Towards sensitive identification of fluorinated graphdiyne configurations by computational X-ray spectroscopy.

Fluorinated graphdiyne (F-GDY) materials exhibit exceptional performance in various applications, such as luminescent devices, electron transport, and energy conversion. Although F-GDY has been successfully synthesized, there is a lack of comprehensive identification of fluorinated configurations, either by theory or experiment. In this work, we investigated seven representative F-GDY configurations with low dopant concentrations and simulated their carbon and fluorine 1s X-ray photoelectron spectroscopy (XPS) and carbon 1s near-edge X-ray absorption fine-structure (NEXAFS) spectra.

Global Impact and Balancing Act: Deciphering the Effect of Fluorination on B 1s Binding Energies in Fluorinated -BN Nanosheets.

X-ray photoelectron spectroscopy (XPS) is an important characterization tool in the pursuit of controllable fluorination of two-dimensional hexagonal boron nitride (-BN). However, there is a lack of clear spectral interpretation, and seemingly conflicting measurements exist. To discern the structure-spectroscopy relation, we performed a comprehensive first-principles study on the boron 1s edge XPS of fluorinated -BN (F-BN) nanosheets.

Simulating temperature and tautomeric effects for vibrationally resolved XPS of biomolecules: Combining time-dependent and time-independent approaches to fingerprint carbonyl groups.

Carbonyl groups (C=O) play crucial roles in the photophysics and photochemistry of biological systems. O1s x-ray photoelectron spectroscopy allows for targeted investigation of the C=O group, and the coupling between C=O vibration and O1s ionization is reflected in the fine structures. To elucidate its characteristic vibronic features, systematic Franck-Condon simulations were conducted for six common biomolecules, including three purines (xanthine, caffeine, and hypoxanthine) and three pyrimidines (thymine, 5F-uracil, and uracil).

Efficient degradation of emerging pollutant-malachite green in water by pulsed discharge plasma on water surface in cooperation with Fe/PMS.

The effective and rapid treatment of emerging pollutants in water is an essential solution to the pollution of water environment. The emerging pollutant-malachite green (MG) wastewater was treated using pulsed discharge plasma on water surface system (WSP) combining Fe/PMS. Compared with WSP alone, the addition of 125 μM Fe and 0.

Core Hole Effect to Valence Excitations: Tracking and Visualizing the Same Excitation in XPS Shake-Up Satellites and UV Absorption Spectra.

Introducing a core hole significantly alters the electronic structure of a molecule, and various X-ray spectroscopy techniques are available for probing the valence electronic structure in the presence of a core hole. In this study, we visually demonstrate the influence of a core hole on valence excitations by computing the ultraviolet absorption spectra and the shake-up satellites in X-ray photoelectron spectra for pyrrole, furan, and thiophene, as complemented by the natural transition orbital (NTO) analysis over transitions with and without a core hole. Employing equivalent core hole time-dependent density functional theory (ECH-TDDFT) and TDDFT methods, we achieved balanced accuracy in both spectra for reliable comparative analysis.

Structural identification of single boron-doped graphdiynes by computational XPS and NEXAFS spectroscopy.

Boron-doped graphdiyne (B-GDY) material exhibits an excellent performance in electrocatalysis, ion transport, and energy storage. However, accurately identifying the structures of B-GDY in experiments remains a challenge, hindering further selection of suitable structures with the most ideal performance for various practical applications. In the present work, we employed density functional theory (DFT) to simulate the X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectra of pristine graphdiyne (GDY) and six representative single boron-doped graphdiynes at the B and C K-edges to establish the structure-spectroscopy relationship.

Interpreting the Cu-O Antibonding Nature in Two Cu-O Complexes from Cu L-Edge X-ray Absorption Spectra.

Cu-O structures play important roles in bioinorganic chemistry and enzyme catalysis, where the bonding between the Cu and O parts serves as a fundamental research concern. Here, we performed a multiconfigurational study on the copper L-edge X-ray absorption spectra (XAS) of two copper enzyme model complexes to gain a better understanding of the antibonding nature from the clearly interpreted structure-spectroscopy relation. We obtained spectra in good agreement with the experiments by using the restricted active space second-order perturbation theory (RASPT2) method, which facilitated reliable chemical analysis.

Efficient degradation of the refractory organic pollutant by underwater bubbling pulsed discharge plasma: performance, degradation pathway, and toxicity prediction.

It is essential to develop an efficient technology for the elimination of refractory contaminants due to their high toxicity. In this study, a novel underwater bubbling pulsed discharge plasma (UBPDP) system was proposed for the degradation of Orange II (OII). The degradation performance experiments showed that by enhancing the peak voltage and pulse frequency, the degradation efficiency of OII increased gradually.

Manipulating spatial alignment of donor and acceptor in host-guest MOF for TADF.

Thermally activated delayed fluorescence (TADF) was achieved when electron-rich triphenylene (Tpl) donors were confined to a cage-based porous metal-organic framework (MOF) host (NKU-111) composed of electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (Tpt) acceptor as the ligand. The spatially separated donor and acceptor molecules in a face-to-face stacking pattern generated strong through-space charge transfer (CT) interactions with a small energy splitting between the singlet and triplet excited states (∼0.1 eV), which enabled TADF.

On the choice of shape and size for truncated cluster-based x-ray spectral simulations of 2D materials.

Truncated cluster models represent an effective way for simulating x-ray spectra of 2D materials. Here, we systematically assessed the influence of two key parameters, the cluster shape (honeycomb, rectangle, or parallelogram) and size, in x-ray photoelectron (XPS) and absorption (XAS) spectra simulations of three 2D materials at five K-edges (graphene, C 1s; CN, C/N 1s; h-BN, B/N 1s) to pursue the accuracy limit of binding energy (BE) and spectral profile predictions. Several recent XPS experiments reported BEs with differences spanning 0.

Vibrationally-Resolved X-ray Photoelectron Spectra of Six Polycyclic Aromatic Hydrocarbons from First-Principles Simulations.

Vibrationally resolved C 1s X-ray photoelectron spectra (XPS) of a series of six polycyclic aromatic hydrocarbons (PAHs; phenanthrene, coronene, naphthalene, anthracene, tetracene, and pentacene) were computed by combining the full core hole density functional theory and the Franck-Condon simulations with the inclusion of the Duschinsky rotation effect. Simulated spectra of phenanthrene, coronene, and naphthalene agree well with experiments both in core binding energies (BEs) and profiles, which validate the accuracy of our predictions for the rest molecules with no high-resolution experiments. We found that three types of carbons (inner C), (peripheral C bonded to three C atoms), and (peripheral C bonded to an H atom) show decreasing BEs.

A theoretical library of N1s core binding energies of polynitrogen molecules and ions in the gas phase.

Polynitrogen molecules and ions are important building blocks of high energy density compounds (HEDCs). High energy bonds formed at the N sites can be effectively probed by X-ray photoelectron spectroscopy (XPS) at the N K-edge. In this work, with the density functional theory and the ΔKohn-Sham scheme, we simulated the N1s ionic potentials (IPs) of 72 common polynitrogen molecules [tetrazoles, pentazole (NH), diazines, triazines, tetrazines, furazans, oxazoles and oxadiazoles], ions [pentazolate anion (cyclo-N), pentazenium cation (N), ], and molecular (NH⋯NH, HO⋯NH) and ionic (NH⋯N, HO⋯N) pairs, as well as mononitrogen relatives.

Breaking inversion symmetry by protonation: experimental and theoretical NEXAFS study of the diazynium ion, NH.

As an example of symmetry breaking in NEXAFS spectra of protonated species we present a high resolution NEXAFS spectrum of protonated dinitrogen, the diazynium ion NH. By ab initio calculations we show that the spectrum consists of a superposition of two nitrogen 1s absorption spectra, each including a π* band, and a nitrogen 1s to H charge transfer band followed by a weak irregular progression of high energy excitations. Calculations also show that, as an effect of symmetry breaking by protonation, the π* transitions are separated by 0.

Theoretical assessment of vibrationally resolved C1s X-ray photoelectron spectra of simple cyclic molecules.

An interface between our in-house DynaVib package and quantum chemistry software Gamess-US is implemented for computing vibrationally-resolved K-edge X-ray photoelectron spectra (XPS) of molecules at the density functional theory level with both the full (FCH) and equivalent (ECH, or Z+1) core-hole approximations. To assess the influence of theoretical parameters (core-hole methods, vibronic coupling models, and basis sets), vibrationally-resolved C1s XPS of six simple cyclic molecules [furan, pyrrole, thiophene; benzene (C6H6 and C6D6); pyridine] were evaluated in the gas phase by both core-hole methods in combination with two time-independent vibronic coupling models, the Duschinsky rotation (DR) method and the linear coupling model (LCM). We achieved excellent/acceptable performance for FCH/Z+1 simulations in comparison with experiments.

Theoretical Spectroscopic Studies on Chemical and Electronic Structures of Selenocysteine and Pyrrolysine.

The chemical and electronic structures of the 21st and 22nd proteinogenic amino acid selenocysteine (Sec), pyrrolysine (Pyl), and their derivatives (deprotonated and protonated ions) were extensively characterized for the first time. Through the fragment based step-by-step research on their potential energy surface (PES), electronic energies of the most stable conformers of Sec, Pyl and the related ions were finally determined at the advanced CBS-QB3 and DSD-PBEP86-D3(BJ)/aug-cc-pVTZ levels, respectively, with the identification of many new low-energy conformers. The infrared spectra (IR) at 298 K of the most abundant conformers in different forms were scaled by comparison with the anharmonic frequency calculations and analyzed comparing with the experimental spectra of similar molecules.

The role of transition dipole phase in atomic attosecond transient absorption from the multi-level model.

Based on a multilevel model considering enough bound electronic states of atoms, we theoretically study the role of the transition dipole phase (TDP) in the attosecond transient absorption (ATA) spectrum of helium in intense laser fields. By solving the stationary Schrödinger equation with B-spline basis sets, we first calculate the transition dipole moments with well-defined phases between the bound states. Using the modified multilevel model, we reveal that the TDP plays an important role in determining the spectral structures if two or more paths populate the excited states from the ground state.

Transient X-ray Absorption Spectral Fingerprints of the S Dark State in Uracil.

Low-lying dark nπ* states play an important role in many photophysical and photochemical processes of organic chromophores. Transient X-ray absorption spectroscopy (TXAS) provides a powerful technique for probing the dynamics of valence states by exciting the electrons into high-lying core excited states. We employ multiconfigurational self-consistent field calculations to investigate the TXAS of uracil along its nonradiative photodecay pathways.

Accurate K-edge X-ray photoelectron and absorption spectra of g-CN nanosheets by first-principles simulations and reinterpretations.

We performed a density functional theory (DFT) study on X-ray photoelectron (XPS) and absorption (XAS) spectra of graphitic carbon nitride (g-C3N4) nanosheets at the N and C K-edges. A combined cluster-periodic approach was employed to calculate XPS spectra, in which the core ionic potential (IP) of the solid 2D material was computed by subtracting the work function (obtained with periodic conditions) from the gas phase IP (obtained with large cluster models). With amino-terminated supermolecules of different sizes, we obtained convergent spectra and provide new assignments for 5 nitrogen [1 sp2; 4 sp3 (bridging, tertiary, and primary/secondary amino nitrogens)] and 4 carbon (all bonded with three nitrogens) local structures.

Study on the light medium separation of waste plastics with hydrocyclones.

The separation of waste plastics is an important part of solid waste recycling. Based on the density difference between high density polyethylene (HDPE) and polypropylene (PP), this paper used the experimental research and CFD numerical simulation to study the separation performance by using the light medium separation technology with hydrocyclones. Results showed that with the increase of feed flow rate, the pressure drop increased as a power function, the Newton efficiency peaked at the feed flow rate of 3.

Thermally Activated Delayed Fluorescence in an Organic Cocrystal: Narrowing the Singlet-Triplet Energy Gap via Charge Transfer.

Harvesting non-emissive spin-triplet charge-transfer (CT) excitons of organic semiconductors is fundamentally important for increasing the operation efficiency of future devices. Here we observe thermally activated delayed fluorescence (TADF) in a 1:2 CT cocrystal of trans-1,2-diphenylethylene (TSB) and 1,2,4,5-tetracyanobenzene (TCNB). This cocrystal system is characterized by absorption spectroscopy, variable-temperature steady-state and time-resolved photoluminescence spectroscopy, single-crystal X-ray diffraction, and first-principles calculations.

On the spectral profile change in the Q band absorption spectra of metalloporphyrins (Mg, Zn, and Pd): A first-principles study.

We performed a systematic study of the vibrationally resolved absorption spectra in the Q band of three metalloporphyrins (Mg, Zn, and Pd) to understand the spectral changes in this series, including both the Franck-Condon (FC) and Herzberg-Teller (HT) contributions. The ground (S) and the lowest singlet excited (S) states were, respectively, simulated by the static and time-dependent density functional theory, with which the Duschinsky rotation effect was considered. Different functionals and basis sets were tested and compared with experiment.

Study of double core hole excitations in molecules by X-ray double-quantum-coherence signals: a multi-configuration simulation.

The multi-configurational self-consistent field method is employed to simulate the two-dimensional all-X-ray double-quantum-coherence (XDQC) spectroscopy, a four-wave mixing signal that provides direct signatures of double core hole (DCH) states. The valence electronic structure is probed by capturing the correlation between the single (SCH) and double core hole states. The state-averaged restricted-active-space self-consistent field (SA-RASSCF) approach is used which can treat the valence, SCH, and DCH states at the same theoretical level, and applies to all types of DCHs (located on one or two atoms, K-edge or L-edge), with both accuracy and efficiency.

Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy.

Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns). We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs) passage through a CoIn.