Excitation Energy Research Articles

Enhancement of NIR‐II Emission of Er3+ by Doping Fe3+ in Double Perovskites: Multimode Luminescence for Versatile Optoelectronic Applications

AbstractErbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near‐infrared range. However, achieving high‐efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f‐4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near‐infrared region (NIR‐II) emission in Cs2NaBiCl6 by incorporating Fe3+ ions. The as‐prepared material demonstrates reversible thermochromism, driven by strong electron‐phonon coupling effect, and exhibits tunable luminescence that can be adjusted by altering excitation energy and temperature. Notably, benefitting from the charge transfer transition of Fe3+‐Cl− along with the influence of Fe3+ doping on the geometrical and electronic structures, the blue‐excitable (450 nm) NIR‐II emission around 1541 nm from Er3+ is realized for the first time, achieving an intensity 16.7 times higher and a maximum photoluminescence quantum yield (PLQY) of 22.5 %. This enhancement enables innovative applications such as two‐dimensional information encryption by the multi‐channel cooperative responses and improved NIR imaging. The study highlights the potential of Fe3+ doping in optimizing absorption and multimode luminescence in perovskites, opening avenues for advanced applications in blue‐excitable NIR light emitting diodes (LEDs), thermometer, anti‐counterfeiting, and NIR imaging.

Machine Learning-Assisted Hartree–Fock Approach for Energy Level Calculations in the Neutral Ytterbium Atom

Data-driven machine learning approaches with precise predictive capabilities are proposed to address the long-standing challenges in the calculation of complex many-electron atomic systems, including high computational costs and limited accuracy. In this work, we develop a general workflow for machine learning-assisted atomic structure calculations based on the Cowan code’s Hartree–Fock with relativistic corrections (HFR) theory. The workflow incorporates enhanced ElasticNet and XGBoost algorithms, refined using entropy weight methodology to optimize performance. This semi-empirical framework is applied to calculate and analyze the excited state energy levels of the 4f closed-shell Yb I atom, providing insights into the applicability of different algorithms under various conditions. The reliability and advantages of this innovative approach are demonstrated through comprehensive comparisons with ab initio calculations, experimental data, and other theoretical results.

Benchmark computations of nearly degenerate singlet and triplet states of N-heterocyclic chromophores. I. Wavefunction-based methods.

In this paper, we investigate the role of electron correlation in predicting the S1-S0 and T1-S0 excitation energies and, hence, the singlet-triplet gap (ΔEST) in a set of cyclazines, which act as templates for potential candidates for fifth generation organic light emitting diode materials. This issue has recently garnered much interest with the focus being on the inversion of the ΔEST, although experiments have indicated near degenerate levels with both positive and negative being within the experimental error bar [J. Am. Chem. Soc. 102, 6068 (1980), J. Am. Chem. Soc. 108, 17(1986)]. We have carried out a systematic and exhaustive study of various excited state electronic structure methodologies and identified the strengths and shortcomings of the various approaches and approximations in view of this challenging case. We have found that near degeneracy can be achieved either with a proper balance of static and dynamic correlation in multireference theories or with state-specific orbital corrections, including its coupling with correlation. The role of spin contamination is also discussed. Eventually, this paper seeks to produce benchmark numbers for establishing cost-effective theories, which can then be used for screening derivatives of these templates with desirable optical and structural properties. Additionally, we would like to point out that the use of domain-based local pair natural orbital-similarity transformed EOM-coupled cluster singles and doubles as the benchmark for ΔEST [as used in J. Phys. Chem. A 126(8), 1378 (2022), Chem. Phys. Lett. 779, 138827 (2021)] is not a suitable benchmark for these classes of molecules.

Exploring ground states of Fermi-Hubbard model on honeycomb lattices with counterdiabaticity

Exploring the ground state properties of many-body quantum systems conventionally involves adiabatic processes, alongside exact diagonalization, in the context of quantum annealing or adiabatic quantum computation. Shortcuts to adiabaticity by counter-diabatic driving serve to accelerate these processes by suppressing energy excitations. Motivated by this, we develop variational quantum algorithms incorporating the auxiliary counter-diabatic interactions, comparing them with digitized adiabatic algorithms. These algorithms are then implemented on gate-based quantum circuits to explore the ground states of the Fermi-Hubbard model on honeycomb lattices, utilizing systems with up to 26 qubits. The comparison reveals that the counter-diabatic inspired ansatz is superior to traditional Hamiltonian variational ansatz. Furthermore, the number and duration of Trotter steps are analyzed to understand and mitigate errors. Given the model’s relevance to materials in condensed matter, our study paves the way for using variational quantum algorithms with counterdiabaticity to explore quantum materials in the noisy intermediate-scale quantum era.

Absence of the third linker domain of ApcE subunit in phycobilisome from Synechocystis 6803 reduces rods-to-core excitation energy transfer.

Phycobilisome (PBS) is a pigment-protein complex utilized by red algae and cyanobacteria in photosynthesis for light harvesting. A cyanobacterium Synechocystis sp. PCC 6803 contains PBS with a tricylindrical core built of allophycocyanin (APC) disks where six phycocyanin (PC) rods are attached. The top core cylinder is seemingly involved in attaching four PC rods and binding orange carotenoid protein (OCP) to quench excess of excitation energy. In this study, we have deleted the third linker domain (LD3) of ApcE subunit of PBS which assembles four APC discs into the top core cylinder. The mutation resulted in PBS with bicylindrical core, structurally comparable to the naturally existing PBS from Synechococcus 7942. Lack of LD3 and the top APC cylinder reduces the excitation energy transfer between PC and APC in the mutant. Moreover, these PBSs are more prone to light induced-photodamage and do not bind to the photoactivated orange carotenoid protein (OCP), a known PBS excitation quencher. These findings highlight the complex and elegant interplay between PBS architecture and functional efficiency, suggesting that in PBSs with naturally tri-cylindrical cores, the top cylinder has essential roles in recruiting the rods and proper binding of OCP and recruitment of the four PC rods.

Ferroelectric Domain Modulation with Tip-Poling Engineering in BiFeO3 Films

BiFeO3 (BFO) films with ferroelectricity are the most promising candidates regarding the next generation of storage devices and sensors. The comprehensive understanding of ferroelectric switchable properties is challenging and critical to robust domain wall nanoelectronics. Herein, the domain dynamic was explored in detail under external bias conditions using scanning probe microscopy, which is meaningful for the understanding of domain dynamics and the foundation of ferroelectric devices. The results show that domain reversal occurred under external electric fields with sufficient energy excitation, combined with the existence of a charged domain wall. These findings extend the domain dynamic and current paths in ferroelectric films and shed light on the potential applications for ferroelectric devices.

Highly Accurate and Robust Constraint-Based Orbital-Optimized Core Excitations.

We adapt our recently developed constraint-based orbital-optimized excited-state method (COOX) for the computation of core excitations. COOX is a constrained density functional theory (cDFT) approach based on excitation amplitudes from linear-response time-dependent DFT (LR-TDDFT), and has been shown to provide accurate excitation energies and excited-state properties for valence excitations within a spin-restricted formalism. To extend COOX to core-excited states, we introduce a spin-unrestricted variant which allows us to obtain orbital-optimized core excitations with a single constraint. Using a triplet purification scheme in combination with the constrained unrestricted Hartree-Fock formalism, scalar-relativistic zero-order regular approximation corrections, and a semiempirical treatment of spin-orbit coupling, COOX is shown to produce highly accurate results for K- and L-edge excitations of second- and third-period atoms with subelectronvolt errors despite being based on LR-TDDFT, for which core excitations pose a well-known challenge. L- and M-edge excitations of heavier atoms up to uranium are also computationally feasible and numerically stable, but may require more advanced treatment of relativistic effects. Furthermore, COOX is shown to perform on par with or better than the popular ΔSCF approach while exhibiting more robust convergence, highlighting it as a promising tool for inexpensive and accurate simulations of X-ray absorption spectra.

Improving Optoelectronic Properties of Acceptor–Donor–Acceptor‐Type Non‐Fullerene Acceptors Containing Extended Fused Ring Donor Units for Efficient Organic Semiconductors

Developing efficient small molecule‐based non‐fullerene acceptors (NFAs) has gained huge attention in fabricating high‐efficiency and stable organic solar cells (OSCs). Herein, we designed and characterized eight new NFAs for OSCs. To investigate the potential of these newly designed NFAs series (IBH1–IBH8) for OSCs, various advanced quantum chemical simulation approaches are used and compared with the synthetic reference molecule IBH–R. Due to the extended donor cores, the IBH1–IBH8 molecules possess strong intramolecular and intermolecular interactions, which helps improve the thin‐film surface crystallinity. Moreover, the designed IBH1–IBH8 molecules present improved UV–visible absorption, narrower bandgaps, lower excitation, and binding energies, and improved photovoltaic characteristics. Furthermore, the impact on the intrinsic properties such as transition density matrix, density of state, electrostatic potential, distribution of frontier molecular orbitals, and reorganizational energies of holes and electrons are estimated. Additionally, the charge‐transfer phenomenon by establishing a donor:acceptor blend (PTB7–Th:IBH4) is analyzed, their geometric analyses are studied, and a good charge‐shifting process is found at the donor:acceptor interface. With these results, we demonstrated the enhancements in the optoelectronic and photovoltaic characteristics of OSCs by performing a simple end‐capped modulation. Hence, these molecules are recommended for the development of efficient and cost‐effective OSCs.

Effective M3Y-P2 interaction of study nuclear energy levels for 48Ti in fp shell model

In the fp-shell area of the 48Ti isotope (Z=22, N=26), examine the nuclear excitation energies using the nuclear shell model. The energy levels, total angular momentum, and parity of the nucleons outside the locked core 40Ca are calculated using the OXBASH algorithm for GX2, GX1A, KB3, and effective M3Y-P2 interactions. mixing together two orbital configurations. There was a good agreement between the model space vectors and energy levels and experimental data, but the agreement decreased when the realistic M3YP-2 interaction was used. The core polarisability effect has been used to accommodate the rejected space: core and higher organization via the L-S shell with an effective M3Y-P2 interaction. A comparison of the theoretical and experimental results has been conducted.

Type-II heterojunction Se-g-C3N4/ZnO coupled MnCo2O4 photocatalyst for enhanced levofloxacin hydrochloride degradation activated by peroxymonosulfate

The advanced oxidation process induced by photocatalysis under visible light undoubtedly possesses greater application potential and cost-effectiveness due to the high excitation energy supply costs. Here, we proposed a novel Type-II heterojunction Se-g-C3N4/ZnO (Se-CN/ZnO) and MnCo2O4 (MCO) photocatalyst for the efficient degradation of levofloxacin hydrochloride (LEV) activated by peroxymonosulfate (PMS) under sunlight. Analysis results confirmed the oxidation process was executed by Se-CN/ZnO synergistic MCO-activated PMS for the responsive degradation of LEV, achieving a removal efficiency greater than 98.6 % within 15 min (kinetic rate constant Kobs = 0.299 min−1), under optimal conditions ([Se-CN/ZnO (300 °C)]0 = 46 mg, [MCO]0 = 1.6 mg, [PMS]0 = 0.27 mM, [Aeration rate]0 = 146 mL/min, pH = 5.5). Effective interfacial transfer and spatial segregation of the photogenerated electron-hole were attributed to the stabilized Type-II energy band structure of Se-CN/ZnO, the rapid cyclic redox of metal ions Mnn+(n = 2,3,4) and Com+(m = 2,3) promoted the activation of PMS reduction of LEV through synergistic action of various endogenous substances. Analysis of the contribution of reactive oxygen species by electron paramagnetic resonance substantiated the dominant role of ·OH and O2·-, and the superiority of the degradation process was further validated with the analysis of the non-toxic and ecological safety characteristics of intermediates. The recommended method of eco-friendly and stable catalytic performance of LEV has engineering application prospects that are incomparable to many publicly available treatment methods.

Ellagic acid/Fe nanocomposite thin film with high power conversion efficiency for photovoltaic devices

This study synthesizes and characterizes an ellagic acid/Fe nanocomposite thin film ([Ellag-A/Fe.6H2O]NCTF) to enhance photovoltaic device efficiency, achieving a notable power conversion efficiency of 14.5%. Using FT-IR, TGA, XRD, SEM, and optical analyses, the nanocomposite's structural, thermal, and optical properties were investigated, revealing a polycrystalline structure with improved thermal stability over pure ellagic acid. Density Functional Theory (DFT) calculations show a large energy gap of 1.08 eV, indicating stability and high excitation energies. The combination of organic ellagic acid with iron nanoparticles makes ([Ellag-A/Fe.6H2O]NCTF a promising material for photovoltaic applications.

Theoretical investigation of iodine plasma through detailed electron impact excitation cross-section calculations and collisional-radiative model analysis

Abstract In the present study, we consider the electron impact excitation of neutral iodine and its application in developing a collisional-radiative model for plasma diagnostics of iodine plasma. Electron impact excitation cross- sections are calculated using fully relativistic distorted wave theory. The required atomic structure calculations for iodine are carried out using the relativistic multi-configuration Dirac-Fock method. The excitation energies obtained are reported and compared with values from the NIST database. The electron impact excitation cross-sections are calculated from the ground (5p5 2P3/2) and first- excited state (5p5 2P1/2) to the several upper fine structure levels. Our cross- section results align well with previous studies, reported by Ambalampitiya et al. [Atoms, 9, 103, 2021] using the Breit-Pauli B-spline R-matrix method. Further calculated cross-section results are incorporated into the collisional-radiative model. Our model also includes electron impact ionization, de-excitation, three- body recombination, and radiative decay. We validate our model using emission spectra from inductively coupled iodine plasma. For this purpose, we used the recorded intensities for the emission lines, 486.23 nm, 511.92 nm, 523.45 nm, 589.40 nm, and 608.24 nm are compared with those obtained from our model to calculate electron temperature and electron density of the iodine plasma.

Vibrational assignments and energy analyses of 3,4-difluorophenylacetylene using resonance-enhanced multiphoton ionization and slow electron velocity-map imaging techniques

Here, we report spectroscopic investigations of 3,4-difluorophenylacetylene applying two-color resonant two-photon ionization (2C-R2PI) and slow electron velocity-map imaging (SEVI) techniques. With the assistance of density functional theory (DFT) calculations, vibrational modes of the S0 neutral ground state, S1 first electronic excited state, and D0 cationic ground state were assigned. The adiabatic excitation energy of the S1 ← S0 electronic transition was determined to be 35639 ± 5 cm−1 from the resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Additionally, the adiabatic ionization potential was found to be 72398 ± 5 cm−1 based on the SEVI spectra.

All-dielectric transmissive narrow-band filters adjustable within wide spectral range

The challenge of obtaining transmission spectra with both a wider tunable spectral range and high resolution persists. In this paper, a novel all- dielectric transmissive grating structure based on Mie resonance is proposed. The structure excites the Mie resonance by embedding a high refractive index contrast grating in a KF-Si film system band-stop filter. The dipole resonance energy is confined within the high refractive index silicon grating material, expanding the cutoff bandwidth of the KF-Si film system to over 400 nm and achieving single-peak transmission in the visible range. And the continuous transmission spectrum has an adjustable range of 300 nm with the highest spectral resolution (FWHM) (∼20 nm) can be achieved by adjusting the grating period. To suppress the coupling energy excitation between the higher-order magnetic dipole and the substrate, a silicon-rich nitride (SRN) matching layer is introduced between the KF-Si film system and the substrate. This layer enhances the intensity of the resonance peaks while simultaneously suppressing the short-wavelength sidebands, thereby improving the saturation and purity of the spectrum. In addition, we obtained a large angular tolerance of up to 15° by stacking the silicon film system. This work is of great significance for the advancement of hyperspectral imaging and display technology.

Exploring Electronic and Conformational Attributes of an Organic Donor‐Bridge‐Acceptor Molecular System

AbstractThis research explores the electronic properties and conformational dynamics of the ZnP‐COPV‐ (Zinc Porphyrin ‐ Carbon bridged Oligo Phenylenevinylene ‐ Fullerene) organic semiconductor via specialized Density Functional Theory (DFT) and Molecular Dynamics (MD) computational techniques. First, through DFT calculations, essential HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital), and Molecular Electrostatic Potential (MEP) electronic attributes are meticulously dissected providing insights into the intricate charge transfer processes between the constituent donor‐acceptor moieties. Furthermore, MD simulations are employed to unveil the molecular system's multifaceted conformational flexibility and stability. The Root‐mean‐squared deviation (RMSD), end‐to‐end distance, and torsional angles quantitative analysis of conformational attributes support the carbon‐bridged oligo‐phenylenevinylene (COPV) molecular wire's ‐skeleton planar and rigid conformation. This minimal end‐to‐end distance variation (within Å) compared to the initially extended structure and the constrained torsional motion (within for ZnP‐COPV and for COPV‐) after thermalization showcases COPV's ability to maintain structural rigidity over time, aligning with the concept of effective ‐conjugation. Finally, through the lens of time dependent (TD)‐DFT, the dynamic evolution of the HOMO–LUMO energy gap, TD‐DFT excitation energies and oscillator strengths are explored as the molecular structure transforms over time. The observed energy gap variation underscores the molecule's adaptability in the face of structural modifications, hinting at an intriguing connection between structural stability and enhanced electronic properties. The research provides a comprehensive understanding of the intricate interplay between conformational dynamics and electronic attributes in organic semiconductors, providing quantitative insights crucial for designing stable, high‐performance materials for cutting‐edge optoelectronic applications and helping advance the collective understanding of sustainable energy conversion.

Nuclear Quantum Effects Have a Significant Impact on UV/Vis Absorption Spectra of Chromophores in Water

Despite the broadly acknowledged importance of solvation effects on measured UV/Vis spectra in the context of solvatochromism or chemical reactions in solution, it is still an open challenge to calculate UV/Vis spectra with predictive accuracy. This is particularly true when it comes to the impact of nuclear quantum effects on these experimental observables. In the present work, we calculate the UV/Vis absorption spectrum of indole in aqueous solution with a combination of a correlated wavefunction method for computing electronic excitation energies and enhanced path integral simulations for rigorous sampling of nuclear configurations including the quantum effects in solution. After validating our approach based on gas‐phase benchmarking, we demonstrate that the lineshape of the spectrum measured in aqueous solution is quantitatively recovered, without the application of any shifting, scaling, or broadening, only after including nuclear quantum effects in addition to thermal fluctuations and solvation at ambient conditions. Our findings demonstrate that nuclear quantum effects are "visible" in UV/Vis spectra of chromophores measured in solution even at room temperature and, therefore, that they must be considered computationally to achieve predictive accuracy.

Entropies, level-density parameters and fission probabilities along the triaxially- and axially-symmetric fission paths in 296Lv

We investigate the variation of statistical properties of the fissile nucleus, especially entropy, and nuclear level density, along different fission paths. The calculations were focused on comparing axial and triaxial trajectories leading to fission of 296Lv. We observe that change of shell effects and their suppression rates with deformation can substantially influence fission dynamics. Furthermore, the fission process exhibits iso-entropic behavior at high excitation energies, while pronounced entropy variations are observed at lower energies. We derive a deformation-dependent level density parameter that plays a critical role in estimating the survival probability of a superheavy nucleus. The competition between different fission paths was further studied by employing a master equation approach, thereby demonstrating the critical role of entropy and thermodynamic properties in shaping fission dynamics within multidimensional deformation spaces.

Influence of Intermolecular Interactions on the Photophysical Properties of Carbazolyl Phosphorescent Molecules

AbstractThe photophysical properties of three carbazolyl phosphorescent molecules with similar structures‐5‐(9H‐carbazole‐9‐group) nicotinitrile (P35N), 5‐(9H‐carbazole‐9‐group) nicotinamide (P35M) and 2‐(9H‐carbazole‐9‐group) isonicotinamide (P25M)‐are investigated theoretically. The influence on luminescence is primarily elucidated through an analysis of geometry, electronic structure, and the dynamic processes occurring within the excited state. Structural analysis indicates that P35M exhibits the most effective luminescence due to minimal structural changes, reduced separation between the electron and hole, and enhanced intermolecular interactions within the crystal. Excited state dynamics and recombination energy analysis indicate that the higher triplet exciton population in the P35M molecule contributes to its long‐lived phosphorescence. Furthermore, the intersystem crossing process for the three molecules is predominantly governed by low‐frequency torsional rotation, while bond stretching vibrations are the primary factor leading to the inactivation of non‐radiative processes. The distinct vibrational channels associated with reverse intersystem crossing and non‐radiative processes present opportunities for further enhancement of the phosphorescent characteristics of these molecules.

Gas-Phase Reactivity of Actinides Monocations with NH3: ICP-MS Experiments Combined with a DFT Study.

The reactivity of actinide monocations (Th+, U+, Np+, Pu+, Am+, and Cm+) with NH3 gas was studied in the reaction cell of an inductively coupled plasma-mass spectrometer (ICP-MS). Only Th+, U+, Np+, and Cm+ react completely with NH3 to form AnNH+, contrary to Pu+ and Am+. Differences in reactivity are found between U+/Pu+, Pu+/Cm+, and Am+/Cm+, which could resolve isobaric interferences in ICP-MS. DFT calculations were performed across the first half of the actinide series. The calculated reaction energy between An+ and NH3 reproduces the experimental trends in reactivity with Th+ > Pa+ > U+ > Np+ > Ac+ > Cm+ > Pu+ > Am+. The reaction path involves the initial formation of an AnNH3+ adduct followed by N-H bond insertion with the formation of HAnNH2+ and H2AnNH+ intermediate species and subsequent H2 loss. The trend in reactivity across the actinides is largely due to the first energy barrier and formation of the HAnNH2+ intermediate species. This limiting step is energetically unfavorable for the Pu+ and Am+ cations. For these cations, the excitation energy required to achieve a reactive configuration with two non-f electrons available for bonding is too high.

Shannon Wavelet‐Based Approximation Scheme for Information Entropy Integrals in Confined Domain

ABSTRACTIn this work, the author attempted to develop a Shannon wavelet‐based numerical scheme to approximate the information entropies in both configuration and momentum space corresponding to the ground and adjacent excited energy states of one‐dimensional Schrödinger equation appearing in non‐relativistic quantum mechanics. The development of this scheme is based on the judicious use of sinc scale functions as an approximation basis and a suitable numerical quadrature to approximate entropies in position and momentum spaces. Priori and posteriori errors appearing in the approximations of wave functions and entropy integrals have been discussed. The scheme (coded in Python) has been subsequently exercised for various exactly solvable and quasi‐exactly solvable non‐relativistic quantum mechanical models in confined domain.