State Energy Research Articles

Carbonate-mediated Mars-van Krevelen mechanism on CuxO/CeO2 catalysts for boosting CO oxidation

Copper-cerium-based catalysts have gained considerable attention for their excellent performance in low-temperature CO oxidation applications. In this context, the carbonate-mediated Mars-van Krevelen (M−vK) pathway stands out as a promising route for enhancing catalytic performance. Herein, we prepared three CuxO/CeO2 nanocatalysts with varying copper content using Cu2O nanocrystals (Cu2O NCs) and Ce-BTC metal–organic frameworks (MOFs) as dual precursors. The optimal catalyst exhibits excellent performance (T100 value of 110 °C) comparable to the precious metal catalyst. Through integrating in-depth experimental results and density functional theory (DFT) calculations, we reveal the intricate interplay of interfacial synergistic catalysis and carbonate-mediated M−vK mechanisms, confirming that carbonate species generated under mild conditions significantly promote CO oxidation on CuxO/CeO2 nanocatalysts. Based on the comparison of the transition state (TS) energy barrier between the traditional and the carbonate-mediated M−vK mechanism reaction paths, we found that carbonate species is easier to form and establish the rate-determining step (viz., carbonate → CO2, the energy barrier of 1.51 eV). This study sheds light on the importance of carbonate species in modulating the catalytic behaviour of copper-cerium catalysts and provides valuable insights for designing efficient catalysts for CO oxidation applications.

Investigation of the microstructural characteristics of laser-cladded Ti6Al4V titanium alloy and its corrosion behavior in simulated body fluid

Laser cladding technology has a wide range of potential industrial applications in the surface strengthening, repair and reuse of orthopedic implants. By employing this technique to conduct same-material surface restoration and enhancement on titanium alloys, it demonstrates significant developmental potential. However, the microstructure of laser additively manufactured titanium alloy differs significantly from that of traditional titanium alloys, which affects its corrosion resistance in human body fluids. To compare the corrosion resistance differences between the cladding layer and the substrate, this study investigates the microstructure of multi-pass laser cladding Ti6Al4V (TC4) titanium alloy and analyzes the corrosion morphology and corrosion products of the cladding layer in simulated body fluids (SBF). By comparing the electrochemical corrosion behavior of laser cladding with that of traditionally manufactured TC4, this research reveals the differences in corrosion resistance between the two titanium alloys. The research demonstrates that the microstructure of cladding primarily consists of prior-β grains and continuous grain boundary α phase, along with a complex basketweave structure composed of fine acicular α phase and lamellar α phase. Additionally, due to the complex thermal cycling process, the acicular α' colonies within the prior-β grains. These features enhance the cladding layer’s resistance to plastic deformation and increase microhardness, though with some uneven distribution. Interestingly, the TC4 cladding layer forms a porous passivation layer after corrosion, primarily composed of a TiO2 passivation film and deposits of hydroxyapatite and other phosphates. Due to the lower β-phase content, finer grains with higher energy states, and a greater proportion of high-angle grain boundaries (HAGBs) in the cladding layer, it exhibits higher electrochemical activity. As a result of these microstructural differences, the corrosion resistance of the TC4 cladding layer in SBF is inferior to that of TC4 manufactured using traditional techniques.

Thermodynamics of AdS-Schwarzschild-like black hole in loop quantum gravity

AbstractWe obtained the metric of the Schwarzschild-like black hole with loop quantum gravity (LQG) corrections in anti-de Sitter (AdS) space-time, under the assumption that the cosmological constant is decoupled in LQG. We investigated its thermodynamics, including the equation of state, criticality, heat capacity, and Gibbs free energy. The $$P-v$$ P - v graph was plotted, and the critical behavior was calculated. It was found that, due to the LQG effect, the quantum-corrected Schwarzschild-AdS black hole exhibits a critical point and a critical ratio of 7/18, which differs from the Reissner–Nordstr$$\ddot{\textrm{o}}$$ o ¨ m-AdS black hole’s ratio of 3/8 (the same as that of the Van der Waals system) slightly. However, there are still some similarities compared to the Van der Waals system, such as the same critical exponents and a similar $$P-v$$ P - v graph. Moreover, it is concluded that the energy-momentum tensor related to the black hole’s mass could violate the conventional first law of thermodynamics. This modified first law may violate the conservation of Gibbs free energy during the small black hole-large black hole phase transitions, potentially indicating the occurrence of the zeroth-order phase transition. The Joule–Thomson expansion was also studied. Interestingly, compared to the Schwarzschild-AdS black hole, the LQG effect leads to inversion points. The inversion curve divides the $$\left( P,T\right) $$ P , T coordinate system into two regions: a heating region and a cooling region, as shown in detail by the inversion curves and isenthalpic curves. The results indicated that there is a minimum inversion mass, below which any black hole will not possess an inversion point.

A biomimetic phosphor that can build a rigid microenvironment for its long-lived afterglow in aqueous medium.

Organic phosphorescent materials have great prospects for application, whose performance particularly depends on the preparation method. Inspired by nature's wisdom, we report a phosphor that can utilize monomers in its environment by polymerization to construct a rigid microenvironment under light illumination, leading to a glow-in-the-dark emulsion with a phosphorescence lifetime of 1 s in water. This phosphor can achieve active growth of the aqueous emulsion with the introduction of more monomers. In the presence of trace amounts of oxygen (which has adverse effects on both polymerization and afterglow), this phosphor can still undergo photo-induced polymerization, removing the influence of oxygen and obtaining afterglow emulsion, demonstrating its adaptability to the environment. This phosphor can also catalyze the polymerization of monomers containing yellow fluorophore, obtaining long-lifetime yellow afterglow emulsion through excited state energy transfer. We have also conducted in-depth studies on the photo-catalytic and phosphorescent properties of this phosphor in model systems. This biomimetic intelligent manufacturing provides a new approach for organic phosphorescent materials and is significant for future applications.

Plasmon–Exciton–Polariton Condensation in Organic Semiconductor‐Covered Plasmonic Lattices

AbstractExciton–polariton condensates featuring collective coherence and large nonlinearities are promising for advancing coherent light sources and functional devices. Nevertheless, their reliance on planar cavities with large lateral device footprints and mode volumes hinders device integration. Plasmon–exciton–polaritons (PEPs), arising from the strong coupling between excitons and plasmons, provide an intriguing platform to explore emergent polariton condensation at the nanoscale due to their ultrasmall mode volumes in metal nanoparticles. However, the substantial radiative and Ohmic losses in metals hamper PEPs condensation, particularly in the short wavelength range (<600 nm). Here, a method is proposed to address metal losses by integrating organic semiconductor neat films onto plasmonic lattices. The use of organic semiconductors with large transition dipole moment and low non‐radiation loss enables efficient coupling between massive excitons and lattice plasmons, leading to high‐density PEPs. This ensures a macroscopic number of polaritons populating the low‐lying band edge at relatively low fluences to obtain bosonic stimulation, resulting in PEP condensation. By tailoring the band structures of plasmonic lattices, the condensation of PEPs are further manipulated into different energy states. These findings offer valuable insights for the design of PEP systems and all‐optical polaritonic devices.

Theoretical analysis and predictions for the two-neutrino double electron capture of 124Xe

Abstract We provide a complete theoretical description of the two-neutrino electron capture in 124Xe, improving both the nuclear and the atomic structure calculations. We improve the general formalism through the use of the Taylor expansion method, leading to higher-order terms in the decay rate of the process. The nuclear part is treated with pn-QRPA and interacting shell model (ISM) methods. The nuclear matrix elements (NMEs) are calculated with the pn-QRPA method with isospin restoration by fixing the input parameters so that the experimental decay rate is reproduced, resulting in values significantly lower than in previous calculations. The validity of the pn-QRPA NMEs is tested by showing their values to be comparable with the ones for double-beta decay with the emission of two antineutrinos of 128,130Te, which have similar pairing features. Within the ISM, we reproduce the total experimental half-life within a factor of two and predict the capture fraction to the KK channel of about 74%. We also predict the capture fractions to other decay channels and show that for the cumulative decay to the KL1–KO1 channels, a capture fraction of about 24% could be observed experimentally. On the atomic side, calculations are improved by accounting for the Pauli blocking of the decay of innermost nucleon states and by considering all s-wave electrons available for capture, expanding beyond the K and L1 orbitals considered in previous studies. We also provide improved atomic relaxation energies of the final atomic states of 124Te, which may be used as input for background modeling in liquid Xenon experiments.

Unexpected XPS Binding Energy Observations Further Highlighted by DFT Calculations of Ruthenocene-Containing [IrIII(ppy)2(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)2(FcCOCHCORc)

The series of iridium(III) complexes, [Ir(ppy)2(RCOCHCOR′)], with R = CH3 and R′ = CH3 (1), Rc (2), and Fc (3), as well as R = Rc and R′ = Rc (4) or Fc (5), and R = R′ = Fc (6), ppy = 2-phenylpyridinyl, Fc = FeII(η5–C5H4)(η5–C5H5), and Rc = RuII(η5–C5H4)(η5–C5H5), has been investigated by single-crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3…, sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f7/2 and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC50 = 25.1 μM) and 3 (IC50 = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC50 = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH2COCH3 (IC50 = 66.6 μM).

Efficient Organic Light-Emitting Diodes Obtained by Introducing Gadolinium (Gd) Complexes Based on Pyrazolone Derivative Ligands as Hole Trappers.

The utilization of lanthanide (Ln) complexes in the realm of organic light-emitting diodes (OLEDs) has garnered extensive interest, particularly in their role as luminescent materials or electron trappers. A series of gadolinium (Gd) complexes with energy levels of high HOMO/LUMO and different triplet state energies were designed and synthesized by introducing substituents with different electronic effects onto the pyrazolone derivative ligands. Subsequently, these complexes were precisely purified by vacuum sublimation and codoped into the light-emitting layer (EML) of the OLEDs. This process was facilitated through the well-matched HOMO/LUMO levels and triplet energies among various functional materials. Consequently, the maximum external quantum efficiencies of blue, red, and green OLEDs were simultaneously enhanced with the ratios of 119%, 28%, and 71%, respectively. This improvement can be credited to the introduction of Gd(III) complex molecules within EMLs, which helps to capture excess holes and improve carriers' balance.

The spectrum of experimentally accessible states for melting and freezing transitions in mesoporous materials.

Structural disorder in mesoporous solids gives rise to complex phase behavior for materials confined within their pore spaces. As a result, a wide spectrum of possible phase configurations associated with spatial distributions of thermodynamic phases throughout the pore networks can be realized in experiments. Despite their importance, quantifying these states remains largely unaddressed. By considering solid-liquid equilibria as a representative example and using a simple random network model, we investigate the spectrum of such states accessible in real experiments and relate this spectrum to the structural characteristics of porous solids. We classify these states by their free energies and demonstrate how network effects break degeneracies for specific phase compositions and temperatures. Furthermore, we identify the experimental conditions that delineate boundary free energy states, differentiating accessible from inaccessible states. The insights from this study on solid-liquid equilibria are also equally applicable to gas-liquid equilibria in confined spaces and contribute to a deeper understanding of relaxation dynamics associated with hysteresis.

Study of isotropic stellar models via durgapal-lake solutions in rastall system

Abstract This manuscript is dealt with the influences of Rastall factor on the physical aspects of isotropic celestial models. In this scenario, both the ideal fluid distribution and static spherically symmetry are taken into consideration. In specifically, the Durgapal-Lake solutions are taken into consideration to analyze the different characteristics of several specific compact star models like Her X-1, Vela X-1, LMC X-4 and RXJ 1856-37. Due to its innovative combination of two methodologies, this solution is a significant advancement on Durgapal-Fuloria and Lake's previous ansatz in enormous crucial eras. Using observed estimates of radii and masses of certain specific star objects, the undefined parameters in Durgapal-Lake ansatz are derived by matching conditions. The consistency of the adopted solutions is examined through the visual interpretation of matter constituents, equation of state factor, energy conditions, mass function and stability criteria corresponding to distinct choices of Rastall factor. The radially symmetric graphs of matter variables as well as the mass function are also displayed. Moreover, We present the graphical analysis for vanishing Rastall factor. It is concluded that in the context of Rastall theory, the stars under examination exhibit stable compositions with Durgapal-Lake solution, while in the context of general relativity, they exhibit instability.

Donor–Acceptor Type Solvatochromic Flavonoid Materials Fluorphores for Polarity Sensing and Real‐Time Temperature Monitoring

AbstractElectron donor–acceptor (D–A) molecules are emerging tools for designing sensitive luminogens, attracting significant research attention. However, due to poor quantum yields under certain conditions, current D–A fluorophores often suffer from fluorescence quenching in practical applications. Developing new D–A dyes and functional composites is crucial for expanding their applications. Here, a novel donor–acceptor type flavonoid dye molecule, namely “AFL”, exhibiting both polarity‐dependent fluorescence emission wavelength shift and viscosity‐dependent intensity change, for polarity measurement and temperature sensing is designed and synthesized. Because the intramolecular charge transfer (ICT) can be enhanced by a decrease of excited state energy caused in high‐polarity organic solvents, AFL undergoes fluorescence emission wavelength shift that shows fluorescence color response to solvents of different polarities and hence differentiates between them. Moreover, the actual temperature can be monitored by the as‐designed AFL@tetradecanoic acid (AFL@TA) sensor. By combining with TA, viscosity sensitively changes upon the temperature change of insoluble composites, thus realizing the fluorescence intensity response to temperature. Remarkable recyclable performance and satisfactory mechanical properties are integrated. This study provides a promising approach to developing a new D–A fluorescent probe and furnishes perspectives on the potential of such D–A type flavonoid material in stimuli‐responsive systems with a focus on visualization sensing technology.

Cluster perturbation theory. X. A parallel implementation of Lagrangian perturbation series for the coupled cluster singles and doubles ground-state energy through fifth order.

We describe an efficient implementation of cluster perturbation and Møller-Plesset Lagrangian energy series through the fifth order that targets the coupled cluster singles and doubles energy utilizing the resolution of the identity approximation. We illustrate the computational performance of the implementation by performing ground state energy calculations on systems with up to 1200 basis functions using a single node and by comparison to conventional coupled cluster singles and doubles calculations. We further show that our hybrid message passing interface/open multiprocessing parallel implementation that also utilizes graphical processing units can be used to obtain fifth order energies on systems with almost 1200 basis functions with a 90min"time to solution" running on Frontier at Oak Ridge National Laboratory.

Inverse Design of Singlet‐Fission Materials with Uncertainty‐Controlled Genetic Optimization

AbstractSinglet fission has shown potential for boosting the efficiency of solar cells, but the scarcity of suitable molecular materials hinders its implementation. We introduce an uncertainty‐controlled genetic algorithm (ucGA) based on ensemble machine learning predictions from different molecular representations that concurrently optimizes excited state energies, synthesizability, and exciton size for the discovery of singlet fission materials. The ucGA allows us to efficiently explore the chemical space spanned by the reFORMED fragment database, which consists of 45,000 cores and 5,000 substituents derived from crystallographic structures assembled in the FORMED repository. Running the ucGA in an exploitative setup performs local optimization on variations of known singlet fission scaffolds, such as acenes. In an explorative mode, hitherto unknown candidates displaying excellent excited state properties for singlet fission are generated. We suggest a class of heteroatom‐rich mesoionic compounds as acceptors for charge‐transfer mediated singlet fission. When included in larger donor‐acceptor systems, these units exhibit localization of the triplet state, favorable diradicaloid character and suitable triplet energies for exciton injection into semiconductor solar cells.

Bonding states underpinning structural transitions in IrTe2 observed with micro-ARPES

Competing interactions in low-dimensional materials can produce nearly degenerate electronic and structural phases. We investigate structural phase transitions in layered IrTe2 for which a number of potential transition mechanisms have been postulated. The spatial coexistence of multiple phases on the micron scale has prevented a detailed analysis of the electronic structure. By exploiting micro-angle-resolved photoemission spectroscopy obtained with synchrotron radiation we extract the electronic structure of the multiple structural phases in IrTe2 in order to address the mechanism underlying the phase transitions. We find direct evidence of lowered energy states that appear in the low-temperature phases, states previously predicted by calculations and extended here. Our results validate a proposed scenario of bonding and antibonding states as the driver of the phase transitions. Published by the American Physical Society 2024

Inverse Design of Singlet-Fission Materials with Uncertainty-Controlled Genetic Optimization.

Singlet fission has shown potential for boosting the efficiency of solar cells, but the scarcity of suitable molecular materials hinders its implementation. We introduce an uncertainty-controlled genetic algorithm (ucGA) based on ensemble machine learning predictions from different molecular representations that concurrently optimizes excited state energies, synthesizability, and exciton size for the discovery of singlet fission materials. The ucGA allows us to efficiently explore the chemical space spanned by the reFORMED fragment database, which consists of 45,000 cores and 5,000 substituents derived from crystallographic structures assembled in the FORMED repository. Running the ucGA in an exploitative setup performs local optimization on variations of known singlet fission scaffolds, such as acenes. In an explorative mode, hitherto unknown candidates displaying excellent excited state properties for singlet fission are generated. We suggest a class of heteroatom-rich mesoionic compounds as acceptors for charge-transfer mediated singlet fission. When included in larger donor-acceptor systems, these units exhibit localization of the triplet state, favorable diradicaloid character and suitable triplet energies for exciton injection into semiconductor solar cells.

Exciton-Exciton Interaction in Monolayer MoSe2 from Mutual Screening of Coulomb Binding.

Excitons in two-dimensional (2D) semiconductors are particularly exciting, as reduced screening and dimensional confinement foster their pronounced many-body interactions. Optical pumping is typically used to create excitons so as to study their properties, but at the same time such pumping can also create unbound charge carriers. This makes experimental determination of the exciton-exciton interactions difficult. Most importantly, the two effects of band gap renormalization and Coulomb screening on the individual exciton resonance energy counteract each other. Here by comparing the influences of exciton and electron density on the exciton ground and excited states energies of monolayer MoSe2 using photoluminescence spectroscopy, we are able to distinctly identify the screening of Coulomb binding by the neutral excitons and by charge carriers. The energy difference between exciton ground state (A-1s) and excited state (A-2s) red-shifts by 5.5 meV when the neutral exciton density increases from 0 to 4 × 1011 cm-2, in contrast to the blue shifts with the increase of either electron or hole density. This energy difference change is attributed to the mutual screening of Coulomb binding of neutral excitons, a many-body effect that is over 5 times magnitude stronger than the conventional estimate of exciton-exciton interactions. From this mutual Coulomb screening we extract an exciton polarizability of α2Dexciton = 2.5 × 10-17 eV(m/V)2. Our finding uncovers a mechanism that dominates the repulsive part of many-body interaction between neutral excitons.

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.

Conformational plasticity links structural instability of NAA10F128I and NAA10F128L mutants to their catalytic deregulation

The acetylation of proteins' N-terminal amino groups by the N-acetyltransferase complexes plays a crucial role in modulating the spatial stability and functional activities of diverse human proteins. Mutations disrupting the stability and function of NAA10 result in X-linked rare genetic disorders. In this study, we conducted a global analysis of the impact of fifteen disease-associated missense mutations in NAA10. The analyses revealed that mutations in specific residues, such as Y43, V107, V111, and F128, predictably disrupted interactions essential for NAA10 stability, while most mutations (except R79C, A111W, Q129P, and N178K) expectedly led to structural destabilization. Mutations in many conserved residues within short linear motifs and post-translational modification sites were predicted to affect NAA10 functionality and regulation. All mutations were classified as pathogenic, with F128I and F128L identified as the most destabilizing mutations. The findings show that the F128L and F128I mutations employ different mechanisms for the loss of catalytic activities of NAA10F128L and NAA10F128I due to their structural instability. These two mutations induce distinct folding energy states that differentially modulate the structures of different regions of NAA10F128L and NAA10F128I. Specifically, the predicted instability caused by the F128I mutation results in decreased flexibility within the substrate-binding region, impairing the substrate peptide binding ability of NAA10F128I. Conversely, F128L is predicted to reduce the flexibility of the region containing the acetyl-CoA binding residues in NAA10F128L. Our study provides insights into the mechanism of catalytic inactivation of mutants of NAA10, particularly elucidating the mechanistic features of the structural and functional pathogenicity of the F128L and F128I mutations.

Enhancing negative thermal quenching in green-emitting perovskite microspheres via shallow trap state modulation

AbstractFor luminescent materials, negative thermal quenching (NTQ), characterized by an increase in the luminescent intensity with temperature, has a large potential in lighting and display technologies. However, leveraging NTQ in metal halide perovskites is challenging, and the mechanism is not well understood. Herein, by utilizing low-temperature photoluminescence, persistent luminescence and thermoluminescence, the origins of NTQ in CsPbBr3 microspheres are systematically studied, which pertain to the liberation of carriers from shallow trap states. Experimental and theoretical investigations reveal that the energy of these shallow defect states is approximately 0.135 eV beneath the conduction band. A rapid thermal treatment increases the density of these shallow traps and amplifies the NTQ effect, resulting in an enhancement of room-temperature photoluminescence by more than 60% compared to that at 150 K. The process also reduces the threshold for amplified spontaneous emission to about 45 W/cm2. Our findings not only provide a deeper understanding of the NTQ phenomenon in CsPbBr3 microspheres but also open new avenues for enhancing the performance of perovskite optoelectronic devices through energy state regulation.

Endo‐Encapsulated Multi‐Resonance Dendrimers with Through‐Space Interactions for Efficient Narrowband Blue‐Emitting Solution‐Processed OLEDs

AbstractDifferent from conventional luminescent dendrimers with fluorophore tethered outside to dendron, here we first developed endo‐encapsulated luminescent dendrimers with multi‐resonance (MR) fluorophore embedded inside of carbazole dendrons by growing dendrons through 1,8‐positions of central carbazole moiety to create a cavity for accommodating the fluorophore. This endo‐encapsulated structure not only shields the fluorophore to fully resist aggregation‐caused spectral broadening, but also induce through‐space interactions between dendron and fluorophore via intramolecular π‐stacking, giving lowered singlet state energy and reduced singlet‐triplet energy splitting to accelerate reverse intersystem crossing (RISC) from triplet to singlet states. The resultant dendrimer containing 1,8‐linked second‐generation carbazole dendrons and boron, sulfur‐doped polycyclic MR fluorophore exhibits narrowband blue emission at 471 nm with FWHM kept at 34 nm even in neat film, together with ~4 times enhancement of RISC rate constant compared to its exo‐tethered counterpart. Solution‐processed OLEDs based on the endo‐encapsulated dendrimer reveal efficient narrowband blue emissions with maximum external quantum efficiency of 22.6 %, representing the best device efficiency for blue‐emitting multi‐resonance dendrimers so far.