and inhibition of competitive H2 evolution. The incorporation of Fe2O3 nanoparticles significantly increased the electronic metal-support interaction effect between the metal components and Nb2C, thereby forming a noticeable electronic cloud bridge to facilitate efficient charge transfer. Ultimately, the synergistic interplay between Cu single atoms and Fe2O3 nanoparticles plays a crucial role in achieving the remarkable removal performance of bromate. This work not only presents a significant instance of a synergistic catalyst involving metal single atoms and metal nanoparticles for effective electrochemical debromination but also advances the understanding of the electronic metal-support interaction.

Low-loss plasmons in Weyl semimetals Mn3Sn

We report the optical reflectance measurement for Weyl semimetal Mn3Sn single crystal at room temperature. We observe a low-loss plasmon in the UV energy ranges. This low plasmonic loss is associated with a large electron scattering rate contributed by electron-electron interaction and scattering of conduction electrons by Mn atoms. The incorporation of more Mn atoms simultaneously adds more elastic scattering centers and increases the strength of electron-electron correlation which generates multiple plasmons with lower plasmonic loss in Mn3+xSn1-x. The UV tunable plasmonic properties in Mn3+xSn1-x have great potential for plasmonic and spintronic applications. We also discuss the plasmonic loss in Mn3Sn to the other conducting materials including correlated and non-correlated systems establishing the crucial role of electron correlation on the plasmonic loss. Our result suggests novel and effective strategies for obtaining lower plasmonic loss in the class of correlated materials.

Pt-Ru atomic alloys confined in mesoporous carbon hollow spheres for accelerating methanol oxidation

Active and durable electrocatalysts are essential for commercializing direct methanol fuel cells. However, Pt-based catalysts, extensively utilized in the methanol oxidation reaction (MOR), are suffered from resource scarcity and CO poisoning, which degrade MOR activity severely. Herein, Pt1Rux bimetallic catalysts were synthesized by confining Pt1Rux alloys within the shells of mesoporous carbon hollow spheres (MCHS) via a vacuum-assisted impregnation method (Pt1Rux@MCHS). The confinement effect induced by mesoporous carbon hollow spheres resulted in a robust structure of Pt1Ru3@MCHS with an ultrafine dispersion of alloy nanoparticles. The experimental and theoretical results confirmed that the boosting electrocatalytic activity and stability of the MOR over Pt1Ru3@MCHS were contributed to the regulated electronic structure as well as the superior CO tolerance of atomic Pt site caused by the electronic interaction between single Pt atoms and Ru nanoparticles. This strategy is versatile for the rational design of Pt-based bimetallic catalysts and has a positive impact on MOR performance.

Tuning d-band center of Pt via Pt-Pt5La heterostructure interface as efficient and stable electrocatalyst for oxygen reduction and methanol oxidation reactions in DMFCs

Developing Pt-based electrocatalysts with superior activity and durability is essential for direct methanol fuel cells (DMFCs), and regulating the interfacial electronic interaction for Pt-based composites can significantly modulate the electrocatalytic performances. Herein, the Pt-Pt5La/C heterostructure catalyst was developed to enhance the catalytic property towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Experimental analyses and theoretical calculations demonstrated the electron redistribution at the interface and reduction of the d-band center of Pt for this unique Pt-Pt5La/C heterostructure. As the results, Pt-Pt5La/C exhibited 5.0- and 6.4-times higher mass activity and specific activity towards alkaline ORR compared to Pt/C, and the excellent electrocatalytic MOR performance due to the interfacial interaction. These superior electrocatalytic property promoted Pt-Pt5La/C as the bifunctional catalyst for DMFC application with outstanding power density and durability. Consequently, this work proposed a novel interfacial regulation strategy for designing Pt-rare earth (RE) alloy heterostructures and their reliable operation of DMFCs.

NiFe layered-double-hydroxide nanosheet arrays grown in situ on Ni foam for efficient oxygen evolution reaction

Developing efficient and stable oxygen evolution reaction (OER) electrocatalysts under various alkaline conditions is crucial for commercial hydrogen (H₂) production. This study synthesized superhydrophilic NiFe LDH/NF with a nanosheet structure. The strong electronic interactions between the metals modify the electronic structures of Ni and Fe. In-situ Raman spectroscopy reveals numerous high-valent nickel intermediates with high OER activity during the reaction, significantly improving the catalyst's overall performance. At room temperature, the NiFe LDH/NF catalyst exhibits a current density of 50/100 mA cm−2 with only 217/233 mV required in 1 M KOH. Moreover, the catalyst requires only 180 mV under industrial conditions (60 °C, 6 M KOH), 243 mV in alkaline artificial seawater, and 280 mV in alkaline natural seawater to achieve 100 mA cm−2. The catalyst also exhibits long-term operational durability under these conditions, indicating a wide range of potential applications.

Efficient High-Order Harmonic Generation from the van der Waals Layered Crystal Copper Indium Thiophosphate.

Layered metal thio- and selenophosphates (MTPs) are a family of van der Waals gapped materials that exhibit a multitude of functionalities in terms of magnetic, ferroelectric, and optical properties. Despite the recent progress in terms of understanding the material properties of these compounds, the potential of MTPs as a material class yet needs further scrutiny, especially in terms of nonlinear optical properties. Recent reports of efficient low-order harmonic generation and extremely high third-order nonlinear optical properties in MTPs suggest the potential application of these materials in integrated nanophotonics. In this article, we investigate the high-order nonlinear response of bulk and exfoliated thin-film crystals of copper indium thiophosphate (CIPS) to intense mid-infrared fields through experimental and computational studies of high-order harmonic generation (HHG). From a driving laser source with a 3.2 μm wavelength, we generate odd and even harmonics up to the 10th order, exceeding the bandgap of the material. We note conversion efficiencies as high as 10-7 measured for the fifth and seventh harmonics and observe that the harmonic intensities follow a power law scaling with the driving laser intensity, suggesting a perturbative nonlinear optical origin of the observed harmonics for both bulk and thin flakes. Furthermore, first-principles calculations suggest that the generation of the highest harmonic orders results from electron-electron interactions, suggesting a correlation-mediated enhancement of the high-order optical nonlinearity.

The superior adsorption capacity of biogenic α-Mn2O3 in comparison to chemogenic α-Mn2O3 for five divalent heavy metal cations and the adsorption mechanism of biogenic α-Mn2O3: Experimental and DFT investigations

Manganese oxides play a crucial role in the adsorption of heavy metals in the environment. However, there is currently a lack of information regarding the comparative adsorption efficiency of heavy metals between biogenic and chemogenic manganese oxides. In this work, we compared the adsorption performance of biogenic and chemogenic α-Mn2O3 towards Pb(II), Cd(II), Cu(II), Zn(II) and Ni(II). Mineral characterization analyses revealed that biogenic α-Mn2O3 exhibited a polycrystalline nature, whereas chemogenic α-Mn2O3 displayed a monocrystalline nature with a lower impurity content compared to biogenic α-Mn2O3. Under acidic conditions, biogenic α-Mn2O3 demonstrated a significantly higher adsorption capacity, ranging from 3 to 6 times greater than its chemogenic counterpart, within an initial heavy metal concentration range of 0.2–1.0 mM. This superiority can be attributed to the presence of more abundant functional groups and a greater content of hydroxyl O species on the surface of biogenic α-Mn2O3 in comparison to chemogenic α-Mn2O3. During the adsorption process of biogenic α-Mn2O3, there were observed ionic exchanges between Mn(II) and these cations. More importantly, biogenic α-Mn2O3 bound with these cations probably through the formation of -O/OH/S complexes. The adsorption selectivity of biogenic α-Mn2O3 towards the five heavy metals was experimentally determined to follow the order of Ni(II) > Pb(II) > Cu(II) > Zn(II) > Cd(II). The electronic interaction between biogenic α-Mn2O3 and these cations indicated that Ni(II), Pb(II) and Cu(II) were more likely to share electrons with O atoms on the surface of biogenic α-Mn2O3 compared to Zn(II) and Cd(II).

Electronic interaction and band alignment between Cu sub-nanometric clusters and ZnIn2S4 nanosheets towards selective photoreduction of CO2 to CO

Engineering the electronic properties of heterogeneous photocatalysts with charge transfer regulated is an effective strategy to boost their CO2 reduction activity. Here, we drew inspiration from the strong metal-support interaction effect, and fabricated ZnIn2S4 supported-Cu sub-nanometric clusters photocatalyst. Within this catalyst, the formed CuS bond would redistribute interfacial charge, resulting in diverse chemical states of Cu atoms and the establishment of Ohmic contact between ZIS and Cu. The built-in electric field of such Ohmic contact benefited the migration of photoexcited electrons from ZIS to Cu. Further mechanistic studies unveiled the crucial role of positively charged Cu atom near the interface in facilitating H2O dissociation, and its adjacent Cu atom at the top-surface adopting a distinct chemical state could activate linear CO2 molecule into a bent configuration. These features substantially lowered energy barriers for CO2 adsorption and subsequent *COOH formation, and Cu-ZIS, accordingly, exhibited a remarkable CO production rate of 60.2 μmol g-1h−1, approximately 20.8-fold enhancement compared to ZIS counterpart.

Linear response theory for light dark matter-electron scattering in materials

We combine the nonrelativistic effective theory of dark matter (DM)-electron interactions with linear response theory to obtain a formalism that fully accounts for screening and collective excitations in DM-induced electronic transition rate calculations for general DM-electron interactions. In the same way that the response of a dielectric material to an external electric field in electrodynamics is described by the dielectric function, so in our formalism the response of a detector material to a DM perturbation is described by a set of which can be directly related to densities and currents arising from the nonrelativistic expansion of the Dirac Hamiltonian. We apply our formalism to assess the sensitivity of non-spin-polarized detectors, and find that in-medium effects significantly affect the experimental sensitivity if DM couples to the detector's electron density, while being decoupled from other densities and currents. Our formalism can be straightforwardly extended to the case of spin-polarized materials. Published by the American Physical Society 2024

Effect of Ni substitution atom on electronic properties and surface oxidation of pyrrhotite

The crystal and surface electronic properties of minerals are fundamentally linked to their flotation behavior. To investigate the effects of Ni substitution for Fe in pyrrhotite on the crystal and surface properties, as well as its oxidation by O2, density functional theory (DFT) was employed to analyze these changes at a microscopic level in both monoclinic and hexagonal pyrrhotite. The findings reveal that Ni substitution increases electron activity in monoclinic pyrrhotite, enhancing its resistance to oxidation by O2, while also strengthening the interaction between Ni-substituted monoclinic pyrrhotite and butyl xanthate. Conversely, in hexagonal pyrrhotite, Ni substitution enhances electron stability but makes it more susceptible to oxidation by O2 and weakens its interaction with butyl xanthate. Understanding the electronic properties and interaction mechanisms of Ni-substituted pyrrhotite with O2 is crucial for elucidating the surface oxidation mechanisms of pyrrhotite. This research offers insights and guidance for optimizing pyrrhotite flotation processes.