Electron-electron Interaction Research Articles

Novel Mn–Bi–S hybrid mesoporous nanosheets as an efficient electrocatalyst for nitrogen reduction reaction

A non-precious and efficient catalyst was developed to enhance N2 adsorption by electronic interaction and ideal synergistic effect to improve the NRR activity.

Electronic interaction between dimethyl carbonate and Li+ studied by attenuated total reflectance far-ultraviolet spectroscopy.

Organic electrolytes with Li+ were analyzed by far-ultraviolet (≤200 nm) spectroscopy, achieved by an attenuated total reflectance setup. The spectra showed a redshift with Li+ addition, attributed to the charge transfer, as revealed by quantum chemical calculations. Multivariate analysis successfully decomposed the spectra into pure solvent and Li-coordinated solvent components.

Non-precious metal high-entropy alloys with d–d electron interactions for efficient and robust hydrogen oxidation reactions in alkaline media

Benefiting from d–d electron interaction within the constituent metals, as-prepared FeCoNiMoW HEAs exhibit optimized adsorption energy for the critical intermediates, and attain improved catalytic ability and inoxidizability for the alkaline HOR.

Copper-based bimetallic metal–organic framework in-situ embedded of heterogeneous Cu nanoparticles for enhanced nonenzymatic glucose sensing

Copper-based metal–organic frameworks (MOFs) are recently emerging as encouraging electrocatalysts with high performance and stability for electrochemical detection of glucose. Herein, a simple one-step solvothermal in-situ derivative strategy is proposed to fabricate the novel heterogeneous electrocatalyst of Cu nanoparticles embedded bimetallic Cu@MCu-BDC-NH2 (M = Ni, Co and Zn) MOFs, which can enhance the conductivity via tailor the electronic structure and heterojunction interface. The optimal bimetallic Cu@CoCu-BDC-NH2 heterostructure exposes more active sites, the electronic interaction between metal-O enhanced the reactivity and electrical conductivity, and prominently boost the kinetics of glucose detection. The optimized Cu@CoCu-BDC-NH2 heterojunction structure as modified electrode nanomaterials exhibit the low detection limit (0.27 μM), wide linear range (0.5 μM–2 mM) and the high sensitivity (21157 μA mM−1 cm−2), which are successfully used in human serum and hold great stability and anti-interference. The density functional theory (DFT) calculation demonstrates that the adsorption energies of Cu@CoCu-BDC-NH2 heterostructure for glucose are −0.3 eV, suggesting good adsorption capacity for glucose. This work not only successfully establish Cu nanoparticles heterostructure interface with bimetallic MOFs for high-performance glucose sensors, but also emphasizes the importance of regulate the electronic microstructure of bimetallic MOFs for enhanced reaction kinetics.

N-Type boron β-diketone-containing conjugated polymers for high-performance room temperature ammonia sensors.

Organic semiconductor (OSC) gas sensors with good mechanical flexibility have received considerable attention as commercial and wearable devices. However, due to poor resistance to moisture and low conductivity, the improvement in the sensing capability of individual OSCs is limited. Reported here is a promising pathway to construct a series of conjugated organic polymers (COPs) with well-defined pyrimidine (Py-COP) or boron β-diketone (BF-COP) units. Unlike traditional metal- or carbon-based hybrid materials, the developed COPs can provide abundant absorption sites for gaseous analytes. As a result, the as-prepared BF-COP results in an excellent sensing response of over 1500 (Ra/Rg) toward 40 ppm of NH3 at room temperature, which is the highest value among those of pristine COPs as n-type sensing materials. Notably, they can maintain their initial sensing responses for two months and 90% relative humidity resistance. Combining the results of in situ Fourier transform infrared spectroscopy and theoretical calculations, the β-diketone skeleton is found to activate the surface electronic environment, verifying that the electron-deficient B ← O groups are adsorption centers. The B/N-heterocyclic decoration effectively modulates the redox properties and electronic interactions, as well as perturbs charge transfer in typical π-conjugated COPs. These results offer insight into developing highly efficient OSC gas sensors, which potentially have broadened sensing applications in the areas of organoboron chemistry.

Partial restoration of aromaticity of pentacene-5,7,12,14-tetrone on Cu(111).

The π-conjugation of organic molecules can be strongly influenced when functional groups are added to a molecule, for example when pentacene is converted into pentacene-5,7,12,14-tetrone (P4O) by substitution of four H-atoms with four O-atoms, leading to four CO double bonds. In fact, although free P4O resembles the parent hydrocarbon pentacene structurally at a first glance, its electronic properties differ drastically and can be more accurately described by three benzene units connected via four carbonyl groups. If P4O is deposited onto Cu(111), the electronic interaction across the interface has previously been reported to fully restore the π-conjugation through a weakening of the CO double bonds and a redistribution of electrons, both of which have been explained with the model of surface-induced aromatic stabilization. Here, we observe for the case of P4O on Cu(111) that the molecule does not exhibit full π-conjugation upon interaction with the surface, likely because of the special electronic nature of the hybridized P4O on Cu(111). Our results are derived from CO-functionalized noncontact atomic force microscopy measurements in combination with dispersion-corrected density functional theory calculations yielding bond lengths and molecular geometries. To characterize the aromaticity, we apply the harmonic oscillator model of aromaticity.

Tuning of the antiferromagnetic-type interaction in photo-excited single-decker porphyrin-lanthanide complexes with different crown capping ligands.

The magnetic interaction between the total angular momentum (J) of the 4f electrons in a lanthanide ion and the orbital angular momentum (L) of a porphyrin in the photo-excited states of 5,10,15,20-tetraphenylporphyrinato Dy(III) complexes capped with a crown ether with one of two different symmetries, 12-crown-4 or 1-aza-12-crown-4, was investigated by temperature- and magnetic dependent magnetic circular dichroism (VT-VH MCD). The analysis was conducted on the complexes with different non-aromatic ligands to investigate how different symmetries of the non-aromatic ligands have an impact on the electronic interaction causing an anti-parallel orientation of J and L. The magnitude of the J-L interaction was determined from simulation-based fitting to experimental ratios. While in both cases an antiferromagnetic-type interaction between J and L was identified, an asymmetric non-aromatic ligand resulted in an increased magnitude of the J-L interaction.

High-Loading Platinum-Cobalt Intermetallic Compounds with Enhanced Oxygen Reduction Activity in Membrane Electrode Assemblies

Platinum-based intermetallic compounds (IMCs) are emerging as promising oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells (PEMFCs). However, large-scale synthesis of supported IMCs catalysts with small particle size and high loading remains a significant challenge, greatly hindering the applications of IMCs in PEMFCs. Herein, carbon-supported PtCo IMCs with a metal loading of ∼40% and a mean size of ∼5 nm were successfully prepared via a simple impregnation method and display excellent performances in membrane electrode assemblies (MEA). The ordering degree of the PtCo IMCs can be tuned by carefully manipulating the annealing conditions. X-ray photoelectron spectroscopy characterizations demonstrate that the electronic interactions between Pt and Co are strengthened due to highly ordered structure of PtCo IMCs, thus promoting the ORR performance. The optimized PtCo IMCs exhibit an excellent ORR performance with a specific activity of 2.02 mA cm−2 and mass activity of 0.92 A mgPt−1 at 0.9 V (vs. RHE), which are approximately 5 times and 6 times higher than those of the commercial Pt/C. More importantly, the PtCo IMCs also display enhanced performance in MEA, and the power density at 1.5 A cm−2 and 2.5 A cm−2 is 0.949 W cm−2 and 1.244 W cm−2, respectively, thus reducing the Pt usage by 40% compared to Pt/C. This work offers a facile route for the scale preparation of platinum-based intermetallic compounds and promotes their practical applications in PEMFCs.

Controlled crystallisation of porous crystals of luminescent platinum(II) complexes by electronic tuning of ancillary ligands.

Porous molecular crystals (PMCs) have gained significant importance as next-generation functional porous materials. However, the selective crystallisation of the PMC phase remains a challenge. Herein, we have systematically controlled the stability of the luminescent PMC phase prepared using the luminescent Pt(II) complex [Pt(pbim)(N^O)] (pbim = 2-phenylbenzimidazolate, N^O = N-heteroaryl carboxylate) with Pt⋯Pt electronic interactions. The PMC phase formation varied significantly among the complexes depending on the heteroaryl group of the ancillary N^O ligand; the oxazolyl-bearing complex did not form a PMC phase, whereas the pyrazyl- and 5-fluoropyridyl-bearing complexes spontaneously formed a porous structure. This difference was rationalised by the π-stacking capability of the heteroaryl group of the ancillary ligand. Furthermore, owing to the presence of the one-dimensional Pt⋯Pt chains in this PMC phase, the photophysical properties of PMCs resulting from the Pt⋯Pt interactions were also significantly changed by the ancillary ligands.

Mechanism of photocatalytic CO2 methanation on ultrafine Rh nanoparticles.

Selective hydrogenation of CO2 to yield CH4 relies on the appropriate catalysts that can facilitate the cleavage of CO bonds and dissociative adsorption of H2. Ultrafine Rh nanoparticles loaded on silica nanospheres were used as a class of photocatalysts to significantly improve the selectivity and reaction rate of producing CH4 from the mixture of CO2 and H2 under the illumination of a broadband visible light source. The intense light scattering resonances in the silica nanospheres generate strong electric fields near the silica surface to enhance the light absorption power in the supported ultrafine Rh nanoparticles, promoting the efficiency of hot electron generation in the Rh nanoparticles. The interaction of the hot electrons with the adsorbate species on the Rh nanoparticle surface weakens the C-O bond to facilitate the deoxygenation of CO2, favoring the production of CH4 with a unity selectivity at a faster rate in the presence of surface adsorbed hydrogen (H*). The systematic studies on reaction kinetics and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy under different conditions, including various temperatures, illumination powers, and feeding gas compositions, reveal the reaction mechanism responsible for CO2 methanation and the role of photoillumination.

Interaction of low-energy electrons with radiosensitizers.

We provide an experimentalist's perspective on the present state-of-the-art in the studies of low-energy electron interactions with common radiosensitizers, including compounds used in combined chemo-radiation therapy and their model systems. Low-energy electrons are important secondary species formed during the interaction of ionizing radiation with matter. Their role in the radiation chemistry of living organisms has become an important topic for more than 20 years. With the increasing number of works and reviews in the field, we would like to focus here on a very narrow area of compounds that have been shown to have radio-sensitizing properties on the one hand, and high reactivity towards low-energy electrons on the other hand. Gas phase experiments studying electron attachment to isolated molecules and environmental effects on reaction dynamics are reviewed for modified DNA components, nitroimidazoles, and organometallics. In the end, we provide a perspective on the future directions that may be important for transferring the fundamental knowledge about the processes induced by low-energy electrons into practice in the field of rational design of agents for concomitant chemo-radiation therapy.

Ultrafast switching in spin field-effect transistors based on borophene nanoribbons.

Borophene, owing to the high mobility and long spin coherent length of its carriers, presents significant opportunities in ultrafast spintronics. In this research, we investigate the spin-dependent conductance of a Datta-Das field-effect transistor (FET) based on an armchair β12-borophene nanoribbon (BNR) using the tight-binding (TB) Hamiltonian in combination with the non-equilibrium Green's function (NEGF) method. The spin FET electrodes are magnetized by ferromagnetic (FM) insulators arranged in both parallel and anti-parallel configurations. This device acts as a controllable spin filter in the presence of Rashba spin-orbit coupling (SOC) for both configurations and its spin current is well modulated by a gate voltage and the strength of the Rashba SOC. For anti-parallel configurations, an energy gap emerges within a certain range of incoming electron energy which can disappear for electrons with flipped spin under the Rashba SOC. Furthermore, our findings indicate that the electron-electron (e-e) interaction helps the spin precession of electrons injected into the spin FET channel, thereby strengthening the Rashba SOC effect. Notably, a gate voltage can adjust the current-voltage (I-V) characteristics of this device. Finally, our calculations demonstrate that under the same conditions, the current magnitude and Ion/Ioff ratio of borophene spin FETs are several times higher than those of graphene and silicene spin FETs.

Heterointerface and crystallinity engineering of Ru/RuS2 dual co-catalysts for enhanced photocatalytic hydrogen evolution

In this paper, the Ru/RuS2 nanoparticles as dual co-catalysts were self-assembled on the surface of g-C3N4 nanotubes (Ru/RuS2/g-C3N4 NTs) for photocatalytic H2 production. The Ru/RuS2/g-C3N4 NTs showed greatly enhanced photocatalytic H2 production activity (1409 μmol·g−1·h−1), 1.16 times of RuS2/g-C3N4 NTs (1212 μmol·h−1·g−1), 10.51 times of Ru/g-C3N4 NTs (134 μmol·g−1·h−1), and 82.88 times of the pure g-C3N4 NTs (17 μmol·g−1·h−1). Besides, the apparent quantum yield value (AQE) of Ru/RuS2/g-C3N4 NTs is 3.92% at 370 nm. Ru/RuS2 as dual co-catalysts are self-assembled on the surface of g-C3N4 NTs and show strong electronic synergistic interaction between the interfaces, reduce ΔGH* of RuS2 and desorption energy of Ru, and promote the selectivity and activity of HER kinetically and thermodynamically respectively, which exhibits higher photogenerated carrier concentration and lower charge migration resistance than RuS2 and Ru, showing the synergistic effect to facilitate the generation and migration of carriers and provides active sites for photocatalysis.

Width effects on bilayer graphene nanoribbon polarons.

Recent progress in nanoelectronics suggests that stacking armchair graphene nanoribbons (AGNRs) into bilayer systems can generate materials with emergent quasiparticle properties. In this context, the impact of width changes is especially relevant. However, its effect on charged carriers remains elusive. In this work, we investigate the effect of width and interlayer interaction changes on polaron states via a hybrid Hamiltonian that couples the electronic and lattice interactions. Results show the rising of two interlayer polarons: the non-symmetric and the symmetric. The coupling strength needed to induce the transition between states depends on the nanoribbon width, being at the most extreme case of ≈174 meV. Electronic properties such as the coupling strength threshold, carrier size, and gap are shown to respect the AGNR width family 3p, 3p + 1, and 3p + 2 rule. The findings demonstrate that strong interlayer interaction simultaneously delocalizes the carriers and reduces the gap up to 0.6 eV. Additionally, it is found that some layers are more prone to share charge, indicating a potential heterogeneous stacking where a particular electronic pathway is favored. The results present an encouraging prospect for integrating AGNR bilayers in future flexible electronics.

Interactions and reactivity in crystalline intermediates of mechanochemical cyclorhodation reactions.

There is experimental evidence that solid mixtures of the rhodium dimer [Cp*RhCl2]2 and benzo[h] quinoline (BHQ) produce two different polymorphic molecular cocrystals called 4α and 4β under ball milling conditions. The addition of NaOAc to the mixture leads to the formation of the rhodacycle [Cp*Rh-(BHQ)Cl], where the central Rh atom retains its tetracoordinate character. Isolate 4β reacts with NaOAc leading to the same rhodacycle while isolate 4α does not under the same conditions. We show that the puzzling difference in reactivity between the two cocrystals can be traced back to fundamental aspects of the intermolecular interactions between the BHQ and [Cp*RhCl2]2 fragments in the crystalline environment. To support this view, we report a number of descriptors of the nature and strength of chemical bonds and intermolecular interactions in the extended solids and in a cluster model. We calculate formal quantum mechanical descriptors based on electronic structure, electron density, and binding and interaction energies including an energy decomposition analysis. Without exception, all descriptors point to 4β being a transient structure higher in energy than 4α with larger local and global electrophilic and nucleophilic powers, a more favorable spatial and energetic distribution of the frontier orbitals, and a more fragile crystal structure.

A high-spin alkylperoxo-iron(iii) complex with cis-anionic ligands: implications for the superoxide reductase mechanism.

The N3O macrocycle of the 12-TMCO ligand stabilizes a high spin (S = 5/2) [FeIII(12-TMCO)(OOtBu)Cl]+ (3-Cl) species in the reaction of [FeII(12-TMCO)(OTf)2] (1-(OTf)2) with tert-butylhydroperoxide (tBuOOH) in the presence of tetraethylammonium chloride (NEt4Cl) in acetonitrile at -20 °C. In the absence of NEt4Cl the oxo-iron(iv) complex 2 [FeIV(12-TMCO)(O)(CH3CN)]2+ is formed, which can be further converted to 3-Cl by adding NEt4Cl and tBuOOH. The role of the cis-chloride ligand in the stabilization of the FeIII-OOtBu moiety can be extended to other anions including the thiolate ligand relevant to the enzyme superoxide reductase (SOR). The present study underlines the importance of subtle electronic changes and secondary interactions in the stability of the biologically relevant metal-dioxygen intermediates. It also provides some rationale for the dramatically different outcomes of the chemistry of iron(iii)peroxy intermediates formed in the catalytic cycles of SOR (Fe-O cleavage) and cytochrome P450 (O-O bond lysis) in similar N4S coordination environments.

Two-dimensional ferromagnetism induced by Jahn-Teller distortion and orbital order

As the dimension of the system decreases, the quantum confinement effect and electronic correlation interaction inside the material will be correspondingly enhanced, often resulting in some novel physical properties. Recently, the freestanding perovskite oxide films down to the monolayer limit have been successfully prepared and can be transferred to any desired substrate, providing a great opportunity to explore the functional properties of two-dimensional perovskites. In perovskite materials, Jahn-Teller distortion and orbital order often cause a variety of correlated electronic behaviors. However, unlike van der Waals materials that retain their structural and chemical bonding characteristics when reduced to the monolayer limit, perovskite materials may undergo structural reconstruction when reduced to two dimensions. Therefore, whether Jahn-Teller distortion and related effects exist in the perovskite monolayer limit, and whether two-dimensional perovskite can exhibit some new properties different from its bulk phase, have become urgent issues to be solved. In this work, perovskite fluoride KCuF<sub>3</sub> and its monolayer have been comparatively studied by means of first-principles calculation, symmetry analysis, and Monte Carlo simulation methods, to reveal the change in lattice dynamics, structural, electronic, and magnetic properties caused by dimensionality reduction in perovskites. The results show that the cooperative Jahn-Teller distortion and the in-plane staggered orbital order occurring in the KCuF<sub>3</sub> bulk can be retained to the monolayer limit. However, unlike the bulk phase, the Jahn-Teller distortion mode appears as a soft mode of the prototype phase in the monolayer, and the insulating property of the monolayer does not rely on the emergence of the Jahn-Teller distortion, but is related to the enhancement of the electronic correlation effect. The staggered orbital order causes the nearest-neighbor exchange interaction to be ferromagnetic, resulting in the monolayer being a two-dimensional ferromagnetic insulator, different from the antiferromagnetic phase in the bulk. Monte Carlo simulations predict that the Curie temperature of the monolayer is about 5 K, which is much lower than the Néel temperature of the bulk phase, indicating that the disappearance of interlayer coupling leads to a significant reduction in the magnetic phase transition temperature. This work provides guidance and reference for the study of two-dimensional perovskite materials and the design of perovskite-based two-dimensional ferromagnets.

What governs magnetic exchange couplings in radical-bridged dinuclear complexes?

Coupling transition metal or lanthanide ions through a radical bridging ligand is a promising route to increase performances in the area of single molecular magnets. A better understanding of the underlying physical mechanisms governing the magnetic exchange couplings is thus of valuable importance to design future compounds. Here, couplings in three series of metal-radical-metal compounds based on transition metal ions are investigated by means of the decomposition/recomposition methods. This work presents the generalisation and first application of the method to systems with an arbitrary number of magnetic centres featuring several unpaired electrons. Thanks to the decomposition into the three main contributions (direct exchange, kinetic exchange, and spin polarisation) as well as a description in terms of electron-electron interactions, we study the influence of the nature of the metal centre and the radical ligand on the couplings. We combine the energetic contributions extracted with orbital and charge population analysis to rationalise the results.

Reformation of La0.7Sr0.3MnO3 properties by using ZnO in La0.7Sr0.3MnO3-ZnO heterostructures grown on (001) oriented Si.

Study of the available density of states (DOS) close-to-zero bias for conduction in strongly correlated electron systems, such as half-metallic La0.7Sr0.3MnO3 (LSMO) and its heterostructures, is important for fundamental and application reasons. As the DOS is proportional to the differential conductance (dI/dV), the dI/dV of a 120 Å LSMO film and its reformation in LSMO/ZnO heterostructures was investigated for different ZnO thicknesses. Unlike in conventional metals, the dI/dV of LSMO exhibits a power-law dependent zero-bias anomaly, i.e., dI/dV ∝ Vm (m ∼ 1) near zero bias in the ferromagnetic metallic state at 10 K. The growth of ZnO on LSMO reforms the linear dI/dVvs. V of LSMO near zero bias to non-linear. The exponent 'm' becomes ∼0.5 for a higher ZnO thickness, revealing increased electron-electron interactions and suppression of Kondo-like, double and superexchange interactions, which are responsible for the depression of the DOS of LSMO near zero bias. In a magnetically disordered state, i.e., around the Curie temperature, ZnO reforms the linear V-shaped dI/dV vs. V of LSMO to parabolic U-shaped dI/dVvs.V and controls the electron concentrations in the t2g-orbitals of Mn realized from the DOS simulations. Additionally, ZnO introduces a peak in the dI/dV vs. V due to Fowler-Nordheim tunnelling, and the peak voltage can be tuned by varying the ZnO thickness or temperature from 300 K to 360 K. Such functions of ZnO yield major perspectives for novel applications in thin-film-based devices.

ЦИФРОВІЗАЦІЯ ЯК ІНСТРУМЕНТ ТА СФЕРА ДЕРЖАВНОЇ ДОПОМОГИ СУБ’ЄКТАМ ГОСПОДАРЮВАННЯ В УКРАЇНІ

The article considers that the issue of state assistance in the digital sector is quite new, and especially relevant for Ukraine during the martial law and during the post-war reconstruction of the country. Understanding the possibilities of digital technology and the risks of being left behind in the race for digital transformation, governments around the world are increasingly putting digital transformation front and centre of their policy agenda to stimulate social development and economic prosperity. This involves significant investment, the need to address legal issues, and requires constant adaptation to the specific conditions of each country. The provision of state assistance in the digital sphere is regulated by the regulations of the EU Commission, in particular the articles regulating the provision of state assistance for innovations. It is noted that the digital portal Diya deserves special attention in the field of development of digital tools of state support for business entities. State assistance in the digital sector is focused on achieving long-term goals for the security of digital infrastructure, digital business transformation and digitalization of public services based on the widespread introduction of digital technologies. The success of digital transformation depends on the coordination of efforts of the state and entrepreneurs to expand the implementation of e-services and the transition to inclusive electronic interaction between state supervision and control bodies and business. The impact of the war proved to be an extremely powerful stimulus to the digitalization of Ukraine. The IT industry has become the only one that in 2022 showed positive growth rates, although its development indicators were much worse than expected (the increase was only 6% against the expected 40%). According to the NBU, in 2022 The IT industry provided foreign exchange earnings to the Ukrainian economy in the amount of $7.34 billion. The volume of exports increased by $400 million compared to pre-war 2021, an increase of 5.8%; the number of IT specialists in Ukraine has reached a record high of 300 thousand people.