Search

Determining the electronic levels associated with polarons, the fundamental charge carriers in organic semiconductors, is key to understanding the charge transport properties of these materials. Recent findings challenge the traditional view of these electronic levels by highlighting the importance of intra‐molecular Coulomb interactions in polarons. Experimental evidence was previously presented for a revised model of the negative polaron in the case of the polymer semiconductor poly(NDI2OD‐T2); there, the addition of an excess electron was seen to lead to the emergence of a singly occupied state within the energy gap of the undoped material and an unoccupied state above the edge of the conduction states. Here, focus is on a small‐molecule semiconductor, C60, and spectral evidence is provided of a similar picture for the new states appearing upon polaron formation. Specifically, direct and inverse photoemission spectroscopy is used to investigate the density of states in C60 films n‐doped with two dimeric dopants. The Coulomb interaction energy (Hubbard U) of the C60 anion is experimentally determined to be ≈1.1 eV, a value that aligns closely with theoretical predictions. [ABSTRACT FROM AUTHOR]

The manipulation of surface catalytic sites has rarely been explored for metal borides, and the subsurface effects on the electrocatalytic activity of the nitrogen reduction reaction (NRR) remain unknown. Herein, this work develops a core–shell nanoparticle catalyst with a Pd core that ensures high electron transfer rates and an Pd16B3 atomical shell that possess tunable active sites for regulating the NRR. The atomic structural evolution from Pd to Pd16B3 is investigated by precisely controlling the B atom diffusion, molecular rearrangement, and d–sp orbital hybridization. Pd/Pd16B3 core–shell nanocrystals exhibit an exceptional NRR performance with a high NH3 Faradaic efficiency of 30.8%, which is superior to those of pristine Pd (1.2%) and B‐doped Pd (4.8%) under identical conditions, and a yield rate of 0.81 µmol h−1 cm−2. This work discovers that the Pd16B3 shell could promote the NRR selectivity by separating the separating the hydrogen evolution reaction proceeded on hole sites and NRR proceeded on bridge sites, and the Pd core could provide the excellent conductivity to Pd16B3 shell through regulated electron interactions. Consequently, the controlled chemical ordering of palladium boride on palladium surfaces provides insight into the synthesis of advanced NRR electrocatalysts. [ABSTRACT FROM AUTHOR]

The low-lying electronic states of ScO2 and ScO2– were studied using the SAC-CI method. The lowest six doublet states (X2B2, 12A1/22A′, 22A1, 12A2, 12B1/12A″, and 22B2) of ScO2 and the valence-bound singlet/triplet states (X1A1, 21A1/13A1, 11A2/13A2, 11B1/13B1, 11B2/13B2, and 21B2/23B2) of ScO2– were optimised, and the relative energies among these electronic states were obtained. The electron detachment energies from the X1A1 state of ScO2– to the lowest six doublet states of ScO2 and from the 13B2 state of ScO2– to the X2B2 state of ScO2 can be compared with the previous experimental photoelectron spectra of ScO2–. The vertical excitation spectra of ScO2 and ScO2– were computed. The singlet/triplet dipole-bound states (1B2(DB)/3B2(DB)) of ScO2– were found. [ABSTRACT FROM AUTHOR]

Edge dislocations are crucial in understanding both mechanical and electrical transport in solid and are modeled as line distributions of dipole moments. The calculation of the electronic spectrum for the two dimensional dipole, represented by the potential energy V (r , θ) = p cos θ / r , has been the topic of several studies that show significant difficulties in obtaining accurate results. In this work, we demonstrate that the source of these difficulties is a logarithmic contribution to the behavior of the wave function at the origin that was neglected by previous authors. By taking into account this non-analytic deviation of the solution of Schrödinger's equation, superior results, with the expected rate of convergence, are obtained. This goal is accomplished by "adapting" general algorithms for solving partial derivative differential equations to include the desired asymptotic behavior. We illustrate this principle for the variational principle and finite difference methods. Accurate energies and wave functions are obtained not only for the ground state but also for the first eleven excited states and are useful for designing nanoelectronic devices. This paper demonstrates that augmentary knowledge about analytic properties of the solutions leads to the improved convergence and stability of numerical methods. [ABSTRACT FROM AUTHOR]

[Display omitted] The electronic properties and structural characteristics of transition metal materials have a significant impact on their electrocatalytic performance. Therefore, precisely controlling the electronic states of core metals and fabricating catalysts with advanced structures are conducive to facilitating electrolysis process. Herein, we manipulate the electronic properties of the electroactive sites of catalysts by controlling the degree of phosphorization during the phosphorization process. The Co x P-FeP@C electrocatalysts, characterized by their sea-urchin morphology, were synthesized by subjecting CoFc-metal organic framework (MOF) precursors to phosphorization for specific time intervals. The optimized Co 2 P-FeP@C-5 electrocatalyst showed the optimum performance towards the oxygen evolution reaction (OER) catalytic efficiency with 239 mV overpotential and the hydrogen evolution reaction (HER) activity with 169 mV overpotential to reach 10 mA·cm−2 in 1.0 M KOH (PH = 13.8). For comparison, the extended duration of phosphorization resulted in the formation of CoP-FeP@C-15 and CoP-FeP@C-30 electrocatalysts, which exhibited compromised electrocatalytic performance due to the transformation of the electroactive core Co 2 P to CoP during subsequent phosphorization processes. The improved interfacial properties between Co 2 P and FeP play a crucial role in enhancing the efficiency of water decomposition, attributed to the higher density of states (DOS) at the Fermi Level and the increased availability of electroactive sites for the adsorption of intermediates and electrolysis. These findings are substantiated by density functional theory (DFT) calculations. This approach offers a highly effective means of manipulating the electronic properties of the electroactive transition metal core by controlling the degree of phosphorization, with the ultimate goal of achieving efficient water splitting. [ABSTRACT FROM AUTHOR]

Synchronous electron diffraction/mass spectrometry was used to study the composition and structure of molecular forms existing in a saturated vapor of cobalt(II) oxopivalate at T = 410 K. It was found that monomeric complexes Co4O(piv)6 dominate in the vapor. The complex geometry possesses the C3 symmetry with bond lengths Co–Oc = 1.975(5) Å and Co–O = 1.963(5) Å, as well as bond angles Oc–Co–O = 111.8(3)°, Co–Oc–Co = 110.4(6)°, O–Co–O = 107.1(3)° in the central OcCo4 fragment and four OcCoO3 fragments. The presence of an open 3d shell for each Co atom leads to the possibility of the existence of electronic states of the Co4O(piv)6 complex with Multiplicities 1, 3, 5, 7, 9, 11, and 13. For them, the CASSCF and XMCQDPT2 calculations predict similar energies, identical shapes of active orbitals, and geometric parameters, the difference between which is comparable with the error of determination by the electron diffraction experiment. QTAIM and NBO analysis show that the Co–Oc and Co–O bonds can be attributed to ionic (or coordination) bonds with a significant contribution of the covalent component. The high volatility and simple vapor composition make it possible to recommend cobalt (II) oxopivalate as precursors in the preparation of oxide films or coatings in the CVD technologies. The features of the electronic and geometric structure of the Co4O(piv)6 complex allows for the conclude that only a very small change in energy is required for the transition from antiferromagnetically to ferromagnetically coupled Co atoms. [ABSTRACT FROM AUTHOR]

Microscopic studies on electrolyte solution/electrode interfaces provide the most fundamental information not only for understanding the electric double layer formed at the interfaces but also for designing sophisticated electrochemical devices. As with various electronic devices, it is critical to understand the electronic structure of the interfaces, but direct assessment has been limited by the presence of solution. This article presents our exploration of the electronic structure of electrochemical interfaces using photoelectron spectroscopy and electrochemical measurements. [ABSTRACT FROM AUTHOR]

With abundant metal site and tunable electronic structure, MXene is considered as a promising electrocatalyst for the conversion of energy molecules. In this review, the latest research progress on inexpensive MXene‐based catalysts for water electrolysis is summarized. Typical preparation and modification methods and their advantages and disadvantages are briefly discussed, with a focus on the regulation and design of the surface interface electronic states, which improve the electrocatalytic performance of MXene‐based materials. The main strategies for the electronic state modification include end‐group modification, heteroatom doping, and heterostructure construction. Some limitations of MXene‐based materials, which should be considered in the rational design of advanced MXene‐based electrocatalyst, are also discussed. Finally, prospects for the rational design of Mxene‐based electrocatalysts is proposed. [ABSTRACT FROM AUTHOR]

Changes in the total quantity of electric charge with time for different ratios of corrosion inhibitors in a steel–organic surfactant–electrolyte system are shown. Approximation equations are derived for each system of the inhibitors to calculate the slow adsorption surface electronic states of the interface. The adsorption surface electronic states are calculated by the Kots equation. The synergic effect of the inhibitors is shown. [ABSTRACT FROM AUTHOR]

Electrochemically converting NO3− into NH3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO3− is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO3− reduction reaction (NO3RR) with dilute NO3− concentration (≤100 ppm NO3−−N). Notably, a linear relationship was established by plotting NH3 yield vs. the oxidation state of Cu, indicating that the increase of Cu+ content leads to an enhanced NO3−‐to‐NH3 conversion activity. Under a low NO3−−N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO3−‐to‐NH3 conversion at −0.55 to −0.6 V vs. RHE, and a record‐high NH3 yield of 309 mmol h−1 gcat−1, which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h−1 gcat−1). This research provides an effective method for conversion of dilute NO3− to NH3, which has certain guiding significance for the efficient and green conversion of wastewater in the future. [ABSTRACT FROM AUTHOR]

The paper presents a method for fast calculating the electronic states in twodimensional quantum structures based on AIIIBV nitrides. The method is based on the representation of electronic states in the form of a linear combination of bulk wave functions of materials, from which quantum structures are made. The parameters and criteria for the selection of bulk wave functions that provides fast convergence of the numerical procedures for calculating the eigenvalues of the quantum Hamiltonian have been considered. The results of the calculations have been given both for one polar InGaN/GaN quantum well and for a system of several quantum wells. Being based on the full band structure of AIIIBV nitrides with a wurtzite-type crystal lattice, the proposed approach takes into account the states far from the center of the Brillouin zone, while preserving the computational efficiency of traditional methods of envelope function in approximating the effective mass. [ABSTRACT FROM AUTHOR]

Molecular level understanding of 3d-transition metal interaction with water molecules in various electronic states is of fundamental significance in chemistry and biology. This study systematically presents the propensity of 3d-transition metals in their variable electronic and spin states towards solvation and splitting water molecules. The topological analysis affirmed that neutral and mono-cationic complexes are prone to be partially covalent in nature from moving low to high spin states; however, coordinate bonding is observed in di- and tri-cationic ion–water complexes. Potential energy surface analysis showed a profound influence of electronic states of 3d-transition metals on the relative feasibility of bond scission and solvation competing pathways. The early neutral, high spin mono-cationic, and di-cationic transition metals prefer solvation over splitting the water molecule. Similarly, mid- and late-transition metal ions in the first two electronic states, irrespective of the spin state, show higher preferences towards solvation. In contrast, neutral and tri-cationic ions tend to form either insertion complexes, hydroxides, or hydrides over the ion–water complexes, suggesting a preference to split the water molecule. Thus, tuning the electronic and micro-environment will help in the design of transition metals catalysts for water splitting. [ABSTRACT FROM AUTHOR]

Edge dislocations are crucial in understanding both mechanical and electrical transport in solid and are modeled as line distributions of dipole moments. The calculation of the electronic spectrum for the two dimensional dipole, represented by the potential energy V(r,θ)=pcosθ/r, has been the topic of several studies that show significant difficulties in obtaining accurate results. In this work, we demonstrate that the source of these difficulties is a logarithmic contribution to the behavior of the wave function at the origin that was neglected by previous authors. By taking into account this non-analytic deviation of the solution of Schrödinger’s equation, superior results, with the expected rate of convergence, are obtained. This goal is accomplished by “adapting” general algorithms for solving partial derivative differential equations to include the desired asymptotic behavior. We illustrate this principle for the variational principle and finite difference methods. Accurate energies and wave functions are obtained not only for the ground state but also for the first eleven excited states and are useful for designing nanoelectronic devices. This paper demonstrates that augmentary knowledge about analytic properties of the solutions leads to the improved convergence and stability of numerical methods.

Exploring highly‐efficient palladium (Pd)‐based electrocatalysts for the alcohol oxidation reaction (AOR) is crucial yet challenging for chemists due to the vague Pd interface with an uncontrollable electronic environment. Herein, an organic heterocyclic strategy is used for the first time to modulate the electronic state of Pd electrocatalysts by anchoring Pd nanoparticles to conjugated microporous polymers (CMPs) with varied S‐, N‐, O‐, or S, N‐heterocycles. Among these CMPs, the S, N‐containing thiazole heterocyclic polymer SNC with Pd catalyst exhibits highly‐efficient current densities of 1575.0 mA mgPd−1 for methanol oxidation and 1071.0 mA mgPd−1 for ethanol oxidation, which are among the highest performance in the heterocyclic modulated Pd systems and surpass the commercial Pd black catalyst. Detailed theory calculations suggest that although the furan (O‐heterocycle) polymer OC has the strongest charge transfer (0.057 |e|) with the Pd cluster, the moderate electron transfer (0.041 |e|) of the Pd/SNC heterojunction with an S···N···Pd noncovalent interaction shows the best catalytic reaction kinetics. Moreover, the d‐band of the Pd/SNC system is closer to the volcano vertex than its counterparts. These results indicate that appropriate electron transfer intensity regulation of Pd electronic state by well‐defined heterocyclic structures may significantly improve AOR activity. [ABSTRACT FROM AUTHOR]

In this paper, we introduce specific approximations to simplify the vibronic treatment in modeling absorption and emission spectra, allowing us to include a huge number of vibronic transitions in the calculations. Implementation of such a simplified vibronic treatment within our general approach for modelling vibronic spectra, based on molecular dynamics simulations and the perturbed matrix method, provided a quantitative reproduction of the absorption and emission spectra of aqueous indole with higher accuracy than the one obtained when using the existing vibronic treatment. Such results, showing the reliability of the approximations employed, indicate that the proposed method can be a very efficient and accurate tool for computational spectroscopy. [ABSTRACT FROM AUTHOR]

The double minimum E 1 Σ u + state in caesium dimer was investigated by analysing spectra of the E 1 Σ u + ← X 1 Σ g + band system, simplified by polarisation labelling. A total of 6727 rotationally resolved transitions to levels situated in the inner well and above the internal barrier were identified and a potential energy curve allowing to reproduce their energies was constructed using the Fourier grid Hamiltonian and inverted perturbation approach methods. The unambiguity of the potential curve in view of lack of data related to levels located in the outer well is discussed. [Display omitted] • Double minimum E(3) 1 Σ u + state of Cs 2 studied by polarisation labelling spectroscopy. • Energies of more than 5600 rovibrational levels determined. • Constructed potential energy curve reproduces positions of levels with rms <0.05 cm−1. • Unambiguity of the experimentally determined potential curve discussed. [ABSTRACT FROM AUTHOR]

In this paper, we design and investigate the stability, electronic characteristics, and transport parameters of a series of 12 two-dimensional materials, including six ternary Al M X 3 and six quaternary Janus Al 2 M 2 X 3 Y 3 (M = Ge, Sn; X / Y = S, Se, and Te; X ≠ Y) monolayers by using first-principles calculations based on the density functional theory. The phonon spectra and Born elastic stability criteria are used to consider the stability of the studied materials. Our examinations indicate that, except for Janus Al 2 Sn 2 S 3 Te 3 monolayer, the other structures are structurally stable. While the ternary Al M X 3 monolayers are found to be indirect semiconductors, quaternary Janus Al 2 M 2 X 3 Y 3 structures can be either direct semiconductors or metallic (Al 2 Ge 2 S 3 Te 3). Interestingly, Mexican hat-like dispersion can be found in the topmost valence band of ternary Al M X 3 monolayers, which are not observed in their corresponding Janus structures. All studied semiconducting materials exhibit a high electron mobility, up to 1. 51 × 1 0 3 cm 2 V−1s−1 for Al 2 Sn 2 Se 3 Te 3 monolayer. The electron mobilities of the studied structures are high directional isotropic along the x and y axes and much higher than those of the hole mobility. The unique electronic and transport features of ternary Al M X 3 and quaternary Janus Al 2 M 2 X 3 Y 3 monolayers can be suitable for applications in electronic nanodevices. [ABSTRACT FROM AUTHOR]

In this paper, we have studied a theoretical and numerical investigation of the electronic properties of finite cylindrical quantum wires (CQWRs), constituted by the periodic alteration of two semiconductor materials of CQWRs GaAs/AlGaAs in the axial direction, the structure sandwiched between two substrates GaAs. The electronic band structure and the electronic transmission spectrum are obtained by means of Green's function approach, taking into account the impact of connection barriers. Our results reveal that the electronic energy levels of CQWRs consist of alternating passbands and bandgaps. The coincidence of incoming electronic waves with these discrete electronic energy levels leads to electron transport during the CQWRs superlattice. We employed an effective mass model dependent on the cell position in the axial direction to solve the Schrodinger equation. This model was adjusted to reflect variations in the confining potentials while accounting for changes in the radial direction. When the radius of the structure is relatively small the electronic states tend towards higher energies due to geometrical confinement. On the other hand, as the radius increases, the passbands and bandgaps move to lower energies. Similarly, the pseudogaps turn into full gaps, and their width increases, and this feature is also observed when the number of cells increases. This property is due to the interaction between the neighboring electrons and the eigenstates of the CQWRs. In addition, the passbands and band gaps shift to high energy when the barrier concentration increases, and the width of band gaps increases also. Finally, we have demonstrated the theoretical design of an optoelectronic device for filtering electronic waves by geometrical and physical parameters, whose electronic band structure of this finite CQWRs superlattice can be controlled. • Effect of cell number N and geometrical parameters on the electronic transmission spectrum in the CQWRs superlattice. • Effect of geometrical and physical parameters on the electronic band structure in a CQWRs superlattice. • The electronic energy levels are very sensitive to the effect of CQWRs radius. • Electronic properties are affected by changes in the geometrical and physical parameters of SL CQWRs. [ABSTRACT FROM AUTHOR]

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerene, can be widely used to store hydrogen, and doping these materials with lithium (Li) generally increases their H2-storage densities. Unfortunately, Li is expensive; therefore, alternative metals are required to realize a hydrogen-based society. Sodium (Na) is an inexpensive element with chemical properties that are similar to those of lithium. In this study, we used density functional theory to systematically investigate how hydrogen molecules interact with Na-doped graphene nanoflakes. A graphene nanoflake (GR) was modeled by a large polycyclic aromatic hydrocarbon composed of 37 benzene rings, with GR-Na-(H2)n and GR-Na+-(H2)n (n = 0–12) clusters used as hydrogen storage systems. Data obtained for the Na system were compared with those of the Li system. The single-H2 GR-Li and GR-Na systems (n = 1) exhibited binding energies (per H2 molecule) of 3.83 and 2.72 kcal/mol, respectively, revealing that the Li system has a high hydrogen-storage ability. This relationship is reversed from n = 4 onwards; the Na systems exhibited larger or similar binding energies for n = 4–12 than the Li-systems. The present study strongly suggests that Na can be used as an alternative metal to Li in H2-storage applications. The H2-storage mechanism in the Na system is also discussed based on the calculated results.

Vanadium tetraoxide (VO4) has several isomers, and VO2(η²-O2) is the most stable one. The low-lying doublet states of VO2(η²-O2) and low-lying singlet states of VO2(η²-O2)− were studied using the SACCI theory. The electron detachment energies from the ground electronic state of VO2(η²-O2)− to the low-lying doublet states of VO2(η²-O2) were obtained. These electron detachment energies can be compared with the previous experimental photoelectron spectrum of VO4−, and possible candidate states for the unassigned bands were found. The ground electronic states of VO2(η²-O2)/VO2(η²-O2)− and seven doublet excited states of VO2(η²-O2) were optimised. The vertical excitation spectra of VO2(η²-O2) and VO2(η²-O2)− were calculated. The lowest doublet/quartet states of VO4 and lowest singlet/triplet states of VO4– were also computed at the BP86/aug-cc-pVTZ level. [ABSTRACT FROM AUTHOR]

Two-colour polarisation labelling experiment measuring excitation spectra of Na 2 in the spectral range 34, 600−39, 400 cm − 1 has furnished observation of the previously unknown 7 1 Π u electronic state. The excited state is characterised by a set of Dunham coefficients describing the f parity levels up to vibrational level v = 28 and the corresponding potential energy curve is constructed by the inverted perturbation approach method. Molecular parameters determined in the fit include T e = 36583.86 ± 0.03 cm − 1 , ω e = 107.50 ± 0.03 cm − 1 and R e = 3.640 ± 0.001 Å. [ABSTRACT FROM AUTHOR]

Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HC2m+1N (m = 0–13) and dinitriles NC2n+2N (n = 0–14). The results of time-dependent density functional theory (TD-DFT) calculations are compared with the available gas-phase and noble gas matrix experimental data. We assessed the performance of fifteen functionals and five basis sets for reproducing (i) vibrationless electronic excitation energies and (ii) vibrational frequencies in the singlet excited states. We found that the basis sets of at least triple-ζ quality were necessary to describe the long molecules with alternate single and triple bonds. Vibrational frequency scaling factors are similar for the ground and excited states. The benchmarked spectroscopic parameters were shown to be acceptably reproduced with adequately chosen functionals, in particular ωB97X, CAM-B3LYP, B3LYP, B971, and B972. Select functionals were applied to study the electronic excitation of molecules up to HC27N and C30N2. It is demonstrated that optical excitation leads to a shift from the polyyne- to a cumulene-like electronic structure. [ABSTRACT FROM AUTHOR]

We investigate the effect of Coulomb interactions on the electronic states of a single perovskite quantum dot (PQD), CsPbBr 3 , 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 (d I /d V ) 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.

We simulate the energy eigenstates of electrons and holes, which underlie terahertz Bloch oscillations observed recently with a peculiar Ď€ / 2 phase shift, in a biased semiconductor superlattice with interminiband mixing. Electron wavefunctions are extended downstream, while some of them have a moderately first-miniband-like nature that partly resembles Wannierâ€"Stark localization upstream. When a typical heavy-hole wavefunction is chosen, a few first-miniband-like electron wavefunctions prove to have large overlap integrals with it under relatively low bias fields. These electron wavefunctions are thus essential for the optical excitation of the Bloch oscillations, supported experimentally by the peak patterns of dc photocurrent spectra. [ABSTRACT FROM AUTHOR]

This study introduces a new strategy utilizing poly(o-phenylenediamine) (POPD) to overcome the limitations of traditional solid-state Z-scheme photocatalysts. POPD was first selected for its tunability, stability, and interfacial compatibility in constructing a novel S-scheme heterojunction between twice-calcined graphite carbon nitride (CN) and zinc aluminate (ZAO). Femtosecond transient absorption spectroscopy (fs-TAS) confirmed that this design optimizes the dynamics of photogenerated charge carriers. Theoretical calculations indicated that close interface coupling through high interfacial binding with CN (-5.21 eV) and ZAO (-17.80 eV). Simultaneously, POPD facilitates the expansion and hybridization of the electronic states of ZAO/POPD/CN (ZPN), thereby optimizing the distribution of excitation energy and enhancing exciton transitions. The optimal ZPN efficiently degrades tetracycline (TC) and completely inactivates Escherichia coli (E. coli) under simulated sunlight. Systematic characterization and theoretical calculations validated the charge transfer pathways within the S-scheme heterojunction. These findings offer new insights into advancing the application of organic polymer in heterojunctions. [Display omitted] • The study introduces poly(o-phenylenediamine) as an effective intermediate. • Poly(o-phenylenediamine) further optimizes the distribution of excitation energy and enhances exciton transitions. • The optimized dynamics of photogenerated charge carriers and the strong interface coupling were demonstrated. [ABSTRACT FROM AUTHOR]

The polarisation labelling spectroscopy technique was applied to study the C 1 Π u ← X 1 Σ g + band system in potassium dimer. About 1100 new rotationally resolved molecular lines were measured in the 22100–24100 cm−1 spectral range. Perturbations of the lowest vibrational levels of the C state were localised and their origin discussed. A set of Dunham coefficients was deduced to fit the unperturbed levels of the C 1 Π u state with 0 ≤ v ≤ 38 and 18 ≤ J ≤ 101 and the potential energy curve of the state was constructed. [Display omitted] • The C(2)1 Π u ← X1 Σ + g band system of K 2 observed by polarisation labelling spectroscopy technique. • More than 1400 transition frequencies measured. • The potential curve of the C1 Π u state constructed from experimental data. • Perturbation of the C state by the 33 Σ + u state observed and partially analysed. [ABSTRACT FROM AUTHOR]

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerene, can be widely used to store hydrogen, and doping these materials with lithium (Li) generally increases their H2-storage densities. Unfortunately, Li is expensive; therefore, alternative metals are required to realize a hydrogen-based society. Sodium (Na) is an inexpensive element with chemical properties that are similar to those of lithium. In this study, we used density functional theory to systematically investigate how hydrogen molecules interact with Na-doped graphene nanoflakes. A graphene nanoflake (GR) was modeled by a large polycyclic aromatic hydrocarbon composed of 37 benzene rings, with GR-Na-(H2)n and GR-Na+-(H2)n (n = 0–12) clusters used as hydrogen storage systems. Data obtained for the Na system were compared with those of the Li system. The single-H2 GR-Li and GR-Na systems (n = 1) exhibited binding energies (per H2 molecule) of 3.83 and 2.72 kcal/mol, respectively, revealing that the Li system has a high hydrogen-storage ability. This relationship is reversed from n = 4 onwards; the Na systems exhibited larger or similar binding energies for n = 4–12 than the Li-systems. The present study strongly suggests that Na can be used as an alternative metal to Li in H2-storage applications. The H2-storage mechanism in the Na system is also discussed based on the calculated results. [ABSTRACT FROM AUTHOR]

The spin polarization of carbon nanomaterials is crucial to design spintronic devices. In this paper, the first‐principles is used to study the electronic properties of two defect asymmetric structures, Cap‐(9, 0)‐Def [6, 6] and Cap‐(9, 0)‐Def [5, 6]. We found that the ground state of Cap‐(9, 0)‐Def [6, 6] is sextet and the ground state of Cap‐(9, 0)‐Def [5, 6] is quartet, and the former has a lower energy. In addition, compared with Cap‐(9, 0) CNTs, the C adatom on C30 causes spin polarization phenomenon and Cap‐(9, 0)‐Def [6, 6] has more spin electrons than Cap‐(9, 0)‐Def [5, 6] structure. Moreover, different adsorb defects reveal different electron accumulation. This finding shows that spin polarization of the asymmetric structure can be adjusted by introducing adatom defects. [ABSTRACT FROM AUTHOR]

Abstract The spin polarization of carbon nanomaterials is crucial to design spintronic devices. In this paper, the first‐principles is used to study the electronic properties of two defect asymmetric structures, Cap‐(9, 0)‐Def [6, 6] and Cap‐(9, 0)‐Def [5, 6]. We found that the ground state of Cap‐(9, 0)‐Def [6, 6] is sextet and the ground state of Cap‐(9, 0)‐Def [5, 6] is quartet, and the former has a lower energy. In addition, compared with Cap‐(9, 0) CNTs, the C adatom on C30 causes spin polarization phenomenon and Cap‐(9, 0)‐Def [6, 6] has more spin electrons than Cap‐(9, 0)‐Def [5, 6] structure. Moreover, different adsorb defects reveal different electron accumulation. This finding shows that spin polarization of the asymmetric structure can be adjusted by introducing adatom defects.

In this work, the influence of an external electric field is studied in two cases: one-phonon resonant Raman scattering and one-phonon electron Raman scattering, processes that occur in a semiconductor quantum wire with cylindrical symmetry and finite potential barriers. Where we have considered that the electric field is homogeneous and transversal to the system axis. To carry out this study, we obtain a mathematical expression for the differential cross-section for both Raman processes, where for one-phonon resonant Raman scattering, intra-band and inter-band optical transitions are considered, while for one-phonon electron Raman scattering, only intra-band optical transitions are considered. Therefore, to determine the electronic states, we use a valid model when the electric field is weak with respect to confinement. In the case of the Fröhlich electron–phonon interaction, we use a model in which the oscillation modes are completely confined, a model that was developed within the framework of a macroscopic continuum model. Then, the singularities present in the Raman spectra and the effect of the electric field on their position and intensity are analyzed. Finally, how the electric field affects the electron–phonon interaction and the selection rules for optical transitions in a semiconductor quantum wire with cylindrical symmetry are shown.

The existing methods for calculating the energy of stationary states relate it to the energy of the electron, considering it negative in the atom. Formally, choosing a point that corresponds to zero potential energy you can assign a negative value to the electron energy. However, this approach does not answer many other questions, for example, the actual value of the energy of stationary states is unknown, but only the difference in energies between stationary states is known; the concept of "minimum energy of the system" loses its meaning (choosing the origin of the energy reference, we replace the minimum with the maximum, or vice versa); the physical reason for the stability of stationary states is not clear; it is impossible to reveal the physical reason for the introduction of selection rules, since the Heisenberg uncertainty relations exclude the analysis of the transition mechanism, replacing it with the concept of a "quantum leap". Let us show that the energy of stationary states is the energy of a spherical capacitor, the covers of which are spheres whose radii are equal to the radius of the nuclear and corresponding stationary state. The energy of the ground state in the hydrogen atom is 0.8563997 MeV. The presence of charges and a magnetic field presupposes the circulation of energy in the volume of the atom (the Poynting vector is not zero). Revealed quantization of the angular momentum of the electromagnetic field in stationary states is L n = n ℏ. The change in the angular momentum of the electromagnetic field during transitions between stationary states in atoms removes the physical grounds for introducing selection rules. The analysis shows that the Heisenberg uncertainty relations are not universal, and their application in each specific case must be justified. [ABSTRACT FROM AUTHOR]

In this paper, we introduce specific approximations to simplify the vibronic treatment in modeling absorption and emission spectra, allowing us to include a huge number of vibronic transitions in the calculations. Implementation of such a simplified vibronic treatment within our general approach for modelling vibronic spectra, based on molecular dynamics simulations and the perturbed matrix method, provided a quantitative reproduction of the absorption and emission spectra of aqueous indole with higher accuracy than the one obtained when using the existing vibronic treatment. Such results, showing the reliability of the approximations employed, indicate that the proposed method can be a very efficient and accurate tool for computational spectroscopy.

Controlling oxygen redox reactions in transition metal oxides offers an attractive route to tune their physical properties; a topotactic structural transformation from their parent phases effectively modifies the electronic state. In this work, infinite-layered SrFeO2 thin films were produced from brownmillerite SrFeO2.5 via low-temperature hydro-reduction. After the structural transition, their out-of-plane lattice constants dramatically shrank by ∼12%; tensilely strained samples exhibited metallic character, whereas the compressively strained ones maintained the insulating behavior of their bulk form. According to X-ray linear dichroism results, this strain-mediated electronic anisotropy may be attributed to electron redistribution within degenerated orbitals. This suggests a possible mechanism for the metallic conductivity of infinite-layered SrFeO2, giving a hint for understanding emergent quantum phenomena, such as the recently discovered superconductivity in nickelates, and stimulating various applications, including in ionic conductivity and oxygen catalysis. [ABSTRACT FROM AUTHOR]

MnGen−/0/+ (n = 1–3) clusters have complicated geometric and electronic structures. In this work, we explored the isomers and electronic states of MnGen−/0/+ (n = 1–3) clusters by using density functional theory, CASPT2, and DMRG‐CASPT2 methods. The DMRG‐CASPT2 method with active spaces up to 23 orbitals could provide accurate relative energies of the low‐lying states. The results showed that the electronic states of MnGen−/0/+ (n = 1–3) have strong multireference wave functions. The hybrid PBE0 functional was sufficient to calculate the relative energies of the electronic states of manganese‐doped germanium clusters. The leading configurations, bond distances, bond orders, harmonic vibrational frequencies, relative energies, and electron detachment energies of the relevant electronic states of MnGen−/0/+ (n = 1–3) were reported. The computational results in this work showed that the DMRG‐CASPT2 method with large active spaces can be employed to study the structures and properties of transitional metal‐containing clusters with strong electron correlation effects. [ABSTRACT FROM AUTHOR]

Tuning the electronic states near the Fermi level can effectively facilitate the reaction kinetics. However, elucidating the role of a specific electronic state of metal oxide in simultaneously regulating the CO2 electroreduction reaction (CO2RR) and competing hydrogen evolution reaction (HER) is still rare, making it difficult to accurately predict the practical CO2RR performance. Herein, replacing the Zn site by heteroatoms with different outer electrons (Mo and Cu) is found to tune both occupied and unoccupied orbitals near the Fermi level of ZnO. Moreover, the different electronic states significantly modulate both CO2RR and HER activity with a totally inverse trend, thus dramatically tuning the practical CO2RR performance. In parallel, the correlation between electronic states, reaction free energies and practical activity is demonstrated. This work provides a possibility for engineering efficient CO2RR eletrocatalysts through tunable composition and electronic structures. [ABSTRACT FROM AUTHOR]

The time‐dependent density functional theory was used to calculate the vibronic absorption spectrum of berberine (BER) in an aqueous solution. The best agreement with the experimental spectrum gives the O3LYP functional. Functionals with long‐range correction showed poor agreement with experiment. The molecular orbitals of BER involved in the electronic transition during light absorption in the visible spectral region have been obtained. The dipole moments and atomic charges of the ground and excited states of the BER molecule have been calculated. Maps of BER electron density and electrostatic potential have been drawn. A significant photoinduced electron transfer from the outer di‐oxygen five‐membered heterocycle to the center of the BER chromophore has been found. According to our calculations, vibronic coupling and Boltzmann distribution play a significant role in the absorption spectrum of BER. [ABSTRACT FROM AUTHOR]

The bandgap of most known two-dimensional materials can be tuned by hydrogenation, although certain 2D materials lack a sufficient wide bandgap. Currently, it would be perfect to design non-toxic, low-cost, and high-performance photocatalysts for photocatalytic water splitting via hydrogenation. We systematically examine the impact of hydrogenation on the optical and electronic characteristics of GeC/g-C 3 N 4 vdW heterostructures (vdWHs) with four different stacking patterns using first-principles calculations. The phonon spectra, interlayer distance, binding energies and ab initio molecular dynamics calculations show the kinetic, mechanical, and thermal stability of GeC/g-C 3 N 4 vdWH after hydrogenation at 300, 500 and 800 K and possesses anisotropic Poisson's ratio, Young's and bulk modulus, suggesting that it's a promising candidate for experimental fabrication. According to an investigation of its electronic properties, GeC/g-C 3 N 4 vdWH has a bandgap of 1.28 eV, but hydrogenation dramatically increases it to 2.47 eV. As a result of interface-induced electronic doping, the electronic states in g-C 3 N 4 might be significantly adjusted by coming into contact with hydrogenated GeC sheets. The vdWH exhibits a type-II semiconductor, which can enhance the spatial separation of electron-hole pairs and has a strong red-shift of absorption coefficient than those of the constituent monolayers. The high potential drop caused by the significant valence and conduction band offsets effectively separated the charge carriers. The absorption coefficient of GeCH 2 /g-C 3 N 4 vdWH is highly influenced by a biaxial compressive strain more than the biaxial tensile strain. Our theoretical research implies that the hydrogenated GeCH 2 /g-C 3 N 4 vdWH possesses tunable optical and electronic behaviour for use as a hole-transport material in solar energy harvesting, nanoelectronic and optoelectronic devices., (© 2024 Wiley-VCH GmbH.)

Density functional theory and multiconfigurational CASPT2 and density matrix renormalization group DMRG‐CASPT2 have been employed to study the low‐lying states of NbGen−/0/+ (n = 1–3) clusters. With the DMRG‐CASPT2 method, the active spaces are extended to a size of 20 orbitals. For most of the states, the CASPT2 relative energies are comparable with the DMRG‐CASPT2 results. The leading configuration, bond distances, vibrational frequencies, and relative energies of the low‐lying states of these clusters were calculated. The ground states of these clusters were computed to be 3Δ, 4Φ, and 5Φ of NbGe−/0/+; 3A2, 4B1, and 3B1 of cyclic‐NbGe2−/0/+; and 1A′, 12A″ and 12A′′ (2E), and 3A″ of tetrahedral‐NbGe3−/0/+ isomers. For NbGe cluster, our calculations proposed that the 6∑ is almost degenerate with the 4Φ with the CASPT2 and DMRG‐CASPT2 relative energies of 0.05 and 0.06 eV. The adiabatic detachment energies of NbGen− (n = 1–3) clusters were estimated to be 1.46, 1.55, and 2.18 eV by the CASPT2 method. The relevant detachment energies of the anionic ground state and the ionization energies of the neutral ground states are evaluated at the CASPT2 level. [ABSTRACT FROM AUTHOR]

First‐principles calculations are performed to investigate the electronic states of 1/1 and 2/1 approximants with the composition Al15Zn40Mg45, which is close to the quasicrystal (QC) Al14.9Zn41.0Mg44.1 in which the superconductivity recently has been discovered. The density of states for the 1/1 approximant shows a wide pseudogap structure near the Fermi level as commonly observed in various approximants of the QCs, whereas those for the 2/1 approximant do not show such a wide pseudogap. Instead of the wide pseudogap, the 2/1 approximant shows a remarkable narrow pseudogap at the Fermi level in contrast to the 1/1 approximant, which shows a shallow hump at the Fermi level within the wide pseudogap. This seems to be consistent with the experimental observation of the electrical resistivity, which increases with decreasing temperature from room temperature down to around the superconducting transition temperature for the 2/1 approximant together with the QC, whereas it monotonically decreases for the 1/1 approximant. [ABSTRACT FROM AUTHOR]

Electronic states of hybrid perovskites enable their exceptional optoelectronic applications. Herein, through heterojunction enhanced exciton dissociation and global tracing of multiple radiative electronic states across wide temperature regions, it has been found that excitons while not free carriers dominate the bandedge photoelectric properties of hybrid lead bromide perovskite (MAPbBr3). MAPbBr3 has exhibited two types of excitons with giant binding energies and superior phase stability. A bound exciton (BE) has been clearly confirmed according to a saturated photo‐induced bleaching behavior and a correlation of the exciton to the perovskite deep trap state. By stabilizing the excitonic phase of polycrystalline MAPbBr3, impressively low‐threshold and high‐gain stimulated emission from the BE has been realized at room temperature. Overall, this work provides new insight into the photophysics characteristics of the hybrid perovskite and more importantly brings huge opportunities for exploiting perovskite excitonic mechanism to realize more abundant optoelectronic applications. [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (ZnO NPs) are used in numerous applications, including sunscreens, cosmetics, textiles, and electrical devices. Increased consumer and occupational exposure to ZnO NPs potentially poses a risk for toxicity. While many studies have examined the toxicity of ZnO NPs, little is known regarding the toxicological impact of inherent defects arising from batch-to-batch variations. It was hypothesized that the presence of varying chemical defects in ZnO NPs will contribute to cellular toxicity in rat aortic endothelial cells (RAECs). Pristine and defected ZnO NPs (oxidized, reduced, and annealed) were prepared and assessed three major cellular outcomes; cytotoxicity/apoptosis, reactive oxygen species production and oxidative stress, and endoplasmic reticulum (ER) stress. ZnO NPs chemical defects were confirmed by X-ray photoelectron spectroscopy and photoluminescence. Increased toxicity was observed in defected ZnO NPs compared to the pristine NPs as measured by cell viability, ER stress, and glutathione redox potential. It was determined that ZnO NPs induced ER stress through the PERK pathway. Taken together, these results demonstrate a previously unrecognized contribution of chemical defects to the toxicity of ZnO NPs, which should be considered in the risk assessment of engineered nanomaterials. [ABSTRACT FROM AUTHOR]