Electronic Coupling Research Articles

Ground state properties of the screened helium atom under harmonic confinement

In this contribution, we show electronic property results for the ground state of the helium atom screened by a Debye plasma under an isotropic harmonic confinement as a function of the screening length (λD) and the angular frequency (ω0). The associate Hamiltonian is solved by expanding the wave function in the Hylleraas basis to incorporate the electron correlation in a simple manner. Furthermore, in order to compare with other findings the Hartree–Fock approach is implemented using a numerical grid method. The main results show that the total energy reaches the ionization threshold by the action of the electron coupling with the plasma medium and the strength of the harmonic confinement. The electron–electron average distance shows the compression of the system as the Debye plasma and the harmonic interactions become strongest (low λD and large ω0 values). We found acceptable results for the electron correlation energy when separate interactions are considered. In the absence of both interactions, the findings are in excellent agreement with other theoretical results.

Manipulating heterointerface to boost formation and desorption of intermediates for highly efficient alkaline hydrogen evolution

Promoting water dissociation and H intermediate desorption play a pivotal role in achieving highly efficient hydrogen evolution reaction (HER) in alkaline media but remain a great challenge. Herein, we rationally develop a unique W-doped NiSx/Ni heterointerface as a favorable HER electrocatalyst which was directly grown on the Cu nanowire foam substrate (W-NiSx/Ni@Cu) by the electrodeposition strategy. Benefiting from the rational design of the interfaces, the electronic coupling of the W-NiSx/Ni@Cu can be efficiently modulated to lower the HER kinetic barrier. The obtained W-NiSx/Ni@Cu exhibits an enhanced HER activity with a low overpotential of 38 mV at 10 mA cm−2 and a small Tafel value of 27.5 mV dec−1, and high stability during HER catalysis. In addition, in-situ Raman spectra reveal that the Ni2+ active sites preferentially adsorb OH intermediate. The theoretical calculation confirms that the water dissociation is accelerated by the construction of W-NiSx/Ni heterointerface and H intermediate desorption can be also promoted by H spillover from S active sites in W-NiSx to Ni active sites in metal Ni. This work offers a valuable reference for rational designing heterointerface of electrocatalysts and provides an available method to accelerate the HER kinetics for the ampere-level current density under low overpotential.

Controlled Self‐Assembly of Zn–Tetraphenylporphyrins for Efficient Photocatalytic Solar H2 Production and Simultaneous Organic Transformation to Valuable Chemicals

Herein, we have designed aqueous dispersed self‐assembled nanostructures with diverse morphologies from the zinc tetraphenyl porphyrin (ZnTPP) monomer employing a simple solution‐based coprecipitation methods. Detail morophological studies have been carried out by various electron microscopy techniques. Finally, the structural features were correlated with the underpinning photophysical processes using steady‐state and time‐resolved spectroscopy. Detailed studies suggest that control morphology and highly defined intermolecular interactions affect the overall photoinduced charge transfer process. Based on the fundamental investigations, all these different types of nanostructures have been utilized as photocatalysts for solar hydrogen production, without using any cocatalysts, and it was found that the spherical nanostructure exhibits significantly higher H2 production rates of ~1682 m mole/ g, which is few folds higher than other 1D and 2D nanostructured materials. The experimental findings were further supported by the TD‐DFT study. Furthermore, the detailed computational studies suggest that the spherical aggregates exhibited a more vital interaction between the ZnTPP molecules, causes significant electronic coupling between bright local excited and charge transfer states, which supports our experimental findings. Finally, we have selectively utilized the oxidative half‐reaction for the simultaneous transformation of glycerol to valuable chemicals along with photocatalytic H2 production through reductive half‐reaction.

Asymmetric aggregation enables red-light CO2 reduction with tunable activity and selectivity by intermolecular electronic coupling

Photocatalytic CO2 reduction to value-added chemicals is a promising way to simultaneously mitigate environmental and energy issues. Integrating low-energy red light harvesting, fast charge separation, and robust CO2 activation in a photosystem is a crucial prerequisite for highly efficient CO2 photoreduction but remains a huge challenge. Herein, we constructed an aggregated [Ru(2, 2'-bipyridine)3]Cl2 (denoted as Ru(bpy)3Cl2) photosystem. Various characterizations combining molecular dynamic simulations and theoretical calculations confirm that the electronic coupling between adjacent Ru(bpy)3Cl2 molecules can induce orbital hybridization, thus broadening the light absorption edge to the red light region. Meanwhile, the asymmetric aggregation of Ru(bpy)3Cl2 enables exciton dissociation and charge transfer through a dipole polarization effect. Significantly, this dipole polarization can also upshift the d-orbital of Ni catalytic centers, greatly strengthening the activation of CO2 and lowering the formation energy barrier of COOH* intermediates. Consequently, the apparent quantum yield (AQY) of aggregates for CO2-to-CO reduction reaches 4.2% at 610 nm, significantly higher than the AQYs of other reported photosystems at wavelengths ≥ 600 nm. More importantly, the catalytic efficiency and selectivity of CO2 reduction can be rationally tuned by controlling the aggregated degrees of Ru(bpy)3Cl2. This work highlights the key role of Ru(bpy)3Cl2 aggregation in prompting red-light harvesting and CO2 activation, which may help boost CO2 photoreduction efficiency from a fresh perspective.

Gold Nanoparticles with N-Heterocyclic Carbene/Triphenylamine Surface Ligands: Stable and Electrochromically Active Hybrid Materials for Optoelectronics.

Organic-hybrid particle-based materials are increasingly important in (opto)electronics, sensing, and catalysis due to their printability and stretchability as well as their potential for unique synergistic functional effects. However, these functional properties are often limited due to poor electronic coupling between the organic shell and the nanoparticle. N-heterocyclic carbenes (NHCs) belong to the most promising anchors to achieve electronic delocalization across the interface, as they form robust and highly conductive bonds with metals and offer a plethora of functionalization possibilities. Despite the outstanding potential of the conductive NHC-metal bond, synthetic challenges have so far limited its application to the improvement of colloidal stabilities, disregarding the potential of the conductive anchor. Here, NHC anchors are used to modify redox-active gold nanoparticles (AuNPs) with conjugated triphenylamines (TPA). The resulting AuNPs exhibit excellent thermal and redox stability benefiting from the robust NHC-gold bond. As electrochromic materials, the hybrid materials show pronounced color changes from red to dark green, a highly stable cycling stability (1000 cycles), and a fast response speed (5.6 s/2.1 s). Furthermore, TPA-NHC@AuNP exhibits an ionization potential of 5.3 eV and a distinct out-of-plane conductivity, making them a promising candidate for application as hole transport layers in optoelectronic devices.

Electronic Couplings and Conversion Dynamics between Localized and Charge Transfer Excitations from Many-Body Green's Functions Theory.

We investigate the determination of electronic coupling between localized excitations (LEs) and charge-transfer (CT) excitations based on many-body Green's functions theory in the GW approximation with the Bethe-Salpeter equation (GW-BSE). Using a small molecule dimer system, we first study the influence of different diabatization methods, as well as different model choices within GW-BSE, such as the self-energy models or different levels of self-consistency, and find that these choices affect the LE-CT couplings only minimally. We then consider a large-scale low-donor morphology formed from rubrene and fullerene and evaluate the LE-CT couplings based on coupled GW-BSE-molecular mechanics calculations. For these disordered systems of bulky molecules, we observe differences in the couplings based on the Edmiston-Ruedenberg diabatization compared to the more approximate Generalize Mulliken-Hush and fragment charge difference diabatization formalisms. In a kinetic model for the conversion between LE and CT states, these differences affect the details of state populations in an intermediate time scale but not the final populations.

Electron Localization and Mobility in Monolayer Fullerene Networks.

The novel 2D quasi-hexagonal phase of covalently bonded fullerene molecules (qHP C60), the so-called graphullerene, has displayed far superior electron mobilities, if compared to the parent van der Waals three-dimensional crystal (vdW C60). Herein, we present a comparative study of the electronic properties of vdW and qHP C60 using state-of-the-art electronic-structure calculations and a full quantum-mechanical treatment of electron transfer. We show that both materials entail polaronic localization of electrons with similar binding energies (≈0.1 eV) and, therefore, they share the same charge transport via polaron hopping. In fact, we quantitatively reproduce the sizable increment of the electron mobility measured for qHP C60 and identify its origin in the increased electronic coupling between C60 units.

Photoreduction of CO2 on Pd-In2O3: Synergistic optimization of progressive electron transfer via amorphous/crystalline Pd and oxygen vacancies

The progressive transfer of photogenerated electrons between the catalyst components and reactants is of great significance for photocatalysis. Amorphous Pd (PdA) and oxygen vacancies (VOs) were simultaneously introduced in Pd-In2O3 exploiting hydrogen-induced amorphization effects; 0.6 wt% Pd-In2O3 exhibited a 4.5-fold increase in activity and a 3.2-fold higher selectivity toward CH3OH + CO (63.62 %) compared with In2O3. Multiple in situ techniques and theoretical calculations revealed that intercomponent electron transfer channels were established via various interface structures formed between PdA or crystalline Pd (PdC) and In2O3; PdA acted as electronic pump, facilitating the transfer and separation of photogenerated electrons, resulting in their subsequent enrichment on the surface of PdA. Simultaneously, PdA acted as electron-donating adsorption site for H2O, increasing the number of electrons received by H2O, further inhibiting the competitive adsorption of H2O and CO2 on VO sites, and promoting the hydrogen evolution reaction. Additionally, the electronic coupling between PdC and VOs could significantly decrease the electron-donating ability of VOs, reducing the number of electrons received by CO2, thus effectively regulating the degree of CO2 reduction. This study employs PdA/PdC and VOs to synergistic optimize the progressive transfer of photogenerated electrons, and presents a novel approach for elucidating the catalytic mechanism.

The dual active sites reconstruction on gelatin in-situ derived 3D porous N-doped carbon for efficient and stable overall water splitting

The exploration of bifunctional electrocatalysts with high activity, stability, and economy is of great significance in promoting the development of water splitting. Herein, a dual active sites heterostructure NiCoS/NC was designed to be derived in situ on 3D N-doped porous carbon (NC) using gelatin as a nitrogen and carbon source. The characterization of experiments suggests that nanoflower-like Ni2CoS4 (abbreviated as NiCoS) was randomly distributed on the NC substrate, and the sheet-like NC formed a highly open porous network structure resembling a honeycomb, which provided more accessible active sites for electrolyte ions. In addition, the special nanostructures of the catalyst materials help to promote the surface reconstruction to the real active substance NiOOH/CoOOH, and the double active sites synergistically reduce the overpotential of OER and improve its kinetics. DFT (Density-functional theory) calculations reveal the electronic coupling of NiCoS/NC in atomic orbitals, modulation of electrons by the heterointerface and N-doping, and synergistic effect of dual active sites improving the inherent catalytic activity. The NiCoS/NC composite electrocatalyst exhibited a 177 mV small OER overpotential and a 132 mV small HER overpotential with Faraday efficiencies as high as 96 % and 98 % at 10 mA cm−2 current density. In the two-electrode system, it also requires only an ultra-low voltage of 1.52 V to achieve a 10 mA cm−2 current density, and it shows excellent long-term water splitting stability. This provides a new idea for the development of transition metal-based bifunctional electrocatalysts.

In-situ synthesis of Ni2P/Ti3C2Tx hybrid nanosheets for enhanced alkaline hydrogen evolution reaction

The development of efficient and low-cost electrocatalysts for hydrogen in alkaline media is crucial for green energy production. Herein, we report an in-situ synthesis strategy of Ni2P/Ti3C2Tx hybrid nanosheets on nickel foam (NF), which is effectively achieved by direct phosphorization of Ni-MOF/Ti3C2Tx. The Ni2P/Ti3C2Tx hybrid nanosheets not only inherit the morphology of the Ni-MOF/Ti3C2Tx precursor, but also possess electronic coupling effects, thereby exhibiting enhanced electrocatalytic performance toward alkaline hydrogen evolution reaction (HER).

Plasma-Engraved Lattice-Matched NiO/NiFe2O4 Heterostructure with Ample Oxygen Vacancies for Efficient Water Electrolysis and Zn-Air Batteries.

Heterogeneous interface and defect engineering offer effective pathways to accelerate oxygen evolution reaction (OER) charge transfer kinetics and motivate optimal intrinsic catalytic activity. Herein, we report the lattice-matched NiO/NiFe2O4 heterostructure with ample oxygen vacancies (Vo-NiO/NiFe2O4) induced by a feasible hydrothermal followed by calcination and plasma-engraving assistant technique, which shows the unique porous microflower arrangement of intertwined nanosheets. Benefitting from the synergetic effects between lattice-matched heterointerface and oxygen vacancies induce the strong electronic coupling, optimized OH-/O2 diffusion pathway and ample active sites, thus-prepared Vo-NiO/NiFe2O4 presents a favorable OER performance with a low overpotential (261 mV @ 10 mA cm-2) and small Tafel slope (39.4 mV dec-1), even surpassing commercial RuO2 catalyst. Additionally, the two-electrode configuration water electrolyzer and rechargeable zinc-air battery assembled by Vo-NiO/NiFe2O4 catalyst show the potential practical application directions. This work provides an innovative avenue for strengthening OER performance toward water electrolysis and Zn-air batteries via the interface and vacancy engineering strategy.

Intercalation in 2D materials and in situ studies.

Intercalation of atoms, ions and molecules is a powerful tool for altering or tuning the properties - interlayer interactions, in-plane bonding configurations, Fermi-level energies, electronic band structures and spin-orbit coupling - of 2D materials. Intercalation can induce property changes in materials related to photonics, electronics, optoelectronics, thermoelectricity, magnetism, catalysis and energy storage, unlocking or improving the potential of 2D materials in present and future applications. In situ imaging and spectroscopy technologies are used to visualize and trace intercalation processes. These techniques provide the opportunity for deciphering important and often elusive intercalation dynamics, chemomechanics and mechanisms, such as the intercalation pathways, reversibility, uniformity and speed. In this Review, we discuss intercalation in 2D materials, beginning with a brief introduction of the intercalation strategies, then we look into the atomic and intrinsic effects of intercalation, followed by an overview of their in situ studies, and finally provide our outlook.

Organic-inorganic hybrid interfaces with π-d electron coupling for preventing metal and sulfur leaching toward enhanced oxygen evolution reaction

Transition metal sulfides (TMSs) catalysts with high catalytic oxygen evolution reaction (OER) activity have been extensively studied, especially Fe and Co-based sulfides. Fe and Co active sites with a strong synergistic effect, which can adjust the electron density distribution and effectively improve the electrocatalytic OER activity. However, TMSs have poor stability in alkaline environment caused by metal ions and sulfur elements are facilitated to dissolve. In this work, TMSs was modified by polyaniline (PANI) to inhibit the precipitation of iron, cobalt, and sulfur elements and enhance its stability under alkaline conditions. Moreover, π-d structure can also be formed by the coating of PANI, which can further adjust its own electronic structure on the basis of stabilizing the TMSs structure, so as to improve the electrochemical performance, rendering them to stably operate at harsh environment for more than 90 h. These findings offer new guidance for improving the electrocatalytic stability of TMSs.

Electronic Couplings for Triplet-Triplet Annihilation Upconversion in Crystal Rubrene.

Triplet-triplet annihilation photon upconversion (TTA-UC) is a process able to repackage two low-frequency photons into light of higher energy. This transformation is typically orchestrated by the electronic degrees of freedom within organic compounds possessing suitable singlet and triplet energies and electronic couplings. In this work, we propose a computational protocol for the assessment of electronic couplings crucial to TTA-UC in molecular materials and apply it to the study of crystal rubrene. Our methodology integrates sophisticated yet computationally affordable approaches to quantify couplings in singlet and triplet energy transfer, the binding of triplet pairs, and the fusion to the singlet exciton. Of particular significance is the role played by charge-transfer states along the b-axis of rubrene crystal, acting as both partial quenchers of singlet energy transfer and mediators of triplet fusion. Our calculations identify the π-stacking direction as holding notable triplet energy transfer couplings, consistent with the experimentally observed anisotropic exciton diffusion. Finally, we have characterized the impact of thermally induced structural distortions, revealing their key role in the viability of triplet fusion and singlet fission. We posit that our approaches are transferable to a broad spectrum of organic molecular materials, offering a feasible means to quantify electronic couplings.

Superconductivity properties of Pd-Heusler rare earth from ab initio and isotropic Eliashberg function

Ab initio was employed to investigate the structural, electronic, and superconducting properties of the Heusler alloys Pd2TmSn, Pd2YbSn, and Pd2LuSn. The results reveal that these alloys exhibit both structural and dynamic stability in a cubic face-centered lattice. The isotropic Eliashberg function was used to calculate the superconductor properties. The phonon–electron couplings fall within the range characteristic of medium-coupling superconductors. Analysis of the Fermi surfaces identifies the presence of necks connecting the first Brillouin zones, which facilitate electron pairing. The calculated superconducting critical temperatures using the Allen–Dynes equation are in agreement with previous experimental and theoretical findings.

Simulation of interlayer coupling for electroactive covalent organic framework design.

Porous, stacked two-dimensional covalent organic frameworks (2D COFs) bearing semiconducting linkers can support directional charge transfer across adjacent layers of the COF. To better inform the current and possible future design rules for enhancing electron and hole transport in such materials, an understanding of how linker selection and functionalization affects interlayer electronic couplings is essential. We report electronic structure simulation and analysis of electronic couplings across adjacent linker units and to encapsulated species in functionalized electroactive 2D COFs. The detailed dependence of these electronic couplings on interlayer interactions is examined through scans along key interlayer degrees of freedom and through configurational sampling from equilibrium molecular dynamics on semiempirical potential energy surfaces. Beyond affirming the sensitivity of the electronic coupling to interlayer distance and orientation, these studies offer guidance toward linker functionalization strategies for enhancing charge carrier transport in electroactive 2D COFs.

Efficient Electron Transfer Driven by Excited-State Structural Relaxation in Corrole-Perylenedimiide Dyad.

A sterically encumbered trans-A2B-corrole possessing a perylenediimide (PDI) scaffold in close proximity to the macrocycle has been synthesized via a straightforward route. Electronic communication as probed via steady-state absorption or cyclic voltammetry is weak in the ground state, in spite of the corrole ring and PDI being bridged by an o-phenylene unit. The TDDFT excited-state geometry optimization suggests after excitation the interchromophoric distance is markedly reduced, thus enhancing the through-space electronic coupling between the corrole and the PDI. This is corroborated by the strong deviation of the emission spectrum originating from both PDI and corrole in the dyad. Selective excitation of both donor and acceptor units triggers efficient sub-picosecond electron transfer and hole transfer, respectively, followed by fast charge recombination. In comparison to previously studied corrole-PDI dyads, both charge separation and charge recombination occur faster, because of the structural relaxation in the excited state.

Nitrogen Effects Endowed by Doping Electron-Withdrawing Nitrogen Atoms into Polycyclic Aromatic Hydrocarbon Fluorescence Emitters.

Unveiling innovative mechanisms to design new highly efficient fluorescent materials and, thereby, fabricate high-performance organic light-emitting diodes (OLEDs) is a concerted endeavor in both academic and industrial circles. Polycyclic aromatic hydrocarbons (PAHs) have been widely used as fluorescent emitters in blue OLEDs, but device performances are far from satisfactory. In response, we propose the concept of "nitrogen effects" endowed by doping electron-withdrawing nitrogen atoms into PAH fluorescence emitters. The presence of the n orbital on the imine nitrogen is conducive to promoting electron coupling, which leads to increased molar absorptivity and an accelerated radiative decay rate of emitters, thereby facilitating the Förster energy transfer (FET) process in the OLEDs. Additionally, electronically withdrawing nitrogen atoms enhances host-guest interactions, thereby positively affecting the FET process and the horizontal orientation factor of the emitting layer. To validate the "nitrogen effects" concept, cobalt-catalyzed multiple C-H annulation has been utilized to incorporate alkynes into the imine-based frameworks, which enables various imine-embedded PAH (IE-PAH) fluorescence emitters. The cyclization demonstrates notable regioselectivity, thereby offering a practical tool to precisely introduce peripheral groups at desired positions with bulky alkyl units positioned adjacent to the nitrogen atoms, which were previously beyond reach through the Friedel-Crafts reaction. Blue OLEDs fabricated with IE-PAHs exhibit outstanding performance with a maximum external quantum efficiency (EQEmax) of 32.7%. This achievement sets a groundbreaking record for conventional blue PAH-based fluorescent emitters, which have an EQEmax of 24.0%.

Engineering Symmetry Breaking in Twisted MoS2-MoSe2 Heterostructures for Optimal Thermoelectric Performance.

Engineering symmetry breaking in thermoelectric materials holds promise for achieving an optimal thermoelectric efficiency. van der Waals (vdW) layered transition metal dichalcogenides (TMDCs) provide critical opportunities for manipulating the intrinsic symmetry through in-plane symmetry breaking interlayer twists and out-of-plane symmetry breaking heterostructures. Herein, the symmetry-dependent thermoelectric properties of MoS2 and MoSe2 obtained via first-principles calculations are reported, yielding an advanced ZT of 2.96 at 700 K. The underlying mechanisms reveal that the in-plane symmetry breaking results in a lowest thermal conductivity of 1.96 W·m-1·K-1. Additionally, the electric properties can be significantly modulated through band flattening and bandgap alteration, stemming directly from the modified interlayer electronic coupling strength owing to spatial repulsion effects. In addition, out-of-plane symmetry breaking induces band splitting, leading to a decrease in the degeneracy and complex band structures. Consequently, the power factor experiences a notable enhancement from ∼1.32 to 1.71 × 10-2 W·m-1·K-2, which is attributed to the intricate spatial configuration of charge densities and the resulting intensified intralayer electronic coupling. Upon simultaneous implementation of in-plane and out-of-plane symmetry breaking, the TMDCs exhibit an indirect bandgap to direct bandgap transition compared to the pristine structure. This work demonstrates an avenue for optimizing thermoelectric performance of TMDCs through the implementation of symmetry breaking.

Synthesis of oxygen vacancies rich CeO2-xNx/GCN hybrid nanostructure with great active interfaces for electrochemical detection of antiviral levofloxacin in pharmaceutical samples

COVID-19 is an emerging viral infectious disease. Severe respiratory problems are considered an important syndrome of COVID-19 in humans. Levofloxacin (LEV), a promising fluoroquinolone antibacterial agent/therapeutic agent for influenza virus (H1N1)-induced pneumonia drug. These have been used as a potent antidote for acute respiratory tract infections. Owing to its excellent pharmacokinetic properties such as potential antiviral and scavenging activity, LEV has been used in controlling and treating COVID-19 during infectious emergencies. Even taking over the dosage of LEV and disposing of the embryonic toxic nature of LEV residues in the pharmaceutical research industry can cause adverse effects on the public health and environment. For this purpose, the development of great analytical tools is important to the detection of antiviral LEV for human health safety and environmental protection. In this work, we report a nitrogen (N) doped strategy to construct the enriched oxygen vacancies (OVs) on CeO2-xNx/GCN-2 hybrid nanostructure as an efficient electrocatalyst for the ultrasensitive detection of antiviral LEV. The effect of the N doping into the CeO2 (CeO2-xNx) lattice with increasing the large amount of OVs and boosted their redox properties (Ce4+→Ce3+), thus provided that a great electrochemically active site. Although the abundant OVs were conformed on the CeO2-xNx/GCN-2 from the peak-area ratio of Ce3+/Ce4+ and O2/O1 by X-ray photoelectron spectroscopy (XPS) assay. Owing to the strong electronic coupling between the OV-rich CeO2-xNx and the conductive GCN surface, thus CeO2-xNx/GCN-2 heterojunction achieved superior analytical performance for LEV oxidation with a good linear range from 0.01 μM to 710 μM, and detection limits of 5.6 nM (S/N = 3), and sensitivity 24.711 μA μM−1 cm−2 at a very low working potential (0.7 V). The proposed hybrid sensor also exploited to the analysis of the pharmaceutical industry wastewater, pharmaceutical tablet and human urine samples with a satisfactory recovery rate.