Physical Chemistry Chemical Physics最新文献

The ground state and excited state resonance dipole-dipole interaction energy between two elongated conducting molecules is explored in this study. We review the current status for ground state interactions. This interaction is found to be of a much longer range than in the case when the molecules are pointlike and nonconducting. These are well known results found earlier by Davies, Ninham, and Richmond, and later, using a different formalism, by Rubio and co-workers. We show how the theory can be extended to excited state interactions. A characteristic property observed from our calculation is that the interaction energy dependence on separation (R) follows f(R)/R² for both resonance and van der Waals cases in the long-range limit. Under some limits, f(R) has a logarithmic dependency, while under others, it has constant values. We predict an unusual slow decay rate for the energy transfer between conducting molecules.

Pyrene and acene derivatives are an important source of materials for optoelectronic device applications both as emitters and organic semiconductors. The mobility of major charge carriers is correlated with the coupling constants of the respective major charge carrier as well as the relaxation energies. Herein, we have applied range-separated density functionals for the estimation of said values. A series of five alkylated derivatives of pyrene laterally extended by heteroaromatic or phenyl groups were explored and contrasted to nascent pyrene, alkylated pyrene and tetracene. The ground state geometries along with absorption properties and relaxation energies are presented as well as a discussion of the suitability of the material toward hole and electron transport materials.

The structures, stability, and electrochemical performances of Janus Ti₂BST (T = O, Se) monolayers as anode materials for Na/K-ion batteries (NIBs/KIBs) are investigated by first-principles calculations. The results demonstrate that Ti₂BST monolayers are mechanically, dynamically, and thermally stable. The electronic structures display good conductivity. Moreover, the low diffusion barriers of 0.107/0.039 eV (0.111/0.063 eV) for Na/K indicate that the Ti₂BSO (Ti₂BSSe) monolayer has excellent rate performance for NIBs/KIBs. Low average open circuit voltages (OCVs) (0.322-0.439 V) can produce a high voltage in NIBs/KIBs. Meanwhile, little structural changes during charge/discharge ensure great cycle stability. Especially, the Ti₂BSO monolayer has a high theoretical capacity of 691.64/537.75 mA h g^-1 for NIBs/KIBs. The outstanding performances demonstrate that the Ti₂BST monolayers are potential anode materials for NIBs/KIBs.

X-ray absorption spectroscopy (XAS) and small-angle X-ray scattering (SAXS) are common materials characterization tools at synchrotron radiation facilities used in many research fields. Since XAS can provide element-specific chemical states and local atomic structures and SAXS can provide nano-scale structural information, their complementary use is advantageous for a comprehensive understanding of multiscale phenomena. This paper presents a new method for simultaneous XAS/SAXS measurements with synchrotron radiation. The method employs a polychromatic X-ray beam as in the energy-dispersive XAS technique and captures both the transmission XAS spectrum and the SAXS intensity distribution with an area X-ray detector, which eliminates the energy scan in the conventional methods and realizes the simultaneous data acquisition in a shorter time. We succeeded in obtaining the atomic and nano-scale structures of Pt and Pt/Pd nanoparticles with a data acquisition time of 0.1 s, suggesting the potential for real-time observation of multiscale phenomena.

An oxybenzone molecule in the gas phase was characterized by mass spectrometry and angle-resolved photoelectron spectroscopy, using both single and multiphoton ionization schemes. A tabletop high harmonic generation source with a monochromator was used for single-photon ionization of oxybenzone with photon energies of up to 35.7 eV. From this, vertical ionization and appearance energies, as well as energy-dependent anisotropy parameters were retrieved and compared with the results from DFT calculations. For two-photon ionization using 4.7 eV light, we found a higher appearance energy than in the extreme ultraviolet (EUV) case, highlighting the possible influence of an intermediate state on the photoionization process. We found no differences in the mass spectra when ionizing oxybenzone by single-photons between 17.2 and 35.7 eV. However, for the multiphoton ionization, the fragmentation process was found to be sensitive to the photoionization order and laser intensity. The "softest" method was found to be two-photon ionization using 4.7 eV light, which led to no measurable fragmentation up to an intensity of 5 × 10¹² W cm^-2.

The present investigation fits the reaction kinetics of a lithium-sulfur (Li-S) battery with polar electrolyte employing a novel two-phase continuum multipore model. The continuum two-phase model considers processes in both the liquid electrolyte phase and the solid precipitates phase, where the diffusion coefficients of the Li⁺ ions in a solvent-softened solid state are determined from molecular dynamics simulations. Solubility experiments yield the saturation concentration of sulfur and lithium sulfides in the polar electrolyte employed in this study. The model describes the transport of dissolved molecular and ion species in pores of different size in solvated or desolvated form, depending on pore size. The Li-S reaction model in this study is validated for electrolyte 1 M LiPF₆ in EC/DMC. It includes seven redox reactions and two cyclic non-electrochemical reactions in the cathode, and the lithium redox reaction at the anode. Electrochemical reactions are assumed to take place in the electrolyte solution or the solid state and cyclic reactions are assumed to take place in the liquid electrolyte phase only. The determination of the reaction kinetics parameters takes place via fitting the model predictions with experimental data of a cyclic voltammetry cycle with in operando UV-vis spectroscopy.

Alkynyl radicals and cations are crucial reactive intermediates in chemistry, but often evade direct detection. Herein, we report the direct observation of the phenylethynyl radical (C₆H₅CC˙) and its cation (C₆H₅CC⁺), which are two of the most reactive intermediates in organic chemistry. The radical is generated via pyrolysis of (bromoethynyl)benzene at temperatures above 1500 K and is characterized by photoion mass-selected threshold photoelectron spectroscopy (ms-TPES). Photoionization of the phenylethynyl radical yields the phenylethynyl cation, which has never been synthesized due to its extreme electrophilicity. Vibrationally-resolved ms-TPES assisted by ab initio calculations unveiled the complex electronic structure of the phenylethynyl cation, which appears at an adiabatic ionization energy (AIE) of 8.90 ± 0.05 eV and exhibits an uncommon triplet (³B₁) ground state, while the closed-shell singlet (¹A₁) state lies just 2.8 kcal mol^-1 (0.12 eV) higher in energy. The reactive phenylethynyl radical abstracts hydrogen to form ethynylbenzene (C₆H₅CCH) but also isomerizes via H-shift to the o-, m-, and p-ethynylphenyl isomers (C₆H₄CCH). These radicals are very reactive and undergo ring-opening followed by H-loss to form a mixture of C₈H₄ triynes, along with low yields of cyclic 3- and 4-ethynylbenzynes (C₆H₃CCH). At higher temperatures, dehydrogenation from the unbranched C₈H₄ triynes forms the linear tetraacetylene (C₈H₂), an astrochemically relevant polyyne.

The biphenyl molecule (C₁₂H₁₀) acts as a fundamental molecular backbone in the stereoselective synthesis of organic materials due to its inherent twist angle causing atropisomerism in substituted derivatives and in molecular mass growth processes in circumstellar environments and combustion systems. Here, we reveal an unconventional low-temperature phenylethynyl addition-cyclization-aromatization mechanism for the gas-phase preparation of biphenyl (C₁₂H₁₀) along with ortho-, meta-, and para-substituted methylbiphenyl (C₁₃H₁₂) derivatives through crossed molecular beams and computational studies providing compelling evidence on their formation via bimolecular gas-phase reactions of phenylethynyl radicals (C₆H₅CC, X²A₁) with 1,3-butadiene-d₆ (C₄D₆), isoprene (CH₂C(CH₃)CHCH₂), and 1,3-pentadiene (CH₂CHCHCHCH₃). The dynamics involve de-facto barrierless phenylethynyl radical additions via submerged barriers followed by facile cyclization and hydrogen shift prior to hydrogen atom emission and aromatization to racemic mixtures (ortho, meta) of biphenyls in overall exoergic reactions. These findings not only challenge our current perception of biphenyls as high temperature markers in combustion systems and astrophysical environments, but also identify biphenyls as fundamental building blocks of complex polycyclic aromatic hydrocarbons (PAHs) such as coronene (C₂₄H₁₂) eventually leading to carbonaceous nanoparticles (soot, grains) in combustion systems and in deep space thus affording critical insight into the low-temperature hydrocarbon chemistry in our universe.

In this study, we developed a high-performance non-enzymatic electrochemical sensor based on urchin-like CoP₃/Cu₃P heterostructured nanorods supported on a three-dimensional porous copper foam, namely, CoP₃/Cu₃P NRs/CF, for the detection of dopamine. Benefiting from the promising intrinsic catalytic activities of CoP₃ and Cu₃P, urchin-like microsphere structures, and a large electrochemically active surface area for exposing numerous accessible catalytic active sites, the proposed CoP₃/Cu₃P NRs/CF shows extraordinary electrochemical response towards the electrocatalytic oxidation of dopamine. As a result, the CoP₃/Cu₃P NRs/CF sensing electrode has a broad detection window (from 0.2 to 2000 μM), low detection limit (0.51 μM), high electrochemical sensitivity (0.0105 mA μM^-1 cm^-2), excellent selectivity towards dopamine in the coexistence of some interfering species, and good stability for dopamine determination. More importantly, the CoP₃/Cu₃P NRs/CF catalyst also exhibits excellent catalytic activity, sensitivity, and selectivity for dopamine detection under simulated human body conditions at a physiological pH of 7.25 (0.1 M PBS) at 36.6 °C.

Nanostructured thermoelectric materials ideally reduce lattice thermal conductivity without harming the electrical properties. Thus, to truly improve the thermoelectric performance, the quality factor, which is proportional to the weighted mobility divided by the lattice thermal conductivity of the material, must be improved. Precipitates of In₂Te₃ form in the state-of-the-art Bi₂Te₃ with crystallographic alignment to the Bi₂Te₃ structure. Like epitaxy in films, this can be called endotaxy in solids. This natural epitaxy in a 3-dimensional solid is ideally situated to scatter phonons but produces minimal electronic scattering and, therefore, maintains high mobility. Here, we study the effects of In-alloying in Bi₂Te₃ at high In concentrations (about 4 at%), enough to produce the endotaxial microstructure. It is found that such concentrations of indium in Bi₂Te₃ significantly alter the electronic structure, reducing the effective mass and weighted mobility so significantly as to effectively destroy the thermoelectric properties even though the lattice thermal conductivity is successfully reduced.