Energy Shift Research Articles

Supramolecular Diodes with Donor-Acceptor Interactions.

Inspired by the initial proposal of σ-bridged donor-acceptor (D-σ-A) single-molecule diodes in 1974, extensive studies over the past 50 years have explored various designs for π-conjugated D-π-A single-molecule diodes due to their feasible chemical synthesis and effective charge transfer. However, the rectification ratio of π-conjugated single-molecule diodes has been long-term limited by the challenge of asymmetric electronic coupling to induce the rectification effect. Here, we present a supramolecular diode constructed through an intramolecular π-π interaction-driven assembly strategy. The asymmetric transmission in this system is tunable via subangström mechanical control, resulting in a rectification ratio of up to 16. Electron transport studies reveal that this through-space D-π-π-A system constructed by the π-π stacking between pyrene (Py) and naphthalenediimide (NDI) is crucial for achieving asymmetric currents under different bias polarization. Theoretical calculations suggest that the intermolecular destructive quantum interference not only enables a sharp variation in electron transmission but also facilitates asymmetric electronic energy shifts through mechanical stretching, significantly improving the rectification ratio. Our work provides a general approach to fabricating and modulating asymmetric molecular architectures through noncovalent supramolecular interactions, showcasing the potential of high-performance single-molecule rectifiers.

SLC13A5 plays an essential role in the energy shift to oxidative phosphorylation in cisplatin-resistant mesothelioma stem cells.

Mesothelioma is a highly aggressive tumor affecting an increasing number of patients worldwide. Owing to the poor clinical outcomes associated with current therapies, the development of novel therapies that target cancer stem cells (CSCs) is desirable. Here, we examined the applicability of our previously established hydrogel-based rapid CSC generation method to human mesothelioma cell lines and further analyzed the characteristics of the induced mesothelioma stem cell (MesoSC) -like cells. Human mesothelioma cell lines cultured on hydrogels presented increased expression of pan-stem cell markers and acquired spheroid formation and early tumorigenicity, suggesting that MesoSC-like cells are highly malignant. Microarray analysis demonstrated that the expression of SLC13A5, a citrate transporter involved in TCA cycle, was significantly induced in the resulting MesoSC-like cells. The overexpression of SLC13A5 resulted in a metabolic shift toward oxidative phosphorylation, increased phosphorylation of ERK and YAP, and increased SOX2 expression, leading to increased cisplatin resistance. scRNA-seq database analysis revealed that clinical mesothelioma samples contained a small number of SLC13A5-expressing cells. Our findings suggest that the hydrogel-based CSC generation method is also effective for human mesothelioma cells and that SLC13A5 may contribute to MesoSC survival. The new properties of MesoSCs revealed in this study may provide clues for establishing future treatments.

Quadrupolar excitons in MoSe2 bilayers

The quest for platforms to generate and control exotic excitonic states has greatly benefited from the advent of transition metal dichalcogenide (TMD) monolayers and their heterostructures. Among the unconventional excitonic states, quadrupolar excitons—a superposition of two dipolar excitons with anti-aligned dipole moments—are of great interest for applications in quantum simulations and for the investigation of many-body physics. Here, we unambiguously demonstrate the emergence of quadrupolar excitons in natural MoSe2 homobilayers, whose energy shifts quadratically in electric field. In contrast to trilayer systems, MoSe2 homobilayers have many advantages, which include a larger coupling between dipolar excitons. Our experimental observations are complemented by many-particle theory calculations offering microscopic insights in the formation of quadrupolar excitons. Our results suggest TMD homobilayers as ideal platform for the engineering of excitonic states and their interaction with light and thus candidate for carrying out on-chip quantum simulations.

Energy Response of Atomic and Molecular Orbitals in Nonuniform Magnetic Fields.

The response of atoms and molecules to nonuniform magnetic fields is far less explored than uniform fields. In this work, we analyze the orbital and spin-Zeeman interactions of the electrons with a spatially nonuniform linearly varying magnetic field at the atomic and molecular orbital levels and their role in shaping the net response. Gauge-origin-invariant finite field restricted Hartree-Fock computations are carried out to examine the orbital-Zeeman effect, while the general Hartree-Fock method with a two-component spinor representation of the orbitals helps gauge the combined space-spin response. The nature of degeneracy lifting of the orbitals is found to be distinct from that for uniform fields. Degeneracy lifting of various orbitals by the so-called "diamagnetic" A2 term is discussed for the first time to the best of our knowledge. A strong directionality of the response is uncovered and explained. Moreover, the role of the reference point for the gradient of the field, which has hitherto been largely ignored, is investigated in detail. The guiding principles for understanding the energy shifts of the atomic and molecular orbitals with change in the reference point are determined, and the minimum energy position and orientation of the ground states of homo- and heterodiatomic molecules relative to the field applied are discussed.

Oxygen K-edge inner-shell calculations of polymers in solutions realized by the extraction of local structures from molecular dynamics simulations.

Inner-shell quantum chemical calculations of large molecular systems, such as polymers and soft matter in solution, were performed to understand the phase transition dynamics of these systems using soft x-ray absorption spectroscopy (XAS). The molecular structures of 40-mer poly(N-isopropylacrylamide) (PNIPAM) chains in solutions were obtained using molecular dynamics simulations. The 5-mer PNIPAM chains with terminated H atoms, including the second coordination shells of the solvent methanol and water molecules, were extracted from the 40-mer PNIPAM chains in solutions. The O K-edge inner-shell spectra of the 5-mer PNIPAM chains were obtained by averaging the inner-shell spectra of 9700 extracted polymer structures. This calculation method can be used to precisely evaluate the energy shifts of the C=O π* peaks of PNIPAM caused by the structural changes of the polymer chains, the substitutions of the hydrogen bonds of the C=O groups in PNIPAM from methanol to water molecules, and the increase in the coordination numbers of solvent molecules with the C=O groups, which were observed in the O K-edge XAS experiments.

Bimetallic AuPd alloy nanoparticles on TiO₂ nanotube arrays: a highly efficient photocatalyst for hydrogen generation.

Decoration of TiO2 nanotube (TNT) arrays by AuPd nanoparticles (NPs) produces a dramatic enhancement in the rate of hydrogen generation through photocatalytic water-splitting under solar illumination. XRD and TEM confirmed alloy formation in bimetallic AuPd NPs while XPS ruled out a core-shell architecture in the AuPd NPs. Well-dispersed, size-controlled AuPd NPs were formed by sequential physical vapor deposition of Au and Pd on TNTs followed by spontaneous thermal dewetting (TNT-AuPd). TNT-AuPd samples were characterized by small tensile microstrains. For comparison purposes and to derive physical insights, an identical method was used to form TNT-Au and TNT-Pd samples wherein TNTs were decorated by monometallic Au and Pd NPs respectively. In every case, an accumulation-type heterointerface between TiO2 and the metallic/bimetallic NPs was indicated by binding energy shifts in the Ti2p high resolution x-ray photoelectron spectra (HR-XPS). Initial and final state effects in the Au4f HR-XPS pointed to a large number of Au atoms in low coordinate sites such as edges, kinks and corners as well as a slower excited atom relaxation in the alloy. A similar preponderance of Pd atoms at low coordinate sites was found along with the presence of a small amount of palladium oxide. TNT-AuPd demonstrated the highest photocatalytic H₂ production rate of 2920 µmol g⁻¹ h⁻¹, which is 8.9 times higher than that of TNTs, 2.1 times that of TNT-Au, and 1.69 times that of TNT-Pd under solar illumination. We studied H₂ generation under UV-filtered solar illumination with TNT-AuPd outperforming monometallic Au- and Pd-NP decorated TNTs, which is attributed to the enhancement of the catalytic activity of Pd in an Au environment, the presence of Pd and Au atoms at low coordinate sites, and photoinduced electron transfer between TNTs and AuPd alloy NPs, where AuPd acts as an efficient electron sink, in turn reducing carrier recombination losses.

Constructing n/n- Type Perovskite Homojunctions to Achieve High-Efficiency and Stable Printable Mesoscopic Perovskite Solar Cells.

In recent years, carbon-based printable mesoscopic perovskite solar cells (p-MPSCs) without hole transport layers have garnered considerable interest because of their outstanding benefits in terms of stability and cost. However, the use of carbon electrodes instead of hole transport materials and noble metal electrodes leads to energy level mismatch, which limits the power conversion efficiency (PCE) of p-MPSCs. In this work, a molecular doping strategy is proposed employing cyclopentylmethanamine to passivate surface and subsurface crystal defects in perovskite layers while inducing an energy shift toward the p-type in the perovskite region within carbon electrodes. This approach facilitates the formation of a perovskite homojunction at carbon micro-interfaces between carbon electrodes and perovskites. Results demonstrate that the formation of this homojunction optimizes the internal energy level alignment of devices, thereby increasing driving force for hole transfer to carbon electrodes. Ultimately, the devices optimized through this strategy increase the PCE from 17.50% to 19.50% while retaining over 92% of the initial PCE after over 150 days in air ambiance. This study provides a straightforward and effective approach for designing high-efficiency and stable p-MPSCs.

Analyzing the dynamic behavior and market efficiency of green energy investments: A geometric and fractional brownian motion approach

ABSTRACT The growing importance of green energy investments necessitates understanding their dynamic behavior and market efficiency, particularly during geopolitical instability. This study examines the performance of three major green energy indices – First Trust NASDAQ Clean Edge Green Energy Index Fund, Invesco Wilder Hill Clean Energy, and S&P Global Clean Energy Index – across distinct macroeconomic periods, including the post-Paris Agreement era, COVID-19 pandemic, Russia-Ukraine conflict, and Israel-Gaza conflict. We apply two advanced stochastic modeling techniques to address the complexities of price movements in these indices: Geometric Brownian Motion and Multifractional Brownian Motion. The Hurst exponent is calculated to evaluate market memory and efficiency during these periods. Our findings demonstrate that while the Geometric Brownian Motion model effectively captures general market trends, the Multifractional Brownian Motion model reflects the nuanced volatilities and structural shifts in green energy markets, particularly during heightened geopolitical tension. The Hurst analysis identifies alternating periods of persistence and anti-persistence, highlighting varying levels of market efficiency and partially challenging the Efficient Market Hypothesis. This study’s novelty lies in applying Geometric Brownian Motion and Multifractional Brownian Motion to green energy indices, providing a comprehensive approach to analyzing their behavior under external shocks. These results contribute to the literature by offering insights into the resilience and efficiency of green energy investments, thus aiding investors and policymakers in navigating the complexities of sustainable finance during global crises.

Machine learning potential model for accelerating quantum chemistry‐driven property prediction and molecular design

AbstractQuantum chemistry (QC) calculations have significantly advanced the development of materials, drugs, and other molecular products. Molecular geometry optimization is an indispensable step for QC calculations. However, its computational cost increases dramatically with increasing molecular system complexity, hindering the large‐scale molecule screening. This work proposes a deep learning‐based molecular potential energy surface prediction tool (DeePEST) to significantly accelerate geometry optimizations. The key of DeePEST involves the development of a novel machine learning potential model for accurate and fast predictions of molecular energy and atomic forces. These predictions enable efficient molecular geometry optimizations for subsequent predictions of QC properties (single‐point energy, dipole moment, HOMO/LUMO, and 13C chemical shifts) and COSMO‐SAC‐based thermodynamic properties (activity coefficient). Moreover, DeePEST facilitates efficient computer‐aided molecular designs that involve QC‐based geometry optimizations. The utilization of DeePEST in geometry optimizations achieves high prediction accuracy approaching to rigorous QC methods while maintaining the computational efficiency of molecular mechanics methods.

Reversal of charge transfer doping on the negative electronic compressibility surface of MoS2

Abstract The strong electron-electron interaction in transition metal dichalcogenides (TMDs) gives rise to phenomena such as strong exciton and trion binding and excitonic condensation, as well as large negative exchange and correlation contributions to the electron energies, resulting in negative electronic compressibility. Here we use angle-resolved photoemission spectroscopy to demonstrate a striking effect of negative electronic compressibility in semiconducting TMD MoS2 on the charge transfer to and from a partial overlayer of monolayer semimetallic WTe2. By systematically monitoring the binding energy shifts in the valence bands of both WTe2 and MoS2 during surface transfer doping with donor (K) and acceptor (F4-TCNQ) species, we observe distinct behaviors: (1) for donor doping, increased MoS2 valence band binding energy is accompanied by a counterintuitive reduction in the binding energy of WTe2 valence bands and core levels; (2) for acceptor doping, the expected decrease in MoS2 binding energies contrasts with an unexpected increase in those of WTe2. The observations imply a reversal of the expected charge transfer; donor (acceptor) deposition decreases (increases) the carrier density in the WTe2 adlayer. The charge transfer reversal is a direct consequence of the negative electronic compressibility of the MoS2 surface layer, for which addition (subtraction) of charge leads to attraction (repulsion) of further charge from neighbouring layers. These findings highlight the importance of many-body interactions for the electrons in transition metal dichalcogenides and underscore the potential for exploring strongly correlated quantum states in two-dimensional semiconductors.

Swift energy shift: Acute exercise reduces cerebral glucose metabolism in cognitively healthy older adults and individuals with Alzheimer's disease.

Swift energy shift: Acute exercise reduces cerebral glucose metabolism in cognitively healthy older adults and individuals with Alzheimer's disease.

Nonclassical Optical Response of Particle Plasmons With Quantum‐Informed Local Optics

AbstractAs the dimensions of plasmonic structures or the field confinement length approach the mean free path of electrons, mesoscopic optical response effects, including nonlocality, electron spill‐in or spill‐out, and Landau damping, are expected to become observable. In this work, a quantum‐informed local analogue model (QILAM) that maps these nonclassical optical responses onto a local dielectric film is presented. The primary advantage of this model lies in its compatibility with the highly efficient boundary element method (BEM), which includes retardation effects with relatively large particle sizes. Furthermore, the approach offers a unified framework that connects two important semiclassical theories: the generalized nonlocal optical response (GNOR) theory and the Feibelman d‐parameters formalism. It is envisioned that QILAM can evolve into a multiscale electrodynamic tool for exploring nonclassical optical responses in diverse plasmonic structures in the future. This can be achieved by directly translating mesoscopic effects into observable phenomena, such as plasmon resonance energy shifts and linewidth broadening in the scattering spectrum.

Navigating a Climate in Crisis through a Biomimetic Epistemology

We have entered a geological epoch where environmental change is driven primarily by human activity. The technology-centric approach to sustainable development as the dominant model of innovation in industrialized countries has led to expansive ecological degradation. This paper critiques this paradigm and builds on existing literature from environmental philosophy to propose a new model of ethical, bio-inspired architectural thinking. Though Biomimicry is often celebrated as a model for nature-inspired innovation, it can inadvertently reinforce notions of mastery over nature, a harmful phenomenon that environmental philosopher Freya Mathews calls ‘anthropocentric triumphalism.’ In response to those challenges, this paper explores the philosophical underpinnings of bio-inspired design to advocate for a transformative pedagogical model within architectural education and practice. By exploring the conflicts implicit in biomimetic processes, we aim to disentangle students’ thinking from techno-centric models and prepare them for the broader societal implications of a necessary energy shift. This exploration emphasizes the importance of cultivating a holistic understanding of ecological systems, urging designers to appreciate the intricate relationships within ecosystems rather than viewing them solely as sources of technological inspiration. By addressing the conflicts inherent in biomimetic processes, this paper calls for a more comprehensive and ethical approach to biomimicry – one that emphasizes both the source of knowledge as well as its application. Ultimately, we seek to foster a responsible relationship between architecture and the natural world, paving the way for a sustainable future that goes beyond mere imitation to encompass true coexistence.

The band structure and carrier recombination mechanism of α/β-phase tellurium homojunction investigated by infrared photoluminescence

During the synthesis of tellurium (Te) crystals, the coexistence of multiple crystalline phases (α-Te, β-Te, and γ-Te) with diverse structures commonly occurs, leading to instability and complexity in the performance of Te-based optoelectronic devices. This study employs physical vapor deposition to synthesize Te crystals of various sizes and morphologies, followed by spatially and temperature-dependent evaluation using Raman mapping and infrared photoluminescence (PL) spectroscopy. Spatially resolved results reveal that the size and morphology of Te crystals significantly influence the energy and peak profiles of Raman and PL spectra. Statistical analysis of spatially random sampling indicates the PL peak energies of Te crystals follow a lognormal distribution in terms of their occurrence frequencies, reflecting the complex interplay of multiple factors during crystal growth. This results in the coexistence of α-Te and β-Te phases, forming α/β-Te heterophase homojunction (HPHJ). Meanwhile, temperature-dependent PL results, obtained for the range of 3–290 K, reveal multi-peak competitive behavior in the PL spectra, accompanied by S-shaped shifts in peak energy. These features can be rationally explained by an interface transition-recombination mechanism based on the I-type α/β-Te HPHJ model. It also confirms infrared PL spectroscopy is an effective method for identifying the crystalline phase composition of Te crystals.

Electronic absorption of ferricenium derivatives: an unexpected twist

Our results revealed that the introduction of either electron-donating or electron-withdrawing group(s) on the cyclopentadienyl rings leads to a substantial red shift of the lowest energy ligand-to-metal charge transfer (LMCT) band, generally known as 2E2g → 2E1u, relative to that of the parent ferricenium complex. The observed stabilization of the lowest unoccupied molecular orbitals (LUMO), i.e. e2g orbitals, in the electron-deficient system, was ascribed to the δ back donation from the iron atom into the antibonding molecular orbitals of the ligand rings. A series of DFT calculations reproduce the experimental trend highlighting the shift in energies of the molecular orbitals involved in the charge transfer transition. The direct relationship between the location of the LMCT band and reduction potential for specific class of substituents is also presented which allows for more informed structural modifications in the development of these complexes.

Energy shift with coupling (ESC): a new quench protection method

Energy shift with coupling (ESC): a new quench protection method

Proton Accumulation Modulated Surface Potential in Proton Conducting Ceramics Revealed by Near-Ambient Pressure X-ray Photoelectron Spectroscopy.

Proton conducting electrochemical cells (PCECs) are efficient and clean intermediate-temperature energy conversion devices. The proton concentration across the PCECs is often nonuniform, and characterizing the distribution of proton concentration can help to locate the position of rate-limiting reactions. However, the determination of the local proton concentration under operating conditions remains challenging. Here, we employed in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to investigate an Au/BaZr0.9Y0.1O3-δ/Au symmetric cell with DC bias of 1 V applied between the working and counter electrodes (CE). The relative intensity of hydroxyl groups, deconvoluted from the O 1s XPS spectra, reveals the distribution of proton concentration across the electrolyte. The applied electric field induces proton accumulation at the counter electrode, imposing binding energy shifts of the surface components for metal elements relative to their lattice components. Combined XPS and impedance analysis suggests that the accumulation layer of protons is much thicker at 500 K compared to that at 670 K, as a result of a larger amount of hydroxyl groups at the lower temperature. This nonuniform distribution of proton concentration affects the chemical environment of metal elements, and the local electrical potential, as revealed by the in situ XPS. This work demonstrates in situ NAP-XPS as a tool to probe the distribution of proton concentration and its impact on the defect chemistry and local electrical potential of PCECs, thereby advancing the understanding of the impact of proton defect chemistry and the performance improvement of PCECs.

Tuning anomalous Hall conductivity via antiferromagnetic configurations in GdPtBi.

The magnetic, electronic, and topological properties of GdPtBi were systematically investigated using first-principles density functional theory (DFT) calculations. Various magnetic configurations were examined, including ferromagnetic (FM) and antiferromagnetic (AFM) states, with particular focus on AFM states where the Gd magnetic moments align either parallel (AFM‖) or perpendicular (AFM⊥) to the [111] crystal direction. For AFM⊥, the in-plane angles ϕ were varied at ϕ = 0°, 15°, and 30° (denoted as AFM⊥,ϕ=0°, AFM⊥,ϕ=15°, and AFM⊥,ϕ=30°, respectively). The ground-state magnetic structure of GdPtBi was validated through dipolar magnetic field calculations at the muon sites, corroborating the internal magnetic fields observed in muon spin relaxation (μSR) experiments. The results indicate that the AFM⊥,ϕ=30° configuration aligns with the μSR-measured internal field. The DFT-calculated band structure and Berry curvature reveal that AFM⊥ belongs to the triple-point semimetals (TPSMs) where the triple-point nodes positioned along the Z-Γ-Z and F-Γ-F paths have energies that shift as the spin-orbit coupling strength varies with ϕ. Notably, this shift in triple-point energy corresponds to a significant change in the anomalous Hall conductivity (AHC, σxy), with a difference of 75.06 Ω-1 cm-1 at the Fermi energy between AFM⊥,ϕ=0° and AFM⊥,ϕ=30°. These findings highlight the potential for controlling the AHC through precise manipulation of the AFM structure.

Improving the accuracy of temperature measurement on TEM samples using plasmon energy expansion thermometry (PEET): Addressing sample thickness effects.

Advances in analytical scanning transmission electron microscopy (STEM) and in microelectronic mechanical systems (MEMS) based microheaters have enabled in-situ materials' characterization at the nanometer scale at elevated temperature. In addition to resolving the structural information at elevated temperatures, detailed knowledge of the local temperature distribution inside the sample is essential to reveal thermally induced phenomena and processes. Here, we investigate the accuracy of plasmon energy expansion thermometry (PEET) as a method to map the local temperature in a tungsten (W) lamella in a range between room temperature and 700 °C. In particular, we address the influence of sample thickness in the range of a typical electron-transparent TEM sample (from 30 nm to 70 nm) on the temperature-dependent plasmon energy. The shift in plasmon energy, used to determine the local sample temperature, is not only temperature-dependent, but in case of W also seems thickness-dependent in sample thicknesses below approximately 60 nm. It is believed that the underlying reason is the high susceptibility of the regions with thinner sample thickness to strain from residual load induced during FIB deposition, together with increased thermal expansion in these areas due to their higher surface-to-volume ratio. The results highlight the importance of considering sample thickness (and especially thickness variations) when analyzing the local bulk plasmon energy for temperature measurement using PEET. However, in case of W, an increasing beam broadening (FWHM) of the bulk plasmon peak with decreasing sample thickness can be used to improve the accuracy of PEET in TEM lamellae with varying sample thickness.

Unravelling the pH-dependent mechanism of ferroelectric polarization on different dynamic pathways of photoelectrochemical water oxidation.

Ferroelectric polarization is considered to be an effective strategy to improve the oxygen evolution reaction (OER) of photoelectrocatalysis. The primary challenge is to clarify how the polarization field controls the OER dynamic pathway at a molecular level. Here, electrochemical fingerprint tests were used, together with theoretical calculations, to systematically investigate the free energy change in oxo and hydroxyl intermediates on TiO2-BaTiO3 core-shell nanowires (BTO@TiO2) upon polarization in different pH environments. We demonstrate that the adsorbate evolution mechanism (AEM) dominated in acidic environments, and both positive and negative polarization resulted in a reduction in the oxo-free energy, which inhibited the reaction kinetics. In the oxide path mechanism (OPM) that occurs in alkaline conditions, the ferroelectric polarization exhibits repulsive adsorbate-adsorbate interaction for OH- coverage and free energy shift of the OH- groups. We elucidate that a weakly alkaline electrolyte is the optimal environment for ferroelectric polarization because the positive polarization promotes OH- coverage and facilitates reaction pathway transfer from AEM to OPM; therefore, BTO@TiO2 exhibited a record polarization enhancement to 0.52 mA cm-2 at 1.23 VRHE in pH = 11. This work provides a more accurate insight into the pH-dependent effect of ferroelectric polarization on the OER dynamic pathway than conventional models that are based solely on the regulation of band bending.