Electron Binding Energies Research Articles

Role of electronic binding energy on the stability of B, C, N, and O in Fe

Using first-principles density functional theory (DFT), we separate the distortion energy (DE) on Fe due to the introduction of solute atoms like B, C, N, and O at different sites from the electronic binding energy (EBE) of a solute atom with Fe. Contrary to the belief that distortion energy alone dictates the preference of solute atoms for a site in bulk, we show that EBE dictates the preference of the O for the octahedral site in Fe, with DE being the highest at the site. The site preference for C and N in bulk Fe is dictated by both DE and EBE. However, DE alone dictates site preference for B. The DE of solute atoms cannot be predicted by calculated radius, which is highest for B and lowest for O. We find that O and B have similar distortion energy due to large charge transfer to the O atom from Fe.

The Contact Electrification Capability of Amino Acids

Triboelectric charging necessitates a frictional contact between two different materials, and contact electrification is typically based on the polarity difference in the triboelectric series. The human skin is a prominent triboelectric material that becomes highly positive during the contact electrification process. However, the reason behind this phenomenon is still remains unrevealed. Herein, we have performed an in-depth analysis of the amino acids present in human skin and quantifying them with regards to triboelectric polarization. The principle focus of this study is based on analyzing those amino acids present in copious amounts in the human skin. The phenomenon of contact electrification is in close relation to the work function and the electron-donating or accepting ability of the material. The standardized experimental as well as computational approaches were employed to analyze the amino acids. Thus, we present an augmented triboelectric series of the amino acids with quantified triboelectric charging polarity by scrutinizing the triboelectric transfer charge, work function, and electron binding energy. Furthermore, a comparison of these properties in the amino acids predominant in the human skin can conclusively render it positive in the series, under contact electrification. The quantification of the triboelectric series may serve as a benchmark for implementing in various applications in the future such as self-powered sensing, or energy harvesting.

Enhanced photocatalytic and antibacterial activities of novel Ag-HA bioceramic nanocatalyst for waste-water treatment

Hydroxyapatite (HA), the most common bioceramic material, offers attractive properties as a catalyst support. Highly crystalline mono-dispersed silver doped hydroxyapatite (Ag-HA) nanorods of 60 nm length was developed via hydrothermal processing. Silver dopant offered enhanced chemisorption for crystal violet (CV) contaminant. Silver was found to intensify negative charge on the catalyst surface; in this regard enhanced chemisorption of positively charged contaminants was accomplished. Silver dopant experienced decrease in the binding energy of valence electron for oxygen, calcium, and phosphorous using X-ray photoelectron spectroscopy XPS/ESCA; this finding could promote electron–hole generation and light absorption. Removal efficiency of Ag-HA nanocomposite for CV reached 88% after the synergistic effect with 1.0 mM H2O2; silver dopant could initiate H2O2 cleavage and intensify the release of active ȮH radicals. Whereas HA suffers from lack of microbial resistance; Ag-HA nanocomposite demonstrated high activity against Gram-positive (S. aureus) bacteria with zone of inhibition (ZOI) mm value of 18.0 mm, and high biofilm inhibition of 91.1%. Ag-HA nanocompsite experienced distinctive characerisitcs for utilization as green bioceramic photocatalyst for wastewater treatment.

Electric and Magnetic Fields Effects in Vertically Coupled GaAs/AlxGa1−xAs Conical Quantum Dots

Vertically coupled quantum dots have emerged as promising structures for various applications such as single photon sources, entangled quantum pairs, quantum computation, and quantum cryptography. We start with a structure composed of two vertically coupled GaAs conical quantum dots surrounded by AlxGa1−x, and the effects of the applied electric and magnetic fields on the energies are evaluated using the finite element method. In addition, the effects are evaluated by including the presence of a shallow-donor impurity. The electron binding energy behavior is analyzed, and the effects on the photoionization cross-section are studied. Calculations are carried out in the effective mass and parabolic conduction band approximations. Our results show a notable dependence on the electric and magnetic fields applied to the photoionization cross-section. In general, it has been observed that both the electric and magnetic fields are useful parameters for inducing blueshifts of the resonant photoionization cross-section structure, which is accompanied by a drop in its magnitude.

Lutidyl Radical Photoelectron Spectra Reveal Additive Substituent Effects on Benzyl Derivatives' Ionization Energy.

Understanding how isomerism influences photoelectron spectra helps in the assignment and analysis of reactive mixtures, especially for heterocycles with numerous isomers. Threshold photoelectron spectra of lutidyl radical isomers, i. e., benzyl derivatives with a nitrogen heteroatom and a methyl substituent, are recorded using vacuum ultraviolet synchrotron radiation. The radicals are produced by flash pyrolysis from aminomethyl methylpyridine precursors. Experimental ionization energies are determined to be 7.54, 7.50, and 7.45 eV for 2,4-, 2,6- and 3,5-lutidyl, respectively, in excellent agreement with composite method calculations. Franck-Condon simulations aid the TPES assignment but are also shown to exhibit artifacts if large-amplitude motions, notably the methyl internal rotation are assumed to be active in the double harmonic approximation. Based on calculated adiabatic ionization energies (AIE) of benzyl, picolyl, and xylyl radicals, the N and CH3 substituent effects are found to be additive, position-dependent and decrease in the para>ortho≳meta order in magnitude with the nitrogen heteroatom increasing and the methyl substituent decreasing the AIE. These effects are discussed in light of the charge distribution upon ionization. The additivity of the substituent effects also helps predict the influence of substituents on the binding energy of the unpaired electron in analogous radicals.

Excited dipole bound electronic states of potassium iodide anions: A theoretical perspective

The information about electronic excited states of molecular anions is of pivotal importance for understanding electron attachment/detachment processes. Here, we present a high-level theoretical study on electronic states of potassium iodide anions (KI−). By the evaluation of different basis sets, we present accurate spectroscopic constants of the anionic ground electronic state using the multireference configuration interaction with Davidson correction method. The equation-of-motion electron-attachment coupled-cluster singles and doubles method is carried out to calculate electron binding energies (EBEs) of electronic states. With the addition of different s-/p-/d-diffusion functions in the basis set, we have identified possible excited dipole bound states (DBSs) of KI−. The results indicate that, owing to the large dipole moment of KI molecules, the anions can hold three excited DBSs, i.e., two σ-type DBSs and one π-type DBS, with the EBEs of 39 meV (σ-DBS1), 4.7 meV (π-DBS), and only 1.8 meV (σ-DBS2) below the neutral ground state. Molecular orbitals, potential energy curves, and spectroscopic constants of DBSs are presented. Our study would shed some light on the electronic states of potassium iodide molecular anions.

Photoelectron Spectroscopy of Oppositely Charged Molecular Switches in the Aqueous Phase: Theory and Experiment.

XUV photoelectron spectroscopy (XPS) is a powerful method for investigating the electronic structures of molecules. However, the correct interpretation of results in the condensed phase requires theoretical models that account for solvation. Here we present experimental aqueous-phase XPS of two organic biomimetic molecular switches, NAIP and p-HDIOP. These switches are structurally similar, but have opposite charges and thus present a stringent benchmark for solvation models which need to reproduce the observed ΔeBE = 1.1 eV difference in electron binding energy compared to the 8 eV difference predicted in the gas phase. We present calculations using implicit and explicit solvent models. The latter employs the average solvent electrostatic configuration and free energy gradient (ASEC-FEG) approach. Both nonequilibrium polarizable continuum models and ASEC-FEG calculations give vertical binding energies in good agreement with the experiment for three different computational protocols. Counterions, explicitly accounted for in ASEC-FEG, contribute to the stabilization of molecular states and reduction of ΔeBE upon solvation.

Immobilization of fatty acid photodecarboxylase in magnetic nickel ferrite nanoparticle

Fatty acid photodecarboxylase in Chlorella variabilis NC64A (CvFAP) performed excellent ability to exclusively decarboxylate renewable fatty acids for C1-shortened hydrocarbons fuel production under visible light. However, the large-scale application by such an approach is limited by the free state of CvFAP catalyst, which is unstable for efficient biofuel production. In this study, CvFAP was immobilized in magnetic nickel ferrite (NiFe2O4) nanoparticles for facile recovery by a simple procedure. The shift of Ni 2p in electron binding energy was detected to clarify the interaction between Ni2+ and histidine of CvFAP. The coordination of NiFe2O4 and CvFAP contributed to an efficient affinity binding with an immobilization capacity of 98 mg/g carrier. Hydrocarbon fuel concentration of 3.7 mM was obtained by NiFe2O4@CvFAP-induced photoenzymatic decarboxylation. The high stability of CvFAP in terms of residual enzyme activity of 79.7% at pH 9.0 and that of 68% at organic solvent ratio of 60%, respectively, were observed.

Multi-interfacial engineering in the hierarchical self-assembled micro-nano dielectric aerogel for wide-band absorption and low infrared emissivity

Radar-infrared (IR) compatible stealth can satisfy the characteristics of excellent electromagnetic wave attenuation property and low infrared emissivity. However, concurrently satisfying these demands is still a great challenge at present. Herein, multi-interfacial engineering strategy was proposed for the preparation of radar-IR compatible stealth materials. ZnO has a high electron binding energy and a large band gap at room temperature, and doping with sulphide can increase the concentration of unconstrained carriers. Therefore, bimetallic sulphide aerogels loaded with ZnO were prepared by means of carbonization and vulcanization, combined with freeze-drying method. When the filling ratio is 20 %, an absorption bandwidth (fe) of 6.62 GHz at a matching thickness of 2.0 mm and a reduction in IR emissivity from 0.920 to 0.539 in the 8–14 μm band are achieved. This work provides a guidance to design and synthesize high-performance absorbers by multi-interfacial engineering for IR-radar compatible stealth application.

A Free Energy Decomposition Analysis: Insight into Binding Thermodynamics from Absolutely Localized Molecular Orbitals.

Traditional energy decomposition analysis (EDA) methods can provide an interpretive decomposition of non-covalent electronic binding energies. However, by definition, they neglect entropic effects and nuclear contributions to the enthalpy. With the objective of revealing the chemical origins of trends in free energies of binding, we introduce the concept of a Gibbs decomposition analysis (GDA) by coupling the absolutely localized molecular orbital treatment of electrons in non-covalent interactions with the simplest possible quantum rigid rotor-harmonic oscillator treatment of nuclear motion at finite temperature. The resulting pilot GDA is employed to decompose enthalpic and entropic contributions to the free energy of association of the water dimer, fluoride-water dimer, and water binding to an open metal site in the metal-organic framework Cu(I)-MFU-4l. The results show enthalpic trends that generally track the electronic binding energy and entropic trends that reveal the increasing price of loss of translational and rotational degrees freedom with temperature.

Photogenerated Ni(I)-Bipyridine Halide Complexes: Structure-Function Relationships for Competitive C(sp2)-Cl Oxidative Addition and Dimerization Reactivity Pathways.

We report the facile photochemical generation of a library of Ni(I)-bpy halide complexes (Ni(I)(Rbpy)X (R = t-Bu, H, MeOOC; X = Cl, Br, I) and benchmark their relative reactivity toward competitive oxidative addition and off-cycle dimerization pathways. Structure-function relationships between the ligand set and reactivity are developed, with particular emphasis on rationalizing previously uncharacterized ligand-controlled reactivity toward high energy and challenging C(sp2)-Cl bonds. Through a dual Hammett and computational analysis, the mechanism of the formal oxidative addition is found to proceed through an SNAr-type pathway, consisting of a nucleophilic two-electron transfer between the Ni(I) 3d(z2) orbital and the Caryl-Cl σ* orbital, which contrasts the mechanism previously observed for activation of weaker C(sp2)-Br/I bonds. The bpy substituent provides a strong influence on reactivity, ultimately determining whether oxidative addition or dimerization even occurs. Here, we elucidate the origin of this substituent influence as arising from perturbations to the effective nuclear charge (Zeff) of the Ni(I) center. Electron donation to the metal decreases Zeff, which leads to a significant destabilization of the entire 3d orbital manifold. Decreasing the 3d(z2) electron binding energies leads to a powerful two-electron donor to activate strong C(sp2)-Cl bonds. These changes also prove to have an analogous effect on dimerization, with decreases in Zeff leading to more rapid dimerization. Ligand-induced modulation of Zeff and the 3d(z2) orbital energy is thus a tunable target by which the reactivity of Ni(I) complexes can be altered, providing a direct route to stimulate reactivity with even stronger C-X bonds and potentially unveiling new ways to accomplish Ni-mediated photocatalytic cycles.

Charge transfer and electronic relaxation effects in the photoemission of EMIM-DCA ionic liquid vapor

Ultraviolet photoelectron spectroscopy (UPS) measurements of EMIM-DCA vapors have been conducted. Density functional theory (DFT), Møller–Plesset perturbation theory (MP2) and many-body perturbation theory calculations (GW) have been used to interpret the experimentally measured spectra. The vapor of ionic liquids normally consists of isolated ion-pairs and the corresponding photoemission spectra should reflect the electronic binding energies of the molecular orbitals. The UPS spectra have revealed that many photolines are shifted when compared to ab initio calculation results. The hybrid DFT functionals, which performed very good in the description of the UPS spectra of many other ionic liquid vapors have shortcomings in the EMIM-DCA case. The MP2 calculation and the quasiparticle GW approach are shown to offer a better description of the experimental UPS spectra. The charge distribution analysis showed that there seems to be a favorable charge transfer from the cation to the anion upon ionization. The new data provides strong support to the argument that in some cases DFT still has difficulties in the modeling of IL ion-pairs.

Combining the Δ-Self-Consistent-Field and GW Methods for Predicting Core Electron Binding Energies in Periodic Solids.

For the computational prediction of core electron binding energies in solids, two distinct kinds of modeling strategies have been pursued: the Δ-Self-Consistent-Field method based on density functional theory (DFT), and the GW method. In this study, we examine the formal relationship between these two approaches and establish a link between them. The link arises from the equivalence, in DFT, between the total energy difference result for the first ionization energy, and the eigenvalue of the highest occupied state, in the limit of infinite supercell size. This link allows us to introduce a new formalism, which highlights how in DFT─even if the total energy difference method is used to calculate core electron binding energies─the accuracy of the results still implicitly depends on the accuracy of the eigenvalue at the valence band maximum in insulators, or at the Fermi level in metals. We examine whether incorporating a quasiparticle correction for this eigenvalue from GW theory improves the accuracy of the calculated core electron binding energies, and find that the inclusion of vertex corrections is required for achieving quantitative agreement with experiment.

Experimental determinations of the energy of the 9.4 keV (M1+E2) nuclear transition in 83Kr and the Kr electron binding energies in different matrices by ICES method

An energy value of 9406.3(5) eV was determined for the 9.4 keV (M1+E2) nuclear transition in 83Kr by the internal conversion electron spectrometry method. This value agrees within 1σ with the most precise values determined previously for which their weighted mean amounts to 9405.9(2) eV. A value of 22745.3(2) eV was obtained directly from our experimental data for the energy difference between the 32.1 keV and 9.4 keV transitions in 83Kr. Electron binding energies (related to the Fermi level) on the K, L, and M1,2,3 subshells of Kr implanted into a polycrystalline Pt matrix were also derived. They were found to be lower by weighted mean values of 11.6(4) and 1.7(6) eV compared to those for free Kr atoms and for Kr in an evaporated 83Rb layer on Al backing, respectively, and higher by a weighted mean value of 2.9(2) eV than the binding energies in Kr in an evaporated layer on polycrystalline Pt backing.

Molecular Anions Perspective.

This Perspective attempts to shed light on developments in the theoretical and experimental study of molecular anions highlighting more recent workers in the field. The species I discuss include (i) valence-bound (singly and multiply charged) anions including atmospheric, catalytic, superhalogen, interfacial, and more; (ii) dipole- and correlation-bound anions including their role as doorways to other states and their appearance "in space", and (iii) metastable anions focusing on tools needed for their theoretical treatment. I also briefly discuss angular distributions of photodetached electrons and their growing utilization in experiments and theory. A recurring theme is the dependence of electron binding energies (EBEs) on the surrounding environment. Some anions that are nonexistent as isolated species evolve to be stable but with small EBEs when weakly solvated (e.g., as in a cluster or at an air-solvent interface). Others existing in isolation only as metastable species become stable when the underlying molecular framework contains one or more positively charged group (e.g., protonated side chains in a peptide) that generates a stabilizing Coulomb potential. On the other hand, a destabilizing Coulomb potential between/among negative sites in a multiply charged anion decreases the EBEs of each such site and generates a repulsive Coulomb barrier that can affect stability.

Synthesis, crystal structure, computational studies, and antioxidant properties of dimethylformamide-bound magnesium tetraphenylporphyrin

The synthesis, characterization and crystal structure of a dimethylformamide (DMF) coordinated magnesium tetraphenylporphyrin, [Mg(TPP)(DMF)]·CH2Cl2 (1), is described. Theoretical studies including optimization of the geometry, simulation of the electronic spectrum and binding energy calculations were performed for the complexes using the DFT method to understand the axial coordination in magnesium porphyrins. To get insight into intermolecular interactions Hirshfeld surface analyses and plotting of the 2D fingerprint was performed. Antioxidant activity was measured for the complex which showed enhanced antioxidant activity in the presence of DMF.

Determination of the Mathematical Model for Plasma Electronic Coefficients of the Earth's Ionosphere

In this research, electron coefficients such as total collision frequency (colt/N), total ionization frequency (viz/N), and Power (P/N) for different gases such as (Ar, He, N2 and O2 (in Earth’s ionosphere have been calculated by applying the Boltzmann equation utilizing BOLSIG +, and it has been discovered that there is a significant impact of reducing the electric field (E/N) on electronic coefficients under which (E/N) increases. In addition, influence of (E/N) on electronic coefficients was studied. Reducing the electric field was chosen in the restricted range (1-100) Td, and the electronic coefficients for gases in the limited range (50-2000) km of the Earth's ionosphere. A positive correlation has been explained between all the plasma electronic coefficients and (E/N) for the four gases. It was found that He gas has higher electronic coefficients than other gases in the Earth's ionosphere because they have lower electron binding energy.

The primary gas phase hydration shell of hydroxide.

The number of water molecules in hydroxide's primary hydration shell has been long debated to be three from the interpretation of experimental data and four from theoretical studies. Here, we provide direct evidence for the presence of a fourth water molecule in hydroxide's primary hydration shell from a combined study based on high-resolution cryogenic experimental photoelectron spectroscopy and high-level quantum chemical computations. Well-defined spectra of OH-(H2O)n clusters (n=2 to 5) yield accurate electron binding energies, which are, in turn, used as key signatures of the underlying molecular conformations. Although the smaller OH-(H2O)3 and OH-(H2O)4 clusters adopt close-lying conformations with similar electron binding energies that are hard to distinguish, the OH-(H2O)5 cluster clearly has a predominant conformation with a four-coordinated hydroxide binding motif, a finding that unambiguously determines the gas phase coordination number of hydroxide to be four.

Intramolecular O···H Hydrogen Bonding of Salicylic Acid: Further Insights from O 1s XPS and 1H NMR Spectra Using DFT Calculations.

Intramolecular hydrogen bonding (HB) is a complex phenomenon that extends beyond a simple valence event, affecting the core electrons of a molecule. Salicylic acid (SA) and its conformers provide an excellent model compound for studying intramolecular HB as the proton donor (H) and acceptor (O) can be toggled by rotating the C-O and C-C bonds to form up to seven potential conformers through various HB. In this study, we computationally investigated intramolecular interactions in SA conformers with and without such HB, by examining their calculated O 1s core electron-binding energy (CEBE) and 1H NMR chemical shifts validated using recent measurements. The quantum mechanically stable SA conformers are fully defined by three rotatable bonds in the compound, which are abstracted as SA(η1η2η3) digital structures, where ηi = 0 if the ηi angles match the most stable SA conformer (000) and ηi = 1 otherwise. Our findings suggest that the stability is dominated by the appearance of the intergroup intramolecular HB of Hp···O (where O is in the carboxylic acid functional group and Hp is the phenolic proton in -OHp), and η3 serves as a switch of such HB. As a result, the (η1η20) SA conformers containing such Hp···O HB are more stable than other SA conformers (η1η21) without such the Hp···O HB. The present density functional theory calculations reveal that this Hp···O HB results in splitting of the O 1s CEBEs of two hydroxyl groups (-OH) by up to 1 eV and deshielding the Hp proton 1H NMR (δHp) up to 11.68 ppm for the (η1η20) conformers. Without such Hp···O HB, the O 1s XPS binding energies of two -OH groups will be closely located in the same band, and the 1H NMR chemical shift of the Hp atom will be as small as an 4.09 ppm SA conformer [SA-G(101)]. The present study indicates that the O 1s CEBE splitting between two -OH groups serves as an indicator of the presence of the Hp···O HB in SA conformers, which is also supported by the 1H NMR results.

Distortion Correction of Low-Energy Photoelectron Spectra of Liquids Using Spectroscopic Data for Solvated Electrons.

Time-resolved photoelectron spectroscopy (TRPES) enables real-time observation of ultrafast electronic dynamics in solutions. When extreme ultraviolet (EUV) probe pulses are employed, they can ionize solutes from all electronic states involved in the dynamics. However, EUV pulses also produce a strong ionization signal from a solvent that is typically 6 orders of magnitude greater than the pump-probe photoelectron signal of solutes. Alternatively, UV probe pulses enable highly sensitive and selective observation of photoexcited solutes because typical solvents such as water are transparent to UV radiation. An obstacle in such UV-TRPES measurements is spectral distortion caused by electron scattering and a yet to be identified mechanism in liquids. We have previously proposed the spectral retrieval (SR) method as an a posteriori approach to removing the distortion and overcoming this difficulty in UV-TRPES; however, its accuracy has not yet been verified by comparison with EUV-TRPES results. In the present study, we perform EUV-TRPES for charge transfer reactions in water, methanol, and ethanol, and verify SR analysis of UV-TRPES. We also estimate a previously undetermined energy-dependent intensity factor and expand the basis sets for SR analysis. The refined SR method is employed for reanalyzing the UV-TRPES data for the formation and relaxation dynamics of solvated electrons in various systems. The electron binding energy distributions for solvated electrons in liquid water, methanol, and ethanol are confirmed to be Gaussian centered at 3.78, 3.39, and 3.25 eV, respectively, in agreement with Nishitani et al. [ Sci. Adv. 2019, 5(8), eaaw6896]. An effective energy gap between the conduction band and the vacuum level at the gas-liquid interface is estimated to be 0.2 eV for liquid water and 0.1 eV for methanol and ethanol.